Kinetics of the Reaction between HF and CaO for Fluoride Emission Control

Basic kinetic data are presented for the reaction between HF and CaO where CaF₂ is the reaction product. Two CaO materials were studied: a reagent-grade CaO and calcined Greer limestone. The reaction is first order with respect to HF, and. the intrinsic rate constants, k₆, have been measured for temperatures ranging from 550 to 800 °C. The diffusion coefficients of HF in CaF₂ are also reported for this temperature range. With limestone or for the reaction system limestone-potlining-air, fusion of the products occurs at temperatures above 790 °C, caused by the eutectic complex NaCa₂FSiO₄. An example of possible application of this reaction in HF emission control is the combustion of potlining produced in aluminum industry in a fluidized bed combustor.