A method of producing phosphoric acid and clean gypsum

Abstract

The invention provides a method for producing phosphoric acid with low sulfuric acid content and cleaning gypsum, and belongs to the field of a production method of phosphoric acid and gypsum. The method comprises the following technical steps of: (1) adding a part of phosphorite total inventory, a part of sulfuric acid total inventory, mixed acid returned by a second separator and washing liquor returned by a washer into a first reaction tank, and reacting for 1-2 hours at the temperature of 60-85DEG C; (2) inputting the obtained slurry into a section reaction tank, adding residual phosphorite to completely consume sulfuric acid in the slurry, and reacting for 1-2 hours at the temperature of 60-80DEG C; (3) inputting the obtained slurry into a first senator to separate out crude phosphoric acid; (4) transferring the crude phosphoric acid-separated slurry into a crystal transferring groove, adding residual sulfuric acid and the washing liquor returned by the washer into the crystal transferring groove, and reacting for 0.5-2 hours under the temperature of 85-105DEG C; and (5) inputting the slurry into the second separator to separate solid from liquid, and transporting the separated filter residue into the washer to be washed to obtain the cleaning gypsum.

Description

technical field [0001] The invention belongs to the field of phosphoric acid and gypsum production methods, and in particular relates to a method for producing crude phosphoric acid with wide concentration and low sulfuric acid content and gypsum with low phosphorus content by using medium and low-grade phosphate rock. Background technique [0002] At present, more than 80% of phosphoric acid is realized by the dihydrate process of decomposing phosphate rock with sulfuric acid. The dihydrate process is easy to operate, but has the following disadvantages: ①The energy consumption in the production process is high; ②The concentration of phosphoric acid obtained is low, and The content of sulfuric acid in it is generally higher than 2%; ③ HPO in the obtained dihydrate gypsum lattice 4 2- The eutectic phenomenon leads to P 2 o 5 Great loss, P 2 o 5 The conversion rate is only 95 ~ 96%; ④ yield is P 2 o 5 The by-product dihydrate gypsum with an output of 4.5 to 5.5 times ...

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Problems solved by technology

[0002] At present, more than 80% of phosphoric acid is realized by the dihydrate process of decomposing phosphate rock with sulfuric acid. The dihydrate process is easy to operate, but has the following disadvantages: ①The energy consumption in the production process is high; ②The concentration of phosphoric acid obtained is low, and The content of sulfuric acid in it is generally higher than 2%; ③ HPO in the obtained dihydrate gypsum lattice 4 2- The eutectic phenomenon leads to P 2 o 5 Great loss, P 2 o 5 The conversion rate is only 95 ~ 96%; ④ yield is P 2 o 5 The by-product dihydrate gypsum with an output of 4.5 to 5.5 times is also due to the phosphorus content in the total input P 2 o 5 Not only cannot be used directly, but also will cause environmental pollution and ecological hazards

However, the above method still has the following disadvantages: 1. excessive sulfuric acid is added in the dihydric stage, and sulfuric acid needs to be added in the crystal transformation stage, which causes the excessive consumption of sulfuric acid in the whole process; and the excessive sulfuric acid added in the dihydric stage will enter the crude phosphoric acid, resulting in a higher content of sulfuric acid in the crude phosphoric acid, which is generally similar to that in the crude phosphoric acid obtained from the dihydrate process; ②In the dihydrate stage, the dilution of high-concentration sulfuric acid and its combination with phosphorus A large amount of heat will be generated during the acidolysis reaction of ore, and these heats will lead to the direct generation of unstable hemihydrate gypsum during acidolysis of phosphate rock. Therefore, the heat must be removed in time by blast cooling, vacuum cooling, etc., but In the crystal transformation stage, it is necessary to use steam heating to provide a higher temperature to promote the dehydration of the dihydrate gypsum crystals, resulting in extremely unreasonable heat utilization in the entire process and high energy consumption; ③ After the decomposition of phosphate rock is completed, the The obtained slurry is subjected to solid-liquid separation to obtain dihydrate gypsum and crude phosphoric acid. The obtained dihydrate gypsum is input into the crystal conversion tank, and sulfuric acid and dilute phosphoric acid are added to re-slurry the dihydrate gypsum before the crystal conversion. This process is not only complicated to operate And it will reduce the production capacity of the separator

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