Pilot-scale grinding and briquetting studies on variable moisture content municipal solid waste bales - Impact on
Jaya Shankar Tumuluru1, Neal A Yancey1, Joshua J Kane1
1Energy Systems Laboratory Energy Systems and Environment Directorate, Idaho National Laboratory, 750 MK Simpson Blvd, Idaho Falls, ID, USA.
Abstract:
Low bulk density, variable moisture content, and particle size of municipal solid waste (MSW) create feeding, handling, storage, and transportation challenges. In this study, MSW bales were size-reduced in stage-1 and stage-2 hammer mill grinders fitted with 50.8-mm and 6.35-, 12.7-, and 19.05-mm screens. Ground MSW was densified further in a pilot-scale briquette press by varying moisture content in the range of 10-25% wet basis (w.b.). At 40% (w.b.) MSW moisture content, the stage-1 grinder fitted with a 50.4-mm screen took about 136kWh/ton, while the stage-2 grinder fitted with a 19.05-mm screen took about 151kWh/ton. The bulk density of MSW after stage-1 and stage-2 grinding was about 25-50 kg/m3. Unit bulk and tapped density were in the range of 680-850 kg/m3, 478-315 kg/m3, and 346-540 kg/m3 post briquetting, and 591-830 kg/m3, 295-458 kg/m3, and 319-519 kg/m3 post five days of storage at 20 °C. The durability was about 93.40-98.54% post briquetting, and after five days of storage. Increasing the moisture content and screen size decreased density and improved durability. Briquetting energy increased to 120 kWh/ton at a higher moisture content and larger grind size. MSW flow characteristics improved after briquetting. Higher lignin content (≈30%) and calorific value (19-21 MJ/kg) suggest MSW is suitable for thermochemical conversion. Ash content in the MSW was in the 11.9-14.8% range. CT-scan images of the briquettes showed a network of interconnected pores formed due to compression of various MSW fractions.
