A method for preparing modified fly ash, its products and applications
By performing multi-stage sorting and ultrasonic modification of fly ash, and combining it with agricultural and forestry waste to prepare a soil conditioner for saline-alkali land, the problems of structural damage to saline-alkali soil and low utilization rate of fly ash have been solved, achieving efficient improvement of saline-alkali land and environmental protection.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- INSTITUTE OF PROCESS ENGINEERING CHINESE ACADEMY OF SCIENCES
- Filing Date
- 2023-02-23
- Publication Date
- 2026-06-30
AI Technical Summary
Existing technologies cannot effectively solve the problem of structural damage in saline-alkali soils, and the comprehensive utilization rate of fly ash is low, leading to environmental pollution and making it difficult to efficiently improve saline-alkali land.
Modified fly ash was prepared by multi-level grading, screening, magnetic separation, and ultrasonic modification of fly ash. It was then mixed with agricultural and forestry waste to prepare a soil conditioner for saline-alkali land. The specific surface area and hydrophilicity of fly ash were increased by organic acid etching reaction, the dense structure of the clay layer was destroyed, and the permeability and aeration of the soil were improved.
It achieves efficient removal of heavy metals from fly ash, improves the adsorption and solidification capacity of salt and alkali ions and the water and fertilizer retention capacity, enhances the permeability and air permeability of the soil, promotes the migration and removal of salt and alkali ions, and improves the growth environment of saline-alkali land.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of comprehensive utilization of solid waste, and particularly relates to a method for preparing modified fly ash, its products, and applications. Background Technology
[0002] Saline-alkali soil is a widely distributed obstacle soil type on Earth. Due to the excessive content of salt and alkali ions, saline-alkali soil is prone to compaction, severely affecting the flow of water, fertilizer, air, and heat, thus impacting plant growth and becoming a significant factor restricting agricultural development. Therefore, research on saline-alkali soil improvement technologies is of great significance for agricultural development and improving farmers' living standards. Many improvement technologies have been developed to address the need for saline-alkali soil improvement, such as the underground pipe salt drainage technology disclosed in CN115428611A, the ecological module technology based on the acid-base neutralization principle disclosed in CN115399173A, and a method for improving saline-alkali soil and enhancing soil fertility by activating phosphate rock powder with humic acid disclosed in CN115287079A. However, these technologies only address the problem locally and cannot fundamentally solve the soil structure damage caused by salt and alkali ions, thus hindering efficient improvement of saline-alkali soil. In particular, there are currently very few publicly disclosed technologies for improving the vertical structure of saline-alkali soil.
[0003] Fly ash is one of the major solid wastes emitted by coal-fired power plants. Currently, the comprehensive utilization rate of fly ash is low, leading to large accumulations of fly ash in several major coal-producing provinces / autonomous regions in northern my country, causing serious pollution to the surrounding environment, including the atmosphere, water bodies, and soil. Agricultural and forestry waste is another major type of agricultural and forestry waste, containing a large amount of organic matter essential for plant growth, but its comprehensive utilization is currently inadequate. If integrated technologies for heavy metal separation, targeted conversion, and soil structure reconstruction of fly ash could be used to prepare excellent saline-alkali soil conditioners from fly ash and agricultural and forestry waste, it could not only alleviate soil salinization but also achieve large-scale disposal of organic waste residues such as fly ash and agricultural and forestry waste, showing broad application prospects. Summary of the Invention
[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method for preparing modified fly ash, its products, and its applications.
[0005] To achieve this objective, the present invention employs the following technical solution:
[0006] In a first aspect, the present invention provides a method for preparing modified fly ash, the method comprising:
[0007] (1) The fly ash is first graded and screened to obtain coarse fly ash and fine fly ash, and the fine fly ash is collected.
[0008] (2) The fine fly ash obtained in step (1) is separated by magnetic separation to collect non-magnetic fly ash;
[0009] (3) Perform a second grading and screening on the non-magnetic fly ash obtained in step (2) to collect coarse ash particles;
[0010] (4) The coarse fly ash obtained in step (3) is subjected to ultrasonic modification to obtain the modified fly ash.
[0011] After multi-stage step-by-step treatment, the fly ash achieves efficient removal of typical heavy metal elements. The fly ash pretreatment technology described in this invention is entirely a physical sorting technology, without the use of chemical agents, thus avoiding secondary pollution and achieving excellent results.
[0012] Preferably, the fly ash in step (1) is the fine ash collected from the flue gas after coal combustion, and its components include silicon dioxide, aluminum oxide, sodium oxide, potassium oxide, calcium oxide, magnesium oxide, ferric oxide, titanium dioxide and carbon.
[0013] Preferably, the grading equipment used in the first grading screening in step (1) includes any one or a combination of at least two of the following: a linear vibrating screen, a circular vibrating screen, or an air classifier.
[0014] Preferably, the particle size of the fine fly ash in step (1) is ≤150μm, for example, 0.1μm, 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, 110μm, 120μm, 130μm, 140μm, 150μm, etc. Other specific values within the above range can be selected, and will not be described in detail here.
[0015] Preferably, the magnetic separation equipment used in step (2) is a medium magnetic field magnetic separator and / or a strong magnetic field magnetic separator.
[0016] Preferably, the magnetic field strength for magnetic separation in step (2) is 500-1500 kA / m, such as 500 kA / m, 600 kA / m, 700 kA / m, 800 kA / m, 900 kA / m, 1000 kA / m, 1100 kA / m, 1200 kA / m, 1300 kA / m, 1400 kA / m, 1500 kA / m, etc. Other specific values within the above range can be selected, and will not be described in detail here.
[0017] Preferably, the grading equipment used in the second grading screening in step (3) includes any one or a combination of at least two of the following: a linear vibrating screen, a circular vibrating screen, or an air classifier.
[0018] Preferably, the particle size of the coarse ash in step (3) is 10-150μm, such as 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, 110μm, 120μm, 130μm, 140μm, 150μm, etc. Other specific values within the above range can be selected, and will not be described in detail here.
[0019] Preferably, the ultrasound includes: soaking the coarse ash obtained in step (3) in clean water, stirring and ultrasound, and separating the solid and liquid.
[0020] Preferably, the temperature of the ultrasound is 20-90℃, such as 20℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, etc. Other specific values within the above range can be selected, and will not be elaborated here.
[0021] Preferably, the ultrasound duration is 0.5-20 min, and the ultrasound frequency is 20-132 kHz. The ultrasound duration can be selected from 0.5 min, 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min, 20 min, etc., and the ultrasound frequency can be selected from 20 kHz, 30 kHz, 40 kHz, 50 kHz, 60 kHz, 70 kHz, 80 kHz, 90 kHz, 100 kHz, 110 kHz, 120 kHz, 130 kHz, 132 kHz, etc. Other specific values within the above range can be selected, and will not be elaborated here.
[0022] The modification effect on fly ash is best when ultrasonication is performed at specific times and frequencies.
[0023] Preferably, the instrument used for the ultrasound is an industrial ultrasonic cleaner.
[0024] Preferably, the stirring speed is 10-650 rpm, such as 10 rpm, 20 rpm, 50 rpm, 100 rpm, 150 rpm, 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, 550 rpm, 600 rpm, 650 rpm, etc. Other specific values within the above range can be selected, and will not be elaborated here.
[0025] Preferably, the solid-liquid separation process further includes a drying step.
[0026] Preferably, the drying temperature is 60-140℃ and the drying time is 2-20h. The drying temperature can be selected from 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, etc., and the drying time can be selected from 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, etc. Other specific values within the above range can be selected, and will not be elaborated here.
[0027] In a second aspect, the present invention provides modified fly ash prepared according to the modified fly ash preparation method described in the first aspect.
[0028] Thirdly, the present invention provides a soil conditioner for saline-alkali land, wherein the raw materials for preparing the soil conditioner include the modified fly ash and organic fertilizer described in the second aspect.
[0029] After pretreatment, fly ash is mixed with agricultural and forestry waste, distiller's grains, and other organic fertilizers and matured. The organic acids produced by the organic fertilizers themselves then etch the surface of the fly ash particles. This process generates a large number of pores, increases the specific surface area of the fly ash, enhances its ability to adsorb and solidify salt and alkali ions, and improves its water and fertilizer retention capacity. On the other hand, it significantly increases the hydrophilicity of the fly ash particle surface, which helps dissolve and remove salt and alkali ions from soil particles and participates in the reconstruction of new soil aggregates, accelerating the migration and removal of salt and alkali ions.
[0030] Preferably, the organic fertilizer includes any one or a combination of at least two of the following: well-rotted straw, distiller's grains, vinegar residue, cow dung, sheep dung, oil residue, sawdust, or humic acid.
[0031] Preferably, the modified fly ash in the saline-alkali soil conditioner has a mass percentage content of 50%-90%, such as 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, etc. Other specific values within the above range can be selected, and will not be elaborated here.
[0032] Preferably, the organic fertilizer comprises, by weight percentage, 0.01%-20% decomposed straw, 0.01%-20% distiller's grains, 0.01%-30% vinegar residue, 0.01%-20% cow manure, 0.01%-20% sheep manure, 0.01%-10% oil residue, 0.01%-10% sawdust, and 0.01%-40% humic acid.
[0033] The mass percentage of the distiller's grains can be selected from 0.01%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc., and the mass percentage of the vinegar residue can be selected from 0.01%, 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 2%, etc. The percentage of cow manure by mass can be selected from 0.01%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc., and the percentage of sheep manure by mass can be selected from 0.01%, 1%, 2%, 3%, 4%, etc. The percentages of oil residue by mass can be selected from 0.01%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc., and the percentages of sawdust by mass can be selected from 0.01%, 1%, 2%, 3%, 4%, etc. The percentage of humic acid can be selected from 0.01%, 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, etc. Other specific values within the above range can be selected, which will not be elaborated here.
[0034] When the organic fertilizer includes the components described above in specific mass percentages, its effectiveness in increasing the specific surface area of fly ash and the hydrophilicity of fly ash particle surfaces is maximized.
[0035] Fourthly, the present invention provides a method for preparing a soil conditioner for saline-alkali land according to the third aspect, the method comprising mixing and maturing the modified fly ash described in the second aspect with organic fertilizer.
[0036] Preferably, the curing temperature is 10℃-40℃ and the curing time is 2-15 days. The curing temperature can be selected from 10℃, 15℃, 20℃, 25℃, 30℃, 35℃, 40℃, etc., and the curing time can be selected from 2 days, 3 days, 4 days, 5 days, 6 days, 7 days, 8 days, 9 days, 10 days, 11 days, 12 days, 13 days, 14 days, 15 days, etc. Other specific values within the above range can be selected, and will not be elaborated here.
[0037] Fifthly, the present invention provides the application of modified fly ash according to the second aspect and / or the saline-alkali soil conditioner according to the third aspect in the improvement of saline-alkali land.
[0038] Preferably, the method of using the saline-alkali soil conditioner includes: mixing the modified fly ash described in the second aspect and / or the saline-alkali soil conditioner described in the third aspect with the deep clay layer of the saline-alkali land, and then mixing the saline-alkali soil conditioner described in the third aspect with the surface soil of the saline-alkali land.
[0039] This invention creatively discovers that uniformly mixing modified fly ash and / or a soil conditioner for saline-alkali land with the deep clay layer of saline-alkali land can completely destroy the dense structure of the clay layer, increase soil permeability and aeration, improve the downward migration channels of salt and alkali ions, and thus accelerate the removal of salt and alkali ions. Then, applying the aforementioned conditioner to the topsoil of saline-alkali land allows the conditioner to replenish the soil's missing micronutrients and organic matter, increase soil porosity, reduce soil bulk density, and facilitate the removal of salt and alkali ions from the soil, providing a favorable growth environment for plants.
[0040] Preferably, the amount of modified fly ash added is 1%-5% of the mass of the mortar layer, such as 1%, 2%, 3%, 4%, 5%, etc. Other specific values within the above range can be selected, and will not be elaborated here.
[0041] When modified fly ash is added at the specific mass percentage mentioned above, it has the best effect on destroying the dense structure of the clay layer and the strongest water permeability and air permeability of the soil.
[0042] Preferably, the amount of the saline-alkali soil conditioner added is 0.5%-10% of the surface soil mass, such as 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc. Other specific values within the above range can be selected, and will not be elaborated here.
[0043] The removal effect of salt and alkali ions is best when the soil conditioner for saline-alkali land is added at the specific mass percentage mentioned above.
[0044] Preferably, the depth of the mortar layer is 0.6-2m from the ground surface, such as 0.6m, 0.8m, 1m, 1.2m, 1.4m, 1.6m, 1.8m, 2m, etc. Other specific point values within the above range can be selected, and will not be elaborated here.
[0045] Preferably, the depth of the surface soil of the saline-alkali land is 10-20cm from the surface, such as 10cm, 12cm, 14cm, 16cm, 18cm, 20cm, etc. Other specific point values within the above range can be selected, and will not be elaborated here.
[0046] Compared with the prior art, the present invention has the following beneficial effects:
[0047] (1) After multi-stage step-by-step treatment, the fly ash achieves efficient removal of typical heavy metal elements; in addition, the fly ash pretreatment technology described in this invention is a physical sorting technology and does not use chemical agents, thus avoiding the generation of secondary pollution.
[0048] (2) After pretreatment, fly ash is mixed and matured with agricultural and forestry waste, distiller's grains and other organic solid wastes. The organic acids generated by the organic solid wastes themselves are used to etch the surface of fly ash particles. On the one hand, a large number of pores are generated, which increases the specific surface area of fly ash, enhances the adsorption and solidification capacity of fly ash for salt and alkali ions, and improves the water and fertilizer retention capacity of fly ash. On the other hand, it will greatly increase the hydrophilicity of fly ash particle surface, which helps to dissolve and remove salt and alkali ions in soil particles and participate in the reconstruction of new soil aggregate structure, accelerating the migration and removal of salt and alkali ions.
[0049] (3) By modifying the fly ash through pretreatment and improving the clay layer of saline-alkali soil, the dense structure of the clay layer can be completely destroyed, the permeability and air permeability of the soil can be increased, the downward migration channel of salt and alkali ions can be improved, and the removal of salt and alkali ions can be accelerated. Detailed Implementation
[0050] To further illustrate the technical means and effects of the present invention, the following describes the technical solution of the present invention in conjunction with preferred embodiments of the present invention. However, the present invention is not limited to the scope of the embodiments.
[0051] Example 1
[0052] This embodiment provides a modified fly ash, the preparation method of which includes the following steps:
[0053] (1) First classification and screening: The fly ash was first classified and screened using an air classifier to obtain coarse fly ash and fine fly ash. Fine fly ash with a particle size ≤100μm was collected.
[0054] (2) Magnetic separation: The fine fly ash obtained in step (1) is added to a magnetic separator and magnetic separation is carried out under the condition of 1000kA / m to collect non-magnetic fly ash;
[0055] (3) Second classification and screening: The non-magnetic fly ash obtained in step (2) is classified and screened a second time using an air classifier to collect coarse ash particles with a particle size of 20-100μm.
[0056] (4) Ultrasonic modification: The coarse fly ash obtained in step (3) is soaked in clean water, and then ultrasonically subjected to 70KHz for 10 minutes under stirring conditions at 50℃ and 350rpm. After solid-liquid separation, it is dried at 100℃ for 10h to obtain the modified fly ash.
[0057] Example 2
[0058] This embodiment provides a modified fly ash, the preparation method of which includes the following steps:
[0059] (1) First classification and screening: The fly ash was first classified and screened using an air classifier to obtain coarse fly ash and fine fly ash. Fine fly ash with a particle size ≤150μm was collected.
[0060] (2) Magnetic separation: The fine fly ash obtained in step (1) is added to a magnetic separator and magnetic separation is carried out under the condition of 500kA / m to collect non-magnetic fly ash;
[0061] (3) Second classification and screening: The non-magnetic fly ash obtained in step (2) is classified and screened a second time using an air classifier to collect coarse ash particles with a particle size of 5-150μm.
[0062] (4) Ultrasonic modification: The coarse fly ash obtained in step (3) is soaked in clean water, and after stirring at 20℃ and 50 rpm for 20 min at 20 kHz, solid-liquid separation is performed, and the fly ash is dried at 55℃ for 20 h to obtain the modified fly ash.
[0063] Example 3
[0064] This embodiment provides a modified fly ash, the preparation method of which includes the following steps:
[0065] (1) First classification and screening: The fly ash was first classified and screened using an air classifier to obtain coarse fly ash and fine fly ash. Fine fly ash with a particle size of ≤80μm was collected.
[0066] (2) Magnetic separation: The fine fly ash obtained in step (1) is added to a magnetic separator and magnetic separation is carried out under the condition of 1500kA / m to collect non-magnetic fly ash;
[0067] (3) Second classification and screening: The non-magnetic fly ash obtained in step (2) is classified and screened a second time using an air classifier to collect coarse ash particles with a particle size of 35-80μm.
[0068] (4) Ultrasonic modification: The coarse fly ash obtained in step (3) is soaked in clean water, and then ultrasonically subjected to 132KHz for 2 minutes under stirring conditions at 90℃ and 600rpm. After solid-liquid separation, it is dried at 140℃ for 2 hours to obtain the modified fly ash.
[0069] Example 4
[0070] This embodiment provides a modified fly ash, the only difference between which is the preparation method and that of Example 1, except that the ultrasonic modification is carried out at 200KHz, and the other operations are the same as in Example 1.
[0071] Example 5
[0072] This embodiment provides a modified fly ash, the only difference between which is the preparation method and that of Example 1, except that the modification is carried out at 10KHz, and the other operations are the same as in Example 1.
[0073] Example 6
[0074] This embodiment provides a modified fly ash, the only difference between which is the preparation method and that of Example 1, except that the ultrasonic modification time is 40 minutes, and the other operations are the same as in Example 1.
[0075] Example 7
[0076] This embodiment provides a modified fly ash, the only difference between which is the preparation method and that of Example 1, except that the ultrasonic modification time is 0.1 min, and the other operations are the same as in Example 1.
[0077] Comparative Example 1
[0078] This comparative example provides a fly ash that differs from Example 1 only in that ultrasonic modification is not performed during the preparation of the fly ash; all other operations are the same as in Example 1.
[0079] Comparative Example 2
[0080] This comparative example provides a modified fly ash, which differs from Example 1 only in that ultrasonic modification is replaced by acid modification in the preparation process of the modified fly ash, while other operations are the same as in Example 1.
[0081] The specific operation of acid modification is as follows: the coarse fly ash obtained in step (3) is added to a 0.5 mol / L citric acid solution, and after soaking and stirring at 55°C and 10 rpm for 3 hours, the solid and liquid are separated, and after drying at 105°C for 24 hours, the modified fly ash is obtained.
[0082] Example 8
[0083] This embodiment provides a soil conditioner for saline-alkali land. The raw materials for preparing the soil conditioner include 70% modified fly ash, 10% distiller's grains, 15% vinegar residue, and 5% cow manure as described in Example 1.
[0084] The preparation method is as follows: mix the raw materials for the preparation of the saline-alkali soil conditioner, and mature at 25°C for 9 days to obtain the final product.
[0085] Example 9
[0086] This embodiment provides a soil conditioner for saline-alkali land. The raw materials for preparing the soil conditioner include 90% modified fly ash, 5% oil residue, and 5% sawdust as described in Example 2.
[0087] The preparation method is as follows: mix the raw materials for the preparation of the saline-alkali soil conditioner, and mature at 10°C for 15 days to obtain the final product.
[0088] Example 10
[0089] This application example provides a soil conditioner for saline-alkali land. The raw materials for preparing the soil conditioner include 50% modified fly ash, 20% humic acid, 10% sheep manure, 10% cow manure, and 10% sawdust, as described in Example 3.
[0090] The preparation method is as follows: mix the raw materials for the preparation of the saline-alkali soil conditioner, and mature at 40°C for 3 days to obtain the final product.
[0091] Examples 11-14
[0092] This embodiment provides four types of soil conditioners for saline-alkali land. The only difference between this embodiment and Example 8 is that the modified fly ash described in Example 1 is replaced in equal amounts with the modified fly ash described in Examples 4-7, while other components and contents remain unchanged.
[0093] The preparation method is described in Example 8.
[0094] Application Example 1
[0095] This application example provides a method for using a soil conditioner for saline-alkali land. The method for using the soil conditioner for saline-alkali land is as follows:
[0096] (1) Mix the modified fly ash described in Example 1 with the mortar layer at a ratio of 3% until uniform;
[0097] (2) Add the soil conditioner for saline-alkali land at a ratio of 6% to the topsoil of the saline-alkali land and mix it evenly.
[0098] Application Example 2
[0099] This application example provides a method for using a soil conditioner for saline-alkali land. The method for using the soil conditioner for saline-alkali land is as follows:
[0100] (1) Mix the soil conditioner for saline-alkali land with the clay layer at a ratio of 1%;
[0101] (2) Add the soil conditioner for saline-alkali land at a ratio of 10% to the topsoil of the saline-alkali land and mix it evenly.
[0102] Application Example 3
[0103] This application example provides a method for using a soil conditioner for saline-alkali land. The method for using the soil conditioner for saline-alkali land is as follows:
[0104] (1) Mix the modified fly ash described in Example 1 with the mortar layer at a ratio of 5% until uniform;
[0105] (2) Add the soil conditioner for saline-alkali land at a ratio of 1% to the topsoil of the saline-alkali land and mix it evenly.
[0106] Application Example 4
[0107] This application example provides a method for using a soil conditioner for saline-alkali land. The method for using the soil conditioner for saline-alkali land is as follows:
[0108] (1) Add the soil conditioner for saline-alkali land at a ratio of 9% to the topsoil of the saline-alkali land and mix it evenly.
[0109] Application Example 5
[0110] This application example provides a method for using a soil conditioner for saline-alkali land. The only difference between this method and Application Example 1 is that the mixing ratio of modified fly ash in step (1) is 0.1%, while the rest of the application method is the same as Application Example 1.
[0111] Application Example 6
[0112] This application example provides a soil conditioner for saline-alkali land and its application method. The only difference between this application example and application example 1 is that the mixing ratio of modified fly ash in step (1) of the application method is 15%, while the rest of the application method is the same as application example 1.
[0113] Application Example 7
[0114] This application example provides a soil conditioner for saline-alkali land and its application method. The only difference between this application example and application example 1 is that the addition ratio of the soil conditioner for saline-alkali land in step (2) of the application method is 0.1%, and the rest of the application method is the same as application example 1.
[0115] Application Example 8
[0116] This application example provides a method for using a saline-alkali soil conditioner. The only difference between this method and application example 1 is that the addition ratio of the saline-alkali soil conditioner in step (2) is 20%. The rest of the application method is the same as application example 1.
[0117] Test Example 1
[0118] Heavy metal removal rate of fly ash
[0119] Test method:
[0120] The contents of cadmium, chromium, arsenic, mercury, and lead were determined using inductively coupled plasma mass spectrometry (ICP-MS). The content and mass changes of heavy metals before and after removal were also measured, and the removal rates of different heavy metals were calculated. The removal rates of heavy metals in the modified fly ash prepared in Examples 1-7 and Comparative Examples 1-2 of this invention were determined using the above method, and the results are shown in Table 1.
[0121] Table 1
[0122]
[0123] As shown in Table 1, the modified fly ash of this invention has a low content of heavy metals. Comparative Examples 1-2 showed the worst heavy metal removal effect, indicating that ultrasound is particularly important for heavy metal removal, and its removal effect is better than that of acid modification. Compared with Examples 1-3, the heavy metal removal rates of Examples 4-7 were lower, indicating that the frequency and duration of ultrasound have a significant impact on heavy metal removal.
[0124] Test Example 2
[0125] Testing the effectiveness of soil conditioner in saline-alkali land
[0126] The soil conditioners described in Examples 8-14 were applied to saline-alkali land in Shizuishan City, Ningxia Hui Autonomous Region, according to the method described in Application Example 1 (the pH value of the saline-alkali soil before improvement was 10.50, the soil salt content was 0.62%, the soil organic matter content was 1.25%, and the soil porosity was 22.26%). The pH value, salt content, organic matter content, and soil porosity of the soil after treatment were measured, and the results are shown in Table 2.
[0127] The saline-alkali soil conditioner described in Example 8 was applied to the saline-alkali land in the Hetao Irrigation District of Inner Mongolia according to the methods described in Application Examples 1-8 (the pH value of the saline-alkali soil before improvement was 10.65, the soil salt content was 0.73%, the soil organic matter content was 1.23%, and the soil porosity was 20.45%). The pH value, salt content, organic matter content, and soil porosity of the soil after treatment were measured, and the results are shown in Table 3.
[0128] Test methods: Mix soil samples with deionized water at a mass:volume ratio of 1 kg:5 L, stir for 5 min, let stand for 1 h, and then measure the pH value of the supernatant using a pH meter. This pH value is the soil pH value. Determine the soil pH before and after treatment with the saline-alkali soil amendment according to the above method. Determine the soil salinity before and after treatment with the saline-alkali soil amendment according to DB37 / T 1303-2009 (gravimetric method for determining total soil salinity). Determine the soil organic matter content before and after treatment with the saline-alkali soil amendment according to NY / T 1121.6-2006 (soil testing part 6: determination of soil organic matter). Determine the soil porosity before and after treatment with the saline-alkali soil amendment according to the ring weighing method.
[0129] Table 2
[0130] Group pH value Salt content (%) Organic matter content (%) Soil porosity (%) Example 8 8.31 0.18 1.43 45.22 Example 9 8.62 0.17 1.38 46.18 Example 10 8.50 0.14 1.34 40.22 Example 11 8.71 0.25 1.34 39.42 Example 12 8.46 0.30 1.44 34.89 Example 13 8.84 0.30 1.29 37.15 Example 14 8.63 0.26 1.28 36.55
[0131] Table 2 shows that the soil conditioners prepared in Examples 8-10 have a good effect on improving saline-alkali soil. After application, the pH of the saline-alkali soil decreased significantly, the salt content decreased significantly, and the organic matter content and soil porosity also improved significantly. Compared with Examples 8-10, Examples 11-14 showed slightly different effects on improving saline-alkali soil, indicating that the frequency and time of ultrasonic modification have a slightly positive impact on soil improvement.
[0132] Table 3
[0133] Group pH value Salt content (%) Organic matter content (%) Soil porosity (%) Application Example 1 8.25 0.24 1.34 43.15 Application Example 2 8.34 0.31 1.29 40.61 Application Example 3 8.49 0.37 1.40 39.84 Application Example 4 8.75 0.65 1.38 26.48 Application Example 5 8.60 0.35 1.29 37.66 Application Example 6 8.58 0.39 1.33 34.06 Application Example 7 8.50 0.37 1.27 37.02 Application Example 8 8.39 0.40 1.31 34.56
[0134] As shown in Table 3, compared with Application Examples 1-3, Application Examples 5-8 all showed poor soil improvement effects, indicating that the amount of soil conditioner and modified fly ash added affects the improvement effect on saline-alkali soil. Application Example 4 showed the worst soil improvement effect, indicating that it is particularly important to treat the clay layer with modified fly ash and / or saline-alkali soil conditioner before using the soil conditioner.
[0135] The applicant declares that this invention illustrates a method for preparing modified fly ash, its products, and applications through the above embodiments. However, this invention is not limited to the above embodiments, meaning that this invention does not necessarily rely on the above embodiments for implementation. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials for the products of this invention, additions of auxiliary components, and selection of specific methods all fall within the protection and disclosure scope of this invention.
[0136] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.
[0137] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.
Claims
1. Use of a modified fly ash and a saline-alkali soil conditioner in the improvement of saline-alkali soil, characterized in that, The method of using the modified fly ash and the saline-alkali soil conditioner includes: mixing the modified fly ash with the deep clay layer of the saline-alkali land, and then mixing the saline-alkali soil conditioner with the surface soil of the saline-alkali land. The method for preparing the modified fly ash includes: (1) The fly ash was first graded and screened to obtain coarse fly ash and fine fly ash, and the fine fly ash was collected. (2) The fine fly ash obtained in step (1) is separated by magnetic separation, and the non-magnetic fly ash is collected; (3) Perform a second grading and screening on the non-magnetic fly ash obtained in step (2) and collect the coarse ash particles; (4) The coarse fly ash obtained in step (3) is subjected to ultrasonic modification to obtain the modified fly ash; The modified fly ash is added at a rate of 1%-5% of the mass of the clay layer; the saline-alkali soil conditioner is added at a rate of 0.5%-10% of the mass of the topsoil. The raw materials for preparing the saline-alkali soil conditioner include modified fly ash and organic fertilizer.
2. The application according to claim 1, characterized in that, The fly ash mentioned in step (1) is the fine ash collected from the flue gas after coal combustion. Its components include silicon dioxide, aluminum oxide, sodium oxide, potassium oxide, calcium oxide, magnesium oxide, ferric oxide, titanium dioxide and carbon.
3. The application according to claim 1, characterized in that, The particle size of the fine fly ash in step (1) is ≤150 μm.
4. The application according to claim 1, characterized in that, The magnetic field strength for magnetic separation in step (2) is 500-1500 kA / m.
5. The application according to claim 1, characterized in that, The coarse ash in step (3) has a particle size of 10-150 μm.
6. The application according to claim 1, characterized in that, The ultrasonic modification includes: soaking the coarse ash obtained in step (3) in clean water, stirring and ultrasonicating, and separating the solid and liquid.
7. The application according to claim 6, characterized in that, The temperature of the ultrasound is 20-90℃.
8. The application according to claim 6, characterized in that, The duration of the ultrasound is 0.5-20 minutes.
9. The application according to claim 6, characterized in that, The ultrasonic frequency is 20-132 kHz.
10. The application according to claim 6, characterized in that, The stirring speed is 10-650 rpm.
11. The application according to claim 6, characterized in that, The solid-liquid separation process also includes a drying step.
12. The application according to claim 11, characterized in that, The drying temperature is 55-140℃, and the time is 2-20 h.
13. The application according to claim 1, characterized in that, The organic fertilizer includes any one or a combination of at least two of the following: well-rotted straw, distiller's grains, vinegar residue, cow dung, sheep dung, oil residue, sawdust, or humic acid.
14. The application according to claim 1, characterized in that, The modified fly ash in the saline-alkali soil conditioner has a mass percentage content of 50%-90%.
15. The application according to claim 13, characterized in that, The organic fertilizer, by mass percentage, includes 0.1%-20% decomposed straw, 0.1%-20% distiller's grains, 0.1%-30% vinegar residue, 0.1%-20% cow manure, 0.1%-20% sheep manure, 0.1%-10% oil residue, 0.1%-10% sawdust, and 0.1%-40% humic acid.
16. The application according to claim 1, characterized in that, The preparation method of the saline-alkali soil conditioner includes mixing and maturing modified fly ash with organic fertilizer.
17. The application according to claim 16, characterized in that, The ripening temperature is 10-40℃, and the time is 2-15 days.
18. The application according to claim 1, characterized in that, The depth of the surface soil in the saline-alkali land is 10-20cm.