Removal of Hydrogen Chloride by Slaked Lime in a Fluidized Bed Reactor

Abstract

A dry hydrogen chloride (HCl) removal process for the Molten Carbonate Fuel Cell (MCFC) power generation system was developed. The fuel gas generated by gasification of organic waste contains HCl. HCl causes not only great damage to a gasification equipment, but also a loss of function of MCFC by the corrosion of electrodes. Therefore, it is very important to remove HCl to around 1 ppm. In the previous research, the fluidized bed reactor for HCl removal by slaked lime was developed. It has been clear that slaked lime was the most appropriate in the calcium absorbent of the HCl removal process at the temperature of 573 K. In this research, the effect of particle size and coexistence gas on the HCl removal reaction was explored. The effect of particle size and pore structure of slaked lime particles to the absorption characteristic of HCl was evaluated by the thermogravimetric analysis and the measurement of the specific surface area for the purpose of scale up of reactor. Consequently, it was revealed that even if the particle size of slaked lime particles became bigger, they had the enough reactivity on the HCl removal reaction. The slaked lime absorption performance in the coexistence of gases was also evaluated. Usually gasification gas consists of 20 to 30 % of hydrogen (H₂), 35 to 45 % of carbon monoxide (CO), 20 to 50 % of carbon dioxide (CO₂) and small amount of HCl, etc. Therefore, the effect of CO₂ on the HCl removal reaction was examined with the thermogravimetric analyzer. As the result, even the coexistence of CO₂, slaked lime could absorb HCl as well as the none existence of CO₂. It was found that the effect of coexistence of CO₂ was very small for the removal of HCl by slaked lime.