EP4259575A1 - Integrated method for the decadmiation of phosphoric acid - Google Patents
Integrated method for the decadmiation of phosphoric acidInfo
- Publication number
- EP4259575A1 EP4259575A1 EP21830526.6A EP21830526A EP4259575A1 EP 4259575 A1 EP4259575 A1 EP 4259575A1 EP 21830526 A EP21830526 A EP 21830526A EP 4259575 A1 EP4259575 A1 EP 4259575A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- phosphoric acid
- cadmium
- content
- sludge
- anhydrite
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 title claims abstract description 246
- 229910000147 aluminium phosphate Inorganic materials 0.000 title claims abstract description 123
- 238000000034 method Methods 0.000 title claims abstract description 73
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical compound [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 claims abstract description 82
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 claims abstract description 76
- 229910052793 cadmium Inorganic materials 0.000 claims abstract description 75
- 239000010802 sludge Substances 0.000 claims abstract description 54
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims abstract description 51
- 229910052925 anhydrite Inorganic materials 0.000 claims abstract description 35
- 229910019142 PO4 Inorganic materials 0.000 claims abstract description 33
- 239000010452 phosphate Substances 0.000 claims abstract description 32
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims abstract description 32
- 239000000203 mixture Substances 0.000 claims abstract description 17
- 230000003750 conditioning effect Effects 0.000 claims abstract description 16
- PASHVRUKOFIRIK-UHFFFAOYSA-L calcium sulfate dihydrate Chemical compound O.O.[Ca+2].[O-]S([O-])(=O)=O PASHVRUKOFIRIK-UHFFFAOYSA-L 0.000 claims abstract description 14
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims abstract description 13
- 230000001143 conditioned effect Effects 0.000 claims abstract description 13
- 229910021653 sulphate ion Inorganic materials 0.000 claims abstract description 13
- 238000004064 recycling Methods 0.000 claims abstract description 11
- 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 abstract description 10
- 238000001953 recrystallisation Methods 0.000 claims abstract description 5
- 239000007787 solid Substances 0.000 claims description 32
- 238000006243 chemical reaction Methods 0.000 claims description 8
- 238000010908 decantation Methods 0.000 claims description 6
- 238000002156 mixing Methods 0.000 claims description 4
- 238000005352 clarification Methods 0.000 claims description 3
- 238000010964 desupersaturation Methods 0.000 claims description 3
- 229910000331 cadmium sulfate Inorganic materials 0.000 claims 1
- DLYUQMMRRRQYAE-UHFFFAOYSA-N tetraphosphorus decaoxide Chemical compound O1P(O2)(=O)OP3(=O)OP1(=O)OP2(=O)O3 DLYUQMMRRRQYAE-UHFFFAOYSA-N 0.000 abstract description 8
- 239000001117 sulphuric acid Substances 0.000 abstract 4
- 235000011149 sulphuric acid Nutrition 0.000 abstract 4
- 238000005530 etching Methods 0.000 abstract 2
- 235000021317 phosphate Nutrition 0.000 description 26
- 235000011132 calcium sulphate Nutrition 0.000 description 23
- 239000001175 calcium sulphate Substances 0.000 description 23
- 239000000243 solution Substances 0.000 description 21
- 239000002253 acid Substances 0.000 description 16
- 238000001914 filtration Methods 0.000 description 14
- 238000004519 manufacturing process Methods 0.000 description 12
- 238000002288 cocrystallisation Methods 0.000 description 8
- 239000013078 crystal Substances 0.000 description 7
- 239000000047 product Substances 0.000 description 7
- 238000011282 treatment Methods 0.000 description 7
- 239000003337 fertilizer Substances 0.000 description 6
- 150000004683 dihydrates Chemical group 0.000 description 5
- 239000002367 phosphate rock Substances 0.000 description 5
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 5
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 4
- 239000011575 calcium Substances 0.000 description 4
- 239000012535 impurity Substances 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- 239000002002 slurry Substances 0.000 description 3
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 2
- 229910052936 alkali metal sulfate Inorganic materials 0.000 description 2
- 229910052791 calcium Inorganic materials 0.000 description 2
- YYRMJZQKEFZXMX-UHFFFAOYSA-N calcium;phosphoric acid Chemical compound [Ca+2].OP(O)(O)=O.OP(O)(O)=O YYRMJZQKEFZXMX-UHFFFAOYSA-N 0.000 description 2
- 235000019838 diammonium phosphate Nutrition 0.000 description 2
- 238000000605 extraction Methods 0.000 description 2
- 239000000706 filtrate Substances 0.000 description 2
- 235000013305 food Nutrition 0.000 description 2
- 238000009434 installation Methods 0.000 description 2
- -1 phosphates ions Chemical class 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 239000002426 superphosphate Substances 0.000 description 2
- 239000005696 Diammonium phosphate Substances 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- LFVGISIMTYGQHF-UHFFFAOYSA-N ammonium dihydrogen phosphate Chemical compound [NH4+].OP(O)([O-])=O LFVGISIMTYGQHF-UHFFFAOYSA-N 0.000 description 1
- 229910000387 ammonium dihydrogen phosphate Inorganic materials 0.000 description 1
- 239000008346 aqueous phase Substances 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 235000013361 beverage Nutrition 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 239000001506 calcium phosphate Substances 0.000 description 1
- 229910000389 calcium phosphate Inorganic materials 0.000 description 1
- 235000011010 calcium phosphates Nutrition 0.000 description 1
- 238000005119 centrifugation Methods 0.000 description 1
- 238000004040 coloring Methods 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- MNNHAPBLZZVQHP-UHFFFAOYSA-N diammonium hydrogen phosphate Chemical compound [NH4+].[NH4+].OP([O-])([O-])=O MNNHAPBLZZVQHP-UHFFFAOYSA-N 0.000 description 1
- 229910000388 diammonium phosphate Inorganic materials 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000008030 elimination Effects 0.000 description 1
- 238000003379 elimination reaction Methods 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229910001385 heavy metal Inorganic materials 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 239000013067 intermediate product Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000004377 microelectronic Methods 0.000 description 1
- 235000019837 monoammonium phosphate Nutrition 0.000 description 1
- 239000006012 monoammonium phosphate Substances 0.000 description 1
- 230000020477 pH reduction Effects 0.000 description 1
- 239000000825 pharmaceutical preparation Substances 0.000 description 1
- 229940127557 pharmaceutical product Drugs 0.000 description 1
- CBMSICGVCDVFQL-UHFFFAOYSA-N phosphonitrate Chemical compound [O-][N+](=O)OP(=O)=O CBMSICGVCDVFQL-UHFFFAOYSA-N 0.000 description 1
- 150000003013 phosphoric acid derivatives Chemical class 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 238000007712 rapid solidification Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 239000011435 rock Substances 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 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 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- 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
- C01B25/237—Selective elimination of impurities
- C01B25/238—Cationic impurities, e.g. arsenic compounds
-
- 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
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
Definitions
- the present invention relates to an integrated process for decadmiation of phosphoric acid by co-crystallization of cadmium in the crystal lattice of calcium sulphate anhydrite.
- Phosphoric acid (H 3 PO 4 ) is an essential product in the manufacture of fertilizers, in particular ternary NPK fertilizers, or binary NP fertilizers, as well as triple superphosphate (TSP).
- Phosphoric acid after purification is also used in the manufacture of food products, in particular for the acidification of beverages, or for the treatment of metal surfaces, in the field of microelectronics or in the pharmaceutical field.
- Phosphate rocks are important sources of raw material for the production of phosphoric acid.
- Phosphoric acid can be produced mainly by two methods: wet process and thermal process.
- the wet process is the most used and the phosphoric acid from this route can be used to produce phosphate fertilizers (DAP or diammonium phosphate, MAP or monoammonium phosphate, TSP or triple superphosphate).
- the acid obtained by thermal process is of higher purity and is generally used for pharmaceutical products or food products.
- phosphoric acid is produced in particular by the action of a strong acid on natural phosphate ore.
- Sulfuric acid is the most commonly used strong acid.
- insoluble calcium sulphate is formed which is separated by filtration to recover said insoluble calcium sulphate.
- the operating conditions are chosen in order to precipitate the calcium sulphate either in its dihydrate form (phosphogypsum), producing phosphorus pentoxide P 2 O 5 generally at a concentration of 26-32% at 70-80°C, or in its hemihydrate form, with P 2 O 5 generally at a concentration of 40-52% at 90-110°C. Evaporation can be used to further concentrate the phosphoric acid later on and thus optimize its quality.
- Cadmium is one of the elements that have experienced strong restrictions at content limits in phosphate and in derivative products. Indeed, during the manufacture of phosphoric acid by the wet process using sulfuric acid, the impurities originating from the phosphate rock are distributed between phosphoric acid and calcium sulphate.
- the European Union is preparing to set up a low cadmium content label applicable to products whose cadmium content is lower at 20 mg/kg P 2 O 5 .
- the document FR2687657 describes a process for decadmiation of a phosphoric acid solution based on an adjustment of the solid content and sulfuric acid in an evaporator reactor operating at a temperature ranging from 84 ° C to 92 ° vs. This adjustment is made for a solid content between 1.3 and 6% in order to have an excess of free calcium sulphate between 1.5 and 6%, this making it possible to have a phosphoric acid with a lower Cd content. at 10ppm.
- the document WO2014027348 describes a process for the manufacture of phosphoric acid with a reduced content of cadmium and calcium sulphate, which process comprises the steps which consist in mixing crude phosphoric acid, having a P 2 O 5 concentration situated between 45 and 55% and containing up to 50 ppm of cadmium, with concentrated sulfuric acid, in order to obtain a calcium sulphate concentration of 4 to 12%; adding 5 to 15% natural phosphate rock to the mixture, so as to obtain phosphoric acid and suspended particles of calcium sulphate; then filtering said particles at a temperature of at least 80°C.
- WO2008113403 describes a process for treating cadmium-bearing solids comprising calcium sulphate anhydrite and/or hemihydrate having a cadmium content, characterized in that it comprises an extraction of cadmium from said cadmium-bearing solids by bringing them into contact with a aqueous solution of alkali metal sulphate, and a solid/liquid separation between a solid phase based on calcium sulphate dihydrate with a depleted cadmium content with respect to said cadmium content of the calcium sulphate anhydrite and/or hemihydrate and an aqueous phase containing alkali metal sulphate and cadmium in solution.
- Document EP0253454 describes a process for removing cadmium from phosphoric acid, based on the co-crystallization of cadmium in calcium sulphate anhydrite. This process, specially designed for the hemihydrate and phosphonitric acid processes, only seems to apply to low-concentration acids (44% P 2 O 5 by weight) and at temperatures ranging from 90 to 110°C. In addition, this process uses a solid content of 10%, for an acid at 44% P 2 O 5 by weight. Decadmiation takes place in the presence of a significant sulfuric excess of 8% (for a 44% P 2 O 5 acid), which requires desulphation after decadmiation. The desulphation is carried out by adding phosphate under conditions which have not been indicated. However, this process generates a discharge of cadmium-containing sludge that is bulky and not very concentrated, which is subsequently filtered and leads to losses of P 2 O 5 .
- the document WO1991000244 describes a process allowing the elimination of cadmium by co-crystallization of a precipitate based on calcium, cadmium, sulphates and phosphates ions.
- This process uses concentrated acid 50-60% P 2 O 5 , in the presence of a sulfuric excess of 1 to 7% and at high temperature (120°C).
- the calcium is introduced in a soluble form obtained by attacking the phosphate with concentrated phosphoric acid at 120°C.
- this process in addition to the complication generated by the multitude of reactors used, requires a very high temperature in a phosphosulphuric medium, which would require the use of noble and consequently expensive materials.
- the problem of managing decadmium sludge by filtration remains a weak point of the process with respect to operability and P 2 O 5 losses.
- Document MA23803 describes a process for the production of decadmium phosphoric acid by co-crystallization of cadmium with calcium sulphate. Decadmiation takes place on the acid at the outlet of the concentration stage, at the temperature of this acid.
- the decadmiation conditions consist of the introduction into the concentrated acid (45-60% P 2 O 5 ) of calcium sulphate in hemihydrate or dihydrate form at a solid rate varying between 0.5 and 10% and readjusting the sulfuric acid level phosphoric content between 60 and 120 g/L.
- the temperature can vary between that of the acid at the outlet of the concentration stage and 50°C. Desulphation takes place in the presence of phosphate.
- the decadmiation sludge and this desulphation can be recycled to the attack tank, to the calcium sulphate filter, or can be separated by conventional separation methods such as decantation, filtration and/or centrifugation with a view to their processing or storage.
- this process does not provide an operational and economical solution for the management of cadmium-containing sludge by recycling to the attack tank or to the calcium sulphate filter.
- An object of the invention is to propose an integrated process for decadmiation of phosphoric acid making it possible to overcome the drawbacks described above.
- the invention proposes an integrated process for decadmiation of phosphoric acid by co-crystallization of cadmium in the crystal lattice of calcium sulphate anhydrite, making it possible, compared to the processes of the state of the art, to minimize the losses of P 2 O 5 , to obtain a very high decadmiation yield and a high P 2 O 5 concentration of the decadmiated phosphoric acid at the end of the process.
- the invention proposes an integrated process for the decadmiation of phosphoric acid, comprising the following steps:
- the decadmiation process is incorporated into a phosphoric acid and fertilizer production line, in the sense that the transfers of flows (phosphate, phosphoric acid, sulfuric acid, water, steam, sludge, etc.) are operated and managed as part of a single transformation chain.
- the decadmiation process, object of the present invention is an integral part of the manufacturing chain of phosphoric acid and fertilizers.
- the decadmiation of phosphoric acid is carried out at a temperature between 50 and 120°C, preferably above 70°;
- the decadmiation of the phosphoric acid is carried out at a pressure of between 10 4 and 10 5 Pa;
- the step of conditioning the cadmium-rich anhydrite sludge comprises adjusting the cadmium content, the P 2 O 5 content, the solid content, the temperature and/or the viscosity of said sludge;
- the cadmium-rich anhydrite sludge has a temperature of between 40 and 60°C, preferably equal to 50°C, and a solids content of between 5 and 25%, preferably equal at 10%;
- the phosphoric acid solution has a mass content of less than 30% in P 2 O 5 , preferably less than 20% in P 2 O 5 , and more preferably less than 10% in P 2 O 5 ;
- said phosphoric acid solution (AP d ) is at a temperature greater than or equal to 40°C, preferably greater than 50°C , and more preferably above 60°C;
- the conditioned sludge has a temperature of between 40 and 80° C., preferably equal to 47° C., and a solid content of between 5 and 20% by weight, preferably equal to 10%;
- the conditioned sludge is introduced into the reactor for attacking the phosphate with sulfuric acid;
- the conditioned sludge is filtered with calcium sulphate dihydrate or hemihydrate obtained by the attack reaction of phosphate with phosphoric acid.
- FIG. 1 is a diagram illustrating the main steps of the acid decadmiation process phosphoric according to the invention.
- the invention relates to an integrated process for decadmiation of phosphoric acid by co-crystallization of cadmium in the crystal lattice of calcium sulphate anhydrite, making it possible, compared to the processes of the state of the art, to minimize the losses of P 2 O 5 , to obtain a very high decadmiation yield and a high P 2 O 5 concentration of the decadmiated phosphoric acid at the end of the process.
- a solution of phosphoric acid is prepared containing cadmium and insoluble calcium sulphate, which can be dihydrate or hemihydrate, according to the process for the production of phosphoric acid .
- sulfuric acid is reacted with rock phosphate ore.
- sulfuric acid (AS) is reacted in a first reactor with phosphate ore (Ph).
- phosphate ore Preferably, it is natural phosphate ore.
- Reaction (a) is as follows, and leads to the formation of phosphoric acid H 3 PO 4 and phosphogypsum CaSO 4 (H 2 O) 2 and hydrofluoric acid HF:
- a step of concentrating the phosphoric acid obtained, referenced 2 in FIG. 1, is carried out so that the titer by weight of the phosphoric acid is between 42% and 61% in P 2 O 5 , preferably between 48% and 61% in P 2 O 5 .
- This concentration step is integrated into the decadmiation process. This makes it possible to avoid having recourse to an evaporator reactor, thus reducing the cost of the process.
- Phosphoric acid possibly decanted, has a solid content of less than 6% by weight, or even less than 4% by weight relative to the weight of the phosphoric acid solution.
- SA sulfuric acid
- Ph phosphate ore
- Reaction (b) is as follows, and leads to the formation of phosphoric acid H 3 PO 4 and calcium sulphate hemihydrate CaSO 4 % (H 2 O) and hydrofluoric acid HF:
- the acid can be treated as it is, which has a title by weight of phosphoric acid between 40% and 50%, or a step of concentration of the phosphoric acid obtained is carried out, so that the title by weight of the phosphoric acid is between 50% and 61% in P2O5.
- Phosphoric acid possibly decanted, has a solid content of less than 6% by weight, or even less than 4% by weight relative to the weight of the phosphoric acid solution.
- the concentration step is typically carried out at a temperature between 70 and 80°C.
- the phosphoric acid (PA) is then readjusted by adding sulfuric acid (AS), in order to have a rate of free sulphate between 1.5% and 10% in weight, preferably between 2.5% and 9% by weight, in the mixture obtained.
- AS sulfuric acid
- Decadmiation can take place in a single reactor, or even several. Decadmiation is carried out at a temperature between 50 and 120°C, preferably above 70°C in order to allow the formation of anhydrite, that is to say anhydrous calcium sulphate CaSO 4 , by recrystallization of the calcium sulfate dihydrate and hemihydrate.
- the phosphoric acid obtained in the concentration step has a certain sulphate content, the consumption of sulfuric acid can be minimized during the decadmiation process.
- the desulphation of the decadmium phosphoric acid solution takes place in the presence of phosphate.
- the amount of phosphate to add depends on its CaO content and the sulphate content that you want to achieve.
- the phosphate is introduced into the phosphoric solution to have a solid content of between 1 and 15% by weight, preferably 7% by weight, and a sulphate content of between 1% and 5% by weight, preferably 3% by weight.
- the process allows decadmiation and desulphation simultaneously or separately. Indeed, it takes advantage of the difference that exists between the kinetics of decadmiation and desulphation. Decadmiation and desulphation can take place in a single reactor, which greatly simplifies the process.
- Steps 5 and 6 in Figure 1 correspond respectively to the desupersaturation and clarification by decantation of the mixture of decadmium phosphoric acid and cadmium-rich anhydrite sludge, in order to separate the final phosphoric acid (P L1 ) having a cadmium content less than 10 ppm, or even less than 2 ppm following the co-crystallization of cadmium in anhydrite crystals, and cadmium-rich sludges (P S1 ) consisting mainly of anhydrite crystals.
- P L1 final phosphoric acid
- P S1 cadmium-rich sludges
- Decadmiation is carried out at atmospheric pressure, that is to say a pressure of 1 atmosphere or 760 mmHg (10 5 Pa), or even at a negative pressure of up to 80 mmHg (10 4 Pa).
- the liquid phase P Li represents the final phosphoric acid with a low cadmium content resulting from the integrated process of decadmiation. It is recovered and may possibly undergo other subsequent treatments.
- Sludges rich in cadmium (P S i) having a temperature of between 40 and 60° C., preferably of the order of 50° C., a solid content of between 5 and 25%, preferably of the order of 10%, undergo a conditioning treatment, stage 7 in FIG. 1, by mixing with a solution of dilute phosphoric acid (AP d ) having a P 2 O 5 titer less than or equal to 61% in P 2 O 5 .
- a dilute phosphoric acid solution is used whose mass titer is less than 30% in P 2 O 5 , preferably less than 20% in P 2 O 5 , and more preferably less than 10% in P 2 O 5 .
- the temperature of the dilute phosphoric acid solution (AP d ) is above 40°C, preferably above 50°C, and more preferably above 60°C.
- the conditioning treatment of cadmium-rich sludge consists of adjusting the composition of the cadmium-rich sludge in terms of cadmium content, P 2 O 5 content, solid content, temperature and viscosity.
- the conditioned sludge thus obtained (P S 2) having a temperature of between 40 and 80° C., preferably of the order of 47° C., and a solid content of between 5 and 20% by weight, preferably of around 10%, are recycled in the phosphate attack step (step 1 in figure 1), where they are introduced into the attack reactor, or filtered at the level of the filtration operation, directly mixed with the slurry of calcium sulphate dihydrate or hemihydrate obtained during the phosphate attack reaction,
- This sludge conditioning treatment mode is an integrated technical solution for the management of cadmium-rich sludge, which makes it possible to minimize P 2 O 5 losses, reduce the investment and footprint of the installation, as well as increase the P 2 O 5 titer at the level of the phosphoric acid preparation step, and the P 2 O 5 yield of the integrated decadmiation process.
- the sludge conditioning treatment mode therefore solves all the cadmium-containing sludge management problems presented in previous patents, namely the losses of P 2 O 5 during the filtration of the sludge (yield of P 2 O 5 ), the investment in filtration, footprint of the installation, management of the solid anhydrite cake rich in cadmium after filtration of the sludge, known for its rapid solidification and its great hardness, which poses evacuation difficulties.
- the integrated decadmiation process according to the invention makes it possible to have a P 2 O 5 yield greater than 99% following the conditioning and recycling treatment of the conditioned sludge.
- the cadmium content in the phosphoric acid is 8 mgCd/KgP 2 O 5 with a solid content of 0.5% and a sulphate content of 1%.
- the sludge after conditioning is recycled in the phosphate attack.
- the P 2 O 5 yield of the integrated decadmiation process is 99.5%.
- the cadmium content in the phosphoric acid is 3 mgCd/KgP 2 O 5 with a solid content of 0.5% and a sulphate content of 1%.
- the sludge after conditioning is recycled in the phosphate attack.
- the P 2 O 5 yield of the integrated decadmiation process is 99%.
- Cadmium-rich sludge characterized by a temperature of 53°C, a P 2 O 5 title of 44%, a solid content of 20%, a sulphate content of 0.8% and a cadmium content of 85 ppm , are conditioned by mixing with dilute phosphoric acid according to a ratio of 35 parts of phosphoric acid to one part of sludge (35/1 m/m), the phosphoric acid is fed at a temperature of 65°C, a P 2 O 5 titer of 28%, a solids content of 5%, a sulphate content of 2% and a cadmium content of 12 ppm.
- the sludge thus conditioned is characterized by a temperature of 47° C., a solid content of 6% by weight and a cadmium content of 56 ppm. They are then recycled to the phosphate attack reactor.
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
- Treatment Of Sludge (AREA)
- Saccharide Compounds (AREA)
- Fertilizers (AREA)
Abstract
Description
Claims
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR2012986A FR3117476B1 (en) | 2020-12-10 | 2020-12-10 | INTEGRATED PHOSPHORIC ACID DECADMIATION PROCESS |
PCT/MA2021/050020 WO2022124875A1 (en) | 2020-12-10 | 2021-12-10 | Integrated method for the decadmiation of phosphoric acid |
Publications (1)
Publication Number | Publication Date |
---|---|
EP4259575A1 true EP4259575A1 (en) | 2023-10-18 |
Family
ID=74347394
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP21830526.6A Pending EP4259575A1 (en) | 2020-12-10 | 2021-12-10 | Integrated method for the decadmiation of phosphoric acid |
Country Status (7)
Country | Link |
---|---|
EP (1) | EP4259575A1 (en) |
CN (1) | CN116745238A (en) |
AU (1) | AU2021398517A1 (en) |
CA (1) | CA3202025A1 (en) |
FR (1) | FR3117476B1 (en) |
MX (1) | MX2023006955A (en) |
WO (1) | WO2022124875A1 (en) |
Family Cites Families (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
NL8601846A (en) | 1986-07-15 | 1988-02-01 | Stamicarbon | METHOD FOR REMOVING HEAVY METALS FROM ACID PHOSPHATE-CONTAINING AQUEOUS MEDIA. |
FR2649391B1 (en) | 1989-07-04 | 1991-10-31 | Pierre Becker | PROCESS FOR TREATING PHOSPHORIC ACID TO ELIMINATE SOME HEAVY METALS |
TNSN92119A1 (en) | 1992-02-07 | 1993-06-08 | Ct D Etudes Et De Rech S Des Phosphates Mineraux Cerphos | PROCESS FOR THE MANUFACTURE OF VERY LOW CADMIUM PHOSPHORIC ACID |
PL2132347T3 (en) | 2007-03-06 | 2011-12-30 | Centre Detudes Et De Rech Des Phosphates Mineraux | Method for processing cadmiferous solids |
WO2014027348A1 (en) | 2012-08-16 | 2014-02-20 | Rotem Amfert Negev Ltd. | Process for manufacturing phosphoric acid with lowered cadmium content |
-
2020
- 2020-12-10 FR FR2012986A patent/FR3117476B1/en active Active
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2021
- 2021-12-10 AU AU2021398517A patent/AU2021398517A1/en active Pending
- 2021-12-10 WO PCT/MA2021/050020 patent/WO2022124875A1/en active Application Filing
- 2021-12-10 EP EP21830526.6A patent/EP4259575A1/en active Pending
- 2021-12-10 MX MX2023006955A patent/MX2023006955A/en unknown
- 2021-12-10 CA CA3202025A patent/CA3202025A1/en active Pending
- 2021-12-10 CN CN202180092654.XA patent/CN116745238A/en active Pending
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FR3117476A1 (en) | 2022-06-17 |
CN116745238A (en) | 2023-09-12 |
CA3202025A1 (en) | 2022-06-16 |
FR3117476B1 (en) | 2023-04-21 |
AU2021398517A1 (en) | 2023-07-27 |
MX2023006955A (en) | 2023-09-28 |
WO2022124875A1 (en) | 2022-06-16 |
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