Fracturing proppant composed of secondary aluminum ash hydrolysis residue and fly ash and its preparation method

Abstract

This invention discloses a fracturing proppant composed of secondary aluminum ash hydrolysis residue and fly ash, and its preparation method. The preparation method includes the following steps: S1: Obtain secondary aluminum ash hydrolysis residue and pretreat it to obtain secondary aluminum ash hydrolysis residue powder one; S2: Detect the MgO content in the secondary aluminum ash hydrolysis residue powder one; if it is less than or equal to 4%, proceed directly to step S3; otherwise, perform acid washing to reduce it to less than or equal to 4%, then wash until neutral and dry, proceed to step S3; S3: Perform high-temperature calcination treatment to obtain secondary aluminum ash hydrolysis residue powder two; S4: Mix the secondary aluminum ash hydrolysis residue powder two with fly ash and manganese ore powder to obtain a mixed raw material; S5: Granulate, dry, and sinter the mixed raw material at high temperature, and obtain the fracturing proppant after cooling. This invention can produce fracturing proppant using only secondary aluminum ash hydrolysis residue, fly ash, and manganese ore powder, reducing the proppant preparation cost while realizing solid waste resource utilization.

Description

Technical Field

[0001] This invention relates to the field of synergistic high-value utilization technology of multi-source solid waste, and in particular to a fracturing proppant that synergistically combines secondary aluminum ash hydrolysis residue and fly ash with its preparation method. Background Technology

[0002] Hydraulic fracturing is a method for enhancing oil and gas production by injecting fracturing fluid into the target reservoir under high pressure, causing the rock mass to fracture and form artificial fractures. To maintain the conductivity of the fractures after pump shutdown, proppant is carried and transported into the fractures by the fracturing fluid, keeping them open under formation pressure, thus forming highly conductive oil and gas seepage channels. Currently, ceramsite fracturing proppant mainly relies on high-grade bauxite (Al2O3 content greater than or equal to 80%) as raw material. However, my country's bauxite resources are relatively scarce, accounting for only 2.4% of the global total, and are mainly composed of medium and low-grade bauxite. As the world's largest importer of bauxite, my country's bauxite imports reached 142 million tons in 2023, with an import dependence rate exceeding 60%. This resource shortage has led to a significant increase in the production cost of ceramsite proppant. According to relevant statistics, the total cost of fracturing operations for a single unconventional oil and gas well is US$3-4 million, of which the amount of fracturing proppant used is approximately 2000 cubic meters. 3 The cost accounts for 15-17% of the total cost of fracturing. Therefore, using other lower-cost silica-alumina materials to replace high-grade bauxite in the preparation of fracturing proppant has become an important research direction to make up for the shortage of raw materials for ceramsite proppant and reduce the construction cost of controlled pressure fracturing.

[0003] In addition, with the development of industrial technology, there is an increasing amount of solid waste, some of which is hazardous waste and poses potential hazards to the environment and health. Therefore, how to treat it to reduce its hazards and further realize the resource utilization of solid waste is a technical problem that urgently needs to be solved.

[0004] Secondary aluminum ash is classified as hazardous waste (hazardous waste code: 321-026-48). It is typically treated using wet processes involving water, acid, or alkali to remove reactive components such as aluminum nitride, fluoride salts, and chlorides, yielding hydrolyzed secondary aluminum ash residue after environmental risks have been eliminated. The main components of this hydrolyzed residue are Al₂O₃, SiO₂, and CaO, with a certain amount of MgO (3%–10%). As a silica-alumina solid waste, it holds promise as a substitute for high-grade bauxite in the preparation of fracturing proppant. However, during the preparation of fracturing proppant, it has been found that it readily induces Kirkendall porosity, significantly deteriorating the mechanical strength of the proppant and making proppant molding difficult. Summary of the Invention

[0005] To address the aforementioned problems, this invention aims to provide a fracturing proppant that synergistically combines secondary aluminum ash hydrolysis slag and fly ash, and its preparation method.

[0006] The technical solution of the present invention is as follows: On the one hand, a method for preparing a fracturing proppant that combines secondary aluminum ash hydrolysis slag and fly ash is provided, comprising the following steps: S1: Obtain secondary aluminum ash hydrolysis residue and pre-treat it to obtain secondary aluminum ash hydrolysis residue powder. S2: Detect the MgO content in the secondary aluminum ash hydrolysis slag powder; If the MgO content is less than or equal to 4%, proceed directly to step S3; If the MgO content is greater than 4%, the secondary aluminum ash hydrolysis slag powder is acid-washed to make its MgO content less than or equal to 4%, then washed to neutral and dried, and then proceeded to step S3. S3: The secondary aluminum ash hydrolysis residue powder one is subjected to high-temperature calcination to remove the gas-producing components, thereby obtaining secondary aluminum ash hydrolysis residue powder two. S4: Mix the secondary aluminum ash hydrolysis residue powder II with fly ash and manganese ore powder to obtain a mixed raw material; S5: The mixed raw materials are granulated, dried, sintered at high temperature, and cooled to obtain the fracturing proppant.

[0007] Preferably, in step S1, the pretreatment includes crushing, drying, ball milling, and sieving processes performed sequentially.

[0008] Preferably, in step S2, hydrochloric acid with a mass fraction of 8-12% is used for pickling.

[0009] Preferably, in step S3, the high-temperature calcination treatment is carried out at 900~1100 ℃ for 30~90 min.

[0010] Preferably, in step S4, the mixture includes, by weight, 70-80 parts of secondary aluminum ash hydrolysis slag powder, 15-25 parts of fly ash, and 3-5 parts of manganese ore powder.

[0011] Preferably, the manganese ore powder contains more than or equal to 80% MnO2.

[0012] Preferably, in step S5, when granulating, raw material balls of 20 / 40 mesh are screened.

[0013] Preferably, in step S5, the heating rate during high-temperature sintering is 3~10 ℃ / min.

[0014] Preferably, in step S5, the high-temperature sintering is carried out at 1320~1400 ℃ for 90~180 min.

[0015] On the other hand, a fracturing proppant combining secondary aluminum ash hydrolysis slag and fly ash is also provided, which is prepared by the fracturing proppant preparation method of any one of the above-mentioned methods.

[0016] The beneficial effects of this invention are: The preparation method of this invention is simple and highly adaptable. It can produce fracturing proppant using only secondary alumina hydrolysis residue, fly ash, and manganese ore powder. This not only opens up a new way for high-value-added resource utilization of secondary alumina hydrolysis residue and fly ash, effectively reducing the production cost of ceramsite proppant and alleviating the dependence of China on imported bauxite resources, but also helps to reduce the amount of solid waste stockpiles and reduce the environmental safety risks caused by solid waste. Attached Figure Description

[0017] 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 some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic flowchart of a method for preparing a fracturing proppant that synergistically combines secondary aluminum ash hydrolysis slag and fly ash; Figure 2 Here is a photograph of the fracturing proppant used in Example 1; Figure 3 Here is a scanning electron microscope image of the fracturing proppant from Example 1; Figure 4 This is a scanning electron microscope image of the fracturing proppant in Comparative Example 2. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and technical features described in this application can be combined with each other. It should also be pointed out that, unless otherwise indicated, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terms "comprising" or "including" and similar words used in this invention refer to elements or objects preceding the word that encompass the elements or objects listed following the word and their equivalents, without excluding other elements or objects.

[0020] On the one hand, such as Figure 1 As shown, this invention provides a method for preparing a fracturing proppant that combines secondary aluminum ash hydrolysis slag and fly ash, comprising the following steps: S1: Obtain secondary aluminum ash hydrolysis residue and pre-treat it to obtain secondary aluminum ash hydrolysis residue powder.

[0021] In one specific embodiment, the pretreatment includes sequential crushing, drying, ball milling, and sieving. Optionally, a 200-mesh sieve is used for sieving to control the fineness of the raw material to less than 74 μm.

[0022] S2: Detect the MgO content in the secondary aluminum ash hydrolysis slag powder; If the MgO content is less than or equal to 4%, proceed directly to step S3; If the MgO content is greater than 4%, the secondary aluminum ash hydrolysis slag powder is acid-washed to make its MgO content less than or equal to 4%, then washed until neutral and dried, and then proceeded to step S3.

[0023] The inventors discovered that when the MgO content is less than or equal to 4%, it can act as a co-solvent. However, when the MgO content is greater than 4%, it easily reacts with Al2O3 during sintering to form magnesium aluminum spinel (MgAl2O4), and then... 2+ With Al 3+ Differences in diffusion rates induce Korkendall porosity, significantly degrading the mechanical strength of the proppant. This invention addresses this by detecting the MgO content in the secondary aluminum ash hydrolysis slag powder and then effectively removing soluble MgO through acid washing, controlling the MgO content to be less than or equal to 4%, thereby suppressing Korkendall porosity and improving the mechanical strength of the proppant.

[0024] In one specific embodiment, hydrochloric acid with a mass fraction of 8-12% is used for pickling.

[0025] S3: The secondary aluminum ash hydrolysis residue powder one is subjected to high-temperature calcination to remove the gas-producing components, thereby obtaining secondary aluminum ash hydrolysis residue powder two.

[0026] In one specific embodiment, the high-temperature calcination treatment is performed at 900~1100 °C for 30~90 min. Optionally, it is performed at 1000 °C for 60 min.

[0027] It should be noted that the purpose of high-temperature calcination is to remove gas-producing components such as gibbsite and aluminum nitride from the secondary aluminum ash hydrolysis slag powder, preventing them from forming pores during subsequent high-temperature sintering, thereby improving the structural density and compressive strength of the proppant. The high-temperature calcination conditions in the above embodiments are only preferred conditions of the present invention, and other high-temperature calcination conditions that can achieve this purpose are also applicable to the present invention.

[0028] S4: Mix the secondary aluminum ash hydrolysis residue powder with fly ash and manganese ore powder to obtain a mixed raw material.

[0029] In one specific embodiment, the mixture comprises, by weight, 70-80 parts of secondary aluminum ash hydrolysis slag powder, 15-25 parts of fly ash, and 3-5 parts of manganese ore powder. Optionally, the manganese ore powder contains MnO2 content greater than or equal to 80%.

[0030] The inventors discovered that the SiO2 content in secondary alumina ash hydrolysis slag powder is typically below 5%, which leads to insufficient liquid phase generation during sintering, making proppant formation difficult. In this invention, by adding fly ash from high-silicon (40-60% SiO2 content) industrial solid waste, the silicon content of the raw material system can be compensated. Furthermore, the Fe2O3, K2O, and P2O5 components contained in the secondary alumina ash hydrolysis slag powder and fly ash can promote crystal phase development and grain growth, further aiding proppant formation. The manganese ore powder, acting as a crystal phase deformer, lowers the sintering temperature, promotes corundum phase development, and improves the density and compressive strength of the green body.

[0031] S5: The mixed raw materials are granulated, dried, sintered at high temperature, and cooled to obtain the fracturing proppant.

[0032] In one specific embodiment, during granulation, raw material pellets are screened at a mesh size of 20 / 40.

[0033] In one specific embodiment, during high-temperature sintering, the heating rate is 3~10 ℃ / min, and then high-temperature sintering is performed at 1320~1400 ℃ for 90~180 min.

[0034] It should be noted that a heating rate that is too slow will lead to low production efficiency; a heating rate that is too fast will easily lead to abnormal crystal growth and increased porosity. If the high-temperature sintering temperature is too low, sintering will be incomplete, resulting in low density and increased breakage rate; if the high-temperature sintering temperature is too high, it will cause over-firing, deformation, and partial melting of the crystals. If the high-temperature sintering time is insufficient, the crystal phase development will be incomplete; if the high-temperature sintering time is too long, the cost will increase.

[0035] On the other hand, the present invention also provides a fracturing proppant that combines secondary aluminum ash hydrolysis residue and fly ash, which is prepared by the fracturing proppant preparation method of any one of the above-mentioned methods.

[0036] Example 1 A fracturing proppant that synergistically combines secondary aluminum ash hydrolysis residue and fly ash is prepared through the following steps: (1) The secondary aluminum ash hydrolysis residue, fly ash and manganese ore powder were added into a ball mill for grinding, and the raw material powder samples were obtained by sieving after ball milling. (2) The MgO content in the secondary aluminum ash hydrolysis residue powder was detected. The secondary aluminum ash hydrolysis residue used in this embodiment had an MgO content of 2.64%, which is less than 4%. (3) The secondary aluminum ash hydrolysis residue powder was calcined at 1000 ℃ for 60 min, and then mixed evenly with fly ash powder and manganese ore powder in a dry state. The mass percentage of the three was 76:20:4. (4) Place the uniformly mixed raw material from step (3) into a disc granulator for granulation. During the granulation process, continuously spray water to ensure that the raw material is fully wetted. Then collect 20 / 40 mesh (pore size 425-850 μm) raw material ball samples. (5) The collected raw material balls were dried at 110 °C for 2 h to completely dehydrate them. Then the dried raw material balls were placed in a muffle furnace and heated to 1340 °C at a heating rate of 5 °C / min, and held for 180 min for sintering. (6) The sintered sample was cooled in the furnace and sieved to obtain 20 / 40 mesh fracturing proppant.

[0037] Example 2 Unlike Example 1, in step (5) of this example, the temperature is raised to 1360 ℃ at a rate of 6 ℃ / min and held for 120 min for sintering.

[0038] Example 3 Unlike Example 1, in step (5) of this example, the temperature is raised to 1380 ℃ at a heating rate of 7 ℃ / min and held for 90 min for sintering.

[0039] Example 4 Unlike Example 1, in step (3) of this example, the mass percentages of secondary aluminum ash hydrolysis slag powder, fly ash powder and manganese ore powder are 70:25:5; in step (5) of this example, when high-temperature sintering is carried out, the temperature is raised to 1360 ℃ at a heating rate of 6 ℃ / min and held for 120 min for sintering.

[0040] Example 5 Unlike Example 1, in step (3) of this example, the mass percentages of secondary aluminum ash hydrolysis slag powder, fly ash powder and manganese ore powder are 80:17:3; in step (5) of this example, when high-temperature sintering is carried out, the temperature is raised to 1360 ℃ at a heating rate of 6 ℃ / min and held for 120 min for sintering.

[0041] Example 6 Unlike Example 1, the MgO content detected in step (2) of this example is 8.63%, which is greater than 4%. The secondary aluminum ash hydrolysis slag powder is pickled with 10% hydrochloric acid for 60 min, washed with water until neutral, dried, and then proceeded to step (3).

[0042] Example 7 Unlike Example 6, in step (5) of this example, the temperature is increased to 1360 ℃ at a heating rate of 6 ℃ / min and held for 120 min for sintering.

[0043] Example 8 Unlike Example 6, in step (5) of this example, the temperature is raised to 1380 ℃ at a heating rate of 7 ℃ / min and held for 90 min for sintering.

[0044] Example 9 Unlike Example 6, in step (3) of this example, the mass percentages of secondary aluminum ash hydrolysis slag powder, fly ash powder and manganese ore powder are 70:25:5; in step (5) of this example, when high-temperature sintering is carried out, the temperature is raised to 1360 ℃ at a heating rate of 6 ℃ / min and held for 120 min for sintering.

[0045] Example 10 Unlike Example 6, in step (3) of this example, the mass percentages of secondary aluminum ash hydrolysis slag powder, fly ash powder and manganese ore powder are 80:17:3; in step (5) of this example, when high-temperature sintering is carried out, the temperature is raised to 1360 ℃ at a heating rate of 6 ℃ / min and held for 120 min for sintering.

[0046] Comparative Example 1 Unlike Example 1, in this comparative example, step (1) uses unhydrolyzed original secondary aluminum ash instead of secondary aluminum ash hydrolysis residue, and step (2) is omitted to directly proceed to step (3).

[0047] Comparative Example 2 Unlike Example 6, in this comparative example, after detecting that the MgO content is greater than 4% in step (2), acid washing is not performed, and the process proceeds directly to step (3).

[0048] Comparative Example 3 Unlike Example 1, this comparative example does not include manganese ore powder, and the mass percentage of secondary aluminum ash hydrolysis residue powder and fly ash powder in step (3) is 76:24.

[0049] Test Example 1 The morphology of the fracturing proppant in each embodiment and comparative example was observed. A photograph of the fracturing proppant in Example 1 is shown below. Figure 2As shown, the scanning electron microscope image is as follows: Figure 3 As shown, the scanning electron microscope image of the fracturing proppant in Comparative Example 2 is as follows: Figure 4 As shown. From Figures 2-4 It can be seen that the main structure of the fracturing proppant of the present invention is a hexagonal prismatic corundum phase (Al2O3), and a large amount of liquid phase material fills the pores, forming a relatively dense structure. In contrast, in Comparative Example 2, when the MgO content of the secondary aluminum ash hydrolysis residue is greater than 4% and no acid washing is performed, the microstructure of its fracturing proppant exhibits a large number of Kokendal pore structures of varying sizes, and the overall density is severely damaged.

[0050] Test Example 2 The performance of the fracturing proppant in each embodiment and comparative example was tested, and the results are shown in Table 1: Table 1 Performance test results of fracturing proppant in each embodiment and comparative example

[0051] Note: In Table 1, the test conditions for the breakage rate were performed in accordance with the "Performance Test of Proppants for Hydraulic Fracturing and Gravel Filling Operations" (SY / T 5108-2014), and the compressive strength was 52 MPa.

[0052] As can be seen from Table 1, the fracturing proppant prepared by the present invention using only secondary aluminum ash hydrolysis residue, fly ash and manganese ore powder has significantly better key indicators such as breakage rate, acid solubility, sphericity and turbidity than the requirements of the SY / T5108-2014 industry standard, and can meet the fracturing construction requirements of deep oil and gas reservoirs under a closure pressure of 52 MPa.

[0053] Comparative Example 1 used secondary alumina ash as raw material. Due to the complex reactive components of its system, it easily generated gas and formed a large number of pores during sintering, resulting in a significant increase in breakage rate and substandard performance. Comparative Example 2 used high-magnesium secondary alumina ash hydrolysis slag but did not acid wash it. During sintering, it easily formed magnesium aluminum spinel and induced Kokendal porosity, severely deteriorating the support strength. Comparative Example 3 did not add manganese ore powder, which led to an increase in the sintering temperature required for the raw material system, insufficient crystal growth, and affected product performance.

[0054] In summary, this invention can completely replace traditional high-grade bauxite by using secondary aluminum ash hydrolysis residue and fly ash as the main raw materials, realizing the high-value resource utilization of these two industrial solid wastes, and effectively solving the disposal problem of large stockpiles of secondary aluminum ash hydrolysis residue and prominent environmental risks.

[0055] This invention, based on the varying MgO content in secondary aluminum ash hydrolysis slag, employs acid washing and sintering processes to produce ceramic proppant suitable for a 52 MPa closure pressure rating. The process is flexible and has a wide range of applications. Furthermore, the entire process requires no external additives or expensive auxiliary materials, relying on the synergistic ceramic formation of the solid waste's own components. The prepared ceramic proppant meets the requirements of the SY / T 5108-2014 industry standard in terms of breakage rate, sphericity, acid solubility, and turbidity.

[0056] The present invention has a simple preparation process, easy-to-control process parameters, readily available raw materials, low production cost, and is easy to promote on an industrial scale. It can alleviate my country's dependence on foreign bauxite and has both environmental benefits and economic value.

[0057] The above description is merely a representative embodiment of the present invention and is not intended to limit the present invention in any way. Any embodiment made by those skilled in the art without departing from the scope of the present invention and utilizing the disclosed technical content is an equivalent embodiment of the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing a fracturing proppant synergistically composed of secondary aluminum ash hydrolysis slag and fly ash, characterized in that, Includes the following steps: S1: Obtain secondary aluminum ash hydrolysis residue and pre-treat it to obtain secondary aluminum ash hydrolysis residue powder. S2: Detect the MgO content in the secondary aluminum ash hydrolysis slag powder; If the MgO content is less than or equal to 4%, proceed directly to step S3; If the MgO content is greater than 4%, the secondary aluminum ash hydrolysis slag powder is acid-washed to make its MgO content less than or equal to 4%, then washed to neutral and dried, and then proceeded to step S3. S3: The secondary aluminum ash hydrolysis residue powder one is subjected to high-temperature calcination to remove the gas-producing components, thereby obtaining secondary aluminum ash hydrolysis residue powder two. S4: Mix the secondary aluminum ash hydrolysis residue powder II with fly ash and manganese ore powder to obtain a mixed raw material; S5: The mixed raw materials are granulated, dried, sintered at high temperature, and cooled to obtain the fracturing proppant.

2. The method for preparing the fracturing proppant of synergistic secondary aluminum ash hydrolysis slag and fly ash according to claim 1, characterized in that, In step S1, the pretreatment includes crushing, drying, ball milling, and sieving processes performed sequentially.

3. The method for preparing the fracturing proppant of synergistic secondary aluminum ash hydrolysis slag and fly ash according to claim 1, characterized in that, In step S2, hydrochloric acid with a mass fraction of 8-12% is used for pickling.

4. The method for preparing the fracturing proppant of synergistic secondary aluminum ash hydrolysis slag and fly ash according to claim 1, characterized in that, In step S3, the high-temperature calcination treatment is carried out at 900~1100 ℃ for 30~90 min.

5. The method for preparing the fracturing proppant of synergistic secondary aluminum ash hydrolysis slag and fly ash according to claim 1, characterized in that, In step S4, the mixture includes, by weight, 70-80 parts of secondary aluminum ash hydrolysis residue powder, 15-25 parts of fly ash, and 3-5 parts of manganese ore powder.

6. The method for preparing the fracturing proppant of synergistic secondary aluminum ash hydrolysis slag and fly ash according to claim 5, characterized in that, The manganese ore powder contains MnO2 content greater than or equal to 80%.

7. The method for preparing the fracturing proppant of synergistic secondary aluminum ash hydrolysis slag and fly ash according to claim 1, characterized in that, In step S5, during granulation, raw material balls of 20 / 40 mesh are screened.

8. The method for preparing the fracturing proppant of synergistic secondary aluminum ash hydrolysis slag and fly ash according to claim 1, characterized in that, In step S5, during high-temperature sintering, the heating rate is 3~10 ℃ / min.

9. The method for preparing the fracturing proppant of synergistic secondary aluminum ash hydrolysis slag and fly ash according to any one of claims 1-8, characterized in that, In step S5, high-temperature sintering is carried out at 1320~1400 ℃ for 90~180 min.

10. A fracturing proppant that synergistically combines secondary aluminum ash hydrolysis slag and fly ash, characterized in that, It is prepared using the method for preparing synergistic secondary aluminum ash hydrolysis residue and fly ash fracturing proppant as described in any one of claims 1-9.

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