deliming

Deliming is a chemical cleaning process used to remove lime deposits—primarily calcium carbonate and calcium hydroxide—from equipment and process streams in various industries. Lime scale forms on heat exchangers, pipes, vessels, and other surfaces that handle lime-containing fluids, reducing heat transfer efficiency, flow, and product quality. Deliming restores equipment performance and reduces the burden on subsequent cleaning steps.

Industries and applications

In papermaking and pulping, lime is used in pulping liquor and cooking processes; deliming removes excess lime from white liquor and process lines to prevent scaling in digesters, washers, and bleaching stages. In dairy, beverage, and other food processing, deliming is employed during CIP (clean-in-place) routines to remove calcium-based scale from pasteurizers, evaporators, and pipelines, enabling more effective subsequent cleaning and sanitization.

Chemicals and methods

Deliming typically involves acid treatment to dissolve lime deposits. Common agents include sulfuric acid, phosphoric acid, nitric acid, or organic acids, sometimes used in combination with CO2 or ammonium salts to convert calcium compounds into soluble forms. The process is conducted with controlled pH and temperature to optimize dissolution while minimizing equipment corrosion. After deliming, surfaces are rinsed, and any necessary neutralization is performed to restore safe process conditions before normal operation resumes.

Considerations

Safety and engineering controls are essential due to the corrosive nature of acids and the handling of calcium-rich waste streams. Materials of construction must resist acidic exposure, and effluents containing dissolved lime salts require appropriate treatment before discharge.

See also: lime scale, descaling, cleaning-in-place.