CN101624532B - Method for hydrogenating and liquefying coal with high content of inert components - Google Patents

Abstract

A method for hydrogenation liquefaction of coal with high content of inert components, which is carried out in the following steps: the first step of swelling treatment, the second step of hydrogenation liquefaction reaction, and the third step of solid-liquid separation. The technical effect of the present invention: in the case of taking into account the liquefaction cost, the oil yield of the Wucaiwan coal hydrogenation liquefaction can be obtained under the condition that the Wucaiwan coal has a high inertite content, a low ratio of hydrogen and carbon elements, and a low volatile matter. Significantly improved, thereby changing the currently accepted view that: when the content of inertinite in coal is high and the ratio of hydrogen to carbon and volatile matter are low, only a low liquefaction rate of coal can be obtained.

Description

Hydrogenation liquefaction method of coal with high content of inert components

technical field

The invention relates to the technical field of direct coal liquefaction, and relates to a hydrogenation liquefaction method for coal with high content of inert components.

Background technique

Xinjiang is very rich in coal resources, and its predicted reserves reach 2.19 trillion tons, exceeding 40% of the national total.

Wucaiwan Coal is located in the Zhundong area. It is the first of the five major coal, electricity and coal chemical industry bases in Xinjiang. It is about to be built into the world's largest open-pit coal mine. The coal in this mining area has the characteristics of many coal seams, large thickness, shallow burial, high moisture, low ash and low sulfur. The coal quality analysis of Wucaiwan coal is shown in Table 1. Its coal quality characteristics can be summarized as "three highs", that is, high inertinite content, high moisture, and high calcium oxide; "three lows", that is, low hydrogen-carbon element ratio, low ash and low sulfur. The ratio of hydrogen to carbon in Wucaiwan coal is low, indicating that the coal contains more aromatic structures; the optimal reaction temperature of inertinites is above 450°C, and the volume percentage of inertinites in Wucaiwan coal is 75% to 85%. For a good liquefaction effect, the temperature required for the reaction is high; the volatile content of Wucaiwan coal is 32.57%, and the ratio of hydrogen to carbon is 0.59. The greater the volatile matter and hydrogen-carbon element ratio of coal (petroleum-hydrogen-carbon ratio is 1.5 to 1.6), the better the coal quality and the easier it is to hydrogenate and liquefy. According to the national coal classification standard (GB5751-86), Wucaiwan coal belongs to the degree of coalification Higher bituminous coal.

The characteristic of direct coal liquefaction is the need for high pressure and high temperature conditions. Therefore, there are strict requirements on equipment performance and process conditions. Therefore, on the premise that the oil yield is as high as possible, further mild liquefaction reaction conditions and cost reduction have always been a hot spot in coal liquefaction research.

The theoretical basis for the swelling mechanism of coal is the two-phase structure model of coal macromolecules. According to the model, the structure of coal can be regarded as composed of macromolecules in a three-dimensional cross-network structure and small molecules embedded in the network. There are interactions such as hydrogen bonds, charge transfer or van der Waals forces between the two. The younger the coal, the more small molecules there are between the networks. The molecular structure of coal is characterized by both the ability to supply hydrogen and the ability to accept hydrogen. Therefore, nucleophilic or electrophilic solvents can break the hydrogen bonds and weaker chemical bonds between the coal molecular structure, reduce its cross-linking degree, and make it fully stretched. Since the 1980s, the swelling equilibrium theory in polymer physics was used to study the cross-linking bond structure of coal macromolecules. Treating coal with polar organic solvents will destroy the cross-linked hydrogen bonds in the coal molecular structure, change the chemical structure of the coal, reduce the free energy association structure, and increase the chemical reactivity of the coal so that it can be used under milder conditions. Direct liquefaction has higher oil yield and conversion.

At present, there have been a lot of researches on the direct liquefaction of swelling coal. The coal quality analysis of different coals is shown in Table 1. As for the hydrogen-to-carbon element ratio of coal, only Wucaiwan coal is less than 0.6, and the other coals are between 0.7 and 0.8. As for the volatile content, except for Wucaiwan coal and South African coal, all of them are less than 0.6. Between 37% and 46%. The higher the hydrogen-to-carbon element ratio and volatile content of coal, the easier it is to liquefy. Therefore, in terms of coal liquefaction, Xinglong coal and Beisu coal are the easiest to liquefy, and Wucaiwan coal is the most difficult to liquefy.

In Table 3:

F.Pinto ^[1] etc(Pinto F, GulyurtluI, Lobo LS et al.Effect of coal pre-treatment with swelling solvents on coal liquefaction[J].fuel, 1999, 78: 629 -634 discloses that South African coal is swollen with tetrahydrofuran, hydrogenated and liquefied under the conditions of initial hydrogen pressure of 7.9MPa (measured at normal temperature), liquefaction temperature of 400°C and reaction time of 30min, and the oil yield reaches 27% from the original 24%. , although the South African coal has a high hydrogen-carbon element ratio of 0.71, the oil yield is low under the above reaction conditions; on the other hand, the liquefied oil yield is only increased by 3 percentage points after the coal is swollen with tetrahydrofuran, and the swelling effect is not significant.

Haoquan Hu ^[2] (Hu Haoquan (Hu Haoquan), Sha Guangyan, Chen Guohua.Effect of solventswelling on liquefaction of Xinglong coal at less severe conditions[J](Influence of swelling treatment on Xinglong coal liquefaction under mild conditions).fuel, 2000, 68: 33-43 disclosed that Xinglong coal was swelled with tetrahydrofuran and pyridine respectively, at a coal dissolving ratio of 2:1 (the mass ratio of tetrahydronaphthalene to coal), initial hydrogen pressure of 4 MPa (measured at room temperature), and liquefaction temperature Under the condition of 350°C and reaction time of 30 minutes, the conversion rate reached 29% and 28% respectively, which increased by 9 and 8 percentage points from the original 20%. The volatile content of Xinglong coal is 40.72%, and the hydrogen-to-carbon ratio is 0.78 , is a high-quality coal that is easy to liquefy. However, due to the low liquefaction temperature, the conversion rate of Xinglong coal is only 20%, and the conversion rate of Xinglong coal after swelling with tetrahydrofuran and pyridine is also <30%, and the swelling effect is still not significant.

Hengfu Shui ^[3] etc(Shui Hengfu, Wang Zhicai, Cao Meixia.Effect of pre-treatment of coal on its solvent extraction and liquefaction properties[J](Swelling pretreatment on solvent extraction and coal liquefaction properties).fuel, 2008.04.28: 1-6 disclosed that Shenhua coal was swollen with tetrahydrofuran and N-methylpyrrolidone respectively, at a coal dissolving ratio of 3:1 (the mass ratio of tetralin to coal) and an initial hydrogen pressure of 4 MPa (measured at room temperature ), the liquefaction temperature of 400°C and the reaction time of 30 minutes under the conditions of hydrogenation and liquefaction, the oil and gas yields increased from the original 21% to 24% and 18%, which increased and decreased by 3 percentage points respectively. At this time, the swelling effect on Shenhua The effect of coal is not obvious, and the N-methylpyrrolidone solvent has a negative effect, that is, the oil and gas yield is lower than before swelling.

Ni Xianzhi ^[4] et al. (Ni Xianzhi, Wang Li, Chen Lihui et al. Research on Hydrogenation Liquefaction Performance of Young Coal Solvent Swelling [J]. Journal of Shandong University of Science and Technology, 2003, 22 (3): 97-100 discloses the use of pyridine to swell coal Village coal is hydrogenated and liquefied under the conditions of coal dissolving ratio of 1.5 to 2:1 (the mass ratio of tetrahydronaphthalene to coal), the initial hydrogen pressure of 10MPa (measured at room temperature), the liquefaction temperature of 400°C and the reaction time of 60min. The yield increased from 18% to 40%, an increase of 22 percentage points. Swelling Beisu coal with pyridine [6] (Ni Xianzhi, Wang Li, Chen Lihui, etc. Research on improving coal liquefaction performance by swelling under ultrasonic radiation[J]. Coal conversion , 2003, 26(4): 37-41 discloses that the coal dissolving ratio is 7:1 (the mass ratio of tetrahydronaphthalene to coal), the hydrogen initial pressure (7MPa to 8MPa) (measured at normal temperature), and the liquefaction temperature of 400 ℃ and reaction time of 90 minutes, the oil yield increased from 57% to 70%, an increase of 13 percentage points. Although the oil yield of the two swelling coals increased by 10 percentage points compared with that before swelling, the Suncun coal liquefaction The initial pressure of hydrogen is as high as 10MPa (measured at room temperature). Such a high pressure makes the final pressure of the liquefaction reaction higher, resulting in high requirements for the material of the reaction equipment and a corresponding increase in the cost of liquefaction; not only the amount of solvent used by Beisu Coal Large (coal melting ratio 7:1) (the mass ratio of tetralin to coal), and the liquefaction reaction time is too long.

Hou Yuchi ^[6] et al. (Hou Yuchi, Lu Jichang, Ma Guobao. Effect of swelling on the structure and liquefaction performance of Shenhua coal[J]. Liaoning Chemical Industry, 2008, 37(6): 381-384 disclosed that Shenhua coal was swollen with pyridine. The coal ratio is 3:1 (the mass ratio of tetrahydronaphthalene to coal), the hydrogen initial pressure is 7MPa (measured at room temperature), the liquefaction temperature is 420°C and the reaction time is 60min. The oil and gas yield (oil and gas yield and) from the original 45% to 62%, an increase of 17 percentage points. On the one hand, Shenhua coal is one of the 14 coals with excellent liquefaction characteristics selected by the Coal Research Institute; on the other hand, the amount of solvent used is large (solvent Coal ratio 3:1). These two aspects make the liquefaction cost high.

Contents of the invention

The invention provides a method for hydrogenation liquefaction of high-content inertite coal, which overcomes the deficiencies of the prior art, solves the problem that Wucaiwan coal is difficult to liquefy, and specifically solves the problem of Wucaiwan coal due to inertite content. Higher, lower ratio of hydrogen and carbon elements, lower volatile matter, resulting in lower liquefaction yield (including oil yield, oil and gas yield, conversion rate) and higher cost.

The technical scheme of the present invention is achieved like this: a kind of hydrotreating liquefaction method of high-content inert component coal, it carries out according to the following steps:

The first step of swelling treatment: mixing the mixture of N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF) and carbon disulfide (CS ₂ ) with Wucaiwan coal at a ratio of 2 to 10:1 Mix while stirring, seal and stand at room temperature for swelling for 0.5 hours to 24 hours, vacuum filter and dry the filter residue to obtain swollen coal; wherein, N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF ) and carbon disulfide (CS ₂ ) form a mixed solution with a volume ratio of 1 to 2:0 to 1:1, and the ratio of the above mixed solution to Wucaiwan coal is in ml/g;

The second step of hydrogenation liquefaction reaction: the required amount of the above-mentioned swelling coal, catalyst ferric oxide, cocatalyst elemental sulfur and hydrogen-donating solvent tetrahydronaphthalene are mixed evenly and poured into the reactor, and the reactor is sealed and poured into the reactor. After the internal replacement with hydrogen, charge to 5MPa to 7MPa at room temperature, control the heating rate of 4°C/min to 5°C/min, and keep the temperature for 30min to 60min after reaching the reaction temperature of 400°C to 460°C, and then put the reactor at 10min Within 15 minutes, it was forced to cool rapidly to 200° C., and then cooled to room temperature to obtain a reaction product; wherein, 20 parts by weight of the above-mentioned swollen coal, 0.57 to 1.43 parts by weight of the catalyst ferric oxide, and 0.46 to 1.43 parts by weight of the promoter elemental sulfur 1.15 parts by weight, the mass ratio of hydrogen-donating solvent tetrahydronaphthalene to swelling coal is 1.5 to 2: 1 (ratio of dissolved coal);

The third step of solid-liquid separation: the solid and liquid phase products of the reaction product are sequentially extracted with n-hexane, toluene and tetrahydrofuran solvents by Soxhlet extractors to obtain liquefied oil, asphaltenes, pre-asphaltenes and liquefied Residue (when extracted by Soxhlet extractor: n-hexane soluble matter is defined as liquefied oil, n-hexane insoluble toluene soluble matter is defined as asphaltenes, toluene-insoluble tetrahydrofuran soluble matter is defined as pre-asphaltene, tetrahydrofuran insoluble matter is defined as for the liquefaction residue).

Below is the further optimization and/or selection to above-mentioned technical scheme:

In the above-mentioned first step of swelling treatment, the obtained filter residue was vacuum-dried for 12 hours to obtain swollen coal.

In the above first step of swelling treatment, the obtained filter residue was first washed with 5 milliliters of absolute ethanol per gram of coal and 5 milliliters of distilled water per gram of coal, and then vacuum-dried for 12 hours to obtain swollen coal.

In the above third step of solid-liquid separation, the extraction time is 48 hours with n-hexane, 48 hours with toluene and 24 hours with tetrahydrofuran.

In the above-mentioned second-step hydrogenation liquefaction reaction, the reactor is sealed and replaced with hydrogen gas with a purity of 99.99% for 3 to 5 times.

In the second step of hydrogenation liquefaction reaction, the stirring speed in the reactor is 300rad/min to 350rad/min.

The technical effect of the present invention: in the case of taking into account the liquefaction cost, the oil yield of the Wucaiwan coal hydrogenation liquefaction can be obtained under the condition that the Wucaiwan coal has a high inertite content, a low ratio of hydrogen and carbon elements, and a low volatile matter. Significantly improved, thereby changing the currently accepted view that: when the content of inertinite in coal is high and the ratio of hydrogen to carbon and volatile matter are low, only a low liquefaction rate of coal can be obtained.

Detailed ways

Embodiment 1: The hydrogenation liquefaction method of this high-content inert component coal is carried out according to the following steps:

The first step of swelling treatment: Stir the mixture of N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF) and carbon disulfide (CS ₂ ) with Wucaiwan coal at a ratio of 2:1 Mix, seal and stand at room temperature to swell for 0.5 hours, vacuum filter and dry the filter residue to obtain swollen coal; wherein, N-methylpyrrolidone (NMP), N, N-dimethylformamide (DMF) and carbon disulfide (CS ₂ ) A mixed solution is formed with a volume ratio of 1:0:1, and the ratio unit of the above mixed solution to Wucaiwan coal is ml/g;

The second step of hydrogenation liquefaction reaction: the required amount of the above-mentioned swelling coal, catalyst ferric oxide, cocatalyst elemental sulfur and hydrogen-donating solvent tetrahydronaphthalene are mixed evenly and poured into the reactor, and the reactor is sealed and poured into the reactor. After the internal replacement with hydrogen, charge to 5MPa MPa at room temperature, control the heating rate of 4°C/min, and keep the temperature at 400°C for 30 minutes, then forcefully cool the reactor to 200°C within 10 minutes, and then lower the temperature to room temperature to obtain a reaction product; wherein, 20 parts by weight of the above-mentioned swollen coal, 0.57 parts by weight of the catalyst ferric oxide, 0.46 parts by weight of the cocatalyst elemental sulfur, and the mass ratio of the hydrogen-donating solvent tetralin to the swollen coal is 1.5:1;

The third step of solid-liquid separation: the solid and liquid phase products of the reaction product are sequentially extracted with n-hexane, toluene and tetrahydrofuran solvents by Soxhlet extractors to obtain liquefied oil, asphaltenes, pre-asphaltenes and liquefied residue.

Embodiment 2: the hydrogenation liquefaction method of this high-content inert component coal is characterized in that it is carried out according to the following steps:

The first step of swelling treatment: Stir the mixture of N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF) and carbon disulfide (CS ₂ ) with Wucaiwan coal at a ratio of 10:1 Mix, seal and stand at room temperature to swell for 24 hours, vacuum filter and dry the filter residue to obtain swollen coal; wherein, N-methylpyrrolidone (NMP), N, N-dimethylformamide (DMF) and carbon disulfide (CS ₂ ) A mixed solution is formed with a volume ratio of 2:0 to 1:1, and the ratio unit of the above mixed solution to Wucaiwan coal is ml/g;

The second step of hydrogenation liquefaction reaction: the required amount of the above-mentioned swelling coal, catalyst ferric oxide, cocatalyst elemental sulfur and hydrogen-donating solvent tetrahydronaphthalene are mixed evenly and poured into the reactor, and the reactor is sealed and poured into the reactor. After the internal replacement with hydrogen, charge to 7MPa at room temperature, control the heating rate of 5°C/min, and keep the temperature at 460°C for 60 minutes, then forcefully cool the reactor to 200°C within 15 minutes, and then cool down to At room temperature, a reaction product was obtained; wherein, 20 parts by weight of the above-mentioned swollen coal, 1.43 parts by weight of the catalyst ferric oxide, 1.15 parts by weight of the cocatalyst elemental sulfur, and the mass ratio of the hydrogen-donating solvent tetrahydronaphthalene to the swollen coal was 2:1;

The third step of solid-liquid separation: the solid and liquid phase products of the reaction product are sequentially extracted with n-hexane, toluene and tetrahydrofuran solvents by Soxhlet extractors to obtain liquefied oil, asphaltenes, pre-asphaltenes and liquefied residue.

Embodiment 3: the hydroliquefaction method of this high-content inert component coal is carried out according to the following steps:

The first step of swelling treatment: mixing the mixture of N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF) and carbon disulfide (CS ₂ ) with Wucaiwan coal at a ratio of 2 to 10:1 Mix while stirring, seal and stand at room temperature for swelling for 0.5 hours to 24 hours, vacuum filter and dry the filter residue to obtain swollen coal; wherein, N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF ) and carbon disulfide (CS ₂ ) form a mixed solution with a volume ratio of 1 to 2:0 to 1:1, and the ratio of the above mixed solution to Wucaiwan coal is in ml/g;

The second step of hydrogenation liquefaction reaction: the required amount of the above-mentioned swelling coal, catalyst ferric oxide, cocatalyst elemental sulfur and hydrogen-donating solvent tetrahydronaphthalene are mixed evenly and poured into the reactor, and the reactor is sealed and poured into the reactor. After the internal replacement with hydrogen, charge to 5MPa to 7MPa at room temperature, control the heating rate of 4°C/min to 5°C/min, and keep the temperature for 30min to 60min after reaching the reaction temperature of 400°C to 460°C, and then put the reactor at 10min Within 15 minutes, it was forced to cool rapidly to 200° C., and then cooled to room temperature to obtain a reaction product; wherein, 20 parts by weight of the above-mentioned swollen coal, 0.57 to 1.43 parts by weight of the catalyst ferric oxide, and 0.46 to 1.43 parts by weight of the promoter elemental sulfur 1.15 parts by weight, the mass ratio of the hydrogen-donating solvent tetrahydronaphthalene to the swelling coal is 1.5 to 2:1;

The third step of solid-liquid separation: the solid and liquid phase products of the reaction product are sequentially extracted with n-hexane, toluene and tetrahydrofuran solvents by Soxhlet extractors to obtain liquefied oil, asphaltenes, pre-asphaltenes and liquefied residue.

Further optimization or selection of the hydroliquefaction method of the above-mentioned high-content inert component coal below:

In the first step of swelling treatment: the obtained filter residue is vacuum dried for 12 hours to obtain swollen coal; or, in the first step of swelling treatment, the obtained filter residue is first washed with 5 ml of absolute ethanol per gram of coal and 5 ml of distilled water per gram of coal , and then vacuum dried for 12 hours to obtain swollen coal.

In the third step of solid-liquid separation, the extraction time was 48 hours with n-hexane, 48 hours with toluene and 24 hours with tetrahydrofuran.

In the second hydrogenation liquefaction reaction, the reactor is sealed and replaced with hydrogen with a purity of 99.99% for 3 to 5 times.

In the second hydrogenation liquefaction reaction, the stirring speed in the reactor is 300rad/min to 350rad/min.

The present invention compares with the test result of prior art as follows:

① Through coal quality analysis, the volume percentage of inertite group in Wucaiwan coal is 75% to 85%, the hydrogen-carbon element ratio is <0.6 and the volatile matter is <37%. Far exceeds the effect of high-quality coal liquefaction, see Table 3 for details.

② Liquefaction under low initial pressure of 5MPa to 7MPa (measured at room temperature), on the one hand, the amount of hydrogen used is low, only about 5% (volume percentage); on the other hand, the final pressure of the reaction is low (13MPa to 17MPa) (at a reaction temperature of measured at 460°C). The cost of liquefaction is reduced from the above two aspects.

③Use N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF) and carbon disulfide (CS ₂ ) [V ₁ : V ₂ : V ₃ =(1 to 2):(0 to 1) :1] The liquefaction effect of Wucaiwan coal is obviously enhanced after swelling, which is manifested under the conditions of 1.5 to 2:1 coal dissolving ratio, 5 to 7 MPa of low hydrogen initial pressure (measured at room temperature), reaction temperature of 460°C and reaction time of 30 to 60 minutes Hydrogenation liquefaction, the oil yield increased from 55% to 70% to 75%, an increase of 5 to 20 percentage points; the oil and gas yield increased from 65% to 73% to 75%, an increase of 8 to 10 percentage points ; The conversion rate is increased from 77% to 80% to 85%, which has increased by 3 to 8 percentage points, see Table 2 and Table 4 for details.

④Change the currently accepted point of view that only a low liquefaction rate can be obtained when the volume percentage of inertite is 75% to 85%, and the hydrogen-carbon element ratio and volatile matter are both low.

Claims (1)

1. a method for hydroliquefaction of high-content inert component Wucaiwan coal, characterized in that it is carried out in the following steps: The first step of swelling treatment: Mix the mixture of N-methylpyrrolidone, N,N-dimethylformamide and carbon disulfide with Wucaiwan coal at a ratio of 2 to 10:1 while stirring, and seal it at room temperature for swelling 0.5 hours to 24 hours, vacuum filtration and drying the filter residue to obtain swelling coal; wherein, N-methylpyrrolidone, N, N-dimethylformamide and carbon disulfide are in a volume ratio of 1 to 2:0 to 1:1 Constitute a mixed solution, the ratio unit of the above mixed solution to Wucaiwan coal is ml/g; The second step of hydrogenation liquefaction reaction: the required amount of the above-mentioned swelling coal, catalyst ferric oxide, cocatalyst elemental sulfur and hydrogen-donating solvent tetrahydronaphthalene are mixed evenly and poured into the reactor, and the reactor is sealed and poured into the reactor. After the internal replacement with hydrogen, charge to 5 MPa to 7 MPa at room temperature, control the heating rate of 4°C/min to 5°C/min, until the reaction temperature is 400°C to 460°C, then keep the temperature constant for 30 minutes to 60min, and then put the reaction The kettle is rapidly and forcibly cooled to 200° C. within 10 minutes to 15 minutes, and then cooled to room temperature to obtain a reaction product; wherein, 20 parts by weight of the above-mentioned swollen coal, 0.57 to 1.43 parts by weight of the catalyst ferric oxide, and 0.46 parts by weight of the cocatalyst elemental sulfur Parts by weight to 1.15 parts by weight, the mass ratio of the hydrogen-donating solvent tetralin to the swelling coal is 1.5 to 2:1; The third step of solid-liquid separation: the solid and liquid phase products of the reaction product are sequentially extracted with n-hexane, toluene and tetrahydrofuran solvents by Soxhlet extractors to obtain liquefied oil, asphaltenes, pre-asphaltenes and liquefied residue; in: In the first step of swelling treatment, the obtained filter residue is first washed with 5 milliliters of absolute ethanol per gram of coal and 5 milliliters of distilled water per gram of coal, and then vacuum-dried for 12 hours to obtain swollen coal; In the third step of solid-liquid separation, the extraction time is 48 hours with n-hexane, 48 hours with toluene and 24 hours with THF; In the second step of hydrogenation liquefaction reaction, seal the reactor and replace it with hydrogen with a purity of 99.99% for 3 to 5 times; In the second hydrogenation liquefaction reaction, the stirring speed in the reactor is 300rad/min to 350rad/min.