Calcium carbide method PVC byproduct hydrochloric acid electrolysis system
By using an electrolytic system for hydrochloric acid produced as a byproduct of the calcium carbide PVC process, hydrochloric acid is decomposed into chlorine and hydrogen, creating a closed-loop recycling system. This solves the problem of ineffective recycling of hydrochloric acid, achieves direct recovery of chlorine and avoids sludge, and reduces enterprise costs and environmental pressure.
Patent Information
- Application Number
- CN202511677182.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-17
- Publication Date
- 2026-01-13
AI Technical Summary
In existing technologies, hydrochloric acid, a byproduct of the calcium carbide process for polyvinyl chloride production, has not been effectively recycled and utilized, resulting in resource waste and sludge generation, which increases the economic burden and environmental pressure on enterprises.
An electrolysis system for hydrochloric acid byproduct of the calcium carbide PVC production process was designed, including a hydrochloric acid tank, an electrolytic cell, a water washing tower, a chlorine water circulation supply device, a hydrogen dryer, and a chlorine dryer. The hydrochloric acid is decomposed into chlorine and hydrogen through the electrolytic cell, and a closed-loop circulation system is constructed. Corrosion-resistant ruthenium-iridium-titanium coated electrodes are used to control the current density and temperature, thereby achieving direct recovery of chlorine and avoiding sludge.
This method achieves efficient resource recovery of chlorine, avoids sludge generation, reduces overall disposal costs, and improves resource utilization and system stability.
Smart Images
Figure CN121320985A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to chemical waste liquid recycling technology, and more specifically, to an electrolysis system for hydrochloric acid byproduct of calcium carbide PVC production. Background Technology
[0002] In the calcium carbide process for polyvinyl chloride (PVC) production, when acetylene undergoes an addition reaction with hydrogen chloride to produce vinyl chloride monomer, excess hydrogen chloride must be used to ensure a high conversion rate of acetylene. This inevitably leads to the generation of a large amount of hydrochloric acid as a byproduct in the subsequent washing process. This hydrochloric acid contains a high concentration of hydrogen chloride, and its chlorine element has significant resource value. However, current industrial practices generally rely on a simple treatment mode of neutralization-pressure filtration-discharge, which uses calcium hydroxide from calcium carbide slag slurry to neutralize the hydrochloric acid and adjust the pH of the solution to the range of 6 to 9. This treatment method solidifies the chlorine element in the hydrochloric acid in the form of calcium chloride, making effective recovery and utilization impossible and resulting in resource waste. At the same time, the neutralization process generates a large amount of sludge containing calcium chloride, heavy metals, and suspended solids, with a water content as high as 60% to 70%. This not only increases the volume and difficulty of disposal of the sludge but also brings potential environmental pollution risks. According to statistics, my country's annual production capacity of calcium carbide-based PVC reaches 18 million tons, and approximately 0.55 to 0.65 tons of hydrochloric acid are generated as a byproduct for every ton of product produced, with a total annual byproduct exceeding 10 million tons. The resulting sludge disposal cost is approximately 80 to 120 yuan per ton, with a total annual cost of 500 to 800 million yuan. This treatment method not only fails to fully utilize the high-value chlorine resources in hydrochloric acid but also adds to the economic burden and environmental pressure on enterprises. Therefore, there is an urgent need for a technical solution that can directly recover chlorine and avoid sludge generation. Summary of the Invention
[0003] The purpose of this invention is to provide a hydrochloric acid electrolysis system for PVC byproducts produced by the calcium carbide process, which has the advantages of directly recovering chlorine and avoiding sludge generation.
[0004] This invention provides an electrolysis system for hydrochloric acid byproduct of the calcium carbide-based PVC production process, the technical solution of which is as follows: It includes a hydrochloric acid tank, an electrolytic cell, a water washing tower, a chlorine water circulation supply device, a hydrogen dryer, and a chlorine dryer; the hydrochloric acid tank is connected to the electrolytic cell via a pipeline with a hydrochloric acid feed pump, the cathode outlet of the electrolytic cell is connected to the hydrogen dryer via a pipeline, the anode outlet of the electrolytic cell is connected to the water washing tower via a pipeline, the gas outlet of the water washing tower is connected to the chlorine dryer via a pipeline, and the spraying mechanism of the water washing tower is connected to the chlorine water circulation supply device.
[0005] Furthermore, the present invention also proposes that the chlorine water circulation supply device includes a vacuum dechlorination tower, a pump, a cooling device, a filtration device, and a chlorine water storage tank connected in sequence by pipelines. The bottom of the water washing tower is connected to the inlet of the vacuum dechlorination tower through a pipeline with a pump, and the chlorine water storage tank is connected to the spray inlet of the vacuum dechlorination tower through a pipeline with a pump.
[0006] Furthermore, the present invention also proposes that the current density of the electrolytic cell be controlled at 150-300 A / dm² and the temperature of the electrolytic cell be controlled at 60-80℃.
[0007] Furthermore, the present invention also proposes that the electrodes of the electrolytic cell are provided with a corrosion-resistant ruthenium-iridium-titanium coating.
[0008] As can be seen from the above, the present invention provides an electrolytic system for hydrochloric acid byproducts of calcium carbide PVC production. The electrolytic system efficiently treats the byproduct hydrochloric acid, realizes the direct resource recovery of chlorine, eliminates the sludge generated in the neutralization process, and produces hydrogen. It has the advantages of directly recovering chlorine and avoiding sludge generation. Attached Figure Description
[0009] Figure 1 This is a schematic diagram of the structure of the present invention. Detailed Implementation
[0010] like Figure 1 As shown in the figure, this embodiment of the invention proposes an electrolysis system for hydrochloric acid byproduct of calcium carbide PVC production, including a hydrochloric acid tank 1, an electrolysis tank 2, a water washing tower 3, a chlorine water circulation supply device 4, a hydrogen dryer 5, and a chlorine dryer 6; the hydrochloric acid tank 1 is connected to the electrolysis tank 2 via a pipeline with a pump, the cathode outlet of the electrolysis tank 2 is connected to the hydrogen dryer 5 via a pipeline, the anode outlet of the electrolysis tank 2 is connected to the water washing tower 3 via a pipeline, the gas outlet of the water washing tower 3 is connected to the chlorine dryer 6 via a pipeline, and the spraying mechanism of the water washing tower 3 is connected to the chlorine water circulation supply device 4.
[0011] The system includes: Hydrochloric acid tank 1, a container for storing byproduct hydrochloric acid to be processed, made of corrosion-resistant materials, primarily for ensuring a stable supply of raw materials for electrolysis; Electrolytic cell 2, the core component, mainly decomposes hydrochloric acid into chlorine and hydrogen; Water washing tower 3 removes acid mist and impurities from the chlorine; Chlorine water circulation supply device 4 treats and recycles the sprayed chlorine water; Hydrogen dryer 5 treats hydrogen using cooling dehumidification or adsorption drying to reduce its water content; and Chlorine dryer 6 dries chlorine using sulfuric acid absorption or molecular sieve adsorption.
[0012] This system achieves the resource utilization of hydrochloric acid, a byproduct of the calcium carbide-based PVC production process, by constructing a complete electrolysis system, avoiding the sludge generation and low-end chlorine solidification problems caused by traditional neutralization methods. Electrolytic cell 2 directly decomposes hydrochloric acid into high-value chlorine and hydrogen gases, with chlorine exiting from the anode outlet and hydrogen from the cathode outlet. A water washing tower 3 and a chlorine water circulation supply device 4 work together to achieve chlorine water recycling. Hydrogen dryer 5 and chlorine dryer 6 process the two gaseous products respectively, ensuring product quality and subsequent utilization value. This system configuration fundamentally solves the problem of disposing of byproduct hydrochloric acid, achieves efficient chlorine recovery and utilization, and avoids the sludge generation and resource waste problems caused by traditional neutralization methods.
[0013] Furthermore, the chlorine gas generated at the anode outlet of electrolytic cell 2 enters the water washing tower 3 through pipelines. In the water washing tower 3, it undergoes treatment by a spray mechanism to remove acid mist and impurities, thus ensuring the purity of the chlorine gas. The spray mechanism of the water washing tower 3 is connected to the chlorine water circulation supply device 4, forming a closed-loop circulation system. This allows the chlorine water generated during the washing process to be recycled, reducing waste emissions and improving resource utilization.
[0014] As a preferred embodiment, the present invention proposes a chlorine water circulation supply device 4 comprising a vacuum dechlorination tower 4-1, a cooling device 4-2, a filtration device 4-3, and a chlorine water storage tank 4-4 connected in sequence via pipelines. The bottom of the water washing tower 3 is connected to the inlet of the vacuum dechlorination tower 4-1 via a pipeline equipped with a pump, and the chlorine water storage tank 4-4 is connected to the spray inlet of the vacuum dechlorination tower 4-1 via a pipeline equipped with a pump.
[0015] The vacuum dechlorination tower 4-1 is a device that operates in a vacuum environment to rapidly release dissolved chlorine. It can be implemented using a vacuum pump in conjunction with a degassing tower structure. Its purpose is to effectively disrupt the dissolution equilibrium of chlorine in water and prevent chlorine loss during circulation. The cooling device 4-2 can be implemented using a plate heat exchanger or a shell-and-tube heat exchanger. Its purpose is to prevent chlorine from redissolving due to temperature increases, thereby enhancing the thoroughness of dechlorination. The filtration device 4-3 can be implemented using a multi-layer filter structure to remove impurities from the chlorinated water. The chlorine water storage tank 4-4 is a container with storage and buffering functions. It can be made of corrosion-resistant materials and equipped with a liquid level control device. Its purpose is to balance the fluctuations in the spray demand and processing capacity of the water washing tower 3, ensuring a continuous and stable supply of circulating water. This solution, by constructing a closed-loop circulation structure of multi-stage treatment units, not only solves the problem of treating dissolved chlorine and impurities in chlorinated water but also achieves efficient recovery and utilization of chlorine resources, significantly improving the system's operational stability and economy.
[0016] The present invention further proposes that the current density of the electrolytic cell 2 be controlled at 150-300A / dm² and the temperature of the electrolytic cell 2 be controlled at 60-80℃.
[0017] Specifically, current density refers to the current intensity passing through a unit electrode area, which can be achieved by adjusting the rectifier output of electrolytic cell 2. This parameter is introduced to ensure that the electrolysis reaction proceeds within its efficient range while avoiding side reactions caused by excessive current. Temperature refers to the actual thermodynamic state of the electrolyte under operating conditions, which can be controlled by a heat exchanger or heating device to maintain suitable conductivity and ion migration efficiency of the electrolyte.
[0018] In detail, the control range of current density and temperature in the above electrolysis system is a precisely calculated technical parameter. When the current density is between 150 and 300 A / dm², sufficient reaction driving force is ensured while avoiding side reactions such as oxygen evolution, thereby protecting the electrode materials and improving product purity. Maintaining the temperature within the range of 60 to 80°C effectively reduces the viscosity and resistance of the electrolyte, reduces energy loss, and suppresses the thermal corrosion tendency of materials. This combination of parameters not only solves the problem of reaction rate imbalance during electrolysis but also significantly improves the system's operational stability and resource recovery efficiency. By rationally matching current density and temperature, the high-value resource utilization of by-product hydrochloric acid is achieved, significantly reducing overall disposal costs.
[0019] The present invention further proposes that the electrodes of the electrolytic cell 2 are provided with a corrosion-resistant ruthenium-iridium-titanium coating.
[0020] Specifically, corrosion-resistant ruthenium-iridium-titanium coatings refer to functional coatings formed on electrode surfaces through specific processes, providing resistance to strong acid corrosion. These coatings can be achieved through methods such as thermal decomposition coating, electroplating deposition, or physical vapor deposition. The purpose of using this coating is to effectively isolate the corrosive medium in the hydrochloric acid electrolysis environment from the electrode substrate, thereby extending the electrode's service life and ensuring system operational stability.
[0021] In detail, this technical solution addresses the electrode corrosion problem in hydrochloric acid electrolysis by applying a ruthenium-iridium-titanium coating to the electrode surface of electrolytic cell 2. During electrolysis, ruthenium exhibits excellent electrochemical catalytic activity, ensuring efficient chlorine evolution reaction; iridium enhances the chemical stability of the coating in acidic media, effectively resisting chloride ion penetration; and the titanium substrate provides good mechanical adhesion and conductivity. This material combination allows the coating to tightly cover the electrode surface, forming a dense protective layer and preventing accelerated localized corrosion caused by impurities in hydrochloric acid. Specifically, within the electrolysis temperature range of 60-80℃, the coating maintains structural integrity, ensuring stable current density in electrolytic cell 2 and preventing secondary pollution caused by coating peeling, thus guaranteeing the reliability of long-term continuous system operation. Combined with the overall design of the electrolysis system, the application of this coating significantly improves the durability of the electrodes in strongly acidic environments containing impurities, effectively solving the problem of rapid electrode corrosion and wear.
Claims
1. A hydrochloric acid electrolysis system for PVC byproducts produced via the calcium carbide process, characterized in that: The system includes a hydrochloric acid tank (1), an electrolytic cell (2), a water washing tower (3), a chlorine water circulation supply device (4), a hydrogen dryer (5), and a chlorine dryer (6). The hydrochloric acid tank (1) is connected to the electrolytic cell (2) via a pipeline with a pump. The cathode outlet of the electrolytic cell (2) is connected to the hydrogen dryer (5) via a pipeline. The anode outlet of the electrolytic cell (2) is connected to the water washing tower (3) via a pipeline. The gas outlet of the water washing tower (3) is connected to the chlorine dryer (6) via a pipeline. The spraying mechanism of the water washing tower (3) is connected to the chlorine water circulation supply device (4).
2. The hydrochloric acid electrolysis system for calcium carbide-based PVC byproducts as described in claim 1, characterized in that: The chlorine water circulation supply device (4) includes a vacuum dechlorination tower (4-1), a cooling device (4-2), a filtration device (4-3), and a chlorine water storage tank (4-4) connected in sequence by pipelines. The bottom of the water washing tower (3) is connected to the inlet of the vacuum dechlorination tower (4-1) through a pipeline with a pump. The chlorine water storage tank (4-4) is connected to the spray inlet of the vacuum dechlorination tower (4-1) through a pipeline with a pump.
3. The hydrochloric acid electrolysis system for calcium carbide-based PVC byproducts as described in claim 1, characterized in that: The current density of the electrolytic cell (2) is controlled at 150-300A / dm², and the temperature of the electrolytic cell (2) is controlled at 60-80℃.
4. The hydrochloric acid electrolysis system for calcium carbide-based PVC byproducts as described in claim 1, characterized in that: The electrodes of the electrolytic cell (2) are coated with a corrosion-resistant ruthenium-iridium-titanium coating.