In-situ desulfurization performance of limestone purge from the calcium looping process during circulating fluidized bed combustion of coal in a 150kW_(th) pilot plant

摘要

The calcium looping process (CaL) provides a possibility of post combustion CO_2 capture. Based on the calcination and carbonation of natural limestone, this high temperature dual fluidized bed process has the potential for low efficiency penalty caused by carbon capture. Its technical viability has been successfully demonstrated at pilot scale [1] [2]. During the continuous calcination/carbonation cycles of the lime particles, the CO_2 capture capacity is decreased due to deactivation processes [3]. Therefore a certain flow of fresh natural limestone needs to be continuously fed to the CaL system and a stream of deactivated purge material has to be extracted out of the fluidized bed reactor system. In industrial scale CaL facilities, these significant streams of highly calcined purge material have to be further used or disposed of. Possible further usage application are the clinker production in the cement industry [4] or the use of these deactivated sorbent streams for sulfur capture in fluidized bed combustion chambers. The latter is investigated experimentally at IFK and presented in this work. The in-situ desulfurization is a well-known SO_2 reduction method for coal fired fluidized bed boilers. Here, natural limestone is fed to the combustion chamber together with the fuel. This way, the SO_2 formed during coal combustion is directly captured in the combustion chamber. The intention of this work is to evaluate the use of deactivated and highly calcined CaL purge as a replacement for natural limestone sorbent.