A method and device for recovering heat from raw coal gas

Abstract

The present invention discloses a method and apparatus for recovering heat from raw coal gas, belonging to the technical field of preparing liquid hydrocarbon mixtures and coal gas from coal. The process includes: extracting high-temperature raw coal gas from a coking unit or a coal dry distillation unit; washing the raw coal gas with heavy oil, adding an additive with catalytic hydrogenation function to the washed heavy oil, and introducing ammonia water to control the washing temperature; the raw coal gas after heavy oil washing enters a heat exchanger for heat recovery; and the raw coal gas after heat recovery is cooled by spraying with water or ammonia water, after which coal tar and coal gas are recovered. The method and apparatus of the present invention can effectively utilize the heat of the high-temperature raw coal gas while reducing the coking property of the material, thereby facilitating the stable operation of the device.

Description

Technical Field

[0001] The invention relates to a method and device for recovering heat from raw coal gas, and belongs to the technical field of preparing liquid hydrocarbon mixture and coal gas from coal. Background Art

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

[0003] There are two main routes to produce liquid hydrocarbons from low-rank coal. One is direct coal liquefaction, which is relatively expensive. The other is coal distillation / coking technology, which is based on the pyrolysis of low-rank coal. It is simple and mature, and the resulting coke or semi-coke is a high-quality fuel and reducing agent required by the metallurgical industry. Liquid hydrocarbons are also obtained, which can be further processed to produce liquid fuels and various chemical raw materials.

[0004] During the coal dry distillation / coking process, the temperature of the discharged raw gas is high, generally reaching over 600°C, accounting for about 37% of the heat expenditure of the coke oven; the raw gas has a complex composition, containing solid coke powder, complex mixed hydrocarbons, complex gas phase, water, etc. Although this gas is rich in heat, it is difficult to recycle the heat. The main problems are the blockage, coking, corrosion, etc. of the heat exchange equipment. In traditional technology, ammonia water is used for spraying and cooling, and all the heat in it is lost, resulting in high energy consumption of the device. Therefore, how to effectively recover the heat in the raw gas, especially how to solve the problems of equipment blockage and coking during heat recovery, is a key concern in this field.

[0005] CN201310391012.7 discloses a coke oven raw gas waste heat recovery and utilization system, comprising a heat exchange medium circulation system and a water supply system. The heat exchange medium circulation system includes a heat exchanger group, a steam drum, and a forced circulation pump. The water inlet of the heat exchanger group is connected to the water outlet of the steam drum via the forced circulation pump, and the water outlet of the heat exchanger group is connected to the water inlet of the steam drum. The steam outlet on the steam drum is connected to the external steam pipe 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 arranged between the buffer water tank and the desalination and deoxygenation water tank, and 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 by setting up multiple parallel heat exchanger groups and adding a control system to detect and deal with failures in a heat exchanger group in a timely manner, thereby improving the safe and normal operation of the system and reducing the accident rate. However, due to the characteristics of raw coal gas, coking and fouling of the heat exchanger group will inevitably occur quickly. Even if a parallel method is used, maintenance of one of the groups will still cause large fluctuations and operational difficulties in normal operation.

[0006] CN201410692354.7 discloses a system and method for dust removal and oil cooling of tar from pyrolysis raw gas, comprising a sequentially connected particulate dust collector, an electrostatic precipitator, a tar refining tower, a gas cooling tower, and an electrostatic tar collector. The present invention installs a tar refining tower between the particulate bed dust collector and the gas cooling tower, fully utilizing the heat of the gas itself. The collected tar is further dehydrated and refined using the "distillation principle," resulting in a short process flow and high-quality tar with low moisture content. This solution directly utilizes the sensible heat carried by the pyrolysis gas as a heat source for the distillation of the water-containing tar in the tar refining tower, achieving efficient heat utilization within the same tar recovery system. The goal is to provide a novel heat recovery process and method for pyrolysis raw gas cooling and tar recovery and refining systems. However, this solution utilizes a particulate dust collector and electrostatic precipitator, which, for raw gas prone to coking and the generation of sludge-like solids, can lead to severe equipment fouling and coking, significantly impacting the operating cycle.

[0007] CN201610213831.6 discloses a system and method for recovering heat from raw gas using washing and rectification. The raw gas undergoes rectification and washing to remove heavy tar and coke powder, resulting in high-boiling-point oil products and high-temperature raw gas. The high-boiling-point oil products and / or high-temperature raw gas are then heat-exchanged to generate high-pressure steam, which is then separated into steam and water, and the separated steam is utilized. The system boasts high dust removal efficiency, stable operation, resistance to clogging, and allows for full heat recovery. However, the system has the following deficiencies: (1) Although the solid dust is basically removed by washing and the problem of equipment blockage caused by coke powder is solved, the bottom temperature of the washing distillation tower is relatively high, and the problem of high-boiling-point components in the raw gas being easily coked at high temperatures has not been solved, which still affects the operation cycle of the device; (2) The high-grade heat source of the raw gas (the heat source has a grade, and the higher the temperature of the heat source, the higher the grade and the stronger the external work ability) is converted into a medium-temperature heat source for external heat exchange, that is, the high-grade heat source of the raw gas at about 600°C is converted into a medium-temperature heat source at 280~330°C for external heat supply (see paragraph 32 of its manual), and the heat source grade is reduced by about 50%; (3) Based on the principle of the distillation tower of the plate tower, although a specially structured "flow-through tower plate" is designed (see paragraph 30 of its manual), the coking properties of the material have not changed, and the coking problem will still exist. After the equipment has been running for a certain period of time, the coking problem will inevitably exist.

[0008] CN201911169496.4 discloses a deep desulfurization system and method for coupling coke oven raw gas and coke. By setting up a high-temperature coke hydrogenation reactor, the hydrogenation reaction of coke can be completed by utilizing the H2 rich in the raw gas itself without the need for additional hydrogenation, thereby transferring the sulfur in the coke to the gas; by setting up a catalytic hydrogenation reactor, a catalyst is used to almost completely convert the organic sulfur in the raw gas into H2S, and the organic and inorganic sulfur in the coke oven gas are efficiently and deeply removed from the source, thereby greatly reducing the sulfur content of the coking benzene product and coke, improving the quality of the benzene product and coke, and reducing the load and difficulty of subsequent fine desulfurization. This method is carried out at high temperature (the coal tar component in the raw coal gas is in the gas phase), for example, the hydrogenation reactor should be controlled at 650~1000℃. Under this condition, the coal tar component will be further dehydrogenated (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, diolefins, aromatic olefins and other easily coking substances. Not only does it fail to pretreat the coal tar, but it also brings more serious coking problems to the subsequent coal tar processing.

[0009] In summary, while existing technologies have extensively researched the utilization of raw gas heat, their coking characteristics remain unchanged, and there's no effective solution to the coking problem, nor has the impact of coking on stable plant operation been addressed. Furthermore, while some solutions have partially recovered heat, the heat utilization rate, particularly for high-grade heat, remains insufficient. Summary of the Invention

[0010] In response to the deficiencies in the prior art, the present invention provides a method and device for recovering heat from raw coal gas and a method for preparing a liquid hydrocarbon mixture from coal. The scheme of the present invention has the advantages of high raw coal gas heat recovery rate, high recovered energy grade, and effective solution to material coking during the heat recovery process.

[0011] The method for recovering heat from raw coal gas of the present invention comprises the following contents:

[0012] (1) Extracting high-temperature raw gas from a coking unit or coal dry distillation unit;

[0013] (2) The raw gas is washed with heavy oil, and an additive with catalytic hydrogenation function is added to the washed heavy oil. Ammonia water is introduced to control the washing temperature. The washing temperature is 10-150°C lower than the raw gas temperature, preferably 30-120°C lower, and most preferably 50-80°C lower;

[0014] (3) The raw gas after heavy oil washing enters the heat exchanger for heat recovery;

[0015] (4) The raw gas after heat recovery is cooled by spraying with water or ammonia water and then the coal tar and gas are recovered.

[0016] In the above method of the present invention, the coking device or coal dry distillation device described in step (1) uses coal as raw material, performs heat treatment, and produces coke and semi-coke, with coal tar and coal gas as by-products. The by-product coal tar and coal gas are recovered from the high-temperature raw coal gas.

[0017] In the above method of the present invention, the temperature of the high-temperature raw gas is 450-850°C, preferably 600-800°C.

[0018] In the above method of the present invention, the heavy oil washing in step (2) is carried out by various methods such as spray washing, bubbling bed washing, pipeline mixer washing, etc. The heavy oil used in the heavy oil washing is heavy coal tar and / or crude oil residue collected during the washing process.

[0019] In the above method of the present invention: the heavy oil washing in step (2) adopts a heavy oil circulation washing method.

[0020] In the above method of the present invention, during the heavy oil washing process described in step (2), the ammonia water introduced is of any concentration, preferably ammonia water having a saturation of 30% to 70% under normal temperature and pressure. The amount introduced is adjusted according to the temperature control value.

[0021] In the above method of the present invention, the ammonia water is introduced in one or more of the following ways: introduced into the raw gas, introduced into the circulating heavy oil, and introduced into the lower part of the washing equipment.

[0022] In the above method of the present invention, the additive having a catalytic hydrogenation function is a substance containing at least one element from Group VIB and Group VIII of the periodic table, preferably a substance containing at least one element from cobalt, molybdenum, nickel, tungsten, and iron.

[0023] In the above method of the present invention, the amount of the additive with catalytic hydrogenation function added is 5-10000 μg / g, preferably 30-5000 μg / g, and most preferably 80-3000 μg / g, based on element weight.

[0024] In the above method of the present invention, the additive having the catalytic hydrogenation function is a solid particle having a particle size of 50 mesh, preferably 100 mesh, and most preferably 200 mesh.

[0025] In the above method of the present invention, the additive with catalytic hydrogenation function contains one or more of oxides, sulfides and sulfates of cobalt, molybdenum, nickel, tungsten and iron.

[0026] In the above-mentioned method of the present invention, the additive having catalytic hydrogenation function is waste hydrogenation catalyst powder. Preferably, the waste catalyst is discarded from processes such as hydrorefining and hydrotreating. This waste catalyst is converted into the required powder for use in the present method and contains two or more elements such as cobalt, molybdenum, nickel, and tungsten. These waste catalysts still have some hydrogenation activity, but may not meet the requirements of their intended use. The catalytically active substances in the waste catalyst are generally in a sulfided state (easily oxidized) and can be added directly after wet pulverization under heavy oil protection.

[0027] In the above method of the present invention: in the heavy oil circulating washing described in step (2), the excess washed heavy oil is discharged regularly or continuously.

[0028] In the above method of the present invention, the heat exchanger in step (3) is a jacketed heat exchanger, a coil heat exchanger, or a spiral tube heat exchanger. The raw gas temperature after heat exchange is 110-300°C, preferably 120-200°C, and more preferably 120-150°C. The temperature of the external heat source can reach 450-600°C, such as for producing high-quality heat sources such as high-temperature superheated steam, which is related to the source temperature of the raw gas.

[0029] In the above method of the present invention: in step (4), the raw coal gas recovered by heat is cooled to 70-85°C by spraying with water or ammonia water, coal tar is recovered from the liquid phase, and the gas phase is further cooled and separated to obtain light coal tar and coal gas.

[0030] The present invention provides a raw gas heat recovery system device, which comprises a raw gas heavy oil washing unit, a raw gas heat recovery unit, and a raw gas spray cooling unit. The raw gas heavy oil washing unit is provided with a heavy oil circulation pipeline.

[0031] The present invention provides a method for preparing a liquid hydrocarbon mixture from coal, comprising the following steps: (1) using low-rank coal as a raw material and performing medium-low temperature dry distillation; (2) recovering heat from the raw coal gas obtained in the dry distillation process using the scheme of the present invention; and (3) the oil phase obtained from the heat recovery process and the oil phase recovered by further cooling the raw coal gas after heat recovery are the prepared liquid hydrocarbon mixture.

[0032] The present invention takes the stable recovery of heat from raw coal gas as a high-quality heat source as its main goal, and achieves the following technical effects: (1) solid dust is basically removed by washing, solving the problem of equipment blockage caused by carrying coke powder; (2) the raw coal gas derived from the dry distillation device is mixed with an appropriate amount of ammonia water and appropriately cooled. The alkalinity of ammonia is conducive to inhibiting the polymerization and coking tendency of coking precursors in the high-temperature raw coal gas, solving the problem that high-boiling point components in the raw coal gas are prone to coking at high temperatures to a certain extent, and ensuring the operation cycle of the device; (3) a high-quality heat source can be obtained. Taking 600℃ raw coal gas as an example, the scheme of the present invention can obtain an external heat source of 500℃, such as high-temperature steam, under stable operating conditions, which is significantly improved compared with the existing technology (such as 280~330℃); (4) taking advantage of the fact that there is a large proportion of hydrogen in the raw coal gas, an additive with catalytic hydrogenation function is added during the high-temperature washing process. During washing, the active groups of the coking precursors (such as diene groups, etc.) are hydrogenated, which has a good anti-coking effect and is conducive to ensuring the long-term operation of the device. (5) The use of ammonia cooling at both ends and heat exchange cooling in the middle section fully utilizes the heat, ensures stable operation of the device, reduces water consumption, and ensures stable operation of subsequent units. In summary, the present invention utilizes the effects of ammonia and the hydrogenation of coking precursors to change the coking characteristics of the complex components of the raw gas, reduces the problem of coking and other factors affecting the stable operation of the device, and at the same time maximizes heat recovery to obtain a high-quality external heat source, achieving outstanding technical effects. DETAILED DESCRIPTION

[0033] The present invention will be further described below through specific embodiments, but the protection scope of the present invention is not limited thereto.

[0034] In the method for recovering heat from raw coal gas of the present invention:

[0035] Step (1) extracting high-temperature raw coal gas from a coking device or a coal dry distillation device. The coking device or the coal dry distillation device can be any technology currently available in the art. Coking usually refers to high-temperature coking, and the temperature can reach 900-1100°C. Dry distillation includes medium-temperature dry distillation (660-750°C), low-temperature dry distillation (500-580°C), etc. Coal is heated and decomposed in an airtight condition to produce coke (or semi-coke), coal tar, crude benzene, coal gas and other products.

[0036] The temperature of high-temperature raw coal gas is related to the operating temperature and process of the coking unit or coal distillation unit, but in general it is a high-temperature, easily coked material.

[0037] In the above-described method of the present invention, conventional scrubbing equipment can be used to scrub heavy oil from raw coal gas. Since the material contains a certain amount of solids, anti-clogging features must be considered in the scrubbing equipment. The scrubbing liquid-to-gas volume ratio can be adjusted specifically for the equipment, generally ranging from 5 to 200 L of liquid per cubic meter of gas. The addition of a catalytic hydrogenation additive to the scrubbing heavy oil is a key aspect of the present invention and a crucial measure for reducing the material's coking potential. The principle is to utilize the hydrogen in the raw coal gas, under the catalytic action of the catalytic hydrogenation additive, to hydrogenate and saturate coking-prone groups such as dienyl and aralkenyl groups, reducing their tendency to aggregate and coke, and ensuring stable operation of the device. Ammonia is introduced to control the scrubbing temperature. Ammonia, being alkaline, alters the material system and also has a certain coking-inhibiting effect. The scrubbing temperature is set lower than the raw coal gas temperature, primarily to recover a portion of the heavy tar. A lower temperature also helps control coking. However, the temperature should not be too high, as this would compromise high-quality heat utilization. This temperature can be determined by balancing several factors, including coking control and heat recovery.

[0038] In the above method of the present invention: the heavy oil washing described in step (2) adopts a heavy oil circulation washing method. The main consideration is that if the operating temperature is high, the amount of heavy tar recovered is small. In order to ensure a certain washing liquid-gas ratio, a circulation washing method is set, and continuous and intermittent discharge is carried out at the same time. The solid matter filtered out of the discharged material can be partially recycled after evaluating the hydrogenation activity, thereby reducing the cost of newly added hydrogenation functional additives.

[0039] In the above method of the present invention: in the heavy oil washing process described in step (2), ammonia water is introduced at any concentration. The ammonia production of the coal chemical enterprise device is excessive, and the ammonia water is generally derived from this device and does not need to be purchased from outside. The ammonia water of this device in this section can be used according to the principle of overall process optimization.

[0040] In the above method of the present invention, the ammonia water is introduced in the following manner: preferably, it is directly injected into the raw coal gas. This manner provides sufficient contact and is beneficial to the uniformity of material property control.

[0041] In the above-mentioned method of the present invention, the additive having a catalytic hydrogenation function is a substance containing at least one element from Group VIB or Group VIII of the periodic table. A wide range of materials are available, and generally, inexpensive waste materials that are easily recyclable, such as spent hydrogenation catalysts and waste ore, can be used. The specific type and amount of additive used are determined based on factors such as available resources and hydrogenation performance.

[0042] In the above-described method of the present invention, the additive having a catalytic hydrogenation function is preferably spent hydrogenation catalyst powder, a readily available and inexpensive resource in the field. Most coal chemical companies possess hydrogenation equipment, making this resource relatively abundant and readily available. During use, the spent hydrogenation catalyst also removes and retains metallic impurities from the tar. The post-use material, which contains a high metal content, can be used for metal recovery. The spent hydrogenation catalyst can be used directly after physical treatment (e.g., pulverization) or after chemical treatment (e.g., charcoal burning).

[0043] In the above-described method of the present invention, the raw gas after heavy oil washing enters a heat exchanger for heat recovery. The heat exchange process and heat exchanger structure can be comprehensively optimized based on the company's heat source conditions. The temperature of the raw gas after heat exchange is correlated with the chlorine content. To prevent ammonium chloride crystallization from clogging heat exchange equipment and pipelines, step-by-step heat exchange methods can be used to fully recover heat.

[0044] In the above method of the present invention: the raw gas after heat recovery is cooled by spraying water or ammonia water to recover coal tar and gas. This operation is a conventional method in the art, but in the present invention, since most of the heat is recovered by heat exchange, the amount of ammonia water required in this step is greatly reduced.

[0045] In the above method of the present invention, coal tar of different properties will be produced in the washing step, the heat exchange step, the final ammonia cooling step and the subsequent coal gas treatment process. These coal tars have a reduced tendency to coke after the previous treatment steps of the present invention, laying a good foundation for subsequent processing, and can be comprehensively processed according to their properties.

[0046] To illustrate the effectiveness of the present invention, a method for testing the coking characteristics of a material is described as follows: a material and porous ceramic beads (volume ratio of 3:1) are placed in a high-temperature stirred tank and maintained at a specific temperature and pressure for a specified period of time. The toluene-insoluble matter is then collected, and the relative amount of this matter is used as the material's coking property. A larger relative amount indicates a greater tendency for the material to coke. The toluene-insoluble matter collection process consists of two steps: The toluene-insoluble matter in the liquid phase is measured according to GB / T 2292-1997; and the toluene-insoluble matter on the porous ceramic beads is determined by thoroughly rinsing them with toluene. The insoluble matter in the toluene-insoluble matter is then collected, and the weight gain of the porous ceramic beads is measured. The sum of these toluene-insoluble matter is the total toluene-insoluble matter.

[0047] Example 1

[0048] The raw gas of a certain enterprise, with a temperature of about 600℃, was cooled to 520℃ with 10% ammonia water. The liquid mixture (heavy tar A1) was collected and used as the washing oil for the next experiment.

[0049] Comparative Example 1

[0050] The raw gas of a certain enterprise, with a temperature of about 600℃, was cooled to 520℃ by water injection. The liquid mixture was collected and filtered to remove solid impurities to obtain heavy tar AD. Further cooling and distillation were carried out to obtain medium tar BD with a distillation range of 280~330℃.

[0051] Example 2

[0052] Raw gas from a certain enterprise, at approximately 600°C, was cooled to 520°C with 10% ammonia solution and then scrubbed with the scrubbing oil obtained in Example 1. A pipeline mixer was used to ensure full gas-liquid contact. The scrubbing temperature was controlled at 520°C, and the inlet liquid-to-gas ratio was set at 30 L of liquid per cubic meter of gas, transferring the majority of solid matter from the gas phase to the liquid phase. Powdered spent hydrogenation catalyst (a diesel hydrogenation waste catalyst containing molybdenum and cobalt as active ingredients) was added to the scrubbing oil at a concentration of 800 μg / g, based on the weight of the metallic molybdenum and cobalt elements.

[0053] The collected liquid phase after washing is filtered to remove solid impurities to obtain heavy tar A2.

[0054] Example 3

[0055] The temperature of the washed gas phase in Example 2 is about 520°C. According to simulation calculation, superheated steam above 480°C can be obtained. The gas phase is cooled to 150°C, collected and filtered to remove solid impurities, and medium tar B is obtained.

[0056] Example 4

[0057] Example 3 The cooled gas phase is sprayed with ammonia water to cool down to 80° C., and the liquid phase is collected and filtered to remove solid impurities to recover light tar C.

[0058] Example 5

[0059] Coking characteristics of various heavy tars were measured. Conditions: temperature 450°C, pressure generated under these conditions, stirring the kettle, and reaction time 15 minutes. The percentage of toluene-insoluble matter collected relative to the weight of the feed (relative value, with AD as 100%) was calculated.

[0060]

[0061] Example 6

[0062] Coking characteristics of various medium-weight tars were measured. Conditions: nitrogen pressure to 8 MPa (gauge pressure), temperature 350°C, stirring in the kettle, and reaction time for 30 minutes. The percentage of toluene-insoluble matter collected relative to the weight of the feed (relative value, with BD as 100%) was calculated.

[0063]

[0064] It can be seen from the above examples and comparative examples that the heavy tar and medium tar of the present invention have a lower coking tendency, which is conducive to the stable operation of the device, and can be recovered to obtain a higher-grade heat source, thereby achieving better technical effects.

[0065] Example 7

[0066] Following the method of Example 2, the mixed ammonia solution was cooled to 500°C for heavy oil scrubbing. The scrubbing temperature was controlled at 500°C, and the inlet liquid-to-gas ratio was set at 5 L liquid / m³ gas, transferring the majority of solid matter from the gas phase to the liquid phase. Spent hydrogenation catalyst powder (a diesel hydrogenation waste catalyst containing molybdenum and cobalt as active ingredients) was added to the scrubbing oil at a concentration of 800 μg / g, based on the weight of the metallic molybdenum and cobalt elements.

[0067] The collected liquid phase after washing is filtered to remove solid impurities to obtain heavy tar A3.

[0068] Example 8

[0069] Following the method of Example 2, the mixed ammonia solution was cooled to 550°C for heavy oil washing. The washing temperature was controlled at 550°C, and the inlet liquid-to-gas volume ratio was set at 100 L liquid / m³ gas, transferring the majority of solid matter from the gas phase to the liquid phase. Spent hydrogenation catalyst powder (diesel hydrogenation waste catalyst containing molybdenum and cobalt as active ingredients) was added to the washing oil at a concentration of 1500 μg / g, based on the weight of the metallic molybdenum and cobalt elements.

[0070] The collected liquid phase after washing is filtered to remove solid impurities to obtain heavy tar A4.

[0071] Example 9

[0072] Following the method of Example 2, the mixed ammonia solution was cooled to 450°C for heavy oil washing. The washing temperature was controlled at 450°C, and the inlet liquid-to-gas volume ratio was set at 40 L liquid / m³ gas, transferring the majority of solid matter from the gas phase to the liquid phase. Spent hydrogenation catalyst powder (spent diesel deep hydrodesulfurization catalyst containing molybdenum, cobalt, and nickel as active ingredients) was added to the washing oil at a concentration of 500 μg / g, calculated as the weight of the metallic molybdenum, cobalt, and nickel elements.

[0073] The collected liquid phase after washing is filtered to remove solid impurities to obtain heavy tar A5.

[0074] Example 10

[0075] Following the method of Example 2, the mixed ammonia solution was cooled to 520°C for heavy oil washing. The washing temperature was controlled at 520°C, and the inlet liquid-to-gas volume ratio was set at 50 L liquid / m³ gas, transferring the majority of solid matter in the gas phase to the liquid phase. A powdered additive containing a hydrogenation component (a mixture of spent diesel deep hydrodesulfurization catalyst containing molybdenum, cobalt, and nickel as active ingredients and molybdenite powder in a 1:1 weight ratio) was added to the washing oil in an amount of 100 μg / g, calculated as the weight of the metallic molybdenum, cobalt, and nickel elements.

[0076] The collected liquid phase after washing is filtered to remove solid impurities to obtain heavy tar A6.

[0077] Example 11

[0078] Examples 7-10: Coking characteristics of various heavy tars. Conditions: Temperature 450°C, pressure generated under these conditions, stirring in the kettle, and 15 minutes. The percentage of toluene-insoluble matter collected relative to the weight of the feed (relative value, with AD as 100%).

[0079]

Claims

1. A method for recovering heat from raw coal gas, comprising the following: (1) Extracting high-temperature raw gas from a coking unit or coal dry distillation unit; (2) The raw gas is washed with heavy oil, and an additive with catalytic hydrogenation function is added to the washed heavy oil. Ammonia water is introduced to control the washing temperature, which is 10~150℃ lower than the raw gas temperature; (3) The raw gas after heavy oil washing enters the heat exchanger for heat recovery; (4) The raw gas after heat recovery is cooled by spraying with water or ammonia water and then the coal tar and gas are recovered.

2. The method according to claim 1, characterized in that: The washing temperature is 30~120℃ lower than the raw gas temperature.

3. The method according to claim 1, characterized in that: The washing temperature is 50~80℃ lower than the raw gas temperature.

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

5. The method according to claim 4, characterized in that: By-product coal tar and coal gas are recovered from high-temperature raw coal gas.

6. The method according to claim 1, characterized in that: The temperature of high-temperature raw gas is 450~850℃.

7. The method according to claim 6, characterized in that: The raw gas temperature is 600~800℃.

8. The method according to claim 1, characterized in that: The heavy oil washing in step (2) is carried out by spray washing, bubbling bed washing or pipeline mixer washing.

9. The method according to claim 1 or 8, characterized in that: The heavy oil used in heavy oil washing is heavy coal tar and / or crude oil residue collected during the washing process.

10. The method according to claim 1, characterized in that: The heavy oil washing in step (2) adopts a heavy oil circulation washing method.

11. The method according to claim 1 or 10, characterized in that: During the heavy oil washing process described in step (2), the ammonia water is introduced at any concentration, and the saturation degree of the ammonia water is 30% to 70% under normal temperature and pressure conditions.

12. The method according to claim 11, characterized in that: The ammonia solution is introduced in one or more of the following ways: introduced into the raw gas, introduced into the circulating heavy oil, or introduced into the lower part of the washing equipment.

13. The method according to claim 1, wherein: The additive having the catalytic hydrogenation function is a substance containing at least one element from Group VIB and Group VIII in the periodic table.

14. The method according to claim 13, characterized in that: The additive having the catalytic hydrogenation function is a substance containing at least one element selected from the group consisting of cobalt, molybdenum, nickel, tungsten and iron.

15. The method according to claim 14, characterized in that: The amount of the additive with catalytic hydrogenation function is 5 to 10,000 μg / g based on element weight.

16. The method according to claim 15, characterized in that: The amount of the additive with catalytic hydrogenation function is 30~5000μg / g based on the weight of the element.

17. The method according to claim 15, characterized in that: The amount of the additive with catalytic hydrogenation function is 80-3000 μg / g based on element weight.

18. The method according to claim 13, wherein: The additive with catalytic hydrogenation function is solid particles.

19. The method according to claim 18, characterized in that: The particle size of the solid particles is that which can pass through a 50-mesh sieve.

20. The method according to claim 19, characterized in that: The particle size of the solid particles is the material passing through a 100-mesh sieve.

21. The method according to claim 19, characterized in that: The particle size of the solid particles is that which can pass through a 200-mesh sieve.

22. The method according to claim 14, characterized in that: The additive with catalytic hydrogenation function contains one or more of oxides, sulfides and sulfates of cobalt, molybdenum, nickel, tungsten and iron.

23. The method according to claim 13, wherein: The additive with catalytic hydrogenation function is spent hydrogenation catalyst powder.

24. The method according to claim 23, characterized in that: The spent hydrogenation catalyst is wet-crushed under heavy oil protection and then added for use.

25. The method according to claim 10, characterized in that: During the heavy oil circulation washing in step (2), the excess washed heavy oil is discharged periodically or continuously.

26. The method according to claim 1, characterized in that: The heat exchanger described in step (3) is a jacketed heat exchanger, a coil heat exchanger, or a spiral tube heat exchanger.

27. The method according to claim 1, characterized in that: The temperature of the raw gas after heat exchange in step (3) is 110~300℃.

28. The method according to claim 1, characterized in that: The temperature of the raw gas after heat exchange in step (3) is 120~200℃.

29. The method according to claim 1, characterized in that: The temperature of the raw gas after heat exchange in step (3) is 120~150℃.

30. The method according to claim 1, wherein: In step (4), the raw coal gas after heat recovery is cooled to 70-85°C by spraying with water or ammonia water, coal tar is recovered from the liquid phase, and the gas phase is further cooled and separated to obtain light coal tar and coal gas.

31. The raw gas heat recovery system device used in the method according to any one of claims 1 to 30, characterized in that: It includes a raw gas heavy oil washing unit, a raw gas heat recovery unit, and a raw gas spray cooling unit.

32. The system device according to claim 31, characterized in that: The raw gas heavy oil washing unit is equipped with a heavy oil circulation pipeline.

33. A method for preparing a liquid hydrocarbon mixture from coal, characterized by comprising The method comprises the following steps: (1) using low-rank coal as raw material to carry out medium-low temperature carbonization; (2) recovering heat from the raw coal gas obtained in the carbonization process by the method described in claim 1; and (3) the oil phase obtained from the heat recovery process and the oil phase recovered by further cooling the raw coal gas after heat recovery are the prepared liquid hydrocarbon mixture.

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