Experimental Study Of Additive Effect On Limestone Desulfurization Efficiency

Dry Desulfurization has the advantages of simple system, saving investment, space small, and low operation fare, etc. Limestone is the preferred desulfurizing sorbent because of its rich resource and cheapness. But the desulfurization efficiency of the limestone is low, especially at high temperature, it get worse. Even though with high Ca/S, the reaction is not completely. Thus, the desulfurization efficiency and absorbent utilization is low, which restrict the popularity of this method .Based on the principle of dry desulfurization,this research is focused on the desulfurization process of coal residue with sulfur of 1.8% and coal with sulfur of 1.98%. NaCl, MgCl₂,CaCl₂,KCl,K₂CO₃ and Pennisetum were chosen as desulfurizing additives, which were add into limestone with different content, respectively. The desulfurization experiment was carried out by sulfur capture, in order to study the effect of the additives on desulfurization efficiency. A thermal-gravity balance and a gas analyzer were used to study the effect of the additives on the allotropic sulfur emission from the coal residue combustion.. The best reaction conditions of the additives and the effect factor on desulfurization efficiency were found out. The experiment results prove the additives can promote the desulfurization efficiency.The results show that the additives have best desulfurization efficiency at 800℃for coal residue, and the optimum mixture ratio are 1.5%NaCl,1%KCl,0.5%MgCl2,1.5%CaCl2,1%K2CO3 and 20% Pennisetum. For coal combustion, the optimum temperature of additive is 800℃, and the optimum mixture ratio are 2%NaCl,1.5%KCl,0.5%MgCl₂,1.5CaCl₂,1%K₂CO₃ and 20% Pennisetum. The additives affect the desulfurization efficiency of limestone by influencing the structure of desulfurizing agent pore apace. Affected by coal property, temperature of combustion and heating rate, the additives have different optimum mixture ratio and effect principle.The research results of thermal-gravity balance experiments show that different additive has different effect on allotropic sulfur emission in the process of the fuel combustion. For coal residue combustion, NaCl mainly affects the pyritic sulfur, aromatic sulfur and thiophentic sulfur. MgCl2 decreases the aromatic sulfur, thiophenic sulfur and pyritic sulfur. K2CO3 decreases the aromatic sulfur, thiophenic sulfur and pyritic sulfur. Pennisetum decreases the thiophenic sulfur aromatic sulfur and pyritic sulfur. For coal combustion, NaCl mainly affects pyritic sulfur and thiophenic sulfur. KCl affects thiophenic sulfur. K2CO3 decreases aromatic sulfur, thiophenic sulfur and pyritic sulfur. Pennisetum decreases thiophenic sulfur and aromatic sulfur and pyritic sulfur.The effect of additive on limestone desulfurization efficiency is researched deeply in this paper. The results offer the technical support for clean combustion of coal and coal residue; and lay the foundation for application of dry desulfurization additive. Therefore this research is worth of reference and application.