A method for preparing an alkali-free silicon fertilizer from a silicon-containing acid treatment solution and an alkali-free silicon fertilizer

Abstract

The application discloses a method for preparing silicon fertilizer from acid treatment liquid containing silicon and a non-alkali silicon fertilizer, and the method comprises the following steps: (1) gelatinizing the acid treatment liquid containing silicon, and filtering and separating to obtain silica gel; and (2) adding calcium agent and / or magnesium agent into the gelatin, adding water to prepare slurry, and reacting, and filtering and separating to obtain the silicon fertilizer. The application develops a comprehensive treatment and resource utilization method aiming at the acid treatment waste liquid of minerals, especially the acid treatment waste liquid of the acid-alkali deslagging method of coal. According to the application, the silica in the acid liquid can be effectively utilized, the high-efficiency silicon fertilizer can be produced, the effective silicon content in the silicon fertilizer is high, the silicon fertilizer does not contain sodium, and the application has high industrial application value.

Description

Technical Field

[0001] This invention relates to a method for preparing alkali-free silicon fertilizer from a silicon-containing acid treatment solution and to the alkali-free silicon fertilizer itself. Background Technology

[0002] China has large coal reserves, but the overall coal quality is poor, with high ash content. After years of mining, coal quality has been continuously declining. Therefore, coal ash removal and refining are necessary to promote its clean and efficient utilization. Traditional coal ash removal methods can be mainly divided into physical and chemical methods. Traditional physical methods are simple and easy to implement, but have poor adaptability and low ash removal efficiency. Chemical methods are highly adaptable and have high ash removal efficiency, but they involve the problem of treating ash removal wastewater. Therefore, the treatment and resource utilization of ash removal wastewater is a technical challenge in coal chemical ash removal.

[0003] In recent years, patented technologies related to coal ash removal and refining can be mainly divided into: physical separation and ash removal methods for coal, such as Chinese patent application 201710999607.9 (a process for preparing ultrapure coal using a physical method for anthracite), Chinese patent application 201610166372.0 (a process for preparing ultrapure coal), Chinese patent application 201110195118.0 (a deep coal purification system and method), and Chinese patent application 97116584.X (deep coal purification). Physical deashing and desulfurization processes, such as Chinese patent application 201210259309.3 (Method for preparing fine coal-water slurry from coal slime in coal preparation plants) and Chinese patent application 200420052870.5 (Ultra-clean coal flotation machine); chemical deashing methods for coal, such as Chinese patent application 201710999565.9 (A process for preparing ultra-pure coal using a physical-chemical method from anthracite) and Chinese patent application 201710999573.3 (A method for preparing ultra-pure coal using a chemical method from anthracite). The process of coal demineralization, Chinese patent application 200380102494.4 (Method for demineralizing coal), Chinese patent application 03262744.0 (Coal acid reaction desulfurization and ash removal device), Chinese patent application 201010513009.4 (Ash removal from coal processing to avoid large amounts of hydrogen fluoride on site), Chinese patent application 201010131521.2 (Dehydration system and process for improving the combined cycle efficiency of coal-fired power generation equipment); coal solvent extraction methods, such as Chinese patents Application 201110373648.X (A method for thermal extraction of coal), Chinese Patent Application 201510979337.6 (A method for effectively improving the yield of thermal extraction of coal), Chinese Patent Application 201020524863.6 (An apparatus for preparing ultrapure coal), Chinese Patent Application 200810019409.2 (A milding process for the separation of all components of coal), and Chinese Patent Application 200910076672.X (A method for coal liquefaction).

[0004] In summary, among the various methods described above, traditional physical methods for coal ash removal and refining are simple and easy to implement, but have poor adaptability and low ash removal efficiency. Chemical methods are highly adaptable and have high ash removal efficiency, but they are accompanied by the problem of wastewater treatment. Although Chinese patent application 201010131521.2 (Dehydration system and process for improving the combined cycle efficiency of coal-fired power plants) proposes an energy-saving reverse osmosis membrane treatment technology for treating wastewater from hydrofluoric acid ash removal, it fails to provide a resource utilization solution. In particular, for the most widely used conventional acid-base method, there is still a lack of solutions for wastewater treatment and resource utilization.

[0005] At the same time, all arable land in China suffers from varying degrees of silicon deficiency. It is estimated that there is a potential shortage of 30-50 million tons in the silicon fertilizer market, with a greater potential for use than nitrogen, phosphorus, and potassium. Traditional silicon fertilizer is made from blast furnace water-quenched slag in steelmaking and ironmaking, but the content of some heavy metals and other harmful elements may exceed the standards, which limits its use.

[0006] In recent years, mineral roasting and hydrothermal activation processes have also been developed, such as Chinese patent application 201010196125.8 (a method for producing silicon-potassium-calcium microporous mineral fertilizer), Chinese patent application 201510291976.3 (a method for producing phosphorus-potassium-silicon-calcium multi-element microporous mineral fertilizer (soil conditioner)), Chinese patent application 202510040893.7 (a method for preparing a soil conditioner rich in citrate-soluble silicon), and Chinese patent application 201611217541.5 (a soil conditioner and its preparation method). These processes require silicon activation under hydrothermal conditions of 160-300℃, and the products contain a certain amount of sodium, which may be detrimental to the soil with long-term use, causing salinization. Summary of the Invention

[0007] The purpose of this invention is to provide a comprehensive treatment and resource utilization method for silica in acidic wastewater containing ash. This method can extract silica and prepare high-efficiency silicon fertilizer, thus enabling the high-value utilization of silica contained in ash.

[0008] To address the shortcomings and challenges of existing technologies, this invention proposes that using acidic wastewater from coal ash removal to produce silicon fertilizer can reduce pollution and achieve the resource utilization of silicon. Accordingly, this invention proposes a resource utilization scheme for silicon-containing solid waste and minerals, especially acidic wastewater from coal acid ash removal, to prepare highly efficient silicon fertilizer under mild conditions and free from harmful elements such as alkali and heavy metals.

[0009] According to the present invention, a method for preparing silicon fertilizer from a silicon-containing acid treatment solution is provided, the method comprising:

[0010] (1) The silica gel was obtained by gelling the silica-containing acid treatment solution and filtering it.

[0011] (2) Add calcium and / or magnesium to the gel, add water to make slurry and react, filter and separate to obtain silicon fertilizer.

[0012] Preferably, the reaction conditions in step (2) include: a temperature of 20-99°C and a time of 0.1-6 hours.

[0013] Preferably, the weight ratio of water used for pulping to gel is 5-100:100, more preferably 10-50:100.

[0014] Preferably, the preparation steps of the silicon-containing acid treatment solution include: optionally treating the silicon-containing mineral with an alkaline method, and then treating it with an acid to obtain the silicon-containing acid treatment solution.

[0015] Preferably, the acid treatment conditions include: the acid being one or more of hydrochloric acid, dilute sulfuric acid, nitric acid, and phosphoric acid; and / or the temperature being 20-200°C, preferably 40-99°C.

[0016] Preferably, the silicon-containing mineral is one or more of the following: coal, coal gangue, nepheline, fly ash, gasification slag, clay, quartz sand, and feldspar.

[0017] Preferably, the Si content in the silicon-containing acid treatment solution, calculated as SiO2, is greater than 1 wt%, more preferably greater than 2 wt%, and even more preferably 2-10 wt%.

[0018] Preferably, in step (2), the molar ratio of calcium and / or magnesium to silicon is 0.6-4:1.

[0019] Preferably, in step (2), the calcium agent is selected from one or more of calcium oxide, calcium hydroxide, and lime emulsion.

[0020] Preferably, the magnesium agent is selected from one or more of magnesium oxide, magnesium hydroxide, and magnesium hydroxide emulsion.

[0021] Preferably, in step (1), the gelation conditions include: a temperature of 20-99°C, preferably 60-90°C; and / or a time of 0.2-48 hours, preferably 0.5-3 hours.

[0022] This invention provides an alkali-free silicon fertilizer obtained by the method of this invention.

[0023] Preferably, the alkali content is less than 0.1% by weight, based on the total weight of the alkali-free silicon fertilizer.

[0024] This invention develops a comprehensive treatment and resource utilization method for acid treatment wastewater from minerals, especially acid treatment wastewater from coal acid-base ash removal processes. Using this invention, silica in the acid solution can be effectively utilized to produce high-efficiency silicon fertilizer. This silicon fertilizer has a high effective silicon content and is sodium-free, making it highly valuable for industrial applications.

[0025] In summary, the resource utilization method for acid treatment solution provided by this invention has the following main features:

[0026] (1) It provides a resource utilization pathway for silicon-containing mineral acid treatment solutions; (2) It prepares high-efficiency silicon fertilizer with an effective silicon content of more than 38%; (3) The silicon fertilizer does not contain sodium, which can avoid soil salinization; (4) The preparation conditions are mild and efficient. Detailed Implementation

[0027] The endpoints and any values ​​of the ranges disclosed herein 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 the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0028] According to the present invention, a method for preparing silicon fertilizer from a silicon-containing acid treatment solution is provided, the method comprising:

[0029] (1) The silica gel was obtained by gelling the silica-containing acid treatment solution and filtering it.

[0030] (2) Add calcium and / or magnesium to the gel, add water to make slurry and react, filter and separate to obtain silicon fertilizer.

[0031] By employing the aforementioned technical solution of the present invention, silicon dioxide in acidic solutions can be effectively utilized to produce high-efficiency silicon fertilizer. The silicon fertilizer has a high effective silicon content and does not contain sodium, making it highly valuable for industrial applications.

[0032] According to the present invention, silicon fertilizer is prepared by reacting with calcium and / or magnesium agents, and the resulting silicon fertilizer is obtained after separation and washing. Due to the excellent reactivity of the gel, compared with traditional mineral roasting and hydrothermal activation processes, the reaction conditions can be significantly reduced, and silicon fertilizer preparation can be completed at lower temperatures and in a shorter time. The effective silicon content of the obtained silicon fertilizer can be greater than 38%, and the alkali content is less than 0.1%.

[0033] According to a preferred embodiment of the present invention, the reaction temperature is 20-99°C, preferably 60-99°C.

[0034] In this invention, the reaction time is adjusted according to the reaction temperature. For this invention, the preferred reaction time is 0.1-6 hours, and more preferably 0.5-3 hours.

[0035] In this invention, the weight ratio of water used for pulping to gel is 5-100:100, preferably 10-50:100. In this invention, water used for pulping refers to water added from other raw materials or additional water besides the water content in the gel.

[0036] According to the present invention, there are no special requirements for the source of the silicon-containing acid treatment solution, nor are there any special requirements for its preparation method. For example, the preparation steps may include: optionally treating the silicon-containing mineral with an alkaline method, and then treating it with an acid to obtain the silicon-containing acid treatment solution.

[0037] According to a preferred embodiment of the present invention, the mineral, such as coal or coal gangue, is preferably subjected to alkaline treatment before acid treatment.

[0038] According to the present invention, the alkali treatment of minerals can be carried out in various ways. For example, coal can be melted with alkali at around 400°C (Jiang Ruiyao, Zhou Shixue, Tan Qi, Han Hong. Nonferrous Mining and Metallurgy, 2006, 22, 151-152), and fly ash can be roasted with sodium carbonate at 800-1350°C, as in Chinese Patent Application 200710087028.3 (Clean Production Process of Alumina and Silica Using High-Alumina Fly Ash).

[0039] According to the present invention, Chinese Patent Application 201710999565.9 (A process for preparing ultrapure coal using a physicochemical method of anthracite), Chinese Patent Application 201710999573.3 (A process for preparing ultrapure coal using a chemical method of anthracite), and Chinese Patent Application 200380102494.4 (Method for demineralizing coal), the alkaline coal reaction conditions of the conventional acid-base method are incorporated herein by reference.

[0040] According to the present invention, the acids used for acid treatment are, for example, hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid.

[0041] According to the present invention, the reaction temperature for acid treatment is, for example, 20-200°C, preferably 40-99°C. Acid treatment forms an acid-treated solution containing silica. If the mineral is a silica-containing acid-soluble mineral, such as nepheline, acid treatment can be performed directly to obtain a silica-containing acid-treated solution.

[0042] According to a preferred embodiment of the present invention, the acid treatment conditions include: the acid is one or more of hydrochloric acid, dilute sulfuric acid, nitric acid and phosphoric acid, preferably hydrochloric acid and / or sulfuric acid.

[0043] The acid treatment conditions in this invention have a wide range of options. According to a preferred embodiment of this invention, the acid treatment conditions include a temperature of 20-200℃, preferably 40-99℃.

[0044] In this invention, there are no special requirements for the concentration of the acid solution used for acid treatment, which can be set to 1-30% by weight, preferably 3-20% by weight, and more preferably 5-15% by weight.

[0045] In this invention, there are no special requirements for the concentration of the alkali solution used for alkali treatment; it can be set to 2-90% by weight.

[0046] In this invention, when the mineral is coal, the temperature of the alkali treatment can be set to 100-250℃.

[0047] According to the present invention, there are no special requirements for the concentration of acid solution during acid treatment. For example, it can be set to 1-30% by weight, preferably 3-20% by weight, and more preferably 5-15% by weight.

[0048] According to the present invention, there are no special requirements for the concentration of the alkali solution during alkali treatment; for example, it can be set to 2-90% by weight.

[0049] According to the present invention, the range of silicon-containing minerals that can be selected is relatively wide, and commonly used ash-containing substances in the art can be used in the present invention. For the present invention, preferably, the silicon-containing minerals are one or more of coal, coal gangue, nepheline, fly ash, gasification slag, clay, quartz sand, and feldspar.

[0050] According to the present invention, preferably in step (2), calcium agent and magnesium agent are added according to the molar ratio of calcium oxide, magnesium oxide and silicon dioxide, and the ratio of (calcium + magnesium) / silicon is 0.6-4:1. The two can be mixed in any proportion.

[0051] According to the present invention, the calcium agent can be a commonly used calcium-containing substance, such as calcium oxide, calcium hydroxide and lime emulsion.

[0052] According to the present invention, the magnesium agent can be a commonly used magnesium-containing substance, such as magnesium oxide, magnesium hydroxide and magnesium hydroxide emulsion.

[0053] According to the present invention, calcium and magnesium agents can be prepared from limestone, dolomite and magnesite, etc., which are widely available. Calcium and magnesium are also nutrients required by plants.

[0054] According to a preferred embodiment of the present invention, in step (2), the molar ratio of calcium and / or magnesium to silicon is 0.6-4:1; preferably, in step (2), the calcium agent is selected from one or more of calcium oxide, calcium hydroxide and lime emulsion; and / or the magnesium agent is selected from one or more of magnesium oxide, magnesium hydroxide and magnesium hydroxide emulsion.

[0055] According to the present invention, in step (1), the silicon-containing acid treatment solution is gelled. Preferably, the Si content in the acid treatment solution, calculated as SiO2, is greater than 1 wt%, more preferably greater than 2 wt%, for example, 2-10 wt%. In one specific embodiment, if the Si content in the third mixture, calculated as SiO2, is less than 0.5 wt%, the solvent is removed and the mixture is concentrated, for example, by rotary evaporation to make the Si content in the third mixture, calculated as SiO2, greater than 1 wt%.

[0056] Therefore, according to a preferred embodiment of the present invention, the Si content in the silicon-containing acid treatment solution, calculated as SiO2, is greater than 1 wt%, preferably greater than 2 wt%, and more preferably 2-10 wt%.

[0057] According to the present invention, during the gelation process, the gelation proceeds slowly and takes a long time, up to 48 hours, at lower temperatures. As the temperature increases, gelation accelerates, but when the temperature exceeds 100°C, significant pressure is generated during gelation, placing stringent requirements on the reaction conditions. Therefore, a temperature below 100°C, such as below 99°C, is preferred to ensure that gelation is carried out under mild conditions. During the gelation process, silica forms a gel and precipitates. During gel washing, sodium ions and harmful heavy metal ions can be effectively separated from the gel, leaving no residue.

[0058] According to a preferred embodiment of the present invention, in step (1), the gelation conditions include a temperature of 20-99°C, preferably 60-90°C.

[0059] According to a preferred embodiment of the present invention, in step (1), the gelation conditions include a time of 0.5-3 hours, preferably 0.2-48 hours.

[0060] According to the present invention, preferably, the conditions for the gelation reaction include: a temperature of 20-99°C and a time of 0.2-48 hours; more preferably, a temperature of 60-90°C and a time of 0.5-3 hours.

[0061] Therefore, the present invention provides a technical solution for the treatment and resource utilization of waste liquid generated from coal ash removal. The technical solution provided by the present invention mainly includes: (1) acid treatment of silicon-containing minerals to obtain acid treatment liquid; (2) gelation of the silicon-containing acid treatment liquid and separation of silica gel by filtration; (3) addition of calcium and / or magnesium agents to the gel according to the formula and slurrying with water; (4) reaction at 20-99℃ for 0.1-6 hours and separation by filtration to obtain high-efficiency silicon fertilizer.

[0062] The method for resource utilization of acid treatment solution provided by this invention has the following main features:

[0063] (1) It provides a resource utilization pathway for silicon-containing mineral acid treatment solutions; (2) It prepares high-efficiency silicon fertilizer with an effective silicon content of more than 38%; (3) The silicon fertilizer does not contain sodium, which can avoid soil salinization; (4) The preparation conditions are mild and efficient.

[0064] The present invention will be described in detail below through embodiments, but this does not limit the present invention.

[0065] In the following examples, the minerals used were coal A (22 wt% ash), coal gangue B (81 wt% ash), and nepheline C. According to NY / T 797-2004, the available silicon in the silicon fertilizer must be greater than 20 wt%. The available silicon content was determined according to NY / T 2272-2012. The alkali content was detected by ICP.

[0066] Example 1

[0067] 100g of coal sample A was mixed with 80g of sodium hydroxide and 320ml of water, and reacted in a high-pressure reactor at 230℃ for 3 hours. After filtration and washing, 10wt% dilute sulfuric acid was added to the filter cake at an acid-to-dry filter cake weight ratio of 1.4:1, and the mixture was leached at 75℃ for 30 minutes. After filtration and washing, an acidic waste liquid with a silica content of 1.5wt% was obtained. The mixture was gelled at 60℃ for 6 hours, and filtered to obtain silica gel and gel filtrate. Calcium oxide was added to the silica gel at a calcium-to-silicon molar ratio of 1.2. After adding an appropriate amount of water and stirring to form a slurry, water was added at a weight ratio of 10:100 to the gel, and the mixture was reacted at 98℃ for 1 hour to obtain silicon fertilizer. The effective silicon content was found to be 39wt%, and the alkali content (calculated as sodium oxide) was 0.01%.

[0068] Example 2

[0069] Take 100g of coal gangue A, mix it with 150g of sodium hydroxide and 100ml of water, and knead it at 150℃ for 9 hours. Dilute with water and cool down, then filter and wash after 1 hour. Add 10wt% dilute hydrochloric acid to the filter cake at an acid-to-dry filter cake ratio of 1.5:1, leach at 60℃ for 30 minutes, and filter to obtain an acid leachate with a silica content of 10wt%. Gel at 20℃ for 36 hours, and filter to obtain silica gel and gel filtrate. In the gel, add calcium oxide and magnesium oxide at a (calcium + magnesium) silicon molar ratio of 1.2 and a calcium-magnesium molar ratio of 1.0, add an appropriate amount of water, stir evenly to form a slurry, and then add water at a weight ratio of 20:100 to gel. Stir and react at 80℃ for 3 hours to obtain silicon fertilizer. The effective silicon content is 32wt%, and the alkali content (calculated as sodium oxide) is 0.03%.

[0070] Example 3

[0071] Take 100g of nepheline C, add 10wt% dilute nitric acid to the filter cake at an acid-nepheline ratio of 2.0:1, leach at 40℃ for 30 minutes, and filter to obtain an acid leachate with a silica content of 6%. Gel at 95℃ for 30 minutes, and filter to obtain silica gel and gel filtrate. Add magnesium oxide to the gel at a magnesium-silicon molar ratio of 3.8, add an appropriate amount of water, stir until homogeneous, and then add water at a weight ratio of 50:100 to the gel. Stir and mix at 60℃ for 3 hours to obtain a silicon fertilizer. Testing shows an effective silicon content of 21wt% and an alkali content (calculated as sodium oxide) of 0.05%.

[0072] Example 4

[0073] Prepared according to the method of Example 2, except that the acid leaching solution obtained by acid washing is reacted again with the filter cake treated by alkali method to obtain a secondary acid leaching solution as raw material. The silica content is 15%, and the other conditions are the same to obtain silicon fertilizer. The effective silicon content is 31 wt%, and the alkali content is 0.01% calculated as sodium oxide.

[0074] Comparative Example 1

[0075] According to Chinese patent application 201611217541.5 (A soil conditioner and its preparation method), the following experiment was conducted: Calcium oxide and coal gangue B were mixed at a calcium-silicon molar ratio of 1.2 and dissolved in a 1.5 mol / L NaOH solution. The solid-liquid ratio was controlled at 1:35 g / mL. The mixed slurry was subjected to a hydrothermal reaction in a reactor at a reaction temperature of 140℃ for 18 hours. After the reaction, the slurry was vacuum filtered, and the solid was washed and dried to obtain the soil conditioner product. The effective silicon content of the product was 22 wt%, and the alkali content (calculated as sodium oxide) was 5%.

[0076] As can be seen from Examples 1, 2, 3 and Comparative Example 1, after gelling the acid-treated solution from coal A, coal gangue B and nepheline C, calcium oxide or magnesium oxide can be added to the separated silica gel, and high-efficiency silicon fertilizer can be prepared under mild conditions. The alkali content is less than 0.1%, which is far lower than that of silicon fertilizer prepared by traditional methods, and will not cause soil salinization.

[0077] Compared with existing technologies, this method has milder conditions, produces silicon fertilizer with high effective silicon content, and has excellent process adaptability. The amount of calcium and magnesium added in the silica gel can vary over a wide range, and all of them can meet the standard requirement of silicon fertilizer with effective silicon content greater than 20%.

[0078] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing alkali-free silicon fertilizer from a silicon-containing acid treatment solution, characterized in that, The method includes: (1) The silica gel was obtained by gelling the silica-containing acid treatment solution and filtering it. (2) Add calcium and / or magnesium to the gel, add water to make slurry and react, filter and separate to obtain silicon fertilizer; The reaction conditions in step (2) include: a temperature of 60-99℃ and a time of 0.1-6 hours, wherein the Si content in the silicon-containing acid treatment solution, calculated as SiO2, is greater than 1 wt%. In step (2), The calcium agent is selected from one or more of calcium oxide, calcium hydroxide, and lime slurry; and / or The magnesium agent is selected from one or more of magnesium oxide, magnesium hydroxide, and magnesium hydroxide emulsion; In step (1), The preparation steps of the silicon-containing acid treatment solution include: treating the silicon-containing mineral with an alkaline method, and then treating it with an acid to obtain the silicon-containing acid treatment solution; The silicon-containing minerals are one or more of the following: coal, coal gangue, nepheline, fly ash, gasification slag, clay, quartz sand, and feldspar.

2. The method according to claim 1, wherein, The reaction conditions in step (2) include: The weight ratio of water used for pulping to gel is 5-100:

100.

3. The method according to claim 2, wherein, The reaction conditions in step (2) include: the weight ratio of water used for pulping to gel is 10-50:

100.

4. The method according to claim 1 or 2, wherein, The silicon-containing acid treatment solution contains more than 2 wt% Si, calculated as SiO2.

5. The method according to claim 4, wherein, The silicon-containing acid treatment solution contains 2-10 wt% Si, calculated as SiO2.

6. The method according to claim 1 or 2, wherein, In step (2), the molar ratio of calcium and / or magnesium to silicon is 0.6-4:

1.

7. The method according to claim 1 or 2, wherein, In step (1), the gelation conditions include a temperature of 20-99°C and / or a time of 0.2-48 hours.

8. The method according to claim 7, wherein, In step (1), the gelation conditions include a temperature of 60-90℃ and / or a time of 0.5-3 hours.