Partially Continuous Countercurrent Process For Converting Gypsum To Ammonium Sulfate And Calcium Carbonate

摘要

The present invention includes a partially continuous countercurrent process for converting gypsum, by reaction with ammonium carbonate, to products of ammonium sulfate and calcium carbonate by introducing the reactants into reactors, mixing the reactants for a predetermined amount of time, employing a novel combination of countercurrent flows coupled with the reactors operated in a batch manner with process recycle of liquids, removing materials from the reactor and separating solids from solutions wherein no reactants are added during the removal process and thus the reactants have sufficient time to react and ensure the desired degree of reaction, yield and purity of product calcium carbonate and ammonium sulfate while minimizing the reaction time.

主权项

1. A partially continuous countercurrent flow process for converting gypsum to ammonium sulfate and calcium carbonate comprising the following steps:
separating an aqueous slurry of gypsum to result in a gypsum liquid residue and a gypsum cake; feeding a flow of reactants being the gypsum cake and a solution of ammonium sulfate and ammonium carbonate into a first reactor for chemical reaction; stopping the flow of reactants into the first reactor for a retention time selected to achieve a preselected degree of chemical reaction to form an ammonium sulfate solution containing a first precipitate calcium carbonate and a gypsum remnant; discharging the ammonium sulfate solution containing a first precipitate calcium carbonate and a gypsum remnant; resuming the flow of reactants into the first reactor; separating the first precipitate calcium carbonate and gypsum remnant from the ammonium sulfate solution to result in a product ammonium sulfate solution and a remnant cake of first precipitate calcium carbonate and gypsum; retaining the product ammonium sulfate solution; feeding a flow of reactants being the remnant cake of first precipitate calcium carbonate and gypsum and ammonium carbonate solution into a second reactor for chemical reaction; stopping the flow of reactants into the second reactor for a retention time selected to achieve a predetermined degree of chemical reaction to form a second precipitate calcium carbonate and a solution of ammonium sulfate and ammonium carbonate; discharging the first and second precipitate calcium carbonate and a solution of ammonium sulfate and ammonium carbonate; resuming the flow of reactants into the second reactor; separating the first and second precipitate calcium carbonate from the solution of ammonium sulfate and ammonium carbonate to result in a product calcium carbonate cake and a residue solution of ammonium sulfate and ammonium carbonate; retaining the product calcium carbonate cake; and adding the residue solution of ammonium sulfate and ammonium carbonate to the first reactor.