Method for preparing silicon-calcium-containing organic fertilizer from coal gasification slag and silicon-calcium-containing organic fertilizer

Abstract

The invention relates to a method for preparing a silicon-calcium-containing organic fertilizer from coal gasification slag and the silicon-calcium-containing organic fertilizer, and the method comprises the following steps: mixing coal gasification slag powder with an activator and water to obtain gasified slag slurry, and carrying out hydrothermal activation reaction on the gasified slag slurry; carrying out solid-liquid separation on a reaction product of the hydrothermal activation reaction, and carrying out forming treatment and drying treatment on a filter cake obtained by separation to obtain the silicon-calcium organic fertilizer. According to the method, carbon residues in the coal gasification slag can be converted into the organic fertilizer, meanwhile, rich but inert mineral elements such as Si, Al, Ca and K in the coal gasification slag are converted into the effective-state silicon-calcium organic fertilizer capable of being absorbed and utilized by plants, so that organic components and inorganic components in the gasification slag are synchronously activated and efficiently utilized, waste is turned into fertilizer, and the environment is protected. And the discharge of solid wastes can be reduced while the high-quality organic fertilizer is prepared.

Description

Technical Field

[0001] The invention belongs to the field of coal-based solid waste treatment, and in particular relates to a method for preparing silicon-calcium organic fertilizer from coal gasification slag and the silicon-calcium organic fertilizer. Background Art

[0002] Coal gasification is a process that uses coal or coal coke as raw materials, oxygen (air, oxygen-enriched or pure oxygen), water vapor or hydrogen as gasifying agents, and converts organic matter in coal or coal coke into gaseous fuel or downstream raw materials through chemical reactions under high temperature conditions. Coal gasification slag is the ash produced during the coal gasification process, and its chemical composition is mainly oxides, silicates, aluminates, calcium, magnesium and other elements. The composition of ash after different types of coal gasification is also different.

[0003] When the gasifier is operated under unstable conditions, the unreacted coke particles will be entrained by the airflow and hit the wall surface, and partially deposited on the surface of the slag layer, resulting in a large difference in carbon content between fine slag and coarse slag. Due to the high carbon content of gasification fine slag, it is not suitable for the production of cement concrete building materials. At present, the disposal of coal gasification ash is mainly landfilled in slag yards, and the disposal cost is high. On the other hand, a large amount of organic fertilizer is required in scenarios such as saline-alkali land and sandy soil management, land reclamation in mining areas, and high-standard farmland construction. However, due to the widespread excessive levels of antibiotics, heavy metals, and salt in poultry and livestock manure, the factory prices of green and clean organic fertilizers such as cattle and sheep manure are high, resulting in a scarcity of high-quality, low-priced organic fertilizer raw materials.

[0004] The potential of coal gasification slag in soil improvement has been widely confirmed, but the direct use of coal gasification slag in soil blending still has problems such as poor performance and large fluctuations in harmful substance levels, which cannot fully exert the effectiveness of coal gasification slag. Centralized disposal and activation of gasification slag through standard chemical processes to form standardized mineral-based organic fertilizer products is a necessary step to realize the application of coal gasification slag as agricultural fertilizer.

[0005] CN114249623A discloses a method for preparing compound fertilizer using coal gasification slag, which includes mixing coal gasification slag with N / P / K fertilizer, clay and poultry manure, and granulating. However, the mechanical compounding method represented by this method does not play a significant "activation" effect on the organic components and inorganic components in the coal gasification slag, and more importantly, it uses the loose porous characteristics of the gasification slag to improve the macroscopic physical structure of the soil.

[0006] CN117384649A discloses a soil conditioner and a method for improving soil properties using the soil conditioner, wherein the water-containing gasified slag is subjected to freeze-thaw cycle modification, and then humic acid, urea, bentonite, and polylactic acid are sequentially added for physical adsorption and coating to form a soil conditioner with water and fertilizer retention capabilities. The micropores or active functional groups on the surface of gasified slag particles are strengthened through physical and chemical modification represented by this scheme, but the role of gasified slag is more like a carrier, and the components in coal gasified slag are not effectively utilized.

[0007] CN115611684A discloses a method for preparing silicon fertilizer using coal gasification slag, which comprises drying the gasification slag, extracting it with hydrochloric acid, adding 5-25% of a solvent to the filter residue and mixing it evenly, and calcining it at 800-1000°C for 0.5-1h. The calcination process represented by this method is mainly aimed at effectively activating the inorganic mineral components in the gasification slag, but the energy consumption of calcination activation is too high. At the same time, although adding a flux can reduce the calcination temperature, it also produces high material costs and high alkalinity residue problems of the product, and the organic components in the gasification slag are consumed by combustion and are not effectively utilized.

[0008] In summary, the prior art does not fully utilize the residual carbon and mineral elements contained therein. Summary of the invention

[0009] The purpose of the present invention is to solve the problem that the residual carbon and mineral elements in the gasification slag are not fully converted and utilized.

[0010] In order to achieve the above object, the first aspect of the present invention provides a method for preparing silicon-calcium organic fertilizer from coal gasification slag, the method comprising: S1. Mixing coal gasification slag powder with an activator and water to obtain a gasification slag slurry, and subjecting the gasification slag slurry to a hydrothermal activation reaction; the content of carbon in the coal gasification slag powder is not less than 42% by weight; the activator contains calcium; and the weight ratio of the coal gasification slag powder to the activator calculated as calcium oxide is 100:(13-20); S2, separating the reaction product of the hydrothermal activation reaction into solid and liquid, and subjecting the filter cake obtained by separation to molding and drying to obtain silicon-calcium organic fertilizer.

[0011] Optionally, the coal gasification slag powder has a carbon content of 43-50 wt %; a silicon content of 25-40 wt % in terms of oxide; and a calcium content of 4.5-6.5 wt % in terms of oxide.

[0012] Optionally, the coal gasification slag is selected from one or a mixture of fine coal gasification slag and coarse ground coal gasification slag; wherein the coarse ground coal gasification slag is obtained by grinding and crushing coarse coal gasification slag; the weight ratio of the fine coal gasification slag to the coarse ground coal gasification slag is 100:(0-20), preferably 100:(0-15).

[0013] Optionally, the carbon content in the fine coal gasification slag is 42-50 wt%; the carbon content in the coarse coal gasification slag is 6-14 wt%.

[0014] Optionally, the activator is selected from one or more of CaO and high-calcium solid waste; the amount of the activator is such that the molar ratio of calcium element to silicon element in the gasification slag slurry is (0.8-1.2):1; based on the weight of the high-calcium solid waste, the content of calcium element is 50-90 wt% in terms of calcium oxide; the high-calcium solid waste is selected from one or more of calcium carbide slag mud, desulfurization gypsum and blast furnace slag.

[0015] Optionally, the solid content of the gasified slag slurry is 10-50 wt%, preferably 25-35 wt%.

[0016] Optionally, the conditions of the hydrothermal activation reaction include: a temperature of 100-200° C., preferably 140-200° C.; and a reaction time of 8-20 h, preferably 10-20 h.

[0017] Optionally, the method further includes: adding an alkaline catalyst to the gasification slag slurry; the alkaline catalyst is selected from one or more of KOH and NaOH; the weight ratio of the alkaline catalyst to the coal gasification slag powder is (0-5):100; under the condition of adding the alkaline catalyst, the temperature of the hydrothermal activation reaction is 100-150°C, and the reaction time is 8-15 h.

[0018] Optionally, the method further comprises: recycling the filtrate obtained by solid-liquid separation in step S1 for preparing gasified slag slurry.

[0019] The second aspect of the present invention provides a silicon-calcium organic fertilizer prepared by the method described in the first aspect of the present invention.

[0020] Through the above technical scheme, the method of the present invention can convert the residual carbon in the coal gasification slag into organic fertilizer, and at the same time convert the mineral elements such as Si, Al, Ca, K, etc., which are abundant but inert in the coal gasification slag, into "effective" silicon-calcium organic fertilizer that can be absorbed and utilized by plants, so that the organic components and inorganic components in the gasification slag are synchronously activated and efficiently utilized, turning waste into fertilizer, and reducing the emission of solid waste while preparing high-quality organic fertilizer.

[0021] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings: Figure 1 It is a schematic diagram of a flow chart of a preferred specific implementation mode of the present invention. DETAILED DESCRIPTION

[0023] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0024] The raw coal is rapidly decomposed at high temperature in the gasifier, and then reacts with the gasifying agent to be converted into synthesis gas. Among them, the gasified slag discharged from the bottom of the gasifier is usually called coarse slag (slag), and the fine slag carried out from the top with the airflow has different composition ratios. Among them, the carbon content in the coarse slag is lower than that in the fine slag, but the content of mineral elements such as Si and Ca is higher. The gasified ash slag produced in the coal gasification process has a large output and complex composition, and is difficult to utilize. If the fine slag can be activated and converted into mineral source organic fertilizer, the carbon reduction gain of the coal gasification slag can be achieved. In order to solve the above problems, the present invention is specially proposed.

[0025] A first aspect of the present invention provides a method for preparing silicon-calcium organic fertilizer from coal gasification slag, the method comprising: S1. Mixing coal gasification slag powder with an activator and water to obtain a gasification slag slurry, and subjecting the gasification slag slurry to a hydrothermal activation reaction; the content of carbon in the coal gasification slag powder is not less than 42% by weight; the activator contains calcium; and the weight ratio of the coal gasification slag powder to the activator calculated as calcium oxide is 100:(13-20); S2, separating the reaction product of the hydrothermal activation reaction into solid and liquid, and subjecting the filter cake obtained by separation to molding and drying to obtain silicon-calcium organic fertilizer.

[0026] The present invention can convert the residual carbon in the coal gasification slag into organic fertilizer, and at the same time convert the mineral elements such as Si, Al, Ca, K, etc., which are abundant but inert in the coal gasification slag, into "effective" silicon-calcium organic fertilizer that can be absorbed and utilized by plants, so that the organic components and inorganic components in the gasification slag are synchronously activated and efficiently utilized, turning waste into fertilizer, and reducing the discharge of solid waste while preparing high-quality organic fertilizer.

[0027] In the present invention, the coal gasification slag contains rich mineral elements, such as Si, Al, Ca, K and other elements, but these elements in the coal gasification slag are in an "inert" state. The present invention can convert the mineral elements in the coal gasification slag into an "effective state" that can be absorbed and utilized by plants by hydrothermal activation of the coal gasification slag powder, so that they can be effectively utilized.

[0028] In some embodiments of the present invention, the carbon content in the coal gasification slag powder is 43-50 wt%, the silicon content in oxide is 25-40 wt%, and the calcium content in oxide is 4.5-6.5 wt%. 2 The content of calcium as CaO is 38.25% by weight, and the content of calcium as CaO is 6.49% by weight.

[0029] In some embodiments of the present invention, the particle size of the coal gasification slag powder is 20-400 μm. Controlling the particle size of the coal gasification slag within a suitable range is beneficial to the activation and conversion of minerals in the coal gasification slag powder.

[0030] In some specific embodiments of the present invention, the coal gasification slag is selected from one of fine coal gasification slag and coarse ground coal gasification slag, or a mixture of both.

[0031] The ground coal gasification slag coarse slag is obtained by grinding and crushing the coal gasification slag coarse slag.

[0032] In some specific embodiments of the present invention, the weight ratio of the fine coal gasification slag to the coarse ground coal gasification slag is 100:(0-20), preferably 100:(0-15). The ratio of the coarse coal gasification slag to the fine coal gasification slag is controlled to avoid excessive addition of the coarse coal gasification slag, resulting in too low an organic matter content in the product.

[0033] In some embodiments of the present invention, the carbon content in the coal gasification slag fine slag is 42-50 wt %. The carbon content in the coal gasification slag fine slag is higher, and the particle size of the coal gasification slag fine slag is smaller, so the coal gasification slag fine slag can be directly used for hydrothermal activation.

[0034] In some embodiments of the present invention, the carbon content is 6-14 wt%. The carbon content of the coarse coal gasification slag after gasification is lower, but it contains rich mineral elements. By grinding the coarse coal gasification slag and using it in combination with the fine coal gasification slag, on the one hand, the minerals in the coarse coal gasification slag can be fully utilized, and on the other hand, solid waste and carbon emissions can be reduced.

[0035] In some embodiments of the present invention, the activator is selected from one or more of CaO and high-calcium solid waste, wherein the high-calcium solid waste is selected from one or more of calcium carbide slag mud, desulfurization gypsum and blast furnace slag.

[0036] In the present invention, under the conditions of hydrothermal activation reaction, the calcium element in industrial CaO and high-calcium solid waste reacts chemically with the mineral elements in the coal gasification slag powder, thereby converting them into an effective state that can be absorbed and utilized by plants. In some specific embodiments, the conditions of the hydrothermal activation reaction include: a temperature of 100-200°C, preferably 140-200°C; a reaction time of 8-20 h, preferably 10-20 h.

[0037] In the present invention, the hydrothermal activation reaction of the gasified slag slurry can be carried out under normal pressure or slightly positive pressure, for example, 0.1-0.2 MPa; it can also be carried out under the autogenous pressure of a sealed reaction system, for example, 0.2-1.5 MPa.

[0038] In some embodiments of the present invention, based on the weight of the high-calcium solid waste, the calcium content is 50-90 wt% in terms of calcium oxide.

[0039] In some embodiments of the present invention, the amount of the activator is such that the molar ratio of calcium to silicon in the gasification slag slurry is (0.8-1.2): 1. This is conducive to the conversion of calcium and silicon from the "inert" state of the coal gasification slag to an effective state.

[0040] In some embodiments of the present invention, the solid content of the gasified slag slurry is 10-50 wt%, preferably 25-35 wt%.

[0041] In some preferred embodiments of the present invention, the method further comprises: adding an alkaline catalyst to the gasified slag slurry, so as to reduce the energy consumption of hydrothermal activation.

[0042] Wherein, the alkaline catalyst is selected from one or more of KOH and NaOH.

[0043] In some preferred embodiments of the present invention, the weight ratio of the alkaline catalyst to the coal gasification slag powder is (0-5): 100. The amount of the alkaline catalyst is controlled so that the pH of the silicon-calcium organic fertilizer meets the pH requirements of the organic fertilizer industry standard NY / T 525-2021.

[0044] Wherein, under the condition of adding alkaline catalyst, too high temperature or too long reaction time will reduce the effective content in the silicon-calcium organic fertilizer product. The temperature of the hydrothermal activation reaction is 100-150°C and the reaction time is 8-15 h.

[0045] In some embodiments of the present invention, the method further comprises: recycling the filtrate obtained by solid-liquid separation in step S1 for preparing gasified slag slurry.

[0046] The invention converts most of the silicon compounds and metal oxides with high activity in the coal gasification slag into effective silicon and effective calcium that can be used by plants by subjecting the coal gasification slag to a hydrothermal activation reaction with an activator.

[0047] The second aspect of the present invention provides a silicon-calcium organic fertilizer prepared by the aforementioned method.

[0048] Preferably, the effective silicon content in the silicon-calcium organic fertilizer is ≥15% by weight, and the effective calcium content is ≥20% by weight.

[0049] The present invention is further described in detail by way of examples. The raw materials used in the examples and comparative examples can all be obtained through commercial sources.

[0050] The organic matter content and pH of the silicon-calcium organic fertilizer obtained in the examples and comparative examples were determined according to the method in the appendix of the organic fertilizer industry standard NY / T525-2021 "Organic Fertilizer". The determination of effective silicon and effective calcium content was carried out in accordance with the industry standard NY T2272-2012 "Determination of Silicon, Magnesium and Calcium Content of Soil Conditioners" of the Ministry of Agriculture and Rural Affairs of the People's Republic of China.

[0051] The coarse coal gasification slag and the fine coal gasification slag in the embodiments and comparative examples are from Ningxia Coal Industry Coal-to-Liquids Company, wherein the Dv10 particle size of the coarse coal gasification slag is 104 μm, the Dv50 particle size is 370 μm, and the Dv90 particle size is 423 μm, and the Dv10 particle size of the fine coal gasification slag is 4.45 μm, the Dv50 particle size is 29.6 μm, and the Dv90 particle size is 117 μm. The composition is shown in Table 1 below.

[0052] Table 1

[0053] Example 1 This embodiment is used to illustrate the method for preparing silicon-calcium organic fertilizer from coal gasification slag of the present invention, comprising the following steps: S1. Mixing coal gasification slag powder with an activator and water to obtain coal gasification slag slurry; wherein the coal gasification slag powder is coal gasification slag fine slag, the activator is industrial CaO (mass fraction is 92.0 wt%), and the weight ratio of coal gasification slag fine slag, the activator and water is 100:18:320; S2, transferring the gasified slag slurry into a hydrothermal reactor, and heating the hydrothermal reactor with direct steam to cause the gasified slag slurry to undergo a hydrothermal activation reaction to obtain a hydrothermal activation reaction product; wherein the temperature of the hydrothermal activation reaction is 180°C and the time is 12 hours; S3. The hydrothermal activation reaction product is subjected to solid-liquid separation, and the filter cake obtained by separation is granulated and dried to obtain silicon-calcium organic fertilizer; and the filtrate is recovered for preparing gasification slag slurry; wherein the weight contents of silicon dioxide and calcium oxide in the filtrate are both less than 100 ppm, and the filtrate is reused; and the filtration losses of silicon and calcium can be ignored.

[0054] The properties of the silicon-calcium organic fertilizer prepared in this example are shown in Table 2.

[0055] Example 2 The method for preparing silicon-calcium organic fertilizer in this embodiment refers to Example 1, which differs from Example 1 in that: The reaction temperature of the hydrothermal activation reaction is 145°C and the time is 16 h. The properties of the silicon-calcium organic fertilizer prepared in this example are shown in Table 2.

[0056] Example 3 The method for preparing silicon-calcium organic fertilizer in this embodiment refers to Example 1, which differs from Example 1 in that: The reaction temperature of the hydrothermal activation reaction is 200°C and the time is 8 hours. The properties of the silicon-calcium organic fertilizer prepared in this example are shown in Table 2.

[0057] Example 4 The method for preparing silicon-calcium organic fertilizer in this embodiment refers to Example 1, which differs from Example 1 in that: The reaction temperature of the hydrothermal activation reaction is 200°C and the time is 10 h. The properties of the silicon-calcium organic fertilizer prepared in this example are shown in Table 2.

[0058] Example 5 The method for preparing silicon-calcium organic fertilizer in this embodiment refers to Example 1, which differs from Example 1 in that: The reaction temperature of the hydrothermal activation reaction is 200°C and the time is 12 h. The properties of the silicon-calcium organic fertilizer prepared in this example are shown in Table 2.

[0059] Example 6 The method for preparing silicon-calcium organic fertilizer in this embodiment refers to Example 1, which differs from Example 1 in that: The reaction temperature of the hydrothermal activation is 140°C and the time is 20 h. The properties of the silicon-calcium organic fertilizer prepared in this example are shown in Table 2.

[0060] Example 7 The method for preparing silicon-calcium organic fertilizer in this embodiment refers to Example 1, which differs from Example 1 in that: The reaction temperature of hydrothermal activation is 140°C and the time is 16 h. The properties of the silicon-calcium organic fertilizer prepared in this example are shown in Table 2.

[0061] Example 8 The method for preparing silicon-calcium organic fertilizer in this embodiment refers to Example 1, which differs from Example 1 in that: The activator used was carbide mud (the mass fraction of CaO was 68.1wt%), and the weight ratio of coal gasification slag fine slag, activator and water was 100:24:320. The properties of the silicon-calcium organic fertilizer prepared in this example are shown in Table 2.

[0062] Example 9 The method for preparing silicon-calcium organic fertilizer in this embodiment refers to Example 1, which differs from Example 1 in that: Catalyst KOH is also added to the gasified slag slurry; The weight ratio of coal gasification slag fines, activator, catalyst KOH and water is 100:18:5:320; The reaction temperature of the hydrothermal activation reaction is 100°C and the time is 8 h. The properties of the silicon-calcium organic fertilizer prepared in this example are shown in Table 2.

[0063] Example 10 The method for preparing silicon-calcium organic fertilizer in this embodiment refers to Example 9, which differs from Example 9 in that: The activator used was carbide mud (the mass fraction of CaO was 68.1wt%), and the weight ratio of coal gasification slag fines, activator, catalyst KOH and water was 100:24:5:320; The reaction temperature of the hydrothermal activation reaction is 120°C and the time is 8 h. The properties of the silicon-calcium organic fertilizer prepared in this example are shown in Table 2.

[0064] Embodiment 11 The method for preparing silicon-calcium organic fertilizer in this embodiment refers to Example 9, which differs from Example 9 in that: The weight ratio of coal gasification slag fine slag, activator, catalyst KOH and water is 100:18:6:320; the properties of the silicon-calcium organic fertilizer prepared in this example are shown in Table 2.

[0065] Example 12 This embodiment is used to illustrate the method for preparing silicon-calcium organic fertilizer from coal gasification slag of the present invention, comprising the following steps: S1. crushing and grinding the coarse coal gasification slag to less than 200 meshes to obtain ground coarse coal gasification slag; mixing the fine coal gasification slag and the ground coarse coal gasification slag in a weight ratio of 100:10 to obtain coal gasification slag powder; S2, mixing coal gasification slag powder with an activator and water to obtain gasification slag slurry; wherein the coal gasification slag powder is coal gasification slag fine slag, the activator is industrial CaO (mass fraction is 92.0 wt%), and the weight ratio of the coal gasification slag fine slag, the activator and water is 110:18:320; S3, transferring the gasified slag slurry into a hydrothermal reactor, and heating the hydrothermal reactor with direct steam to cause the gasified slag slurry to undergo a hydrothermal activation reaction to obtain a hydrothermal activation reaction product; wherein the temperature of the hydrothermal activation reaction is 180°C and the time is 12 hours; S4. The hydrothermal activation reaction product is subjected to solid-liquid separation, and the filter cake obtained by separation is granulated and dried to obtain silicon-calcium organic fertilizer. The filtrate is recovered for preparing gasification slag slurry; wherein the content of silicon dioxide and calcium oxide in the filtrate is both less than 100 ppm, and the filtrate is reused, and the filtration loss of silicon and calcium can be ignored.

[0066] The properties of the silicon-calcium organic fertilizer prepared in this example are shown in Table 2.

[0067] Comparative Example 1 The method for preparing silicon-calcium organic fertilizer in this comparative example refers to Example 1, which differs from Example 1 in that: The activator used was carbide mud (the mass fraction of CaO was 68.1wt%), and the weight ratio of coal gasification slag fine slag, activator and water was 100:24:320. The properties of the silicon-calcium organic fertilizer prepared in this comparative example are shown in Table 2.

[0068] Comparative Example 2 The method for preparing silicon-calcium organic fertilizer in this comparative example refers to Example 12, which differs from Example 12 in that: The coal gasification slag powder is obtained by mixing fine coal gasification slag and ground coarse coal gasification slag in a weight ratio of 100:20. The properties of the silicon-calcium organic fertilizer prepared in this comparative example are shown in Table 2.

[0069] Comparative Example 3 The method for preparing silicon-calcium organic fertilizer in this comparative example refers to Example 1, which differs from Example 1 in that: In step S1, no activator is added to the coal gasification slag slurry, that is, the coal gasification slag slurry includes coal gasification slag fine slag and water in a weight ratio of 100:320. The properties of the silicon-calcium organic fertilizer prepared in this comparative example are shown in Table 2.

[0070] Table 2

[0071] It can be found from the above table that compared with Comparative Example 3, the present invention can simultaneously activate and efficiently utilize the organic components and inorganic components in the coal gasification slag by adding an activator containing calcium during the hydrothermal activation process of the coal gasification slag, and is suitable for use as an organic fertilizer.

[0072] According to Examples 1-7, it can also be found that by increasing the temperature of the hydrothermal activation reaction, the activation time can be shortened, thereby improving production efficiency. In Examples 3-5, when the reaction temperature of the hydrothermal activation is high, the degree of organic decomposition and the degree of activator reaction increase, and the effective silicon content in the product can be increased and the pH value of the product can be reduced within the appropriate reaction time range; however, when the reaction time is insufficient, the effective silicon content in the product is significantly reduced, and when the reaction time is too long, the organic matter in the gasified slag raw material is deeply decomposed, so that the content of organic matter in the product decreases. In Examples 2 and 6-7, when the temperature of the hydrothermal activation reaction is low, if the activation reaction time is too short, the activator reaction is insufficient, resulting in low organic matter and effective silicon content in the product, and even if the activation reaction time is extended, the content of organic matter and effective silicon in the product is not significantly improved. In Comparative Example 1, when the amount of activator is insufficient, the organic matter content in the product decreases slightly, while the effective silicon and effective calcium contents decrease significantly, the effective silicon content is less than 15wt%, and the effective calcium content is less than 20wt%, which does not meet the standard.

[0073] According to the data in the above Examples 9-11, it can be known that adding an appropriate amount of catalyst to the gasification slag slurry can achieve the activation effect of organic matter and effective silicon at normal pressure and low temperature (100°C), and the product pH is within the qualified range; according to the results in Example 11, it can be known that when an excessive amount of catalyst is added, the pH of the product exceeds 9, which does not meet the industry standard and is unqualified.

[0074] According to the data in Example 12, when the coarse coal gasification slag is added to the fine coal gasification slag, the effective silicon content in the product is significantly increased, but the organic matter content is correspondingly reduced. In Comparative Example 2, when the proportion of the coarse coal gasification slag added is too high, the organic matter content in the product is less than 30wt%, which does not meet the industry standard.

[0075] 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.

[0076] 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.

[0077] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for preparing silicon-calcium organic fertilizer from coal gasification slag, characterized in that: The method comprises: S1. Mixing coal gasification slag powder with an activator and water to obtain a gasification slag slurry, and subjecting the gasification slag slurry to a hydrothermal activation reaction; the content of carbon in the coal gasification slag powder is not less than 42% by weight; the activator contains calcium; and the weight ratio of the coal gasification slag powder to the activator calculated as calcium oxide is 100:(13-20); S2, separating the reaction product of the hydrothermal activation reaction into solid and liquid, and subjecting the filter cake obtained by separation to molding and drying to obtain silicon-calcium organic fertilizer.

2. The method according to claim 1, wherein: The coal gasification slag powder has a carbon content of 43-50 wt %; a silicon content of 25-40 wt % in terms of oxide; and a calcium content of 4.5-6.5 wt % in terms of oxide.

3. The method according to claim 1, wherein: The coal gasification slag is selected from one of fine coal gasification slag and coarse ground coal gasification slag, or a mixture of both; Wherein, the ground coal gasification slag coarse slag is obtained by grinding and crushing the coal gasification slag coarse slag; The weight ratio of the fine coal gasification slag to the coarse ground coal gasification slag is 100:(0-20), preferably 100:(0-15).

4. The method according to claim 3, wherein: The carbon content in the coal gasification slag fine slag is 42-50 wt%; The carbon content in the crude coal gasification slag is 6-14 wt%.

5. The method according to claim 1, wherein: The activator is selected from one or more of CaO and high-calcium solid waste; The amount of the activator is such that the molar ratio of calcium element to silicon element in the gasified slag slurry is (0.8-1.2):1; Based on the weight of the high-calcium solid waste, the content of calcium in terms of calcium oxide is 50-90 wt%; The high-calcium solid waste is selected from one or more of carbide slag mud, desulfurization gypsum and blast furnace slag.

6. The method according to claim 1, wherein: The solid content of the gasified slag slurry is 10-50 wt %, preferably 25-35 wt %.

7. The method according to claim 1, wherein: The conditions of the hydrothermal activation reaction include: a temperature of 100-200° C., preferably 140-200° C.; and a reaction time of 8-20 h, preferably 10-20 h.

8. The method according to claim 1, wherein: The method further comprises: adding an alkaline catalyst to the gasified slag slurry; The alkaline catalyst is selected from one or more of KOH and NaOH; The weight ratio of the alkaline catalyst to the coal gasification slag powder is (0-5):100; Under the condition of adding an alkaline catalyst, the temperature of the hydrothermal activation reaction is 100-150° C. and the reaction time is 8-15 h.

9. The method according to claim 1, wherein: The method further comprises: recycling the filtrate obtained by solid-liquid separation in step S1 for preparing gasified slag slurry.

10. A silicon-calcium organic fertilizer prepared by the method described in any one of claims 1 to 9.

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