A combined process for treating coal tar

Abstract

The present invention provides a combined process method for treating coal tar, which comprises the following steps: (1) coal tar raw material enters a fractionation unit to obtain light distillate oil and heavy distillate oil; (2) the light distillate oil obtained in step (1) is mixed with a first hydrogen stream and then enters a microbubble generator to obtain a first mixed stream; the heavy distillate oil is mixed with a second hydrogen stream to obtain a second mixed stream; (3) the first mixed stream and the second mixed stream obtained in step (2) respectively enter an ebullating bed hydrogenation reaction zone through a gas-liquid distribution plate, undergo hydrogenation reaction in the presence of hydrogen, and the reaction effluent is subjected to gas-liquid separation to obtain a gas phase effluent and a liquid phase effluent; (4) the liquid phase effluent obtained in step (3) enters a fixed bed hydrogenation reaction zone, and the reaction effluent is separated to obtain products such as liquefied gas, naphtha, and crude white oil. The method has a high hydrogenation conversion rate and low production cost, and can also inhibit the condensation and coking reaction of unsaturated olefins contained in the coal tar, thereby achieving long-term stable operation of the device.

Description

Technical Field

[0001] The invention belongs to the technical field of coal chemical industry, and relates to a combined process method for treating coal tar, in particular to a combined ebullated bed-fixed bed process method for treating coal tar. Background Art

[0002] Coal tar contains a large amount of unsaturated hydrocarbons, such as olefins. During fixed-bed hydrogenation, these hydrocarbons easily condense and form coke upon heating, leading to blockage of the reactor feed port and increased bed pressure drop. While using an ebullated-bed reactor for coal tar hydrogenation effectively reduces the risk of pressure buildup and coking by providing a uniform distribution of the gas, liquid, and solid phases, the ebullated-bed reactor has been found to still experience bubble blockage and coking during actual operation.

[0003] CN101250433A discloses a coal tar hydrogenation process, comprising pre-treating coal tar to obtain a coal tar hydrogenation feed; feeding the obtained coal tar hydrogenation feed upward into a pre-hydrogenation reactor; feeding the obtained pre-hydrogenation product oil downward into a main hydrogenation fixed-bed reactor; and feeding the obtained main hydrogenation product oil into a fractionation system to obtain gasoline, diesel, and light fuel oil fractions. This invention utilizes a fixed bed for coal tar hydrogenation pretreatment, but the bed is prone to temperature runaway and pressure rise issues. Furthermore, compared with ebullating bed coal tar hydrogenation, the operating cycle is short and the economic benefits are low.

[0004] CN107298984A discloses a method for hydrogenating a full-fraction coal tar ebullated bed reactor. The method comprises heating the full-fraction coal tar to the required temperature for the ebullated bed hydrogenation reaction and then mixing it with circulating oil from the ebullated bed reactor. The mixture is mixed with hydrogen in a hydrogen mixer to dissolve the hydrogen and then enters a gas-liquid separator. The gas phase at the top of the gas-liquid separator enters a fixed-bed hydrogenation reactor from the top of the reactor, while the liquid phase dissolved with hydrogen at the bottom of the gas-liquid separator enters the ebullated bed reactor from the bottom of the reactor to contact the ebullated bed hydrogenation catalyst for hydrogenation. A gas-liquid-solid three-phase separator is disposed in the upper portion of the ebullated bed reactor. The gas phase separated by the three-phase separator is discharged from the top of the ebullated bed reactor to the fixed-bed hydrogenation reactor, and a small portion of the liquid phase separated by the three-phase separator is passed through a circulation system as circulating oil. The ebullated bed feed in this invention is full-fraction coal tar and circulating oil. During the heating process to the reaction temperature, the feed is prone to coking, which can cause blockage of the gas-liquid separator, resulting in biased flow and dead zones in the system. Summary of the Invention

[0005] During their research, the inventors discovered that coal tar contains a large amount of unsaturated olefins, such as dienes and polyenes. These olefins have a greater tendency to condense than aromatics, leading to a greater tendency to form coke at temperatures above 180°C. In conventional ebullated-bed coal tar hydrogenation systems, hydrogen is typically dispersed in the reactor as 3-5 mm bubbles. These large bubbles have a small mass transfer area, resulting in a low probability of contact with the catalyst's active centers. This makes it difficult for the unsaturated olefins in the coal tar to come into contact with hydrogen for hydrogenation and saturation reactions. Consequently, the dienes and polyenes tend to condense and form coke.

[0006] In response to the deficiencies in the prior art, the present invention provides a combined process method for treating coal tar, which has a high hydrogenation conversion rate and low production cost. At the same time, it can inhibit the condensation and coking reaction of unsaturated olefins contained in coal tar, thereby achieving long-term stable operation of the device.

[0007] The present invention provides a combined process for treating coal tar, which comprises the following contents:

[0008] (1) Coal tar feedstock enters the fractionation unit to produce light distillate oil and heavy distillate oil;

[0009] (2) The light distillate oil obtained in step (1) is mixed with the first hydrogen stream and then enters the microbubble generator to obtain a first mixed stream; the heavy distillate oil is mixed with the second hydrogen stream to obtain a second mixed stream;

[0010] (3) The first mixed stream and the second mixed stream obtained in step (2) enter the ebullated bed hydrogenation reaction zone through a gas-liquid distribution plate respectively, and undergo hydrogenation reaction in the presence of hydrogen. The reaction effluent is subjected to gas-liquid separation to obtain a gas phase effluent and a liquid phase effluent;

[0011] (4) The liquid effluent obtained in step (3) enters the fixed bed hydrogenation reaction zone, and the reaction effluent is separated to obtain products such as naphtha and crude white oil.

[0012] In step (1) of the method of the present invention, the coal tar raw material is preferably pretreated before entering the fractionation unit, and the pretreatment process includes dehydration treatment and desolidification treatment. The dehydration treatment and desolidification treatment can adopt one or more methods that can achieve coal tar dehydration treatment and desolidification treatment in the prior art. Specifically, in the present invention, the coal tar dehydration treatment can adopt at least one of chemical demulsification separation method, gravity sedimentation method, centrifugal separation method, and microwave radiation method, and the desolidification treatment can adopt centrifugation method and / or membrane filtration method.

[0013] In step (1) of the method of the present invention, the fractionation unit can be any one of a single-stage evaporator, atmospheric distillation, and reduced pressure distillation.

[0014] In step (1) of the method of the present invention, the olefin components in the coal tar are substances that easily form coke and are mostly present in the fraction below 180°C. The cutting temperature of the light distillate oil and the heavy distillate oil is 150°C to 260°C, preferably 180°C to 230°C.

[0015] In step (2) of the method of the present invention, the microbubble generator mainly produces micron-sized and millimeter-sized bubbles, and its main function is to provide a hydrogen source for the coal tar hydrodeoxygenation and denitrification reactions. The microbubble generator can be one or more of the following types: Venturi type, jet type, high-speed rotary cutting type, and microporous membrane type.

[0016] In step (2) of the method of the present invention, the first hydrogen stream accounts for 2% to 70% of the total hydrogen stream volume, preferably 10% to 30%; the total hydrogen stream volume is the sum of the first hydrogen stream volume and the second hydrogen stream volume.

[0017] In step (3) of the method of the present invention, the light distillate oil and the first hydrogen stream enter the microbubble generator for mixing. To ensure the viscosity of the mixed material and prevent olefin coking, the feed temperature of the first mixed stream is 80°C to 170°C, preferably 100°C to 130°C.

[0018] In step (3) of the method of the present invention, in order to ensure the fluidity of the oil product and meet the feed temperature of the second mixed flow, the feed temperature of the second mixed flow is controlled to be 150°C to 240°C, preferably 170°C to 220°C.

[0019] In step (3) of the method of the present invention, at least one ebullated bed reactor is provided in the ebullated bed hydrogenation reaction zone; the ebullated bed reactor may adopt any one of the prior arts in the art, preferably an ebullated bed reactor with a three-phase separator developed by Sinopec (Dalian) Petrochemical Research Institute Co., Ltd. The reactor utilizes the principles of centrifugal separation and cyclone separation, and can fully separate gases, liquids, and solids with large density and weight differences, thereby better solving the problem of difficulty in separating emulsions containing microbubbles.

[0020] In step (3) of the method of the present invention, the gas-liquid distribution plate is arranged above the bottom feed port of the ebullated bed reactor; the gas-liquid distribution plate is provided with a gas-liquid distributor and a microbubble discharge pipe; the first mixture flows through the microbubble discharge pipe into the ebullated bed reactor, and the second mixture flows through the gas-liquid distributor into the ebullated bed reactor.

[0021] In step (3) of the method of the present invention, the gas-liquid distributors are arranged on the gas-liquid distribution plate at intervals along the circumferential direction to form a circle, and the gas-liquid distribution plate is provided with several circles of gas-liquid distributors at intervals along the axial direction; the microbubble discharge ports of the microbubble discharge pipe are arranged on the gas-liquid distribution plate at intervals along the circumferential direction to form a circle, and the gas-liquid distribution plate is provided with several circles of microbubble discharge ports at intervals along the axial direction; the several circles of gas-liquid distributors and the several circles of microbubble discharge ports are arranged on the gas-liquid distribution plate in a concentric form.

[0022] In step (3) of the method of the present invention, the plurality of circles of gas-liquid distributors and the plurality of circles of microbubble outlets are alternately arranged in a concentric manner on the gas-liquid distribution plate.

[0023] In step (3) of the method of the present invention, the gas-liquid distributors are evenly spaced along the circumferential direction on the gas-liquid distribution plate to form a circle.

[0024] In step (3) of the method of the present invention, the microbubble discharge ports of the microbubble discharge pipe are evenly spaced along the circumferential direction on the gas-liquid distribution plate to form a circle.

[0025] In step (3) of the method of the present invention, the angle formed by the discharge direction of the gas-liquid distributor and the vertical direction of the ebullated bed reactor is 45 to 135 degrees; the discharge direction of the microbubble discharge pipe is parallel to the vertical direction of the ebullated bed reactor.

[0026] In step (3) of the method of the present invention, the gas-liquid distributor is one or more of a bubble cap type, a porous coil type, and a porous row tube type. The second mixture flows through the gas-liquid distributor to mainly generate millimeter-scale and centimeter-scale bubbles, which provide power for the circulating fluidization in the ebullating bed reactor.

[0027] In step (3) of the method of the present invention, the ebullated bed hydrogenation reaction zone is filled with a catalyst, the catalyst comprising a carrier and an active metal component, the carrier comprising alumina, and the active metal component comprising molybdenum and / or nickel. Specifically, in the present invention, the catalyst may be the FEC-10 catalyst with stepped channels developed by Sinopec (Dalian) Petrochemical Research Institute Co., Ltd.

[0028] In step (3) of the method of the present invention, the operating conditions of the ebullated bed hydrogenation reaction zone are as follows: reaction temperature 340°C to 420°C, reaction pressure 13MPa to 17MPa, volume space velocity 0.2h -1 ~1.2h -1 , hydrogen-oil volume ratio 300~1000; preferably, reaction temperature 350 ℃~400 ℃, reaction pressure 14MPa~16MPa, volume space velocity 0.5h -1 ~1.0h -1 , hydrogen-to-oil volume ratio is 500-800.

[0029] In step (4) of the method of the present invention, the liquid effluent obtained in step (3) preferably first enters a fractionation system for cutting to obtain a light component and a heavy component, and the heavy component then enters the fixed bed hydrogenation reaction zone; wherein part or all of the light component is circulated to the microbubble generator, and further preferably, part or all of the light component is mixed with the light distillate oil and the first hydrogen stream before entering the microbubble generator.

[0030] In step (4) of the method of the present invention, in order to satisfy the microbubble generator to generate a slug flow (Reynolds number Re> 24770), the light component needs to have a low viscosity under working conditions; the viscosity of the light component (40 ° C) is < 10mm 2 / s, preferably viscosity (40℃) < 8mm 2 / s.

[0031] In step (4) of the method of the present invention, the cutting point between the light component and the heavy component is 170-350°C, preferably 180-230°C.

[0032] In step (4) of the method of the present invention, the fixed bed hydrogenation reaction zone preferably includes a fixed bed hydrofining reaction zone and a fixed bed hydrocracking reaction zone; the fixed bed hydrofining reaction zone and the fixed bed hydrocracking reaction zone can be arranged in one reactor, or can be arranged in more than one reactor respectively.

[0033] In step (4) of the method of the present invention, the fixed-bed hydrorefining reaction zone is loaded with at least one hydrorefining catalyst. The hydrorefining catalyst comprises a carrier and an active metal component. The carrier comprises alumina, and the active metal component may be one or more of nickel and molybdenum. The active metal component is present in an amount of 10 to 80 wt.% as a metal oxide, based on the weight of the catalyst.

[0034] In step (4) of the method of the present invention, the fixed-bed hydrocracking reaction zone is loaded with at least one hydrocracking catalyst. The hydrocracking catalyst comprises a molecular sieve and an active metal component. The molecular sieve may be a Y-type and / or a β-type molecular sieve. The active metal component may be one or more of nickel, cobalt, and tungsten. The active metal component is present in an amount of 5 to 40 wt.% as a metal oxide, based on the weight of the catalyst.

[0035] In step (4) of the method of the present invention, the operating conditions of the fixed bed hydrogenation reaction zone are as follows: reaction temperature 350°C to 450°C, reaction pressure 14MPa to 19MPa, volume space velocity 0.5h -1 ~1.5h -1 , hydrogen-oil volume ratio 500~1500; preferably, reaction temperature 380 ℃~420 ℃, reaction pressure 15MPa~18MPa, volume space velocity 0.6h -1~1.3h -1 , hydrogen-to-oil volume ratio is 800-1300.

[0036] The method of the present invention has the following advantages:

[0037] (1) The gas-liquid distributor and microbubble generator of the ebullated bed coal tar hydrogenation reaction unit are combined to generate micron, millimeter and centimeter-level bubbles that are evenly distributed in the ebullated bed reactor. The multi-level bubbles work together to ensure full fluidization of the catalyst while increasing the liquid residence time to ensure the circulating fluidization of the fluid.

[0038] (2) Microbubble generators are used to generate micron-sized hydrogen bubbles. By reducing the bubble size, the mass transfer area is increased, the reaction rate is improved, and the coal tar hydrogenation reaction is promoted, thus achieving the goal of low energy consumption (low temperature, low pressure) and low cost conversion.

[0039] (3) Cut the oil generated in the ebullated bed and feed part or all of the light fraction into the microbubble generator to increase the liquid feed amount of the microbubble generator and reduce the viscosity of the liquid in the microbubble generator system to ensure that the hydrogen content and gas-liquid mass transfer area of ​​the ebullated bed hydrogenation reaction unit meet the reaction requirements.

[0040] (4) The coal tar cut fractions are processed separately, and the low-viscosity light fraction is fed into the ebullated bed reactor in the form of an emulsion with hydrogen through a microbubble generator at low temperature. This not only avoids the clogging of the microbubble generator by large molecules, but also avoids the high-temperature condensation of olefins and polyenes in the light fraction, which leads to coking at the feed port of the ebullated bed reactor. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a schematic flow chart of the combined process for treating coal tar used in Examples 1-3.

[0042] Among them, 1 is hydrogen material, 2 is coal tar, 3 and 12 are fractionation units, 4 is a microporous membrane tube, 5 is a gas-liquid distributor, 6 is an ebullated bed hydrogenation reactor, 7 and 10 are high-pressure separators, 8 and 11 are low-pressure separators, 9 is a fixed bed hydrogenation reactor, 13 and 14 are coal tar raw materials entering the fractionation unit to obtain light distillate oil and heavy distillate oil, 15 and 16 are the first hydrogen flow and the second hydrogen flow, 17 is the reaction effluent of the ebullated bed hydrogenation reactor, 18 is gas, 19 is naphtha, and 20 is crude white oil.

[0043] Figure 2 This is a schematic flow chart of the combined process for treating coal tar used in Examples 4-5.

[0044] Among them, 1 is the hydrogen feed, 2 is coal tar, 3, 9, and 13 are the fractionation unit, 4 is a microporous membrane tube, 5 is a gas-liquid distributor, 6 is an ebullated-bed hydrogenation reactor, 7 and 11 are high-pressure separators, 8 and 12 are low-pressure separators, and 10 is a fixed-bed hydrogenation reactor. 14 and 15 are the coal tar feed entering the fractionation unit to obtain light distillate and heavy distillate, respectively. 16 and 17 are the first hydrogen stream and the second hydrogen stream, respectively. 18 is the reaction effluent of the ebullated-bed hydrogenation reactor. 19 and 20 are the light and heavy components obtained by cutting the fractionation system, respectively. 21 is gas, 22 is naphtha, and 23 is crude white oil.

[0045] Figure 3 The flow chart of the combined process method for treating coal tar is shown in FIG.

[0046] Among them, 1 is hydrogen feed, 2 is coal tar, 3 is a gas-liquid distributor, 4 is an ebullated-bed hydrogenation reactor, 5 and 8 are high-pressure separators, 6 and 9 are low-pressure separators, 7 is a fixed-bed hydrogenation reactor, 10 is a fractionation unit, 11 is the reaction effluent of the ebullated-bed hydrogenation reactor, 12 is gas, 13 is naphtha, and 14 is crude white oil.

[0047] Figure 4 This is a schematic diagram of the gas-liquid distribution plate layout. The gas-liquid distributors and microbubble membrane tubes are arranged in concentric circles, with six microbubble membrane tubes arranged in each of the two inner circles and twelve gas-liquid distributors arranged in each of the two outer circles.

[0048] Figure 5 This is a schematic diagram of the gas-liquid distributor arrangement. The gas-liquid distributors and microbubble membrane tubes are arranged in a staggered concentric circle pattern. From the inner circle to the outer circle (the inner circle is the center of the circle, and the outer circle is the bed wall), the arrangement is as follows: 6 microbubble membrane tubes, 6 gas-liquid distributors, 12 microbubble membrane tubes, and 12 gas-liquid distributors.

[0049] Figure 6 The diagram below shows the layout of the gas-liquid distribution plate. The gas-liquid distributors are arranged in concentric circles, with the number of gas-liquid distributors arranged from the inner circle to the outer circle being 6, 6, 12, and 12 respectively. Implementation Method

[0050] The method of the present invention is further described below with reference to the accompanying drawings, specific examples, and comparative examples, but the following examples do not limit the method of the present invention. In the context of the present invention, all % are by mass unless otherwise specified.

[0051] The method provided by the present invention is described below with reference to the accompanying drawings.

[0052] like Figure 1As shown, coal tar 2 enters the fractionation unit 3 for cutting to obtain light distillate oil 13 and heavy distillate oil 14; the light distillate oil 13 is mixed with the first hydrogen stream 15 and enters the ebullated bed hydrogenation reactor 6 through the microporous membrane tube 4 of the microbubble generator, and the heavy distillate oil 14 is mixed with the second hydrogen stream 16 and enters the ebullated bed hydrogenation reactor 6 through the gas-liquid distributor 5; the ebullated bed liquid phase effluent 17 passes through the high-pressure separator 7 and the low-pressure separator 8 in sequence for gas-liquid separation and then enters the fixed bed hydrogenation reactor 9, and the fixed bed liquid phase effluent passes through the high-pressure separator 10 and the low-pressure separator 11 in sequence for gas-liquid separation, and is finally cut by the fractionation tower 12 to obtain naphtha 19 and crude white oil 20.

[0053] like Figure 2 As shown, coal tar 2 first enters the fractionation unit 3 for cutting to obtain light distillate oil 14 and heavy distillate oil 15; the light distillate oil 14 is mixed with the first hydrogen stream 16 and passes through the microporous membrane tube 4 of the microbubble generator to enter the ebullated bed hydrogenation reactor 6, and the heavy distillate oil 15 is mixed with the second hydrogen stream 17 and passes through the gas-liquid distributor 5 to enter the ebullated bed hydrogenation reactor 6; the ebullated bed liquid phase effluent 18 is sequentially passed through the high-pressure separator 7 and the low-pressure separator 8 for gas-liquid separation, and the separated liquid phase is cut through the fractionation tower 9 to obtain a light component 19 and a heavy component 20, wherein the light component 19 is refluxed back to the ebullated bed reactor 6 through the microporous membrane tube 4 of the microbubble generator, and the heavy component 20 enters the fixed bed hydrogenation reactor 10 for hydrorefining and hydrocracking, and the fixed bed liquid phase effluent is sequentially passed through the high-pressure separator 11 and the low-pressure separator 12 for gas-liquid separation, and finally cut through the fractionation unit 13 to obtain naphtha 22 and crude white oil 23.

[0054] like Figure 3 As shown, coal tar 2 is mixed with hydrogen flow 1 and enters into the ebullated bed hydrogenation reactor 4. The ebullated bed liquid phase effluent 11 passes through the high-pressure separator 5 and the low-pressure separator 6 in sequence for gas-liquid separation and then enters into the fixed bed hydrogenation reactor 7. The fixed bed liquid phase effluent passes through the high-pressure separator 8 and the low-pressure separator 9 in sequence for gas-liquid separation and finally is cut by the fractionation unit 10 to obtain naphtha 13 and crude white oil 14.

[0055] The following examples will further illustrate the method provided by the present invention, but are not intended to limit the present invention.

[0056] The raw materials used in the examples and comparative examples of this patent are full-fraction coal tar that has been pretreated by dehydration and desolidification. The specific properties are shown in Table 1.

[0057] Table 1 Coal tar raw material properties

[0058]

[0059] The microbubble generator used in the embodiment of this patent is a microporous membrane tube; an ebullated bed reactor is provided in the ebullated bed hydrogenation reaction zone, and the catalyst loaded is a commercially available FEC-10 catalyst developed by Sinopec (Dalian) Petrochemical Research Institute Co., Ltd.; a fixed bed reactor is provided in the fixed bed hydrogenation reaction zone, and the fixed bed reactor is respectively loaded with a hydrorefining catalyst and a hydrocracking catalyst in accordance with the contact direction with the logistics, with a loading volume ratio of 1:1. The hydrorefining catalyst used is a commercially available FHMJ-2 catalyst developed by Sinopec (Dalian) Petrochemical Research Institute Co., Ltd.; the hydrocracking catalyst used is a commercially available FHMJ-3 catalyst developed by Sinopec (Dalian) Petrochemical Research Institute Co., Ltd.

[0060] Example 1

[0061] (1) Coal tar raw material is subjected to vacuum distillation to obtain light distillate oil and heavy distillate oil, with a cut point of 180℃;

[0062] (2) The light distillate oil obtained in step (1) is mixed with the first hydrogen stream and then enters the microbubble generator to obtain a first mixed stream; the heavy distillate oil is mixed with the second hydrogen stream to obtain a second mixed stream; the first hydrogen stream accounts for 10% of the total hydrogen stream volume; the temperature of the first mixed stream is 80°C, and the temperature of the second mixed stream is 170°C;

[0063] (3) The first mixed flow and the second mixed flow obtained in step (2) enter the ebullated bed hydrogenation reaction zone respectively through a gas-liquid distribution plate; the gas-liquid distribution plate is provided with a gas-liquid distributor and a micro-bubble discharge pipe, the first mixed flow enters the ebullated bed hydrogenation reaction zone through the micro-bubble discharge pipe, and the second mixed flow enters the ebullated bed hydrogenation reaction zone through the gas-liquid distributor, and the hydrogenation reaction is carried out in the presence of hydrogen, and the reaction effluent is subjected to gas-liquid separation to obtain a gas phase effluent and a liquid phase effluent; the structure of the gas-liquid distribution plate is as follows Figure 4 As shown, the gas-liquid distributor and the microporous membrane tube are arranged in concentric circles, the inner layer is the microporous membrane tube, and the outer layer is the gas-liquid distributor;

[0064] (4) The liquid effluent obtained in step (3) enters the fixed bed hydrogenation reaction zone, and the reaction effluent is separated to obtain naphtha, crude white oil and hydrogenation tail oil.

[0065] The operating conditions are shown in Table 2:

[0066] Table 2 Operating conditions

[0067]

[0068] Example 2

[0069] (1) Coal tar raw material is subjected to vacuum distillation to obtain light distillate oil and heavy distillate oil, with a cut point of 200℃;

[0070] (2) The light distillate oil obtained in step (1) is mixed with the first hydrogen stream and then enters the microbubble generator to obtain a first mixed stream; the heavy distillate oil is mixed with the second hydrogen stream to obtain a second mixed stream; the first hydrogen stream accounts for 20% of the volume of the total hydrogen stream; the temperature of the first mixed stream is 90°C, and the temperature of the second mixed stream is 195°C;

[0071] (3) The first mixed flow and the second mixed flow obtained in step (2) enter the ebullated bed hydrogenation reaction zone respectively through a gas-liquid distribution plate, wherein the gas-liquid distribution plate is provided with a gas-liquid distributor and a micro-bubble discharge pipe. The first mixed flow enters the ebullated bed hydrogenation reaction zone through the micro-bubble discharge pipe, and the second mixed flow enters the ebullated bed hydrogenation reaction zone through the gas-liquid distributor. A hydrogenation reaction is carried out in the presence of hydrogen, and the reaction effluent is subjected to gas-liquid separation to obtain a gas phase effluent and a liquid phase effluent; the structure of the gas-liquid distribution plate is as follows: Figure 4 As shown, the gas-liquid distributor and the microporous membrane tube are arranged in concentric circles, the inner layer is the microporous membrane tube, and the outer layer is the gas-liquid distributor;

[0072] (4) The liquid effluent obtained in step (3) enters the fixed bed hydrogenation reaction zone, and the reaction effluent is separated to obtain naphtha and crude white oil.

[0073] The operating conditions are shown in Table 3:

[0074] Table 3 Operating conditions

[0075]

[0076] Example 3

[0077] (1) Coal tar raw material is subjected to vacuum distillation to obtain light distillate oil and heavy distillate oil; the cut point is 230℃;

[0078] (2) The light distillate oil obtained in step (1) is mixed with the first hydrogen stream and then enters the microbubble generator to obtain a first mixed stream; the heavy distillate oil is mixed with the second hydrogen stream to obtain a second mixed stream; the first hydrogen stream accounts for 30% of the volume of the total hydrogen stream; the temperature of the first mixed stream is 100°C, and the temperature of the second mixed stream is 220°C;

[0079] (3) In step (2), the first mixed flow and the second mixed flow enter the ebullated bed hydrogenation reaction zone respectively through a gas-liquid distribution plate, the gas-liquid distribution plate is provided with a gas-liquid distributor and a micro-bubble discharge pipe, the first mixed flow enters the ebullated bed hydrogenation reaction zone through the micro-bubble discharge pipe, and the second mixed flow enters the ebullated bed hydrogenation reaction zone through the gas-liquid distributor, and the hydrogenation reaction is carried out in the presence of hydrogen, and the reaction effluent is subjected to gas-liquid separation to obtain a gas phase effluent and a liquid phase effluent; the structure of the gas-liquid distribution plate is as follows: Figure 5As shown, the gas-liquid distributor and the microporous membrane tube are arranged in a staggered concentric circle;

[0080] (4) The liquid effluent obtained in step (3) enters the fixed bed hydrogenation reaction zone, and the reaction effluent is separated to obtain naphtha and crude white oil.

[0081] The operating conditions are shown in Table 4:

[0082] Table 4 Operating conditions

[0083]

[0084] Example 4

[0085] The process flow and operating conditions of this embodiment are basically the same as those of Example 1, except that: the liquid effluent obtained from the ebullating bed hydrogenation reaction zone enters the fractionation system for cutting to obtain light components and heavy components, wherein the heavy components enter the fixed bed hydrogenation reaction zone; all the light components are mixed with the light distillate oil and the first hydrogen stream and then enter the microbubble generator.

[0086] The cutting point between light component and heavy component is 350℃, and the viscosity of light component (40℃) is 8.46mm 2 / s.

[0087] Example 5

[0088] The process flow and operating conditions of this embodiment are basically the same as those of Example 1, except that: the liquid effluent obtained from the ebullating bed hydrogenation reaction zone enters the fractionation system for cutting to obtain light components and heavy components, wherein the heavy components enter the fixed bed hydrogenation reaction zone; all the light components are mixed with the light distillate oil and the first hydrogen stream and then enter the microbubble generator.

[0089] The cutting point between light component and heavy component is 280℃, and the viscosity of light component (40℃) is 4.79mm 2 / s.

[0090] Comparative Example

[0091] The process flow and operating conditions of this embodiment are basically the same as those of Example 1. The difference is that the coal tar is not cut and directly enters the ebullated bed reactor. There is no microbubble generator in the ebullated bed reactor. Only a gas-liquid distributor is set. The gas-liquid distributor is arranged as follows: Figure 6 Shown are arranged in concentric circles.

[0092] The reaction results of the embodiments and comparative examples are shown in Table 5.

[0093] Table 5 Reaction results after 600h operation

[0094]

Claims

1. A combined method for treating coal tar, characterized in that: The method includes the following: (1) Coal tar feedstock enters the fractionation unit to produce light distillate oil and heavy distillate oil; (2) The light distillate oil obtained in step (1) is mixed with the first hydrogen stream and then enters the microbubble generator to obtain a first mixed stream; the heavy distillate oil is mixed with the second hydrogen stream to obtain a second mixed stream; (3) The first mixed stream and the second mixed stream obtained in step (2) enter the ebullated bed hydrogenation reaction zone through a gas-liquid distribution plate respectively, and undergo hydrogenation reaction in the presence of hydrogen. The ebullated bed hydrogenation reaction effluent is subjected to gas-liquid separation to obtain a gas phase effluent and a liquid phase effluent; (4) The liquid effluent obtained in step (3) enters the fixed bed hydrogenation reaction zone, and the fixed bed hydrogenation reaction effluent is separated to obtain naphtha and crude white oil products; In step (1), the cutting temperature of the light distillate oil and the heavy distillate oil is 150°C to 260°C; In step (3), the ebullated bed hydrogenation reaction zone is provided with at least one ebullated bed reactor; In step (3), the gas-liquid distribution plate is arranged above the bottom feed port of the ebullated bed reactor; the gas-liquid distribution plate is provided with a gas-liquid distributor and a microbubble discharge pipe; the first mixture flows through the microbubble discharge pipe into the ebullated bed reactor, and the second mixture flows through the gas-liquid distributor into the ebullated bed reactor; In step (3), the gas-liquid distributors are arranged on the gas-liquid distribution plate at intervals along the circumferential direction to form a circle, and the gas-liquid distribution plate is provided with several circles of gas-liquid distributors at intervals along the axial direction; the microbubble discharge ports of the microbubble discharge pipe are arranged on the gas-liquid distribution plate at intervals along the circumferential direction to form a circle, and the gas-liquid distribution plate is provided with several circles of microbubble discharge ports at intervals along the axial direction; the several circles of gas-liquid distributors and the several circles of microbubble discharge ports are arranged on the gas-liquid distribution plate in a concentric form.

2. The method according to claim 1, wherein: In step (1), the coal tar raw material is pretreated before entering the fractionation unit, and the pretreatment process includes dehydration treatment and solid removal treatment; the dehydration treatment adopts at least one of chemical demulsification separation method, gravity sedimentation method, centrifugal separation method, and microwave radiation method, and the solid removal treatment adopts centrifugation method and / or membrane filtration method.

3. The method according to claim 1, wherein: In step (1), the cutting temperature of the light distillate oil and the heavy distillate oil is 180°C to 230°C.

4. The method according to claim 1, wherein: In step (2), the microbubble generator is one or more of the following: Venturi type, jet type, high-speed rotary cutting type, and microporous membrane type.

5. The method according to claim 1, wherein: In step (2), the first hydrogen flow accounts for 2% to 70% of the volume of the total hydrogen flow.

6. The method according to claim 5, characterized in that: In step (2), the first hydrogen flow accounts for 10% to 30% of the volume of the total hydrogen flow.

7. The method according to claim 1, wherein: In step (3), the feed temperature of the first mixed flow is controlled to be 80°C to 170°C.

8. The method according to claim 1, wherein: In step (3), the feed temperature of the first mixed flow is controlled to be 100°C to 130°C.

9. The method according to claim 1, wherein: In step (3), the feed temperature of the second mixed flow is controlled to be 150°C to 240°C.

10. The method according to claim 9, characterized in that: In step (3), the feed temperature of the second mixed flow is controlled to be 170°C to 220°C.

11. The method according to claim 1, wherein: In step (3), the ebullated bed hydrogenation reaction zone is filled with a catalyst, the catalyst comprising a carrier and an active metal component, the carrier comprising alumina, and the active metal component comprising molybdenum and / or nickel.

12. The method according to claim 1, wherein: In step (3), the operating conditions of the ebullated bed hydrogenation reaction zone are as follows: reaction temperature 340℃~420℃, reaction pressure 13MPa~17MPa, volume space velocity 0.2h -1 ~1.2h -1 , hydrogen-to-oil volume ratio is 300-1000.

13. The method according to claim 12, wherein: In step (3), the operating conditions of the ebullated bed hydrogenation reaction zone are as follows: reaction temperature 350°C to 400°C, reaction pressure 14MPa to 16MPa, volume space velocity 0.5h -1 ~1.0h -1 , hydrogen-to-oil volume ratio is 500-800.

14. The method according to claim 1, wherein: The liquid effluent obtained in step (3) enters the fractionation system for cutting to obtain light components and heavy components, and the heavy components enter the fixed bed hydrogenation reaction zone; wherein part or all of the light components are circulated to the microbubble generator.

15. The method according to claim 14, characterized in that: Part or all of the light component is mixed with the light distillate oil and the first hydrogen flow and then enters the microbubble generator.

16. The method according to claim 14, wherein: The cutting point between the light component and the heavy component is 170-350°C.

17. The method according to claim 16, wherein: The cutting point between the light component and the heavy component is 180-230°C.

18. The method according to claim 1, wherein: In step (4), the fixed bed hydrogenation reaction zone includes a fixed bed hydrofining reaction zone and a fixed bed hydrocracking reaction zone; the fixed bed hydrofining reaction zone and the fixed bed hydrocracking reaction zone are arranged in one reactor, or are respectively arranged in more than one reactor.

19. The method according to claim 1, wherein: In step (4), the operating conditions of the fixed bed hydrogenation reaction zone are as follows: reaction temperature 350°C to 450°C, reaction pressure 14MPa to 19MPa, volume space velocity 0.5h -1 ~1.5h -1 , hydrogen-to-oil volume ratio is 500-1500.

20. The method according to claim 19, wherein: In step (4), the operating conditions of the fixed bed hydrogenation reaction zone are as follows: reaction temperature 380℃~420℃, reaction pressure 15MPa~18MPa, volume space velocity 0.6h -1 ~1.3h -1 , hydrogen-to-oil volume ratio is 800-1300.

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