A treatment system and method for recycling coal gasification ash water

Abstract

The present invention discloses a treatment system and method for recycling coal gasification ash water. The treatment system includes a stripping tower, an acid gas separator, a circulating ash water device and an external discharged wastewater device; wherein, the stripping tower includes an ash water to be treated inlet, a steam inlet, an ammonia-containing gas outlet and a low-concentration ash water outlet; the ash water to be treated inlet is used to provide the ash water to be treated to the stripping tower, and the steam inlet is used to provide the required steam to the stripping tower; the acid gas separator includes an acid gas separator inlet, an acidic gas outlet and a high-concentration ash water outlet; the ammonia-containing gas outlet is connected to the acid gas separator inlet; the low-concentration ash water outlet is respectively connected to the inlet of the circulating ash water device and the inlet of the external discharged wastewater device. The present invention can effectively reduce the ammonia nitrogen concentration in the recycled ash water, thereby reducing the supplement amount of fresh water and the discharge amount of wastewater, and alleviating the enrichment problem of ammonia in the water circulation system, and the treatment system has the advantages of simple process, easy adjustment, etc.

Description

Technical Field

[0001] The present invention relates to a treatment system and method for recycling coal gasification ash water. Background Art

[0002] Coal gasification is the industrial source and foundation of coal chemical industry. Its process is that coal reacts chemically with gasifying agents to convert coal into fuel gas or chemical synthesis gas, also known as raw gas. It should be noted that nitrogen is one of the major elements in coal, with a content usually of 1-3%. During the gasification process, the nitrogen element in coal is released into the gas-phase products, forming different nitrogen-containing pollutants. The nitrogen-containing pollutants in the raw gas are mainly NH3. After being washed in the water scrubber, part of the NH3 still exists in the gas phase and is carried into the subsequent conversion unit with the synthesis gas; the other part of the NH3 dissolves into the liquid phase and enters the slag water treatment system with the black water. Most of the existing slag water treatment systems adopt a multi-stage flash evaporation mode, whose function is to recover the heat in the black water and separate the solids and dissolved gases contained in the black water, so as to be recycled in the form of ash water. The ash water used for recycling greatly supplements the water consumption required for system operation. However, over a long period, ammonia will accumulate in the system. The accumulation of ammonia in the water cycle will cause ammonium salt crystallization, resulting in pipeline blockage and corrosion, affecting the safe and stable operation of production equipment. In addition, it will also cause the ammonia nitrogen content in the wastewater to exceed the standard, increasing the difficulty of wastewater treatment.

[0003] Most of the existing ash water recycling processes for coal gasification systems are as Figure 1 shown, that is, the ash water after slag water treatment directly enters the circulation system. At the same time, in order to prevent indicators such as the alkalinity and salt content in the water from exceeding the limit values, it is necessary to discharge wastewater from the ash water system and supplement fresh water into the circulation system. It should be noted that in order to keep the ammonia nitrogen content in the water circulation system and the discharged wastewater below a certain limit, the discharged wastewater volume and the fresh water supplement volume of the existing coal gasification process are very large. Especially when the nitrogen content of the raw coal is relatively high, or when ammonia-containing waste liquid is used for pulping, this problem is particularly prominent.

[0004] Patent document CN113845263A discloses an equipment and process for reducing the ammonia nitrogen index of a coal gasification water system. It sequentially transports the black water to high-pressure, low-pressure, and vacuum flash separation towers, and transports the steam separated by the high-pressure flash separation tower to an acidic separation tower. The acidic separation tower transports the separated liquid phase to a stripping tower; at the same time, the steam separated by the low-pressure and vacuum flash separation towers is also transported to the stripping tower; the stripping tower combines the collected liquid phase with the liquid phase separated by the multi-stage flash separation tower and transports them together to a settling tank. The upper clear liquid (i.e., ash water) of the settling tank can be recycled. Although this treatment method reduces the ammonia nitrogen content in the ash water to a certain extent, it only strips the gas phase after flash separation, and the flow rate of this stream is relatively low, still causing the problem of ammonia nitrogen accumulation in the system.

[0005] Therefore, it is necessary to optimize the grey water reuse process to reduce the ammonia nitrogen content in the circulating grey water, which can not only reduce the supplement amount of fresh water and the discharge amount of wastewater, but also slow down the enrichment problem of ammonia in the water circulation system. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the defects that the existing grey water reuse process consumes a large amount of fresh water to maintain the ammonia nitrogen content in the wastewater and has a high wastewater discharge amount, and to provide a treatment system and method for coal gasification grey water reuse. The present invention can effectively reduce the ammonia nitrogen concentration in the reused grey water, thereby reducing the supplement amount of fresh water and the discharge amount of wastewater, and alleviating the enrichment problem of ammonia in the water circulation system. Moreover, the treatment system has the advantages of simple process, easy adjustment, etc., and is particularly suitable for the grey water reuse treatment of coal gasification processes with a relatively high nitrogen content in raw coal or using ammonia-containing waste liquid for pulping.

[0007] The present invention solves the above technical problems through the following technical solutions.

[0008] The present invention provides a treatment system for coal gasification grey water reuse, which includes a stripping tower, an acid gas separator, a circulating grey water device and an external discharged wastewater device;

[0009] Among them, the stripping tower includes an inlet for grey water to be treated, a steam inlet, an ammonia-containing gas outlet and a low-concentration grey water outlet; the inlet for grey water to be treated is used to provide grey water to be treated to the stripping tower, and the steam inlet is used to provide the required steam to the stripping tower;

[0010] The acid gas separator includes an acid gas separator inlet, an acidic gas outlet and a high-concentration grey water outlet;

[0011] The ammonia-containing gas outlet is connected to the acid gas separator inlet;

[0012] The low-concentration grey water outlet is respectively connected to the inlet of the circulating grey water device and the inlet of the external discharged wastewater device.

[0013] In the present invention, preferably, the treatment system for coal gasification grey water reuse further includes a water washing tower and a slag water treatment system. The water washing tower includes a raw coal gas inlet and a black water outlet; the slag water treatment system includes a black water inlet and an outlet for grey water to be treated;

[0014] The raw coal gas inlet of the water washing tower is used to provide raw coal gas to the water washing tower; the black water outlet of the water washing tower is connected to the black water inlet of the slag water treatment system; the outlet for grey water to be treated of the slag water treatment system is connected to the inlet for grey water to be treated of the stripping tower.

[0015] Among them, preferably, the water scrubber can be a conventional water scrubber in the art, which is used to wash the raw coal gas to obtain syngas and black water. The water scrubber generally further includes a syngas outlet, and the syngas outlet can be connected to a subsequent shift unit.

[0016] Among them, preferably, the slag water treatment system can be a conventional flash evaporation system in the art, such as a three-stage flash evaporation system or a two-stage flash evaporation system. The three-stage flash evaporation system can include a high-pressure flash evaporation tower, a low-pressure flash evaporation tower, and a vacuum flash evaporation tower connected in sequence. The operating pressure of the high-pressure flash evaporation tower can be 0.7 - 1.4 MPaG. The operating pressure of the low-pressure flash evaporation tower can be 0.2 - 0.3 MPaG. The operating pressure of the vacuum flash evaporation tower can be -0.05 - -0.07 MPaG.

[0017] In the present invention, the stripping tower can be a conventional stripping tower in the art. After the grey water to be treated is transported to the stripping tower, it directly mass transfers with the high-temperature steam transported from the steam inlet to the stripping tower. The high-pressure steam flows vertically upward and carries the stripped components (high-concentration ammonia) away from the stripping tower. At the same time, the ammonia concentration in the treated grey water leaving the stripping tower is much lower than the concentration when it enters the stripping tower, thereby obtaining ammonia-containing gas and low-concentration grey water.

[0018] Among them, preferably, the stripping tower is of plate tower or packed tower structure, and more preferably of plate tower.

[0019] Among them, preferably, the grey water inlet to be treated is arranged above the stripping tower.

[0020] Among them, preferably, the steam inlet is arranged below the stripping tower.

[0021] In the present invention, the acid gas separator can be a conventional acid gas separator in the art, which is used to separate the ammonia-containing gas recovered from the top of the stripping tower to obtain acid gas and high-concentration grey water.

[0022] Among them, the acid gas outlet can be connected to a burner; the high-concentration grey water outlet can be connected to a sewage treatment device. The sewage treatment device can be a conventional sewage treatment device in the art.

[0023] In the present invention, preferably, after the ammonia-containing gas outlet is connected to a heat exchanger and then connected to the inlet of the acid gas separator. The heat exchanger can be a conventional heat exchanger in the art, which is used to recover the heat in the ammonia-containing gas recovered from the top of the stripping tower. This heat can be used for other purposes, such as for producing hot water and preheating boiler make-up water, or the heat can also be integrated into other evaporation devices for comprehensive utilization.

[0024] In the present invention, preferably, the treatment system for recycling coal gasification ash water further includes a three-way valve; the first end of the three-way valve is connected to the low-concentration ash water outlet of the stripping tower, the second end of the three-way valve is connected to the inlet of the circulating ash water device, and the third end of the three-way valve is connected to the inlet of the wastewater discharging device.

[0025] In the present invention, preferably, the circulating ash water device includes an ash water pump, which is used to pressurize the low-concentration ash water and transport the low-concentration ash water back for reuse to a specified device. For example, the low-concentration ash water can be reused to one or more of the slag treatment system, the water washing tower, and the lock hopper flushing water tank.

[0026] In the present invention, preferably, the wastewater discharging device includes a flow regulating valve and a wastewater discharging pipeline; the flow regulating valve is arranged in the wastewater discharging pipeline, and adjusts and controls the amount of discharged ash water according to indexes such as the ammonia nitrogen content of the discharged wastewater required by the system.

[0027] The present invention also provides a treatment method for recycling coal gasification ash water, which is carried out by using the treatment system for recycling coal gasification ash water as described above, and includes the following steps:

[0028] S1. Transport the ash water to be treated and steam to the stripping tower to obtain ammonia-containing gas and low-concentration ash water;

[0029] S2. Transport the ammonia-containing gas to the acid gas separator to obtain acid gas and high-concentration ash water;

[0030] Transport a part of the low-concentration ash water to the circulating ash water device and another part to the wastewater discharging device.

[0031] In S1, when the ash water to be treated comes from the slag treatment system, all the effluent of the slag treatment system can enter the stripping tower, or enter the stripping tower at a certain ratio.

[0032] Preferably, the proportion of the ash water to be treated entering the stripping tower in the effluent of the upstream equipment (such as the slag treatment system) is 5-20%, for example, 10% or 15%.

[0033] In S1, when the ash water to be treated comes from the slag treatment system, in order to enhance the stripping effect, chemical drugs can be added to the effluent of the slag treatment system to convert the fixed ammonium salts in the effluent of the slag treatment system into free ammonium salts, so that the steam can carry away more ammonia nitrogen and greatly improve the efficiency of the stripping tower.

[0034] In S1, the steam can come from the utility engineering, or a reboiler can be additionally arranged at the bottom of the stripping tower to provide the required steam.

[0035] The positive and progressive effects of the present invention are as follows:

[0036] Compared with the traditional greywater reuse process, the treatment device and method of the present invention can effectively reduce the ammonia nitrogen concentration in the recycled greywater, significantly reduce the make-up amount of fresh water and the discharge amount of wastewater, and alleviate the enrichment problem of ammonia in the water circulation system. Moreover, the treatment system has the advantages of simple process and easy adjustment, and is particularly suitable for the greywater reuse treatment of coal gasification processes with a high nitrogen content in raw coal or using ammonia-containing waste liquid for pulping. Description of the Drawings

[0037] Figure 1 It is a schematic diagram of an existing coal gasification greywater reuse process.

[0038] Figure 2 It is a schematic diagram of the coal gasification greywater reuse process of Example 1.

[0039] Figure 3 It is a graph showing the relationship between the make-up amount of fresh water and the change in ammonia nitrogen concentration in wastewater under Condition 3.

[0040] Figure 4 It is a schematic diagram of the coal gasification greywater reuse treatment system of Example 1.

[0041] Description of the Reference Numerals

[0042] Stripping Tower 1

[0043] Acid Gas Separator 2

[0044] Greywater Inlet to be Treated 3

[0045] Steam Inlet 4

[0046] Ammonia-containing Gas Outlet 5

[0047] Low-concentration Greywater Outlet 6

[0048] Acidic Gas Outlet 7

[0049] High-concentration Greywater Outlet 8

[0050] Heat Exchanger 9

[0051] Three-way Valve 10

[0052] Greywater Pump 11

[0053] Flow Control Valve 12 Detailed Embodiments

[0054] The present invention will be further described below by way of examples, but the present invention is not limited to the scope of the described examples.

[0055] Example 1

[0056] As Figure 2 And Figure 4As shown in the figure, Embodiment 1 provides a treatment system for recycling coal gasification ash water, which includes a stripping tower 1, an acid gas separator 2, a circulating ash water device, and an external wastewater discharge device. Among them, the stripping tower 1 includes an ash water to be treated inlet 3, a steam inlet 4, an ammonia-containing gas outlet 5, and a low-concentration ash water outlet 6. The ash water to be treated inlet 3 is used to supply the ash water to be treated to the stripping tower 1, and the steam inlet 4 is used to supply the required steam to the stripping tower 1. The acid gas separator includes an acid gas separator inlet, an acid gas outlet 7, and a high-concentration ash water outlet 8. The ammonia-containing gas outlet 5 is connected to the acid gas separator inlet. The low-concentration ash water outlet 6 is respectively connected to the inlet of the circulating ash water device and the inlet of the external wastewater discharge device.

[0057] The treatment system for recycling coal gasification ash water further includes a water washing tower and a slag water treatment system. The water washing tower includes a raw coal gas inlet and a black water outlet. The slag water treatment system includes a black water inlet and an ash water to be treated outlet. The raw coal gas inlet of the water washing tower is used to supply raw coal gas to the water washing tower. The black water outlet of the water washing tower is connected to the black water inlet of the slag water treatment system. The ash water to be treated outlet of the slag water treatment system is connected to the ash water to be treated inlet 3 of the stripping tower 1. The water washing tower is used to wash the raw coal gas to obtain syngas and black water. The water washing tower generally also includes a syngas outlet, and the syngas outlet is connected to the subsequent conversion unit. The slag water treatment system is a three-stage flashing system. The three-stage flashing system includes a high-pressure flashing tower, a low-pressure flashing tower, and a vacuum flashing tower connected in sequence.

[0058] After the ash water to be treated is transported to the stripping tower 1, it directly mass-transfers with the high-temperature steam transported from the steam inlet 4 to the stripping tower 1. The high-pressure steam flows vertically upward and carries the stripped component (high-concentration ammonia) away from the stripping tower 1. At the same time, the ammonia concentration in the treated ash water leaving the stripping tower 1 is much lower than the concentration when it enters the stripping tower 1, thereby obtaining ammonia-containing gas and low-concentration ash water.

[0059] The stripping tower 1 is a plate tower. The ash water to be treated inlet 3 is provided above the stripping tower 1. The steam inlet 4 is provided below the stripping tower 1.

[0060] The acid gas separator 2 is used to separate the ammonia-containing gas recovered from the top of the stripping tower 1 to obtain acid gas and high-concentration ash water. The acid gas outlet 7 is connected to a burner; the high-concentration ash water outlet 8 is connected to a sewage treatment device.

[0061] After the ammonia-containing gas outlet 5 is connected to the heat exchanger 9, it is then connected to the acid gas separator inlet. The heat exchanger 9 is used to recover the heat in the ammonia-containing gas recovered from the top of the stripping tower 1.

[0062] The treatment system for recycling coal gasification ash water further includes a three-way valve 10. The first end of the three-way valve 10 is connected to the low-concentration ash water outlet 6 of the stripping tower 1, the second end of the three-way valve 10 is connected to the inlet of the circulating ash water device, and the third end of the three-way valve 10 is connected to the inlet of the external wastewater discharge device.

[0063] The circulating grey water device comprises a grey water pump 11, which is used to pressurize low-concentration grey water and transport the low-concentration grey water back to a designated device.

[0064] The external wastewater discharge device includes a flow regulating valve 12 and an external wastewater discharge pipeline; the flow regulating valve 12 is arranged in the external wastewater discharge pipeline to adjust and control the external ash water volume according to the indicators such as the ammonia nitrogen content of the external wastewater required by the system.

[0065] The treatment method for coal gasification ash water reuse adopted in Example 1 is carried out using the treatment system for coal gasification ash water reuse as described above, which includes the following steps: S1. The ash water to be treated and steam are transported to a stripping tower 1 to obtain ammonia-containing gas and low-concentration ash water; S2. The ammonia-containing gas is transported to an acid gas separator 2 to obtain acid gas and high-concentration ash water; a part of the low-concentration ash water is transported to a circulating ash water device, and the other part is transported to an external wastewater discharge device.

[0066] This example is for a multi-nozzle opposed water-coal slurry gasification device in a chemical plant, with a gasifier pressure of 4.0 MPa, an operating temperature of 1200°C, and a daily coal processing capacity of 2,000 tons. The following working conditions are analyzed using industrial operation data combined with Aspen Plus process simulation.

[0067] Working condition 1: Using Figure 1 For the device shown, when the plant uses fresh water for pulping (pulping concentration 60%), the NH3 flow rate at the gasifier outlet is 5.36 kmol / h, the discharge of external wastewater is 94.77 t / h, the fresh water replenishment is 18.8 t / h, the total amount of ammonia nitrogen in the external wastewater is 30.80 kg / h, and the ammonia nitrogen concentration in the external wastewater is 325 mg / L. The total amount of ammonia nitrogen in the external wastewater and the ammonia nitrogen concentration in the external wastewater of working condition 1 are set to the original values.

[0068] Condition 2: Use Figure 1 In the device shown, when the factory uses 30t / h caprolactam benzene extraction residual liquid as waste liquid for pulping (pulping concentration 60%), the NH3 flow rate at the gasifier outlet is 17.90kmol / h, which is about 2.34 times higher than that in operating condition 1. The wastewater discharge is 94.77t / h. At this time, the total amount of ammonia nitrogen in the discharged wastewater is 41.98kg / h, and the ammonia nitrogen concentration in the discharged wastewater is 443mg / L.

[0069] Condition 3: Due to the high content of NH3, the synthesis gas will carry more NH3 into the subsequent units, which will have a corresponding impact on the water circulation system and the discharged wastewater. In order to restore the ammonia nitrogen concentration in the discharged wastewater to normal, it is necessary to adjust and increase the discharge of the discharged wastewater to reduce the ammonia nitrogen concentration in the discharged wastewater, and at the same time, it is necessary to add corresponding fresh water to maintain the normal operation of the water circulation system.

[0070] Using the device as Figure 1 shown, in operating condition 3, based on operating condition 2, by increasing the amount of supplementary fresh water, the ammonia nitrogen concentration in the discharged wastewater is reduced.

[0071] As Figure 3 shown (the relationship between the fresh water replenishment amount and the change in ammonia nitrogen concentration in the discharged wastewater), in order to restore the ammonia nitrogen concentration in the discharged wastewater to the original value of 325 mg / L, it is necessary to increase the fresh water replenishment amount to approximately 70 t / h, which is 51.2 t / h higher than that in operating conditions 1 and 2. At the same time, the discharged wastewater volume is correspondingly increased to 145.97 t / h. Thus, it can be seen that in order to control the ammonia nitrogen concentration in the discharged wastewater below a certain level, a large amount of fresh water needs to be replenished, increasing the operating cost and wasting water resources.

[0072] Operating condition 4: Using the device and method of Example 1, based on operating condition 2, the ash water in the slag water treatment system is steam-stripped. The high-concentration ammonia-containing gas at the top of the stripping tower 1 is discharged from the system and sent to sewage treatment. The low-concentration ash water at the bottom of the stripping tower 1 is partially discharged and partially recycled to the washing tower and enters the circulation system, thereby effectively reducing the ammonia nitrogen concentration in the discharged wastewater and the recycling system.

[0073] When the steam-stripping ash water ratio (the ratio of the ash water to be treated entering the stripping tower to the effluent of the slag water treatment system) is 10%, without increasing the fresh water replenishment amount relative to operating condition 2, the total amount and concentration of ammonia nitrogen in the discharged wastewater are effectively reduced.

[0074] The comparison results of operating conditions 1 to 4 are shown in Table 1. The comparison shows that simply increasing the fresh water volume (operating condition 3) to reduce the ammonia nitrogen concentration in the discharged wastewater to its original value requires a large amount of fresh water, not only greatly increasing the treatment cost but also causing waste of water resources; using the method of Example 1 can significantly reduce the ammonia nitrogen concentration in the discharged wastewater without increasing the fresh water volume. When the steam-stripping ash water ratio is 10%, the concentration in the discharged wastewater is already close to the original value.

[0075] In addition, Table 2 shows the change in the ammonia nitrogen concentration in the discharged wastewater when using the device and method of Example 1 and only changing the steam-stripping ash water ratio while keeping the discharged wastewater volume unchanged. As shown in Table 2, after the ash water in the slag water treatment system passes through the stripping tower 1 and the low-concentration ash water is returned to the system for circulation, compared with directly recycling the effluent of the slag water treatment system, the ammonia nitrogen concentration in the discharged wastewater can be significantly reduced. When the steam-stripping ash water ratio is 10%, the ammonia nitrogen concentration in the discharged wastewater is already close to the original value. Continuing to increase the steam-stripping ash water ratio, the ammonia nitrogen concentration in the discharged wastewater will be further reduced.

[0076] Table 1 Comparison of the adjustment of ammonia nitrogen concentration in discharged wastewater by supplementary fresh water and steam-stripping

[0077]

[0078] Table 2 Adjustment of ammonia nitrogen concentration in the discharged wastewater based on the stripping tower

[0079] Stripping ash water ratio External wastewater discharge volume t / h Total ammonia nitrogen in external wastewater kg / h Ammonia nitrogen concentration in external wastewater mg / L 0％ 94.77 30.80 325 5％ 94.77 36.01 380 10％ 94.77 31.08 328 15％ 94.77 27.01 285 20％ 94.77 23.52 248

[0080] Although the specific embodiments of the present invention have been described above, those skilled in the art should understand that this is only an example. The protection scope of the present invention is defined by the appended claims. Without departing from the principles and essence of the present invention, those skilled in the art can make various changes or modifications to these embodiments, but these changes and modifications all fall within the protection scope of the present invention.

Claims

1. A treatment method for recycling coal gasification ash water, characterized in that, The treatment system for coal gasification ash water reuse is used, and the treatment system for coal gasification ash water reuse is composed of a water washing tower, a slag water treatment system, a stripping tower, an acid gas separator, a circulating ash water device and an external wastewater discharge device; The stripping tower comprises an inlet for gray water to be treated, a steam inlet, an outlet for ammonia-containing gas and an outlet for low-concentration gray water; the inlet for gray water to be treated is used to provide gray water to be treated to the stripping tower, and the steam inlet is used to provide required steam to the stripping tower; the inlet for gray water to be treated is arranged above the stripping tower; the steam inlet is arranged below the stripping tower; The acid gas separator comprises an acid gas separator inlet, an acid gas outlet and a high-concentration ash water outlet; The ammonia-containing gas outlet is connected to the acid gas separator inlet; The low-concentration grey water outlet is respectively connected to the inlet of the grey water circulation device and the inlet of the wastewater discharge device; The water washing tower includes a raw gas inlet and a black water outlet; the slag water treatment system includes a black water inlet and an outlet for gray water to be treated; The raw gas inlet of the water scrubber is used to provide raw gas to the water scrubber; the black water outlet of the water scrubber is connected to the black water inlet of the slag water treatment system; the gray water outlet to be treated of the slag water treatment system is connected to the gray water inlet to be treated of the stripping tower; It includes the following steps: S1. The treated grey water and steam are transported to the stripping tower to obtain ammonia-containing gas and low-concentration grey water; in S1, the proportion of the treated grey water entering the stripping tower to the effluent of the upstream equipment is 10%-20%; S2. The ammonia-containing gas is transported to the acid gas separator to obtain acid gas and high-concentration ash water; A portion of the low-concentration grey water is transported to the circulating grey water device, and another portion is transported to the external wastewater device.

2. The treatment method for recycling coal gasification ash water according to claim 1, wherein, The slag water treatment system is a three-stage flash evaporation system or a two-stage flash evaporation system.

3. The treatment method for recycling coal gasification ash water according to claim 2, characterized in that, The three-stage flash distillation system comprises a high-pressure flash distillation tower, a low-pressure flash distillation tower and a vacuum flash distillation tower which are connected in sequence.

4. The treatment method for recycling coal gasification ash water according to claim 1, characterized in that The stripping tower is a plate tower or a packed tower structure.

5. The treatment method for recycling coal gasification ash water according to claim 1, characterized in that, The acid gas outlet is connected to the burner; The high-concentration grey water outlet is connected to a sewage treatment device.

6. The treatment method for recycling coal gasification ash water according to claim 1, characterized in that, The ammonia-containing gas outlet is connected to the heat exchanger and then connected to the acid gas separator inlet.

7. The treatment method for recycling coal gasification ash water according to claim 1, characterized in that, The treatment system for recycling coal gasification ash water consists of a water washing tower, a slag water treatment system, a stripping tower, an acid gas separator, a circulating ash water device, an external wastewater discharge device and a three-way valve; the first end of the three-way valve is connected to the low-concentration ash water outlet of the stripping tower, the second end of the three-way valve is connected to the inlet of the circulating ash water device, and the third end of the three-way valve is connected to the inlet of the external wastewater discharge device.

8. The treatment method for recycling coal gasification ash water according to claim 1 or 7, characterized in that, The circulating grey water device comprises a grey water pump; The external wastewater discharge device comprises a flow regulating valve and an external wastewater discharge pipeline; the flow regulating valve is arranged in the external wastewater discharge pipeline.

9. The treatment method for recycling coal gasification ash water according to claim 1, characterized in that, In S1, the proportion of the untreated grey water entering the stripping tower to the effluent of the upstream equipment is 10% or 15%.

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