Discussion on the solution of high chloride ion content in desulfurized gypsum

                         Discussion on the solution of high chloride ion content in desulfurized gypsum

So far, the application of desulfurized gypsum in China is mainly concentrated in the production of cement and gypsum board. At the same time, great progress has been made in the fields of gypsum powder, plastering gypsum, high-strength gypsum and agriculture. In the application of desulfurized gypsum, there are many practical problems, including product moisture regain, sagging, yellowing and so on. These problems are inseparable from the excessive chloride ion content in the products.
Chloride ion is an impurity ion in desulfurized gypsum. During the combustion of fuel, the chlorine in it is converted into HCl in the flue gas. As the flue gas enters the desulfurization system, it is absorbed in the absorption tower and enters the slurry in the form of soluble salt; Another part of chloride ion is brought in by process water. There are many factors that affect the concentration of chloride ions in the slurry: the chloride ions entering the make-up water, the concentration of HCl in the flue gas and the chloride ions removed in the production process. Excessive chloride ion content in desulfurization gypsum will have many adverse effects, including production process equipment, desulfurization efficiency and the performance of desulfurization gypsum products.
Then, when desulfurized gypsum is used in gypsum and cement products, what are the requirements for chloride ion content? How to detect it?
Flue gas desulfurization gypsum
Chloride ion shall be determined according to the method specified in gb/t 176.
GB/T 21371-2019
Industrial by-product gypsum used in cement
Not more than 0.5%
It shall be carried out according to gb/t5484, and the determination of chloride ion in gb/t 5484 shall be carried out according to gb/t 176.
JC/T 2074-2011
Flue gas desulfurization gypsum
Solution to high chloride ion content of desulfurized gypsum
The conventional measures that the power plant can take include:
① Continuous dehydration of slurry of absorption tower; ② Maintain desulfurization wastewater treatment system
Continuous operation with maximum output of the system; ③ Slurry replacement.
Other technical transformation measures include:
① Transformation of vacuum belt dehydrator; ② Optimize the gypsum and filter cloth washing water of the dehydration belt conveyor; ③ Desulfurization water source reconstruction; ④ Transformation of wastewater system.
Direct utilization method:
① Calcine anhydrite; ② Add admixtures mineral admixtures, adjust water cement ratio, and solidify chloride ions