Increasing Efficiency and Reliability of Hybrid Engines (SOFC+μGTE) Operation by Hydrogen Separation from A High Temperature CO-containing Flow Using Molecular Ceramic Membranes

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Solid oxide fuel cell (SOFC) and micro gas turbine engine (μGTE) hybrids are at present the most promising power plants in light of the current reorientation of the world's economy from fossil fuels to hydrogen. This is due to a positive effect of combining SOFC and μGTE, which improves efficiency. On one hand, a fuel after reforming supplies SOFC where it converts a portion of its chemical energy in the exothermal reaction into electrical one. The synthetic gas after fuel cell with a temperature of 850 to 1100°C at the SOFC exit is delivered to μGTE that, by heat generated at the reaction in SOFC, provides a pressure and the air and synthetic gas temperature required at its entry. On the other hand, turbine exhaust gases are employed to provide water vapor for steam and steam-air reforming of the primary fuel. Thus, the total efficiency of a hybrid engine can be 55-70%.; a specific efficiency within this range is a function of the purity of the syngas that reacts in SOFC; the less CO in it, the higher the efficiency of the electrochemical reactions and reliability of the fuel cell operation. H 2 separation from a high temperature CO-containing mixture could be achieved using molecular ceramic membranes (MCM) mounted downstream of the reformer and guiding the flow that contains hydrogen towards SOFC and CO towards μGTE combustor. This paper presents test findings for MCMs on separation of high temperature CO-H 2 gas mixtures. The initial trial models of disc MCMs were manufactured of zeolite ZSM-5 with nano pores formed all over its volume with sizes required to ensure CO/H 2 separation. The membrane test was carried out on a special purpose experimental hydrogen test bed allowing flow temperatures up to 800°C and higher, with pressure up to 2 MPa. This test bed allows also investigation of the water vapor on the membrane material, etc. On the basis of these tests, a conclusion could be drawn that achievement of such characteristics as H 2 purity (CO admixture > 0.01%) and high temperature flow operation conditions (temperature > 800°C, pressure ≥ 1MPa) are quite real, and membrane devices can be designed, manufactured and tested which will widen the scope of SOFC applications to industry through use of natural gas instead of pure hydrogen both as independent power sources and with SOFC incorporated into hybrid engines.