Comparative study of steam injection modes for a proposed biomass-driven cogeneration cycle: Performance improvement and CO2 emission reduction

Biomass fuel energy can be utilized in cogeneration cycles through the gasification process. This reduces pollution and increases the efficiency of conventional cycles, and makes use of renewable energy instead of fossil fuels. In this paper, in order to generate both electricity and cooling, a cogeneration system has been proposed using biomass fuels. Then, various ways of injecting steam into each proposed cycle are proposed in order to improve its efficiency and performance. The following cycles are suggested and modeled: CHP with the steam injection into the combustion chamber, CHP with the steam injection into gasifier, and CHP with the steam injection into the gasifier and combustion chamber simultaneously. All proposed cycles are initially analyzed from energy, exergy, exergoeconomic, and environmental perspectives. Following analyses of the cycles, results are compared and discussed to select the cycle with the best balance in terms of thermodynamics, economics and pollutant emissions. Then, a parametric study is discussed in which, along with determining the influence of changing an important thermodynamic parameter on cycle performance, the simultaneous influence of two parameters is calculated and verified. The results show that the steam-injected gasifier cycle is about 5.43% more efficient than the steam-injected combustion chamber cycle, and its carbon dioxide emissions are about 5.2% lower. Also, the cycle by simultaneous injection of steam into both the gasifier and combustion chamber offers the highest efficiency and pollution reduction. Additionally, by simultaneously increasing the mass flow rates of steam injection into the proposed system with simultaneous steam injection into both the gasifier and combustion chamber, the exergy efficiency and costs are increased by 11.2% and 3.5% respectively, and CO2 emission are reduced by 12.5%.