The Removal of HC1 by CaO in the Presence of Steam

摘要

In the off-gas treatment process of incineration for solid waste and other fuels, Ca-based sorbents are used to capture HCl to produce CaCl_2. In this paper, the effect of steam to the reaction with Ca~(2+)/Cl~-molar ratio of 1 and 2 has been investigated in the temperature range from 160℃ to 750℃ in a fluidized-bed reactor. CaO with sands as the bed materials reacts with the input gas, which consists of 4 % O_2, 1000 ppm HCl, 1.5 % - 15 % steam, and the balance gas of N_2. An ion meter is used to measure the Cl~- concentration of the alkali solution in the absorber so as to obtain the removal efficiency (RE) of HCl. The results show that HCl removal by CaO sorbents reveal different trend at different operating temperature in the presence of steam. At 160℃, the effect of steam is not obvious with the RE of approximately 20% to 40%. As the steam concentration increases, the RE decreases at 380℃. At 580℃ and 750℃, the RE decrease at the steam concentration of 5% and 10% and then increase at 15%. It reveals that CaO reacts more completely with HCl at 580℃ than other temperatures in the steam concentration of 5%, 10% and 15%. It also indicates that the presence of steam prevents the reaction progress and the RE with the steam concentration of 5%, 10% and 15% are much lower than 1.5%. It explains that the reaction process depends on the exposed surface area of reactant and the diffusion process of gaseous HCl through the product layer.