FSA Neutralization with Calcium Compounds

As environmental regulations continue to restrict chemical processing emissions, phosphate plant operators will eventually be required to neutralize fluoride waste materials. Most phosphate plants currently use direct contact barometric condensers with recirculating cooling pond water that is saturated with fluoride salts. Most of this fluoride is allowed to precipitate as the recirculating water cools in large cooling pond systems. When forced to treat fluoride contaminated water, phosphate producers typically use lime or limestone neutralization prior to discharging effluent. A better environmental alternative is to use scrubbers to remove fluorides as fluosilicic acid prior to condensing the vapors in barometric condensers. If a market cannot be found for the fluosilicic acid, it can then be neutralized with phosphate rock to produce a weak phosphoric acid. This technique is not currently used because it is not profitable. This paper discusses Fluosilicic Acid neutralization with several calcium compounds such as phosphate rock, lime and limestone.