Solvent for preparing chemical ultra-pure coal from long flame coal and preparation method and application thereof

Abstract

This invention relates to the field of coal chemical technology, and discloses a solvent for preparing chemically ultrapure coal from long-flame coal, its preparation method, and its application. The solvent comprises the following components in parts by weight: 100-200 parts deionized water, 40-60 parts dilute nitric acid with a concentration of 10-20 wt%, 15-25 parts sodium dodecyl sulfate, and 5-15 parts ferric nitrate. The preparation method is as follows: Weighing: Weigh deionized water, dilute nitric acid, sodium dodecyl sulfate, and ferric nitrate according to the proportions; Mixing: Mix the weighed components evenly to form a mixed solution; Dissolving: Stir the mixed solution at 50-70°C until completely dissolved; Filtration: Filter the dissolved solution to obtain the final solvent. The solvent of this invention can effectively remove minerals and organic impurities from long-flame coal during chemical treatment, improving the purity of the coal, and is suitable for large-scale industrial production. This invention not only improves the purity of coal but also reduces production costs, simplifies the operation process, and reduces environmental pollution, providing a new solution for the high-purity preparation of long-flame coal.

Description

Technical Field

[0001] This invention relates to the field of coal chemical technology, and in particular to solvents for preparing chemically ultrapure coal from long-flame coal, their preparation methods, and applications. Background Technology

[0002] Long-flame coal is a common coal resource, widely used in power, chemical, and metallurgical industries due to its excellent combustion performance. Its main characteristics include high volatile matter, low ash content, medium calorific value, and ease of crushing and processing. These properties make long-flame coal easy to ignite, burn quickly, have a high calorific value, and be convenient to transport and use. However, long-flame coal contains a relatively high amount of minerals (such as silicates and carbonates) and organic impurities (such as resins and bitumen). These impurities not only affect the combustion efficiency of the coal but also generate large amounts of smoke and harmful gases during combustion, causing serious environmental pollution. Furthermore, these impurities can also affect the performance of coal in certain specific applications, such as coking and activated carbon production.

[0003] Traditional methods for purifying long-flame coal mainly include physical and chemical methods. Physical methods, such as screening, gravity separation, and flotation, can remove some large particles of impurities, but their effectiveness in removing fine mineral and organic impurities is limited. Screening removes large particles of impurities through screens, but it is not effective in removing fine impurities; gravity separation uses density differences for separation by gravity, but its effectiveness is limited for impurities with similar densities; flotation removes impurities through bubble flotation, but it requires complex equipment, consumes a lot of energy, and has high processing costs.

[0004] Chemical methods such as acid washing, alkali washing, and solvent extraction, while more effective at removing impurities from coal, also present some problems. Acid washing uses acidic solutions (such as sulfuric acid and hydrochloric acid) to remove mineral impurities, but it generates a large amount of waste liquid, which can pollute the environment if not properly treated. Alkali washing uses alkaline solutions (such as sodium hydroxide) to remove organic impurities, which also generates a large amount of waste liquid and is complex to operate. Solvent extraction uses organic solvents (such as alcohols and ketones) to remove organic impurities, but the solvents are expensive and require complex separation and recovery processes.

[0005] In addition, existing technologies have the following problems: First, the purification efficiency is low; many chemical solvents can only remove some organic impurities but cannot effectively remove mineral impurities. Second, environmental problems are prominent; many chemical solvents are highly corrosive and toxic, and the waste liquid after treatment is difficult to dispose of, easily causing environmental pollution. Third, the economic efficiency is poor; existing chemical purification methods are costly and not conducive to large-scale industrial application. Fourth, the operation is complex; the chemical purification process requires strict control of reaction conditions, making the operation relatively complex and not easy to scale up for industrial production. Finally, the equipment requirements are high; existing chemical purification methods usually require complex equipment and high energy consumption, increasing equipment investment and operating costs.

[0006] Therefore, there is an urgent need for solvents, preparation methods, and applications for the preparation of chemically ultrapure coal from long-flame coal to solve the aforementioned technical problems. Summary of the Invention

[0007] The purpose of this invention is to overcome the above-mentioned technical problems and provide a solvent for preparing chemically ultrapure coal from long-flame coal, as well as its preparation method and application.

[0008] To achieve the above objectives, the present invention is implemented according to the following technical solution: The solvent used for preparing chemically ultrapure coal from long-flame coal comprises the following components in parts by weight: 100-200 parts deionized water, 40-60 parts dilute nitric acid with a concentration of 10-20 wt%, 15-25 parts sodium dodecyl sulfate, and 5-15 parts ferric nitrate.

[0009] In this invention, dilute nitric acid is the main solvent, sodium dodecyl sulfate (SDS) is the auxiliary solvent, and ferric nitrate is the catalyst. Sodium dodecyl sulfate and dilute nitric acid synergistically form solubilizing micelles, and ferric nitrate plays a catalytic role in the solubilizing micelle environment. The three work together to simultaneously and deeply remove organic and mineral impurities from long-flame coal without introducing interfering impurities such as chloride ions.

[0010] This invention also includes a method for preparing a solvent for preparing chemically ultrapure coal from long-flame coal, comprising the following steps: a1 Weighing: Weigh out deionized water, dilute nitric acid, sodium dodecyl sulfate, and ferric nitrate according to the proportions; a2 mixing: Mix the weighed components thoroughly to form a mixed solution; A3 Dissolution: Stir the mixed solution at 50-70℃ until completely dissolved; A4 filtration: Filter the dissolved solution to obtain the final solvent.

[0011] During the dissolution process, moderate heating can significantly improve the solubility of surfactants and the uniformity of the system; the filtration process can remove insoluble impurities, and the filtration accuracy is controlled within 5-15μm.

[0012] The present invention also includes the application of the solvent described above or the solvent prepared by the above preparation method in the preparation of chemically ultrapure coal from long-flame coal.

[0013] The application process includes the following steps: S1 Pretreatment: The long-flame coal is crushed and screened to obtain pretreated long-flame coal; S2 immersion: The pretreated long-flame coal is immersed in a solvent to obtain the immersion product; S3 Separation: The product after soaking is separated into solid and liquid components to obtain soaked coal and waste liquid; the waste liquid is then centrally neutralized. S4 Washing: Washing the soaked coal with water; S5 Drying: The washed coal is dried to obtain chemically ultrapure coal.

[0014] Preferably, in step S1, the particle size of the pretreated long-flame coal is 0.5-2 mm.

[0015] Preferably, in step S2, the mass ratio of solvent to pretreated long-flame coal is 3:1; the soaking time is 12 hours; and stirring is performed during the soaking process at a speed of 200 rpm.

[0016] The soaking time can be adjusted according to the impurity content of the coal. Stirring during soaking ensures that the coal and solvent are in full contact.

[0017] Preferably, in step S3, a centrifuge is used for separation, with a centrifuge speed of 4000 rpm and a separation time of 10 minutes.

[0018] Preferably, in step S4, water is used to rinse multiple times, with each rinse lasting 5 minutes, until the washing water is clear.

[0019] Specifically, the rinsing should be performed 3 times.

[0020] Preferably, in step S5, the drying temperature is 100°C and the drying time is 4 hours.

[0021] The resulting chemically pure coal has a moisture content of less than 5%.

[0022] Mechanism of action: This invention effectively removes minerals and organic impurities from long-flame coal by optimizing the composition and usage of the solvent, thereby improving the purity of the coal.

[0023] This invention uses dilute nitric acid as the main solvent, sodium dodecyl sulfate as the auxiliary solvent, and ferric nitrate as the catalyst. This combination can significantly improve the solvent's solubility and purification efficiency, while also being low-cost, safe and easy to operate, and environmentally friendly.

[0024] Dilute nitric acid, as a strong oxidizing inorganic acid, possesses extremely strong dissolving and oxidizing properties, effectively dissolving organic impurities in long-flame coal, such as resins and bitumen. These organic impurities easily produce smoke and harmful gases during combustion; the dissolving effect of nitric acid can significantly reduce the content of these impurities. Furthermore, dilute nitric acid can react chemically with certain minerals to form soluble salts, thereby effectively removing mineral impurities. For example, dilute nitric acid can react with metal ions such as calcium and magnesium to generate soluble nitrates, facilitating subsequent separation and washing.

[0025] Sodium dodecyl sulfate (SLS) was chosen as the auxiliary solvent. This anionic surfactant significantly reduces the surface tension of water, enhancing the wettability and penetration of the solvent onto the coal surface. This helps the solvent penetrate more effectively into the micropores and fissures of the coal, improving the dissolution and removal of impurities. It also disperses fine particles and impurities in the coal, preventing them from re-aggregating, thus improving separation and washing efficiency. This is particularly important for removing fine mineral and organic impurities. Furthermore, SLS exhibits a good synergistic effect with the main solvent, increasing its solubility by forming micellar structures, thus helping to dissolve more organic and inorganic impurities. This synergistic effect significantly improves the solvent's purification effect.

[0026] Ferric nitrate was chosen as the catalyst. This strong acid catalyst significantly promotes chemical reactions under acidic conditions without introducing chloride ions that contaminate ultrapure coal. In the purification process of long-flame coal, ferric nitrate accelerates the reaction between the main solvents, such as dilute nitric acid, and minerals and organic impurities in the coal, improving the reaction rate and efficiency. The iron ions in ferric nitrate exhibit excellent catalytic activity, promoting the dissolution and chelation reactions of certain metal ions, thus aiding in the removal of metallic impurities from the coal. By optimizing the solvent composition and usage, this solvent effectively removes minerals and organic impurities from long-flame coal, significantly improving the coal's purity.

[0027] The solvent of this invention exhibits an inseparable synergistic effect among dilute nitric acid, sodium dodecyl sulfate, and ferric nitrate: Dilute nitric acid provides acidity and oxidizing properties, which are fundamental to the dissolution reaction. Sodium dodecyl sulfate forms micelles in dilute nitric acid solution; its hydrophobic core effectively encapsulates and solubilizes nonpolar organic macromolecules (such as resins and asphaltenes) in coal, greatly improving the "contact" and "dissolution" efficiency of nitric acid on these substances. This solubilizing effect cannot be achieved by using nitric acid alone or by using nitric acid with other non-surfactant auxiliaries. Ferric nitrate, in this acidic micelle system, has Fe... 3+Ions can efficiently catalyze the oxidative cracking of sulfur- and nitrogen-containing heterocyclic organic compounds by nitric acid and promote the complexation and dissolution of aluminosilicate minerals. The synergistic effect of these three components achieves simultaneous and deep removal of organic and inorganic impurities from long-flame coal, resulting in ultrapure coal with an ash content of less than 1%. The synergistic effect of this specific combination far exceeds the effects of any single component or any combination of two components.

[0028] Beneficial effects: The solvent of this invention can effectively remove minerals and organic impurities from long-flame coal during chemical processing, improving coal purity and making it suitable for large-scale industrial production. This invention not only improves the purity of long-flame coal but also reduces production costs, simplifies the operation process, and reduces environmental pollution, providing a new solution for the high-purity preparation of long-flame coal. Detailed Implementation

[0029] The present invention will be further described below with reference to specific embodiments. The illustrative embodiments and descriptions herein are used to explain the present invention, but are not intended to limit the present invention.

[0030] Example 1 A method for preparing a solvent for producing chemically ultrapure coal from long-flame coal includes the following steps: (1) Weighing: First, accurately weigh each component according to the predetermined ratio: 150 g of deionized water, 50 g of 15wt% dilute nitric acid, 20 g of sodium dodecyl sulfate, and 10 g of ferric nitrate; (2) Mixing: Place the weighed components into a suitable container and mix them evenly with a stirrer to form a mixed solution; the stirring time is about 10 minutes to ensure that the components are fully dispersed; (3) Dissolving: Place the mixed solution in a heating device and stir at 70°C for 30 minutes until all components are completely dissolved. During the dissolving process, pay attention to temperature control to avoid overheating that could lead to solvent decomposition or deterioration; (4) Filtration: The dissolved solution is filtered through a multi-stage filter to remove insoluble impurities and obtain the final solvent. The filtration precision of the filter is controlled at about 10 μm to ensure the purity of the solvent.

[0031] The method for purifying long-flame coal using the above-mentioned solvent includes the following steps: 1. Coal pretreatment: (1) Crushing: long-flame coal blocks are placed into a jaw crusher for crushing to reduce the particle size initially; (2) Screening: the crushed coal is screened through a vibrating screen to ensure uniform particle size, and the final particle diameter is controlled between 0.5-2mm.

[0032] 2. Soaking: (1) Preparation: Place the pretreated long-flame coal into a suitable reaction vessel, and then add the pre-prepared solvent. The mass ratio of solvent to coal is 3:1; (2) Soaking: Seal the reaction vessel and soak the coal in the solvent for 12 hours.

[0033] 3. Stirring: During the soaking process, use a mechanical stirrer to continuously stir the solution in the reaction vessel at a speed of 200 rpm.

[0034] 4. Separation: After soaking, the mixture in the reaction vessel is poured into a centrifuge for separation. The centrifuge speed is controlled at 4000 rpm, and the separation time is 10 minutes. After centrifugation, the coal and waste liquid are separated, yielding preliminarily purified coal.

[0035] 5. Washing: Place the preliminarily purified coal into a washing tank and rinse it multiple times with clean water. Each rinse should last 5 minutes, and the process should be repeated three times until the wash water is clear.

[0036] 6. Drying: Place the washed coal into a hot air dryer for drying. Control the drying temperature at 100℃ and the drying time at 4 hours to ensure that the moisture content of the coal is reduced to below 5%.

[0037] The long-flame coal processed in this embodiment has an ash content of 8.50%, a total sulfur content of 2.80%, and a volatile matter content of 38.5%.

[0038] Example 2 The preparation method of the solvent used to prepare chemically ultrapure coal from long-flame coal is the same as in Example 1, except for the weighing step (1). The components weighed are: 100 g of deionized water, 40 g of 10 wt% dilute nitric acid, 15 g of sodium dodecyl sulfate, and 5 g of ferric nitrate. The steps and process parameters for treating long-flame coal with this solvent are completely consistent with those in Example 1.

[0039] Example 3 The preparation method of the solvent used to prepare chemically ultrapure coal from long-flame coal is the same as in Example 1, except for the weighing step (1). The components weighed are: 200 g of deionized water, 60 g of 20 wt% dilute nitric acid, 25 g of sodium dodecyl sulfate, and 15 g of ferric nitrate. The steps and process parameters for treating long-flame coal with this solvent are completely consistent with those in Example 1.

[0040] Comparative Example 1 (Single Component Comparison: Contains only acid) The difference between this comparative example and Example 1 is that the only solvents used are: 150 g of deionized water and 50 g of 15 wt% dilute nitric acid.

[0041] The steps and process parameters for treating long-flame coal with this solvent are completely consistent with those in Example 1.

[0042] Comparative Example 2 (Binary Component Comparison: No Catalyst) The difference between this comparative example and Example 1 is that the solvent used consists of: 150 g of deionized water, 50 g of 15 wt% dilute nitric acid, and 20 g of sodium dodecyl sulfate.

[0043] The steps and process parameters for treating long-flame coal with this solvent are completely consistent with those in Example 1.

[0044] Comparative Example 3 (Binary Component Comparison: No Surfactant) The difference between this comparative example and Example 1 is that the solvent used consists of: 150 g of deionized water, 50 g of 15 wt% dilute nitric acid, and 10 g of ferric nitrate.

[0045] The steps and process parameters for treating long-flame coal with this solvent are completely consistent with those in Example 1.

[0046] Comparative Example 4 The solvent used consists of the following components: 80 g of deionized water, 30 g of 8 wt% dilute nitric acid, 10 g of sodium dodecyl sulfate, and 3 g of ferric nitrate.

[0047] The steps and process parameters for treating long-flame coal with this solvent are completely consistent with those in Example 1.

[0048] Comparative Example 5 The difference between this comparative example and Example 1 is that the solvent used consists of: 250 g of deionized water, 80 g of 25 wt% dilute nitric acid, 30 g of sodium dodecyl sulfate, and 20 g of ferric nitrate.

[0049] The steps and process parameters for treating long-flame coal with this solvent are completely consistent with those in Example 1.

[0050] Comparative Example 6 (Single Component Comparison: Contains Surfactant Only) The difference between this comparative example and Example 1 is that the solvent used consists of 150 g of deionized water and 20 g of sodium dodecyl sulfate. This system is used to verify the solubilizing and dispersing ability of surfactants on organic macromolecules under non-oxidizing conditions.

[0051] The steps and process parameters for treating long-flame coal with this solvent are completely consistent with those in Example 1.

[0052] Comparative Example 7 (Single Component Comparison: Catalyst Only) The difference between this comparative example and Example 1 is that the solvent used consists of 150 g of deionized water and 10 g of ferric nitrate. This system is used to verify the effectiveness of the catalyst acting alone in the absence of a strong acid environment and surfactant.

[0053] The steps and process parameters for treating long-flame coal with this solvent were completely consistent with those in Example 1, and the reaction could not be started.

[0054] Experimental Data and Effect Analysis The untreated raw long-flame coal (untreated raw coal), as well as the purified coal samples obtained after treatment in Examples 1-3 and Comparative Examples 1-5, were tested for various physicochemical properties. The test results are shown in the table below:

[0055] Data analysis and beneficial effects: 1. Verification of the effect of simultaneous deep removal: As shown in the table above, the original long-flame coal had an ash content as high as 8.50% and a total sulfur content of 2.80%. After treatment with the solvent of the present invention, the ash content of the ultrapure coal obtained in Examples 1 to 3 was consistently below 1.2%, the total sulfur content was reduced to below 0.52%, and the organic matter removal rate reached over 92%. This fully demonstrates that the solvent of the present invention can effectively remove minerals and organic impurities from long-flame coal during chemical treatment, significantly improving the purity of the coal.

[0056] 2. The irreplaceable nature of the ternary synergistic effect: When using only dilute nitric acid (Comparative Example 1), the ash content decreased to approximately 3.5%, but the removal of organic impurities was incomplete. After adding sodium dodecyl sulfate (Comparative Example 2), the ash content decreased to approximately 2.8%, and the removal of organic impurities improved somewhat, but the improvement in mineral removal was limited. After adding ferric nitrate (Comparative Example 3), the ash content decreased to approximately 2.5%, and the catalytic oxidation effect was evident, but coal particle agglomeration was severe, resulting in uneven reaction. Only when all three components coexisted (as in Examples 1 to 3) could the ash content be stably below 1.0%, with good coal dispersibility and a uniform and thorough reaction. This fully demonstrates that the ternary components are indispensable and together constitute a highly efficient purification system.

[0057] When nitric acid was used (Comparative Example 1), the ash content was reduced to 3.5%, mainly due to the acid dissolving carbonates and metal oxides. In Example 1, due to the catalytic effect of ferric nitrate and the penetration of SDS into the micropores, the ash content was reduced to below 1.0%, indicating that the three substances synergistically and significantly enhanced the ability to destroy sparingly soluble aluminosilicates.

[0058] Testing revealed that while Comparative Example 6 (SDS only) could remove some surface organic matter, its removal rate for resins and asphaltenes embedded in the coal matrix was only 60%. In Example 1, the strong oxidizing properties of nitric acid broke down large organic molecules into smaller molecules, which were then solubilized and encapsulated by SDS micelles, thus achieving the removal of organic matter.

[0059] This is an effect that cannot be achieved by simple pickling or simple surfactants.

[0060] Comparative Example 7 demonstrates that a single catalyst cannot initiate the reaction; Comparative Examples 1 and 6 demonstrate a significant "weakest link" effect with a single functional component. Only when nitric acid (providing H₂) is the reaction initiated can the reaction proceed. + And oxidizing properties), SDS (provides penetration and solubility), ferric nitrate (provides Fe) 3+ Only when catalytic oxidation, catalytic oxidation, and other processes coexist can the simultaneous and in-depth removal of organic and inorganic impurities from long-flame coal be achieved.

[0061] 3. Verification of boundary effects within the parameter range: When the formulation ratio exceeds the lower limit of the range defined in this invention (Comparative Example 4), the purification effect drops sharply due to insufficient acidity and surfactant concentration, which prevents the formation of an effective solubilizing micelle environment. When it exceeds the upper limit of the range (Comparative Example 5), although the purification effect is better than that of a single component, the reaction kinetics are limited due to excessive dilution of the system, resulting not only in failure to achieve the best effect but also in waste of raw materials. This further verifies the scientific validity and necessity of the specific parameter range of "100-200 parts of deionized water, 40-60 parts of 10-20 wt% dilute nitric acid, 15-25 parts of sodium dodecyl sulfate, and 5-15 parts of ferric nitrate".

[0062] In summary, this invention not only improves the purity of long-flame coal, reduces production costs, simplifies the operation process, and reduces environmental pollution, but also provides a new solution for the high-purity preparation of long-flame coal, which is suitable for large-scale industrial production.

[0063] The technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made in accordance with the technical solutions of the present invention fall within the protection scope of the present invention.

Claims

1. A solvent for preparing chemically ultrapure coal from long-flame coal, characterized in that, The components include the following parts by weight: 100-200 parts deionized water, 40-60 parts dilute nitric acid with a concentration of 10-20 wt%, 15-25 parts sodium dodecyl sulfate, and 5-15 parts ferric nitrate.

2. The method for preparing the solvent for preparing chemically ultrapure coal from long-flame coal according to claim 1, characterized in that: Includes the following steps: a1 Weighing: Weigh out deionized water, dilute nitric acid, sodium dodecyl sulfate, and ferric nitrate according to the proportions; a2 mixing: Mix the weighed components thoroughly to form a mixed solution; A3 Dissolution: Stir the mixed solution at 50-70℃ until completely dissolved; A4 filtration: Filter the dissolved solution to obtain the final solvent.

3. The application of the solvent described in claim 1 or the solvent prepared by the preparation method described in claim 2 in the preparation of chemically ultrapure coal from long-flame coal.

4. The application according to claim 3, characterized in that, Includes the following steps: S1 Pretreatment: The long-flame coal is crushed and screened to obtain pretreated long-flame coal; S2 immersion: The pretreated long-flame coal is immersed in a solvent to obtain the immersion product; S3 Separation: The product after soaking is separated into solid and liquid components to obtain soaked coal and waste liquid; the waste liquid is then centrally neutralized. S4 Washing: Washing the soaked coal with water; S5 Drying: The washed coal is dried to obtain chemically ultrapure coal.

5. The application according to claim 3, characterized in that: In step S1, the pretreated long-flame coal has a particle size of 0.5-2 mm.

6. The application according to claim 3, characterized in that: In step S2, the mass ratio of solvent to pretreated long-flame coal is 3:1; the soaking time is 12 hours; and stirring is carried out during the soaking process at a speed of 200 rpm.

7. The application according to claim 3, characterized in that: In step S3, a centrifuge is used for separation. The centrifuge speed is 4000 rpm and the separation time is 10 minutes.

8. The application according to claim 3, characterized in that: In step S4, water is used to rinse the water multiple times, with each rinse lasting 5 minutes, until the water runs clear.

9. The application according to claim 3, characterized in that: In step S5, the drying temperature is 100℃ and the drying time is 4 hours.

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