Study on Thermal Decomposition Process of Semidry Flue Gas Desulfurization Ash

Abstract

Semidry flue gas desulfurization ash (FGDA) is a kind of solid waste, which is mainly composed of CaSO3 and produced by coal-fired power plants. Thermal decomposition has been considered as a promising method for FGDA treatment. However, strict equipment requirements and the high energy consumption brought by the high decomposition temperature do hinder the industrial application of the thermal treatment methods. In order to solve these issues, the mechanism of FGDA thermal decomposition was investigated, with emphasis on the effect of additives, impurities, and reaction conditions. The results showed that the temperature, reductant of carbon powder, and the impurity of Ca­(OH)2 in the FGDA promoted the decomposition efficiency of CaSO3, while CaCO3 in the FGDA had a negative effect on CaSO3 decomposition. An optimal increase of the thermal decomposition efficiency of FGDA was achieved by using carbon powder as a reducing additive. Furthermore, the decomposition temperature of FGDA was decreased from 1100 to 1000 °C. The decomposition efficiency of CaSO3 increased from 55.56% to 89.48% at 1000 °C. The content of active CaO in the roasting product reached 40%, which is a potential desulfurizer.

Behavior of CaO Formation by Decomposition of Desulfurization Ash Considered under Minimum Energy Conditions

“…However, the complex chemical composition and spatial structure of desulfurization ash do not allow for large-scale use in construction and other fields [6][7]. In addition， compared with natural gypsum, the use of DA for construction purposes is limited due to the fluidity and thixotropy caused by the small particle size; thus, DA cannot replace natural gypsum [8][9][10]。 Therefore, the chemical decomposition and recycling of DA to form raw industrial materials is a development with great potential for application. DA is regarded as a polymer of element S, especially in the desulfurization process with calcium-based desulfurizers, the process of decomposing DA will produce sulfur-containing flue gas with high concentration, which can enter the industrial acid production system to produce industrial sulfuric acid.…”

“…While studying solid reduction, the essence is still the gas-solid reaction through the gasification of the reducing agent followed by reduction. Jia et al [16], Niu et al [17], Xu et al [18] and E.M van der Merwe et al [19] used solid carbon to carry out reductive decomposition, proving that the formation of CaO and CaS in the process of solid carbon reduction decomposition is a parallel competitive reaction and that the reaction follows a typical gas-solid reaction model. Factors such as reaction temperature and reducibility [20] determine the direction of the reaction.…”

Mechanical enhancement of epoxidized natural rubber by flue gas desulfurization ash as the sole reinforcing filler

“…Flue gas desulfurization ash (FGDA) is a substance created during the semidry desulfurization process, which involves using Ca(OH) 2 to react with SO 2 generated from fossil fuel combustion in an absorption tower. [1][2][3][4][5][6][7][8] With the increase in the amount of FGDA, it is a challenge to expand its application. The main components of FGDA are CaCO 3 , CaSO 4 , CaSO 3 , Ca(OH) 2 , and CaSO 3 Á0.5H 2 O.…”

Experiment and Mechanism Analysis of Desulfurization with a MgO-Based Desulfurizer Fixed Bed Method

“…The method has a relatively high desulfurization efficiency, but the calcium sulfate produced by the method causes equipment fouling and the calcium chloride generated by Cl–Ca 2+ in the flue gas causes corrosion to equipment . To improve the defect, Yang et al have recently shown some improved FGD and semidry techniques . In all the methods, a wet magnesium oxide method is developed and popularized.…”

“…1 To improve the defect, Yang et al have recently shown some improved FGD and semidry techniques. 2 In all the methods, a wet magnesium oxide method is developed and popularized. Wet magnesium oxide is the reaction of MgO and water to produce a magnesium hydroxide slurry for flue gas desulfurization.…”