Pressurised fluidised bed combustion (PFBC) promises even lower emissions of air pollutant substances than already achieved by atmospheric FBC and allows to burn low rank coal. The elevated heat-transfer rate results in a more compact design. A PFBC-fired steam generator for the heat and power plant of the Technical University of Aachen (RWTH) is under construction. Being part of RWTH’s heat and power supply, a high reliability and a wide range of operation is mandatory. With these two aims in mind a scheme consisting of a turbo-charger’s compressor followed by an electrically driven compressor was chosen for the supply of air. The turbocharger’s turbine is fed by stack-gas previously cleaned by means of a pressure-tube-filter at moderate temperatures. Both machines are serial products. While the turbocharger’s speed is determined by the operating conditions, the electrically driven compressor is controlled by adjustable inlet guide vanes. In the pressurised mode of operation, the load of the steam-generator can be varied between some 30 % and 100 % of maximum output. The turbocharger may be bypassed to operate the system at atmospheric conditions. in this mode, 15 % to some 50 % of the operating range is covered.

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