Silicon fertilizer and preparation method thereof

Abstract

The invention provides a silicon fertilizer and a preparation method thereof, and relates to the technical field of coal-based solid waste treatment and resource utilization. The preparation method of the silicon fertilizer provided by the invention comprises the following steps: mixing active coal gangue powder, calcium-based solid waste powder and plant ash powder to obtain a mixed material; and calcining the mixed material to obtain the silicon fertilizer. All solid waste raw materials are adopted, the requirement for industrial chemical resources is reduced, the production cost and energy consumption of the silicon fertilizer are greatly reduced, meanwhile, the advantage of improving the fertilizer efficiency of the silicon fertilizer is achieved, and a new direction is provided for resource utilization of bulk solid waste.

Description

Technical Field

[0001] The present invention relates to the technical field of coal-based solid waste treatment and resource utilization, and in particular to a silicon fertilizer and a preparation method thereof. Background Art

[0002] Coal gangue is one of the industrial solid wastes with the largest annual discharge and cumulative stockpile in my country. It has the dual attributes of being dangerous and a resource, and is a valuable silicon-rich resource. The main mineral components are clay minerals such as kaolinite, followed by quartz, feldspar, mica, pyrite, etc. The main chemical composition is SiO 2 (40%~60%) and Al 2 O 3 (15%~40%), followed by Fe 2 O 3 , CaO, MgO, Na 2 O.K 2 O, SO 3 , and is accompanied by rich trace elements, such as Ti, Ga, Co, Cu, Zn, Mn, Mo, etc. The chemical composition and mineral composition of coal gangue are relatively close to those of soil, and it has homology with soil, and is a huge potential raw material for the preparation of silicon-based fertilizers / amendments.

[0003] Silicon is the second most abundant nutrient in the earth's crust. Silicon in soil is usually in the form of silicon dioxide (SiO 2 ) and various silicate forms, among which SiO 2 It accounts for 50% to 70% of the total mass of soil, but plants usually cannot directly obtain it. The main form of silicon in the liquid phase in the soil is monosilicic acid (H 4 SiO 4 ), effective silicon is dissolved from silicate minerals in the form of H 4 SiO 4 It is the only form of silicon that can be absorbed and utilized by plants. Studies have shown that nearly half of my country's cultivated land has silicon deficiency problems. Silicon-deficient soil (soil with effective silicon content less than 100 mg kg -1 ) accounts for more than 40% of agricultural soil area. Applying silicon fertilizer not only means reducing the amount of pesticide application (40% to 70%), the amount of traditional mineral fertilizer application (10% to 40%) and the amount of irrigation water (30% to 40%), but also does not reduce crop yields. Therefore, the production and application of silicon fertilizer has very obvious social and economic benefits.

[0004] In the early days of silicon fertilizer development, people simply crushed and sieved slag to prepare silicon fertilizer. Although this method has low production cost and simple operation, the effective content of silicon fertilizer produced is low and the application amount is large. On this basis, scientists have proposed methods such as microbial cultivation, high-temperature sintering, and hydrothermal synthesis. However, the preparation time using microbial cultivation methods is usually long, and hydrothermal synthesis is not suitable for large-scale industrial production. Therefore, the high-temperature sintering method is currently used to mix silicon-rich raw materials such as coal gangue with industrial chemicals such as flux and additives in a certain proportion, melt at high temperature, destroy the lattice, and convert it into an effective silicon component that is easily absorbed by plants. After sufficient reaction, it is cooled and ground into silicon fertilizer. The silicon fertilizer made by this method is mainly silicon-potassium fertilizer, silicon-calcium fertilizer, etc., mostly citrate-soluble silicon fertilizer, which has the characteristics of being insoluble in water but soluble in acid. For example, a Chinese patent with publication number CN109928782A discloses a method for preparing silicon fertilizer from coal gangue, wherein the coal gangue is mixed with an activator limestone and an auxiliary agent, and calcined at a temperature of 800 to 1300°C to prepare silicon fertilizer. However, the above preparation method needs to be carried out at a higher temperature, and auxiliary agents such as industrial chemicals need to be added to realize the activation process of coal gangue. A Chinese patent with publication number CN114956872A discloses a method for preparing silicon fertilizer from activated coal gangue, wherein the coal gangue and organic solid waste are mixed, and silicon fertilizer is prepared after pyrolysis treatment at 710 to 725°C and calcination treatment at 820 to 890°C. The above preparation method realizes the synergistic resource utilization of inorganic and organic solid wastes, but the preparation process is complicated, the energy consumption is high, and the fertilizer efficiency of the obtained silicon fertilizer needs to be further improved.

[0005] Research has found that my country's industrial production produces a large amount of calcium-based industrial solid waste every year, such as carbide slag, blast furnace slag, steel slag, papermaking mud, etc. The main component is Ca(OH) 2 、CaCO 3 、SiO 2 , MgO, etc. At the same time, my country is also rich in various types of solid waste resources from planting industries. There are nearly 20 kinds of important crop straws alone, and the output is huge, with an annual output of about 700 million tons. The main component of its wood ash is K 2 O, CaO, MgO, etc. have huge potential for resource utilization, and their high-value utilization methods need to be developed urgently. Summary of the invention

[0006] In view of this, the object of the present invention is to provide a silicon fertilizer and a preparation method thereof, which has the advantages of improving the fertilizer efficiency of silicon fertilizer, reducing production costs and energy consumption, and realizing the preparation of high-efficiency silicon fertilizer that meets the requirements of "Silicon Calcium Potassium Magnesium Fertilizer (GB / T 36207-2018)" with zero chemical additives.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The present invention provides a method for preparing silicon fertilizer, comprising the following steps:

[0009] Mixing activated coal gangue powder, calcium-based solid waste powder and wood ash powder to obtain a mixed material;

[0010] The mixed material is calcined to obtain silicon fertilizer.

[0011] Preferably, the particle size of the activated coal gangue powder is ≤600 μm.

[0012] Preferably, the method for preparing the activated coal gangue powder comprises: crushing, grinding and screening the coal gangue in sequence to obtain the activated coal gangue powder;

[0013] The coal gangue is aluminum-silicon type coal gangue; the chemical composition of the coal gangue satisfies: Al 2 O 3 With SiO 2 The mass ratio is >0.3.

[0014] Preferably, the particle size of the calcium-based solid waste powder is ≤350 μm.

[0015] Preferably, the method for preparing the calcium-based solid waste powder comprises: crushing, grinding and screening the calcium-based solid waste in sequence to obtain the calcium-based solid waste powder;

[0016] The calcium-based solid waste includes one or more of limestone, carbide slag, smelting slag, papermaking white mud, salt mud and magnesium slag;

[0017] The calcium content of the calcium-based solid waste is ≥30wt%, and the calcium and magnesium content is ≥40wt%;

[0018] The calcium content is measured as the mass percentage of calcium oxide, and the calcium and magnesium contents are measured as the mass percentage of calcium oxide and magnesium oxide.

[0019] Preferably, the particle size of the wood ash powder is ≤350 μm.

[0020] Preferably, the method for preparing the wood ash powder comprises: grinding and calcining the biomass raw material in sequence to obtain the wood ash powder;

[0021] The biomass raw material includes one or more of melon seed shells, peach pit shells, olive residues, sunflower straw, rice straw and wheat straw;

[0022] The calcination temperature is 500±25°C, the time is 1h, and the heating rate to the calcination temperature is 10°C / min; the calcination atmosphere is air atmosphere;

[0023] The potassium content of the wood ash powder is ≥30wt%;

[0024] The potassium content is measured in percentage by mass of potassium oxide.

[0025] Preferably, the mass ratio of the activated coal gangue powder, the calcium-based solid waste powder and the wood ash powder is 5-6:1-4:1-4.

[0026] Preferably, the calcination temperature is 550-900° C., and the holding time is 1.5-3 hours; the heating rate from room temperature to the calcination temperature is 5-15° C. / min.

[0027] The present invention provides a silicon fertilizer prepared by the preparation method described in the above technical solution, wherein SiO 2 The effective silicon content of the silicon fertilizer is ≥20wt%; the moisture content is ≤3wt%; and the particles passing through a 250μm standard sieve are ≥80wt%.

[0028] The present invention provides a method for preparing silicon fertilizer, comprising the following steps: mixing activated coal gangue powder, calcium-based solid waste powder and wood ash powder to obtain a mixture; calcining the mixture to obtain silicon fertilizer. The present invention uses activated coal gangue powder as a silicon source, calcium-based solid waste powder and wood ash powder as additives, wherein the calcium-based solid waste powder and the wood ash powder provide the silicon fertilizer with alkali metal oxides required for the activation process during the calcination process. While meeting the requirements of using coal-based solid waste, industrial waste residue and agricultural waste as raw materials and without consuming chemical raw materials, silicon fertilizer that meets the standard requirements of "Silicon Calcium Potassium Magnesium Fertilizer (GB / T36207-2018)" can be prepared. The present invention organically combines citric acid-soluble silicon fertilizer with water-soluble silicon fertilizer, improves the fertilizer efficiency of silicon fertilizer to a certain extent, achieves the best combination of waste residues, maximizes utilization, and gives the product excellent comprehensive performance.

[0029] The present invention adopts all solid waste raw materials, reduces the demand for industrial chemical resources, greatly reduces the production cost and energy consumption of silicon fertilizer, and at the same time has the advantage of improving the fertilizer efficiency of silicon fertilizer, providing a new direction for the resource utilization of bulk solid waste. DETAILED DESCRIPTION

[0030] The endpoints and any values ​​of the ranges disclosed in the present invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in the present invention.

[0031] The present invention provides a method for preparing silicon fertilizer, comprising the following steps:

[0032] Mixing activated coal gangue powder, calcium-based solid waste powder and wood ash powder to obtain a mixed material;

[0033] The mixed material is calcined to obtain silicon fertilizer.

[0034] The present invention mixes activated coal gangue powder, calcium-based solid waste powder and wood ash powder to obtain a mixed material. In the present invention, the mass ratio of the activated coal gangue powder, calcium-based solid waste powder and wood ash powder is preferably 5-6:1-4:1-4, more preferably 5-6:2-3:2-3.

[0035] In the present invention, the particle size of the activated gangue powder is preferably ≤600 μm, more preferably 250-600 μm. In the present invention, the particle size of the activated gangue powder is conducive to the full contact and reaction of the materials during the calcination process, and is conducive to the destruction of the kaolinite crystal structure in the gangue. If the particle size of the material after grinding is too small, the powder particles will agglomerate and generate dust.

[0036] In the present invention, the preparation method of the activated coal gangue powder preferably comprises: crushing, grinding and screening the coal gangue in sequence to obtain the activated coal gangue powder. In the present invention, the coal gangue is preferably aluminum-silicon type coal gangue; the chemical composition of the coal gangue preferably satisfies: Al 2 O 3 With SiO 2 The mass ratio of SiO in the coal gangue is preferably greater than 0.3, and more preferably greater than 0.5. 2 The mass percentage of is preferably ≥40%, more preferably ≥50%. In the present invention, as the aluminum-silicon ratio increases, the content of aluminosilicate minerals increases, that is, the content of kaolinite increases; and kaolinite has a high reactivity, and stimulating its activity is the premise and key to achieving efficient utilization of aluminosilicate minerals in coal gangue.

[0037] In the present invention, the particle size of the calcium-based solid waste powder is preferably ≤350 μm, more preferably ≤250 μm.

[0038] In the present invention, the preparation method of the calcium-based solid waste powder preferably includes: crushing, grinding and screening the calcium-based solid waste in sequence to obtain calcium-based solid waste powder. In the present invention, the calcium-based solid waste preferably includes one or more of limestone, carbide slag, smelting slag, papermaking white mud, salt mud and magnesium slag, more preferably one or more of carbide slag, smelting slag and magnesium slag; the smelting slag preferably includes steel slag and / or blast furnace slag. In the present invention, the calcium content in the calcium-based solid waste is preferably ≥30wt%, more preferably ≥35wt%; the calcium and magnesium content in the calcium-based solid waste is preferably ≥40wt%, more preferably ≥45wt%.

[0039] In the present invention, the particle size of the wood ash powder is preferably ≤350 μm, more preferably ≤250 μm.

[0040] In the present invention, the method for preparing the wood ash powder preferably comprises: grinding and calcining the biomass raw materials in sequence to obtain the wood ash powder. In the present invention, the biomass raw materials preferably include one or more of melon seed shells, peach kernel shells, olive residues, sunflower straw, rice straw and wheat straw, more preferably one or more of melon seed shells, olive residues and sunflower straw. In the present invention, the potassium content in the wood ash powder is preferably ≥30wt%, more preferably ≥40wt%; the potassium content is measured as a mass percentage of potassium oxide. In the present invention, the calcination temperature is preferably 500±25℃, the time is preferably 1h, the heating rate to the calcination temperature is preferably 10℃ / min; the calcination atmosphere is preferably an air atmosphere.

[0041] In the present invention, the industrial chemical additives containing calcium, magnesium and potassium utilize alkali metal oxides to destroy the structure of silicon-containing minerals such as kaolinite and quartz in coal gangue at high temperature, transforming them into new silicate mineral phases, thereby improving the reaction activity. Commonly used calcium-containing industrial chemical additives include limestone (CaCO 3 ), quicklime (CaO), etc. Commonly used magnesium-containing industrial chemical additives include magnesium carbonate (MgCO 3 ), magnesium oxide (MgO), etc. Commonly used potassium-containing industrial chemical additives include potassium carbonate (K 2 CO 3 ), potassium hydroxide (KOH), potassium chloride (KCl), etc. The calcium content (w (CaO) )≥30%, calcium and magnesium content (w (CaO+MgO) )≥40%, potassium content in wood ash (w (K2O) )≥30%, it is a good effective source of calcium, magnesium and potassium. The specific reaction process is shown in the following formula:

[0042] Al 2 Si 2 O 5 (OH) 4 +2CaCO 3 =Ca 2 Al 2 SiO 7 +SiO 2 +2CO 2 (g)+2H 2 O#(1)

[0043] Al 2 Si 2 O 5 (OH) 4 +CaCO 3 =CaAl 2 Si 2 O8 +CO 2 (g)+2H 2 O#(2)

[0044] Al 2 Si 2 O 5 (OH) 4 +K 2 CO 3 =2KAlSiO 4 +CO 2 (g)+2H 2 O#(3)

[0045] SiO 2 +CaCO 3 +MgCO 3 →CaMgSiO 4 +2CO 2 (g)#(4).

[0046] The present invention uses the activated coal gangue powder as a silicon source raw material, and the calcium-based solid waste powder and the plant ash powder as additives, and can directly calcine to prepare silicon fertilizer without adding any industrial chemical additives. Not only can the fertilizer effect of the silicon fertilizer be improved, but the prepared silicon fertilizer has the characteristics of both citric acid solubility and water solubility, and can further increase the content of effective silicon in the obtained granular high-efficiency silicon fertilizer.

[0047] After obtaining the mixed material, the present invention calcines the mixed material to obtain silicon fertilizer. In the present invention, the calcination temperature is preferably 550-900°C, more preferably 750-850°C; the holding time is preferably 1.5-3h, more preferably 2-2.5h; the heating rate from room temperature to the calcination temperature is preferably 5-15°C / min, more preferably 6-10°C / min. In the present invention, the calcination atmosphere is preferably air.

[0048] In the present invention, the reaction temperature range of silicon-containing minerals in coal gangue is concentrated between 650 and 980°C. Above this temperature, the reaction activity will drop sharply. Kaolinite in coal gangue absorbs heat and loses crystal water at around 500°C, and the crystal structure is destroyed and transformed into amorphous metakaolinite. Due to the removal of hydroxyl groups in metakaolinite, the hexacoordinated Al in the kaolinite structure is VI Transformed to pentacoordinated Al v and tetracoordinated Al IV At the same time, the kaolinite structure layer is seriously distorted, and the long-range ordered structure is broken, resulting in a large number of defects in the metakaolinite, which is amorphous and easy to react with alkali metal oxides, thus increasing its activity. The coordinated calcination of multiple solid wastes can greatly improve the reactivity of silicon-containing minerals in coal gangue and reduce the reaction temperature range.

[0049] After the calcination is completed, the present invention also preferably includes cooling, crushing and screening in sequence. In the present invention, the particle size of the clinker obtained after the crushing is preferably ≤300μm, more preferably ≤250μm. In the present invention, the temperature after the cooling is preferably ≤30°C, more preferably 25°C; the cooling time is preferably 10 to 20 minutes.

[0050] The present invention provides a silicon fertilizer prepared by the preparation method described in the above technical solution. In the present invention, the silicon fertilizer is in granular form. In the present invention, SiO 2 The effective silicon content of the silicon fertilizer is ≥20wt%; the moisture content is ≤3wt%; and the number of particles passing through a 250μm standard sieve is ≥80wt%. The silicon fertilizer provided by the present invention meets the standard requirements of "Silicon Calcium Potassium Magnesium Fertilizer (GB / T 36207-2018)".

[0051] In the present invention, the chemical components contained in calcium-based solid waste and plant ash are similar to the component characteristics of industrial chemicals. The present invention uses them in conjunction with coal gangue to prepare silicon fertilizer, which can reduce the amount of industrial chemicals used. The present invention not only reduces the production cost and energy consumption of silicon fertilizer, but also can further improve the fertilizer effect and utilization efficiency of silicon fertilizer, promotes the resource utilization of bulk solid waste, and has very important practical significance.

[0052] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0053] The effective silicon content in the examples and comparative examples is determined in accordance with the national standard GB / T 20412-2021 "Calcium Magnesium Phosphate Fertilizer", and the effective silicon content is qualified if it exceeds 20%. The moisture content and fineness index are in accordance with the agricultural standard NY / T3036-2016 "Determination of moisture content, particle size and fineness of fertilizers and soil conditioners". The mercury, arsenic, cadmium, lead and chromium content indexes are determined in accordance with the Ministry of Agriculture and Rural Affairs standard NY / T 1978-2022 "Determination of mercury, arsenic, cadmium, lead, chromium and nickel content in fertilizers".

[0054] Example 1

[0055] (1) Al 2 O 3 With SiO 2 The mass ratio of coal gangue = 0.65, W CaO+MgO = 61.24wt% magnesium slag and W K2O=32.6wt% melon seed shell ash (melon seed shell raw material is subjected to a grinding process, and then calcined for 1h in an air atmosphere at a heating rate of 10°C / min and a calcination temperature of 500±25°C to obtain melon seed shell ash powder) and respectively ball-milled in a planetary ball mill (rotation speed of 450rpm, time of 20min) and sieved to obtain active coal gangue powder with a particle size of ≤250μm, magnesium slag powder with a particle size of ≤250μm, and melon seed shell ash powder with a particle size of ≤250μm;

[0056] (2) fully mixing activated coal gangue powder, magnesium slag powder and melon seed shell ash powder in a mass ratio of 5:2:3 to obtain a mixed material;

[0057] (3) placing the mixed material obtained in step (2) in a ceramic ash dish, heating it in a muffle furnace under air atmosphere, with a heating rate of 9° C. / min, a calcination temperature of 800° C., and a holding time of 2 h;

[0058] (4) The clinker obtained in step (3) is immediately taken out, cooled to 25° C. in an air atmosphere, and crushed and sieved to obtain granular high-efficiency silicon fertilizer.

[0059] In the granular high-efficiency silicon fertilizer obtained in this embodiment, effective silicon (in the form of SiO 2 The content of silicon (calculated) is 24.23wt%, including 5.38wt% water-soluble effective silicon, 18.85wt% citric acid-soluble effective silicon, 0.15wt% moisture content, and 92wt% fineness (passing 250μm standard sieve), which meets the requirements of Silicon Calcium Potassium Magnesium Fertilizer (GB / T36207-2018).

[0060] Example 2

[0061] (1) Al 2 O 3 With SiO 2 The mass ratio of coal gangue = 0.52, W CaO+MgO =73.8wt% steel slag and W K2O =36.5wt% olive residue ash (after the olive residue is subjected to a grinding process, it is calcined at a heating rate of 10°C / min, a calcination temperature of 500±25°C, and an air atmosphere for 1h to obtain olive residue ash powder) and respectively ball-milled in a planetary ball mill (rotation speed of 450rpm, time of 20min) and sieved to obtain active coal gangue powder with a particle size of ≤250μm, steel slag powder with a particle size of ≤250μm, and olive residue ash powder with a particle size of ≤250μm;

[0062] (2) fully mixing activated coal gangue powder, steel slag powder and olive residue ash powder in a mass ratio of 6:3:1 to obtain a mixed material;

[0063] (3) placing the mixed material obtained in step (2) in a ceramic ash dish, and heating it in a muffle furnace under air atmosphere, with a heating rate of 6° C. / min, a calcination temperature of 850° C., and a holding time of 2 h;

[0064] (4) The clinker obtained in step (3) is immediately taken out, cooled to 25° C. in an air atmosphere, and crushed and sieved to obtain granular high-efficiency silicon fertilizer.

[0065] In the granular high-efficiency silicon fertilizer obtained in this embodiment, effective silicon (in the form of SiO 2 The content of silicon (calculated) is 27.33wt%, including 6.01wt% water-soluble effective silicon, 21.32wt% citric acid-soluble effective silicon, 0.16wt% moisture content, and 96% fineness (passing 250μm standard sieve), which meets the requirements of Silicon Calcium Potassium Magnesium Fertilizer (GB / T36207-2018).

[0066] Example 3

[0067] (1) Al 2 O 3 With SiO 2 The mass ratio of coal gangue = 0.58, W CaO+MgO = 49.5wt% limestone and W CaO+MgO =40.0wt% sunflower straw ash (sunflower straw is ground and calcined for 1h in an air atmosphere at a heating rate of 10°C / min and a calcination temperature of 500±25°C to obtain sunflower straw ash powder) and respectively ball-milled in a planetary ball mill (rotation speed of 450rpm for 20min) and sieved to obtain active coal gangue powder with a particle size of ≤250μm, limestone powder with a particle size of ≤250μm and sunflower straw ash powder with a particle size of ≤250μm;

[0068] (2) fully mixing activated coal gangue powder, limestone powder and sunflower straw ash powder in a mass ratio of 5:4:1 to obtain a mixed material;

[0069] (3) placing the mixed material obtained in step (2) in a ceramic ash dish, heating it in a muffle furnace under air atmosphere, with a heating rate of 10° C. / min, a calcination temperature of 750° C., and a holding time of 2 h;

[0070] (4) The clinker obtained in step (3) is immediately taken out, cooled to 25° C. in an air atmosphere, and crushed and sieved to obtain granular high-efficiency silicon fertilizer.

[0071] In the granular high-efficiency silicon fertilizer obtained in this embodiment, effective silicon (in the form of SiO 2The content of silicon (calculated) is 21.23wt%, including 6.33wt% water-soluble effective silicon, 15.00wt% citric acid-soluble effective silicon, 0.19wt% moisture content, and 95wt% fineness (passing 250μm standard sieve), which meets the requirements of Silicon Calcium Potassium Magnesium Fertilizer (GB / T36207-2018).

[0072] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing silicon fertilizer, comprising the following steps: Mixing activated coal gangue powder, calcium-based solid waste powder and wood ash powder to obtain a mixed material; The mixed material is calcined to obtain silicon fertilizer.

2. The preparation method according to claim 1, characterized in that: The particle size of the activated coal gangue powder is ≤600 μm.

3. The preparation method according to claim 1 or 2, characterized in that: The preparation method of the activated coal gangue powder comprises: crushing, grinding and screening the coal gangue in sequence to obtain the activated coal gangue powder; The coal gangue is aluminum-silicon type coal gangue; the chemical composition of the coal gangue satisfies: the mass ratio of Al2O3 to SiO2 is greater than 0.

3.

4. The preparation method according to claim 1, characterized in that: The particle size of the calcium-based solid waste powder is ≤350 μm.

5. The preparation method according to claim 1 or 4, characterized in that: The preparation method of the calcium-based solid waste powder comprises: crushing, grinding and screening the calcium-based solid waste in sequence to obtain the calcium-based solid waste powder; The calcium-based solid waste includes one or more of limestone, carbide slag, smelting slag, papermaking white mud, salt mud and magnesium slag; The calcium content of the calcium-based solid waste is ≥30wt%, and the calcium and magnesium content is ≥40wt%; The calcium content is measured as the mass percentage of calcium oxide, and the calcium and magnesium contents are measured as the mass percentage of calcium oxide and magnesium oxide.

6. The preparation method according to claim 1, characterized in that: The particle size of the wood ash powder is ≤350 μm.

7. The preparation method according to claim 1 or 6, characterized in that: The method for preparing the wood ash powder comprises: grinding and calcining the biomass raw material in sequence to obtain the wood ash powder; The biomass raw material includes one or more of melon seed shells, peach pit shells, olive residues, sunflower straw, rice straw and wheat straw; The calcination temperature is 500±25°C, the time is 1h, and the heating rate to the calcination temperature is 10°C / min; the calcination atmosphere is air atmosphere; The potassium content of the wood ash powder is ≥30wt%; The potassium content is measured in percentage by mass of potassium oxide.

8. The preparation method according to claim 1, characterized in that: The mass ratio of the activated coal gangue powder, the calcium-based solid waste powder and the wood ash powder is 5-6:1-4:1-4.

9. The preparation method according to claim 1, characterized in that: The calcination temperature is 550-900° C., and the heat preservation time is 1.5-3 hours; the heating rate from room temperature to the calcination temperature is 5-15° C. / min.

10. The silicon fertilizer prepared by the preparation method according to any one of claims 1 to 9, characterized in that: Calculated in terms of SiO2, the effective silicon content of the silicon fertilizer is ≥20wt%; the moisture content is ≤3wt%; and the number of particles passing through a 250μm standard sieve is ≥80wt%.