Method of solvent extraction purification of wet method phosphoric acid produced from medium and low grade phosphosus ore

Abstract

A process for preparing wet phosphoric acid from medium-or low-grade phosphorus are through solvent extracting and purifying includes such steps as concentrating the crude wet phosphoric acid, defluorinating, desulfurizing, decoloring, filtering, counter current extracting in the mixture of n-butanol, methylisobutyl ketone and synergist by 7-10 stages while adding sulfuric acid at the 3rd or the 7th stage, counter current washing with phosphoric acid solution containing Na salt by 4-5 stages, counter-current reverse extracting of organic phase with distilled water by 3-5 stages, concentrating, recovering solvent, decoloring, filtering, adding the phosphoric acid solution of BaCO3 for removing ''SO4'' radicals, decoloring, filtering and concentrating.

Description

technical field [0001] The invention relates to the refining technology of wet-process phosphoric acid, in particular to the refining technology of solvent extraction wet-process phosphoric acid. Background technique [0002] At present, the world's energy shortage has caused the price of thermal phosphoric acid to rise continuously; in my country, phosphate rocks are mainly of medium and low grades, and the reserves of high-grade phosphoric rocks are not much, so wet-process phosphoric acid has gradually replaced thermal phosphoric acid. Wet-process phosphoric acid, especially the wet-process phosphoric acid produced with medium and low-grade phosphate rock, has high impurity content, and its purification is inevitable. There are many purification methods, such as chemical precipitation, ion exchange, crystallization, solvent precipitation, solvent extraction and so on. Among them, solvent extraction is the most effective method at present. For 42wt%~54wt%P 2 o 5 For hi...

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Problems solved by technology

The method described in the Chinese patent CN1217705A needs to be operated at a temperature of 30-80°C, which in itself increases the consumption of energy and the volatilization of the extraction agent; and a large amount of solvents that are completely soluble in water are used during extraction, which makes the burden of solvent recovery considerable. heavy, resulting in higher production costs

[0015] Due to the high content of impurities Mg, Al, Fe, etc. in Hubei original acid, if it is concentrated to 45wt%~50wt%P according to the method of US4377562 2 o 5 Phosphoric acid for extraction will cause the aqueous phase to become a mass of colloids or liquids with high viscosity and cannot be carried out

Adding sulfuric acid during extraction can indeed improve the fluidity of the aqueous phase, but almost every level needs to be added from the third level of the water phase inlet, which will increase the difficulty of the subsequent washing steps; for the washing of the extracted organic phase, US4377562 Ten-stage countercurrent washing is used, which not only requires a large equipment capacity, but also consumes a large amount of phosphoric acid used for washing; although it can reduce the impurity content in the product phosphoric acid, it will also seriously reduce the production capacity of the equipment, because the product phosphoric acid is used in large quantities for washing with acid

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