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CN-119284848-B - Preparation method of crude desulfurization semi-hydrated phosphoric acid in semi-hydrated wet phosphoric acid process

CN119284848BCN 119284848 BCN119284848 BCN 119284848BCN-119284848-B

Abstract

The invention provides a preparation method of crude desulfurization semi-hydrated phosphoric acid in a semi-hydrated wet phosphoric acid process. According to the invention, caO in the decomposing tank and SO 4 2‑ in the crystal growing tank are utilized to send the slurry in the two tanks into the coarse desulfurization reaction tank together for mixed reaction to realize desulfurization, SO that the desulfurization slurry filtering step is simplified. And further, the desulfurized slurry is cooled by adopting vacuum flash evaporation and then enters a vacuum filtration system, so that a large amount of scale in the system is avoided, and fluorine generated by vacuum flash evaporation and vacuum filtration is recovered. The invention can realize the desulfurization purpose without adding any desulfurizing agent, can reduce the cost of the crude desulfurizing agent and shorten the process flow of the crude desulfurizing process, and also avoids the P 2 O 5 waste caused by adding phosphate concentrate in the traditional crude desulfurizing process. The method has the advantages of simple desulfurization process and low cost, and reduces the cleaning frequency of the slurry vacuum filtration system and improves the system start-up rate.

Inventors

  • MA YONGQIANG
  • Jiang jican
  • Cui Fumao
  • WU XIAO
  • ZHOU YUWEN

Assignees

  • 广西鹏越生态科技有限公司

Dates

Publication Date
20260505
Application Date
20241129

Claims (10)

  1. 1. The preparation method of the crude desulfurization semi-aqueous phosphoric acid in the semi-aqueous wet phosphoric acid process is characterized by comprising the following steps: 1) Feeding the slurry after crystal growth in the crystal growth tank back into a dissolution tank, adding phosphate concentrate for dissolution, allowing the obtained dissolution slurry to enter a decomposition tank for decomposition reaction, allowing the obtained decomposition slurry to overflow into a crystallization tank, adding concentrated sulfuric acid for reaction and crystallization, and allowing the slurry to enter the crystal growth tank for crystal growth to obtain the slurry after crystal growth; A part of the slurry after crystal growth is returned to the dissolution tank; The ratio of the slurry after crystal growth returned into the dissolving tank to the phosphate concentrate is (15-30) m 3 :1 t; 2) Feeding the slurry after crystal growth in the crystal growth tank and the slurry in the decomposing tank together into a coarse desulfurization reaction tank for mixing and stirring reaction to obtain coarse desulfurization reaction slurry; 3) And cooling the crude desulfurization reaction slurry obtained in the steps through vacuum flash evaporation, and then enabling the obtained low-temperature slurry to enter a liquid seal tank, and performing vacuum filtration to obtain the crude desulfurized semi-hydrated phosphoric acid.
  2. 2. The preparation method according to claim 1, wherein the phosphate concentrate comprises ：P 2 O 5 ：30%~38%、CaO：45%~55%、MgO：0.3%~1.6%、H 2 O：5%~15%、Fe 2 O 3 ：0.3%~2.3% and 0.4% -1% of Al 2 O 3 in mass percent.
  3. 3. The preparation method according to claim 1, wherein the mass content of P 2 O 5 in the liquid phase of the decomposer is 40% -45%; In the decomposing tank liquid phase, the mass content of SO 4 2- is 0.2% -0.6%; The mass content of CaO in the liquid phase of the decomposing tank is 1.0% -1.6%.
  4. 4. The preparation method according to claim 1, wherein the temperature of the decomposition reaction is 90-105 ℃; the mass ratio of the phosphate concentrate to the concentrated sulfuric acid is (0.5-1.0): 1; the crystallization temperature is 95-105 ℃.
  5. 5. The preparation method according to claim 1, wherein the mass content of P 2 O 5 in the liquid phase of the crystallization tank is 40% -45%; The mass content of SO 4 2- in the liquid phase of the crystallization tank is 1.8% -2.2%; the mass content of CaO in the liquid phase of the crystallization tank is 0.1% -0.5%.
  6. 6. The preparation method of claim 1, wherein the mass content of P 2 O 5 in the liquid phase of the crystal growth tank is 40% -45%; the mass content of SO 4 2- in the crystal growing tank liquid phase is 1.5% -2.0%; The mass content of CaO in the liquid phase of the crystal growing tank is 0.1% -0.5%.
  7. 7. The preparation method of claim 1, wherein the temperature of the crystal growth is 95-105 ℃; in the step 2), the mass ratio of the slurry after crystal growth to the slurry in the decomposing tank is (1-2), namely (1-2).
  8. 8. The preparation method according to claim 1, wherein the residence time of the mixing and stirring reaction is 0.15-1.5 h; the temperature of the mixing and stirring reaction is 70-105 ℃; the temperature of the low-temperature slurry is 70-105 ℃.
  9. 9. The method according to claim 1, wherein the low-temperature slurry entering the liquid seal tank is partially refluxed to the crude desulfurization reaction tank, and the other part of the low-temperature slurry is subjected to subsequent vacuum filtration; the mass ratio of one part of low-temperature slurry to the other part of low-temperature slurry is (3-8) 1; the preparation method also comprises the step of carrying out multistage countercurrent washing on the generated fluorine-containing secondary steam in the vacuum flash evaporation cooling process to recover fluorine.
  10. 10. The preparation method of claim 1, wherein the mass content of P 2 O 5 in the crude desulfurized semi-aqueous phosphoric acid is 40% -45%; In the semi-hydrated phosphoric acid after coarse desulfurization, the mass content of SO 4 2- is 0.2% -1.1%; The mass content of CaO in the semi-hydrated phosphoric acid after coarse desulfurization is 0.1% -0.9%; the preparation method also comprises the steps of vacuum filtering the tail gas, washing the tail gas, and recovering fluorine.

Description

Preparation method of crude desulfurization semi-hydrated phosphoric acid in semi-hydrated wet phosphoric acid process Technical Field The invention belongs to the technical field of semi-water wet-process phosphoric acid processes, relates to a preparation method of crude desulfurization semi-water phosphoric acid in the semi-water wet-process phosphoric acid process, and particularly relates to a method for crude desulfurization and slurry cooling in the semi-water wet-process phosphoric acid process. Background At present, the wet-process phosphoric acid desulfurization mainly adopts concentrate and phosphoric acid to react (calcium desulfurization) +solid-liquid separation, and because the reaction temperature of the concentrate and the phosphoric acid is low, the reaction activity is affected to cause the concentrate yield to be greatly reduced, meanwhile, a filter pressing system is required to be independently arranged, the whole flow is longer, the operation cost is high, and meanwhile, P 2O5 is wasted. Because the temperature of the semi-aqueous wet phosphoric acid reaction slurry is high, solid-liquid separation is carried out in a vacuum state, flash evaporation of filtrate is easy to occur, and a large amount of fluorosilicate (sodium potassium) and calcium sulfate are easy to be produced to precipitate so as to cause system blockage. The sediment is easy to be accumulated at the positions of a pump shell, a valve and the like in actual production, so that the problems of pump flow reduction, out-of-control of an instrument valve and the like occur, particularly the filtering rate of phosphogypsum is influenced, the system start-up rate is reduced, and the wet-process phosphoric acid production is severely restricted. In the industrial production of the prior art, the sulfate radical content in the dilute phosphoric acid is generally reduced by adding a phosphorus ore pulp or phosphorus ore powder as a desulfurizing agent into the dilute phosphoric acid obtained after slurry filtration. The method for reducing the concentration of SO 42- in dilute phosphoric acid disclosed in China patent CN102431981 adopts a mode of adding phosphorus ore pulp into dilute phosphoric acid obtained by extraction and filtration in a phosphoric acid extraction tank, and reacts in a desulfurization tank to reduce the content of free sulfuric acid in the dilute phosphoric acid. Although the content of sulfate radical in the dilute phosphoric acid can be reduced by adopting the method of adding phosphate ore into the dilute phosphoric acid, the method has the defects of long desulfurization time, sedimentation and filtration of the phosphoric acid after desulfurization, difficult treatment of sedimentation slag, high phosphorus residue of filter residues and the like. In addition, the wet-process phosphoric acid slurry vacuum filtration system pipeline is easy to cause system blockage due to the generated fluorosilicate (sodium potassium) and calcium sulfate. In the prior art, a method of adding a scale inhibitor is often adopted, the scale inhibitor contains an organic phosphonic acid polymer, so that the operation cost is increased, and the subsequent production is easily influenced by the added organic matters. Therefore, how to find a more suitable desulfurization method in the semi-aqueous wet-process phosphoric acid process, and solve the above problems existing in the desulfurization process in the existing semi-aqueous wet-process phosphoric acid process, has become one of the problems to be solved by many first-line researchers in the industry. Disclosure of Invention In view of the above, the technical problem to be solved by the invention is to provide a preparation method of crude desulfurization semi-aqueous phosphoric acid in a semi-aqueous wet phosphoric acid process, in particular to a method for crude desulfurization and slurry cooling in a semi-aqueous wet phosphoric acid process. The desulfurization process provided by the invention is simple and low in cost, reduces the cleaning frequency of the slurry vacuum filtration system and improves the start-up rate of the system. The invention provides a preparation method of crude desulfurization semi-hydrated phosphoric acid in a semi-hydrated wet phosphoric acid process, which comprises the following steps: 1) Feeding the slurry after crystal growth in the crystal growth tank back into a dissolution tank, adding phosphate concentrate for dissolution, allowing the obtained dissolution slurry to enter a decomposition tank for decomposition reaction, allowing the obtained decomposition slurry to overflow into a crystallization tank, adding concentrated sulfuric acid for reaction and crystallization, and allowing the slurry to enter the crystal growth tank for crystal growth to obtain the slurry after crystal growth; A part of the slurry after crystal growth is returned to the dissolution tank; 2) Feeding the slurry after crystal growth in the crystal growth