Energy-saving and resource-recycling double-effect zero-emission process for high-flash gas in coal chemical industry

Abstract

The invention relates to the technical field of coal chemical industry flash steam treatment, in particular to a coal chemical industry high flash steam energy-saving and resource-recycling double-effect zero-emission process which comprises the steps that gathered high-pressure flash steam enters a newly-added low-pressure steam generator after being converged, and generated steam can enter a steam pipe network at the same time; steam cooled by the low-pressure steam generator enters a gas-liquid separator for gas-liquid separation, and then enters a washing tower for washing fine ash recovery raw materials and cooling; according to the coal chemical industry high-flash gas energy-saving and resource recovery double-effect zero-emission process, a high-pressure flash tank is arranged to convey a mixed solution discharged through multiple paths to a low-pressure steam generator in a unified temperature range, high-flash gas in the low-pressure steam generator is subjected to waste heat utilization, high-temperature heat energy is utilized to generate saturated steam, and the saturated steam is conveyed to a factory for use; part of the mixture of the acid gas and the aqueous solution is separated through the gas-liquid separator, and the high-flash gas is washed and cooled through the washing tower, so that resource waste caused by torch emission is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of flash steam treatment in coal chemical industry, in particular to a "double-effect" zero-emission process of high flash gas energy saving and resource recovery in coal chemical industry. Background Art

[0002] Water-coal slurry pressurized gasification technology and wide-temperature and sulfur-resistant partial conversion process. The main process units include coal slurry preparation, gasification, conversion, flare, ash water treatment, ammonia evaporation and ash water pretreatment. The black water flash evaporation system of the gasification unit is a four-stage system, namely high-pressure flash evaporation, medium-pressure flash evaporation, low-pressure flash evaporation and vacuum flash evaporation. The operating pressure of high-pressure flash evaporation is about 3.45MPa, the operating pressure of medium-pressure flash evaporation is about 0.8MPa, the operating pressure of low-pressure flash evaporation is about 0.2MPa, and the operating pressure of vacuum flash evaporation is about -70kPa. However, high flash gas contains a large amount of high-temperature heat energy, and condensation and cooling through air coolers wastes a lot of high flash gas heat energy; secondly, the content of effective components such as carbon monoxide and hydrogen in the non-condensable gas of high flash gas is as high as more than 50%, and it also contains a certain amount of ammonia. When it is discharged through the flare, a lot of effective gas components are lost; thirdly, high flash gas non-condensable gas contains a certain amount of ammonia and hydrogen sulfide. When it is discharged through the flare, the discharge of sulfur dioxide, nitrogen oxides and ammonia increases, posing a great environmental and safety risk; fourthly, the air cooler consumes huge amounts of electricity, and a large area of ​​heat radiation is generated during the operation of the air cooler. Working in this area causes serious harm to the occupational health and hygiene of employees. Summary of the Invention

[0003] The purpose of the present invention is to provide a coal chemical high flash gas energy saving and resource recovery "double-effect" zero-emission process to solve the problems raised in the above background technology.

[0004] To achieve the above object, the present invention provides the following technical solutions: A "double-effect" zero-emission process for high flash gas energy saving and resource recovery in coal chemical industry, comprising: high-temperature black water discharged from each series entering a high-pressure flash tank; the high-pressure flash gas collected is then merged and enters a newly added low-pressure steam generator; the low-pressure steam generator and the boiler water preheated by the boiler feed water preheater are heat exchanged to produce low-pressure saturated steam as a by-product; the generated steam can simultaneously enter the steam network; the steam cooled by the low-pressure steam generator enters the gas-liquid separator for gas-liquid separation; the high flash gas from the gas-liquid separator enters the boiler feed water preheater to preheat the boiler water; the high flash gas from the boiler feed water preheater then enters the washing tower to wash fine ash, recover raw materials and cool down; and finally is pressurized by the high flash gas compressor and sent to the gasification synthesis gas main.

[0005] Furthermore, the high-pressure flash steam of the high-pressure flash tank is 230-240°C, 3.4MPaG, the high-temperature black water discharged from the gasifier is 240-265°C, 8.5MPa and the high-temperature black water discharged from the scrubber is 240-259°C, 8.4MPa and enters the high-pressure flash tank respectively. In the present invention, the high-pressure flash tank collects the black water collected from multiple paths inside, and cools and steam-presses the black water at a temperature of about 240°C under an operating pressure of 3.45 MPa. The high-pressure flash gas is uniformly transported and cooled within the corresponding temperature range and pushed to the next low-pressure steam generator by steam.

[0006] Specifically, the mixed high-pressure flash steam discharged from the high-pressure flash tank enters the low-pressure steam generator and cooperates with the boiler feed water preheater to generate 1.2MPaG low-pressure saturated steam. The generated steam can simultaneously enter the 1.2MPaG and 0.5MPaG steam pipelines for use by other users in the plant.

[0007] In the present invention, the boiler feed water preheater cooperates with the low-pressure steam generator to produce 1.2MPaG low-pressure saturated steam as a by-product of heat exchange. The produced low-pressure steam is transported to the factory area through the connected steam pipe network, and the waste heat is recovered and reused to reduce heat waste.

[0008] Secondly, the high flash gas in the low pressure steam generator is cooled to 205°C and enters the gas-liquid separator. In the present invention, steam and liquid are separated in a gas-liquid separator, and the separated steam enters the boiler feed water preheater under pressure, and is preheated with the boiler water by the heat of the hot steam, and the heat is recovered and utilized again. The separated liquid is an ammonia water mixture, and NH3 in the high flash gas is recovered and utilized.

[0009] It should be noted that the high flash gas separated in the gas-liquid separator enters the boiler feed water preheater, and the high flash gas out of the boiler feed water preheater is 160-181°C. The high flash gas out of the boiler feed water preheater enters the scrubbing tower. In the present invention, the boiler feed water preheater cools the high flash gas to 160-181°C and pushes it to the scrubber under pressure for preheating recovery and resource recovery, reducing the direct discharge of CO, H2, CO2, H2S, and NH3 in the acid gas into the torch combustion, resulting in the waste of effective gas.

[0010] Furthermore, two layers of spraying are provided at the lower part of the washing tower, and a circulating pump and a circulating water heat exchanger are provided at the bottom outside the washing tower, and the incoming gas is sprayed and washed using the circulating grey water in the tower kettle.

[0011] In the present invention, a circulating pump extracts the gray water solution at the bottom of the scrubber and recovers the heat in cooperation with a circulating water heat exchanger. At the same time, the gray water solution continuously sprays the incoming high flash gas at the bottom of the scrubber to recover the acidic gas in the high flash gas.

[0012] It is worth adding that six layers of tower trays are set on the upper part of the washing tower, which are four layers of fixed valves and two layers of sieve plates from top to bottom. Cold sealing water is used to wash and cool the flash gas again. The temperature of the flash gas leaving the washing tower drops to below 45°C. Finally, it is pressurized to 8.5MPaG by a high-flash gas compressor and sent to the gasification synthesis gas main.

[0013] In the present invention, with the cooperation of the six-layer tower tray, the high flash gas on the ascending discharge side is filtered and cooled again, and the multiple layers are fully filtered and contacted to achieve contact and cooling of the high flash gas. With the cooperation of the high flash gas compressor, the high flash gas after washing and cooling is pressurized and transported to the synthesis gas main pipe, and then centrally transported to the next processing device.

[0014] In addition, a phosphate dosing device is provided at the connecting pipe between the high-pressure flash tank and the low-pressure steam generator to improve the boiler water quality in the low-pressure steam generator and prevent scaling.

[0015] In the present invention, the phosphate dosing device is added from the pipeline between the high-pressure flash tank and the low-pressure steam generator, and the phosphate mixture enters the low-pressure steam generator, thereby reducing scaling of the inner wall and reducing the thickening of the inner wall after scaling, which affects the efficiency of the low-pressure steam generator in generating saturated steam.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention uses a high-pressure flash tank to uniformly heat the mixed solution discharged from multiple paths and transport it to a low-pressure steam generator. The boiler feedwater preheater is connected to the gas-liquid separator to utilize the waste heat of the high-pressure flash gas in the low-pressure steam generator. The high-temperature thermal energy is used to generate saturated steam and transport it to the factory for use. After passing through the gas-liquid separator, some acidic gases and the aqueous solution mixture are separated. The high-pressure flash gas is then washed and cooled in a scrubber to recover ammonia, hydrogen sulfide, sulfur dioxide, and nitrogen oxides, thereby reducing the waste of resources caused by flaring. 2. The present invention cooperates with a circulating water heat exchanger to continuously extract and spray the gray water at the bottom of the washing tower, wash the high flash gas entering the washing tower, and recover the acidic gas. The washing tower is equipped with six tower trays to cool the internal high flash gas again. Finally, the high flash gas is pressurized by a high flash gas compressor to cool the high flash gas, recover heat and resources, and then centrally transport and discharge it. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a process flow chart of the present invention.

[0018] The meaning of each number in the figure is: 1. High-pressure flash tank; 2. Low-pressure steam generator; 3. Gas-liquid separator; 4. Boiler feed water preheater; 5. Scrubber; 6. High flash gas compressor; 7. Circulating water heat exchanger; 8. Circulation pump. DETAILED DESCRIPTION

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0020] See also Figure 1 , this embodiment provides a technical solution: A coal chemical high flash gas energy saving and resource recovery "double-effect" zero-emission process, including the high-temperature black water discharged from each series entering the high-pressure flash tank 1, the high-pressure flash steam collected after merging, and then entering the newly added low-pressure steam generator 2. The high-pressure flash steam of the high-pressure flash tank 1 is 230-240℃, 3.4MPaG, the high-temperature black water discharged from the gasifier is 240-265℃, 8.5MPa, and the high-temperature black water discharged from the scrubber is 240-259℃, 8.4MPa, respectively entering the high-pressure flash tank 1. In the present invention, the high-pressure flash tank 1 collects the black water collected from multiple paths inside, and cools and steam-presses the water at a temperature of 230-240°C under an operating pressure of 3.45 MPa. The high-pressure flash gas is uniformly transported and cooled within the corresponding temperature range and pushed to the next low-pressure steam generator 2 by steam.

[0021] Furthermore, the low-pressure steam generator 2 and the boiler water preheated by the boiler feed water preheater 4 produce low-pressure saturated steam as a by-product through heat exchange. The generated steam can enter the steam network at the same time. The mixed high-pressure flash steam discharged from the high-pressure flash tank 1 enters the low-pressure steam generator 2 and cooperates with the boiler feed water preheater 4 to produce 1.2MPaG low-pressure saturated steam. The generated steam can enter the 1.2MPaG and 0.5MPaG steam networks at the same time for use by other users in the plant. In the present invention, the boiler feed water preheater 4 cooperates with the low-pressure steam generator 2 to produce 1.2 MPaG low-pressure saturated steam as a by-product of heat exchange, and transports the produced low-pressure steam to the factory area through the connected steam pipe network, thereby recovering and reusing the waste heat and reducing heat waste.

[0022] Specifically, the steam cooled by the low-pressure steam generator 2 enters the gas-liquid separator 3 for gas-liquid separation, and the high flash gas from the gas-liquid separator 3 enters the boiler feed water preheater 4. After the high flash gas in the low-pressure steam generator 2 is cooled to 205°C, it enters the gas-liquid separator 3. In the present invention, steam and liquid are separated in the gas-liquid separator 3, and the separated steam enters the boiler feed water preheater 4 under pressure extrusion, and is preheated with the boiler water by the heat of the hot steam, and the heat is recovered and utilized again. The separated liquid is an ammonia water mixture, and NH3 in the high flash gas is recovered and utilized.

[0023] It should be noted that the high flash gas from the boiler feed water preheater 4 is preheated to the boiler water, then enters the scrubber 5 to wash the fine ash, recover the raw materials and cool it down, and is finally pressurized by the high flash gas compressor 6 and sent to the gasification synthesis gas main.

[0024] Furthermore, the high flash gas separated in the gas-liquid separator 3 enters the boiler feed water preheater 4, and the high flash gas out of the boiler feed water preheater 4 is 160-181°C. The high flash gas out of the boiler feed water preheater 4 enters the scrubbing tower 5. In the present invention, the boiler feed water preheater 4 cools the high flash gas to 160-181°C and pushes it to the scrubber 5 under pressure for preheating recovery and resource recovery, thereby reducing the direct discharge of CO, H2, CO2, H2S, and NH3 in the acid gas into the flare, resulting in the waste of effective gas.

[0025] Specifically, two layers of spraying are provided at the lower part of the washing tower 5 , and a circulating pump 8 and a circulating water heat exchanger 7 are provided at the outer bottom of the washing tower 5 , and the incoming gas is sprayed and washed using the circulating grey water in the tower kettle.

[0026] In the present invention, the circulating pump 8 extracts the gray water solution from the bottom of the washing tower 5 and recovers the heat in cooperation with the circulating water heat exchanger 7. At the same time, the gray water solution continuously sprays the incoming high flash gas at the bottom of the washing tower 5 to recover the acidic gas in the high flash gas.

[0027] It is worth adding that six layers of tower trays are arranged on the top of the washing tower 5, which are composed of four layers of fixed valves and two layers of sieve plates from top to bottom. Cold sealing water is used to wash and cool the flash gas again. The temperature of the flash gas leaving the washing tower 5 drops to below 45°C. Finally, it is pressurized to 8.5MPaG by the high-flash gas compressor 6 and sent to the gasification synthesis gas main.

[0028] In the present invention, with the cooperation of the six-layer tower tray, the high flash gas on the ascending discharge side is filtered and cooled again, and the multiple layers are fully filtered and contacted to achieve contact and cooling of the high flash gas. With the cooperation of the high flash gas compressor 6, the high flash gas after washing and cooling is pressurized and transported to the synthesis gas main pipe, and then transported to the next processing device in a centralized manner.

[0029] In addition, a phosphate dosing device is provided at the connecting pipe between the high-pressure flash tank 1 and the low-pressure steam generator 2 to improve the boiler water quality in the low-pressure steam generator and prevent scaling.

[0030] In the present invention, the phosphate dosing device is added from the pipeline between the high-pressure flash tank 1 and the low-pressure steam generator 2, and the phosphate mixture enters the low-pressure steam generator 2, thereby reducing scaling of the inner wall and reducing the thickening of the inner wall after scaling, which affects the efficiency of the low-pressure steam generator 2 in generating saturated steam.

[0031] When the coal chemical high flash gas energy saving and resource recovery "double-effect" zero-emission process of this embodiment is used, the high-pressure flash tank 1 is first connected to the two groups of low-pressure steam generators 2 through corresponding connecting pipes, and a phosphate dosing device is provided in the middle of the connecting pipe to transport the corresponding hydrochloric acid mixture to the low-pressure steam generator 2. The bottom of the low-pressure steam generator 2 is connected to the gas-liquid separator 3 through the corresponding connecting pipe. The high-flash gas coming out of the gas-liquid separator 3 enters the boiler feed water preheater 4, and the low-pressure saturated steam generated in the low-pressure steam generator 2 is simultaneously transported to the corresponding steam pipe network to utilize the high-temperature waste heat. The high-flash gas after heat recovery in the boiler feed water preheater 4 enters the washing tower 5. With the cooperation of the circulating water heat exchanger 7 and the circulating pump 8, the high-flash gas entering the washing tower 5 is recovered as raw materials to reduce the waste of acidic gas raw materials. The multi-layer trays in the washing tower 5 fully contact and cool the high flash gas. Finally, with the cooperation of the high flash gas compressor 6, the high flash gas recovered from the processed and cooled raw materials is pressurized and concentrated for transportation and discharge, reducing heat waste in this process and increasing energy consumption. At the same time, the acidic raw material gas in the high mountain is recovered to reduce the waste of raw materials caused by direct discharge through the flare and avoid waste of effective gas. At the same time, the whole process is pushed by steam to reduce energy consumption.

Claims

1. A coal chemical high flash gas energy saving and resource recovery "double effect" zero emission process, characterized by: The high-temperature black water discharged from each series enters the high-pressure flash tank, and the high-pressure flash gas collected is merged and enters the newly added low-pressure steam generator. The low-pressure steam generator and the boiler water preheated by the boiler feed water preheater are heat exchanged to produce low-pressure saturated steam as a by-product. The generated steam can enter the steam network at the same time. The steam cooled by the low-pressure steam generator enters the gas-liquid separator for gas-liquid separation. The high flash gas from the gas-liquid separator enters the boiler feed water preheater to preheat the boiler water. The high flash gas from the boiler feed water preheater then enters the washing tower to wash the fine ash, recover the raw materials and cool down. Finally, it is pressurized by the high flash gas compressor and sent to the gasification synthesis gas main.

2. The coal chemical high flash gas energy saving and resource recovery "double-effect" zero-emission process according to claim 1 is characterized by: The high-pressure flash steam of the high-pressure flash tank is 230-240°C and 3.4MPaG, the high-temperature black water discharged from the gasifier is 240-265°C and 8.5MPa, and the high-temperature black water discharged from the washing tower is 240-259°C and 8.4MPa, which enter the high-pressure flash tank respectively.

3. The coal chemical high flash gas energy saving and resource recovery "double-effect" zero-emission process according to claim 1 is characterized by: The mixed high-pressure flash steam discharged from the high-pressure flash tank enters the low-pressure steam generator and cooperates with the boiler feed water preheater to generate 1.2MPaG low-pressure saturated steam. The generated steam can simultaneously enter the 1.2MPaG and 0.5MPaG steam pipelines for use by other users in the plant.

4. The coal chemical high flash gas energy saving and resource recovery "double-effect" zero-emission process according to claim 1 is characterized by: The high flash gas in the low-pressure steam generator is cooled to 205° C. and then enters the gas-liquid separator.

5. The coal chemical high flash gas energy saving and resource recovery "double-effect" zero-emission process according to claim 1 is characterized by: The high flash gas separated in the gas-liquid separator enters the boiler feed water preheater, and the high flash gas leaving the boiler feed water preheater has a temperature of 160-181° C. The high flash gas leaving the boiler feed water preheater enters the scrubbing tower.

6. The coal chemical high flash gas energy saving and resource recovery "double-effect" zero-emission process according to claim 1 is characterized by: The lower part of the washing tower is provided with two layers of spraying, and the outer bottom of the washing tower is provided with a circulating pump and a circulating water heat exchanger, and the gray water circulating in the tower kettle is used to spray and wash the incoming gas.

7. The coal chemical high flash gas energy saving and resource recovery "double-effect" zero-emission process according to claim 1 is characterized by: The washing tower is equipped with six layers of tower trays, which are composed of four layers of fixed valves and two layers of sieve plates from top to bottom. Cold sealing water is used to wash and cool the flash gas again. The temperature of the flash gas leaving the washing tower drops to below 45°C. Finally, it is pressurized to 8.5MPaG by a high-pressure flash gas compressor and sent to the gasification synthesis gas main.

8. The coal chemical high flash gas energy saving and resource recovery "double-effect" zero-emission process according to claim 1 is characterized by: A phosphate dosing device is provided at the connecting pipe between the high-pressure flash tank and the low-pressure steam generator to improve the boiler water quality in the low-pressure steam generator and prevent scaling.

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