Written by Xu Gaodong and translated by Xin Xue
"2009 National Titanium Dioxide Industry Annual Meeting" organized by China Coating Industry Association TiO2 Branch successfully closed in Chengdu, Sichuan on December 4, 2009. The meeting mainly summarized the operational status and development trends of domestic tio2 industry in 2009, introduced and interpreted the national industrial policy guidance as well as about ten issues such as "production license", "export guidelines" and "clean production standards". Most of the issues referred to "environmental protection", "energy-saving and emission reduction", "green production" and other words related to environmental protection. Therefrom, it＇s easy for us to understand that resources-saving and green production have been the important factors deciding the fate of tio2 enterprises. Most probably, this annual meeting will become the driving force promoting the reform and innovation of China＇s tio2 industry. And it may also be an important signal which indicated that China＇s tio2 industry will be geared to international standards.
During the meeting, Liu Changhe, the leader of China Coating Industry Association TiO2 Branch Expert Group, pointed out that nowadays sulfuric acid process is developing rapidly and advanced chlorination process manufacturing equipment with a production capacity of 10,000 tons is operating stably when he introduced the "Emission Standards for TiO2 Industrial Pollutants"(a discussion paper of the expert group). He also said that China first tried to produce tio2 using sulfuric acid process in 1957 but till the year 2007 it already had a production capacity of 1.1 million tons. Large-scale titanium dioxide manufacturers have an annual output of more than 150,000 tons. In recent years, rutile tio2 has developed quickly and its production capacity accounts for 45% of the total tio2 output, basically satisfying the demand of domestic market. However, in terms of environmental protection, tio2 industry has been following the national emission standards for general industrial waste. With regard to waste gas and waste water, manufactures usually implement the national standard GB16297, GB8978, but for sludge discharge, there are no standards to abide by. Because of the rapid development of tio2 industry and the lag of the disposal of three wastes, sulfuric acid titanium dioxide products were included in the "double high product" list in the year 2009 . In this case, in order to control the pollution tio2 industry caused, the government introduced the draft of "Emission Standards for Industrial Pollutants from Inorganic Pigment Titanium Dioxide Industry" in 2008. But generally speaking, the indicators this draft proposed are alienated from the actual affordability of tio2 plants. Therefore, there are difficulties for tio2 plants to meet these standards under the current limited conditions of capital, technology, equipment and management level. In order to help domestic enterprises to have a comprehensive understanding of the emission standards for tio2 pollutants, members of tio2 expert group read and translated the European emission standards for tio2 industry, which stipulate less monitoring items than the draft of emission standards China introduced by contrast. Nevertheless, the draft is acceptable because the monitoring items it prescribed do not exceed those in the general emission standards for industrial waste internationally. What＇s more, it can not only provide some reliable environmental protection guarantee for tio2 production but also ensure a certain degree of titanium dioxide production capacity. Besides, through comparison, we also found that the European emission standards for chlorination process tio2 are much stricter than those of sulfuric acid process. Thus we can see that chlorination process is safer and cleaner and so it should be the developing direction of the domestic tio2 technology.
In the meeting, Liu Changhe introduced the access conditions of tio2 industry(draft), which referred to the following details: "Enterprise should adopt the certification of Environmental Management System ISO14000-1996 or ISO14001-2004 " and "The products for export rebates must pass the cleaner production examination and verification from the local environmental protection department". These green barriers aiming at tio2 business can effectively eliminate the backward production capacity of some serious pollution and create a good atmosphere of green production for tio2 industry. Besides, in his draft, the formulation "Verifying Conditions for Enterprises Applying for Export Rebates " also put forward the environmental protection issues as critical items. These verifying conditions stipulated that the discharge and treatment of three wastes must meet the special standards. For instance, plants must have their own waste water treatment locations which are able to meet the demand of themselves; Tio2 production should accord with the national emission standards for three wastes, that is, effluent standards for enterprises (adding the emission requirements for Fe2 + and the emission standards for Chloride, namely, 350mg / l), atmospheric emission and control standards for enterprises(having complete waste acid treatment equipment, having an operating cycle of more than one year, and the monthly operating rate being above 70%) as well as residue discharge and disposal standards for enterprises(having closed treatment process or disposal sites for industrial residue and being able to discharge and dispose toxic and hazardous wastes reasonably ); The waste acid treatment of tio2 enterprises should meet the requirements of circular economy.
Subsequently, Liu Changhe described the general situation of the key scientific and technological support issues related to the development of tio2 industry during the "12th five-year plan". In his introduction, he referred to scientific and technological projects which are directly related to the green production of tio2 enterprises. And one of them is "Study on the Technology and Equipment of Complete Sets of Continuous Acid Hydrolysis Process". He said that this project would play an active role in promoting the green production of domestic tio2 enterprises in the future because it is conductive to simplifying the process of operations and reducing waste emissions. During the sulfuric acid process, acid solution unit is a key link which controls the whole production process and plays a vital role in the subsequent procedures. The current mature processes include intermittent and continuous acid hydrolysis process. Compared with intermittent acid hydrolysis process, continuous acid hydrolysis process can be controlled and regulated continuously and thus stable indicators can be ensured. Besides, in this process, the tail gas can be treated more easily and greater environmental effects can be achieved due to the balanced heat, uniform acidolysis exhaust and a small amount of acid mist entrained in the exhaust. Moreover, owing to the comprehensive regulation to the reaction, the amount of waste acid recycling is greatly increased. If the density of the waste acid achieved 55%, all the waste acid generated during the whole process would form a closed cycle, resolving the waste acid treatment problems. Furthermore, it has higher degree of automation and its equipment occupies smaller areas. Therefore, it＇s internationally recognized as one of the environmental technologies in sulfuric acid tio2 process. Ever since it was successfully developed, continuous acid hydrolysis process has been well applied in foreign tio2 plants using sulfuric acid process. While in China, it was developed a little later, hence only Panzhihua titanium dioxide plant applies this process at the moment.
As sulfuric acid process generates a great amount of wastewater, waste gas and residue, and as many countries have been pushing on the environmental management and protection work with measured strokes, the environmental governance of tio2 industry has become more and more urgent and prominent, which greatly limited the survival and development of sulfuric acid titanium dioxide. In this case, Panzhihua Iron and Steel Group has been committing themselves to the sustainable healthy development of tio2 industry and the environmental management and protection work all along. In 2007, it successfully introduced the continuous acid hydrolysis process technology from South Korea. As China doesn＇t have successful experience to learn, the advantages of this system doesn＇t been given full play and there still exist many problems in applying it despite that the main technical and economic indicators basically reached the attachment＇s requirements of the introduced technology after technical staff＇s digestion, absorption and independent innovation.
In order to successfully solve the issues of governing acidolysis exhaust and waste acid which have been troubling sulfuric acid tio2 industry and to release the environmental protection pressures of tio2 industry, it＇s necessary for tio2 enterprises to jointly make technological breakthrough with domestic research institutions and institutes of higher learning on the basis of introducing new technologies so that they can constantly open up their awareness of independent innovation, gradually consolidate their own technology research results and develop complete sets of technology and equipment of continuous acid hydrolysis, which has great significance in enhancing the overall technical level of China＇s tio2 industry and realizing the cleaner production of sulfuric acid tio2 industry as soon as possible. Luckily, Shandong Dongjia and other domestic representative tio2 enterprises have done a lot of research work in this area and have come to fruition. Once this tio2 project was implemented fluently, tio2 production would realize energy-saving and emission reduction shortly and satisfying technical objectives would be achieved. Till then, the exhaust emission will meet the standards and the closed-loop recycling of waste acid will be realized. Besides, waste acid emission reductions will reach 2.5t/t and the continuous operation time of the main reactor will be not less than 6 months. Moreover, other objectives will also be achieved, for instance, acid hydrolysis rate ≥ 96%, titanium processing capacity ≥ 5t / h and titanium recovery rate ≥ 95%.
Liu Changhe introduced another scientific research project related to energy-saving and emission reduction titled "R & D And Demonstration Projects about Energy-saving Effective Large Equipment for Concentrating Waste Acid from Sulfuric Acid TiO2". He pointed out that sulfuric acid process account for 97% of the production capacity of tio2 industry and waste acid concentration issues are the biggest problems it encounters in the cleaner production. At present, because of the fouling of the graphite evaporator and the low running rate of the pipe plugging device, equipments using for waste acid concentration are often in the maintenance state, which affects the recovery of waste acid. The graphite pieces are easily damaged due to the frequent disassembly and cleaning, which results in the high maintenance costs and low running rate of equipment. Owing to the above situation, the cost of concentrating H2SO4 waste liquor from the density of 20% to 80% is as high as above 400 yuan/ton, almost equal to the price of bought waste acid, which seriously interfere the competitiveness of sulfuric acid tio2, increased the running pressure of environmental protection equipment and can＇t meet the requirements of cleaner production. Currently, the waste acid treatment cost at home is 800 yuan for per tonne of tio2, lower than the cost at abroad, which is 180~200 USD. However, from the perspective of economic situation and titanium dioxide prices, the ratio of treatment costs to profits is too large domestically, namely, the input is too large and the profit is too small, which is not conductive to the sustainable development of tio2 enterprises. Therefore, the industry association established the project of researching an energy-saving effective large equipment for concentrating waste acid to solve this difficult tio2 production issue.
This demonstration project is expected to reduce the existing energy consumption by 30% and to decrease the waste acid treatment cost to less than 400 yuan for per tonne of tio2. Besides, a demonstration project for waste acid concentration will be set up to assort the equipment whose capacity is 40000 tons tio2 per year. Seen from the quality indicators and loop using of this research project, the waste acid can be re-used to produce tio2 with Ilmenite when it＇s concentrated to a kind of liquid-phase sulfuric acid with a density of 60-65%, while it can be re-used to produce tio2 with titanium slag when it＇s concentrated to a kind of liquid-phase sulfuric acid with a density of 70-75%. Therefore, this project has huge economical and social efficiencies in that it not only resolve the environmental protection issues but also maximize the utilization of resources.
The purposes of the above "Industry Access Conditions" and "Science and Technology Projects" issued by tio2 industry are both to control the waste emmissions of tio2 production. Hence the implementation of these regulations or scientific research items is bound to greatly promote the cleaner production of China＇s tio2 industry.
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