CN115583666B - Method for producing phosphogypsum by semi-water-dihydrate wet phosphoric acid process - Google Patents
Method for producing phosphogypsum by semi-water-dihydrate wet phosphoric acid process Download PDFInfo
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- PASHVRUKOFIRIK-UHFFFAOYSA-L calcium sulfate dihydrate Chemical compound O.O.[Ca+2].[O-]S([O-])(=O)=O PASHVRUKOFIRIK-UHFFFAOYSA-L 0.000 title claims abstract description 208
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 title claims abstract description 78
- 229910000147 aluminium phosphate Inorganic materials 0.000 title claims abstract description 39
- 238000000034 method Methods 0.000 title claims abstract description 37
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 21
- 239000002002 slurry Substances 0.000 claims abstract description 121
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 71
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims abstract description 68
- 239000011574 phosphorus Substances 0.000 claims abstract description 68
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims abstract description 43
- 239000002367 phosphate rock Substances 0.000 claims abstract description 36
- OJMIONKXNSYLSR-UHFFFAOYSA-N phosphorous acid Chemical compound OP(O)O OJMIONKXNSYLSR-UHFFFAOYSA-N 0.000 claims abstract description 19
- 238000001914 filtration Methods 0.000 claims abstract description 15
- 239000013078 crystal Substances 0.000 claims abstract description 13
- 238000006243 chemical reaction Methods 0.000 claims abstract description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 45
- ZOMBKNNSYQHRCA-UHFFFAOYSA-J calcium sulfate hemihydrate Chemical compound O.[Ca+2].[Ca+2].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O ZOMBKNNSYQHRCA-UHFFFAOYSA-J 0.000 claims description 39
- 239000007791 liquid phase Substances 0.000 claims description 31
- 239000002253 acid Substances 0.000 claims description 25
- 239000007787 solid Substances 0.000 claims description 22
- ODINCKMPIJJUCX-UHFFFAOYSA-N Calcium oxide Chemical compound [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 claims description 20
- 238000003756 stirring Methods 0.000 claims description 16
- 239000000843 powder Substances 0.000 claims description 15
- 230000032683 aging Effects 0.000 claims description 11
- YYRMJZQKEFZXMX-UHFFFAOYSA-L calcium bis(dihydrogenphosphate) Chemical compound [Ca+2].OP(O)([O-])=O.OP(O)([O-])=O YYRMJZQKEFZXMX-UHFFFAOYSA-L 0.000 claims description 11
- 239000001506 calcium phosphate Substances 0.000 claims description 11
- 229910000150 monocalcium phosphate Inorganic materials 0.000 claims description 11
- 235000019691 monocalcium phosphate Nutrition 0.000 claims description 11
- 239000000292 calcium oxide Substances 0.000 claims description 10
- 235000012255 calcium oxide Nutrition 0.000 claims description 10
- 238000002156 mixing Methods 0.000 claims description 10
- 239000000047 product Substances 0.000 claims description 9
- 238000002425 crystallisation Methods 0.000 claims description 7
- 230000008025 crystallization Effects 0.000 claims description 7
- 239000012043 crude product Substances 0.000 claims description 6
- 239000000203 mixture Substances 0.000 claims description 4
- 238000004090 dissolution Methods 0.000 claims description 2
- 238000004537 pulping Methods 0.000 claims description 2
- 239000011260 aqueous acid Substances 0.000 claims 1
- 230000018044 dehydration Effects 0.000 abstract description 3
- 238000006297 dehydration reaction Methods 0.000 abstract description 3
- 239000010440 gypsum Substances 0.000 abstract description 3
- 229910052602 gypsum Inorganic materials 0.000 abstract description 3
- 150000004683 dihydrates Chemical class 0.000 abstract 1
- 230000004048 modification Effects 0.000 abstract 1
- 238000012986 modification Methods 0.000 abstract 1
- 230000001131 transforming effect Effects 0.000 abstract 1
- 239000007790 solid phase Substances 0.000 description 7
- 239000000706 filtrate Substances 0.000 description 4
- 238000000354 decomposition reaction Methods 0.000 description 2
- 229940057307 dihydrate calcium sulfate Drugs 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 229940095672 calcium sulfate Drugs 0.000 description 1
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Inorganic materials [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 150000003013 phosphoric acid derivatives Chemical class 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F11/00—Compounds of calcium, strontium, or barium
- C01F11/46—Sulfates
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B25/00—Phosphorus; Compounds thereof
- C01B25/16—Oxyacids of phosphorus; Salts thereof
- C01B25/18—Phosphoric acid
- C01B25/22—Preparation by reacting phosphate-containing material with an acid, e.g. wet process
- C01B25/222—Preparation by reacting phosphate-containing material with an acid, e.g. wet process with sulfuric acid, a mixture of acids mainly consisting of sulfuric acid or a mixture of compounds forming it in situ, e.g. a mixture of sulfur dioxide, water and oxygen
- C01B25/228—Preparation by reacting phosphate-containing material with an acid, e.g. wet process with sulfuric acid, a mixture of acids mainly consisting of sulfuric acid or a mixture of compounds forming it in situ, e.g. a mixture of sulfur dioxide, water and oxygen one form of calcium sulfate being formed and then converted to another form
- C01B25/229—Hemihydrate-dihydrate process
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B11/00—Calcium sulfate cements
- C04B11/26—Calcium sulfate cements strating from chemical gypsum; starting from phosphogypsum or from waste, e.g. purification products of smoke
Abstract
The invention discloses a method for producing high-quality phosphogypsum by a semi-water-dihydrate wet phosphoric acid process, which mainly comprises the following steps: 1. dewatering phosphorite slurry; 2. premixing and dissolving ground phosphate rock; 3. crystallizing and filtering mainly semi-hydrated gypsum slurry; 4. transforming and filtering crystal forms mainly comprising dihydrate gypsum slurry; 5. reslurry and dehydration of phosphogypsum; 6. phosphogypsum modification and complete crystal form conversion. The method is simple, easy to control, environment-friendly, digestible dilute sulfuric acid, high in phosphorus yield and good in phosphogypsum quality.
Description
Technical Field
The invention relates to the technical field of phosphorus chemical industry, in particular to a method for producing high-quality phosphogypsum by a semi-water-dihydrate wet phosphoric acid process.
Technical Field
The annual production amount of phosphogypsum is 2 hundred million tons, the accumulated accumulation amount exceeds 60 hundred million tons, the comprehensive utilization rate is only about 25 percent, the comprehensive utilization rate of phosphogypsum is closely related to the quality of phosphogypsum, and the improvement of the quality of phosphogypsum by adopting a new wet phosphoric acid process is a core measure of the optimization of the phosphogypsum process for realizing the dynamic balance of phosphogypsum production and marketing, and is an important ring for improving the comprehensive utilization rate of phosphogypsum.
Disclosure of Invention
The invention aims to provide a method for producing high-quality phosphogypsum by a semi-water-dihydrate wet-process phosphoric acid process, which has the advantages of simple process, environment protection and boosting green recycling economy.
In order to solve the technical problems, the invention provides a method for producing high-quality phosphogypsum by a semi-water-dihydrate wet phosphoric acid process, which comprises the following technical scheme:
a method for producing phosphogypsum by a semi-water-dihydrate wet phosphoric acid process comprises the following steps:
(1) Dewatering the phosphorite slurry to obtain phosphorite powder;
(2) Adding phosphate rock powder into concentrated sulfuric acid for dissolution to obtain slurry I;
(3) Adding concentrated sulfuric acid into the slurry I for crystallization to obtain slurry II;
(4) Filtering the slurry II to obtain crude products of intermediate acid, semi-hydrated acid and phosphogypsum;
(5) Adding concentrated sulfuric acid into the phosphogypsum crude product for conversion to obtain slurry III;
(6) Filtering the slurry III, adding water, re-pulping and dehydrating to obtain phosphogypsum;
(7) Mixing phosphogypsum and quicklime uniformly, and aging to obtain a phosphogypsum fine product.
The water content of the phosphate rock powder in the step (1) after dehydration is lower than 12%; adding phosphoric acid with the mass concentration of 20-35% into the ground phosphate rock for premixing to obtain slurry containing monocalcium phosphate;
the mass fraction of the concentrated sulfuric acid in the step (2) is 96-98%, the concentrated sulfuric acid is added and stirred at the temperature of 90-100 ℃ to obtain slurry I, the solid content in the slurry I is 25-30%, and the mass fraction of the liquid-phase sulfate radical is 0.5-1.2%.
The mass fraction of the concentrated sulfuric acid in the step (3) is 96-98%, the concentrated sulfuric acid is added and stirred at the temperature of 90-100 ℃ to obtain a second slurry, and the solid content in the second slurry is 25-30 percent, the mass fraction of the liquid phase sulfate radical is 2.0 to 4.0 percent, and the liquid phase P 2 O 5 The concentration is 36-43wt%; the solid content comprises 75-81% of calcium sulfate hemihydrate crystal and 12-18% of calcium sulfate dihydrate.
The mass fraction of the second liquid phase sulfate radical of the slurry obtained in the step (3) is 2.0-4.0%, if the content of the second liquid phase sulfate radical is too low or too high, gypsum crystallization in the second slurry can be obviously changed, so that the filtration in the subsequent step (4) is difficult, and the water-soluble phosphorus and the total phosphorus of the phosphogypsum crude product obtained in the step (4) are higher.
The intermediate acid in the step (4) is phosphoric acid, and the mass fraction of the phosphoric acid is 36-43%; the semi-aqueous return acid contains 20-35% of phosphoric acid and 2-4% of sulfuric acid by mass fraction; the phosphogypsum comprises 75-81% of calcium sulfate hemihydrate by mass, 12-18% of calcium sulfate dihydrate by mass, 3-6% of water-soluble phosphorus, 4-7% of total phosphorus and less than 20% of attached water.
The semi-water return acid is recycled to the step (1), the ground phosphate rock is premixed to be decomposed into slurry containing monocalcium phosphate, stirring is carried out in the premixing process, and meanwhile, the mass fraction of liquid-phase sulfate radical in the slurry is controlled to be less than 0.1%, and the phosphorite decomposition rate is mainly improved in the premixing process. If the liquid-phase sulfate exceeds 2.0%, or if the concentrated sulfuric acid is directly added to dissolve the phosphorite, the wrapping phenomenon may occur, and the total phosphorus of the phosphogypsum crude product obtained in the step (4) is finally affected to be higher.
Adding concentrated sulfuric acid into the step (5), stirring for 2-4 hours at 55-75 ℃ to obtain slurry III, wherein the solid content of the slurry III is 30-35%, the mass fraction of liquid-phase sulfate radical is 5.0-9.0%, and the mass fraction of P is the same as that of the slurry III 2 O 5 The concentration is 8-15wt%. At higher conversion temperatures, P 2 O 5 The higher the concentration is, the lower the corresponding mass fraction of the liquid phase sulfate radical is controlled, if the conversion temperature, the mass fraction of the liquid phase sulfate radical and P are 2 O 5 The low concentration matching degree can influence the conversion of calcium sulfate hemihydrate into calcium sulfate dihydrate, and further influence the higher water-soluble phosphorus of phosphogypsum obtained after filtering in the subsequent step (6).
The phosphogypsum obtained after filtering in the step (6) comprises 10-20% of calcium sulfate hemihydrate with the mass fraction of 71-81% of calcium sulfate dihydrate, 0.6-1.0% of water-soluble phosphorus, 0.8-1.3% of total phosphorus and less than 20% of attached water;
the phosphogypsum obtained after re-slurry dehydration in the step (6) contains 10-20% of calcium sulfate hemihydrate, 71-81% of calcium sulfate dihydrate, less than 0.2% of water-soluble phosphorus, about 0.2-0.5% of total phosphorus and less than 12% of attached water.
And (3) uniformly mixing phosphogypsum and quicklime in the step (7), controlling the initial pH value of the phosphogypsum to be 6-12, aging for more than 3 days to obtain a phosphogypsum fine product with the calcium sulfate dihydrate content of more than 90%, preferably aging for more than 7 days to obtain a phosphogypsum fine product with the calcium sulfate dihydrate content of more than 92%, wherein the mass fraction of the calcium sulfate dihydrate in the phosphogypsum fine product is more than 90%, the water-soluble phosphorus is less than 0.1%, the total phosphorus is 0.2-0.5%, the adhering water is less than 12%, and the pH value is 4-11.
The invention also adopts the technical scheme that the semi-hydrated calcium sulfate and dihydrate calcium sulfate containing double-crystalline phosphogypsum produced by the semi-hydrated-dihydrate phosphoric acid process has the content of 10-20 percent, the content of dihydrate calcium sulfate is 71-81 percent, the water-soluble phosphorus is about 0.6-1.0 percent, the total phosphorus is about 0.8-1.3 percent, and the attached water is less than 20 percent;
or the content of calcium sulfate hemihydrate produced by the semi-water-dihydrate wet phosphoric acid process is 10-20%, the content of calcium sulfate dihydrate is 71-81%, the content of water-soluble phosphorus is less than 0.2%, the total phosphorus is about 0.2-0.5%, and the content of attached water is less than 12%.
The invention provides a method for producing high-quality phosphogypsum by a semi-water-dihydrate wet phosphoric acid process, wherein the total phosphorus content of phosphogypsum can be reduced to 0.2-0.5%, the water-soluble phosphorus content is less than 0.1%, the attached water content is less than 12%, the calcium sulfate dihydrate content is more than 90%, and meanwhile, the pH value of phosphogypsum can be adjusted according to different application scenes;
the phosphorus recovery rate is high, and the average phosphorus yield can reach more than 98 percent;
finished acid P 2 O 5 The concentration is 36-43wt%, and the steam required for subsequent DAP or PPA concentration production is less, so that the energy is saved and the consumption is reduced.
Detailed Description
The present invention is further illustrated by the following examples, but the scope of the invention is not limited to the examples.
Example 1
The embodiment of the invention provides a method for producing high-quality phosphogypsum by a semi-water-dihydrate wet-process phosphoric acid process, which comprises the following steps:
dewatering the phosphorite slurry to obtain phosphorite powder with 12% of water content;
conveying the phosphate rock powder to a premixing tank by adopting a belt, adding phosphoric acid with the mass fraction of 20% for premixing, decomposing the phosphate rock into monocalcium phosphate, stirring to generate premixed slurry, and controlling the mass fraction of liquid-phase sulfate radical of the premixed slurry to be less than 0.1%;
the premixed slurry enters a dissolving tank, concentrated sulfuric acid (96-98% by mass) is added, and the mixture is stirred at 90-100 ℃ to further decompose phosphorite to generate slurry (1), wherein the solid content of the slurry (1) is controlled to be 25-30%, and the mass fraction of liquid-phase sulfate radical in the slurry (1) is controlled to be 0.5-0.7%;
feeding the slurry (1) into a crystallization tank, adding concentrated sulfuric acid (96-98% by mass), stirring at 90-100 ℃ to promote phosphogypsum to form mixed crystals mainly comprising calcium sulfate hemihydrate crystals, stirring to generate a slurry (2), controlling the solid content of the slurry (2) to be 25-30%, controlling the calcium sulfate hemihydrate content in the solid-phase phosphogypsum of the slurry (2) to be 78-80%, the calcium sulfate dihydrate content to be 12-15%, and controlling the mass fraction of liquid-phase sulfate radical in the slurry (2) to be 3.5-4.0%, wherein the solid-phase phosphogypsum is P 2 O 5 The concentration is 38-42wt%;
filtering the slurry (2) and recovering 38-42% of intermediate acid (product phosphoric acid), semi-hydrated acid (the semi-hydrated acid contains 30-31% of phosphoric acid and 2.0-2.8% of sulfuric acid by mass percent) and phosphogypsum (1), wherein the phosphogypsum (1) contains 78-80% of calcium sulfate hemihydrate, 12-15% of calcium sulfate dihydrate, 5-7% of total phosphorus (the semi-hydrated acid contains 3-4% of water-soluble phosphorus) and 18-19% of attached water; the semi-water return acid is recycled into the phosphate rock powder for premixed decomposition to obtain monocalcium phosphate, and the mass fraction of the liquid-phase sulfate radical of the premixed slurry is controlled to be less than 0.1 percent;
phosphogypsum (1) enters a conversion tank, and meanwhile, a proper amount of concentrated sulfuric acid is added, and stirred at 55-75 ℃ to generate slurry (3), the solid content of the slurry (3) is controlled to be 30-35%, the sulfate radical mass fraction of filtrate of the slurry (3) is controlled to be 6.0-7.0%, and P is controlled 2 O 5 The concentration is 8-14wt%;
filtering the slurry (3) to obtain filtrate and phosphogypsum (2), wherein the content of calcium sulfate hemihydrate in the phosphogypsum (2) is 10-15%, the content of calcium sulfate dihydrate is 78-83%, the content of water-soluble phosphorus is 0.6-1.0%, the total phosphorus is 0.8-1.3%, and the content of attached water is 19-20%;
delivering phosphogypsum (2) to a reslurry tank through a belt, adding water for reslurry to generate slurry (4), and controlling the solid content of the slurry (4) to be 30-40%;
dewatering the slurry (4) to obtain phosphogypsum (3), wherein the content of calcium sulfate hemihydrate in the phosphogypsum (3) is 10-15%, the content of calcium sulfate dihydrate is 78-83%, the content of water-soluble phosphorus is 0.1-0.2%, the total phosphorus is about 0.3-0.4%, and the content of attached water is 10-12%;
uniformly mixing phosphogypsum (3) and quicklime, controlling the initial pH value of the phosphogypsum to be 6-8, aging for more than 3 days to obtain phosphogypsum (4), completely converting calcium sulfate hemihydrate in the phosphogypsum (4) into calcium sulfate dihydrate, wherein the content of the calcium sulfate dihydrate is 91-93%, the water-soluble phosphorus is less than 0.1%, the total phosphorus is about 0.2-0.5%, the attached water is less than 9-11%, and the pH value is 4-5.
Example 2
The embodiment of the invention provides a method for producing high-quality phosphogypsum by a semi-water-dihydrate wet-process phosphoric acid process, which comprises the following steps:
dewatering the phosphorite slurry to obtain phosphorite powder with 11% of water content;
conveying the phosphate rock powder to a premixing tank by adopting a belt, adding phosphoric acid with the mass fraction of 20% for premixing, decomposing the phosphate rock into monocalcium phosphate, stirring to generate premixed slurry, and controlling the mass fraction of liquid-phase sulfate radical of the premixed slurry to be less than 0.1%;
the premixed slurry enters a dissolving tank, concentrated sulfuric acid (96-98% by mass) is added, and the mixture is stirred at 90-100 ℃ to further decompose phosphorite to generate slurry (1), wherein the solid content of the slurry (1) is controlled to be 28-30%, and the mass fraction of liquid-phase sulfate radical in the slurry (1) is controlled to be 0.8-1.0%;
feeding the slurry (1) into a crystallization tank, adding concentrated sulfuric acid (96-98% by mass), stirring at 90-100deg.C to promote phosphogypsum to form mixed crystal mainly comprising calcium sulfate hemihydrate crystal, stirring to obtain slurry (2), controlling solid content of the slurry (2) at 28-30%, and controlling calcium sulfate hemihydrate content in solid phase phosphogypsum of the slurry (2) at 78-81% of calcium sulfate dihydrate content of 13-16%, and controlling the mass fraction of liquid-phase sulfate radical in slurry (2) to 2.5-3.0%, P 2 O 5 The concentration is 38-42.5wt%;
filtering the slurry (2) and recovering 37.8-42% of intermediate acid (product phosphoric acid), semi-hydrated acid (the semi-hydrated acid contains 20-29% of phosphoric acid and 2.0-2.6% of sulfuric acid by mass percent) and phosphogypsum (1), wherein the phosphogypsum (1) contains 78-81% of calcium sulfate hemihydrate, 13-16% of calcium sulfate dihydrate and 4-7% of total phosphorus (the semi-hydrated acid contains 3-5% of water-soluble phosphorus), and the attached water is 18.5-19.5%; the semi-water return acid is recycled into the phosphate rock powder for decomposing to obtain monocalcium phosphate, and the mass fraction of the liquid-phase sulfate radical of the premixed slurry is controlled to be less than 0.1 percent;
phosphogypsum (1) enters a conversion tank, and meanwhile, a proper amount of concentrated sulfuric acid is added, stirring is carried out at the temperature of 55-75 ℃ to generate slurry (3), the solid content of the slurry (3) is controlled to be 31-34%, the calcium sulfate hemihydrate content in the solid phase phosphogypsum of the slurry (3) is controlled to be 13-16%, the calcium sulfate dihydrate content is controlled to be 77-81%, the mass fraction of liquid phase sulfate radical of the slurry (3) is controlled to be 7.0-8.0%, and P is controlled 2 O 5 The concentration is 11-15wt%;
filtering the slurry (3) to obtain filtrate and phosphogypsum (2), wherein the content of calcium sulfate hemihydrate in the phosphogypsum (2) is 13-15%, the content of calcium sulfate dihydrate is 77-81%, the content of water-soluble phosphorus is 0.6-0.9%, the total phosphorus is 0.8-1.1%, and the content of attached water is 19-20%;
delivering phosphogypsum (2) to a reslurry tank through a belt, adding water for reslurry to generate slurry (4), and controlling the solid content of the slurry (4) to be 32-40%;
dewatering the slurry (4) to obtain phosphogypsum (3), wherein the content of calcium sulfate hemihydrate in the phosphogypsum (3) is 13-15%, the content of calcium sulfate dihydrate is 77-81%, the water-soluble phosphorus is less than 0.2%, the total phosphorus is about 0.2-0.5%, and the attached water is 10-11.5%;
uniformly mixing phosphogypsum (3) and quicklime, controlling the initial pH value of the phosphogypsum to be 6-8, aging for more than 3 days to obtain phosphogypsum (4), completely converting calcium sulfate hemihydrate in the phosphogypsum (4) into calcium sulfate dihydrate, wherein the content of the calcium sulfate dihydrate is 92.2-93.5%, the water-soluble phosphorus is less than 0.1%, the total phosphorus is about 0.2-0.5%, the attached water is 10-11%, and the pH value is 4-5.
Example 3
The embodiment of the invention provides a method for producing high-quality phosphogypsum by a semi-water-dihydrate wet-process phosphoric acid process, which comprises the following steps:
dewatering the phosphorite slurry to obtain phosphorite powder with 12% of water content;
conveying the phosphate rock powder to a premixing tank by adopting a belt, adding phosphoric acid with the mass fraction of 20% for premixing, decomposing the phosphate rock into monocalcium phosphate, stirring to generate premixed slurry, and controlling the mass fraction of liquid-phase sulfate radical of the premixed slurry to be less than 0.1%;
the premixed slurry enters a dissolving tank, concentrated sulfuric acid (96-98% by mass) is added, and the mixture is stirred at 90-100 ℃ to further decompose phosphorite to generate slurry (1), wherein the solid content of the slurry (1) is controlled to be 25-30%, and the mass fraction of liquid-phase sulfate radical in the slurry (1) is controlled to be 1.0-1.2%;
feeding the slurry (1) into a crystallization tank, adding concentrated sulfuric acid (96-98% by mass), stirring at 90-100 ℃ to promote phosphogypsum to form mixed crystals mainly comprising calcium sulfate hemihydrate crystals, stirring to generate a slurry (2), controlling the solid content of the slurry (2) to be 25-30%, controlling the calcium sulfate hemihydrate content in the solid-phase phosphogypsum of the slurry (2) to be 75-81%, the calcium sulfate dihydrate content to be 12-18%, and controlling the mass fraction of liquid-phase sulfate radical in the slurry (2) to be 2.5-3.5%, wherein P is the content of calcium sulfate hemihydrate in the solid-phase phosphogypsum of the slurry 2 O 5 The concentration is 38-41wt%;
filtering the slurry (2) and recovering 37.5-41% of intermediate acid (product phosphoric acid), semi-hydrated acid (the semi-hydrated acid contains 20-28% of phosphoric acid and 2.1-2.5% of sulfuric acid by mass percent) and phosphogypsum (1), wherein the phosphogypsum (1) contains 75-81% of calcium sulfate hemihydrate, 12-18% of calcium sulfate dihydrate, 5-7% of total phosphorus (the semi-hydrated acid contains 5-6% of water-soluble phosphorus) and 19-20% of attached water; the semi-water return acid is recycled into the phosphate rock powder for decomposing to obtain monocalcium phosphate, and the mass fraction of the liquid-phase sulfate radical of the premixed slurry is controlled to be less than 0.1 percent;
phosphogypsum (1) enters a conversion tank, and meanwhile, a proper amount of concentrated sulfuric acid is added, stirring is carried out at the temperature of 55-75 ℃ to generate slurry (3), the solid content of the slurry (3) is controlled to be 32-35%, the calcium sulfate hemihydrate content in the solid phase phosphogypsum of the slurry (3) is controlled to be 11-15%, the calcium sulfate dihydrate content is controlled to be 76-80%, the mass fraction of liquid phase sulfate radical of the slurry (3) is controlled to be 5.0-7.0%, and P is controlled 2 O 5 The concentration is 8-12wt%;
filtering the slurry (3) to obtain filtrate and phosphogypsum (2), wherein the content of calcium sulfate hemihydrate in the phosphogypsum (2) is 10-15%, the content of calcium sulfate dihydrate is 76-80%, the content of water-soluble phosphorus is 0.7-1.0%, the total phosphorus is 0.8-1.3%, and the content of attached water is 19-20%;
delivering phosphogypsum (2) to a reslurry tank through a belt, adding water for reslurry to generate slurry (4), and controlling the solid content of the slurry (4) to be 32-40%;
dewatering the slurry (4) to obtain phosphogypsum (3), wherein the content of calcium sulfate hemihydrate in the phosphogypsum (3) is 10-15%, the content of calcium sulfate dihydrate is 76-81%, the water-soluble phosphorus is less than 0.2%, the total phosphorus is about 0.2-0.5%, and the attached water is 11-12%;
uniformly mixing phosphogypsum (3) and quicklime, controlling the initial pH value of the phosphogypsum to be 6-8, aging for more than 3 days to obtain phosphogypsum (4), completely converting calcium sulfate hemihydrate in the phosphogypsum (4) into calcium sulfate dihydrate, wherein the content of the calcium sulfate dihydrate is 90.6-91.5%, the water-soluble phosphorus is less than 0.1%, the total phosphorus is about 0.2-0.5%, the attached water is 9-11%, and the pH value is 4-5.
Example 4
Compared with the embodiment 1, the method has the advantages that dilute phosphoric acid with the mass concentration of 20% is not added for premixing, the dehydrated phosphate rock powder is directly added into concentrated sulfuric acid with the mass fraction of 96-98%, and the slurry (1) is obtained by stirring at the temperature of 90-100 ℃ after the concentrated sulfuric acid is added. The content of calcium sulfate hemihydrate in the finally obtained phosphogypsum (3) is 10-20%, the content of calcium sulfate dihydrate is 70-80%, the water-soluble phosphorus is less than 0.2%, the total phosphorus is about 0.5-0.8%, and the attached water is less than 12%;
uniformly mixing phosphogypsum (3) and quicklime, controlling the initial pH value of the phosphogypsum to be 6-8, aging for more than 3 days to obtain phosphogypsum (4), completely converting calcium sulfate hemihydrate in the phosphogypsum (4) into calcium sulfate dihydrate, wherein the content of the calcium sulfate dihydrate is 90.8%, the water-soluble phosphorus is less than 0.1%, the total phosphorus is about 0.5-0.8%, the attached water is 9-11%, and the pH value is 4-5.
Example 5
Compared with the embodiment 1 of the application, the premixed slurry enters a dissolving tank, meanwhile, concentrated sulfuric acid (96-98% by mass) is added to further decompose phosphorite, the phosphorite stays for 4 hours to generate slurry (1), the mass fraction of liquid-phase sulfate radical of the slurry (1) is controlled to be 1.5%, the temperature of the slurry (1) is controlled to be 90-100 ℃, and the solid content of the slurry (1) is controlled to be 37%;
the content of calcium sulfate hemihydrate in the finally obtained phosphogypsum (3) is 15-27%, the content of calcium sulfate dihydrate is 60-77%, the content of water-soluble phosphorus is less than 0.2%, the total phosphorus is about 0.4-1.1% (the fluctuation range is large and unstable), and the content of attached water is less than 12%;
uniformly mixing phosphogypsum (3) and quicklime, controlling the initial pH value of the phosphogypsum to be 6-8, aging for more than seven days to obtain phosphogypsum (4), completely converting calcium sulfate hemihydrate in the phosphogypsum (4) into calcium sulfate dihydrate, wherein the content of the calcium sulfate dihydrate is 89.5%, the water-soluble phosphorus is less than 0.1%, the total phosphorus is about 0.4-1.1%, the attached water is 8-10%, and the pH value is 4-5.
Example 6
Compared with the embodiment 1 of the application, the slurry (1) enters a crystallization tank, meanwhile, concentrated sulfuric acid (96-98% by mass) is added to promote phosphogypsum to form mixed crystals mainly comprising calcium sulfate hemihydrate crystals, the mixed crystals stay for 3 hours to generate the slurry (2), and the mass fraction of the liquid-phase sulfate radical of the slurry (2) is controlled to be 1.2%, P 2 O 5 The concentration is 41wt percent, the temperature of the slurry (2) is controlled to be 90-100 ℃, and the solid content of the slurry (3) is controlled to be 36 percent;
the content of calcium sulfate hemihydrate in the finally obtained phosphogypsum (3) is 5-18%, the content of calcium sulfate dihydrate is 68-82%, the water-soluble phosphorus is about 0.8-1.5%, the total phosphorus is about 1.1-1.9%, and the attached water is less than 12%;
uniformly mixing phosphogypsum (3) and quicklime, controlling the initial pH value of the phosphogypsum to be 6-8, aging for more than seven days to obtain phosphogypsum (4), completely converting calcium sulfate hemihydrate in the phosphogypsum (4) into calcium sulfate dihydrate, wherein the content of the calcium sulfate dihydrate is 91.5%, the water-soluble phosphorus is less than 0.2%, the total phosphorus is about 1.0-1.9%, the attached water is 8.5-10%, and the pH value is 3.2-5.6.
Example 7
Compared with the embodiment 1 of the application, the phosphogypsum (1) enters the conversion tank, and meanwhile, a proper amount of concentrated sulfuric acid is added to stay for 1.5 hours to generate the slurry (3), and the mass fraction of the liquid-phase sulfate radical of the slurry (3) is controlled at 11.5 percent, P 2 O 5 The concentration is 15wt%, the temperature of the slurry (3) is controlled at 80 ℃, and the solid content of the slurry (3) is controlled at 27%;
the content of calcium sulfate hemihydrate in the finally obtained phosphogypsum (3) is 17-26%, the content of calcium sulfate dihydrate is 65-75%, the water-soluble phosphorus is about 0.4-0.7%, the total phosphorus is about 0.7-1.0%, and the attached water is less than 12%;
uniformly mixing phosphogypsum (3) and quicklime, controlling the initial pH value of the phosphogypsum to be 6-8, aging for more than seven days to obtain phosphogypsum (4), completely converting calcium sulfate hemihydrate in the phosphogypsum (4) into calcium sulfate dihydrate, wherein the content of the calcium sulfate dihydrate is 92.6%, the water-soluble phosphorus is less than 0.1%, the total phosphorus is about 0.7-1.0%, the attached water is 8-10%, and the pH value is 3.8-4.7.
Claims (7)
1. A method for producing phosphogypsum by a semi-water-dihydrate wet phosphoric acid process is characterized by comprising the following steps:
(1) Dewatering the phosphorite slurry to obtain phosphorite powder, wherein the water content of the phosphorite powder after dewatering is lower than 12%; adding phosphoric acid with the mass concentration of 20-35% into the ground phosphate rock for premixing to obtain slurry containing monocalcium phosphate, and controlling the mass fraction of liquid-phase sulfate radical in the slurry to be less than 0.1%;
(2) Adding concentrated sulfuric acid into the slurry containing monocalcium phosphate for dissolution to obtain slurry I, wherein the solid content of the slurry I is 25-30%, and the mass fraction of liquid-phase sulfate radical is 0.5-1.2%;
(3) Adding concentrated sulfuric acid into the slurry I for crystallization to obtain slurry II, wherein the solid content of the slurry II is 25-30%, the mass fraction of liquid-phase sulfate radical is 2.0-4.0%, and the liquid-phase P is the same as that of the slurry II 2 O 5 The concentration is 36-43wt%; the solid content comprises 75-81% of calcium sulfate hemihydrate crystal and 12-18% of calcium sulfate dihydrate;
(4) Filtering the slurry II to obtain crude products of intermediate acid, semi-hydrated acid and phosphogypsum; the phosphogypsum comprises 75-81% of calcium sulfate hemihydrate by mass, 12-18% of calcium sulfate dihydrate by mass, 3-6% of water-soluble phosphorus, 4-7% of total phosphorus and less than 20% of attached water;
(5) Adding concentrated sulfuric acid into the phosphogypsum crude product for conversion to obtain slurry III;
(6) Filtering the slurry III, adding water, re-pulping and dehydrating to obtain phosphogypsum;
(7) Mixing phosphogypsum and quicklime uniformly, controlling the initial pH value of phosphogypsum to be 6-12, aging for more than 3 days to obtain a phosphogypsum refined product, wherein the mass fraction of calcium sulfate dihydrate in the phosphogypsum refined product is more than 90%, the water-soluble phosphorus is less than 0.1%, the total phosphorus is 0.2-0.5%, the attached water is less than 12%, and the pH value is 4-11.
2. The method for producing phosphogypsum by using the semi-water-dihydrate wet process phosphoric acid process according to claim 1, wherein the mass fraction of the concentrated sulfuric acid in the step (2) is 96-98%, and the slurry I is obtained by adding the concentrated sulfuric acid and stirring at the temperature of 90-100 ℃.
3. The method for producing phosphogypsum by using the semi-water-dihydrate wet process phosphoric acid process according to claim 2, wherein the mass fraction of the concentrated sulfuric acid in the step (3) is 96-98%, and the slurry II is obtained by adding the concentrated sulfuric acid and stirring at the temperature of 90-100 ℃.
4. The method for producing phosphogypsum by using the semi-water-dihydrate wet-process phosphoric acid process according to claim 3, wherein the intermediate acid in the step (4) is phosphoric acid, and the mass fraction of phosphoric acid is 36-43%; the semi-aqueous acid return comprises 20-35% of phosphoric acid and 2-4% of sulfuric acid by mass.
5. The method for producing phosphogypsum by using the semi-water-dihydrate wet-process phosphoric acid process according to claim 4, wherein the semi-water return acid is recycled to the step (1), and the ground phosphate rock is premixed and decomposed into a slurry containing monocalcium phosphate.
6. The method for producing phosphogypsum by using the semi-water-dihydrate wet process phosphoric acid process according to claim 5, wherein concentrated sulfuric acid is added in the step (5), and the mixture is stirred at 55-75 ℃ to obtain slurry III.
7. The method for producing phosphogypsum by using the semi-water-dihydrate wet process phosphoric acid process according to claim 5, wherein the phosphogypsum obtained in the step (6) contains 10-20% by mass of calcium sulfate hemihydrate, 71-81% by mass of calcium sulfate dihydrate, less than 0.2% by mass of water-soluble phosphorus, 0.2-0.5% by mass of total phosphorus and less than 12% by mass of adhering water.
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| CN202211310519.0A CN115583666B (en) | 2022-10-25 | 2022-10-25 | Method for producing phosphogypsum by semi-water-dihydrate wet phosphoric acid process |
| PCT/CN2023/089825 WO2024087546A1 (en) | 2022-10-25 | 2023-04-21 | Method for producing phosphogypsum by hemihydrate-dihydrate wet process phosphoric acid process |
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| CN116283015A (en) * | 2023-02-24 | 2023-06-23 | 宜都兴发化工有限公司 | Method for preparing self-hardening spherical cement retarder by using double-crystalline phosphogypsum |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4452770A (en) * | 1981-12-14 | 1984-06-05 | United States Gypsum Company | Phosphoanhydrite process |
| CN105948009A (en) * | 2016-04-28 | 2016-09-21 | 昆明川金诺化工股份有限公司 | Energy-saving semihydrate-dihydrate wet-process phosphoric acid and white gypsum coproduction method |
| CN106431034A (en) * | 2016-08-31 | 2017-02-22 | 贵州川恒化工股份有限公司 | Method for producing building gypsum powder from semi-hydrate phosphogypsum |
| CN109734344A (en) * | 2019-03-05 | 2019-05-10 | 昆明川金诺化工股份有限公司 | A method of cement retarder is prepared using half water ardealite |
| CN112194109A (en) * | 2020-09-30 | 2021-01-08 | 湖北宜化松滋肥业有限公司 | Method for producing phosphoric acid and coproducing gypsum by semi-water-dihydrate wet-process phosphoric acid process |
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| CN115583666B (en) * | 2022-10-25 | 2024-03-29 | 宜都兴发化工有限公司 | Method for producing phosphogypsum by semi-water-dihydrate wet phosphoric acid process |
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| US4452770A (en) * | 1981-12-14 | 1984-06-05 | United States Gypsum Company | Phosphoanhydrite process |
| CN105948009A (en) * | 2016-04-28 | 2016-09-21 | 昆明川金诺化工股份有限公司 | Energy-saving semihydrate-dihydrate wet-process phosphoric acid and white gypsum coproduction method |
| CN106431034A (en) * | 2016-08-31 | 2017-02-22 | 贵州川恒化工股份有限公司 | Method for producing building gypsum powder from semi-hydrate phosphogypsum |
| CN109734344A (en) * | 2019-03-05 | 2019-05-10 | 昆明川金诺化工股份有限公司 | A method of cement retarder is prepared using half water ardealite |
| CN112194109A (en) * | 2020-09-30 | 2021-01-08 | 湖北宜化松滋肥业有限公司 | Method for producing phosphoric acid and coproducing gypsum by semi-water-dihydrate wet-process phosphoric acid process |
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