阅读说明：本技术 低阶煤分级转化的方法和用于低阶煤分级转化的系统 (Method and system for low-rank coal fractional conversion ) 是由 王卫平 吴治国 王蕴 王鹏飞 崔龙鹏 邹亮 于 2018-08-13 设计创作，主要内容包括：本发明涉及低阶煤分级转化技术领域,公开了一种低阶煤分级转化的方法和用于低阶煤分级转化的系统。该方法包括：(1)将低阶煤预处理,得到细煤粉和粗煤粉；(2)将粗煤粉热解,得到煤焦油和含酚废水等；(3)热解焦进行第一气化反应,得到第一粗合成气和热半焦；(4)所述第一粗合成气分离得到第一细焦粉和第二粗合成气；(5)第二粗合成气与活性金属元素盐制备加氢催化剂；(6)煤焦油进行加氢裂化反应；(7)细煤粉、含酚废水等制备焦煤浆进行第二气化反应。本发明实现了煤热解气化技术与制取清洁燃料技术深度耦合,解决了低阶煤炭资源的分级高效利用和清洁转化难题,具有煤转化率高、集成性好、催化剂成本低、不外排危固危废等特点。(The invention relates to the technical field of low-rank coal graded conversion, and discloses a low-rank coal graded conversion method and a system for low-rank coal graded conversion. The method comprises the following steps: (1) pretreating low-rank coal to obtain fine coal powder and coarse coal powder; (2) pyrolyzing the crude coal powder to obtain coal tar, phenol-containing wastewater and the like; (3) carrying out a first gasification reaction on the pyrolysis coke to obtain a first crude synthesis gas and hot semicoke; (4) separating the first crude synthesis gas to obtain first fine coke powder and second crude synthesis gas; (5) preparing a hydrogenation catalyst from the second crude synthesis gas and active metal element salt; (6) carrying out hydrocracking reaction on the coal tar; (7) fine coal powder, phenol-containing waste water and the like are used for preparing coke slurry to carry out secondary gasification reaction. The invention realizes the deep coupling of the coal pyrolysis gasification technology and the clean fuel preparation technology, solves the difficult problems of grading high-efficiency utilization and clean conversion of low-rank coal resources, and has the characteristics of high coal conversion rate, good integration, low catalyst cost, no external discharge of dangerous and solid hazardous wastes and the like.)

1. A method for graded conversion of low-rank coal is characterized by comprising the following steps:

1) pretreating low-rank coal to obtain fine coal powder and coarse coal powder;

2) pyrolyzing the coarse coal powder to obtain coal tar, coal gas, pyrolysis coke and phenolic wastewater;

3) carrying out a first gasification reaction on the pyrolysis coke to obtain a first crude synthesis gas carrying fine coke powder and a hot semi-coke, and returning the hot semi-coke to the pyrolysis process to be used as a heat source for pyrolysis;

4) performing first cyclone separation on the first crude synthesis gas to obtain first fine coke powder and second crude synthesis gas carrying second fine coke powder;

5) contacting the second crude synthesis gas with a solution of soluble salt containing active metal elements, and performing second cyclone separation to deposit the soluble salt on the second fine coke powder and volatilize the solvent to obtain a slurry bed hydrogenation catalyst and a third crude synthesis gas containing the solvent;

6) contacting the coal tar obtained by pyrolysis and optional heavy oil of a refinery with the slurry bed hydrogenation catalyst and carrying out hydrocracking reaction to obtain light distillate oil, tail oil and tailings, returning the tail oil to carry out the hydrocracking reaction, and carrying out hydrofining reaction on the light distillate oil to obtain diesel oil and/or gasoline;

7) and mixing the fine coal powder, the phenol-containing wastewater, the first fine coke powder and the tailings to obtain coke slurry, and performing a second gasification reaction on the coke slurry to obtain fourth crude synthesis gas and ash.

2. The method according to claim 1, wherein in the step 1), the weight ratio of the fine coal powder to the coarse coal powder is 1: 0.25-5;

preferably, the particle size of the coarse coal powder is 150-1000 μm.

3. The method of claim 1, wherein in step 2), the pyrolysis conditions comprise: the temperature is 400-700 ℃, and the pressure is 0.05-4 MPa.

4. The method of claim 1, wherein in step 3), the conditions of the first gasification reaction comprise: the temperature is 600-1000 ℃, and the pressure is 0.05-4 MPa;

preferably, the gasifying agents adopted by the first gasification reaction are water vapor and oxygen;

more preferably, the volume ratio of the water vapor to the oxygen is 1-20: 1.

5. The method according to claim 1, wherein in step 4), the first fine coke powder has an average particle size of 80 to 500 μm, and the second fine coke powder has an average particle size of 10 to 100 μm;

preferably, the average particle size of the first fine coke powder is 100-300 μm, and the average particle size of the second fine coke powder is 10-80 μm.

6. The method according to claim 1, wherein, in step 5), the active metal element is selected from at least one of W, Mo, Ni, Co, and Fe;

preferably, the loading amount of the active metal element calculated by oxide is 2-50 wt% based on the total weight of the slurry bed hydrogenation catalyst.

7. The method as claimed in any one of claims 1 and 5 to 6, wherein the temperature of the secondary cyclone in step 5) is 200 to 500 ℃.

8. The process of any one of claims 1 and 5-6, wherein in step 6), the hydrocracking reaction conditions comprise: the temperature is 360-480 ℃, and preferably 380-450 ℃; the pressure is 10-20 MPa, preferably 12-16 MPa; the liquid hourly space velocity is 0.5-1.5 h^-1；

Preferably, the slurry bed hydrogenation catalyst is used in an amount of 0.1 to 10 wt% based on the weight of the slurry bed feed oil.

9. The method of claim 1, wherein the tail oil has a boiling point greater than 400 ℃ in step 6).

10. The method according to claim 1, wherein in step 7), the solid content of the coke coal slurry is 55-68 wt%;

preferably, in the coke coal slurry, the content of the first fine coke powder is not more than 40 wt%, and the content of the tailings is not more than 20 wt%.

11. The process according to claim 1 or 10, wherein in step 7) the conditions of the second gasification reaction comprise: the temperature is 1200-1800 ℃, and the pressure is 0.5-8 MPa;

preferably, the gasifying agents adopted by the second gasification reaction are water vapor and oxygen;

more preferably, the volume ratio of the water vapor to the oxygen is 1-20: 1.

12. The method of claim 1, wherein the method further comprises:

8) transforming and purifying the fourth raw synthesis gas and optionally at least part of the third raw synthesis gas to obtain hydrogen; returning at least part of the obtained hydrogen to the hydrocracking reaction and/or the hydrofining reaction to be used as a hydrogen source.

13. A system for staged conversion of low rank coal, the system comprising: the system comprises a pretreatment unit, a pyrolysis unit, a first gasification reaction unit, a first cyclone separation unit, a second cyclone separation unit, a slurry bed reaction unit, a hydrofining unit and a second gasification reaction unit; wherein the content of the first and second substances,

the pretreatment unit is used for pretreating low-rank coal to obtain fine coal powder and coarse coal powder;

the pyrolysis unit is used for pyrolyzing the coarse coal powder to obtain coal tar, coal gas, pyrolysis coke and phenol-containing wastewater;

the first gasification reaction unit is used for carrying out first gasification reaction on the pyrolysis coke to obtain first crude synthesis gas carrying fine coke powder and hot semicoke, and returning the hot semicoke to the pyrolysis unit to be used as a heat source for pyrolysis;

the first cyclone separation unit is used for separating the first crude synthesis gas to obtain first fine coke powder and second crude synthesis gas carrying second fine coke powder;

the second cyclone separation unit is used for contacting the second crude synthesis gas with a solution of soluble salt containing active metal elements, performing second cyclone separation, depositing the soluble salt on the second fine coke powder and volatilizing the solvent to obtain a slurry bed hydrogenation catalyst and a third crude synthesis gas containing the solvent;

the slurry bed reaction unit is used for enabling the coal tar obtained by pyrolysis and optional heavy oil of a refinery to contact with the slurry bed hydrogenation catalyst and carry out hydrocracking reaction to obtain light distillate oil, tail oil and tailings, returning the tail oil to carry out the hydrocracking reaction, and sending the light distillate oil to the hydrofining unit;

the hydrofining unit is used for carrying out hydrofining reaction on the light distillate to obtain gasoline and/or diesel oil;

the second gasification reaction unit is used for mixing the fine coal powder, the phenol-containing wastewater, the first fine coke powder and the tailings to obtain a coke slurry, and performing a second gasification reaction on the coke slurry to obtain a fourth crude synthesis gas and ash.

14. The system of claim 13, wherein the pyrolysis unit comprises a pyrolysis furnace and an oil-gas separation device, the pyrolysis furnace is used for performing pyrolysis reaction on coal tar to obtain pyrolysis oil gas and pyrolysis coke, and the oil-gas separation device is used for performing oil-gas separation on the pyrolysis oil gas to obtain coal gas, coal tar and phenol-containing wastewater;

preferably, the slurry bed reaction unit comprises a slurry bed reactor and a hydrogenation tar separation device, the slurry bed reactor is used for carrying out the hydrocracking reaction to obtain hydrogenation tar, and the hydrogenation tar separation device is used for separating the hydrogenation tar to obtain light distillate oil, tail oil and tailings.

15. The system according to claim 13, wherein the first gasification reaction unit comprises a primary gasifier, which is a fluidized bed gasifier or a moving bed gasifier, preferably a fluidized bed gasifier.

16. The system of claim 13, wherein the second gasification reaction unit comprises a mixing device and a secondary gasifier, and the mixing device is used for mixing the fine coal powder, the phenolic wastewater, the first fine coke powder and the tailings to obtain a coke slurry; the secondary gasification furnace is used for carrying out a second gasification reaction on the coke slurry to obtain a fourth crude synthesis gas and ash;

preferably, the secondary gasification furnace is an entrained flow gasification furnace.

17. The system of claim 13, wherein the system further comprises:

and the raw synthesis gas conversion and purification unit is used for converting and purifying the fourth raw synthesis gas and optionally at least part of the third raw synthesis gas to obtain hydrogen, and returning at least part of the obtained hydrogen to the slurry bed reaction unit and/or the hydrofining unit to be used as a hydrogen source.

Technical Field

The invention relates to the technical field of low-rank coal graded conversion, in particular to a method for low-rank coal graded conversion and a system for low-rank coal graded conversion.

Background

China is a country with abundant coal resources, and in a long period of time in the future, coal still dominates the energy structure of China, wherein the storage amount of low-rank coal represented by lignite and low-rank bituminous coal accounts for about 55% of the total amount of the coal resources, so that the efficient utilization of the low-rank coal is important daily. However, low-rank coal has a low degree of coalification, a high water content, a low efficiency in direct combustion or gasification, and a large amount of pollutants and carbon emissions, and cannot fully utilize the resource value thereof, resulting in a great waste of coal resources. Therefore, the grading utilization of coal resources, especially low-rank coal resources, is considered to be an effective way for clean and efficient utilization of coal, and is also a key development direction of coal chemical industry in China.

In addition, with the rapid increase in economy, the demand of society for petroleum products is increasing day by day. The coal tar extracted by the coal grading conversion technology is hydrogenated to produce clean gasoline and diesel oil, which is beneficial to supplement of petroleum resources. The new environmental protection regulations put higher demands on the utilization and treatment of waste residues, waste water and hazardous wastes of refineries and chemical plants, so that the part of materials also face the difficult problems of harmless treatment and resource utilization.

The coal grading utilization poly-generation technology is one of the ways to realize the high-efficiency utilization of coal grading and quality grading, and various technologies are developed at present, and most of the technologies realize the pyrolysis and gasification of coal in the form of a fluidized bed or an entrained flow bed.

CN105154121A discloses a poly-generation system and method for low-rank coal grading utilization. The system comprises: the system comprises a raw material coal pyrolysis and dry distillation system and an entrained flow bed dry powder gasification system, wherein the pyrolysis and dry distillation system mainly generates tar, coal gas, semicoke and the like, the semicoke is ground and then enters the entrained flow bed dry powder gasification system, the synthesis gas generated after gasification is purified and converted to obtain hydrogen, and the hydrogen is used for producing oil products by tar hydrogenation. In the invention, the semicoke can enter the entrained flow bed dry powder gasification system after being ground, the equipment is seriously abraded and corroded due to the high hardness of the semicoke, and the utilization efficiency of coal is too low because the discharged part is pyrolysis ash slag with high carbon content.

CN106336906A discloses a system and a method for processing low-rank coal. The system comprises: 1) the pyrolysis unit is used for pyrolyzing the low-rank coal powder, filtering and cooling pyrolysis oil gas and separating an oil-water mixture; 2) the gas is subjected to desulfurization and decarburization treatment to obtain a product gas; 3) the sulfur recovery unit is used for recovering hydrogen sulfide in the acid gas obtained after desulfurization and decarburization, wherein the hydrogen sulfide is converted into elemental sulfur to be used as a pre-vulcanizing agent of the pyrolysis oil gas treatment unit; 4) the pyrolysis oil gas treatment unit is used for reacting a pre-vulcanizing agent, hydrogen, a catalyst and coal tar; 5) and the solid slag processing unit is used for processing solid slag and extracted coal to prepare the ferronickel alloy. In the invention, although the treatment of the low-rank coal leads the carbon conversion rate of the coal to be higher, the problems of complicated solid slag unit flow, high operation difficulty and the like exist.

Disclosure of Invention

The invention aims to provide a novel method for low-rank coal fractional conversion and a system for low-rank coal fractional conversion. The method and the system can realize the full conversion of the low-rank coal, can effectively improve the conversion rate of the low-rank coal and the utilization efficiency of the semicoke, and the whole system does not discharge hazardous solids and is environment-friendly.

According to a first aspect of the present invention, there is provided a method for low-rank coal staged conversion, the method comprising:

1) pretreating low-rank coal to obtain fine coal powder and coarse coal powder;

2) pyrolyzing the coarse coal powder to obtain coal tar, coal gas, pyrolysis coke and phenolic wastewater;

3) carrying out a first gasification reaction on the pyrolysis coke to obtain a first crude synthesis gas carrying fine coke powder and a hot semi-coke, and returning the hot semi-coke to the pyrolysis process to be used as a heat source for pyrolysis;

4) performing first cyclone separation on the first crude synthesis gas to obtain first fine coke powder and second crude synthesis gas carrying second fine coke powder;

5) contacting the second crude synthesis gas with a solution (namely, a catalyst solution) containing soluble salts of active metal elements, performing second cyclone separation, depositing the soluble salts on the second fine coke powder, and volatilizing the solvent to obtain a slurry bed hydrogenation catalyst and a third crude synthesis gas containing the solvent;

6) contacting the coal tar obtained by pyrolysis and optional heavy oil of a refinery with the slurry bed hydrogenation catalyst and carrying out hydrocracking reaction to obtain light distillate oil, tail oil and tailings, returning the tail oil to carry out the hydrocracking reaction, and carrying out hydrofining reaction on the light distillate oil to obtain diesel oil and/or gasoline;

7) and mixing the fine coal powder, the phenol-containing wastewater, the first fine coke powder and the tailings to obtain coke slurry, and performing a second gasification reaction on the coke slurry to obtain fourth crude synthesis gas and ash.

According to a second aspect of the present invention, there is provided a system for low-rank coal staged conversion, the system comprising: the system comprises a pretreatment unit, a pyrolysis unit, a first gasification reaction unit, a first cyclone separation unit, a second cyclone separation unit, a slurry bed reaction unit, a hydrofining unit and a second gasification reaction unit; wherein the content of the first and second substances,

the pretreatment unit is used for pretreating low-rank coal to obtain fine coal powder and coarse coal powder;

the pyrolysis unit is used for pyrolyzing the coarse coal powder to obtain coal tar, coal gas, pyrolysis coke and phenol-containing wastewater;

the first gasification reaction unit is used for carrying out first gasification reaction on the pyrolysis coke to obtain first crude synthesis gas carrying fine coke powder and hot semicoke, and returning the hot semicoke to the pyrolysis unit to be used as a heat source for pyrolysis;

the first cyclone separation unit is used for separating the first crude synthesis gas to obtain first fine coke powder and second crude synthesis gas carrying second fine coke powder;

the second cyclone separation unit is used for contacting the second crude synthesis gas with a solution of soluble salt containing active metal elements, performing second cyclone separation, depositing the soluble salt on the second fine coke powder and volatilizing the solvent to obtain a slurry bed hydrogenation catalyst and a third crude synthesis gas containing the solvent;

the slurry bed reaction unit is used for enabling the coal tar obtained by pyrolysis and optional heavy oil of a refinery to contact with the slurry bed hydrogenation catalyst and carry out hydrocracking reaction to obtain light distillate oil, tail oil and tailings, returning the tail oil to carry out the hydrocracking reaction, and sending the light distillate oil to the hydrofining unit;

the hydrofining unit is used for carrying out hydrofining reaction on the light distillate to obtain gasoline and/or diesel oil;

the second gasification reaction unit is used for mixing the fine coal powder, the phenol-containing wastewater, the first fine coke powder and the tailings to obtain a coke slurry, and performing a second gasification reaction on the coke slurry to obtain a fourth crude synthesis gas and ash.

Compared with the prior art, the method and the system of the invention realize the grading high-efficiency full conversion of the low-rank coal (the carbon conversion rate reaches more than 99.5 percent), can effectively extract the oil gas in the coal, and simultaneously solve the problem of resource utilization of hazardous wastes such as phenol-containing wastewater, hydrogenation tailings and the like in the pyrolysis process, particularly,

1) according to the invention, the crude coal powder obtained by pretreating the low-rank coal is pyrolyzed, so that the pyrolysis efficiency of the coal and the yield of pyrolysis oil gas are greatly improved; the phenol-containing wastewater obtained by pyrolysis oil-gas separation is used for preparing coke slurry, so that organic matters such as phenol and the like are decomposed into hydrogen and CO at high temperature, and the problem of resource utilization of the phenol-containing wastewater is solved;

2) the slurry bed hydrogenation catalyst takes fine coke powder generated by pyrolysis gasification as a carrier, and the preparation process of the catalyst and the separation process of the fine coke powder are carried out simultaneously, so that the coupling of preparation and separation is realized, the preparation process of the catalyst is simplified, the cost of the catalyst is reduced due to the reasonable utilization of the fine coke powder, and the utilization efficiency of coal resources is improved;

3) the invention can simultaneously treat various residual oil, tank bottom oil, heavy oil containing solid waste oil and the like in a refinery, and realize the deep coupling of the coal pyrolysis gasification technology and the oil refining technology;

4) in the system, the fine coke powder generated by the first gasification reaction unit has low gasification activity, and the phenol-containing wastewater and the hydrogenation tailings are added, so that the defect of low fine coke powder activity is overcome, and the stable operation of the second gasification reaction unit is ensured; in the second gasification reaction unit, the ash slag after high-temperature reaction is molten glass (liquid slag) and is discharged after being cooled, so that the environment is not polluted.

Drawings

FIG. 1 is a process flow diagram of a low-rank coal staged conversion method of the invention.

Description of the reference numerals

a: a coal bunker b: pyrolysis furnace

c: oil-gas separation equipment d: first-stage gasification furnace

e: primary cyclone separator f: two-stage cyclone separator

g: slurry bed reactor h: hydrogenation tar separation equipment

i: a mixing device j: two-stage gasification furnace

k: raw synthesis gas shift, purification unit 1: coarse coal powder

2: 3, fine coal powder: pyrolytic coke

4: and 5, pyrolysis oil gas: thermal semicoke

6: third raw synthesis gas 7: gas (es)

8: coal tar 9: phenol-containing wastewater

10: first raw synthesis gas 11: gasifying agent

12: second raw synthesis gas 13: first fine coke powder

14: catalyst solution 15: slurry bed hydrogenation catalyst

16: heavy oil from refinery 17: tail oil

18: hydrogen 19: hydrogenated tar

20: light distillate 21: tailings

22: gasifying agent 23: fourth crude synthesis gas

24: ash and slag

Detailed Description

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

According to a first aspect of the present invention, there is provided a method for low-rank coal staged conversion, the method comprising:

1) pretreating low-rank coal to obtain fine coal powder and coarse coal powder;

2) pyrolyzing the coarse coal powder to obtain coal tar, coal gas, pyrolysis coke and phenolic wastewater;

3) carrying out a first gasification reaction on the pyrolysis coke to obtain a first crude synthesis gas carrying fine coke powder and a hot semi-coke, and returning the hot semi-coke to the pyrolysis process to be used as a heat source for pyrolysis;

4) performing first cyclone separation on the first crude synthesis gas to obtain first fine coke powder and second crude synthesis gas carrying second fine coke powder;

5) contacting the second crude synthesis gas with a solution of soluble salt containing active metal elements, and performing second cyclone separation to deposit the soluble salt on the second fine coke powder and volatilize the solvent to obtain a slurry bed hydrogenation catalyst and a third crude synthesis gas containing the solvent;

6) contacting the coal tar obtained by pyrolysis and optional heavy oil of a refinery with the slurry bed hydrogenation catalyst and carrying out hydrocracking reaction to obtain light distillate oil, tail oil and tailings, returning the tail oil to carry out the hydrocracking reaction, and carrying out hydrofining reaction on the light distillate oil to obtain diesel oil and/or gasoline;

7) and mixing the fine coal powder, the phenol-containing wastewater, the first fine coke powder and the tailings to obtain coke slurry, and performing a second gasification reaction on the coke slurry to obtain fourth crude synthesis gas and ash.

In step 1), the method of pretreatment may include: and crushing and screening the low-rank coal to obtain the fine coal powder and the coarse coal powder.

In the present invention, "coarse" and "fine" are relative concepts, and specifically mean that the average particle size of the fine coal powder is smaller than that of the coarse coal powder, for example, when the particle size of the coarse coal powder is denoted as d, the particle size of the fine coal powder is smaller than d.

In the method, the granularity of the coarse coal powder can be 100-3000 mu m. Under the optimal condition, the particle size of the coarse coal powder is 150-1000 microns, so that the pyrolysis efficiency can be further improved, the operation difficulty can be reduced, and the pyrolysis oil gas dust carrying capacity caused by misoperation is reduced.

More preferably, the fine coal powder has a particle size of not more than 200 μm.

In the method of the present invention, the amount of the fine coal powder and the coarse coal powder may be determined specifically according to the grindability of the raw material coal, the operating conditions of the pyrolysis unit and the second gasification unit, and the like. Generally, the weight ratio of the fine coal powder to the coarse coal powder can be 1: 0.25-5, preferably 1: 1-4.

In step 2), the operating conditions of the pyrolysis can be selected with reference to the prior art. In the invention, the pyrolysis temperature is preferably 400-700 ℃, more preferably 450-600 ℃, and the pressure is 0.05-4 MPa.

The pyrolysis of the coarse coal fines may be carried out in a circulating fluidized bed or moving bed pyrolysis furnace as is conventional in the art. When the pyrolysis is carried out in a circulating fluidized bed, the method of the present invention may optionally further comprise returning at least a portion of the third raw syngas obtained from the subsequent second cyclone to the pyrolysis as a fluidizing medium.

It will be understood by those skilled in the art that the coarse coal fines undergo pyrolysis reactions to produce pyrolysis oil and gas and pyrolysis coke. The pyrolysis oil gas contains coal gas, phenol-containing wastewater and coal tar components; wherein the pyrolytic coke is a pyrolytic solid product, and the carbon content of the pyrolytic coke is 50-80 wt%. The pyrolysis oil gas is separated through oil-gas separation equipment to obtain the coal gas, the phenolic wastewater and the coal tar, and the separated coal tar usually contains the oil gas and carries dust.

In the step 2), the heat source adopted in the pyrolysis process is mainly provided by the hot semicoke obtained by the subsequent first gasification reaction. In addition, in addition to providing a heat source with the hot semicoke, it may also be provided by raw syngas.

In step 3), the gasifying agent used in the first gasification reaction can be selected according to the prior art, and is selected from water vapor and oxygen-containing gas, and the oxygen-containing gas can be oxygen or air. Preferably, the gasifying agent is water vapor and oxygen. Wherein, the volume ratio of the water vapor to the oxygen can be 1-20: 1, and the preferential ratio is 1-15: 1.

In step 3), the conditions of the first gasification reaction include: the temperature is 600-1000 ℃, preferably 700-950 ℃, and the pressure is 0.05-4 MPa, preferably 0.1-4 MPa. In the present invention, the pressure means gauge pressure.

In the step 3), the temperature of the hot semicoke obtained through the first gasification reaction is usually 550-950 ℃, and therefore, the hot semicoke can be used as a heat source for pyrolysis.

In the present invention, the first gasification reaction is performed in a primary gasification furnace, which may be selected from a fluidized bed gasification furnace or a moving bed gasification furnace, and is preferably a fluidized bed gasification furnace.

In step 4), the first cyclone separation is carried out in a primary cyclone separator. The present invention is not particularly limited with respect to the specific operating conditions of the primary cyclone separation, as long as at least a portion of the fine coke powder in the primary raw syngas, i.e., the primary fine coke powder, is separated. According to the principle of cyclone separation, the first fine coke powder has a larger particle size than the second fine coke powder.

Preferably, the average particle size of the first fine coke powder is 80-500 μm, and the average particle size of the second fine coke powder is 10-100 μm. More preferably, the average particle size of the first fine coke powder is 100-300 μm, and more preferably 100-200 μm; the average particle size of the second fine coke powder is 10-80 μm.

In the present invention, the average particle size of the fine coke powder means the particle size of 50% by weight of the fine coke powder, which is determined by the laser particle sizer method.

In step 5), the second cyclone separation is carried out in a secondary cyclone separator. And in the separation process, the soluble salt is deposited on the surface and the holes of the second fine coke powder, and simultaneously the solvent is volatilized to obtain a slurry bed hydrogenation catalyst and a third crude synthesis gas, wherein the slurry bed hydrogenation catalyst is discharged from the bottom of the separator, and the third crude synthesis gas is discharged from the upper part of the separator.

In the step 5), in order to promote the effective separation of the solvent and the catalyst, the temperature of the second cyclone separation is preferably 200-500 ℃.

In the catalyst solution, the active metal element refers to an active component of the slurry bed hydrogenation catalyst, and can be selected by referring to the existing hydrocracking reaction technology. In the present invention, the active metal element is preferably at least one selected from Fe, Ni, Mo, Co, and W, and more preferably Fe. The solvent is typically water. In the present invention, the soluble salt of iron is preferably at least one of ferrous sulfate, ferric nitrate and ferric sulfate. The concentration of the catalyst solution may be 5 to 60% by weight.

Preferably, the loading amount of the active metal element in terms of oxide is 2 to 50 wt% based on the total weight of the slurry bed hydrogenation catalyst. In the invention, the load capacity is calculated according to the feeding amount.

In the step 6), the hydrocracking reaction is carried out in a slurry bed reactor. In order to simultaneously realize the coupling with the oil refining technology, in the step 6), heavy oil of a refinery can be introduced to carry out the hydrocracking reaction together with the coal tar. Generally, the mass ratio of the coal tar to the heavy oil in the refinery can be 1: 0.01-5.

The heavy oil of the refinery is not particularly limited, and may be, for example, various kinds of atmospheric and vacuum residues, catalytic oil slurries, bottom oils, waste oils generated in the refinery, and the like.

The conditions of the hydrocracking reaction can be carried out with reference to the prior art. For the present invention, preferably, the hydrocracking reaction conditions include: the temperature is 360-480 ℃, and the preferable temperature is 380-450 ℃; the pressure is 10-20 MPa, and the preferable pressure is 12-16 MPa; the liquid hourly space velocity is 0.5-1.5 h^-1。

Preferably, the slurry bed hydrogenation catalyst is used in an amount of 0.1 to 10 wt%, and more preferably 0.15 to 8 wt%, based on the total weight of the slurry bed feed oil.

Herein, "slurry bed feed oil" refers to the raw oil subjected to the hydrocracking reaction, and when the raw oil is only the coal tar, the slurry bed feed oil refers to the coal tar; when the raw oil is the coal tar and the refinery heavy oil, the slurry bed feed oil refers to the coal tar and the refinery heavy oil.

It will be understood by those skilled in the art that the hydrocracking reaction produces hydrogenated tar, which is further cut to produce the light fraction oil and the heavy fraction oil, and the heavy fraction oil is filtered to produce the tail oil and the tailings. Typically, the oil content in the tailings is no greater than 50 wt%. And returning the tail oil to the slurry bed reactor to continue the hydrocracking reaction to obtain the light distillate oil. Preferably, the boiling point of the tail oil is more than 400 ℃, so that more light distillate oil can be obtained.

The specific process flow of the light distillate oil hydrofining to prepare diesel oil and/or gasoline in step 6) is well known in the art, and the invention is not particularly limited thereto. For example, the hydrorefining catalyst used is Ni, Mo, W as active metals. The catalyst is commercially available.

Typically, the hydrofinishing reaction conditions include: the hydrogen partial pressure is 8-20 MPa, preferably 10-18 MPa; the temperature is 340-420 ℃, and preferably 350-400 ℃; the volume ratio of the hydrogen to the oil is 600-1800; the hourly space velocity of the raw material liquid is 0.1-1.5 h^-1。

In the step 7), the fine coal powder, the phenol-containing wastewater, the first fine coke powder and the tailings are mixed in a stirring kettle to obtain the coke coal slurry. The second gasification reaction is carried out in a secondary gasifier, preferably an entrained flow gasifier. And the hot coal slurry enters the entrained-flow gasifier through a nozzle, and reacts with a gasifying agent to generate fourth crude synthesis gas and obtain ash. Preferably, the gasifying agents adopted by the second gasification reaction are water vapor and oxygen; the volume ratio of the water vapor to the oxygen is 1-20: 1. In addition, the gasifying agent may be selected with reference to the first gasification reaction.

In the step 7), the solid content of the coke coal slurry is preferably 55-68 wt%. In this step, it is possible to select whether or not to concentrate the phenol-containing wastewater before the mixing, according to the solid content required for the coking coal slurry.

In addition, in order to further reduce the ash content in the coke coal slurry and reduce the oxygen consumption and slow down the abrasion of the gasification furnace, it is further preferable that the content of the first fine coke powder in the coke coal slurry is not more than 40 wt%, and the content of the tailings is not more than 20 wt%.

In step 7), the temperature of the second gasification reaction can be determined according to the ash melting point of the ash of the coke slurry. For the present invention, preferably, the conditions of the second gasification reaction include: the temperature is 1200-1800 ℃ and the pressure is 0.5-8 MPa.

It should be understood by those skilled in the art that the ash is a molten liquid slag due to the high temperature of the second gasification reaction, forms a vitreous body after cooling, and thus has no pollution to the environment and can be used as an additive for building materials such as cement.

According to the method of the present invention, preferably, the method further comprises:

8) transforming and purifying the fourth raw synthesis gas and optionally at least part of the third raw synthesis gas to obtain hydrogen; returning at least part of the obtained hydrogen to the hydrocracking reaction and/or the hydrofining reaction to be used as a hydrogen source. In addition, the hydrogen can be used as chemical raw material gas. The methods of such transformation, purification and the specific implementation devices are well known in the art and will not be described in detail herein.

The invention realizes the deep coupling of the coal pyrolysis gasification technology and the clean fuel preparation technology, solves the difficult problems of grading high-efficiency utilization and clean conversion of low-rank coal resources, and has the characteristics of high coal conversion rate, good integration, low catalyst cost, no external discharge of dangerous and solid hazardous wastes and the like

According to a second aspect of the present invention, there is provided a system for low-rank coal staged conversion, the system comprising: the device comprises a pretreatment unit, a pyrolysis unit, a first gasification reaction unit, a first cyclone separation unit, a second cyclone separation unit, a slurry bed reaction unit, a hydrofining unit and a second gasification reaction unit.

The pretreatment unit is used for pretreating low-rank coal to obtain fine coal powder and coarse coal powder;

the pyrolysis unit is used for pyrolyzing the coarse coal powder to obtain coal tar, coal gas, pyrolysis coke and phenol-containing wastewater;

the first gasification reaction unit is used for carrying out first gasification reaction on the pyrolysis coke to obtain first crude synthesis gas carrying fine coke powder and hot semicoke, and returning the hot semicoke to the pyrolysis unit to be used as a heat source for pyrolysis;

the first cyclone separation unit is used for separating the first crude synthesis gas to obtain first fine coke powder and second crude synthesis gas carrying second fine coke powder;

the second cyclone separation unit is used for contacting the second crude synthesis gas with a solution of soluble salt containing active metal elements, performing second cyclone separation, depositing the soluble salt on the second fine coke powder and volatilizing the solvent to obtain a slurry bed hydrogenation catalyst and a third crude synthesis gas containing the solvent;

the slurry bed reaction unit is used for enabling the coal tar obtained by pyrolysis and optional heavy oil of a refinery to contact with the slurry bed hydrogenation catalyst and carry out hydrocracking reaction to obtain light distillate oil, tail oil and tailings, returning the tail oil to carry out the hydrocracking reaction, and sending the light distillate oil to the hydrofining unit;

the hydrofining unit is used for carrying out hydrofining reaction on the light distillate to obtain gasoline and/or diesel oil;

the second gasification reaction unit is used for mixing the fine coal powder, the phenol-containing wastewater, the first fine coke powder and the tailings to obtain a coke slurry, and performing a second gasification reaction on the coke slurry to obtain a fourth crude synthesis gas and ash.

In the system, the pyrolysis unit may include a pyrolysis furnace and an oil-gas separation device, the pyrolysis furnace is configured to perform a pyrolysis reaction on the coal tar to obtain pyrolysis oil gas and pyrolysis coke, and the oil-gas separation device is configured to separate the pyrolysis oil gas to obtain coal gas, coal tar and phenol-containing wastewater.

The pyrolysis furnace may be selected from a circulating fluidized bed or moving bed pyrolysis furnace.

The oil-gas separation equipment is not particularly limited, and only the separation effect can be achieved, and the oil-gas separation equipment can be a water washing tower, an oil washing tower and the like.

In the system of the present invention, the first gasification reaction unit includes a primary gasification furnace. The primary gasifier may be selected from a fluidized bed gasifier or a moving bed gasifier, preferably a fluidized bed gasifier.

In the system of the present invention, the first cyclone separation unit comprises a primary cyclone separator, and the second cyclone separation unit comprises a secondary cyclone separator. When the pyrolysis furnace is a circulating fluidized bed pyrolysis furnace, the second cyclone separation unit is further configured to return at least part of the third raw syngas to the pyrolysis unit as a fluidizing medium.

In the system, the slurry bed reaction unit comprises a slurry bed reactor and a hydrogenation tar separation device, the slurry bed reactor is used for carrying out the hydrocracking reaction to obtain hydrogenation tar, and the hydrogenation tar separation device is used for separating the hydrogenation tar to obtain light distillate oil, tail oil and tailings.

The hydrogenated tar separation apparatus of the present invention is not particularly limited as long as the above separation effect can be achieved, and is selected from, for example, an atmospheric and vacuum distillation apparatus, a solvent extraction apparatus, and the like.

In the system, the second gasification reaction unit comprises a mixing device and a secondary gasification furnace, wherein the mixing device is used for mixing the fine coal powder, the phenolic wastewater, the first fine coke powder and the tailings to obtain the coke coal slurry. The secondary gasification furnace is used for carrying out a second gasification reaction on the coke coal slurry to obtain a fourth crude synthesis gas and liquid slag, and is preferably an entrained flow gasification furnace. Such as stirred tanks, liquid-solid mixers, etc.

According to the system of the present invention, preferably, the system further comprises: and a crude synthesis gas conversion and purification unit.

And the raw synthesis gas conversion and purification unit is used for converting and purifying the fourth raw synthesis gas and optionally at least part of the third raw synthesis gas to obtain hydrogen, and returning at least part of the obtained hydrogen to the slurry bed reaction unit and/or the hydrofining unit to be used as a hydrogen source. Such raw synthesis gas shift, purification units are well known in the art and will not be described in detail herein.

Additionally, the method of the first aspect of the invention may be implemented in a system of the second aspect of the invention. According to a preferred embodiment, the present invention provides a process route shown in fig. 1 for the fractional conversion of low rank coal, as follows:

1) crushing and screening low-rank coal in a coal bunker a to obtain coarse coal powder 1 and fine coal powder 2;

2) pyrolyzing the coarse coal powder 1 by a pyrolysis furnace b to obtain pyrolysis coke 3 and pyrolysis oil gas 4, and separating the pyrolysis oil gas 4 by an oil-gas separation device c to obtain coal gas 7, coal tar 8 and phenol-containing wastewater 9;

3) the pyrolysis coke 3 enters a first-stage gasification furnace d and is subjected to a first gasification reaction with a gasification agent 11 to obtain first crude synthesis gas 10 carrying fine coke powder and hot semicoke 5, and the hot semicoke 5 is sent into a pyrolysis furnace b to provide a heat source for pyrolysis of the crude coal powder;

4) the first crude synthesis gas 10 enters a primary cyclone separator e for separation to obtain first fine coke powder 13 and second crude synthesis gas 12 carrying second fine coke powder;

5) the second crude synthesis gas 12 enters a secondary cyclone separator f, contacts with a catalyst solution 14 and is subjected to solvent separation, and a slurry bed hydrogenation catalyst 15 is obtained at the bottom of the separator;

6) the slurry bed hydrogenation catalyst 15, coal tar 8 and optional heavy oil 16 enter a slurry bed reactor g for hydrocracking reaction, the obtained hydrogenated tar 19 is cut by hydrogenated tar separation equipment h to obtain light distillate oil 20 and heavy distillate oil, the heavy distillate oil is filtered to obtain tail oil 17 and tailings 21, and the tail oil 17 returns to the slurry bed reactor g for hydrocracking reaction; the light distillate oil 20 enters a hydrofining unit to carry out hydrofining reaction to obtain gasoline and/or diesel oil;

7) mixing the fine coal powder 2, the phenol-containing wastewater 9, the first fine coke powder 13 and the tailings 21 in a mixing device i to obtain coke slurry; the coke slurry enters a secondary gasification furnace j, and is subjected to a second gasification reaction with a gasification agent 22 to obtain a fourth crude synthesis gas 23 and ash 24;

8) and (3) performing conversion and purification on the fourth raw synthesis gas 23 through a raw synthesis gas conversion and purification unit k to obtain hydrogen 18, and returning part of the hydrogen 18 to the slurry bed reactor g to serve as a hydrogen source.

The third raw synthesis gas 6 can be at least partially returned to the pyrolysis furnace b for use as a fluidizing medium, and can also be at least partially mixed with the fourth raw synthesis gas 23 to be shifted and purified by a raw synthesis gas shift and purification unit k. In addition, fly ash is preferentially removed before the conversion and purification.

The system can realize the grading full conversion of the low-rank coal, avoid the discharge of waste residues and phenol-containing wastewater and realize the resource utilization of the waste residues and phenol-containing wastewater.

The present invention will be described in detail below by way of examples.

In the following examples and comparative examples,

the treated low-rank coal is lignite, and the pretreatment process comprises the following steps: the brown coal is crushed and sieved into fine coal powder with the granularity of less than 150 mu m and coarse coal powder with the granularity of 150-1000 mu m, and the mass ratio of the fine coal powder to the coarse coal powder is 3: 7. The results of the compositional analysis of the two types of pulverized coal are shown in Table 1, wherein M is_adDenotes the water content, A_dRepresents ash content, V_dafDenotes volatiles, wherein the subscript ad denotes an air drying base, d denotes a drying base, daf denotes a dry ashless base, F_CdRepresents fixed carbon.

The heavy oil subjected to hydrocracking together with coal tar is atmospheric residue and catalytic cracking slurry oil, and the respective properties are shown in table 2.

By the carbon conversion rate of raw material coal, the yield of light distillate oil, the yield of waste residue and 1000Nm³The coal consumption of the syngas reflects the effect of the present invention and the results are shown in table 3.

The waste residue refers to solids discharged outside the whole system, and comprises oil-containing tailings discharged outside the slurry bed reactor, fly ash removed before the synthesis gas is purified, and ash generated by the second gasification furnace.

The waste residue yield refers to the percentage of the weight of the waste residue in the whole system in the weight of the raw material coal;

wherein the carbon conversion rate of the raw material coal is calculated according to the following formula:

the carbon conversion rate of the raw material coal is (1-weight of carbon in the waste residue/weight of carbon in the raw material coal) x 100%;

the yield of the light distillate oil is the percentage of the weight of the light distillate oil in the sum of the weight of the coal tar and the weight of the heavy oil;

1000Nm³the coal consumption of the synthesis gas means 1000Nm generated by the secondary gasification furnace³Raw synthesis gas weight of raw coal consumed.

TABLE 1

TABLE 2

The following examples are all combined with FIG. 1 to illustrate the low rank coal staged conversion process and system of the present invention. The pyrolysis furnace is a circulating fluidized bed pyrolysis furnace, the first-stage gasification furnace is a fluidized bed gasification furnace, and the second-stage gasification furnace is an entrained flow gasification furnace.