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In the mid-1970s, ion exchange membranes for alkali production began to be widely used in the world. Since the introduction of the first set of ion membrane devices in China in 1985, the development of ion-exchange membrane caustic soda in China has progressed by leaps and bounds. In July 1993, China's first domestically produced ion-exchange membrane caustic soda plant was successfully tested at the Zhuozhou Chemical Plant in Hebei Province, which ended the passive situation in which ion-exchange membrane caustic soda production technology completely relied on imported equipment. Today, China's ion-exchange membrane caustic soda production has accounted for more than 60% of the total output of caustic soda. Domestically-made devices also support the production capacity of ion-exchange membrane caustic soda.
The chlor-alkali product that goes hand in hand with caustic soda is polyvinyl chloride (PVC). In 1958, China's first PVC production plant was built in Jinxi Chemical Plant, with a production capacity of 3,000 tons and using calcium carbide process. In 1976, the Beijing No. 2 Chemical Plant introduced the 80,000-tonne ethylene oxide chlorination VCM plant of Hoechst. This is the first oxychlorination monomer production facility in China. As China is rich in coal and less oil, calcium carbide process PVC has gradually become a production line in line with national conditions.
In the initial period of reform and opening up, China's calcium carbide PVC plant has a maximum capacity of only 50,000 tons/year. Until 2004, Tianjin Daxie Chemical Co., Ltd. developed and designed a fully automatic 200,000-ton/year PVC production line, and possessed the independent intellectual property rights of the process technology. It was only in China that a full set of localization of large-scale PVC production from process to equipment was realized. . In 2006, Jinxi Chemical Machinery (Group) Co., Ltd. independently researched and developed 135 cubic meters of polymerization tanks, marking the development of large-scale PVC in China has reached the world advanced level.
The direct result of production process upgrades and equipment enlargement is the expansion of the production scale of caustic soda and PVC enterprises. The average capacity of China's caustic soda production capacity from the initial stage of reform and opening up to reach 110,000 tons in 2007, the average production capacity of PVC production equipment from less than 10,000 tons / year reached 100,000 tons in 2007. The scale of production capacity naturally increases the ability of the chlor-alkali industry to save energy and reduce consumption.
The drop in energy consumption of products has opened the way for the chlor-alkali industry to develop a recycling economy. In accordance with the principle of “reduction, reuse, and recycling†of the recycling economy, the treatment of waste gas, liquid waste, and waste residues in the production process will be strengthened, and this will become the focus of environmental protection work in the chlor-alkali industry. According to industry statistics, from 1981 to 2008, the average tons of alkaline electricity consumption (30% caustic soda) dropped from 2607 kWh to 2394 kWh, and the average amount of alkali-consuming steam (30% caustic soda) dropped from 4.6 tons to 1.6 tons.
In 2005, Shandong Binhua Group took the lead in independently developing a membrane desulphurization process. Compared with the traditional methods of plutonium, calcium, and freezing, the use of this technology can not only greatly reduce the emission of harmful substances, but also can significantly reduce the cost of production, and has a profound significance for achieving clean production in the chlor-alkali industry. In October 2006, Shandong Shouguang Xinlong Sinochem Group successfully developed the domestic first dry acetylene generator, which was quickly promoted throughout the country. The technology is less investment, no acetylene gas emissions, water conservation, and calcium carbide slag processing costs are low. In addition, the development of PVC centrifuge mother liquor recycling technology and carbide slag comprehensive utilization technology have also realized the double benefits of turning waste into treasure. The VCM rectification tail gas pressure swing adsorption process has also led to a significant reduction in PVC emissions from PVC tail gas. The emission index has dropped from an average of 8% to 10% in the industry from 1995 to the current average of 1% to 2%.
In the past 60 years, in order to meet the needs of development in various fields such as light industry, textiles, petrochemicals, pharmaceuticals, metallurgy, electric power, agriculture, and military industry, the variety of chlor-alkali products has been increasing. From the early days of the founding of New China, hydrochloric acid, liquid chlorine, bleaching powder, etc. Species, to the current thousands of species. Among them, the chlorine products are becoming the economic growth point of the chlor-alkali industry and become an important symbol of the optimization and upgrading of China's chlor-alkali industry. At present, China has formed a considerable scale of chlorine product production system, PVC brand has been developed from a dozen before the reform and opening up to today's more than 100 kinds; more and more varieties of exports, product quality is also continuing to improve . In addition, methane chloride, paraffin wax chlorinated derivatives, epichlorohydrin, chlorobenzene and its derivatives have also made considerable progress.
At present, China is already a large chlor-alkali industry, but it is not yet a strong country. Whether it is the scale of production, product structure, or product quality, there is still a gap between China and developed countries. Therefore, today’s achievements are only a cornerstone of the future.
Chlor-alkali industry optimizes and upgrades in process innovation
As one of the main products of the chlor-alkali industry, the growth of 1234 times the output of caustic soda to a certain extent reflects the climbing speed of China's chlor-alkali industry. The leap in production can not be separated from the innovation of production technology and the upgrading of equipment. In the past 60 years, the production process of caustic soda in China has undergone great changes. From the early days of the founding of New China, the causticization method, diaphragm electrolysis method, mercury electrolysis method, vertical adsorption diaphragm electrolysis method, to the metal anode diaphragm method of the 1970s, and then Later, the ion exchange membrane method, China has been exploring advanced caustic soda production process.