Gasification of Municipal Solid Waste: Thermodynamic Equilibrium Analysis Using Gibbs Energy Minimization Method and CFD Simulation of a Downdraft Gasifier

Abstract

Millions of tons of municipal solid waste (MSW) are generated annually, posing dramatic threats to our environment. To reduce its environmental impact, MSW can be segregated and thermochemically converted into clean syngas (CO and H2) fuel via gasification process. The feasibility of Gasification of MSW depends on its composition and quantity. In this work, assessment of the gasification metric of MSW is conducted under steam (H2O) as gasification moderator in a pilot scale 20kW gasifier. The characteristic of local MSW are experimentally determined using Flash 2000 organic analyzer (CHNS-O), the thermo-gravimetric analyzer (TGA) and bomb calorimeter following ASTM standards and arriving to molar formula of MSW. A thermodynamic equilibrium model based on Gibbs energy minimization method is used for the steam gasification of MSW to assess the composition of syngas. Using the baseline operating condition from the thermodynamic equilibrium model, a reactive high fidelity numerical model of a downdraft gasifier is developed to gain more fidelity. Result of gasification efficiency of thermodynamic model is 64% while reactive model gives 7% additional efficiency. Nonetheless, the stipulated efficiency and the high-quality syngas produced via the steam gasification of MSW suggest the viability of the process scale up.