Desulfurization Product Characteristics And Utilization

The lime or limestone is sorbent which is widely used in FGD. FGD by-products mainly include gypsum produced by wet FGD and residues produced by dry and semi-dry desulfurization. FGD by-products are increasing with running of desulfurization equipments, so the comprehensive utilization of FGD by-products must be resolved quickly, or it will influence the process of FGD technologies.The main substance of FGD by-products is CaSO₃, and its property can influence the comprehensive utilization of FGD residues greatly. The thermal stability of CaSO₃ under the atmosphere of oxidation and N₂ is studied in this paper. The experiments show that "CaSO₃ is more stable under the atmosphere of oxygen or air when the temperature is under 450℃. The CaSO₃ can be oxidized to CaSO₄ quickly when the temperature is above 459℃ and the oxygen is enough. The CaSO₃ begins to decompose when the temperature is above 700℃. The decomposition degree of CaSO₃ is increasing with the increase of calefactive velocity when the temperature is from 700℃ to 1100℃. The calculation of material balance and thermal balance are also performed in this paper taking using the flue gas to oxidize CaSO₃ for example.A kind of comprehensive utilization technics is brought forward in this paper. This technics can make full use of desulfurization by-products produced by these integrated equipments of dust removal and FGD technics of fired brick plant with gangue. The decomposition degree of CaSO₃ in this technics is analyzed, and the material balance calculation and industry experiment are performed. The results indicate that this technics can utilize the desulfurization by-products produced by itself, and all the parameters of brick accord with the national standard when mix the CaSO₃ of 1.2% into material of making brick. Although there is the phenomenon of panto-frost, the parameters are above the national standard. So it is a good way to utilize desulfurization by-products synthetically.The feasibility of FGD residues acting as cement retarder is also studied in this paper by experiments. These experiments indicate semi-dry FGD residues acting as cement retarder is feasible replacing gypsum partly. The setting times, invariability and strength accord with the national standard, and the effectiveness of the desulfurization residues reaction retardation is higher than gypsum. But the right amount of mixing desulfurization residues into cement must be confirmed by experiment.