Method for preparing high-activity MgO phosphorus-containing dolomite from phosphate tailings
By activating phosphorus tailings through flotation and CO2 partial pressure calcination, highly active MgO-containing dolomite was prepared, solving the problem of phosphorus tailings storage, providing inexpensive and highly active magnesium cement raw materials, and realizing resource utilization.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-14
- Publication Date
- 2026-04-03
AI Technical Summary
Existing technologies have failed to effectively utilize phosphorus tailings, resulting in their stockpiling occupying land resources and lacking reasonable ways to reduce and comprehensively utilize them. In particular, the characteristics of phosphorus tailings have not been fully utilized in the preparation of dolomite materials.
Carbon fluorophosphate was removed from the phosphorus tailings by flotation, and then CaCl2 was added under CO2 partial pressure for calcination and activation to stimulate MgO activity, thus preparing highly active MgO-containing dolomite.
It has enabled the resource-based treatment of phosphorus tailings, provided inexpensive raw materials for magnesium cement and dolomite products, improved the activity and water resistance of calcined products, reduced grinding and crushing processes, and expanded the sources of inexpensive raw materials for the magnesium cement industry.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of solid waste reduction and comprehensive utilization technology, and in particular to a method for preparing highly active MgO-containing dolomite using phosphorus tailings. Background Technology
[0002] With the continuous development of the phosphate chemical industry and the ongoing phosphate mining and beneficiation, my country's phosphate tailings ponds are basically operating at saturation or overload. The existing tailings ponds can no longer meet the needs of the sustainable development of the phosphate chemical industry, while also occupying a large amount of land resources. In recent years, the country has proposed a "green development" strategy, requiring strengthened resource utilization of tailings, solid waste, and wastewater, reducing the generation and storage of mining solid waste such as tailings, gangue, and waste rock, striving to achieve "zero discharge" of mineral processing wastewater from key enterprises, and achieving a 100% harmless disposal rate for hazardous solid waste.
[0003] Existing research indicates that phosphorus tailings contain low levels of fluoroapatite, with dolomite minerals being the primary component. The ore samples exhibit fine grain size, while fluoroapatite is of higher grade in coarser grains. Phosphorus tailings can be considered phosphorus-bearing dolomite, and currently, there is no reasonable approach for large-scale reduction and comprehensive utilization. Meanwhile, although Yunnan province is rich in dolomite resources, mining faces limitations due to complex geology, terrain constraints, high mining costs, and environmental impact.
[0004] In line with the general trend of optimizing resource allocation and conforming to national policies and regulations, the comprehensive treatment of phosphorus tailings and the research on using dolomite, which has the potential to be a fine-grained filler or contains phosphorus-containing dolomite, to prepare dolomite-based multi-component materials is an important topic with significant application value and socio-economic significance. The fine-grained nature of dolomite minerals in phosphorus tailings allows it to replace a portion of pure dolomite in the preparation of dolomite-based multi-component materials. However, current research mostly focuses on the calcination process and equipment of dolomite and its applications, with little attention paid to the treatment processes and application expansion of phosphorus tailings. Summary of the Invention
[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method for preparing highly active MgO-containing dolomite using phosphorus tailings, aiming to solve the problem that existing technologies do not process phosphorus tailings to use as pure dolomite materials.
[0006] The solution of the present invention is: A method for preparing highly active MgO-containing phosphorus dolomite from phosphorus tailings includes the following steps: S1. The phosphorus tailings are subjected to flotation to remove carbophosphate and obtain intermediate products. S2. The intermediate product is dried, crushed, and calcined and activated under CO2 partial pressure conditions after the additives are added to obtain MgO-activated phosphorus-containing dolomite.
[0007] As a preferred technical solution, the calcination temperature is 760-790℃ and the calcination time is 100-150min.
[0008] As a preferred technical solution, the partial pressure of CO2 is 0.9 to 1.5 atm.
[0009] As a preferred technical solution, the auxiliary agent is CaCl2; the amount of CaCl2 added is 1% to 3% of the mass of the intermediate product.
[0010] As a preferred technical solution, the calcination and activation process further includes grinding; the specific surface area of the ground material is 450–550 m². 2 / g.
[0011] As a preferred technical solution, the aeration volume for flotation is 1.0–1.5 m³. 3 / (m 2 •min); scraper speed is 25~30r / min.
[0012] As a preferred technical solution, a modifier is added during the flotation process. The modifier is sulfuric acid, and the dosage is 1.5 to 6.0 kg / t.
[0013] As a preferred technical solution, the moisture content after drying is 1-5%, and all the particles after crushing pass through a 1mm fine sieve.
[0014] Compared with the prior art, the advantages of the present invention are: The resource-based treatment method for phosphorus tailings provided by this invention first removes carbon fluorophosphate from the phosphorus tailings, then adds additives and calcines and activates them under CO2 partial pressure conditions to activate the MgO in phosphorus-containing dolomite, releasing the small-size effect of phosphorus tailings in magnesium cement and dolomite products and the activity of MgO in phosphorus-containing dolomite, thereby transforming phosphorus tailings into a raw material that can be used to prepare magnesium cement or dolomite products, realizing the resource-based treatment of phosphorus tailings as solid waste.
[0015] Traditional methods of producing magnesium cement from dolomite require processes such as mining, crushing, grinding, and calcination to meet product requirements. The MgO-activated phosphorus-containing dolomite obtained through this invention, whose raw material is tailings from phosphate rock flotation, offers the following advantages: no grinding or crushing processes are required; the phosphorus-containing dolomite processed by this invention has lower acquisition costs; the calcined product has higher activity, and the phosphorus element in the product is activated after calcination, which can improve the water resistance of magnesium cement products to a certain extent; the phosphorus-containing dolomite in this invention has a finer calcination finer particle size, and the uncalcined decomposed CaCO3 acts as a filler micro-aggregate, filling the voids in the magnesium cement and improving its strength. Attached Figure Description
[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.
[0017] Figure 1 The image shows the XRD results of the phosphate tailings from Example 1. Figure 2 This is a graph showing the TG-DSC variation of the phosphorus tailings in Example 1. Detailed Implementation
[0018] To address the problems mentioned in the background art, the present invention provides a method for preparing highly active MgO-containing phosphorus dolomite from phosphorus tailings, comprising the following steps: The phosphorus tailings were subjected to flotation to remove carbophosphate and obtain intermediate products. The intermediate product was dried, crushed, and calcined and activated under CO2 partial pressure to obtain MgO-activated phosphorus-containing dolomite.
[0019] Phosphate tailings refer to the waste residue generated during phosphate mining and beneficiation, mainly composed of minerals not extracted during beneficiation, gangue minerals, and residues of beneficiation reagents. Directly applying phosphate tailings to magnesium-based cementitious material mineral admixtures may lead to insufficient hydration of the magnesium cementitious material. This invention addresses this issue by focusing on the inherent mineral properties of phosphate tailings and, based on the high proportion of dolomite in phosphate tailings, specifically utilizing flotation to further enrich them, thereby increasing the proportion of dolomite in the phosphate tailings from a mineral perspective.
[0020] This invention takes into account the fact that phosphorus tailings have a fine particle size, contain a large amount of dolomite, and have a low impurity content. Through drying, crushing, adding additives, and pressurized calcination, residual organic reagents are removed from the tailings, altering the particle shape of the dolomite and effectively activating the MgO activity in the dolomite while inhibiting the decomposition of CaCO3. "MgO activation" refers to the process of thermal activation (calcination) that decomposes the originally chemically inert, well-crystallized magnesium-containing minerals (mainly dolomite CaMg(CO3)2) in the phosphorus tailings, transforming them into highly reactive amorphous or microcrystalline magnesium oxide (MgO).
[0021] The resource-based treatment method for phosphorus tailings provided by this invention first removes fluorophosphate from the phosphorus tailings, then adds additives and calcines and activates them under CO2 partial pressure conditions. This activates the MgO in the phosphorus-containing dolomite, releasing the small-size effect of the phosphorus tailings in magnesium cement and dolomite products, and enhancing the activity of the MgO in the phosphorus-containing dolomite. This transforms the phosphorus tailings into a raw material that can be used to prepare magnesium cement or dolomite products, thus achieving the resource-based treatment of phosphorus tailings as solid waste. The resource-based treatment method for phosphorus tailings provided by this invention not only effectively expands the source of inexpensive raw materials for the magnesium cement industry, but also provides a practical and feasible disposal approach for the large-scale reduction and utilization of phosphorus tailings.
[0022] Among them, the intermediate products obtained by flotation of phosphorus tailings to remove fluoroapatite include two products: concentrate and tailings. The concentrate has a P2O5 grade of 10-16% and an MgO grade of 7-11%, while the tailings have a P2O5 grade of 2.5-4% and an MgO grade of 15-18%.
[0023] Among them, the MgO grade of phosphorus-containing dolomite obtained by flotation removal of carbon fluoroapatite from phosphorus tailings and calcination activation treatment to obtain MgO activation has a grade of 23-26% and a P2O5 grade of 2-3%.
[0024] In some embodiments, the calcination temperature is 760–790°C, for example, it can be any value between 760°C, 770°C, 780°C, 790°C or 760–790°C, and the calcination time is 100–150 min, for example, it can be any value between 100 min, 120 min, 130 min, 150 min or 100–150 min.
[0025] In some embodiments, the partial pressure of CO2 is 0.9 to 1.5 atm, for example, it can be 0.9 atm, 1.0 atm, 1.1 atm, 1.2 atm, 1.3 atm, 1.4 atm, 1.5 atm or any value between 0.9 and 1.5 atm.
[0026] In some embodiments, the auxiliary agent is CaCl2; Optionally, the amount of CaCl2 added is 1% to 3% of the mass of the intermediate product, for example, it can be any value between 1%, 2%, 3% or 1% to 3%.
[0027] In some embodiments, the calcination and activation process further includes grinding; the specific surface area of the ground material is 450–550 m². 2 / g, for example, can be 450m 2 / g、460m 2 / g、470m 2 / g、490m 2 / g、500m 2 / g、510m 2 / g、520m 2 / g、530m 2 / g、540m 2 / g、550m 2 / g or 450~550m 2 Any value between / g.
[0028] In some embodiments, the aeration rate for flotation is 1.0–1.5 m³. 3 / (m 2 (·min), for example, can be 1.0m 3 / (m 2 ·min), 1.1m 3 / (m 2 ·min), 1.2m 3 / (m 2 ·min), 1.3m 3 / (m 2 ·min), 1.4m 3 / (m 2 ·min), 1.5m 3 / (m 2 (min) or 1.0~1.5m 3 / (m 2 Any value between ·min); the scraper speed is 25 to 30 r / min, for example, it can be 25 r / min, 26 r / min, 27 r / min, 28 r / min, 29 r / min, 30 r / min or any value between 25 and 30 r / min.
[0029] In some embodiments, a modifier, namely sulfuric acid, is added during the flotation process at a dosage of 1.5-6.0 kg / t, for example, it can be any value between 1.5 kg / t, 2.0 kg / t, 2.5 kg / t, 3.0 kg / t, 3.5 kg / t, 4.0 kg / t, 4.5 kg / t, 5.0 kg / t, 5.5 kg / t, 6.0 kg / t, or 1.5-6.0 kg / t.
[0030] In some embodiments, the moisture content after drying is 1% to 5%, and all the crushed particles pass through a 1mm fine sieve.
[0031] The phosphorus tailings after flotation are prone to agglomeration during drying due to their fine particle size and the presence of residual reagents. Drying and sieving operations ensure the uniform combination of raw materials and calcination aids for subsequent calcination, thereby improving the decomposition effect of MgO.
[0032] The MgO-activated phosphorus-containing dolomite provided by this invention can have MgO activity effect and cementing effect, morphological effect and reduction effect, and micro-aggregate effect when forming magnesium-based cementitious materials (magnesium cement), thereby promoting the hydration reaction of magnesium-based cementitious materials and reducing the addition of water.
[0033] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific embodiments.
[0034] Example 1: The main chemical components of the phosphate tailings used, compared with those of dolomite, are shown in Table 1; the mineral composition and content are shown in Table 2; the results of multi-element chemical analysis are shown in Table 3; and the XRD analysis is shown in [Table 1]. Figure 1 The changes in thermogravimetric analysis-differential scanning calorimetry (TG-DSC) of the phosphate tailings samples are shown in the figure. Figure 2 It can be seen that the main mineral in phosphorus tailings is dolomite, while the content of fluoroapatite in phosphorus tailings samples is relatively low. The degree of liberation of dolomite monomers increases with decreasing grain size, and dolomite intergrowths are mainly associated with fluoroapatite.
[0035] Table 1. Analysis results of major chemical components of phosphate tailings compared with dolomite (unit: wt. / %) Table 2 Results of the determination of the degree of liberation of dolomite monomers in phosphate tailings Table 3. Results of multi-element chemical analysis of phosphate tailings (wt. / %) Example 1 provides a method for preparing highly active MgO-containing dolomite from phosphate tailings, comprising the following steps: (1) The phosphorus tailings are subjected to flotation treatment. The aeration rate of the flotation machine is 1.3 m³ / s. 3 / (m 2 The scraper speed is 28 r / min. The residual collector in the process of obtaining phosphorus tailings by phosphate rock flotation is fully utilized. The modifier is added as sulfuric acid, with a dosage of 1.5 kg / t. Finally, most of the carbon fluorophosphate is removed to obtain the intermediate product.
[0036] (2) After drying the phosphorus tailings treated in step (1) at 100°C, crush them until they all pass through a 1mm fine sieve, add 2wt.% CaCl2 as a calcination aid, mix, and calcine at 780°C for 120 minutes under CO2 pressure of 1.2 atm. Then, after natural cooling, grind them to a specific surface area of 500 m². 2 / g yielded the MgO-activated phosphorus-containing dolomite of Example 1.
[0037] Example 2: Example 2 provides a method for preparing highly active MgO-containing dolomite using phosphate tailings, which differs from Example 1 in that: (1) The aeration volume of the flotation machine is: 1.0 m³ / s. 3 / (m 2 The scraper speed is 25 r / min, which fully utilizes the residual collector in the process of obtaining phosphate tailings from phosphate rock flotation. The modifier is added as sulfuric acid at a dosage of 3 kg / t. Finally, most of the carbofluoroapatite is removed to obtain the intermediate product.
[0038] (2) After drying the phosphorus tailings treated in step (1) at 100°C, crush them until they all pass through a 1mm fine sieve, add 2wt.% CaCl2 as a calcination aid, mix, and calcine at 780°C for 120 minutes under CO2 pressure of 0.9 atm. Then, after natural cooling, grind them to a specific surface area of 500 m². 2 / g, yielding the MgO-activated phosphorus-containing dolomite of Example 2.
[0039] The other steps are the same as in Example 1.
[0040] Example 3: Example 3 provides a method for preparing highly active MgO-containing dolomite from phosphate tailings, which differs from Example 1 in that: (1) The aeration rate of the flotation machine is 1.5m³. 3 / (m 2 The scraper speed is 30 r / min, fully utilizing the residual collector in the phosphate tailings flotation process. Sulfuric acid is added as a modifier at a dosage of 6.0 kg / t. This process ultimately removes most of the carbofluoroapatite, yielding the intermediate product.
[0041] (2) After drying the phosphorus tailings treated in step (1) at 100°C, crush them until they all pass through a 1mm fine sieve, add 2wt.% CaCl2 as a calcination aid, mix, and calcine at 780°C for 120 minutes under CO2 pressure of 1.5 atm. Then, after natural cooling, grind them to a specific surface area of 500 m². 2 / g, yielding the MgO-activated phosphorus-containing dolomite of Example 3.
[0042] The other steps are the same as in Example 1.
[0043] Comparative Example 1: Comparative Example 1 provides a method for preparing highly active MgO-containing dolomite using phosphate tailings, which differs from Example 1 in that: (2) After drying the phosphorus tailings treated in step (1) at 100°C, crush them until they all pass through a 1mm fine sieve, add 2wt.% MgCl2 as a calcination aid, mix, and calcine at 780°C for 120 minutes under CO2 pressure of 1.2 atm. Then, after natural cooling, grind them to a specific surface area of 500 m². 2 / g, yielding MgO-activated phosphorus-containing dolomite of Comparative Example 1.
[0044] The other steps are the same as in Example 1.
[0045] Comparative Example 2: Comparative Example 2 provides a method for preparing highly active MgO-containing dolomite using phosphate tailings, which differs from Example 1 in that: (2) After drying the phosphorus tailings treated in step (1) at 100°C, crush them until they all pass through a 1mm fine sieve, add 2wt.% CaCl2 as a calcination aid, mix, and calcine at 800°C for 120 minutes under CO2 pressure of 1.2 atm. Then, after natural cooling, grind them until the specific surface area is 500 m². 2 / g, yielding MgO-activated phosphorus-containing dolomite of Comparative Example 2.
[0046] The other steps are the same as in Example 1.
[0047] Comparative Example 3: Comparative Example 3 provides a method for preparing highly active MgO-containing dolomite using phosphate tailings, which differs from Example 1 in that: (2) After drying the phosphorus tailings treated in step (1) at 100°C, crush them until they all pass through a 1mm fine sieve, add 2wt.% CaCl2 as a calcination aid, mix, and calcine at 750°C for 120 minutes under CO2 pressure of 1.2 atm. Then, after natural cooling, grind them to a specific surface area of 500 m². 2 / g, yielding MgO-activated phosphorus-containing dolomite of Comparative Example 3.
[0048] The other steps are the same as in Example 1.
[0049] Comparative Example 4: Comparative Example 4 provides a method for preparing highly active MgO-containing dolomite using phosphate tailings, which differs from Example 1 in that: (2) After drying the phosphorus tailings treated in step (1) at 100°C, crush them until they all pass through a 1mm fine sieve, add 2wt.% CaCl2 as a calcination aid, mix, and calcine at 780°C for 120 minutes under CO2 pressure of 0 atm. Then, after natural cooling, grind them to a specific surface area of 500 m². 2 / g, yielding MgO-activated phosphorus-containing dolomite of Comparative Example 4.
[0050] The other steps are the same as in Example 1.
[0051] Comparative Example 5: Comparative Example 5 provides a method for preparing highly active MgO-containing dolomite using phosphate tailings, which differs from Example 1 in that: (2) After drying the phosphorus tailings treated in step (1) at 100°C, crush them until they all pass through a 1mm fine sieve, add 2wt.% CaF2 as a calcination aid, mix, and calcine at 780°C for 120 minutes under CO2 pressure of 1.2 atm. Then, after natural cooling, grind them until the specific surface area is 500 m². 2 / g, yielding MgO-activated phosphorus-containing dolomite of Comparative Example 5.
[0052] The other steps are the same as in Example 1.
[0053] Comparative Example 6: Comparative Example 6 provides a method for preparing highly active MgO-containing phosphorus dolomite using phosphorus tailings, which differs from Example 1 in that: (2) After drying the phosphorus tailings treated in step (1) at 100°C, crush them until they all pass through a 1mm fine sieve, add 2wt.% MgF2 as a calcination aid, mix, and calcine at 780°C for 120 minutes under CO2 pressure of 1.2 atm. Then, after natural cooling, grind them to a specific surface area of 500 m². 2 / g, yielding MgO-activated phosphorus-containing dolomite of Comparative Example 6.
[0054] The other steps are the same as in Example 1.
[0055] The MgO content of the phosphorus-containing dolomite activated by MgO in each embodiment and comparative example was tested, and the performance comparison is shown in Table 4.
[0056] Table 4. Performance comparison of MgO-activated phosphorus-containing dolomite in each example and comparative example (unit: %) The method described in Example 1 for treating phosphate tailings yields the highest MgO decomposition rate while inhibiting CaCO3 decomposition, providing a stable raw material supply for downstream utilization of phosphate tailings. In Example 2, the method reduces CO2 pressure, leading to CaCO3 decomposition and increased CaO content. In Example 3, increased sulfuric acid dosage increases tailings treatment costs, but increased CO2 pressure simultaneously inhibits the decomposition of both MgCO3 and CaCO3, resulting in lower MgO and CaO contents and the lowest loss on ignition compared to the previous example. Comparative Example 1, using MgCl2 instead of CaCl2, produces a product with lower MgO and higher CaO content, and increased loss on ignition, demonstrating a significant difference. Comparative Example 2, calcined at 800℃, shows increased CaCO3 decomposition and the highest loss on ignition; the large amount of CaO produced negatively impacts subsequent product performance. Comparative Example 3, calcined at 750℃, shows insufficient MgCO3 decomposition, resulting in a lower MgO content in the product.
[0057] Comparative Example 4: Calcination was carried out without the addition of CO2 partial pressure. The low CO2 concentration in the furnace may have led to instability in the calcination process, resulting in unexpected decomposition of CaCO3. This caused an increase in the CaO content and loss on ignition in the product, failing to effectively achieve the expected effect of inhibiting CaCO3 decomposition. In Comparative Example 5, replacing the additive with CaF2 increased the MgO and CaO content in the product, but also increased the loss on ignition. Furthermore, its activation effect was not improved compared to CaCl2. Considering both cost and effectiveness, this was not the preferred solution. In Comparative Example 6, replacing the additive with MgF2 significantly reduced the MgO content in the product; it failed to effectively activate MgO, and its effect was far inferior to CaCl2. In conclusion, the treatment of phosphate tailings under the conditions of Example 1 yielded a moderate MgO and CaO content with lower additive costs, making it the optimal solution after comparison.
[0058] When preparing products from activated phosphate tailings, the key to controlling the MgO content is ensuring sufficient reactants while avoiding poor stability; the key to controlling the CaO content is maintaining a suitable weakly alkaline environment for phase formation and preventing the formation of harmful byproducts. The synergistic effect of these two factors is a prerequisite for obtaining materials with ideal strength, water resistance, and durability.
[0059] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.
Claims
1. A method for preparing highly active MgO-containing phosphorus dolomite from phosphorus tailings, characterized in that, Includes the following steps: S1. The phosphorus tailings are subjected to flotation to remove carbophosphate and obtain intermediate products. S2. The intermediate product is dried, crushed, and calcined and activated under CO2 partial pressure conditions after the additives are added to obtain MgO-activated phosphorus-containing dolomite.
2. The method for preparing highly active MgO-containing dolomite from phosphorus tailings as described in claim 1, characterized in that: The calcination temperature is 760–790℃, and the calcination time is 100–150 min.
3. The method for preparing highly active MgO-containing dolomite from phosphorus tailings as described in claim 1, characterized in that: The partial pressure of CO2 is 0.9–1.5 atm.
4. The method for preparing highly active MgO-containing dolomite from phosphate tailings as described in claim 1, characterized in that: The auxiliary agent is CaCl2; the amount of CaCl2 added is 1% to 3% of the mass of the intermediate product.
5. The method for preparing highly active MgO-containing phosphorus dolomite from phosphorus tailings as described in claim 1, characterized in that: The calcination and activation process further includes grinding; the specific surface area of the ground material is 450–550 m². 2 / g.
6. The method for preparing highly active MgO-containing dolomite from phosphate tailings as described in claim 1, characterized in that: The aeration rate for the flotation process is 1.0–1.5 m³. 3 / (m 2 •min); scraper speed is 25~30r / min.
7. The method for preparing highly active MgO-containing phosphorus dolomite from phosphorus tailings as described in claim 6, characterized in that: A modifier, sulfuric acid, is added during the flotation process at a dosage of 1.5–6.0 kg / t.
8. The method for preparing highly active MgO-containing dolomite from phosphate tailings as described in claim 1, characterized in that: The moisture content after drying is 1-5%, and all the crushed particles pass through a 1mm fine sieve.