WO2022140804A1 - Method for filtering impurities in concentrated extracted phosphoric acid for enhancement of diammonium phosphate fertilizer content and for treatment of post-filtration solid waste into phosphate fertilizer, np fertilizer or npk fertilizer. - Google Patents
Method for filtering impurities in concentrated extracted phosphoric acid for enhancement of diammonium phosphate fertilizer content and for treatment of post-filtration solid waste into phosphate fertilizer, np fertilizer or npk fertilizer. Download PDFInfo
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- WO2022140804A1 WO2022140804A1 PCT/VN2021/000024 VN2021000024W WO2022140804A1 WO 2022140804 A1 WO2022140804 A1 WO 2022140804A1 VN 2021000024 W VN2021000024 W VN 2021000024W WO 2022140804 A1 WO2022140804 A1 WO 2022140804A1
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- 239000002686 phosphate fertilizer Substances 0.000 title claims abstract description 109
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 title claims abstract description 107
- 239000003337 fertilizer Substances 0.000 title claims abstract description 85
- 238000000034 method Methods 0.000 title claims abstract description 56
- MNNHAPBLZZVQHP-UHFFFAOYSA-N diammonium hydrogen phosphate Chemical compound [NH4+].[NH4+].OP([O-])([O-])=O MNNHAPBLZZVQHP-UHFFFAOYSA-N 0.000 title claims abstract description 49
- 229910000388 diammonium phosphate Inorganic materials 0.000 title claims abstract description 49
- 239000005696 Diammonium phosphate Substances 0.000 title claims abstract description 47
- 235000019838 diammonium phosphate Nutrition 0.000 title claims abstract description 47
- 239000002910 solid waste Substances 0.000 title claims abstract description 38
- 238000001914 filtration Methods 0.000 title claims abstract description 31
- 239000012535 impurity Substances 0.000 title claims abstract description 20
- 229910000147 aluminium phosphate Inorganic materials 0.000 title description 3
- 238000004519 manufacturing process Methods 0.000 claims abstract description 50
- 229920002401 polyacrylamide Polymers 0.000 claims abstract description 42
- 239000013049 sediment Substances 0.000 claims abstract description 24
- 238000000926 separation method Methods 0.000 claims abstract description 16
- 150000001768 cations Chemical class 0.000 claims abstract description 15
- 239000000203 mixture Substances 0.000 claims abstract description 15
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 15
- 229910052979 sodium sulfide Inorganic materials 0.000 claims abstract description 14
- 239000000701 coagulant Substances 0.000 claims abstract description 10
- 239000007788 liquid Substances 0.000 claims abstract description 9
- 238000004062 sedimentation Methods 0.000 claims abstract description 9
- 238000011084 recovery Methods 0.000 claims abstract description 7
- 238000003756 stirring Methods 0.000 claims abstract description 7
- GRVFOGOEDUUMBP-UHFFFAOYSA-N sodium sulfide (anhydrous) Chemical compound [Na+].[Na+].[S-2] GRVFOGOEDUUMBP-UHFFFAOYSA-N 0.000 claims abstract 4
- 238000002156 mixing Methods 0.000 claims description 21
- 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 19
- 229910052921 ammonium sulfate Inorganic materials 0.000 claims description 17
- BFNBIHQBYMNNAN-UHFFFAOYSA-N ammonium sulfate Chemical compound N.N.OS(O)(=O)=O BFNBIHQBYMNNAN-UHFFFAOYSA-N 0.000 claims description 15
- 235000011130 ammonium sulphate Nutrition 0.000 claims description 15
- 229910052586 apatite Inorganic materials 0.000 claims description 14
- VSIIXMUUUJUKCM-UHFFFAOYSA-D pentacalcium;fluoride;triphosphate Chemical compound [F-].[Ca+2].[Ca+2].[Ca+2].[Ca+2].[Ca+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O VSIIXMUUUJUKCM-UHFFFAOYSA-D 0.000 claims description 14
- 150000001450 anions Chemical group 0.000 claims description 10
- ZHZFKLKREFECML-UHFFFAOYSA-L calcium;sulfate;hydrate Chemical compound O.[Ca+2].[O-]S([O-])(=O)=O ZHZFKLKREFECML-UHFFFAOYSA-L 0.000 claims description 10
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 claims description 6
- PASHVRUKOFIRIK-UHFFFAOYSA-L calcium sulfate dihydrate Chemical compound O.O.[Ca+2].[O-]S([O-])(=O)=O PASHVRUKOFIRIK-UHFFFAOYSA-L 0.000 claims description 3
- XLYOFNOQVPJJNP-ZSJDYOACSA-N heavy water Substances [2H]O[2H] XLYOFNOQVPJJNP-ZSJDYOACSA-N 0.000 claims description 3
- 239000002245 particle Substances 0.000 claims description 3
- 239000001103 potassium chloride Substances 0.000 claims description 3
- 235000011164 potassium chloride Nutrition 0.000 claims description 3
- 239000000047 product Substances 0.000 description 47
- 239000002253 acid Substances 0.000 description 26
- 150000003839 salts Chemical class 0.000 description 17
- 229910019142 PO4 Inorganic materials 0.000 description 15
- 229910052751 metal Inorganic materials 0.000 description 11
- 239000002184 metal Substances 0.000 description 11
- VDQVEACBQKUUSU-UHFFFAOYSA-M disodium;sulfanide Chemical compound [Na+].[Na+].[SH-] VDQVEACBQKUUSU-UHFFFAOYSA-M 0.000 description 9
- 238000006243 chemical reaction Methods 0.000 description 8
- 230000007423 decrease Effects 0.000 description 7
- 229910004725 CaSiF6 Inorganic materials 0.000 description 5
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 5
- 229910052925 anhydrite Inorganic materials 0.000 description 5
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical compound [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 5
- 230000003247 decreasing effect Effects 0.000 description 4
- 238000001125 extrusion Methods 0.000 description 4
- 150000003013 phosphoric acid derivatives Chemical class 0.000 description 4
- 238000004458 analytical method Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 229910001385 heavy metal Chemical class 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 235000021049 nutrient content Nutrition 0.000 description 3
- 235000021317 phosphate Nutrition 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- 238000005086 pumping Methods 0.000 description 3
- 239000002699 waste material Substances 0.000 description 3
- -1 Fe(H2PO4)3 Chemical class 0.000 description 2
- YUWBVKYVJWNVLE-UHFFFAOYSA-N [N].[P] Chemical compound [N].[P] YUWBVKYVJWNVLE-UHFFFAOYSA-N 0.000 description 2
- WZLMXYBCAZZIRQ-UHFFFAOYSA-N [N].[P].[K] Chemical compound [N].[P].[K] WZLMXYBCAZZIRQ-UHFFFAOYSA-N 0.000 description 2
- 239000011575 calcium Substances 0.000 description 2
- 238000005345 coagulation Methods 0.000 description 2
- 230000015271 coagulation Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 description 2
- 229910000399 iron(III) phosphate Inorganic materials 0.000 description 2
- 230000014759 maintenance of location Effects 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 2
- 239000010452 phosphate Substances 0.000 description 2
- 230000000717 retained effect Effects 0.000 description 2
- QORWJWZARLRLPR-UHFFFAOYSA-H tricalcium bis(phosphate) Chemical compound [Ca+2].[Ca+2].[Ca+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O QORWJWZARLRLPR-UHFFFAOYSA-H 0.000 description 2
- 229910000391 tricalcium phosphate Inorganic materials 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 1
- 229910003638 H2SiF6 Inorganic materials 0.000 description 1
- 229910021570 Manganese(II) fluoride Inorganic materials 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 238000003915 air pollution Methods 0.000 description 1
- 239000004411 aluminium Chemical class 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical class [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 150000001399 aluminium compounds Chemical class 0.000 description 1
- 229940077746 antacid containing aluminium compound Drugs 0.000 description 1
- 229910052793 cadmium Inorganic materials 0.000 description 1
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 description 1
- FUFJGUQYACFECW-UHFFFAOYSA-L calcium hydrogenphosphate Chemical compound [Ca+2].OP([O-])([O-])=O FUFJGUQYACFECW-UHFFFAOYSA-L 0.000 description 1
- YYRMJZQKEFZXMX-UHFFFAOYSA-N calcium;phosphoric acid Chemical compound [Ca+2].OP(O)(O)=O.OP(O)(O)=O YYRMJZQKEFZXMX-UHFFFAOYSA-N 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 125000003917 carbamoyl group Chemical group [H]N([H])C(*)=O 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 230000001112 coagulating effect Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 239000002274 desiccant Substances 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- CTNMMTCXUUFYAP-UHFFFAOYSA-L difluoromanganese Chemical compound F[Mn]F CTNMMTCXUUFYAP-UHFFFAOYSA-L 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 235000012438 extruded product Nutrition 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 238000005189 flocculation Methods 0.000 description 1
- 230000016615 flocculation Effects 0.000 description 1
- 150000004679 hydroxides Chemical class 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 229910052976 metal sulfide Inorganic materials 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 229910052958 orpiment Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 230000008635 plant growth Effects 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- 239000002689 soil Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- ZEFWRWWINDLIIV-UHFFFAOYSA-N tetrafluorosilane;dihydrofluoride Chemical compound F.F.F[Si](F)(F)F ZEFWRWWINDLIIV-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C05—FERTILISERS; MANUFACTURE THEREOF
- C05B—PHOSPHATIC FERTILISERS
- C05B17/00—Other phosphatic fertilisers, e.g. soft rock phosphates, bone meal
-
- 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
- C01B25/234—Purification; Stabilisation; Concentration
-
- C—CHEMISTRY; METALLURGY
- C05—FERTILISERS; MANUFACTURE THEREOF
- C05B—PHOSPHATIC FERTILISERS
- C05B7/00—Fertilisers based essentially on alkali or ammonium orthophosphates
Definitions
- the present invention relates to the field of fertilizer manufacture, particularly a method for filtering impurities in concentrated extracted phosphoric acid (H 3 PO 4 ) which is used in the manufacture of diammonium phosphate (DAP) fertilizer ((NH 4 ) 2 HPO 4 ) for enhancement of the fertilizer content, and for treatment of post-filtration solid waste (solid residue) into phosphate fertilizer ( P 2 O 5 ), nitrogen-phosphorus (NP) fertilizer or nitrogen-phosphorus-potassium (NPK) fertilizer having a maximum amount of effective P 2 O 5 component.
- DAP diammonium phosphate
- NP nitrogen-phosphorus
- NPK nitrogen-phosphorus-potassium
- DAP fertilizer production technology comprises two stages: manufacturing H 3 PO 4 and manufacturing DAP from the obtained H 3 PO 4 .
- H 3 PO 4 has been manufactured by two methods, namely the thermal method from elemental phosphorus and the wet method by means of processing apatite ore ( Ca 3 F(PO 4 ) 3 ) with sulfuric acid ( H 2 SO 4 ) (the dehydrate method), therefore this product is referred to as extracted H 3 PO 4 , which is less costly than H 3 PO 4 obtained by the thermal method.
- the process for manufacturing (extracting) dilute H 3 PO 4 is carried out according to the following reaction:
- the solution of extracted H 3 PO 4 generally has a concentration in the range of 25 - 28% by mass with respect to P 2 O 5 .
- the apatite ore also contains other metal impurities partly dissolved in newly formed H 3 PO 4 , and residual H 2 SO 4 , for example:
- the remaining metal impurities together with generated metal salts, H 2 SiF 6 and salts CaSiF 6 , MgSiF 6 thereof are considered the impurities existing in solution.
- Such impurities existing in solution will significantly affect the concentration process as well as the DAP manufacturing process.
- Particular impurity contents are presented in Table 1 below.
- dilute H 3 PO 4 solution with a concentration in the range of 25 - 28% by mass is concentrated to a concentration in the range of 45 - 50% by mass, with respect to P 2 O 5 , so as to be used in the DAP production technology.
- salt systems as CaSO 4 - H 3 PO 4 - H 2 O, MgSiF 6 - H 3 PO 4 - H 2 O, and CaSiF 6 - H 3 PO 4 - H 2 O shall precipitate.
- Table 2 Components in extracted H 3 PO 4 after concentration, equivalent to the P 2 O 5 content in the range of 45%-49%
- H 3 PO 4 is neutralized to obtain a pH of 3.5 - 5
- phosphate salts of iron, aluminium and other heavy metals in one hand form hydroxides, and in the other hand form FePO 4 , A1PO 4 , MnPO 4 , Ca 3 (PO 4 ) 2 , etc., which are stable phosphate salts.
- the said salts together with impurities such as CaSO 4 MnF 2 , CaSiF 6 , will degrade the quality of DAP product, make it unqualified in terms of the N and P 2 O 5 contents.
- Such sediments degrade the quality of DAP fertilizer, in other words they cause a degradation in quality of the DAP fertilizer, a slow dissolution and unqualified contents of N and P 2 O 5 .
- Another objective of the present invention is to treat solid waste from SS after being separated from concentrated H 3 PO 4 solution into phosphate fertilizer (P 2 O 5 ), nitrogen-phosphorus (NP) fertilizer or nitrogen-phosphorus-potassium (NPK) fertilizer having a maximum amount of effective P 2 O 5 component.
- P 2 O 5 phosphate fertilizer
- NP nitrogen-phosphorus
- NPK nitrogen-phosphorus-potassium
- the present invention relates to:
- a method for filtering impurities in concentrated extracted H 3 PO 4 for enhancement of diammonium phosphate (DAP) fertilizer content comprising:
- step (iii) adding the solution obtained in step (ii), as a sedimentation aid, to the concentrated H 3 PO 4 solution in step (i) with the proportion of 12.5 - 20.0 L per ton of concentrated H 3 PO 4 and regularly stirring, to coagulate and flocculate suspended sediment (SS); and
- step (v) reducing residual H 3 PO 4 in the solid waste obtained in step (iv) by adding 8-25% by mass of fine grained apatite ore with particle size of 65-70 ⁇ m and the P 2 O 5 content in the range of 30-42% by mass to total amount of the solid waste, uniformly mixing, and retaining for 24-72 hours, to obtain a semi-product for manufacturing phosphate fertilizer (P 2 O 5 ), NP fertilizer or NPK fertilizer.
- P 2 O 5 phosphate fertilizer
- NP fertilizer NP fertilizer
- NPK fertilizer NPK fertilizer
- step (vi) manufacturing phosphate fertilizer (P 2 O 5 ) by uniformly mixing the semi-product obtained from step (v) with calcium sulfate hydrate, in particular calcium sulfate dihydrate (CaSO 4 ZHaO) and/or calcium sulfate hemihydrate (CaSO 4 .1/2H 2 O), preferably calcium sulfate hemihydrate, wherein the mass ratio of semi-product : calcium sulfate hydrate is in the range of 1 : 0.5 - 1 : 1.5.
- calcium sulfate hydrate in particular calcium sulfate dihydrate (CaSO 4 ZHaO) and/or calcium sulfate hemihydrate (CaSO 4 .1/2H 2 O), preferably calcium sulfate hemihydrate, wherein the mass ratio of semi-product : calcium sulfate hydrate is in the range of 1 : 0.5 - 1 : 1.5.
- step (vii) manufacturing NP fertilizer by uniformly mixing the semi-product obtained from step (v) with ammonium sulfate - (NBU ⁇ SO*, wherein the mass ratio of the semi-product : ammonium sulfate is in the range of 1 : 0.5 - 1 : 2.
- step (viii) manufacturing NPK fertilizer by mixing the NP fertilizer obtained from step (vii) with a proper amount of potassium chloride (KC1), depending on the KaO content requirement for the fertilizer.
- KC1 potassium chloride
- Fig.l is a schematic diagram showing a screw extrader used in examples.
- Fig.2 shows a blade provided at an extrusion die head.
- Fig.3 shows an extrusion die having multiple forming holes.
- the present invention provides a method for filtering impurities in concentrated extracted H 3 PO 4 for enhancement of diammonium phosphate (DAP) fertilizer content comprising:
- H 3 PO 4 has the content with respect to P 2 O 5 of less than 45% by mass, then such metal salts as Fe(H 2 PO 4 ) 3 , Al(H 2 PO 4 ) 3 , Mn(H 2 PO 4 ) 3 , etc., H 2 S1F6 and its salts CaSiF 6 , MgSiF 6 as generated will be considered impurities which exist in solution and incompletely precipitate, leading to the fact that the DAP fertilizer quality cannot meet the requirements.
- metal salts as Fe(H 2 PO 4 ) 3 , Al(H 2 PO 4 ) 3 , Mn(H 2 PO 4 ) 3 , etc., H 2 S1F6 and its salts CaSiF 6 , MgSiF 6 as generated will be considered impurities which exist in solution and incompletely precipitate, leading to the fact that the DAP fertilizer quality cannot meet the requirements.
- concentrated H 3 PO 4 has the content with respect to P 2 O 5 of more than 49% by mass, said acid shall become thickened, resulting in a low rate of clean acid recovery, and a decrease in the DAP fertilizer productivity.
- concentrated H 3 PO 4 has a temperature in the range of 45 - 90°C.
- the method according to the present invention is implemented straight after the concentration process so as to utilize the thermal from the process, lowering energy costs to heat the acid.
- PAM polyacrylamide
- PAM in the cation form with negative charge serves to flocculate suspended sediment
- PAM in the anion form is also used in combination to enhance the ability of binding suspended sediment in concentrated H 3 PO 4 .
- the mass ratio of PAM in the anion form: PAM in the cation form is in the range of
- the total amount of PAM per ton of concentrated H 3 PO 4 is more than 70 g, there will be a PAM redundancy in the concentrated H 3 PO 4 solution, the acid solution becomes viscous, resulting in an ineffective operation of the solid waste separator.
- the Na 2 S amount of less than 20 g per ton of concentrated H 3 PO 4 will not be sufficient to enhance the liquidity of the PAM solution for an easy pumping, and will not be sufficient to precipitate cadmium and heavy metals in concentrated H 3 PO 4 into metal sulfides, for example under the following reactions:
- the proportion of water : PAM : Na 2 S per ton of concentrated H 3 PO 4 is 15 L : 65 g : 30 g.
- the mass ratio of PAM in the anion form: PAM in the cation form is
- step (iii) Adding the solution obtained in step (ii), as a sedimentation aid, to the concentrated H 3 PO 4 solution in step (i) with the proportion of 12.5 - 20.0 L per ton of concentrated H 3 PO 4 and regularly stirring, to coagulate and flocculate suspended sediment.
- step (iv) Filtering for solid-liquid separation of the solution obtained from step (iii), clean H 3 PO 4 solution obtained after separation is used for manufacturing DAP, wherein the recovery rate of H 3 PO 4 solution qualified for the DAP manufacture is 80-85% and the SS content in the post-filtration solution is less than l% by mass.
- Solid-liquid separation process can be implemented by a hydraulic press or a filter press.
- the invention is not limited thereto, any method and means for solid-liquid separation known in the art which can separate the solid phase in the form of solid waste from the liquid phase can be used.
- the method according to the present invention further comprises:
- step (v) reducing residual H 3 PO 4 in the solid waste obtained in step (iv) by adding 8-25% by mass of apatite ore with particle size of 65-70 ⁇ m and the P 2 O 5 content in the range of 30-42% by mass to total amount of the solid waste, uniformly mixing, and retaining for 24-72 hours, to obtain a semi-product for manufacturing phosphate fertilizer (P 2 O 5 ), NP fertilizer or NPK fertilizer.
- step (v) Some reactions occurring in step (v) are as follows:
- the concentration of residual free H 3 PO 4 in the finished fertilizer is still high, affecting the plant growth.
- the concentration of residual free H 3 PO 4 significantly decreases, but the effective P 2 O 5 content also decreases.
- the semi-product will be stiffened, affecting the use in following steps of the manufacturing process because the loosening of the semi-product will be required.
- the method according to the present invention further comprises:
- step (vi) manufacturing phosphate fertilizer (P 2 O 5 ) by uniformly mixing the semi-product obtained from step (v) with calcium sulfate hydrate, in particular calcium sulfate dihydrate (CaSO 4 .2H 2 O) and/or calcium sulfate hemihydrate (CaSO 4 .1/2H 2 O), preferably calcium sulfate hemihydrate having a mass ratio of the semi-product : calcium sulfate hydrate in the range of 1 : 0.5 - 1 : 1.5.
- calcium sulfate hydrate in particular calcium sulfate dihydrate (CaSO 4 .2H 2 O) and/or calcium sulfate hemihydrate (CaSO 4 .1/2H 2 O
- calcium sulfate hemihydrate having a mass ratio of the semi-product : calcium sulfate hydrate in the range of 1 : 0.5 - 1 : 1.5.
- step (v) Some reactions occurring in step (v) are as follows: 4 If the content by mass of calcium sulfate hydrate is more than 1.5 parts per 1 part of the semi-product, the P 2 O 5 amount in the product is low.
- the CaSO 4 amount will be insufficient to exchange with phosphate metal salts in the solid waste.
- the mass ratio of the semi-product : calcium sulfate hydrate is within the said range, it is possible to obtain the P 2 O 5 content in the range of 16-30% by mass, which can meet various demands from clients. For example, if it is desired to increase the P 2 O 5 content, the consumed calcium sulfate hydrate should be decreased.
- Phosphate fertilizer obtained in this step may be further dried to a desired humidity and fine ground to obtain the finished phosphate fertilizer (P 2 O 5 ).
- the method according to the present invention further comprises:
- step (vii) manufacturing NP fertilizer by uniformly mixing the semi-product obtained from step (v) with ammonium sulfate - (NH 4 ) 2 SO 4 having a mass ratio of the semi-product : ammonium sulfate in the range of 1 : 0.5 - 1 : 2.
- step (v) Some reactions occurring in step (v) are as follows: If the content by mass of ammonium sulfate is more than 2 parts per 1 part of the semi-product, the large amount of ammonium sulfate in the fertilizer will acidify soil.
- the amount of ammonium sulfate will be insufficient to exchange with phosphate metal salt radicals in the solid waste.
- the NP fertilizer obtained in this step can be dried to a desired humidity and fine ground to obtain the finished NP fertilizer.
- the method according to the present invention further comprises:
- step (viii) manufacturing NPK fertilizer by mixing the NP fertilizer obtained from step (vii) with a proper amount of potassium chloride (KC1), depending on the KzO content requirement for the fertilizer, wherein the NP fertilizer may either be dried and fine ground or not.
- KC1 potassium chloride
- polyacrylamide having the chemical formula of CONH 2 (CH 2 -CH-)n, including polyacrylamide in the cation form and polyacrylamide in the anion form;
- a tank for storing concentrated extracted H 3 PO 4 (acid tank) in the form of a circular tank equipped with stirring shaft having a speed in the range of 120 - 300 rpm;
- a tank for preparing coagulant mixture (coagulant mixture tank) in the form of a circular tank equipped with stirring shaft having a speed in the range of 400 - 500 rpm and having a volume equal to about 1/40 of the acid tank volume; - a solid-liquid separator in the form of a filter press; and
- a screw extruder as shown in Figs. 1-3, including: motor 1 attached to screw 3 to rotate the same; feeding hopper 2 for feeding materials to screw 3; and extrusion die 5 for shaping extruded product.
- the extruder further comprises cutter 4 adjacent to extrusion die 5.
- Tanks and solid-liquid separator are common in the art, thus not necessary to be further described.
- Example 1 Separation filtering of suspended sediment (SS) in concentrated extracted H 3 PO 4 having components shown in Table 3 below.
- the solution in the acid tank is pumped to the solid-liquid separator, which is a filter press to filter for separating suspended sediment from the acid solution.
- the clean H 3 PO 4 solution obtained is subjected to the DAP manufacturing process, while the solid waste is subjected to step (v) to treat the residual acid.
- Total amount of the solid waste obtained is 1800 kg. Components in the solid waste are shown in Table 5 below. Table 5: Components in the solid waste obtained after filtering suspended sediment
- the DAP obtained can provide an excellent total nutrient content, which is higher than DAP 64% product containing 18% by mass of total N and 46% by mass of P 2 O 5 , as requested by clients.
- Example 2 Separation filtering of suspended sediment (SS) in concentrated extracted H 3 PO 4 having components shown in Table 7 below.
- the amount of recovered effective P 2 O 5 for manufacturing DAP takes 81.1 % by mass of the original P 2 O 5 amount, lower than the case of using an acid with P 2 O 5 content of 45% by mass. This shows that the higher concentration of acid is used, the lower DAP productivity is obtained. Therefore, as discussed, the acid content is preferably in the range of 45 - 49% by mass.
- Total amount of the solid waste obtained is 2300 kg, taking 23% by mass of total amount of original concentrated extracted acid solution, wherein P 2 O 5 remained in the waste takesl8.9% by mass of the original P 2 O 5 amount.
- Table 10 Quality criteria of the DAP fertilizer manufactured from the H 3 PO 4 solution after separating suspended sediment according to Table 8
- the DAP obtained can provide an excellent total nutrient content, which is higher than DAP 64% product containing 18% by mass of total N and 46% by mass of P 2 O 5 , as requested by clients.
- Example 3 Treating solid waste from SS obtained in Example 1 into phosphate fertilizer (P 2 O 5 ), NP fertilizer or NPK fertilizer
- Phosphate fertilizer can be manufactured according to the requirement regarding P 2 O 5 content.
- Maximum P 2 O 5 content obtainable with the method according to the present invention corresponds to a mixing ratio of 0.5 parts of calcium sulfate hemihydrate per 1 part of the semi-product after the reduction of residual acid. As such, the maximum P 2 O 5 content will be The amount of calcium sulfate hemihydrate should not be less than 0.5 parts per 1 part of the semi-product because the amount of CaSO* will be insufficient to exchange with other metal salts present in the semi-product. Therefore, when being dissolved in water, metal salts shall be converted into stable phosphates, causing a loss in P 2 O 5 and a difficulty in drying the product.
- the P 2 O 5 content will be less than the minimum content of 16% according to the National Standard TCVN 4440:2018 on single super phosphate fertilizers.
- Total amount of the phosphate fertilizer having the minimum P 2 O 5 content of 16% can be calculated as follows:
- Step 1 Total amount of the semi-product and a half of the calcium sulfate hemihydrate are uniformly mixed in the extruder for 3 - 5 times. With such mixing ratio, the phosphate fertilizer has sufficient humidity for the extruder to operate, and creates a competent medium for exchange reactions.
- Step 2 The remaining calcium sulfate hemihydrate is added and uniformly mixed.
- the calcium sulfate hemihydrate serves as a filler as well as a desiccant. There is no need to dry the obtained phosphate fertilizer.
- step (v) The semi-product obtained from step (v) and ammonium sulfate are uniformly mixed with the mass ratio thereof being 1 : 1.
- Table 13 Quality analysis result of NP fertilizer .
- Example 4 Treating the solid waste from SS obtained in Example 2 into NPK fertilizer
- Example 2300 kg of the solid waste of Example 2 are uniformly mixed wife 345 kg of apatite ore having fee P 2 O 5 content of 32% by mass (equivalent to 15% by mass of fee solid waste) in a screw extruder as shown in Fig. 1, to reduce residual free H 3 PO 4 present in the solid waste.
- Total amount of the NP fertilizer can be calculated as follows:
- Nutrient content in the NPK fertilizer is as follows:
- the NPK fertilizer is obtained with a N:P:K ratio being 11: 13.5 : 5.
- the recovery rate of H 3 PO 4 solution qualified for the DAP manufacture is within the range of 80- 85%, higher than those of 25-40% obtained with the sedimentation method of the prior art.
- the method according to the present invention creates low-quality HaPO 4 (in the waste) only in the range of 15- 20%, much lower than those of 60-75% in the sedimentation method.
- the solid waste after separation filtering is treated into the semi-product which is used as the material for manufacturing phosphate fertilizer (P 2 O 5 ), NP fertilizer or NPK fertilizer.
- phosphate fertilizer P 2 O 5
- NP fertilizer NPK fertilizer
- the semi-product according to the present invention can provide not only NP fertilizer with better quality, but also other high quality products such as phosphate fertilizer and NPK fertilizer. This will bring about value added for fertilizer manufacturing plants.
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Abstract
The invention relates to a method for filtering impurities in concentrated extracted H3PO4 for enhancement of diammonium phosphate (DAP) fertilizer content, and for treatment of post-filtration solid waste into phosphate fertilizer, NP fertilizer or NPK fertilizer comprising: (i) preparing concentrated extracted H3PO4 having a content, with respect to P2O5, in the range of 45-49% by mass and having a temperature in the range of 45 - 100°C; (ii) preparing a solution of coagulant mixture by adding polyacrylamide (PAM), in the form of cation alone or in the form of cation-anion combination, and Na2S to water, wherein the proportion of water : PAM : Na2S per ton of concentrated H3PO4 is (12.5-20 L) : (60-70 g) : (20-50 g), respectively; (iii) adding the solution obtained in step (ii), as a sedimentation aid, to the concentrated H3PO4 solution in step (i) with the proportion of 12.5 -20.0 L per ton of concentrated H3PO4 and regularly stirring, to coagulate and flocculate suspended sediment (SS); and (iv) filtering for solid-liquid separation of the solution obtained from step (iii), clean H3PO4 solution obtained after separation is used for manufacturing DAP, wherein the recovery rate of H3PO4 solution qualified for the DAP manufacture is 80-85% and the SS content in the post-filtration solution is less than 1% by mass.
Description
Method for filtering impurities in concentrated extracted phosphoric acid for enhancement of diammonium phosphate fertilizer content and for treatment of post-filtration solid waste into phosphate fertilizer, NP fertilizer or NPK fertilizer
Technical field
The present invention relates to the field of fertilizer manufacture, particularly a method for filtering impurities in concentrated extracted phosphoric acid (H3PO4) which is used in the manufacture of diammonium phosphate (DAP) fertilizer ((NH4)2HPO4) for enhancement of the fertilizer content, and for treatment of post-filtration solid waste (solid residue) into phosphate fertilizer ( P2O5), nitrogen-phosphorus (NP) fertilizer or nitrogen-phosphorus-potassium (NPK) fertilizer having a maximum amount of effective P2O5 component.
Prior art
DAP fertilizer production technology comprises two stages: manufacturing H3PO4 and manufacturing DAP from the obtained H3PO4. H3PO4 has been manufactured by two methods, namely the thermal method from elemental phosphorus and the wet method by means of processing apatite ore ( Ca3F(PO4)3) with sulfuric acid ( H2SO4) (the dehydrate method), therefore this product is referred to as extracted H3PO4, which is less costly than H3PO4 obtained by the thermal method.
Technical processes for manufacturing extracted H3PO4 are divided into two stages, comprising manufacturing dilute H3PO4 and manufacturing concentrated H3PO4.
The process for manufacturing (extracting) dilute H3PO4 is carried out according to the following reaction:
Ca3F(PO4)3 + 5H2SO4 -> 3H3PO4 + 5CaSO4 + HF
Depending on the ore quality, the ore humidity and the H2SO4 concentration, the solution of extracted H3PO4 generally has a concentration in the range of 25 - 28% by mass with respect to P2O5.
In practice, the apatite ore also contains other metal impurities partly dissolved in newly formed H3PO4, and residual H2SO4, for example:
The remaining metal impurities together with generated metal salts, H2SiF6 and salts CaSiF6, MgSiF6 thereof are considered the impurities existing in solution. Such impurities existing in solution will significantly affect the concentration process as well as the DAP manufacturing process. Particular impurity contents are presented in Table 1 below.
Table 1 : Impurity contents in the solution of extracted H3PO4 before concentration, equivalent to the P2O5 content in the range of 25-28% by mass
Next, dilute H3PO4 solution with a concentration in the range of 25 - 28% by mass is concentrated to a concentration in the range of 45 - 50% by mass, with respect to P2O5, so as to be used in the DAP production technology. However, during the concentration process, such salt systems as CaSO4 - H3PO4 - H2O, MgSiF6 - H3PO4 - H2O, and CaSiF6 - H3PO4 - H2O shall precipitate. In addition, when the P2O5 concentration in the systems increases due to the concentration process, the solubilities of CaSO4, MgSiF6 CaSiF6 as well as other soluble salts such as Fe(H2PO4)3, A1(H2PO4)3, Mn(H2PO4)3, etc., will remarkably be decreased. This means that the more the solution is concentrated, the more precipitates occur (as indicated by an increase in impurity contents in Table 2), causing the acid to thicken.
Table 2: Components in extracted H3PO4 after concentration, equivalent to the P2O5 content in the range of 45%-49%
In the DAP manufacturing stage, when H3PO4 is neutralized to obtain a pH of 3.5 - 5, phosphate salts of iron, aluminium and other heavy metals in one hand form hydroxides, and in the other hand form FePO4, A1PO4, MnPO4, Ca3(PO4)2, etc., which are stable phosphate salts. Being insoluble and losing effective P2O5 amount, and thus not useful for crops, the said salts together with impurities such as CaSO4 MnF2, CaSiF6, will degrade the quality of DAP product, make it unqualified in terms of the N and P2O5 contents.
. Phosphate salts of heavy metals, earth alkaline metals, such as A1PO4, FePO4, Ca3(PO4)2, etc., with pH = 3.5 - 5 are insoluble, thus being unable to be absorbed by crops. Only salt NH4MgPO4 is absorbable to crops.
Such sediments degrade the quality of DAP fertilizer, in other words they cause a degradation in quality of the DAP fertilizer, a slow dissolution and unqualified contents of N and P2O5.
In order to decrease the suspended sediment content, known methods merely use the sedimentation process, however these methods have disadvantages in that the volume of the tank for to-be-concentrated solution is large, the time for the suspended sediment to settle is long and H3PO4 qualified for the DAP manufacture can only be recovered with the rate of 25-40%. Because of the increased content of suspended sediment, in case where remaining H3PO4 is used for manufacturing a fertilizer, quality of the fertilizer will be quite low.
Summary of the invention
It is therefore an objective of the present invention to overcome
disadvantages of the technologies of the prior art, so as to effectively reduce suspended sediment (SS) in concentrated extracted H3PO4 to be less than 1% by mass which is impossible to the known methods, thus recovering a maximum amount of clean H3PO4.
Another objective of the present invention is to treat solid waste from SS after being separated from concentrated H3PO4 solution into phosphate fertilizer (P2O5), nitrogen-phosphorus (NP) fertilizer or nitrogen-phosphorus-potassium (NPK) fertilizer having a maximum amount of effective P2O5 component.
To obtain the said objectives, the present invention relates to:
[1] A method for filtering impurities in concentrated extracted H3PO4 for enhancement of diammonium phosphate (DAP) fertilizer content, comprising:
(1) preparing concentrated extracted H3PO4 having a content, with respect to P2O5, in the range of 45-49% by mass and having a temperature in the range of 45 - 100°C;
(ii) preparing a solution of coagulant mixture by adding polyacrylamide (PAM), in the form of cation alone or in the form of cation-anion combination, and Na2S to water, wherein the proportion of water : PAM : NaiS per ton of concentrated H3PO4 is (12.5-20 L) : (60-70 g) : (20-50 g), respectively;
(iii) adding the solution obtained in step (ii), as a sedimentation aid, to the concentrated H3PO4 solution in step (i) with the proportion of 12.5 - 20.0 L per ton of concentrated H3PO4 and regularly stirring, to coagulate and flocculate suspended sediment (SS); and
(iv) filtering for solid-liquid separation of the solution obtained from step (iii), clean H3PO4 solution obtained after separation is used for manufacturing DAP, wherein the recovery rate of H3PO4 solution qualified for the DAP manufacture is 80-85% and the SS content in the post-filtration solution is less than 1% by mass.
[2]. The method according to [1], further comprising:
(v) reducing residual H3PO4 in the solid waste obtained in step (iv) by adding 8-25% by mass of fine grained apatite ore with particle size of 65-70 μm
and the P2O5 content in the range of 30-42% by mass to total amount of the solid waste, uniformly mixing, and retaining for 24-72 hours, to obtain a semi-product for manufacturing phosphate fertilizer (P2O5), NP fertilizer or NPK fertilizer.
[3]. The method according to [2], further comprising:
(vi) manufacturing phosphate fertilizer (P2O5) by uniformly mixing the semi-product obtained from step (v) with calcium sulfate hydrate, in particular calcium sulfate dihydrate (CaSO4 ZHaO) and/or calcium sulfate hemihydrate (CaSO4.1/2H2O), preferably calcium sulfate hemihydrate, wherein the mass ratio of semi-product : calcium sulfate hydrate is in the range of 1 : 0.5 - 1 : 1.5.
[4]. The method according to [3], wherein the obtained phosphate fertilizer is dried to a desired humidity and fine ground to obtain the finished phosphate fertilizer (P2O5).
[5]. The method according to [2], further comprising:
(vii) manufacturing NP fertilizer by uniformly mixing the semi-product obtained from step (v) with ammonium sulfate - (NBU^SO*, wherein the mass ratio of the semi-product : ammonium sulfate is in the range of 1 : 0.5 - 1 : 2.
[6]. The method according to [5], wherein theNP fertilizer obtained is dried to a desired humidity and fine ground to obtain the finished NP fertilizer.
[7]. The method according to [5] or [6], further comprising:
(viii) manufacturing NPK fertilizer by mixing the NP fertilizer obtained from step (vii) with a proper amount of potassium chloride (KC1), depending on the KaO content requirement for the fertilizer.
[8]. The method according to any one of preceding items, wherein the proportion of water : PAM : Na2S per ton of concentrated H3PO4 is 15 L : 65 g : 30 g.
[9]. The method according to any one of preceding items, wherein the mass ratio of PAM in the anion form : PAM in the cation form is in the range o
[10]. The method according to any one of preceding items, wherein the mass ratio of PAM in the anion form : PAM in the cation form is
Brief description of drawings
Fig.l is a schematic diagram showing a screw extrader used in examples.
Fig.2 shows a blade provided at an extrusion die head.
Fig.3 shows an extrusion die having multiple forming holes.
Detailed description of the invention
Hereinafter, the present invention will be described in detail as to each step and implementation conditions, as well as preferred embodiments thereof.
In an embodiment, the present invention provides a method for filtering impurities in concentrated extracted H3PO4 for enhancement of diammonium phosphate (DAP) fertilizer content comprising:
(i) Preparing concentrated extracted H3PO4 having a content, with respect to P2O5, in the range of 45-49% by mass and having a temperature in the range of 45 - 100°C.
If concentrated H3PO4 has the content with respect to P2O5 of less than 45% by mass, then such metal salts as Fe(H2PO4)3, Al(H2PO4)3, Mn(H2PO4)3, etc., H2S1F6 and its salts CaSiF6, MgSiF6 as generated will be considered impurities which exist in solution and incompletely precipitate, leading to the fact that the DAP fertilizer quality cannot meet the requirements.
If concentrated H3PO4 has the content with respect to P2O5 of more than 49% by mass, said acid shall become thickened, resulting in a low rate of clean acid recovery, and a decrease in the DAP fertilizer productivity.
If the temperature of concentrated H3PO4 is less than 45°C, an increase in the viscosity of concentrated H3PO4 will affect the acid recovery.
If the temperature of concentrated H3PO4 is higher than 100°C, the coagulation and flocculation of suspended sediment in next step (iii) will be affected, and the equipments will be damaged faster.
Preferably, concentrated H3PO4 has a temperature in the range of 45 - 90°C.
More preferably, the method according to the present invention is implemented straight after the concentration process so as to utilize the thermal from the process, lowering energy costs to heat the acid.
(ii) Preparing a solution of coagulant mixture by adding polyacrylamide (PAM), in the form of cation alone or in the form of cation-anion combination, and Na2S to water, wherein the proportion of water : PAM : Na2S per ton of concentrated H3PO4 is (12.5-20 L) : (60-70 g) : (20-50 g), respectively;
If the amount of water is less than 12.5 L per ton of concentrated H3PO4, it will be difficult for PAM to be dissolved, the solution of coagulant mixture will be thick, viscous, difficult for pumping, as a result the quantitative pumping will be inaccurate.
If the amount of water is more than 20 L per ton of concentrated H3PO4, concentrated H3PO4 is diluted, and more energy will be consumed to dry the fertilizer product.
Using PAM in the cation form with negative charge serves to flocculate suspended sediment Preferably, in addition to PAM in the cation form, PAM in the anion form is also used in combination to enhance the ability of binding suspended sediment in concentrated H3PO4. According to an embodiment, the mass ratio of PAM in the anion form: PAM in the cation form is in the range of
If this ratio is less than the ability of coagulating aluminium compounds in concentrated H3PO4 is not high. If this ratio is higher than both PAMs in the anion form and cation form are incompatible with each other, causing a decrease in coagulation effect
If the total amount of PAM per ton of concentrated H3PO4 is less than 60 g, there will be an incompetency in creating bonds with suspended sediment (SS) existing in concentrated H3PO4, resulting in the fact that SS cannot be exhaustively filtered by the solid waste separator.
If the total amount of PAM per ton of concentrated H3PO4 is more than 70 g, there will be a PAM redundancy in the concentrated H3PO4 solution, the acid solution becomes viscous, resulting in an ineffective operation of the solid waste separator.
The Na2S amount of less than 20 g per ton of concentrated H3PO4 will not
be sufficient to enhance the liquidity of the PAM solution for an easy pumping, and will not be sufficient to precipitate cadmium and heavy metals in concentrated H3PO4 into metal sulfides, for example under the following reactions:
If the Na2S amount is more than 50 g per ton of concentrated H3PO4, when mixing the solution of coagulant mixture with concentrated H3PO4, H2S generated according to the following reaction will become redundant, causing air pollution.
Preferably, the proportion of water : PAM : Na2S per ton of concentrated H3PO4is 15 L : 65 g : 30 g.
Preferably, the mass ratio of PAM in the anion form: PAM in the cation form is
(iii) Adding the solution obtained in step (ii), as a sedimentation aid, to the concentrated H3PO4 solution in step (i) with the proportion of 12.5 - 20.0 L per ton of concentrated H3PO4 and regularly stirring, to coagulate and flocculate suspended sediment.
(iv) Filtering for solid-liquid separation of the solution obtained from step (iii), clean H3PO4 solution obtained after separation is used for manufacturing DAP, wherein the recovery rate of H3PO4 solution qualified for the DAP manufacture is 80-85% and the SS content in the post-filtration solution is less than l% by mass.
Solid-liquid separation process can be implemented by a hydraulic press or a filter press. However, the invention is not limited thereto, any method and means for solid-liquid separation known in the art which can separate the solid phase in the form of solid waste from the liquid phase can be used.
According to an embodiment, the method according to the present invention further comprises:
(v) reducing residual H3PO4 in the solid waste obtained in step (iv) by adding 8-25% by mass of apatite ore with particle size of 65-70 μm and the P2O5
content in the range of 30-42% by mass to total amount of the solid waste, uniformly mixing, and retaining for 24-72 hours, to obtain a semi-product for manufacturing phosphate fertilizer (P2O5), NP fertilizer or NPK fertilizer.
If the apatite ore amount is less than 8% by mass, the concentration of residual free H3PO4 in the finished fertilizer is still high, affecting the plant growth.
If the apatite ore amount is more than 25% by mass, the concentration of residual free H3PO4 significantly decreases, but the effective P2O5 content also decreases.
If retention time is shorter than 24 hours, residual H3PO4 cannot completely react with apatite ore.
If retention time is longer than 72 hours, the semi-product will be stiffened, affecting the use in following steps of the manufacturing process because the loosening of the semi-product will be required.
According to an embodiment, the method according to the present invention further comprises:
(vi) manufacturing phosphate fertilizer (P2O5) by uniformly mixing the semi-product obtained from step (v) with calcium sulfate hydrate, in particular calcium sulfate dihydrate (CaSO4.2H2O) and/or calcium sulfate hemihydrate (CaSO4.1/2H2O), preferably calcium sulfate hemihydrate having a mass ratio of the semi-product : calcium sulfate hydrate in the range of 1 : 0.5 - 1 : 1.5.
During the mixing period, metal salts will intensively exchange with acid stronger than H3PO4, releasing less soluble salts such as CaHPO4 and forming hydrated salts, therefore the obtained phosphate fertilizer has a low humidity, which advantageously reduces the energy consumption to dry the finished
phosphate fertilizer. Some reactions occurring in step (v) are as follows: 4
If the content by mass of calcium sulfate hydrate is more than 1.5 parts per 1 part of the semi-product, the P2O5 amount in the product is low.
If the content by mass of calcium sulfate hydrate is less than 0.5 parts per 1 part of the semi-product, the CaSO4 amount will be insufficient to exchange with phosphate metal salts in the solid waste.
With the adjustment of the mass ratio of the semi-product : calcium sulfate hydrate to be within the said range, it is possible to obtain the P2O5 content in the range of 16-30% by mass, which can meet various demands from clients. For example, if it is desired to increase the P2O5 content, the consumed calcium sulfate hydrate should be decreased.
Phosphate fertilizer obtained in this step may be further dried to a desired humidity and fine ground to obtain the finished phosphate fertilizer (P2O5).
According to an embodiment, the method according to the present invention further comprises:
(vii) manufacturing NP fertilizer by uniformly mixing the semi-product obtained from step (v) with ammonium sulfate - (NH4)2SO4 having a mass ratio of the semi-product : ammonium sulfate in the range of 1 : 0.5 - 1 : 2.
During the mixing period, metal salts will intensively exchange with acid stronger than H3PO4, releasing salts such as (NH4)2HPO4 and forming hydrated salts, therefore the obtained NP fertilizer has a low humidity, which advantageously reduces the energy consumption to dry the finished NP fertilizer. Some reactions occurring in step (v) are as follows:
If the content by mass of ammonium sulfate is more than 2 parts per 1 part
of the semi-product, the large amount of ammonium sulfate in the fertilizer will acidify soil.
If the content by mass of ammonium sulfate is less than 0.5 parts per 1 part of the semi-product, the amount of ammonium sulfate will be insufficient to exchange with phosphate metal salt radicals in the solid waste.
The NP fertilizer obtained in this step can be dried to a desired humidity and fine ground to obtain the finished NP fertilizer.
According to an embodiment, the method according to the present invention further comprises:
(viii) manufacturing NPK fertilizer by mixing the NP fertilizer obtained from step (vii) with a proper amount of potassium chloride (KC1), depending on the KzO content requirement for the fertilizer, wherein the NP fertilizer may either be dried and fine ground or not.
Examples
Hereinafter, examples relating to steps of separation filtering of suspended sediment (SS) in concentrated extracted H3PO4, and treating the solid waste from SS into phosphate fertilizer (P2O5), NP fertilizer or NPK fertilizer in the method according to the present invention will be described.
Preparing:
- concentrated extracted H3PO4: 10 tons;
- sedimentation aid: polyacrylamide (PAM) having the chemical formula of CONH2(CH2-CH-)n, including polyacrylamide in the cation form and polyacrylamide in the anion form;
- Na2S;
- a tank for storing concentrated extracted H3PO4 (acid tank) in the form of a circular tank equipped with stirring shaft having a speed in the range of 120 - 300 rpm;
- a tank for preparing coagulant mixture (coagulant mixture tank) in the form of a circular tank equipped with stirring shaft having a speed in the range of 400 - 500 rpm and having a volume equal to about 1/40 of the acid tank volume;
- a solid-liquid separator in the form of a filter press; and
- a screw extruder, as shown in Figs. 1-3, including: motor 1 attached to screw 3 to rotate the same; feeding hopper 2 for feeding materials to screw 3; and extrusion die 5 for shaping extruded product. Preferably, the extruder further comprises cutter 4 adjacent to extrusion die 5.
Tanks and solid-liquid separator are common in the art, thus not necessary to be further described.
Example 1: Separation filtering of suspended sediment (SS) in concentrated extracted H3PO4 having components shown in Table 3 below.
(i) 10 tons of concentrated extracted H3PO4 having a temperature of 50°C are pumped to the acid tank. The acid is taken straight after the concentration process so as to utilize the thermal from the process, lowering energy costs to heat the acid.
(ii) 150 L of water are pumped to the coagulant mixture tank. 600g of PAM in the cation form are weighted and gradually added to the tank while being stirred. After that further 50g of PAM in the anion form are added and stirred until
completely dissolved. Finally, 300g of Na2S are added and stirred until completely dissolved.
(iii) The coagulant mixture is pumped to the acid tank while being stirred at the speed of 150 rpm.
(iv) After 15 minutes of stirring, the solution in the acid tank is pumped to the solid-liquid separator, which is a filter press to filter for separating suspended sediment from the acid solution. The clean H3PO4 solution obtained is subjected to the DAP manufacturing process, while the solid waste is subjected to step (v) to treat the residual acid.
Total amount of the solid waste obtained is 1800 kg. Components in the solid waste are shown in Table 5 below.
Table 5: Components in the solid waste obtained after filtering suspended sediment
It can be seen from Table 3 and Table 4 that the content of SS in the H3PO4 solution is decreased by ten times (from 8.9% to 0.77%), showing a significant separation of impurities which degrade the DAP fertilizer quality.
From Table 3 and Table 5, it is possible to calculate the P2O5 amount obtained in the acid solution for manufacturing DAP to take 85.2% by mass of the original P2O5 amount.
The solid waste is separated with an amount of up to 18% by mass with respect to the total mass of the original concentrated extracted acid solution, wherein the P2O5 amount remaining in the waste takes 14.8% by mass of the original P2O5 amount.
Table 6: Quality criteria of the DAP fertilizer manufactured from the H3PO4 solution after separating suspended sediment according to Table 4
It can be seen from Table 6 that after filtering to remove impurities, the DAP obtained can provide an excellent total nutrient content, which is higher than DAP 64% product containing 18% by mass of total N and 46% by mass of P2O5, as requested by clients.
Example 2: Separation filtering of suspended sediment (SS) in concentrated extracted H3PO4 having components shown in Table 7 below.
Preparation and filtering steps are implemented as in Example 1. Quality of H3PO4 solution after filtering suspended sediment and components in the postfiltration solid waste of Example 2 are shown in Table 8 and Table 9 below.
Table 8: Quality criteria of H3PO4 solution after filtering suspended sediment
It can be seen from Table 7 and Table 8 that the content of SS in the H3PO4 solution is decreased by 40 times (from 12.7% to 0.32%), showing a significant separation of impurities which degrade the DAP fertilizer quality.
From Table 7 and Table 9, with similar calculation as in Example 1, the
amount of recovered effective P2O5 for manufacturing DAP takes 81.1 % by mass of the original P2O5 amount, lower than the case of using an acid with P2O5 content of 45% by mass. This shows that the higher concentration of acid is used, the lower DAP productivity is obtained. Therefore, as discussed, the acid content is preferably in the range of 45 - 49% by mass.
Total amount of the solid waste obtained is 2300 kg, taking 23% by mass of total amount of original concentrated extracted acid solution, wherein P2O5 remained in the waste takesl8.9% by mass of the original P2O5 amount.
Table 10: Quality criteria of the DAP fertilizer manufactured from the H3PO4 solution after separating suspended sediment according to Table 8
It can be seen from Table 10 that after filtering to remove impurities, the DAP obtained can provide an excellent total nutrient content, which is higher than DAP 64% product containing 18% by mass of total N and 46% by mass of P2O5, as requested by clients.
Example 3: Treating solid waste from SS obtained in Example 1 into phosphate fertilizer (P2O5), NP fertilizer or NPK fertilizer
(v) Reducing residual H3PO4 in the solid waste obtained in step (iv) of Example 1.
1800 kg of the solid waste in Example 1 are uniformly mixed with 144 kg of apatite ore having the P2O5 content of 32% by mass (equivalent to 8% by mass of the solid waste) in the screw extruder as shown in Fig.l. For the solid waste and the apatite ore to be uniformly mixed, so that acid can well penetrate into ore grains to completely decompose apatite, the mixture thereof can be allowed to run through the extruder for 2 - 5 times. After mixing, the obtained mixture is retained for 36 hours, providing 1944 kg of a semi-product for manufacturing phosphate fertilizer (P2O5), NP fertilizer or NPK fertilizer. After reducing residual free H3PO4, the P2O5 content in the semi-product decreases and can be calculated as
follows:
1944
(vi) Manufacturing phosphate fertilizer (P2O5) from the semi-product obtained in step (v)
Phosphate fertilizer can be manufactured according to the requirement regarding P2O5 content. Maximum P2O5 content obtainable with the method according to the present invention corresponds to a mixing ratio of 0.5 parts of calcium sulfate hemihydrate per 1 part of the semi-product after the reduction of residual acid. As such, the maximum P2O5 content will be The
amount of calcium sulfate hemihydrate should not be less than 0.5 parts per 1 part of the semi-product because the amount of CaSO* will be insufficient to exchange with other metal salts present in the semi-product. Therefore, when being dissolved in water, metal salts shall be converted into stable phosphates, causing a loss in P2O5 and a difficulty in drying the product. If the amount of calcium sulfate hemihydrate is more than 1.5 parts per 1 part of the semi-product, the P2O5 content will be less than the minimum content of 16% according to the National Standard TCVN 4440:2018 on single super phosphate fertilizers.
• Manufacturing phosphate fertilizer with the maximum P2O5 content of24.4%
Required amount of the calcium sulfate hemihydrate can be calculated as follows: 1944 kg of the semi-product x 0.5 = 972 kg of the calcium sulfate hemihydrate
1944 kg of the semi-product are uniformly mixed with 972 kg of the calcium sulfate hemihydrate in the screw extruder as shown in Fig.1 to provide 2916 kg of finished phosphate fertilizer. For the solid waste of the semi-product and the calcium sulfate hemihydrate to be uniformly mixed, the mixture thereof can be allowed to run through the extruder for 2 - 5 times.
Table 11 : Quality analysis result of the phosphate fertilizer with the maximum P2O5 content of 24.4%
The result shows that the effective P2O5 takes 93% by mass of the total P2O5.
Manufacturing phosphate fertilizer with the minimum P2O5 content of 16%
For manufacturing phosphate fertilizer with the minimum P2O5 content of 16%, total parts by mass of the semi-product + the calcium sulfate hemihydrate after mixing will be — - =2.29 parts. That is to say, in this case, the mass ratio of the semi-product : the calcium sulfate hemihydrate will be 1 : 1.29.
Total amount of the phosphate fertilizer having the minimum P2O5 content of 16% can be calculated as follows:
1944 kg of the semi-product + (1.29 x 1944) kg the calcium sulfate hemihydrate = 4451 kg.
Implementation manner:
Step 1 : Total amount of the semi-product and a half of the calcium sulfate hemihydrate are uniformly mixed in the extruder for 3 - 5 times. With such mixing ratio, the phosphate fertilizer has sufficient humidity for the extruder to operate, and creates a competent medium for exchange reactions.
Step 2: The remaining calcium sulfate hemihydrate is added and uniformly mixed. In this step, the calcium sulfate hemihydrate serves as a filler as well as a desiccant. There is no need to dry the obtained phosphate fertilizer.
The result shows that the effective P2O5 takes 92.5% by mass of the total
P2O5.
(vii) Manufacturing NP fertilizer
The semi-product obtained from step (v) and ammonium sulfate are uniformly mixed with the mass ratio thereof being 1 : 1.
The amount of obtained NP fertilizer can be calculated as follows: 1944 kg of the semi-product + 1944 kg of ammonium sulfete = 3888 kg.
The result shows that fee effective P2O5 takes 94% by mass of fee total P2O5.
Example 4: Treating the solid waste from SS obtained in Example 2 into NPK fertilizer
2300 kg of the solid waste of Example 2 are uniformly mixed wife 345 kg of apatite ore having fee P2O5 content of 32% by mass (equivalent to 15% by mass of fee solid waste) in a screw extruder as shown in Fig. 1, to reduce residual free H3PO4 present in the solid waste.
For fee solid waste and fee apatite ore to be uniformly mixed, so feat acid can well penetrate into ore grains to completely decompose apatite, the mixture thereof can be allowed to run through fee extruder for 2 - 5 times. After mixing, fee obtained mixture is retained for 36 hours, providing 2645 kg of a semiproduct. After reducing residual free H3PO4, fee P2O5 content in the semi-product decreases and can be calculated as follows:
For manufacturing NP fertilizer wife fee minimum P2O5 content of 15%, total parts by mass of the semi-product + ammonium sulfate after mixing will be =2.4 parts. That is to say, in this case, fee mass ratio of the semi-product :
ammonium sulfate will be 1 : 1.4.
Total amount of the NP fertilizer can be calculated as follows:
2645 kg of the semi-product + (1.4 x 2645) kg of ammonium sulfate = 6348 kg.
In 6348 kg of the NP fertilizer:
- N content (from ammonium sulfate) = 12.25%
- P2O5 content = 15%.
The NP fertilizer is dried and mixed with 634 kg of KC1 (i.e., 10% by mass), providing 6348+634 = 6982kg of NPK fertilizer.
Nutrient content in the NPK fertilizer is as follows:
N = 12.25% x 0.9 = 11%
Effective P2O5= 15% x 0.9 = 13.5%
K2O = 634/6982 x 0.62 x 0.9 = 5%
Therefore, according to this Example, the NPK fertilizer is obtained with a N:P:K ratio being 11: 13.5 : 5.
Effects of the present invention
By the method according to the present invention, the recovery rate of H3PO4 solution qualified for the DAP manufacture is within the range of 80- 85%, higher than those of 25-40% obtained with the sedimentation method of the prior art. As such, from the same material which is the post-concentration extracted H3PO4 solution, there is an increase in the DAP productivity because the method according to the present invention creates low-quality HaPO4(in the waste) only in the range of 15- 20%, much lower than those of 60-75% in the sedimentation method.
By using the recovered H3PO4 solution according to the present invention, the quality of DAP fertilizer can meet the minimum standard N=18%, P2O5 - 46% as desired by clients.
By the method according to the present invention, the solid waste after
separation filtering is treated into the semi-product which is used as the material for manufacturing phosphate fertilizer (P2O5), NP fertilizer or NPK fertilizer. In the common DAP manufacturing processes, sediment after the natural sedimentation can be used for manufacturing low-quality NP fertilizer only. However, the semi-product according to the present invention can provide not only NP fertilizer with better quality, but also other high quality products such as phosphate fertilizer and NPK fertilizer. This will bring about value added for fertilizer manufacturing plants.
Claims
1. A method for filtering impurities in concentrated extracted H3PO4 for enhancement of diammonium phosphate (DAP) fertilizer content, comprising:
(i) preparing concentrated extracted H3PO4 having a content, with respect to P2O5, in the range of 45-49% by mass and having a temperature in the range of 45 - 100°C;
(ii) preparing a solution of coagulant mixture by adding polyacrylamide (PAM), in the form of cation alone or in the form of cation-anion combination, and Na2S to water, wherein the proportion of water : PAM : NaiS per ton of concentrated H3PO4 is (12.5-20 L) : (60-70 g) : (20-50 g), respectively;
(iii) adding the solution obtained in step (ii), as a sedimentation aid, to the concentrated H3PO4 solution in step (i) with the proportion of 12.5 - 20.0 L per ton of concentrated H3PO4 and regularly stirring, to coagulate and flocculate suspended sediment (SS); and
(iv) filtering for solid-liquid separation of the solution obtained from step (iii), clean H3PO4 solution obtained after separation is used for manufacturing DAP, wherein the recovery rate of H3PO4 solution qualified for the DAP manufacture is 80-85% and the SS content in the post-filtration solution is less than 1% by mass.
2. The method according to claim 1, further comprising:
(v) reducing residual H3PO4 in the solid waste obtained in step (iv) by adding 8-25% by mass of apatite ore with particle size of 65-70 μm and the P2O5 content in the range of 30-42% by mass to total amount of the solid waste, uniformly mixing, and retaining for 24-72 hours, to treat the solid waste into a semi-product for manufacturing phosphate fertilizer (P2O5), NP fertilizer or NPK fertilizer.
3. The method according to claim 2, further comprising:
(vi) manufacturing phosphate fertilizer (P2O5) by uniformly mixing the semiproduct obtained from step (v) with calcium sulfate hydrate, in particular calcium sulfate dihydrate (CaSO4.2H2O) and/or calcium sulfate hemihydrate
(CaSO4.1/2H2O), preferably calcium sulfate hemihydrate, wherein the mass ratio of semi-product : calcium sulfate hydrate is in the range of 1 : 0.5 - 1 : 1.5.
4. The method according to claim 3, wherein the obtained phosphate fertilizer is dried to a desired humidity and fine ground to obtain the finished phosphate fertilizer (P2O5).
5. The method according to claim 2, further comprising:
(vii) manufacturing NP fertilizer by uniformly mixing the semi-product obtained from step (v) with ammonium sulfate - (NH4)2SO4 having a mass ratio of the semi-product : ammonium sulfate in the range of 1 : 0.5 to 1 : 2.
6. The method according to claim 5, wherein the NP fertilizer obtained is dried to a desired humidity and fine ground to obtain the finished NP fertilizer.
7. The method according to claim 5 or 6, further comprising:
(viii) manufacturing NPK fertilizer by mixing the NP fertilizer obtained from step (vii) with a proper amount of potassium chloride (KC1), depending on the K2O content requirement for the fertilizer.
8. The method according to anyone of preceding claims, wherein the proportion of water: PAM : Na2S per ton of concentrated H3PO4 is 15 L : 65 g : 30 g.
9. The method according to anyone of preceding claims, wherein the mass ratio of PAM in the anion form: PAM in the cation form is in the range of
10. The method according to anyone of preceding claims, wherein the mass ratio of PAM in tiie anion form: PAM in the cation form is
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CN111662098A (en) * | 2020-07-06 | 2020-09-15 | 四川大学 | Monoammonium phosphate suspension fertilizer containing medium trace elements and preparation method thereof |
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JPH0891971A (en) * | 1994-07-29 | 1996-04-09 | Miyama Kk | Manufacture of fertilizer |
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