A device and method for treating space furnace gasification black water

Abstract

This invention relates to the field of wastewater treatment technology, specifically to a treatment device and method for black water from aerospace furnace gasification. The treatment device includes a high flash tank, a true flash tank, and a settling tank. An alkali addition device is connected to the black water delivery pipeline of the high flash tank. By removing calcium and magnesium ions at the source of the black water, source treatment is achieved. At the same time, the expensive equipment or the large area of ​​the settling tank are eliminated, reducing equipment scaling problems. Various components in the black water are fully utilized as resources.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a device and method for treating black water from aerospace furnace gasification. Background Technology

[0002] The coal chemical industry generates gasified black water during the production process using aerospace furnaces. This black water contains a large amount of coal ash, as well as calcium and magnesium metals and gases such as carbon dioxide and hydrogen sulfide dissolved in water. Under normal circumstances, the gasified black water is sent to a settling tank after two-stage flash evaporation, where flocculants are added for sedimentation. The slurry is then filtered and treated.

[0003] Although new gasification processes have been industrialized on a large scale and can operate stably for extended periods, the slag and wastewater treatment systems are not yet perfect; in particular, the black water produced by coal gasification contains high levels of calcium. 2+ and Mg 2+ The water has high hardness and is prone to scaling at high temperatures, which can cause pipe blockage. In addition, existing calcium and magnesium ion hardness removal devices have the problems of large footprint, high investment, and short operating time.

[0004] Therefore, there is a need for a device and method for the resource utilization of gasified black water, which can be used to treat the gasified black water and delay scaling. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a device and method for treating gasified black water from aerospace furnaces, thereby delaying the scaling problem of the gasified black water. Another objective of this invention is to simplify the treatment device for gasified black water, reducing equipment investment and floor space requirements.

[0006] A treatment device for gasified black water from an aerospace furnace includes a gasified black water conveying pipeline, wherein an alkali addition device is connected to the gasified black water conveying pipeline, and the alkali addition device includes an alkali storage device storing an alkali solution with a mass fraction of 25% sodium hydroxide solution.

[0007] Adding alkali solution can induce the precipitation of calcium and magnesium ions. Simultaneously, the abundant solid particles in the gasified black water act as crystallization nuclei and crystallization aids, promoting the growth of calcium and magnesium ions on their surface to form precipitates. The high temperature of the gasified black water before flash evaporation, approximately 200°C, also promotes precipitation. Furthermore, during flash evaporation, the high-pressure differential of the gasified black water, agitated during alkali addition and transport, further promotes the growth of calcium and magnesium precipitate crystals. The high solids content of the black water, combined with the concentration of calcium and magnesium ions on the solid particles in the fluid, reduces the adhesion of calcium and magnesium ions to pipe and container walls, minimizing blockages and extending the system's operating cycle.

[0008] Before entering the high flash tank, the gasification black water from the aerospace furnace contains a high concentration of dissolved carbon dioxide. After adding sodium hydroxide solution, the carbon dioxide reacts with the calcium and magnesium ions in the gasification black water to produce precipitation. The pH is adjusted rapidly, and the carbon dioxide in the gasification black water can be fully utilized, reducing subsequent inputs.

[0009] Furthermore, the alkali addition device also includes an alkali addition pipeline, which is equipped with an alkali flow meter and an alkali regulating valve.

[0010] Furthermore, the alkali addition device makes the ratio of the hardness of the gasified black water in the gasified black water conveying pipeline to the mass concentration of sodium hydroxide in the gasified black water after alkali addition 1:0.5-0.6.

[0011] A suitable concentration can effectively utilize carbon dioxide to form calcium and magnesium precipitates while saving costs.

[0012] Furthermore, the gasified black water conveying pipeline is connected to a high flash tank at its end, a true flash tank at its lower end, and a settling tank at its lower end; wherein a pH meter is installed on the pipeline connecting the high flash tank and the true flash tank.

[0013] The alkali addition pipeline is installed on the gasified black water delivery pipeline to accelerate the pH adjustment of the gasified black water, reduce scaling and blockage in the pipeline, and the alkali flow meter and alkali regulating valve can work together with the pH meter to adjust the pH of the gasified black water so that the concentration of alkali added to the gasified black water is suitable for the formation of calcium and magnesium precipitates.

[0014] Furthermore, a high flash pressure reducing valve is provided on the gasified black water conveying pipeline, and an alkali spray nozzle is provided inside the gasified black water conveying pipeline. The alkali spray nozzle is located between the high flash pressure reducing valve and the high flash tank, and the alkali spray nozzle is connected to the alkali addition pipeline.

[0015] Furthermore, it also includes a slurry pump and a filter press, wherein the inlet of the slurry pump is connected to the lower end of the settling tank, and the outlet of the slurry pump is connected to the filter press.

[0016] Slurry pumps and filter presses can dewater slurry, and the resulting filter cake can be recycled.

[0017] Furthermore, it also includes a boiler, the fuel of which is coal and the filter cake pressed out by the filter press.

[0018] The filter cake that settles from the gasified black water is fed into a boiler for incineration, which reduces the amount of coal used.

[0019] A method for treating black water from aerospace furnace gasification includes the following steps:

[0020] Step S1: Add sodium hydroxide to the gasified black water before it enters the high flash tank to obtain alkali-added gasified black water;

[0021] Step S2: The alkaline-treated gasified black water obtained in step S1 is subjected to high flash and true flash to obtain atmospheric pressure gasified black water;

[0022] Step S3: The atmospheric pressure gasification black water obtained in step S2 is settled to obtain slurry and supernatant; wherein, the supernatant is reused.

[0023] Step S4: Dewater the slurry obtained in step S3 to obtain filter cake; the filter cake is then co-fired with coal.

[0024] The method for treating gasified black water from aerospace furnaces of the present invention can make full use of the carbon dioxide in the gasified black water to treat the calcium and magnesium ions in the gasified black water, and the resulting product can also be utilized as a resource.

[0025] Furthermore, the ratio of hardness to sodium hydroxide mass concentration in the alkali-treated gasified black water is 1:0.55, and the total hardness in the supernatant is 500-600 mg / L.

[0026] It facilitates the reaction between carbon dioxide and calcium and magnesium ions, promotes the precipitation of calcium and magnesium ions, and does not affect the reuse of the supernatant.

[0027] Furthermore, the filter cake contains uniformly distributed calcium carbonate and magnesium carbonate.

[0028] The filter cake is co-fired with coal, and the calcium carbonate in the filter cake acts as a sulfur fixative to achieve in-furnace desulfurization in circulating fluidized bed boilers, which can save the amount of ammonia water used in existing ammonia desulfurization methods.

[0029] Beneficial effects

[0030] 1. This invention removes calcium and magnesium ions at the source of gasified black water, achieving source treatment. It fully utilizes the characteristics of black water, such as high solid content, high temperature, high flow rate, and rich carbon dioxide, to promote the precipitation of calcium and magnesium ions and reduce scaling and clogging problems in reaction pipe sections, downstream black water system pipelines and equipment, enabling the system to operate effectively for a long time.

[0031] 2. This invention does not require an additional calcium and magnesium settling tank, resulting in lower investment and cost savings. Calcium and magnesium precipitates do not require manual cleaning, thus saving labor costs.

[0032] 3. The treatment method of the present invention enables full utilization of dissolved carbon dioxide in gasified black water, reducing the equipment investment required for carbon dioxide replenishment.

[0033] 4. This invention makes full use of calcium carbonate in the filter cake as a desulfurizing agent, thereby reducing the consumption of desulfurizing agent (ammonia water) in circulating fluidized bed boilers. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the structure of the present invention.

[0035] The attached diagram is labeled as follows: 1. Alkali flow meter; 2. Alkali regulating valve; 3. High flash pressure reducing valve; 4. High flash tank; 5. True flash tank; 6. Settling tank; 7. Slurry pump; 8. Coal; 9. Filter press; 10. Boiler; 11. pH meter. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the research and development background of this invention will be introduced first.

[0037] The existing aerospace furnace gasification black water treatment equipment includes a gasification black water conveying pipeline, a high flash tank 4, a true flash tank 5, a settling tank 6, a sedimentation tank, and a filter press 9. The gasification black water discharged from the aerospace furnace has a solid content of about 24,000 mg / L and contains metal ions such as coal ash, calcium and magnesium, as well as gases such as carbon dioxide and hydrogen sulfide dissolved in water. Part of it comes from the aerospace furnace (designed to be 120 t / h) and part comes from the scrubbing tower (each aerospace furnace is equipped with a scrubbing tower, designed to be 30 t / h). The two aerospace furnaces together send about 300 t / h of gasification black water to the high flash tank 4. Through high-pressure flash evaporation, the temperature of the gasification black water is reduced from 200℃ to 158℃, and the pressure is reduced from 3.8 MPa (absolute pressure, the same below) to 0.6 MPa. The steam volume after high flash is 30 t / h, and the condensate volume after high flash is 270 t / h.

[0038] Approximately 270 t / h of gasified black water from the bottom of the high flash tank 4 is fed into the true flash tank 5 for flash evaporation, where the temperature drops from 158℃ to 98℃ and the pressure drops from 0.6 MPa to 0.09 MPa. The steam volume after vacuum flash evaporation of the gasified black water from the bottom of the high flash tank 4 is 28 t / h, and the condensate volume after vacuum flash evaporation is 242 t / h.

[0039] The gasified black water after two-stage flash evaporation is sent to settling tank 6, where flocculant is added for sedimentation. The slurry is then sent to a filter press for filtration, with a daily filter cake production of 240-300 cubic meters. The filter cake contains 25%-35% residual carbon and is sold externally. In 2024, the gasification filter cake was classified as solid waste, making it more difficult to sell externally and posing a risk of system shutdown.

[0040] The present invention will be further described in detail below with reference to specific embodiments:

[0041] like Figure 1 As shown, a treatment device for gasified black water from an aerospace furnace includes a gasified black water conveying pipeline, and an alkali addition device is connected to the gasified black water conveying pipeline. The alkali addition device includes an alkali storage device storing an alkali solution with a mass fraction of 25% sodium hydroxide solution.

[0042] The partial pressure of carbon dioxide inside the aerospace furnace is 0.38 MPa, and the dissolved carbon dioxide content is approximately 100 Nm³. 3 / h, which is 333 L / m³ of carbon dioxide dissolved in the gasified black water. 3The amount of carbon dioxide is about twice that required for the formation of calcium and magnesium precipitates, providing excess carbon dioxide for the precipitation. The solid content in the gasified black water is 20,000-30,000 mg / L, and the calcium and magnesium ion content is 1200-1500 mg / L. The carbon dioxide dissolved in the water cannot directly react with the calcium and magnesium ions to form precipitates; a reaction requires an alkaline environment. An alkali addition device and nozzle are added to a short section after the high-flash pressure reducing valve 3 at the high-flash inlet, providing a suitable pH range (calculated to be 10-12) in the initial stage of the reaction between carbon dioxide and calcium and magnesium ions. The combination of calcium and magnesium ions with carbonate ions forms light calcium carbonate, which grows on the surface of solid particles in the black water. After the pressure is reduced by the high-flash pressure reducing valve 3 upstream of the high-flash tank 4, the pressure of the gasified black water decreases to 0.6 MPaG. A short pipe section of about 0.5 m serves as the reaction section. Although the partial pressure of carbon dioxide decreases, it remains in the reaction section and does not enter the flash tank. The carbon dioxide is not released from the black water and remains mixed with the gasified black water, providing favorable reaction conditions.

[0043] The original carbon dioxide-based calcium and magnesium hardness removal device used the supernatant from settling tank 6 (gasified ash water, temperature 80℃, turbidity 10-20 NTU) as the reaction raw material. By adding alkali and carbon dioxide gas to the ash water, calcium and magnesium ions reacted to form calcium magnesium carbonate precipitates. After precipitation, the ash water was returned to the gasification system for recycling. The precipitation reaction was concentrated at the alkali addition point and proceeded rapidly, resulting in severe scaling and pipe blockage at this location. The equipment needed to be disassembled and cleaned approximately every 10-20 days. Because the generated light calcium magnesium carbonate precipitates slowly, a separate, large-area sedimentation tank needed to be installed outside settling tank 6, significantly reducing production space, and the precipitated sludge required manual cleaning.

[0044] The abundant solid particles in the gasified black water act as crystallizers. The agitation of the high-pressure differential gasified black water promotes the collision of light calcium and magnesium carbonate, which in turn promotes grain growth and accelerates the formation of calcium and magnesium precipitates. This promotes the growth of calcium and magnesium carbonate particles on the surface of solid particles, forming calcium and magnesium ion precipitates. In addition, the flushing effect of the high-solids black water helps to prevent crystallization on the pipe wall. The high temperature of the gasified black water at 200℃ can accelerate the formation of calcium carbonate crystal precipitates.

[0045] The alkali addition device also includes an alkali addition pipeline, on which an alkali flow meter 1 and an alkali regulating valve 2 are provided.

[0046] The alkali addition device ensures that the ratio of the hardness of the gasified black water in the gasified black water conveying pipeline to the mass concentration of sodium hydroxide in the gasified black water after alkali addition is 1:0.5-0.6.

[0047] The gasified black water conveying pipeline is connected to a high flash tank 4 at its end, and the lower end of the high flash tank 4 is connected to a true flash tank 5. The lower end of the true flash tank 5 is connected to a settling tank 6. A pH meter 11 is installed on the pipeline connecting the high flash tank 4 and the true flash tank 5.

[0048] The gasified black water conveying pipeline is equipped with a high flash pressure reducing valve 3, and an alkali spray nozzle is installed inside the gasified black water conveying pipeline. The alkali spray nozzle is located between the high flash pressure reducing valve 3 and the high flash tank 4, and the alkali spray nozzle is connected to the alkali addition pipeline.

[0049] It also includes a slurry pump 7 and a filter press 9. The inlet of the slurry pump 7 is connected to the lower end of the settling tank 6, and the outlet of the slurry pump 7 is connected to the filter press 9.

[0050] It also includes a boiler 10, the fuel of which is coal 8 and filter cake pressed out by the filter press 9.

[0051] A method for treating black water from aerospace furnace gasification includes the following steps:

[0052] Step S1: Add sodium hydroxide to the gasified black water before it enters the high flash tank 4 to obtain alkali-added gasified black water;

[0053] Step S2: The alkaline-treated gasified black water obtained in step S1 is subjected to high flash and true flash to obtain atmospheric pressure gasified black water;

[0054] Step S3: The atmospheric pressure gasification black water obtained in step S2 is settled to obtain slurry and supernatant; wherein, the supernatant is reused.

[0055] Step S4: Dewater the slurry obtained in step S3 to obtain filter cake; the filter cake is then co-fired with coal 8.

[0056] The method for treating gasified black water from aerospace furnaces of the present invention can make full use of the carbon dioxide in the gasified black water to treat the calcium and magnesium ions in the gasified black water, and the resulting product can also be utilized as a resource.

[0057] The filter cake contains calcium carbonate and magnesium carbonate evenly distributed.

[0058] The calcium and magnesium precipitate after the reaction and the concentrated gasified black water enter the settling tank 6. Using existing flocculation and settling equipment, the sedimentation is accelerated after adding flocculants. The separated slurry is pumped 7 to the filter press 9 for filtration. The gasified filter cake containing calcium and magnesium carbonate has a water content of about 35%-40%, a lower heating value of 1100-1500 kcal / kg, and a yield of about 150-180 t / d. It is then sent to the thermal power plant and mixed with coal 8 before being sent to the boiler 10 for use as fuel. The calcium carbonate in the filter cake acts as a desulfurizing agent. Compared with the existing method of adding calcium carbonate as a desulfurizing agent to coal 8, this method results in more thorough mixing of calcium carbonate and higher desulfurization efficiency.

[0059] By adding alkali to precipitate and separate calcium carbonate at a rate of approximately 210 kg / h to 300 kg / h, it is mixed with the filter cake and coal 8 and sent to boiler 10 for combustion as a desulfurizing agent. The effectiveness of calcium carbonate as a desulfurizing agent is about 30%. This can save the amount of ammonia water with an effective ammonia content of 25% in the existing ammonia desulfurization method, save 4500 kcal / kg of coal 8, reduce solid waste emissions, and recover about 100 tons of water per day.

[0060]

[0061] This method removes calcium and magnesium ions at the source of black water gasification, achieving source control. Existing gasification descaling methods also use devices that use carbon dioxide with alkali or directly with sodium carbonate to promote the precipitation of calcium and magnesium ions as a bypass for grey water. These methods suffer from several drawbacks: difficulty in precipitation formation; the need for large-scale sedimentation tanks (calcium and magnesium ions combine with carbonate ions to form light calcium carbonate, which is usually produced by chemical reactions and is suspended in water as flocculent particles, making it difficult to precipitate and separate); and the need for manual removal of the calcium and magnesium precipitate, resulting in high labor intensity. Furthermore, the method requires significant investment and a large land area for new sedimentation tanks. This method overcomes these shortcomings, simultaneously achieving calcium and magnesium precipitation, resource utilization of carbon in the filter cake, reducing carbon dioxide emissions, and saving on the investment and construction costs of sedimentation tanks.

[0062] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Claims

1. A treatment device for gasified black water from an aerospace furnace, comprising a gasified black water conveying pipeline, characterized in that, The gasified black water conveying pipeline is connected to an alkali addition device, which includes an alkali storage device storing a 25% (by mass) sodium hydroxide solution. The gasified black water conveying pipeline is connected to a high-pressure flash tank (4) at its end, and the lower end of the high-pressure flash tank (4) is connected to a vacuum flash tank (5). The lower end of the vacuum flash tank (5) is connected to a settling tank (6). The gasified black water conveying pipeline is equipped with a high-flash pressure reducing valve (3), and an alkali spray nozzle is installed inside the gasified black water conveying pipeline. The alkali spray nozzle is located between the high-flash pressure reducing valve (3) and the high-pressure flash tank (4), and the alkali spray nozzle is connected to the alkali addition pipeline. The alkali addition device also includes an alkali addition pipeline, on which an alkali flow meter (1) and an alkali regulating valve (2) are provided. It also includes a slurry pump (7) and a filter press (9), wherein the inlet of the slurry pump (7) is connected to the lower end of the settling tank (6) and the outlet of the slurry pump (7) is connected to the filter press (9). The temperature of the black water vaporized before flash evaporation is 200℃. The solid content of the gasified black water is 20,000-30,000 mg / L, the calcium and magnesium ion content is 1,200-1,500 mg / L, and the gasified black water flow rate is 300 t / h. The partial pressure of carbon dioxide inside the aerospace furnace is 0.38 MPa, and the dissolved carbon dioxide content is 100 Nm³. 3 / h.

2. The treatment device for black water from aerospace furnace gasification according to claim 1, characterized in that, The alkali addition device ensures that the ratio of the hardness of the gasified black water in the gasified black water conveying pipeline to the mass concentration of sodium hydroxide in the gasified black water after alkali addition is 1:0.5-0.

6.

3. The treatment device for black water from aerospace furnace gasification according to claim 1, characterized in that, A pH meter (11) is installed on the pipeline connecting the high-pressure flash tank (4) and the vacuum flash tank (5).

4. The treatment device for black water from aerospace furnace gasification according to claim 1, characterized in that, It also includes a boiler (10) fueled by coal (8) and filter cake pressed by the filter press (9).

5. A method for treating black water from aerospace furnace gasification, using the treatment apparatus for black water from aerospace furnace gasification as described in any one of claims 1-4, characterized in that, Includes the following steps: Step S1: Add sodium hydroxide to the gasified black water before it enters the high-pressure flash tank (4) to obtain alkali-added gasified black water; Step S2: The alkali-added gasified black water obtained in step S1 is mixed in the reaction tube section and then subjected to high flash and true flash to obtain atmospheric pressure gasified black water. Step S3: The atmospheric pressure gasification black water obtained in step S2 is settled to obtain slurry and supernatant; wherein, the supernatant is reused. Step S4: Dewater the slurry obtained in step S3 to obtain filter cake; the filter cake is then co-fired with coal (8).

6. The method for treating black water from aerospace furnace gasification according to claim 5, characterized in that, The ratio of hardness to sodium hydroxide mass concentration in the alkaline gasified black water is 1:0.55, and the total hardness in the supernatant is 500-600 mg / L.

7. The method for treating black water from aerospace furnace gasification according to claim 5, characterized in that, The filter cake contains calcium carbonate and magnesium carbonate evenly distributed.

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