CN-121990714-A - Method and device for treating coal gasification black water

CN121990714ACN 121990714 ACN121990714 ACN 121990714ACN-121990714-A

Abstract

The invention relates to the technical field of coal gasification, in particular to a method and a device for treating coal gasification black water. The method comprises the steps of 1) filtering coal gasification black water to obtain filtered clear liquid and solid impurities, 2) recycling the filtered clear liquid obtained in the step 1), wherein one part of the filtered clear liquid is directly returned to the front system reuse water and heat, the other part of the filtered clear liquid is used as a back flushing liquid to back flush the solid impurities to obtain back flush black water, and/or the other part of the filtered clear liquid is used as the front system reuse liquid, the other part of the filtered clear liquid is used as the back flushing liquid to back flush the solid impurities to obtain back flush black water, 3) carrying out multistage flash evaporation treatment, sedimentation and standing separation on the back flush black water obtained in the step 2) to obtain grey water and slurry, carrying out sewage treatment on the grey water, and carrying out solid-liquid separation treatment on the slurry. The invention can improve energy utilization, reduce energy consumption and reduce equipment investment and occupied area.

Inventors

WANG BAOMING
WAN HAIQING
ZHANG HUIPING
ZHANG QIAN

Assignees

上海戊正工程技术有限公司

Dates

Publication Date: 20260508
Application Date: 20260210

Claims (10)

1. A method of treating coal gasification black water, the method comprising the steps of: 1) Filtering the coal gasification black water S1 to obtain a filtered clear liquid S4 and solid impurities; 2) Recycling the filtered clear liquid S4 obtained in the step 1), wherein one recycling mode is to directly send part of the filtered clear liquid S4 back to the reuse water and heat of a front system, and the other part of the filtered clear liquid is used as a back flushing liquid S6 to back flush solid impurities to obtain back flush black water S7, and/or the second recycling mode is to recycle waste heat of the filtered clear liquid S4, wherein one part of the cooled filtered clear liquid is used as the reuse liquid S5 of the front system, and the other part of the cooled filtered clear liquid is used as the back flushing liquid S6 to back flush the solid impurities to obtain back flush black water S7; 3) Carrying out multistage flash evaporation treatment, sedimentation and standing separation on the back flush black water S7 obtained in the step 2) to obtain grey water S24 and slurry S25, carrying out sewage treatment on the grey water S24, and carrying out solid-liquid separation treatment on the slurry S25.
2. The method of treating coal gasification black water according to claim 1, further comprising any one or more of the following conditions: A1 In the step 1), the working temperature of the coal gasification black water S1 is 190-250 ℃, the pressure is 3.0-6.5 MPaG, the content of solid suspended matters is 0.1-4.0 wt%, and the average particle size of solid particles is 0.5-100 μm; a2 In step 1), the content of solid suspended matters in the filtered clear liquid S4 is less than 20 mg/L; a3 In step 1), the filtering is performed in a filter, wherein the filter is operated intermittently in 2-20 groups.
3. The method for treating coal gasification black water according to claim 1, wherein in step 1), the coal gasification black water S1 is swirled to obtain swirled concentrated black water S3 and overflow material S2, and the overflow material S2 is filtered to obtain filtered clear liquid S4 and solid impurities.
4. The method of treating coal gasification black water according to claim 3, further comprising any one or more of the following conditions: B1 In the step 1), the coal gasification black water S1 is concentrated in a grading way through rotational flow, and the solid suspended matter content of the concentrated black water S3 after rotational flow is 3-100 times of the solid suspended matter content of the coal gasification black water S1; B2 In the step 1), the temperature of the concentrated black water S3 after rotational flow is 190-250 ℃ and the pressure is 2.8-6.3 MPaG; b3 In the step 3), the concentrated black water S3 and the back flush black water S7 after rotational flow are subjected to multistage flash evaporation treatment together, and are settled and kept stand for separation to obtain gray water S24 and slurry S25.
5. The method of treating coal gasification black water according to claim 4, further comprising any one or more of the following conditions: C1 In the step 2), the working temperature of the filtered clear liquid S4 is 190-250 ℃, and the working pressure is reduced by 0.1-0.5 MPa; c2 Step 2), in the recycling mode I, the pressure is increased by 0.2-0.6 MPa; C3 In the first recycling mode of the step 2), the filtered clear liquid S4 is pressurized and sent back to the quenching zone of the gasification furnace of the front system and the heat carried by the directly recycled water in the synthetic gas separation and washing tower; C4 In the step 2), in the first recycling mode, the mass ratio of the filtered clear liquid S4 to the backwash liquid S6 sent back to the front system is 6-9:1-4; C5 Step 2), in the second recycling mode, the pressure is increased by 0.2-1.0 MPa; C6 In the second recycling mode of the step 2), steam with the pressure of 0.3-1.1 MPa and the temperature of 133-185 ℃ is generated through waste heat recovery; C7 In the second recycling mode of the step 2), after waste heat recovery, cooling to 160-180 ℃; C8 In the second recycling mode of the step 2), waste heat recovery is carried out on the filtered clear liquid S4, and a part of the cooled filtered clear liquid S4 is sent back to a quenching zone of a gasification furnace of a pre-system and is recycled by a synthetic gas separation washing tower; C9 In the second recycling mode of the step 2), the mass ratio of the recycled liquid S5 and the backwash liquid S6 of the front system is 6-9:1-4; C10 When the pressure difference between the front and the rear of the filter adopted by the filtering is 0.15-0.5 MPa, switching to a back flushing regeneration working condition, and back flushing the solid impurities by using a back flushing liquid S6 to obtain back flushing black water S7.
6. The method for treating coal gasification black water according to claim 1, wherein in step 3), the multi-stage flash evaporation comprises high pressure flash evaporation, low pressure flash evaporation and vacuum flash evaporation.
7. A device for treating coal gasification black water is characterized by comprising a filter (2), wherein the filter (2) comprises a material inlet (21), a filtered clear liquid outlet (22), a back flushing inlet (23) and a back flushing outlet (24), The waste heat boiler (13) is further included, the filtered clear liquid outlet (22) is communicated with a feed inlet of the waste heat boiler (13), and a discharge outlet of the waste heat boiler (13) is respectively communicated with the back flushing inlet (23) and the front system; the multi-stage flash evaporation device further comprises a multi-stage flash evaporation unit and a sedimentation tank (14), wherein the sedimentation tank (14) comprises a sedimentation feed inlet (141), a grey water outlet (142) and a slurry outlet (143), the back flushing outlet (24) is communicated with the feed inlet of the multi-stage flash evaporation unit, and the discharge outlet of the multi-stage flash evaporation unit is communicated with the sedimentation feed inlet (141).
8. The apparatus for treating coal gasification black water according to claim 7, further comprising any one or more of the following conditions: d1 The device comprises a cyclone (1), wherein the cyclone (1) comprises a black water feed inlet (101), an overflow discharge outlet (102) and a cyclone black water outlet (103), the cyclone black water outlet (103) is communicated with the feed inlet of the multi-stage flash evaporation unit, and the overflow discharge outlet (102) is communicated with a material inlet (21) of the filter (2); D2 A filtrate buffer tank (6) and a filtrate recycling pump (16) are arranged on the communicating pipe of the filtered clear liquid outlet (22) and the waste heat boiler (13); D3 -said filters (2) comprise a plurality of groups, each of said filters (2) being connected in parallel; D4 The filter (2) is one of a variable gap back flush filter, a micro-channel filter, a rotary drum filter and a centrifugal filter; D5 The multistage flash evaporation unit comprises a high-pressure flash evaporation tank (3), a low-pressure flash evaporation tank (4) and a vacuum flash evaporation tank (5) which are sequentially communicated, the high-pressure flash evaporation tank (3) is communicated with the filter (2), and the vacuum flash evaporation tank (5) is communicated with the sedimentation tank (14); D6 The device is characterized by further comprising a water washing tower (7), a low-flash condenser (11) and a low-flash separation tank (8) which are sequentially communicated, wherein the water washing tower (7) is respectively communicated with the high-pressure flash tank (3) and the low-pressure flash tank (4).
9. The apparatus for treating coal gasification black water according to claim 8, further comprising any one or more of the following conditions: D51 In feature D5), the high pressure flash tank (3) comprises a high pressure flash feed (31), a high pressure flash top outlet (32) and a high pressure flash bottom outlet (33), the high pressure flash feed (31) being in communication with the cyclone black water outlet (103) or the backwash outlet (24), respectively, the high pressure flash bottom outlet (33) being in communication with the low pressure flash tank (4); D52 In feature D5), the low pressure flash tank (4) comprises a low pressure flash feed inlet (41), a low pressure flash top outlet (42), a low pressure flash bottom outlet (43) and a low pressure flash reflux inlet (44), the high pressure flash tank (3) is in communication with the low pressure flash feed inlet (41), the low pressure flash bottom outlet (43) is in communication with the vacuum flash tank (5); D53 In feature D5), the vacuum flash tank (5) comprises a vacuum flash feed (51), a vacuum flash top outlet (52) and a vacuum flash bottom outlet (53), the vacuum flash feed (51) being in communication with the low pressure flash tank (4), the vacuum flash bottom outlet (53) being in communication with the settling tank (14); D61 In the characteristic D6), the water scrubber (7) comprises a water scrubber top outlet (71), a water scrubber bottom outlet (72), a water feeding port (73), a first gas phase feeding port (74) and a second gas phase feeding port (75), wherein the first gas phase feeding port (74) is communicated with the high-pressure flash tank (3), a high-flash heat exchanger (10) is arranged on a communication pipeline between the first gas phase feeding port (74) and the high-pressure flash tank (3), the second gas phase feeding port (75) is communicated with the low-pressure flash tank (4), and the water scrubber top outlet (71) is communicated with the low-flash condenser (11); D62 In feature D6), the low flash separation tank (8) includes a low flash separation feed inlet (81), a low flash separation top outlet (82), and a low flash separation bottom outlet (83), the low flash separation feed inlet (81) being in communication with the low flash condenser (11).
10. The apparatus for treating coal gasification black water according to claim 9, further comprising any one or more of the following conditions: E1 -the device further comprises a grey water tank (15), the grey water outlet (142) being in communication with the grey water tank (15), the low flash separation bottom outlet (83) being in communication with the grey water tank (15); E2 The device also comprises a true flash condenser (12) and a true flash separating tank (9), which are sequentially communicated with a vacuum flash top outlet (52), wherein the true flash separating tank (9) is communicated with the settling tank (14).

Description

Method and device for treating coal gasification black water Technical Field The invention relates to the technical field of coal gasification, in particular to a method and a device for treating coal gasification black water. Background Coal gasification is a process in which coal is used as a raw material, oxygen and the like are used as gasifying agents under the conditions of high temperature and high pressure, and the coal is converted into synthesis gas (the main component of the synthesis gas is CO+H 2) through chemical reaction. Coal gasification is a core technology and a tap technology for clean utilization of coal, and is a foundation for developing process industries such as synthesis of coal-based bulk chemicals and liquid fuels, integrated gasification combined power generation, poly-generation systems, hydrogen production, fuel cells, indirect liquefaction of coal and the like. At present, the coal gasification technology in the large-scale coal chemical production process mostly adopts a large-scale entrained-flow gasification technology, and is divided into a coal water slurry gasification technology and a dry powder coal gasification technology according to different material conveying modes. Regardless of the gasification technology, the synthesis gas scrubbing and black water treatment system directly affects the long-period stable operation of the gasification system. At present, the coal chemical industry slag water units at home and abroad mostly adopt a multi-stage flash evaporation and natural sedimentation process to treat black water. The multistage flash evaporation and natural sedimentation process adopts three stages of flash evaporation of a high-pressure flash evaporation tank, a low-pressure flash evaporation tank and a vacuum flash evaporation tank to perform flash evaporation cooling, and then performs natural sedimentation on black water to separate solids in the black water, so that the flash evaporation sedimentation system is utilized to realize cooling and depressurization, heat recovery and liquid-solid separation. When the three-stage flash evaporation black water treatment system of Chinese patent CN115340138A recovers heat in black water and recycles the black water, the black water is subjected to flash evaporation to reduce pressure and lower temperature, the black water is subjected to solid removal, and then is returned to a gasifier quenching zone and a synthesis gas separation washing tower of the front system to be respectively used as quenching water and washing water, the temperature and the pressure are required to be raised, the water in the black water is firstly subjected to temperature and pressure reduction and then is subjected to temperature and pressure raising, so that the cold and hot diseases in the chemical process are obtained, and the heat utilization rate is extremely low. Specifically, high-pressure steam and low-pressure steam are output to black water from a gasification system through a solid-liquid separation device by multistage flash evaporation, concentrated black water is discharged, solids are separated through solid-liquid separation equipment, and clarified ash water is obtained, the clarified ash water is subjected to heat exchange with the low-pressure steam and the high-pressure flash steam which are obtained by flash evaporation of the black water in sequence through a heat exchange device comprising a low-pressure flash stripping tower and a high-pressure flash stripping tower, and the clarified ash water is heated and then is pressurized and sent into a quenching zone of a gasification furnace and a synthetic gas separation washing tower of a front system. Vacuum flash evaporation generates a large amount of low-pressure flash steam, and part of steam at the top of the low-pressure flash stripping tower is not condensed, so that a large amount of circulating water is consumed to condense and cool the two flash gases. The black water flash evaporation and solid sedimentation equipment has large volume, high equipment investment and large occupied area. Disclosure of Invention In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to provide a method and apparatus for treating coal gasification black water, which improves energy utilization, reduces energy consumption, and reduces equipment investment and floor space, thereby solving the problems in the prior art. The technical scheme of the invention is as follows: in one aspect, the invention provides a method of treating coal gasification black water, the method comprising the steps of: 1) Filtering the coal gasification black water to obtain filtered clear liquid and solid impurities; 2) Recycling the filtered clear liquid obtained in the step 1), wherein one recycling mode is to directly send a part of the filtered clear liquid back to the front system reuse water and heat, and the other part of the filtered clear liquid is use