CO2 Regeneration of Used Alkali Carbonates for High-Temperature Desulfurization in Gasification

Gasification systems are expected to be the next-generation, highly efficient, and environmentally friendly energy conversion technology of carbonaceous resources. However, those systems are still ongoing development. Our previous studies suggested that molten alkali carbonates can be used to enhance gasification reactions and absorb H2S and COS at high temperatures. Furthermore, sulfurized alkali carbonates can be regenerated using steam and CO2. However, employing only waste-gas CO2 would further decrease releases of this greenhouse gas. Therefore, regeneration characteristics of used alkali carbonates using only CO2 as the regeneration agent were studied in this paper. Chemical equilibrium simulation of the regeneration process was carried out using Factsage 6.2 software for selecting the optimum condition for experiments. An electrically heated quartz tube was used for conducting the experiments. Na2S center dot 9H(2)O and K2S were placed inside the tube, and CO2 was introduced with the hourly space velocity of 59.72 h(-1). Experimental results showed that CO2 flow into the used alkali carbonates at 900 K resulted in around 92% conversion from alkali sulfides into alkali carbonates. Thermogravimetric analysis at 650, 750, 800, 873, and 900 K gave rate constants (k) of 0.2022, 0.2171, 0.2588, 0.3885, and 0.3926 min(-1), respectively.