化学链制氧技术中铜-锆氧载体的动力学分析

化学链空气分离制氧是利用氧载体在脱氧反应器中脱氧-在吸氧反应器中吸氧、再生实现连续或间断制氧的新颖技术。本研究通过机械混合法制备铜-锆氧载体, 并对制备材料的物相组成、表面形貌及比表面积进行表征, 在STA409PC热重分析仪上采用程序升温法作相关机理探索, 分析气体流量、样品质量、升温速率、惰性载体添加比例对铜-锆氧载体脱氧和吸氧性能的影响。采用等转化率法求解活化能, 采用主曲线法确定动力学模型机理函数。 结果表明, 所制备的铜-锆氧载体物相稳定, 没有烧结现象的发生, 随ZrO₂添加比例的增大, 制备氧载体的比表面积逐渐增大; 当气体流量大于30 mL/min, 样品质量小于10 mg时, 氧载体的转化速率已不受样品传热和传质等内外扩散的影响; 随升温速率的增大及惰性载体添加比例的减小, 氧载体反应起始温度、最大反应速率出现温度及转化完全温度均向高温移动。等转化率法计算得到不同转化率下氧载体的活化能基本相同, 且不同惰性载体添加比例下活化能数值也相差不大; 氧载体脱氧和氧化反应都可用成核和核增长机理模型描述, 但模型中两种反应的级数不同, 前者为3, 后者为1.5。

Kinetics Analysis of Cu-Zr Oxygen Carrier for Chemical Looping Oxygen Production

2 oxygen carrier was prepared by mechanical mixing. BET, SEM and XRD were used to analyze the specific surface area, surface morphology and phases of oxygen carrier. The phases of oxygen carrier are only CuO and ZrO₂. There is no agglomeration in the surface of oxygen carrier. The BET values increase with the increase of weight ratio of binder. The mechanism experiments were carried out in STA409PC thermal analyzer and the temperature programmed thermogravimetry was used to investigate the effects of gas flow, sample mass, heating rate and weight ratio of binder on reduction and oxidation reactions. The results show that the CuO/ZrO₂ oxygen carrier has high reactivity of releasing and adsorbing oxygen. When the gases flows are higher than 30 mL/min and sample mass is less than 10 mg, the reaction rates are not controlled by the internal and external diffusion through gas film around the particle. Besides the start and end points, all peaks of DTG curves of reduction-oxidation reactions move forward to high temperature with an increase heating rate. The time for overall conversion decreases with the increase of weight ratio of binder. Based on the experimental data, the kinetics of the CuO/ZrO₂ oxygen carrier was determined by the isoconversional model. The differences of distributed activation energy, calculated at different conversion ratios, are all very small. The reduction-oxidation reactions of CuO/ZrO₂ oxygen carrier are one-step and the mechanism functions can be explained by nucleation and nuclei growth theory. The kinetics equations of reduction and oxidation reaction are]]>