Modeling and simulation on hydrogen-rich syngas production via gasification of palm kernel shell

The high world energy demand has caused sustained growth in the use of fossil fuels, depleting its reserves, raising the cost of energy in many places, and contributing significantly to climate change [1]. Biomass is considered a sustainable energy source by having a net neutral production of carbon dioxide [2], such that it can partially replace fossil fuels. One of the ways of using biomass is to obtain new energy vectors, such as hydrogen, whose production from residual biomass is technically and economically feasible [3]. On the other hand, the Aspen Plus simulation software has been used in various petrochemical processes, such as methanol synthesis, indirect liquefaction and hydrogasification of coal, combined cycles in power plants; however, its application in biomass transformation processes has been limited [4]. Therefore, in this research the gasification process of palm kernel shell (PKS) was modeled and simulated at steady-state using Aspen Plus, varying the temperature (750 to 950 °C) and the steam/biomass ratio (S/B) between 0 and 2.5 (w/w), to determine its effect on the production of H₂ present in the syngas. The kinetic parameters of the gasification were determined by means of a thermogravimetric analysis (TG/DTG) using two gasifying agents (CO₂ and steam) and applying three semi-empirical kinetic models to interpret the experimental results (linear model, grain model, and volumetric model). Linear model and grain model have the best fit with the experimental results of PKS gasification with steam and CO₂, with R² values of 0.966 and 0.965, respectively. The simulation allowed obtaining results with a good fit with the experimental data (RMSE 0.135) and with greater precision compared to another model simulated in Aspen Plus (RSME 0.282) [4]. The yield of H₂ production as a function of temperature and S/B ratio was estimated by a multiple linear regression model, obtaining that its production oscillates between 80 and 109 g H₂/kg PKS, reaching its maximum peak at 950 °C and an S/B ratio of 0, and the minimum production at a temperature of 700 °C and an S/B ratio of 2.5.

References
1. BP Global Organization, (2015) BP Statistical review of world energy, London.
2. Marrugo, G. et al. (2016) Characterization of colombian agroindustrial biomass residues as energy resources. Energy and Fuels 30, 8386–98.
3. Li, J. et al. (2009) H2 rich gas production by steam gasification of palm oil wastes over supported tri-metallic catalyst. Int J Hydrog Energy 34, 9108–15.
4. Nikoo, M. and Mahinpey N. (2008) Simulation of biomass gasification in fluidized bed reactor using Aspen Plus. Biomass and Bioenergy 32, 1245–54.