59830 - Part-Load Operation of Gas Turbines Induced by Co-Gasification of Coal and Biomass in an Integrated Gasification Combined Cycle Power Plant 

The need to decarbonize the power sector is crucial for meeting the emissions reduction targets set in the Paris Agreement on climate change. Even though the use of coal dropped in the United States and Europe, growth occurred in South and Southeast Asia and coal remains the largest source of generated electricity. In the short term, a shift from coal to biomass can be a valuable option.

This study takes inspiration from a previous work focused on the simulations of the Willem-Alexander Centrale power plant located in Buggenum (the Netherlands), based on the IGCC technology, under both design and off-design conditions. These latter included co-gasification of coal and biomass, in proportions of 30:70, in three different fuel mixtures. Since the model was found to be accurate in comparison with the operational data, here attention is drawn to the gas turbine (GT) behavior. Given the fixed size of the gasifier, any drop in the energy content of the coal/biomass blend, with respect to 100% coal, translates into a reduction in the GT load. Accordingly, part-load strategies, such as fuel-only (TIT) control and IGV control, were investigated with the aim of maximizing the net electric efficiency of the IGCC plant. This was done for different GT models from leading manufactures on a comparable size, in the range between 190-200 MW. The influence of fuel quality on the power plant performance was discussed for several binary blends, over a wide range of LHV, while ensuring a volume fraction of hydrogen in the syngas entering the GT combustor within the limit of 30%. The optimized combination of IGV and TIT control was found to improve the IGCC net efficiency as compared with the pre-programmed “target" exhaust temperature which matches the spec for the selected GT engine.

The study was carried out through the commercial code Thermoflex®: mass and energy balances are computed in a steady environment thus neglecting dynamic aspects.