Non-isothermal kinetics and characteristics of calcium carbide nitridation reaction with calcium-based additives

The nitridation reaction of calcium carbide and N₂ at high temperatures is the key step in the production of lime-nitrogen. However, the challenges faced by this process, such as high energy consumption and poor product quality, are mainly attributed to the lack of profound understanding of the reaction. This study aimed to improve this process by investigating the non-isothermal kinetics and reaction characteristics of calcium carbide nitridation reaction at different heating rates (10, 15, 20, and 30 °C·min⁻¹) using thermogravimetric analysis. The kinetic equation for the nitridation reaction of additive-free calcium carbide sample was obtained by combining model-free methods and model-fitting method. The effect of different calcium-based additives (CaCl₂ and CaF₂) on the reaction was also investigated. The results showed that the calcium-based additives significantly reduced reaction temperature and activation energy E_a by about 40% with CaF₂ and by 55%–60% with CaCl₂. The reaction model f(α) was also changed from contracting volume (R3) to 3-D diffusion models with D3 for CaCl₂ and D4 for CaF₂. This study provides valuable information on the mechanism and kinetics of calcium carbide nitridation reaction and new insights into the improvement of the lime-nitrogen process using calcium-based additives.