Method for purifying black water in coal water slurry gasification reactor or carbon washing tower

Abstract

The invention discloses a method for purifying black water in a coal water slurry gasification reactor or a carbon washing tower, which comprises the following steps of: introducing the black water into a descaling softener, adding a scale inhibitor or an acid solution into the descaling softener, and fully mixing the black water and a medicament under the stirring action; and the black water treated by the descaling softener enters a filter, so that solid and liquid of the black water are separated, and filter residues and clear liquid are obtained. The black water is guided into the descaling softener for primary treatment, and the scale inhibitor or the acid solution is added and stirred and mixed, so that a scale layer can be effectively prevented from being formed. Solid-liquid separation is achieved through the subsequent filtering step, filter residues and clear liquid are obtained, a foundation is laid for subsequent treatment and utilization, black water is primarily purified, and pollution to the environment is reduced.

Description

Technical Field

[0001] The present invention relates to the field of black water treatment. More specifically, the present invention relates to a method for purifying black water from a water-coal slurry gasification reactor or a carbon washing tower. Background Art

[0002] The water-coal slurry gasification process is a process of converting water-coal slurry into syngas. Water-coal slurry is a combustible liquid formed by mixing pulverized coal with water. Through a gasification reactor, a gas mixture rich in combustible gases can be obtained, which is usually called syngas or coal gas. The wastewater directly discharged from the bottom of the gasification reactor and the carbon washing tower is black in color because it contains a large amount of gasification residual carbon, so it is called black water. The temperature of the black water is 220 - 270 °C, and the pressure is 4 - 6.5 MPa.

[0003] Existing black water purification technologies that can be industrially applied: In the first step, flash evaporation technology is adopted to separate acidic gases and water vapor in the black water. Flash evaporation is generally multi-stage flash evaporation, and the solids after flash evaporation still remain in the liquid. In the second step, the liquid remaining after flash evaporation is called grey water. The grey water enters a sedimentation tank, and a flocculant or electro-chemical flocculation is added to cause some particulate matters to flocculate and settle. The main function of adding a flocculant to the grey water is to coagulate the solid impurities in the water into large chunks, facilitating subsequent filtration and precipitation, thereby improving the water quality. Through adsorption and bridging effects, the flocculant aggregates the suspended particles and colloidal substances in the water into larger flocs, which are more easily separated from the water to achieve the purpose of purifying the water quality. The settled flocs are returned to the coal blending for use, and the remaining liquid enters the downstream device. In the third step, the liquid in the upper part of the sedimentation tank enters the grey water tank. A dispersant needs to be added before entering the grey water tank. The main purpose of adding a dispersant to the grey water is to prevent solid particles from aggregating and depositing, reducing scaling and equipment corrosion. Through physical or chemical actions, the dispersant disperses the suspended solids, microcrystals and other particles in the grey water in the water, preventing them from aggregating and depositing, thereby inhibiting the formation of hard scale. In addition, the dispersant can also form stable complexes with hard water ions such as calcium and magnesium in the grey water, reducing their concentration and further inhibiting the formation of hard scale. Part of the water after the grey water tank is heated and pressurized and then enters the gasification reactor for continued use, and part of it enters the sewage treatment; part of the liquid in the grey water tank is discharged, and part of it is heated and recycled and enters the carbon washing tower or the gasification reactor.

[0004] The existing process flow is relatively long, and it is very difficult to remove the tiny solids in the black water. In the black water treatment, the equipment and pipelines are very prone to scaling, resulting in blockage or reduced heat exchanger efficiency. At the same time, flocculants and dispersants need to be added, which requires a large investment in equipment and operation costs and is not conducive to maintenance. Summary of the Invention

[0005] The object of the present invention is to provide a method for purifying the black water of a water-coal slurry gasification reactor or a carbon washing tower. By directly introducing the black water into a scale removal and softening device for preliminary treatment, this process does not require cumbersome steps such as multi-stage flashing and flocculation in a sedimentation tank, and the process flow is short. Adding a scale inhibitor or an acid solution to the scale removal and softening device and stirring and mixing can effectively remove scale-forming substances such as calcium and magnesium in the black water and prevent the formation of a scale layer. Compared with the prior art, this method avoids the use of flocculants and dispersants, not only reducing the chemical agent cost and equipment investment, but also reducing the secondary pollution problem that may be brought about by the use of chemical agents. Subsequently, solid-liquid separation can be achieved through a simple filtration step to obtain filter residue and clear liquid, laying a foundation for subsequent treatment and utilization, preliminarily purifying the black water, and reducing environmental pollution.

[0006] To achieve these objects and other advantages of the present invention, there is provided a method for purifying the black water of a water-coal slurry gasification reactor or a carbon washing tower, including: Introducing the black water into a scale removal and softening device, adding a scale inhibitor or an acid solution to the scale removal and softening device, and fully mixing the black water with the chemical agent under stirring; The black water treated by the scale removal and softening device enters a filter to separate the solid and liquid of the black water, obtaining filter residue and clear liquid; Introducing the filter residue into a filter residue tank, and after flashing the solid-containing water in the filter residue tank, it is recycled for coal blending or dried into dry slag; After the clear liquid is subjected to high-pressure flashing, a part is used as the quench water for the carbon washing tower and the gasification reactor, and the other part continues to be subjected to low-pressure flashing and vacuum flashing and then is used for coal slurry preparation or discharged as sewage.

[0007] Preferably, in the method for purifying the black water of the water-coal slurry gasification reactor or the carbon washing tower, the filter uses a microsphere metal powder coated filter element, the filtration accuracy is 0.1 μm, the operating pressure is 4 - 6.5 MPa, solid particles with a particle size > 0.1 μm are separated, and clear liquid with a solid content < 50 ppm is obtained.

[0008] Preferably, in the method for purifying the black water of the water-coal slurry gasification reactor or the carbon washing tower, the step of using a part of the clear liquid as the quench water for the carbon washing tower and the gasification reactor and using the other part for coal slurry preparation after continuing low-pressure flashing and vacuum flashing after high-pressure flashing includes: High-pressure flashing: subjecting the clear liquid to high-pressure flashing under the conditions of a pressure of 1.0 - 2.0 MPa and a temperature of 150 - 180 °C, and after flashing, the clear liquid is divided into two parts; The first part of the clear liquid is directly recycled to the quench water system of the carbon washing tower and the gasification reactor; After the second-stage supernatant undergoes low-pressure flashing and vacuum flashing in sequence, it enters the pH adjustment tank. In the pH adjustment tank, a NaOH solution with a mass concentration of 5-10% is added to the supernatant through a static mixer to adjust the pH of the supernatant to 6.5-7.5. The adjusted supernatant is transported to the water supply system of the gasification reactor by a centrifugal pump and mixed with fresh water for coal slurry preparation. Among them, an on-line pH meter and a turbidity meter are arranged at the outlet of the pH adjustment tank to monitor the pH value and turbidity of the supernatant in real time, control the turbidity of the supernatant ≤ 10 NTU. At the same time, the temperature of the recycled supernatant is reduced to ≤ 40 °C through a heat exchanger.

[0009] Preferably, in the method for purifying the black water of the water coal slurry gasification reactor or the carbon washing tower, it further includes: When the filter cake in the filter reaches the preset thickness, slag discharge operation is carried out, so that the filter cake and the solution attached to the filter cake and mixed therein are flushed into the filter residue tank together.

[0010] Preferably, in the method for purifying the black water of the water coal slurry gasification reactor or the carbon washing tower, the scale removal and softening device includes: A shell, which is a hollow cylindrical shape, and a fluid outlet is arranged at the upper part of the shell; A premixing chamber, which is hollow inside and has an open top in a cylindrical shape, and is vertically arranged inside the lower part of the shell and is separated from the bottom of the shell by a preset distance; At least one black water inlet pipe, each black water inlet pipe is connected to the side wall of the lower part of the premixing chamber and is communicated with the inside of the premixing chamber; At least one chemical agent inlet pipe, each chemical agent inlet pipe is connected to the side wall of the lower part of the premixing chamber and is communicated with the inside of the premixing chamber; A baffle component, which includes an outer baffle plate and an inner baffle plate arranged at intervals. The main body of the outer baffle plate is in a cylindrical shape and is fixed on the inner side wall of the shell. Wave-shaped structures are arranged on the inner side wall of the outer baffle plate and the outer side wall of the inner baffle plate, and the wave crests and wave troughs on the outer baffle plate are respectively opposite to the wave crests and wave troughs on the inner baffle plate. The upper part of the inner baffle plate is in a cylindrical shape and is located above the premixing chamber and is separated from the premixing chamber by a preset distance. The lower part of the inner baffle plate is in a cylindrical shape and covers the outside of the premixing chamber; A stirring component, which includes a stirring shaft, multiple first stirring blades, multiple second stirring blades and multiple third stirring blades; the stirring shaft is rotatably connected to the top and bottom of the shell, and vertically penetrates through the inner baffle plate and the premixing chamber and is rotatably connected to both the inner baffle plate and the premixing chamber; each first stirring blade is located inside the premixing chamber, and there are first stirring blades above and below the inlets of the black water inlet pipe and the chemical agent inlet pipe. Each second stirring blade is located below the premixing chamber, and each third stirring blade is located above the outer baffle plate and the inner baffle plate; A flow guiding assembly, which includes a plurality of flow guiding plates that are staggered and arranged at intervals. The plurality of flow guiding plates are respectively located on the inner side wall of the lower part of the inner baffle plate and the outer side wall of the premixing chamber. The flow guiding plates on the inner baffle plate are frustum-shaped with a circular bottom and are separated from the premixing chamber by a preset distance. The flow guiding plates on the premixing chamber are frustum-shaped with a circular top and are separated from the inner baffle plate by a preset distance. The flow guiding plate located at the uppermost part is arranged on the premixing chamber. Along the generatrix direction of each flow guiding plate, there are multiple circles of annular protrusions arranged at intervals, and at least one pair of openings is arranged on each circle of protrusions. The openings on the adjacent protrusions of each flow guiding plate are arranged staggeredly; the fluid on the flow guiding plate on the inner baffle plate can flow into the innermost protrusion on the flow guiding plate below it, and the fluid on the flow guiding plate on the premixing chamber can flow outside the outermost protrusion on the flow guiding plate below it. Preferably, in the method for purifying black water in the water coal slurry gasification reactor or the carbon washing tower, the scale removal and softening device further includes: At least one ultrasonic component, which is arranged at the bottom of the housing, and the probe of each ultrasonic component is in contact with the bottom of the housing.

[0011] Preferably, in the method for purifying black water in the water coal slurry gasification reactor or the carbon washing tower, each chemical agent introduction pipe tangentially enters from the lower part of the premixing chamber and is separated from the bottom of the premixing chamber by a preset distance, and the height of each chemical agent introduction pipe is lower than the height of each black water introduction pipe.

[0012] Preferably, in the method for purifying black water in the water coal slurry gasification reactor or the carbon washing tower, there are 3 - 6 black water introduction pipes, and all the black water introduction pipes are evenly distributed on the same circumference, and spiral swirl nozzles are used at the outlets of each black water introduction pipe.

[0013] Preferably, in the method for purifying black water in the water coal slurry gasification reactor or the carbon washing tower, the inner baffle plate is connected to the premixing chamber through a plurality of first connecting rods and is connected to the housing through a plurality of second connecting rods, and the premixing chamber is connected to the housing through a plurality of third connecting rods. Each first connecting rod, each second connecting rod, and each third connecting rod are separated from the stirring assembly by a preset distance.

[0014] Preferably, in the method for purifying black water in the water coal slurry gasification reactor or the carbon washing tower, the housing, the stirring shaft, the inner baffle plate, the outer baffle plate, the premixing chamber, and each flow guiding plate are coaxially arranged. The angle between the generatrix of each flow guiding plate and the vertical direction is 30 - 45 degrees, and the cross-section of each circle of protrusions is an arc arched upward.

[0015] The present invention has at least the following beneficial effects: In the gasification reactor of the present invention or the equipment downstream of the carbon scrubber, the medium no longer contains solids. This key achievement has brought a series of positive impacts. On the one hand, it reduces the losses caused by the friction and wear of solid particles inside the equipment, significantly reducing the maintenance frequency of the equipment, thereby extending the service life of the equipment and reducing the high investment costs brought by equipment replacement and maintenance. On the other hand, the medium without solids makes the operation process smoother and more stable, reducing the work difficulty of the operators and the risk of accidents caused by improper operation. The reliability of the entire system is significantly enhanced, ensuring the production continuity and bringing more stable economic benefits to the enterprise.

[0016] The present invention uses the black water at the outlet of the gasification reactor or the carbon scrubber as the raw material. This raw material selection method not only makes full use of the characteristics of the black water but also greatly promotes the purification efficiency and purification effect. The specific composition and state of the black water make the purification process more efficient, capable of quickly separating impurities and harmful substances therein. At the same time, for the filter, this raw material can provide a suitable operating environment for it, effectively reducing blockage and pollution, extending the service life of the filter, ensuring its long-term stable operation, and ensuring that the quality of the purified black water always remains at a high level.

[0017] The scale removal and softening device set in the present invention can operate stably in a high-temperature environment. By adding chemicals and achieving uniform mixing with the help of an efficient mixing device, it can effectively prevent the formation of black water scale. This characteristic avoids equipment failures and energy waste caused by scaling, ensuring the efficient operation of the equipment. At the same time, the high-precision filter set can also operate at high temperature, avoiding the complex process of first cooling and then heating in the traditional process, directly reducing a large amount of energy consumption. This not only reduces the energy cost but also reduces the carbon emissions caused by energy consumption, conforming to the development concept of green environmental protection.

[0018] The present invention adopts a filter with a filtration accuracy of 0.1 μm, which can effectively intercept tiny solid impurities, making the solid content in the purified black water ≤ 50 ppm, improving the purification quality of the black water, meeting higher usage requirements, and reducing the blockage and wear of subsequent equipment. The online cleaning and regeneration system equipped with the high-precision filter of the present invention is the key to enhancing its performance. This system can real-time monitor the operating state of the filter. When it detects a scaling trend on the inner wall or filter element of the filter, it automatically starts the cleaning and regeneration program. In this way, it can not only effectively prevent the influence of scaling on the filtration effect but also significantly extend the service life of the filter element, reducing the filter element replacement cost. At the same time, it ensures that the filter is always in an efficient operating state, ensuring the stable and reliable purification quality of the black water and reducing the secondary treatment cost caused by poor filtration effect.

[0019] The filter residue after the filter of the present invention can directly enter the water-coal slurry for coal blending after flash evaporation and concentration. This process realizes the recycling of resources. The unreacted pulverized coal contained in the filter residue can be reused, improving the conversion rate of the pulverized coal and reducing the waste of coal resources. At the same time, the cost and difficulty of filter residue treatment are reduced, and environmental pollution is decreased. In addition, the clear water purified from the black water by the filter can be directly recycled through a high-pressure flash evaporation tank and used as the quench water for the carbon washing tower and the gasification reactor, improving the utilization rate of water resources, reducing the consumption of fresh water resources, and achieving the goal of energy conservation and emission reduction.

[0020] The clear water purified from the black water of the present invention does not need to add flocculants and dispersants anymore, which directly reduces the procurement cost of the chemicals. At the same time, it avoids the pollution of the water quality by the chemicals, reducing the difficulty and cost of subsequent sewage treatment. A part of the discharged sewage does not contain solids, greatly simplifying the subsequent sewage treatment process and reducing the investment and operation cost of sewage treatment equipment. This not only saves a large amount of funds for the enterprise but also reduces environmental pollution, having significant environmental protection benefits and helping the enterprise achieve sustainable development.

[0021] Through an innovative process flow, the present invention abandons cumbersome links such as traditional multi-stage flash evaporation and sedimentation tank flocculation, directly introducing the black water into a scale and hardness removal softener for preliminary treatment, simplifying the operation process, reducing equipment investment and floor area. At the same time, equipment such as the scale and hardness removal softener and the filter work together to form an efficient purification system. Each link cooperates closely and promotes each other, further improving the overall treatment efficiency and effect and realizing the optimization and upgrading of the process.

[0022] The internal structure of the scale and hardness removal softener of the present invention is ingenious. The premixing chamber, baffle components, stirring components, and diversion components cooperate with each other, making the mixing uniformity of the black water and the chemicals exceed 95%, significantly improving the sewage treatment effect. Designs such as the tangential entry of the chemical introduction pipe and the use of a spiral swirl nozzle for the black water introduction pipe further strengthen the mixing effect. At the same time, the connections of each component are firm. The inner baffle plate, premixing chamber, and the shell are connected by connecting rods and maintain an appropriate distance from the stirring components, and each component is coaxially arranged to ensure the stable layout and reliable operation of the equipment.

[0023] The present invention directly recycles the quench water through high-pressure flash evaporation (1.0 - 2.0 MPa); the combined low-pressure + vacuum flash evaporation with pH adjustment (6.5 - 7.5) and temperature reduction (≤40°C) increases the clear liquid recycling rate to 90%, saves 30% - 50% of water, and reduces carbon emissions by 40%.

[0024] The present invention reduces the sewage discharge by 60%, directly recycles the filter residue for coal blending, and has efficient resource recycling; the comprehensive energy consumption and cost are reduced by 25%, meeting the requirements of green production.

[0025] The present invention solves the technical problems of high water content in filter residue and low reuse rate of clarified liquid in the black water treatment of water coal gasification through the innovation of adding scale inhibitors or acid solutions in the scale removal and softening device, filtering by a high-precision filter, and the process of reusing clarified liquid.

[0026] Other advantages, objectives, and features of the present invention will be partially reflected by the following description and partially understood by those skilled in the art through the research and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a process flow chart of a method for purifying black water from a water coal gasification reactor or a carbon washing tower according to an embodiment of the present invention; Figure 2 is a process flow block diagram of a method for purifying black water from a water coal gasification reactor or a carbon washing tower according to an embodiment of the present invention; Figure 3 is a structural schematic diagram of a scale removal and softening device according to an embodiment of the present invention; Figure 4 is a structural schematic diagram of a guide plate according to an embodiment of the present invention; Among them, the reference numerals are as follows: scale removal and softening device - 1; filter - 2; filter residue tank - 3; flash tank - 4; dryer - 5; high-pressure flash tank - 6; low-pressure flash tank - 7; vacuum flash tank - 8; housing - 101; fluid outlet - 102; premixing chamber - 103; black water inlet pipe - 104; chemical agent inlet pipe - 105; outer baffle - 106; inner baffle - 107; stirring shaft - 108; first stirring blade - 109; second stirring blade - 110; third stirring blade - 111; guide plate - 112; protrusion - 113; opening - 114; ultrasonic component - 115; first connecting rod - 116; second connecting rod - 117; third connecting rod - 118. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] The following further describes the present invention in detail with reference to the drawings, so that those skilled in the art can implement it according to the description in the specification.

[0029] It should be noted that in the description of the present invention, the orientation or positional relationship indicated by the terms "horizontal", "longitudinal", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0030] As Figure 1 and Figure 2As shown, the present invention provides a method for purifying the black water of a water coal slurry gasification reactor or a carbon washing tower, including: Introduce the black water into a scale removal and softening device 1, and add a scale inhibitor or an acid solution to the scale removal and softening device 1 to fully mix the black water with the agent under stirring. The black water treated by the scale removal and softening device 1 enters a filter 2 to separate the solid and liquid of the black water, obtaining filter residue and clear liquid. During the gasification process, after the coal slurry undergoes reactions such as combustion and cracking in the combustion chamber, a large amount of carbon dioxide and water in the generated process gas form HCO 3- . At high temperatures, HCO 3- will decompose into CO 3 2- , which combines with Ca 2+ , Mg 2+ and other ions in the black water to form carbonates such as CaCO 3 , MgCO 3 and the like, thereby adhering to the vessel wall or pipeline to form scale. The scale removal and softening device 1 mainly adjusts the pH value of the black water and the addition of scale inhibitor dispersant to ensure that the black water entering the filter 2 is not prone to scale formation.

[0031] Using the black water discharged from the gasification reactor or the carbon washing tower as raw material, it enters the high-precision filter 2 through the scale removal and softening device 1. At this position, the temperature of the black water is ≥200°C, and the pressure is ≥3.5 MPa. At high temperatures, the grease is in a liquid state, with a small viscosity, and the liquid can easily pass through the filter element, while the solid is intercepted and separated.

[0032] The black water generated by the water coal slurry gasification reactor or the carbon washing tower has a relatively high temperature and pressure and contains a large amount of impurities. In practical applications, first, the black water is introduced into the scale removal and softening device 1 through a pipeline. The scale removal and softening device 1 is usually a closed container equipped with a stirring device inside. Add an appropriate amount of scale inhibitor or acid solution to the scale removal and softening device 1. The scale inhibitor can be a common organic phosphonate scale inhibitor, and the acid solution can be dilute hydrochloric acid or dilute sulfuric acid, etc. Start the stirring device to fully mix the black water with the agent. The stirring time and speed are adjusted according to the flow rate and properties of the black water. Generally, the stirring time is 10 - 30 minutes, and the stirring speed is 100 - 300 revolutions per minute. The black water treated by the scale removal and softening device 1 flows into the filter 2 through a pipeline. The filter 2 can adopt a high-precision cartridge filter. When the black water passes through the filter element, the solid impurities are intercepted on the surface of the filter element, and the liquid passes through the filter element, thereby realizing solid-liquid separation to obtain filter residue and clear liquid.

[0033] In this solution, the black water is introduced into the scale and hardness remover 1 for preliminary treatment. By adding a scale inhibitor or acid solution and stirring and mixing, the hardness components in the black water can be effectively removed, preventing the formation of scale layers. The subsequent filtration step achieves solid-liquid separation, obtaining filter residue and clear liquid, laying a foundation for subsequent treatment and utilization, preliminarily purifying the black water, and reducing environmental pollution.

[0034] The filter residue is introduced into the filter residue tank 3. After the solid-containing water in the filter residue tank 3 is flash-evaporated in the flash tank 4, it is recycled for coal blending or dried into dry slag through the dryer 5. Recycling for coal blending means that during the black water treatment process in the water coal slurry gasification reactor or the carbon washing tower, the solid-containing water in the filter residue tank 3 can be recycled back to the coal blending link for utilization after flash evaporation. During the preparation of water coal slurry, pulverized coal needs to be mixed with water in a certain proportion to make water coal slurry. And these solid-containing filter residues contain unreacted pulverized coal and other solid substances, which have a certain calorific value and utilization value. Recycling the solid-containing water in the filter residue tank 3 for coal blending after flash evaporation can, on the one hand, improve the conversion rate of unreacted pulverized coal, making more full use of coal resources; on the other hand, it can reduce the raw material cost and the usage amount of new pulverized coal. At the same time, it also reduces the treatment amount of filter residue, reduces the impact on the environment, and to a certain extent realizes the recycling of resources and energy conservation and emission reduction.

[0035] After the clear liquid is flash-evaporated under high pressure in the high-pressure flash tank 6, a part is used as the quench water for the carbon washing tower and the gasification reactor, and the other part continues to be flash-evaporated under low pressure in the low-pressure flash tank 7 and flash-evaporated under vacuum in the vacuum flash tank 8, and then used for coal slurry preparation or discharged as sewage.

[0036] For the filter residue obtained by filtering through the filter 2, it is introduced into the filter residue tank 3 through a pipeline. The filter residue tank 3 is a storage container for temporarily storing the filter residue. The solid-containing water in the filter residue tank 3 can be flash-evaporated through the flash tank 4. Flash evaporation is a process of suddenly reducing the pressure to cause part of the water in the solid-containing water to evaporate rapidly. The steam after flash evaporation can be recycled, and the solid-containing water can be recycled for coal blending to improve the utilization rate of coal. Or the solid-containing water after flash evaporation is dried through the dryer 5 to become dry slag, which is convenient for storage and transportation.

[0037] For the clear liquid obtained by filtering through the filter 2, it is introduced into the high-pressure flash tank 6 for high-pressure flash evaporation. A part of the clear liquid after high-pressure flash evaporation can be used as the quench water for the carbon washing tower and the gasification reactor, playing a role in cooling and washing. The other part of the clear liquid continues to be flash-evaporated under low pressure and flash-evaporated under vacuum to further remove the impurities and water in it, and finally used for coal slurry preparation or discharged as sewage.

[0038] This solution conducts reasonable subsequent treatment and utilization of the filter residue and clear liquid obtained by filtering with filter 2. The water containing solids in the filter residue tank 3 is recycled for coal blending or dried into dry residue after flash evaporation, realizing the recycling of resources and reducing production costs. After high-pressure flash evaporation, part of the clear liquid is used as quench water, and part is further treated and then used for coal slurry preparation or discharged, improving the utilization rate of water resources and reducing waste discharge.

[0039] In another solution, in the purification method of the black water of the water coal slurry gasification reactor or the carbon washing tower, the filter uses a microsphere metal powder coated filter element, with a filtration accuracy of 0.1 μm, an operating pressure of 4 - 6.5 MPa, separating solid particles with a particle size > 0.1 μm, and obtaining filter residue and clear liquid with a solid content < 50 ppm.

[0040] When using filter 2 with a filtration accuracy of 0.1 μm, it is necessary to select appropriate filter element materials and structures. This solution selects a coated sintered filter element, which is not only corrosion-resistant and high-temperature resistant, but also has a high filtration accuracy, and the solid content in the purified black water is ≤ 50 ppm. When installing filter 2, it is necessary to ensure that the filter element is installed correctly and sealed well to avoid black water leakage. When the black water enters filter 2, due to the filtration accuracy of the filter element being 0.1 μm, it can effectively intercept solid particles with a diameter greater than or equal to 0.1 μm, greatly reducing the solid content in the purified clear liquid. As the filtration progresses, a filter cake will gradually accumulate on the surface of the filter element, and it is necessary to clean or replace the filter element regularly to ensure the filtration effect.

[0041] This solution uses filter 2 with a filtration accuracy of 0.1 μm, which can effectively remove finer impurities in the black water, improve the filtration effect, make the quality of the purified black water higher, meet higher usage requirements, and at the same time reduce the blockage and wear of subsequent equipment.

[0042] In another solution, in the purification method of the black water of the water coal slurry gasification reactor or the carbon washing tower, after the clear liquid undergoes high-pressure flash evaporation, part of it is used as quench water for the carbon washing tower and the gasification reactor, and the steps for using the other part for coal slurry preparation after continuous low-pressure flash evaporation and vacuum flash evaporation include: High-pressure flash evaporation: The clear liquid is subjected to high-pressure flash evaporation under the conditions of a pressure of 1.0 - 2.0 MPa and a temperature of 150 - 180 °C, and the clear liquid after flash evaporation is divided into two parts; The first part of the clear liquid is directly recycled to the quench water system of the carbon washing tower and the gasification reactor; The second part of the clear liquid undergoes low-pressure flash evaporation and vacuum flash evaporation in sequence, and then enters the pH adjustment tank. In the pH adjustment tank, a NaOH solution with a mass concentration of 5 - 10% is added to the clear liquid through a static mixer to adjust the pH of the clear liquid to 6.5 - 7.5; the adjusted clear liquid is transported to the water replenishment system of the gasification reactor by a centrifugal pump and mixed with fresh water for coal slurry preparation; Among them, an on-line pH meter and a turbidimeter are set at the outlet of the pH adjustment tank to monitor the pH value and turbidity of the clarified liquid in real time, control the turbidity of the clarified liquid ≤ 10 NTU. At the same time, the temperature of the recycled clarified liquid is reduced to ≤ 40 °C through a heat exchanger. High-pressure flash evaporation (1.0 - 2.0 MPa, 150 - 180 °C) makes full use of the waste heat and residual pressure of the clarified liquid. The first part of the clarified liquid separated is directly recycled as quench water, reducing the consumption of fresh water and heat energy loss; the second part of the clarified liquid recovers energy step by step through low-pressure flash evaporation and vacuum flash evaporation, reducing the comprehensive energy consumption by about 35%, and realizing the efficient cascade utilization of energy.

[0043] NaOH solution (5 - 10% concentration) is added through a static mixer to precisely adjust the pH of the clarified liquid to 6.5 - 7.5, neutralize the residual acidic substances, avoid the corrosion of the recycled water to the carbon washing tower, gasification reactor and pipeline, and extend the service life of the equipment. At the same time, the on-line pH meter and turbidimeter monitor in real time to ensure that the turbidity of the clarified liquid ≤ 10 NTU and the pH is stable, ensuring the safety and reliability of the recycled water quality.

[0044] The adjusted clarified liquid is mixed with fresh water for coal slurry preparation, and the recycling rate is increased to more than 90%, reducing the fresh water demand by 30 - 50%. The trace minerals in the clarified liquid can also improve the fluidity of the coal slurry and improve the gasification efficiency, realizing the resource utilization of wastewater and the synergistic optimization of the process.

[0045] The temperature of the recycled clarified liquid is reduced to ≤ 40 °C through a heat exchanger, which not only avoids the thermal shock of high-temperature water to the coal slurry preparation system, but also reduces the thermal stress of the equipment and improves the operation safety. At the same time, the low-temperature clarified liquid is easier to be evenly mixed with fresh water, ensuring the stability of the coal slurry ratio.

[0046] The multi-stage flash evaporation process reduces the sewage discharge by more than 60%. Combined with a high recycling ratio, it significantly reduces the sewage treatment load and chemical consumption. In addition, the heat energy recovery and water-saving measures reduce the comprehensive operation cost by about 25%, having both environmental and economic benefits.

[0047] The prior art does not disclose the precise pH adjustment (6.5 - 7.5) before the recycling of the clarified liquid. Through this step, this application avoids the corrosion of the recycled water to the equipment.

[0048] The prior art focuses on the preliminary solid-liquid separation of the black water. Through the full-process design of descaling - filtration - recycling, this application solves the problems of high water content of the filter residue, strong scaling property of the clarified liquid and low recycling rate in the traditional process.

[0049] The recycling rate of the clarified liquid is increased from 50% in the traditional process to 90%, the energy consumption of the filter residue incineration is reduced by 40%, and the equipment scaling cycle is extended by more than 3 times.

[0050] In another solution, the purification method of the black water of the water coal slurry gasification reactor or the carbon washing tower further includes: When the filter cake in the filter 2 reaches the preset thickness, the slag discharge operation is carried out, so that the filter cake, the solution attached to the filter cake and the solution mixed therein are flushed into the slag pot 3 together.

[0051] During the operation of the filter 2, the thickness of the filter cake should be monitored in real time. The thickness of the filter cake can be indirectly monitored by devices such as pressure sensors or liquid level sensors. When the filter cake reaches the preset thickness, the slag discharge operation is started. The slag discharge operation can be carried out by reverse flushing. Reverse flushing is to introduce reverse water flow into the filter 2, so that the filter cake, the solution attached to the filter cake and the solution mixed therein are flushed into the slag pot 3 together. After the slag discharge operation is completed, the filter 2 can continue to operate normally.

[0052] In another solution, in the purification method of the black water of the water coal slurry gasification reactor or the carbon washing tower, as Figure 3 and Figure 4 shown, the scale removal and softening device 1 includes: A housing 101, which is a hollow cylindrical shape, and a fluid outlet 102 is provided at the upper part of the housing 101; A premixing chamber 103, which is hollow inside and has an open top, is cylindrical, and is vertically arranged inside the lower part of the housing 101 and is separated from the bottom of the housing 101 by a preset distance; At least one black water inlet pipe 104, each black water inlet pipe 104 is connected to the side wall of the lower part of the premixing chamber 103 and is communicated with the inside of the premixing chamber 103; At least one chemical agent inlet pipe 105, each chemical agent inlet pipe 105 is connected to the side wall of the lower part of the premixing chamber 103 and is communicated with the inside of the premixing chamber 103; A baffle component, which includes an outer baffle plate 106 and an inner baffle plate 107 arranged at intervals. The main body of the outer baffle plate 106 is cylindrical and is fixed on the inner side wall of the housing 101. Wave-shaped structures are provided on the inner side wall of the outer baffle plate 106 and the outer side wall of the inner baffle plate 107, and the wave crests and wave troughs on the outer baffle plate 106 are respectively opposite to the wave crests and wave troughs on the inner baffle plate 107. The upper part of the inner baffle plate 107 is cylindrical and is located above the premixing chamber 103 and is separated from the premixing chamber 103 by a preset distance. The lower part of the inner baffle plate 107 is cylindrical and covers the outside of the premixing chamber 103; A stirring assembly, which includes a stirring shaft 108, multiple first stirring blades 109, multiple second stirring blades 110, and multiple third stirring blades 111; the stirring shaft 108 is rotatably connected to both the top and bottom of the housing 101, vertically penetrates through the inner baffle 107 and the premixing chamber 103, and is rotatably connected to both the inner baffle 107 and the premixing chamber 103; each first stirring blade 109 is located within the premixing chamber 103, and there are first stirring blades 109 both above and below the inlets of the black water inlet pipe 104 and the chemical agent inlet pipe 105, each second stirring blade 110 is located below the premixing chamber 103, and each third stirring blade 111 is located above the outer baffle 106 and the inner baffle 107; A flow guiding assembly, which includes multiple staggered and spaced-apart flow guiding plates 112. The multiple flow guiding plates 112 are respectively located on the inner side wall of the lower part of the inner baffle 107 and the outer side wall of the premixing chamber 103. The flow guiding plates 112 on the inner baffle 107 are frustum-shaped and are separated from the premixing chamber 103 by a preset distance. The flow guiding plates 112 on the premixing chamber 103 are frustum-shaped and are separated from the inner baffle 107 by a preset distance. The uppermost flow guiding plate 112 is arranged on the premixing chamber 103. Multiple annular protrusions 113 are spaced along the generatrix direction of the flow guiding plate 112. At least one pair of openings 114 are arranged on each circle of protrusions 113. The openings 114 on the adjacent protrusions 113 of each flow guiding plate 112 are arranged staggeredly. The fluid on the flow guiding plate 112 on the inner baffle 107 can flow into the innermost protrusion of the flow guiding plate 112 below it. The fluid on the flow guiding plate 112 on the premixing chamber 103 can flow outside the outermost protrusion of the flow guiding plate 112 below it.

[0053] The housing 101 of the scale and hardness remover 1 is a hollow cylinder made of stainless steel material to ensure its strength and corrosion resistance. A fluid outlet 102 is provided at the upper part of the housing 101 for discharging the treated black water. The premixing chamber 103 is cylindrical and is vertically arranged inside the lower part of the housing 101, separated from the bottom of the housing 101 by a certain distance, providing space for the preliminary mixing of black water and chemicals. The black water inlet pipe 104 and the chemical inlet pipe 105 are both connected to the lower side wall of the premixing chamber 103, enabling the black water and chemicals to be fully mixed in the premixing chamber 103. The main body of the outer baffle 106 of the baffle assembly is cylindrical and is fixed on the inner side wall of the housing 101. The wavy structure on its inner side wall can change the flow direction of the fluid and increase the mixing effect. The upper part of the inner baffle 107 is located above the premixing chamber 103, and the lower part covers the outside of the premixing chamber 103, playing a role in guiding the fluid flow. The stirring shaft 108 of the stirring assembly is rotationally connected to the top and bottom of the housing 101 and is driven to rotate by a motor. The first stirring blade 109 is located inside the premixing chamber 103 and is provided both above and below the inlets of the black water inlet pipe 104 and the chemical inlet pipe 105, capable of fully stirring the black water and chemicals in the premixing chamber 103. The second stirring blade 110 is located below the premixing chamber 103 to further stir the mixture. The third stirring blade 111 is located above the outer baffle 106 and the inner baffle 107 to promote the mixing of the fluid in the baffle assembly. The multiple guide plates 112 of the guide assembly are staggered on the lower inner side wall of the inner baffle 107 and the outer side wall of the premixing chamber 103. The guide plates 112 on the inner baffle 107 are frustum-shaped with a downward taper, and the guide plates 112 on the premixing chamber 103 are frustum-shaped. The annular protrusions 113 and openings 114 on the guide plates 112 can change the flow path of the fluid, increasing the mixing and reaction time.

[0054] The operation method of the scale and hardness remover 1 is as follows: After starting the equipment, the black water enters the premixing chamber 103 through the black water inlet pipe 104, and the chemicals enter the premixing chamber 103 through the chemical inlet pipe 105. Since both enter from the side walls at the lower part of the premixing chamber 103, the black water and chemicals quickly converge in the premixing chamber 103, forming an initial flow field conducive to mixing.

[0055] At this time, the first stirring blade 109 located inside the premixing chamber 103 and above and below the inlets of the black water inlet pipe 104 and the chemical inlet pipe 105 starts to work. Driven by the stirring shaft 108, the first stirring blade 109 rotates at a high speed to preliminarily stir and mix the black water and chemicals, enabling them to be initially contacted and fused, laying a foundation for subsequent deep mixing. This initial mixing method is efficient, greatly improving the initial mixing efficiency, contributing to enhancing the overall mixing uniformity, and laying a solid foundation for achieving high-quality mixing in the subsequent process.

[0056] The mixed fluid flows downward from above the premixing chamber 103 and passes through the frustum-shaped flow guiding plates 112 arranged in an interleaved manner. These flow guiding plates 112 are provided with multiple rings of annular protrusions 113, and the openings 114 on the adjacent protrusions 113 of each flow guiding plate 112 are arranged staggeredly. When the fluid flows through the flow guiding plates 112, under the action of the annular protrusions 113 and the openings 114, the flow direction and flow velocity of the fluid are continuously changed, forming a complex turbulent flow field. The fluids in different flow layers interpenetrate and collide with each other, further promoting mixing, effectively increasing the mixing degree between fluids, improving the mixing effect, making the mixing more sufficient and uniform, and providing a higher-quality basic fluid for the subsequent stirring and mixing processes.

[0057] Next, the fluid reaches the second stirring blade 110. The second stirring blade 110 is located below the premixing chamber 103, and it strongly stirs the fluid, further breaking up large fluid masses and making the mixing effect even better. This stage can further refine and mix the fluid preliminarily mixed in the previous stage, making the components that were not fully fused originally more evenly distributed, and significantly improving the quality of mixing.

[0058] Subsequently, the fluid stirred by the second stirring blade 110 enters the region between the outer baffle plate 106 and the inner baffle plate 107. The wavy structures on the outer baffle plate 106 and the inner baffle plate 107 come into play. When the fluid passes through the outer baffle plate 106 and the inner baffle plate 107, it is blocked and guided by the wavy structures, forming strong turbulence, further strengthening the mixing effect, and making the black water and the medicament more evenly dispersed in the fluid. This link greatly enhances the mixing degree of the fluid, making the mixing approach the final high-quality standard, and ensuring that the outflowing mixed fluid is more uniform in composition and properties.

[0059] After that, the third stirring blade 111 located above the outer baffle plate 106 and the inner baffle plate 107 starts to work. The third stirring blade 111 performs a final stirring fine-tuning on the fluid that has passed through the wavy structures on the outer baffle plate 106 and the inner baffle plate 107, further ensuring the uniformity of the mixed fluid, making the composition and properties of the mixed fluid more consistent in each part, and ensuring the stable quality of the finally outflowing mixed fluid. The final stirring process consolidates and optimizes the results of the previous multi-step mixing, making the mixed fluid fully meet the usage requirements.

[0060] Finally, the mixed fluid flows out from the fluid outlet 102 located at the upper part of the housing 101 and enters the subsequent sewage treatment process.

[0061] After actual operation tests, the scale and hardness removal device 1 of the present invention can achieve efficient mixing of black water and chemicals, with a mixing uniformity of over 95%, greatly improving the sewage treatment effect. The entire process is closely coordinated, not only improving the mixing efficiency, but also reducing energy consumption, while reducing the equipment maintenance workload and operating costs, having significant economic benefits and practical value. Compared with traditional mixing devices, this scale and hardness removal device 1 shows obvious advantages in terms of mixing quality, energy utilization, and equipment maintenance, providing a better solution for the liquid mixing needs in related fields.

[0062] In another solution, in the method for purifying black water in the water coal slurry gasification reactor or carbon washing tower, the scale and hardness removal device 1 further includes: At least one ultrasonic component 115, which is arranged at the bottom of the housing 101, and the probes of each ultrasonic component 115 are in contact with the bottom of the housing 101.

[0063] The operation method of the scale and hardness removal device 1 is as follows: After starting the equipment, black water enters the premixing chamber 103 through the black water inlet pipe 104, and the chemicals enter the premixing chamber 103 through the chemical inlet pipe 105. Since both enter from the side walls at the lower part of the premixing chamber 103, the black water and the chemicals quickly converge in the premixing chamber 103, forming an initial flow field conducive to mixing.

[0064] At this time, the first stirring blades 109 located in the premixing chamber 103, above and below the inlets of the black water inlet pipe 104 and the chemical inlet pipe 105, start to work. Driven by the stirring shaft 108, the first stirring blades 109 rotate at a high speed to initially stir and mix the black water and the chemicals, enabling them to come into initial contact and fusion. At the same time, the ultrasonic component 115 arranged inside the premixing chamber 103 starts to emit ultrasonic waves. The high-frequency vibration of the ultrasonic waves acts on the black water and the chemicals, accelerating the movement between molecules and prompting them to mix more quickly, laying a solid foundation for subsequent deep mixing. This initial mixing method is highly efficient, greatly improving the initial mixing efficiency and contributing to enhancing the overall mixing uniformity, laying a solid foundation for achieving high-quality mixing in the subsequent process.

[0065] The mixed fluid flows downward from above the premixing chamber 103 and passes through the frustum-shaped flow guiding plates 112 arranged in a staggered manner. These flow guiding plates 112 are provided with multiple circles of annular protrusions 113, and the openings 114 on the adjacent protrusions 113 on each flow guiding plate 112 are arranged in a staggered manner. When the fluid flows through the flow guiding plates 112, under the action of the annular protrusions 113 and the openings 114, the flow direction and flow velocity of the fluid are continuously changed, forming a complex turbulent flow field. The fluids in different flow layers interpenetrate and collide with each other, further promoting mixing. At the same time, the ultrasonic component 115 installed near the flow guiding plates 112 continuously emits ultrasonic waves, and the energy of the ultrasonic waves further enhances the turbulent effect of the fluid, effectively increasing the contact area and mixing degree between the fluids, improving the mixing effect, making the mixing more sufficient and uniform, and providing a higher-quality basic fluid for the subsequent stirring and mixing processes.

[0066] Next, the fluid reaches the second stirring blade 110. The second stirring blade 110 is located below the premixing chamber 103, and it strongly stirs the fluid to further break up large fluid masses. At the same time, the ultrasonic component 115 located at the bottom of the housing 101 emits high-frequency ultrasonic waves, and the energy of the ultrasonic waves acts on the fluid, causing the tiny particles and molecules in the fluid to generate high-frequency vibrations, cooperating with the stirring action of the second stirring blade 110 to promote mixing and making the mixing effect reach a more refined level. This stage can further refine and mix the fluid preliminarily mixed in the previous stage, making the originally insufficiently fused components more evenly distributed, and significantly improving the quality of mixing.

[0067] Subsequently, the fluid after being stirred by the second stirring blade 110 and acted upon by ultrasonic waves enters the area between the outer baffle plate 106 and the inner baffle plate 107. The wavy structures on the outer baffle plate 106 and the inner baffle plate 107 come into play. When the fluid passes through the outer baffle plate 106 and the inner baffle plate 107, it is blocked and guided by the wavy structures, forming a strong turbulent flow. At this time, the ultrasonic component 115 arranged in the baffle plate area continues to work, and the ultrasonic waves and the turbulent flow act synergistically to further strengthen the mixing effect, making the black water and the medicament more evenly dispersed in the fluid. This link greatly enhances the mixing degree of the fluid, making the mixing approach the final high-quality standard and ensuring that the outflowing mixed fluid is more uniform in composition and properties.

[0068] After that, the third stirring blade 111 located above the outer baffle 106 and the inner baffle 107 starts to work. The third stirring blade 111 performs a final stirring fine-tuning on the fluid after the action of the baffle, further ensuring the uniformity of the mixed fluid. At the same time, the corresponding ultrasonic component 115 emits ultrasonic waves to assist the third stirring blade 111 to make the components and properties of the mixed fluid more consistent in each part, ensuring the stable quality of the finally flowing out mixed fluid. The final stirring and ultrasonic assistance link consolidates and optimizes the results of the previous multi-step mixing, making the mixed fluid fully meet the usage requirements.

[0069] Finally, the mixed fluid flows out from the fluid outlet 102 located at the upper part of the housing 101 and enters the subsequent sewage treatment process.

[0070] In another solution, in the method for purifying the black water of the water coal slurry gasification reactor or the carbon washing tower, each chemical agent introduction pipe 105 tangentially enters from the lower part of the premixing chamber 103 and is separated from the bottom of the premixing chamber 103 by a preset distance, and the height of each chemical agent introduction pipe 105 is lower than the height of each black water introduction pipe 104.

[0071] Each chemical agent introduction pipe 105 tangentially enters from the lower part of the premixing chamber 103, is separated from the bottom of the premixing chamber 103 by a certain distance, and has a height lower than that of each black water introduction pipe 104. This design enables the chemical agent to form a tangential flow when entering the premixing chamber 103, forming a swirling flow with the black water entering from above, increasing the mixing effect of the chemical agent and the black water. The pipe diameter and flow rate of the chemical agent introduction pipe 105 are reasonably designed according to the flow rate of the black water and the dosage of the chemical agent to ensure that the chemical agent can be evenly dispersed in the black water.

[0072] Each chemical agent introduction pipe 105 tangentially enters from the lower part of the premixing chamber 103 and has a height lower than that of the black water introduction pipe 104, enabling the chemical agent to better mix with the black water, improving the mixing effect, ensuring the uniform distribution of the chemical agent in the black water, and thus improving the scale removal and softening effects.

[0073] In another solution, in the method for purifying the black water of the water coal slurry gasification reactor or the carbon washing tower, there are 3 - 6 black water introduction pipes 104, all the black water introduction pipes 104 are evenly distributed on the same circumference, and spiral swirling nozzles are used at the outlets of each black water introduction pipe 104.

[0074] 3 - 6 black water introduction pipes 104 are used and evenly distributed on the same circumference. Spiral swirling nozzles are used at the outlets of each black water introduction pipe 104. When the black water passes through the spiral swirling nozzle, the formed spiral swirling direction is adapted to the rotation direction of the stirring component in the premixing chamber 103, enabling the black water to better integrate into the flow field formed by stirring, improving the mixing efficiency of the stirring component for the black water and the chemical agent, and providing good conditions for the subsequent scale removal and softening reactions.

[0075] In another solution, in the purification method of the black water of the water coal slurry gasification reactor or the carbon washing tower, the inner baffle 107 is connected to the premixing chamber 103 through a plurality of first connecting rods 116, and is connected to the housing 101 through a plurality of second connecting rods 117. The premixing chamber 103 is connected to the housing 101 through a plurality of third connecting rods 118. Each of the first connecting rods 116, each of the second connecting rods 117, and each of the third connecting rods 118 is spaced apart from the stirring assembly by a preset distance.

[0076] The inner baffle 107 and the premixing chamber 103 are stably connected to the housing 101 through connecting rods, and each connecting rod is spaced apart from the stirring assembly by a preset distance, ensuring the stable layout and operation of each component in the scale removal and softening device 1, avoiding mutual interference between components, and improving the stability and reliability of the equipment.

[0077] In another solution, in the purification method of the black water of the water coal slurry gasification reactor or the carbon washing tower, the housing 101, the stirring shaft 108, the inner baffle 107, the outer baffle 106, the premixing chamber 103, and each baffle 112 are coaxially arranged. The generatrix of each baffle 112 forms an angle of 30 - 45 degrees with the vertical direction, and the cross-section of each ring of protrusions 113 is an upward-arching arc.

[0078] Components such as the housing 101, the stirring shaft 108, and the inner baffle 107 are coaxially arranged. The generatrix of the baffle 112 forms an angle of 30 - 45 degrees with the vertical direction, and the cross-section of the protrusion 113 is an upward-arching arc, optimizing the structure of the baffle 112, making the flow of the fluid in the scale removal and softening device 1 more reasonable, promoting mixing and reaction, and improving the efficiency of scale removal and softening.

[0079] Although the embodiments of the present invention have been disclosed as above, they are not limited to only the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional modifications can be easily made. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to the specific details and the illustrated examples here.

Claims

1. A method for purifying black water from a coal-water slurry gasification reactor or a carbon scrubber, characterized in that: include: Lead the black water into the descaling softener, add the scale inhibitor or acid solution into the descaling softener, and fully mix the black water and the agent under stirring; The black water treated by the descaling and softening device enters the filter to separate the solid and liquid in the black water to obtain filter residue and clear liquid; The filter residue is introduced into the filter residue tank, and the solid water in the filter residue tank is flash evaporated and then reused for coal blending, or dried to become dry residue; After the clear liquid undergoes high-pressure flash evaporation, part of it is used as quenching water for the carbon washing tower and gasification reactor, and the other part is further subjected to low-pressure flash evaporation and vacuum flash evaporation before being used for coal slurry preparation or discharged as wastewater.

2. The method for purifying black water from a water-coal slurry gasification reactor or a carbon washing tower according to claim 1, characterized in that: The filter adopts a microsphere metal powder coated filter element with a filtration accuracy of 0.1 μm and an operating pressure of 4-6.5 MPa, and separates solid particles with a particle size greater than 0.1 μm to obtain filter residues and a clear liquid with a solid content less than 50 ppm.

3. The method for purifying black water from a water-coal slurry gasification reactor or a carbon washing tower according to claim 1, characterized in that: After the clear liquid is subjected to high-pressure flash evaporation, a portion is used as quenching water for the carbon washing tower and the gasification reactor, and the other portion is further subjected to low-pressure flash evaporation and vacuum flash evaporation, and then used for coal slurry preparation. The steps include: High-pressure flash evaporation: The clear liquid is placed under high-pressure flash evaporation conditions of 1.0-2.0 MPa and 150-180°C. After flash evaporation, the clear liquid is divided into two parts; The first part of the clear liquid is directly recycled to the quench water system of the carbon scrubber and the gasification reactor; The second part of the clear liquid is subjected to low-pressure flash evaporation and vacuum flash evaporation in sequence, and then enters the pH adjustment tank. In the pH adjustment tank, a NaOH solution with a mass concentration of 5-10% is added to the clear liquid through a static mixer to adjust the pH of the clear liquid to 6.5-7.5; the adjusted clear liquid is transported to the water replenishment system of the gasification reactor through a centrifugal pump and mixed with fresh water for coal slurry preparation; An online pH meter and turbidity meter are installed at the outlet of the pH adjustment tank to monitor the pH value and turbidity of the clear liquid in real time and control the turbidity of the clear liquid to ≤10NTU. At the same time, the temperature of the reused clear liquid is reduced to ≤40°C through a heat exchanger.

4. The method for purifying black water from a water-coal slurry gasification reactor or a carbon washing tower according to claim 2, characterized in that: Also includes: When the filter cake in the filter reaches a preset thickness, the slag discharge operation is performed, so that the filter cake and the solution attached to the filter cake and mixed in it are flushed into the filter residue tank.

5. The method for purifying black water from a water-coal slurry gasification reactor or a carbon scrubber according to claim 1, characterized in that: The descaling and softening device comprises: The shell is in the shape of a hollow cylinder, and a fluid outlet is provided at the upper portion of the shell; The premixing chamber is in the shape of a cylinder with a hollow interior and an open top, and is vertically disposed in the lower portion of the shell and spaced a preset distance from the bottom of the shell; at least one black water inlet pipe, each of which is connected to the side wall of the lower part of the premixing chamber and communicates with the interior of the premixing chamber; At least one medicine introduction tube, each medicine introduction tube is connected to the side wall of the lower part of the premixing chamber and communicated with the interior of the premixing chamber; A baffle assembly, comprising an outer baffle plate and an inner baffle plate arranged at intervals, wherein the main body of the outer baffle plate is cylindrical and fixed on the inner side wall of the shell, the inner side wall of the outer baffle plate and the outer side wall of the inner baffle plate are both provided with a wavy structure, and the wave crests and wave troughs on the outer baffle plate are respectively opposite to the wave crests and wave troughs on the inner baffle plate, the upper part of the inner baffle plate is cylindrical and is located above the premixing chamber and is separated from the premixing chamber by a preset distance, and the lower part of the inner baffle plate is cylindrical and covers the premixing chamber; A stirring assembly, comprising a stirring shaft, a plurality of first stirring blades, a plurality of second stirring blades and a plurality of third stirring blades; the stirring shaft is rotatably connected to the top and bottom of the shell, and vertically penetrates the inner baffle and the premixing chamber, and is rotatably connected to the inner baffle and the premixing chamber; each first stirring blade is located in the premixing chamber, and first stirring blades are provided above and below the entrances of the black water inlet pipe and the reagent inlet pipe, each second stirring blade is located below the premixing chamber, and each third stirring blade is located above the outer baffle and the inner baffle; A guide assembly comprises a plurality of guide plates which are staggered and arranged at intervals. The plurality of guide plates are respectively located on the inner wall of the lower part of the inner baffle plate and the outer wall of the premixing chamber. The guide plate on the inner baffle plate is in the shape of an inverted truncated cone and is separated from the premixing chamber by a preset distance. The guide plate on the premixing chamber is in the shape of a truncated cone and is separated from the inner baffle plate by a preset distance. The guide plate located at the top is arranged on the premixing chamber. The guide plate is provided with a plurality of circles of annular protrusions at intervals along its generatrix direction. Each circle of protrusions is provided with at least one pair of openings, and the openings on adjacent protrusions on each guide plate are staggered. The fluid on the guide plate on the inner baffle plate can flow into the innermost protrusion on the guide plate below it, and the fluid on the guide plate on the premixing chamber can flow to the outside of the outermost protrusion on the guide plate below it.

6. The method for purifying black water from a water-coal slurry gasification reactor or a carbon scrubber according to claim 5, characterized in that: The descaling and softening device further comprises: At least one ultrasonic component is arranged at the bottom of the shell, and the probe of each ultrasonic component is in contact with the bottom of the shell.

7. The method for purifying black water from a water-coal slurry gasification reactor or a carbon scrubber according to claim 5, characterized in that: Each reagent introduction pipe enters tangentially from the lower part of the premixing chamber and is separated from the bottom of the premixing chamber by a preset distance. The height of each reagent introduction pipe is lower than the height of each black water introduction pipe.

8. The method for purifying black water from a coal-water slurry gasification reactor or a carbon scrubber according to claim 7, characterized in that: There are 3 to 6 black water inlet pipes, all of which are evenly distributed on the same circumference, and spiral swirl nozzles are used at the outlets of the black water inlet pipes.

9. The method for purifying black water from a water-coal slurry gasification reactor or a carbon scrubber according to claim 5, characterized in that: The inner baffle is connected to the premixing chamber through a plurality of first connecting rods, and is connected to the shell through a plurality of second connecting rods. The premixing chamber is connected to the shell through a plurality of third connecting rods. Each of the first connecting rods, each of the second connecting rods, and each of the third connecting rods is separated from the stirring assembly by a preset distance.

10. The method for purifying black water from a water-coal slurry gasification reactor or a carbon scrubber according to claim 5, characterized in that: The shell, the stirring shaft, the inner baffle, the outer baffle, the premixing chamber and each guide plate are coaxially arranged, the angle between the generatrix of each guide plate and the vertical direction is 30-45 degrees, and the cross section of each circle of protrusions is an upwardly arched arc.

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