Kinetic calculations for the thermal decomposition of calcium propionate under non-isothermal conditions

Calcium propionate (CP) is shown to be useful for simultaneous SO₂/NO reduction in coal-fired power plants and its thermal decomposition characteristics are measured by thermogravimetric analysis in a feasibility study into more complete reduction of these hazardous gases. Calcium carbonate (CC), which has been used primarily for in-furnace desulfuration, was used for comparison. The thermal decomposition of this organic calcium-based sorbent began at low temperature, i.e. the carboxylic radical was evaporated from 565 K to 759 K for CP and the corresponding mass loss percentage was 47.79%. The residual was subsequently decomposed to release carbon dioxide between 843 K and 1012 K. The latter phase of the process occurred more readily than with CC because of the loose structure of CP resulting from evaporation of the carboxylic radical in the low temperature zone, which could be seen directly by scanning electron microscope. The maximum mass loss rates of this phase occurred at temperatures of 972 K and 1012 K for CP and CC, respectively. The Ozawa-Flynn-Wall method was used to calculate the activation energy during the thermal decomposition process at heating rates of 5, 7.5, 10 and 15 K/min. The result further confirmed the multistage characteristic of CP thermal decomposition, which could be seen in differential thermogravimetry curves. The reaction orders of CP in the conversion range 20%–80%, calculated using the Avrami theory were from 0.061 to 0.608, smaller than those of CC, which were 1.647 to 2.084.