Numerical Analysis of a Combined Heat and Power Generation Technology from Residual Biomasses

Abstract

Energy valorization of organic waste material is nowadays an assessed practice of circular economy. Combined heat and power (CHP) technologies based on biomass gasification represent viable substitutes to traditional energy conversion units based on combustion, whose need has recently experienced a huge growth, due to the increasing concerns about the release of greenhouse gases (GHGs) emissions and the related effects on climate changes. At present, only a few solutions have yet achieved a level of full development for commercialization. One of them is the system developed by CMD, the CMD ECO20, made of a gasifier, a syngas cleaning system and a spark ignition internal combustion engine working as a co-generator. In the present work, a numerical model is developed to study this system into detail and search for optimal controlling parameters. The simulation relies on a combined use of the Thermoflex™ environment and a proper one-dimensional (1D) model of the engine module built within GT-Suite®. An original contribution is given to the turbulent combustion model that accounts for the laminar flame speed of the specific syngas. The numerical model, that covers the entire biomass-to-energy conversion process, is validated under real operative conditions. The final purpose of the work is the optimization of input parameters, as the initial biomass moisture content, the equivalence ratio at the gasifier or the timing of spark advance, to maximize the system electrical energy output.