The use of highly active calcium hydroxide in desulfurization

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1. Highly efficient modified calcium hydroxide (slaked lime) is primarily used for flue gas desulfurization and denitrification in waste incineration plants, enabling a 35% reduction in the amount of conventional calcium hydroxide required. 2. High specific surface area: BET (specific surface area) > 40 m2/g, which is 3 times higher than that of ordinary calcium hydroxide. This improves the efficiency in removing SO2 and HCl, **reduces the amount of fly ash generated, and thus significantly lowers operating costs. In the flue gas desulfurization industry, it isn’t the case that a higher content of slaked lime is always better. Taking slaked lime with 95% purity as an example, the 95% slaked lime available in China almost always contains some calcium oxide; its actual calcium hydroxide content is far from 95%, as the current standards require first determining the amount of calcium oxide in the slaked lime and then multiplying it by a factor of around 1.3 to calculate the amount of calcium hydroxide. Calcium oxide has a very low surface area, and it hardly participates in reactions. The specific surface area of slaked lime with a purity of 95% available in China is generally around 15 to 18. In actual reaction processes, its effectiveness is similar to that of ordinary 90% calcium hydroxide. Based on our factory’s investigations, only 50% to 60% of the ordinary 90% and 95% slaked lime participates in reactions in waste incineration plants; the remaining portion does not react and ends up in the waste ash, resulting in significant waste. The reaction rate of slaked lime with a high specific surface area is much higher than that of ordinary slaked lime, allowing for complete reaction, preventing waste of resources, reducing costs, and minimizing equipment wear. Introduction to calcium hydroxide with a high specific surface area: Calcium hydroxide (slaked lime, hydrated lime) refers to a powdered substance obtained by reacting quicklime with a controlled excess of water, typically containing less than 1% free water. Below 350°C: CaO + H2O → Ca(OH)2 + 276 (Kcal/KgCaO). In the 1980s, calcium hydroxide with a high specific surface area was primarily used to remove acidic gases from exhaust gases. It is evident that increasing the surface area of calcium hydroxide helps to improve efficiency; therefore, efforts were made to develop calcium hydroxide with a high specific surface area. It is widely used in the synthesis of pharmaceuticals and food additives, the production of high-tech biomaterials such as HA, the synthesis of VC phospholipids as feed additives, the production of food-grade konjac, calcium compounds, as well as calcium naphthenate, calcium lactate, calcium citrate, and additives for cola, and in the synthesis of other high-quality organic chemicals. Surface area characterization methods: (1) BET method for measuring specific surface area ； (2) Measure the total pore volume and pore size distribution ； (3) Measure particle size and distribution ； (4) Electron microscopy observation of particle morphology. There are currently two methods for producing calcium hydroxide with a high specific surface area: one involves drying and grinding lime milk, resulting in calcium hydroxide with a specific surface area of up to 30 m2/g (referred to as the wet method) ； Secondly, high-specific-area calcium hydroxide can be obtained through various methods (referred to as the dry method), such as: (1) digestion using water or alcohol solutions ； (2) Sucrose aqueous solution ； (3) Add sulfonated lignin ； (4) Derivatives of amines, etc. The parameters of the digestion process also affect the surface area, such as water temperature, the degree of calcination of quicklime, the size of the quicklime particles fed in, the specific surface area of quicklime, the residence time of the material in the digester, and its maximum temperature. Calcium hydroxide has a wide range of applications, but it is necessary to design the production process accordingly based on the specific application scenario – in other words, to tailor the production of \"specialized calcium hydroxide\" in order to achieve optimal performance. For use in pharmaceuticals, for example, high-purity calcium hydroxide is required, with the levels of harmful heavy metals such as lead, arsenic, and mercury meeting the standards specified in pharmacopoeias ； Another example is the removal of acidic gases, where calcium hydroxide with a high specific surface area is used to achieve high efficiency. Main application areas: ● Environmental protection (production of bleaching powder, water softeners, treatment of acidic water, wastewater treatment, desulfurization and dechlorination of flue gases from waste incineration, etc.). ) ● Chemical production (various calcium salts, etc.) ● Lubricant production (lubricant additives such as high-alkali-value calcium sulfonates, calcium-based greases, etc.) ● Food and pharmaceutical uses (food additives such as calcium lactate, medical calcium hydroxide pastes, etc.)