Thermal Performance of an Indirectly Heated Biogasification Based Combined Cycle Plant Employing Reciprocating Compressor

Biomass based Indirectly Heated combined heat and power plant can be an excellent option for community scale power generation. The thermal performance of such a plant employing air-turbo generator block and bottoming steam turbine block has been analyzed over a range of pressure ratio (2-16) and for different turbine inlet air temperatures (1073, 1273 and 1373K). The conventional GT combustion chamber is replaced by a burner and heat exchanger. The conventional axial compressor-gas turbine assembly is replaced by double acting reciprocating compressor and a turbo generator assembly. The main objective of using reciprocating compressor is to reduce the work requirement. Double acting reciprocating compressor is used instead of single acting to avoid the pulsating flow. The simulation of thermodynamic model is done by Athena Visual Studio software. For base case configuration, (topping cycle pressure ratio 4, gas flow rate of 90 Nm3/hr and turbine inlet temperature (TIT)= 1273K) the turbocharger unit provides about 35.9 kW electrical output, while work requirement for compressor and pump unit is about 15.04 kW respectively. This work is supplies by the steam cycle which is about 17.05 kW. It is seen from the analysis that up to the pressure ratio 5 (cut-off point) the steam cycle can drive the work consuming components and beyond this pressure ratio an auxiliary power source is required to drive them. It is also seen from the analysis at TIT 1073 K this cut-off point is bellow pressure ratio 4 while at TIT 1373 K the cut-off point is above pressure ratio 5.