Tower type air stripping defluorination method for phosphoric acid

Abstract

The invention discloses a tower type air stripping defluorination method for phosphoric acid. The method includes: firstly mixing the raw material fluorine-containing phosphoric acid, a defluorination agent and defluorinated phosphoric acid flowing out of the bottom of a defluorination tower to obtain low fluorine phosphoric acid, then heating the low fluorine phosphoric acid to 90-105DEG C, and leading it into the defluorination tower; spraying the low fluorine phosphoric acid in the tower through at least one layer of nozzles at the upper part inside the defluorination tower, introducing air from the lower part of the defluorination tower to make the low fluorine phosphoric acid and air fully contact to complete defluorination; discharging the fluorine-containing exhaust gas generated during defluorination from the top of the defluorination tower, mixing part or all of the defluorinated phosphoric acid generated at the bottom of a defluorination tower with the fluorine-containing phosphoric acid and the defluorination agent to obtain the low fluorine phosphoric acid to carry out defluorination circulation, and leading the other part of the defluorinated phosphoric acid out of the defluorination tower to obtain a finished phosphoric acid product. The process provided by the invention can reduce the fluorine content of phosphoric acid to a phosphorus-fluorine ratio (P2O5/F) of greater than or equal to 260, and compared with the prior art, the fluorine content of the phosphoric acid is significantly reduced.

Description

technical field [0001] The invention belongs to the technical field of defluorination, and in particular relates to a tower-type air stripping phosphoric acid defluorination method. Background technique [0002] Since the 1950s, countries around the world have used wet-process phosphoric acid produced from phosphate rocks as a raw material to produce calcium phosphate salts as feed additives, among which calcium hydrogen phosphate is the main one. Feed grade phosphate is mainly calcium hydrogen phosphate (CaHPO 4 2H 2 O) DCP, calcium dihydrogen phosphate (Ca(H 2 PO 4 ) 2 ·H 2 O) MCP and tricalcium phosphate (Ca 3 (PO 4 ) 2 ·H 2 O) TCP. DCP and TCP are mainly used in the production of livestock and poultry feed, and MCP is mainly used in the production of aquatic feed. [0003] The source of phosphorus in feed-grade calcium hydrogen phosphate is mainly wet-process phosphoric acid. Generally, dilute phosphoric acid (with a concentration of 24% to 27%P) produced by a...

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Problems solved by technology

[0007] However, the tank-type defluorination process needs to blow high-temperature air into the phosphoric acid tank, and the air pipe is inserted below the phosphoric acid liquid level. The hot air contacts with the phosphoric acid to increase the temperature of the phosphoric acid and achieve the purpose of defluorination. Generally, multiple deoxidation tanks are required to carry out the process. , such as four 8-meter-high defluorination tanks with a height of 6 meters, the investment of this method is relatively high

In addition, since the continuous phase is phosphoric acid and the dispersed phase is air, part of the phosphoric acid in the defluorination tank is not in sufficient contact with the air, which affects the defluorination effect; the heating method is to blow hot air into the tank, and the air needs to be heated with steam; The method needs to blow hot air to 1-1.5 meters below the liquid level in the phosphoric acid tank, the fan needs high wind pressure (15000Pa), high power consumption, and the tank-type defluorination process is difficult for continuous production

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