Considerable studies have been reported on the coal pyrolysis process and the formation of SO 2 and NO x processors such as H 2 S, COS, SO 2 , HCN, and NH 3 in inert atmospheres. Similar studies in CO 2 atmosphere also need to be accomplished for better understanding of the combustion characteristics and the SO 2 /NO x formation mechanism of oxy-fuel combustion, which is one of the most important technologies for CO 2 capture. In this study, thermogravimetry coupled with Fourier Transform Infrared (TG-FTIR) analysis was employed to measure the volatile yield and gas evolution features during coal pyrolysis process in CO 2 atmosphere. Results show that replacing N 2 with CO 2 does not influence the starting temperature of volatile release but seems to enhance the volatile releasing rate even at 480 °C. At about 760 °C, CO 2 prevents the calcite from decomposing. In CO 2 atmosphere, the volatile yield increases as the temperature increases and decreases as the heating rate increases. COS is monitored during coal pyrolysis in CO 2 atmosphere while there are only H 2 S and SO 2 formed in N 2 atmosphere. The COS is most likely formed by the reaction between CO 2 and H 2 S. No NH 3 was monitored in this study. In CO 2 atmosphere, the gasification of char elevates the conversion of char-N to HCN. The HCN yield increases as the temperature increases and decreases as the heating rate increases.

The calcium-based sorbent cyclic calcination/carbonation reaction is an effective technique for capturing CO 2 from combustion processes. The CO 2 capture capacity for CaO modified with ethanol/water solution was investigated over longterm calcination/carbonation cycles. In addition, the SEM micrographs and pore structure for the calcined sorbents were analyzed. The carbonation conversion for CaO modified with ethanol/water solution is greater than that for CaO hydrated with distilled water and is much higher than that for calcined limestone. Modified CaO achieves the highest conversion for carbonation at the range of 650-700°C. Higher values of ethanol concentration in solution result in higher carbonation conversion for modified CaO, and lead to better anti-sintering performance. After calcination, the specific surface area and pore volume for modified CaO are higher than those for hydrated CaO, and are much greater than those for calcined limestone. The ethanol molecule enhances H 2 O molecule affinity and penetrability to CaO in the hydration reaction so that the pores in CaO modified are obviously expanded after calcination. CaO modified with ethanol/ water solution can act as a new and promising type of calcium-based regenerable CO 2 sorbent for industrial applications.

No abstract

No abstract

No abstract