A method for ammonia extraction from coal gasification grey water

Abstract

The present application belongs to the technical field of coal gasification ash water ammonia extraction, and particularly relates to a coal gasification ash water ammonia extraction method. After the hardness of the coal gasification ash water is removed, the ash water is sent to an inclined plate sedimentation tank, and the ash water is subjected to enhanced sedimentation and mud removal in the inclined plate sedimentation tank, so as to improve the mud removal efficiency of the inclined plate sedimentation tank and further reduce the load and cleaning frequency of a subsequent precision filter. The filter material of the precision filter of the present application is alkali-resistant glass filter material, which can effectively prevent problems such as filter material hardening and flow interruption, and has good filtering effect, clean backwashing and low backwashing water consumption. A baffle tray for blocking suspended particles is arranged in the ammonia recovery tower of the present application, so as to avoid the clogging of the cap cover tray and the guide fixed valve tray due to the retention and hardening of suspended particles. The present application prolongs the service life of the ammonia recovery tower from about 20 days to more than 6 months, greatly improves the stable operation period of the ammonia recovery tower, and also reduces the parking and maintenance frequency and maintenance cost of the ammonia recovery tower.

Description

Technical Field

[0001] This invention belongs to the field of ammonia extraction technology from coal gasification ash water, specifically a method for ammonia extraction from coal gasification ash water. Background Technology

[0002] Coal-water slurry gasification, as the most effective clean coal technology for improving coal utilization, is widely used not only in the production of basic chemical raw materials such as fertilizers, methanol, and ethylene glycol, but also in producing large amounts of steam for internal use by enterprises. It is a mainstream technology for large-scale, efficient, and clean coal utilization. However, the coal gasification process generates a large amount of ash water, which mainly comes from quench water and washing water from the gasification process. This ash water contains high levels of suspended solids, colloids, solid particles, hardness, COD, ammonia nitrogen, and other substances. Ammonia nitrogen is a nutrient element for nitrogen fertilizer, and its discharge into water bodies will cause eutrophication, leading to excessive growth of aquatic microorganisms, oxygen deficiency, and foul odors. Therefore, it is necessary to recover and treat the ammonia in the ash water.

[0003] Because my country's coal and water resources are distributed inversely, modern coal chemical projects are mostly built in water-scarce regions such as Inner Mongolia, Ningxia, Shaanxi, and Xinjiang. To reduce water consumption in coal gasification units and conserve water resources, the ash water produced by these units is treated through flocculation and sedimentation before being recycled. However, to avoid the accumulation of ammonia nitrogen, calcium and magnesium ions, and other harmful components in the ash water, a portion of the flocculated and precipitated ash water is usually sent to an ash water ammonia extraction unit for hardening removal and ammonia recovery. However, in existing ash water ammonia extraction processes, the untimely removal of sediment and sludge after hardening removal results in a high amount of suspended solids in the ash water entering the subsequent filtration unit. This causes the filtration unit to be overloaded and its filtration effect to be poor. Consequently, the ash water entering the ammonia recovery tower has a high amount of suspended solids, leading to severe blockage of the ammonia recovery tower. This forces the ash water ammonia extraction unit to shut down for maintenance after a short period of operation, seriously affecting its long-term operation. In addition, the existing filtration device is a fiber ball filter, which is a new type of precision water filtration equipment. Fiber ball filter media has the characteristics of low density, good flexibility, compressibility and large porosity. When in use, its large specific surface area and porosity adsorb and trap suspended particles in the water at the same time, giving full play to the deep interception capacity of the filter media. However, after filtration, the fiber ball filter media turns into mud balls, which are not cleaned by backwashing, thus reducing the filtration efficiency and requiring a large amount of water for backwashing. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention provides a method for ammonia extraction from coal gasification ash water. This invention reduces suspended solids in the ash water after hard filtration, reduces the load on the filtration device while achieving good filtration results. It also ensures thorough backwashing with low backwashing water consumption. Furthermore, it prevents the ammonia recovery tower from clogging, thereby reducing the frequency and cost of maintenance for the ammonia recovery tower and filtration device. This ensures the long-term stable operation of the coal gasification ash water ammonia extraction device.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: A method for ammonia extraction from coal gasification ash water, comprising the following steps:

[0006] S1: The coal gasification ash water is sent to the hardening removal device, and the hardened ash water is sent to the inclined plate sedimentation tank. Several sludge hoppers are set at the bottom of the inclined plate sedimentation tank. Each sludge hopper is equipped with a sludge discharge pipe for intermittent sludge discharge. The intermittent time is 2 hours to 6 hours, and the sludge discharge time is 5 minutes to 20 minutes. The clear liquid ash water obtained at the top of the inclined plate sedimentation tank is sent to the buffer tank a.

[0007] S2: The grey water in buffer tank a of S1 is sent to a precision filter for filtration. The filter media in the precision filter is alkali-resistant glass filter media. The grey water filtered by the precision filter is sent to buffer tank b.

[0008] S3: The ash water in buffer tank b of S2 is sent to the ammonia recovery tower for distillation to recover ammonia. The ammonia-containing process gas at the top of the ammonia recovery tower is condensed by the condenser and then absorbed by the integrated reactor to produce ammonia water. Wastewater is produced in the bottom of the ammonia recovery tower. The ammonia recovery tower is equipped with trays, which are arranged from top to bottom as the first tray, the second tray, the third tray, and the fourth tray. The first tray is a cap tray, the second tray is a baffle tray, the third tray is a cap tray, and the fourth tray is a guide valve tray.

[0009] Furthermore, the ammonia nitrogen in the coal gasification ash water is 800 mg / L to 1500 mg / L (e.g., ammonia nitrogen of 800 mg / L, 900 mg / L, 1000 mg / L, 1100 mg / L, 1200 mg / L, 1300 mg / L, 1400 mg / L, 1500 mg / L), the hardness is 600 mg / L to 1200 mg / L (e.g., hardness of 600 mg / L, 700 mg / L, 800 mg / L, 1100 mg / L, 900 mg / L, 1000 mg / L, 1100 mg / L, 1200 mg / L), and the pH is 8.5 to 9.5 (e.g., pH of 8.5, 8.6, 8.7, 8.8, 8.9, 9.0, 9.1, 9.2, 9.3, 9.4, 9.5).

[0010] Furthermore, the hardness of the clear ash water obtained from the upper part of the inclined plate sedimentation tank is 40 mg / L to 100 mg / L (for example, hardness of 20 mg / L, 30 mg / L, 40 mg / L, 50 mg / L, 60 mg / L, 70 mg / L, 80 mg / L, 90 mg / L, 100 mg / L).

[0011] Furthermore, the first tray has 2-6 layers, the second tray has 1-5 layers, the third tray has 6-25 layers, and the fourth tray has 26-43 layers.

[0012] Furthermore, the ammonia-containing process gas at the top of the ammonia recovery tower is absorbed by the integrated reactor to form ammonia water with a mass concentration of 15% to 20%; the ammonia nitrogen content in the wastewater produced at the bottom of the ammonia recovery tower is 20 mg / L to 100 mg / L.

[0013] Furthermore, the top pressure of the ammonia recovery tower is -5 kPa to 10 kPa; the bottom temperature of the ammonia recovery tower is 100°C to 110°C.

[0014] Furthermore, the alkali-resistant glass filter media has an amorphous granular structure and consists of two layers. The upper layer of alkali-resistant glass filter media has a size of 0.5 mm to 1.2 mm (e.g., filter media sizes of 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, and 1.2 mm), and a thickness of... The size of the first layer is 600mm to 1200mm; the size of the second layer of alkali-resistant glass filter media is 1.0mm to 3.0mm (e.g., filter media sizes of 1.0mm, 1.2mm, 1.4mm, 1.6mm, 1.8mm, 2.0mm, 2.2mm, 2.4mm, 2.6mm, 2.8mm, 3.0mm), and the thickness is 200mm to 500mm.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] 1. In this invention, after the coal gasification ash water is dehardened, it is sent to an inclined plate sedimentation tank. In the inclined plate sedimentation tank, the ash water is settled and sludge is removed. The sludge is discharged intermittently and the sludge discharge time is strictly controlled to improve the sludge removal efficiency of the inclined plate sedimentation tank, thereby reducing the load and cleaning frequency of the subsequent precision filter.

[0017] 2. The precision filter media of the present invention uses alkali-resistant glass filter media. The material of the filter media is amorphous aluminosilicate, and the surface is permanently negatively charged, which has the property of inhibiting the growth of microorganisms. It can effectively prevent biological accumulation and filter media caking. It has hydrophilic and oleophobic properties, which can effectively prevent problems such as filter media caking and flow interruption. It has good filtration effect, and backwashing is clean and requires less backwashing water.

[0018] 3. The present invention provides a baffle tray inside the ammonia recovery tower to block suspended particles in the ash water entering the ammonia recovery tower, thereby preventing suspended particles in the ash water from accumulating and clogging the cap tray and guide valve tray, thus extending the operating cycle of the ammonia recovery tower.

[0019] 4. In summary, this invention extends the service life of the ammonia recovery tower from about 20 days to more than 6 months by using chemical hardening agents, enhanced sludge removal in the sedimentation tank, precision filter filtration, and baffle tray blocking. This greatly improves the stable operation period of the ammonia recovery tower and also reduces the frequency and cost of shutdown and maintenance of the ammonia recovery tower. Attached Figure Description

[0020] Figure 1 This is a process flow diagram of the apparatus of the present invention;

[0021] Figure 2 This is a perspective view of the baffle tray of the present invention;

[0022] In the diagram: 1-Hardness removal device; 2-Inclined plate sedimentation tank; 3-Buffer tank a; 4-Precision filter; 5-Ash water pump a; 6-Buffer tank b; 7-Ash water pump b; 8-Feed preheater; 9-Ammonia recovery tower; 10-Reboiler; 11-Wastewater pump; 12-Condenser; 13-Ammonia condensate tank; 14-Combined reactor; 15-Ammonia water tank; 16-Pipeline a; 17-Baffle tray. Detailed Implementation Example 1

[0023] refer to Figure 1 and Figure 2 To reduce clogging of the precision filter 4 and ammonia recovery tower 9, decrease maintenance frequency and costs, ensure long-term stable operation of the coal gasification ash water ammonia extraction unit, and guarantee timely treatment of the coal gasification ash water, this invention provides a method for coal gasification ash water ammonia extraction, comprising the following steps:

[0024] S1: Ash water produced by the coal gasification unit: 100 m³ / h, temperature 70℃, ammonia nitrogen 800 mg / L, hardness 600 mg / L, hardness expressed as Ca... 2+ and Mg 2+ The total amount of ash water, with a pH of 8.5, is fed into a hardening removal device 1. This device 1 includes a first reaction tank, a second reaction tank, a third reaction tank, and a fourth reaction tank arranged sequentially along the water flow direction. The ash water enters the first reaction tank, where 32% sodium hydroxide is added to adjust the pH to 11.5. After treatment in the first reaction tank, the ash water enters the second reaction tank, where sodium carbonate is added. After treatment in the second reaction tank, the ash water enters the third reaction tank, where sodium carbonate is added... PAC reagent is added, and the ash water is treated in the third reaction tank and then enters the fourth reaction tank. PAM reagent is added in the fourth reaction tank. The ash water treated in the fourth reaction tank is sent to the inclined plate sedimentation tank 2. The ash water stays in the inclined plate sedimentation tank 2 for 2 hours for sedimentation and sludge discharge. Several sludge hoppers are set at the bottom of the inclined plate sedimentation tank 2. Each sludge hopper is equipped with a sludge discharge pipe for intermittent sludge discharge. The interval is 6 hours and the sludge discharge time is 5 minutes. The clear ash water obtained at the top of the inclined plate sedimentation tank 2 is sent to the buffer tank a3. The hardness of the clear ash water is reduced to 40 mg / L.

[0025] S2: The grey water in buffer tank a3 of S1 is sent to precision filter 4 for filtration via grey water pump a5. The filter media in precision filter 4 is alkali-resistant glass filter media. The alkali-resistant glass filter media is made of amorphous aluminosilicate with a permanently negatively charged surface, which inhibits microbial growth and effectively prevents biological accumulation and filter media caking. It also has hydrophilic and oleophobic properties, effectively preventing problems such as filter media caking and flow interruption. The alkali-resistant glass filter media is filled in two layers. The diameter of the upper layer of alkali-resistant glass filter media is 0.5 mm to 0.8 mm, and the filling thickness is 600 mm. The diameter of the lower layer of alkali-resistant glass filter media is 1.0 mm to 2.0 mm, and the filling thickness is 200 mm. The grey water filtered by precision filter 4 is sent to buffer tank b6. After a period of use, precision filter 4 is cleaned with clean water and agitated with compressed air for 5 minutes. Compared with fiber ball filter media, this greatly reduces the amount of water used for cleaning.

[0026] S3: The ash water in buffer tank b6 of S2 is sent to ammonia recovery tower 9 for distillation and ammonia recovery via ash water pump b7. A feed preheater 8 is installed on the pipeline connecting ash water pump b7 and the ash water inlet of ammonia recovery tower 9. The ammonia-containing process gas at the top of ammonia recovery tower 9 is condensed by condenser 12, and the condensate enters ammonia condensate tank 13. The uncondensed ammonia-containing process gas is absorbed by integrated reactor 14 to form ammonia water, which is stored in ammonia water tank 15. Part of the condensate in ammonia condensate tank 13 is returned to the top of ammonia recovery tower 9, and the other part is sent to ammonia water tank 15. The ammonia water in ammonia water tank 15 is then sent out of the ash water ammonia extraction device. Wastewater is produced at the bottom of ammonia recovery tower 9 and is sent to feed preheater 8 via wastewater pump 11 to preheat the ash water. The wastewater from the bottom of ammonia recovery tower 9 is used to preheat the ash water entering ammonia recovery tower 9, reducing the heat consumption of ammonia recovery tower 9. Water flows out of the feed preheater 8 and is sent to the downstream unit through pipe a16; the ammonia recovery tower 9 is equipped with trays, which are arranged from top to bottom as a first tray, a second tray, a third tray, and a fourth tray; the first tray has 2 layers of cap trays, the second tray has 1 layer of baffle tray 17, the third tray has 6 layers of cap trays, and the fourth tray has 26 layers of guide valve trays; the ash water inlet of the ammonia recovery tower 9 is located between the first and second trays; a reboiler 10 is installed in the bottom of the ammonia recovery tower 9 and connected to the ammonia recovery tower 9; the edge of the baffle tray 17 is equipped with a serrated baffle to block particulate matter leaking from the ash water, preventing blockage of the cap tray and the guide valve tray, thereby ensuring the long-term operation of the ammonia recovery tower 9; the top pressure of the ammonia recovery tower 9 is -5 kPa. ~0 kPa, the bottom temperature of the tower is 100℃~105℃, the reflux flow rate at the top of the tower is adjusted in a timely manner according to the production situation, and is generally controlled at 5 m³ / h. The process gas at the top of the tower is absorbed by the integrated reactor to form ammonia water with a mass concentration of 15%. The ammonia nitrogen in the wastewater produced from the bottom of the ammonia recovery tower 9 is 20 mg / L.

[0027] The guided solid valve tray is composed of two types of solid valves: flat-leg guided solid valves and high-low-leg guided solid valves. The high-low-leg guided solid valves have a large thrust and are prone to creating bow-shaped areas of stagnation dead zones on both sides of the tray. By regularly arranging the high-low-leg guided solid valves on the tray, the stagnation dead zones are effectively eliminated. The guided solid valves are also regularly arranged on the guided solid valve tray according to the different liquid flow intensities, which effectively reduces the liquid level gradient. At the same time, a bubble propeller is arranged in the liquid phase inlet area of ​​the guided solid valve tray. The bubble propeller is in a normally open state, and its guide holes along the flow direction can effectively push the liquid forward, thus effectively reducing the liquid level gradient. Example 2

[0028] refer to Figure 1 and Figure 2 To reduce clogging of the precision filter 4 and ammonia recovery tower 9, decrease maintenance frequency and costs, ensure long-term stable operation of the coal gasification ash water ammonia extraction unit, and guarantee timely treatment of the coal gasification ash water, this invention provides a method for coal gasification ash water ammonia extraction, comprising the following steps:

[0029] S1: Ash water produced by the coal gasification unit: 100 m³ / h, temperature 70℃, ammonia nitrogen 1200 mg / L, hardness 900 mg / L, hardness expressed as Ca... 2+ and Mg 2+ The total amount of ash water, with a pH of 9.0, is fed into a hardening removal device 1. The hardening removal device 1 includes a first reaction tank, a second reaction tank, a third reaction tank, and a fourth reaction tank arranged sequentially along the water flow direction. The ash water enters the first reaction tank, where 32% sodium hydroxide is added to adjust the pH to 11.8. After treatment in the first reaction tank, the ash water enters the second reaction tank, where sodium carbonate is added. After treatment in the second reaction tank, the ash water enters the third reaction tank, where sodium carbonate is added... PAC reagent is added, and the ash water is treated in the third reaction tank and then enters the fourth reaction tank. PAM reagent is added in the fourth reaction tank. The ash water treated in the fourth reaction tank is sent to the inclined plate sedimentation tank 2. The ash water stays in the inclined plate sedimentation tank 2 for 3 hours for sedimentation and sludge discharge. Several sludge hoppers are set at the bottom of the inclined plate sedimentation tank 2. Each sludge hopper is equipped with a sludge discharge pipe for intermittent sludge discharge. The interval is 4 hours and the sludge discharge time is 12 minutes. The clear ash water obtained at the top of the inclined plate sedimentation tank 2 is sent to the buffer tank a3. The hardness of the clear ash water is reduced to 70 mg / L.

[0030] S2: The grey water in buffer tank a3 of S1 is sent to precision filter 4 for filtration via grey water pump a5. The filter media in precision filter 4 is alkali-resistant glass filter media. The alkali-resistant glass filter media is made of amorphous aluminosilicate with a permanently negatively charged surface, which inhibits microbial growth and effectively prevents biological accumulation and filter media caking. It also has hydrophilic and oleophobic properties, effectively preventing problems such as filter media caking and flow interruption. The alkali-resistant glass filter media is filled in two layers. The diameter of the upper layer of alkali-resistant glass filter media is 0.6 mm to 1.0 mm, and the filling thickness is 800 mm. The diameter of the lower layer of alkali-resistant glass filter media is 1.5 mm to 2.5 mm, and the filling thickness is 350 mm. The grey water filtered by precision filter 4 is sent to buffer tank b6. After a period of use, precision filter 4 is cleaned with clean water and agitated with compressed air for 8 minutes. Compared with fiber ball filter media, this greatly reduces the amount of water used for cleaning.

[0031] S3: The ash water in buffer tank b6 of S2 is sent to ammonia recovery tower 9 for distillation and ammonia recovery via ash water pump b7. A feed preheater 8 is installed on the pipeline connecting ash water pump b7 and the ash water inlet of ammonia recovery tower 9. The ammonia-containing process gas at the top of ammonia recovery tower 9 is condensed by condenser 12, and the condensate enters ammonia condensate tank 13. The uncondensed ammonia-containing process gas is absorbed by integrated reactor 14 to form ammonia water, which is stored in ammonia water tank 15. Part of the condensate in ammonia condensate tank 13 is returned to the top of ammonia recovery tower 9, and the other part is sent to ammonia water tank 15. The ammonia water in ammonia water tank 15 is then sent out of the ash water ammonia extraction device. Wastewater is produced at the bottom of ammonia recovery tower 9 and is sent to feed preheater 8 via wastewater pump 11 to preheat the ash water. The wastewater from the bottom of ammonia recovery tower 9 is used to preheat the ash water entering ammonia recovery tower 9, reducing the heat consumption of ammonia recovery tower 9. Water flows out of the feed preheater 8 and is sent to the downstream unit through pipe a16; the ammonia recovery tower 9 is equipped with trays, which are arranged from top to bottom as a first tray, a second tray, a third tray, and a fourth tray; the first tray has 4 layers of cap trays, the second tray has 3 layers of baffle trays 17, the third tray has 15 layers of cap trays, and the fourth tray has 34 layers of guide valve trays; the ash water inlet of the ammonia recovery tower 9 is located between the first and second trays; a reboiler 10 is installed in the bottom of the ammonia recovery tower 9 and connected to the ammonia recovery tower 9; the edge of the baffle tray 17 is equipped with serrated baffles to block particulate matter leaking from the ash water, preventing blockage of the cap trays and guide valve trays, thereby ensuring the long-term operation of the ammonia recovery tower 9; the top pressure of the ammonia recovery tower 9 is 0 kPa. The pressure is ~5 kPa, the bottom temperature of the tower is 103℃~108℃, the reflux flow rate at the top of the tower is adjusted in a timely manner according to the production situation, and is generally controlled at 5 m³ / h. The process gas at the top of the tower is absorbed by the integrated reactor to form ammonia water with a mass concentration of 18%. The ammonia nitrogen in the wastewater produced from the bottom of the ammonia recovery tower 9 is 60 mg / L.

[0032] The guided solid valve tray is composed of two types of solid valves: flat-leg guided solid valves and high-low-leg guided solid valves. The high-low-leg guided solid valves have a large thrust and are prone to creating bow-shaped areas of stagnation dead zones on both sides of the tray. By regularly arranging the high-low-leg guided solid valves on the tray, the stagnation dead zones are effectively eliminated. The guided solid valves are also regularly arranged on the guided solid valve tray according to the different liquid flow intensities, which effectively reduces the liquid level gradient. At the same time, a bubble propeller is arranged in the liquid phase inlet area of ​​the guided solid valve tray. The bubble propeller is in a normally open state, and its guide holes along the flow direction can effectively push the liquid forward, thus effectively reducing the liquid level gradient. Example 3

[0033] refer to Figure 1 and Figure 2 To reduce clogging of the precision filter 4 and ammonia recovery tower 9, decrease maintenance frequency and costs, ensure long-term stable operation of the coal gasification ash water ammonia extraction unit, and guarantee timely treatment of the coal gasification ash water, this invention provides a method for coal gasification ash water ammonia extraction, comprising the following steps:

[0034] S1: Ash water produced by the coal gasification unit: 100 m³ / h, temperature 70℃, ammonia nitrogen 1500 mg / L, hardness 1200 mg / L, hardness expressed as Ca... 2+ and Mg 2+ The total amount of ash water, with a pH of 9.5, is fed into a hardening removal device 1. The hardening removal device 1 includes a first reaction tank, a second reaction tank, a third reaction tank, and a fourth reaction tank arranged sequentially along the water flow direction. The ash water enters the first reaction tank, where 32% sodium hydroxide is added to adjust the pH to 12.0. After treatment in the first reaction tank, the ash water enters the second reaction tank, where sodium carbonate is added. After treatment in the second reaction tank, the ash water enters the third reaction tank, where sodium carbonate is added... After being treated in the third reaction tank, the ash water containing PAC reagent enters the fourth reaction tank. PAM reagent is then added to the fourth reaction tank. The ash water treated in the fourth reaction tank is then sent to the inclined plate sedimentation tank 2. The ash water remains in the inclined plate sedimentation tank 2 for 4 hours for sedimentation and sludge removal. Several sludge hoppers are installed at the bottom of the inclined plate sedimentation tank 2, and each sludge hopper is equipped with a sludge discharge pipe for intermittent sludge discharge. The interval is 2 hours, and the sludge discharge time is 20 minutes. The clear ash water obtained at the top of the inclined plate sedimentation tank 2 is sent to the buffer tank a3. The hardness of the clear ash water is reduced to 100 mg / L.

[0035] S2: The grey water in buffer tank a3 of S1 is sent to precision filter 4 for filtration via grey water pump a5. The filter media in precision filter 4 is alkali-resistant glass filter media. The alkali-resistant glass filter media is made of amorphous aluminosilicate with a permanently negatively charged surface, which inhibits microbial growth and effectively prevents biological accumulation and filter media caking. It also has hydrophilic and oleophobic properties, effectively preventing problems such as filter media caking and flow interruption. The alkali-resistant glass filter media is filled in two layers: the diameter of the upper layer is 0.8 mm to 1.2 mm, and the filling thickness is 1200 mm; the diameter of the lower layer is 2.0 mm to 3.0 mm, and the filling thickness is 500 mm. The grey water filtered by precision filter 4 is sent to buffer tank b6. After a period of use, precision filter 4 is cleaned with clean water and agitated with compressed air for 10 minutes. Compared with fiber ball filter media, this greatly reduces the amount of water used for cleaning.

[0036] S3: The ash water in buffer tank b6 of S2 is sent to ammonia recovery tower 9 for distillation and ammonia recovery via ash water pump b7. A feed preheater 8 is installed on the pipeline connecting ash water pump b7 and the ash water inlet of ammonia recovery tower 9. The ammonia-containing process gas at the top of ammonia recovery tower 9 is condensed by condenser 12, and the condensate enters ammonia condensate tank 13. The uncondensed ammonia-containing process gas is absorbed by integrated reactor 14 to form ammonia water, which is stored in ammonia water tank 15. Part of the condensate in ammonia condensate tank 13 is returned to the top of ammonia recovery tower 9, and the other part is sent to ammonia water tank 15. The ammonia water in ammonia water tank 15 is then sent out of the ash water ammonia extraction device. Wastewater is produced at the bottom of ammonia recovery tower 9 and is sent to feed preheater 8 via wastewater pump 11 to preheat the ash water. The wastewater from the bottom of ammonia recovery tower 9 is used to preheat the ash water entering ammonia recovery tower 9, reducing the heat consumption of ammonia recovery tower 9. Water flows out of the feed preheater 8 and is sent to the downstream unit through pipe a16; the ammonia recovery tower 9 is equipped with trays, which are arranged from top to bottom as a first tray, a second tray, a third tray, and a fourth tray; the first tray has 6 layers of cap trays, the second tray has 5 layers of baffle trays 17, the third tray has 25 layers of cap trays, and the fourth tray has 43 layers of guide valve trays; the ash water inlet of the ammonia recovery tower 9 is located between the first and second trays; a reboiler 10 is installed in the bottom of the ammonia recovery tower 9 and connected to the ammonia recovery tower 9; the edge of the baffle tray 17 is equipped with serrated baffles to block particulate matter leaking from the ash water, preventing blockage of the cap trays and guide valve trays, thereby ensuring the long-term operation of the ammonia recovery tower 9; the top pressure of the ammonia recovery tower 9 is 5 kPa. The pressure is ~10 kPa, the bottom temperature of the tower is 106℃~110℃, the reflux flow rate at the top of the tower is adjusted in a timely manner according to the production situation, and is generally controlled at 5 m³ / h. The process gas at the top of the tower is absorbed by the integrated reactor to form ammonia water with a mass concentration of 20%. The ammonia nitrogen in the wastewater produced from the bottom of the ammonia recovery tower 9 is 100 mg / L.

[0037] The guided solid valve tray is composed of two types of solid valves: flat-leg guided solid valves and high-low-leg guided solid valves. The high-low-leg guided solid valves have a large thrust and are prone to creating bow-shaped areas of stagnation dead zones on both sides of the tray. By regularly arranging the high-low-leg guided solid valves on the tray, the stagnation dead zones are effectively eliminated. The guided solid valves are also regularly arranged on the guided solid valve tray according to the different liquid flow intensities, which effectively reduces the liquid level gradient. At the same time, a bubble propeller is arranged in the liquid phase inlet area of ​​the guided solid valve tray. The bubble propeller is in a normally open state, and its guide holes along the flow direction can effectively push the liquid forward, thus effectively reducing the liquid level gradient.

[0038] The working principle of this invention: After hardening, the coal gasification ash water is sent to the inclined plate sedimentation tank 2. In the inclined plate sedimentation tank 2, the ash water undergoes sedimentation and sludge removal. Sludge is discharged intermittently, and the sludge discharge time is strictly controlled to improve the sludge removal efficiency of the inclined plate sedimentation tank 2, thereby reducing the load and cleaning frequency of the subsequent precision filter 4. The precision filter 4 of this invention uses alkali-resistant glass filter media. The filter media is made of amorphous aluminosilicate with a permanently negative charge on the surface, which has the property of inhibiting microbial growth and effectively preventing biological accumulation and filter media caking. It also has hydrophilic and oleophobic properties, which effectively prevent problems such as filter media caking and flow interruption. The filtration effect is good, and the backwashing is clean and the backwashing water consumption is low. This invention incorporates a baffle tray 17 within the ammonia recovery tower 9 to block suspended particles from the ash water entering the tower. This prevents these particles from accumulating and clogging the cap tray and guide valve tray, thereby extending the operating cycle of the ammonia recovery tower 9. In summary, this invention extends the service life of the ammonia recovery tower 9 from approximately 20 days to over 6 months through chemical hardening, enhanced sludge removal in the sedimentation tank, filtration by the precision filter 4, and the baffle tray 17. This ensures timely treatment of coal gasification ash water, significantly improves the stable operation cycle of the ammonia recovery tower 9, and reduces the frequency and cost of shutdowns for inspection and maintenance.

[0039] The above specific embodiments are merely examples of the content of this invention. Any modifications and variations made to this creation by those skilled in the art are within the scope of the patent of this invention, and are not limited to the embodiments described.

Claims

1. A method for ammonia stripping of coal gasification grey water, characterized by: The method comprises the following steps: S1: coal gasification grey water is sent to a hardness removal device, and the grey water after hardness removal is sent to an inclined plate sedimentation tank, a plurality of hoppers are arranged at the bottom of the inclined plate sedimentation tank, a mud discharge pipeline is arranged in each hopper for intermittent mud discharge, the intermittent time is 2-6 hours, the mud discharge time is 5-20 minutes, and the clear liquid grey water obtained at the upper part of the inclined plate sedimentation tank is sent to a buffer tank a; S2: the grey water in the buffer tank a in S1 is sent to a precision filter for filtration, the filter material in the precision filter is alkali-resistant glass filter material; the grey water filtered by the precision filter is sent to a buffer tank b; S3: the grey water in the buffer tank b in S2 is sent to an ammonia recovery tower for rectification and recovery of ammonia, the ammonia-containing process gas at the top of the ammonia recovery tower is condensed by a condenser and then absorbed by a comprehensive reactor to produce ammonia water, and wastewater is produced at the tower bottom of the ammonia recovery tower, a tray is arranged in the ammonia recovery tower, and the trays are sequentially arranged from top to bottom as a first-stage tray, a second-stage tray, a third-stage tray and a fourth-stage tray; the first-stage tray is a cap tray, the second-stage tray is a baffle tray, the third-stage tray is a cap tray, and the fourth-stage tray is a guide valve tray.

2. The method of claim 1, wherein: The ammonia nitrogen in the coal gasification grey water is 800-1500 mg / L, the hardness is 600-1200 mg / L, and the pH is 8.5-9.

5.

3. The method of claim 1, wherein: The hardness of the clear liquid grey water obtained at the upper part of the inclined plate sedimentation tank is 40-100 mg / L.

4. The method of claim 1, wherein: The first-stage tray is provided with 2-6 layers, the second-stage tray is provided with 1-5 layers, the third-stage tray is provided with 6-25 layers, and the fourth-stage tray is provided with 26-43 layers.

5. The method of claim 1, wherein: The ammonia-containing process gas at the top of the ammonia recovery tower is absorbed by the comprehensive reactor to form ammonia water, and the mass concentration of the ammonia water is 15%-20%; the ammonia nitrogen content in the wastewater produced at the tower bottom of the ammonia recovery tower is 20-100 mg / L.

6. The method of claim 1, wherein: The top pressure of the ammonia recovery tower is-5 KPa-10 KPa, and the temperature at the tower bottom of the ammonia recovery tower is 100-110 DEG C.

7. The method of claim 1, wherein: The alkali-resistant glass filter material has an amorphous particle structure, and is divided into two layers, the upper layer of the alkali-resistant glass filter material has a size of 0.5-1.2 mm and a thickness of 600-1200 mm, and the lower layer of the alkali-resistant glass filter material has a size of 1.0-3.0 mm and a thickness of 200-500 mm.

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