Patent ID: 6179901
Filing Date: 2001-01-30
Classification: B01D

Abstract:
A method for producing an aqueous solution of hydrofluoric acid by scrubbing fluorine values from a hot gaseous mixture produced during the defluorination of phosphate rock, the method comprising the steps of:a) withdrawing the hot gaseous mixture from a defluorination kiln;b) cooling the hot gaseous mixture by passing it through a heat exchanger;c) conveying the cooled gaseous mixture to a first scrubber adjacent the heat exchanger and thence sequentially through a plurality of series-connected scrubbers comprising at least the first scrubber and a last scrubber, and conveying the scrubbed gaseous mixture from the last scrubber to an exhaust means;d) absorbing a respective portion of the fluorine values within each scrubber by:d1) pumping a liquid from a respective sump portion of that scrubber through a respective plurality of spray heads into the gas mixture;d2) capturing a respective fraction of the sprayed liquid in a respective porous polymeric pad adjacent a respective upper end of that scrubber and causing the captured sprayed liquid to flow into the respective sump portion;d3) pumping a respective portion of the liquid from the respective sump portion to a respective liquid outlet;e) withdrawing, from the respective liquid outlet of each scrubber, a predetermined quantity of liquid, and conveying the predetermined quantity of liquid withdrawn from the liquid outlet of the first scrubber into a storage tank as the aqueous solution of hydrofluoric acid;f) replacing the predetermined quantity of liquid in each respective sump, except for that of the last scrubber, with the predetermined quantity of liquid withdrawn from the next sequential scrubber, and replacing the predetermined quantity of liquid in the last scrubber with the predetermined quantity of make-up water.