(2010) Transforming municipal solid waste (MSW) into fuel via the gasification/pyrolysis process

Kwon E., Westby K.J., Castaldi M.J.

(American Society of Mechanical Engineers) 18th Annual North American Waste-to-Energy Conference, NAWTEC18 ISSN:  Vol. Issue. Article No. DOI: 10.1115/nawtec18-3559

Municipal solid waste (MSW) gasification/pyrolysis enhancement using CO₂ as gasification medium has been studied to understand the performance under various reaction conditions. MSW gasification/pyrolysis has been characterized thermo-gravimetrically under various atmospheres covering the gasification/pyrolysis process, which has been used as a basis for scale-up experimental work using a flow-through reactor (FTR) and drop tube reactor (DTR) (0.5 g/min of sample, 4-5 sec residence time, 500°C-1000°C). For example, FTR has been used to carry out the fast pyrolysis process having a nominal heating rate of 800°C/min. Oils produced from the FTR have been condensed and analyzed with GC/MS. Among identified chemical species in the pyrolysis sample, the 10 most abundant compounds (benzene, toluene, styrene, limonene, 2,3- dimethyl-1-heptene, benzoic acid, ethylbenzene, indole, xylene, and d-allose) in the pyrolysis oil sample were determined and quantified. These 10 abundant chemical species are substantially reduced in the presence of CO₂. This leads to a substantial increase of C_1-5 hydrocarbons in gaseous (non-condensable) products and a reduction of pyrolysis oil (~20%) as well. In addition, MSW samples have been tested in the DTR at a temperature range from 500°C and 1000°C under various atmospheres with CO₂ concentrations of 0% and 30%. The release of all chemical species from the DTR was determined using μ-GC. For example, CO (~30%), H₂ (~25%), and CH₄ (~10%) under the presence of CO₂ were generated and introducing CO₂ into the gasification process substantially enhanced syngas production. Finally, steam gasification using different ratios of biomass to polyethylene has been explored to better understand the enhanced steam gasification of MSW that is mostly composed of biomass and polymer. Overall thermal degradation trend is the similar, but steam gasification of MSW needs a relatively long residence time and high temperature as compared to biomass. © 2010 by ASME.