Quicklime is a commonly used desiccant for removing water vapor using chemical absorption. It is also used in the steel, pesticide, pharmaceutical, desiccant, leather, and alcohol dehydration industries. It is particularly suitable for products in puffed foods, shiitake mushrooms, wood ear mushrooms, and other local specialties, as well as products in the instrumentation, pharmaceutical, clothing, electronics and telecommunications, leather, and textile industries.
Lime and limestone are widely used as building materials and are also important raw materials for many industries. Limestone can be directly processed into stone or burned into quicklime. Lime exists in two forms: quicklime and slaked lime. The main component of quicklime is CaO. It is generally in lumps; pure quicklime is white, while quicklime containing impurities is light gray or light yellow. Quicklime absorbs moisture or becomes slaked lime when water is added. Slaked lime, also called hydrated lime, has Ca(OH)2 as its main component. Slaked lime is mixed into lime slurry, lime paste, lime mortar, etc., and used as a coating material and brick/tile adhesive. Soda ash is produced from limestone, salt, ammonia, and other raw materials through a multi-step reaction process (Solvay process). Caustic soda is produced by reacting slaked lime and soda ash (causticization process). There are a total of 1,286 mineral deposits, including 257 large deposits, 481 medium-sized deposits, and 486 small deposits (large deposits have ore reserves greater than 80 million tons, medium deposits have 40-80 million tons, and small deposits have less than 40 million tons), with a total proven ore reserve of 54.2 billion tons, of which limestone reserves are 50.4 billion tons, accounting for 93%, and marble reserves are 3.8 billion tons, accounting for 7%. The reserves of quicklime are widely distributed across 29 provinces, municipalities, and autonomous regions, excluding Shanghai. Shaanxi Province boasts the largest reserves at 4.9 billion tons, followed by Anhui Province, Guangxi Zhuang Autonomous Region, and Sichuan Province (including Chongqing Municipality), each with reserves of 3.4-3 billion tons. Shandong, Hebei, Henan, Guangdong, Liaoning, Hunan, and Hubei provinces each hold 3-2 billion tons. Heilongjiang, Zhejiang, Jiangsu, Guizhou, Jiangxi, Yunnan, Fujian, Shanxi, Xinjiang, Jilin, Inner Mongolia, Qinghai, and Gansu provinces each hold 2-1 billion tons. Beijing, Ningxia, Hainan, Tibet, and Tianjin provinces each hold 200-500 million tons.
The treatment of quicklime in wastewater has become a major issue concerning the harmonious development of the economy and society. The state has adopted strict measures to control the growth of industrial pollutant emissions, increasing the treatment and upgrading efforts in the papermaking, brewing, chemical, and printing and dyeing industries, and eliminating outdated processes and equipment that are high in water consumption and cause heavy pollution. As my country's industrialization and urbanization continue to advance, the discharge of wastewater from quicklime industry and urban sewage is increasing year by year. Substandard discharges have placed enormous pressure on and caused harm to the environment. Quicklime is being used in key industries such as steel, power, chemicals, and coal to promote wastewater recycling and improve the reuse rate of industrial water. At the same time, the processes and technologies for treating wastewater from quicklime industry are constantly improving, which also presents new requirements for quicklime-based flocculants used in water treatment.
