Study on alkali-metal vapor removal for high-temperature cleaning of coal gas

Six natural mineral sorbents and a series of self-made sorbents were used to remove alkali-metal vapor from high-temperature coal gas. Results indicate that the self-made sorbent GM6 is the best sorbent with the highest sodium compound content, under the conditions of 1173 K, a gas velocity of 16 L/min, a reaction time of 3 h, and a NaCl concentration of 0.13 mg/L. It is shown that the sodium compound content is dependent on the chemical constituents and the microporous structure of sorbent, based on the surface area data. Results of X-ray diffraction (XRD) analysis and the kinetics indicate that the adsorption process of GM6 is physical adsorption in an N-2 atmosphere and it is controlled by the diffusion of a sodium resultant layer. The adsorption process in a N-2/H2O(2%) atmosphere is mainly a chemical adsorption that is controlled by both the chemical control and the product-layer diffusion control.