Thermodynamic Analyses of Biomass Post-Firing and Co-Firing Combined Cycles

In the present work, the results are reported of energy and exergy analyses of three biomass-related processes for electricity generation: externally fired biomass combined cycle, biomass integrated co-firing combined cycle and biomass integrated post-firing combined cycle. The energy efficiency for the biomass integrated post-firing combined cycle is 3% to 6% points higher than for the other cycles. The energy and exergy efficiencies are maximized for the three configurations at particular values of compressor pressure ratio, and increase with gas turbine inlet temperature. As pressure ratio increases, the mass of air per mass of steam decreases for biomass integrated post-firing combined cycle, but pressure ratio has little influence on the ratio of mass of air per mass of steam for the other cycles. The gas turbine exergy efficiency is the highest for the three configurations. The combustion chamber for the co-firing cycle exhibits the highest exergy efficiency and that for the post-firing cycle the lowest.