Dust removal method for crude synthesis gas of coal gasification system

Abstract

The invention provides a dust removal method for crude synthesis gas of a coal gasification system, which belongs to the technical field of coal chemical industry and comprises the following steps: introducing the crude synthesis gas with solid particles discharged by a gasification furnace into a gas-solid separation unit to separate solids in the crude synthesis gas; solids intercepted by the gas-solid separation unit are discharged out of the coal gasification system; introducing the filtered synthesis gas into a washing tower, and washing the synthesis gas with washing water; discharging the washed synthesis gas from the washing tower; according to the invention, the crude synthesis gas is purified in a mechanical filtration manner, the amount of solids entering the washing tower is reduced, the synthesis gas washing process is optimized, the production process is simplified, pollution and water consumption are reduced, energy waste is reduced, and equipment investment and operation cost are reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of coal chemical industry, and in particular relates to a dust removal method for raw synthetic gas in a coal gasification system. Background Art

[0002] Coal gasification technology plays a pivotal role in the coal chemical industry. Domestic coal gasification technology mainly adopts the fluidized bed process. The crude synthesis gas generated by the gasifier contains a large amount of solids and water. Before entering the subsequent device, the crude synthesis gas needs to be desolidified; but the temperature of the crude synthesis gas exceeds 200°C and the pressure exceeds 4.0MPa. The pressure of the crude synthesis gas generated by some gasifiers even exceeds 6.0MPa, which is extremely difficult to handle. Generally, the crude synthesis gas containing solids needs to be introduced into the washing tower for washing and desolidification treatment; the washing water containing solids at the bottom of the washing tower enters the subsequent flash evaporation device. At the same time, in order to ensure a good washing and desolidification effect, a cyclone separator or a Venturi mixer needs to be added before the crude synthesis gas enters the washing tower to pre-treat the crude synthesis gas.

[0003] During the actual operation, the solids in the crude synthesis gas are washed away by washing water in the washing tower. The solids contained in this washing water will contaminate the washing tower, resulting in poor operation of the washing tower and shortened operation cycle. At the same time, the washing water containing solids at the bottom of the washing tower enters the subsequent flash evaporation system, which will also cause scaling of the equipment and shorten the equipment operation cycle. Summary of the invention

[0004] An embodiment of the present invention provides a dust removal method for raw synthesis gas in a coal gasification system, aiming to reduce the solid content in the raw synthesis gas before the raw synthesis gas enters a washing tower.

[0005] To achieve the above object, the technical solution adopted by the present invention is: A method for removing dust from raw synthesis gas in a coal gasification system is provided, comprising the following steps: The raw synthesis gas with solid particles discharged from the gasifier is introduced into a gas-solid separation unit to separate the solids in the raw synthesis gas; the solids intercepted by the gas-solid separation unit are discharged from the coal gasification system; The filtered synthesis gas is passed into a scrubbing tower, where the synthesis gas is scrubbed with scrubbing water; The scrubbed synthesis gas is discharged from the scrubbing tower.

[0006] In a possible implementation, the gas-solid separation unit includes at least one filter, and the filter is backwashed within a first preset time, and the backwashing lasts for a second preset time.

[0007] In a possible implementation, when there are more than two filters, the filters are connected in parallel.

[0008] In a possible implementation, the first preset time range is 10 to 60 minutes, and the second preset time range is 1 to 60 seconds.

[0009] In a possible implementation, when the solid content of the filtered raw synthesis gas is greater than 1000 ppm, the filtered raw synthesis gas is introduced into a pretreatment device, and the pretreatment device cleans or performs secondary separation on the raw synthesis gas.

[0010] In a possible implementation, the filter component in the gas-solid separation unit is one or more of a metal powder sintered membrane, a metal wire mesh membrane, and a powder mesh composite membrane.

[0011] In a possible implementation, when the filter component is a powder mesh composite membrane, the filter layer precision of the powder mesh composite membrane is 0.45~150μm, and the base material precision is 30~200μm; When the filter element is a metal powder sintered film, the accuracy of the metal powder sintered film is 5~150μm; When the filter component is a metal mesh membrane, the accuracy of the metal mesh membrane is 5~150μm.

[0012] The present invention provides a dust removal method for raw synthesis gas in a coal gasification system. Compared with the prior art, the present invention adopts mechanical filtration to purify the raw synthesis gas, reduces the amount of solids entering the washing tower, optimizes the synthesis gas washing process, simplifies the production process, reduces pollution and water consumption, reduces energy waste, and reduces equipment investment and operating costs; the filter unit is provided with a backwashing function, and the occurrence of scaling can be reduced by providing a filter element, thereby extending the service life of the filter equipment; the solid content in the raw synthesis gas after mechanical filtration purification is greatly reduced, which reduces the pollution of the washing tower, improves the operation effect of the washing tower, and extends the operation cycle of the washing tower. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A schematic diagram of a process flow of a method for removing dust from raw synthesis gas in a coal gasification system provided by an embodiment of the present invention; Figure 2 A schematic diagram of the connection between a gas-solid separation unit and a lock hopper in a method for removing dust from raw synthesis gas in a coal gasification system provided by an embodiment of the present invention; Figure 3 A schematic diagram of membrane filtration and backwashing of a dust removal method for raw synthesis gas in a coal gasification system provided in an embodiment of the present invention.

[0014] Explanation of the accompanying drawings: 1. gasification furnace; 2. gas-solid separation unit; 3. washing tower; 4. lock hopper. DETAILED DESCRIPTION

[0015] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0016] Please also read Figures 1 to 3 , now a dust removal method for raw syngas of a coal gasification system provided by the present invention is described. The dust removal method for raw syngas of a coal gasification system comprises the following steps: raw syngas with solid particles discharged from a gasifier is passed into a gas-solid separation unit to separate solids in the raw syngas; solids intercepted by the gas-solid separation unit are discharged from the coal gasification system; the filtered syngas is passed into a washing tower, and the syngas is washed with washing water; the washed syngas is discharged from the washing tower. The filter component in the gas-solid separation unit is one or more of a metal powder sintered membrane, a metal wire mesh membrane, and a powder mesh composite membrane; the filter layer precision of the powder mesh composite membrane is 0.45~150μm, preferably 10~100μm; the substrate precision is 30~200μm, preferably 30~120μm. The precision of the metal powder sintered membrane and the metal wire mesh membrane is 5~150μm, preferably 10~100μm.

[0017] The present invention provides a dust removal method for raw synthesis gas in a coal gasification system. Compared with the prior art, the present invention adopts mechanical filtration to purify the raw synthesis gas, reduces the amount of solids entering the washing tower, optimizes the synthesis gas washing process, simplifies the production process, reduces pollution and water consumption, reduces energy waste, and reduces equipment investment and operating costs; the filter unit is provided with a backwashing function, and the occurrence of scaling can be reduced by providing a filter element, thereby extending the service life of the filter equipment; the solid content in the raw synthesis gas after mechanical filtration purification is greatly reduced, which reduces the pollution of the washing tower, improves the operation effect of the washing tower, and extends the operation cycle of the washing tower.

[0018] It should be noted that the crude synthesis gas discharged from the gasifier is in a state of high temperature and high pressure, that is, the temperature of the crude synthesis gas is 215°C and the pressure of the crude synthesis gas is 4.2MPa; after the crude synthesis gas is directly introduced into the gas-solid separation unit, the gas-solid separation unit can filter the crude synthesis gas, and there is no need to set a booster pump at the air inlet position of the gas-solid separation unit. Through the above-mentioned setting of the present application, the solid content in the crude synthesis gas can be reduced. When the crude synthesis gas is cleaned by the washing tower, when cleaning the same content of solids, the washing tower can clean more crude synthesis gas, thereby improving the equipment operation cycle.

[0019] In some embodiments, Figure 1As shown, the gas-solid separation unit includes at least one filter, and the filter is backwashed within a first preset time, and the backwashing lasts for a second preset time. The first preset time ranges from 10 to 60 minutes, and the second preset time ranges from 1 to 60 seconds.

[0020] It should be noted that there can be one filter or more than two filters; when there is one filter, the filter is arranged in series with the gasifier and the washing tower; when there are more than two filters, the filters are arranged in parallel and the filter is arranged in series with the gasifier and the washing tower.

[0021] Exemplarily, the filter includes two parts, the upper part is the main filter, and the lower part is connected to the lock bucket through a valve. During normal filtration, the valve between the two is opened, and the lock bucket receives solids; when the solids need to be discharged, the valve between the lock bucket and the main filter is closed, and the discharge valve is opened, and the lock bucket releases pressure to discharge the solids; after the lock bucket has discharged the solids, the lock bucket is pressurized, and the valve is reopened to connect with the main filter to receive the solids from the main filter; during the entire filtration process, the main filter always works normally.

[0022] Exemplarily, a booster pipe is connected to the lock hopper, and the other end of the booster pipe is connected to the pipe for discharging raw synthesis gas from the gasifier, and a valve is provided on the booster pipe. When the lock hopper is connected to the main filter, the valve of the booster pipe is closed; when solids need to be discharged, the valve between the lock hopper and the main filter is closed, and the lock hopper is depressurized to discharge solids; when the discharge is completed, the discharge valve of the lock hopper is closed, and the valve of the booster pipe is opened to increase the pressure in the lock hopper.

[0023] Exemplarily, a backwashing pipeline is provided on the filter, and when the filter is backwashed, purified synthesis gas is introduced to backwash the filter; the backwashing pressure of the purified synthesis gas is 6.4 MPa, the backwashing duration is 8 seconds, and the backwashing cycle is 30 minutes.

[0024] Exemplarily, carbon monoxide or hydrogen may be introduced to backwash the filter; of course, the above gases may also be mixed to serve as backwash gas.

[0025] In some embodiments, Figure 1 As shown, when the solid content of the filtered raw synthesis gas is greater than 1000 ppm, the filtered raw synthesis gas is introduced into a pretreatment device, and the pretreatment device cleans or performs secondary separation on the raw synthesis gas.

[0026] It should be noted that the pretreatment device is a cyclone separator or a venturi scrubber, and the washing water used in the pretreatment device is the washing water or filtrate in the washing tower.

[0027] Exemplarily, the single backwashing time of the filter is 1 to 60 seconds, preferably 3 to 30 seconds; the backwashing cycle is preferably 15 to 30 minutes.

[0028] Embodiment 1: The crude syngas (215℃, 4.2 MPa) from the gasifier enters the gas-solid separation unit, and the solids are intercepted by the wire mesh. The intercepted solids are discharged from the lock bucket system. The initially purified crude syngas then enters the scrubber for scrubbing and dust removal. The purified syngas discharged from the bottom of the scrubber enters the subsequent device. Part of the washing water containing solids at the bottom of the tower is pumped to the middle of the scrubber for use as circulating washing water, and part is sent to the flash tank. The gas-solid separation unit is equipped with 3 parallel filters, which are equipped with tubular wire mesh filter elements with a filtration accuracy of 10μm; the recoil medium is purified syngas, the recoil pressure is 6.4MPa, the recoil time is 8 seconds, and the recoil cycle is 30min; the solid content of the syngas after filtering through the wire mesh is 68ppm.

[0029] Comparative Example 1: The crude syngas (215℃, 4.2 MPa) from the gasifier enters the gas-solid separation unit, and the solids are intercepted by the wire mesh. The intercepted solids are discharged from the lock bucket system. The initially purified crude syngas then enters the scrubber for scrubbing and dust removal. The purified syngas discharged from the bottom of the scrubber enters the subsequent device. Part of the washing water containing solids at the bottom of the tower is pumped to the middle of the scrubber as circulating washing water, and part is sent to the flash tank. The gas-solid separation unit is equipped with three parallel filters, and the filter is equipped with a tubular wire mesh filter element. The wire mesh filter element is a three-layer wire mesh sintered structure with a filtration accuracy of 180μm; the recoil medium is purified syngas, the recoil pressure is 6.4MPa, the recoil time is 8 seconds, and the recoil cycle is 30min; the solid content of the syngas after filtering through the wire mesh is higher than 700ppm.

[0030] Comparative Example 2: The crude syngas (215℃, 4.2 MPa) from the gasifier enters the gas-solid separation unit, and the solids are intercepted by the wire mesh. The intercepted solids are discharged from the lock bucket. The crude syngas that has been initially purified then enters the scrubber for scrubbing and dust removal. The purified syngas discharged from the bottom of the scrubber enters the subsequent device. Part of the washing water containing solids at the bottom of the tower is pumped to the middle of the scrubber as circulating washing water, and part is sent to the flash tank. The gas-solid separation unit is equipped with 3 parallel filters, which are equipped with tubular powder mesh composite filter elements with a filtration accuracy of 200μm; the recoil medium is purified syngas, the recoil pressure is 6.4MPa, the recoil time is 8 seconds, and the recoil cycle is 30min; the solid content of the syngas filtered by the tubular powder mesh composite filter element is higher than 300ppm.

[0031] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for removing dust from raw synthesis gas in a coal gasification system, characterized in that: The following steps are involved: The raw synthesis gas with solid particles discharged from the gasifier is introduced into a gas-solid separation unit to separate the solids in the raw synthesis gas; The solids intercepted by the gas-solid separation unit are discharged from the coal gasification system; The filtered synthesis gas is passed into a scrubbing tower, where the synthesis gas is scrubbed with scrubbing water; The scrubbed synthesis gas is discharged from the scrubbing tower.

2. The method for removing dust from raw synthesis gas in a coal gasification system according to claim 1, characterized in that: The gas-solid separation unit includes at least one filter, and the filter is backwashed within a first preset time, and the backwashing lasts for a second preset time.

3. The method for removing dust from raw synthesis gas in a coal gasification system according to claim 2, characterized in that: When there are more than two filters, the filters are set in parallel.

4. The method for removing dust from raw synthesis gas in a coal gasification system according to claim 2, characterized in that: The first preset time range is 10 to 60 minutes, and the second preset time range is 1 to 60 seconds.

5. The method for removing dust from raw synthesis gas in a coal gasification system according to claim 1, characterized in that: When the solid content of the filtered raw synthesis gas is greater than 1000 ppm, the filtered raw synthesis gas is introduced into a pretreatment device, and the pretreatment device cleans or performs secondary separation on the raw synthesis gas.

6. The method for removing dust from raw synthesis gas in a coal gasification system according to claim 1, characterized in that: The filter component in the gas-solid separation unit is one or more of a metal powder sintered membrane, a metal wire mesh membrane, and a powder mesh composite membrane.

7. A method for removing dust from raw synthesis gas in a coal gasification system according to claim 1 or 6, characterized in that: When the filter element is a powder mesh composite membrane, the filter layer accuracy of the powder mesh composite membrane is 0.45~150μm, and the base material accuracy is 30~200μm; When the filter element is a metal powder sintered film, the accuracy of the metal powder sintered film is 5~150μm; When the filter component is a metal mesh membrane, the accuracy of the metal mesh membrane is 5~150μm.

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