Neutralisation of Acid Water in the Chemical Industry with Limestone

The replacement of lime with limestone for the neutralisation of acid water was investigated through batch and semi-continuous studies. A fluidised-bed reactor with multiple stages of increasing diameters is preferred for the limestone neutralisation process as it allows fluidisation of the bigger particles but also prevents washout of the smaller particles in the case where ungraded particle size limestone is used. It was determined that the rate of neutralisation is influenced by the particle size of limestone and the type of metal in solution. Sulphate is removed as gypsum to the level where the water is saturated with calcium sulphate, while CO₂ is produced as a by-product.