Highly active calcium-based desulfurizer

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Application of calcium hydroxide desulfurizer with high specific surface area. In recent years, dry flue gas desulfurization technology has been increasingly used in small- and medium-sized flue gas desulfurization systems; this technology is mature and operates stably. Among them, the SDS desulfurization process route using sodium bicarbonate as the alkali source has rapidly gained market share due to its advantages such as high desulfurization efficiency, wide availability of desulfurizers, and low difficulty in engineering implementation. As the number of installations increases, the drawbacks of this technological approach become apparent; how to dispose of desulfurization ash has thus become 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 falls under the category of general solid waste that is difficult to dispose of in compliance with regulations. According to authoritative statistics, the coke industry alone generates as much as 300,000 tons of sodium-based desulfurization ash annually. When adding power plant boilers, hot blast stoves, reheating furnaces in steel plants, as well as glass and cement kilns, the volume of sodium-based desulfurization ash increases manifold. Some enterprises rent premises to build warehouses for storage, while others sell the waste to qualified organizations for disposal. The cost ranges from 300 to 500 yuan per ton, thereby increasing the burden on enterprises. 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 introduces new responsibilities for enterprises that generate solid wastes, and stipulates severe penalties for any illegal acts. Corporate pressure is surging! Highly active calcium hydroxide with a large specific surface area features porosity, high reactivity, good dispersibility, and high utilization rate. Its specific surface area (BET) exceeds 40 m²/g, which is 3–4 times that of ordinary calcium hydroxide. Its desulfurization efficiency is over 95% ； The pore volume of high-specific-surface-area calcium hydroxide reaches over 0.2 cm³/g; HCl and SO₂ in flue gas undergo adsorption and absorption reactions rapidly, with a utilization rate exceeding 85% ； High-specific-surface-area calcium hydroxide has good flowability and is unlikely to clog pipes during use. In the 1980s, Europe, the United States, and Japan began to widely use high-specific-surface-area calcium hydroxide for desulfurization in waste-to-energy plants and thermal power plants, successfully replacing baking soda. It is currently recognized internationally as an excellent dry desulfurization product. In 2010, Lhoist introduced a highly reactive calcium hydroxide desulfurizer in China for use in flue gas treatment in waste incineration plants, glass furnaces, and ceramic kilns. This marked the beginning of the application of calcium-based desulfurizers with high specific surface area in China. The main components of the desulfurization by-products—such as calcium sulfate, calcium carbonate, and calcium hydroxide—are general solid wastes that can be recycled. However, due to the high cost of the desulfurizer, it has not been widely adopted. After months of research and development, and thanks to the efforts of scientific and technical personnel, a calcium hydroxide with high reactivity and a large specific surface area has been successfully developed. Its specific surface area (BET) exceeds 45 m²/g. Industrial-scale production has also been achieved, and the product was launched on the market in June 2021. The HNPS desulfurization package developed by the company has undergone pilot tests and industrial applications by various users over several months. It demonstrates excellent operating performance, low costs, and has received high satisfaction from users. Currently, it has been successfully applied in coke pusher surface stations, environmental dust removal for dry quenching, and desulfurization of coke oven flue gas. Advantages of the HNPS desulfurization technology: 1. It utilizes a calcium-based desulfurizer with high reactivity and large specific surface area, which is directly injected into the flue gas duct and thoroughly mixed with the flue gas. This enables effective adsorption and absorption of acidic components in the flue gas, resulting in high desulfurization efficiency ； 2. The HNPS dry flue gas desulfurization process is adopted; there is no temperature drop during the reaction process. The existing bag filter or a newly installed bag filter is used to remove solid waste. The calcium-based solid waste is resistant to moisture absorption, non-corrosive, and does not cake. 3. Compared to SDS, desulfurization using this method has virtually no temperature restrictions; there is no need to install a grinding system on-site, resulting in low investment and operating costs. It can directly replace baking soda in existing SDS processes ； 4. The main components of desulfurization by-products, such as calcium sulfate, calcium carbonate, and calcium hydroxide, are all classified as general solid waste and can be recycled and utilized ； 5. Few devices and equipment, flexible layout, and low investment ； Tank trucks are used for feeding; the system is completely sealed, with no dust generated on site ； Roots blowers or compressed air conveyance consume little power. ①⑧③②②⑥①⑨⑧⑧⑨