Overview of environmental management work in titanium dioxide industry at home and abroad

Environmental issues together with population, food, energy and war have become the most concerned and urgent issues for people in the world, and they are also the symbols of civilization in modern society. 20 titanium dioxide pigment century emergence of human life brought colorful products to enrich and beautify the human culture and life, but 60 years later to the growing awareness of this superior white pigment to the environment The harm, if not carefully managed, is not a question of sustainable development, but a problem involving the survival crisis of this industry. Fortunately, the “three wastes” (waste water, waste gas, waste residue) treatment in the production of titanium dioxide is not technically difficult, and it can be discharged after being qualified except for economic problems. China's titanium dioxide industry started late, and the "three wastes" treatment measures are relatively simple. Environmental protection is China's basic national policy. Doing a good job in environmental management in titanium dioxide production is an important guarantee for the sustainable development of China's titanium dioxide industry.

Sulfuric acid production of titanium dioxide have a lot of waste, by-produced, according to incomplete statistics two tonne depending on the starting titania (titanium iron ore) and a different level of average yield byproduct ferrous sulfate (heptahydrate) 2.5 ~ 4t, about 20% of the waste 7~llt of sulfuric acid, 100~250t of acid waste water, 15000~20000m ^{3 of} acid dusty waste gas, 0.2~0.3t of waste residue (dry basis), about 4t of sulfuric acid required for producing 1t of titanium dioxide, except for the part which produces ferrous sulfate The rest are all turned into waste water, waste gas and waste slag. With such a large amount of waste emissions, almost no other chemical products can compare with it. Much less waste discharge when the chlorination process titanium dioxide production, is recognized as a "clean" production process, but if the "three wastes" a calculation prepared material (synthetic rutile) the degree of contamination of the inner Not small. Since the 1960s, as countries have become more and more strict with environmental governance work, the environmental governance of the titanium dioxide industry has become very urgent and prominent. At the same time, the environmental protection measures of various companies are also coming under the pressure of environmental protection. The more perfect.

As early as the late 1960s, due to stricter environmental regulations in various countries, the sulfuric acid titanium dioxide factory was constantly attacked by the masses and attacked by the government and environmental protection departments. Some factories were forced to fine, stop or shut down, and some factories were converted to chlorination. Production or use of high-titanium slag as raw materials to reduce waste and auxiliary emissions. All existing sulfuric acid plants have to invest heavily in new and improved “three wastes” treatment plants, and their equipment depreciation and operating costs account for almost 20% of production costs. ~30%, a 50kt/a titanium dioxide factory's "three wastes" treatment facilities cost 15 million US dollars (in the early 1980s), so the production cost of titanium dioxide increased year by year.

In the 1960s, Ishihara Corporation of Japan was protested by nearby fishermen. The Japan Coast Guard Agency conducted a mandatory investigation of the company’s Yokkaichi factory. Due to the small size of the country, its environmental protection law is even stricter than that of the United States. Therefore, the environmental management and comprehensive utilization of the titanium dioxide industry in Japan has been carried out relatively early. For example, Ishihara Corporation generally used neutralization in the 1950s and used sulfuric acid in 1961. Ammonium sulphate, the Glauber's salt factory and gypsum factory and the famous factory for the purification of synthetic rutile with waste sulfuric acid in 1970; Japan Imperial Chemical Company also built a 10t/a sulphuric acid sulphate production plant; Japan Titanium Industry Co., Ltd. In 1983, magnetic iron oxide for magnetic tape production was successfully produced using ferrous sulfate.

Compared with Japan, Western Europe and the United States control looser. In the 1960s, the wastes of the European (including the United Kingdom) titanium dioxide factory were mainly discharged by ship to the North Sea. Only the original West Germany will discharge 170x10 ⁴ t of waste acid and the North Sea in 1 year. 12x10 ⁴ t ferrous sulfate (the reason is that the seawater in the North Sea is alkaline), the area of ​​the sea has been dyed red due to the oxidation of ferrous sulfate. In the early 1980s, Greenpeace in Western Europe intercepted Kronos several times at sea. The vessel prevented it from dumping waste acid into the high seas. Italy's Montessen company was temporarily shut down due to the abandonment of waste at sea and the formation of a large amount of "red mud" on the coast. It was once stopped by fishermen in Corsica and neighboring countries (France); formerly France's Thain-Mullu The company is also subject to restrictions on the discharge of waste from the Yale River. The National Lead Company (NL) and Cyanamide Company also experienced water pollution incidents. In 1976, NL's Seriville plant and the March 1978 St. Louis plant were forced to suspend production. Finally, NL reached an agreement with the Environmental Protection Agency. The agreement was fined $15 million, costing $40 million to establish a waste treatment plant in St. Louis, and fined $1,000 a day before pollution control. Now the company (NL) was once the United States and the world's largest sulfuric acid plant was forced to close. In all production lines in the United States, some factories are moved to foreign subsidiaries for production. The US cyanamide company also spent $17 million to set up a waste treatment plant in Savannah, which uses lime to neutralize 1325 m ³ of concentrated waste acid to form gypsum, and the filter gypsum regenerates 13248 m ³ of acid waste every day. To continue to use lime to neutralize and discharge, the cost per ton of waste acid treatment is as high as 90 US dollars. The treatment cost is very expensive. The by-product gypsum is 5 times of the production of titanium dioxide. The price per ton of agricultural gypsum is only 4 US dollars. At $13, the income from gypsum is far from offsetting the cost of processing. The neutralized wastewater sometimes contains traces of iron oxide, which is less than 10×10 ^-6 and is colorless and transparent in the beaker with the naked eye, but still reddish when discharged in large quantities. Japan's Ishihara Corporation processes 20X10 ⁴ m ³ of wastewater plant every day, using ultra-high-speed filtration of 35m3 / h, so that the insoluble matter in the wastewater is reduced to below 5X10 ^-6 , the transparency of water can ensure more than 70cm, of course, the processing cost is also high. It is said that the environmental protection regulations of Mie Prefecture in Japan are not only in Japan but also the most stringent in the world. The treatment facilities established by Ishihara Corporation in accordance with the above requirements were put into operation in February 1975.

After the foreign titanium dioxide factory experienced the pollution incident in the 1960s and 1970s, governments (including the European Community) have successively formulated strict emission restrictions, forcing the titanium dioxide factory to continuously improve the “three wastes” treatment measures and switch to acid solubility. Titanium slag is produced as raw materials to reduce emissions and reduce the burden of treatment. After the 1980s, the sulfuric acid plants in Europe, the United States, Japan, Australia and other countries have been able to fully control the emission after reaching the standard. For example, Bayer, Saatchi, Germany, and recently the new titanium dioxide group in Malaysia can do waste in Malaysia. Does not discharge production.

At present, all the titanium dioxide factories in China are sulfuric acid. Due to the small scale, scattered layout and absolute absolute emissions, there have not been any pollution accidents that seriously affect the ecological environment like foreign countries. However, in the late 1980s, nearly 100 large-scale sulfuric acid plants were built in various parts of the country due to the “titanium white fever” that swept the whole country. Some factories had almost no control measures. The masses had great opinions. Many small factories later were in the local environmental protection department. Under the intervention, they were forced to stop production. Some large factories and key enterprises have also added “three wastes” treatment devices such as: acid hydrolysis waste water spray, calcined waste water spray or electrostatic defogging, acid waste water using dolomite, limestone , lime Neutralization, etc., although not perfect, the pollution level has been reduced. Entering the 1990s because the state has increased the intensity of environmental governance, to further strengthen national awareness of environmental protection, environmental protection around the factory faces increasing the intensity of some of the urban area is located in the historic old mill (such as Wuxi, Zhangjiagang, Shanghai Hangzhou, Jining and other places have also been forced to close, and other factories have set aside huge sums to further improve and build the “three wastes” facilities, otherwise they will face the risk of production suspension.

As the production of chlorinated titanium dioxide in China has just started, it will take some time to reach industrialized continuous production, and the acid-soluble slag has not been promoted and applied due to cost. Therefore, the current “three wastes” treatment problem of the sulfuric acid plant is not only improved. The environment and pollution reduction are also related to the survival and development of the titanium dioxide industry in our national language.