K2CO3修饰的铁锆复合氧载体-煤焦化学链气化制氢反应特性研究

以K₂CO₃修饰的Fe₂O₃和ZrO₂复合型氧化物为氧载体(K3-Fe70Zr30),在固定床装置上考察了温度和原料配比对煤焦化学链制氢过程中产气率及组成的影响。程序升温实验结果表明,煤焦与氧载体500 ℃时开始反应,温度高于750 ℃时反应速率快速增大;而还原态氧载体与水蒸气400 ℃时开始反应,当温度高于500 ℃时出口氢气浓度明显增大。恒温实验表明,随温度升高,产品气中CO/CO₂体积比增大,导致产氢量降低。随煤焦与氧载体比例增加,产品气体中CO/CO₂体积比增加,而产氢量先增大后降低,其最大值可达1.734 L/g。K3-Fe70Zr30氧载体在前两次循环能维持良好的反应活性,但在第3次循环反应中活性降低,而重新添加K₂CO₃之后氧载体活性恢复,表明氧载体活性降低主要是由于K₂CO₃的流失所致。

Reaction characteristics research of coal char chemical looping gasification for hydrogen production with an Fe-Zr oxygen carrier modified by K2CO3

In this study, an Fe-Zr oxide (Fe₂O₃ and ZrO₂) modified by K₂CO₃ was used as the oxygen carrier (denoted as K3-Fe70Zr30) to analyze the effects of the temperature and the char mass ratio on the gas yield and composition during coal char chemical looping gasification for hydrogen production. The results of temperature-programmed experiments show that the reaction of oxygen carrier and coal char starts at 500 ℃, and the reaction rate increases sharply after 750 ℃; the reduced oxygen carrier begins to react with steam when the temperature reaches 400 ℃, and the concentration of hydrogen significantly increases after 500 ℃. The results of isothermal experiments indicate that the reaction rate accelerates with increasing reaction temperature. However, the ratio of CO/CO₂ volume ratio increases, resulting in the H₂ production decreases as the temperature raises. In addition, an increase in char ratio increases the ratio of CO/CO₂ volume ratio in the outlet gas increases, which leads to the hydrogen production firstly increase and reaches a maximum value of 1.734 L/g, and then decrease. The activity of oxygen carrier can keep stable during the first 2 redox cycles, but it decreases in the 3rd cycle. The activity can be renewed by supplement of K₂CO₃, which suggests that the loss of K₂CO₃ can contribute to the decreased activity.