Method for mild liquefaction quality-divided conversion of low-rank coal in non-hydrogen atmosphere

Abstract

The invention relates to the technical field of clean and efficient utilization of coal, and discloses a method for mild liquefaction quality-divided conversion of low-rank coal in a non-hydrogen atmosphere, which comprises the following steps: S1, pretreatment of a coal sample: after naturally drying the low-rank coal sample in air for 45-50 hours, crushing the low-rank coal sample by using a crusher, the method comprises the following steps of: selecting the low-rank coal as a raw material, screening by using a screening assembly until the particle size is less than 75 microns, crushing, putting into a sealing bag, and putting into a dryer for later use. Aiming at the process properties of the low-rank coal, on the basis of deeply analyzing the physical and chemical processes and behaviors of direct coal liquefaction, researching a mild liquefaction quality-divided conversion method of the low-rank coal in a non-hydrogen atmosphere; the method has the advantages that the method is simple and easy to operate, sufficient conversion of easily-reacted components in the coal is achieved, improvement of the yield of limited light component oil gas under severe conditions is not pursued, more attention can be paid to preparation of asphaltene of high-added-value carbon materials and heavy components such as coal liquefaction residues with high caking property, a brand-new way is provided for quality-divided conversion of low-rank coal, and the method is worthy of popularization and application. Meanwhile, high-efficiency clean low-carbon utilization of the low-rank coal is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of clean and efficient utilization of coal, and in particular to a method for mild liquefaction and fractionation conversion of low-rank coal in a non-hydrogen atmosphere. Background Art

[0002] In the next few decades, coal will still dominate the energy structure. Low-rank coal resources are relatively abundant, but due to many inherent deficiencies (such as high water content and lack of adhesion, etc.), they have not been fully developed and utilized. They are generally used for combustion, which not only causes environmental pollution and high carbon emissions due to direct combustion, but also causes waste of this precious resource. Therefore, it is of great significance to develop clean and efficient coal conversion technology.

[0003] Coal fractionation and utilization technology is a hot topic for achieving large-scale clean and efficient coal conversion today. Low-rank coal has high chemical activity and strong reactivity, and most of them have the characteristics of low ash and low sulfur. If low-rank coal is fractionated and converted, the different chemical structures in the coal are converted into heavy components and light components respectively, and further converted into chemicals and high-tech carbon materials. This is an important direction for achieving efficient conversion of low-rank coal. At present, the methods for efficient utilization of low-rank coal mainly include liquefaction, gasification and pyrolysis. Direct liquefaction usually converts coal into oil and gas compounds under high temperature (>400℃) and high initial hydrogen reaction pressure (>10MPa). The operating conditions are relatively harsh, and the solid-liquid separation methods such as vacuum distillation are not effective. The utilization rate of liquefied residue is low and the economic benefits are not high.

[0004] At present, the research on coal liquefaction catalysts under non-hydrogen atmosphere (N2, CH4, CO, CO+H2O) is still in its infancy, and there are still many problems to be solved. The present invention reduces the process cost by adjusting the coal liquefaction reaction conditions (lowering the coal liquefaction reaction temperature and pressure), selecting a suitable iron-based catalyst and changing the reaction atmosphere, and converts low-rank coal into three-phase products with high added value, gas, liquid (crude oil), and solid (asphaltene, liquefied residue) under mild liquefaction conditions. Crude oil can be refined to obtain about 1 million tons of automotive fuel and chemical products; asphaltene is used as an intermediate phase raw material to prepare about 500,000 tons of advanced carbon materials (needle coke, thermal insulation / thermal conductivity carbon or carbon fiber, etc.). These products, especially automotive oil and advanced carbon materials such as needle coke, thermal insulation / thermal conductivity carbon or carbon fiber, are in short supply in the market and have a large profit margin. In addition, by gently liquefying, modifying, improving the quality and increasing the viscosity of low-rank coal, it can be used for coal blending for coking or preparing carbonized coke. This can not only make up for the shortage of cementitious coal resources in my country, but also achieve clean, efficient and low-carbon utilization of huge low-rank coal resources and improve the added value and resource utilization rate of low-rank coal. To this end, a method for mild liquefaction and quality-differentiation conversion of low-rank coal in a non-hydrogen atmosphere is proposed. Summary of the invention

[0005] The object of the present invention is to provide a method for mild liquefaction and fractionation conversion of low-rank coal in a non-hydrogen atmosphere to solve the problems raised in the above-mentioned background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for mild liquefaction and fractionation conversion of low-rank coal in a non-hydrogen atmosphere, comprising the following steps:

[0007] S1. Pretreatment of coal samples: After the low-rank coal samples are naturally dried in the air for 45-50 hours, they are crushed using a crusher and sieved using a screening component to a particle size of less than 75 μm. After crushing, they are packed into sealed bags and placed in a dryer for standby use;

[0008] S2, mild liquefaction experiment, take 10-20g of pretreated coal powder, iron-based catalyst and hydrogen supply solvent and add them into the reactor, the initial pressure of the atmosphere in the reactor is 2.0-4.0MPa, the reaction temperature is 300-400℃, and the constant temperature reaction is carried out for 30-60 minutes. After the reaction is completed, the reactor is cooled to below 35℃, the inner wall of the reactor is cleaned with a cleaning component, and the gas product and solid-liquid mixture obtained by the mild liquefaction reaction are collected;

[0009] S3, separation of solid and liquid products, subjecting the solid-liquid mixture after the reaction to graded extraction to obtain liquefied oil, asphaltene and residual coal respectively.

[0010] Preferably, in S1 above, the iron-based catalyst is selected from at least one of ferrous sulfide, iron powder, iron oxide, and ferrous sulfate, and accounts for 1-3% of the mass percentage of the coal sample.

[0011] Preferably, in S2, the hydrogen supply solvent is selected from at least one of methylnaphthalene, tetralin, phenol, dihydrophenanthrene, and dihydroanthracene, and the ratio of the coal sample to the hydrogen supply solvent is controlled at 1:1-4;

[0012] The atmosphere is one of methane or nitrogen.

[0013] Preferably, in S3, the liquefied oil is a n-hexane soluble matter, the asphaltenes are a tetrahydrofuran soluble matter, and the residual coal is a tetrahydrofuran insoluble matter.

[0014] Preferably, in S3, the following sub-steps are included:

[0015] S301, taking out the solid-liquid mixture after the reaction and filtering it, transferring the product on the filter paper to a filter paper tube after filtering, placing it in a Soxhlet extractor, extracting it with n-hexane, receiving the filtrate in a 500 mL flask, and extracting until the reflux liquid is substantially colorless;

[0016] S302, taking out the filter paper tube from the Soxhlet extraction tube, putting it into a vacuum drying oven at 45°C and drying it for 8 hours, taking it out, cooling it to room temperature and then weighing it, while rotary evaporating to recover n-hexane and collecting n-hexane solubles;

[0017] S303, placing the weighed filter paper tube into a Soxhlet extractor and extracting with tetrahydrofuran until the reflux liquid is substantially colorless, the time is 45-50 hours, taking out the filter paper tube, drying and weighing, recovering tetrahydrofuran by rotary evaporation, and collecting the tetrahydrofuran soluble matter and the tetrahydrofuran insoluble matter in the filter paper tube.

[0018] Preferably, the screening assembly comprises a support frame and a first motor, a reciprocating screw is fixed to the output shaft end of the first motor, a support plate is threadedly connected to the outer side of the reciprocating screw, a cross plate is fixed to the top of the support frame, and a screen is installed at the bottom of the inner wall of the cross plate.

[0019] Preferably, a brush plate slidably connected to the top of the screen is fixed at the bottom of the support plate, a plurality of bristles are fixedly inserted into the bottom of the brush plate, and a sliding column is movably penetrated at one side of the support plate.

[0020] Preferably, a baffle is fixed on the top of the support frame, discharge holes are opened on both sides of the baffle, a recovery box located on the lower side of the screen is inserted into one side of the support frame, one side of the first motor and the sliding column is fixed to the top side of the baffle, and one end of the reciprocating screw rod is rotatably connected to the top side of the baffle through a bearing;

[0021] A feeding pipe is provided on the top of the screen, and the feeding end of the feeding pipe is connected to the discharging end of the crusher. Preferably, the cleaning component comprises a second motor, a rotating shaft is fixed to the output shaft end of the second motor, and a plurality of stirring blades are fixed to the outer side of the rotating shaft;

[0022] A first connecting rod is fixed to the top of the outer side of the stirring blade, a second connecting rod is fixed to one side of the bottom of the first connecting rod, and a scraper slidably connected to the inner wall of the reactor is fixed to one side of the second connecting rod.

[0023] Preferably, a feeding pipe is provided at the top of the reactor, a discharge pipe is provided at the bottom of the reactor, the bottom of the second motor is fixed at the top center of the reactor, and the outer side of the rotating shaft is rotatably connected to the top side of the reactor through a sealed bearing.

[0024] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects:

[0025] 1. Experimental data show that in the mild liquefaction reaction of low-rank coal, when methane or nitrogen is used as the reaction atmosphere, the coal conversion rate, oil and gas yield and asphaltene yield are all higher than those in the hydrogen atmosphere. Therefore, the coal liquefaction process under the non-hydrogen atmosphere reduces the use of hydrogen, thereby reducing the environmental pollution problems that may be generated in the hydrogen preparation process, such as waste gas and wastewater. At the same time, through the efficient use of coal resources, the pollutant emissions generated by the direct combustion of coal are also reduced. Compared with the traditional hydrogen atmosphere coal liquefaction technology, this technical solution does not require complex hydrogen preparation and purification equipment. Through steps such as graded extraction, it realizes the effective separation of coal liquefaction products, obtains valuable products such as liquefied oil, asphaltene and residual coal, and improves resource utilization.

[0026] 2. The present invention targets the technological properties of low-rank coal. Based on an in-depth analysis of the physical and chemical processes and behaviors of direct coal liquefaction, the present invention studies the method of mild liquefaction and fractionation of low-rank coal in a non-hydrogen atmosphere, thereby achieving full conversion of the easily reactive components in the coal. Instead of blindly pursuing the improvement of the oil and gas yield of limited light components under harsh conditions, the present invention can focus more on heavy components such as asphaltene for preparing high value-added carbon materials and coal liquefaction residue with high adhesion, thus providing a new way for the fractionation and fractionation of low-rank coal and achieving efficient, clean and low-carbon utilization of low-rank coal. The present invention not only has significant economic benefits, but also has good social benefits and has a good application prospect.

[0027] 3. The reciprocating screw is driven by the first motor to rotate, thereby driving the support plate and the brush plate to move on the top of the screen, thereby cleaning the screen. The brush plate not only cleans the coal powder residue on the screen, but also pushes the larger coal powder to the discharge holes on both sides of the baffle through the action of the baffle bristles. The staff can easily collect the coal powder and crush it again, thereby improving the utilization rate of the coal powder and the overall processing efficiency.

[0028] 4. The output shaft of the second motor drives the rotating shaft to rotate, and the rotating shaft drives the first connecting rod, the second connecting rod and the scraper to rotate. At this time, the scraper scrapes off the residual material on the inner wall of the reactor. The scraper can effectively scrape off the residual material on the inner wall of the reactor, avoiding material waste and preventing safety accidents caused by long-term accumulation of materials. The scraper can timely remove these residues to reduce safety risks and ensure the smooth progress of the production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 This is a flow chart of separation and extraction of coal liquefaction products of the present invention;

[0031] Figure 2 It is a structural schematic diagram of the recycling box of the present invention;

[0032] Figure 3 It is a schematic diagram of the structure of the screen of the present invention;

[0033] Figure 4 It is a structural schematic diagram of the brush plate of the present invention;

[0034] Figure 5 It is a schematic diagram of the appearance structure of the reactor of the present invention;

[0035] Figure 6 It is a schematic diagram of the structure of the stirring blade of the present invention;

[0036] Figure 7 It is a schematic diagram of the scraper structure of the present invention.

[0037] Explanation of the reference numerals: 101, support frame; 102, recovery box; 103, cross plate; 104, baffle; 105, sliding column; 106, screen; 107, support plate; 108, reciprocating screw; 109, first motor; 110, discharge hole; 111, brush plate; 2, feed pipe; 301, discharge pipe; 302, first connecting rod; 303, second motor; 304, feeding pipe; 305, rotating shaft; 306, stirring blade; 307, second connecting rod; 308, scraper; 4, reactor. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the conditions under which this application can be implemented. Therefore, they have no substantive technical significance. Any structural modification, change in proportional relationship or adjustment of size should still fall within the scope of the technical content disclosed in this application without affecting the effects and purposes that can be achieved by this application.

[0040] Embodiment 1

[0041] See also Figure 1-7The present invention provides a technical solution: a method for mild liquefaction and fractionation conversion of low-rank coal in a non-hydrogen atmosphere, comprising the following steps:

[0042] S1. Pretreatment of coal samples: After the low-rank coal samples are naturally dried in the air for 48 hours, they are crushed using a crusher and sieved using a screening component to a particle size of less than 75 μm. After crushing, they are packed into sealed bags and placed in a dryer for standby use;

[0043] In S1, the iron-based catalyst is selected from at least one of ferrous sulfide, iron powder, iron oxide, and ferrous sulfate, and accounts for 1-3% of the mass percentage of the coal sample.

[0044] S2, mild liquefaction experiment, take 10-20g of pretreated coal powder, iron-based catalyst and hydrogen supply solvent and add them into reactor 4, the initial pressure of the atmosphere in reactor 4 is 2.0-4.0MPa, the reaction temperature is 300-400℃, and the constant temperature reaction is carried out for 30-60 minutes. After the reaction is completed, reactor 4 is cooled to below 35℃, and the inner wall of reactor 4 is cleaned with a cleaning component, and the gas product and solid-liquid mixture obtained by the mild liquefaction reaction are collected at the same time;

[0045] The hydrogen supply solvent is selected from at least one of methylnaphthalene, tetralin, phenol, dihydrophenanthrene and dihydroanthracene, and the ratio of the coal sample to the hydrogen supply solvent is controlled at 1:1-4; the atmosphere is one of methane or nitrogen.

[0046] S3, separation of solid-liquid products, the solid-liquid mixture after the reaction is subjected to graded extraction to obtain liquefied oil, asphaltene and residual coal respectively. After the reaction is completed, the gas product is collected using an aluminum foil gas sampling bag and analyzed by gas chromatography; the solid-liquid mixture is extracted and separated using a Soxhlet extractor with a volume of 250 mL.

[0047] The following sub-steps are included:

[0048] S301, taking out the solid-liquid mixture after the reaction and filtering it, transferring the product on the filter paper to a filter paper tube after filtering, placing it in a Soxhlet extractor, extracting it with n-hexane, receiving the filtrate in a 500 mL flask, and extracting until the reflux liquid is substantially colorless;

[0049] S302, taking out the filter paper tube from the Soxhlet extraction tube, putting it into a vacuum drying oven at 45°C and drying it for 8 hours, taking it out, cooling it to room temperature and then weighing it, while rotary evaporating to recover n-hexane and collecting n-hexane solubles;

[0050] S303, placing the weighed filter paper tube into a Soxhlet extractor and extracting with tetrahydrofuran until the reflux liquid is substantially colorless, the time is 45-50 hours, taking out the filter paper tube, drying and weighing, recovering tetrahydrofuran by rotary evaporation, and collecting the tetrahydrofuran soluble matter and the tetrahydrofuran insoluble matter in the filter paper tube.

[0051] Liquefied oil is n-hexane soluble, asphaltene is tetrahydrofuran soluble, and residual coal is tetrahydrofuran insoluble.

[0052] The screening assembly includes a support frame 101 and a first motor 109. A reciprocating screw 108 is fixed to the output shaft end of the first motor 109. The outer side of the reciprocating screw 108 is threadedly connected to a support plate 107. A cross plate 103 is fixed to the top of the support frame 101. A screen 106 is installed at the bottom of the inner wall of the cross plate 103. The first motor 109 drives the reciprocating screw 108 to rotate, thereby driving the support plate 107 and the brush plate 111 to move on the top of the screen 106, thereby realizing the cleaning of the screen 106. The brush plate 111 not only cleans the coal powder residue on the screen 106;

[0053] The screen 106 is a 200-mesh standard screen. A brush plate 111 slidably connected to the top of the screen 106 is fixed at the bottom of the support plate 107. A number of bristles are fixedly inserted at the bottom of the brush plate 111. A sliding column 105 is movably penetrated on one side of the support plate 107. A baffle 104 is fixed on the top of the support frame 101. Discharge holes 110 are provided on both sides of the baffle 104. The staff will remove the coal powder that has been brushed to one side of the discharge hole 110, and then crush the larger coal powder again. A recovery box 102 located on the lower side of the screen 106 is inserted on one side of the support frame 101. The first motor 109 and one side of the sliding column 105 are fixed to the top side of the baffle 104. One end of the reciprocating screw 108 is rotatably connected to the top side of the baffle 104 through a bearing.

[0054] A feed pipe 2 is provided on the top of the screen 106 , the feed end of the feed pipe 2 is connected to the discharge end of the crusher, and the discharge end of the feed pipe 2 is located at the center of the screen 106 .

[0055] When the crushed coal powder is conveyed to the inner side of the baffle 104 through the feeding pipe 2 and filtered by the screen 106, the coal powder that meets the requirements passes through the screen 106 and falls into the inner side of the recovery box 102. A switch (not shown in the figure) is installed on one side of the support frame 101. Pressing the switch controls the output shaft of the first motor 109 to drive the reciprocating screw 108 to rotate. At this time, the reciprocating screw 108 is threadedly connected with the support plate 107, so that the support plate 107 moves on the top of the screen 106 along the sliding column 105. At this time, the brush plate 111 brushes the coal powder remaining on the top of the screen 106, so that the coal powder with a size less than 75 μm passes through the screen 106, and the coal powder with a larger size is brushed on the bottom plate of the brush plate 111. Under the action of the bristles, the coal powder is pushed to the discharge holes 110 on both sides of the baffle 104. At this time, the staff will remove the coal powder brushed to one side of the discharge hole 110, and then crush the larger coal powder again. The reciprocating screw rod 108 is driven to rotate by the first motor 109, thereby driving the support plate 107 and the brush plate 111 to move on the top of the screen 106, so that the screen 106 is cleaned. The brush plate 111 not only cleans the coal powder residue on the screen 106, but also pushes the larger coal powder to the discharge holes 110 on both sides of the baffle 104 through the action of the bristles. The staff can easily collect the coal powder and crush it again, thereby improving the utilization rate of the coal powder and the overall processing efficiency;

[0056] The cleaning component includes a second motor 303, a rotating shaft 305 is fixed to the output shaft end of the second motor 303, and a plurality of stirring blades 306 are fixed to the outside of the rotating shaft 305; a first connecting rod 302 is fixed to the top of the outside of the stirring blade 306, a second connecting rod 307 is fixed to one side of the bottom of the first connecting rod 302, and a scraper 308 slidably connected to the inner wall of the reactor 4 is fixed to one side of the second connecting rod 307; a feeding pipe 304 is provided on the top of the reactor 4, and the feeding pipe 304 is used to add raw materials to the reactor 4; a discharge pipe 301 is provided at the bottom of the reactor 4, and the discharge pipe 301 is used to discharge the reacted materials; the bottom of the second motor 303 is fixed to the top center of the reactor 4, and the outside of the rotating shaft 305 is rotatably connected to the top side of the reactor 4 through a sealed bearing.

[0057] After the discharge pipe 301 of the reactor 4 discharges the gaseous product and the solid-liquid mixture obtained by the mild liquefaction reaction, the second motor 303 is started, and the output shaft of the second motor 303 drives the rotating shaft 305 to rotate, and the rotating shaft 305 drives the first connecting rod 302, the second connecting rod 307 and the scraper 308 to rotate. At this time, the scraper 308 scrapes off the material remaining on the inner wall of the reactor 4 to prevent the gaseous product and the solid-liquid mixture obtained by the liquefaction reaction from remaining on the inner wall of the reactor 4. The scraper 308 can effectively scrape off the material remaining on the inner wall of the reactor 4 to ensure that these materials are completely discharged, thereby avoiding material waste and preventing safety accidents caused by materials after long-term accumulation. The scraper 308 can timely remove these residues, which can reduce safety risks and ensure the smooth progress of the production process.

[0058] Weigh 15g of dry coal powder, 3g of iron oxide, and 30mL of tetralin into a magnetic stirring reactor 4. After checking the airtightness, repeatedly flush 3MPa of nitrogen into the reactor to exhaust the air in the reactor and use it as a reaction atmosphere. Set the heating program to react at 350°C for 30min. After the temperature in the reactor drops below 35°C, collect the gas in the reactor with an air bag for later use. Then open the reactor 4 to collect liquid and solid products. According to the solubility and polarity of the coal liquefaction products, the coal liquefaction products are gradually separated to obtain asphaltene and coal residue. At this time, the low-rank coal conversion rate is 64.74%, the asphaltene yield is 41.17%, and the oil and gas yield is 23.57%.

[0059] Embodiment 2

[0060] This embodiment is different from the first embodiment in that:

[0061] Weigh 15g dry coal powder, 3g iron oxide, and 30mL tetralin into a magnetic stirring reactor 4. After checking the air tightness, repeatedly flush 3MPa nitrogen into the reactor to exhaust the air in the reactor, and then use the reaction gas methane to exhaust the nitrogen in the same way. Set the temperature program to react at 350℃ for 30min. After the temperature in the reactor drops below 35℃, collect the gas in the reactor with an air bag for standby use, then open the reactor 4 to collect liquid and solid products. According to the solubility and polarity of the coal liquefaction products, the coal liquefaction products are gradually separated to obtain asphaltene and coal residue. The conversion rate of low-rank coal is 58.12%, the asphaltene yield is 38.23%, and the oil and gas yield is 19.89%.

[0062] Comparative Example

[0063] Weigh 15g dry coal powder, 3g iron oxide, and 30mL tetralin into a magnetic stirring reactor 4. After checking the air tightness, repeatedly flush 3MPa nitrogen into the reactor to exhaust the air in the reactor, and then use the reaction gas hydrogen to exhaust the nitrogen in the same way. Set the temperature program to react at 350℃ for 30min. After the temperature in the reactor drops below 35℃, collect the gas in the reactor with an air bag for standby use, then open the reactor 4 to collect liquid and solid products. According to the solubility and polarity of the coal liquefaction products, the coal liquefaction products are gradually separated to obtain asphaltene and coal residue. The conversion rate of low-rank coal is 49.17%, the asphaltene yield is 40.24%, and the oil and gas yield is 8.93%.

[0064] The coal conversion rate and product yield of Example 1, Example 2 and Comparative Example are summarized as follows:

[0065]

[0066] Through the data analysis of the examples and comparative examples, the conversion rate, oil and gas yield and asphaltene yield of low-rank coal in a methane and nitrogen atmosphere, an initial pressure of 2.0-4.0 MPa, a reaction temperature of 300-400°C, and a mild liquefaction reaction system are all higher than those in a hydrogen reaction atmosphere. In the coal liquefaction reaction process, the catalyst, hydrogen supply solvent and coal are in the liquefaction system, and there is a synergistic effect between the hydrogen supply solvent and the catalyst.

[0067] After low-rank coal is thermally cracked, the hydrogen free radicals generated by the hydrogen-donating solvent are stable, and the weak bonds and some bridge bonds of the coal dissolved in the solvent begin to break. The iron-based catalyst also promotes the breaking of chemical bonds in the coal. Tetralin produces hydrogen during the liquefaction process. Part of the hydrogen combines with free radical fragments to produce oil, gas, asphaltene and other substances, and the other part forms hydrogen. In the nitrogen and methane atmosphere, the sources of hydrogen in the coal liquefaction process are mainly the active hydrogen generated by the cracking of the coal itself and the active hydrogen generated by the conversion of the hydrogen-donating solvent into naphthalene. Among them, the amount of active hydrogen generated by the coal itself is relatively small, and the hydrogen is mainly provided by tetralin.

[0068] The addition of Fe2O3 catalyst promotes the dehydrogenation reaction of tetralin during coal liquefaction, improves the conversion rate of tetralin, and increases the amount of active hydrogen in the liquefaction system. A part of it is used to stabilize the free radical fragments produced by thermal cracking of coal to produce oil, gas, asphaltene and other substances, and the remaining hydrogen combines to generate hydrogen. Therefore, under mild liquefaction reaction conditions for low-rank coal, non-hydrogen atmosphere can completely replace the expensive hydrogen as the reaction atmosphere.

[0069] In summary, the above experimental data show that in the mild liquefaction reaction of low-rank coal, when methane or nitrogen is used as the reaction atmosphere, the coal conversion rate, oil and gas yield and asphaltene yield are all higher than those in the hydrogen atmosphere. The coal liquefaction process under the non-hydrogen atmosphere reduces the use of hydrogen, thereby reducing the environmental pollution problems that may be generated in the hydrogen preparation process, such as waste gas and wastewater. At the same time, through the efficient use of coal resources, the pollutant emissions generated by the direct combustion of coal are also reduced. Compared with the traditional hydrogen atmosphere coal liquefaction technology, this technical solution does not require complex hydrogen preparation and purification equipment. Through steps such as graded extraction, it realizes the effective separation of coal liquefaction products, and obtains valuable products such as liquefied oil, asphaltene and residual coal, thereby improving resource utilization.

[0070] It will be appreciated by those skilled in the art that the features described in the various embodiments and / or claims of the present invention may be combined and / or combined in various ways, even if such combinations and / or combinations are not explicitly described in the present invention. In particular, the features described in the various embodiments and / or claims of the present invention may be combined and / or combined in various ways without departing from the spirit and teachings of the present invention. All of these combinations and / or combinations fall within the scope of the present invention.

Claims

1. A method for mild liquefaction and fractionation of low-rank coal in a non-hydrogen atmosphere, characterized in that: The following steps are involved: S1. Pretreatment of coal samples: After the low-rank coal samples are naturally dried in the air for 45-50 hours, they are crushed using a crusher and sieved using a screening component to a particle size of less than 75 μm. After crushing, they are packed into sealed bags and placed in a dryer for standby use; S2, mild liquefaction experiment, take 10-20g of pretreated coal powder, iron-based catalyst and hydrogen supply solvent and add them into the reactor (4), the initial pressure of the atmosphere in the reactor (4) is 2.0-4.0MPa, the reaction temperature is 300-400°C, and the constant temperature reaction is carried out for 30-60 minutes. After the reaction is completed, the reactor (4) is cooled to below 35°C, and the inner wall of the reactor (4) is cleaned using a cleaning component, and the gas product and solid-liquid mixture obtained by the mild liquefaction reaction are collected at the same time; S3, separation of solid and liquid products, subjecting the solid-liquid mixture after the reaction to graded extraction to obtain liquefied oil, asphaltene and residual coal respectively.

2. The method for mild liquefaction and fractionation conversion of low-rank coal in a non-hydrogen atmosphere according to claim 1, characterized in that: In S1, the iron-based catalyst is selected from at least one of ferrous sulfide, iron powder, iron oxide, and ferrous sulfate, and accounts for 1-3% of the mass percentage of the coal sample.

3. The method for mild liquefaction and fractionation conversion of low-rank coal in a non-hydrogen atmosphere according to claim 1, characterized in that: In S2, the hydrogen supply solvent is selected from at least one of methylnaphthalene, tetralin, phenol, dihydrophenanthrene, and dihydroanthracene, and the ratio of the coal sample to the hydrogen supply solvent is controlled at 1:1-4; The atmosphere is one of methane or nitrogen.

4. The method for mild liquefaction and fractionation conversion of low-rank coal in a non-hydrogen atmosphere according to claim 1, characterized in that: In S3, the liquefied oil is a n-hexane soluble matter, the asphaltenes are a tetrahydrofuran soluble matter, and the residual coal is a tetrahydrofuran insoluble matter.

5. The method for mild liquefaction and fractionation conversion of low-rank coal in a non-hydrogen atmosphere according to claim 1, characterized in that: In S3, the following sub-steps are included: S301, taking out the solid-liquid mixture after the reaction and filtering it, transferring the product on the filter paper to a filter paper tube after filtering, placing it in a Soxhlet extractor, extracting it with n-hexane, receiving the filtrate in a 500 mL flask, and extracting until the reflux liquid is substantially colorless; S302, taking out the filter paper tube from the Soxhlet extraction tube, putting it into a vacuum drying oven at 45°C and drying it for 8 hours, taking it out, cooling it to room temperature and then weighing it, while rotary evaporating to recover n-hexane and collecting n-hexane solubles; S303, placing the weighed filter paper tube into a Soxhlet extractor and extracting with tetrahydrofuran until the reflux liquid is substantially colorless, the time is 45-50 hours, taking out the filter paper tube, drying and weighing, recovering tetrahydrofuran by rotary evaporation, and collecting the tetrahydrofuran soluble matter and the tetrahydrofuran insoluble matter in the filter paper tube.

6. The method for mild liquefaction and fractionation conversion of low-rank coal in a non-hydrogen atmosphere according to claim 1, characterized in that: The screening assembly comprises a support frame (101) and a first motor (109); a reciprocating screw (108) is fixed to the output shaft end of the first motor (109); a support plate (107) is threadedly connected to the outer side of the reciprocating screw (108); a transverse plate (103) is fixed to the top of the support frame (101); and a screen (106) is installed at the bottom of the inner wall of the transverse plate (103).

7. The method for mild liquefaction and fractionation conversion of low-rank coal in a non-hydrogen atmosphere according to claim 6, characterized in that: A brush plate (111) is fixed at the bottom of the support plate (107) and is slidably connected to the top of the screen (106). A plurality of bristles are fixedly inserted into the bottom of the brush plate (111). A sliding column (105) is movably penetrated through one side of the support plate (107).

8. The method for mild liquefaction and fractionation conversion of low-rank coal in a non-hydrogen atmosphere according to claim 7, characterized in that: A baffle (104) is fixed on the top of the support frame (101), and discharge holes (110) are opened on both sides of the baffle (104). A recovery box (102) located below the screen (106) is inserted into one side of the support frame (101). One side of the first motor (109) and the sliding column (105) are fixed to one side of the top of the baffle (104), and one end of the reciprocating screw rod (108) is rotatably connected to one side of the top of the baffle (104) through a bearing. A feed pipe (2) is provided on the top of the screen (106), and the feed end of the feed pipe (2) is connected to the discharge end of the crusher.

9. The method for mild liquefaction and fractionation conversion of low-rank coal in a non-hydrogen atmosphere according to claim 8, characterized in that: The cleaning component comprises a second motor (303), a rotating shaft (305) is fixed to the output shaft end of the second motor (303), and a plurality of stirring blades (306) are fixed to the outer side of the rotating shaft (305); A first connecting rod (302) is fixed to the top of the outer side of the stirring blade (306), a second connecting rod (307) is fixed to one side of the bottom of the first connecting rod (302), and a scraper (308) slidably connected to the inner wall of the reaction kettle (4) is fixed to one side of the second connecting rod (307).

10. The method for mild liquefaction and fractionation conversion of low-rank coal in a non-hydrogen atmosphere according to claim 9, characterized in that: The top of the reactor (4) is provided with a feeding pipe (304), the bottom of the reactor (4) is provided with a discharging pipe (301), the bottom of the second motor (303) is fixed at the top center of the reactor (4), and the outer side of the rotating shaft (305) is rotatably connected to one side of the top of the reactor (4) via a sealed bearing.

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