CN112194109B - Method for producing phosphoric acid and coproducing gypsum by semi-water-dihydrate wet-process phosphoric acid process - Google Patents
Method for producing phosphoric acid and coproducing gypsum by semi-water-dihydrate wet-process phosphoric acid process Download PDFInfo
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- CN112194109B CN112194109B CN202011064979.0A CN202011064979A CN112194109B CN 112194109 B CN112194109 B CN 112194109B CN 202011064979 A CN202011064979 A CN 202011064979A CN 112194109 B CN112194109 B CN 112194109B
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- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B25/00—Phosphorus; Compounds thereof
- C01B25/16—Oxyacids of phosphorus; Salts thereof
- C01B25/18—Phosphoric acid
- C01B25/22—Preparation by reacting phosphate-containing material with an acid, e.g. wet process
- C01B25/222—Preparation by reacting phosphate-containing material with an acid, e.g. wet process with sulfuric acid, a mixture of acids mainly consisting of sulfuric acid or a mixture of compounds forming it in situ, e.g. a mixture of sulfur dioxide, water and oxygen
- C01B25/228—Preparation by reacting phosphate-containing material with an acid, e.g. wet process with sulfuric acid, a mixture of acids mainly consisting of sulfuric acid or a mixture of compounds forming it in situ, e.g. a mixture of sulfur dioxide, water and oxygen one form of calcium sulfate being formed and then converted to another form
- C01B25/229—Hemihydrate-dihydrate process
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Abstract
The invention relates to the technical field of phosphorus chemical industry, in particular to a method for producing phosphoric acid and gypsum by a semi-water-dihydrate wet-process phosphoric acid process, which specifically comprises the following steps: dehydrating the phosphate rock slurry by using a ceramic filter; adding an acid solution into the dehydrated phosphate ore slurry for premixing to obtain a first slurry; adding sulfuric acid into the first slurry for dissolving, and controlling the mass concentration of sulfate radicals to be 0.1-0.5% to obtain second slurry; adding sulfuric acid into the second slurry for crystallization, and controlling the mass concentration of sulfate radicals to be 1.8-2.5% to obtain third slurry; carrying out vacuum cooling on the third slurry, then filtering, and collecting to obtain semi-hydrated gypsum, first filtrate and finished phosphoric acid; and adding sulfuric acid into the semi-hydrated gypsum for conversion, controlling the mass concentration of sulfate radicals to be 7-11% to obtain a fourth slurry, filtering the fourth slurry, and collecting to obtain dihydrate gypsum and a second filtrate.
Description
Technical Field
The invention relates to the technical field of phosphatization chemical industry, in particular to a method for producing phosphoric acid and co-producing gypsum by a semi-water-dihydrate wet-process phosphoric acid process.
Background
At present, in the phosphorus chemical industry of China, the production method of wet-process phosphoric acid mainly adopts a dihydrate wet-process phosphoric acid process route which takes phosphorite and sulfuric acid as main raw materials, namely, wet-process dilute phosphoric acid with the concentration of phosphorus pentoxide of 8-33 percent is produced by the reaction of the sulfuric acid and the phosphorite, namely, the extraction of the phosphorite, and then filtration and washing are carried out, and phosphogypsum with calcium sulfate dihydrate as a main component is produced as a byproduct. The process route has the defects of high cost consumption and low yield.
Disclosure of Invention
In view of the above, the invention provides a method for producing phosphoric acid and gypsum by a semi-water-dihydrate wet-process phosphoric acid process, which reduces the production cost consumption and improves the yield.
The invention provides a method for producing phosphoric acid and gypsum by a semi-water-dihydrate wet-process phosphoric acid process, which comprises the following steps:
s1, dehydrating the phosphorite slurry by using a ceramic filter;
s2, adding the dehydrated phosphate rock slurry into a premixing tank to be premixed with an acid solution to obtain a first slurry;
s3, adding the first slurry into a dissolving tank, adding sulfuric acid, dissolving at 93-98 ℃, and controlling the mass concentration of sulfate radicals in the dissolving tank to be 0.1-0.5% and the mass concentration of calcium oxide to be 1-2% to obtain a second slurry; the excessive calcium oxide quantity is large, the reaction rate is reduced, the phosphorite decomposition rate is influenced, the pseudo-decomposed phosphorite is increased, and the load of the device is influenced; the excessive amount of calcium oxide is small, namely the supersaturation degree of calcium oxide is not enough, so that the reaction speed is too high, the number of generated crystal nuclei is too large, the crystals are fine, and stable hemihydrate gypsum cannot be generated in serious cases; the lower sulfate radical content and the proper calcium oxide content in the dissolving tank are favorable for generating stable hemihydrate gypsum crystals;
s4, adding the second slurry into a crystallization tank, then adding sulfuric acid to crystallize at 95-98 ℃, and controlling the mass concentration of sulfate radicals in the crystallization tank to be 1.8-2.5% to obtain a third slurry; the content of sulfate radicals in the crystallization tank is high, which is beneficial to further decomposing phosphorite and eliminating supersaturation, and the crystal generated in the dissolution tank further grows in the crystallization tank to obtain thick, uniform and stable semi-water crystal which is easy to filter and wash;
s5, carrying out vacuum cooling on the third slurry, then filtering, and collecting to obtain semi-hydrated gypsum, first filtrate and finished phosphoric acid;
s6, adding the semi-hydrated gypsum and sulfuric acid into a conversion tank for conversion at the temperature of 60-70 ℃, controlling the mass concentration of sulfate radicals in the conversion tank to be 7-11% to obtain a fourth slurry, filtering the fourth slurry, and collecting the dihydrate gypsum and a second filtrate; the low temperature of 60-70 ℃ is beneficial to the conversion of the hemihydrate gypsum, and the sulfate radical content of 7-11% is beneficial to improving the conversion rate of phosphorus.
Further, in step S1, the phosphorus ore slurry used contains phosphorus pentoxide in an amount of 30% or more, magnesium oxide in an amount of 0.8% or less, and acid-insoluble substances (insoluble SiO)2And dispersible argillaceous) is less than or equal to 16 percent.
If P in the phosphorite slurry2O5Low grade and impurityThe mass content is too high, more sulfuric acid can be consumed, the gypsum crystallization is poor, the filtering performance is poor, the long-period operation of production is influenced, the phosphorite slurry with the phosphorus pentoxide mass content being more than or equal to 30% can be selected to reduce the consumption of the sulfuric acid, and the coarse, neat and easily-filtered gypsum crystal can be obtained.
The main component of the acid insoluble substance is insoluble SiO2And the dispersive argillaceous substance does not participate in the reaction (can not be decomposed by sulfuric acid) in the extraction process, and the dispersivity argillaceous substance mixed in the slurry can increase the viscosity of the slurry, reduce the polymerization speed of crystal nuclei, make gypsum crystals fine, easily block filter cloth during filtering, influence filtering and washing, and finally cause the reduction of phosphorus yield, so that the quality content of acid insoluble substances is required to be ensured to be less than or equal to 16%.
Further, in step S1, the phosphorite slurry is dehydrated until the water content is less than or equal to 15%; when the phosphorite pulp with low water content is adopted for production, the washing water consumption of the semi-hydrated gypsum and the dihydrate gypsum can be greatly reduced.
Further, the acid solution used in step S2 is derived from the first filtrate and the second filtrate; the concentration of the phosphorus pentoxide in the first filtrate is low, and the impurity content is high, so that the first filtrate can be used as return acid.
Further, in step S5, cooling the third slurry to 80-85 ℃ under a pressure of 11-13 Kpa; the pressure condition of the filtration is 40-50 Kpa.
Further, in step S5, the mass concentration of phosphorus pentoxide in the finished phosphoric acid is 38-45%.
In the above method, the general chemical reaction equation of the semi-water reaction is:
Ca5F(PO4)3+5H2SO4＝＝＝5CaSO4·1/2H2O+3H3PO4+HF↑；
the chemical reaction equation of the dihydrate conversion process is as follows:
CaSO4·1/2H2O+3/2H2O＝＝＝CaSO4·2H2O
3/2H2O+CaHPO4·1/2H2O+H2SO4＝＝＝CaSO4·2H2O+H3PO4
the technical scheme provided by the invention has the beneficial effects that: the method provided by the invention firstly dehydrates the phosphorite slurry to reduce the water content of the phosphorite slurry, thereby reducing the washing water consumption of the subsequent semi-hydrated gypsum and the dihydrate gypsum; the method provided by the invention uses P2O5The high-grade phosphorite pulp is beneficial to reducing the consumption of sulfuric acid and ensuring that thick, tidy and easily filtered and washed gypsum crystals are obtained; the method provided by the invention strictly controls the temperature and the sulfate radical content in the dissolving and crystallizing processes, so that the generated hemihydrate gypsum crystal is stable and easy to filter, and further, the separation of phosphoric acid solution and solid gypsum is facilitated.
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FIG. 1 is a schematic flow diagram of a method for producing phosphoric acid and co-producing gypsum by a semi-water-dihydrate wet-process phosphoric acid process.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be further described with reference to the accompanying drawings.
Referring to fig. 1, an embodiment of the present invention provides a method for producing phosphoric acid and gypsum by a semi-hydrated-dihydrate wet-process phosphoric acid process, including the following steps:
step S1, selecting phosphate ore pulp with the mass content of phosphorus pentoxide being more than or equal to 30%, the mass content of magnesium oxide being less than or equal to 0.8% and the mass content of acid insoluble substances being less than or equal to 16%, and dehydrating the phosphate ore pulp by using a ceramic filter until the water content is less than or equal to 15%;
step S2, adding the dehydrated phosphate rock slurry into a premixing tank to be premixed with an acid solution to obtain a first slurry;
step S3, adding the first slurry into a dissolving tank, then adding sulfuric acid to dissolve at 93-98 ℃, and controlling the mass concentration of sulfate radical in the dissolving tank to be 0.1-0.5% and the mass concentration of calcium oxide to be 1-2% to obtain a second slurry;
s4, adding the second slurry into a crystallization tank, then adding sulfuric acid to crystallize at 95-98 ℃, and controlling the mass concentration of sulfate radicals in the crystallization tank to be 1.8-2.5% to obtain a third slurry;
s5, cooling the third slurry to 80-85 ℃ under the pressure condition of 11-13Kpa, then filtering under the condition of 40-50Kpa, and collecting to obtain semi-hydrated gypsum, first filtrate and finished phosphoric acid with the mass concentration of phosphorus pentoxide of 38-45%; the impurity content in the filtrate discharged firstly during filtration is high, the concentration of phosphorus pentoxide is lower, the filtrate is marked as first filtrate, and the first filtrate can be used as acid return;
s6, adding the semi-hydrated gypsum and the sulfuric acid into a conversion tank for conversion at the temperature of 60-70 ℃, controlling the mass concentration of sulfate radicals in the conversion tank to be 7-11% to obtain a fourth slurry, filtering the fourth slurry, and collecting the dihydrate gypsum and a second filtrate.
The method provided by the present invention will be described in detail with reference to examples.
Example 1:
in example 1, the mass concentration of sulfuric acid was 98.2%, and the specific gravity was 1.82; the phosphorus pentoxide content in the phosphorus ore pulp is 30% by mass, the magnesium oxide content is 0.6% by mass, and the acid insoluble content is 15% by mass.
Dehydrating the phosphorite slurry by using a ceramic filter until the water content is less than or equal to 15%; adding the dehydrated phosphate rock slurry into a premixing tank to be premixed with acid solution (from the first filtrate and the second filtrate) to obtain first slurry; adding the first slurry into a dissolving tank, then adding sulfuric acid to dissolve at 95 ℃, and controlling the mass concentration of sulfate radicals and the mass concentration of calcium oxide in the dissolving tank to be 0.2% and 1.5% to obtain second slurry; adding the second slurry into a crystallization tank, then adding sulfuric acid for crystallization at the temperature of 96 ℃, and controlling the mass concentration of sulfate radicals in the crystallization tank to be 2.0% to obtain a third slurry; cooling the third slurry to 80 ℃ under the pressure condition of 12Kpa, then filtering under the condition of 40Kpa, and collecting to obtain semi-hydrated gypsum, a first filtrate and finished phosphoric acid with the mass concentration of phosphorus pentoxide being 42%, wherein the first filtrate can be used as return acid; adding the semi-hydrated gypsum and sulfuric acid into a conversion tank for conversion at 65 ℃, controlling the mass concentration of sulfate radicals in the conversion tank to be 8% to obtain a fourth slurry, filtering the fourth slurry, and collecting to obtain the dihydrate gypsum and a second filtrate.
Fluorine-containing gas generated in the production process is made into fluosilicic acid solution through centralized absorption treatment; the generated tail gas is washed by circulating cooling water, and after the condensable gas is washed away, the non-condensable gas is pumped and exhausted into the atmosphere by a vacuum pump.
Example 2:
in example 2, the mass concentration of sulfuric acid was 98.2%, and the specific gravity was 1.82; the phosphorus pentoxide content in the phosphorus ore pulp is 32%, the magnesium oxide content is 0.6%, and the acid insoluble content is 15%.
Dehydrating the phosphorite slurry by using a ceramic filter until the water content is less than or equal to 15%; adding the dehydrated phosphate rock slurry into a premixing tank to be premixed with acid solution (from the first filtrate and the second filtrate) to obtain first slurry; adding the first slurry into a dissolving tank, then adding sulfuric acid to dissolve at 96 ℃, and controlling the mass concentration of sulfate radicals and the mass concentration of calcium oxide in the dissolving tank to be 0.3% and 1.2%, so as to obtain second slurry; adding the second slurry into a crystallization tank, then adding sulfuric acid to crystallize at 96 ℃, and controlling the mass concentration of sulfate radicals in the crystallization tank to be 2.2% to obtain a third slurry; cooling the third slurry to 82 ℃ under the pressure condition of 13Kpa, then filtering under the condition of 45Kpa, and collecting the semi-hydrated gypsum, the first filtrate and finished phosphoric acid with the phosphorus pentoxide mass concentration of 43%, wherein the first filtrate can be used as return acid; adding the semi-hydrated gypsum and the sulfuric acid into a conversion tank for conversion at 68 ℃, controlling the mass concentration of sulfate radicals in the conversion tank to be 9% to obtain fourth slurry, filtering the fourth slurry, and collecting to obtain the dihydrate gypsum and second filtrate.
Fluorine-containing gas generated in the production process is made into fluosilicic acid solution through centralized absorption treatment; the generated tail gas is washed by circulating cooling water, and after the condensable gas is washed away, the non-condensable gas is pumped and exhausted into the atmosphere by a vacuum pump.
The features of the embodiments and embodiments described herein above may be combined with each other without conflict.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (4)
1. A method for producing phosphoric acid and co-producing gypsum by a semi-hydrated-dihydrate wet-process phosphoric acid process is characterized by comprising the following steps:
s1, dehydrating the phosphorite slurry by using a ceramic filter;
s2, adding an acid solution into the dehydrated phosphate rock slurry for premixing to obtain a first slurry; dehydrating the phosphorite slurry until the water content is less than or equal to 15 percent;
s3, adding sulfuric acid into the first slurry for dissolving, wherein the dissolving temperature is 93-98 ℃; controlling the mass concentration of sulfate radicals to be 0.1-0.5% to obtain second slurry;
s4, adding sulfuric acid into the second slurry for crystallization, wherein the crystallization temperature is 95-98 ℃; controlling the mass concentration of sulfate radicals to be 1.8-2.5% to obtain third slurry;
s5, cooling the third slurry to 80-85 ℃ under the pressure condition of 11-13Kpa in vacuum, and then filtering, wherein the pressure condition of filtering is 40-50 Kpa; collecting to obtain semi-hydrated gypsum, first filtrate and finished phosphoric acid; s6, adding sulfuric acid into the semi-hydrated gypsum for conversion, controlling the mass concentration of sulfate radicals to be 7-11% to obtain a fourth slurry, filtering the fourth slurry, and collecting the obtained dihydrate gypsum and a second filtrate.
2. The method for producing phosphoric acid and gypsum by using the semi-hydrated-dihydrate wet-process phosphoric acid process as claimed in claim 1, wherein in the step S1, the phosphorus ore pulp is used, and the phosphorus pentoxide content is greater than or equal to 30%, the magnesium oxide content is less than or equal to 0.8%, and the acid-insoluble content is less than or equal to 16%.
3. The method for producing phosphoric acid and gypsum according to the semi-hydrated-dihydrate wet phosphoric acid process of claim 1, wherein the acid solution used in step S2 is derived from the first filtrate and the second filtrate.
4. The method for producing phosphoric acid and gypsum through the semi-hydrated-dihydrate wet-process phosphoric acid process according to claim 1, wherein in the step S5, the mass concentration of phosphorus pentoxide in the finished phosphoric acid is 38-45%.
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| CN112897490B (en) * | 2021-04-02 | 2022-02-11 | 中国五环工程有限公司 | Method for producing wet-process phosphoric acid by multi-recrystallization semi-water-dihydrate and semi-water-dihydrate wet-process phosphoric acid production system |
| CN113173566B (en) * | 2021-04-21 | 2022-03-25 | 中国五环工程有限公司 | High-yield hydrated crystalline phase reconstruction wet-process phosphoric acid production process |
| CN113185160B (en) * | 2021-04-21 | 2022-03-29 | 中国五环工程有限公司 | Method for controlling coarse large crystal of semi-hydrated gypsum |
| CN115583666B (en) * | 2022-10-25 | 2024-03-29 | 宜都兴发化工有限公司 | Method for producing phosphogypsum by semi-water-dihydrate wet phosphoric acid process |
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| US20120039785A1 (en) * | 2010-08-10 | 2012-02-16 | Wellthought Products, Inc. | Process for Producing Products Under Very Low Supersaturation |
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| CN1421385A (en) * | 2002-12-25 | 2003-06-04 | 云南红磷化工有限责任公司 | Production process of semiwater-diaquo phosphoric acid |
| CN102001636A (en) * | 2010-09-26 | 2011-04-06 | 四川大学 | Method for producing broad-concentration phosphoric acid and clean plaster by middle-low grade phosphorus ore wet process |
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