What is the difference between Calcium Carbide method and the Ethylene method？

The Calcium Carbide method and the Ethylene method are the two main production processes for PVC resin powder (Polyvinyl Chloride powder). They have significant differences, mainly in terms of raw materials, production processes, environmental impact, product quality, and costs and market influence.

1. Raw Materials

Calcium Carbide Method: The main raw material is coal. Coal is mixed with limestone at high temperatures to produce calcium carbide. Calcium carbide reacts with water to generate acetylene, which is then polymerized with hydrochloric acid under a catalyst to form vinyl chloride. Vinyl chloride is then polymerized to form PVC.

Ethylene Method: The raw material is petroleum. Petroleum is cracked to produce ethylene, which is then chlorinated or oxychlorinated to synthesize 1,2-dichloroethane. The dichloroethane is cracked to produce vinyl chloride, which is then polymerized to form PVC.

2. Production Process

Calcium Carbide Method: The production process includes acetylene preparation and purification, vinyl chloride synthesis, product refining, and vinyl chloride polymerization. The process and equipment are relatively simple, but energy consumption is high, especially because the catalyst (mercury salts) is toxic and causes significant environmental pollution.

Ethylene Method: The production process includes ethylene cracking, chlorination or oxychlorination, dichloroethane cracking, vinyl chloride synthesis, and polymerization. The process is longer but relatively simple and easy to control, allowing for large-scale production with strong product adaptability.

3. Environmental Impact

Calcium Carbide Method: This method has high energy consumption and pollution, making it a high-energy, high-pollution process. During production, large amounts of carbide slag, wastewater, and dust are generated, and the mercury salts used as catalysts are toxic.

Ethylene Method: The Ethylene method is relatively more environmentally friendly. Chlorine is fully utilized, and all waste products (“three wastes”: waste gas, waste water, and waste solids) can be treated without discharge. The chlorination conversion rate and selectivity are high, and the raw materials and wastewater produced can be incinerated or processed, meeting environmental standards.

4. Product Quality

Calcium Carbide Method: The product quality is generally inferior. The sanitary performance indicators of Calcium Carbide PVC are not as good as those of Ethylene method PVC. In fields that require strict impurity content, such as medical or drinking water pipes, where higher added value is expected, Calcium Carbide PVC has difficulty entering the market. Additionally, the calcium carbide process produces vinyl chloride monomer with higher moisture and acetylene content, which makes it challenging to produce high-quality PVC products.

Ethylene Method: The product quality is superior to that of Calcium Carbide PVC. Ethylene method PVC performs better in terms of sanitary properties and thermal stability, making it suitable for high-quality product applications.

5. Cost and Market Influence

Calcium Carbide Method: The raw materials, coal and electricity, are sourced domestically, so production is generally not affected by international market fluctuations, depending mainly on the domestic market situation. When oil prices are high, the Calcium Carbide method has a clear cost advantage in production. However, with the impact of national energy-saving and emission-reduction policies and the depletion of mercury resources, the future viability of the Calcium Carbide PVC method may face significant challenges.

Ethylene Method: The raw materials are derived from petroleum, and the product profitability is closely tied to oil prices. The Ethylene method is widely recognized as an energy-efficient and environmentally friendly advanced production route and is commonly adopted by developed countries. As the production capacity of Ethylene method PVC powder increases, its market share is gradually rising, leading to intensifying market competition.