Can the environmental protection dilemma of titani

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Can the environmental protection dilemma of titanium dioxide produced by sulfuric acid be overcome?

at present, the global output value of titanium dioxide is about US $11billion, which is the third largest inorganic chemical product after synthetic ammonia and phosphoric acid. Titanium dioxide is listed as a key chemical affecting the development of national economy in many countries, and the per capita consumption of titanium dioxide is also regarded as an important indicator reflecting the level of national economic development. Since 2000, China's titanium dioxide industry has developed rapidly, and its annual production capacity has increased from 340000 tons to 1.8 million tons. It has become the world's second largest titanium dioxide producer after the United States

however, there is a problem that cannot be ignored. The production process of titanium dioxide in China is basically sulfuric acid method. A large amount of waste sulfuric acid, acidic wastewater, waste residue and waste gas are discharged in the production process. Many manufacturers are seriously polluted and environmental protection problems are prominent. Since 2005, titanium dioxide by sulfuric acid method has been listed in the environmental protection blacklist such as the restricted catalogue of industrial structure adjustment, the catalogue of prohibited import processing trade, and the catalogue of double high (high pollution, high environmental risk) products by the state, and the whole industry is facing great environmental protection pressure

then, can the environmental protection dilemma of titanium dioxide by sulfuric acid method be overcome? Where is the way out for this industry? Recently, the Ministry of environmental protection commissioned relevant experts to conduct a special research on this. Also interviewed about this

There are four major environmental protection problems in the industry. Liu Hanjie, head of the expert research group, told that although China's titanium dioxide industry has made great progress in recent years, the environmental pollution problems and potential environmental risks in the industry can not be ignored. Specifically, it is mainly manifested in the following aspects

first, there are many factories with small scale, and the proportion of heavy pollution production capacity is too large. Statistics show that there are about 100 titanium dioxide production plants in the world, including 63 in China, not including enterprises under construction and preparation in China. Although the number of Chinese enterprises accounts for more than 60% of the world, their output only accounts for about 20% of the world. The average annual capacity of a single plant in other countries in the world is 60000 ~ 80000 tons, while that in China is only 22700 tons. Moreover, titanium dioxide is mostly produced by traditional sulfuric acid process in China, which has serious pollution and high treatment cost. According to the survey, among the existing 1.8 million tons of titanium dioxide production capacity in China, only 30000 tons are produced by chlorination method with low emission of three wastes, accounting for less than 2%; The output of titanium dioxide produced by chlorination in other parts of the world accounts for more than 76%

second, the emission per unit product is large, and the consumption of resources and energy is high. The traditional sulfuric acid method is used to produce titanium dioxide. The production of titanium dioxide consumes 100 ~ 150 tons of fresh water per ton, and the comprehensive energy consumption is about 1.6 tons of standard coal. At the same time, it produces about 8 tons of waste sulfuric acid with a concentration of 20%, 100 tons of acid waste water, 8 tons of waste residue, and 25000 cubic meters of waste gas containing sulfur dioxide, acid mist and dust. Based on the comparable caliber, the industrial wastewater emission, exhaust gas emission and sulfur dioxide emission per 10000 yuan output value of the domestic titanium dioxide industry are 3.85, 1.03 and 2.13 times of the average level of the chemical industry, respectively, and 3-8 times of the indicators of the new material industry development guide for all industrial industries. Due to the large amount of sewage discharge, pollution accidents in the domestic titanium dioxide industry occur frequently, causing contradictions between the masses and manufacturers, and even causing inter provincial disputes. Some pollution incidents are also listed as the top ten environmental violations in the country

third, it is not difficult to treat the three wastes, but it has the characteristics of low energy consumption and high cost. The waste gas produced by titanium dioxide production is mainly acid mist and dust, which can be effectively treated by spray washing and gravity sedimentation; The waste residue produced can be treated by landfill, neutralization and other technologies; Ferrous sulfate heptahydrate, waste acid and gypsum residue can be recycled as products or comprehensively utilized. Although it is not difficult to treat the three wastes produced by titanium dioxide production, the treatment cost is high due to the large treatment capacity. It is understood that the treatment cost of pollutants in the traditional sulfuric acid method is as high as 1900 yuan per ton of products, while the treatment cost of chlorination method is only 800 yuan per ton of products. Due to the low grade and low price of titanium dioxide produced by sulfuric acid method, the treatment cost of its three wastes is close to the production profit

fourth, domestic low-level redundant construction is still expanding rapidly, and the possibility of environmental pollution caused by overcapacity will increase in the future. According to the survey, the production capacity of titanium dioxide under construction and proposed in China has reached 1.28 million tons/year and 1.6 million tons/year respectively. Among them, only about 20% plan to adopt chlorination method. If we consider the risks such as intellectual property disputes and the lack of titanium raw materials, this proportion will have to decline. It is estimated that by 2015, the total production capacity of titanium dioxide in China will reach 4.68 million tons, close to the global total output of titanium dioxide of 5million tons in 2009. If the macro situation changes at that time, such as the state controlling the ownership of private cars and adjusting real estate policies, which leads to the shrinkage of titanium dioxide end consumption market, then the environmental risk caused by overcapacity may be transformed into real environmental pollution due to the high cost of industrial pollution control

enterprises strive to achieve cleaner production

in this adjustment 1 There are earthquake sources around. Experts in the research center found that some domestic enterprises have achieved gratifying breakthroughs in solving the environmental protection problems of titanium dioxide produced by sulfuric acid process. Among them, Henan baililian Chemical Co., Ltd. adopted the concept of circular economy, systematically improved and transformed the traditional sulfuric acid process, and developed a cleaner production process of titanium dioxide by the combined production of pyrite and titanium, which made the production of titanium dioxide by the sulfuric acid process achieve a new innovation

it is understood that Bailian has been exploring the transformation of the traditional sulfuric acid method since 2004. They have successively implemented more than 30 technical transformation measures, and finally formed a cleaner production process of titanium dioxide with independent innovation technology. At present, the enterprise has built 600000 tons/year sulfuric acid, 120000 tons/year titanium dioxide, 20000 tons/year ferrous sulfate monohydrate, 10000 tons/year iron oxide black, 6000 kg/year scandium oxide and other co production units

Yang Minle, executive deputy general manager and chief engineer of Bailian company, told that the company's sulfuric acid and titanium dioxide CO production has realized the utilization of low-temperature waste heat in sulfuric acid production; Using ferrous sulfate heptahydrate to produce ferrous sulfate monohydrate, mother liquor to produce iron oxide black; The alkaline wastewater from the production of iron oxide black is used in the flotation of titanium ore with acidolysis residue. At the same time, the enterprise has achieved a number of technical improvements and innovations in the traditional sulfuric acid titanium dioxide production process, such as the acid hydrolysis residue flotation titanium ore recycling technology, vacuum jet refrigeration and waste heat lithium bromide refrigeration technology combined for crystallization process production, metatitanic acid calcination pre drying technology and dispersant compounding technology. In the process of developing co production cleaner production process, the company obtained 3 invention patents and 13 utility model patents. In addition, the quality of iron oxide black products produced by the company has been higher than that produced by imported technology

through the transformation, Bll also achieved the comprehensive utilization of waste and by-products, the utilization of waste heat, and the recycling of waste water, better realizing the goal of cleaner production and the concept of developing circular economy. Compared with the traditional sulfuric acid titanium dioxide production process, the comprehensive energy consumption per ton of titanium dioxide in this enterprise is reduced from 2.19 tons of standard coal to 1.23 tons of standard coal; The discharge of titanium dioxide wastewater per ton is reduced from more than 100 tons to less than 60 tons; The sulfur, iron, titanium and scandium resources in the raw materials have been reasonably recycled, and the total yield of titanium has increased from less than 82% to more than 87%; The product variety has increased from a single variety to more than 10 kinds; Various indicators of product quality have been continuously improved. Energy consumption has decreased by about 40%, water consumption has decreased by 35%, power consumption has decreased by 13%, and natural gas consumption has decreased by more than 10%. Good economic and environmental benefits have been achieved

it is learned that in addition to Henan baililian company, Sichuan longmang group and Wuhan Fangyuan company have also carried out cleaner production technology transformation of titanium dioxide process by sulfuric acid method

according to the spray concentration phosphoric acid process in phosphorus chemical production, Sichuan longmang group has developed the spray concentration technology for waste acid treatment. The process flow is that the waste acid of titanium dioxide is concentrated to 45% by spray concentration tower at one time, and then used to react with phosphate rock to produce phosphoric acid, and finally generate phosphate fertilizer. The fuel gas entering the spray concentration tower is coal-fired purification tail gas, boiler high-temperature tail gas, and high-temperature tail gas generated by natural gas or fuel oil combustion. This process simplifies the waste acid concentration process, cancels the heat exchanger and other equipment, and can use the waste heat of boiler tail gas to reduce the concentration cost

after years of efforts, Wuhan Fangyuan company has adopted the waste acid flue gas steam secondary concentration process to build an 8000 ton/year titanium dioxide waste acid recovery unit, realizing the concentration and reuse of waste acid. The continuous operation of the industrial device has proved that the process technology is advanced, the device design and equipment selection are reasonable before selecting the fixture, and the operation is stable. All the waste sulfuric acid is reused, and the economic benefit of 1.4 million yuan is achieved. At the same time, the company has carried out comprehensive utilization of titanium gypsum. Titanium gypsum slag has been reduced by more than 25%. After neutralization and treatment of dilute acidic wastewater, it is discharged with neutral water to meet the standard. The concentration of exhaust smoke and dust, ringer blackness and other indicators have reached the discharge standard of the functional area

waste acid is the main waste liquid discharged from titanium dioxide production by sulfuric acid method. According to the investigation, some domestic enterprises have finally found appropriate reuse solutions through continuous research and development. First, the waste acid is directly returned to the acidolysis system of titanium dioxide production to replace commercial sulfuric acid; Second, it is used to neutralize calcium carbide mud, which solves the problem of waste residue treatment in the region; Third, concentrate and reuse waste acid to produce sulfuric acid products; Fourth, extract precious metals from waste acid to improve economic benefits. For example, Bailian company cooperates with Hunan rare earth Co., Ltd. to extract rare earth scandium oxide from waste acid. The project was implemented in 2011, and qualified scandium oxide products have been produced, realizing the transformation of waste into treasure. At present, in the international market, pure scandium oxide costs 3000 yuan per gram, which is more than 10 times more expensive than gold

the way out lies in the development of circular economy

at present, the chlorination method is basically used in the production of titanium dioxide in developed countries in Europe and the United States. This method has advanced technology and low emissions of three wastes. Then, why doesn't China engage in chlorination titanium dioxide? Liuhanjie told: it's too difficult to do it. Technology import, foreign companies engage in technology blockade, do not sell; Develop it by yourself. A powerful domestic company has developed it for more than 20 years, and only a small device with an annual output of 15000 tons has been put into production. Its technology cannot compete with foreign devices

it is learned that due to the difficulty of the production technology of titanium dioxide by chlorination, the complex structure of key equipment, the need to use special materials with high temperature resistance, corrosion resistance and oxidation resistance, and the huge investment required for research and development to form commercial production, this technology has been monopolized by a few European and American companies. China faces several insurmountable difficulties in developing titanium dioxide by chlorination

first, in terms of key equipment, the production capacity of a single set of foreign devices can reach more than 100000 tons, while China has only one 15000 ton chlorination titanium dioxide device officially put into production. The chlorination furnaces of foreign devices are boiling chlorination furnaces; The furnace developed in China is molten salt chlorination furnace. Although it can adapt to domestic titanium resources, it is still difficult to overcome the problems of molten salt waste residue treatment and large-scale equipment

second, in terms of titanium resources, the content of calcium and magnesium in domestic titanium ore is high, which cannot be removed in production, and the quality of titanium dioxide cannot be improved. If the imported high titanium slag with calcium and magnesium content less than 1% is used as raw material, it will not be competitive economically. Even foreign titanium dioxide giants dare not import high titanium slag to launch the chlorination titanium dioxide project in China. People may remember,

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