Wet-process two-stage phosphoric acid concentration method

Abstract

The invention discloses aprocess of two-stage condensing phosphoric acid with wet method. It comprises condensing phosphoric acid, clarifying, adsorbing with fluorine and water circulation system; and it employs a two-stage condensing course in series: adding diluted phosphoric acid into the first stage condensing closed circuit, heating with steam, steaming out of water in a short time invacuum condition to condense phosphoric acid into mediate acid, clarifying to remove part of suspending soild and getting clean acid A; putting acid A to the second condensing system to be condensed into diluted phosphoric acid, clarifying and getting clean acid B, that is the finished product. The left acid by clarifying in the two stages is used for preparing compound fertilizer or is recoveried after press filtration; the SiF4 and HF in steam is adsorbed through two-stage adverse current and is prepared into side product of fluosilicic acid. The invention smploys a two-stage condensing process, which improvese heat and mass transferring process, saves investment at the same production capability; reduces phosphoric acid circulation amount and circulating water consumption; reduces phosphoric acid viscosity and improves concentration and quality of finished product.

Description

technical field [0001] The invention belongs to the field of phosphoric acid production and relates to a two-stage concentration method for wet-process phosphoric acid. Background technique [0002] Wet-process phosphoric acid is the basic intermediate product of the phosphate compound fertilizer industry and the phosphate industry. It has a very important position and is in great demand. At present, my country has formed about 5 million tons / year P 2 o 5 production capacity. In most cases, the post-processing of phosphoric acid requires the use of concentrated phosphoric acid, which requires the use of various concentration methods to concentrate the filter-grade dilute phosphoric acid. The method widely used at present is the forced circulation vacuum concentration method using single-stage concentration technology. [0003] Single-stage concentration from 24 to 26%P 2 o 5 Dilute phosphoric acid is concentrated to 48-52% finished concentrated phosphoric acid at one t...

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Problems solved by technology

[0003] Single-stage concentration from 24 to 26%P 2 o 5 Dilute phosphoric acid is concentrated to 48-52% finished concentrated phosphoric acid at one time. It has the following disadvantages: the heat transfer efficiency of circulating concentrated phosphoric acid is low, and the heater needs to have a large heating area; the solubility of impurities in concentrated phosphoric acid is small, and it is easy to crystallize. Precipitation, in order to prevent fouling in the circulation loop, the temperature rise of phosphoric acid after heating should be controlled to be low, so the amount of acid circulation is large and the power consumption is large; the boiling point of concentrated phosphoric acid is high, and to maintain a low boiling point, the flash chamber The pressure should be controlled lower. Under this pressure, the evaporation intensity of the flash chamber is also low; the flash chamber, heater, circulation pump and other equipment have larger specifications and require more investment; when the impurity content in dilute phosphoric acid is high , it will bring difficulties to the concentration operation and reduce the concentration and quality of the finished phosphoric acid

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