RELIABILITY OF CERAMIC MEMBRANES OF BSCF FOR OXYGEN SEPARATION IN A PILOT MEMBRANE REACTOR

In the framework of CCS Technology an oxyfuel combustion process was designed for coal fired power plants. Heart of the process is an oxygen separation module which allows enriching recirculated flue gas with oxygen for combustion in a special developed burner. This German project OXYCOAL-AC has choosen BSCF (Ba0.5Sr0.5Co0.8Fe0.2O3-x) as membrane material. BSCF is well known as the MIEC ceramic with highest oxygen flux but information about thermo mechanical data are relatively poor. The membrane components in the reactor are manufactured as one side closed tubes from BSCF powder by isostatic pressing and firing in air at 1100 degrees C. The dimensions of the sintered tubes are 500 mm length and 15 mm outer diameter. The wall thickness is about 0.85 mm. The tubes are integrated in a special designed module which can hold up to 600 membrane tubes so that a membrane are of 14 m(2) can produce about 0.5 tons oxygen per day. The module operates at 850 degrees C with air pressure of 15-20 bar on the feed side and a vacuum of 0.5 - 0.8 bar on the permeate side. For calculation a reliable long term operation in a power plant respectively other applications firstly the long term behavior of the ceramic material and the chosen joint patch has to be investigated. Neglecting the chemical reactivity of BSCF this paper concentrates on the mechanical strength at operating temperature.