CN116768172A - Wet-process phosphoric acid suspension crystallization purification process - Google Patents
Wet-process phosphoric acid suspension crystallization purification process Download PDFInfo
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- CN116768172A CN116768172A CN202310580114.7A CN202310580114A CN116768172A CN 116768172 A CN116768172 A CN 116768172A CN 202310580114 A CN202310580114 A CN 202310580114A CN 116768172 A CN116768172 A CN 116768172A
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- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 title claims abstract description 390
- 229910000147 aluminium phosphate Inorganic materials 0.000 title claims abstract description 195
- 239000000725 suspension Substances 0.000 title claims abstract description 84
- 238000002425 crystallisation Methods 0.000 title claims abstract description 83
- 230000008025 crystallization Effects 0.000 title claims abstract description 83
- 238000000034 method Methods 0.000 title claims abstract description 71
- 238000000746 purification Methods 0.000 title claims abstract description 34
- 239000007788 liquid Substances 0.000 claims abstract description 71
- 239000013078 crystal Substances 0.000 claims abstract description 67
- 238000005406 washing Methods 0.000 claims abstract description 66
- 239000012452 mother liquor Substances 0.000 claims abstract description 38
- 238000010438 heat treatment Methods 0.000 claims abstract description 31
- 239000002002 slurry Substances 0.000 claims abstract description 31
- 238000000926 separation method Methods 0.000 claims abstract description 16
- 238000002844 melting Methods 0.000 claims abstract description 15
- 230000008018 melting Effects 0.000 claims abstract description 15
- 238000001816 cooling Methods 0.000 claims description 84
- 238000003756 stirring Methods 0.000 claims description 24
- 239000000047 product Substances 0.000 claims description 13
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 13
- 239000000706 filtrate Substances 0.000 claims description 12
- 238000011084 recovery Methods 0.000 claims description 9
- 239000002699 waste material Substances 0.000 claims description 9
- 239000012535 impurity Substances 0.000 claims description 7
- 229910052742 iron Inorganic materials 0.000 claims description 5
- 229910052801 chlorine Inorganic materials 0.000 claims description 4
- 239000000460 chlorine Substances 0.000 claims description 4
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims description 3
- 229910052731 fluorine Inorganic materials 0.000 claims description 3
- 229910018072 Al 2 O 3 Inorganic materials 0.000 claims description 2
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims description 2
- 229910052708 sodium Inorganic materials 0.000 claims description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims 3
- PXGOKWXKJXAPGV-UHFFFAOYSA-N Fluorine Chemical compound FF PXGOKWXKJXAPGV-UHFFFAOYSA-N 0.000 claims 2
- 229910052785 arsenic Inorganic materials 0.000 claims 2
- 239000011737 fluorine Substances 0.000 claims 2
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 claims 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims 1
- 229910052782 aluminium Inorganic materials 0.000 claims 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims 1
- 150000001450 anions Chemical class 0.000 claims 1
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 claims 1
- 239000011575 calcium Substances 0.000 claims 1
- 229910052791 calcium Inorganic materials 0.000 claims 1
- 150000001768 cations Chemical class 0.000 claims 1
- 239000011777 magnesium Substances 0.000 claims 1
- 229910052749 magnesium Inorganic materials 0.000 claims 1
- 239000011734 sodium Substances 0.000 claims 1
- 230000003068 static effect Effects 0.000 abstract description 5
- 238000000576 coating method Methods 0.000 abstract description 2
- DLYUQMMRRRQYAE-UHFFFAOYSA-N tetraphosphorus decaoxide Chemical compound O1P(O2)(=O)OP3(=O)OP1(=O)OP2(=O)O3 DLYUQMMRRRQYAE-UHFFFAOYSA-N 0.000 description 14
- 238000004537 pulping Methods 0.000 description 9
- 238000007599 discharging Methods 0.000 description 8
- 239000002367 phosphate rock Substances 0.000 description 7
- OJMIONKXNSYLSR-UHFFFAOYSA-N phosphorous acid Chemical compound OP(O)O OJMIONKXNSYLSR-UHFFFAOYSA-N 0.000 description 7
- 238000000605 extraction Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 239000002253 acid Substances 0.000 description 3
- 229910021645 metal ion Inorganic materials 0.000 description 3
- 238000000638 solvent extraction Methods 0.000 description 3
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000007865 diluting Methods 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- -1 iron-magnesium-aluminum Chemical compound 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000009388 chemical precipitation Methods 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 238000005342 ion exchange Methods 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000001953 recrystallisation Methods 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
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- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The application belongs to the technical field of wet phosphoric acid purification, and provides a wet phosphoric acid suspension crystallization purification process, which is used for heating and slurrying industrial grade phosphoric acid; introducing the pulpified phosphoric acid into a suspension crystallizer, and performing suspension crystallization to obtain slurry; carrying out solid-liquid separation on the obtained slurry to obtain phosphoric acid crystals and phosphoric acid mother liquor; the obtained phosphoric acid crystal is washed by the washing liquid and then enters a melting tank, a part of phosphoric acid is cooled and then returns to the solid-liquid separator as the washing liquid, and a part of phosphoric acid is extracted as a phosphoric acid product. The technical scheme of the application can realize high-purity crystallization products in the suspension crystallization process, the temperature and gradient conditions of suspension crystallization are controllable, and the crystallization speed is high. The static crystallization process is not needed again, the crystallization state at different temperatures is needed to be mastered for a long time during static crystallization, and the blade coating process of the bulk crystallization product is avoided.
Description
Technical Field
The application belongs to the technical field of wet-process phosphoric acid purification by a sulfuric acid method, and relates to a purification method for obtaining high-purity food-grade wet-process phosphoric acid.
Background
At present, the basic reserve of phosphorite in China is 32.4 hundred million tons, and it has been ascertained that phosphorite resources are distributed in 27 provinces (autonomous regions), but the distribution is centralized, and the distribution is mainly in five provinces of Hubei, sichuan, guizhou, yunnan and Hunan, the total reserve of phosphorite resources in five provinces exceeds 80%, but with the consumption of phosphorite resources, most of the phosphorite resources exhibit low grade characteristics, and the utilization of low grade phosphorite resources is greatly dependent on the technical level of wet phosphoric acid. The wet phosphoric acid has the characteristics of low-grade phosphorite utilization and low process energy consumption compared with the hot phosphoric acid, but has the inherent defects of high impurity content of phosphoric acid and high purification difficulty.
With the rise of new energy, the demand for high-purity phosphoric acid is increasing, so that the purification of phosphoric acid is particularly urgent. The phosphoric acid purifying method has a plurality of chemical precipitation, solvent extraction, crystallization, ion exchange and the like, and the solvent extraction is taken as a main flow process route in China at present, wherein the extraction process taking Vat Fu as a main flow process can continuously and industrially produce food grade phosphoric acid, and the Sichuan Dai and Hua Shi solvent extraction purifying processes meet the industrial phosphoric acid requirement.
Analysis of the wet phosphoric acid produced by collophanite in the Hubei area shows that the content of the iron-magnesium-aluminum sesquioxide in the acid is high, the MER value (the percentage ratio of the sum of the percentage of the sesquioxide in the phosphoric acid to the percentage of phosphorus pentoxide) is as high as 8 percent, and when dilute phosphoric acid is concentrated, the acid viscosity is high, the energy consumption is high during concentration due to the influence of iron-magnesium-aluminum ions, the acid concentration is difficult, and the subsequent extraction efficiency is greatly improved.
Disclosure of Invention
In order to solve the problems, the main purpose is to provide a wet-process phosphoric acid suspension crystallization purification process aiming at the defects existing in the prior extraction technology. Can effectively remove impurities under the condition of high impurity content of wet-process phosphoric acid to obtain high-purity wet-process purified phosphoric acid. The crystallization degree of the whole process is high.
The wet process phosphoric acid suspension crystallization purification process comprises the following steps:
(1) Heating and slurrying industrial grade phosphoric acid;
(2) Introducing the phosphoric acid pulpified in the step (1) into a suspension crystallizer, and performing suspension crystallization to obtain slurry;
(3) Carrying out solid-liquid separation on the slurry obtained in the step (2) to obtain phosphoric acid crystals and phosphoric acid mother liquor;
(4) And (3) washing the phosphoric acid crystals obtained in the step (3) by using a washing liquid, then feeding the washing liquid into a melting tank, cooling a part of phosphoric acid, returning the cooled phosphoric acid to a solid-liquid separator as the washing liquid, and extracting a part of phosphoric acid as a phosphoric acid product.
The industrial grade phosphoric acid is concentrated phosphoric acid with phosphorus pentoxide content of 30-63%, and is subjected to gradual cooling crystallization, wherein the crystallization level is 2-4, so as to obtain high-purity phosphoric acid crystals and mother liquor.
Washing the obtained phosphoric acid crystals with low-temperature desalted water, and centrifugally filtering to obtain the high-purity phosphoric acid crystals with the phosphorus pentoxide content of 61.5-70%.
And (3) diluting the high-purity phosphoric acid crystal with the phosphorus pentoxide content of 70% or above obtained in the step 2 of the post-purification working procedure by desalted water to obtain food-grade phosphoric acid with the phosphorus pentoxide content of 55% or diluting to obtain food-grade phosphoric acid with the phosphorus pentoxide content of 61.5%.
And returning the mother liquor obtained in the post-purification step to the extraction step.
The application has the beneficial effects that
According to the application, phosphoric acid with different quality can be produced by post-purification according to the process requirement, meanwhile, the dependence on materials can be reduced by a low-temperature crystallization process scheme, and the requirements can be met by common domestic 316L or 2205.
The technical scheme of the application can realize high-purity crystallization products in the suspension crystallization process, the temperature and gradient conditions of suspension crystallization are controllable, and the crystallization speed is high. The static crystallization process is not needed again, the crystallization state at different temperatures is needed to be mastered for a long time during static crystallization, and the blade coating process of the bulk crystallization product is avoided.
Drawings
FIG. 1 is a flow chart of a wet process phosphoric acid suspension crystallization purification process.
Detailed Description
For a better understanding of the present application, the following examples are set forth to further illustrate the application.
A wet-process phosphoric acid suspension crystallization purification process comprises the following steps:
(1) Heating and slurrying industrial grade phosphoric acid;
(2) Introducing the phosphoric acid pulpified in the step (1) into a suspension crystallizer, and performing suspension crystallization to obtain slurry;
(3) Carrying out solid-liquid separation on the slurry obtained in the step (2) to obtain phosphoric acid crystals and phosphoric acid mother liquor;
(4) And (3) washing the phosphoric acid crystals obtained in the step (3) by using a washing liquid, then feeding the washing liquid into a melting tank, cooling a part of phosphoric acid, returning the cooled phosphoric acid to a solid-liquid separator as the washing liquid, and extracting a part of phosphoric acid as a phosphoric acid product.
In technical grade phosphoric acid with P 2 O 5 The phosphorus pentoxide content is 30-63%, wherein the impurities include Fe, mg, al, na, ca, as, F, and Cl sulfate, and F content is 0.5-0.6% - 0.2 to 0.4 percent of chlorine and 0.3 to 0.5 percent of SO 4 2- 0.5 to 0.6 percent of Fe 2 O 3 2.5-3.5% of Al 2 O 3 0.3 to 0.4 percent of Na 2 O, 0.3-0.4% CaO, 2.0-3.5% MgO, 10-50ppm As.
In the technical scheme of the application, industrial grade crude phosphoric acid is used as a raw material, so that the industrial preparation method of phosphoric acid with higher requirements on food grade specification is realized.
In the step (1), the temperature of the slurry is increased to 30-35 ℃, and the slurry is stirred at 100-150r/min in the process of cooling the slurry.
In the technical scheme of the application, the phosphoric acid is cooled and pulped, and the phosphoric acid is stirred to form a uniformly mixed state in the process of reducing the temperature to 30-35 ℃.
Furthermore, the temperature rise and slurrying are carried out at a temperature lower than 50 ℃ in the domestic 316L or 2205 material setting, so that metal ions in the stainless steel material can be effectively shielded, such as components of Fe, cr, ni and the like, are prevented from immersing into phosphoric acid again, and the temperature rise condition is an essential means of the application.
In the present application, fe, mg, al, as, ca, na is exemplified, and the metal ion concentration in the obtained phosphoric acid is less than 20ppm, and further less than 10ppm. The total metal ion content is less than 100ppm, preferably less than 50ppm, preferably less than 10ppm.
Cooling the pulpified phosphoric acid to 25-30 ℃ in the step (2), and then introducing the pulpified phosphoric acid into a suspension crystallizer, wherein the suspension crystallization process adopts gradient cooling to 1-10 ℃ and the gradient cooling stage number is 2-6, and is equal gradient and/or non-equal gradient cooling; in the preferred scheme, the gradient cooling stage number is 2-4, and the aim is to realize the principle of saving cost and control the cooling crystallization scheme as few as possible.
In some specific embodiments, the gradient cooling stage number is 2, the temperature of the pulpified phosphoric acid is reduced to 25 ℃ and then reduced to (10-15) +/-0.5 ℃ at 0.1-2.0 ℃/min, and the temperature is kept for 1-20min;
then cooling to (1-5) +/-0.5 ℃ at 0.1-2.0 ℃/min, and preserving heat for 1-10min.
Or in other embodiments, the gradient cooling stage number is 3, the temperature of the pulpified phosphoric acid is reduced to 25 ℃ and then reduced to (15-20) +/-0.5 ℃ at 0.1-2.0 ℃/min, and the temperature is kept for 1-20min;
then cooling to (10-15) +/-0.5 ℃ at 0.1-2.0 ℃/min, and preserving heat for 1-20min;
then cooling to (1-5) +/-0.5 ℃ at 0.1-1.0 ℃/min, and preserving heat for 1-10min.
Or in other embodiments, the gradient cooling stage number is 4, the temperature of the pulpified phosphoric acid is reduced to 25 ℃ and then reduced to 15-20+/-0.5 ℃ at 0.1-2.0 ℃/min, and the temperature is kept for 1-20min;
then cooling to (10-15) +/-0.5 ℃ at 0.1-2.0 ℃/min, and preserving heat for 1-20min;
then cooling to (5-10) +/-0.5 ℃ at 0.1-1.0 ℃/min, and preserving heat for 1-20min;
then cooling to (1-5) +/-0.5 ℃ at 0.1-1.0 ℃/min, and preserving heat for 1-10min.
The stirring speed in the crystallization process carried out by gradient cooling of the suspension crystallizer in the step (2) is 10-100r/min, more preferably 10-60r/min, and still more preferably 10-50r/min.
In the step (2), the stirring speed is 10r/min, 20r/min, 30r/min, 40r/min and 50r/min in the crystallization process by gradient cooling of the suspension crystallizer.
In the application, after the pulping process, the obtained high-purity phosphoric acid is subjected to gradient or non-gradient cooling in a suspension crystallizer under the stirring condition, phosphoric acid crystal particles are suspended in the mother liquor and slowly grow in the mother liquor, and lamellar and blocky phosphoric acid crystal blocks are not formed under the stirring condition as in a static crystallization mode, but a large amount of fine crystal slurry is formed in the suspension mother liquor. During the gradual decrease in temperature, the crystals in the suspension slowly stabilize and form dense crystalline particles, removing impurity components.
The suspension crystallization equipment comprises a stirring and solid-liquid separation device, and the product from the suspension crystallization equipment is directly subjected to solid-liquid separation to separate the obtained fine crystal product from mother liquor.
The gradient cooling stage number of the application is 2-4, which can be carried out in one suspension crystallization device or in a plurality of suspension crystallization devices.
Gradually cooling down in a suspension crystallizer. The process of crystallization in a plurality of suspension crystallization devices means that the crystallization is carried out by cooling at a certain temperature in one device, then the crystallization is carried out by transferring the crystallization into another device and cooling the crystallization relative to the previous device, and the like.
In the experiments carried out, it was found that the finer grains formed were larger after the multistage crystallization process. If the gradient cooling stage number is 4, the granularity is 800-1250 μm; when the gradient cooling stage number is 3, the granularity is 500-850 μm; when the gradient cooling stage number is 2, the granularity is 350-550 μm. The larger the granularity is, the easier the solid-liquid separation is performed in the washing process, and the crystallization product is reduced to enter the phosphoric acid mother liquor.
And (3) sending the phosphoric acid mother liquor obtained by separation in the step (3) into a cyclone for fine crystal recovery, sending the recovered fine crystals into the step (1) for heating and slurrying, and discharging the fine crystal mother liquor as waste liquid.
The recovered low-temperature high-concentration fine crystals are supplemented to the step (1) for heating and slurrying, and the solubility of the crystals is higher in the heating and slurrying process due to smaller granularity of the fine crystals, so that supersaturated solution of liquid phase is easier to form in the solution in the step (1), and crystallization in a suspension crystallizer is facilitated after slurrying.
And (3) washing the obtained crystals in the step (4) by using low-temperature desalted water as a washing liquid, and returning filtrate in the washing process to the suspension crystallizer in the step (2).
In some embodiments, the temperature of the low temperature desalted water is 5-10 ℃, which is less different from the direct temperature of the obtained crystals, further reducing the problem of recrystallization. The obtained washing filtrate is directly added into the suspension crystallizer at low temperature, which is helpful for reducing the temperature of phosphoric acid after pulping and reducing the heat loss.
In the step (4), the temperature is increased to 30-35 ℃ in a melting tank for heating and melting, 5-20% of phosphoric acid solution by weight is cooled and then is returned to a solid-liquid separator as another washing solution, and 85-95% of phosphoric acid by weight is extracted as a product.
In the application, the concentration of the high-purity high-concentration phosphoric acid solution reaches 83-85%.
The product with the concentration is returned to solid-liquid separation in a mass fraction of 5-20%, and is mixed with the formed crystallization slurry, so that the purity of the crystallization product in the slurry is increased again, and the stability of the crystallization product is realized.
Example 1
A wet-process phosphoric acid suspension crystallization purification process comprises the following steps:
(1) Heating the technical grade phosphoric acid to 30-35 ℃, and pulping and mixing uniformly under 150r/min stirring;
(2) Cooling the pulpified phosphoric acid in the step (1) to 25-28 ℃, introducing the cooled phosphoric acid into a suspension crystallizer, and carrying out suspension crystallization at the stirring speed of 50r/min to obtain pulp, wherein the built-in material is domestic 316L.
The gradient cooling stage number is 3, the temperature of the pulpified phosphoric acid is reduced to 25 ℃, then the temperature is reduced to 20+/-0.5 ℃ at 1.0 ℃/min, and the temperature is kept for 5min;
then cooling to 15+/-0.5 ℃ at the speed of 1.0 ℃/min, and preserving heat for 10min;
then cooling to 5+/-0.5 ℃ at 0.3 ℃/min, and preserving heat for 15min.
(3) Carrying out solid-liquid separation on the slurry obtained in the step (2) to obtain phosphoric acid crystals and phosphoric acid mother liquor;
and (3) sending the separated phosphoric acid mother liquor into a cyclone to carry out fine crystal recovery, sending the recovered fine crystal into the step (1) to carry out heating slurrying, and discharging the fine crystal mother liquor as waste liquid.
(4) Washing the phosphoric acid crystals obtained in the step (3) by using low-temperature desalted water as a washing liquid, and returning filtrate in the washing process to the suspension crystallizer in the step (2); washing with washing liquid, heating to 30-35deg.C in a melting tank, cooling to obtain 10% phosphoric acid, and returning to solid-liquid separator as washing liquid, wherein 90% phosphoric acid is extracted.
Example 2
The wet-process phosphoric acid suspension crystallization purification process using the physicochemical properties of the wet-process phosphoric acid as in example 1 comprises the following steps:
(1) Heating the technical grade phosphoric acid to 35-50 ℃, and pulping under 150r/min stirring;
(2) Cooling the pulpified phosphoric acid in the step (1) to 25-30 ℃, introducing the cooled phosphoric acid into a suspension crystallizer, and carrying out suspension crystallization at a stirring speed of 30r/min to obtain slurry;
the gradient cooling stage number is 4, the temperature of the pulpified phosphoric acid is reduced to 25 ℃, then the temperature is reduced to 20 ℃ at 1.0 ℃/min, and the temperature is kept for 10min;
then cooling to 15+/-0.5 ℃ at a speed of 1.0 ℃/min, and preserving heat for 8min;
then cooling to 10+/-0.5 ℃ at 0.5 ℃/min, and preserving heat for 6min;
then cooling to 1+/-0.5 ℃ at 0.5 ℃/min, and preserving heat for 4min.
(3) Carrying out solid-liquid separation on the slurry obtained in the step (2) to obtain phosphoric acid crystals and phosphoric acid mother liquor;
and (3) sending the separated phosphoric acid mother liquor into a cyclone to carry out fine crystal recovery, sending the recovered fine crystal into the step (1) to carry out heating slurrying, and discharging the fine crystal mother liquor as waste liquid.
(4) Washing the phosphoric acid crystals obtained in the step (3) by using low-temperature desalted water as a washing liquid, and returning filtrate in the washing process to the suspension crystallizer in the step (2); washing with washing liquid, heating to 30-35deg.C in a melting tank, cooling to obtain 10 wt% phosphoric acid, and returning to solid-liquid separator as washing liquid, wherein 90 wt% phosphoric acid is extracted.
Example 3
The wet-process phosphoric acid suspension crystallization purification process using the physicochemical properties of the wet-process phosphoric acid as in example 1 comprises the following steps:
(1) Heating the technical grade phosphoric acid to 35-50 ℃, and pulping under 150r/min stirring;
(2) Cooling the pulpified phosphoric acid in the step (1) to 25-30 ℃, introducing the cooled phosphoric acid into a suspension crystallizer, and carrying out suspension crystallization at a stirring speed of 50r/min to obtain slurry;
the gradient cooling stage number is 3, only the pulpified phosphoric acid is cooled to 25 ℃ and then cooled to 20+/-0.5 ℃ at 0.5 ℃/min, and the temperature is kept for 5min;
then cooling to 10+/-0.5 ℃ at 0.5 ℃/min, and preserving heat for 5min;
then cooling to 1+/-0.5 ℃ at 0.5 ℃/min, and preserving heat for 5min.
(3) Carrying out solid-liquid separation on the slurry obtained in the step (2) to obtain phosphoric acid crystals and phosphoric acid mother liquor;
and (3) sending the separated phosphoric acid mother liquor into a cyclone to carry out fine crystal recovery, sending the recovered fine crystal into the step (1) to carry out heating slurrying, and discharging the fine crystal mother liquor as waste liquid.
(4) Washing the phosphoric acid crystals obtained in the step (3) by using low-temperature desalted water as a washing liquid, and returning filtrate in the washing process to the suspension crystallizer in the step (2); washing with washing liquid, heating to 30-35deg.C in a melting tank, cooling to obtain 10 wt% phosphoric acid, and returning to solid-liquid separator as washing liquid, wherein 90 wt% phosphoric acid is extracted.
Example 4
The wet-process phosphoric acid suspension crystallization purification process using the physicochemical properties of the wet-process phosphoric acid as in example 1 comprises the following steps:
(1) Heating the technical grade phosphoric acid to 35-50 ℃, and pulping under 150r/min stirring;
(2) Cooling the pulpified phosphoric acid in the step (1) to 25-30 ℃, introducing the cooled phosphoric acid into a suspension crystallizer, and carrying out suspension crystallization at a stirring speed of 50r/min to obtain slurry;
the gradient cooling stage number is 3, only the pulpified phosphoric acid is cooled to 25 ℃ and then cooled to 20+/-0.5 ℃ at 2.5 ℃/min, and the temperature is kept for 5min;
then cooling to 10+/-0.5 ℃ at 2.5 ℃/min, and preserving heat for 5min;
then cooling to 1+/-0.5 ℃ at 2.5 ℃/min, and preserving heat for 5min.
(3) Carrying out solid-liquid separation on the slurry obtained in the step (2) to obtain phosphoric acid crystals and phosphoric acid mother liquor;
and (3) sending the separated phosphoric acid mother liquor into a cyclone to carry out fine crystal recovery, sending the recovered fine crystal into the step (1) to carry out heating slurrying, and discharging the fine crystal mother liquor as waste liquid.
(4) Washing the phosphoric acid crystals obtained in the step (3) by using low-temperature desalted water as a washing liquid, and returning filtrate in the washing process to the suspension crystallizer in the step (2); washing with washing liquid, heating to 30-35deg.C in a melting tank, cooling to obtain 10 wt% phosphoric acid, and returning to solid-liquid separator as washing liquid, wherein 90 wt% phosphoric acid is extracted.
Example 5
The wet-process phosphoric acid suspension crystallization purification process using the physicochemical properties of the wet-process phosphoric acid as in example 1 comprises the following steps:
(1) Heating the technical grade phosphoric acid to 35-50 ℃, and pulping under 150r/min stirring;
(2) Cooling the pulpified phosphoric acid in the step (1) to 25-30 ℃, introducing the cooled phosphoric acid into a suspension crystallizer, and carrying out suspension crystallization at a stirring speed of 50r/min to obtain slurry;
the gradient cooling stage number is 3, only the pulpified phosphoric acid is cooled to 25 ℃ and then cooled to 20+/-0.5 ℃ at 0.5 ℃/min, and the temperature is kept for 5min;
then cooling to 10+/-0.5 ℃ at 2.5 ℃/min, and preserving heat for 5min;
then cooling to 1+/-0.5 ℃ at 2.5 ℃/min, and preserving heat for 5min.
(3) Carrying out solid-liquid separation on the slurry obtained in the step (2) to obtain phosphoric acid crystals and phosphoric acid mother liquor;
and (3) sending the separated phosphoric acid mother liquor into a cyclone to carry out fine crystal recovery, sending the recovered fine crystal into the step (1) to carry out heating slurrying, and discharging the fine crystal mother liquor as waste liquid.
(4) Washing the phosphoric acid crystals obtained in the step (3) by using low-temperature desalted water as a washing liquid, and returning filtrate in the washing process to the suspension crystallizer in the step (2); washing with washing liquid, heating to 30-35deg.C in a melting tank, cooling to obtain 10 wt% phosphoric acid, and returning to solid-liquid separator as washing liquid, wherein 90 wt% phosphoric acid is extracted.
Example 6
The wet-process phosphoric acid suspension crystallization purification process using the physicochemical properties of the wet-process phosphoric acid as in example 1 comprises the following steps:
(1) Heating the technical grade phosphoric acid to 35-50 ℃, and pulping under 150r/min stirring;
(2) Cooling the pulpified phosphoric acid in the step (1) to 25-30 ℃, introducing the cooled phosphoric acid into a suspension crystallizer, and carrying out suspension crystallization at a stirring speed of 50r/min to obtain slurry;
the gradient cooling stage number is 3, the temperature of the pulpified phosphoric acid is reduced to 25 ℃ and then reduced to 22+/-0.5 ℃ at 0.5 ℃ per minute, and the temperature is kept for 5 minutes;
then cooling to 20+/-0.5 ℃ at 0.5 ℃/min, and preserving heat for 5min;
then cooling to 1+/-0.5 ℃ at 0.5 ℃/min, and preserving heat for 5min.
(3) Carrying out solid-liquid separation on the slurry obtained in the step (2) to obtain phosphoric acid crystals and phosphoric acid mother liquor;
and (3) sending the separated phosphoric acid mother liquor into a cyclone to carry out fine crystal recovery, sending the recovered fine crystal into the step (1) to carry out heating slurrying, and discharging the fine crystal mother liquor as waste liquid.
(4) Washing the phosphoric acid crystals obtained in the step (3) by using low-temperature desalted water as a washing liquid, and returning filtrate in the washing process to the suspension crystallizer in the step (2); washing with washing liquid, heating to 30-35deg.C in a melting tank, cooling to obtain 10 wt% phosphoric acid, and returning to solid-liquid separator as washing liquid, wherein 90 wt% phosphoric acid is extracted.
Example 7
The wet-process phosphoric acid suspension crystallization purification process using the physicochemical properties of the wet-process phosphoric acid as in example 1 comprises the following steps:
(1) Heating the technical grade phosphoric acid to 35-50 ℃, and pulping under 150r/min stirring;
(2) Cooling the pulpified phosphoric acid in the step (1) to 25-30 ℃, introducing the cooled phosphoric acid into a suspension crystallizer, and carrying out suspension crystallization at a stirring speed of 20r/min to obtain slurry;
the gradient cooling stage number is 2, the temperature of the pulpified phosphoric acid is reduced to 25 ℃, then reduced to 15+/-0.5 ℃ at 1.0 ℃/min, and the temperature is kept for 10min;
then cooling to 1+/-0.5 ℃ at 1.0 ℃/min, and preserving heat for 10min.
(3) Carrying out solid-liquid separation on the slurry obtained in the step (2) to obtain phosphoric acid crystals and phosphoric acid mother liquor;
and (3) sending the separated phosphoric acid mother liquor into a cyclone to carry out fine crystal recovery, sending the recovered fine crystal into the step (1) to carry out heating slurrying, and discharging the fine crystal mother liquor as waste liquid.
(4) Washing the phosphoric acid crystals obtained in the step (3) by using low-temperature desalted water as a washing liquid, and returning filtrate in the washing process to the suspension crystallizer in the step (2); washing with washing liquid, heating to 30-35deg.C in a melting tank, cooling to obtain 10 wt% phosphoric acid, and returning to solid-liquid separator as washing liquid, wherein 90 wt% phosphoric acid is extracted.
Example 8
The method and procedure were the same as in example 1, except that the stirring speed was 80r/min.
Example 9
The method and procedure were the same as in example 1, except that the stirring speed was 120r/min.
Example 10
The method and the steps are the same as in example 1, only the recovered fine-grain mother liquor is sent to the suspension crystallization in step (2), and meanwhile, the washed filtrate is supplemented to step (1) for heating and slurrying.
Example 11
The method and the steps are the same as in the example 1, only the washed filtrate and the recovered fine crystal mother liquor are fully supplemented into the suspension crystallizer of the step (2), and the slurry is obtained by stirring. And (3) heating the mixture to 30-35 ℃ in a melting tank to completely extract the phosphoric acid which is heated and melted.
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Claims (14)
1. The wet process phosphoric acid suspension crystallization purification process is characterized by comprising the following steps of:
(1) Heating and slurrying industrial grade phosphoric acid;
(2) Introducing the phosphoric acid pulpified in the step (1) into a suspension crystallizer, and performing suspension crystallization to obtain slurry;
(3) Carrying out solid-liquid separation on the slurry obtained in the step (2) to obtain phosphoric acid crystals and phosphoric acid mother liquor;
(4) And (3) washing the phosphoric acid crystals obtained in the step (3) by using a washing liquid, then feeding the washing liquid into a melting tank, cooling a part of phosphoric acid, returning the cooled phosphoric acid to a solid-liquid separator as the washing liquid, and extracting a part of phosphoric acid as a phosphoric acid product.
2. According to claim 1The wet process phosphoric acid suspension crystallization purification process is characterized in that P is adopted in industrial grade phosphoric acid 2 O 5 The content of the impurities is 30-63%, wherein the impurities comprise iron, magnesium, aluminum, sodium, calcium, arsenic, fluorine, chlorine and sulfate, the content of fluorine is 0.5-0.6%, the content of chlorine is 0.2-0.4%, and the content of SO 4 2- 0.3-0.5%、Fe 2 O 3 0.5-0.6%、Al 2 O 3 2.5-3.5%、NaO 0.3-0.4%、CaO 0.3-0.4%、MgO 2.0-3.5%、As 10-50ppm。
3. The wet process phosphoric acid suspension crystallization purification process according to claim 1, wherein the temperature of the slurry in the step (1) is increased to 30-35 ℃, and the slurry is stirred at 100-150r/min during the temperature reduction.
4. The wet-process phosphoric acid suspension crystallization purification process according to claim 1, wherein a seed crystal is further added in the cooling and slurrying process in the step (1), wherein the seed crystal is phosphoric acid with the mass concentration of 80-85%, the total anion content is lower than 10ppm, and the total cation content is lower than 10ppm.
5. The wet-process phosphoric acid suspension crystallization purification process according to claim 1, wherein in the step (2), the pulpified phosphoric acid is cooled to 25-30 ℃ and then is introduced into a suspension crystallizer, the suspension crystallization process adopts gradient cooling to 1-10 ℃, the gradient cooling stage number is 2-6, and the gradient cooling is equal gradient and/or non-equal gradient cooling.
6. The wet-process phosphoric acid suspension crystallization purification process according to claim 5, wherein in the step (2), the pulpified phosphoric acid is cooled to 25-30 ℃ and then is introduced into a suspension crystallizer, the suspension crystallization process adopts gradient cooling to 1-5 ℃, the gradient cooling stage number is 2-4, and the gradient cooling is equal gradient and/or non-equal gradient cooling.
7. The wet process phosphoric acid suspension crystallization purification process according to claim 6, wherein the gradient cooling stage number is 2, the slurried phosphoric acid is cooled to 25 ℃ and then cooled to (10-15) ± 0.5 ℃ at 0.1-2.0 ℃/min, and the temperature is kept for 1-20min;
then cooling to (1-5) +/-0.5 ℃ at 0.1-2.0 ℃/min, and preserving heat for 1-10min.
8. The wet process phosphoric acid suspension crystallization purification process according to claim 6, wherein the gradient cooling stage number is 3, the slurried phosphoric acid is cooled to 25 ℃ and then cooled to (15-20) ± 0.5 ℃ at 0.1-2.0 ℃/min, and the temperature is kept for 1-20min;
then cooling to (10-15) +/-0.5 ℃ at 0.1-2.0 ℃/min, and preserving heat for 1-20min;
then cooling to (1-5) +/-0.5 ℃ at 0.1-1.0 ℃/min, and preserving heat for 1-10min.
9. The wet process phosphoric acid suspension crystallization purification process according to claim 6, wherein the gradient cooling stage number is 4, the slurried phosphoric acid is cooled to 25 ℃ and then cooled to (15-20) ± 0.5 ℃ at 0.1-2.0 ℃/min, and the temperature is kept for 1-20min;
then cooling to (10-15) +/-0.5 ℃ at 0.1-2.0 ℃/min, and preserving heat for 1-20min;
then cooling to (5-10) +/-0.5 ℃ at 0.1-1.0 ℃/min, and preserving heat for 1-20min;
then cooling to (1-5) +/-0.5 ℃ at 0.1-1.0 ℃/min, and preserving heat for 1-10min.
10. The process according to claim 5, wherein the stirring speed of the suspension crystallizer in the step (2) is 10-100r/min, more preferably 10-60r/min, still more preferably 10-50r/min.
11. The wet process phosphoric acid suspension crystallization purification process according to claim 10, wherein the stirring speed in the crystallization process carried out by gradient cooling of the suspension crystallizer in the step (2) is 10r/min, 20r/min, 30r/min, 40r/min and 50r/min.
12. The wet process phosphoric acid suspension crystallization purification process according to claim 1, wherein the phosphoric acid mother liquor separated in the step (3) is sent to a cyclone for fine crystal recovery, the recovered fine crystals are sent to the step (1) for temperature rise and slurry, and the fine crystal mother liquor is discharged as waste liquid.
13. The wet process phosphoric acid suspension crystallization purification process according to claim 1, wherein the obtained crystals in step (4) are washed by using low temperature desalted water as a washing liquid, and the temperature of the low temperature desalted water is controlled to be 2-10 ℃; the filtrate from the washing process is returned to the suspension crystallizer of step (2).
14. The process according to claim 1, wherein in the step (4), the temperature is raised to 30 to 35 ℃ in the melting tank to heat and melt, and the phosphoric acid solution of 5 to 20% by weight is cooled and returned to the solid-liquid separator as another washing solution, and the phosphoric acid of 80 to 95% by weight is extracted as a product.
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