Kinetics of the Oxy-fuel Combustion of High-Ash-Content Coal from the Candiota Mine, Rio Grande do Sul

Abstract

The work presents a kinetic study of the oxy-fuel combustion reaction of coal with a high content extracted from the Candiota mine, Rio Grande do Sul. The aim of the study was to collect data of the southern Brazil coal in oxy-fuel combustion conditions. In this technology, combustion burning occurs with a mixture of O 2 and a high CO 2 content. The experiments were performed isothermally at temperatures of 873−1173 K at atmospheric pressure, with O 2 concentrations ranging between 10 and 30% (v/v) in CO 2 . Initially, the coal pyrolysis temperature was determined to eliminate volatile matter, thus avoiding its influence on the oxy-fuel combustion reaction. The experimental results were treated mathematically with models from the literature to determine the kinetic parameters, including the activated energy and reaction order.

Demineralization of Brazilian Coals for Use in Gasification and Oxy-Fuel Combustion Processes, Aiming to Reduce CO2 Emissions

“…From Figure 6, it can be observed that increasing the temperature also increased the speed of consumption of char (i.e., increased the reaction rate) for the concentrations of 10 For the four temperatures studied, it was observed that increasing the concentration of O 2 in the reagent gas increased the oxy-fuel combustion reaction rate of the demineralized char samples. No overlap of the curves was observed with increasing temperature, as was seen for the ROM samples and as reported by Nunes et al 53 Despite the increase in O 2 concentration, the similar behaviors of the curves indicate a strong resistance to mass transfer.…”

“…An increase in the gasification start temperature of approximately 160 K was therefore observed for demineralized Candiota coal. This increase in temperature might indicate that the mineral matter could be acting as a Boudouard reaction catalyst, as suggested by Alonso et al, 54 Wigley et al, 55 Backreedy et al, 56 Liu et al 57 Su et al, 58 53 a reduction in surface area and an increased average pore diameter were observed compared for the Candiota char.…”

“…Considering the data presented in Table in light of the results published by Nunes et al, a reduction in surface area and an increased average pore diameter were observed compared for the Candiota char.…”

“…In Figure 4, the mass loss curve in a CO 2 atmosphere for demineralized Candiota coal starts after 1173 K. In a study of Candiota "run of mine" (ROM) coal, Nunes et al 53 found that coal gasification occurred at approximately 1013 K.…”

“…Effect of Temperature. The temperatures used for the oxy-fuel combustion reaction in this work were 873, 973, 1073, and 1173 K. These temperatures were previously selected based on thermogravimetric testing with ROM samples, according to Nunes and Marcilio 59 and Nunes et al, 53 so that we could compare the results obtained with demineralized and ROM samples using the same temperatures and O 2 concentrations in CO 2 .…”