New technology for the abatement of SO_2 in non-ferrous pyrometallurgical processes by a dry limestone scrubber

摘要

The neutralization process of SO_2 from coal burning plants is a well-defined technology using limestone to form CaSO_4 according to the following reaction: CaCO_3 + SO_2(g) + 1/2 O_2(g) = CaSO_4 This paper presents the results of a study carried out to validate the option of capturing SO_2 using gases from a non-ferrous smelter; SO_2 content was up to 12 percent using a three-stage fluidized bed reactor. The difference in SO_2 content affects equilibrium conditions and kinetics, rendering a direct extrapolation of the high efficiency achieved for low SO_2 content impossible. The R&D program consisted of a laboratory study using a semi-pilot operation of a one-stage fluidized bed reactor and the construction and operation of a three-step reactor prototype. Results show that the reaction proceeds according to the unreacted core model that imposes a compromise between CaCO_3 conversion and SO_2 capture. For high SO_2 capture, the calcine from the reactor contained CaSO_4 and CaO. A complete capture of SO_2 from gases with 8 vol.percent can be achieved with a mean reaction time of two hours at 800 deg C.