Session: 1.1.1 - Fuels, Combustion & Material Handling

Paper Number: 108770

108770 - Co-Gasification of Gypsum and Municipal Solid Waste Components in CO2 Atmosphere 

In the United States only 12% of the 284 million tons on municipal solid waste (MSW) generated per annum is processed for energy recovery using a total of 87 incinerators in the country. The limitation to process more MSW through energy recovery, includes concerns over lack of control of air emissions from the operational facilities, high investment cost and the US has had available land. This then attracts the other option of landfilling, that although appears to be inexpensive for the disposal of wastes but it causes long term issues of slow release of many volatile gases, greenhouse gases, odours to the near-by communities and leachate to the water shed that causes health issues. However, landfill option is not a sustainable solution so that one must seek some permanent sustainable solution. In addition to the MSW generated, large amounts of wall boards are also disposed-off annually. In recent times the CO2 emission to the environment is also increasing very rapidly.  We seek the disposal of both MSW and wall board (gypsum) in the same process using CO2 as he gasifying. In this paper our interest is using gypsum in municipal solid waste using CO₂ assisted gasification. MSW is in the category of feeds that generate char and tars which lowers the gasification efficiency and often these by-products remain as waste streams because further processing requires high investment cost. CO₂ is able to react with char through the Boudouard reaction to form CO and in the same vein gypsum can react with char to produce CaS, CaO, and CO. Therefore, utilizing these three-waste stream has a huge advantage and offers synergistic potential. Therefore, this paper examines this significant gap in the literature on gypsum-MSW mixtures using CO2 as the gasifying agent under lab scale reactor conditions that provided precise control over temperature and residence times in the reactor.  In this work we examine the impact of varying proportions of gypsum during co-gasification of MSW and gypsum mixtures using CO2 as the gasification agent. The oxidation conditions and temperature were held constant, at 25% CO₂ and 900^oC. We examine the impact of gypsum mass fraction in the feed on the evolutionary behaviour of the syngas as well as its composition. We repeat the experiment and change the feedstock to single components (Wood, PET). Increasing the gypsum proportion had a negative impact on syngas yield. The yield reduced by 35% when gypsum was added at equal proportions (1:1) of MSW. Adding gypsum to wood increased the yield of syngas by 7%, the optimum syngas yield was achieved at 5:1 ratio of wood to gypsum. The yield of syngas also reduced with increase in gypsum for PET. However, the syngas quality improved with gypsum addition as the yields of hydrocarbon was reduced. The components with a tendency to form char show greater yields of syngas with the addition of gypsum. The syngas yield for wood was 25% more than that of MSW and 60% more than PET. This is because the gypsum reacts with char in solid-solid reaction phase producing CO and the reaction of CO2 + C = CO has an impact to the syngas yield. Detailed results obtained as well as suitable fraction of gypsum addition to waste will be reported in the full paper for efficient disposal of gypsum with other waste streams.  

Presenting Author: Ashwani Gupta UMD

Presenting Author Biography: Distinguished University Professor , University of Maryland, Honorary Fellow ASME and Royal Aeronautical Society (UK) and Fellow of SAE, AIAA and AAAS.