Fluogypsum is an industrial waste residue produced from fluorite and concentrated sulfuric acid. For every 1 ton of hydrofluoric acid produced, 3.6 tons of anhydrous fluogypsum are generated. The production reaction equation is shown as follows:
H2SO4+CaF2 → 2HF↑ +CaSO4
When fluorine gypsum is discharged from the reactor, the material temperature is 180 ~ 230℃, the gas temperature is 800 ~ 1000℃, the discharged gypsum is anhydrous calcium sulfate, belonging to ⅡCaSO4. At the beginning of the kiln, fluoropgypsum contains residual fluorite and sulfuric acid, and the content of fluorine and sulfuric acid in the leaching solution is relatively high, which exceeds the limit of the "Hazardous Waste Identification Standard", and the environmental protection department requires that it should not be placed in a pile. For this reason, Chinese hydrogen fluoride enterprises mostly use the lime neutralization method, which means that the freshly baked gypsum is added to the lime powder to neutralize when PH=7 or so. The lime is added to neutralize the sulfuric acid and produce calcium sulfate. The purity of the discharged fluoropgypsum can reach 80% ~ 90%. Utilization status of fluoropgypsum: At present, there are 88 hydrogen fluoride enterprises in China, and the waste residue of fluoropgypsum is mainly used as cement retarder in cement factories. Its price ranges from 40 yuan /T to 100 yuan /T. In recent years, the cement production capacity has declined, and the outlet of fluoropgypsum has become a problem, which affects the normal production of enterprises. Since 2018, the treatment of fluoropgypsum has become a major environmental protection problem for major aluminum fluoride enterprises. Application of fluoropgypsum: The company has been committed to the application of fluoropgypsum technology research, has obtained invention patents: ①ZL201010587404.7,②ZL201110398888.5, are connected with various aluminum fluoride enterprises, develop suitable products, better resource utilization, in 2013 and 2014 respectively in Henan Xinxiang, Hunan Chenzhou gypsum building machine with fluorine gypsum gypsum block production. The inspection completely meets the standard requirements of gypsum block. The walls of the fluoroogypsum blocks produced in the workshop of our company in 2012 remained intact until 2017, indicating that the fluoroogypsum blocks can fully meet the technical requirements and are successful. Due to the lack of urgency, the application market has not been developed. With the increasing pressure of comprehensive utilization of fluoropgypsum resources, the industrial production of fluoropgypsum will be formed.
