A process for the production of phosphoric acid

Abstract

The present application belongs to the technical field of phosphoric acid preparation, and particularly relates to a production process of phosphoric acid, comprising the following steps: A, crushing and blending phosphate ore into ore slurry; B, adding dilute hydrochloric acid and dilute sulfuric acid to the ore slurry to perform extraction reaction, obtaining extraction slurry, and filtering the extraction slurry to obtain a mixed solution of phosphoric acid and calcium chloride and silicon residue; C, adding sulfuric acid to the mixed solution of calcium chloride to obtain calcium sulfate dihydrate, and then adding a crystal modifier to obtain calcium sulfate dihydrate whiskers, and vacuum filtering to extract the calcium sulfate dihydrate whiskers. In the present application, phosphate ore is mixed with dilute hydrochloric acid and dilute sulfuric acid to generate a mixed solution of phosphoric acid and calcium chloride, and the silicon residue which does not react is filtered out. Sulfuric acid is added to the mixed solution, and a calcium sulfate crystal modifier is added to the mixed solution to generate calcium sulfate dihydrate whiskers with a length-diameter ratio greater than or equal to 200, and the calcium sulfate dihydrate whiskers and the phosphoric acid generated have high purity, length-diameter ratio and whiteness.

Description

Technical Field

[0001] This invention belongs to the field of phosphoric acid preparation technology, and specifically relates to a phosphoric acid production process. Background Technology

[0002] Phosphogypsum is a solid waste product generated from the wet-process phosphoric acid production. Traditional phosphoric acid production using concentrated sulfuric acid and phosphate rock slurry typically produces 4.5–5.5 tons of phosphogypsum as a byproduct for every 1 ton of phosphoric acid produced. Currently, most phosphogypsum in China is still stored in stockpiles, which not only occupies land resources but also causes serious pollution to the ecological environment.

[0003] To address the environmental pollution problem caused by phosphogypsum, the government requires a solution at its source, which necessitates changing the traditional phosphoric acid production process. Summary of the Invention

[0004] This invention provides a process for producing phosphoric acid, which addresses the technical problems existing in the background art.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0006] A process for producing phosphoric acid includes the following steps:

[0007] A. Crush the raw phosphate ore and mix it into a slurry;

[0008] B. Add dilute hydrochloric acid and dilute sulfuric acid to the slurry to carry out the extraction reaction, obtain the extraction slurry, and filter the extraction slurry to obtain a mixed solution of phosphoric acid and calcium chloride and silica slag.

[0009] C. Add sulfuric acid to a calcium chloride mixed solution to react and obtain calcium sulfate dihydrate. Then add a crystal-changing agent to react and obtain calcium sulfate dihydrate whiskers. Finally, filter under vacuum to extract the calcium sulfate dihydrate whiskers.

[0010] Optionally, in step A, the slurry has a mass fraction of 70%.

[0011] Optionally, in step A, the phosphate ore, after being crushed, has a pass rate of more than 80% through a 100-mesh sieve.

[0012] Optionally, in step B, the mass ratio of the dilute sulfuric acid to the phosphate rock in step A is 1:1.5, and the mass ratio of the dilute sulfuric acid to the phosphate rock in step A is 1:10.

[0013] Optionally, in step C, the sulfuric acid has a mass fraction of 98%.

[0014] Optionally, in step C, the mass ratio of the sulfuric acid to the phosphate rock ore in step A is 1:10.

[0015] Optionally, in step C, the crystallization agent is succinic acid, and the amount of crystallization agent added is 0.15% of the mass of the phosphate rock in step A.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] This invention changes the traditional process of producing phosphoric acid and by-product phosphogypsum from concentrated sulfuric acid and phosphate rock slurry. Instead, it uses a mixture of phosphate rock and dilute hydrochloric acid / sulfuric acid to generate a phosphoric acid + calcium chloride mixed solution. Unreacted silica slag (used in the production of construction sand) is filtered out. Sulfuric acid is added to the phosphoric acid and calcium chloride mixed solution, and under controlled stirring intensity and reaction time, high-purity calcium sulfate dihydrate is produced. A calcium sulfate crystallizing agent is added to the mixed solution to generate calcium sulfate dihydrate whiskers with an aspect ratio greater than or equal to 200. These whiskers are precipitates, and vacuum filtration is used to separate the solid and liquid components of the calcium sulfate dihydrate and the phosphate-hydrochloric acid mixture, producing high-purity, high-aspect-ratio, and high-whiteness calcium sulfate dihydrate whiskers and phosphoric acid (mixed with a small amount of hydrochloric acid for compound fertilizer production). All products are finished products: phosphoric acid, gypsum whiskers, and construction sand; no waste is generated. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0019] Example 1

[0020] 100 kg of raw phosphate ore was crushed and ground. The ground ore powder was passed through a 100-mesh sieve. Water was added to the ore powder to make a slurry, with the water ratio being 70% of the ore powder. The slurry was added to an extraction reactor, along with 67 kg of dilute hydrochloric acid and 10 kg of dilute sulfuric acid, to carry out the extraction reaction, obtaining an extraction slurry. The extraction slurry was filtered to obtain a wet-process phosphoric acid and calcium chloride mixed solution and silica slag. 10 kg of sulfuric acid was added to the calcium chloride mixed solution to generate high-purity calcium sulfate dihydrate. 0.15 kg of succinic acid was added to the generated calcium sulfate dihydrate solution, and the mixture was placed in an autoclave and autoclaved at 110℃ for 4 hours to generate calcium sulfate dihydrate whiskers. The calcium sulfate dihydrate whiskers were extracted by vacuum filtration. The final obtained calcium sulfate dihydrate had a purity of 98.5%, a whisker whiteness of 92, and an aspect ratio ≥200.

[0021] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope described in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A process for the production of phosphoric acid, characterized in that, The method comprises the following steps: A. crushing and preparing phosphate ore into a slurry; B. adding dilute hydrochloric acid and dilute sulfuric acid to the slurry to perform an extraction reaction, obtaining an extraction slurry, and filtering the extraction slurry to obtain a mixed solution of phosphoric acid and calcium chloride and a silicon residue; C. adding sulfuric acid to the mixed solution of calcium chloride to obtain calcium sulfate dihydrate, adding a crystal transformation agent to obtain calcium sulfate dihydrate whiskers, and finally performing vacuum filtration to extract the calcium sulfate dihydrate whiskers; In step A, the mass fraction of the slurry is 70%; In step A, the passing rate of the crushed phosphate ore through a 100-mesh screen is greater than 80%; In step B, the mass ratio of the dilute hydrochloric acid to the phosphate ore in step A is 1:1.5, and the mass ratio of the dilute sulfuric acid to the phosphate ore in step A is 1:10; In step C, the mass fraction of the sulfuric acid is 98%; In step C, the mass ratio of the sulfuric acid to the phosphate ore in step A is 1:10; The crystal transformation agent is succinic acid.

2. The process for the production of phosphoric acid as claimed in claim 1 wherein, In step C, the amount of the crystal transformation agent added is 0.15% of the mass of the phosphate ore in step A.