Thermal interaction between limestone and silica

A thermodynamic analysis of the interaction between limestone and silica is carried out under normal pressure with the use of the TERRA program system. An equilibrium system is considered. The thermodynamic parameters are calculated with a step-by-step increase in temperature. The temperature of calcium silicate synthesis with respect to the initial mixture composition is found. At all possible ratios between limestone and silica, the products of the chemical reaction are determined. The reaction heat, synthesis temperature, enthalpy increment, and heat content are determined. It is shown that wollastonite isothermal synthesis proceeds at 550 K at a constant heat content, and rankinite isothermal synthesis proceeds at 750 K at a constant heat content as well. The reaction heat increases with rising limestone content until rankinite starts to form and then decreases to zero. The interaction between limestone and silica produces carbon dioxide gas, whose content grows simultaneously with the rising reaction heat. When the rankinite yield is maximal, the amount of carbon dioxide diminishes to zero, because free limestone forms and CO2 is buried. On the basis of the results, the conclusion is drawn that the reaction proceeds with a latent exotherm due to latent limestone dissociation and formation of lime during the thermal interaction between limestone and silica.