Char gasification, calcium

Since a char particle typically contains < 2% Ca (w/w), while the char surface is > 200 m /g, the Thiele moduli for the calcium reactions are likely to be much smaller than those associated with char gasification even when the turnover numbers for the reactions are of the same order of magnitude. Thus, we will assume that the sulfur reactions are kinetically controlled while the gasification is diffusion limited. In that case HjS and 00S concentrations... 

Catalysis of Lignite Char Gasification by Exchangeable Calcium and Magnesium... 

Reactivity results for the 1273 K chars reacted in 0.1 MPa CO2 and 3.1 kPa steam at 1053 K are shown in Figures 3 and 4, respectively. The same trends evident for the 1273 K chars reacted in 0.1 MPa air are also seen in these reactant gases. Two regions of reactivity behavior are present in both cases. Calcium is seen to be a good char gasification catalyst, while Mg has very little catalytic effect. 

The two series studied have been prepared from chars with different ash contents, as a result of the acid- and water-washing treatments at which the starting material was submitted. The inorganic matter is constituted mainly by potassium salts and, to a lesser extent, also by sodium and calcium salts, which are known catalysts for the carbon gasification reaction with CO2. Figure 1 plots... 

Huggins FE, Shah N, Huffman GP, Lytle FW, Greegor RB, Jenkins RG (1988b) In situ XAFS investigation of calcium and potassium catalytic species during pyrolysis and gasification of lignite chars. Fuel 67 1662-1667... 

Jiang, M., Hu, J., Wang, J. (2013). Calcium-promoted catalytic activity of potassium carbonate for steam gasification of coal char effect of hydrothermal pretreatment. Fuel, 109, 14-20. 

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