ABSTRACT
Biomass gasification involves the production of a gaseous fuel by partial oxidation of a solid fuel. Clean synthetic (syn) gas, produced from partial combustion of biomass can be burnt either in a gas turbine or a diesel engine combustion chamber to run a biomass based integrated energy system. By properly arranging the plant components, the simultaneous benefit of power and cooling can be obtained with the integrated system approach. In the current work, different options in integrated power systems and integrated combined power cooling systems are developed and discussed. Modeling and performance evaluation of such integrated energy systems have been addressed. In case of only power systems, a maximum of four power systems can be integrated as per the available heat recovery. In a combined power and cooling systems, maximum of three power systems can be integrated with one cooling system. It has been found that the combined power and cooling integration results high fuel efficiency compared to the only power integrated systems. The optimum compressor pressure ratio is decreasing with the integration of supplementary firing (SF) to the combined cycle power plant. Biomass has great potential as a renewable and clean energy for producing electricity, process heat and cooling with the integrated energy system approach. Gasification is a degradation process consisting of a sequence of thermal and thermochemical processes which converts the carbon in the solid fuel with restricted air into gases, leaving an inert residue. Biomass can be gasified in various ways by
properly controlling the mix of fuel, air, and steam within the gasifier. The gasification of coal and biomass began in about 1800 and by about 1850 gas light for streets was common place. Due to its higher efficiency, it is desirable that gasification becomes increasingly applied in future rather than direct combustion. The current work is relevant because efficient conversion processes are required for renewable resources in order to compete with fossil fuels. Gasification of biomass is an attractive technology for combined heat, power and cooling production. Mark and Mike [1] discussed the use of biomass gasification process as the key element in an advanced gas turbine combined cycle system. Savola [2] simulated the possibilities to increase the power production and the power-to-heat ratio of 1-20 MWcombined heat and power plants using biomass fuels with optimization tools. Margaret and Pamela [3] reported that the biomass systems produce very low levels of particulates, NOx, and SOx compared to the fossil systems. The biomass systems consume very small quantities of natural resources and have a positive net energy balance as they use renewable energy instead of non-renewable fossil fuels. Co-firing of biomass with coal offers us an opportunity to reduce the environmental burdens associated with the coal fired power systems. Anil et al. [4] solved the equations containing four atom balances (C, O, H, and N) and equilibrium relations for gas compositions using MATLAB at atmospheric conditions. Laihong et al. [5] simulated the processes, including chemical reactions and heat/mass balance with Aspen Plus software. Madhukar and Goswami [6] used a thermodynamic equilibrium model to predict the chemical composition of the products of biomass gasification. They carried out first law analysis for wood (designated by CH1.5O0.7) and showed that the optimum conditions for hydrogen production occurred at a gasification temperature of 1,000K, steam biomass ratio of 3 and equivalence ratio of 0.1. Krzysztof et al. [7] compared different types of biofuels for their gasification efficiency and evaluated for exergy efficiency. Rutherford [8] modeled biomass gasifier and studied the effects of steam fuel ratio and moisture content in biomass without taking solid carbon content in the synthetic (syn) gas. Although a lot of research and development work has been carried out during the past decade the commercial breakthrough for this technology is still to come. The detailed models of the integrated energy systems using biomass as a single fuel are not reported so far in the literature. The main objective of the current work is to present the new trends in the integrated power systems and integrated combined power and cooling systems. The current work is giving the conceptual suggestions in the combinations in the integrated energy systems.
