Method for deeply removing acid gas from anolyte and concentrating anolyte in nickel-cobalt electrolysis process

Abstract

The invention discloses a method for deeply removing acid gas from anolyte and concentrating the anolyte in a nickel-cobalt electrolysis process. The system comprises an anolyte storage tank, a heat pump and a flash tank which are sequentially connected through pipelines, two liquid inlets in the top end of the flash tank are connected with the cold side and the hot side of the heat pump respectively, and a liquid outlet in the bottom end of the flash tank is connected with an anolyte circulating pipeline and an anolyte outlet pipeline respectively. And the anolyte circulating pipeline is connected with the hot side of the heat pump through a circulating pump. Mainly according to the principle that the higher the vacuum degree of water is under the vacuum condition, the lower the boiling point of the water is, materials are continuously evaporated under the higher vacuum condition. Meanwhile, the solubility of acid radical ions in the solution is relatively low under the condition of relatively low temperature, so that a relatively high deacidification effect can be realized; and the flash steam is condensed through chilled water, and the chilled water is circularly refrigerated by the cold side of the heat pump to maintain continuous evaporation of the material at a low temperature, so that the purpose of concentration is achieved, and the balance of the metal content and the volume of the anolyte in the nickel-cobalt electrolysis process is further achieved.

Description

Technical Field

[0001] The invention relates to the technical field of nonferrous hydrometallurgical processes, and in particular to a method for deeply removing acidic gases and concentrating anolyte in a nickel-cobalt electrolysis process. Background Art

[0002] There are three common ways to deeply deacidify and concentrate the anolyte. Compressed air blowing method: air is passed into the acid mist absorption tower, and the air contacts the liquid phase on the surface of the filler. The blown acid gas is neutralized by the alkali solution and then discharged in compliance with the standard. The acid gas content in the solution can be reduced after deacidification by this method. The disadvantage is that the acid gas blown by air has low purity and cannot be recycled and reused. It can only be absorbed by alkali solution. This method has a low deacidification rate, a large amount of alkali solution consumption, and cannot concentrate the solution; the chemical deacidification method basically utilizes the oxidizing property of the acid gas, and adds reducing substances to the anolyte to cause an oxidation-reduction reaction to remove the acid gas. Because chemical deacidification consumes a large amount of reducing agent, the cost is high, and there is a risk of introducing other impurities, and the solution cannot be concentrated; the vacuum deacidification method uses Henry's law-the solubility of the gas in the liquid phase is proportional to the partial pressure of the gas in the gas phase. Therefore, the vacuum deacidification method is to use steam to boil the anode liquid in the deacidification tower under a certain vacuum degree, and use the generated water vapor bubbles to take away the acidic gas. The formed acidic liquid is used for acid preparation in other processes, and the acidic gas is absorbed by liquid alkali. This method improves the acid gas recovery rate and also plays a role in concentrating the anode liquid, but the consumption of steam and alkali solution is relatively large.

[0003] The above three methods deacidify or concentrate the anolyte to different degrees, but there are still problems such as high reagent and energy consumption. Summary of the invention

[0004] The present invention aims to solve the problems existing in the prior art and provides a method for deeply removing acidic gases and concentrating the anolyte in the nickel-cobalt electrolysis process. The method mainly utilizes the principle that the higher the vacuum degree of water is, the lower the boiling point is, so that the material is continuously evaporated under higher vacuum conditions. At the same time, the solubility of acidic gases in the solution is lower under lower temperature conditions, so that a higher deacidification effect can be achieved. The flashed steam is condensed by chilled water, and the chilled water is circulated and refrigerated by the cold side of a heat pump to maintain the continuous evaporation of the material at a low temperature, so as to achieve the purpose of concentration.

[0005] The method for deep removal of acidic gas and concentration of anolyte in the nickel-cobalt electrolysis process of the present invention is completed by the following system and process: A system for deeply removing acidic gases and concentrating anolyte comprises an anolyte storage tank, a heat pump and a flash tank which are sequentially connected by pipelines, wherein the anolyte inlet at the top of the flash tank is connected to the hot side of the heat pump, the anolyte outlet at the bottom of the flash tank is respectively connected to the anolyte circulation pipeline and the anolyte outlet pipeline, the anolyte circulation pipeline is connected to the hot side of the heat pump through a circulation pump, and the anolyte outlet pipeline is connected to a material storage tank 1; the condensate outlet at the bottom of the flash tank is respectively connected to the condensate outlet pipeline and the condensate circulation pipeline, the condensate outlet pipeline is connected to a material storage tank 2, the condensate circulation pipeline is respectively connected to the cold side of the heat pump and a plate heat exchanger, and the plate heat exchanger and the cold side of the heat pump are both connected to the chilled water inlet at the top of the flash tank; the acid gas outlet on the flash tank is connected to an acid mist absorption tower, and the acid mist absorption tower is connected to a vacuum system; the acid mist absorption tower is connected to an absorption liquid tank, and the absorption liquid tank is connected to the acid mist absorption tower through a return liquid pump.

[0006] The process of deep removal of acidic gas and concentration of anolyte is as follows: the anolyte in the anolyte storage tank from the electrolysis process is sent to the flash tank, the anolyte is evaporated and concentrated in the flash tank under the vacuum conditions provided by the vacuum system to form deacidified anolyte, and the flash tank is evacuated to -95kpa ~ -100kpa; a part of the deacidified anolyte after evaporation and concentration enters the material storage tank 1 through the anolyte outlet pipe, and a part of the deacidified anolyte enters the hot side of the heat pump through the anolyte circulation pipe, and is heated by the heat pump. The heated deacidified anolyte enters the flash tank to balance the temperature of the anolyte from the electrolysis process, so as to ensure that the anolyte entering the flash tank continues to evaporate at a low temperature; During the evaporation, concentration and deacidification process of the anolyte in the flash tank, flash steam and acidic gas will be generated in the flash tank. The flash steam is condensed by the chilled water from the plate heat exchanger to form condensed water. Part of the condensed water enters the material storage tank 2 and is opened to the condensation water pool. Part of the condensed water enters the cold side of the heat pump through the condensation water circulation pipeline to circulate and heat the deacidified and concentrated anolyte, balancing the temperature of the deacidified anolyte to ensure that the anolyte continues to evaporate at low temperature. The acidic gas overflowed during the evaporation and concentration in the flash tank enters the acid mist absorption tower under the action of the vacuum system, is absorbed by the sprayed alkali solution, and is sent to the absorption liquid tank for export. In this way, the deep deacidification and concentration of the electrolytic anolyte is achieved.

[0007] Flash steam is generated during the evaporation and deacidification of the anode liquid. Chilled water is introduced into the flash tank to condense the flash steam. Part of the condensed water in the condensed water circulation pipeline is cooled by the plate heat exchanger to form chilled water. The other part of the condensed water entering the cold side of the heat pump heats up the deacidified anode liquid entering the hot side of the heat pump. The condensed water temperature on the cold side of the heat pump drops and enters the flash tank through the chilled water inlet together with the chilled water cooled from the plate heat exchanger to condense the flash steam generated during the evaporation and concentration process. The condensed water then enters the cold side of the heat pump and the plate heat exchanger, thereby realizing the recycling of the condensed water.

[0008] The flash tank is kept in a vacuum state to ensure that the electrolytic anolyte continues to boil at a low boiling point. The vacuum system can continuously provide negative pressure to the flash tank and pump it to -97kpa, so that the boiling point of the anolyte is maintained at 28°C to promote the continuous evaporation and deacidification of the anolyte.

[0009] Beneficial technical effects of the present invention: The process for deeply removing acidic gases and concentrating the anolyte during nickel-cobalt electrolysis of the present invention has a simple process flow. Without consuming external steam, the secondary steam latent heat of evaporating water and the heat of electrolysis by-products are used for concentration, thereby achieving the purpose of deeply deacidifying and concentrating the electrolyte and maintaining the balance of metal and volume in the production system. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a system flow chart of the present invention. DETAILED DESCRIPTION

[0011] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0012] like Figure 1 As shown, the system for deeply removing acidic gas and concentrating anolyte comprises an anolyte storage tank, a heat pump, and a flash tank connected in sequence by pipelines, the anolyte inlet at the top of the flash tank is connected to the hot side of the heat pump, the anolyte outlet at the bottom of the flash tank is respectively connected to the anolyte circulation pipeline and the anolyte outlet pipeline, the anolyte circulation pipeline is connected to the hot side of the heat pump through the circulation pump, and the anolyte outlet pipeline is connected to the material storage tank 1; the condensate outlet at the bottom of the flash tank is respectively connected to the condensate outlet pipeline and the condensate circulation pipeline, the condensate outlet pipeline is connected to the material storage tank 2, the condensate circulation pipeline is respectively connected to the cold side of the heat pump and the plate heat exchanger, and the plate heat exchanger and the cold side of the heat pump are both connected to the chilled water inlet at the top of the flash tank; the acid gas outlet on the flash tank is connected to the acid mist absorption tower, and the acid mist absorption tower is connected to the vacuum system; the acid mist absorption tower is connected to the absorption liquid tank, and the absorption liquid tank is connected to the acid mist absorption tower through the return liquid pump.

[0013] The process of deep removal of acidic gas and concentration of anolyte is as follows: the anolyte in the anolyte storage tank from the electrolysis process is sent to the flash tank, the anolyte is evaporated and concentrated in the flash tank under the vacuum conditions provided by the vacuum system to form deacidified anolyte, and the flash tank is evacuated to -97kpa; a part of the deacidified anolyte after evaporation and concentration enters the material storage tank 1 through the anolyte outlet pipe, and a part of the deacidified anolyte enters the hot side of the heat pump through the anolyte circulation pipe, and is heated by the heat pump. The heated deacidified anolyte enters the flash tank to balance the temperature of the anolyte from the electrolysis process, so as to ensure that the anolyte entering the flash tank continues to evaporate at a low temperature; During the evaporation, concentration and deacidification process of the anolyte in the flash tank, flash steam and acidic gas will be generated in the flash tank. The flash steam is condensed by the chilled water from the plate heat exchanger to form condensed water. Part of the condensed water enters the material storage tank 2 and is opened to the condensation water pool. Part of the condensed water enters the cold side of the heat pump through the condensation water circulation pipeline to circulate and heat the deacidified and concentrated anolyte, balancing the temperature of the deacidified anolyte to ensure that the anolyte continues to evaporate at low temperature. The acidic gas overflowed during the evaporation and concentration in the flash tank enters the acid mist absorption tower under the action of the vacuum system, is absorbed by the sprayed alkali solution, and is sent to the absorption liquid tank for export. In this way, the deep deacidification and concentration of the electrolytic anolyte is achieved.

[0014] Flash steam is generated during the evaporation and deacidification of the anode liquid. Chilled water is introduced into the flash tank to condense the flash steam. Part of the condensed water in the condensed water circulation pipeline is cooled by the plate heat exchanger to form chilled water. The other part of the condensed water entering the cold side of the heat pump heats up the deacidified anode liquid entering the hot side of the heat pump. The condensed water temperature on the cold side of the heat pump drops and enters the flash tank through the chilled water inlet together with the chilled water cooled from the plate heat exchanger to condense the flash steam generated during the evaporation and concentration process. The condensed water then enters the cold side of the heat pump and the plate heat exchanger, thereby realizing the recycling of the condensed water.

[0015] The flash tank is kept in a vacuum state to ensure that the electrolytic anolyte continues to boil at a low boiling point. The vacuum system can continuously provide negative pressure to the flash tank and pump it to -97kpa, so that the boiling point of the anolyte is maintained at 28°C to promote the continuous evaporation and deacidification of the anolyte. The heat pump adopts the Carnot principle, according to the solution exchange temperature, and is equipped with tetrafluoroethane as a refrigerant, so that the heat energy of the low-level heat source on the cold side of the heat pump is transferred to the high-level heat source on the hot side of the heat pump.

[0016] The vacuum system can provide negative pressure for the flash tank, making its vacuum degree reach -97kpa. At this time, the boiling point of the anolyte is 28℃. The anolyte is evaporated based on the principle that the higher the vacuum degree, the lower the boiling point of water under vacuum conditions, to achieve the purpose of deacidification and concentration. The vacuum system provides negative pressure for the flash tank and pumps it to vacuum. It is an existing conventional vacuum device. In the process of evaporating and concentrating the anolyte, the flash tank will produce flash steam and reduce the solubility of the acid gas in the anolyte.

[0017] In summary, according to the present invention, after the anolyte from the electrolysis process is pumped to the flash tank for concentration and removal of acidic gas, a part of the anolyte is stored in the material storage tank 1 for standby use; the anolyte from the electrolysis process enters the hot side of the heat pump for temperature increase; at the same time, during the deep dechlorination and concentration process, the flash tank will generate flash steam, and after the flash steam is condensed by chilled water, a part of the condensed water is stored in the material storage tank 2 and pumped to the condensed water pool, and the other part of the condensed water is pumped to the cold side of the heat pump to increase the temperature of the anolyte after deacidification and concentration on the hot side of the heat pump, and the remaining condensed water is cooled by the plate heat exchanger and then opened to the flash tank for condensing the steam generated by flash evaporation; in this process, the vacuum system provides negative pressure for the flash tank to make it a vacuum state, and at the same time, the acidic gas generated during the deep deacidification and concentration process is absorbed into the acid mist absorption tower for spraying and absorption with alkali solution, and the absorbed liquid enters the absorption liquid tank for export. This process mainly uses the principle that the higher the vacuum degree of water, the lower the boiling point. When the flash tank is evacuated to -97kpa, the boiling point of water is 28°C, so that the material continues to evaporate under higher vacuum conditions. At the same time, the solubility of acid radical ions in the solution is low under lower temperature conditions, which can achieve a higher deacidification effect; the flash steam is condensed by chilled water, and the chilled water is circulated and refrigerated by the cold side of the heat pump to maintain the continuous evaporation of the material at low temperature, achieve the purpose of concentration, and then achieve the balance between the metal content and volume of the anode liquid during the nickel-cobalt electrolysis process.

[0018] The above is only a preferred embodiment of the present invention and does not limit the present invention. It should be pointed out that for ordinary technicians in this field, under the technical enlightenment provided by the present invention, other equivalent improvements can be made, all of which can achieve the purpose of the present invention and should be regarded as the protection scope of the present invention.

Claims

1. A method for deep removal of acidic gases and concentration of anolyte in nickel-cobalt electrolysis, characterized in that: Completed by the following systems and processes: A system for deeply removing acidic gases and concentrating anolyte, comprising an anolyte storage tank, a heat pump, and a flash tank connected in sequence through pipelines, wherein the anolyte inlet at the top of the flash tank is connected to the hot side of the heat pump, the anolyte outlet at the bottom of the flash tank is respectively connected to the anolyte circulation pipeline and the anolyte outlet pipeline, the anolyte circulation pipeline is connected to the hot side of the heat pump through a circulation pump, and the anolyte outlet pipeline is connected to a material storage tank 1; the condensate outlet at the bottom of the flash tank is respectively connected to the condensate outlet pipeline and the condensate circulation pipeline, the condensate outlet pipeline is connected to a material storage tank 2, the condensate circulation pipeline is respectively connected to the cold side of the heat pump and the plate heat exchanger, the plate heat exchanger and the cold side of the heat pump are both connected to the chilled water inlet at the top of the flash tank; the acid gas outlet on the flash tank is connected to an acid mist absorption tower, and the acid mist absorption tower is connected to a vacuum system; The process of deep removal of acidic gas and concentration of anolyte is as follows: the anolyte in the anolyte storage tank from the electrolysis process is sent to the flash tank, the anolyte is evaporated and concentrated in the flash tank under the vacuum conditions provided by the vacuum system to form deacidified anolyte, and the flash tank is evacuated to -95kpa ~ -100kpa; a part of the deacidified anolyte after evaporation and concentration enters the material storage tank 1 through the anolyte outlet pipe, and a part of the deacidified anolyte enters the hot side of the heat pump through the anolyte circulation pipe, and is heated by the heat pump. The heated deacidified anolyte enters the flash tank to balance the temperature of the anolyte from the electrolysis process, so as to ensure that the anolyte entering the flash tank continues to evaporate at a low temperature; During the evaporation, concentration and deacidification process of the anode liquid in the flash tank, flash steam and acidic gas will be generated in the flash tank. The flash steam is condensed by the chilled water from the plate heat exchanger to form condensed water. Part of the condensed water enters the material storage tank 2, and part of the condensed water enters the cold side of the heat pump through the condensed water circulation pipeline to circulate and heat the deacidified and concentrated anode liquid to ensure that the anode liquid continues to evaporate at low temperature; the acidic gas enters the acid mist absorption tower under the negative pressure of the vacuum system and is absorbed under the spraying action of the alkali solution.

2. The method for deep removal of acidic gases and concentration of anolyte in nickel-cobalt electrolysis according to claim 1, characterized in that: The acid mist absorption tower is connected to an absorption liquid tank, and the absorption liquid tank is connected to the acid mist absorption tower through a return liquid pump.

3. The method for deep removal of acidic gases and concentration of anolyte in nickel-cobalt electrolysis according to claim 1, characterized in that: Part of the condensed water in the condensed water circulation pipeline is cooled by the plate heat exchanger to form chilled water, and the other part of the condensed water entering the cold side of the heat pump heats up the deacidified anode liquid entering the hot side of the heat pump. The temperature of the condensed water on the cold side of the heat pump drops, and the condensed water enters the flash tank through the chilled water inlet together with the chilled water cooled by the plate heat exchanger to condense the flash steam generated in the evaporation and concentration process. The condensed water then enters the cold side of the heat pump and the plate heat exchanger, thereby realizing the recycling of the condensed water.

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