CN107557068A - A kind of method of coal tar hydrogenating and a kind of system for coal tar hydrogenating - Google Patents

Abstract

The invention relates to the field of coal tar processing, and discloses a method for hydrogenation of coal tar and a system for hydrogenation of coal tar. The method includes: introducing coal tar raw materials into a pretreatment unit for water and/or impurity removal Pretreatment: introducing the above-mentioned obtained materials into the slurry-bed hydrogenation reactor of the slurry-bed hydrogenation unit for hydrogenation conversion; sequentially separating and fractionating the above-mentioned obtained materials to obtain light distillates, middle distillates and heavy distillates and recirculating part of the middle distillate and the remaining heavy distillate back into the slurry bed hydrogenation reactor for hydroconversion; and introducing the light distillate and the remaining middle distillate into the finishing reactor of the fixed bed hydrogenation unit for Hydrofining reaction. The method provided by the invention utilizes the combination of a slurry bed and a fixed bed to realize the clean and efficient utilization of coal tar resources, maximize the liquid yield, improve the utilization rate and utilization value of coal tar resources, and prolong the life of the device. Operating cycle.

Description

A method for hydrogenation of coal tar and a system for hydrogenation of coal tar

technical field

The invention relates to the field of coal tar processing, in particular to a method for hydrogenating coal tar and a system for hydrogenating coal tar.

Background technique

With the sustained and rapid development of social economy, my country's demand for petroleum products is also increasing.

However, petroleum is a non-renewable energy source and is facing a crisis of depletion. In contrast, China has relatively abundant coal reserves, so producing liquid fuel from coal has become a basic direction of coal processing and utilization.

With the rapid development of the domestic coal chemical industry, especially the modern coal chemical industry, the output of coal tar is increasing, and the clean processing and effective utilization of coal tar are becoming more and more important. At present, the conventional coal processing method is to cut various fractions with concentrated components through pretreatment distillation, and then use acid-base washing, distillation, polymerization, crystallization and other methods to process the various fractions to extract pure products; After alkali refining, it is directly burned as low-quality fuel oil, or directly emulsified as emulsified fuel. Sulfur, nitrogen and other impurities contained in coal tar become sulfur and nitrogen oxides during the combustion process and are released into the atmosphere, causing air pollution, while the acid-base refining process will produce a large amount of sewage, which will seriously pollute the environment. Therefore, whether it is from the perspective of environmental protection or comprehensive utilization of the environment, it is hoped to find an effective chemical processing method to improve the quality of coal tar in order to expand its own value. How to effectively utilize coal tar resources and make it meet the requirements of environmental protection has always been the research direction of various countries.

CN1766058A discloses a method for hydrogenation treatment of full fractions of coal tar, and specifically discloses that the full fractions of coal tar are first directly entered into a suspension bed hydrogenation device, or mixed uniformly with a homogeneous catalyst and then entered into a suspension bed device for hydrogenation and light treatment. Qualitative reaction, the stream generated after the reaction passes through the distillation device to cut water, <370°C fraction and >370°C tail oil, of which the <370°C fraction enters the fixed bed reactor for hydrofining reaction, and then cuts the refined product Gasoline at <150°C and diesel at 150-370°C are produced, while tail oil at >370°C is recycled back to the suspension bed reactor for further conversion into light oil. After the <370°C light oil fraction in the prior art enters the fixed-bed hydrotreating, the product diesel oil is still poor in quality, high in density and low in cetane number. Aromatic reactor, on the one hand, the method of this prior art increases the investment of the device and complicates the flow process; The process of the method is complicated and the liquid yield is low.

CN101885982A discloses a coal tar suspension bed hydrogenation method with a heterogeneous catalyst, the method includes coal tar raw material pretreatment and distillation separation, coal tar heavy distillate suspension bed hydrocracking and light distillate conventional fixed bed upgrading The process of processing. After the hydrogenation reaction product is separated into light oil, most of the catalyst-containing tail oil is directly recycled to the suspension bed reactor, and a small part of the tail oil is recycled to the suspension bed reactor after catalyst removal treatment, further lightening, heavy oil All or the largest amount of recycling, in order to achieve the largest amount of coal tar production of light oil and the purpose of catalyst recycling. The raw material of the suspended bed reactor in this invention is the heavy fraction of coal tar > 370°C. During the suspension bed reaction process provided by it, the asphaltenes in the heavy fraction > 370°C are more likely to undergo free radical reactions and mutually polymerize to form coke. , which increases the probability of clogging the internal components of the reactor and affects the normal operation of the device.

CN103059973A discloses a slurry-bed and fixed-bed coupling method for hydrogenation of full fractions of coal tar, which mainly includes coal tar raw material pretreatment, slurry-bed hydrocracking, initial hydrogenation product fractionation, fixed-bed hydrofining and product refining. Distill five units. The whole distillate oil of coal tar is pretreated by dehydration, dust removal, etc., mixed with hydrocracking catalyst and preheated, and then enters the slurry bed reactor for hydrocracking reaction. In the fixed bed hydrofining unit, the middle distillate and catalyst are recycled to the slurry bed hydrogenation reactor, and the heavy components are filtered to remove part of the catalyst and the coke produced by cracking is returned to the tar pretreatment unit for recycling hydrogenation. Gasoline and diesel products are obtained by rectification after conventional hydrotreating of light components. In the method provided by this prior art, the light, medium and heavy fractions provided actually correspond to fractions below <370°C diesel oil, >370°C wax oil fractions and heavy fractions heavier than wax oil, which adopt conventional slurry state bed process, the fixed-bed hydrogenation unit only processes diesel fractions below <370°C, and the conversion of >370°C fractions requires a higher conversion depth, which increases energy consumption. Moreover, the slurry bed hydrocracking of the prior art uses a cracking agent containing molecular sieves. Due to the high nitrogen content in the coal tar raw material, nitrogen compounds have a significant inhibitory effect on the activity of the molecular sieve cracking agent and can easily cause the cracking agent to be deactivated. , the molecular sieve cracking agent used in conventional petroleum-based raw materials is not suitable for slurry bed coal tar hydrocracking. And in this prior art, after fixed-bed hydrotreating, the product diesel oil property is still relatively poor, cetane number is on the low side.

In the above-mentioned prior art, the hydrogenation of slurry bed coal tar is mainly based on the ideas of slurry bed hydrogenation of petroleum-based heavy raw materials such as atmospheric residue and vacuum residue, and its main purpose is to realize the hydrogenation of heavy raw materials. Lightening and removal of impurities in raw materials, etc.

However, it is easy to coke to generate coke or deposit down to block the internal components of the reactor by adopting the method of the above-mentioned prior art, which is also one of the main reasons why the current coal tar slurry bed hydrogenation unit cannot operate stably for a long period.

Contents of the invention

The purpose of the present invention is to prevent asphaltene deposition or coking in the slurry bed hydrogenation reactor to generate coke, to maximize the liquid yield, to improve the utilization rate and value of coal tar resources, and to extend the operation of the device to a certain extent cycle.

In order to achieve the above object, in a first aspect, the present invention provides a method for hydrogenation of coal tar, the method comprising:

(1) Introducing the coal tar raw material into a pretreatment unit for water removal and/or impurity removal pretreatment;

(2) In the presence of hydrogen and a slurry bed catalyst, the material obtained in step (1) is introduced into a slurry bed hydrogenation reactor of a slurry bed hydrogenation unit for hydrogenation conversion;

(3) separating and fractionating the material obtained through step (2) successively to obtain light distillate, middle distillate and heavy distillate;

(4) part of the heavy fraction is thrown out; and part of the middle distillate and the remaining part of the heavy fraction are recycled back to the slurry bed hydrogenation reactor for hydroconversion; and the light The high-quality fraction and the remaining part of the middle distillate are introduced into the refining reactor of the fixed-bed hydrogenation unit for hydrofinishing reaction; and

(5) Separating and fractionating the effluent of the refining reactor in sequence to obtain a naphtha fraction and a diesel fraction.

In a second aspect, the present invention provides a system for coal tar hydrogenation, the system comprising:

preprocessing unit;

The slurry bed hydrogenation unit includes a slurry bed hydrogenation reactor, and the material treated by the pretreatment unit enters the slurry bed hydrogenation reactor for hydrogenation conversion;

A first separation unit having a light distillate transfer line, a first middle distillate transfer line, a second middle distillate transfer line, a first heavy distillate transfer line, and a second heavy distillate transfer line, from a slurry bed hydrogenation unit Materials are sequentially separated and fractionated in the first separation unit to obtain light distillate, middle distillate and heavy distillate, part of the heavy distillate is thrown out through the first heavy distillate delivery pipeline, and the rest of the heavy distillate is recycling a fraction through said second heavy distillate transfer line and a portion of said middle distillate through said first middle distillate transfer line back to said slurry bed hydrogenation reactor;

a fixed bed hydrogenation unit comprising a finishing reactor, the remainder of said middle distillate from the slurry bed hydrogenation unit being introduced through said second middle distillate transfer line and said light distillate being introduced through said light distillate transfer line into said second middle distillate transfer line carry out the hydrofinishing reaction in the above-mentioned refining reactor; and

In the second separation unit, the material from the fixed-bed hydrogenation unit is sequentially separated and fractionated in the second separation unit.

The present invention utilizes the characteristics of strong adaptability of the raw material of the slurry bed hydrogenation reactor, and first converts the inferior coal tar raw material with high metal content and high mechanical impurity content, realizes the lightening of the coal tar raw material, and recycles part of the middle distillate Return to the slurry bed hydrogenation reactor to inhibit the precipitation and deposition of asphaltenes or the formation of coke by coking. Then use the advantages of large hydrogenation depth and good product quality in the subsequent fixed-bed hydrogenation reactor to finally obtain clean and high value-added products.

The method provided by the invention effectively combines the slurry bed and the fixed bed, realizes the clean and efficient utilization of coal tar resources, maximizes the liquid yield, improves the utilization rate and utilization value of coal tar resources, and prolongs the The operating cycle of the device.

The method provided by the present invention not only solves the problem that the operation period of the coal tar fixed-bed hydrogenation unit is seriously affected due to the high content of metals and mechanical impurities in the raw material of the whole distillate of coal tar, but also recycles part of the middle distillate back to the slurry bed The hydrogenation reactor, while realizing the lightening of coal tar and maximizing the liquid yield, can also effectively inhibit the precipitation and deposition of asphaltene in coal tar or coking to form coke, ensuring the long-term stable operation of the device.

Other features and advantages of the present invention will be described in detail in the detailed description that follows.

Description of drawings

The accompanying drawings are used to provide a further understanding of the present invention, and constitute a part of the description, together with the following specific embodiments, are used to explain the present invention, but do not constitute a limitation to the present invention. In the attached picture:

Fig. 1 is the process flow diagram of a kind of coal tar hydrogenation method of the present invention.

Explanation of reference signs

1. Coal tar raw material 2. Pretreatment unit 3. Water and mechanical impurities

4. Slurry bed catalyst 5. Slurry bed hydrogenation reactor 6. The first separation unit

7. The first hydrogen-rich gas 8. The first cycle hydrogen compressor 9. New hydrogen

10. The first circulating hydrogen 11. The first separated water 12. The first fractionation tower

13. Tower top reflux tank 14. First tower top gas 15. Second separated water

16. Light distillate 17. Middle distillate 18. Heavy distillate

19. External rejection of heavy distillate 20. Refining reactor 21. Refining effluent

22. Second separation unit 23. Third separation water 24. Second liquid hydrocarbon stream

25. The second hydrogen-rich gas 26. The second fractionation tower 27. The second tower top gas

28. Naphtha fraction 29. Diesel fraction 30. Second cycle hydrogen compressor

31. Second cycle hydrogen

detailed description

Specific embodiments of the present invention will be described in detail below. It should be understood that the specific embodiments described here are only used to illustrate and explain the present invention, and are not intended to limit the present invention.

Neither the endpoints nor any values of the ranges disclosed herein are limited to such precise ranges or values, and these ranges or values are understood to include values approaching these ranges or values. For numerical ranges, between the endpoints of each range, between the endpoints of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, these values Ranges should be considered as specifically disclosed herein.

In a first aspect, the present invention provides a method for hydrogenation of coal tar, the method comprising:

(1) Introducing the coal tar raw material into a pretreatment unit for water removal and/or impurity removal pretreatment;

(2) In the presence of hydrogen and a slurry bed catalyst, the material obtained in step (1) is introduced into a slurry bed hydrogenation reactor of a slurry bed hydrogenation unit for hydrogenation conversion;

(3) separating and fractionating the material obtained through step (2) successively to obtain light distillate, middle distillate and heavy distillate;

(4) part of the heavy fraction is thrown out; and part of the middle distillate and the remaining part of the heavy fraction are recycled back to the slurry bed hydrogenation reactor for hydroconversion; and the light The high-quality fraction and the remaining part of the middle distillate are introduced into the refining reactor of the fixed-bed hydrogenation unit for hydrofinishing reaction; and

(5) Separating and fractionating the effluent of the refining reactor in sequence to obtain a naphtha fraction and a diesel fraction.

In the present invention, "part of the heavy fraction" means a part of all the heavy fractions obtained in step (3); , the remainder in all the heavy fractions obtained in step (3). In other words, the "part of the heavy fraction" and the "remaining portion of the heavy fraction" constitute the entire heavy fraction obtained in step (3).

The aforementioned coal tar hydrogenation method provided by the present invention has the characteristics of high liquid yield, good product quality, simple process, long device operation period and the like.

The aforementioned naphtha fraction and diesel fraction of the present invention can be taken out of the device as products.

The method of the present invention has no particular limitation on the specific operation mode of the pretreatment unit for removing water and/or removing impurities, as long as the purpose of preliminary removal of water and mechanical impurities in the coal tar raw material can be achieved. For example, means such as sedimentation and/or centrifugation can be used to perform pretreatment for water removal and/or impurity removal.

The method of the present invention has no special requirements on the specific operation method of the gas-liquid separation and fractionation, for example, gas-liquid separation can be performed in a conventional gas-liquid separation device, and fractionation can be performed in a fractionation tower, for example.

The inventors of the present invention found in research that asphaltene in coal tar is a precursor of coking, and it is easy to crack at high temperature to generate free radicals. When the stability of the colloidal system is good, the asphaltene in the coal tar raw material is in a peptized state, and the free radicals generated by heating in the liquid phase will be affected by a strong cage effect, making it easier for the asphaltene free radicals to interact with the colloidal system. The surrounding smaller molecules or other free radicals react and annihilate, resulting in less chance of asphaltene radicals meeting each other, and it is not easy to further condense to form coke. However, as the conversion depth of the slurry bed hydrogenation reactor increases, the stability of the colloidal system decreases rapidly. At this time, the asphaltenes are separated from the reaction bulk phase to form a new liquid phase. The asphaltenes are easy to combine with each other through free radical reactions to form larger asphaltene molecules until coke is formed. Therefore, in order to avoid the separation of asphaltenes from the bulk phase and mutual polymerization to form coke, it is necessary to avoid the mutual polymerization of asphaltene through free radical reaction to form coke during the slurry bed reaction process.

In order to avoid asphaltenes being mutually polymerized to form coke through free radical reactions during the slurry bed reaction, the inventors of the present invention considered providing hydrogen-donating components around asphaltene radicals, because the presence of hydrogen-donating components can timely Effectively provide hydrogen to asphaltene radicals, and make hydrogen react with asphaltene radicals to annihilate them. The inventor of the present invention finds after creative research that partially hydrogenated aromatic hydrocarbons such as monocyclic aromatic hydrocarbons and bicyclic aromatic hydrocarbons with cycloalkane rings have good hydrogen supply properties, such as indane or tetrahydronaphthalene or naphthalene, etc. In view of this, In the present invention, a part of the middle distillate having a relatively large amount of this structure is recycled back to the slurry bed hydrogenation reactor as a hydrogen-donating component of asphaltene free radicals, so as to suppress the precipitation and deposition of asphaltenes when the reaction conversion depth is high Or coke to form coke. The inventors of the present invention have found that the part of the middle distillate that is recycled back to the slurry bed hydrogenation reactor accounts for 20 to 50% by weight of the total amount of the middle distillate obtained after step (3), more preferably When the content is 25-45% by weight, the operation period of the device can be obviously extended, the coal tar can be lightened and the liquid yield can be maximized at the same time, and the generation of coke can be significantly reduced.

Preferably, the final boiling point of the light distillate is 150-200°C; the final boiling point of the middle distillate is 330-400°C; more preferably, the final boiling point of the light distillate is 170-190°C ; The final boiling point of the middle distillate is 360-390°C. In the present invention, it needs to be specified that the fraction whose distillation range is less than or equal to the final boiling point of the light fraction is the light fraction; similarly, the fraction whose distillation range is greater than the final boiling point of the light fraction Point and less than or equal to the final boiling point of the middle distillate is the middle distillate; and, the fraction with a boiling range greater than the final boiling point of the middle distillate is the heavy distillate.

The slurry bed catalyst may be a homogeneous slurry bed catalyst or a heterogeneous slurry bed catalyst. In the present invention, the slurry bed catalyst is preferably a heterogeneous slurry bed catalyst. More preferably, the slurry bed catalyst is a highly dispersed heterogeneous slurry bed catalyst. The highly dispersed heterogeneous slurry bed catalyst may be selected from at least one of iron-based catalysts, iron-based compounds and iron-based carbon-based supported catalysts. The iron-based catalyst is selected from at least one of pyrite, hematite and red mud; the iron _- based compound is selected from at least one of _Fe2S , _Fe2O3 and _{Fe3O4 ;} the The iron-based carbon-based supported catalyst includes a carrier and an active metal element loaded on the carrier, and the carrier is a carbon-based material selected from at least one of coal powder, activated carbon, graphite and carbon black. The active metal element is selected from at least one of W, Mo, Ni, Co and Fe.

Preferably, the average particle diameter of the iron-based catalyst is 10-200 μm.

Preferably, based on the total weight of the coal tar raw material, the amount of the slurry bed catalyst in terms of active metal elements contained therein is 0.1-3.5 wt%, preferably 0.15-2.5 wt%. To illustrate more specifically, when the slurry-bed catalyst is an iron-based catalyst and/or an iron-based compound, the amount of the slurry-bed catalyst is based on the content of iron contained therein; when the slurry-bed catalyst When it is an iron-based carbon-based supported catalyst, the amount of the slurry bed catalyst is based on the content of active metal elements contained therein (such as W, Mo, Ni, Co and Fe that may be contained).

Preferably, the part of the heavy fraction that is thrown out accounts for 3 to 16% by weight of all the heavy fractions obtained after step (3); more preferably accounts for all the heavy fractions obtained after step (3). 5 to 10% by weight of the total fraction.

Preferably, the conditions for performing hydroconversion in the slurry-bed hydrogenation reactor include: a reaction temperature of 400-460°C, a hydrogen partial pressure of 8.0-15.0MPa, and a volume space velocity of 0.5-2.0h ^-1 , The volume ratio of hydrogen to oil is 500-1500; more preferably, the conditions for hydroconversion include: reaction temperature of 410-440°C, hydrogen partial pressure of 8.5-12.0MPa, volume space velocity of 0.6-1.5h ^-1 , hydrogen oil The volume ratio is 600-1200.

Preferably, the conditions for hydroconversion in the slurry-bed hydrogenation reactor are controlled such that the solids content in the feed to the finishing reactor of the fixed-bed hydrogenation unit is ≯0.01% by weight and the metal content is ≯10 μg/ g.

Preferably, the conditions for carrying out the hydrofinishing reaction in the refining reactor include: the hydrogen partial pressure is 8.0-20.0MPa, more preferably 10.0-19.0MPa; the reaction temperature is 340-420°C, more preferably 350-400 °C; the volume ratio of hydrogen to oil is 600-1800; the hourly volume space velocity of the raw material liquid is 0.1-1.5h ^-1 .

The hydrofinishing reaction can be carried out in the presence of a hydrofinishing catalyst.

Preferably, the hydrotreating catalyst contains a carrier, an active component loaded on the carrier and an optional coagent; the metal element of the active component is selected from Group VIB metal elements and Group VIII At least one of the group metal elements. The optionally contained active auxiliary means that the active auxiliary may or may not contain an active auxiliary.

Preferably, in the hydrorefining catalyst, the carrier is silica-alumina, the Group VIB metal element is molybdenum and/or tungsten, and the Group VIII metal element is cobalt and/or nickel.

According to a preferred embodiment, in the hydrorefining catalyst, the carrier is silica-alumina, the Group VIII metal element loaded on the carrier is nickel and the Group VIII metal element is cobalt and/or nickel, and the hydrorefining catalyst contains a coagent whose active element is phosphorus; based on the total weight of the hydrorefining catalyst, the content of nickel in terms of oxide 1-10% by weight, the sum of molybdenum and tungsten as oxides is greater than 10% by weight and less than or equal to 50% by weight, the content of phosphorus as oxides is 1-9% by weight, and the balance is carrier . The sum of the molybdenum and tungsten contents calculated as oxides is greater than 10% by weight and less than or equal to 50% by weight. wt% to less than or equal to 50 wt%; if only one of molybdenum and tungsten is contained, the content of molybdenum or tungsten calculated as oxide is greater than 10 wt% to less than or equal to 50 wt%.

Preferably, in the carrier of the hydrorefining catalyst, the content of silicon oxide is 2-45% by weight, and the content of aluminum oxide is 55-98% by weight.

Since the mixed oil of light distillate and middle distillate still contains a small amount of impurities such as metals, in order to avoid the activity of the hydrofinishing catalyst from being affected by impurities such as metals, and to prevent the bed pressure drop of the refining reactor from rising too fast, it is preferable to The top of the refining reactor is filled with a small amount of hydrogenation protection catalyst. More preferably, the loading volume ratio of the hydrogenation protection catalyst to the hydrofinishing catalyst is 0.05˜0.2:1.

In the refining reactor, the hydrogenation protection catalyst can be loaded in a graded arrangement of various protection catalysts, preferably five kinds of hydrogenation protection catalysts in a graded arrangement. The gradation mode of the hydrogenation protection catalyst is that the hydrogenation protection catalyst I, the hydrogenation protection catalyst II, the hydrogenation protection catalyst III, the hydrogenation protection catalyst IV and the hydrogenation protection catalyst V are loaded sequentially along the reactant flow direction; The active metal elements in the protection catalyst I, the hydrogenation protection catalyst II, the hydrogenation protection catalyst III, the hydrogenation protection catalyst IV and the hydrogenation protection catalyst V are at least selected from the group VIB metal elements and/or the VIII group metal elements A sort of.

Preferably, the hydrogenation protection catalyst I is a hydrogenation protection catalyst in the shape of a porous cylinder supported by silicon oxide or aluminum oxide, and its average particle diameter is 15-17 mm. The hydrogenation protection catalyst I has a relatively high porosity and a super-large pore structure, and can accommodate solid particles and the like carried in the coal tar raw material.

Preferably, the hydrogenation protection catalyst II is a hydrogenation protection catalyst in the shape of a honeycomb cylinder with an average particle diameter of 9-11 mm. Based on the total weight of the hydrogenation protection catalyst II, the hydrogenation protection catalyst II contains 0.05-0.2% by weight of nickel oxide, 0.5-1.0% by weight of molybdenum oxide, and the balance is carrier. The hydrogenation protection catalyst II has a relatively high porosity and a macroporous structure, and can accommodate impurities such as particles and metals carried in the coal tar raw material.

Preferably, the hydrogenation protection catalyst III is a hydrogenation protection catalyst having a Raschig ring shape and an average particle diameter of 5.6-6.5 mm. The hydrogenation protection catalyst III contains 0.1-0.5% by weight of nickel oxide, 0.5-2.5% by weight of molybdenum oxide, and the rest is silicon oxide or aluminum oxide as a carrier. The hydrogenation protection catalyst III has high porosity and macroporous structure, can accommodate impurities such as metals in coal tar raw materials, and can hydrogenate and saturate olefins and diolefins.

Preferably, the hydrogenation protection catalyst IV is a hydrogenation protection catalyst having a Raschig ring shape and an average particle diameter of 2.5-3.5 mm. The hydrogenation protection catalyst IV contains 0.1-1.0% by weight of nickel oxide, 1.0-5.5% by weight of molybdenum oxide, and the rest is silicon oxide or aluminum oxide as a carrier. The hydrogenation protection catalyst IV can remove impurities such as metals in the coal tar raw material.

Preferably, the hydrogenation protection catalyst V is a hydrogenation protection catalyst in the shape of a clover with an average particle diameter of 2.5-3.5 mm. The hydrogenation protection catalyst V contains 0.5-1.5% by weight of nickel oxide, 1.5-6.5% by weight of molybdenum oxide, and the rest is silicon oxide or aluminum oxide as a carrier. The hydrogenation protection catalyst V can remove impurities such as metals in the coal tar raw material.

There is no special requirement on the packing volume ratio among the above-mentioned various hydrogenation protection catalysts, and those skilled in the art can use the conventional packing volume ratio in the field to pack the above-mentioned various hydrogenation protection catalysts.

The coal tar refers to the coal tar produced by coal pyrolysis or coal gas production or other processes. At least one of low-temperature coal tar, medium-temperature coal tar and high-temperature coal tar produced during low-temperature coking, medium-temperature coking and high-temperature coking). In the present invention, the distillation range of the low-temperature coal tar may be 50-450°C; the distillation range of the medium-temperature coal tar may be 50-600°C; and the distillation range of the high-temperature coal tar may be 50-650°C.

In a second aspect, the present invention also provides a system for coal tar hydrogenation, the system comprising:

preprocessing unit;

The slurry bed hydrogenation unit includes a slurry bed hydrogenation reactor, and the material treated by the pretreatment unit enters the slurry bed hydrogenation reactor for hydrogenation conversion;

A first separation unit having a light distillate transfer line, a first middle distillate transfer line, a second middle distillate transfer line, a first heavy distillate transfer line, and a second heavy distillate transfer line, from a slurry bed hydrogenation unit Materials are sequentially separated and fractionated in the first separation unit to obtain light distillate, middle distillate and heavy distillate, part of the heavy distillate is thrown out through the first heavy distillate delivery pipeline, and the rest of the heavy distillate is recycling a fraction through said second heavy distillate transfer line and a portion of said middle distillate through said first middle distillate transfer line back to said slurry bed hydrogenation reactor;

a fixed bed hydrogenation unit comprising a finishing reactor, the remainder of said middle distillate from the slurry bed hydrogenation unit being introduced through said second middle distillate transfer line and said light distillate being introduced through said light distillate transfer line into said second middle distillate transfer line carry out the hydrofinishing reaction in the above-mentioned refining reactor; and

In the second separation unit, the material from the fixed-bed hydrogenation unit is sequentially separated and fractionated in the second separation unit.

The pretreatment unit may contain dehydration and/or mechanical impurity removal devices for sedimentation and centrifugation.

Preferably, the first separation unit and the second separation unit respectively include a gas-liquid separation device and a fractionation tower connected in sequence through pipelines; in the first separation unit, the inlet of the gas-liquid separation device is connected to the The outlet of the slurry bed hydrogenation unit is connected, and the outlet of the fractionation tower is connected with the inlet of the fixed bed hydrogenation unit through a pipeline; in the second separation unit, the inlet of the gas-liquid separation device is connected with the fixed bed hydrogenation unit through a pipeline. The outlet connection of the bed hydrogenation unit, and the outlet of the fractionation column lead the product out of the system through pipelines.

Preferably, the system further includes a circulating hydrogen unit, the first separation unit and the second separation unit are respectively connected to the circulating hydrogen unit through pipelines, so that the first separation unit and the second separation unit The gas phase material obtained enters the recycle hydrogen unit.

In the first separation unit, the material from the outlet of the slurry bed hydrogenation unit is introduced into the gas-liquid separation device of the first separation unit through a pipeline for gas-liquid separation, and the gas phase material obtained enters the hydrogen circulation In the unit to further remove impurities to obtain the hydrogen-containing stream therein, and the liquid phase material obtained by gas-liquid separation through the gas-liquid separation device enters the fractionation tower of the first separation unit through the pipeline for fractionation, and fractionation obtains different distillation ranges The intermediate product, and part of the intermediate product is recycled back to the slurry bed hydrogenation unit through the first middle distillate transfer line, while another part of the intermediate product is introduced into the fixed bed hydrogenation unit through the second middle distillate transfer line . And the product obtained at the outlet of the fixed-bed hydrogenation unit enters the gas-liquid separation device of the second separation unit through a pipeline for gas-liquid separation, and the gas phase material obtained enters the circulating hydrogen unit to further remove impurities to The hydrogen-containing stream is obtained, and the liquid phase material obtained by gas-liquid separation through the gas-liquid separation device enters the fractionation tower of the second separation unit through the pipeline for fractionation, and fractionation obtains products of different distillation ranges, and the obtained The product is led out of the system through the pipeline.

Preferably, the circulating hydrogen unit is respectively connected to the slurry bed hydrogenation unit and the fixed bed hydrogenation unit through pipelines to supplement the slurry bed hydrogenation unit and the fixed bed hydrogenation unit with hydrogen stream.

Preferably, the circulating hydrogen unit contains at least one circulating hydrogen compressor. In particular, the first separation unit and the second separation unit are respectively connected to one or more cycle hydrogen compressors in the cycle hydrogen unit through pipelines to obtain The hydrogen-containing stream in the gas phase material obtained from the separation unit.

According to a kind of preferred embodiment, the present invention provides the process route as shown in Figure 1 to carry out coal tar hydrogenation, and some auxiliary equipment in the figure are not marked as heat exchanger, preheating furnace etc. Those of ordinary skill are well known, and concrete process route is as follows:

The coal tar raw material 1 is introduced into the pretreatment unit 2 for settling and centrifugal separation to remove water and mechanical impurities 3; then the effluent from the pretreatment unit 2, the slurry bed catalyst 4 and the first circulating hydrogen 10 are introduced into the slurry bed together Hydroconversion is carried out in the slurry bed hydrogenation reactor 5 of the hydrogenation unit; then the effluent of the slurry bed hydrogenation reactor 5 is introduced into the gas-liquid separation device of the first separation unit 6 for gas-liquid separation, and the separation is obtained The first separated water 11, the first hydrogen-rich gas 7 and the first liquid hydrocarbon stream, the first hydrogen-rich gas 7 is pressurized by the first cycle hydrogen compressor 8 in the cycle hydrogen unit and mixed with new hydrogen 9 as First recycle hydrogen 10 for slurry bed hydrogenation unit. The first liquid hydrocarbon stream obtained from the first separation unit 6 enters the first fractionation tower 12 of the first separation unit for distillation and cutting to obtain gas phase light components, middle distillate 17 and heavy distillate 18 respectively; The cut gas phase light components enter the top reflux tank 13 of the first fractionation tower 12 to separate oil, water and gas to obtain the second separated water 15, the first overhead gas 14 and the light fraction of the oil phase respectively 16, wherein the separated first overhead gas 14 is taken out of the system as fuel gas, part of the middle distillate 17 is recycled back to the slurry bed hydrogenation reactor 5 for hydrogenation conversion, and the remaining part of the middle distillate 17 is Together with the light distillate 16 and the second recycled hydrogen 31, it enters the refining reactor 20 of the fixed-bed hydrogenation unit for hydrotreating reaction. A part of the heavy fraction 18 cut out in the first fractionation tower 12 is thrown out of the system as an external heavy fraction 19, and the remaining part of the heavy fraction is recycled back to the slurry bed hydrogenation reactor 5 for further hydrogenation transform. The refined effluent 21 in the refined reactor 20 of the fixed-bed hydrogenation unit enters the gas-liquid separation device of the second separation unit 22 for gas-liquid separation to obtain the third separated water 23, the second hydrogen-rich gas 25 and the second liquid Hydrocarbon stream 24; wherein, the second hydrogen-rich gas 25 is pressurized by the second cycle hydrogen compressor 30 in the cycle hydrogen unit and then mixed with fresh hydrogen 9 as the second cycle hydrogen 31 of the fixed bed hydrogenation unit. The second liquid hydrocarbon stream 24 enters the second fractionation tower 26 of the second separation unit for distillation and cutting to obtain the second overhead gas 27, naphtha fraction 28, and diesel fraction 29 as the fuel gas leaving the system, wherein, Naphtha fraction 28 and diesel fraction 29 exit the system as products.

Method of the present invention has following advantage:

(1) The present invention utilizes the slurry bed hydrogenation reactor to realize the lightening of coal tar, and the slurry bed reaction product can meet the feeding requirements of the subsequent fixed bed hydrogenation unit, greatly improving the utilization rate of coal tar resources and use value;

(2) While using the slurry bed hydrogenation reactor to realize coal tar lightening, part of the middle distillate is recycled back to the slurry bed hydrogenation reactor, which effectively inhibits the precipitation and deposition of asphaltenes and the formation of coke by coking, maximizing The liquid yield is greatly improved, and the long-term stable operation of the device is ensured.

(3) The combination method of slurry bed hydrocracking and fixed bed hydrogenation upgrading can take into account the advantages of strong adaptability of slurry bed raw materials and good quality of fixed bed products, and realize the clean and efficient utilization of coal tar resources. To a certain extent, alleviate the shortage of petroleum-based resources.

The present invention will be described in detail below by way of examples. Unless otherwise specified, all raw materials used below were purchased commercially. The properties of the coal tar raw materials used below are shown in Table 1.

The refining reactor of the fixed-bed hydrogenation unit is filled with hydrogenation protection catalyst and hydrorefining catalyst, and the hydrogenation protection catalyst is loaded on the top of the reactor, which is packed in five kinds of hydrogenation protection catalysts, and the hydrogenation protection catalyst is loaded sequentially along the direction of the reactant flow. Protected Catalyst I, Hydrogenated Protected Catalyst II, Hydrogenated Protected Catalyst III, Hydrogenated Protected Catalyst IV and Hydrogenated Protected Catalyst V are RGC-20, RGC-30E, RGC-30A, RGC-30B, RGC- 1, and the loading volume ratio of hydrogenation protection catalyst I, hydrogenation protection catalyst II, hydrogenation protection catalyst III, hydrogenation protection catalyst IV and hydrogenation protection catalyst V is 1:2:1.5:1.5:2.

The trade name of the hydrofinishing catalyst is RTC-2, based on the total weight of the hydrofinishing catalyst, the content of nickel as oxide is 2.4% by weight, and the content of molybdenum as oxide is 8.3% by weight , the content of tungsten in terms of oxides is 16.7% by weight, the content of phosphorus in terms of oxides is 2.0% by weight, and the balance is carrier silica-alumina, based on the carrier, the content of silicon oxide is 20.0 % by weight, the content of alumina is 80.0% by weight.

A highly dispersed heterogeneous slurry bed catalyst is used in the slurry bed hydrogenation reactor of the slurry bed hydrogenation unit. The highly dispersed heterogeneous slurry bed catalyst is a highly dispersed iron-based carbon-based supported catalyst, and its composition is : Activated carbon is used as a carrier, and the active metal components are Fe and Mo. Moreover, the weight ratio of Fe and Mo in the highly dispersed iron-based carbon-based supported catalyst in terms of elements is 1:0.2.

The catalysts of the above commercial brands are all produced by Changling Catalyst Factory of Sinopec Catalyst Branch.

In the following examples and comparative examples, unless otherwise specified, based on the hydrofinishing catalyst, the loading volume of the hydrofinishing catalyst is 10% of the hydrofinishing catalyst.

Table 1

Coal tar raw material Density(20℃)/(g/cm ³ ) 1.0430 Carbon residue/weight% 6.50 Nitrogen content/(μg/g) 6800 Sulfur content/(μg/g) 2500 C content/weight% 81.83 H content/weight% 8.17 Asphaltene content/wt% 16.0 Distillation range ASTM D-1160/℃ IBP 165 50% 387 95% 512 Metal content/(μg/g) Fe 98.7 Ni <0.1 V 0.1 Na 25.0 Ca 100.9 Al 13.4

Example 1

Based on the total weight of the coal tar raw material, the dosage of the slurry bed catalyst is 1.5% by weight based on the active metal elements contained therein. After mixing the coal tar raw material in Table 1 with the aforementioned highly dispersed heterogeneous slurry bed catalyst, they enter the slurry bed hydrogenation reactor together with hydrogen for hydrogenation conversion, and the effluent of the slurry bed hydrogenation reactor enters The first separation unit performs gas-liquid separation and separates water, and the separated first liquid hydrocarbon stream enters the first separation unit, and is distilled and cut into light distillate, middle distillate and heavy distillate. Wherein, the 7.5% by weight of all the heavy fractions cut out by the first separation unit is thrown out of the device, and the rest of the heavy fractions are circulated back to the slurry bed hydrogenation reactor for further conversion. 35% by weight of all middle distillates cut out by distillation in the first separation unit are recycled back to the slurry bed hydrogenation reactor for further conversion. The remaining part of the middle distillate and all the light distillate are mixed with hydrogen and then enter the refining reactor of the fixed bed hydrogenation unit, where they contact and react with the hydrofining catalyst, and the refined effluent of the refining reactor enters the second separation unit for gas-liquid separation. Water is separated, and the separated second liquid hydrocarbon product enters the second separation unit, and is distilled and cut into naphtha fraction and diesel fraction. Among them, naphtha fraction and diesel fraction are taken out of the device as products.

The specific reaction conditions involved in the above examples are shown in Table 2, and the properties of the product obtained after slurry bed hydrogenation are shown in Table 3. The properties of the naphtha product and diesel product fractionated by the second separation unit are shown in Table 4.

It can be seen from Table 3 that after hydrogenation in a slurry bed, the metal content in the product is less than 10 μg/g, and the content of mechanical impurities is less than 0.01% by weight, which can meet the feed requirements of the subsequent fixed bed hydrogenation unit.

Moreover, in this example, part of the middle distillate was recycled back to the slurry bed hydrogenation reactor, and there was no problem of asphaltene precipitation and deposition blocking the internal components of the reactor. The continuous operation period of the slurry bed hydrogenation device exceeded 5000h, and The amount of coke generated is 3.53% less than that in Comparative Example 1, and the corresponding liquid yield is 5.4% higher; while the continuous operation period of the slurry bed hydrogenation unit in the method of Comparative Example 1 is only 1080h.

This shows that adopting the method of the present invention can effectively inhibit asphaltene precipitation and coking to form coke, maximize the liquid yield and ensure the long-term stable operation of the device.

It can also be seen from Table 4 that the diesel product of this example has a sulfur content of less than 10 μg/g, a freezing point of -16°C, and a cetane number of 45.9, which can be used as a low-sulfur clean diesel blending component. The sulfur content of the naphtha fraction is less than 10μg/g, and the aroma potential reaches 68.9, which can be used as a high aroma potential reformate.

That is to say, the method provided by the present invention can significantly improve the continuous operation period of the device and improve the liquid collection on the basis of ensuring the properties of the diesel product.

Example 2

Present embodiment adopts the method similar to embodiment 1 to carry out, and difference is:

In the present embodiment, based on the total weight of the coal tar raw material, the amount of the slurry bed catalyst based on the active metal elements contained therein is 2.0% by weight; % by weight is thrown out of the device, and the remaining part of the heavy fraction is recycled back to the slurry bed hydrogenation reactor for further conversion. And the middle distillate of 45% by weight of the whole middle distillate cut out by the distillation of the first separation unit is recycled back to the slurry bed hydrogenation reactor for further conversion, and the remaining part of the middle distillate is mixed with all the light distillate and hydrogen and enters the fixed bed The refining reactor of the hydrogenation unit contacts and reacts with the hydrotreating catalyst.

The specific reaction conditions involved in the above examples are shown in Table 2, and the properties of the product obtained after slurry bed hydrogenation are shown in Table 3. The properties of the naphtha product and diesel product fractionated by the second separation unit are shown in Table 4.

It can be seen from Table 3 that after hydrogenation in a slurry bed, the metal content in the product is less than 10 μg/g, and the content of mechanical impurities is less than 0.01% by weight, which can meet the feed requirements of the subsequent fixed bed hydrogenation unit.

Moreover, in this example, part of the middle distillate was recycled back to the slurry bed hydrogenation reactor, and there was no problem of asphaltene precipitation and deposition blocking the internal components of the reactor. The continuous operation period of the slurry bed hydrogenation device exceeded 5000h, and The amount of coke generated is 2.42 percentage points less than that in Comparative Example 1, and the corresponding liquid yield is 3.63 percentage points higher; while the continuous operation period of the slurry bed hydrogenation unit in the method of Comparative Example 1 is only 1080h.

This shows that adopting the method of the present invention can effectively inhibit asphaltene precipitation and coking to form coke, maximize the liquid yield and ensure the long-term stable operation of the device.

It can also be seen from Table 4 that the diesel product of this example has a sulfur content of less than 10 μg/g, a freezing point of -18°C, and a cetane number of 47.4, which can be used as a low-sulfur clean diesel blending component. The sulfur content of the naphtha fraction is less than 10μg/g, and the aroma potential reaches 66.7, which can be used as a high aroma potential reformate.

That is to say, the method provided by the present invention can significantly improve the continuous operation period of the device and improve the liquid collection on the basis of ensuring the properties of the diesel product.

Example 3

Present embodiment adopts the method similar to embodiment 1 to carry out, and difference is:

In the present embodiment, based on the total weight of the coal tar raw material, the amount of the slurry bed catalyst based on the active metal elements contained therein is 0.5% by weight; % by weight is thrown out of the device, and the remaining heavy fraction is circulated back to the slurry bed hydrogenation reactor for further conversion. And the middle distillate of 25% by weight of all the middle distillates cut out by the distillation of the first separation unit is recycled back to the slurry bed hydrogenation reactor for further conversion, and the remaining middle distillate and all the light distillates are mixed with hydrogen and then enter the fixed bed hydrogenation reactor. The refining reactor of the hydrogen unit reacts in contact with the hydrofining catalyst.

The specific reaction conditions involved in the above examples are shown in Table 2, and the properties of the product obtained after slurry bed hydrogenation are shown in Table 3. The properties of the naphtha product and diesel product fractionated by the second separation unit are shown in Table 4.

It can be seen from Table 3 that after hydrogenation in a slurry bed, the metal content in the product is less than 10 μg/g, and the content of mechanical impurities is less than 0.01% by weight, which can meet the feed requirements of the subsequent fixed bed hydrogenation unit.

Moreover, in this example, part of the middle distillate was recycled back to the slurry bed hydrogenation reactor, and there was no problem of asphaltene precipitation and deposition blocking the internal components of the reactor. The continuous operation period of the slurry bed hydrogenation device exceeded 5000h, and The amount of coke generated is 3.78% less than that in Comparative Example 1, and the corresponding liquid yield is 6.12% higher; while the continuous operation period of the slurry bed hydrogenation unit in the method of Comparative Example 1 is only 1080h.

This shows that adopting the method of the present invention can effectively inhibit asphaltene precipitation and coking to form coke, maximize the liquid yield and ensure the long-term stable operation of the device.

It can also be seen from Table 4 that the diesel product of this example has a sulfur content of less than 10 μg/g, a freezing point of -15°C, and a cetane number of 44.1, which can be used as a low-sulfur clean diesel blending component. The sulfur content of the naphtha fraction is less than 10μg/g, and the aroma potential reaches 70.1, which can be used as a high aroma potential reformate.

That is to say, the method provided by the present invention can significantly improve the continuous operation period of the device and improve the liquid collection on the basis of ensuring the properties of the diesel product.

Comparative example 1

This comparative example adopts the method similar to embodiment 2 to carry out, difference is:

In this comparative example, the middle distillate in the slurry bed hydrogenation reaction product was not recycled back to the slurry bed hydrogenation reactor for further conversion.

Although this comparative example also removes metals and mechanical impurities in the coal tar raw material, realizing the lightening of the coal tar raw material. However, during the operation of the slurry bed hydrogenation reactor, asphaltenes precipitated and deposited and blocked the internal components of the reactor, resulting in the failure of the slurry bed hydrogenation unit to operate normally, and its continuous operation period was only 1080h.

In addition, since the middle distillate was not recycled back to the slurry bed hydrogenation reactor in this comparative example, asphaltene was separated from the reaction bulk phase as the reaction proceeded, and coke was formed through free radical reaction combination and mutual polymerization.

It can be seen from Table 3 that the coke yield of Comparative Example 1 is 2.42 percentage points higher than that of Example 2, and the corresponding liquid yield is 3.63 percentage points lower.

The specific reaction conditions of this comparative example are shown in Table 2, and the properties of the product after slurry bed hydrogenation are shown in Table 3.

The properties of the naphtha product and diesel product fractionated by the second separation unit are shown in Table 4.

Table 2

project Example 1 Example 2 Example 3 Comparative example 1 Slurry bed hydrogenation reactor Hydrogen partial pressure/MPa 9.0 10.5 8.5 10.5 Reaction temperature/℃ 420 435 410 435 Hydrogen oil ratio/(Nm ³ /m ³ ) 800 1000 800 1000 Volumetric space velocity/h ^-1 0.8 0.6 1.2 0.6 Fixed bed hydrofinishing reactor Hydrogen partial pressure/MPa 17.0 15.0 18.0 15.0 Reaction temperature/℃ 360 370 380 370 Hydrogen oil ratio/(Nm ³ /m ³ ) 1500 1200 1800 1200 Volumetric space velocity/h ^-1 0.8 1.2 0.5 1.2

table 3

project Example 1 Example 2 Example 3 Comparative example 1 Product distribution/wt% of slurry bed hydrogenation unit dry gas + liquefied petroleum gas 4.20 5.00 3.42 6.43 coke 3.35 4.46 3.10 6.88 Liquid product yield/wt% 94.03 92.26 94.75 88.63 <180°C light distillate 16.76 20.44 13.19 19.46 180～380℃ middle distillate 47.22 49.03 44.81 46.44 >380℃heavy distillate 30.05 22.79 36.75 22.73 Total metal content/(μg/g) 5.7 2.0 7.0 2.5 Mechanical impurities/wt% 0.006 0.002 0.008 0.002 Slurry bed continuous operation cycle/h >5000 >5000 >5000 1080

Table 4

project Example 1 Example 2 Example 3 Comparative example 1 Total liquid yield/wt% 88.45 85.81 89.74 83.46 Liquid product distribution/wt% Product naphtha fraction 30.90 34.37 29.56 37.31 Diesel Distillate 69.10 65.63 70.44 62.69 Product Naphtha Distillate Properties Density(20℃)/(g/cm ³ ) 0.7629 0.7610 0.7666 0.7574 Sulfur content/(μg/g) 5.0 3.2 7.5 3.0 C content/weight% 85.35 85.10 85.60 85.07 H content/weight% 14.65 14.90 14.40 14.93 Fang Qian/% 68.9 66.7 70.1 66.0 Product Diesel Distillate Properties Density(20℃)/(g/cm ³ ) 0.8513 0.8455 0.8560 0.8420 Sulfur content/(μg/g) 7.5 4.3 9.6 2.6 C content/weight% 86.56 86.25 87.63 86.20 H content/weight% 13.44 13.75 12.37 13.80 Freezing point/℃ -16 -18 -15 -17 cetane number 45.9 47.4 44.1 46.3 Distillation range of product diesel oil fraction (ASTMD-1160)/℃ IBP 160 163 163 161 50% 266 257 268 253 95% 360 359 360 354

It can be seen from the above results that the method provided by the present invention has the advantages of long operating period of the device and high liquid yield, and can take into account the advantages of strong adaptability of the raw material of the slurry bed hydrogenation reactor and good product quality of the fixed bed reactor, and improve It improves the utilization rate and value of coal tar resources, and provides an effective way to use coal tar as a cheap and inferior resource.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention. These simple modifications All belong to the protection scope of the present invention.

In addition, it should be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable way if there is no contradiction. The combination method will not be described separately.

In addition, various combinations of different embodiments of the present invention can also be combined arbitrarily, as long as they do not violate the idea of the present invention, they should also be regarded as the disclosed content of the present invention.

Claims (15)

1. a kind of method of coal tar hydrogenating, this method include：

(1) coal tar raw material introducing pretreatment unit is removed water and/or cleaned pretreatment；

(2) in the presence of hydrogen and slurry bed catalyst, the material that will be obtained through step (1) introduces the slurry of slurry bed system hydrogenation unit Hydro-conversion is carried out in state bed hydroprocessing reactor；

(3) material obtained through step (2) is separated and is fractionated successively, obtained light fraction, midbarrel and heavy and evaporate Point；

(4) will be got rid of outside the heavy end of part；And heavy end described in the part midbarrel and remainder is followed Hydro-conversion is carried out in slurry bed system hydrogenation reactor described in loopback；And evaporated middle described in the light fraction and remainder Separate and hydrofining reaction is carried out in the finishing reactor of fixed bed hydrogenation unit；And

(5) effluent of the finishing reactor is separated and is fractionated successively, obtain naphtha cut and diesel oil distillate.

2. the method according to claim 11, wherein, the part centre being recycled back in the slurry bed system hydrogenation reactor Cut accounts for after step (3) 20~50 weight % of the whole midbarrel total amounts obtained, preferably accounts for after step (3) and obtains Whole midbarrel total amounts 25~45 weight %.

3. method according to claim 1 or 2, wherein, the end point of distillation of the light fraction is 150~200 DEG C；In described Between cut the end point of distillation be 330~400 DEG C；Preferably

The end point of distillation of the light fraction is 170~190 DEG C；The end point of distillation of the midbarrel is 360~390 DEG C.

4. according to the method described in any one in claim 1-3, wherein, the slurry bed catalyst is heterogeneous slurry bed system Catalyst, the heterogeneous slurry bed catalyst are selected from Fe-series catalyst, the carbon-based loaded catalyst of iron series compound and iron system At least one of；

The Fe-series catalyst is selected from least one of troilite, bloodstone and red mud, it is preferable that the Fe-series catalyst Average grain diameter is 10-200 μm；

The iron series compound is selected from Fe₂S、Fe₂O₃And Fe₃O₄At least one of；

The carbon-based loaded catalyst of iron system includes the active metallic element of carrier and load on the carrier, the load Body is the carbon-based material selected from least one of coal dust, activated carbon, graphite and carbon black, the active metallic element be selected from W, At least one of Mo, Ni, Co and Fe.

5. according to the method described in any one in claim 1-4, wherein, using the gross weight of the coal tar raw material as base Standard, the slurry bed catalyst are preferably using the dosage that the active metallic element wherein contained is counted as 0.1~3.5 weight % 0.15~2.5 weight %.

6. according to the method described in any one in claim 1-5, wherein, the part heavy end got rid of outside is accounted for through step (3) 3~16 weight % of the whole heavy end total amounts obtained afterwards；It is preferred that the whole heavys obtained are accounted for after step (3) 5~10 weight % of cut total amount.

7. according to the method described in any one in claim 1-6, wherein, added in the slurry bed system hydrogenation reactor The condition of hydrogen conversion includes：Reaction temperature is 400~460 DEG C, and hydrogen dividing potential drop be 8.0~15.0MPa, volume space velocity for 0.5~ 2.0h^-1, hydrogen to oil volume ratio is 500~1500；Preferably,

Carrying out the condition of hydro-conversion includes：Reaction temperature is 410~440 DEG C, and hydrogen dividing potential drop is 8.5~12.0MPa, volume space velocity For 0.6~1.5h^-1, hydrogen to oil volume ratio is 600~1200.

8. according to the method described in any one in claim 1-6, wherein, hydrofinishing is carried out in the finishing reactor The condition of reaction includes：Hydrogen dividing potential drop is 8.0~20.0MPa, preferably 10.0~19.0MPa；Reaction temperature is 340~420 DEG C, Preferably 350~400 DEG C；Hydrogen to oil volume ratio is 600~1800；Volume space velocity is 0.1~1.5h during material liquid^-1。

9. according to the method described in any one in claim 1-6 and 8, wherein, the hydrofining reaction is in hydrofinishing Carried out in the presence of catalyst；In the Hydrobon catalyst containing carrier and load active component on the carrier and The coagent optionally contained；The metallic element of the active component is selected from vib metals element and group VIII metal member At least one of element.

10. according to the method for claim 9, wherein, in the Hydrobon catalyst, the carrier be silica- Aluminum oxide, the vib metals element loaded on the carrier be molybdenum and/or tungsten and group VIII metallic element be cobalt and/ Or nickel.

11. according to the method for claim 9, wherein, in the Hydrobon catalyst, the carrier be silica- Aluminum oxide, the vib metals element loaded on the carrier is molybdenum and/or tungsten and group VIII metallic element is nickel, institute It is phosphorus to state the active element in coagent；Preferably,

In the Hydrobon catalyst, on the basis of the gross weight of the Hydrobon catalyst, the nickel in terms of oxide Content be 1-10 weight %, the content sum of the molybdenum counted using oxide and tungsten as more than 10 weight % to being less than or equal to 50 weights % is measured, the content of the phosphorus counted using oxide is carrier as 1-9 weight %, surplus.

12. the method according to claim 10 or 11, wherein, in the carrier, the content of silica is 2-45 weights % is measured, the content of aluminum oxide is 55-98 weight %.

13. according to the method described in any one in claim 9-12, wherein, the top loading of the finishing reactor, which has, to be added The admission space ratio of hydrogen guard catalyst, the hydrogenation protecting catalyst and the Hydrobon catalyst is 0.05~0.2：1.

14. according to the method for claim 1, wherein, the coal tar raw material be selected from coalite tar, medium temperature coal tar and At least one of high temperature coal-tar.

15. a kind of system for coal tar hydrogenating, the system includes：

Pretreatment unit；

Slurry bed system hydrogenation unit, including slurry bed system hydrogenation reactor, the material after pretreatment unit is handled enter the slurry Hydro-conversion is carried out in state bed hydroprocessing reactor；

First separative element, there is light fraction feed-line, the first midbarrel feed-line, the second midbarrel delivery pipe Line, the first heavy end feed-line and the second heavy end feed-line, the material from slurry bed system hydrogenation unit is described Separated and be fractionated successively in first separative element to obtain light fraction, midbarrel and heavy end, part is described heavy For matter cut by being got rid of outside the first heavy end feed-line, remainder heavy end is defeated by second heavy end Pipeline is sent to be recycled back to the slurry bed system hydrogenation reaction by the first midbarrel feed-line with the part midbarrel Device；

Fixed bed hydrogenation unit, including finishing reactor, midbarrel described in the remainder from slurry bed system hydrogenation unit are led to Cross the second midbarrel feed-line and described refine is introduced by the light fraction feed-line with the light fraction Hydrofining reaction is carried out in reactor；And

Second separative element, the material from fixed bed hydrogenation unit are separated and divided successively in second separative element Evaporate.