Environmental, Water Resources, and Coastal Engineering Seminar Series

Fitts-Woolard Hall 3301

Methods to measure heat generation from ash in landfills

Abstract: In recent years, there have been reports of a few municipal solid waste landfills experiencing temperatures as high as 100ºC. These landfills are referred to as elevated temperature landfills (ETLFs). ETLFs require increased monitoring and management. A recently published landfill heat accumulation model identified reactions that contribute significant heat to landfills, including the hydration and carbonation of Ca-containing wastes such as ash. Model predictions were based on published information on reaction thermodynamics and kinetics. However, there is limited data on heat evolution from ash. This study aims to develop laboratory methods to measure heat evolution from Ca-containing ash under landfill-relevant conditions (presence of water and abundance of CO₂). A semi-adiabatic reactor system was developed. The reactor consists of four major parts: an insulated container (dewar flask), insulation, a sample container, and a center channel to hold a temperature sensor. The temperature sensor is connected to a data acquisition device (LabJack). The reactor is characterized for heat loss so that temperature data during ash reaction can be used to calculate the rate and extent of heat generation. Reactor characterization involves the determination of two parameters; the coefficient of heat loss and the thermal capacity. Validation experiments were conducted by measuring heat evolution from the hydration of pure CaO and the carbonation of pure Ca(OH)₂ and comparing those to theory. In the case of Ca(OH)₂, a continuous stream of N₂/CO₂ was provided, and the CO₂ uptake was compared to theoretical expected uptake. Heat evolution and CO₂ uptake data were used to calculate the heat generation rate. This heat and rate will be used to better parameterize models of heat generation and accumulation in landfills. The coefficient of heat loss and thermal capacity was measured to be 105 J‧hr^-1‧K^-1 and 1200 J‧K^-1_, respectively. The validation experiments yielded an efficiency between 103 and 106% for hydration and between 104 and 107% for carbonation, respectively. Work is in progress to parameterize the landfill model.

Biography: Asmita Narode is a Ph.D. student working with Dr. Morton Barlaz at NC State. Her work focuses on measuring heat generation from ash that is disposed of in landfills. She completed her undergraduate in Civil Engineering in India and her M.S. in environmental engineering at Georgia Tech. Before starting her Ph.D., Asmita worked for a consulting firm.