煤焦与水蒸气的气化实验及表观反应动力学分析

Experimental Study and Apparent Reaction Kinetics Analysis on the Char-steam Gasification

在Thermax500型热重分析仪上对褐煤煤焦与水蒸气的气化反应进行了实验研究,并采用n级速率方程和Langmuir-Hinshelwood(L-H)速率方程考察了反应气体分压的影响。实验系统压力为0.1和0.6MPa,其中0.1MPa下水蒸气浓度分别为5%,10%和20%,0.6MPa下的水蒸气浓度为20%。气化反应在恒温条件下进行,温度分别为850、875、900、925、950和1000℃。实验发现,反应速率随温度和压力的增大而加快,900℃以下为化学反应控制区,不同压力下的表观活化能数值接近,而900℃以上由于受到扩散阻力的作用,表观活化能不同程度降低。采用n级速率方程计算得到褐煤煤焦与水蒸气的反应级数n为0.34,活化能E为153.7kJ·mol-1,采用L-H方程得到活化能为207.1kJ·mol-1,其速率方程可更精确地描述水蒸气压力的影响。

The gasification reaction of lignite coal char and steam was studied with a Thermax500 pressurized thermogravimetric analyzer （PTGA）. An nth order expression and Langmuir-Hinshelwood （L-H） expression were applied to describe the effect of pressure and temperature on the reaction. The system pressures were 0.1 and 0.6 MPa, and the steam molar fractions were 5%, 10% and 20% at 0.1MPa, while was 20% at 0.6 MPa. The isotherm experimental method was applied and the reaction temperatures were 850, 875, 900, 925, 950 and 1 000 ℃. The results show that when the temperature is lower than 900 ℃, the reaction rates increase with temperature and pressure, which is kinetic controlled. The apparent activation energies are in the reaction controlled regime and become small when temperature is higher than 900℃. In the nth order expression, the order n is 0.34 and the activation energy is 153.7 kJ·mol^-1. In the L-H expression, the activation energy is 207.1 kJ·mol^-l. It is found that L-H expression is more accurate than the nth order expression in describing the effect of steam partial pressure on gasification.