Kinetics of Coal-Char Gasification with Steam at Elevated Pressures
1. Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, China;
2. University of Chinese Academy of Sciences, Beijing 100049, China
Abstract To better illustrate the effects of pressure on the coal-char gasification with steam, the kinetics of three different ranks of typical Chinese coal-char gasification with steam was investigated at elevated pressures (up to 2.0 MPa) in a pressurized fixed bed differential (PFBD) reactor. The nth-order rate equation applied to different pressures was discussed and a simple empirical rate equation was proposed. In addition, the effects of pressure on the kinetic parameters of coal-char gasification with steam were described well. The results show that the global nth-order rate equation including the only item of steam partial pressure is not appropriate for the gasification when the total system pressure changes, while the proposed simple empirical rate equation brings the variables of temperature, total pressure and steam molar fraction, which can describe well the effects of total pressure on the coal-char gasification rate. It indicates that the effect of steam molar fraction is greater than that of the total system pressure. For HLH char, the correlation exponent with respect to steam molar fraction does not change with the increase of the total pressure, while for SM char and JC char, it increases as the total pressure increases.
