(613d) Pyrolysis and Gasification of Municipal Solid Waste

Pyrolysis
and gasification of Municipal Solid Waste (MSW)

Sireesha Aluri¹,
Pradeep K. Agrawal¹, John D. Muzzy¹, Carsten Sievers¹,
Derrick W. Flick², and John P. Henley³

¹School
of Chemical & Biomolecular Engineering, Georgia Institute of technology, Atlanta,
Georgia 30332; ²The Dow Chemical Company, Freeport, Texas, 77541; ³The Dow Chemical Company, Midland, Michigan

The
biggest challenge in processing Municipal Solid Waste (MSW) is its variability.
A part of MSW is recycled and/or used in heat recovery, and the rest is either discarded
in landfills or incinerated. The discarded portion further undergoes
pre-processing techniques to form Refuse Derived Fuel (RDF). Our goal is to
utilize this RDF to produce syngas via pyrolysis and gasification. Different
individual components were analyzed to determine the differences and
similarities between each. Paper (Tissue paper, paperboard), plastics (LDPE,
PET), food waste (orange peels, dog food), wood (pine), textile (cotton, PET)
and rubber (SBR) fractions were selected to mimic the actual RDF produced.

Experiments
with each of the individual components and the model MSW were carried out in a
Thermogravimetric Analyzer (TGA) separately to understand if the effect of
mixing the components is additive, inhibitive or synergistic. Pyrolysis studies
were carried out at temperatures between 30 ? 1000 °C
and at atmospheric pressure with a heating rate of 20 K/min. Gasification
studies were conducted after the pyrolysis step, at 800 °C and with CO₂
as the gasifying medium.

Individual
components had char content from 10 ? 32% (except for LDPE ~0%). DSC studies
showed endothermic behavior for all components except food waste and rubber.
Model MSW pyrolysis showed an additive behavior which was verified by comparing
the weight loss curve with the addition of individual curves, which had a
reproducibility of 98% or more. Gas analysis showed that major gas components
released were CO and CO₂ below 550 °C and H₂
and CH₄ between 550 and 900 °C. Gasification results
showed that there is a synergistic effect observed in the gasification of MSW,
which could be attributed to the inorganic content distribution during the
process. ?K' present in orange peel is mobile at higher temperatures and aids
in the gasification of entire MSW sample rather than just the orange peel. This
theory was verified by comparison with individual curve addition.