| CPC C05B 11/08 (2013.01) [C01B 7/196 (2013.01); C01B 33/10705 (2013.01)] | 19 Claims |
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1. A method for a graded utilization of fluorine and silicon resources in a phosphate ore, comprising:
Step (1), acidification: mixing sulfuric acid or phosphoric acid with the phosphate ore for reacting to produce dilute phosphoric acid or phosphate fertilizer while generating tail gas including fluorine and silicon;
Step (2), absorption: obtaining an acidic solution including fluorine and silicon by absorbing the tail gas with water;
Step (3), osmosis thickening: obtaining a dilute solution by performing an osmosis operation on the acidic solution using a driving solution, wherein the driving solution absorbs part of solvent of the acidic solution to obtain the dilute solution; and the acidic solution increases in concentration to obtain a concentrated solution; and the osmosis operation is a forward osmosis, wherein the driving solution is a phosphate solution or a phosphoric acid solution, and the dilute solution includes a dilute phosphate solution or a dilute phosphoric acid solution;
Step (4), concentration and filtration: performing a concentration operation by passing silicon fluoride gas into the concentrated solution to continuously increase concentration of the concentrated solution; and filtering and separating the concentrated solution to obtain silicon dioxide (SiO2), a fluorine-containing solution, and waste gas;
Step (5), extraction: obtaining a loaded phase and a raffinate by adding an extract phase to the fluorine-containing solution, mixing and extracting thoroughly, and separating phases;
Step (6), liquid adsorption: obtaining a refined solution by adsorbing and removing impurities from the raffinate;
Step (7), dehydration: obtaining crude silicon tetrafluoride (SiF4) and an HF-sulfuric acid (H2504) solution by adding a dehydrant to the refined solution and mixing thoroughly, and producing anhydrous hydrogen fluoride with a purity of not less than 99% and waste sulfuric acid as a by-product by performing steam stripping and distillation on the separate HF—H2SO4 solution;
Step (8), decontamination: obtaining decontamination gas by adsorbing impurities in the crude SiF4 by gaseous adsorption; and
Step (9), low-temperature distillation: obtaining impurity gas, and SiF4 with a purity of not less than 99% by performing a low-temperature distillation on the decontamination gas to remove impurities with low and high boiling points.
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