Development of a Pressurized MCFC/MGT Hybrid System

Abstract

A pressurized molten carbonate fuel cell (MCFC) and a micro gas turbine (MGT) hybrid power system has been developed to demonstrate high power generation efficiency (target of 55%), very low NOx emissions, and the operation using high-temperature gasification gas (biogas) as its fuel. The MCFC generator is pressurized, and is operating on process air supplied by the compressor of the MGT and reformed fuel. The power system achieves increased power output and higher efficiency thanks to its utilization by the gas turbine generator of thermal energy from the pressurized MCFC exhaust gas. The MGT is a single-shaft gas turbine that powers a high-speed direct-drive alternator. A heat recovery steam generator (HRSG) and the low-temperature heat exchanger of a hot water driven absorption refrigeration machine are also equipped using the heat recovered from the MGT exhaust gas. The MGT combustor plays an important role during system start-up. But the system is able to operate with no combustor firing in the range of 75% to 100% load. Therefore the NOx emissions are almost zero. The demonstration of this system was carried out at the 2005 World Exposition, Aichi, Japan. Wood waste that had to be cut during the construction of the EXPO 2005 site and waste plastic bottles at 1200°C in a high-temperature gasifier produce hydrogen and carbon monoxide. The MCFC/MGT hybrid system can use both high-temperature gasification gas (biogas) as well as Town Gas as its fuel. This system was started in February 22nd, and was operated by controlling from Distributed Power Supply Management System. A maximum efficiency was 52% at 300kW, and the total on-site operating time reached about 5200 hours with no failures. After the end of the half-year term of Aichi Expo., this system will be located to Central Japan Airport City, and the endurance test of next phase will be continued there.