“New directions for desulfurization in steel enterprises during the 12th Five-Year Plan period

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During the 12th Five-Year Plan period, the focus of control on desulfurization will shift from the thermal power sector in the previous five-year period to the steel industry. Should the desulfurization of sintering machines in steel companies follow the model used for desulfurization in thermal power plants during the 11th Five-Year Plan period, or is it possible to find an innovative approach? The model of thermal power plant desulfurization. During the 15th Five-Year Plan period, target requirements were set for controlling the total amount of SO2 emissions, but the targets for reducing SO2 emissions were not met. In 2005, the total SO2 emissions from thermal power generation increased by 101% compared to 2000, becoming the main cause of the loss of control over SO2 pollution control. During the 11th Five-Year Plan period, thanks to a series of key policy measures and the cooperation of environmental protection agencies at all levels, the goals set out in ** were achieved ahead of schedule. In 2005, the total installed capacity of thermal power plants across the country was 385 million kilowatts, with desulfurization units accounting for only 12% of this total. By 2008, the capacity of desulfurization units alone had reached 379 million kilowatts, accounting for about 66% of the total thermal power capacity. By the end of the 11th Five-Year Plan period, a total of 565 million kilowatts worth of desulfurization facilities had been installed in coal-fired power plants across the country, representing 80% of all thermal power units in the country. Our country took 5 years to almost complete the desulfurization task that the United States took over 30 years to accomplish. According to statistics, over 90% of these 565 million kilowatts worth of desulfurization units use the limestone-gypsum method. Assuming that a 300MW unit burns coal with a sulfur content of 1%, and operates for 5,000–6,000 hours per year, this will result in the production of 45,000–50,000 tons of desulfurization gypsum per year; in total, 75,000–84,000 tons of such gypsum will be produced each year. The reality that must be faced is that desulfurization gypsum in our country cannot be used directly due to impurities and moisture content that do not meet the required standards; the utilization rate is only around 30%. Nearly 40 million tons of gypsum are discarded or landfilled each year, thereby causing further environmental pollution. It is imperative to upgrade desulfurization technologies. It is certain that steel companies can no longer rely on the traditional limestone-gypsum method for desulfurization. The composition of sintering flue gas is complex, resulting in lower quality gypsum as a by-product, making it difficult to reuse. The operation costs of the limestone-gypsum method are high; against the backdrop of declining profit margins in steel companies, desulfurization costs have become a heavy burden for them. The investment in sintering desulfurization equipment accounts for about 20% to 50% of the investment in sintering machines, while the operating cost for desulfurizing per ton of sintered ore is 5 to 14 yuan. The \"Pollution Emission Standards for Thermal Power Plants (Second Draft for Public Comment)\」adjust the nitrogen oxide emission limit for coal-fired power plants from 200 mg/cubic meter to 100 mg/cubic meter; it adjusts the sulfur dioxide emission limit to 100 mg/cubic meter; and it adjusts the dust emission concentration limit to 30 mg/cubic meter. Due to its inherent defects, the limestone-gypsum method finds it difficult to achieve high desulfurization efficiency; therefore, an upgrade of desulfurization technologies is imperative. The innovative path for steel companies in desulfurization: Energy conservation paves the way for the future, and sustainable energy can transform lives. The process of using wet magnesium oxide to produce magnesium sulfate heptahydrate offers high desulfurization efficiency and high economic value for the by-products. Taking the full flue gas desulfurization project for the 200m2 sintering machine at Chengde Shengfeng Iron and Steel Co., Ltd. as an example. The total investment in this project is 35 million yuan. After its completion, the annual operating costs will amount to 16 million yuan. Once the desulfurization by-products are converted into magnesium sulfate heptahydrate, and based on the current market price of MgSO4·7H2O, the annual sales revenue is estimated to be 26.3 million yuan. This desulfurization system generates a gross profit of 10.3 million yuan for Shengfeng Steel each year. According to statistics, the total area of sintering machines across the country is 53,820 m2. By using the wet magnesium oxide process to produce magnesium sulfate heptahydrate, it is possible to increase annual corporate profits for the entire industry by nearly 2.8 billion yuan, while ensuring that sulfur dioxide emissions remain below 100 mg/m3. Since there are relatively few actual engineering cases of this desulfurization technology being applied in domestic power plants compared to the limestone-gypsum method, some steel companies are not yet familiar with this technology. At present, relevant **departments need to adopt new cooperation models to encourage steel companies that require desulfurization to use the most advanced technologies. In the current market, there are still few cases of desulfurization of sintering plants using innovative business models. However, this represents the future direction for desulfurization in steel plant sintering processes. For example, Beijing Shinen Zhongjing adopts a market-based environmental management mechanism based on DBO (Design, Build, Operate), and implements a business partnership model in which the revenue from selling magnesium sulfate heptahydrate is used to cover the operating costs of the projects. To date, there is experience in building and operating more than a dozen such sintering plants, and all of these projects have achieved good economic returns.