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. The objective of this study is to develop laboratory methods to measure heat evolution from Ca-containing ash under landfill-relevant conditions. A method is under development to build a semi-adiabatic reactor system. 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. Heat evolution from the hydration of pure CaO and the carbonation of pure Ca(OH)2 is being measured. In the case of Ca(OH)2, a continuous stream of N2/CO2 is provided. Heat evolution data will be used with a model describing the system to compare measured and theoretical heat. Coal and municipal solid waste ash samples will then be tested to calculate the heat generation rate. This rate will then be used to better parameterize models of heat generation and accumulation in landfills. Figure 1 illustrates the reactor system. The coefficient of heat loss and thermal capacity was measured to be 120 J.hr-1.K-1 and 1700 J.K-1, respectively. In preliminary work, we encountered k values of 1.91 and 0.3 hr-1 for hydration and carbonation of CaO and Ca(OH)2, respectively. Once confirmation experiments with CaO and Ca(OH)2 are complete, heat release from ash samples will be measured.

Development of methods to measure heat released from hydration and carbonation of ash in landfills

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.