Thermo-Equilibrium modelingof a biomass gasifier using Aspen HYSYS

Abstract

India is one of the largest developing countries in which electricity requirement is kept on increasing. To fulfill such a huge requirement, a sustainable energy source is required. In some of the rural areas, it is difficult to establish a grid connection for the supply of electricity hence; off-grid electricity is required from economically available resources. Biomass gasification is one of the suitable options for the same. It is used to generate producer gas by incomplete combustion of biomass in the presence of sub-stoichiometric air/oxygen. The producer gas coming out from the gasifier can be used further to run the engine to generate electricity. The modeling of the gasification process is very important to reduce the dependency on the experiments. It can be carried out by various commercially available software/simulators such as Aspen HYSYS, Aspen Plus, etc. Various models could be prepared in those simulators such as zero-dimensional (0D), one-dimensional (1D), two dimensional, etc. In the zero-dimensional model, point analysis is carried out whereas, in the one-dimensional model, at least one of the properties is assumed to vary along with one of the dimensions. In the present study, the 0D and 1D models were formulated for simulating the gasification process using Aspen HYSYS simulator. A conversion reactor and a Gibbs reactor were used to model the gasification process with feedstock and air as inputs and producer gas (mainly H2, CO, CO2, N2) as output in the 0D model. In the 1D model, four different reactors for ash-free and five different reactors for ash-based modeling are used to model the gasifier process. The results obtained from both the simulations were then compared with the experimental results available in the literature. Average root mean square error (RMSE) for 0D and 1D models were calculated and found 4.43 and 2.84, respectively.