After 60 years＇ development, China has become the country where tio2 industry develop most dynamically all over the world. Along with the rapid development of China economy, great changes took place in the look and pattern of domestic tio2 industry and remarkable achievements have been made in the industry. Particularly in recent ten years, domestic tio2 industry has entered a new round of growth cycle in that its comprehensive strength has been improved constantly, a considerable scale has been formed and overall level of the enterprises has been continuously increased. In recent years, new technology, new process and effective equipment are applied extensively. New processes include pre-mix process of acid solution, vacuum crystallization, membrane filter press used for washing process instead of Moore Leaf Filter and rotary kiln exhaust gas waste heat used for waste acid concentration process etc. New equipments and technologies are as follows: wind-swept grinding machines which replaced raymond machine, large-scale irrigation acidolysis and hydrolysis reactor whose volumes are more than or equal to 100m3, disk filter used for ferrous separation instead of centrifuges, large leaf filter(F = 200m3 ) used for washing, Φ3200 × 53000mm rotary kiln, roll mill used for intermediate crushing instead of raymond machine, spray drying or flash drying replacing belt dryer and DCS control technology etc. All these technologies and equipments contribute to improving the technical level and market competitiveness of the enterprises by reducing the material and energy consumption, improving the production efficiency, automation level of the production equipment as well as the quality of the products.
However, there are also some prominent problems constraining the development of the industry, such as environmental protection and energy saving etc. It＇s known to all that sulfuric acid process has been the focal point of the environmental protection department＇s inspection because its vast "three wastes" discharges. Although tio2 manufacturers continuously increase their investments in environmental protection and have done a lot of jobs on comprehensive utilization, they are still a little far from the increasingly stringent environmental requirements. Then what should China＇s tio2 enterprises do to implement clean production in accordance with the requirements of sustainable development and recycling economy? Tio2 expert Guo Zhenglong proposed the following measures. At first, tio2 enterprises must establish a new concept of environmental governance and change the end treatment to a whole process of cleaner production; Secondly, some backward enterprises should be closed, merged or transformed according to the environmental indicators; Thirdly, enterprises should increase investment in environmental protection and improve environmental protection facilities; Besides, manufacturing enterprises should put emphasis on the treatment and comprehensive utilization of the waste by-product sulfuric acid with a concentration of 20%. The most fundamental way of realizing cleaner production is to change the structure of the mineral resources, use acid-soluble titania slag to replace low-grade titanium ore and achieve the aim of "zero waste acid emissions" through concentration, recovery and comprehensive utilization.
About the current situation of energy-saving and emission reduction and the hot topic of future comprehensive treatment, Yao Hengping, the director of China Coating Association Tio2 Branch, made an in-depth elaboration in his annual report "Implementing the Ideas of Scientific Development to Enhance the Competitiveness of Titanium Dioxide Industry ".
Yao Hengping pointed out that the jobs of energy-saving and emission reduction in China have achieved remarkable results but we still need to make further efforts. Ever since the second half of 2007, the government has strengthened supervision of the titanium dioxide industry from the level of legislation and normative management. Subsequently, some bad events in the industry were exposed by the media because of the mismatch of the "three wastes" treatment facilities, the abnormal operation and management as well as excessive discharge. In the full glare of the government and the media, comprehensive treatment was carried out in some regions and many enterprises redoubled efforts to govern "three wastes". After the implementation of the national circular economy promotion law, a lot of enterprises have strengthened the work of energy-saving and emission reduction. On the whole, the technology of concentrating and comprehensively utilizing waste acid has made obvious progress; The recycling of low-temperature heat from sulfuric acid system has been initiated; The comprehensive utilization of calcium sulfate and other solid wastes has entered the phase of large-scale experiment. The work of "three wastes" treatment, energy-saving and emission reduction have raised the level of enterprise management; The reduction of material and energy consumption has increased enterprises＇ ability to withstand the financial crisis and accelerated the recovery of corporate profitability. However, under the great pressure of national environmental protection policies, some tio2 companys have to be closed as they could not meet the discharge standards and lacked the capacity to survive. Therefore, for the survival of tio2 enterprises and the development of the industry, we shall continue to attach great importance to environmental protection and improve the level of governance by increasing investment in technological reform and improving the treatment facilities. In addition, Yao Hengping made important instructions on the direction and prospects of future energy-saving and emission reduction in tio2 industry. From now on, the state will accelerate its pace of establishing mechanism to eliminate heavily polluting enterprises. "Notification about Suitably Carrying out Environmental Impact Assessment under Current Economic Situation " just issued by the Ministry of Environmental Protection required that relevant official departements should strictly control over the assessment and approval of "high pollution, high emission and resource-based" construction projects. It addressed a new warning to the industry development. At present, tio2 plants don＇t have a good image in the society due to the fact that sulfuric acid process discharges a great amount of "three wastes" and individual enterprises do not truly pay attention to waste treatment. What＇s worse, early in this year, some tio2 plants were exposed or ordered to stop production for rectification because of environment pollution, which further added pressure to the industry. In order to improve the image of the industry, tio2 industry issued "Green Environmental Protection Declaration" to the whole society some time ago after three years＇ communication and discussion. Guided by the declaration, enterprises should make further efforts in comprehensively utilizing and governing "three wastes" and strive to achieve new breakthroughs in the comprehensive utilization. Through the joint efforts of China Coating Association and TiO2 Branch, recently, China Ministry of Industry and Information Technology finally arranged a special fund to support the energy-saving and emission reduction work of tio2 industry. From the present situation and the global perspective, firstly we should establish a new philosophy of environmental governance, changing end treatment to a whole process of cleaner production and changing passive treatment to comprehensive utilization; Secondly, we should blaze a trail of environmental production with Chinese characteristics through strict governance and management and in accordance with the indicators of national environmental standards; Thirdly, we should increase investment in environmental protection and improve the operation of environmental protection facilities from a strategic perspective. Finally, we should vigorously promote the industrialization of chlorination process. Chlorination process is conductive to alleviating the environmental pressures of domestic tio2 industry as high-grade titanium slag is used as raw material in the chlorination process and the production process discharges less solid waste. At present, chlorination process is the developing direction of titanium dioxide industry in the world and it has been adopted by a lot of developed countries because in addition to the environmental advantages its superiorities in quality, costs and investment have become increasingly evident.In China, the government encourages enterprises to put more investments into the chlorination tio2 production project. Therefore, in order to increase the comprehensive competitive ability of domestic tio2 industry in the whole world and to satisfy the demand of different customers, we should take various forms to propel the industrialization of chlorination tio2.
Over the past ten years, with the rapid development of domestic economy, China＇s inland tio2 production industry has gained great improvement in production technology, device size, production volume and quality. However, the regulations, industrial stength and the ability of the enterprises were extremely weak when the industry was faced with environmental problems due to the shackles of mindset and the traditional thought. To this end, Gong Jiazhu, the general manager of Chengdu Challenging Technological Innovation Co., Ltd and the expert of energy-saving and emission reduction, gave a report titled "The Evolution of Environmental Policy in EU Titanium Dioxide Production Industry and The Environmental Emission Standards" in Chengdu tio2 annual meeting, providing a theoretical basis for the new norms of tio2 circular economy and the new environmental regulations. In his report, Gong Jiazhu pointed out that the general waste treatment policy had been changing since the founding of European Commission in 1958. Firstly, the single waste control policy was gradually developed to a comprehensive control method in which environmental protection was integrated into the major policy categories. After years of exploration, the European Union environmental regulations for the titanium dioxide industry become more and more scientific and rational, and we can learn from them in some respects. The original EU rules aiming at the waste problems in titanium dioxide industry emphasized the use of standard methods to monitor to prove that pollution control measures are effective, but quantitative emission standards were not included in them. Such rules are not scientific enough, therefore, the "first derivative rule" and the "second derivative rule" appeared subsequently. The"first derivative rule", which was born in 1982 and was also directing at tio2 industry, focused on detection and control methods. It was greatly improved compared with the original rules, but there were still some sensitive issues in it. The "second derivative rule", also known as the reconciled rule, was passed in 1992. It revised the first derivative rule and is the criteria of tio2 industry. It implicitly encourage the production and marketing of concomitant products. The main conditions of the rule are as follows. Any form of wastes are forbidden to discharge from June 15, 1993; Coercive measures are suggested to use to prohibit discharge of wastes into the waters of the island, regional water and marine; Sulfuric acid compounds whose quantity is limited include "weak acid", gas and dust emissions. In addition, the rule also summarized the state＇s responsibility to the reconciled rule. If EU regulations were adopted by China, domestic tio2 manufacturers would be faced with severe challenges since most of them apply sulfuric acid process. Nevertheless, the environmental problems of sulfuric acid process can be well resolved through technical innovation. The possible concomitant output of sulfuric acid process include acid dipping soil (acid solution residue), green vitriol (ferrous sulfate heptahydrate, FeSO4 · 7H2O), ferrous sulfate monohydrate, ferric sulfate, iron oxide, white gypsum, red gypsum and carbon dioxide. In fact, they can be utilized comprehensively. For example, the unreacted solid not leaching out (acid solution residue) can be used to produce cement, blast furnace repair materials and asphalt additives. As a low-value product, green vitriol is easy to be oxidized unless it＇s reserved in acid solution. It can be used in water treatment. It＇s newly used to reduce the impact of hexavalent chromium in cement. Besides, green vitriol can be further processed into a ferrous sulfate, which can be taken as nutritional supplement ingredients for animal feed. And PFS is a more valuable product and it can also be used for water treatment. PFS is produced by using nitrate to oxidize the by-products of green vitriol and then drying the resultant. By-products like metal salts, white gypsum and red gypsum are produced when titanium dioxide plants recycle the concentrated waste acid. Metal salts settle down while evaporating the concentrated waste acid. Through calcination and contact absorption, the mixture of these salts and pyrite can be used to produce sulfuric acid. And metal oxides, mainly consisting of iron oxide, produced by calcination, can be used to produce pigments or be taken as the raw material of steel plant; White gypsum refers to the nonferrous gypsum which generates in the first phase when limestone (CaCO3) is taken as the neutralization media. When lime (Ca (OH) 2) is added to the remaining solution and the complete neutralization reaction occurs, the mixture of iron hydroxide and gypsum, namely red gypsum, is produced. White gypsum can be used to produce the filler of plastic sheeting, cement and paper. Red gypsum can be used as soil modifier as it can repair the destroyed soil ion balance caused by salt leaching.
Ten years＇ ago, the device size of China＇s tio2 industry is only 190,000 tons, and that of rutile is only above 20,000 tons. But ten years later, our device capacity has already reached 1.6 million tons and China has become a great power in the world to use titanium feedstock and produce titanium dioxide. Thanks to the joint efforts of all the enthusiastic personnel concerning about tio2 industry, it＇s possible for us to expand the production capacity, improve the products＇ quality and establish the new philosophy of circular economy, energy-saving, emission reduction and environmental protection. The research work about European tio2 industry over the past 30 years, the analysis of the development and requirement of European environmental regulations as well as the study and innovation of these results will help domestic tio2 industry to make the most appropriate choice in the new legal environment.
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