Thermal decomposition kinetics of Brazilian limestones: effect of CO₂partial pressure

Abstract

The influence of the partial pressure of carbon dioxide (CO2) on the thermal decomposition process of a calcite (CI) and a dolomite (DP) is investigated in this paper using a thermogravimetric analyser. The tests were non-isothermal at five different heating rates in dynamic atmosphere of air with 0% and 15% carbon dioxide (CO2). In the atmosphere without CO2, the average activation energies (E(alpha)) were 197.4 kJ mol(-1) and 188.1 kJ mol(-1) for CI and DP, respectively. For the DP with 15% CO2, two decomposition steps were observed, indicating a change of mechanism. The values of E(alpha) for 15% CO2 were 378.7 kJ mol(-1) for the CI, and 299.8 kJ mol(-1) (first decomposition) and 453.4 kJ mol(-1) (second decomposition) for the DP, showing that the determination of E(alpha) for DP should in this case be considered separately in those two distinct regions. The results obtained in this study are relevant to understanding the behaviour changes in the thermal decomposition of limestones with CO2 partial pressure when applied to technologies, such as carbon capture and storage (CCS), in which carbon dioxide is present in high concentrations.

Use of a fluidized bed combustor and thermogravimetric analyzer for the study of coal ignition temperature

“…The model is based on isoconversional techniques and different values of activation energy are obtained for each conversion value normalized between 0 and 1, i.e. its value is obtained for each physical and chemical processing that occurs during the reaction [37]. The conversion (a) of a chemical reaction is given by:…”

“…Under nonisothermal conditions, the temperature varies at a constant heating rate (b = dT/dt) and Eq. (2) is described an isoconversional linear integral method [35][36][37][38][39].…”

“…2represents the value of a given conversion (a). Therefore, the activation energy (E a ) is obtained as a function of the conversion [35][36][37][38]. ln b=T 2…”

Kinetics of limestone decomposition in hot metal

“…It can play a role as raw material in fusing agent in metallurgical industry, cement industry, additive for composite material, and so on [1][2][3][4][5]. Many researchers have studied the limestone decomposition in the temperature near the critical temperature of limestone decomposition [6][7][8][9][10][11][12][13][14][15][16]. The unreacted core model have been widely used in metallurgical industry, and mass transfer driven by concentration gradient has been used to describe the model [17].…”

Technology Development for Strong Reduction of Energy Consumption and Co2 Emission in Lime and Cement Manufacture

“…Nevertheless, the fuel combustion generates a CO 2 partial pressure of about 20 KPa inside the furnace that demands a temperature of at least 800°C to achieve this equilibrium pressure; such temperature differences for 0 and 15% CO 2 has also been reported by L. Tian [5] and I. Avila [6]. In actual industrial practice, limestone calcination is carried out at 1,200°C to achieve an acceptable decomposition speed and rate.…”