Alkaline agent for chemical deep deliming of ultra-pure coal as well as preparation method and application of alkaline agent

Abstract

The invention belongs to the technical field of coal, and particularly discloses an alkaline agent for chemical deep deliming of ultra-pure coal and a preparation method and application of the alkaline agent, and the alkaline agent is prepared from a quaternary ammonium alkali solution, a strong alkali solution, an NH3.H2O solution and a sodium fluoride solution according to the volume ratio of (2-3): (1-2): (1-2): (2-3). Compared with the prior art, the compound agent has high alkalinity and complexing capacity, and after deep deliming is conducted through the compound agent, clean coal with the ash content being 2% + / -0.2% can be prepared into ultra-pure coal with the ash content being lower than 0.2%; the preparation method of the alkaline compound agent is simple and easy to operate, the obtained product is high in quality, the coal ash content of the prepared ultra-pure coal is smaller than 0.2%, deep deashing of the coal is achieved, and further comprehensive utilization of the coal is facilitated.

Description

Technical Field

[0001] The present invention relates to the field of coal technicians, in particular to an alkaline agent for chemical deep deashing of ultra-pure coal, its preparation method and application. Background Art

[0003] Ultra-pure coal is one of the current coal deep processing technologies and can be used to prepare high-value-added products such as coal-based carbon materials, but it has high requirements for ash content. Currently, the preparation methods of ultra-pure coal can be divided into two major categories: physical methods and chemical methods. Physical methods include flotation method, selective flocculation technology, etc.; chemical methods include conventional acid-base method, pickling method, hydrofluoric acid method, etc. Existing ultra-pure coal preparation technologies still have some limitations. For example, the physical method has a low product yield and limited deep deashing efficiency; the chemical method has a high process cost and strong reagent corrosiveness. Traditional coal deashing methods often fail to meet the deep deashing standard required for ultra-pure coal. Therefore, it is of great significance to develop new and efficient deashing technologies.

[0004] Chemical deashing to prepare ultra-pure coal is one of the common ultra-pure coal preparation technologies. Using chemical agents for coal deashing has the advantages of high product quality and good deashing effect. The obtained ultra-pure coal products can be used as raw materials for high-value-added carbon materials, which is conducive to further promoting the efficient comprehensive utilization of coal. However, there is currently a lack of chemical deashing agents with strong pertinence, good effects and easy implementation, as well as related agent preparation methods. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides an alkaline agent for chemical deep deashing of ultra-pure coal, its preparation method and application.

[0006] To achieve the above object, the present invention is implemented according to the following technical scheme:

[0007] One technical solution of the present invention is an alkaline agent for chemical deep deashing of ultra-pure coal, which is composed of a quaternary ammonium hydroxide solution, a strong base solution, an NH3·H2O solution, and a sodium fluoride solution with a volume ratio of (2-3):(1-2):(1-2):(2-3).

[0008] Further, the quaternary ammonium hydroxide is tetramethylammonium hydroxide (CH3)4NOH.

[0009] Further, the concentration of the tetramethylammonium hydroxide (CH3)4NOH solution is 3-5 mol / L, the concentration of the strong base solution is 6-9 mol / L, the concentration of the NH3·H2O solution is 7-10 mol / L, and the concentration of the sodium fluoride solution is 3-5 mol / L.

[0010] Further, the strong base solution is a NaOH solution or a KOH solution.

[0011] The second technical solution of the present invention is a preparation method of an alkaline agent for chemical deep deashing of ultra-pure coal, including the following steps:

[0012] S1. First, prepare tetramethylammonium hydroxide (CH3)4NOH;

[0013] S1-1. Dissolve 3-5 mol of tetramethylammonium chloride in 1 L of methanol solution to obtain a methanol solution of tetramethylammonium chloride with a concentration of 3-5 mol / L;

[0014] S1-2. Add 1 L of KOH solution or NaOH solution with a concentration of 3-5 mol / L to the methanol solution of tetramethylammonium chloride, continuously stir during the process, and let it stand for 10-15 min after full reaction to generate tetramethylammonium hydroxide and potassium chloride precipitate;

[0015] S1-3. Filter and separate the precipitate from the reactant obtained in step S1-2 to obtain a tetramethylammonium hydroxide solution with a concentration of 3-5 mol / L;

[0016] S2. Slowly add the (CH3)4NOH solution, strong base solution, NH3·H2O solution, and sodium fluoride solution with a volume ratio of (2-3):(1-2):(1-2):(2-3) into a beaker one by one, stir for 10-15 min, mix evenly, and then obtain the alkaline agent for chemical deep deashing of ultra-pure coal after cooling.

[0017] The third technical solution of the present invention is the application of an alkaline agent for chemical deep deashing of ultra-pure coal in chemical deep deashing of ultra-pure coal.

[0018] Compared with the prior art, the present invention has strong alkalinity and complexing ability. After using this compound agent for deep deashing, clean coal with an ash content of 2% ± 0.2% can be prepared into ultra-pure coal with an ash content of less than 0.2%; the preparation method of the alkaline compound agent of the present invention is simple, easy to operate, and the obtained product has high quality. The ash content of the prepared ultra-pure coal is less than 0.2%, realizing deep deashing of coal, which is beneficial to the further comprehensive utilization of coal. Description of the Drawings

[0019] Figure 1 It is a flow chart for preparing ultra-pure coal by chemical method. Detailed Embodiments

[0020] To make the purpose, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with embodiments. The specific embodiments described here are only used to explain the present invention and are not used to limit the invention.

[0021] The raw materials and reagents used in the following embodiments are all commercially available unless otherwise specified; among them:

[0022] Preparation of NaOH solution: Calculate and weigh a certain mass of NaOH and a certain volume of deionized water according to the required concentration. Slowly add NaOH to the beaker containing deionized water, and continuously stir with a glass rod during the process. After complete dissolution and cooling, transfer it to a volumetric flask. Rinse the glass rod and the beaker 2 - 3 times with deionized water, transfer the rinsing solution to the volumetric flask and make up the volume. The concentration of the prepared NaOH solution is 6 - 9 mol / L;

[0023] Preparation of KOH solution: Calculate and weigh a certain mass of KOH and a certain volume of deionized water according to the required concentration. Slowly add KOH to the beaker containing deionized water, and continuously stir with a glass rod during the process. After complete dissolution and cooling, transfer it to a volumetric flask. Rinse the glass rod and the beaker 2 - 3 times with deionized water, transfer the rinsing solution to the volumetric flask and make up the volume. The concentration of the prepared KOH solution is 6 - 9 mol / L;

[0024] Preparation of NH₃·H₂O: Calculate the amount of concentrated NH₃·H₂O required according to the required concentration and volume. Weigh a certain volume of concentrated NH₃·H₂O and deionized water. Slowly pour the concentrated NH₃·H₂O into the beaker containing deionized water, stirring while pouring, and continuously stir with a glass rod during the process. After complete dissolution and cooling, transfer it to a volumetric flask. Rinse the glass rod and the beaker 2 - 3 times with deionized water, transfer the rinsing solution to the volumetric flask and make up the volume. The concentration of the prepared NH₃·H₂O solution is 7 - 10 mol / L;

[0025] Preparation of sodium fluoride solution: Calculate the amount of sodium fluoride required according to the required concentration and volume. Weigh a certain mass of sodium fluoride and deionized water. Put the sodium fluoride solid into the beaker, add deionized water and stir continuously. After complete dissolution, transfer it to a volumetric flask. Rinse the glass rod and the beaker 2 - 3 times with deionized water, transfer the rinsing solution to the volumetric flask and make up the volume. The concentration of the prepared sodium fluoride solution is 3 - 5 mol / L;

[0026] Preparation of tetramethylammonium hydroxide (CH₃)₄NOH:

[0027] Dissolve 3 - 5 mol of tetramethylammonium chloride in 1 L of methanol solution to obtain a methanol solution of tetramethylammonium chloride with a concentration of 3 - 5 mol / L; Add 1 L of KOH solution or NaOH solution with a concentration of 3 - 5 mol / L to the methanol solution of tetramethylammonium chloride, and continuously stir during the process. After sufficient reaction, let it stand for 10 - 15 min to form tetramethylammonium hydroxide and potassium chloride precipitate; Separate the precipitate from the obtained reactant by filtration to obtain a tetramethylammonium hydroxide solution with a concentration of 3 - 5 mol / L.

[0028] Example 1

[0029] Add the (CH3)4NOH solution with a concentration of 3 mol / L, KOH solution with a concentration of 6 mol / L, NH3·H2O solution with a concentration of 7 mol / L, and sodium fluoride solution with a concentration of 3 mol / L in a volume ratio of 2:1:1:2 to the beaker one by one slowly, stir for 10 - 15 min, mix evenly, and obtain the alkaline agent sample 1 after cooling.

[0030] Example 2

[0031] Add the (CH3)4NOH solution with a concentration of 5 mol / L, NaOH solution with a concentration of 9 mol / L, NH3·H2O solution with a concentration of 10 mol / L, and sodium fluoride solution with a concentration of 5 mol / L in a volume ratio of 3:2:2:3 to the beaker one by one slowly, stir for 10 - 15 min, mix evenly, and obtain the alkaline agent sample 2 after cooling.

[0032] Example 3

[0033] Add the (CH3)4NOH solution with a concentration of 4 mol / L, KOH solution with a concentration of 8 mol / L, NH3·H2O solution with a concentration of 9 mol / L, and sodium fluoride solution with a concentration of 4 mol / L in a volume ratio of 2:2:2:2 to the beaker one by one slowly, stir for 10 - 15 min, mix evenly, and obtain the alkaline agent sample 3 after cooling.

[0034] Example 4

[0035] Add the (CH3)4NOH solution with a concentration of 4 mol / L, NaOH solution with a concentration of 7 mol / L, NH3·H2O solution with a concentration of 8 mol / L, and sodium fluoride solution with a concentration of 3 mol / L in a volume ratio of 3:1:1:3 to the beaker one by one slowly, stir for 10 - 15 min, mix evenly, and obtain the alkaline agent sample 4 after cooling.

[0036] Example 5

[0037] Add the (CH3)4NOH solution with a concentration of 5 mol / L, KOH solution with a concentration of 7 mol / L, NH3·H2O solution with a concentration of 10 mol / L, and sodium fluoride solution with a concentration of 4 mol / L in a volume ratio of 2.5:1.5:1.5:2.5 to the beaker one by one slowly, stir for 10 - 15 min, mix evenly, and obtain the alkaline agent sample 5 after cooling.

[0038] Comparative Example 1

[0039] Weigh a KOH solution with a concentration of 6 mol / L and a NaOH solution with a concentration of 6 mol / L in a volume ratio of 1:1. Slowly add the KOH solution to the beaker containing the NaOH solution, and continuously stir with a glass rod during the process. After full dissolution and cooling, transfer it to a volumetric flask. Rinse the glass rod and the beaker 2 - 3 times with deionized water, transfer the rinsing solution to the volumetric flask and make up the volume to obtain the alkaline agent sample 6.

[0040] Comparative Example 2

[0041] The difference from Comparative Example 1 is that NH₃·H₂O solution is used instead of the KOH solution to obtain the alkaline agent sample 7.

[0042] Comparative Example 3

[0043] The difference from Comparative Example 1 is that NH₃·H₂O solution is used instead of the NaOH solution to obtain the alkaline agent sample 8.

[0044] To verify the deep deashing effect of the above alkaline agent samples 1 - 8, use alkaline agent samples 1 - 8 for ultra - clean coal deashing respectively. The specific steps are as follows:

[0045] (1) Prepare experimental instruments and reagents

[0046] Instruments: ball mill, electro - thermal magnetic stirrer, blast drying oven, muffle furnace, analytical balance;

[0047] Reagents: alkaline agent samples 1 - 8, and acidic reagent (taking HNO₃ as an example for specific implementation).

[0048] (2) Prepare coal samples

[0049] Prepare clean coal with an ash content of 2% ± 0.2%, and pass it through a 200 - mesh sieve after grinding.

[0050] (3) Prepare ultra - clean coal

[0051] A. Alkaline washing

[0052] Take 10 g of clean coal, add 60 g of one of the alkaline agent samples 1 - 8 to the clean coal, stir well and then place it in a reaction kettle for high - temperature and high - pressure heating. The heating and stirring temperature under this condition is not lower than 150 °C, and the heating and stirring time is not less than 1 hour; add a certain proportion of water to the obtained alkali - washed coal, and the ratio of alkali - washed coal to water is 10 ± 1:1. Stir well and then place it in a centrifuge for centrifugation. After centrifugation, pour off the supernatant, centrifuge 2 - 3 times until the supernatant is clear, filter by suction, dry, and detect the ash content.

[0053] B. Acid washing

[0054] Take 10 g of alkali-washed coal after drying, add 80 g of the above HNO3 solution for acid leaching, stir well and then carry out acid leaching. Under this condition, the heating and stirring temperature is not lower than 75 °C, and the heating and stirring time is not less than 1 hour; the acid-washed coal obtained is centrifuged 1-2 times again, filtered, washed, dried, and the ash content is detected. The specific flow chart is as shown in Figure 1 shown.

[0055] The specific chemicals used and the ash removal effect are shown in Table 1 below.

[0056] Table 1 Ash removal effect of different alkaline chemicals

[0057]

[0058]

[0059] It can be seen from Table 1 that the chemical deep ash removal effect of the chemical agent prepared from the alkaline chemical is the best, and the ash content after alkali treatment is 1.6 ± 0.1%; after further treatment with the acidic chemical, the ash content after acid treatment is 0.19 ± 0.05%. After acid-base ash removal by the above processing method, clean coal with an ash content of 2 ± 0.2% can be prepared into ultra-clean coal with an ash content < 0.2%.

[0060] The ash removal principle of the present invention is as follows: During the chemical ash removal process, some silicon- and aluminum-containing minerals in coal, such as silicate minerals, can be removed during the alkali leaching process. The main mechanism is that OH in the alkali solution - reacts with acidic oxides in silicate through acid-base reaction and ions in the alkali solution exchange with ions on the mineral surface; the alkaline chemical of the present invention can have an electrostatic attraction effect with some negatively charged mineral particles in coal, and then form a complex. This complexation helps the agglomeration and precipitation of minerals, facilitating their separation from coal, so that the minerals can be removed from coal.

[0061] The technical solution of the present invention is not limited to the limitations of the above specific embodiments. Any technical deformation made according to the technical solution of the present invention falls within the protection scope of the present invention.

Claims

1. An alkaline reagent for chemical deep deashing of ultra-pure coal, characterized in that, It is composed of a quaternary ammonium hydroxide solution, a strong base solution, an NH₃·H₂O solution, and a sodium fluoride solution with a volume ratio of (2~3):(1~2):(1~2):(2~3).

2. The alkaline agent for chemical deep deashing of ultra-pure coal according to claim 1, wherein: The quaternary ammonium hydroxide is tetramethylammonium hydroxide (CH₃)₄NOH.

3. The alkaline agent for chemical deep deashing of ultra-pure coal according to claim 2, characterized in that: The concentration of the tetramethylammonium hydroxide (CH₃)₄NOH solution is 3 - 5 mol / L, the concentration of the strong base solution is 6 - 9 mol / L, the concentration of the NH₃·H₂O solution is 7 - 10 mol / L, and the concentration of the sodium fluoride solution is 3 - 5 mol / L.

4. The alkaline agent for chemical deep deashing of ultra-pure coal according to claim 1, characterized in that: The strong base solution is a NaOH solution or a KOH solution.

5. A preparation method of an alkaline agent for chemical deep deashing of ultra-pure coal as described in any one of claims 1-4, characterized in that, It includes the following steps: S1. First, prepare tetramethylammonium hydroxide (CH₃)₄NOH; S1-1. Dissolve 3 - 5 mol of tetramethylammonium chloride in 1 L of methanol solution to obtain a methanol solution of tetramethylammonium chloride with a concentration of 3 - 5 mol / L; S1-2. Add 1 L of a KOH solution or a NaOH solution with a concentration of 3 - 5 mol / L to the methanol solution of tetramethylammonium chloride, continuously stir during the process, let it react fully and then stand for 10 - 15 min to generate tetramethylammonium hydroxide and potassium chloride precipitate; S1-3. Filter and separate the precipitate from the reactant obtained in step S1-2 to obtain a tetramethylammonium hydroxide solution with a concentration of 3 - 5 mol / L; S2. Slowly add the (CH₃)₄NOH solution, the strong base solution, the NH₃·H₂O solution, and the sodium fluoride solution with a volume ratio of (2~3):(1~2):(1~2):(2~3) into a beaker one by one, stir for 10 - 15 min, mix evenly, and after cooling, obtain the alkaline agent for ultra-pure coal chemical deep deashing.

6. Application of the alkaline agent for ultra-pure coal chemical deep deashing according to any one of claims 1 - 4 in ultra-pure coal chemical deep deashing.

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