CN114380520B - Method for pretreating phosphogypsum, phosphogypsum crude product and recycled product - Google Patents

Method for pretreating phosphogypsum, phosphogypsum crude product and recycled product Download PDF

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CN114380520B
CN114380520B CN202210111704.0A CN202210111704A CN114380520B CN 114380520 B CN114380520 B CN 114380520B CN 202210111704 A CN202210111704 A CN 202210111704A CN 114380520 B CN114380520 B CN 114380520B
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phosphogypsum
humidity
condition
temperature
dynamic environment
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CN114380520A (en
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石存兰
索也兵
张彦林
高宁
魏泽林
陈蛟龙
杜程
李恒
赵旭东
罗翊伦
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China Building Materials Industry Planning And Research Institute
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China Building Materials Industry Planning And Research Institute
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    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B11/00Calcium sulfate cements
    • C04B11/26Calcium sulfate cements strating from chemical gypsum; starting from phosphogypsum or from waste, e.g. purification products of smoke
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01FCOMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F11/00Compounds of calcium, strontium, or barium
    • C01F11/46Sulfates
    • C01F11/468Purification of calcium sulfates
    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B11/00Calcium sulfate cements
    • C04B11/02Methods and apparatus for dehydrating gypsum
    • C04B11/028Devices therefor characterised by the type of calcining devices used therefor or by the type of hemihydrate obtained
    • C04B11/032Devices therefor characterised by the type of calcining devices used therefor or by the type of hemihydrate obtained for the wet process, e.g. dehydrating in solution or under saturated vapour conditions, i.e. to obtain alpha-hemihydrate
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01PINDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00Physical properties of inorganic compounds
    • C01P2006/80Compositional purity

Abstract

The invention relates to the field of industrial pretreatment, in particular to a method for pretreating phosphogypsum, a phosphogypsum crude product and a recovered product. The pretreatment method comprises the following steps: placing the phosphogypsum in a first dynamic environment and a second dynamic environment which alternately occur, wherein the first dynamic environment is carried out in a closed environment, and switching is carried out when a first condition is reached or after the first condition is maintained for a period of time; the second dynamic environment is carried out in a non-closed environment, and switching is carried out when a second condition is reached; the first condition includes: the first temperature is 60-80 ℃, and the first humidity is 80-98%; the second condition includes: the second temperature is 80-98 ℃, and the second humidity is 60-80%; and the difference between the first temperature and the second temperature is not less than 10 ℃, and the difference between the first humidity and the second humidity is not less than 10%. The method can effectively remove impurities and free water in the phosphogypsum, and can recycle the phosphogypsum, thereby saving energy and protecting environment; fresh phosphogypsum can be directly treated.

Description

Method for pretreating phosphogypsum, phosphogypsum crude product and recycled product
Technical Field
The invention relates to the field of industrial pretreatment, in particular to a method for pretreating phosphogypsum, and a phosphogypsum crude product and a recovery product obtained after the pretreatment.
Background
The phosphogypsum is solid waste discharged during the production of phosphate fertilizer and phosphoric acid, and 4.5-5t of phosphogypsum is generated every 1t of phosphoric acid. Besides the main component calcium sulfate, the phosphogypsum also contains impurities such as phosphoric acid, silicon, magnesium, iron, aluminum, organic impurities and the like.
And the resource utilization of the phosphogypsum is not satisfactory in China and abroad. An important reason for limiting the resource utilization of phosphogypsum is that there is no cost-effective way to treat the large amount of free water and impurities contained in phosphogypsum. The prior art generally adopts the modes of water washing, flotation and placement when the phosphogypsum is pretreated.
The washing method is the most common mode for pre-treating the phosphogypsum, the treated phosphogypsum has stable performance, the crystal of the phosphogypsum after washing is clean and clear, the outline is clear, and the microstructure of a cementing material and a hardened body thereof is close to that of natural gypsum. But the disadvantages of water washing are very obvious, mainly including large primary investment of the production line, high water consumption and energy consumption, secondary pollution caused by sewage discharge after water washing, and the like.
The flotation method is a method of removing organic matter floating on the water surface by flotation equipment by utilizing the characteristic that the organic matter floats on the water surface during water washing. The method consumes less water compared with water washing, but the method is only effective in removing organic matters and is not as remarkable in the removal amount of soluble impurities as the water washing, so that the method is only suitable for phosphogypsum with specific impurity distribution.
In addition, standing is also a common method for pre-treating phosphogypsum, and long-time standing can enable impurities in the phosphogypsum to be gradually discharged or digested through percolate, so that the method is usually a necessary method for matching other methods. Phosphogypsum can be processed and utilized into downstream products after being placed and aged for 3-5 years; in the conventional pretreatment such as water washing method, most of the used phosphogypsum is the phosphogypsum which is placed for more than two years. A large amount of phosphogypsum occupies a large area of land, and harmful heavy metal chemical substances such as arsenic, cadmium, mercury and the like contained in the phosphogypsum have influence on the environment for hundreds of years.
Therefore, it is very important to find a cost effective, environmentally friendly and not requiring pre-placement of phosphogypsum pre-treatment process.
Disclosure of Invention
The invention aims to overcome the problems of high cost, high energy consumption, environmental friendliness and the like of the existing phosphogypsum pretreatment method, and provides a method for pretreating phosphogypsum, and a phosphogypsum crude product and a recovered product obtained after the pretreatment. The method can effectively remove acid, impurities and free water in the phosphogypsum, and can recycle the removed components, thereby saving energy and protecting environment; the method can directly treat the fresh phosphogypsum without placing and aging in advance, thereby avoiding a plurality of problems caused by placing.
In order to achieve the above object, a first aspect of the present invention provides a method of pre-treating phosphogypsum, which comprises: placing phosphogypsum in a first dynamic environment and a second dynamic environment which alternately occur, wherein the first dynamic environment is carried out in a closed environment, and the second dynamic environment is switched when a first condition is reached or is maintained for a period of time under the first condition; the second dynamic environment is carried out in a non-closed environment, and is switched to the first dynamic environment when a second condition is reached; the first condition includes: the first temperature is 60-80 ℃, and the first humidity is 80-98%; the second condition includes: the second temperature is 80-98 ℃, and the second humidity is 60-80%; and the difference between the first temperature and the second temperature is not less than 10 ℃, and the difference between the first humidity and the second humidity is not less than 10%.
The inventors of the present invention found that by placing phosphogypsum in a changing specific environment, under the influence of the change of the external environment, the acids and other impurities in the phosphogypsum are displaced into the steam and condensed and collected with the steam; the free water content in the treated phosphogypsum is also obviously reduced, so that a large amount of cost is saved for the subsequent dewatering process; therefore, the purposes of rapidness, effectiveness, economy and environmental protection can be realized, and the method can be suitable for various types of phosphogypsum without placing and aging in advance, thereby avoiding various problems caused by placing.
To further improve the efficiency of acid and impurity removal, the first and second conditions are defined by one or more of:
in a preferred embodiment, the first temperature is 65 ℃ to 75 ℃, more preferably 68 ℃ to 72 ℃.
In a preferred embodiment, the first humidity is 85% to 95%, more preferably 88% to 92%.
In a preferred embodiment, the second dynamic environment is switched after a period of time at a first condition (i.e. at an equilibrium at which the saturated vapor pressure is substantially reached) for a period of time in the range of 1-10min, preferably 3-8min.
In a preferred embodiment, the second temperature is from 85 ℃ to 95 ℃, more preferably from 88 ℃ to 92 ℃.
In a preferred embodiment, the second humidity is 65% to 75%, more preferably 68% to 72%.
In a preferred embodiment, the difference between the first temperature and the second temperature is 15 ℃ to 25 ℃.
In a preferred embodiment, the difference between the first humidity and the second humidity is 15% to 25%.
In the present invention, the humidity refers to relative humidity.
In the present invention, the first dynamic environment is performed under a closed condition, and the second dynamic environment is performed under an unsealed condition. The switching mode is that the closed environment and the non-closed environment are switched mutually.
In the first dynamic environment, in a closed environment, the humidity gradually rises while the temperature gradually falls, and in the process, free water in the phosphogypsum carries acid and impurities to be released and stays in the environment in the form of water vapor. At a given temperature and humidity, the vapor pressure achieved in a closed environment will saturate and remain constant.
Preferably, therefore, the first condition comprises: the first vapor pressure is a saturated vapor pressure. Typically 25kPa to 38kPa.
In the second dynamic environment, the closed environment is released, and the water vapor is released and collected in the form of condensed water, so that the acid and impurities carried in the water vapor can be recycled.
Preferably, the second condition comprises: the second vapor pressure is from 12kPa to 30kPa, more preferably from 15kPa to 25kPa.
In the present invention, it is not limited whether water or other ingredients are additionally added to the environment. In a typical embodiment, the increasing water vapour in the first dynamic environment comes from water inside the phosphogypsum, so no additional water needs to be added to the environment.
Preferably, the method of the present invention comprises a total of 3-8 (more preferably 3-5) combinations of the first dynamic environment and the second dynamic environment.
In the present invention, preferably, the process of pre-treating phosphogypsum is completed within a time of 2 h.
In the present invention, the duration of each time the first dynamic environment is the time for the system to change from the first condition to the second condition, which can be determined according to the actual situation. Preferably, the duration of the first dynamic environment is 5-20min. The preprocessing method comprises a first dynamic environment for multiple times, and the sum of the time lengths of the first dynamic environment included in the preprocessing method is within 1 h.
In the present invention, the duration of each time the second dynamic environment is the time for the system to change from the second condition to the first condition, which may be determined according to actual conditions, or may be adjusted by controlling the release rate of the water vapor. Preferably, the duration of the second dynamic environment is 3-15min. The preprocessing method comprises a plurality of times of second dynamic environments, and the sum of the time lengths of the second dynamic environments in the preprocessing method is within 1 h.
Unlike the prior art, the process of the present invention allows the direct treatment of fresh phosphogypsum without standing or other pre-treatment.
The method of the invention can achieve satisfactory effect when treating various types and components of phosphogypsum. Typically, the phosphogypsum before pre-treatment mainly comprises calcium sulphate dihydrate, free water and impurities, wherein the impurities comprise organic impurities mainly comprising H and inorganic impurities 2 SO 4 、HF、H 3 PO 4 And the inorganic impurities mainly comprise oxides and soluble inorganic salts of metals such as magnesium, iron and aluminum.
In the present invention, the content of the free water is determined in the following manner: dry subtraction method (GB/T5383-2012).
In the present invention, the inorganic impurities are mainly metal elements other than Ca, and are usually present in the form of water-soluble salts, mainly including: magnesium, iron, aluminum, and the like. The determination method comprises the following steps: x-ray fluorescence spectrometer (Thermo ARL Advant' X).
The content of the organic impurities can be calculated by a difference subtraction method or can be directly measured.
After pretreatment by the method of the invention, free water and impurities can be substantially removed. And both the removed water and impurities can be recycled or formed as by-products to commercial value.
Therefore, preferably, the method further comprises: and collecting and recycling the gas released in the phosphogypsum pretreatment process.
The collection method includes, for example: condensing the gas and collecting condensed water. Because the released gas contains a large amount of water vapor, the acid and the impurities can be remained in the condensed water in a condensation mode, so that the acid and the impurities with higher concentration can be obtained, and the subsequent recovery treatment is facilitated. Compared with the prior art that the washing method can generate a large amount of secondary pollution wastewater, the method of the invention not only can not generate secondary pollution, but also can fully utilize resources and generate good economic benefit.
The recovery treatment may be carried out in a manner conventional in the art, and conventional purification methods may be selected according to the particular ingredients and requirements, for example, a mixture of ingredients may be obtained, or individual ingredients may be sequentially extracted.
In a second aspect of the invention there is provided a crude phosphogypsum product obtained after pre-treatment by the method of the first aspect.
A third aspect of the present invention provides a recycled product obtained after a recycling treatment by the method of the first aspect.
The recovered product is a mixture or separated component of the organic impurities and the inorganic impurities.
Through the technical scheme, compared with the prior art, the invention at least has the following advantages:
(1) The impurity removal rate is high, and a satisfactory pretreatment effect can be obtained;
(2) The time required by pretreatment is short;
(3) The operation is simple and convenient, and a complex process is not needed;
(4) The cost is low: the equipment cost is low, the raw material cost is low, the energy consumption is low, and the labor cost is low;
(5) A large amount of free water in the phosphogypsum can be removed, and a large amount of time and cost are saved for the subsequent dewatering step;
(6) No secondary pollution is generated;
(7) The removed components can be effectively recycled, so that the energy is saved, the environment is protected, and considerable economic value can be brought;
(8) Fresh phosphogypsum can be used, long-time placing and aging in advance are not needed, and the problems of land occupation, environmental pollution and the like caused by long-time placing are avoided.
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
Detailed Description
The present invention will be described in detail below by way of examples. The described embodiments of the invention are only some of the embodiments of the invention, and not all of them. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the following examples, the phosphogypsum used is fresh phosphogypsum from gasseri (vitex) fertilizer limited.
Example 1
1 ton of phosphogypsum is placed in a drying chamber, the phosphogypsum is continuously heated, and meanwhile, the temperature, the humidity and the vapor pressure in the environment are monitored, and the following processes are carried out:
(1) An initial stage: in a closed environment, in the process of gradually increasing the temperature, water in the phosphogypsum enters air, the environment humidity is increased, and the steam pressure is increased; the steam pressure gradually reaches saturation, the temperature of the system is 71 ℃, the humidity is 89%, the first condition is reached, and the next operation is carried out after 5min of maintenance;
(2) A second dynamic environment phase: removing the closed environment, discharging the steam through a pipeline, condensing and collecting the steam, and reducing the steam pressure and the humidity in the drying chamber; when the temperature is 90 ℃ and the humidity reaches 71%, judging that a second condition is reached; carrying out the next operation;
(3) A first dynamic environment phase: the environment is sealed, and under the heating action, the humidity in the drying chamber rises and the steam pressure rises; the steam pressure gradually reaches saturation, the temperature of the system is 71 ℃, the humidity is 88%, the first condition is reached, and after 5min is maintained, the next operation is carried out;
repeating the step (2) and the step (3) to complete 5 groups (so as to complete the step (3) + the step (2) once, and calculating a first dynamic environment once in the initial stage).
Obtaining a phosphogypsum crude product. The whole process takes about 1h30min.
The resulting condensed water of the released steam is collected.
Example 2
Placing 1 ton of phosphogypsum in a drying chamber, continuously heating the phosphogypsum, monitoring the temperature, the humidity and the vapor pressure in the drying chamber, and carrying out the following processes:
(1) An initial stage: in a closed environment, in the process of gradually increasing the temperature, water in the phosphogypsum enters air, the environment humidity is increased, and the steam pressure is increased; the steam pressure gradually reaches saturation, the temperature of the system is 68 ℃, the humidity is 92%, the first condition is reached, and the next operation is carried out after the first condition is maintained for 7 min;
(2) A second dynamic environment phase: removing the closed environment, discharging the steam through a pipeline, condensing and collecting the steam, and reducing the steam pressure and the humidity in the drying chamber; when the temperature is 88 ℃ and the humidity reaches 72%, judging that a second condition is reached; carrying out the next operation;
(3) A first dynamic environment phase: the environment is sealed, and under the heating action, the humidity in the drying chamber rises and the steam pressure rises; the steam pressure gradually reaches saturation, the temperature of the system is 68 ℃, the humidity is 91%, the first condition is reached, and the next operation is carried out after the first condition is maintained for 7 min;
and (4) repeating the step (2) and the step (3) to complete 4 groups.
Obtaining a phosphogypsum crude product. The whole process takes about 1 hour and 25min.
The resulting condensed water from the steam released in the first dynamic environment stage is collected.
Example 3
The process of example 1 was followed except that in the first dynamic environment stage, the process was not maintained at the saturated vapor pressure environment for a period of time, but was contacted with the closed environment as soon as the saturated vapor pressure was reached.
The other operations are the same as the example 1, and after about 1h and 5min, a phosphogypsum crude product and condensed water are finally obtained.
Example 4
The procedure of example 1 was followed, except that the determination of the second condition was changed to: the temperature was 95 ℃ and the humidity was 66%.
The other operations are the same as example 1, and after about 1h and 45min, a phosphogypsum crude product and condensed water are obtained.
Example 5
The procedure of example 1 was followed, except that the determination of the second condition was changed to: the temperature was 85 ℃ and the humidity was 75%.
The other operations are the same as the example 1, and after about 1h and 5min, a phosphogypsum crude product and condensed water are obtained.
Comparative example 1
In an open environment, 1 ton of phosphorus stone is placed in a drying chamber for continuous heating, and simultaneously temperature and humidity monitoring is carried out, and the temperature of the phosphogypsum is maintained within the range of 88 +/-2 ℃. And (5) setting a condensation pipe in a subsequent link, and collecting condensed water.
After the same time as in example 1, the drying was terminated. Obtaining a phosphogypsum crude product.
Comparative example 2
1 ton of aged phosphogypsum is treated by a water washing method (the source is the same as that of the embodiment, and the aged phosphogypsum is placed for 2 years), and the specific process comprises the following steps:
the phosphogypsum is directly washed by water, and the washing and purifying effects are judged by measuring the pH value of the phosphogypsum.
The whole treatment process takes 3-7 days.
Waste water of 5 tons is produced.
Test example
(1) Free water removal (%)
The removal rates of free water in the above examples and comparative examples were respectively detected and calculated, specifically:
measuring the content of free water before and after treatment, calculating the weight of the free water before and after treatment according to the weight of the materials before and after treatment, and further calculating the removal rate;
removal rate (%) = (m) 0 -m 1 )÷m 0 ×100%;
Wherein: m is 0 -mass of free water before disposal, unit: g;
m 1 -mass of free water after treatment, unit: g;
the results are shown in Table 1.
TABLE 1
Free water removal%
Example 1 98.8
Example 2 97.4
Example 3 91.1
Example 4 94.2
Example 5 92.6
Comparative example 1 88.2
Comparative example 2 -
As can be seen from Table 1, the method of the present invention enables free water to be effectively removed, can provide gypsum with low free water content for the subsequent calcination process, and is helpful for improving the treatment effect of the subsequent process.
(2) Percent recovery of impurities (%)
The recovery rates of impurities in the above examples and comparative examples were detected and calculated, respectively, specifically:
measuring the content of calcium before and after treatment, and subtracting the weight of calcium sulfate dihydrate (calculated from Ca) and free water from the total weight of the material to obtain the weight of impurities (mainly including inorganic impurities such as magnesium, iron, aluminum, etc., and mainly including H) 2 SO 4 、HF、H 3 PO 4 And organic impurities) and further calculating the recovery rate;
recovery (%) = (n) 0 -n 1 )÷n 0 ×100%;
Wherein: n is 0 -mass of pre-treatment impurity, unit: g;
n 1 -mass of impurities after treatment, unit: g;
the results are shown in Table 2.
TABLE 2
Percent of impurity recovery%
Example 1 95.6
Example 2 94.2
Example 3 87.3
Example 4 92.3
Example 5 88.6
Comparative example 1 85.2
Comparative example 2 -
As can be seen from table 2, the method of the embodiment of the present invention can effectively recover inorganic impurities and organic impurities in phosphogypsum, achieve full utilization of resources, and is more environmentally friendly without discharging a large amount of wastewater as in comparative example 2.
(3) Cost and commercial value
The method of the invention is close to zero in cost, because the cost is mainly reflected in energy consumption generated by heating equipment and cost of large-scale site required by long-term storage of the phosphogypsum originally, and the part of energy consumption in the invention can directly utilize heat generated in the subsequent calcining procedure and does not need long-term storage of the phosphogypsum, thereby greatly reducing the cost.
The method is mainly embodied in the aspect of commercial value, and on one hand, the gypsum crude product with better quality can be obtained; on the other hand, organic and inorganic impurities in the phosphogypsum can be almost completely recovered, and byproducts can be obtained and sold commercially, so that considerable economic return can be obtained. In the prior art, the impurities of the phosphogypsum are basically digested in the stockpiling process, so that a byproduct is difficult to obtain. Therefore, the method of the invention has low cost and can bring considerable economic value.
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.

Claims (11)

1. A method of pre-treating phosphogypsum, characterised in that it comprises: placing phosphogypsum in a first dynamic environment and a second dynamic environment which alternately occur, wherein the first dynamic environment is carried out in a closed environment, and the second dynamic environment is switched when a first condition is reached or is maintained for a period of time under the first condition; the second dynamic environment is carried out in a non-closed environment, and is switched to the first dynamic environment when a second condition is reached; the first condition includes: the first temperature is 60-80 ℃, and the first humidity is 80-98%; the second condition includes: the second temperature is 80-98 ℃, and the second humidity is 60-80%; the difference between the first temperature and the second temperature is not less than 10 ℃, and the difference between the first humidity and the second humidity is not less than 10%;
the duration of the first dynamic environment is 5-20min, and the sum of the durations of the first dynamic environment included in the method is within 1 h;
the duration of the second dynamic environment is 3-15min, and the sum of the durations of the second dynamic environment included in the method is within 1 h.
2. The method of claim 1, wherein the first condition comprises: the first temperature is 65-75 ℃, the first humidity is 85% -95%, and the first vapor pressure is saturated vapor pressure.
3. The method of claim 2, wherein the first condition comprises: the first temperature is 68-72 ℃, the first humidity is 88-92%, and the first vapor pressure is saturated vapor pressure.
4. The method of claim 1, wherein the method comprises: and switching to a second dynamic environment after maintaining for a period of time under the first condition, wherein the maintaining time under the first condition is 1-10min.
5. The method of claim 4, wherein the method comprises: and switching to a second dynamic environment after maintaining for a period of time under the first condition, wherein the maintaining time under the first condition is 3-8min.
6. The method of claim 1, wherein the second condition comprises: the second temperature is 85-95 ℃, and the second humidity is 65-75%.
7. The method of any of claims 6, wherein the second condition comprises: the second temperature is 88-92 ℃, and the second humidity is 68-72%.
8. The method of claim 1, wherein the difference between the first temperature and the second temperature is 15-25 ℃ and the difference between the first humidity and the second humidity is 15-25%.
9. The method according to any one of claims 1-8, wherein the method further comprises: and collecting the condensate of the gas after the pretreatment method, and recycling.
10. A crude phosphogypsum obtained after pre-treatment by the method of any one of claims 1 to 8.
11. A recycled product obtained after recycling treatment by the method of claim 9.
CN202210111704.0A 2022-01-29 2022-01-29 Method for pretreating phosphogypsum, phosphogypsum crude product and recycled product Active CN114380520B (en)

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US7585485B2 (en) * 2006-07-03 2009-09-08 Tripoliven, C.A. Process for the physiochemical conditioning of chemical gypsum or phospho-gypsum for use in formulation for cement and other construction materials
CN104628274A (en) * 2014-12-03 2015-05-20 昆明理工大学 Method and device for preparing high-strength alpha hemihydrate gypsum by using phosphogypsum
CN106977123A (en) * 2017-03-31 2017-07-25 合肥学院 A kind of citric acid for being used to remove impurity fluorine in ardealite adds water the process washed
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