Methods and systems for preparing special fuels from coal tar

Abstract

This invention relates to the field of special fuel technology and discloses a method for preparing special fuels from coal tar, comprising: (1) performing a first fractionation on the raw coal tar to obtain a distillate oil with a distillation range of 180-420℃; (2) extracting the distillate oil to obtain an extract and a raffinate, and then performing adsorption separation on the raffinate to obtain a purified oil product; (3) optionally hydrorefining the purified oil product; (4) performing a second fractionation on the purified oil product and / or the hydrorefined product to cut it into No. 1 distillate oil, No. 2 distillate oil, and No. 3 distillate oil; (5) alkylating the No. 1 distillate oil to obtain No. 1 special oil; hydrosaturating the No. 2 distillate oil to obtain No. 2 special oil; and cracking cycloisomerizing the No. 3 distillate oil to obtain No. 3 special oil; and (6) then refining and blending. This method can flexibly prepare special fuels with different properties, and the fuel density and calorific value range are large.

Description

Technical Field

[0001] This invention relates to the field of special fuel technology, and specifically to a method and system for preparing special fuels from coal tar. Background Technology

[0002] Coal tar is a liquid byproduct produced during the deep processing of coal. It has a pungent odor and can be classified into low-temperature coal tar, medium-temperature coal tar, and high-temperature coal tar according to different pyrolysis temperatures. The composition and properties of medium- and low-temperature coal tar differ greatly from those of petroleum, possessing many advantages that petroleum feedstocks do not have, such as a high mass fraction of aromatics and cycloalkanes. After further processing, it can be transformed into high-value-added specialty fuels.

[0003] High-density special fuels are those with a density greater than 0.85 g / cm³. 3 Liquid fuels have high density and volumetric calorific value, and can provide more energy with a fixed fuel tank, making them an effective means of improving the performance of aircraft, rockets and other aerospace vehicles.

[0004] Currently, aviation specialty fuels are mainly petroleum-based, while coal-based specialty fuels are being produced, especially those with a density greater than 0.85 g / cm³. 3 Research on specialty fuels is limited, with most studies focusing on fuels with a density less than 0.85 g / cm³. 3 Special fuels, and the yield of special fuels is low. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of single source of special fuel, low density and low yield of special fuel in the existing technology, and to provide a method and system for preparing special fuel from coal tar. The special fuel obtained by this method has the characteristics of high fuel density and wide calorific value range, and can be applied to different application scenarios.

[0006] To achieve the above objectives, the present invention provides a method for preparing special fuels from coal tar, the method comprising: (1) The raw coal tar is subjected to a first fractionation to obtain a distillate oil with a distillation range of 180-420℃; (2) Extract the distillate oil to obtain an extract containing aromatic compounds with heteroatoms and a raffinate. Then, the raffinate is separated by adsorption to obtain a purified oil product. (3) The purified oil is optionally hydrotreated; (4) The impurity-removed oil and / or hydrorefined product are subjected to a second fractionation to be divided into No. 1 distillate with a distillation range of <230℃, No. 2 distillate with a distillation range of 230-280℃ and No. 3 distillate with a distillation range of >280℃. (5) Alkylate the No. 1 distillate oil to obtain No. 1 special oil; Hydrogen saturation treatment of No. 2 distillate oil yields No. 2 specialty oil; The No. 3 distillate oil was subjected to cracking and cyclic isomerization treatment to obtain the No. 3 special oil. (6) Refine and compound No. 1 special oil, No. 2 special oil and No. 3 special oil.

[0007] A second aspect of the present invention provides a special fuel prepared by the above method.

[0008] Preferably, the density of the special fuel is 0.78-0.95 g / mL.

[0009] Preferably, the net calorific value of the special fuel is 35-43 MJ / L.

[0010] A third aspect of the present invention provides a system for preparing special fuels from coal tar, comprising: The first fractionation unit is used to perform the first fractionation of the raw material coal tar. The refining unit includes an extraction unit and an adsorption separation unit connected in sequence for extracting and adsorbing the distillate oil from the first fractionation unit; the separation unit also optionally includes a hydrorefining unit connected to the purified oil outlet of the adsorption separation unit. The second fractionation unit is connected to the outlet of the impurity-removed oil product of the adsorption separation unit and / or the outlet of the hydrorefining unit, and is used to perform a second fractionation on the products of the impurity-removed oil product and / or the hydrorefining treatment; the second fractionation unit includes a No. 1 distillate oil outlet, a No. 2 distillate oil outlet and a No. 3 distillate oil outlet. The conversion unit includes an alkylation unit connected to the No. 1 distillate oil outlet of the second fractionation unit, a hydrogenation saturation unit connected to the No. 2 distillate oil outlet of the second fractionation unit, and a cracking cycloisolation unit connected to the No. 3 distillate oil outlet of the second fractionation unit. The compounding unit is connected to the alkylation unit, the hydrogenation saturation unit, and the cracking cycloisomerization unit, respectively, and is used to refine and compound specialty oils from the above units.

[0011] This invention is based on a separation-then-conversion approach. Through the aforementioned technical solution, firstly, aromatic compounds containing heteroatoms in coal tar are removed using efficient separation methods. The remaining heteroatoms are then purified through hydrogenation or other depurification methods as needed. Next, a second fractionation process is performed, and components with different distillation ranges are selectively processed to obtain three specialty oil components. These specialty oil components are then blended to leverage the advantages of each key component, resulting in a high-density specialty fuel that meets the required specifications. The blending ratio can be adjusted during the blending process to obtain specialty fuels with different properties, resulting in a wide range of fuel densities and calorific values, expanding application scenarios, and making the preparation method of specialty fuels more flexible. Attached Figure Description

[0012] Figure 1 This is a process flow diagram of the method for preparing special fuels from coal tar provided in Embodiment 1 of the present invention.

[0013] Explanation of reference numerals in the attached figures 1-First fractionation unit, 2-Refining unit, 3-Second fractionation unit, 4-Alkylation unit, 5-Hydrogenation saturation unit, 6-Cracking cycloisolation unit, 7-Compound unit. Detailed Implementation

[0014] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0015] The first aspect of this invention provides a method for preparing special fuels from coal tar, the method comprising: (1) The coal tar is subjected to a first fractionation to obtain a distillate oil with a distillation range of 180-420℃; (2) Extract the distillate oil to obtain an extract containing aromatic compounds with heteroatoms and a raffinate. Then, the raffinate is separated by adsorption to obtain a purified oil product. (3) The purified oil is optionally hydrotreated; (4) The impurity-removed oil and / or hydrorefined product are subjected to a second fractionation to be divided into No. 1 distillate with a distillation range of <230℃, No. 2 distillate with a distillation range of 230-280℃ and No. 3 distillate with a distillation range of >280℃. (5) Alkylate the No. 1 distillate oil to obtain No. 1 special oil; Hydrogen saturation treatment of No. 2 distillate oil yields No. 2 specialty oil; The No. 3 distillate oil was subjected to cracking and cyclic isomerization treatment to obtain the No. 3 special oil. (6) Refine and compound No. 1 special oil, No. 2 special oil and No. 3 special oil.

[0016] The method provided in this invention first fractionates the raw coal tar to obtain distillate oil with a suitable distillation range, then performs extraction, adsorption, and hydrogenation refining. Subsequently, it is fractionated into three distillate oils, which are then subjected to alkylation, deep hydrogenation saturation, and cracking isomerization, respectively. The alkylated specialty oil, the hydrogenated saturated specialty oil, and the cracked isomerized specialty oil are then refined and blended to obtain coal-based high-density specialty fuel.

[0017] In this invention, "coal tar" refers to a liquid byproduct produced during the deep processing of coal. This invention does not specifically limit the source and composition of the coal tar. Preferably, the raw material coal tar is low-temperature coal tar, medium-temperature coal tar, or medium-low-temperature coal tar. Low-temperature coal tar refers to a liquid product produced by low-rank coals such as lignite and long-flame coal at a pyrolysis final temperature of 400-600℃ through a low-temperature dry distillation process (such as solid heat carrier dry distillation or rotary kiln dry distillation). Medium-temperature coal tar refers to a liquid product produced by low-rank coals such as lignite, long-flame coal, and non-caking coal at a pyrolysis final temperature of 600-800℃ through a medium-temperature dry distillation process (such as internally heated vertical furnace dry distillation or medium-temperature coke oven dry distillation). Medium-low-temperature coal tar is a mixture of low-temperature coal tar and medium-temperature coal tar with a density of 1.08 g / cm³. 3 the following.

[0018] In this invention, the aromatic compounds containing heteroatoms are generally phenolic compounds, and the heteroatoms are generally oxygen atoms.

[0019] In this invention, medium- and low-temperature coal tar is used as the raw material, which is beneficial for preparing specialty fuels with superior performance. Petroleum-based fuel production involves extracting and lightly refining qualified fractions from raw materials, a simple process with low cost. Coal tar-based fuel production involves artificially synthesizing qualified fractions and performance through deep modification, a complex process with high cost, but it can utilize coal resources to achieve diversified supply of aviation kerosene, and the product has a wider freezing point adjustment range.

[0020] In this invention, there are no particular limitations on the specific conditions of the first fractionation in step (1). As long as a distillate oil with a distillation range of 180-420℃ can be obtained, those skilled in the art can adjust the fractionation conditions according to actual needs.

[0021] Preferably, the first fractionation can be vacuum distillation to prevent thermal cracking and condensation of coal tar. Preferably, the vacuum degree of the first fractionation system is 8-10 kPa and the reflux ratio is 1.5-2.5. In this invention, the vacuum degree of the fractionation is absolute pressure.

[0022] Before the first fractionation, those skilled in the art can also perform conventional desalting, dehydration, and removal of mechanical impurities on the raw materials as needed, and the present invention does not have any particular limitations on this.

[0023] According to the present invention, the distillate oil is extracted to obtain an extract containing heteroatom compounds and a raffinate, and then the raffinate is separated by adsorption to obtain a purified oil product.

[0024] According to the present invention, preferably, the content of heteroatom compounds in the purified oil is not higher than 10 wt%.

[0025] In this invention, the extraction and adsorption in step (2) can be carried out using conventional methods in the art. Preferably, step (2) includes: mixing the extractant with the distillate oil under stirring conditions, then allowing it to stand and separate to obtain the extract and the raffinate; then adding an adsorbent to the obtained raffinate for adsorption separation to obtain the purified oil.

[0026] Preferably, the mass ratio of the extractant to the distillate oil is 1:(1-3), for example, it can be a specific mass ratio such as 1:1, 1:2, 1:3 or any range between the two.

[0027] Preferably, the mixing temperature is 25-50℃, the stirring time is 30-60 min, and the standing time is 1-3 h.

[0028] Preferably, the extractant is at least one of alcohols, alkanolamines, and amides, and more preferably at least one of diethylene glycol, formamide, and ethanolamine.

[0029] Preferably, the adsorbent is an adsorbent that preferentially adsorbs aromatic compounds containing heteroatoms, such as modified activated carbon (loaded with metals such as Zn, Cu, etc., or loaded with acidic substances such as H2SO4, H3PO4, etc.) or modified molecular sieve adsorbents.

[0030] In this invention, the purified oil product may be hydrotreated or not, depending on actual needs. Preferably, when the content of heteroatom compounds in the purified oil product is higher than 5 wt%, the purified oil product is hydrotreated.

[0031] The present invention does not particularly limit the conditions for the hydrorefining process, and conventional conditions in the art can be used. Preferably, the conditions for the hydrorefining process include: a temperature of 300-350℃, more preferably 320-340℃; a pressure of 12-18 MPa, more preferably 15-18 MPa; a hydrogen-to-oil ratio of 1200-1500, more preferably 1300-1500; and a feed space velocity of 0.5-2 h⁻¹. -1 Preferably, it is 0.5-1.5h. -1 .

[0032] Any conventional hydrorefining catalyst in the art can be used, such as NiMo / Al2O3, CoMo-based catalysts, NiW-based catalysts, etc.

[0033] In this invention, there are no particular limitations on the specific conditions for the second fractionation in step (4). As long as distillate oils with different distillation ranges can be obtained, those skilled in the art can adjust the fractionation conditions according to actual needs.

[0034] Preferably, the second fractionation can be carried out using a multi-side-line vacuum distillation column, and can also be configured with a steam jet pump, a mechanical vacuum pump, and a combined vacuum system as needed. Preferably, the conditions for the second fractionation include: 35-45 theoretical plates, a vacuum degree of 8-10 kPa, and a reflux ratio of 2.5-3.5.

[0035] In this invention, a No. 1 specialty oil is obtained by alkylating a No. 1 distillate oil. Preferably, the No. 1 specialty oil has a pour point of -47 to -60°C, more preferably -55 to -60°C. Those skilled in the art can obtain the aforementioned No. 1 specialty oil by adjusting the alkylation conditions.

[0036] According to some preferred embodiments of the present invention, in step (5), the alkylation treatment is carried out in the presence of an alkylation catalyst. The alkylation catalyst may employ a composition conventional in the art.

[0037] Preferably, the alkylation catalyst comprises HY molecular sieve.

[0038] More preferably, the alkylation treatment conditions include: a temperature of 190-230℃, preferably 200-220℃, a pressure of 2-4 MPa, preferably 2-3 MPa, and a feed space velocity of 1-5 h⁻¹. -1 Preferably 2-3 hours -1 .

[0039] In this invention, the No. 2 distillate oil is subjected to hydrogenation saturation treatment to obtain the No. 2 special oil. Preferably, the density of the No. 2 special oil is not less than 0.85 g / mL, and more preferably 0.87-0.88 g / mL. Those skilled in the art can obtain the above-mentioned No. 2 special oil by adjusting the conditions of hydrogenation saturation treatment.

[0040] Preferably, in step (5), the hydrogenation saturation treatment is carried out in the presence of a hydrogenation saturation catalyst. The hydrogenation saturation catalyst can have a composition conventional in the art.

[0041] Preferably, the hydrogenation saturation catalyst comprises a USY molecular sieve and a noble metal component supported on the USY molecular sieve.

[0042] Preferably, the noble metal component is at least one of Pt, Pd and Ru, with Pt being the most preferred.

[0043] Preferably, based on the total amount of the hydrogenation saturated catalyst, the content of the noble metal component, calculated by element, is 1-1.5 wt%, more preferably 1.2-1.4 wt%.

[0044] Preferably, the conditions for the hydrogenation saturation treatment include: a temperature of 220-320℃, more preferably 280-300℃; a pressure of 10-15 MPa, more preferably 12-15 MPa; a hydrogen-to-oil ratio of 1000-1200, more preferably 1100-1200; and a feed space velocity of 1-2 h⁻¹. -1 Preferably 1-1.5h -1 .

[0045] In this invention, the No. 3 distillate oil is subjected to cracking cyclic isomerization treatment to obtain a No. 3 specialty oil. Preferably, the density of the No. 3 specialty oil is not less than 0.94 g / mL, and more preferably 0.94-0.95 g / mL. Those skilled in the art can obtain the above-mentioned No. 3 specialty oil by adjusting the conditions of the cracking cyclic isomerization treatment.

[0046] Preferably, the cracking ring isomerization treatment is carried out in the presence of a cracking ring isomerization catalyst.

[0047] Preferably, the cracking cyclic isomeric catalyst is a bimetallic catalyst, wherein the first metal component is selected from at least one of Ni, Pt and Ru, preferably Pt, and the second metal component is Mo and / or Pd, preferably Pd.

[0048] Preferably, based on the total amount of the cracking cyclic isomeric catalyst, the content of the first metal component is 1-2 wt%, preferably 1.5-1.8 wt%, and the content of the second metal component is 0.5-1.5 wt%, preferably 0.7-0.9 wt%.

[0049] Preferably, the conditions for the cracking cycloisomerization treatment include: a temperature of 300-380℃, preferably 330-360℃; a pressure of 8-10 MPa, preferably 9-10 MPa; and a feed space velocity of 0.5-2 h⁻¹. -1 Preferably 0.5-1h -1 .

[0050] According to the present invention, the compounding ratio of No. 1 special oil, No. 2 special oil and No. 3 special oil can be flexibly adjusted according to the needs of actual application scenarios to adapt to different requirements. Preferably, the mass ratio of No. 1 special oil, No. 2 special oil and No. 3 special oil is 1:(2-2.5):(1.5-2.5), more preferably 1:(2.1-2.4):(1.7-1.9).

[0051] Preferably, the conditions for the refined compounding include: a temperature of 240-280℃, more preferably 245-260℃, and a pressure of 8-12MPa, more preferably 9-11MPa.

[0052] A second aspect of the present invention provides a special fuel prepared by the above method.

[0053] Preferably, the density of the special fuel is 0.78-0.95 g / mL, and more preferably 0.85-0.95 g / mL.

[0054] Preferably, the net calorific value of the special fuel is 35-43 MJ / L, and more preferably 40-43 g / mL.

[0055] Preferably, the special fuel has a pour point of -40 to -55°C, more preferably -50 to -55°C.

[0056] A third aspect of the present invention provides a system for preparing special fuels from coal tar, such as... Figure 1 As shown, it includes: First fractionation unit 1 is used to perform first fractionation on raw coal tar; The refining unit 2 includes an extraction device and an adsorption separation device connected in sequence for extracting and adsorbing the distillate oil from the first fractionation unit; the separation unit may also optionally include a hydrorefining device connected to the purified oil outlet of the adsorption separation device. The second fractionation unit 3 is connected to the outlet of the impurity-removed oil product of the adsorption separation unit and / or the outlet of the hydrorefining unit, and is used to perform a second fractionation on the products of the impurity-removed oil product and / or the hydrorefining treatment; the second fractionation unit includes a No. 1 distillate oil outlet, a No. 2 distillate oil outlet and a No. 3 distillate oil outlet. The conversion unit includes an alkylation unit 4 connected to the No. 1 distillate oil outlet of the second fractionation unit, a hydrogenation saturation unit 5 connected to the No. 2 distillate oil outlet of the second fractionation unit, and a cracking cycloisolation unit 6 connected to the No. 3 distillate oil outlet of the second fractionation unit. The compounding unit 7 is connected to the alkylation unit, the hydrogenation saturation unit, and the cracking cycloisomerization unit, respectively, and is used to refine and compound special oils from the above units.

[0057] Preferably, the extraction device includes an extract outlet and a raffinate outlet, the raffinate outlet being connected to the inlet of the adsorption separation device, and the extract outlet being connected to the inlet of the alkylation device.

[0058] The present invention will be described in detail below through embodiments.

[0059] In the following examples, the density was measured using an Anton Paar DMA4501 density meter; The pour point was determined according to GB / T 510-2018, the method for determining the pour point of petroleum products. The net calorific value was measured using the Parr Instrument Company oxygen bomb calorimeter method.

[0060] The coal tar used in the following examples has a density of 1.06 g / cm³. 3 Medium and low temperature coal tar.

[0061] Example 1 (1) The raw coal tar is fed into the first fractionation unit. The fractionation conditions are vacuum distillation with a vacuum degree of 10 kPa and a reflux ratio of 2 to obtain a distillate oil with a distillation range of 180-420℃. (2) Ethanolamine was added to the distillate oil, and the amount of extractant added was 1 times that of the distillate oil. The mixture was stirred at 50°C for 60 min, and then allowed to stand for 2 hours to obtain the upper extract and the lower raffinate. Activated carbon loaded with 3 wt% ZnO was added to the raffinate for adsorption separation. The mass ratio of the adsorbent added to the raffinate was 0.3:1, resulting in a purified oil product. The purified oil product contained 8 wt% aromatic compounds with heteroatoms. The purified oil was subjected to a process at 340℃, 16MPa, and 0.8h. -1 Hydrorefining is carried out under a hydrogen-to-oil ratio of 1400. The hydrorefining catalyst is 1.8wt%Ni-8wt%Mo / Al2O3. The refined oil enters the second fractionation unit. (3) In the second fractionation unit, the fractionation conditions use a multi-side-line vacuum tower (35 theoretical plates), a combined vacuum system of steam jet pump and mechanical vacuum pump; vacuum degree 8 kPa, fluctuation less than 0.3 kPa, reflux ratio 3.5, and the impurity-free oil obtained in step (2) is cut into No. 1 distillate oil (density 0.785 g / mL, pour point -45℃) at 180-230℃, No. 2 distillate oil (density 0.887 g / mL, pour point -40℃) at 230-280℃, and No. 3 distillate oil (density 0.91 g / mL, pour point 20℃) at >280℃. (4) The No. 1 distillate oil obtained in step (3) was subjected to a temperature of 200℃ and its own pressure for 2 hours. -1 Alkylation was carried out under HY molecular sieve conditions to obtain Special Oil No. 1; the pour point of Special Oil No. 1 is -60℃.

[0062] (5) The No. 2 distillate oil obtained in step (3) was subjected to a temperature of 280℃, 12MPa, and a hydrogen-to-oil ratio of 1200 for 1 hour. -1 Deep saturation was carried out under the conditions of Pt / USY catalyst (Pt content 1.2wt%) to obtain special oil No. 2, which has a density of 0.875 g / mL.

[0063] (6) The No. 3 distillate oil obtained in step (3) was subjected to a temperature of 350℃, 10MPa, and 0.6h. -1 Cracking isomerization was carried out under the conditions of PtPd-USY molecular sieve catalyst (1.8wt% Pt, 0.8wt% Pd) to obtain No. 3 special oil; the density of No. 3 special oil is 0.94 g / mL.

[0064] (7) Special oils No. 1, No. 2 and No. 3 are refined and compounded at 240℃ and 12MPa in a mass ratio of 1:2.4:2.9 to obtain high-density special fuel.

[0065] Based on the above experiments, the density of the produced special fuel is 0.91 g / mL, the net calorific value is 43 MJ / L, and the pour point is -58℃.

[0066] Example 2 (1) The raw coal tar is fed into the first fractionation unit. The fractionation conditions are vacuum distillation, vacuum degree 10 kPa, reflux ratio 2, to obtain distillate oil with a distillation range of 180-420℃. (2) Diethylene glycol was added to the distillate oil, and the amount of extractant added was 1 times that of the distillate oil. The mixture was stirred at 50°C for 80 min, and then allowed to stand for 2 hours to obtain the upper extract and the lower raffinate. Activated carbon loaded with H3PO4 (acid-to-carbon mass ratio 2:1) was added to the raffinate for adsorption and separation. The mass ratio of the adsorbent added to the raffinate was 0.3:1 to obtain a purified oil product. The purified oil product contained 8.6 wt% aromatic compounds with heteroatoms. The purified oil was subjected to a process at 340℃, 16MPa, and 0.5h. -1 Hydrogen refining is carried out under a hydrogen-to-oil ratio of 1500, and the extract is then fed into an alkylation unit. (3) In the second fractionation unit, the fractionation conditions use a multi-side-line vacuum tower (35 theoretical plates), a combined vacuum system of steam jet pump and mechanical vacuum pump; vacuum degree 8 kPa, fluctuation less than 0.3 kPa, reflux ratio 3.5, and the impurity-free oil obtained in step (2) is cut into No. 1 distillate oil (density 0.79 g / mL, pour point -44℃) at 180-230℃, No. 2 distillate oil (density 0.881 g / mL, pour point -40℃) at 230-280℃, and No. 3 distillate oil (density 0.916 g / mL, pour point 20℃) at >280℃. (4) The No. 1 distillate oil obtained in step (3) was subjected to a temperature of 210℃ and its own pressure for 2.5 hours. -1 Alkylation was carried out under HY molecular sieve conditions to obtain Special Oil No. 1; the pour point of Special Oil No. 1 is -58℃.

[0067] (5) The No. 2 distillate oil obtained in step (3) was subjected to 240℃, 10MPa, and 1h. -1 With a hydrogen-to-oil ratio of 1400 and deep saturation under the conditions of Pt / USY catalyst (Pt content 1.3wt%), Special Oil No. 2 was obtained, with a density of 0.871 g / mL.

[0068] (6) The No. 3 distillate oil obtained in step (3) was subjected to 360℃, 10MPa, and 0.6h. -1Cracking isomerization was carried out under the conditions of PtPdUSY molecular sieve catalyst (1.7wt%Pt, 0.75wt%Pd) to obtain No. 3 special oil; the density of No. 3 special oil is 0.944g / mL.

[0069] (7) Special oils No. 1, No. 2 and No. 3 are refined and compounded at 240℃ and 12MPa in a mass ratio of 1:2.3:1.9 to obtain high-density special fuel.

[0070] Based on the above experiments, the density of the produced special fuel is 0.881 g / mL, the net calorific value is 42.4 MJ / L, and the pour point is -56℃.

[0071] Example 3 The method is the same as in Example 1, except that No. 1, No. 2 and No. 3 special oils are blended in a mass ratio of 1:2.5:1.7. The resulting special fuel has a density of 0.857 g / mL, a net calorific value of 41.8 MJ / L and a pour point of -55℃.

[0072] Example 4 The method is the same as in Example 1, except that in step (4), the alkylation treatment conditions are a temperature of 280°C, a pressure of 5 MPa, and a feed space velocity of 0.8 h⁻¹. -1 The pour point of Special Oil 1 is -40℃.

[0073] Specialty oils No. 1, No. 2, and No. 3 were blended in the same proportions as in Example 1. The resulting specialty fuel had a density of 0.882 g / mL, a net calorific value of 42.0 MJ / L, and a pour point of -43°C.

[0074] Example 5 The method is the same as in Example 1, except that the hydrogenation saturation treatment conditions in step (5) are 240°C, 10 MPa, and the feed space velocity is 1.8 h⁻¹. -1 The density of the No. 2 special oil produced is 0.858 g / mL.

[0075] Specialty oils No. 1, No. 2, and No. 3 were blended in the same proportions as in Example 1. The resulting specialty fuel had a density of 0.864 g / mL, a net calorific value of 37.2 MJ / L, and a pour point of -55°C.

[0076] Example 6 The method is the same as in Example 1, except that in step (6), the temperature of the cracking isomerization treatment is 380°C, the pressure is 10 MPa, and the feed space velocity is 0.5 h⁻¹. -1 The density of the No. 3 specialty oil produced is 0.84 g / cm³. 3 .

[0077] Specialty oils No. 1, No. 2, and No. 3 were blended in the same proportions as in Example 1. The resulting specialty fuel had a density of 0.852 g / mL, a net calorific value of 41.4 MJ / L, and a pour point of -55°C.

[0078] Comparative Example 1 The preparation was carried out according to the method in CN103289740A. Light oil was subjected to high-pressure hydrocatalytic distillation cracking and fractionated into fractions with temperatures below 180℃, above 180℃ but below 360℃, and above 360℃, yielding gasoline with a density of 0.72 g / cm³. 3 Diesel fuel density is 0.84 g / cm³ 3 The density cannot meet the high density requirements of the special oils in the embodiments of the present invention.

[0079] As can be seen from the above examples and comparative examples, the method provided by the present invention can produce special fuels with high fuel density and a wide range of calorific values, which can be applied to different application scenarios.

[0080] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing special fuels from coal tar, characterized in that, The method includes: (1) The raw coal tar is subjected to a first fractionation to obtain a distillate oil with a distillation range of 180-420℃; (2) Extract the distillate oil to obtain an extract containing heteroatom compounds and a raffinate, and then separate the raffinate by adsorption to obtain a purified oil product; (3) The purified oil is optionally hydrotreated; (4) The impurity-removed oil and / or hydrorefined product are subjected to a second fractionation to be divided into No. 1 distillate with a distillation range of <230℃, No. 2 distillate with a distillation range of 230-280℃ and No. 3 distillate with a distillation range of >280℃. (5) Alkylate the No. 1 distillate oil to obtain No. 1 special oil; Hydrogen saturation treatment of No. 2 distillate oil yields No. 2 specialty oil; The No. 3 distillate oil was subjected to cracking and cyclic isomerization treatment to obtain the No. 3 special oil. (6) Refine and compound No. 1 special oil, No. 2 special oil and No. 3 special oil.

2. The method according to claim 1, wherein, The raw material coal tar is medium-temperature coal tar, low-temperature coal tar, or medium-low temperature coal tar.

3. The method according to claim 1, wherein, Step (2) includes: mixing the extractant with the distillate oil under stirring conditions, then allowing it to stand and separate to obtain the extract and the raffinate; then adding an adsorbent to the raffinate for adsorption and separation to obtain the purified oil. Preferably, the mass ratio of the extractant to the distillate oil is 1:(1-3). Preferably, the mixing temperature is 25-50℃, the stirring time is 30-60 min, and the standing time is 1-3 h; Preferably, the extractant is at least one of alcohols, alkanolamines, and amides, and more preferably at least one of diethylene glycol, formamide, and ethanolamine; Preferably, the adsorbent is an adsorbent that preferentially adsorbs compounds containing heteroatoms; Preferably, the mass ratio of the adsorbent added to the raffinate is (0.3-0.5):1; Preferably, the content of heteroatom compounds in the purified oil obtained by the extraction and adsorption is not higher than 10 wt%. Preferably, the conditions for the hydrorefining treatment include: a temperature of 300-350℃, a pressure of 15-18 MPa, a hydrogen-to-oil ratio of 1000-1500, and a feed space velocity of 0.5-1.5 h⁻¹. -1 .

4. The method according to any one of claims 1-3, wherein, The pour point of the No. 1 special oil is -47 to -60°C, preferably -55 to -60°C; Preferably, in step (5), the alkylation treatment is carried out in the presence of an alkylation catalyst; Preferably, the alkylation catalyst comprises HY molecular sieve; Preferably, the alkylation treatment conditions include: a temperature of 190-230°C, a pressure of 2-4 MPa, and a feed space velocity of 1-5 h⁻¹. -1 .

5. The method according to any one of claims 1-4, wherein, The density of the No. 2 special oil is not less than 0.85 g / mL, preferably 0.87-0.88 g / mL; Preferably, in step (5), the hydrogenation saturation treatment is carried out in the presence of a hydrogenation saturation catalyst; Preferably, the hydrogenation saturation catalyst comprises a USY molecular sieve and a noble metal component supported on the USY molecular sieve; Preferably, the noble metal component is Pt and / or Pd; Preferably, based on the mass of the USY molecular sieve, the content of the noble metal component, calculated as an element, is 1-1.5 wt%. Preferably, the conditions for the hydrosaturation treatment include: a temperature of 220-320℃, a pressure of 10-15 MPa, a hydrogen-to-oil ratio of 1000-1200, and a feed space velocity of 1-2 h⁻¹. -1 .

6. The method according to any one of claims 1-5, wherein, The density of the No. 3 special oil is not less than 0.94 g / mL, preferably 0.94-0.95 g / mL.

7. The method according to any one of claims 1-6, wherein, The cracking ring isomerization treatment is carried out in the presence of a cracking ring isomerization catalyst; Preferably, the cracking cyclic isomeric catalyst is a bimetallic catalyst, wherein the first metal component is selected from at least one of Ni, Pt and Ru, and the second metal component is selected from Mo and / or Pd; Preferably, based on the total amount of the cracking cyclic isomer catalyst, the content of the first metal component is 1-2 wt%, and the content of the second metal component is 0.5-1.5 wt%. Preferably, the conditions for the cracking cycloisomerization treatment include: a temperature of 300-380℃, a pressure of 8-10 MPa, and a feed space velocity of 0.5-2 h⁻¹. -1 .

8. The method according to any one of claims 1-7, wherein, In step (6), the mass ratio of No. 1 special oil, No. 2 special oil and No. 3 special oil is 1:(2-2.5):(1.5-2.5), preferably 1:(2.1-2.4):(1.7-1.9). Preferably, the conditions for the refined compounding include: a temperature of 240-280℃ and a pressure of 8-12MPa.

9. The special fuel obtained by the method according to any one of claims 1-8; Preferably, the density of the special fuel is 0.78-0.95 g / mL; Preferably, the net calorific value of the special fuel is 35-43 MJ / L.

10. A system for preparing special fuels from medium- and low-temperature coal tar, comprising: The first fractionation unit is used to perform the first fractionation of the raw material coal tar. The separation unit includes an extraction device and an adsorption separation device connected in sequence, used to extract and adsorb the distillate oil from the first fractionation unit; The separation unit may also optionally include a hydrorefining unit connected to the purified oil outlet of the adsorption separation unit; The second fractionation unit is connected to the outlet of the impurity-removed oil product of the adsorption separation unit and / or the outlet of the hydrorefining unit, and is used to perform a second fractionation on the products of the impurity-removed oil product and / or the hydrorefining treatment; the second fractionation unit includes a No. 1 distillate oil outlet, a No. 2 distillate oil outlet and a No. 3 distillate oil outlet. The conversion unit includes an alkylation unit connected to the No. 1 distillate oil outlet of the second fractionation unit, a hydrogenation saturation unit connected to the No. 2 distillate oil outlet of the second fractionation unit, and a cracking cycloisolation unit connected to the No. 3 distillate oil outlet of the second fractionation unit. The compounding unit is connected to the alkylation unit, the hydrogenation saturation unit and the cracking cycloisomerization unit respectively, and is used to refine and compound the specialty oils from the above units. Preferably, the extraction device includes an extract outlet and a raffinate outlet, the raffinate outlet being connected to the inlet of the adsorption separation device, and the extract outlet being connected to the inlet of the alkylation device.

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