Effect of Addition of Ammonium Compounds on the Dissolution Rate of a South African Magnesium-Based Material

Abstract

High dissolution rates provide better alkalinity that is important for sulphur dioxide (SO₂) absorption. Therefore the rate at which magnesite dissolves is very important in wet flue gas desulphurisation process (FGD). In this study, we investigated the use of ammonium compounds for enhancing the dissolution rate of magnesium-based compounds. The dissolution rates were determined by using the shrinking core model (SCM) with surface control, i.e, [1 − (1 − X)^1/3] = k_rt. The dissolution characteristics were investigated under the following conditions by using the pH-Stat method: temperature, 60°C; pH, 5; stirrer speed, 200 rpm; particle size 45 μm. The addition of ammonium compounds helps improve the dissolution rate of magnesium-based compounds. Upon the addition of 0.5 g of ammonium nitrate, the dissolution rate constants increased by 122%. The dissolution reaction conformed to the SCM, and chemical reaction control was the rate-controlling step.