Multi-stage flash evaporation acid recycling system

Abstract

The present application relates to a multi-stage flash evaporation acid recovery system, which includes 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 that is connected to the first feed port of the high-pressure reaction kettle for preheating the slurry. The flash evaporation unit includes at least one flash evaporation tank that is connected to the first discharge port of the high-pressure reaction kettle for flash evaporation of the post-reaction slurry. The steam outlet of the flash evaporation tank is connected via a steam pipe to the heat exchanger of the preheating tower. A gas-liquid separator is mounted on the steam pipe to separate sulfuric acid droplets from the steam. Compared to existing technology, the multi-stage flash evaporation acid recovery system provided by this application features a gas-liquid separator on the steam pipe of the flash evaporation tank, which separates and recovers the sulfuric acid from the steam. This design requires only the pipeline in front of the gas-liquid separator to be treated for corrosion resistance, thus avoiding scaling in the preheating tower, reducing the cost of pipeline corrosion treatment, and minimizing the waste of sulfuric acid.

Description

[0001] Description

[0002] MULTI-STAGE FLASH EVAPORATION ACID RECYCLING SYSTEM

[0003] FIELD OF THE DISCLOSURE

[0004] The present application relates to the field of chemical engineering equipment, particularly to a multi-stage flash evaporation acid recycling system.

[0005] BACKGROUND

[0006] Flash evaporation is a process where high-pressure pulp from a high-pressure reaction kettle is introduced into a lower-pressure container. Due to the sudden pressure drop, the pulp becomes saturated steam and saturated pulp at the lower pressure of the container. The boiling point of a substance is directly proportional to pressure. Thus, high-pressure, high- temperature pulp can be depressurized to reduce its boiling point and enter flash evaporation. The function of a flash evaporation tank is to provide a space for rapid vaporization and gas-liquid separation of the fluid .

[0007] In the hydrometallurgical process of laterite nickel ore, pulp, sulfuric acid, and steam are usually injected into a high-pressure reaction kettle for smelting to extract nickel and cobalt from the laterite nickel ore. After the reaction, the pulp and sulfuric acid enter the flash evaporation tank for depressurization, generating steam while also causing some sulfuric acid droplets to be stirred up by the vibration of the steam, forming acid mist that is expelled along with the steam.

[0008] Since the steam contains sulfuric acid, using this steam to preheat the pulp will cause the preheating tower to scale due to the reaction between the sulfuric acid and the pulp, leading to scaling; in addition, it will also cause corrosion of the steam pipeline and additional consumption of sulfuric acid.

[0009] SUMMARY

[0010] In light of this, there is a need to provide a multi-stage flash evaporation acid recycling system to address the technical issues in existing technologies where the steam generated from the flash evaporation tank contains sulfuric acid, leading to scaling inside the preheating tower, corrosion of the steam pipeline, and increased consumption of sulfuric acid during the preheating of the pulp.

[0011] The present application provides a multi-stage flash evaporation acid recycling system, which includes a preheating unit, a high-pressure reaction kettle, a flash evaporation unit, and a gas-liquid separator. The preheating unit includes at least one preheating tower, which is connected to the first feed port of the high-pressure reaction kettle and is used to preheat the pulp. The flash evaporation unit includes at least one flash evaporation tank, which is connected to the first discharge port of the high-pressure reaction kettle and is used for flash evaporation of the post-reaction pulp. The steam outlet of the flash evaporation tank is connected to the heat exchanger of the preheating tower via a steam pipe, and the gas-liquid separator is set on the steam pipe to separate sulfuric acid droplets from the steam.

[0012] Further, the preheating unit includes multiple preheating towers connected in series, and the flash evaporation unit includes multiple flash evaporation tanks connected in series. The preheating towers and flash evaporation tanks correspond one-to-one based on their position relative to the high-pressure reaction kettle, with the steam outlet of the flash evaporation tank connected via the steam pipe to the corresponding heat exchanger of the preheating tower.

[0013] Further, the preheating tower has a second feed port, a second discharge port, and a heat exchanger interface, with the second discharge port of the preheating tower connected to the second feed port of the next preheating tower.

[0014] Further, the flash evaporation tank has a third feed port, a third discharge port, and a steam outlet, with the third discharge port of the flash evaporation tank connected to the third feed port of the next flash evaporation tank, and the steam outlet of the flash evaporation tank connected via the steam pipe to the corresponding heat exchanger interface of the preheating tower.

[0015] Further, the gas-liquid separator includes a shell and a liquid distribution baffle. The shell has a separation chamber and forms an air inlet, an air outlet, and a liquid outlet that communicate with the separation chamber. The liquid distribution baffle is set on the air flow path between the air inlet and the air outlet, with the liquid outlet located below the liquid distribution baffle; the air inlet is connected to the steam outlet of the flash evaporation tank, and the air outlet is connected to the heat exchanger interface of the preheating tower.

[0016] Further, the bottom surface of the shell is sloped, with the liquid outlet located at the lowest point of the slope.

[0017] Further, the liquid distribution baffle has multiple folding structures to create multiple folded flow paths within the separation chamber. When steam passes through the flow paths, the sulfuric acid droplets will impact the liquid distribution baffle and f all .

[0018] Further, the gas-liquid separator also includes a liquid storage tank, with the upper end of the liquid storage tank connected to the liquid outlet and the lower end having a closable liquid outlet .

[0019] Further, the system also includes a sulfuric acid collection tank, with the liquid outlet connected to the sulfuric acid collection tank via a sulfuric acid pipe, and a valve is set on the sulfuric acid pipe.

[0020] Further, the steam pipe is in contact with the sulfuric acid collection tank to heat the sulfuric acid inside the tank.

[0021] Compared to existing technologies, the multi-stage flash evaporation acid recycling system provided by the present application has a gas-liquid separator on the steam pipe of the flash evaporation tank to separate and recover the sulfuric acid from the steam. Only the pipeline in front of the gas-liquid separator needs to be treated for corrosion resistance, which avoids scaling in the preheating tower, reduces the cost of pipeline corrosion treatment, and also reduces the waste of sulfuric acid.

[0022] The above description is only an overview of the technical solution of the present application. For a clearer understanding of the technical means of the present application and to implement it according to the content of the specification, the best embodiment of the present application and its detailed description are given below in conjunction with the drawings . The specific implementation of the present application is detailed in the following examples and drawings .

[0023] BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The figures described herein are provided for further understanding of the present application and form a part of the present application. The illustrative embodiments and their description are used to explain the present application and do not constitute an undue limitation on the scope of the present application. In the figures:

[0025] •Figure 1 is a structural schematic diagram of a preferred embodiment of the multi-stage flash evaporation acid recycling system provided by the present application.

[0026] • Figure 2 is a cross-sectional view of the gas-liquid separator in Figure 1.

[0027] DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0028] The following describes the preferred embodiment of the present application in detail, with the figures forming a part of the present application and used together with the examples of the present application to explain the principles of the present application, not to limit the scope of the present application.

[0029] Please refer to Figure 1, which shows a multi-stage flash evaporation acid recycling system provided by the present application. This system can be used in the smelting of laterite nickel ore to recover sulfuric acid from the steam generated in the flash evaporation tank to prevent corrosion of the pipeline.

[0030] It should be noted that the multi-stage flash evaporation acid recycling system of the present application is used but not limited to the smelting of laterite nickel ore and can also be applied to other smelting processes that require the use of sulfuric acid and flash evaporation tanks. In the present application, only the application of the multi-stage flash evaporation acid recycling system in the smelting of laterite nickel ore is used as an example for illustration, and the principle of the application of the multi-stage flash evaporation acid recycling system in other ore smelting is essentially the same as that in the smelting of laterite nickel ore, which is not repeated here.

[0031] In the present embodiment, the multi-stage flash evaporation acid recycling system includes a preheating unit 1, a high-pressure reaction kettle 2, a flash evaporation unit 3, and a gas-liquid separator 4. The preheating unit 1 includes at least one preheating tower, which is connected to the first feed port of the high-pressure reaction kettle 2 and is used to preheat the pulp. The pulp is first transported to the preheating tower for preheating to a certain temperature before being transported to the high-pressure reaction kettle 2 for reaction. The flash evaporation unit 3 includes at least one flash evaporation tank, which is connected to the first discharge port of the high-pressure reaction kettle 2 and is used for flash evaporation of the post-reaction pulp to depressurize and cool down the pulp. The steam outlet of the flash evaporation tank is connected to the heat exchanger of the preheating tower via a steam pipe 5, and the gas-liquid separator 4 is set on the steam pipe 5 to separate sulfuric acid droplets from the steam, preventing corrosion of the steam pipe and also allowing for the full recovery of sulfuric acid in the steam. Only the pipeline in front of the gas-liquid separator 4 needs to be treated for corrosion resistance, reducing the cost of pipeline corrosion treatment.

[0032] In some embodiments, the preheating unit 1 includes multiple preheating towers connected in series, and the flash evaporation unit includes multiple flash evaporation tanks connected in series. The preheating towers and flash evaporation tanks correspond one-to-one based on their position relative to the high-pressure reaction kettle 2, with the steam outlet of the flash evaporation tank connected via the steam pipe 5 to the corresponding heat exchanger of the preheating tower.

[0033] In the present embodiment, the preheating unit 1 includes three preheating towers connected in series, named in order of their proximity to the high-pressure reaction kettle 2 as the third preheating tower 13, the second preheating tower 12, and the first preheating tower 11. The pulp 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 reaction kettle 2 for reaction.

[0034] Similarly, the flash evaporation unit 3 also includes three flash evaporation tanks connected in series, named in order of their proximity to the high-pressure reaction kettle 2 as the first flash evaporation tank 31, the second flash evaporation tank 32, and the third flash evaporation tank 33. The pulp after reaction in the high-pressure reaction kettle 2 first enters the first flash evaporation tank 31 for the first flash evaporation, then enters the second flash evaporation tank 32 for the second flash evaporation, and finally enters the third flash evaporation tank 33 for the third flash evaporation.

[0035] The steam generated by the first flash evaporation tank 31, after being treated by the first gas-liquid separator 41 to remove sulfuric acid, enters the heat exchanger of the first preheating tower 11 to preheat the pulp using its own heat. The steam generated by the second flash evaporation tank 32, after being treated by the second gas-liquid separator 42 to remove sulfuric acid, enters the heat exchanger of the second preheating tower 12 to preheat the pulp using its own heat. The steam generated by the third flash evaporation tank 33, after being treated by the third gas-liquid separator 43 to remove sulfuric acid, enters the heat exchanger of the third preheating tower 13 to preheat the pulp using its own heat.

[0036] In the present embodiment, both the preheating unit 1 and the flash evaporation unit 3 are three-stage structures, containing three corresponding preheating towers and flash evaporation tanks. In other embodiments, other numbers of preheating towers and flash evaporation tanks can be included, with connection methods similar to the present embodiment.

[0037] In some embodiments, the preheating tower has a second feed port, a second discharge port, and a heat exchanger interface, with the second discharge port of the preheating tower connected to the second feed port of the next preheating tower. It should be noted that, taking Figure 1 as an example, the second feed port of the preheating tower that performs the first preheating, i.e., the third preheating tower 13, is connected to the pulp supply equipment. The second discharge port of the preheating tower that performs the last preheating, i.e., the first preheating tower, is connected to the first feed port of the high-pressure reaction kettle 2.

[0038] In some embodiments, the flash evaporation tank has a third feed port, a third discharge port, and a steam outlet, with the third discharge port of the flash evaporation tank connected to the third feed port of the next flash evaporation tank, and the steam outlet of the flash evaporation tank connected via the steam pipe to the corresponding heat exchanger interface of the preheating tower. It should be noted that, taking Figure 1 as an example, the third feed port of the flash evaporation tank that performs the first flash evaporation, i.e., the first flash evaporation tank 31 , is connected to the first discharge port of the high-pressure reaction kettle 2. The third discharge port of the flash evaporation tank that performs the last flash evaporation, i.e., the third flash evaporation tank 33, is connected to the subsequent pulp processing equipment .

[0039] Please refer to Figure 2. In some embodiments, the gas-liquid separator 4 includes a shell 401 and a liquid distribution baffle

[0040] 402, The shell 401 has a separation chamber and forms an air inlet

[0041] 403, an air outlet 404, and a liquid outlet 405 that communicate with the separation chamber. The liquid distribution baffle 402 is set on the air flow path between the air inlet 403 and the air outlet

[0042] 404, capable of blocking the steam flow to cause sulfuric acid droplets to hit the liquid distribution baffle 402 and gather into larger droplets that flow down. The liquid outlet 405 is located below the liquid distribution baffle, for the discharge of separated sulfuric acid. The air inlet 404 is connected to the steam outlet of the flash evaporation tank, and the air outlet 405 is connected to the heat exchanger interface of the preheating tower.

[0043] In some embodiments, the bottom surface of the shell 401 is sloped, with the liquid outlet 405 located at the lowest point of the slope, facilitating the gathering of sulfuric acid at the liquid outlet 405.

[0044] In some embodiments, the liquid distribution baffle 402 has multiple folding structures to create multiple folded flow paths within the separation chamber. When steam passes through the flow paths, the sulfuric acid droplets will impact the liquid distribution baffle 402 and fall. The multiple folding structures ensure the effective separation of sulfuric acid droplets from the steam, ensuring that the steam discharged from the air outlet 404 is free of sulfuric acid.

[0045] In some embodiments, the gas-liquid separator 4 also includes a liquid storage tank 406, with the upper end of the liquid storage tank 406 connected to the liquid outlet 405, and the lower end having a closable liquid outlet 407. The separated sulfuric acid gathers in the liquid storage tank 406 for temporary storage, and when a certain amount is stored, the liquid outlet 407 is opened to discharge. Due to the high-pressure steam filled in the gas-liquid separator 4, the pressure of the high-pressure steam can automatically push out the sulfuric acid when the liquid outlet 407 is opened.

[0046] In some embodiments, the system also includes a sulfuric acid collection tank 6, with the liquid outlet 407 connected to the sulfuric acid collection tank 6 via a sulfuric acid pipe, and a valve is set on the sulfuric acid pipe to achieve closure of the liquid outlet 407. The sulfuric acid separated by each gas-liquid separator 4 can be collected in the same sulfuric acid collection tank 6 for centralized collection and recycling. It is easy to understand that the sulfuric acid collection tank 6 includes necessary discharge structures to discharge the collected sulfuric acid.

[0047] 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 tank, accelerating the evaporation of water in the collected dilute sulfuric acid, and increasing the concentration of sulfuric acid to reduce the workload for the subsequent treatment and reuse of this sulfuric acid. Therefore, the sulfuric acid collection tank 6 is open at the top or includes an exhaust pipe or similar structure to discharge the evaporated steam.

[0048] In actual use, an appropriately temperatured steam pipe 5 should be selected to heat the sulfuric acid to a suitable temperature . This prevents the sulfuric acid from boiling violently and producing acid mist 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 interior of the sulfuric acid collection tank 6. When passing through the interior, the heating effect is better, but additional acid-resistant corrosion treatment is required for the outer wall of the steam pipe 5.

[0049] Compared to existing technologies, the multi-stage flash evaporation acid recycling system provided by the present application has a gas-liquid separator on the steam pipe of the flash evaporation tank to separate and recover the sulfuric acid from the steam. Only the pipeline in front of the gas-liquid separator needs to be treated for corrosion resistance, which avoids scaling in the preheating tower, reduces the cost of pipeline corrosion treatment, and also reduces the waste of sulfuric acid.

[0050] The above description is only the best specific implementation of the present application, but the scope of protection of the present application is not limited to this. Any person skilled in the art, within the technical scope disclosed by the present application, can easily think of variations or substitutions, which should be covered within the scope of protection of the present application .

Claims

WHAT IS CLAIMED IS1. A multi-stage flash evaporation acid recovery system, characterized in that it comprises: a preheating unit, a high-pressure reaction kettle, a flash evaporation unit, and a gas-liquid separator, wherein the preheating unit includes at least one preheating tower, said preheating tower is connected to the first feed port of the high-pressure reaction kettle for preheating the slurry, the flash evaporation unit includes at least one flash evaporation tank, said flash evaporation tank is connected to the first discharge port of the high-pressure reaction kettle for flash evaporation of the post-reaction slurry, the steam outlet of the flash evaporation tank is connected via a steam pipe to the heat exchanger of the preheating tower, and the gas-liquid separator is mounted on the steam pipe to separate sulfuric acid droplets from the steam.

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

3. The multi-stage flash evaporation acid recovery system as claimed in claim 2, characterized in that the preheating tower has a second feed port, a second discharge port, and a heat exchanger interface, and the second discharge port of the preheating tower is connected to the second feed port of the next preheating tower.

4. The multi-stage flash evaporation acid recovery system as claimed in claim 3, characterized in that the flash evaporation tank has a third feed port, a third discharge port, and a steam outlet, and the third discharge port of the flash evaporation tank is connected to the third feed port of the next flash evaporation tank, and the steam outlet of the flash evaporation tank is connected viathe steam pipe to the heat exchanger interface of the corresponding preheating tower.

5. The multi-stage flash evaporation acid recovery system as claimed in claim 1, characterized in that the gas-liquid separator includes a housing and a liquid distribution baffle, the housing has a separation chamber and forms an air inlet, an air outlet, and a liquid outlet that communicate with the separation chamber, the liquid distribution baffle is set on the air flow path between the air inlet and the air outlet, and the liquid outlet is located below the liquid distribution baffle; the air inlet is connected to the steam outlet of the flash evaporation tank, and the air outlet is connected to the heat exchanger interface of the preheating tower.

6. The multi-stage flash evaporation acid recovery system as claimed in claim 5, characterized in that the bottom surface of the housing is sloped, and the liquid outlet is located at the lowest point of the slope.

7. The multi-stage flash evaporation acid recovery system as claimed in claim 5, characterized in that the liquid distribution baffle has multiple folding structures to create multiple folded flow paths within the separation chamber, and when the steam passes through the flow paths, the sulfuric acid droplets will impact the liquid distribution baffle and fall.

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

9. The multi-stage flash evaporation acid recovery system as claimed in claim 8, characterized in that it further includes a sulfuric acid collection tank, the liquid outlet is connected to the sulfuric acid collection tank via a sulfuric acid pipe, and a valve is provided on the sulfuric acid pipe.

10. The multi-stage flash evaporation acid recovery system as claimed in claim 9, characterized in that the steampipe is in contact with the sulfuric acid collection tank to heat the sulfuric acid inside the tank.

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