Aqueous citric acid as a promising cleaning agent of whey evaporators

Scale in evaporators for lactose production was identified as mainly calcium citrate tetrahydrate with phosphate contaminations. Dissolution of 3.00 g of scale in aqueous solutions of 0.100, 0.500, and 1.00 mol L⁻¹ citric acid with final volumes of 100, 50, and 25 mL was investigated. The highest concentration of citric acid was the most effective for all the investigated volumes. From the citric acid solutions, spontaneously supersaturated in calcium citrate tetrahydrate during scale dissolution in the smaller volumes for all citric acid concentrations, calcium citrate tetrahydrate slowly precipitated in acceptable purity for technical use. Dissolution efficiency of aqueous solutions of 0.200 mol L⁻¹ nitric acid combined with 0.100, 0.500, and 1.00 mol L⁻¹ citric acid with final volumes of 100, 50, and 25 mL showed synergistic effect especially for the higher concentrations and lower volumes of two acids.