Preparation method of modified fly ash for saline-alkali soil improvement and product and application thereof

Abstract

The invention relates to a preparation method of modified fly ash for saline-alkali soil improvement and a product and application of the modified fly ash, and the preparation method comprises the following steps: sequentially carrying out classified screening, magnetic separation and alkaline modification on fly ash to obtain the modified fly ash. The invention also provides a fly ash based soil conditioner, and the fly ash based soil conditioner comprises the modified fly ash. By adding the fly ash-based soil conditioner into the saline-alkali soil, the content of trace elements and organic matters in the saline-alkali soil is increased, formation of granular structures in the soil and reconstruction of soil structures are promoted, effective pores of the soil are increased, water permeability and air permeability are improved, the desalting rate of the soil is remarkably increased, and the saline-alkali soil is improved. Therefore, the saline-alkali soil is improved.

Description

Technical Field

[0001] The invention belongs to the field of soil improvement, and relates to a preparation method of modified fly ash for improving saline-alkali land, and a product and application thereof. Background Art

[0002] Saline-alkali soil is a type of obstructive soil widely distributed in the world. At present, the global saline-alkali soil area is about 954.4 million hectares, and it is increasing at a rate of more than 100 million hectares per year. 6 hm 2 The coastal saline-alkali soil is a special type of saline-alkali land. Due to its unique climate characteristics and long-term immersion in seawater, the soil has a high salt content, is solid and compacted, has a high bulk density and small pores. Dredger fill soil is a special type of coastal saline-alkali soil formed during land reclamation. As a saline sludge, it basically does not have the complete structure of soil, and the parent material of the soil is too saline and basically has no water permeability and air permeability. If it is to become healthy soil suitable for plant growth, it is necessary to constantly seek new technologies and carry out large-scale improvements.

[0003] CN115136764A discloses a reverse salt discharge method for improving saline-alkali land. Pipelines, water content sensors and salt sensors are buried under the soil layer to be improved. A control system controls a water pump to inject water into the pipeline, and the water content sensor and the salt sensor feed back values ​​to the control system to control the amount of injected water. Water is injected in a circular manner until the salt content value under the required standard is reached. After the last water injection operation is completed, the soil salt formed on the surface of the soil layer is dried in the sun, and the reverse salt discharge method is used to discharge the salt under the soil layer back to the surface, which is convenient for direct unified treatment at a later stage. However, the process is relatively cumbersome, and the engineering workload is large, requiring a large amount of water resources and labor.

[0004] CN114316998A discloses a saline-alkali soil improver and its preparation method, wherein desulfurized gypsum and aluminum silicate are used as regulators, palmitic acid and stearic acid are used as auxiliary agents, and microbial fermentation agents, straw, cow dung, water, etc. are added to prepare the improver and apply it to saline-alkali soil. This chemical improver can effectively prevent the soil from returning to salt when the surface water evaporates strongly, and the effect is fast and the improvement effect is obvious, but it cannot fundamentally change the properties of saline-alkali soil, and it is only a temporary solution. In addition, the desulfurized gypsum in the applied improver itself is a salt, which will increase the soil salinity and easily form salinized soil.

[0005] CN115261026A discloses a saline-alkali soil conditioner and a method for improving it, wherein activated carbon modified with nitric acid, cellulose-degrading bacteria, and a composite bacterial agent of phosphate-dissolving bacteria, and a composite fertilizer are applied to saline-alkali soil for improvement. This improvement technology adopts a combination of physical and biological repair to achieve the purpose of improving the soil structure of saline-alkali land, reducing salinity, increasing soil nutrient content, reducing the content of organic pollutants in the soil, and improving saline-alkali land in a lasting and effective manner; CN115181574A discloses a saline-alkali soil conditioner and a method for preparing it, which is mainly organic nutrients, adds a small amount of inorganic NPK nutrients, and is equipped with modified biomass charcoal and microbial agents to condition the saline-alkali soil, which can quickly adjust the physical and chemical properties of the soil, improve the soil enzyme activity and microbial content level, improve the crop growth environment, and fundamentally alleviate the level of soil salinization. Both of the above methods can improve saline-alkali soil to a certain extent, but the implementation cost is high, and the improvement cycle is long, which is not suitable for large-scale improvement.

[0006] In view of the deficiencies in the prior art, the present invention uses fly ash after directional modification as a raw material to prepare a soil conditioner, and provides a method for improving coastal saline-alkali soil (dredge fill soil). Summary of the invention

[0007] In view of the deficiencies in the prior art, the object of the present invention is to provide a method for preparing modified fly ash for improving saline-alkali land, and its product and application.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a method for preparing modified fly ash for improving saline-alkali land, the preparation method comprising:

[0010] (1) Classifying and screening fly ash to obtain coarse fly ash and fine fly ash, and collecting the fine fly ash;

[0011] (2) performing magnetic separation on the fine fly ash obtained in step (1) to collect non-magnetic fly ash;

[0012] (3) The non-magnetic fly ash obtained in step (2) is modified by an alkali method to obtain the modified fly ash.

[0013] The present invention firstly performs graded screening and magnetic separation on fly ash to remove most of the heavy metals in the fly ash, and the removal process is a purely physical separation, which will not damage the particle structure inside the fly ash and will not affect the properties of the fly ash after separation.

[0014] The particles of blown fill soil are extremely small and do not have the aggregate structure of normal soil at all. The soil has extremely high salinity, viscosity and density, and is basically not permeable to water and air, making it extremely difficult to wash and drain salt. In order to reshape the aggregate structure of blown fill soil, the present invention uses an alkali method to modify the obtained non-magnetic fly ash. A large number of hydroxyl groups will be grafted onto the surface of the fly ash particles modified by the alkali solution, which can significantly enhance the hydrogen bonding force with the mineral molecular groups in the soil particles, thereby promoting the bonding of fine soil particles, gradually forming a soil aggregate structure, and achieving structural remodeling. Not only can the number of effective pores inside the soil be increased, but the permeability and air permeability are also improved accordingly, and the effects of washing and draining salt are greatly improved. Adding organic fertilizers can increase the nutrient content in the soil, supplement the nutrients necessary for crop growth, improve the soil ecological environment, and further promote crop growth.

[0015] Preferably, the particle size of the fine fly ash in step (1) is 120-250 μm, for example, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm, 210 μm, 220 μm, 230 μm, 240 μm, 250 μm, etc. Other specific point values ​​within the above numerical range can be selected and will not be described here one by one.

[0016] The particle size of fly ash is also very important for soil permeability. Fly ash particles with larger particle sizes have a stronger adsorption effect on fine soil particles, which increases soil porosity and improves permeability.

[0017] Preferably, the grading equipment used for the grading screening includes any one of a linear vibrating screen, a circular vibrating screen or an air flow classifier, or a combination of at least two of them.

[0018] Preferably, the magnetic field strength of the magnetic separation in step (2) is 500-1600 kA / m, for example 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, 1600 kA / m, etc. Other specific point values ​​within the above numerical range can be selected and will not be described one by one here.

[0019] Preferably, the magnetic separation equipment used in the magnetic separation in step (2) is a magnetic separator.

[0020] Preferably, the alkaline modification in step (3) comprises: immersing and stirring the non-magnetic fly ash obtained in step (2) in an alkaline solution, and performing solid-liquid separation to obtain the modified fly ash.

[0021] Preferably, the molar concentration of the alkaline solution is 0.1-2 mol / L, for example, 0.1 mol / L, 0.3 mol / L, 0.5 mol / L, 0.7 mol / L, 0.9 mol / L, 1 mol / L, 1.2 mol / L, 1.4 mol / L, 1.6 mol / L, 1.8 mol / L, 2 mol / L, etc. Other specific point values ​​within the above numerical range can be selected, which will not be described one by one here.

[0022] The concentration of alkali is very important to the permeability of the soil. When the alkali concentration is too high, the soil permeability rate will be reduced, and the improvement effect will also be inhibited.

[0023] Preferably, the alkaline solution comprises sodium hydroxide and / or potassium hydroxide.

[0024] Preferably, the temperature of the immersion stirring is 20-95° C., and the time is 0.5-5 h.

[0025] The temperature of the immersion and stirring can be selected from 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 95°C, etc., and the time can be selected from 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, etc. Other specific point values ​​within the above numerical range can be selected, and they will not be described one by one here.

[0026] The temperature and time of alkali modification will affect the modification effect of fly ash.

[0027] Preferably, the rotation speed of the immersion stirring is 10-700rpm, for example, 10rpm, 50rpm, 100rpm, 150rpm, 200rpm, 250rpm, 300rpm, 350rpm, 400rpm, 450rpm, 500rpm, 550rpm, 600rpm, 650rpm, 700rpm, etc. Other specific point values ​​within the above numerical range can be selected, which will not be repeated here.

[0028] Preferably, the ratio of the alkaline solution to fly ash is (2-10) L:1 kg, wherein the specific point values ​​in (2-10) can be selected from 2, 3, 4, 5, 6, 7, 8, 9, 10, etc., and other specific point values ​​within the above numerical range can be selected, which will not be repeated here.

[0029] Preferably, washing is further included after the solid-liquid separation.

[0030] Preferably, the washing method includes pulp washing and / or shower washing.

[0031] Preferably, the washing liquid used for washing comprises water.

[0032] Preferably, the liquid-to-solid ratio of the washing is (2-10) L:1 kg, wherein the specific point values ​​in (2-10) can be selected from 2, 3, 4, 5, 6, 7, 8, 9, 10, etc., and other specific point values ​​within the above numerical range can be selected, which will not be repeated here.

[0033] In a second aspect, the present invention provides a modified fly ash prepared according to the method for preparing modified fly ash for improving saline-alkali land according to the first aspect.

[0034] In a third aspect, the present invention provides a fly ash-based soil conditioner for improving saline-alkali land, wherein the raw materials for preparing the fly ash-based soil conditioner for improving saline-alkali land include the modified fly ash and organic fertilizer described in the second aspect.

[0035] Preferably, the mass percentage of the modified fly ash in the fly ash-based soil conditioner for saline-alkali land improvement is 60-90%, for example, 60%, 65%, 70%, 75%, 80%, 85%, 90%, etc. Other specific point values ​​within the above numerical range can be selected, and they will not be described one by one here.

[0036] When the modified fly ash is added to the fly ash-based soil conditioner for saline-alkali land improvement at the above-mentioned specific mass percentage, the soil conditioner has the best improvement effect on the saline-alkali land soil.

[0037] Preferably, the organic fertilizer comprises any one of residues, straw, excrement or sawdust, or a combination of at least two of them; the residue comprises any one of vinegar residues, wine residues or oil residues, or a combination of at least two of them.

[0038] Preferably, the organic fertilizer comprises, by mass percentage, 0.5-20% of vinegar residue, 0.5-30% of wine residue, 0.5-30% of oil residue, 0.5-10% of straw, 0.5-20% of sawdust, and 0.5-10% of feces.

[0039] The mass percentage of the vinegar residue can be selected from 0.5%, 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, etc.; the mass percentage of the wine residue can be selected from 0.5%, 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, etc.; the mass percentage of the oil residue can be selected from 0.5%, 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26 The mass percentage of the straw can be selected from 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc., the mass percentage of the sawdust can be selected from 0.5%, 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, etc., the mass percentage of the feces can be selected from 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc., and other specific point values ​​within the above numerical range can be selected, which will not be repeated here.

[0040] Preferably, the excrement comprises cow dung and / or sheep dung.

[0041] In a fourth aspect, the present invention provides a method for preparing a fly ash-based soil conditioner for improving saline-alkali land according to the third aspect, the preparation method comprising: mixing and composting the modified fly ash described in the second aspect with organic fertilizer.

[0042] Preferably, the composting temperature is 25-65°C, and the time is 10-60 days. The temperature can be selected from 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, etc., and the time can be selected from 10 days, 15 days, 20 days, 25 days, 30 days, 35 days, 40 days, 45 days, 50 days, 55 days, 60 days, etc. Other specific point values ​​within the above numerical range can be selected, and they will not be repeated here one by one.

[0043] The composting temperature and time in the preparation method of fly ash-based soil conditioner for saline-alkali land improvement are very important for the effect of the conditioner.

[0044] In a fifth aspect, the present invention provides a use of the modified fly ash according to the second aspect or the saline-alkali land soil conditioner according to the third aspect in improving saline-alkali land.

[0045] Preferably, the method for using the fly ash-based soil conditioner for improving saline-alkali land comprises: mixing and cultivating the fly ash-based soil conditioner described in the third aspect with coastal saline-alkali soil.

[0046] Preferably, the coastal saline-alkali soil is filled soil in coastal areas.

[0047] Preferably, the addition amount of the fly ash-based soil conditioner for saline-alkali land improvement is 20-70% of the mass of the saline-alkali soil, for example 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, etc. Other specific point values ​​within the above numerical range can be selected, which will not be described here one by one.

[0048] Preferably, the cultivation temperature is 25-65°C, and the time is 1-60 days. The cultivation temperature can be selected from 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, etc., and the time can be selected from 1 day, 5 days, 10 days, 15 days, 20 days, 25 days, 30 days, 35 days, 40 days, 45 days, 50 days, 55 days, 60 days, etc. Other specific point values ​​within the above numerical range can be selected, and they will not be repeated here.

[0049] Preferably, the culture is also stirred, and the frequency of stirring is 3-7 days / time, for example 3 days / time, 4 days / time, 5 days / time, 6 days / time, 7 days / time, etc. Other specific point values ​​within the above numerical range can be selected, which will not be described one by one here.

[0050] Preferably, the raw materials mixed with the coastal saline-alkali soil for cultivation also include nutrients.

[0051] Preferably, the nutrients include any one of nitrogen fertilizer, potassium fertilizer or phosphorus fertilizer, or a combination of at least two of them.

[0052] Preferably, the mass ratio of nitrogen, potassium and phosphorus in the mixed cultivation raw materials is (3-8):(5-10):1, wherein the specific point values ​​in (3-8) can be selected from 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, etc., wherein the specific point values ​​in (5-10) can be selected from 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, etc., and other specific point values ​​within the above numerical range can be selected, which will not be repeated here.

[0053] Preferably, the mass percentage of water in the mixed cultivation is 5-40%, for example 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, etc. Other specific points within the above numerical range can be selected and will not be described here one by one.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] (1) The preparation method provided by the present invention firstly classifies and screens the fly ash and performs magnetic separation to remove most of the heavy metals in the fly ash without causing pollution to the soil.

[0056] (2) The preparation method provided by the present invention is to prepare modified fly ash by reacting fly ash with alkali. A large number of hydroxyl groups are grafted on the surface of the modified fly ash particles, which can significantly enhance the hydrogen bonding force with the fine soil particles in the saline-alkali soil, thereby enhancing the bonding effect between the fine soil particles, promoting the formation of soil aggregate structure, and realizing the remodeling of the saline-alkali soil structure. It can not only increase the number of effective pores inside the soil, greatly improve the water permeability and air permeability, but also play a role in loosening the soil, reducing the bulk density of the soil, and regulating the water, fertilizer, gas and heat of the soil.

[0057] (3) The fly ash-based soil conditioner prepared by the present invention is rich in a variety of trace elements and organic nutrients that are beneficial to crop growth, and can supplement and balance the nutrients in saline-alkali soil. The organic matter therein is also beneficial to coordinate the pH value of the soil, improve the soil ecological environment, and further promote the growth of crops.

[0058] (4) The present invention uses fly ash solid waste as the main raw material to prepare a soil conditioner, which has a simple process and low cost. It can not only improve the coastal saline-alkali soil, but also realize the high added value utilization of fly ash, and has broad application prospects. DETAILED DESCRIPTION

[0059] In order to further explain the technical means and effects adopted by the present invention, the technical solution of the present invention is further described below in conjunction with the preferred embodiments of the present invention, but the present invention is not limited to the scope of the embodiments.

[0060] If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the field or the product instructions are used. If no manufacturer is specified for the reagents or instruments used, they are all conventional products that can be purchased through regular channels.

[0061] The fly ash, vinegar residue, wine residue, oil residue, crop straw, wood chips, animal manure and other materials required in the present invention can be taken from or purchased from corresponding production plants: for example, the fly ash described in the present invention is taken from a power plant, and the fly ash used in the following embodiments is taken from a power plant in Maliantai; the vinegar residue, wine residue, oil residue and straw are taken from corresponding production plants, and the wine residue, vinegar residue, oil residue and straw used in the following embodiments are taken from wineries, vinegar factories, oil mills and farms in Zhejiang Province respectively; the cow dung and sheep dung are taken from breeding farms, and the cow dung and sheep dung used in the following embodiments are taken from breeding farms in Zhejiang Province.

[0062] Example 1

[0063] This embodiment provides a modified fly ash for improving saline-alkali land. The preparation method of the modified fly ash for improving saline-alkali land includes:

[0064] (1) Classification and screening: Use a linear vibrating screen with a screening particle size of 180 μm to classify and screen the fly ash and collect fine fly ash;

[0065] (2) Magnetic separation: The fine fly ash obtained in step (1) is subjected to magnetic separation at 1000 kA / m to collect non-magnetic fly ash;

[0066] (3) Alkali modification: The non-magnetic fly ash obtained in step (2) was reacted with 1 mol / L sodium hydroxide solution at a liquid-to-solid ratio of 5 L:1 kg at 60° C. for 2.5 h, with a stirring speed of 180 rpm. After the reaction was completed, the solid and liquid were separated and washed with water, wherein the ratio of water to fly ash was 5 L:1 kg, to obtain alkali-modified fly ash.

[0067] Example 2

[0068] This embodiment provides a modified fly ash for improving saline-alkali land. The preparation method of the modified fly ash for improving saline-alkali land includes:

[0069] (1) Classification and screening: Use a linear vibrating screen with a screening particle size of 250 μm to classify and screen the fly ash and collect fine fly ash;

[0070] (2) Magnetic separation: Magnetic separation is performed at 500 kA / m to collect non-magnetic fly ash;

[0071] (3) Alkali modification: The non-magnetic fly ash obtained in step (2) was reacted with 2 mol / L sodium hydroxide solution at a liquid-to-solid ratio of 10 L:1 kg at 95° C. for 1 h, with a stirring speed of 700 rpm, solid-liquid separation, and washed with water, wherein the ratio of water to fly ash was 8 L:1 kg, to obtain alkali-modified fly ash.

[0072] Example 3

[0073] This embodiment provides a modified fly ash for improving saline-alkali land. The preparation method of the modified fly ash for improving saline-alkali land includes:

[0074] (1) Classification and screening: Use a linear vibrating screen with a screening particle size of 120 μm to classify and screen the fly ash and collect fine fly ash;

[0075] (2) Magnetic separation: Magnetic separation is performed at 1600 kA / m to collect non-magnetic fly ash;

[0076] (3) Alkali modification: The non-magnetic fly ash obtained in step (2) was reacted with 0.5 mol / L sodium hydroxide solution at a liquid-to-solid ratio of 2L:1kg at 20°C for 5h, with a stirring speed of 50rpm, solid-liquid separation, and washed with water, wherein the ratio of water to fly ash was 3L:1kg, to obtain alkali-modified fly ash.

[0077] Example 4

[0078] The present embodiment provides a modified fly ash for improving saline-alkali land. The preparation method thereof is different from that of the embodiment 1 only in that step (3) is "the non-magnetic fly ash obtained in step (2) is reacted with 5 mol / L sodium hydroxide solution at a liquid-to-solid ratio of 5 L:1 kg at 60° C. for 2.5 h, with a stirring speed of 180 rpm. After the reaction is completed, the solid and liquid are separated, and the fly ash is washed with water, wherein the ratio of water to fly ash is 5 L:1 kg, to obtain alkali-modified fly ash". The other operations are the same as those of the embodiment 1.

[0079] Example 5

[0080] The present embodiment provides a modified fly ash for improving saline-alkali land. The preparation method thereof is different from that of the embodiment 1 only in that step (3) is "the non-magnetic fly ash obtained in step (2) is reacted with 0.05 mol / L sodium hydroxide solution at a liquid-to-solid ratio of 5 L:1 kg at 60° C. for 2.5 h, with a stirring speed of 180 rpm. After the reaction is completed, the solid and liquid are separated and washed with water, wherein the ratio of water to fly ash is 5 L:1 kg, to obtain alkali-modified fly ash". The other operations are the same as those of the embodiment 1.

[0081] Example 6

[0082] The present embodiment provides a modified fly ash for improving saline-alkali land. The preparation method thereof is different from that of the embodiment 1 only in that step (3) is "the non-magnetic fly ash obtained in step (2) is reacted with 1 mol / L sodium hydroxide solution at a liquid-to-solid ratio of 5 L:1 kg at 100° C. for 2.5 h, with a stirring speed of 180 rpm. After the reaction is completed, the solid and liquid are separated and washed with water, wherein the ratio of water to fly ash is 5 L:1 kg, to obtain alkali-modified fly ash". The other operations are the same as those of the embodiment 1.

[0083] Example 7

[0084] The present embodiment provides a modified fly ash for improving saline-alkali land. The preparation method thereof is different from that of the embodiment 1 only in that step (3) is "the non-magnetic fly ash obtained in step (2) is reacted with 1 mol / L sodium hydroxide solution at a liquid-to-solid ratio of 5 L:1 kg at 10° C. for 2.5 h, with a stirring speed of 180 rpm. After the reaction is completed, the solid and liquid are separated and washed with water, wherein the ratio of water to fly ash is 5 L:1 kg, to obtain alkali-modified fly ash". The other operations are the same as those of the embodiment 1.

[0085] Example 8

[0086] The present embodiment provides a modified fly ash for improving saline-alkali land. The preparation method thereof is different from that of the embodiment 1 only in that step (3) is "the non-magnetic fly ash obtained in step (2) is reacted with 1 mol / L sodium hydroxide solution at a liquid-to-solid ratio of 5 L:1 kg at 60° C. for 6 h, with a stirring speed of 180 rpm. After the reaction is completed, the solid and liquid are separated and washed with water, wherein the ratio of water to fly ash is 5 L:1 kg, to obtain alkali-modified fly ash". The other operations are the same as those of the embodiment 1.

[0087] Example 9

[0088] The present embodiment provides a modified fly ash for improving saline-alkali land. The preparation method thereof is different from that of the embodiment 1 only in that step (3) is "the non-magnetic fly ash obtained in step (2) is reacted with 1 mol / L sodium hydroxide solution at a liquid-to-solid ratio of 5 L:1 kg at 60° C. for 0.1 h, with a stirring speed of 180 rpm. After the reaction is completed, the solid and liquid are separated and washed with water, wherein the ratio of water to fly ash is 5 L:1 kg, to obtain alkali-modified fly ash". The other operations are the same as those of the embodiment 1.

[0089] Example 10

[0090] This embodiment provides a modified fly ash for improving saline-alkali land. The preparation method thereof is different from that of Embodiment 1 only in that step (1) is "using a linear vibrating screen with a screening particle size of 80 μm to grade and screen the fly ash and collect fine-grained fly ash", and the other operations are the same as those of Embodiment 1.

[0091] Comparative Example 1

[0092] This comparative example provides a modified fly ash for improving saline-alkali land. The preparation method thereof is different from that of Example 1 only in that no grading and screening is performed, and other operations are the same as those of Example 1.

[0093] Comparative Example 2

[0094] This comparative example provides a modified fly ash for improving saline-alkali land. The preparation method thereof is different from that of Example 1 only in that magnetic separation is not performed, and other operations are the same as those of Example 1.

[0095] Comparative Example 3

[0096] This comparative example provides a fly ash for improving saline-alkali land. The preparation method thereof is different from that of Example 1 only in that no alkali modification is performed, and other operations are the same as those of Example 1.

[0097] Application Example 1

[0098] This application example provides a fly ash-based soil conditioner for improving saline-alkali land. The raw materials for preparing the fly ash-based soil conditioner for improving saline-alkali land include 70% of the modified fly ash for improving saline-alkali land described in Example 1, 8% of cow dung, 8% of vinegar residue, 8% of straw, and 6% of sawdust.

[0099] The preparation method comprises the following steps: mixing the raw materials for preparing the saline-alkali land soil conditioner, fermenting and culturing at 45°C for 60 days, turning the soil conditioner at a frequency of 5 days per time during the culturing, and obtaining the fly ash-based soil conditioner.

[0100] Application Example 2

[0101] This application example provides a fly ash-based soil conditioner for improving saline-alkali land. The raw materials for preparing the fly ash-based soil conditioner for improving saline-alkali land include 60% of the modified fly ash for improving saline-alkali land described in Example 2, 15% of wine slag, 15% of oil slag, and 10% of sheep manure.

[0102] The preparation method comprises the following steps: mixing the raw materials for preparing the saline-alkali soil conditioner, fermenting and culturing at 25°C for 120 days, turning the soil conditioner at a frequency of 3 days per time during the culturing, and obtaining the fly ash-based soil conditioner.

[0103] Application Example 3

[0104] This application example provides a fly ash-based soil conditioner for improving saline-alkali land. The raw materials for preparing the fly ash-based soil conditioner for improving saline-alkali land include 90% of the modified fly ash for improving saline-alkali land described in Example 3, 5% of straw, and 5% of cow dung.

[0105] The preparation method comprises the following steps: mixing the raw materials for preparing the saline-alkali soil improver, fermenting and culturing at 65°C for 10 days, turning the soil at a frequency of 7 days per time during the culturing, and obtaining the fly ash-based soil conditioner.

[0106] Application Example 4-10

[0107] This application example provides seven fly ash-based soil conditioners for saline-alkali land improvement. The only difference between it and application example 1 is that the modified fly ash for saline-alkali land improvement described in example 1 is replaced by the modified fly ash for saline-alkali land improvement described in examples 4-10 in equal amounts, and other components and contents remain unchanged.

[0108] The preparation method is as in Application Example 1.

[0109] Application Example 11

[0110] This application example provides a fly ash-based soil conditioner for saline-alkali land improvement, and the only difference between it and Application Example 1 is that the fly ash-based soil conditioner for saline-alkali land improvement does not contain wine dregs, vinegar dregs, straw and sawdust, and their reduced mass is distributed to the mass of modified fly ash for saline-alkali land improvement, and other components and contents remain unchanged.

[0111] The preparation method is as in Application Example 1.

[0112] Application Example 12

[0113] This application example provides a fly ash-based soil conditioner for improving saline-alkali land. The raw materials for preparing the fly ash-based soil conditioner for improving saline-alkali land include 50% of the modified fly ash for improving saline-alkali land described in Example 1, 15% of cow dung, 10% of vinegar residue, 15% of straw, and 10% of sawdust.

[0114] The preparation method is as in Application Example 1.

[0115] Application Example 13

[0116] This application example provides a fly ash-based soil conditioner for saline-alkali land improvement, which differs from application example 1 only in the preparation method, which is as follows: mixing the raw materials for preparing the saline-alkali land soil conditioner, fermenting and culturing at 10° C. for 60 days, turning the soil at a frequency of 5 days / time during the culture, to obtain the fly ash-based soil conditioner. Other components and contents remain unchanged.

[0117] Application Example 14

[0118] This application example provides a fly ash-based soil conditioner for saline-alkali land improvement, which differs from application example 1 only in the preparation method, which is as follows: mixing the raw materials for preparing the saline-alkali land soil conditioner, fermenting and culturing at 45°C for 140 days, turning the soil at a frequency of 5 days / time during the culture, to obtain the fly ash-based soil conditioner. Other components and contents remain unchanged.

[0119] Comparative Application Examples 1-3

[0120] This comparative application example provides three fly ash-based soil conditioners for saline-alkali land improvement. The only difference between it and Application Example 1 is that the modified fly ash for saline-alkali land improvement described in Example 1 is replaced by the modified fly ash for saline-alkali land improvement described in Comparative Examples 1-3 in equal amounts, and other components and contents remain unchanged.

[0121] The preparation method is as in Application Example 1.

[0122] Comparative Application Example 4

[0123] This comparative application example provides a fly ash-based soil conditioner for improving saline-alkali land. The only difference between it and Application Example 1 is that it does not contain modified fly ash, and its reduced mass is distributed to the mass of wine dregs, vinegar dregs, straw, and sawdust, while other components and contents remain unchanged.

[0124] The preparation method is as in Application Example 1.

[0125] Test Example 1

[0126] The soil conditioner described in Application Examples 1-14 and Comparative Application Examples 1-4 was evenly spread on the blower fill soil, and the soil was plowed by a tiller at a depth of 20 cm. The soil was turned over every 5 days during cultivation. The ratio of the fly ash-based soil conditioner to the saline-alkali soil was 60:40, and water was applied regularly at an amount of 30% of the total amount of the mixed cultured material. The soil properties were monitored after 60 days of action.

[0127] Soil penetration rate test

[0128] Add air-dried soil to the cutter ring according to bulk density and soak it in water for 24 hours to make it saturated with water; put an empty cutter ring on top of the cutter ring and glue it with melted wax, place it on top of the funnel, and place an empty beaker below; add water to the empty cutter ring to 5 cm, and after adding water, start timing from the moment the funnel just starts dripping water, replace the beaker every 2 minutes to record the water seepage amount Q1, replace the beaker every 3 minutes to record the water seepage amount Q2, and then replace the beaker every 5 minutes to record the water seepage amount Q3, Q4..., each time the beaker is replaced, the water surface of the upper cutter ring must be added to the original height, and the water temperature must be recorded. The experimental duration is set to 60 minutes, and the results are calculated according to the following formula.

[0129] Soil permeability coefficient K: =Q n ×10×l / t n ×S×h(mm / min)

[0130] Where: Q n ----Water seepage during the interval (mm); t n ----Interval time (min); l----Soil height in the lower ring cutter (cm); h----Water level height in the upper ring cutter (cm); S----Ring cutter bottom area (cm 3 ), the test results are shown in Table 1.

[0131] Table 1

[0132]

[0133]

[0134] It can be seen from the data in Table 1 that the modified soil conditioner provided by the present invention can effectively improve the permeability of dredger fill soil, improve the water permeability and air permeability of the soil, and lay the foundation for its effective salt removal. Alkali modification can significantly increase the grafting amount of hydroxyl groups on the surface of fly ash particles, thereby increasing the strength of the conditioner's action on the soil to a certain extent, and the soil's permeability is also enhanced. The concentration of alkali is very important to the soil's permeability. When the alkali concentration is too high, the permeability rate is reduced, and the improvement effect will also be inhibited. The time and temperature of alkali modification are also very important for the modification effect of fly ash. Fly ash particles with larger particle sizes also have a stronger adsorption effect on fine soil particles, increase soil porosity, and strengthen permeability. The proportion of modified fly ash in the soil conditioner will affect the ability of the conditioner to act on the soil, but when adding organic fertilizer alone, the effect of improving soil properties is not obvious. The temperature and time of the conditioner's decomposition are also one of the factors affecting the soil's permeability.

[0135] Soil quality testing

[0136] The soil conditioner and nitrogen, phosphorus and potassium fertilizers described in Application Examples 1-14 and Comparative Application Examples 1-4 were evenly spread on the blower fill soil, and plowed by a tiller with a plowing depth of 20 cm. The ratio of the nitrogen, phosphorus and potassium fertilizers was 3:5:1, and the soil was turned over at a frequency of 5 days / time during cultivation. The ratio of the fly ash-based soil conditioner to the saline-alkali soil was 60:40, and water was applied regularly, with the amount of water being 30% of the total amount of the mixed cultured material. After 60 days of action, the soil quality was tested, and the salt content, water-stable aggregates, bulk density and porosity of the soil before and after improvement were determined. The specific test method is as follows:

[0137] The soil salt content was determined according to standard DB37 / T 1303-2009 (gravimetric method for determining total salt content in soil), and the sample to be tested was soil after irrigation with water.

[0138] The content of water-stable aggregates in soil was determined according to standard NY / T 1121.19-2008.

[0139] Soil bulk density was determined according to standard NY / T 121.4-2006.

[0140] The internal porosity of the soil was determined by the ring knife weighing method (soil physical property determination).

[0141] The test results are shown in Table 2.

[0142] Table 2

[0143]

[0144]

[0145] As shown in Table 2, the soil bulk density after being improved by the saline-alkali soil conditioner described in Example 1 was reduced by 0.15 g / cm 3 The compactness of the soil was improved, the content of water-stable aggregates increased by 8.61%, and the porosity increased by 7.15%, indicating that the internal structure of the soil tended to be good, the water permeability and air permeability were enhanced, and it was more conducive to drainage and salt discharge. The soil salt content after measurement was reduced by 3.46g / kg, which shows that after the blown fill soil was improved by the modified soil conditioner, the small soil particles gradually adhered into large soil aggregates under the action of the conditioner, and the internal pores increased accordingly, thereby reducing the soil bulk density and significantly improving the soil structure.

[0146] After fly ash is alkali-modified, the improvement performance of the conditioner can be further improved, but too high or too low alkali concentration will also inhibit the improvement effect. During the modification process, the concentration of alkali solution in the range of 0.1-2 mol / L is more conducive to reducing soil bulk density, increasing soil porosity and increasing the content of soil water-stable aggregates. The temperature and time of alkali modification will also affect the improvement effect.

[0147] When only organic fertilizer is added as saline-alkali soil conditioner without modified fly ash, the overall changes in soil bulk density, water-stable aggregate content, porosity and salt content are small. Therefore, adding only organic fertilizer is not effective in improving dredger fill soil. The temperature and time of the saline-alkali soil conditioner's composting will also affect the improvement effect.

[0148] The applicant declares that the present invention uses the above-mentioned embodiments to illustrate the preparation method of modified fly ash for improving saline-alkali land, its products and applications, but the present invention is not limited to the above-mentioned embodiments, that is, it does not mean that the present invention must rely on the above-mentioned embodiments to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of various raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0149] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0150] 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 further describe various possible combinations.

Claims

1. A method for preparing modified fly ash for improving saline-alkali land, characterized in that: The preparation method comprises: (1) Classifying and screening fly ash to obtain coarse fly ash and fine fly ash, and collecting the fine fly ash; (2) performing magnetic separation on the fine fly ash obtained in step (1) to collect non-magnetic fly ash; (3) The non-magnetic fly ash obtained in step (2) is modified by an alkali method to obtain the modified fly ash.

2. The method for preparing modified fly ash for improving saline-alkali land according to claim 1, characterized in that: The particle size of the fine fly ash in step (1) is 120-250 μm; Preferably, the magnetic field strength of the magnetic separation in step (2) is 500-1600 kA / m.

3. The method for preparing modified fly ash for improving saline-alkali land according to claim 1 or 2, characterized in that: The alkaline modification in step (3) comprises: immersing and stirring the non-magnetic fly ash obtained in step (2) in an alkaline solution, and performing solid-liquid separation to obtain the modified fly ash; Preferably, the molar concentration of the alkaline solution is 0.1-2 mol / L; Preferably, the alkaline solution comprises sodium hydroxide and / or potassium hydroxide; Preferably, the temperature of the immersion stirring is 20-95°C and the time is 0.5-5h; Preferably, the rotation speed of the immersion stirring is 10-700 rpm; Preferably, the ratio of the alkaline solution to fly ash is (2-10) L: 1 kg.

4. The modified fly ash prepared by the method for preparing modified fly ash for improving saline-alkali land according to any one of claims 1 to 3.

5. A fly ash-based soil conditioner for improving saline-alkali land, characterized in that: The raw materials for preparing the fly ash-based soil conditioner for improving saline-alkali land include the modified fly ash and organic fertilizer described in claim 4.

6. The fly ash-based soil conditioner for improving saline-alkali land according to claim 5, characterized in that: The mass percentage of the modified fly ash in the fly ash-based soil conditioner for improving saline-alkali land is 60-90%; Preferably, the organic fertilizer comprises any one of residue, straw, excrement or sawdust or a combination of at least two thereof, and the residue comprises any one of vinegar residue, wine residue or oil residue or a combination of at least two thereof; Preferably, the organic fertilizer comprises, by mass percentage, 0.5-20% of vinegar residue, 0.5-30% of wine residue, 0.5-30% of oil residue, 0.5-10% of straw, 0.5-20% of sawdust, and 0.5-10% of feces; Preferably, the excrement comprises cow dung and / or sheep dung.

7. The method for preparing the fly ash-based soil conditioner for improving saline-alkali land according to claim 5 or 6, characterized in that: The preparation method comprises: mixing and composting the modified fly ash according to claim 4 with organic fertilizer.

8. The method for preparing the fly ash-based soil conditioner for improving saline-alkali land according to claim 7, characterized in that: The composting temperature is 25-65°C and the time is 10-60 days.

9. Use of the modified fly ash according to claim 4 or the saline-alkali land soil conditioner according to claim 5 or 6 in improving saline-alkali land.

10. The use according to claim 9, characterized in that: The method for using the fly ash-based soil conditioner for improving saline-alkali land comprises: mixing and cultivating the fly ash-based soil conditioner according to claim 5 or 6 with coastal saline-alkali soil; Preferably, the coastal saline-alkali soil is filled soil in the coastal area; Preferably, the added amount of the fly ash-based soil conditioner for improving saline-alkali land is 20-70% of the mass of the saline-alkali soil; Preferably, the cultivation temperature is 25-65°C and the time is 1-60 days; Preferably, the culture is also stirred, and the frequency of stirring is 3-7 days / time; Preferably, the raw materials mixed with the coastal saline-alkali soil for cultivation also include nutrients; Preferably, the nutrients include any one of nitrogen fertilizer, potassium fertilizer or phosphorus fertilizer, or a combination of at least two; Preferably, the mass ratio of nitrogen, potassium and phosphorus in the mixed culture raw material is (3-8):(5-10):1; Preferably, the mass percentage of water in the mixed cultivation is 5-40%.

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