Increased maize power production through an integrated biogas-gasification-SOFC power system

This work is aimed at demonstrating by modeling and simulation how a synergy of state-of-the-art technologies can boost of about 50% the maximum power output that can be obtained from maize silage biogas power plants. The starting point is the subdivision of the maize plant into grains and stover (that is composed of cobs, stalks and leaves). Grains are rich of starch, soluble sugars, fat and protein suitable for the anaerobic digestion, instead the stover is rich of hemicellulose and lignin which are characterized by a slow and incomplete degradability. This consideration brings to the core of the paper: grains are used as fuel in an anaerobic digester, while stover is converted into syngas in a fixed bed downdraft gasifier reactor. The biological degradation of grains is based on equilibrium kinetic models obtained from literature review, the stover gasification is modeled with an equilibrium model implemented in Python™ language. Biogas and syngas streams are used together as fuel in a Solid Oxide Fuel Cell (SOFC) conversion unit modeled through a MatlabTM script. Simulations were done considering a conventional maize silage biogas power plant with 100 kW electrical nominal power. Results outlined that the SOFC has a higher conversion rate than the conventional IC engine, in fact the replacement of the generator with a SOFC increases the power output of the plant to about 118 kW. Finally, the combined effects of coupling digestion of grains with the gasification of the stover and the use of a SOFC boost the peaks power output to 150 kW.