Hydrogenation of solid fuels. Coal hydrogenation method Coal hydrogenation reaction

To obtain valuable chemical compounds from coal, heat treatment processes (semi-coking, coking) or heat treatment in the presence of hydrogen under pressure (hydrogenation) are used.

Thermal decomposition of coal is accompanied by the formation of coke, tar and gases (mainly methane). Coal semi-coking resins mainly contain aromatic compounds. Brown coal semi-coking tars, along with aromatic compounds, also contain a significant amount of saturated cycloalkanes and alkanes. Coke is the target product of semi-coking. During the thermal processing of coal in the presence of hydrogen, it is possible to almost completely convert the organic mass of coal into liquid and gaseous hydrocarbons.

Thus, coal hydrogenation can be used to obtain not only motor and aviation fuels, but also the main petrochemical raw materials.

Hydrogenation liquefaction of coal is a complex process, including, on the one hand, the disaggregation of the structure of the organic mass of coal with the breaking of the least strong valence bonds under the influence of temperature, and on the other hand, the hydrogenation of broken and unsaturated bonds. The use of hydrogen is necessary both to increase the H:C ratio in products due to direct hydrogenation and to stabilize the degradation products of eliminated macromolecules.

The implementation of the process of coal hydrogenation under relatively low pressure - up to 10 MPa - is possible with the use of a hydrogen donor-paste former of oil or coal origin and the use of efficient catalysts.

One of the main problems in coal liquefaction is the optimization of the process of hydrogen transfer from donor-paste formers to coal matter. There is an optimal degree of hydrogen saturation of donor molecules. The paste-forming agent should contain 1-2% more hydrogen than in coal liquefaction products. The introduction of substituents of various types into the structure of donors affects both the thermodynamic and kinetic characteristics. The transfer of hydrogen from donors to carriers - molecules of aromatic compounds - proceeds stepwise according to the free radical mechanism.

At low pressure (up to 10 MPa), the use of donors allows coal to add no more than 1.5% hydrogen, and for deep liquefaction of coal (90% or more), it is necessary to add up to 3% hydrogen, which can be done by introducing it from the gas phase.

The molybdenum catalyst used in combination with iron and other elements significantly intensifies the process, increases the depth of coal liquefaction and reduces the molecular weight of the products.

The main primary products of coal hydrogenation are hydrogenate and sludge containing ~15% solids (ash, unconverted coal, catalyst). Gaseous hydrogenation products containing C1-C4 hydrocarbons, ammonia, hydrogen sulfide, carbon oxides mixed with hydrogen are sent for purification by short cycle adsorption, and gas with 80-85% hydrogen content is returned to the process.

During the condensation of the hydrogenate, water is separated, which contains dissolved ammonia, hydrogen sulfide and phenols (a mixture of mono- and polyhydric).

Below is a schematic diagram of the chemical processing of coal (Scheme 2.3).

The water condensate contains 12-14 g/l of phenols of the following composition (in % (wt.):

To obtain phenols, aromatic hydrocarbons and olefins, a scheme for the chemical processing of coal liquefaction products has been developed, which includes: distillation to separate the fraction from bp. up to 513 K; isolation and processing of crude phenols; hydrotreating of the dephenolized wide fraction with bp. up to 698 K; distillation of the hydrotreated product into fractions with bp. up to 333, 333-453, 453-573 and 573-673 K; hydrocracking of medium fractions in order to increase the yield of gasoline fractions; catalytic reforming of fractions with bp. up to 453 K; extraction of aromatic hydrocarbons; pyrolysis of raffinate gasoline.

When processing brown coal from the Borodino deposit of the Kansko-Achinsk coal basin, in terms of dry weight of coal, the following compounds can be obtained (in wt. %)):

In addition, 14.9% of C1-C2 hydrocarbon gases can be isolated; 13.4% - liquefied hydrocarbon gases C 3 -C 4 , as well as 0.7% ammonia and 1.6% hydrogen sulfide.

Hydrogenation (hydrogenation) of solid fuel is the process of converting the organic part of the fuel into liquid products enriched with hydrogen and used as liquid fuel. The problem of solid fuel hydrogenation has arisen in connection with the increased consumption of oil and the need to efficiently use low-calorie and high-ash fossil coals, which are difficult to burn. On an industrial scale, hydrogenation of solid fuels was first organized in Germany in the 1930s and was developed due to the need to use heavy resinous oils with a high sulfur content for the production of motor fuels. Currently, installations for destructive dehydrogenation of fuels with a capacity of 200 to 1600 tons / day are operating in various countries.

Hydrogenation of solid fuel is a destructive catalytic process occurring at a temperature of 400-560°C under a hydrogen pressure of 20-10 MPa. Under these conditions, intermolecular and interatomic (valence) bonds break in the organic mass of the fuel and the reactions of destruction and depolymerization of high-molecular structures of coal proceed.

The problem of solid fuel hydrogenation has arisen in connection with the increased consumption of oil and the need to efficiently use low-calorie and high-ash fossil coals, which are difficult to burn. On an industrial scale, hydrogenation of solid fuels was first organized in Germany in the 1930s and was developed due to the need to use heavy resinous oils with a high sulfur content for the production of motor fuels. Currently, installations for destructive dehydrogenation of fuels with a capacity of 200 to 1600 tons / day are operating in various countries.

Hydrogenation of solid fuel is a destructive catalytic process occurring at a temperature of 400-560°C under a hydrogen pressure of 20 -

10 MPa. Under these conditions, intermolecular and interatomic (valence) bonds break in the organic mass of the fuel and the following reactions occur:

destruction and depolymerization of high-molecular structures of coal

(C)n + nH2 → CnH2n;

hydrogenation of the resulting alkenes;

destruction of higher alkanes with subsequent hydrogenation of alkenes and the formation of alkanes of lower molecular weight

CnH2n+2 → CmH2m+2 + CpH2p + H2 → CpH2p+2;

hydrogenation of condensed aromatic systems followed by ring breaking and dealkylation

opening of five-membered rings with the formation of isoalkanes and others.

Since the hydrogenation process proceeds in an excess of hydrogen, the polymerization and polycondensation reactions of the primary degradation products are suppressed, and at a sufficiently high hydrogen/carbon ratio, compaction products are almost not formed.

Simultaneously with the hydrogenation of carbon compounds, reactions of hydrogenation of compounds containing sulfur, oxygen and nitrogen proceed according to reactions similar to the reactions of hydrotreatment of petroleum products (Chapter VII).

The hydrogenation process is catalytic. As catalysts, contact masses based on compounds of molybdenum, nickel or iron with various activators are used, for example:

MoO3 + NiS + CaO + BaO + A12O3.

catalyst activator carrier

By changing the process parameters (temperature, pressure, contact time) and the composition of the catalyst, the hydrogenation process can be directed towards obtaining products of a given composition. The yield of liquid and gaseous products of solid fuel hydrogenation essentially depends on the content of volatile substances in it, that is, on the degree of its coalification. Coals with a high degree of coalification (anthracite, lean coals) cannot be used as raw materials for hydrogenation. Suitable fuels for this purpose are brown coals or hard coals with a hydrogen/carbon ratio of at least 0.06 and an ash content of not more than 0.13 wt. USD

The process of hydrogenation of solid fuels can be carried out in the liquid or vapor phase. Of the many technological schemes for liquid-phase hydrogenation, the most economical is the cyclic scheme. It differs from others by lower hydrogen consumption, lower process temperature and pressure, and allows full use of all components of the processed raw materials. A schematic diagram of such a hydrogenation plant is shown in Fig. 1.8.

As a result of the hydrogenation of all types of solid fuels, a liquid product containing isoalkanes and naphthenes is formed, which is used as a feedstock for catalytic reforming and hydrocracking, as well as boiler fuel and gas.

Figure 1.8. Cyclic scheme of liquid-phase hydrogenation of fuel: 1 - apparatus for preparing raw materials; 2 - pump for pasta; 3 - hydrogenation reactor; 4 - centrifuge; 5, 6 - distillation plants; 1 - neutralizer; 8 - hydrotreating reactor

Hydrogenation processing of coal is the most versatile method of direct liquefaction. The theoretical foundations for the effect of hydrogen on organic compounds under pressure were developed at the beginning of the 20th century. Academician V.N. Ipatiev. The first extensive studies on the application of hydrogenation processes to coal processing were carried out by German scientists in the 1910s-1920s. In the period 1920-1940s. in Germany, a number of industrial enterprises were created on the basis of this technology. In the 1930s-1950s. Experimental and industrial installations for the direct liquefaction of coal by the method of hydrogenation were built in the USSR, England, the USA, and some other countries.

As a result of hydrogenation processing, the organic mass of coal is dissolved and saturated with hydrogen to a degree that depends on the purpose of the target products. The production of commercial motor fuels is ensured by processing the liquid products obtained at the first (liquid-phase) stage by the methods of vapor-phase hydrogenation.

During liquid-phase hydrogenation of coals in the temperature range of 300-500°C, the complex matrix of coal is destroyed, accompanied by the breaking of chemical bonds and the formation of active free radicals. The latter, being stabilized by hydrogen, form smaller molecules than the initial macromolecules. The recombination of free radicals also leads to the formation of macromolecular compounds. Hydrogen, necessary for the stabilization of radicals, is partially provided by the use of solvents - hydrogen donors. These are compounds that, interacting with coal, are dehydrogenated at high temperatures, and the atomic hydrogen released in this case joins the products of coal destruction. The hydrogen donor solvent is also a paste-forming agent. To be in the conditions of the hydrogenation process in the liquid phase, it must have a boiling point above 260°C. Condensed aromatic compounds, primarily tetralin, have good hydrogen-donor properties. The higher-boiling compounds of this group (naphthalene and cresol) are less active, but when they are mixed with tetralin, a synergistic effect occurs: a mixture of equal parts of tetralin and cresol has a higher donor ability than either separately.

In practice, not individual substances, but distillate fractions of coal liquefaction products with a high content of condensed aromatic compounds, are most widely used as hydrogen donor solvents. Harmful impurities in solvents are polar compounds, such as phenols, as well as asphaltenes, the content of which should not exceed 10-15%. To maintain donor properties, the circulating solvent undergoes hydrogenation. With the help of a solvent, it is usually possible to "transfer" to coal no more than 1.5% (mass.) of hydrogen. Increasing the depth of transformation of the organic mass of coal is achieved by introducing gaseous molecular hydrogen directly into the reactor.

Based on numerous studies, it has been established that coals of low stages of metamorphism are preferable for hydrogenation processing into liquid products.

Table 3.5. Characteristics of brown coals of the Kansk-Achinsk and hard coals of the Kuznetsk basins

Kansko-Achinsk basin

Field

ma and brown coals with a vitrinite reflectivity index L° = 0.35-0.95 and the content of inert petrographic microcomponents is not higher than 15% (wt.). These coals must contain 65-86% (wt.) carbon, more than 5% (wt.) hydrogen and not less than 30% (wt.) volatile substances based on organic mass. The ash content in them should not exceed 10% (wt.), since the high ash content adversely affects the material balance of the process and makes it difficult to operate the equipment. In our country, brown coals of the Kan-sko-Achinsk and hard coals of the Kuznetsk basins meet these requirements to the greatest extent (Table 3.5).

The suitability of coals for the production of liquid fuels by hydrogenation can be estimated from elemental composition data. I. B. Rapoport found that the yield of liquid hydrogenation products per organic mass of coal decreases with an increase in the mass ratio of carbon to hydrogen in its composition and reaches a minimum value (72%) at C:H=16. Statistical analysis of the composition and ability to liquefy American coals made it possible to establish with a correlation of 0.86 the following linear dependence of the yield of liquid products [C? g, % (wt.)] from the content [% (wt.)] (in the initial demineralized carbon of hydrogen and organic sulfur:

A slightly different linear relationship with a correlation of 0.85 was obtained in the study of Australian coals:

Brown coals are easily liquefied, but, as a rule, they contain a lot of oxygen (up to 30% per WMD), the removal of which requires a significant consumption of hydrogen. At the same time, the content of nitrogen in them, which also requires hydrogen to remove, is lower than in bituminous coals.

Important physical characteristics are porosity and solvent wettability. The degree of fluidization of coals is significantly affected by the mineral impurities and microelements contained in them. Providing a physical and catalytic effect in the liquefaction processes, they violate the direct relationship between the yield of liquid products and the composition of the organic part of the coal.

The main parameters affecting the degree of liquefaction of coal and the properties of the products obtained by liquid-phase hydrogenation are the temperature and pressure at which the process is carried out. The optimal temperature regime for liquid-phase hydrogenation is in the range of 380-430°C and for each specific coal lies in its own narrow range. At temperatures above 460°C, there is a sharp increase in gas formation and the formation of cyclic structures. With an increase in process pressure, the rate of coal liquefaction increases.

There are two methods for the implementation of liquid-phase hydrogenation processing of coal in order to obtain synthetic motor fuels - thermal dissolution and catalytic hydrogenation.

Thermal dissolution is a mild form of chemical conversion of coal. When interacting with a solvent-hydrogen donor, part of the organic matter of the coal goes into solution and, after separation of the solid residue, it usually represents a high-boiling extract of coal, freed from minerals, sulfur-, oxygen- and nitrogen-containing compounds and other undesirable impurities. To increase the degree of coal conversion, hydrogen gas can be supplied to the solution. Depending on the type of initial coal, solvent, and process conditions, products for various purposes can be obtained by thermal dissolution.

For the first time, the technology of thermal dissolution of coal was proposed by A. Pott and X. Brochet in the 1920s. By the beginning of the 1940s, a plant with a capacity of 26.6 thousand tons of extract per year was operating on the basis of this technology in Germany.

At this plant, a paste consisting of one part of crushed coal and two parts of a solvent was heated in a tube furnace to 430 ° C under a pressure of 10-15 MPa. Liquid products were separated from the undissolved coal and its mineral part by filtration at a temperature of 150°C and a pressure of 0.8 MPa. A mixture of tstraline, cresol, and medium oil of liquid-phase hydrogenation of coal tar pitch was used as a solvent. The yield of an extract with a softening point of 220°C and a content of 0.15-0.20% (wt.) of ash was about 75% (wt.) of the organic matter of coal. The extract was mainly used as a raw material for obtaining high quality electrode coke.

Since the 1960s, a number of countries have developed and implemented in pilot and demonstration plants a new generation of processes based on the thermal dissolution of coal. According to the intended purpose, they can be divided into two types: 1) processes in which only primary solid or liquid products are obtained under normal conditions, intended, as a rule, for combustion in furnaces of power plants, and 2) processes involving the processing of primary products into more qualified (primarily into motor) fuels through secondary processes of thermal processing, hydrogenation and refining.

The process of extraction purification of coal SRC (Solvent Refined Coab) developed in the USA in the basic version SRC-I is carried out at a temperature in the reactor of 425–470°C, a pressure of 7–10 MPa, and a residence time in the reaction zone of “30 min. The main product of the process is a coal extract purified from sulfur, which hardens at a temperature of 150-200 °C.

In a modified version of the SRC-II process, the scheme of which is shown in fig. 3.2, by increasing the pressure to 14 MPa and increasing the residence time of the coal paste in the reaction zone, liquid fuel of a wide fractional composition is obtained as the main target product. The initial coal after grinding and drying is mixed with hot coal suspension. The resulting paste, together with hydrogen, is passed through a fired heater and then sent to the reactor. The required temperature and partial pressure of hydrogen are maintained by supplying cold hydrogen to several points of the reactor. The reaction products are first separated in gas separators. The gas separated from liquid products, containing predominantly (stage I) hydrogen and gaseous hydrocarbons with an admixture of hydrogen sulfide and carbon dioxide, after cooling to 38°C, is sent to the acid gas purification system. At the cryogenic plant, gaseous hydrocarbons C 3 -C 4 and purified hydrogen are released (it is returned to the process). The remaining methane fraction after methanation of the carbon monoxide contained in it is fed into the fuel network. Liquid pro-

Rice. 3.2. Scheme of the process of thermal dissolution of BIS-I coal:

1 - mixer for making pasta; 2 - furnace for heating the paste; 3 - reactor; 4 - block of gas separators; 5 - acid gas absorber; 6 - cryogenic gas separation; 7 - fuel gas purification unit; 8 - separation of gaseous hydrocarbons; 9-unit for purification of syngas and hydrogen evolution; 10 - sulfur recovery unit; II - residue gasification reactor; 12 - atmospheric column; 13 - vacuum'column;

1 - dried powdered coal; II - hydrogen; III - coal suspension; IV - process fuel; V - sulfur; VI - oxygen: VII - water vapor; VIII - inert residue; IX - the rest of the mineral part of the coal; X - liquid product after gas separation; LU - fuel gas; HC - ethane; XIII - propane; XIV - butanes; XV - gasoline fraction for purification and reforming; XVI - middle distillate for refining; XVII-

heavy distillate products from gas separators enter the atmospheric column, where they are separated into gasoline fraction (28-193°C), middle distillate (193-216°C) and heavy distillate (216-482°C). Formed at the first stage of separation in gas separators, the coal suspension is divided into two streams: one is fed to the displacement with the original coal, the other - to the vacuum column. From the top of the vacuum column, part of the liquid distillate contained in the suspension is discharged into the atmospheric column, and the remainder from the bottom goes to obtain synthesis gas used to produce hydrogen or as fuel,

Based on dry deashed bituminous coal, the yield of products in the EIS-C process at a hydrogen consumption of 4.4% (wt.) is [% (wt.)] :

The process of thermal dissolution of coal EDS ("Exxon Donor Solvent") is intended for the production of synthetic oil with its subsequent processing into motor fuels. According to this technology, coal after grinding and drying is mixed with a hot hydrogen donor solvent. As the latter, a fraction of 200-430°C of the liquid product of the process is used, which is preliminarily hydrogenated in an apparatus with a stationary layer of Co-Mo catalyst. The mixture is fed into an ascending flow reactor together with gaseous hydrogen, where thermal dissolution of coal occurs at a temperature of 430-480°C and a pressure of 14-17 MPa. The resulting products are separated (in a gas separator and by vacuum distillation) into gases and fractions boiling up to 540°C and a residue >540°C, which also contains unreacted coal and ash. Product yield, conversion rate and other process parameters depend on the type of coal being processed. The yield and composition of liquid products is also influenced by the recycling of the residue. For example, at. in various technological design of the process (without recirculation of the residue-I and with recirculation of the residue - II), the yield of fractions is: [% (wt.)] :

Depending on the type of raw material, the yield of liquid products on dry and deashed coal with complete recirculation of the residue can vary from 42 to 51% (wt.), and the yield of gases Ci-C 3 - from 11 to 21% (wt.). All resulting fractions must be hydrotreated to remove sulfur and nitrogen. The content of heterocompounds increases with an increase in the boiling point of the fractions.

Two variants of the technological scheme of the EDS process are proposed, differing in the methods of producing hydrogen and fuel gas. In the first variant, hydrogen is produced by steam reforming of light gases that are part of the process products, and fuel gas is obtained by processing the vacuum distillation residue of the liquid product of the process at a coking unit with coke gasification (“Flexicoking”), which simultaneously produces an additional amount of light liquid products. The thermal efficiency of such a process is about 56%.

The second option provides maximum flexibility in the range of products. About half of the vacuum residue is processed at the Flexicoking unit to obtain liquid products and fuel gas, and hydrogen is produced from the remaining amount. Thus, light hydrocarbon gases obtained by thermal dissolution are a commercial product. The thermal efficiency of this option reaches 63%.

On the basis of EDS technology in the United States, a demonstration plant with a capacity of 250 tons of coal per day was put into operation in 1980, capital investments in the construction of which amounted to $370 million. $1.4 billion (in 1982 prices).

The advantages of thermal dissolution processes include a lower operating temperature than in coal pyrolysis and the possibility of varying the quality of the resulting liquid product over a relatively wide range by changing the process parameters. At the same time, during thermal dissolution, deep conversion of coal is achieved at a high process pressure, and macromolecular compounds predominate in the composition of the resulting products. The presence of the latter is due to the fact that already at low temperatures, the processes of recombination of the resulting free radicals begin to occur, accompanied by the formation of secondary aromatic structures that are less reactive than the initial organic matter of coal. The presence of hydrogen donors and molecular hydrogen dissolved in the paste in the reaction mixture cannot sufficiently prevent these processes from occurring. In the industrial implementation of this method, a number of difficulties arise. A difficult technical problem is the separation of unreacted coal and ash from liquid products. The resulting target product is liquid under process conditions, but under normal conditions it can be semi-solid and even solid, which is difficult to transport, store and process into final products.

catalytic hydrogenation. An increase in the degree of coal conversion, an improvement in the composition of the resulting liquid products, and a decrease in the pressure of the hydrogenation process are possible with the use of catalysts. The latter contribute to the transfer of hydrogen from the solvent to the coal and activate molecular hydrogen, converting it into an atomic form.

Research in the field of direct hydrogenation processing of coal using catalysts was started by German scientists F. Bergius and M. Pier in 1912. As a result of these works, in 1927, the first industrial installation for catalytic hydrogenation of coal with a capacity of 100 thousand tons per year of liquid products was built (Bergius-Peer process). By the beginning of the 1940s, there were already 12 enterprises of this type operating in Germany, which produced up to 4.2 million tons of motor fuels per year, primarily aviation gasoline. In 1935, an enterprise for the hydrogenation of coal was built in England, and in the USA, work in this area was carried out on a large pilot plant in the period 1949-1953.

In the Soviet Union, research on the hydrogenation of domestic coals was started by N. M. Karavaev and I. B. Rapoport in 1929. Later, A. D. Petrov, A. V. Lozovoy, B. N. Dolgov made a significant contribution to the development of these works. , D. I. Orochko, A. V. Frost, V. I. Karzhev and a number of other Soviet scientists. In 1937, the first plant in our country for the hydrogenation processing of brown coal was designed and put into operation in the city of Kharkov. By the beginning of the 1950s, several more similar enterprises were built.

In industrial installations of those years, three- and four-stage coal processing schemes were used. At the stage of liquid-phase hydrogenation, the paste - 40% coal and 60% high-boiling coal product with the addition of an iron catalyst - was exposed to hydrogen gas at a temperature of 450-490 °C and a pressure of up to 70 MPa in a system of three or four sequentially located reactors. The degree of conversion of coal into liquid products and gas was 90-95% (wt.). Since economical methods of catalyst regeneration were not developed at that time, in most cases cheap low-activity catalysts based on iron oxides and sulfides were used. After passing through the system of reactors and the hot separator at a temperature of 440–450°C, the circulating hydrogen-containing gas and liquid products were removed from above. Then, in the cold separator, the gas was separated from the liquid and, after washing, was returned to the cycle mixed with fresh hydrogen. After a two-stage pressure reduction to separate hydrocarbon gases and water, the liquid product was subjected to distillation, with the separation of a fraction with an end boiling point of up to 320-350 °C and a residue (heavy oil, it was used to dilute the hydrogenation sludge before centrifugation).

Liquid-phase hydrogenation was carried out according to two schemes: with a closed cycle (complete recirculation) through the paste-forming agent and with an excess of heavy oil. According to the first scheme, the majority of hydrogenation plants operated, mainly focused on the production of gasoline and diesel fuel. When working with an excess of heavy oil, the capacity of the installation for coal increased by 1.5-2 times, but heavy oil had to be subjected to separate hydrogenation processing into lighter-boiling products or used to produce electrode coke.

When processing coals with a cycle closed according to the paste-forming agent, the yield of liquid products boiling up at temperatures up to 320 °C was 55-61% (mass) at a hydrogen consumption of up to 6% (mass). These products, containing 10-15% phenols, 3-5% nitrogenous bases, and 30-50% aromatic hydrocarbons, were then subjected to two-stage vapor phase hydrogenation on a stationary bed of hydrocracking catalysts. The total yield of gasoline with an octane number of 80-85 according to the motor method reached 35% (mass), and with the simultaneous production of gasoline and diesel fuel, their total yield was about 45% (mass) in the calculation of the initial coal; hydrogen was obtained by gasification of coal or semi-coke.

Sludge containing up to 25% solids was sent for processing, which was the most cumbersome and energy-intensive stage of the entire technological cycle. After dilution with a heavy fraction of the hydrogenate to a solids content of 12-16% (wt.), the sludge was subjected to centrifugation. The residue with a solids content of about 40% was processed by semi-coking in drum rotary kilns with a capacity of 10-15 t/h, and light liquid coking products were mixed with the distillate fraction of the hydrogenate. The heavy oil distillation obtained by centrifugation was returned to the pasta cycle.

The low activity of the catalyst, difficulties in processing sludge, and other factors necessitated the use of high pressures and large amounts of hydrogen in the process. The installations had a low unit productivity, they were distinguished by a significant energy intensity.

In various fields, I S ° Z Dany p ° second generation R ° combs in various countries, and above all in the USSR, USA and Germany

In the development of these processes, the main focus of research has been on reducing equipment productivity pressure, reducing energy costs, and improving sludge processing and catalyst regeneration. To date, about 20 options for the technological design of processes for the direct hydrogenation catalytic liquefaction of coal in elm plants have been proposed, from laboratory to demonstration plants, with a capacity of 50 to 600 tons / day for P coal.

BergiusN-Pipia FRG The so-called "new German technology" for coal hydrogenation has been developed on the basis of the previously used R U Pira process using a non-recoverable iron catalyst. Unlike the old process, a circulating middle distillate is used to make a paste (instead of a centrifuge overflow). Liquid products are separated from the solid residue by vacuum distillation (instead of centrifugation), and the sludge is gasified to produce hydrogen. In Bottrop (Germany) on the basis of this new

Among the processes of catalytic hydrogenation of coal developed abroad, one of the most prepared for industrial implementation is the H-Coa1 process (USA). According to this technology, liquid-phase hydrogenation is carried out using a fluidized bed of an active finely dispersed Co-Mo catalyst according to the scheme shown in Fig. 3.3.

Dry crushed coal is mixed with recycled hydrogenation product to form a paste containing 35-50% (wt.) coal, into which compressed hydrogen is then introduced. The resulting mixture is heated and fed under the distribution grate into the reactor with a fluidized catalyst bed. The process is carried out at a temperature of 425-480 °C and a pressure of about 20 MPa. The reaction products and unconverted coal are continuously removed from the reactor at the top, and the spent catalyst at the bottom. Constant circulating and regeneration of the catalyst ensure that its high activity is maintained.

Vapors removed from the reactor, after condensation, are separated into hydrogen, hydrocarbon gases and light distillate. Gases are sent for purification, and hydrogen for recirculation. Liquid products from the top of the reactor enter the separator, in which a fraction is separated, which is then subjected to distillation to obtain light and heavy distillates. From the first, gasoline and diesel fractions are obtained. The residual product discharged from the bottom of the separator is divided in hydrocyclones into two streams: with a low and high solids content.

The first stream is used as a paste-forming agent, and the second one is treated with a precipitator, and the separated sludge containing up to 50% of solid particles is gasified to produce hydrogen. The liquid product remaining after the separation of the sludge is subjected to vacuum distillation to obtain a heavy distillate and a residue used as boiler fuel.

The yield of target products in the process "H-Coa1" reaches 51.4% (wt.) on the organic mass of coal, including gasoline fraction (28-200°C) -25.2% (wt.), middle distillate (200 -260°C) - 12.9% (wt.) and heavy distillate - 13.3% (wt.). The consumption of hydrogen for liquid-phase hydrogenation is 4.7% (wt.). The process has been worked out on a pilot plant with a coal capacity of 600 tons per day.

In our country, the Institute of Combustible Fossils (IGI), together with the institutes Grozgiproneftekhim and VNIIneftemash, carried out a wide range of studies in the 1970s in the field of hydrogenation processing of coal in liquid

Rice. 3.3. Scheme of the process of hydrogenation liquefaction of coal "H-Coa1":

1 stage of coal preparation; 2 - heater; 3 - reactor with a fluidized bed of catalyst; 4 - capacitor; 5 - hydrogen extraction unit; 6 - high-speed separator; 7 - atmospheric column; 8 - hydrocycloes; 9 - separator; 10 - vacuum column; 1 - coal; II - hydrogen; III - recycled heavy distillate; IV - paste; V is the level of hydrogenate; VI - fluidized catalyst level; VII - regenerated catalyst; VIII - steam-gas phase; IX - condensed phase; X - spent catalyst; XI - liquid; XII - resins; XIII - gaseous hydrocarbons, ammonia and hydrogen sulfide for the separation and production of sulfur; XIV - light distillate for refining; XV - heavy distillate; XVI - non-recycled oil residue for hydrogen production; XVII-heavy distillate for refining; XVIII-

residual fuel cue fuels. The result of the research was a new technological process (IGI process), in which, thanks to the use of a regenerated active catalyst and inhibitory additives, the use of improved sludge processing technology and a number of other technological solutions, it was possible to reduce the pressure to 10 MPa while ensuring a high yield of liquid hydrogenation products. significantly reduced specific capital and operating costs and made it possible to use high-performance reactors with a capacity of 250-500 m 3, which are already used in the oil refining industry.The IGI process is being tested at large pilot plants.

According to the IGI technology, coal is pre-crushed by crushing to a particle size of 5-13 mm, subjected to high-speed drying in vortex chambers to a residual moisture content of 1.5% (wt.), Then it is secondarily crushed by vibration grinding to a particle size of less than 100 microns.

A catalyst of 0.2% Mo and 1.0% Fe(III) is applied to the pulverized coal. This combination makes it possible to achieve a degree of conversion of the organic mass of coal up to 83%. The maximum activity of the catalyst is ensured when it is applied from solution onto dried coal. Joint vibro-grinding of coal and catalyst salts is also effective, since this opens the micropores of the structure of the organic mass of coal and ensures complete and uniform deposition of the catalyst on the surface of the coal.

In addition to the catalyst, inhibitors can be introduced into the reaction zone, such as quinoline, anthracene, and other compounds that stabilize free radicals and activate the destruction of the organic part of coal due to the release of atomic hydrogen during their decomposition. The introduction of 1-5% of these additives provides an increase in the degree of conversion of coal and the yield of liquid products by 10-15%.

Coal with a catalyst applied to it enters the pasta preparation system. As a paste-forming agent, coal distillate with a boiling point of 300-400°C is used, which is preliminarily hydrogenated under a pressure of 10 MPa at a separate stage. For the normal conduct of the process, the paste is prepared with an equal ratio of coal and solvent; with a higher content of coal, the transport of the paste in the system is difficult due to its high viscosity. Coal-oil paste, into which gaseous hydrogen is introduced, is preheated in a tubular furnace and enters the system of hollow unheated reactors at a space velocity of 1.0-1.5 h -1 . During the stay of the paste in the reactor (30-60 min), coal hydrogenation reactions proceed with the formation of hydrocarbon gases (% -C4, ammonia, hydrogen sulfide and carbon oxides [up to 10% (wt.)], water and liquid products. Since the process proceeds with heat release, a cold hydrogen-containing gas is fed into the reactors to control the temperature; it also serves as a mixing agent.

The hydrogenation reaction products from the reactor are sent to a hot separator. From the top of the separator, a steam-gas stream is discharged containing gases and light liquid products, and from the bottom - sludge, consisting of liquid products boiling over above 300-325°C, unreacted coal, ash and a catalyst.

The total solids content of this sludge is 10-15% (wt.). The gas-vapor stream is cooled and separated into a liquid part and a hydrocarbon gas containing 75-80% (vol.) of hydrogen, C1-C4 hydrocarbons, ammonia, hydrogen sulfide and carbon oxides. After the separation of other gases by short cycle adsorption, hydrogen is returned to the process. Hydrocarbon gas is used to produce hydrogen in the amount of 50-60% of its consumption in the process. The rest of the required hydrogen is produced in a separate plant by gasification of coal or residues from sludge processing.

Table 3.6. Characterization of liquid products of various coal hydrogenation processes in comparison with oil

The processing of sludge, one of the most technically complex stages of the process, is carried out in the IGI scheme in two stages. At the first stage, the sludge is filtered to a residual solids content of about 30% (wt.), and at the second it is subjected to vacuum distillation to a content of 50-70% (wt.) solids in the resulting residue. This residual product is incinerated in a liquid bottom cyclone furnace. During combustion, molybdenum by 97-98% passes into the gas phase (1M02O3) and is deposited on the ash, from which it is then extracted by hydrometallurgy methods for reuse. The heat released during combustion can be used to generate 2.5-2.8 thousand kWh of electricity, or 11 tons of steam per each ton of sludge residue.

Liquid products of coal hydrogenation processing differ from ordinary oil in elemental composition and lower hydrogen content, as well as in the presence of significant amounts of nitrogen- and oxygen-containing compounds and alkenes (Table 3.6). Therefore, in order to obtain commercial motor fuels, they must be subjected to secondary gas-phase hydrogenation processing.

In the scheme of the IGI process, the hydrotreatment of a wide distillate of liquid-phase coal hydrogenation with a boiling point of up to 400 °C is carried out under a pressure of 10 MPa sequentially in two temperature zones of the reactor in order to avoid undesirable polymerization reactions leading to the formation of high-boiling compounds. In the first zone at 230-250°С

Hydrogenated part of the alkenes, the most prone to polymerization. Then, at a temperature of l; 400 ° C, the main mass of alkenes and partially aromatic compounds are hydrogenated; the destruction of sulfur-, oxygen- and nitrogen-containing compounds also occurs. Hydrotreating is carried out in the presence of aluminum-cobalt-molybdenum catalysts widely used in oil refining. However, in a number of cases, due to the high content of heteroatomic compounds in coal distillates, these catalysts are not efficient enough or are quickly poisoned. Therefore, new stable catalysts are required.

The characteristics of the initial distillate of brown coal hydrogenation using the IGI technology and the products of its hydrotreatment are given in Table. 3.7. The primary distillate products of liquid-phase coal hydrogenation are unstable. During storage, they change color and form insoluble precipitates, which are caused by the presence of

Table 3.7. Characteristics and yield of distillate of liquid-phase hydrogenation of brown coal and products of its hydrotreatment

composition in trace amounts of nitrogen-containing compounds of a non-basic nature, such as pyrrole. These compounds may not be completely removed during hydrotreatment, and in order to obtain sufficiently stable products, it is recommended to include adsorption and extractive denitrogenation of a wide hydrogenation distillate or its fractions in the general scheme of the process.

Fraction i. k.- 180 ° C hydrotreated distillate has an octane number of 66 (motor method) and is characterized by an increased content of actual resins and nitrogenous compounds. To obtain a component of high-octane motor gasoline, its deep hydrotreatment and subsequent reforming are required. The diesel fraction, due to the high content of aromatic hydrocarbons, has a relatively low cetane number. A fraction with a boiling point of 300-400°C, part of which is used as a paste-forming component, can serve as a feedstock for hydrocracking to produce gasoline and diesel fractions. The material balance of hydrogenation of brown coal of the Kansk-Achinsk basin according to two options for the IGR technology is presented below (in the numerator I option - processing of sludge to a solids content of 70%, in the denominator II option - the same, 50%):

~ Received

Taken [% (wt.)] [% (wt.)]

As can be seen, with the complete processing of coal, 45-55% (mass) of motor fuels and chemical products are obtained.

Jet fuel of the TS-1 type can also be obtained from the products of coal liquefaction by the IGR method. To do this, the 120-230°C fraction isolated from the total distillate of liquid-phase hydrogenation after “dephenolization” must go through three stages in succession: low-temperature hydrogenation (6 MPa, 230°C, wide-pore aluminum-nickel-molybdenum catalyst), hydrotreatment (6 MPa, 380°C and the same catalyst) and the hydrogenation of aromatic hydrocarbons (6 MPa, 290°C, commercial aluminum palladium sulfide catalyst). The third stage is necessary if the hydrotreated fraction 120-230°C contains more than 22%

Rice. 3.4. The scheme for the production of motor fuels by hydrogenation of coal using IGI technology - Grozgipro-Neftekhim:

1-preparation of coal; 2 - coal liquefaction; 3 -- hydrogen production; 4 - isolation of solid residue; 5 6, 10 - rectification; 7 - sludge disposal unit; 8 - isolation of phenols; 9 - hydrogenation; 11 - hydrotreating and reforming; 12, 14 - hydrocracking; 13 - isomerization and hydrogenation;

1 - coal; 11 - paste former; III - catalyst; IV-hydrogen; V - gases C 4 and CO; VI - liquid products of hydrogenation; VII - Г4Нз, Нг$ and CO2; VIII - Fraction >400 °С; IX - solid residue; X - water; XI - feiol, cresols; XII - "fraction of n. k. - 180 ° С; XIII - fraction 180-300 °C; XIV - fraction 300-400 °C; XV - ash for the production of building materials; XVI - process steam; XVII - electricity; XVIII - gasoline; XIX - jet fuel; XX - diesel fuel

^ mass.) aromatic hydrocarbons. But data.

By including in the technological scheme of various sets of processes for the processing of hydrogenated product and its fractions in the IGI process, it is possible to change the ratio of the resulting gasoline and diesel fuel - from 1: 0 to 1: 2.6. To maximize gasoline production, diesel fractions can be hydrocracked. The scheme for obtaining motor fuels according to one of the options based on the IGI technology is shown in fig. 3.4. When organizing the production of 3 million tons per year of motor fuels under this scheme, 19.7 million tons per year of brown coal from the Kansk-Achinsk basin will be required, including 9 million tons for hydrogenation, 3 million tons for gasification to produce hydrogen and 7.3 million tons for energy needs. In this case, the following products can be produced (in million tons per year): gasoline - 1.45, diesel fuel - 1.62, liquefied gases - 0.65, ammonia - 0.07 and sulfur - 0.066. Thermal k. and. of such production is 55%.

In foreign processes of coal hydrogenation, it is also planned to use various options for upgrading and recycling liquid products. For example, in the project of a complex for processing 30 thousand tons per day of bituminous coals based on the BIS-I process, all liquid hydrogenation products are subjected to hydrocracking with a degree of conversion of about 50%. The resulting gasoline fraction after additional hydrotreatment should be sent to reforming to obtain a motor gasoline component with an octane rating of 100 (research method). In general, the complex is expected to receive the following products (thousand tons per day): motor gasoline - 2.78, middle distillates - 8.27, heavy fuel oil - 4.75, liquefied gases - 0.64 and sulfur - 0.12 . Capital costs for the construction of the complex are estimated at $5.7 billion (in 1982 prices). Annual operating costs at 90% capacity loading will be (in million dollars): the cost of coal - 420, energy costs - 101, catalysts and chemicals - 77, operating materials - 114, personnel maintenance (1900 people) - 79.

As the available estimates show, the reduced costs for the production of motor fuels from coal by the hydrogenation method using the technologies developed to date are several times higher than the costs for obtaining them from petroleum feedstock with an average cost of producing the latter. However, the cost difference can be reduced when compared to fuels produced from oil produced, for example, by costly enhanced oil recovery techniques or from deep sea offshore areas.

The ongoing research and development work in the field of coal hydrogenation processing in many countries is aimed at improving the technological and instrumental design of processes, developing new catalysts and additives, and increasing the energy efficiency of all stages. These searches can provide a reduction in the unit costs of obtaining motor fuels from coal. A combination of coal hydrogenation and gasification processes in a single flow without complicating the stages of separation of liquefaction products and without loss of energy spent on heating raw materials should be considered promising.

Gasification of coal and synthesis of hydrocarbon fuels

When obtaining motor fuels from coal by indirect liquefaction, the first stage is gasification.

Solid fuel gasification is a thermal process during which the organic part of the fuel in the presence of oxidizing agents (air or technical oxygen, water vapor) is converted into a mixture of combustible gases.

Already at the beginning of the 19th century, gas obtained by distillation of coal was used to light streets in major cities around the world. Initially, it was obtained in the process of coking, but by the middle of the century, residue-free gasification of coke and coal was carried out on an industrial scale in cyclic, and then in continuously operating gas generators. At the beginning of this century, coal gasification was widespread in many countries of the world, primarily for the production of energy gases. By 1958, about 2,500 gas generators of various sizes and designs were operating in the USSR, which ensured the production of about 35 billion m 3 per year of energy and process gases from various types of solid fuels. However, due to the subsequent rapid growth in production and transportation of natural gas, the volume of gasification of solid fuels both in our country and abroad has significantly decreased.

Coal gasification is carried out at high temperatures and is a multistage heterogeneous physical and chemical process. The organic mass of coal, primarily carbon, which is part of it, interacts with gaseous oxidizers. In this case, the following primary reactions of carbon with oxygen and water vapor occur:

In addition to the indicated reaction products, during the gasification of coals, pyrolysis products are formed in the first stage of their heating.

* Heats of reactions are given at a temperature of 15 °C and a pressure of 0.1 MPa.

Liza. During gasification, as a rule, almost the entire organic part of coal turns into gas and, in some cases, partially into tar, and the mineral part with a small admixture of unreacted fuel forms ash or liquid slag.

In contrast to hydrogenation, the requirements for raw materials for gasification processes do not have significant restrictions on the stage of metamorphism and petrographic composition, but the role of mechanical and thermal strength, sintering, moisture content, ash and sulfur is very significant. A number of restrictions on these parameters are reduced after pre-treatment of coal - drying, oxidation, etc. The most significant indicator of the use of coal in certain gasification processes is the melting temperature of ash residues. It determines the temperature range of the main process and the choice of the ash removal system.

The activity of solid fuels and the rate of gasification largely depend on the mineral components that act as catalysts. The relative catalytic effect of trace elements of fossil coals during gasification can be represented by the following series:

The main parameters characterizing the individual processes of gasification of solid fuels include: the method of supplying heat to the reaction zone; a method for supplying a gasifying agent; type of gasifying agent; process temperature and pressure;

method of formation of mineral residue and its unloading. All these parameters are interconnected and are largely determined by the design features of gas generators.

According to the method of heat supply necessary to compensate for the endothermic effect of the reaction of carbon with water vapor, gasification processes are divided into autothermal and allothermic. Autothermal processes are most widely used; in them, heat is obtained by burning part of the coal introduced into the process. In allothermic processes, heat is supplied by direct heating of coal by a circulating solid, liquid, or gaseous coolant, indirect heating of the coolant through the reactor wall, or by means of a heating element immersed in the reactor.

To organize the process of interaction between the fuel and the oxidizer in the reactor, a continuous moving layer of coarse coal, a cocurrent flow of coal and oxidizer in the entrainment mode, and a fluidized bed of fine-grained coal are used. In gas generators with a continuous bed, the downward movement of lumpy fuel and the upward movement of the flow of hot gases are organized. This principle determines the high chemical and thermal activity of the process and makes it possible to gasify most types of coals, with the exception of caking coals. The specific productivity of such gas generators is limited by the entrainment of fine fractions of coal, which is partially offset by an increase in pressure. Moderate temperatures in the upper part of the coal layer cause an increased content of methane in the product gas [up to 10-12% (vol.)], as well as the formation of significant amounts of by-products such as tars, liquid hydrocarbons and phenols.

Crushed coal is loaded into gas generators with a fluidized bed - the particle size is 0.5-8.0 mm. The fluidization mode is supported by the supply of a gasifying agent. Good mixing in the bed ensures high rates of heat and mass transfer, and during gasification practically no by-product liquid products are formed. The content of methane in the resulting gas usually does not exceed 4% (vol.). At the same time, in fluidized bed processes, small fuel particles are carried away, which reduces the degree of conversion in one pass and complicates the operation of the equipment of subsequent technological stages.

Pulverized coal is processed in entrainment gas generators. It is introduced into the reactor in a cocurrent flow with steam-oxygen blast, while in the reaction zone the temperature reaches 2000°C. In such gas generators it is possible to process all types of coals. The reactions in them take place at a high rate, which ensures a high specific productivity. Product gas practically does not contain methane, tar and liquid hydrocarbons. But due to the high operating temperature, the oxygen consumption in such gas generators is greater than in gas generators with a continuous or fluidized fuel bed, and an efficient heat recovery system is required to ensure high thermal efficiency. When operating such gas generators, one should strictly observe the mode of supply of raw materials, since due to the small amount of coal simultaneously located in the reactor, any violation of the mode leads to a process stop.

One option for entrainment gasification is to use a water-coal slurry instead of dry pulverized fuel. This facilitates the supply of fuel to the reactor and eliminates the need to use bunker systems for its loading.

Typically, the gasifying agents in gasification processes are air, oxygen, and steam. With steam-air blast, there is no need for an air separation unit, which reduces the cost of the process, but the resulting gas is low-calorie, since it is highly diluted with atmospheric nitrogen. Therefore, in gasification schemes, preference is given to steam-oxygen blast and the ratio of steam to oxygen is determined by the conditions. carrying out the process. In hydrogasification processes, hydrogen is used as one of the gasifying agents, and a high-calorific gas rich in methane is obtained.

The gasification temperature, depending on the chosen technology, can vary widely - from 850 to 2000 °C. The temperature regime is determined by the reactivity of coal, the melting temperature of ash, and the required composition of the resulting gas. In autothermal processes, the temperature in the reactor is controlled by the ratio of steam:oxygen in the blast. For allothermic processes, it is limited by the maximum possible heating temperature of the coolant.

In various gasification processes, the pressure can vary from atmospheric to 10 MPa. An increase in pressure creates favorable conditions for an increase in temperature and energy efficiency of the process, and contributes to an increase in the concentration of methane in the product gas. Gasification under pressure is preferable in cases of obtaining gas, which is then used in synthesis, which are carried out at high pressures (costs for synthesis gas compression are reduced). With an increase in pressure, it is possible to increase the rate of gasification and the unit power of gas generators. When gasifying lumpy and coarse-grained fuel, the gasification rate is proportional to the square root of the pressure value, and when gasifying fine-grained and pulverized fuel, it is proportional to the pressure value .

In gas generators with liquid ash removal, the process is carried out at temperatures above the ash melting point (usually above 1300-1400 °C). "Dry-ash" gas generators operate at lower temperatures, and the ash is removed from them in solid form.

In addition to carbon monoxide and hydrogen, the gasification gas contains compounds containing sulfur and ammonia, which are poisons for catalysts for subsequent synthesis, as well as phenols, resins, and liquid hydrocarbons. These compounds are removed in the purification stage following the gas generator. In industrial gasification processes, methods of physical and chemical absorption of these components are used to clean synthesis gas from sulfur compounds and carbon dioxide. Methanol, propylene carbonate, N-methylpyrrolidone, sulfolane and diisopropanolamine, dimethyl and polyethylene glycols, ethanolamines, etc. are used as absorbers.

To ensure the optimal ratio of CO: Hg in the synthesis gas, the technological scheme usually includes a special

Fig. "3.5. Scheme of the coal gasification process 1 - coal drying and grinding; 2_ - air separation; 3 - gasification; 4 - ash or slag utilization; 5 - raw gas purification; 6 - CO conversion;

I - coal; II - water vapor; III - nitrogen; IV-oxygen; V - ash or slag; VI - raw gas; VII - purified gas; VIII - NgB, GShz, resins; /.X - synthesis gas; X - C0 3

ny unit for catalytic conversion of carbon monoxide with steam.

The scheme of the gasification process with the production of synthesis gas ready for further processing is shown in fig. 3.5.

To achieve maximum thermal efficiency and. e. process, the gas generator must operate at elevated pressure, with a low consumption of oxygen and water vapor, and low heat losses. It is also desirable that the minimum amount of by-products is obtained during gasification and the process is suitable for processing various coals. However, some of these factors are mutually exclusive. For example, it is impossible to ensure a low consumption of oxygen and thus avoid by-products. Therefore, in each specific case, it is required to choose the optimal combination of process parameters.

Currently, more than 50 types of gas generators have been developed, but only * four of them have found industrial application: Lurgi, Winkler, Koppers-Totzek and Texaco gas generators. The main indicators of gasification processes carried out on the basis of these devices are given in Table. 3.8.

The Lurgi process was first applied on an industrial scale in 1936 in Germany. In 1952, the second generation of gas generators of this type was created, and to date, more than 100 installations with Lurgi generators have been built in different countries. The productivity of a single unit increased from 8 to 75 thousand m 3 /h for dry gas.

In Lurgi gas generators, lump coal is introduced into the reaction zone through a sealed hopper and gasified in a countercurrent steam-oxygen mixture. The latter is fed under the grate, which supports the layer of coal; dry ash is discharged through the same grate. The volume-ratio of steam:oxygen is chosen such that the temperature of the coal bed is below the melting point of the ash. In the cooling jacket of the generator, saturated water vapor is formed.

The coal entering the gasifier passes through three heating zones in succession. In the first zone - the upper part of the reaction

tora - at a temperature of 350 ° C, it is dried with hot gases, in the middle - at a temperature of l; 600 ° C, coal undergoes semi-coking with the formation of gases, tar and semi-coke .. In the third zone, located at the base of the gas generator, at a temperature of 870 ° C, as a result reactions of fuel with steam and oxygen, a gas is formed that contains practically no methane. The gas passes through the coal bed from bottom to top, while its temperature decreases, and methane formation reactions begin to occur in the colder zones of the reactor. Thus, the resulting product gas contains unsaturated hydrocarbons and resins, which requires mandatory gas purification and causes a high consumption of water for cooling and removing unwanted components. The gas also contains an increased amount of methane [up to 8-12% (vol.)] 1 .

The Lurgi gasification process is characterized by a high degree of carbon conversion, reaching 99%. The thermal efficiency of the gas generator is 75-85%. The advantage of the Lurgi process is that it is carried out at elevated pressure, which significantly increases the unit productivity of the gas generator and reduces the cost of gas compression when it is used in further synthesis.

The Winkler process is the first commercial coal gasification process. The maximum unit capacity of operating gas generators of this type is currently 33 thousand m 3 of gas per hour. The process is based on the processing of coal in a fluidized bed at atmospheric pressure. The temperature in the bed is maintained at 30-50°C below the softening temperature of the ash, which is removed from the reactor in dry form.

The Winkler gas generator is an apparatus lined from the inside with a refractory material, a fluidized bed is created by blowing a steam-oxygen mixture through crushed coal. Larger coal particles are gasified directly in the bed, while fine particles are carried out. it and are gasified at a temperature of 1000-1100°C in the upper part of the reactor, where the gasifying agent is additionally supplied. Due to intensive heat and mass transfer in the reactor, the resulting gas is not contaminated with pyrolysis products and contains little methane. About 30% of the ash is removed from the bottom of the reactor in a dry form using a screw conveyor, the rest is carried out by the gas stream and captured in a cyclone and scrubbers.

The Winkler process provides high productivity, the ability to process various coals and control the composition of end products. However, in this process, the losses of unreacted *coal are high - up to 25-30% (wt.) carried out from the reactor, which leads to heat losses and a decrease in the energy efficiency of the process. The fluidized bed is highly sensitive to changes in the process regime, and low pressure limits the performance of gas generators.

The representative of the processes of gasification of pulverized fuel in the entrainment mode is the process "Korregv-T^gek". The first industrial gas generator of this type with a capacity of 4 thousand m 3 per hour of synthesis gas was created in 1952; modern gas generators have a gas capacity of 36-50 thousand m 3 /h.

The gas generator is a water-cooled conical apparatus. It is equipped with two or four burners located opposite each other and is lined from the inside with a heat-resistant material. The high turbulence of the reagents, achieved by supplying counter-flows of the fuel mixture from opposite sides of the chamber, ensures the reactions proceed at high rates and improve the composition of the resulting gas.

Coal is pre-crushed to particles no larger than 0.1 mm and dried to a residual moisture content of not more than 8% (wt.). Coal dust from the bunkers is supplied to the burners with a flow of part of the oxygen necessary for the process. The rest of the oxygen is saturated with water vapor, heated and injected directly into the chamber. Superheated water vapor is introduced into the reactor through a tubular jacket, which creates a curtain that protects the reactor walls from exposure to high temperatures. At a temperature of gases in the combustion zone up to 2000°C, the carbon of the fuel almost completely reacts in 1 s. Hot generator gas is cooled in the waste heat boiler to 300°C and "washed" with water in the scrubber to a dust content of less than 10 mg/m 3 . The sulfur contained in coal is 90% converted into hydrogen sulfide and 10% into carbon sulphide. The slag is removed in liquid form and then granulated.

Due to the high temperature of the process, coals of any type, including sintering ones, can be used for gasification, and the resulting gas is poor in methane and does not contain condensable hydrocarbons, which facilitates its subsequent “cleaning”. The disadvantages of the process include low pressure and increased oxygen consumption.

The Texaso process is based on the gasification of a coal-water slurry in a vertical lined gas generator operating at pressures up to 4 MPa. It has been tested in pilot plants and a number of large commercial gas generators are under construction. The Texaso process does not require preliminary drying of coal, and the suspension form of the raw material simplifies the design of its supply unit. The disadvantages of the process include increased consumption of fuel and oxygen, which is due to the supply of additional heat for the evaporation of water.

The work currently being carried out to improve autothermal processes is mainly aimed at increasing the gasification pressure, increasing unit power and thermal efficiency. reactors, minimizing the formation of by-products. In autothermal gasification processes, up to 30% of coal is spent not on the formation of gas, but on obtaining the necessary heat. This has a negative effect on process economics, especially when the cost of coal mining is high. Therefore, considerable attention has recently been paid to the development of schemes for the allothermal gasification of solid fuels using heat obtained from metal melts or from high-temperature nuclear reactors.

Melt processes are a variant of coal gasification in entrainment mode. In them, coal and a gasifying agent are fed to the surface of molten metals, slags or salts, which play the role of heat carriers. The most promising process is with a melt of iron, since it is possible to use the free capacities of oxygen converters available in a number of countries in the ferrous metallurgy. In this process, the gas generator is a hollow, refractory-lined apparatus-converter with a bath of molten (temperature 1400-1600°C) iron. Coal dust mixed with oxygen and water vapor is fed from the top of the apparatus perpendicular to the surface of the melt at high speed. This flow, as it were, blows off the sludge formed on the surface of the melt and mixes the melt, increasing the surface of its contact with coal. Due to the high temperature, gasification is very fast. The degree of carbon conversion reaches 98%, and thermal efficiency. d. is 75-80%. It is assumed that iron also plays the role of a gasification catalyst. When lime is added to the melt, the latter interacts with coal sulfur, forming calcium sulfide, which is continuously removed along with the slag. As a result, it is possible to release the synthesis gas from the sulfur contained in the coal by 95%. The synthesis gas obtained in the melt process contains 67% (vol.) CO and 28% (vol.) H 2 . Losses of iron, which must be replenished, are 5-15 g/m 3 gas.

A promising large-scale and relatively inexpensive source of high-potential heat for the gasification of solid fuels can be a high-temperature gas-cooled nuclear reactor, which is currently under development and pilot testing. The reactor provides a supply of high-potential heat (950°C) for the process of coal gasification. The heat from the intermediate helium circuit will be transferred to the steam gasification reactor directly to the coal, which, under the influence of water vapor, will turn into synthesis gas. During gasification using the thermal energy of a high-temperature nuclear reactor, the need for coal to produce an equal amount of synthesis gas compared to autothermal processes will be reduced by 30-50%, while the environmental cleanliness of the process will increase.

From synthesis gas, depending on the process conditions and the catalyst used, a wide range of hydrocarbons and oxygen-containing compounds can be obtained. On an industrial scale, based on synthesis gas, the production of such products as methanol, liquid hydrocarbons, etc. is currently carried out.

Back in 1925, F. Fischer and H. Tropsch carried out the synthesis of aliphatic hydrocarbons from CO and H 2 , which was named after them. The synthesis was carried out on iron and cobalt catalysts at atmospheric pressure and a temperature of 250-300 °C. In research and industrial practice, modifications of cobalt and iron catalysts, fused, sintered, cemented and deposited on diatomaceous earth, kaolin and other supports with various structural (A1 2 03, V2O5, Si0 2) and chemical (CuO, CaO, ZnO, K2O) promoters ". In the presence of iron catalysts, the formation of olefins and oxygen-containing compounds increases. Cobalt catalysts contribute to the formation of predominantly normal alkanes, largely high molecular weight.

The parameters of the Fischer-Tropsch synthesis process and the composition of the resulting products are significantly affected by the design of the reactors used. In apparatuses with a stationary catalyst bed, operating at low temperatures, mainly aliphatic hydrocarbons are obtained. In fluidized bed reactors, where reactions are carried out at higher temperatures, significant amounts of olefins and oxygenates are present in the products.

The first industrial installations for the Fischer-Tropsch synthesis were put into operation in the mid-1930s in Germany and England. By 1943, the total capacity of the created installations for the production of motor fuels by this method exceeded 750 thousand tons per year. Most of them used a stationary cobalt catalyst bed. A pilot plant with a fluidized bed of an iron catalyst with a capacity of 365 thousand tons per year of hydrocarbon products was operated in 1948-1953. in USA. The domestic pilot plant for the Fischer-Tropsch synthesis has been operated in Dzerzhinsk since 1937 for a number of years. Since 1952, the production of hydrocarbons from synthesis gas has been operating in Novocherkassk, where synthesis is carried out in reactors with a fixed bed of cobalt catalyst, and the target products are liquid hydrocarbon solvents, raw materials for detergents and other chemical products.

In 1954-1957. an industrial enterprise for the processing of coal into liquid motor fuels SLAB-1 was built in South Africa with a capacity of 230 thousand tons per year of liquid products. Later, two more similar enterprises were created in the same place - BABO-P (1981) and BABO-SH (1983), with a nominal capacity of 2200 thousand tons per year of liquid products each.

At all enterprises, gasification of high-ash (up to 30%) bituminous coal containing 1% sulfur and having a calorific value of 23 MJ/kg is carried out in pressurized gas generators. The basic technological scheme of the FUNCTION is shown in fig. 3.6. Here, reactors of two designs are used: with a stationary and fluidized bed of a catalyst (at other plants - only reactors with a fluidized bed). In each fixed bed reactor, the catalyst is placed in pipes (more than 2000 pieces, 12 m long and 50 mm in inner diameter). The gas passes through the pipes at a high linear velocity, which ensures rapid removal of reaction heat and the creation of almost isothermal conditions along almost the entire length of the pipes. At a working pressure in the reactor of 2.7 MPa and a temperature of about 230 °C, the maximum yield of alkanes is achieved.

Rice. 3.6. Scheme of the FALLING plant:

1 - oxygen production; 2 - gas generators 3 - power station; 4 - process "Fenosolvan"; 5 - separation; 6 - processing of resins and oils; 7 - process "Rectizol>; 8, 9 - Fischer-Tropsch synthesis reactors with a stationary and fluidized catalyst bed, respectively; 10 - conversion; 11 - release of oxygen-containing compounds; 12 - purification of paraffins; 13 - processing of liquid products; 14 - oligomerization of olefins; 15 - cryogenic separation; 16 - ammonia synthesis;

I - air; II - coal; III - water; IV - pitch; V - creosote; VI - benzene-toluene-cresol fraction; VII - wide gasoline fraction; VIII - phenols; IX - alcohols; ketones; XI - liquid products; XII - purified paraffins; XIII - boiler fuel; XIV - diesel fuel; XV - gasoline; XVI - fuel gas to the city network; XVII - 0 2 ; XVIII - N2; XIX - gases C 3 -C 4; XX - H 2 ; XXI - sour reptiles:

XXII - YHz; XXIII - (MVDgBO

In reactors with a fluidized catalyst bed (diameter 2.2 m and height 36 m), synthesis is carried out at a temperature of 300-350 ° C and a pressure of 2-3 MPa, the gas flow into the reactor reaches 100 thousand m 3 / h. The reaction products enter the settling section and then into cyclones to separate the trapped catalyst dust. The ratio of Hg:CO in the raw synthesis gas is 2.4-2.8, the resulting liquid products are characterized by a high content of olefins. All types of reactors at BABOB plants use alkali-promoted iron-based catalysts; these catalysts are cheap and provide a low yield of methane; coal consumption for obtaining 1 ton of liquid products is 5.6-6.4 tons. To obtain motor fuels that meet the requirements of standards for fuels from oil, the products obtained are subjected to refinement: gasoline fractions - purification and reforming, propylene and butenes - polymerization . Thermal efficiency complex for processing coal into motor fuels using the Fischer-Tropsch synthesis is 35-40%. The properties of gasoline and diesel fractions obtained in various types of reactors differ significantly (Table 3.9). Along with motor fuels, these plants produce ammonia, sulfur and other chemical products.

Like other liquefaction processes, the processing of coal by gasification followed by the synthesis of motor fuels requires high capital and operating costs. For example, capital investments for the construction of the ZABOL-P plant amounted to about 4 billion dollars (in 1980 prices). With 8,000 hours of operation, the total operating costs at this plant are $987 million per year (in 1980 prices), including:

• Coal cost 125
• Staff maintenance 80
• Electricity 80
• Catalysts and reagents 24
• Water 2
• Auxiliary materials 80 and repair
• Overhead 80
• Depreciation charges 520

Compared to hydrogenation processes, the method of coal liquefaction through the Fischer-Tropsch synthesis is simpler in terms of instrumentation and operating conditions, but its thermal efficiency is about 15% lower.

The invention relates to chemical technology, namely to the liquefaction of coal and can be used to produce synthetic motor fuels. The method of coal hydrogenation includes the preparation of a coal-oil paste containing coal, a paste-forming agent based on products of thermal modification of a high-boiling fraction of coal hydrogenate in a water vapor environment on iron oxides at a temperature of 450-500 ° C and an iron-containing catalyst subjected to mechanochemical treatment and dispersed using ultrasound in the fraction of products hydrogenation of coal, boiling off at a temperature of 180-300°C and taken in an amount of 5-20% by weight of the above paste-forming agent, followed by its introduction into the paste-forming agent. Next, the coal-oil paste is heated at elevated pressure in a hydrogen medium, followed by separation of the target products. The technical result of the invention is to improve the quality of distillate fractions of liquid products of coal hydrogenation by reducing the sulfur content without reducing their yield. 1 tab.

The invention relates to chemical technology, namely to the liquefaction of coal, and can be used to obtain distillate fractions of liquid coal products with a low sulfur content, which are components of synthetic motor fuels.

Coal hydrogenation is carried out at an elevated temperature under hydrogen pressure in the presence of catalysts in a paste-forming medium with hydrogen-donor properties. A number of methods are known for the hydrogenation of coal using powdered iron ore or iron-containing waste from ore processing activated with sulfur additives or sulfur-containing compounds as catalysts. The conversion of coal increases with the joint processing of catalysts and sulfur in energy-intensive mills - activators.

The disadvantage of the above methods is the high sulfur content in the resulting distillate fractions.

Closest to the proposed invention is a method of coal hydrogenation, including the preparation of coal-oil paste from coal, a paste-forming agent and an iron-containing catalyst subjected to mechanochemical treatment together with sulfur, heating the paste at elevated pressure in a hydrogen environment, followed by isolation of target products. A high-boiling fraction of coal hydrogenate is used as a paste-forming agent after its thermal cracking in an environment of water vapor on iron oxides at a temperature of 450-500°C, followed by mixing the paste-forming agent with a catalyst before preparing coal-oil paste.

The disadvantage of this method is the low quality of the target products due to the high sulfur content in the distillate fractions. The products obtained in the process of hydrogenation cannot be used as components of motor fuels without additional hydrotreatment. In addition, the disadvantages of the method include the duration and insufficient degree of dispersion of the catalyst in a viscous paste-forming agent by mechanical stirring.

The objective of the invention is to improve the quality of distillate fractions of liquid products of coal hydrogenation by reducing the sulfur content without reducing their yield.

The task is achieved by the fact that in the method of coal hydrogenation, including the preparation of coal-oil paste from coal, a paste-forming agent based on the products of thermal modification of the high-boiling fraction of coal hydrogenate in water vapor on iron oxides at a temperature of 450-500 ° C and an iron-containing catalyst subjected to mechanochemical processing, heating the paste at elevated pressure in a hydrogen medium, followed by isolation of the target products, according to the invention, the catalyst subjected to mechanochemical treatment is dispersed using ultrasound in the fraction of hydrogenation products boiling at a temperature of 180-300 ° C and taken in an amount of 5-20% by weight of the paste-forming agent followed by introduction into the paste former.

A comparative analysis with the prototype shows that the distinguishing features are:

The use of a mixture of 95-80 wt.% of the products of thermal modification of the high-boiling fraction of coal hydrogenate in an environment of water vapor on iron oxides at a temperature of 450-500 ° C and 5-20 wt.% of the fraction of coal hydrogenation products boiling in the range of 180-300 °C.

It is known that the mechanical processing of ore materials in energy-intensive activator mills is accompanied not only by a decrease in the particles of the crushed material, but also by their intensive aggregation with the formation of agglomerates having a complex structure. When such materials are added to the oil-coal paste with intensive stirring, the destruction of agglomerates does not occur, which significantly reduces the efficiency of using such catalytic systems. The destruction of agglomerates can be achieved by sonication under certain conditions in water and in a number of organic solvents. Preliminary studies have shown that the effective dispersion of iron ore catalysts by this method in the products of thermal modification of the high-boiling fraction of coal hydrogenate in water vapor on iron oxides, used in the prototype as a paste-forming agent, cannot be achieved due to the high viscosity of the latter. We have found that the dispersion of the catalyst using ultrasound is carried out in the environment of hydrogenation products boiling in the range of 180-300°C, followed by adding the resulting mixture in the required amount to the paste former.

The essence of the invention is illustrated by specific examples.

Example 1. The hydrogenation of coal is carried out in a laboratory rotary autoclave with a capacity of 0.25 liters. As a paste-forming agent, a fraction boiling over above 400°C is used, the products of thermal modification at 470°C of the residues of distillation of coal hydrogenate in water vapor in the presence of iron oxides.

The preparation of a catalyst for the process of coal hydrogenation is carried out as follows: the flotation concentrate of the tailings of the electromagnetic separation of iron ores is preliminarily subjected to mechanochemical treatment in a mill-activator of a centrifugal planetary type (AGO-2). Next, 8.8 g of ore catalyst, 110 g of steel balls with a diameter of 8 mm are loaded into the activator drum with a capacity of 0.15 liters, 40 ml of distilled water and 0.16 g of sodium hydroxide (0.1 M solution) are added, after which it is closed and processing is carried out for 30 minutes at a drum rotation speed of 1820 rpm. Under these conditions, the centrifugal acceleration developed by the grinding media is 600 m×s -2 .

An aliquot is taken from the resulting pulp at the rate of 0.30 g of ore material, added to 0.30 g of a fraction of coal hydrogenation products boiling in the range of 180-300 ° C (2.5% by weight of the paste-forming agent), and sonicated using a dispersant UZD1-0.063/22 for 3 min. In the resulting mixture, after dispersion, intensive formation of a precipitate was noted. The resulting catalyst slurry is added to 11.7 g of a fraction boiling above 400°C of the products of thermal modification of the residues of distillation of coal hydrogenate in a vapor medium at 470°C in the presence of iron oxides, and intensively stirred for 15 minutes. The ratio of the fraction of products of thermal modification of the residues of distillation of coal hydrogenate in water vapor in the presence of iron oxides (component 1) and products of coal hydrogenation boiling in the range of 180-300°C (component 2) in the paste-forming agent is 97.5 wt.% and 2, 5 wt.%, respectively.

Coal is added to the prepared mixture of paste-forming agent and catalyst (coal:paste-forming ratio = 1:1). The autoclave is closed, hydrogen is supplied to a pressure of 5.0 MPa. With continuous rotation, the autoclave is heated, upon reaching 430°C, maintained at this temperature for 60 minutes. Then the autoclave is cooled, the products boiling away under conditions equivalent to the boiling point range under normal conditions above 180°C are distilled off directly from the autoclave under vacuum. The products are separated into aqueous and hydrocarbon fractions (hereinafter referred to as the fraction with a boiling point above 180°C) by decantation. Then the contents of the autoclave are extracted with toluene, a fraction is distilled off from the extract, which boils away in the range of 180-300°C. The sulfur content in the obtained fractions is determined by the standard method using the analyzer "Flash EA-1112, Thermo Quest". The results obtained are shown in the table.

Example 2. Similar to example 1, except that after mechanochemical activation of the catalyst, an aliquot of 0.30 g of ore material is taken from the obtained pulp, added to 0.60 g of the fraction of coal hydrogenation products, boiling in the range of 180-300 ° C (5.0% by weight of the paste-forming agent) and sonicated using a dispersant UZD1-0.063/22 for 3 minutes. After dispersion, a homogeneous mixture is formed, the formation of a precipitate is not observed for more than 1 hour after dispersion.

The resulting catalyst slurry is added to 11.4 g of the fraction boiling above 400°C of the products of thermal modification of the residues of distillation of coal hydrogenate in water vapor at 470°C in the presence of iron oxides and intensively stirred for 15 minutes. The ratio of the fraction of products of thermal modification of the residues of distillation of coal hydrogenate in water vapor in the presence of iron oxides (component 1) and products of coal hydrogenation, boiling away in the range of 180-300°C (component 2) in the paste-forming agent is 95 wt.% and 5 wt.% , respectively.

Example 3. Analogously to example 1, except that after mechanochemical activation of the catalyst, an aliquot of 0.30 g of ore material is taken from the obtained pulp, added to 1.2 g of the fraction of coal hydrogenation products, evaporating in the range of 180-300 ° C (10.0% by weight of the paste-forming agent), and sonicated using a dispersant UZD1-0.063/22 for 3 minutes. After dispersion, a homogeneous mixture is formed, the formation of a precipitate is not observed for more than 1 hour after the completion of the dispersion.

The resulting catalyst slurry is added to 10.8 g of a fraction boiling above 400°C of the products of thermal modification of the residues of distillation of coal hydrogenate in vapor at 470°C in the presence of iron oxides and intensively stirred for 15 minutes. The ratio of the fraction of products of thermal modification of the residues of distillation of coal hydrogenate in a vapor medium in the presence of iron oxides (component 1) and coal hydrogenation products boiling away in the range of 180-300 ° C (component 2) in the paste-forming agent is 90 wt.% and 10 wt.%, respectively.

Example 4. Analogously to example 1, except that after mechanochemical activation of the catalyst, an aliquot of 0.30 g of ore material is taken from the obtained pulp, added to 2.4 g of the fraction of coal hydrogenation products, evaporating in the range of 180-300 ° C (20% by weight of the paste-forming agent), and sonicated using a dispersant UZD1-0.063/22 for 3 minutes. After dispersion, a homogeneous mixture is formed, the formation of a precipitate is not observed for more than 1 hour.

The resulting catalyst slurry is added to 9.6 g of a fraction boiling above 400°C of the products of thermal modification of the residues of distillation of coal hydrogenate in vapor at 470°C in the presence of iron oxides and intensively stirred for 15 minutes. The ratio of the fraction of products of thermal modification of the residues of distillation of coal hydrogenate in a vapor medium in the presence of iron oxides (component 1) and products of coal hydrogenation boiling away in the range of 180-300°C (component 2) in a paste-forming agent is 80 wt.% and 20 wt.% , respectively.

Example 5. Similar to example 1, except that after the mechanochemical activation of the catalyst, an aliquot of 0.30 g of ore material is taken from the obtained pulp, added to 3 g of the fraction of coal hydrogenation products boiling in the range of 180-300 ° C (25 0% to the mass of the paste-forming agent), and sonicated using a dispersant UZD1-0.063/22 for 3 minutes. After dispersion, a homogeneous mixture is formed, the formation of a precipitate is not observed for more than 1 hour.

The resulting catalyst pulp is added to 9 g of a fraction boiling above 400°C of the products of thermal modification of the residues of distillation of coal hydrogenate in vapor at 470°C in the presence of iron oxides, and intensively stirred for 15 minutes. The ratio of the fraction of products of thermal modification of the residues of distillation of coal hydrogenate in a vapor medium in the presence of iron oxides (component 1) and products of coal hydrogenation, boiling away in the range of 180-300°C (component 2) in a paste-forming agent, is 75 wt.% and 25 wt.% , respectively.

The results obtained show a decrease in the degree of conversion and the yield of distillate fractions.

Example 6. (Implementation of the prototype method).

Hydrogenation of coal is carried out in a laboratory rotating autoclave with a capacity of 0.25 liters. As a paste-forming agent, a fraction is used that boils over above 400°C the products of thermal cracking in an environment of water vapor of the residues of the distillation of coal hydrogenate. Steam cracking is carried out at 470°C, a pressure of 3 atm in the absence of hydrogen in the presence of iron oxides.

The preparation of a catalyst for the process of coal hydrogenation is carried out as follows: the flotation concentrate of the tailings of the electromagnetic separation of iron ores is preliminarily subjected to mechanochemical treatment together with elemental sulfur in a mill-activator of a centrifugal planetary type (AGO-2), at the rate of 0.30 g of catalyst (2.5 wt.% to the weight of dry coal) and 0.24 g of sulfur (2.0 wt.% to the weight of dry coal). Further, 8.8 g of ore catalyst, 7.0 g of elemental sulfur and 110 g of steel balls with a diameter of 8 mm are loaded into the activator drum with a capacity of 0.15 liters until the drum is completely filled with 80 ml of distilled water and 0.32 g of sodium hydroxide (0 ,1 M solution), after which it is closed and processed for 30 minutes at a drum rotation speed of 1820 rpm. Under these conditions, the centrifugal acceleration developed by the grinding media is 600 m×s -2 . The resulting pulp of the catalyst is introduced into the paste with vigorous stirring for 1 hour.

Coal is added to the prepared mixture of paste-forming agent and catalyst (coal:paste-forming ratio = 1:1). The autoclave is closed, hydrogen is supplied to a pressure of 5.0 MPa. With continuous rotation, the autoclave is heated, upon reaching 430°C, maintained at this temperature for 60 minutes. Then the autoclave is cooled, the products boiling away under conditions equivalent to the boiling point range under normal conditions below 180°C are distilled off directly from the autoclave under vacuum. The products are separated into an aqueous fraction and a hydrocarbon fraction (hereinafter referred to as the fraction with a boiling point below 180°C) by decantation. Then the contents of the autoclave are extracted with toluene, a fraction is distilled off from the extract, which boils away in the range of 180-300°C. The sulfur content in the obtained fractions is determined by the standard method using the analyzer "Flash EA-1112, Thermo Quest". The results obtained are shown in the table.

Thus, in the proposed invention, the dispersion of the catalyst using ultrasound in the fraction of coal hydrogenation products, boiling in the range of 180-300°C and taken in an amount of 5-20% by weight of the paste-forming agent, allows you to drastically reduce the sulfur content in distillate products, to obtain comparable with the prototype indicators for the degree of conversion of coal and the yield of distillate fractions.

A method for coal hydrogenation, including the preparation of a coal-oil paste containing coal, a paste-forming agent based on products of thermal modification of a high-boiling fraction of coal hydrogenate in an environment of water vapor on iron oxides at a temperature of 450-500 ° C and an iron-containing catalyst subjected to mechanochemical treatment, heating the paste at elevated pressure in hydrogen medium with subsequent isolation of the target products, characterized in that the catalyst subjected to mechanochemical treatment is dispersed using ultrasound in the fraction of coal hydrogenation products, boiling off at a temperature of 180-300 ° C and taken in an amount of 5-20% by weight of the above paste-forming agent, with subsequent introduction into the paste former.

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The invention relates to chemical technology, namely the liquefaction of coal and can be used to produce synthetic motor fuels

Destructive hydrogenation is carried out in order to obtain light liquid fuels - gasoline and kerosene - from solid or heavy liquid fuels. By its chemistry, this is a very complex process, in which the splitting (destruction) of high-molecular compounds (coal macromolecules) occurs simultaneously with the formation of simpler saturated and unsaturated hydrocarbons and fragments and the addition of hydrogen to the fragments - at the site of double bonds and to aromatic hydrocarbons. Depolymerization and other processes also occur.
The addition of hydrogen (hydrogenation) is accompanied by a decrease in volume and release of heat. The occurrence of hydrogenation reactions is promoted by an increase in pressure and removal of reaction heat.
Usually the hydrogenation of coals is carried out at a pressure of 2000-7000 ncm2 and a temperature of 380-490 ° C. Catalysts are used to speed up the reaction - oxides and sulfides of iron, tungsten, molybdenum with various activators.
Due to the complexity of the hydrogenation process, the process of obtaining light fuel from coal - gasoline and kerosene - is carried out in two stages - in the liquid and vapor phases. The most suitable for hydrogenation are young black and brown coals containing a significant amount of hydrogen. Coals are considered the best, in which the ratio between carbon and hydrogen is not more than 16-17. Harmful impurities are sulfur, moisture and ash. Permissible moisture content 1-2%, ash 5-6%, sulfur content should be minimal. In order to avoid a high consumption of hydrogen, oxygen-rich fuels (eg wood) are not hydrogenated.
The technology of the hydrogenation process is as follows. Finely ground coal (up to 1 mm) with the desired ash content is mixed with a catalyst, most often iron oxides, dried and carefully ground in a pestle mill with oil, which is obtained by separating hydrogenation products. The content of coal in the paste should be 40-50%. The paste is fed into the hydrogenation unit with a pestle pump at the required pressure; fresh and circulating hydrogen is supplied there by compressors 2 and 3. The mixture is preheated in heat exchanger 4 by heat
Coming from the hydrogenation column, vapors and gases, and then in a tube furnace 5 to 440 ° C and enters the hydrogenation column 6, where the temperature rises to 480 ° due to the heat of reaction. After that, the reaction products are separated in the separator, the upper part of which leaves vapors and gases, and the sludge from the lower part.
The gas-vapor mixture is cooled in the heat exchanger 4 and the water cooler 8 to 50°C and separated 9. After the pressure is removed, the condensate is distilled, obtaining a "broad fraction" (300-350°) and heavy oil. The broad fraction after the extraction of phenols from it enters the second stage of hydrogenation. The sludge separated in the separator 7 is separated by centrifugation into a heavy oil and a solid residue, which is subjected to semi-coking. As a result, a heavy oil and a fraction are formed, which are added to the broad one. Ash residues are used as fuel. Heavy oils are used to make pasta. The gases separated in the separator 9, after the absorption of hydrocarbons in the scrubber 10 by pressurized oils, are returned to the process by means of the circulation pump 3.
Hydrogenation in the second stage is most often carried out in the presence of WSo under a pressure of 3000 nm2 at 360-445°C. Gasoline and kerosene or diesel fuel are isolated from the resulting hydrogenation product. There are no unsaturated hydrocarbons in the fuel obtained by hydrogenation, and sulfur is in the form of hydrogen sulfide, which is easily removed by washing with alkali and then with water. Destructive hydrogenation is carried out in columns made of alloy steels containing chromium, nickel, molybdenum. The wall thickness is up to 200 l and the height is up to 18 m and the diameter is 1 m. In columns for hydrogenation in the vapor phase, the catalyst is placed on mesh shelves.
The yield of gasoline can reach 50-53% per combustible mass of coal.