Highly active calcium-based desulfurizer specifically for coke oven flue gas – as a substitute for baking soda

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In recent years, dry flue gas desulfurization technology has been increasingly used in small and medium-sized flue gas desulfurization systems; it is a mature technology with stable operation. Among them, the SDS desulfurization process using sodium bicarbonate as the base source has seen its market share increase rapidly, thanks to advantages such as high desulfurization efficiency, wide availability of the desulfurizing agent, and low difficulty in implementation. As the number of installations increases, the disadvantages of this technical approach have begun to become apparent, and how to deal with desulfurization ash has turned into a new environmental challenge. Sodium-based desulfurization ash is a mixture of sodium sulfate, sodium sulfite, and sodium carbonate; it has good water solubility and belongs to the category of general solid waste that is difficult to dispose of in compliance with regulations. According to official statistics, the coking industry alone generates as much as 300,000 tons of sodium-based desulfurization ash each year; when accounting for the power boilers, hot blast stoves, and heating furnaces in steel plants, as well as glass and cement kilns, the amount of sodium-based desulfurization ash increases even further. Some companies rent premises to build warehouses for storing these items, while others sell them to qualified agencies for disposal; the cost per ton ranges from 100 to 500 yuan, which adds to the financial burden on these companies. On September 1, 2020, the revised Law of the People’s Republic of China on the Prevention and Control of Environmental Pollution by Solid Wastes came into full effect. It introduced new obligations for enterprises that generate solid waste, stipulating strict penalties for any illegal activities. Business pressures are soaring! Highly active calcium hydroxide with a high specific surface area features porosity, high activity, good dispersibility, and high utilization efficiency. Its specific surface area (BET) is over 40 m2/g, which is 3–4 times that of ordinary calcium hydroxide, while its desulfurization efficiency is above 95% ； The pore volume of calcium hydroxide with a high specific surface area exceeds 0.2 cm3/g, enabling rapid adsorption and absorption of HCl and SO2 in flue gas, with an utilization rate of over 85% ； Calcium hydroxide with a high specific surface area has good fluidity and is less likely to clog pipes during use. In the 1980s, Europe, the United States, and Japan began to use high-specific-area calcium hydroxide extensively for desulfurization in waste-to-energy plants and thermal power plants, successfully replacing soda ash; it is currently recognized worldwide as an excellent dry desulfurization agent. In 2010, Lhoist introduced a highly active calcium hydroxide desulfurization agent in China, which was used for treating flue gases from waste incineration plants, glass furnaces, and ceramic kilns. This marked the beginning of the use of calcium-based desulfurization agents with high specific surface area in China. The main by-products of desulfurization are calcium sulfate, calcium carbonate, calcium hydroxide, and other common solid wastes that can be recycled. However, due to the high cost of these desulfurization agents, they have not been widely used. After months of intensive research and the efforts of scientific and technical personnel, highly active calcium hydroxide with a high specific surface area was successfully developed; its specific surface area (BET) exceeded 45 m2/g. Industrial production was established, and it was launched on the market in June 2021. The HNPS desulfurization system developed by the company has undergone pilot tests and industrial use over several months with different users; it exhibits good operational performance, low costs, and satisfies the users. Currently, it has been successfully applied at the coke oven pusher ground station for dust removal in the dry quenching process of coke, as well as for the desulfurization of coke oven flue gas. For detailed information, please contact Manager Zhang at ①⑧③②②⑥①⑨⑧⑧⑨