Method for treating high-grade cement by using phosphogypsum after flotation
By using a calibrator to adjust the pH value and stirring and heating treatment in the phosphogypsum treatment, the problem of difficult removal of eutectic phosphorus impurities and washing water to produce acidic wastewater is solved, which significantly improves cement performance and reduces treatment costs.
Patent Information
- Application Number
- CN202510389097.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-31
- Publication Date
- 2025-07-01
AI Technical Summary
The prior art is difficult to effectively remove eutectic phosphorus impurities in phosphogypsum, affecting cement performance, and water washing treatment will produce a large amount of acidic wastewater, increasing economic costs.
The pH value is adjusted in the acid flotation solution by using a calibration agent (alkaline regulator and biomass ash), and the pH value is adjusted by stirring and heat treatment, and the decomposition of phosphogypsum is promoted, the solid solution structure of eutectic phosphorus is destroyed, the acidic impurities are neutralized, and the generation of acidic wastewater is reduced.
Significantly eliminate the activity of phosphorus impurities in cement, neutralize the pH value of the flotation solution, avoid the generation of acidic wastewater, improve the performance of cement glue sand, and reduce treatment costs.
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Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of solid waste utilization, and particularly relates to a method for treating phosphogypsum after flotation for high-grade cement. Background Art
[0002] Phosphogypsum is an industrial by-product generated in the production process of wet-process phosphoric acid. The phosphorus impurities contained therein are soluble phosphorus, eutectic phosphorus and insoluble phosphorus, and their contents are relatively high and will have a greater impact on the properties of phosphogypsum. Soluble phosphorus usually exists in the forms of phosphoric acid, dihydrogen phosphate radical and hydrogen phosphate radical. In the aspect of resource utilization of phosphogypsum, when phosphogypsum hydrates, soluble phosphorus will react with Ca 2+ to generate Ca3(PO4)2, which hinders the continuous hydration of phosphogypsum and will make phosphogypsum acidic, causing corrosion to gypsum products and equipment. Eutectic phosphorus is formed by dihydrogen phosphate radical replacing SO4 in the gypsum lattice 2- , generating CaSO4·2H2O and CaHPO4·2H2O existing in the form of solid solution. When it hydrates, eutectic phosphorus is released from the lattice to generate calcium phosphate, reducing the pH value of phosphogypsum, prolonging its setting time and resulting in a loose structure of hydration products.
[0003] Phosphogypsum has the characteristics of huge output, strong pollution and low utilization rate. The resource utilization of phosphogypsum as a cement retarder can not only consume a large amount of phosphogypsum, but also has a high added value, which is one of the important measures for treating phosphogypsum. However, excessive addition of phosphogypsum will affect the strength of concrete. Therefore, a large amount of phosphogypsum cannot be directly added to high-grade cement, and phosphogypsum needs to be effectively treated, that is, harmless treatment technologies for phosphogypsum such as water washing, roasting, flotation, neutralization, etc. are adopted, so as to broaden the comprehensive utilization ways of phosphogypsum and increase the doping ratio of non-carbonate raw materials such as phosphogypsum in the production of cement clinker, and can more effectively realize the resource recycling of solid wastes such as phosphogypsum.
[0004] At present, soluble phosphorus impurities in phosphogypsum are mainly removed in large amounts by water washing and flotation. However, eutectic phosphorus impurities in phosphogypsum are firmly combined and deeply hidden, which not only cannot be eradicated, but also consume a large amount of water resources, resulting in a relatively high economic cost. Another method of flotation after mechanical ball milling can effectively reduce the content of eutectic phosphorus in phosphogypsum, but it cannot solve the problem of phosphogypsum sticking with acidic impurities after flotation, and subsequent water washing will increase the water consumption and wastewater treatment cost. Therefore, how to treat phosphogypsum to effectively reduce the damage of eutectic phosphorus impurities to the performance of cement and avoid the generation of a large amount of acidic wastewater caused by phosphogypsum sticking with acidic impurities during water washing has become a technical problem to be solved in this field. Summary of the Invention
[0005] The object of the present invention is to provide a treatment method for using flotation phosphorus gypsum in high-grade cement, which is used to solve the technical problems in the prior art that the treatment of phosphorus gypsum is difficult to remove eutectic phosphorus impurities, which affects the performance of cement, and a large amount of acidic wastewater is generated during the treatment by water washing.
[0006] The described treatment method for using flotation phosphorus gypsum in high-grade cement includes the following steps:
[0007] Prepare a phosphorus gypsum slurry with a specific solid content from the flotation phosphorus gypsum solution to obtain slurry A;
[0008] The flotation phosphorus gypsum is the phosphorus gypsum flotation under acidic pH conditions;
[0009] Add a corrector to slurry A to adjust the pH to obtain slurry B;
[0010] Put slurry B into a stirring and heating device and stir and mix for a period of time to obtain slurry C;
[0011] Filter slurry C to obtain the filter residue, which is the treated phosphorus gypsum product.
[0012] Preferably, the corrector includes 50%-80% of an alkaline regulator and 20%-50% of biomass ash. The corrector is prepared by mechanical activation, with a specific surface area ≥ 350 m 2 / g and an average particle size ≤ 100 nm.
[0013] Preferably, the alkaline regulator is any one or a mixture of quicklime powder, slag powder, and clinker powder, wherein the mass fraction of CaO ≥ 40 wt%, and the mass fraction of impurities K2O + Na2O ≤ 2 wt%.
[0014] Preferably, the biomass ash is any one or a mixture of rice husk ash, bamboo charcoal ash, or straw ash, wherein the mass fraction of SiO2 ≥ 60 wt%, and the mass fraction of impurities K2O + Na2O ≤ 3 wt%.
[0015] Preferably, the solid content of phosphorus gypsum in slurry A is 16%-35%, and the dosage of the corrector is 1.5-5% of the solid content ratio of phosphorus gypsum in slurry A.
[0016] Preferably, the alkaline regulator and biomass ash in the corrector are added separately to slurry A.
[0017] Preferably, the flotation phosphorus gypsum solution is obtained by flotation under acidic pH conditions, and the pH value range of slurry B is between 8 and 13.
[0018] Preferably, the stirring rate of slurry B is between 35 Hz and 42 Hz.
[0019] Preferably, the heating temperature of slurry B is between 30°C and 50°C.
[0020] Preferably, the stirring and heating reaction time is between 60 min and 150 min.
[0021] The advantages of the present invention are as follows: Under the conditions of an acidic flotation solution, through the "gradient neutralization - lattice reconstruction" dual-effect mechanism of the corrector, the acidic substances in the water washing are neutralized, avoiding the generation of a large amount of acidic wastewater, and the solid solution structure of eutectic phosphorus can be destroyed. By heating and stirring, the decomposition of phosphogypsum is promoted. The acidic impurities and the dissolved phosphate radicals undergo an anchoring reaction under the action of the corrector, continuously promoting the forward decomposition of phosphogypsum. Thus, this solution significantly eliminates the activity of phosphorus impurities in flotation phosphogypsum in cement and simultaneously neutralizes the pH value of the flotation solution. It neither generates a large amount of acidic wastewater during the treatment, increasing the wastewater discharge and treatment costs, nor can it significantly optimize the performance of the corresponding cement mortar when used in the production of high-grade cement, solving the technical problems existing in the prior art. Detailed implementation mode
[0022] The following is a more detailed description of the specific implementation mode of the present invention through the description of examples to help those skilled in the art have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention.
[0023] The present invention provides a method for treating flotation phosphogypsum for high-grade cement, including the following steps.
[0024] The flotation phosphogypsum solution is formulated into a phosphogypsum slurry with a specific solid content to obtain slurry A.
[0025] A corrector is added to slurry A to adjust the pH to obtain slurry B.
[0026] Slurry B is put into a stirring and heating device and stirred and mixed for a period of time to obtain slurry C.
[0027] Slurry C is filtered to obtain the filter residue, which is the treated phosphogypsum product.
[0028] The corrector includes an alkaline regulator and biomass ash. The alkaline regulator and biomass ash can be mixed and added together, or separately added to the phosphogypsum slurry. The corrector is prepared by mechanical activation from 50% - 80% alkaline regulator and 20% - 50% biomass ash, with a specific surface area ≥ 350 m2 / g and an average particle size ≤ 100 nm.
[0029] The biomass ash is any one or a mixture of rice husk ash, bamboo charcoal ash or straw ash. The mass fraction content of SiO2 is ≥ 60 wt%, and the mass fraction content of impurities K2O + Na2O is ≤ 3 wt%.
[0030] The alkaline regulator is any one of quicklime powder, slag powder, and clinker powder, or it can also be a mixture of any two or three of them, where the mass fraction content of CaO ≥ 40 wt%, and the mass fraction content of impurities K2O + Na2O ≤ 2 wt%.
[0031] The specific implementation examples of the above method for treating flotation phosphorus gypsum with high-grade cement are as follows.
[0032] Example 1
[0033] In this example, the solid content of the flotation phosphorus gypsum slurry is 16% and the pH is 4. After adding quicklime powder (alkaline regulator) with a solid content ratio of 1% (relative to the solid content of phosphorus gypsum in the phosphorus gypsum slurry), the pH becomes 13. Then, biomass ash with a solid content ratio of 0.5% is added, and it is stirred at a stirring speed of 42 Hz for 60 min. The stirring temperature is 30°C. The filter residue is obtained by filtering the stirred liquid, and thus the phosphorus gypsum product is obtained.
[0034] Example 2
[0035] In this example, the solid content of the flotation phosphorus gypsum slurry is 28% and the pH is 5. After adding slag powder (alkaline regulator) with a solid content ratio of 3% (relative to the solid content of phosphorus gypsum in the phosphorus gypsum slurry), the pH becomes 9. Then, biomass ash with a solid content ratio of 1% is added, and it is stirred at a stirring speed of 35 Hz for 150 min. The stirring temperature is 50°C. The filter residue is obtained by filtering the stirred liquid, and thus the phosphorus gypsum product is obtained.
[0036] Example 3
[0037] In this example, the solid content of the flotation phosphorus gypsum slurry is 26% and the pH is 4. After adding clinker powder (alkaline regulator) with a solid content ratio of 2% (relative to the solid content of phosphorus gypsum in the phosphorus gypsum slurry), the pH becomes 11. Then, biomass ash with a solid content ratio of 2% is added, and it is stirred at a stirring speed of 42 Hz for 120 min. The stirring temperature is 40°C. The filter residue is obtained by filtering the stirred liquid, and thus the phosphorus gypsum product is obtained.
[0038] Example 4
[0039] In this example, the solid content of the flotation phosphorus gypsum slurry is 32% and the pH is 4. After adding an alkaline regulator with a solid content ratio of 4% (relative to the solid content of phosphorus gypsum in the phosphorus gypsum slurry), the pH becomes 12. The alkaline regulator includes quicklime powder with a solid content ratio of 2% and slag powder with a solid content ratio of 2% (relative to the solid content of phosphorus gypsum in the phosphorus gypsum slurry). Then, biomass ash with a solid content ratio of 1% is added, and it is stirred at a stirring speed of 42 Hz for 90 min. The stirring temperature is 40°C. The filter residue is obtained by filtering the stirred liquid, and thus the phosphorus gypsum product is obtained.
[0040] Example 5
[0041] In this example, the solid content of the phosphogypsum slurry after flotation is 27% and the pH is 4. After adding an alkaline regulator with a phosphogypsum solid content ratio of 4%, the pH becomes 12. The alkaline regulator includes clinker powder with a phosphogypsum solid content ratio of 2% and slag powder with a phosphogypsum solid content ratio of 2%. Then, biomass ash with a phosphogypsum solid content ratio of 1% is added, and it is stirred at a stirring speed of 42 Hz for 120 min by a stirring device. The stirring temperature is 40°C. The filter residue is filtered from the stirred liquid to obtain the phosphogypsum product.
[0042] Example 6
[0043] In this example, the solid content of the phosphogypsum slurry after flotation is 32% and the pH is 3. After adding an alkaline regulator with a phosphogypsum solid content ratio of 4%, the pH becomes 12. The alkaline regulator includes quicklime powder with a phosphogypsum solid content ratio of 2% and clinker powder with a phosphogypsum solid content ratio of 2%. Then, biomass ash with a phosphogypsum solid content ratio of 1% is added, and it is stirred at a stirring speed of 42 Hz for 90 min by a stirring device. The stirring temperature is 40°C. The filter residue is filtered from the stirred liquid to obtain the phosphogypsum product.
[0044] Example 7
[0045] In this example, the solid content of the phosphogypsum slurry after flotation is 35% and the pH is 3. After adding an alkaline regulator with a phosphogypsum solid content ratio of 4%, the pH becomes 10. The alkaline regulator includes quicklime powder with a phosphogypsum solid content ratio of 1%, clinker powder with a phosphogypsum solid content ratio of 1%, and slag powder with a phosphogypsum solid content ratio of 2%. Then, 1% biomass ash is added, and it is stirred at a stirring speed of 42 Hz for 120 min by a stirring device. The stirring temperature is 40°C. The filter residue is filtered from the stirred liquid to obtain the phosphogypsum product.
[0046] The phosphogypsum products obtained in the above examples are used to replace natural gypsum and mixed and ground with clinker according to the Tongling Conch P·II portland cement formula. The obtained cement is the final product. A cement mortar performance comparison experiment is carried out between the product of the present invention, the natural gypsum reference group, and the flotation-washed phosphogypsum. Among them, the reference group is the Tongling Conch P·II portland cement formula, the blank group is that the flotation phosphogypsum is directly used as a cement retarder, and the water-washed control group is that the flotation phosphogypsum is treated by water washing. The impurity content of the treated phosphogypsum is detected, and the experimental results are shown in Table 1.
[0047] Table 1 Phosphogypsum element analysis results
[0048]
[0049] According to the data in Table 1, it shows that after flotation, phosphogypsum can effectively remove some impurities. The ability to remove impurity phosphorus in this part is poor, mainly because part of the phosphorus impurities in phosphogypsum exist in the form of eutectic. Through physical flotation means, the surface of phosphogypsum can be treated. The main function of phosphogypsum in this flotation process is to remove impurities and improve the grade of calcium sulfate.
[0050] Under the conditions of an acidic flotation solution, the corrector undergoes a "gradient neutralization - lattice reconstruction" dual-effect mechanism: CaO in the corrector preferentially neutralizes free acid (H+), while active SiO2 / Al2O3 undergoes a coordination reaction with eutectic phosphorus, destroying the solid solution structure of CaHPO4·2H2O. By heating and stirring the phosphogypsum slurry, the decomposition of phosphogypsum is promoted. Under the action of the corrector, an anchoring reaction occurs with acidic impurities and dissolved phosphate radicals in the solution, and the forward decomposition of phosphogypsum is promoted, thereby significantly eliminating the activity of phosphorus impurities in cement and neutralizing the pH value of the flotation solution. After treating the flotation phosphogypsum and then using it to produce high-grade cement, the corresponding cement mortar is significantly optimized in performance, as can be seen specifically in Table 2.
[0051] Table 2 Performance test results of cement mortar
[0052]
[0053] The data in Table 2 show that the setting performance and mechanical strength performance of the blank group (untreated phosphogypsum) are lower than those of natural gypsum. This type of phosphogypsum is a flotation product under acidic conditions. The data in Table 1 show that washing phosphogypsum cannot reduce the content of impurity phosphorus. Combining with the shortened setting time and improved mechanical strength of phosphogypsum in Table 2, it shows that the acidity in phosphogypsum has a certain impact on its performance. Under acidic flotation conditions, it is very necessary to wash the acid from phosphogypsum. The treatment process of the present invention replaces the acid-washing industry, greatly saving water resources and wastewater disposal costs. By modifying phosphogypsum in the treatment method of the present invention, the performance of the cement is basically the same as that of natural gypsum, and even slightly improved.
[0054] The above has made an exemplary description of the present invention. Obviously, the specific implementation of the present invention is not limited by the above methods. As long as various non-substantive improvements are made using the inventive concept and technical solutions of the present invention, or the inventive concept and technical solutions of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.
Claims
1. A method for treating phosphogypsum after flotation for high-grade cement, characterized in that: The following steps are involved: The phosphogypsum solution after flotation is prepared into a phosphogypsum slurry with a specific solid content to obtain slurry A; The phosphogypsum after flotation is the phosphogypsum that is floated under the condition of slightly acidic pH; Adding a corrector to slurry A to adjust the pH to obtain slurry B; Put slurry B into a stirring and heating device and stir and mix for a period of time to obtain slurry C; The slurry C is filtered to obtain the filter residue, which is the treated phosphogypsum product.
2. The method for treating high-grade cement using post-flotation phosphogypsum according to claim 1, characterized in that: The corrector includes 50%-80% alkaline regulator by mass and 20%-50% biomass ash by mass. The corrector is prepared by mechanical activation and has a specific surface area of ≥350m 2 / g, average particle size ≤100nm.
3. The method for treating high-grade cement using post-flotation phosphogypsum according to claim 2, characterized in that: The alkaline regulator is a mixture of any one or more of quicklime powder, slag powder and clinker powder, wherein the mass fraction content of CaO is ≥40wt%, and the mass fraction content of impurities K2O+Na2O is ≤2wt%.
4. The method for treating high-grade cement using post-flotation phosphogypsum according to claim 2, characterized in that: The biomass ash is a mixture of any one or more of rice husk ash, bamboo charcoal ash or straw ash, wherein the mass fraction content of SiO2 is ≥60wt%, and the mass fraction content of impurities K2O+Na2O is ≤3wt%.
5. The method for treating high-grade cement using post-flotation phosphogypsum according to claim 1, characterized in that: The solid content of phosphogypsum in slurry A is 16%-35%, and the dosage of the correction agent is 1.5-5% of the solid content of phosphogypsum in slurry A.
6. The method for treating high-grade cement using post-flotation phosphogypsum according to claim 1, characterized in that: The alkaline regulator and biomass ash in the corrector are added to slurry A separately.
7. The method for treating high-grade cement using post-flotation phosphogypsum according to claim 1, characterized in that: The flotation is carried out under the condition of slightly acidic pH to obtain the post-flotation phosphogypsum solution, and the pH value of the slurry B ranges from 8 to 13.
8. The method for treating high-grade cement using post-flotation phosphogypsum according to claim 1, characterized in that: The stirring rate of slurry B was between 35 Hz and 42 Hz.
9. The method for treating high-grade cement using post-flotation phosphogypsum according to claim 1, characterized in that: The heating temperature of slurry B is between 30°C and 50°C.
10. The method for treating post-flotation phosphogypsum for high-grade cement according to claim 1, characterized in that: The stirring and heating reaction time is between 60min and 150min.