Plant Design for Regeneration of Spent Bleaching Clay by Boil-Off Method and Acid Treatment

There are significant economic and environmental benefits to the recycling of the waste generated by edible oil refineries, spent bleaching clay is one of the major ones. These spent bleaching clays are disposed into landfills which causes environmental pollution in addition to odors and fire hazards. The amount of fresh clay used in edible oil refineries in Saudi Arabia is estimated to be 6000 tons per year. Thus, boil-off method followed by acid activation is explored in this paper as a chemical recycling method for spent bleaching clay. This treatment can remove the adsorbed oil content and reactivate the clay to recover the bleaching ability where it can be sold again with a reasonable price. The proposed process handles a feed of 26 tons per day of spent bleaching clay, the suggested design achieves a deoiled and activated clay with bleaching ability as fresh one. The plant includes batch reactors to carry out the oil removal by boil-off method then followed by acid activation. After both reactors, filter presses combined with washing process to separate the filtrate and neutralize the products. Heat exchangers, dryers and storage equipment are also included in the design. The suggested design requires a capital investment of $2.079 MM and the cash flows of this plant suggests that it will break even by around 5.2 years.