Pilot Plant Combustion Tests of Low-Volatile and High-Sulphur Coal for the 55 MW_el CFBC Cao Ngan Power Plant, Vietnam

Circulating Fluid Bed technology has made a rapid and successful entry into power and steam generation marketplace in many countries. As one of the first CFB based power plants in Vietnam the 2 × 55 MW_e Cao Ngan project will follow this trend towards clean coal technology. The Cao Ngan CFB boiler is designed to burn a blend of low-volatile, high-sulphur coals from two local mines complying with strict environmental regulations, 500 mg/Nm³ for SO₂ and 300 mg/NM³ for NO_x. Combustion tests were carried out at the University of Bochum, Institute of Energy Plant Technology, Germany, in a pilot-CFB combustor (100 kW_th) in order to check the combustion behaviour and the emission characteristics. In these tests a blend of the two different coals was burned at different temperature levels (830 °C, 860 °C, 890 °C) and at each temperature level the desulphurisation efficiency was tested with two different kind of limestone and different Ca/S-ratios: Furthermore the experimental analysis comprised the determination of the conventional emissions (NO_x, CO), ignition characteristics for start-up and part load behaviour. During all tests samples of bed and filter ash were taken for further analysis, e.g. burnout, particle size distribution etc.. Earlier comparable combustions tests carried out in the pilot-CFB combustor and large scale CFB boilers has proven, that the results are transferable to large scale commercial plants: This is valid especially for the major emissions e.g. SO₂ and NO_x. The current paper will explain the design principles and the basic lay-out of the Cao Ngan CFB boiler. In addition, details of the results of combustion tests carried out in a pilot- CFBC at the University of Bochum, Institute of Energy Plant Technology, Germany, will be presented.