Session: 1.1.2 - Fuels, Combustion & Material Handling

Paper Number: 108773

108773 - Metals Recovery and Syngas Evolution During Co-Gasification of Municipal Solid Waste and Gypsum 

Valuable materials can be recovered when the two-waste material are co-processed. Synergetic interaction between MSW and gypsum are expected to improve the conversion efficiency of MSW to syngas and convert the gypsum to valuable chemicals such as limestone/dolomite or quicklime and calcium sulphide. Co-processing of MSW with this low value gypsum with can potentially provide improved product recovery and simultaneously provide economic viability. The impact of gypsum incorporation into MSW conversion, in 1:1 mixture of MSW with gypsum from drywall wastes using micro-scale mass loss kinetics along with macro-scale syngas evolution and conversion at different temperatures and in pyrolytic and oxidizing environments provided favourable results. Gypsum incorporation led to increased syngas production and decreased char yields as the char was oxidized by CaSO4. In this work thermodynamic equilibrium analysis is used to investigate the fate of metals during co-gasification of MSW and gypsum. Aspen Plus was combined with Thermocalcs to develop a process model that considers the conversion of metals during gasification. Aspen plus was used to simulate the formation and composition of major gas components and light hydrocarbons with respect to process parameters of temperature and feed mass ratio. Thermocalcs was used for determining the formation of different metal phases and composition during gasification. The results from aspen plus showed that temperatures below 900^oC suppressed the transformation of sulphur in gypsum to SO₂ through formation of solid CaS, however, the feed mass ratio of MSW: CaSO4 should be 2:1 and above. Thermocalcs shows that at 900^oC, the major minerals formed are Alabandite 6 wt%, Melilite 2 wt%, Wollastite 1.4 wt%, Pyrrhotite 0.1 wt% sphene 0.2 wt% of the total products formed. No solid carbon was formed and about 90 wt% of the products leaving as gas comprised of 22% CO and 19% H₂. Alabandite, is a mineral of CaS mixed with traces on MnS, FeS, and MgS. Alabandite dominated in the solid products. Melilite represented calcium silicates of aluminium and magnesium. Wollastonite is represented as calcium inosilicate mineral (CaSiO3) containing small amounts of iron and magnesium. This is the same result observed in Aspen Plus that at 900^oC, CaS is dominant over CaO and gypsum addition improves the quality of the syngass by reducing hydrocarbonas and solid carbon. The results show that syngas as well as useful minerals can be recovered during the co-gasification of MSW and gypsum. These results show that syngenetic benefits are realized when two different low value waste materials are co-processed together. The results obtained will be presented in the full paper.

Presenting Author: Ashwani Gupta UMD

Presenting Author Biography: Distinguished University Professor at the University of Maryland College Park, MD