Crown provides several bleaching processes using bleaching clay alone or in combination with special sorbents. Special sorbents reduce residual gums or soap in oils that have not been water-washed prior to bleaching.
Classic or traditional bleaching and packed bed bleaching are the lowest-capital cost options, while Crown's DoublePass bleaching process provides the lowest operating costs.
In classic or traditional bleaching, oil and bleaching clay are mixed, bleached and filtered.
DoublePass bleaching pre-bleaches the oil by mixing it with a special sorbent or bleaching clay, then drying and filtering in a filter containing partially spent bleaching clay. Bleaching clay is then mixed with the pre-bleached oil, bleached and filtered in a clean filter. DoublePass bleaching is the most efficient process for reducing bleaching clay consumption and oil losses.
Packed bed bleaching is a less common process that pushes the oil through a series of filters pre-coated with a bed of fresh bleaching clay.
Two other less common processes, simultaneous bleaching and sequential bleaching, mix the oil with special sorbents and bleaching clay prior to bleaching and filtering. These two bleaching processes are typically used to replace an existing water-washing step in neutralizing.