高铝耐火砖负载NiO氧载体的沼气化学链重整制氢流化床实验研究

Chemical Looping Reforming of Biogas for Hydrogen Generation Using a High-Aluminum Refractory Brick Supported NiO Oxygen Carrier

沼气含有60%CH4和40%CO2,可作为有效的化学链重整(chemical looping reforming,CLR)制氢原料。以耐高温和高强度的高铝耐火砖为惰性载体,采用浸渍法制备Ni基氧载体。在批次进料流化床反应器中开展多种反应条件下CLR实验研究,并对比沼气干重整和沼气湿重整特性。结果显示,湿重整环境下沼气能够更好的转化为目标产物H2。合理的控制反应条件,能够更进一步将沼气的CO2转化为CO,从而提高沼气中各组分的利用程度。提高反应温度和水蒸气浓度有利于产生较多的H2和CO,具有较高的H2产率和H2/CO摩尔比。155次循环测试中,氧载体的物理化学性能保持较好,能够得到稳定的H2浓度。氧载体的机械性能较好,155次循环后仍能满足流化床的使用要求,磨损率仅为0.034%/h。较高反应温度下,氧载体颗粒未出现烧结、流化性能稳定。热平衡模拟显示,可通过调节氧载体与沼气比例达到系统的自热运行,然而需要以降低H2产率为代价。因此,在大型CLR系统中,需要开展经济与能耗的整体评估,以优化沼气CLR的整体性能。

Biogas typically containing 60%CH4 and 40%CO2, of which CH4 can be used as an effective feedstock of chemical looping reforming(CLR) for H2 generation. Ni O was impregnated on high-temperature resistant and high-crushing strength refractory brick for the preparation of oxygen carrier material. A laboratory-scale fluidized bed reactor was then used to investigate the properties of biogas CLR under various reaction conditions, where dry reforming and wet reforming pathways were compared as well. It was found that biogas exhibited a better conversion under wet reforming than under dry reforming conditions for H2 generation. Noticeably, under well controlled operation condition, CO2 of biogas can be highly converted to CO, resulting in high-degree utilization of biogas. Increasing operation temperature and H2 O steam concentration in the fluidized bed, more H2 and CO can be obtained, leading to higher H2/CO ratio and H2 yield from biogas. During the 155 cycles in the fluidized bed, the oxygen carrier particles showed satisfactory physical and chemical properties and stable H2 concentration at reactor exit. After 155 cycles, good crushing strength and satisfying attrition rate of oxygen carrier particles were detected, sufficient for use in fluidized bed systems. Under the tests at high temperatures, no agglomeration of oxygen carrier particles was found, suggesting the stablefluidization ability. Auto-thermal CLR can be realized by tuning the oxygen-carrier to biogas ratio, according heat balance calculation. However, H2 yield must be decreased to reach auto-thermal CLR. In this sense, detailed evaluation of economic and energy should be done to optimize the characteristics of large-scale systems.