A method for improving the CO recycling rate in a carbonyl nickel production line

Abstract

The application discloses a method for improving CO recycling rate in a carbonyl nickel production line and belongs to the technical field of carbonyl nickel refining. The method is aimed at the industry pain point that N2 enrichment in the CO recycling process in the carbonyl nickel production leads to inefficient recycling of CO. Unreacted CO-containing synthesis tail gas from a synthesis kettle and decomposition CO generated by decomposition of carbonyl nickel are collected together as a gas to be purified and recovered, pressurized to 0.3-0.5 MPa, and then sent to a pressure swing adsorption CO purification device filled with copper adsorbent, so that N2 impurities in the gas are removed, high-purity CO product gas with a CO purity of greater than or equal to 98% and an N2 content of less than or equal to 1% is obtained, and the gas is sent back to the synthesis kettle for recycling. The application completely solves the problem of N2 enrichment, realizes efficient recycling of all the CO, improves the recycling rate to more than 95%, greatly reduces the production cost, improves the efficiency of the carbonylation reaction, reduces the safety and environmental protection risks, and has the advantages of simple process, good economy and easy industrialization.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal metallurgy technology, specifically relating to carbonyl nickel refining production technology, and particularly to a method for improving the carbon monoxide recovery rate in a carbonyl nickel production line. Background Technology

[0002] The carbonyl process is the core technology for preparing ultra-high purity metallic nickel. Due to its advantages such as high product purity, short process flow, and environmental friendliness, it is widely used in the field of high-end nickel material preparation. The core processes of a carbonyl nickel production line are the carbonyl nickel synthesis process and the carbonyl nickel decomposition process: In the synthesis process, carbon monoxide (CO) reacts with nickel-containing raw materials in a synthesis reactor to produce carbonyl nickel. Due to reaction equilibrium limitations, the single-pass utilization rate of CO in this process is only 50%~60%. In the decomposition process, carbonyl nickel is thermally decomposed to obtain ultra-high purity metallic nickel, while simultaneously releasing high-purity CO.

[0003] To reduce production costs, the industry standard practice is to recover and reuse unreacted CO from the synthesis process and CO produced from the decomposition process. However, in actual industrial continuous production, trace amounts of N2 carried in the raw material CO, as well as N2 mixed in by minor leaks at system sealing points, do not participate in the carbonylation reaction and will continuously accumulate in the synthesis reactor during the circulation process. As the number of cycles increases, the N2 concentration in the gas phase of the synthesis reactor continues to rise. On the one hand, this significantly reduces the CO partial pressure, leading to a significant decrease in the carbonylation reaction rate and a substantial reduction in production line capacity and reaction efficiency. On the other hand, when the N2 concentration in the circulating gas reaches a certain level, the purity of the gaseous CO cannot meet the process requirements of the carbonylation reaction, necessitating the discharge of large amounts of circulating tail gas containing high CO concentrations.

[0004] CO is a highly toxic, flammable, and explosive gas. Large-scale emissions not only result in significant waste of raw materials and substantial increases in production costs, but also pose significant safety and environmental risks. Currently, there is no mature solution to this problem. Some companies have attempted to remove N2 from circulating gas using cryogenic separation, but this process involves large investments, high energy consumption, and complex operations, making it unsuitable for small-to-medium volume purification of circulating gas in nickel carbonyl production lines and hindering stable industrial application. Therefore, developing a low-cost, efficient, and easily industrialized method for CO purification and reuse to address the industry's pain point of N2 enrichment in circulating gas is a pressing technical issue for the nickel carbonyl industry. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a method to improve the CO recycling rate in a nickel carbonyl production line. This method fundamentally solves the core problem of N2 enrichment during the CO recycling process in nickel carbonyl production, achieving efficient and full CO recycling, significantly reducing production costs, improving carbonylation reaction efficiency, and simultaneously reducing safety and environmental risks. The process is simple and easy to industrialize.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for improving the CO recovery rate in a nickel carbonyl production line, the nickel carbonyl production line including a nickel carbonyl synthesis step and a nickel carbonyl decomposition step; in the nickel carbonyl synthesis step, CO reacts with nickel-containing raw materials in a synthesis reactor to generate nickel carbonyl, and the reaction produces synthesis tail gas containing unreacted CO; in the nickel carbonyl decomposition step, nickel carbonyl is decomposed to obtain metallic nickel and decomposed CO; the method recovers and reuses the synthesis tail gas and decomposed CO, including the following steps: S1 Tail Gas Collection: The synthesis tail gas discharged from the synthesis reactor and the decomposed CO produced in the nickel carbonyl decomposition process are collected together to obtain the gas to be purified and recovered. S2 Pressure Swing Adsorption Purification: The gas to be purified and recovered is pressurized to 0.3-0.5MPa and then sent to a pressure swing adsorption CO purification device. The purification device is filled with copper adsorbent. The N2 impurities in the gas to be purified and recovered are removed by the pressure swing adsorption process, and high-purity CO product gas with CO purity ≥98% and N2 content ≤1% is obtained. S3 Recycling: The high-purity CO product gas is pressurized and sent back to the synthesis reactor of the nickel carbonyl synthesis process for recycling as raw material gas for carbonylation reaction.

[0007] Further, in step S2, the pressure swing adsorption process sequentially includes adsorption, pressure equalization, displacement, reverse release, and evacuation steps; after desorbing the CO adsorbed in the copper-loaded adsorbent using a vacuum pump, it is sent to a CO product gas holder for storage. The copper-loaded adsorbent has high selective adsorption performance for CO, and can efficiently adsorb CO in the gas phase under a set adsorption pressure, while impurities such as N2 are not adsorbed and are discharged from the system with the adsorption tail gas, thereby achieving efficient separation of CO and N2.

[0008] Furthermore, in step S1, the collected gas to be purified and recovered contains 75%-92% CO by volume, 6%-20% N2 by volume, and the remainder consists of a small amount of impurities such as nickel carbonyl and water.

[0009] Furthermore, in step S3, the high-purity CO product gas is pressurized by a compressor to the pressure required for the carbonylation reaction and then sent into the synthesis reactor to achieve full recycling of the synthesis tail gas and decomposed CO.

[0010] Furthermore, the N2 volume fraction in the carbonylation reaction feed gas fed into the synthesis reactor is controlled below 1% to ensure stable CO partial pressure in the carbonylation reaction and maintain a high reaction rate.

[0011] The present invention has the following significant advantages over the prior art: 1. This invention fundamentally solves the long-standing problem of N2 enrichment in the industry, achieving efficient and full CO recycling. Through a pressure swing adsorption purification process with specific parameters, this invention precisely removes N2 impurities from the circulating gas, stably increasing the CO purity in the recovered gas to over 98% and controlling the N2 content to below 1%. This completely avoids the continuous enrichment of N2 in the circulating system, achieving full recycling of synthesis tail gas and decomposed CO. The CO recycling rate has increased from less than 60% in existing technologies to over 95%, significantly reducing raw material CO consumption and lowering the production cost per ton of nickel by more than 15%.

[0012] 2. Stable improvement of carbonylation reaction efficiency and production line capacity. This invention stably controls the N2 content in the feed gas entering the synthesis reactor to below 1%, ensuring the stability of the CO partial pressure inside the synthesis reactor, avoiding the decrease in reaction rate caused by N2 enrichment, improving carbonylation reaction efficiency by more than 20%, significantly increasing production line capacity, and greatly improving product quality stability.

[0013] 3. Significantly reduces safety and environmental risks. This invention significantly reduces the amount of exhaust gas containing highly toxic CO, decreasing the total amount of exhaust gas emissions by more than 90%. This reduces the safety risks of CO leakage, poisoning, and explosion at the source, while also reducing waste gas emissions, meeting the production requirements of green metallurgy.

[0014] 4. Excellent economic efficiency and easy industrialization. This invention adopts pressure swing adsorption (PSA) technology, which reduces investment costs by more than 60% and operating energy consumption by more than 70% compared with existing purification technologies such as cryogenic separation. The process is simple, easy to operate, and stable. It can be directly connected to existing nickel carbonyl production lines without large-scale modification of the main process, making it easy to promote and apply industrially. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments and comparative examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0016] Example 1 The method for improving CO recycling rate in a nickel carbonyl production line provided in this embodiment has the following specific process steps: S1 Tail Gas Collection: The synthesis tail gas discharged from the nickel carbonyl synthesis reactor 1 and the decomposed CO produced by the decomposition reactor 2 are sent to the purification gas holder 3 and mixed to obtain the purification and recovery gas. After testing, the volume fraction of CO in the purification and recovery gas is 85%, the volume fraction of N2 is 12%, and the remainder is a small amount of impurities such as nickel carbonyl and water.

[0017] S2 Pressure Swing Adsorption Purification: The gas to be purified and recovered is pressurized to 0.4 MPa by the pressurizing compressor 4 and then sent to the pressure swing adsorption CO purification device 5. The purification device is filled with copper-loaded adsorbent and undergoes adsorption, pressure equalization, displacement, reverse release, and evacuation processes in sequence. Impurities such as N2 are discharged from the system with the adsorption tail gas. After the CO adsorbed in the copper-loaded adsorbent is desorbed by the vacuum pump, it is sent to the product gas holder 6 for storage. After testing, the high-purity CO product gas has a CO volume fraction of 98.5% and an N2 volume fraction of 0.8%.

[0018] S3 Recycling: The high-purity CO product gas is pressurized to the process pressure required for the carbonylation reaction by the circulating compressor 7 and then sent back to the synthesis reactor 1 as the raw material gas for the carbonylation reaction, realizing the full recycling of synthesis tail gas and decomposed CO.

[0019] In this embodiment, after 30 days of continuous operation, there was no enrichment of N2 in the system, the N2 content of the raw material gas in the synthesis reactor was stably controlled below 1%, the CO recovery rate was stable above 96%, the carbonylation reaction efficiency was improved by 22% compared with the original process, and the CO raw material consumption per ton of nickel was reduced by 18%.

[0020] Example 2 The method for improving CO recycling rate in a nickel carbonyl production line provided in this embodiment includes the following steps: S1 Tail Gas Collection: The synthesis tail gas discharged from the synthesis reactor and the decomposed CO produced by the decomposition reactor are collected together to obtain the gas to be purified and recovered. After testing, the volume fraction of CO in the gas to be purified and recovered is 78%, the volume fraction of N2 is 18%, and the remainder is a small amount of impurities.

[0021] S2 Pressure Swing Adsorption Purification: The gas to be purified and recovered is pressurized to 0.3 MPa and then sent to the pressure swing adsorption CO purification unit. Copper adsorbent is loaded and N2 impurities are removed by pressure swing adsorption process to obtain high-purity CO product gas. After testing, the CO volume fraction in the product gas is 98.2% and the N2 volume fraction is 0.9%.

[0022] S3 Recycling: High-purity CO product gas is pressurized and sent back to the synthesis reactor for recycling.

[0023] This embodiment ran continuously for 15 days, with no N2 enrichment in the system, and the CO recovery rate remained stable at over 95.5%. The carbonylation reaction efficiency was improved by 19% compared to the original process.

[0024] Example 3 The method for improving CO recycling rate in a nickel carbonyl production line provided in this embodiment includes the following steps: S1 Tail Gas Collection: The synthesis tail gas discharged from the synthesis reactor and the decomposed CO produced by the decomposition reactor are collected together to obtain the gas to be purified and recovered. After testing, the volume fraction of CO in the gas to be purified and recovered is 90%, the volume fraction of N2 is 8%, and the remainder is a small amount of impurities.

[0025] S2 Pressure Swing Adsorption Purification: The gas to be purified and recovered is pressurized to 0.5 MPa and then sent to the pressure swing adsorption CO purification unit. Copper adsorbent is loaded and N2 impurities are removed by pressure swing adsorption process to obtain high-purity CO product gas. After testing, the CO volume fraction in the product gas is 99.1% and the N2 volume fraction is 0.4%.

[0026] S3 Recycling: High-purity CO product gas is pressurized and sent back to the synthesis reactor for recycling.

[0027] This embodiment ran continuously for 15 days, with no N2 enrichment in the system, and the CO recovery rate remained stable at over 97%. The carbonylation reaction efficiency was improved by 25% compared to the original process.

[0028] Comparative Example This comparative example uses the conventional CO recycling process of existing carbonyl nickel production lines, directly pressurizing and sending the synthesis tail gas discharged from the synthesis reactor and the decomposed CO produced by the decomposition reactor back to the synthesis reactor for recycling, without undergoing pressure swing adsorption purification treatment.

[0029] The results showed that by the fifth cycle, the N2 volume fraction in the gas phase of the synthesis reactor had increased to 16%, the CO purity had dropped to 79%, and the carbonylation reaction rate had decreased by 30%. By the eighth cycle, the N2 volume fraction had increased to 25%, and the CO purity had dropped to 70%, which could not meet the carbonylation reaction process requirements. Therefore, all the recycled tail gas had to be discharged, the CO recovery rate was only 55%, the cost of nickel raw materials per ton was high, and the discharge of tail gas brought great safety and environmental risks.

Claims

1. A method for improving the CO recovery rate in a nickel carbonyl production line, the nickel carbonyl production line comprising a nickel carbonyl synthesis step and a nickel carbonyl decomposition step; in the nickel carbonyl synthesis step, CO reacts with nickel-containing raw materials in a synthesis reactor to generate nickel carbonyl, and a synthesis tail gas containing unreacted CO is produced after the reaction; in the nickel carbonyl decomposition step, nickel carbonyl is decomposed to obtain metallic nickel and decomposed CO; the method recovers and reuses the synthesis tail gas and decomposed CO, characterized in that, Includes the following steps: S1 Tail Gas Collection: The synthesis tail gas discharged from the synthesis reactor and the decomposed CO produced in the nickel carbonyl decomposition process are collected together to obtain the gas to be purified and recovered. S2 Pressure Swing Adsorption Purification: The gas to be purified and recovered is pressurized to 0.3-0.5MPa and then sent to a pressure swing adsorption CO purification device. The purification device is filled with copper adsorbent. The N2 impurities in the gas to be purified and recovered are removed by the pressure swing adsorption process, and high-purity CO product gas with CO purity ≥98% and N2 content ≤1% is obtained. S3 Recycling: The high-purity CO product gas is pressurized and sent back to the synthesis reactor of the nickel carbonyl synthesis process for recycling as raw material gas for carbonylation reaction.

2. The method for improving CO recovery rate in a nickel carbonyl production line according to claim 1, characterized in that, In step S2, the pressure swing adsorption process includes adsorption, pressure equalization, displacement, reverse release, and evacuation steps in sequence; after desorbing the CO adsorbed in the copper-loaded adsorbent by a vacuum pump, it is sent to the CO product gas holder for storage.

3. The method for improving CO recycling rate in a nickel carbonyl production line according to claim 1, characterized in that, In step S1, the volume fraction of CO in the collected gas to be purified and recovered is 75%-92%, and the volume fraction of N2 is 6%-20%.

4. The method for improving CO recycling rate in a nickel carbonyl production line according to claim 1, characterized in that, In step S3, the high-purity CO product gas is pressurized by a compressor to the pressure required for the carbonylation reaction and then sent to the synthesis reactor to achieve full recycling of the synthesis tail gas and decomposed CO.

5. The method for improving CO recovery rate in a nickel carbonyl production line according to claim 1, characterized in that, The N2 volume fraction in the carbonylation reaction feed gas fed into the synthesis reactor is controlled to be below 1%.