CN113443614A - Method for converting calcium sulfate dihydrate into alpha-calcium sulfate hemihydrate in dihydrate-hemihydrate wet-process phosphoric acid leaching process - Google Patents
Method for converting calcium sulfate dihydrate into alpha-calcium sulfate hemihydrate in dihydrate-hemihydrate wet-process phosphoric acid leaching process Download PDFInfo
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- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 title claims abstract description 180
- 238000000034 method Methods 0.000 title claims abstract description 100
- 229910000147 aluminium phosphate Inorganic materials 0.000 title claims abstract description 84
- 238000002386 leaching Methods 0.000 title claims abstract description 43
- 230000008569 process Effects 0.000 title claims abstract description 38
- JIUIIWVYHWSFAZ-UHFFFAOYSA-N ac1o0v2m Chemical compound O.O.O.O.O JIUIIWVYHWSFAZ-UHFFFAOYSA-N 0.000 title claims abstract description 17
- PASHVRUKOFIRIK-UHFFFAOYSA-L calcium sulfate dihydrate Chemical compound O.O.[Ca+2].[O-]S([O-])(=O)=O PASHVRUKOFIRIK-UHFFFAOYSA-L 0.000 title abstract description 34
- 239000013078 crystal Substances 0.000 claims abstract description 84
- 239000002131 composite material Substances 0.000 claims abstract description 83
- 239000000654 additive Substances 0.000 claims abstract description 80
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 77
- 238000006243 chemical reaction Methods 0.000 claims abstract description 63
- 230000000996 additive effect Effects 0.000 claims abstract description 59
- 230000009466 transformation Effects 0.000 claims abstract description 28
- 239000006172 buffering agent Substances 0.000 claims abstract description 24
- 229910052602 gypsum Inorganic materials 0.000 claims abstract description 23
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims abstract description 21
- 239000012752 auxiliary agent Substances 0.000 claims abstract description 19
- XLYOFNOQVPJJNP-ZSJDYOACSA-N heavy water Substances [2H]O[2H] XLYOFNOQVPJJNP-ZSJDYOACSA-N 0.000 claims abstract description 19
- 239000002367 phosphate rock Substances 0.000 claims abstract description 12
- OJMIONKXNSYLSR-UHFFFAOYSA-N phosphorous acid Chemical compound OP(O)O OJMIONKXNSYLSR-UHFFFAOYSA-N 0.000 claims abstract description 12
- 230000001131 transforming effect Effects 0.000 claims abstract description 10
- 239000002270 dispersing agent Substances 0.000 claims abstract description 9
- -1 organic acid salt Chemical class 0.000 claims abstract description 6
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical compound [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 claims description 78
- 229910052925 anhydrite Inorganic materials 0.000 claims description 30
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 claims description 27
- KDYFGRWQOYBRFD-UHFFFAOYSA-N Succinic acid Natural products OC(=O)CCC(O)=O KDYFGRWQOYBRFD-UHFFFAOYSA-N 0.000 claims description 18
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 14
- 239000002253 acid Substances 0.000 claims description 11
- 239000002994 raw material Substances 0.000 claims description 10
- 239000002202 Polyethylene glycol Substances 0.000 claims description 9
- 235000006408 oxalic acid Nutrition 0.000 claims description 9
- 229920001223 polyethylene glycol Polymers 0.000 claims description 9
- OTYBMLCTZGSZBG-UHFFFAOYSA-L potassium sulfate Chemical compound [K+].[K+].[O-]S([O-])(=O)=O OTYBMLCTZGSZBG-UHFFFAOYSA-L 0.000 claims description 8
- 229910052939 potassium sulfate Inorganic materials 0.000 claims description 8
- 235000011151 potassium sulphates Nutrition 0.000 claims description 8
- CSNNHWWHGAXBCP-UHFFFAOYSA-L Magnesium sulfate Chemical compound [Mg+2].[O-][S+2]([O-])([O-])[O-] CSNNHWWHGAXBCP-UHFFFAOYSA-L 0.000 claims description 6
- KDYFGRWQOYBRFD-NUQCWPJISA-N butanedioic acid Chemical compound O[14C](=O)CC[14C](O)=O KDYFGRWQOYBRFD-NUQCWPJISA-N 0.000 claims description 6
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims description 5
- 239000000872 buffer Substances 0.000 claims description 5
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 claims description 4
- 229910052938 sodium sulfate Inorganic materials 0.000 claims description 4
- 235000011152 sodium sulphate Nutrition 0.000 claims description 4
- LZZYPRNAOMGNLH-UHFFFAOYSA-M Cetrimonium bromide Chemical compound [Br-].CCCCCCCCCCCCCCCC[N+](C)(C)C LZZYPRNAOMGNLH-UHFFFAOYSA-M 0.000 claims description 3
- 229920000858 Cyclodextrin Polymers 0.000 claims description 3
- DBMJMQXJHONAFJ-UHFFFAOYSA-M Sodium laurylsulphate Chemical compound [Na+].CCCCCCCCCCCCOS([O-])(=O)=O DBMJMQXJHONAFJ-UHFFFAOYSA-M 0.000 claims description 3
- DIZPMCHEQGEION-UHFFFAOYSA-H aluminium sulfate (anhydrous) Chemical compound [Al+3].[Al+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O DIZPMCHEQGEION-UHFFFAOYSA-H 0.000 claims description 3
- HTZCNXWZYVXIMZ-UHFFFAOYSA-M benzyl(triethyl)azanium;chloride Chemical compound [Cl-].CC[N+](CC)(CC)CC1=CC=CC=C1 HTZCNXWZYVXIMZ-UHFFFAOYSA-M 0.000 claims description 3
- WOWHHFRSBJGXCM-UHFFFAOYSA-M cetyltrimethylammonium chloride Chemical compound [Cl-].CCCCCCCCCCCCCCCC[N+](C)(C)C WOWHHFRSBJGXCM-UHFFFAOYSA-M 0.000 claims description 3
- 229910000365 copper sulfate Inorganic materials 0.000 claims description 3
- ARUVKPQLZAKDPS-UHFFFAOYSA-L copper(II) sulfate Chemical compound [Cu+2].[O-][S+2]([O-])([O-])[O-] ARUVKPQLZAKDPS-UHFFFAOYSA-L 0.000 claims description 3
- CVOQYKPWIVSMDC-UHFFFAOYSA-L dipotassium;butanedioate Chemical compound [K+].[K+].[O-]C(=O)CCC([O-])=O CVOQYKPWIVSMDC-UHFFFAOYSA-L 0.000 claims description 3
- 229910052943 magnesium sulfate Inorganic materials 0.000 claims description 3
- 235000019341 magnesium sulphate Nutrition 0.000 claims description 3
- DCKVFVYPWDKYDN-UHFFFAOYSA-L oxygen(2-);titanium(4+);sulfate Chemical compound [O-2].[Ti+4].[O-]S([O-])(=O)=O DCKVFVYPWDKYDN-UHFFFAOYSA-L 0.000 claims description 3
- 150000003839 salts Chemical class 0.000 claims description 3
- HFHDHCJBZVLPGP-UHFFFAOYSA-N schardinger α-dextrin Chemical compound O1C(C(C2O)O)C(CO)OC2OC(C(C2O)O)C(CO)OC2OC(C(C2O)O)C(CO)OC2OC(C(O)C2O)C(CO)OC2OC(C(C2O)O)C(CO)OC2OC2C(O)C(O)C1OC2CO HFHDHCJBZVLPGP-UHFFFAOYSA-N 0.000 claims description 3
- ZNCPFRVNHGOPAG-UHFFFAOYSA-L sodium oxalate Chemical compound [Na+].[Na+].[O-]C(=O)C([O-])=O ZNCPFRVNHGOPAG-UHFFFAOYSA-L 0.000 claims description 3
- 229940039790 sodium oxalate Drugs 0.000 claims description 3
- 229940074404 sodium succinate Drugs 0.000 claims description 3
- ZDQYSKICYIVCPN-UHFFFAOYSA-L sodium succinate (anhydrous) Chemical compound [Na+].[Na+].[O-]C(=O)CCC([O-])=O ZDQYSKICYIVCPN-UHFFFAOYSA-L 0.000 claims description 3
- 229910000348 titanium sulfate Inorganic materials 0.000 claims description 3
- IMFACGCPASFAPR-UHFFFAOYSA-N tributylamine Chemical compound CCCCN(CCCC)CCCC IMFACGCPASFAPR-UHFFFAOYSA-N 0.000 claims description 3
- NWONKYPBYAMBJT-UHFFFAOYSA-L zinc sulfate Chemical compound [Zn+2].[O-]S([O-])(=O)=O NWONKYPBYAMBJT-UHFFFAOYSA-L 0.000 claims description 3
- 229910000368 zinc sulfate Inorganic materials 0.000 claims description 3
- 229960001763 zinc sulfate Drugs 0.000 claims description 3
- 239000002002 slurry Substances 0.000 abstract description 22
- 238000004519 manufacturing process Methods 0.000 abstract description 17
- 239000010440 gypsum Substances 0.000 abstract description 16
- 150000004683 dihydrates Chemical class 0.000 abstract description 15
- 239000002910 solid waste Substances 0.000 abstract description 4
- 229910052920 inorganic sulfate Inorganic materials 0.000 abstract description 3
- 150000001875 compounds Chemical class 0.000 description 24
- 229940095672 calcium sulfate Drugs 0.000 description 21
- 239000012071 phase Substances 0.000 description 20
- 239000007790 solid phase Substances 0.000 description 12
- 229910019142 PO4 Inorganic materials 0.000 description 10
- 238000000926 separation method Methods 0.000 description 10
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 9
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 9
- 239000010452 phosphate Substances 0.000 description 9
- 239000011574 phosphorus Substances 0.000 description 9
- 229910052698 phosphorus Inorganic materials 0.000 description 9
- 239000007787 solid Substances 0.000 description 9
- 238000002441 X-ray diffraction Methods 0.000 description 8
- 239000004372 Polyvinyl alcohol Substances 0.000 description 6
- 229920002451 polyvinyl alcohol Polymers 0.000 description 6
- 239000000243 solution Substances 0.000 description 6
- 239000001384 succinic acid Substances 0.000 description 6
- 238000009826 distribution Methods 0.000 description 5
- 238000001878 scanning electron micrograph Methods 0.000 description 5
- YIXJRHPUWRPCBB-UHFFFAOYSA-N magnesium nitrate Chemical compound [Mg+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O YIXJRHPUWRPCBB-UHFFFAOYSA-N 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 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 description 3
- 238000001914 filtration Methods 0.000 description 3
- 238000005406 washing Methods 0.000 description 3
- XYFCBTPGUUZFHI-UHFFFAOYSA-N Phosphine Chemical compound P XYFCBTPGUUZFHI-UHFFFAOYSA-N 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 150000001768 cations Chemical class 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000007791 liquid phase Substances 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000003607 modifier Substances 0.000 description 2
- 230000006911 nucleation Effects 0.000 description 2
- 238000010899 nucleation Methods 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- 239000012266 salt solution Substances 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- QNRATNLHPGXHMA-XZHTYLCXSA-N (r)-(6-ethoxyquinolin-4-yl)-[(2s,4s,5r)-5-ethyl-1-azabicyclo[2.2.2]octan-2-yl]methanol;hydrochloride Chemical compound Cl.C([C@H]([C@H](C1)CC)C2)CN1[C@@H]2[C@H](O)C1=CC=NC2=CC=C(OCC)C=C21 QNRATNLHPGXHMA-XZHTYLCXSA-N 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- ABLZXFCXXLZCGV-UHFFFAOYSA-N Phosphorous acid Chemical compound OP(O)=O ABLZXFCXXLZCGV-UHFFFAOYSA-N 0.000 description 1
- 229910004074 SiF6 Inorganic materials 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 239000002671 adjuvant Substances 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- AZDRQVAHHNSJOQ-UHFFFAOYSA-N alumane Chemical class [AlH3] AZDRQVAHHNSJOQ-UHFFFAOYSA-N 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 229910052681 coesite Inorganic materials 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 229920001577 copolymer Polymers 0.000 description 1
- 229910052593 corundum Inorganic materials 0.000 description 1
- 229910052906 cristobalite Inorganic materials 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 229940057307 dihydrate calcium sulfate Drugs 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000012065 filter cake Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229940057306 hemihydrate calcium sulfate Drugs 0.000 description 1
- 238000001027 hydrothermal synthesis Methods 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 238000005191 phase separation Methods 0.000 description 1
- OTYNBGDFCPCPOU-UHFFFAOYSA-N phosphane sulfane Chemical compound S.P[H] OTYNBGDFCPCPOU-UHFFFAOYSA-N 0.000 description 1
- 229910000073 phosphorus hydride Inorganic materials 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 239000002455 scale inhibitor Substances 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 229910052682 stishovite Inorganic materials 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 229910052905 tridymite Inorganic materials 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
- 229910001845 yogo sapphire Inorganic materials 0.000 description 1
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-
- 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
- C01B25/231—Dihydrate-hemihydrate process
-
- 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
- C01F11/466—Conversion of one form of calcium sulfate to another
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/10—Particle morphology extending in one dimension, e.g. needle-like
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
Abstract
The invention discloses a method for converting calcium sulfate dihydrate into alpha-calcium sulfate hemihydrate in a dihydrate-hemihydrate wet-process phosphoric acid leaching process, which comprises the following steps: leaching phosphorite and phosphoric acid by sulfuric acid at low temperature, and simultaneously reacting to produce CaSO4·2H2O; and a second stage: the temperature is increased to more than 100 ℃, the reaction process is in a crystal transformation stage, and the generated CaSO is transformed by adding a composite crystal transformation agent on the premise of not separating and leaching phosphoric acid4·2H2O is converted into alpha-CaSO with controllable appearance and length-diameter ratio4·0.5H2And O. The invention promotes the flaky CaSO by using the composite additive with the main components of inorganic sulfate transforming agent, organic acid salt buffering agent, water-soluble dispersant and auxiliary agent, in the one-step wet-process phosphoric acid production process, on the premise of not separating phosphoric acid slurry4·2H2O conversion to columnalpha-CaSO in the form of4·0.5H2And O, realizing the direct high-added-value utilization of the dihydrate gypsum solid waste in the production process of the phosphoric acid.
Description
Technical Field
The invention belongs to the technical field of wet-process phosphoric acid production, and particularly relates to a method for converting calcium sulfate dihydrate into alpha-calcium sulfate hemihydrate in a dihydrate-hemihydrate wet-process phosphoric acid leaching process.
Background
The wet process phosphoric acid production process distinguishes the process by producing phosphogypsum types, and the main components of dihydrate phosphogypsum, hemihydrate phosphogypsum and anhydrous phosphogypsum are CaSO respectively4·2H2O、α-CaSO4·0.5H2O and CaSO4. The existing mature and industrialized wet-process phosphoric acid process comprises the following steps: the dihydrate, dihydrate-hemihydrate and hemihydrate processes. The semi-water-semi-water method can be divided into a semi-water-di-water dilute acid method (one-step method) and a semi-water-di-water concentrated acid method (two-step method), the industrial application of the two-step method is only realized in the current stage of the two-water-semi-water method, and the one-step phosphoric acid leaching process is rarely reported.
The global storage of phosphate ore is 678 hundred million tons, the domestic storage of phosphate ore is 31 hundred million tons, and each 1 ton of P is produced in wet-process phosphoric acid2O5To produce about 5 tons of phosphogypsum, 6 and 7 hundred million tons of phosphogypsum are produced in 2015 and 2016 of phosphoric acid production in China, respectively, wherein P in dihydrate phosphogypsum is produced2O5The residual amount was about 1%. Under the existing dihydrate wet-process phosphoric acid production process, the generated dihydrate gypsum is characterized by flaky rhombic crystals and wider size distribution. The main disadvantages of the sheet dihydrate phosphogypsum produced in the wet-process phosphoric acid process are that calcium sulfate crystals in the solid are easy to stack layer by layer when the solid-liquid phase is separated, the separation rate is reduced in the filtration and washing processes, the residual phosphorus content in the gypsum is high, and the dihydrate calcium sulfate used as the main component in the dihydrate phosphogypsum is low in additional utilization value compared with the hemihydrate calcium sulfate, and is a solid waste in industrial production. The dihydrate process and the dihydrate phosphogypsum not only bring about the loss of phosphorus resources, but also bring about the waste and pollution of sulfur resources.
A great deal of research shows that the liquid-solid phase separation efficiency in wet-process phosphoric acid mainly depends on the properties of a calcium sulfate filter cake, including the morphology, the particle size and the size distribution of calcium sulfate crystals. Therefore, the preparation of rod-shaped alpha-CaSO with uniform size distribution in the one-step dihydrate-hemihydrate process is required4·0.5H2And O can improve the separation rate, improve the recovery rate of residual phosphorus and realize high value-added utilization of calcium sulfate.
Prior art is disclosedThe scale inhibitor in the wet phosphoric acid filtration system comprises 5-15% of organic phosphonic acid, 40-65% of a phosphine-containing polymer, 25-40% of a sulfonic acid copolymer, 0.05-0.5% of an aluminum salt and 4-10% of water. The dispersant mainly acts on K which is easy to concentrate at pump housings, valves and the like in actual production+、Na+、Ca2+Plasma metal ion and SiF6 2-、SO4 2-The deposit formed, but the crystals ultimately formed, are dihydrate gypsum and cannot be converted to hemihydrate gypsum.
And preparing magnesium nitrate and washed gypsum into slurry, adjusting the pH of the system to-2-6 by using nitric acid or sulfuric acid, heating the slurry to 100 ℃ under normal pressure, stirring, and carrying out hydrothermal reaction, wherein the mass ratio of the magnesium nitrate solution to the gypsum is 1: (0.1-0.4) optionally adding CaSO4·2H2Conversion of O to alpha-CaSO4·0.5H2And O. However, the process system conditions are too harsh, the gypsum needs to be separated and washed, the pH needs to be adjusted, the dosage proportion of the additive is too high, and the process is not suitable for being used with CaSO in wet-process phosphoric acid4·2H2Conversion of O to alpha-CaSO4·0.5H2O。
In addition, the phosphogypsum (the main component is CaSO)4·2H2O) preparation of alpha-CaSO4·0.5H2O whisker, the characteristic of this method lies in using sulfuric acid as leaching chemicals, to the phosphoric acid industry of wet process, although this method does not introduce other substances besides leaching phosphoric acid, this method needs to go on under the normal temperature again, and the concentrated sulfuric acid consumption and weight ratio of the phosphogypsum reach 10: 1, the investment cost is too high, and the process route cannot be realized.
The wet-process phosphoric acid process can prepare the semi-hydrated gypsum by a one-step method, is simple, but has the defect that the phosphoric acid leaching temperature needs to be raised to 130 ℃, and the semi-hydrated gypsum can be prepared by one step after the wet-process phosphoric acid leaching is finished. If the reaction temperature of phosphoric acid leaching is simply reduced, the CaSO is increased4·2H2O crystal alpha-CaSO4·0.5H2Difficulty of O, low temperatureIs unfavorable for alpha-CaSO4·0.5H2The generation of O crystal needs to seek auxiliary means to promote alpha-CaSO4·0.5H2And (4) generating O.
In summary, in the existing wet-process phosphoric acid industry, semi-hydrated gypsum with uniform appearance, size and particle size distribution is difficult to produce by phosphoric acid leaching at low temperature (about 100 ℃), and the method of adding a salt solution by washing phosphogypsum (the mass ratio of the salt solution to the gypsum is far more than 1: 1) cannot be realized in the wet-process phosphoric acid industry.
Therefore, it is necessary to develop a method for converting calcium sulfate dihydrate into calcium sulfate alpha-hemihydrate in a dihydrate-hemihydrate wet leaching phosphoric acid process to solve the above problems.
Disclosure of Invention
Aiming at the problems, the invention provides a method for converting calcium sulfate dihydrate into alpha-calcium sulfate hemihydrate in a dihydrate-hemihydrate wet-process phosphoric acid leaching process, so as to solve the problems in the background technology.
In order to achieve the purpose, the invention provides the following technical scheme: a method for converting calcium sulfate dihydrate into calcium sulfate alpha-hemihydrate in a dihydrate-hemihydrate wet-process phosphoric acid leaching process comprises the following steps:
the first stage is as follows: leaching phosphorite and phosphoric acid by sulfuric acid at low temperature, and simultaneously reacting to produce CaSO4·2H2O；
And a second stage: the temperature is increased to more than 100 ℃, the reaction process is in a crystal transformation stage, and the generated CaSO is transformed by adding a composite crystal transformation agent on the premise of not separating and leaching phosphoric acid4·2H2O is converted into alpha-CaSO with controllable appearance and length-diameter ratio4·0.5H2O。
Further, on the premise of not changing the phosphoric acid leaching process of the first stage, the composite crystal transformation agent is added into the raw material reaction tank in the second stage, and the conversion of CaSO4 & 2H2O to alpha-CaSO 4 & 0.5H2O is realized by adding concentrated sulfuric acid with the mass fraction of 98% instead of the second stage.
Further, the composite crystal transformation agent consists of a transformation agent, a buffering agent, a phase transfer agent and an auxiliary agent;
the transforming agent is one or more of sulfate such as sodium sulfate, potassium sulfate, magnesium sulfate, zinc sulfate, copper sulfate, aluminum sulfate and titanium sulfate;
the buffering agent consists of succinic acid, sodium succinate, succinic acid, potassium succinate, oxalic acid and sodium oxalate;
the phase transfer agent consists of CTAB, TEBA, SDS, CTAC, polyethylene glycol, tributylamine and cyclodextrin;
the conversion agent is a sulfate compound, the buffering agent is an organic weak acid or an organic weak acid salt, the dispersing agent is a water-soluble phase transfer agent, and the auxiliary agent is water.
Further, the content of the transfer agent in the composite crystal transformation agent is 30-40% of the mass percentage of the composite crystal transformation agent, the content of the buffer agent is less than 10% of the mass percentage of the composite crystal transformation agent, the content of the phase transfer agent is less than 10% of the mass percentage of the composite crystal transformation agent, and the content of the auxiliary agent is less than 30-40% of the mass percentage of the composite crystal transformation agent.
Further, calcium sulfate obtained after the reaction in the first stage is finished is flaky CaSO4·2H2O, the width is 30-40 μm, and the length is 50-60 μm;
obtaining columnar alpha-CaSO after the second stage reaction4·0.5H2O, the width is 40-60 μm, and the length is 80-120 μm.
Further, the CaSO generated by adding additive4·2H2O is converted into alpha-CaSO with controllable appearance and length-diameter ratio4·0.5H2O comprises:
in the crystal transformation system, the added composite additive is added in three steps, and the method and the dosage are as follows:
in the temperature rise stage of less than or equal to 8min, the adding amount of the composite additive accounts for 60-75% of the total amount;
in the stable conversion stage of 8-120min, the adding amount of the composite additive is 10-25% of the total amount;
in the crystal growing stage of 120-150min, the adding amount of the composite additive is 5-25% of the total amount.
Further, in the first stage, the phosphorite is extracted by sulfuric acid under the condition that the temperature is less than or equal to 85 ℃.
The invention has the technical effects and advantages that:
1. the invention promotes the flaky CaSO by using the composite additive with the main components of inorganic sulfate transforming agent, organic acid salt buffering agent, water-soluble dispersant and auxiliary agent, in the one-step wet-process phosphoric acid production process, on the premise of not separating phosphoric acid slurry4·2H2Conversion of O to columnar alpha-CaSO4·0.5H2And O, realizing the direct high-added-value utilization of the dihydrate gypsum solid waste in the production process of the phosphoric acid.
2. The invention can promote CaSO generated in the phosphoric acid leaching process by utilizing the composite additive under the condition of low use content4·2H2Conversion of O to alpha-CaSO4·0.5H2O, and the shape and the size of the gypsum crystal are uniform. The addition of sulfate in the composite additive can increase the supersaturation degree of calcium sulfate in the system, and the metal cation can induce the conversion of dihydrate crystal to hemihydrate crystal. Buffering agents, dispersing agents and adjuvants are advantageous for alpha-CaSO4·0.5H2The nucleation growth of the O crystal ensures that the crystal growth size and the appearance are uniform, and the purity of the crystal prepared by the reaction is close to 100 percent.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and drawings.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and those skilled in the art can also obtain other drawings according to the drawings without creative efforts.
Fig. 1 shows an SEM image of (a) first stage calcium sulfate in an embodiment of the invention; (b) SEM image of calcium sulfate without additive addition in the second stage; (c) an XRD pattern of the first stage calcium sulfate; (d) the XRD pattern of calcium sulfate without additives in the second stage;
figure 2 shows SEM and XRD patterns of phosphogypsum after phosphoric acid leaching with the addition of a co-additive in example 1 of the invention;
figure 3 shows SEM and XRD patterns of phosphogypsum after phosphoric acid leaching with the addition of a co-additive in example 2 of the invention;
figure 4 shows SEM and XRD patterns of phosphogypsum after phosphoric acid leaching with the addition of a co-additive in example 3 of the invention;
figure 5 shows SEM and XRD patterns of phosphogypsum after phosphoric acid leaching with the addition of a co-additive in example 4 of the invention;
figure 6 shows SEM and XRD patterns of phosphogypsum after phosphoric acid leaching with the addition of a co-additive in example 5 of the invention;
figure 7 shows the SEM and XRD patterns of phosphogypsum after phosphoric acid leaching with the co-additive addition in example 6 of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The conventional wet phosphoric acid process is illustrated below: mixing phosphorus ore slurry (mixture of ground and wet ground slurry of phosphorus ore) with concentrated H2SO4And concentrated H3PO4The mixed acid reacts in the reaction tank, slurry after reaction is separated by methods such as filtration, the separated solid phase is phosphogypsum, and the liquid phase is concentrated by a concentration system and then is used for preparing phosphoric acid and downstream products. The main component of the phosphogypsum obtained by the conventional process is flaky calcium sulfate dihydrate, the size distribution is wide, the phosphogypsum is not beneficial to washing, the residual phosphorus rate of gypsum is high, and the phosphorus recovery rate is reduced.
Example 1:
the invention provides a method for converting calcium sulfate dihydrate into alpha-calcium sulfate hemihydrate in a dihydrate-hemihydrate wet-process phosphoric acid leaching process, which is shown in figures 1-6, and the embodiment of the invention takes phosphate ore of phosphate ore in certain areas of Hubei as a raw material, wherein the content Wt (%) of the phosphate ore is as follows:
| composition (I) | P2O5 | MgO | CaO | Al2O3 | Fe2O3 | K2O | N2O | SiO2 | F | Others |
| Content/% | 31.18 | 1.07 | 45.51 | 2.88 | 3.16 | 3.20 | 1.63 | 2.64 | 2.73 |
The first stage is as follows: leaching phosphorite by sulfuric acid at low temperature (less than or equal to 85 ℃), leaching phosphoric acid, and simultaneously reacting to produce CaSO4·2H2O (calcium sulfate dihydrate).
And a second stage: the temperature is increased to more than 100 ℃, the reaction process is in a crystal transformation stage, and the generated CaSO is transformed by adding a composite crystal transformation agent on the premise of not separating and leaching phosphoric acid4·2H2O is converted into alpha-CaSO with controllable appearance and length-diameter ratio4·0.5H2O (calcium sulfate hemihydrate). Namely, on the premise of not changing the phosphoric acid leaching process of the first stage, the composite crystal transformation agent is added into the raw material reaction tank in the second stage, and the CaSO is realized by adding concentrated sulfuric acid with the mass fraction of 98 percent in the second stage instead of the first stage4·2H2O to alpha-CaSO4·0.5H2And (4) converting O. The invention does not change the conventional phosphoric acid leaching process, has simple operation, low cost and lower uncertain factors, and does not cause adverse effect on the production yield of phosphoric acid.
Wherein the adding amount of the composite crystal transformation agent is less than or equal to 10 percent of the total mass of the wet-process phosphoric acid system, and the composite crystal transformation agent consists of a transformation agent, a buffering agent, a phase transfer agent and an auxiliary agent.
The transforming agent is one or more of sulfate such as sodium sulfate, potassium sulfate, magnesium sulfate, zinc sulfate, copper sulfate, aluminum sulfate and titanium sulfate, the content of the transforming agent in the composite crystal transforming agent is 30-40% of the mass percent of the composite crystal transforming agent, and the transforming agent is a sulfate compound. The buffer is composed of succinic acid, sodium succinate, succinic acid, potassium succinate, oxalic acid and sodium oxalate, the content of the buffer is less than 10 percent of the mass percent of the composite crystal modifier, and the buffer is organic weak acid or organic weak acid salt. The phase transfer agent consists of CTAB, TEBA, SDS, CTAC, polyethylene glycol, tributylamine and cyclodextrin, the content of the phase transfer agent is less than 10 percent of the mass percent of the composite crystal transfer agent, and the water-soluble phase transfer agent is a dispersant. The auxiliary agent is water, and the content of the auxiliary agent is less than 30-40% of the composite crystal modifier by mass percent.
As shown in the figure 1 (a) and the figure 1 (c), phosphorus element in phosphate ore is extracted by using a wet-process phosphoric acid process, the mesh number of the phosphate ore is between 100 and 150 meshes, in the wet-process phosphoric acid process, concentrated sulfuric acid with the mass fraction of 98 percent and concentrated phosphoric acid are prepared into phosphorus-sulfur mixed acid at low temperature (less than or equal to 85 ℃) to leach phosphate ore, phosphoric acid is leached, after the reaction of the first stage is finished, part of phosphate slurry is taken to carry out solid-liquid separation, and the separated solid phase is dried in vacuum at 45 ℃ to obtain an SEM image and an XRD image of the solid phase, namely the SEM image and the XRD image of phosphogypsum.
As shown in fig. 1 (b) and 1 (d), a trace amount of solid phase sample is taken for detection, the reaction stability of the system is not affected, the temperature of the system is continuously increased to be more than 100 ℃, no substance is added into the system for the second stage reaction, after the second stage reaction is finished, the phosphoric acid slurry is subjected to liquid-solid separation, and the separated solid phase is dried in vacuum at 45 ℃ to obtain an SEM image and an XRD image of the solid.
In the fig. 1 (a) and 1 (c), the phosphogypsum obtained by the first stage of reaction is a flaky crystal, the width of the crystal is 30-40 μm, the length of the crystal is 50-60 μm, and the crystal form of calcium sulfate is CaSO4·2H2O；
In the fig. 1 (b) and 1 (d), the phosphogypsum obtained by the second stage of reaction is a columnar crystal, the width of the crystal is 40-60 μm, the length of the crystal is 80-120 μm, and the crystal form of calcium sulfate is CaSO4·2H2And O, no substance is added in the second stage for reaction, and the appearance, the size and the crystal form of the crystal generated in the first stage are not influenced.
Example 2:
the same phosphorite in the embodiment 1 is used as a raw material, the reaction conditions in the first stage are the same, but the compound additive is added in three steps in the second stage, and the specific operation is as follows: adding 60-75% of the total amount of the composite additive in a temperature rise stage of less than or equal to 8 min; adding 10-25% of the total amount of the compound additive at the stable conversion stage of 8-120 min; 5-25% of the total amount of the composite additive is added in the crystal growing stage of 120-150 min.
A transfer agent, a buffering agent and a phase transfer agent in the composite additive adopt mixed components, wherein the transfer agent adopts sodium sulfate which accounts for 40 percent of the total amount of the composite additive; the buffering agent selects succinic acid accounting for 2.5 percent of the total amount of the compound addition and oxalic acid accounting for 2.5 percent of the total amount of the compound addition; the phase transfer agent selects polyethylene glycol accounting for 2.5 percent of the total amount of the composite additives and polyvinyl alcohol accounting for 2.5 percent of the total amount of the composite additives; the auxiliary agent is water; the mass fractions of the mixed components in the composite additive are respectively 40%, 5% and 50%.
As shown in fig. 2 (a) and 2 (b), after the second-stage reaction, the phosphoric acid slurry was subjected to liquid-solid separation, and the separated solid phase was dried under vacuum at 45 ℃.
In fig. 2 (a) and 2 (b), the phosphogypsum obtained in the second stage of reaction is columnar crystal with the width of 8-10 μm and the length of 30-40 μm, and the crystal form of calcium sulfate is alpha-CaSO4·0.5H2O, realizes CaSO when phosphoric acid slurry is not separated in the wet-process phosphoric acid production4·2H2O to alpha-CaSO4·0.5H2And (4) converting O.
Example 3:
the same phosphorite in the embodiment 1 is used as a raw material, the reaction conditions in the first stage are the same, but the compound additive is added in three steps in the second stage, and the specific operation is as follows: adding 60-75% of the total amount of the composite additive in a temperature rise stage of less than or equal to 8 min; adding 10-25% of the total amount of the compound additive at the stable conversion stage of 8-120 min; 5-25% of the total amount of the composite additive is added in the crystal growing stage of 120-150 min.
A transfer agent, a buffering agent and a phase transfer agent in the composite additive adopt mixed components, wherein the transfer agent adopts potassium sulfate which accounts for 40 percent of the total amount of the composite additive; the buffering agent selects succinic acid accounting for 2.5 percent of the total amount of the compound addition and oxalic acid accounting for 2.5 percent of the total amount of the compound addition; the phase transfer agent selects polyethylene glycol accounting for 2.5 percent of the total amount of the composite additives and polyvinyl alcohol accounting for 2.5 percent of the total amount of the composite additives; the auxiliary agent is water; the mass fractions of the mixed components in the composite additive are respectively 40%, 5% and 50%.
As shown in fig. 3 (a) and 3 (b), after the second-stage reaction, the phosphoric acid slurry was subjected to liquid-solid separation, and the separated solid phase was dried under vacuum at 45 ℃.
In FIGS. 3 (a) and 3 (b), the phosphogypsum obtained by the second stage of reaction is a columnar crystal with a crystal width of 12-15 μm and a length of 40-50 μm, and the crystal form of calcium sulfate is alpha-CaSO4·0.5H2O, realizes CaSO when phosphoric acid slurry is not separated in the wet-process phosphoric acid production4·2H2O to alpha-CaSO4·0.5H2And (4) converting O.
Example 4:
the same phosphorite in the embodiment 1 is used as a raw material, the reaction conditions in the first stage are the same, but the compound additive is added in three steps in the second stage, and the specific operation is as follows: adding 60-75% of the total amount of the composite additive in a temperature rise stage of less than or equal to 8 min; adding 10-25% of the total amount of the compound additive at the stable conversion stage of 8-120 min; 5-25% of the total amount of the composite additive is added in the crystal growing stage of 120-150 min.
A transfer agent, a buffering agent and a phase transfer agent in the composite additive adopt mixed components, wherein the transfer agent adopts potassium sulfate which accounts for 40 percent of the total amount of the composite additive; the buffering agent selects succinic acid accounting for 2.5 percent of the total amount of the compound addition and oxalic acid accounting for 2.5 percent of the total amount of the compound addition; the phase transfer agent selects polyethylene glycol accounting for 2.5 percent of the total amount of the composite additives and polyvinyl alcohol accounting for 2.5 percent of the total amount of the composite additives; the auxiliary agent is water; the mass fractions of the mixed components in the composite additive are respectively 40%, 5% and 50%.
As shown in fig. 4 (a) and 4 (b), after the second-stage reaction, the phosphoric acid slurry was subjected to liquid-solid separation, and the separated solid phase was dried under vacuum at 45 ℃.
In FIGS. 4 (a) and 4 (b), the phosphogypsum obtained by the second stage of reaction is a columnar crystal with a crystal width of 10-12 μm and a length of 35-45 μm, and the crystal form of calcium sulfate is alpha-CaSO4·0.5H2O, realizes that the phosphorus is not separated in the wet-process phosphoric acid productionCaSO in acid slurry4·2H2O to alpha-CaSO4·0.5H2And (4) converting O.
Example 5:
the same phosphorite in the embodiment 1 is used as a raw material, the reaction conditions in the first stage are the same, but the compound additive is added in three steps in the second stage, and the specific operation is as follows: adding 60-75% of the total amount of the composite additive in a temperature rise stage of less than or equal to 8 min; adding 10-25% of the total amount of the compound additive at the stable conversion stage of 8-120 min; 5-25% of the total amount of the composite additive is added in the crystal growing stage of 120-150 min.
A transfer agent, a buffering agent and a phase transfer agent in the composite additive adopt mixed components, wherein the transfer agent adopts potassium sulfate which accounts for 40 percent of the total amount of the composite additive; the buffering agent selects succinic acid accounting for 2.5 percent of the total amount of the compound addition and oxalic acid accounting for 2.5 percent of the total amount of the compound addition; the phase transfer agent selects polyethylene glycol accounting for 2.5 percent of the total amount of the composite additives and polyvinyl alcohol accounting for 2.5 percent of the total amount of the composite additives; the auxiliary agent is water; the mass fractions of the mixed components in the composite additive are respectively 40%, 5% and 50%.
As shown in fig. 5 (a) and 5 (b), after the second-stage reaction, the phosphoric acid slurry was subjected to liquid-solid separation, and the separated solid phase was dried under vacuum at 45 ℃.
In fig. 5 (a) and 5 (b), the phosphogypsum obtained by the second stage of reaction is a columnar crystal with the width of 12-15 μm and the length of 25-30 μm, and the crystal form of calcium sulfate is alpha-CaSO4·0.5H2O, realizes CaSO when phosphoric acid slurry is not separated in the wet-process phosphoric acid production4·2H2O to alpha-CaSO4·0.5H2And (4) converting O.
Example 6:
the same phosphorite in the embodiment 1 is used as a raw material, the reaction conditions in the first stage are the same, but the compound additive is added in three steps in the second stage, and the specific operation is as follows: adding 60-75% of the total amount of the composite additive in a temperature rise stage of less than or equal to 8 min; adding 10-25% of the total amount of the compound additive at the stable conversion stage of 8-120 min; 5-25% of the total amount of the composite additive is added in the crystal growing stage of 120-150 min.
A transfer agent, a buffering agent and a phase transfer agent in the composite additive adopt mixed components, wherein the transfer agent adopts potassium sulfate which accounts for 40 percent of the total amount of the composite additive; the buffering agent selects succinic acid accounting for 2.5 percent of the total amount of the compound addition and oxalic acid accounting for 2.5 percent of the total amount of the compound addition; the phase transfer agent selects polyethylene glycol accounting for 2.5 percent of the total amount of the composite additives and polyvinyl alcohol accounting for 2.5 percent of the total amount of the composite additives; the auxiliary agent is water; the mass fractions of the mixed components in the composite additive are respectively 40%, 5% and 50%.
As shown in fig. 6 (a) and 6 (b), after the second-stage reaction, the phosphoric acid slurry was subjected to liquid-solid separation, and the separated solid phase was dried under vacuum at 45 ℃.
In FIGS. 6 (a) and 6 (b), the phosphogypsum obtained by the second stage of reaction is a columnar crystal with a crystal width of 8-10 μm and a length of 25-30 μm, and the crystal form of calcium sulfate is alpha-CaSO4·0.5H2O, realizes CaSO when phosphoric acid slurry is not separated in the wet-process phosphoric acid production4·2H2O to alpha-CaSO4·0.5H2And (4) converting O.
Example 7:
the same phosphorite in the embodiment 1 is used as a raw material, the reaction conditions in the first stage are the same, but the compound additive is added in three steps in the second stage, and the specific operation is as follows: adding 60-75% of the total amount of the composite additive in a temperature rise stage of less than or equal to 8 min; adding 10-25% of the total amount of the compound additive at the stable conversion stage of 8-120 min; 5-25% of the total amount of the composite additive is added in the crystal growing stage of 120-150 min.
A transfer agent, a buffering agent and a phase transfer agent in the composite additive adopt mixed components, wherein the transfer agent adopts potassium sulfate which accounts for 40 percent of the total amount of the composite additive; the buffering agent selects succinic acid accounting for 2.5 percent of the total amount of the compound addition and oxalic acid accounting for 2.5 percent of the total amount of the compound addition; the phase transfer agent selects polyethylene glycol accounting for 2.5 percent of the total amount of the composite additives and polyvinyl alcohol accounting for 2.5 percent of the total amount of the composite additives; the auxiliary agent is water; the mass fractions of the mixed components in the composite additive are respectively 40%, 5% and 50%.
As shown in fig. 7 (a) and 7 (b), after the second-stage reaction, the phosphoric acid slurry was subjected to liquid-solid separation, and the separated solid phase was dried in vacuum at 45 ℃.
In FIGS. 7 (a) and 7 (b), the phosphogypsum obtained by the second stage of reaction is a columnar crystal with a crystal width of 15-20 μm and a length of 35-40 μm, and the crystal form of calcium sulfate is alpha-CaSO4·0.5H2O, realizes CaSO when phosphoric acid slurry is not separated in the wet-process phosphoric acid production4·2H2O to alpha-CaSO4·0.5H2And (4) converting O.
The invention utilizes the composite additive with the main components of inorganic sulfate transforming agent, organic acid salt buffering agent, water-soluble dispersant and auxiliary agent to promote the flaky CaSO in the one-step wet-process phosphoric acid production process on the premise of not separating phosphoric acid slurry4·2H2Conversion of O to columnar alpha-CaSO4·0.5H2And O, realizing the direct high-added-value utilization of the dihydrate gypsum solid waste in the production process of the phosphoric acid.
The composite additive used in the invention can promote CaSO generated in the phosphoric acid leaching process under the condition of low use content4·2H2Conversion of O to alpha-CaSO4·0.5H2O, and the shape and the size of the gypsum crystal are uniform. The addition of sulfate in the composite additive can increase the supersaturation degree of calcium sulfate in the system, and the metal cation can induce the conversion of dihydrate crystal to hemihydrate crystal. The buffering agent, the dispersing agent and the auxiliary agent are beneficial to the nucleation growth of the alpha-CaSO 4 & 0.5H2O crystal, so that the growth size and the appearance of the crystal are uniform, and the purity of the crystal prepared by the reaction is close to 100 percent.
Although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (7)
1. A method for converting calcium sulfate dihydrate into calcium sulfate alpha-hemihydrate in a dihydrate-hemihydrate wet-process phosphoric acid leaching process is characterized by comprising the following steps: the method comprises the following steps:
the first stage is as follows: leaching phosphorite and phosphoric acid by sulfuric acid at low temperature, and simultaneously reacting to produce CaSO4·2H2O；
And a second stage: the temperature is increased to more than 100 ℃, the reaction process is in a crystal transformation stage, and the generated CaSO is transformed by adding a composite crystal transformation agent on the premise of not separating and leaching phosphoric acid4·2H2O is converted into alpha-CaSO with controllable appearance and length-diameter ratio4·0.5H2O。
2. The method for converting calcium sulfate dihydrate into calcium sulfate alpha-hemihydrate in a dihydrate-hemihydrate wet leaching phosphoric acid process according to claim 1, characterized in that:
on the premise of not changing the phosphoric acid leaching process of the first stage, the composite crystal transformation agent is added into the raw material reaction tank in the second stage, and the conversion of CaSO4 & 2H2O into alpha-CaSO 4 & 0.5H2O is realized by adding concentrated sulfuric acid with the mass fraction of 98% in the second stage instead.
3. The method for converting calcium sulfate dihydrate into calcium sulfate alpha-hemihydrate in a dihydrate-hemihydrate wet leaching phosphoric acid process according to claim 2, characterized in that:
the composite crystal transfer agent consists of a conversion agent, a buffering agent, a phase transfer agent and an auxiliary agent;
the transforming agent is one or more of sulfate such as sodium sulfate, potassium sulfate, magnesium sulfate, zinc sulfate, copper sulfate, aluminum sulfate and titanium sulfate;
the buffering agent consists of succinic acid, sodium succinate, succinic acid, potassium succinate, oxalic acid and sodium oxalate;
the phase transfer agent consists of CTAB, TEBA, SDS, CTAC, polyethylene glycol, tributylamine and cyclodextrin;
the conversion agent is a sulfate compound, the buffering agent is an organic weak acid or an organic weak acid salt, the dispersing agent is a water-soluble phase transfer agent, and the auxiliary agent is water.
4. The method for converting calcium sulfate dihydrate into calcium sulfate alpha-hemihydrate in a dihydrate-hemihydrate wet leaching phosphoric acid process according to claim 3, wherein:
the content of the transfer agent in the composite crystal transformation agent is 30-40% of the mass percent of the composite crystal transformation agent, the content of the buffer agent is less than 10% of the mass percent of the composite crystal transformation agent, the content of the phase transfer agent is less than 10% of the mass percent of the composite crystal transformation agent, and the content of the auxiliary agent is less than 30-40% of the mass percent of the composite crystal transformation agent.
5. The method for converting calcium sulfate dihydrate into calcium sulfate alpha-hemihydrate in a dihydrate-hemihydrate wet leaching phosphoric acid process according to claim 1, characterized in that:
the calcium sulfate obtained after the first-stage reaction is flaky CaSO4·2H2O, the width is 30-40 μm, and the length is 50-60 μm;
obtaining columnar alpha-CaSO after the second stage reaction4·0.5H2O, the width is 40-60 μm, and the length is 80-120 μm.
6. The method for converting calcium sulfate dihydrate into calcium sulfate alpha-hemihydrate in a dihydrate-hemihydrate wet leaching phosphoric acid process according to claim 1, characterized in that:
the CaSO generated by adding additive4·2H2O is converted into alpha-CaSO with controllable appearance and length-diameter ratio4·0.5H2O comprises:
in the crystal transformation system, the added composite additive is added in three steps, and the method and the dosage are as follows:
in the temperature rise stage of less than or equal to 8min, the adding amount of the composite additive accounts for 60-75% of the total amount;
in the stable conversion stage of 8-120min, the adding amount of the composite additive is 10-25% of the total amount;
in the crystal growing stage of 120-150min, the adding amount of the composite additive is 5-25% of the total amount.
7. The method for converting calcium sulfate dihydrate into calcium sulfate alpha-hemihydrate in a dihydrate-hemihydrate wet leaching phosphoric acid process according to claim 1, characterized in that:
in the first stage, the phosphorite is extracted by sulfuric acid at the temperature of less than or equal to 85 ℃.
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| CN115448351A (en) * | 2022-08-29 | 2022-12-09 | 浙江博明环保节能科技有限公司 | Preparation method of alpha semi-hydrated gypsum |
| CN117534109A (en) * | 2023-09-28 | 2024-02-09 | 湖北三峡实验室 | Method for increasing grain size of decomplexing precipitated calcium sulfate crystal |
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| CN117534109A (en) * | 2023-09-28 | 2024-02-09 | 湖北三峡实验室 | Method for increasing grain size of decomplexing precipitated calcium sulfate crystal |
| CN117534109B (en) * | 2023-09-28 | 2024-08-13 | 湖北三峡实验室 | Method for increasing grain size of decomplexing precipitated calcium sulfate crystal |
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