A raw coal gas heat recovery, coal tar pretreatment device and application

Abstract

This invention discloses a device for recovering heat from raw coal gas and pretreating coal tar, comprising: a fluidized bed hydrogenation reactor and internal components. The internal components include a heat exchanger in the middle and a gas-liquid-solid three-phase separator in the upper part. The heat exchanger position in the fluidized bed hydrogenation reactor is filled with microspherical catalysts or microspherical inert packing. In operation, the microspherical catalysts or microspherical inert packing are in a boiling state, scouring the outer surface of the heat exchanger tube bundle. This invention can recover heat from high-temperature raw coal gas while effectively pretreating coal tar, laying the foundation for subsequent processing.

Description

Technical Field

[0001] This invention relates to a device and application for recovering heat from raw coal gas and pretreating coal tar, and belongs to the technical field of preparing liquid hydrocarbon mixtures and coal gas from coal. Background Technology

[0002] my country's energy resources are unevenly distributed, characterized by "abundant coal, scarce oil, and limited gas." Coal resources are plentiful, accounting for 94.3% of proven fossil fuel reserves and contributing approximately 70% of total primary energy consumption. Among these abundant coal resources, low-rank coal has the largest reserves, accounting for 55% of proven reserves. While low-rank coal is difficult to use directly as fuel, it is a high-quality feedstock for producing liquid hydrocarbons from coal.

[0003] There are two main routes for producing liquid hydrocarbons from low-rank coal. One is direct coal liquefaction technology, which is relatively expensive. The other is coal dry distillation / coking technology, which is based on the pyrolysis reaction of low-rank coal. It is characterized by its simple and mature technology, and the coke or semi-coke obtained is a high-quality fuel and a raw material such as a reducing agent required by the metallurgical industry. At the same time, liquid hydrocarbons (i.e., coal tar) are obtained, which can be further processed to produce liquid fuels and various chemical raw materials.

[0004] During coal dry distillation / coking, the discharged raw coal gas has a high temperature, generally exceeding 600℃, accounting for about 37% of the heat output from the coke oven. The raw coal gas has a complex composition, containing solid coke powder, complex mixed hydrocarbons, complex gas phases, and water. Although this gas possesses abundant heat, its recovery and utilization are difficult, primarily due to issues such as clogging, coking, and corrosion of heat exchange equipment. Traditional technologies use ammonia water for spray cooling, resulting in complete heat loss and high energy consumption. Therefore, effectively recovering the heat from the raw coal gas, especially addressing issues like equipment clogging and coking during heat recovery, is a key focus in this field.

[0005] CN 201310391012.7 discloses a coke oven gas waste heat recovery and utilization system, including a heat exchange medium circulation system and a water supply system. The heat exchange medium circulation system includes heat exchanger groups, a steam drum, and a forced circulation pump. The inlet of the heat exchanger group is connected to the outlet of the steam drum via the forced circulation pump, and the outlet of the heat exchanger group is connected to the inlet of the steam drum. The steam outlet on the steam drum is connected to an external steam pipeline network. The water supply system includes a buffer water tank, a water supply pump, a feed water pump, and a desalination and deoxygenation water tank. The feed water pump is located between the buffer water tank and the desalination and deoxygenation water tank. The buffer water tank is connected to the steam drum via the water supply pump. This solution increases the safety and reliability of the heat exchange system, improves the safe and normal operation of the system, and reduces the accident rate by setting up multiple parallel heat exchanger groups and adding a control system to detect and handle the failure of a heat exchanger group in a timely manner. However, given the characteristics of raw coal gas, coking and fouling of the heat exchanger units will inevitably occur rapidly. Even if a parallel connection is used, maintenance of one of the units will still cause significant fluctuations and operational difficulties to normal operation.

[0006] CN201410692354.7 discloses a system and method for dust removal and tar recovery from pyrolysis raw coal gas, comprising a particulate dust collector, an electrostatic precipitator, a tar refining tower, a coal gas cooling tower, and an electrostatic tar collector connected in sequence. This invention sets up a tar refining tower between the particulate dust collector and the coal gas cooling tower, fully utilizing the heat of the coal gas itself. Through the "distillation principle," the collected tar is further dehydrated and refined, resulting in a short process flow and tar with low moisture content and high quality. This scheme directly uses the sensible heat carried by the pyrolysis coal gas as the heat source for the distillation of water-containing tar in the tar refining tower, achieving efficient heat utilization within the same tar recovery system. The aim is to provide a novel heat recovery process and method for pyrolysis raw coal gas cooling and tar recovery refining systems. However, in this scheme, the use of particulate dust collectors and electrostatic precipitators can lead to severe scaling and coking of the equipment, particularly for raw coal gas prone to coking and producing sludge-like solids, significantly impacting the operating cycle.

[0007] CN201610213831.6 discloses a raw coal gas heat recovery system and method based on washing and distillation. The raw coal gas undergoes washing and distillation to remove heavy tar and coke powder, yielding high-boiling-point oil and high-temperature raw coal gas. The high-boiling-point oil and / or high-temperature raw coal gas are then used to generate high-pressure steam through heat exchange. The high-pressure steam is then separated into steam and water, and the separated steam is utilized. This system features high dust removal efficiency, stable operation, resistance to clogging, and full heat recovery and utilization. However, the system has the following shortcomings: (1) Although the solid dust has been basically removed by washing, and the equipment blockage caused by carrying coke powder has been solved, the temperature at the bottom of the washing distillation tower is high, and the problem that the high boiling point components in the raw coal gas are prone to coking at high temperature has not been solved, which still affects the operation cycle of the device; (2) Based on the principle of plate distillation tower, although a special structure of "through-flow tray" (see paragraph 30 of its instruction manual) has been designed, the coking properties of the material have not changed, and the coking problem still exists; (3) The coking characteristics of the obtained coal tar have not changed, and the problems of coking and equipment blockage in subsequent processing are still prominent.

[0008] CN 201911169496.4 discloses a deep desulfurization system and method for coupling coke oven gas and coke. By setting up a high-temperature coke hydrogenation reactor, the hydrogenation reaction of coke can be completed using the H2 content of the raw coal gas itself without the need for additional hydrogenation, thereby transferring sulfur from the coke to the coal gas. By setting up a catalytic hydrogenation reactor, a catalyst is used to almost completely convert the organic sulfur in the raw coal gas into H2S, which efficiently and deeply removes organic and inorganic sulfur from the coke oven gas at the source, thereby greatly reducing the sulfur content of coking benzene products and coke, improving the quality of benzene products and coke, and reducing the load and difficulty of subsequent fine desulfurization. This method is carried out at high temperatures (where the coal tar components in raw coal gas are in the gas phase), such as controlling the hydrogenation reactor at 650~1000℃. Under these conditions, the coal tar components will undergo further dehydrogenation (hydrogenation / dehydrogenation is reversible; under certain conditions, such as low temperature and high pressure, it is mainly hydrogenation, and under certain conditions, such as high temperature and low pressure, it is mainly dehydrogenation), causing hydrocarbons to generate more unsaturated olefins, dienes, aromatic olefins, and other substances that are prone to coking. This not only fails to pretreat the coal tar but also brings more serious coking problems to subsequent coal tar processing.

[0009] Although existing technologies have conducted considerable research on the utilization of raw coal gas heat, they have not changed its coking characteristics, there is no good solution to the coking problem, and the impact of coking on the stable operation of the equipment remains unresolved.

[0010] Eluting bed hydrotreating is a traditional heavy oil processing technology in this field, and there are many research and industrial application examples of its use in coal tar processing. However, in existing technologies, eluting bed coal tar hydrotreating technology focuses on the hydrogenation of coal tar and has not extended to related solutions for simultaneously processing coal tar and recovering heat from raw coal gas. A typical solution is a combined fluidized bed-fixed bed processing technology for full-fraction coal tar disclosed in CN201811618736.X. In this combined process, full-fraction coal tar feedstock and additives are mixed in a pretreatment tank. After mixing, liquid-solid separation is performed. The resulting liquid phase material enters a fluidized bed hydrogenation reactor for hydrogenation. The resulting effluent enters a separator for gas-liquid separation, yielding gas and liquid phase materials. The liquid phase material is divided into two streams: a first liquid phase material and a second liquid phase material. The first liquid phase material is recycled back to the pretreatment tank; the second liquid phase material enters a fixed bed hydrogenation reactor for hydrogenation. The reaction effluent is fractionated to obtain naphtha, diesel oil, and hydrogenated tail oil.

[0011] Coal tar is a liquid mixed hydrocarbon recovered from raw coal gas. It has a complex composition and a significant tendency to coke. The traditional method is to hydrogenate it under mild conditions to hydrogenate and saturate the diene and aromatic groups that are prone to coking, thereby alleviating the problems in subsequent processing.

[0012] CN 200710034412.7 discloses a pretreatment method for coal tar, which involves mixing coal tar with distillate oil and aromatics respectively, and then performing a two-step extraction process to remove most of the impurities from the coal tar. This method can achieve a coal tar utilization rate of up to 90%. When the pretreated coal tar is used for hydroreconstitution to produce fuel oil, it can delay coking of the hydroreconstitution catalyst and extend the operating cycle of the unit. However, this method still loses a significant amount of coal tar feedstock in the pretreatment step, and the two-step extraction requires energy-intensive steps such as solvent recovery, resulting in high operating costs.

[0013] CN 200810030954.1 discloses a coal tar hydrogenation process, comprising: pre-treating coal tar to obtain a coal tar hydrogenation feed; the obtained coal tar hydrogenation feed entering a pre-hydrogenation fixed-bed reactor from bottom to top; the obtained pre-hydrogenation product entering a main hydrogenation fixed-bed reactor from top to bottom; and the obtained main hydrogenation product entering a fractionation system to obtain gasoline fraction, diesel fraction, and light fuel oil fraction. This scheme employs an upflow pre-hydrogenation fixed-bed reactor connected in series with a downflow main hydrogenation fixed-bed reactor, changing the flow direction in the process and increasing the residence time of the reactants on the catalyst bed. This can effectively inhibit or slow down the coking reaction of coal tar at high temperatures and extend the continuous operation cycle of the coal tar hydrogenation unit. However, the upflow hydrogenation method used in this scheme to alleviate coking has limited effectiveness, only improving catalyst bed blockage; the problem of coking causing catalyst inactivation remains unresolved.

[0014] CN 201010621125.8 discloses a combined hydrogenation method for coal tar and coking distillate, comprising: (1) mixing coal tar feedstock and coking distillate feedstock and introducing hydrogen into a hydrogenation pretreatment reactor for de-diolefin reaction; (2) directly mixing the effluent from the hydrogenation pretreatment reactor with the material heated by a heater in step (4) of the hydrocracking reaction to reach the required temperature at the inlet of the hydrogenation reactor; (3) introducing the effluent from the hydrogenation reactor into a separation system to separate circulating hydrogen, gasoline fraction, diesel fraction and heavy oil fraction; (4) mixing the heavy oil fraction and circulating hydrogen from step (3) into the hydrocracking reactor, and directly mixing the effluent from the hydrocracking reactor with the effluent from the hydrogenation pretreatment reactor after heating by a heater into the hydrogenation reactor. This scheme uses a pre-hydrogenated saturated diene method to solve the coking problem in the hydrogenation treatment unit for coal tar and coking distillate.

[0015] The unit that recovers coal tar from raw coal gas is independent of the subsequent processing unit. It needs to go through storage and transportation. In these stages, the precursors of coal tar coking form preliminary polymers under the action of oxygen (raw coal gas contains a small amount of nitrogen, and storage and transportation inevitably involve contact with oxygen) and active sulfur. These preliminary polymers are very easy to form coking products after the temperature rises. Therefore, it is difficult and the effect is not ideal to solve the coking problem of coal tar in the later processing. Summary of the Invention

[0016] To address the shortcomings of existing technologies, this invention provides a raw coal gas heat recovery and coal tar pretreatment device. This device organically combines the work of raw coal gas heat recovery and coal tar pretreatment, which are performed in two separate units in existing technologies, into one device. While recovering the heat of raw coal gas, it changes the coking characteristics of coal tar, ensuring the stable operation of the heat recovery device. At the same time, it effectively pretreats the coal tar for subsequent processing units, effectively solving the coking problem in subsequent coal tar processing.

[0017] The present invention relates to a raw coal gas heat recovery and coal tar pretreatment device, comprising the following:

[0018] (1) A fluidized bed hydrogenation reactor, including a vertical cylindrical body and internal components;

[0019] (2) The internal components of the fluidized bed hydrogenation reactor include: a heat exchanger in the middle and a gas-liquid-solid three-phase separator in the upper part;

[0020] (3) The bottom of the fluidized bed hydrogenation reactor is provided with a feed inlet and the top is provided with a gas phase material outlet. The side wall of the gas-liquid-solid three-phase separator is provided with a liquid phase outlet.

[0021] (4) The heat exchanger position inside the fluidized bed hydrogenation reactor is filled with microspherical catalyst or microspherical inert packing.

[0022] (5) Under operating conditions: the microsphere catalyst or microsphere inert packing is in a boiling state, scouring the outer surface of the heat exchanger tube bundle; in the gas-liquid-solid three-phase separator area, the separated gas phase is discharged from the top of the reactor, the liquid phase is discharged from the liquid phase outlet, and the microsphere catalyst or microsphere inert packing is circulated back to the middle and lower part of the reactor.

[0023] In the device of this invention, the vertical cylindrical body of the fluidized bed hydrogenation reactor includes an upper head, a lower head, and a central cylindrical body.

[0024] In the device of this invention, the heat exchanger is a shell-and-tube heat exchanger, and the gap between the tubes is more than 3 times the diameter of the microspherical catalyst or microspherical inert packing, preferably 3 to 20 times, and most preferably 5 to 10 times. The shell-and-tube heat exchanger is a conventional structure in the art, and the tube bundles are preferably arranged vertically. To prevent localized blockage of the material, the gap between the tube bundles is maximized while meeting the heat exchange area requirements, ensuring the fluidity of the material in a boiling state.

[0025] In the device of this invention, the three-phase separator is a double-sleeve structure with openings at both ends. The upper edge of the outer sleeve is higher than the upper edge of the inner sleeve, and the lower edge of the outer sleeve is higher than the upper edge of the inner sleeve. The area between the outer sleeve and the fluidized bed hydrogenation reactor cylinder is the liquid phase zone, the area between the two sleeves is the solid particle settling zone, and the area inside the inner sleeve is the gas-liquid-solid material rising zone.

[0026] In the device of this invention, the upper part of the inner sleeve of the three-phase separator is a cylindrical cylinder, and the lower part is a frustum-shaped cylinder structure. The liquid phase material outlet is set at the reactor wall position corresponding to the liquid phase zone between the outer sleeve and the fluidized bed hydrogenation reactor body.

[0027] In the device of this invention, the reactor cylinder corresponding to the three-phase separator has an enlarged diameter structure.

[0028] In the device of the present invention, the internal components include a material distributor, which is located in the lower part of the fluidized bed hydrogenation reactor.

[0029] In the device of this invention, the three-phase separator adopts the three-phase separator structure of the fluidized bed hydrogenation reactor researched and designed by the Fushun Petrochemical Research Institute of Sinopec. The fluidized bed hydrogenation reactor including this three-phase separator has achieved good results in industrial use. For details, please refer to relevant patents, such as CN 200810012191.8, etc.

[0030] In the apparatus of this invention, the diameter of the microspherical catalyst or microspherical inert packing is 0.2~1.2 mm, preferably 0.4~0.8 mm; preferably, the loading amount of the microspherical catalyst or microspherical inert packing is 5%~60% of the reactor volume under static conditions, preferably 10%~40%. The microspherical catalyst is a hydrogenation catalyst with hydrogenation activity, and the microspherical inert packing is an inert alumina microsphere, ceramic microsphere, etc., without catalytic activity. Given that the activity of the microspherical catalyst is lost relatively quickly under this reaction conditions, microspherical inert packing is preferred, as is waste fluidized bed hydrogenation catalyst discharged from other fluidized bed hydrogenation devices. The main function of the microspherical catalyst or microspherical inert packing is to flush the surface of the heat exchanger tube bundle, effectively control the accumulation of scale and coking in the heat exchanger tube bundle, and maintain high heat exchange efficiency over a long period.

[0031] This invention provides an application of a raw coal gas heat recovery and coal tar pretreatment device, in which raw coal gas exported from a coking unit or coal dry distillation unit is directly fed into a fluidized bed hydrogenation reactor, and coal tar pretreatment is carried out simultaneously with heat recovery.

[0032] In this invention, the average reaction temperature in the fluidized bed hydrogenation reactor is 180~420℃, preferably 220~380℃, and most preferably 260~350℃. The reaction temperature is controlled by heat exchange and the heat of the raw coal gas is recovered. The gas phase discharged from the top of the fluidized bed hydrogenation reactor is cooled by heat exchange and / or ammonia spraying to recover light coal tar and coal gas. The liquid phase material discharged from the fluidized bed hydrogenation reactor (containing suspended solids; in this application, for ease of description, the liquid phase material discharged from the fluidized bed hydrogenation reactor contains suspended solids and is still referred to as liquid phase material, which does not include microspherical catalysts or microspherical inert packings) is separated to obtain heavy coal tar after solid impurities are removed.

[0033] In the application of this invention, the coking device or coal dry distillation device is a device that uses coal as raw material, performs heat treatment to produce coke and semi-coke, and produces coal tar and coal gas as by-products.

[0034] In the application of this invention, the temperature of the raw coal gas is 450~850℃, preferably 600~800℃.

[0035] In this invention, the fluidized bed hydrogenation reactor operates at atmospheric pressure, or by increasing the pressure to a level not exceeding 6 MPa gauge pressure. Increased pressure facilitates the hydrogenation reaction but increases equipment investment and operating costs; adjustments can be made based on specific circumstances.

[0036] In this invention, the fluidized bed hydrogenation reactor is filled with heavy oil at least half its volume before the introduction of raw coal gas, and microspherical catalysts or microspherical inert packings are added at the same time, so that the heavy oil remains in a liquid phase under reaction conditions.

[0037] In this invention, the heavy oil can be derived from the heavy coal tar or other heavy hydrocarbons of this device.

[0038] In this invention, a heavy oil suspension bed hydrogenation catalyst is added to the fluidized bed hydrogenation reactor. This catalyst includes a powdered suspension bed hydrogenation catalyst, a water-soluble suspension bed hydrogenation catalyst, or an oil-soluble suspension bed hydrogenation catalyst. The suspension bed hydrogenation catalyst contains at least one element from Group VIB and Group VIII of the periodic table. Specifically, the suspension bed hydrogenation catalyst contains at least one element from cobalt, molybdenum, nickel, tungsten, and iron.

[0039] In the application of this invention, the amount of additive added to the suspended bed hydrogenation catalyst is 50~50000 μg / g, preferably 100~10000 μg / g, and most preferably 500~5000 μg / g, based on elemental weight.

[0040] In the application of this invention, the powdered suspension bed hydrogenation catalyst is a material that passes through a 50-mesh sieve, preferably a 100-mesh sieve, and most preferably a 200-mesh sieve.

[0041] In the application of this invention, the suspended bed hydrogenation catalyst contains one or more of the oxides, sulfides, sulfates, and organic compounds of cobalt, molybdenum, nickel, tungsten, and iron.

[0042] In this invention, the powdered suspended bed hydrogenation catalyst is a waste hydrogenation catalyst powder; preferably, the waste hydrogenation catalyst is added after wet pulverization under heavy oil protection.

[0043] In the application of this invention, the suspended bed hydrogenation catalyst can be prepared according to existing techniques in the art. Examples include the dispersed (solid powder) suspended bed hydrogenation catalyst disclosed in CN200510047529.X, the oil-soluble suspended bed hydrogenation catalyst disclosed in CN 01106013.1, and the water-soluble suspended bed hydrogenation catalyst disclosed in CN 02109397.0. Other suspended bed hydrogenation catalysts from existing technologies can also be used. The simplest and most effective method is to use pulverized waste hydrogenation catalyst.

[0044] In this invention, the fluidized bed hydrogenation reactor is operated with a partial recirculation of the discharged heavy coal tar to maintain the boiling state of the microspherical catalyst or microspherical inert packing. The liquid hourly space velocity (LISH) of the fluidized bed hydrogenation reactor, based on the discharged heavy coal tar (excluding the recirculation volume), is 0.1–10 h⁻¹. -1 Preferably 0.4~3 h -1 .

[0045] This invention aims to recover heat from raw coal gas while pretreating coal tar, achieving the following technical effects: (1) The heat recovery of raw coal gas and the pretreatment of coal tar are organically coupled, changing the existing technology of pretreatment in subsequent coal tar processing units, realizing synchronous pretreatment in coal tar recovery, solving the stable operation problem of coking in the heat recovery device of raw coal gas, and solving the problem of coking precursors aggravating coking in the section between coal tar recovery and subsequent processing, simplifying the process and equipment of subsequent processing units; (2) A fluidized bed hydrogenation reactor is adopted, in which the hydrogenation catalyst is a suspended bed catalyst. Fluidized bed refers to a fluidized state microspherical catalyst or microspherical inert packing. Under the scouring action of microspherical catalyst or microspherical inert packing, The surface of the heat exchanger tube bundle is not prone to scale and coking, and can maintain a high heat exchange efficiency for a long period of time; (3) Although the suspended bed hydrogenation is a relatively weak hydrogenation method, before coal tar forms coking precursors during subsequent storage and transportation, simple suspended bed hydrogenation can effectively hydrogenate diene and aromatic groups, which is easier and more effective than in the coal tar hydrogenation unit; (4) The process is simple. It utilizes the state and properties of coal tar in the raw coal gas and the hydrogen present in the raw coal gas. One process realizes multiple functions such as heat recovery, coal tar recovery, and coal tar pretreatment, which is conducive to reducing equipment investment; (5) Although the fluidized bed hydrogenation, suspended bed hydrogenation process and catalyst are existing technologies in this field, the main purpose of application is to obtain light hydrocarbon products by hydrocracking of heavy hydrocarbons. Because the hydrogenation efficiency of the suspended bed hydrogenation technology is relatively low, there is no existing technology to use suspended bed hydrogenation for the pretreatment of coal tar. In addition, in the method of this invention, the fluidized bed and suspended bed hydrogenation are not directly used for the pretreatment of recovered coal tar. Instead, the pretreatment is carried out at the same time as the heat recovery process of coal tar recovery. Furthermore, the pretreatment is avoided before the initial formation of coking polymerization precursors during processing, storage and transportation, as well as the accumulation of scale and coking on the surface of the heat exchanger. This achieves a better pretreatment result with a poor hydrogenation effect, and keeps the heat exchanger clean with the boiling particles. (6) The fluidized bed hydrogenation reactor is in a state close to full back-mixing. The materials are fully mixed and the temperature inside the reactor is uniform, which is conducive to controlling the coking reaction. (7) The full back-boiling state of the fluidized bed further improves the effect of suspended bed hydrogenation. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of a raw coal gas heat recovery and coal tar pretreatment device according to the present invention.

[0047] Figure 2 This is a schematic diagram of another structure of the raw coal gas heat recovery and coal tar pretreatment device of the present invention. Detailed Implementation

[0048] The present invention will be further described below through specific embodiments, but this does not limit the scope of protection of the present invention.

[0049] In this invention: raw coal gas is extracted from a coking unit or a coal dry distillation unit. The coking unit or coal dry distillation unit can be any existing technology in the field. Coking usually refers to high-temperature coking, with temperatures reaching 900-1100℃. Dry distillation includes medium-temperature dry distillation (660-750℃), low-temperature dry distillation (500-580℃), etc. Coal is heated and decomposed under air-isolated conditions to produce coke (or semi-coke), coal tar, crude benzene, coal gas, and other products.

[0050] The temperature of high-temperature raw coal gas is related to the operating temperature and process of the coking unit or coal dry distillation unit, but overall it is a high-temperature material that is prone to coking.

[0051] In this invention, the suspended bed hydrogenation catalyst is preferably spent hydrogenation catalyst powder, which is a readily available and inexpensive resource in the field. Most coal chemical enterprises possess hydrogenation equipment, making this resource relatively abundant and easily accessible. During use, the spent hydrogenation catalyst can simultaneously remove and contain metallic impurities from tar, resulting in a high metal content in the post-use material, which can be used for metal recovery. The spent hydrogenation catalyst can be used directly after physical treatment (e.g., pulverization) or after certain chemical treatments (e.g., carbonization).

[0052] In this invention, since most of the heat is recovered through heat exchange during the fluidized bed reaction, the amount of ammonia required for subsequent steps is greatly reduced.

[0053] To illustrate the effectiveness of this invention, a method for detecting the coking characteristics of materials is established as follows: The material and porous ceramic microspheres (volume ratio 3:1) are placed in a high-temperature stirred tank and maintained at a certain temperature and pressure for a certain period. Then, the toluene-insoluble matter is collected. This relative amount is used as the coking property of the material; the larger the relative amount, the greater the tendency for the material to coke. The toluene-insoluble matter collection process includes two parts: Toluene-insoluble matter in the liquid phase is determined according to GB / T 2292—1997; Toluene-insoluble matter on the porous ceramic microspheres is determined by thoroughly rinsing with toluene, collecting the insoluble matter in the rinsing toluene, and detecting the weight gain of the porous ceramic microspheres. The sum of the above toluene-insoluble matter is the total toluene-insoluble matter.

[0054] Example 1

[0055] A device for recovering heat from raw coal gas and pretreating coal tar (e.g.) Figure 11 is the raw coal gas inlet, 2 is the fluidized bed reactor shell, 3 is the material distributor, 4 is the gas phase material outlet, and 5 is the liquid phase material outlet (the liquid phase material contains solid impurities, referred to as liquid phase material for convenience). The gas-liquid-solid three-phase separator includes an inner cylinder 6 and an outer cylinder 7. The upper edge of the outer cylinder 7 is higher than the upper edge of the inner cylinder 6, and the lower edge of the outer cylinder 7 is higher than the lower edge of the inner cylinder 6. The annular gap between the outer cylinder 7 and the inner cylinder 6 is the settling zone for the liquid phase material and the microspherical catalyst (or microspherical inert packing). The space between the outer cylinder 7 and the reactor shell is the liquid phase material collection zone, and the inside of the inner cylinder is the gas-liquid-solid material rising zone. To make the gas-liquid-solid three-phase separator operate more efficiently, the lower part of the inner cylinder is an enlarged frustum structure (flared mouth structure). 8 is the microspherical catalyst (or microspherical inert packing). Solid impurities in the liquid phase material are not shown in the diagram. 9 is the material discharge outlet. 12 is a shell-and-tube heat exchanger, 10 is the heat exchange medium outlet, and 11 is the heat exchange medium inlet.

[0056] Example 2

[0057] A device for recovering heat from raw coal gas and pretreating coal tar (e.g.) Figure 2 Compared with Example 1, the upper part of the fluidized bed reactor shell is provided with a diameter expansion section, and the gas-liquid-solid three-phase separator is set in the diameter expansion section, which can reduce the material flow rate at the location of the gas-liquid-solid three-phase separator and improve the gas-liquid-solid separation effect.

[0058] Example 3 and Comparative Example 1

[0059] Cold model experiment. The apparatus (transparent plexiglass) of Example 2 was used. The heat exchanger tube bundle was coated with starch paste and coated with a suitable amount of carbon black. Kerosene and nitrogen were passed through the apparatus (nitrogen to kerosene volume ratio of 500:1 under standard conditions, kerosene volume hourly space velocity 4 h⁻¹). -1 After half an hour, most of the carbon black remained in the heat exchanger tube bundle, but no carbon black was observable in the discharged kerosene. Then, 0.4 mm α-alumina microspheres (30% of the reactor's nominal capacity) were added, and kerosene was circulated to keep the α-alumina microspheres boiling (under the same conditions). The discharged kerosene contained a significant amount of observable carbon black. After half an hour, the carbon black on the surface of the heat exchanger tube bundle was basically cleaned.

[0060] Examples of the effects of coal tar pretreatment are shown below.

[0061] Comparative Example 2

[0062] A company uses raw coal gas at a temperature of approximately 600°C. It directly cools the gas by spraying ammonia water and recovers coal tar (without storage), which is conventional coal tar D1.

[0063] Comparative Example 3

[0064] A coal tar processing company purchases medium- and low-temperature coal tar, which is the company's conventional coal tar raw material D2.

[0065] Example 4

[0066] A company's waste gas, with a temperature of approximately 600℃, was directly introduced into a structure such as... Figure 2 The fluidized bed hydrogenation reactor shown (filled with 2 / 3 volume coal tar D1 and 10% volume 0.4 mm α-alumina microspheres) has an average reaction temperature of 320℃ and a liquid hourly space velocity of 4.0 h⁻¹. -1 The reactor is equipped with a tubular heat exchanger to control the reaction temperature and recover the heat of the raw coal gas through heat exchange. Waste hydrogenation catalyst (diesel hydrogenation waste catalyst with molybdenum and cobalt as active materials) powder is added to the reactor, and the amount added is 2500 μg / g based on the weight of metallic molybdenum and cobalt.

[0067] The material discharged from the reactor undergoes gas-liquid separation at the same temperature as the reaction temperature. The liquid phase is filtered to remove solid impurities, yielding heavy coal tar.

[0068] The gas phase is cooled to 80°C by ammonia spraying before recovering light coal tar and coal gas.

[0069] After 240 hours of stable operation, heavy coal tar A1 and light coal tar B1 were obtained. A portion of A1 and B1 were mixed in the original proportion (i.e., the yield ratio of A1 and B1) to form a full-fraction coal tar sample C1.

[0070] Comparative Example 4

[0071] Referring to the reaction conditions of Example 4, conventional coal tar D2 was used as raw material for hydrogenation reaction with an external hydrogen source and a hydrogen-to-oil volume ratio of 600:1 (under standard conditions). The reaction products were collected to obtain coal tar D3.

[0072] Comparative Example 5

[0073] Following the method of Example 4, without using α-alumina microspheres, heavy tar D4 was obtained.

[0074] Example 5

[0075] Example 4 and the comparative example were used to test the coking characteristics of coal tar. Conditions: temperature 350℃, nitrogen pressurization to 8 MPa (gauge pressure), high-pressure stirred tank, time 30 minutes. The percentage of toluene-insoluble matter by weight of the feed was collected (relative value, with D1 as 100%).

[0076]

Claims

1. A method for recovering heat from raw coal gas and pretreating coal tar, wherein, The raw coal gas heat recovery and coal tar pretreatment device includes: (1) A fluidized bed hydrogenation reactor, including a vertical cylindrical body and internal components; (2) The internal components of the fluidized bed hydrogenation reactor include: a heat exchanger in the middle and a gas-liquid-solid three-phase separator in the upper part; (3) The bottom of the fluidized bed hydrogenation reactor is provided with a feed inlet and the top is provided with a gas phase material outlet. The side wall of the gas-liquid-solid three-phase separator is provided with a liquid phase outlet. (4) The heat exchanger position inside the fluidized bed hydrogenation reactor is filled with microspherical catalyst or microspherical inert packing; (5) Under operating conditions: the microsphere catalyst or microsphere inert packing is in a boiling state, scouring the outer surface of the heat exchanger tube bundle; in the gas-liquid-solid three-phase separator area, the separated gas phase is discharged from the top of the reactor, the liquid phase is discharged from the liquid phase outlet, and the microsphere catalyst or microsphere inert packing is circulated back to the middle and lower part of the reactor. The heat exchanger is a shell-and-tube heat exchanger, and the gap between the tubes is more than three times the diameter of the microspherical catalyst or microspherical inert packing. The diameter of the microspherical catalyst or microspherical inert packing is 0.2~1.2 mm; the loading amount of the microspherical catalyst or microspherical inert packing is 5%~60% of the reactor volume under static conditions; The method includes: raw coal gas with a temperature of 450~850℃ exported from a coking unit or a coal dry distillation unit is directly fed into a fluidized bed hydrogenation reactor to perform coal tar pretreatment while recovering heat. The average reaction temperature in the fluidized bed hydrogenation reactor is 180~420 ℃. The reaction temperature is controlled by heat exchange and the heat of the raw coal gas is recovered. The gas phase discharged from the top of the fluidized bed hydrogenation reactor is cooled by heat exchange and / or ammonia spraying to recover light coal tar and coal gas. The liquid phase containing suspended solids is discharged from the fluidized bed hydrogenation reactor. After separating the solid impurities, heavy coal tar is obtained. The fluidized bed hydrogenation reactor operates at atmospheric pressure, or at a gauge pressure not exceeding 6 MPa by pressurization. Before introducing raw coal gas, the fluidized bed hydrogenation reactor is filled with heavy oil at least half its volume, and microspherical catalysts or microspherical inert packings are added at the same time. The heavy oil is kept in a liquid phase under reaction conditions. The heavy oil comes from heavy coal tar or other heavy hydrocarbons from this unit.

2. The method according to claim 1, characterized in that: The average reaction temperature in the fluidized bed hydrogenation reactor is 220~380 ℃.

3. The method according to claim 1, characterized in that: The average reaction temperature in the fluidized bed hydrogenation reactor is 260~350 ℃.

4. The method according to claim 1, characterized in that: The coking unit or coal dry distillation unit is a device that uses coal as raw material, performs heat treatment to produce coke and semi-coke, and produces coal tar and coal gas as by-products.

5. The method according to claim 1, characterized in that: The temperature of the raw coal gas is 600~800 ℃.

6. The method according to claim 1, characterized in that: A heavy oil suspension bed hydrogenation catalyst, including a water-soluble suspension bed hydrogenation catalyst or an oil-soluble suspension bed hydrogenation catalyst, is added to the fluidized bed hydrogenation reactor. The suspension bed hydrogenation catalyst contains at least one element from Group VIB and Group VIII of the periodic table.

7. The method according to claim 6, characterized in that: The heavy oil suspension bed hydrogenation catalyst is a powdered suspension bed hydrogenation catalyst added to the fluidized bed hydrogenation reactor.

8. The method according to claim 6, characterized in that: The suspended bed hydrogenation catalyst is a substance containing at least one element selected from cobalt, molybdenum, nickel, tungsten, and iron.

9. The method according to claim 6, characterized in that: The amount of additive added to the suspended bed hydrogenation catalyst is 50~50000 μg / g by element weight.

10. The method according to claim 9, characterized in that: The amount of additive added to the suspended bed hydrogenation catalyst is 100~10000 μg / g by element weight.

11. The method according to claim 9, characterized in that: The amount of additive added to the suspended bed hydrogenation catalyst is 500~5000 μg / g by element weight.

12. The method according to claim 7, characterized in that: The powdered suspension bed hydrogenation catalyst is a material that has passed through a 50-mesh sieve.

13. The method according to claim 12, characterized in that: The powdered suspension bed hydrogenation catalyst is a material that has passed through a 100-mesh sieve.

14. The method according to claim 12, characterized in that: The powdered suspension bed hydrogenation catalyst is a material that has passed through a 200-mesh sieve.

15. The method according to claim 7, characterized in that: Suspended bed hydrogenation catalysts contain one or more of the following: oxides, sulfides, sulfates, and organic compounds of cobalt, molybdenum, nickel, tungsten, and iron.

16. The method according to claim 7, characterized in that: The powdered suspended bed hydrogenation catalyst is a waste hydrogenation catalyst powder.

17. The method according to claim 16, characterized in that: It is added to waste hydrotreating catalyst after wet crushing under heavy oil protection.

18. The method according to claim 1, characterized in that: The fluidized bed hydrogenation reactor is operated in a manner that partially recycles the discharged heavy coal tar in order to maintain the boiling state of the microspherical catalyst or microspherical inert packing.

19. The method according to claim 18, characterized in that: The liquid hourly space velocity (LHSV) of the fluidized bed hydrogenation reactor, excluding the liquid phase of the discharged heavy coal tar (excluding the circulating volume), is 0.1–10 h⁻¹. -1 .

20. The method according to claim 19, characterized in that: The liquid hourly space velocity (LHSV) of the fluidized bed hydrogenation reactor, excluding the liquid phase of the discharged heavy coal tar (excluding the circulating volume), is 0.4–3 h⁻¹. -1 .

21. The apparatus for recovering heat from raw coal gas and pretreating coal tar used in any of the methods described in claims 1-20.

22. The apparatus according to claim 21, characterized in that: The vertical cylindrical body includes an upper end cap, a lower end cap, and a central cylindrical body.

23. The apparatus according to claim 21, characterized in that: The heat exchanger is a shell-and-tube heat exchanger, and the gap between the tubes is 3 to 20 times the diameter of the microspherical catalyst or microspherical inert packing.

24. The apparatus according to claim 21, characterized in that: The heat exchanger is a shell-and-tube heat exchanger, and the gap between the tubes is 5 to 10 times the diameter of the microspherical catalyst or microspherical inert packing.

25. The apparatus according to claim 21, characterized in that: The three-phase separator is a double-sleeve structure with openings at both ends. The upper edge of the outer sleeve is higher than the upper edge of the inner sleeve, and the lower edge of the outer sleeve is higher than the upper edge of the inner sleeve. The liquid phase zone is between the outer sleeve and the fluidized bed hydrogenation reactor cylinder, the solid particle settling zone is between the two sleeves, and the rising zone of gas, liquid, and solid materials is inside the inner sleeve.

26. The apparatus according to claim 25, characterized in that: The upper part of the inner sleeve is a cylindrical tube, and the lower part is a frustum-shaped tube structure.

27. The apparatus according to claim 21, characterized in that: A liquid phase material outlet is set at the location on the reactor wall corresponding to the liquid phase zone between the outer sleeve and the fluidized bed hydrogenation reactor cylinder.

28. The apparatus according to claim 21, characterized in that: The reactor shell corresponding to the three-phase separator has an enlarged diameter structure.

29. The apparatus according to claim 21, characterized in that: The internal components include a material distributor, which is located in the lower part of the fluidized bed hydrogenation reactor.

30. The apparatus according to claim 21, characterized in that: The diameter of the microspherical catalyst or microspherical inert packing is 0.4~0.8 mm; the loading amount of the microspherical catalyst or microspherical inert packing is 10%~40% of the reactor volume under static conditions.

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