Optimization of Oxygen Permeable Membrane by Applying to Hydrogen Production System Based on Partial Oxidation of Methane

将基于二氧化铈的透氧膜安装在不锈钢分离器上作为模块，并优化其混合电导率，以实现高系统制氢效率。在2006财年，研究了透氧膜组件的制备及其甲烷重整性能，以及膜的混合氧化离子和电子电导率。通过在780 ~ 950℃的温度下操作，可以得到预期的氢气量。采用Hebb-Wagner极化技术分离混合离子电导率和电子电导率；在900℃时，通过降低空气压力，在氧分压为10^<-7> bar的条件下，主载流子由氧化离子转变为电子。2007财年，对透氧膜组件的热平衡和基于固体氧化物电解质的氢电联产系统的火用分析进行了研究。根据上述混合电导率，在780℃的工作条件下，在150 sccm的甲烷输入速率下，膜组件的发热量为8.4 W。采用20mol% sm掺杂的CeO_2、Ba_<0.5>Sr_<0.5>Co_<0.8>Sr_<0.2>O_<3-δ>、（Ce_<0.8>Sm_<0.2>）O_2-50vol%NiO分别作为电解质、阴极和阳极作为固体氧化物燃料电池体系。以Ar-10%CH_4为燃料，在700℃下，电流密度为288 mA/cm^2，功率密度最高可达131 mW/cm^2。在此基础上，构造了用能罗经图；在最佳工况下，火用效率达到46.7%。另一方面，在短路模式下，对应于透氧膜，效率为22.8%。

A ceria-based oxygen permeable membrane was mounted on a stainless-steel separator to be a module and to optimize its mixed conductivity in the context of achieving high system efficiency for hydrogen production. For FY2006, 1) fabrication of the oxygen permeable membrane module and their methane reforming properties, and 2) mixed oxide-ion and electronic conductivity of the membrane were investigated. Expected amount of hydrogen was obtained by operating the module at around 780 to 950℃. The mixed ionic and electronic conductivities were separated by means of the Hebb-Wagner polarization technique; at 900℃, major carrier was found to be switched from oxide-ion to electron at an oxygen partial pressure of 10^<-7> bar by reducing the pressure from air. For FY2007, 1) heat balance of the oxygen permeable membrane module, and 2) exergy analysis of co-production system of hydrogen and electricity based on solid-oxide electrolytes were examined. Based on the mixed conductivity mentioned above, under an operating condition at 780℃ and a rate of 150 sccm methane input, the membrane module was found to emit a heat of 8.4 W. As a solid-oxide fuel cell system, 20mol%Sm-doped CeO_2, Ba_<0.5>Sr_<0.5>Co_<0.8>Sr_<0.2>O_<3-δ>, (Ce_<0.8>Sm_<0.2>)O_2-50vol%NiO were used as an electrolyte, cathode and anode, respectively. By supplying Ar-10%CH_4 as a fuel, the highest power density of 131 mW/cm^2 was attained at a current density of 288 mA/cm^2 at 700℃. Based on these value, an exergy compass diagram was constructed; under the optimum condition, an exergy efficiency reached to 46.7%. On the other hand, under short-circuited mode, which corresponds to an oxygen permeable membrane, the efficiency was 22.8%.