Modeling of a Downdraft Gasifier Combined with Externally Fired Gas Turbine using rice straw for generating electricity in Egypt

Egyptian farms produce annually about 43.640 Mega ton of the agricultural. 16 Mega ton from these residues has been utilized and about 27.64 Mega ton (63.34%) of the total agricultural wastes would be remain as a type of contamination. Hence, there is an urgent need to exploit these wastes especially the rice straw as priceless residue for electrical generation using the biomass gasification process. This paper is focused on modelling of a small scale power plant consists of a Downdraft Gasifier Combined with Externally Fired Gas Turbine which will deliver power on scale down to 71 kw and thermal energy (259 kWth). The developed power plant is modelled using Cycle-Tempo software. The results of modelling of the developed power plant revealed that, the increase of gasification temperature would decrease the calorific value of the produced gas and the contrarily occurred with the volume flow and the air-biomass ratio then, a large amount of N2 is appeared and the H2 would be reduced. Consequentially, the suitable temperature of gasification is 773.65°C. Regarding the G-EFGT, the system modelling indicate that, the electric efficiency for the fired turbine decreases when the hot side temperature difference (Ths) rises from 50°C to 200°C. Therefore at high Ths, and Turbine inlet temperature (TIT) not exceeds 850°C, the system needs a reaction temperature of 1250°C at external oven.