A multi-stage flash evaporation acid liquid recycling system

Abstract

The application relates to a multistage flash evaporation acid liquid recycling system, which comprises a preheating unit, a high-pressure reaction kettle, a flash evaporation unit and a gas-liquid separator. The preheating unit comprises at least one preheating tower which is communicated with a first feeding port of the high-pressure reaction kettle and is used for preheating ore pulp. The flash evaporation unit comprises at least one flash evaporation tank which is communicated with a first discharging port of the high-pressure reaction kettle and is used for flash evaporation of the reacted ore pulp. The steam outlet of the flash evaporation tank is communicated with a heat exchanger of the preheating tower through a steam pipe, and the gas-liquid separator is arranged on the steam pipe and is used for separating sulfuric acid liquid drops in water vapor. Compared with the prior art, the multistage flash evaporation acid liquid recycling system provided by the application is provided with the gas-liquid separator on the steam pipeline of the flash evaporation tank, sulfuric acid in steam is separated and recovered, only the pipeline before the gas-liquid separator needs to be subjected to corrosion prevention treatment, scaling of the preheating tower is avoided, the cost of pipeline corrosion prevention treatment is reduced, and waste of sulfuric acid is reduced.

Description

Technical Field

[0001] This application relates to the field of chemical equipment technology, and in particular to a multi-stage flash evaporation acid recovery system. Background Technology

[0002] Flash evaporation involves transferring a high-pressure slurry from a high-pressure reactor into a lower-pressure container. The sudden pressure drop transforms the slurry into saturated steam and saturated slurry at the lower pressure of the container. Since the boiling point of a substance is proportional to its pressure, this decompression lowers the boiling point of the high-pressure, high-temperature slurry, allowing it to enter the flash evaporation process. The purpose of the flash evaporator is to provide a space for rapid vaporization and gas-liquid separation of the fluid.

[0003] In the hydrometallurgical process for laterite nickel ore, ore slurry, sulfuric acid, and steam are typically injected into a high-pressure reactor for smelting to extract nickel and cobalt from the ore. After the reaction, the ore slurry and sulfuric acid are introduced into a flash tank for depressurization. As steam is generated, some sulfuric acid droplets are also agitated by the vibrations caused by the steam, forming acid mist that is discharged along with the steam.

[0004] Because steam contains sulfuric acid, when using this steam to preheat the slurry, the sulfuric acid will react with the slurry in the preheating tower to produce precipitation, resulting in scaling inside the preheating tower; in addition, it will also cause corrosion of the steam pipes and additional consumption of sulfuric acid. Utility Model Content

[0005] In view of this, it is necessary to provide a multi-stage flash acid recovery system to solve the technical problem that the steam generated by the flash tank contains sulfuric acid, which causes scaling inside the preheating tower, corrodes the steam delivery pipeline, and increases sulfuric acid consumption when preheating the slurry.

[0006] This application provides a multi-stage flash acid recovery system, which includes: a preheating unit, a high-pressure reactor, a flash unit, and a gas-liquid separator. The preheating unit includes at least one preheating tower connected to the first inlet of the high-pressure reactor for preheating the slurry. The flash unit includes at least one flash tank connected to the first outlet of the high-pressure reactor for flashing the reacted slurry. The steam outlet of the flash tank is connected to the heat exchanger of the preheating tower via a steam pipe. The gas-liquid separator is installed on the steam pipe for separating sulfuric acid droplets from the water vapor.

[0007] Furthermore, the preheating unit includes multiple preheating towers connected in series, and the flash evaporation unit includes multiple flash tanks connected in series. The preheating towers and flash tanks correspond one-to-one according to their position relative to the high-pressure reactor. The steam outlet of the flash tank is connected to the heat exchanger of the corresponding preheating tower via a steam pipe.

[0008] Furthermore, the preheating tower has a second inlet, a second outlet, and a heat exchanger interface, and the second outlet of the preheating tower is connected to the second inlet of the next preheating tower.

[0009] Furthermore, the flash tank has a third feed inlet, a third discharge outlet, and a steam outlet. The third discharge outlet of the flash tank is connected to the third feed inlet of the next flash tank, and the steam outlet of the flash tank is connected to the heat exchanger interface of the corresponding preheating tower through a steam pipe.

[0010] Furthermore, the gas-liquid separator includes a shell and a liquid-separating baffle. The shell has a separation chamber and also forms an air inlet, an air outlet, and a liquid outlet that connect the separation chamber. The liquid-separating baffle is arranged on the airflow path between the air inlet and the air outlet, and the liquid outlet is located below the liquid-separating baffle. The air inlet is connected to the steam outlet of the flash tank, and the air outlet is connected to the heat exchanger interface of the preheating tower.

[0011] Furthermore, the bottom surface of the outer shell is sloped, and the liquid outlet is located at the lowest point of the slope.

[0012] Furthermore, the separating baffle has multiple bends to divide the flow into multiple bends within the separation chamber. When water vapor passes through the flow, sulfuric acid droplets will impact the separating baffle and drip off.

[0013] Furthermore, the gas-liquid separator also includes a liquid storage tank, with an outlet connected to the upper end of the tank and a closable drain port at the lower end.

[0014] Furthermore, it also includes a sulfuric acid collection tank, with the drain outlet connected to the sulfuric acid collection tank via a sulfuric acid pipe, which is equipped with a valve.

[0015] Furthermore, the steam pipe comes into contact with the sulfuric acid collection tank to heat the sulfuric acid inside the tank.

[0016] Compared with the prior art, the multi-stage flash evaporation acid recovery system provided in this application is equipped with a gas-liquid separator on the steam pipeline of the flash tank to separate and recover sulfuric acid from the steam. Only the pipeline before the gas-liquid separator needs to be treated with anti-corrosion, which avoids scaling in the preheating tower, reduces the cost of pipeline anti-corrosion treatment, and also reduces the waste of sulfuric acid.

[0017] The above description is merely an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it according to the contents of the specification, the preferred embodiments of this application are described in detail below with reference to the accompanying drawings. The specific implementation methods of this application are given in detail in the following embodiments and their accompanying drawings. Attached Figure Description

[0018] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0019] Figure 1 is a schematic diagram of a preferred embodiment of the multi-stage flash acid recovery system provided in this application;

[0020] Figure 2 for Figure 1 Cross-sectional view of a gas-liquid separator. Detailed Implementation

[0021] The preferred embodiments of this application are described in detail below with reference to the accompanying drawings, which constitute a part of this application and are used together with the embodiments of this application to illustrate the principles of this application, but are not intended to limit the scope of this application.

[0022] Please see Figure 1 This application provides a multi-stage flash acid recovery system. This system can be applied in the smelting of laterite nickel ore to recover sulfuric acid from the steam generated in the flash tank, thereby preventing sulfuric acid from corroding pipelines.

[0023] It should be noted that the multi-stage flash acid recovery system of this application is used, but not limited to, in the smelting of laterite nickel ore, and can also be applied to other smelting production processes that require sulfuric acid and flash tanks. In this application, only the application of the multi-stage flash acid recovery system in the smelting of laterite nickel ore is used as an example for illustration. The principle of the multi-stage flash acid recovery system applied to the smelting of other ores is essentially the same as that applied to the smelting of laterite nickel ore, and will not be elaborated here.

[0024] This multi-stage flash evaporation acid recovery system includes a preheating unit 1, a high-pressure reactor 2, a flash evaporation unit 3, and a gas-liquid separator 4. The preheating unit 1 includes at least one preheating tower connected to the first inlet of the high-pressure reactor 2 for preheating the slurry. The slurry is first transported to the preheating tower and preheated to a certain temperature before being transported to the high-pressure reactor 2 for reaction. The flash evaporation unit 3 includes at least one flash tank connected to the first outlet of the high-pressure reactor 2 for flash evaporation of the reacted slurry, reducing pressure and temperature. The steam outlet of the flash tank is connected to the heat exchanger of the preheating tower via a steam pipe 5. The steam generated by the flash tank still has a high temperature and can be used to preheat the slurry to fully utilize energy. The gas-liquid separator 4 is installed on the steam pipe 5 to separate sulfuric acid droplets from the steam. This prevents sulfuric acid from corroding the steam pipe and also fully recovers sulfuric acid from the steam. Furthermore, only the pipeline upstream of the gas-liquid separator 4 needs anti-corrosion treatment, reducing the cost of pipeline anti-corrosion treatment.

[0025] In some embodiments, the preheating unit 1 includes a plurality of preheating towers connected in series, and the flash unit includes a plurality of flash tanks connected in series. The preheating towers and flash tanks correspond one-to-one according to their positions relative to the high-pressure reactor. The steam outlet of the flash tank is connected to the heat exchanger of the corresponding preheating tower via a steam pipe 5.

[0026] Combination Figure 1 In this embodiment, the preheating unit 1 includes three preheating towers connected in series, named first preheating tower 11, second preheating tower 12, and third preheating tower 13 according to their position relative to the high-pressure reactor 2. The slurry first enters the third preheating tower 13 for the first preheating, then enters the second preheating tower 12 for the second preheating, then enters the first preheating tower 11 for the third preheating, and finally enters the high-pressure reactor 2 for reaction.

[0027] Similarly, the flash unit 3 also includes three flash tanks connected in series, named first flash tank 31, second flash tank 32, and third flash tank 33 according to their position relative to the high-pressure reactor 2. The slurry after reaction in the high-pressure reactor 2 first enters the first flash tank 31 for the first flash evaporation, then enters the second flash tank 32 for the second flash evaporation, and finally enters the third flash tank 33 for the third flash evaporation.

[0028] Steam generated in the first flash tank 31, after passing through the first gas-liquid separator 41 to remove sulfuric acid, enters the heat exchanger of the first preheating tower 11, where it preheats the slurry using its own heat. Steam generated in the second flash tank 32, after passing through the second gas-liquid separator 42 to remove sulfuric acid, enters the heat exchanger of the second preheating tower 12, where it preheats the slurry using its own heat. Steam generated in the third flash tank 33, after passing through the third gas-liquid separator 43 to remove sulfuric acid, enters the heat exchanger of the third preheating tower 13, where it preheats the slurry using its own heat.

[0029] In this embodiment, both the preheating unit 1 and the flash evaporation unit 3 are three-stage structures, containing three corresponding preheating towers and flash evaporators. In other embodiments, other numbers of preheating towers and flash evaporators may be included, with a connection method similar to this embodiment.

[0030] In some embodiments, the preheating tower has a second inlet, a second outlet, and a heat exchanger interface, and the second outlet of the preheating tower is connected to the second inlet of a next preheating tower. It should be noted that... Figure 1 For example, the second inlet of the preheating tower 13, which performs the first preheating, is connected to the slurry supply equipment. The second outlet of the first preheating tower, which performs the final first preheating, is connected to the first inlet of the high-pressure reactor 2.

[0031] In some embodiments, the flash tank has a third feed inlet, a third discharge outlet, and a steam outlet. The third discharge outlet of the flash tank is connected to the third feed inlet of the next flash tank, and the steam outlet of the flash tank is connected to the heat exchanger interface of the corresponding preheating tower via a steam pipe. It should also be noted that, with... Figure 1 For example, the third inlet of the flash tank 31, which performs the first flash evaporation, is connected to the first outlet of the high-pressure reactor 2. The third outlet of the flash tank 33, which performs the last flash evaporation, is connected to the subsequent slurry processing equipment.

[0032] Please see Figure 2 In some embodiments, the gas-liquid separator 4 includes a housing 401 and a liquid-separating baffle 402. The housing 401 has a separation chamber and also forms an air inlet 403, an air outlet 404, and a liquid outlet 405 communicating with the separation chamber. The liquid-separating baffle 402 is disposed in the airflow path between the air inlet 403 and the air outlet 404, and can block the steam airflow so that sulfuric acid droplets collide with the liquid-separating baffle 402 and converge into large droplets that flow down. The liquid outlet 405 is located below the liquid-separating baffle and is used to discharge the separated sulfuric acid. The air inlet 404 is connected to the steam outlet of the flash tank, and the air outlet 405 is connected to the heat exchanger interface of the preheating tower.

[0033] In some embodiments, the bottom surface 401 of the housing is a slope, and the outlet 405 is located at the lowest point of the slope so that sulfuric acid can be collected at the outlet 405.

[0034] In some embodiments, the diverting baffle 402 has multiple bends to create multiple bends in the separation chamber. When water vapor passes through the flow channels, sulfuric acid droplets impact the diverting baffle 402 and drip off. This multi-bend structure effectively separates sulfuric acid droplets from the water vapor, ensuring that the water vapor discharged from the outlet 404 does not contain sulfuric acid.

[0035] In some embodiments, the gas-liquid separator 4 further includes a storage tank 406, with an outlet 405 connected to the upper end of the storage tank 406 and a closable drain port 407 at the lower end. The separated sulfuric acid is collected in the storage tank 406 for temporary storage. When a certain amount is stored, the drain port 407 is opened to discharge it. Since the gas-liquid separator 4 is filled with high-pressure steam, the pressure of the high-pressure steam can automatically push out the sulfuric acid after the drain port 407 is opened.

[0036] In some embodiments, the system further includes a sulfuric acid collection tank 6, with a drain port 407 connected to the sulfuric acid collection tank 6 via a sulfuric acid pipe. A valve is installed on the sulfuric acid pipe to close the drain port 407. The sulfuric acid separated by each gas-liquid separator 4 can be collected and reused in the same sulfuric acid collection tank 6. It is readily understood that the sulfuric acid collection tank 6 includes the necessary discharge structure to discharge the collected sulfuric acid.

[0037] In some embodiments, one or more steam pipes 5 are in contact with the sulfuric acid collection tank 6 to heat the sulfuric acid inside the collection tank 6, accelerating the evaporation of water in the collected dilute sulfuric acid and increasing the concentration of sulfuric acid, thereby reducing the workload of recycling this portion of sulfuric acid. Therefore, the sulfuric acid collection tank 6 is open or includes an exhaust pipe or similar structure to discharge the evaporated water vapor.

[0038] In practical use, a steam pipe 5 with an appropriate temperature should be selected to heat the sulfuric acid to the suitable temperature. This avoids the situation where the sulfuric acid boils violently and generates acid fumes again. The steam pipe 5 can be in contact with the outer wall of the sulfuric acid collection tank 6, or it can pass through the inside of the sulfuric acid collection tank 6. The heating effect is better when it passes through the inside, but the outer wall of the steam pipe 5 needs to be treated with additional acid corrosion resistance.

[0039] Compared with the prior art, the multi-stage flash evaporation acid recovery system provided in this application is equipped with a gas-liquid separator on the steam pipeline of the flash tank to separate and recover sulfuric acid from the steam. Only the pipeline before the gas-liquid separator needs to be treated with anti-corrosion, which avoids scaling in the preheating tower, reduces the cost of pipeline anti-corrosion treatment, and also reduces the waste of sulfuric acid.

[0040] The above description is merely a preferred embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A multi-stage flash evaporation acid recovery system, characterized in that, It includes: The system includes a preheating unit, a high-pressure reactor, a flash evaporation unit, and a gas-liquid separator. The preheating unit includes at least one preheating tower connected to the first inlet of the high-pressure reactor for preheating the slurry. The flash evaporation unit includes at least one flash tank connected to the first outlet of the high-pressure reactor for flash evaporating the reacted slurry. The steam outlet of the flash tank is connected to the heat exchanger of the preheating tower via a steam pipe. The gas-liquid separator is installed on the steam pipe for separating sulfuric acid droplets from water vapor.

2. The multi-stage flash evaporation acid reuse system according to claim 1, characterized in that, The preheating unit includes multiple preheating towers connected in series, and the flash evaporation unit includes multiple flash tanks connected in series. The preheating towers and flash tanks correspond one-to-one according to their position relative to the high-pressure reactor. The steam outlet of the flash tank is connected to the heat exchanger of the corresponding preheating tower via the steam pipe.

3. The multi-stage flash evaporation acid reuse system according to claim 2, characterized in that, The preheating tower has a second inlet, a second outlet, and a heat exchanger interface. The second outlet of the preheating tower is connected to the second inlet of the next preheating tower.

4. The multi-stage flash evaporation acid reuse system according to claim 3, characterized in that, The flash tank has a third inlet, a third outlet, and a steam outlet. The third outlet of the flash tank is connected to the third inlet of the next flash tank. The steam outlet of the flash tank is connected to the heat exchanger interface of the corresponding preheating tower through the steam pipe.

5. The multi-stage flash evaporation acid reuse system according to claim 1, characterized in that, The gas-liquid separator includes a shell and a liquid-separating baffle. The shell has a separation chamber and also forms an air inlet, an air outlet, and a liquid outlet that communicate with the separation chamber. The liquid-separating baffle is disposed on the airflow path between the air inlet and the air outlet, and the liquid outlet is located below the liquid-separating baffle. The air inlet is connected to the steam outlet of the flash tank, and the air outlet is connected to the heat exchanger interface of the preheating tower.

6. The multi-stage flash evaporation acid reuse system according to claim 5, characterized in that, The bottom surface of the outer shell is a slope, and the liquid outlet is located at the lowest point of the slope.

7. The multi-stage flash evaporation acid reuse system according to claim 5, characterized in that, The liquid-separating baffle has multiple bends to divide the separation chamber into multiple bends in the flow channel. When water vapor passes through the flow channel, sulfuric acid droplets will hit the liquid-separating baffle and drip off.

8. The multi-stage flash evaporation acid reuse system according to claim 5, characterized in that, The gas-liquid separator also includes a liquid storage tank, the upper end of which is connected to the liquid outlet, and the lower end of which has a closable drain port.

9. The multi-stage flash evaporation acid reuse system according to claim 8, characterized in that, It also includes a sulfuric acid collection tank, and the drain outlet is connected to the sulfuric acid collection tank through a sulfuric acid pipe, which is equipped with a valve.

10. The multi-stage flash evaporation acid reuse system according to claim 9, characterized in that, The steam pipe comes into contact with the sulfuric acid collection tank to heat the sulfuric acid inside the collection tank.

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