Coal gasification with in situ CO2 capture by the synthetic CaO sorbent in a 1 kWth dual fluidised-bed reactor

Abstract

Coal gasification with in situ CO2 capture is believed to be able to produce highly concentrated H2 with little or no CO2 compared with the conventional process. This has been demonstrated by other researchers working on a single fluidised bed by continuously feeding the CaO sorbent. This work presents the results of coal gasification with in situ CO2 capture by a synthetic CaO sorbent in a 1 kWth dual fluidised-bed reactor at atmospheric pressure, which has not been reported in the literature. The synthetic CaO sorbent is cyclically used by going through multiple carbonation/calcination cycles during coal gasification.The effect of temperature on coal gasification was firstly investigated with silica sands or the synthetic CaO sorbent as the heat carrier. H2 concentration was raised from normally <12% to >15% with the addition of the synthetic CaO sorbent instead of silica sands at 740–800 °C. A long-term test at 740 °C confirmed the advantages of the addition of the synthetic CaO sorbent. However, CO2 concentration was not reduced to a very low level. This was not improved significantly by reducing the gasification temperature to 700 °C. Mechanical and chemical properties of the sorbent were also analysed in this work.