燃煤过程中碱金属迁移规律的模拟研究与预测分析

基于ASPEN PLUS 平台，对燃煤过程中碱金属迁移规律进行了模拟研究和预测。模拟结果表明，在850K~1650K气态碱金属物质随反应温度的升高而增加；1400K以下，气相中以NaCl、KCl为主，Na2SO4蒸气量明显高于K2SO4；1500K以下，气态碱金属释放量随着煤中氯质量分数的增加而增加；一定温度下，气态碱金属质量分数随压力的升高而降低；常压下煤中氯的质量分数0.1%，温度降到972K时气态碱金属的质量分数可降到2.4×10－8；而当氯的质量分数分别为0.05%和0.01%时，为达到同样的气态碱金属质量分数，温度需分别降到990K和1025K。模拟结果为燃煤联合循环发电系统的设计和优化提供了参考依据。

Modeling and prediction of migration mechanism of alkali metals during coal-fired process

The control of the amount of alkali vapors in the flue gas at the gas turbine inlet is very important for the coal fired combined cycle power system. Based on the Gibbs free energy minimization principle of chemical equilibrium, two models of coal fired process and alkali migration were developed using Aspen Plus software to explore the migration mechanisms of alkali metals during coal fired process. Moreover, the effect of conditions on the limit level of alkali vapors were predicted. The model results show that in a wide reactor temperature range from 850K to 1650K, the concentration of alkali vapors increases with increasing the reactor temperature. Below 1400K NaCl vapor and KCl vapor are the major alkali metal species in the gaseous phase, and the concentration of Na2SO4 vapor is much higher than that of K2SO4 vapor. At below 1500K, concentrations of alkali vapors increase with the increase of chlorine in coal. At a constant temperature, concentrations of alkali vapors decrease with increasing the reactor pressure. Under atmospheric pressure, the concentration of alkali vapors is decreased to 2.4×10－8 by weight in 972K with 0.1% chlorine in coal, and when the chlorine in coal are 0.05% and 0.01%, the reactor temperature should be increased to 990K and 1025K to limit concentrations of alkali vapors lower than 2.4×10－8, respectively.