Method for alkali regeneration of coal ash removal alkali liquor and method for coal ash removal

Abstract

The present application relates to the field of coal descaling, and discloses a method for regenerating alkali from coal descaling alkali liquor and a method for coal descaling. The regeneration method comprises: mixing the coal descaling alkali liquor with a reagent, performing a first reaction, and optionally filtering to obtain a reaction liquid; heating the obtained reaction liquid to 250-350 DEG C, maintaining the temperature for 0.1-6 h, and optionally cooling, supplementing water and filtering to obtain regenerated alkali liquor. Alternatively, the coal descaling alkali liquor is heated to 250-350 DEG C, maintained for 0.1-6 h, cooled and supplemented with water, and optionally filtered to obtain a treatment liquid; a reagent is added to the treatment liquid, a second reaction is performed, and optionally filtered to obtain regenerated alkali liquor. Alternatively, a reagent is added to the coal descaling alkali liquor, heated to 250-350 DEG C, maintained for 0.1-6 h, a third reaction is performed, cooled and supplemented with water, a fourth reaction is performed, and optionally filtered to obtain regenerated alkali liquor. The present application realizes regeneration of alkali from coal descaling alkali liquor, reduces the consumption of alkali, and improves the economic efficiency of coal descaling.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of coal descaling, in particular to a method for regenerating alkali of coal descaling alkali liquor and a method for coal descaling. BACKGROUND

[0002] Carbon materials are usually made from high-quality petroleum coke with low ash and impurities. With the increase of imported low-quality petroleum in China and the improvement of petroleum refining technology, the petroleum coke used for carbon materials is increasingly scarce. At present, only a small amount of low-ash anthracite is used to replace petroleum coke to prepare carbon materials. However, the low-ash anthracite resources in China are also very limited, and the ash content is still higher than the requirement of carbon materials for raw materials. If the ash content and volatile matter of coal are reduced to prepare corresponding low-ash and high-carbon materials, the indicators of which are close to or better than those of petroleum coke, it is possible to realize large-scale replacement of petroleum coke and find an effective way for high-value utilization of coal. Therefore, the key to preparing high-quality carbon materials from coal instead of petroleum coke is descaling.

[0003] Traditional coal descaling mainly includes jigging, dense medium separation and flotation. The descaling efficiency is relatively low, and the ash content can only reach about 10-30%, which cannot be used as carbon materials, and only a small amount can be used as high-ash carbon materials, such as electrode paste and high-ash carbon blocks. Based on traditional coal descaling, refined descaling can be divided into two categories: physical method and chemical method. Physical method refined descaling generally needs to use superfine grinding technology to dissociate the secondary mineral particles in coal after crushing. Then, the coal particles are captured by non-polar oil to separate from the minerals. Or improved flotation column is also helpful to obtain low-ash coal. The particles of coal and minerals can also be sorted and descaled according to their different electrical properties. According to different situations, the descaling efficiency of physical method refined descaling is relatively high, and the ash content is about 3-10%. Physical method refined descaling can replace petroleum coke and wood raw materials to prepare high-ash and low-quality activated carbon. Chemical method refined descaling uses chemical reagents to react with minerals in coal, which can not only efficiently remove secondary minerals in coal, but also remove primary minerals formed by all inorganic elements in plants during coal formation. Chemical method is mainly divided into four types: hydrofluoric acid method, conventional acid-base method, molten alkali leaching method and chemical coal method. The conventional acid-base method uses alkali to react with mineral ash in coal to generate acid-soluble products, which then react with acid to enter the liquid phase, and are separated from organic matter by filtration, washing and other processes. The conventional acid-base chemical descaling has comprehensive advantages in descaling efficiency, economy and environmental benefits. The descaling by conventional chemical method can obtain coal with ash content less than 1% or even lower, which can replace petroleum coke to prepare carbon anode and other carbon materials, such as supercapacitor electrode, high-quality activated carbon, and advanced carbon materials such as graphene.

[0004] In the conventional acid-base method of ash removal, sodium hydroxide solution needs to react with coal and contained minerals. In this process, on the one hand, the silicon-aluminum minerals in the coal are dissolved in the alkali solution after the reaction with the alkali solution, mainly in the form of sodium silicate and sodium aluminate, causing alkali loss, on the other hand, a certain amount of alkali-soluble organic matter and sulfide can also be generated during the alkali treatment of coal, which also causes alkali loss. Alkali is the most important reagent consumption in the conventional ash removal of coal, and is the main cost component of coal ash removal. However, the silicon-aluminum minerals dissolved in the alkali solution and the generated alkali-soluble organic matter and sulfide consume the alkali solution and reduce the effective alkali content, which will lead to the accumulation of the alkali solution for treating coal and reduce the economy of coal ash removal. Therefore, the regeneration and reuse of the alkali solution is the key technology for the chemical ash removal of coal and the preparation of coal-based carbon materials. At present, for the regeneration of the alkali solution for coal ash removal, the alkali loss caused by the dissolution of silicon-aluminum mineral components in the alkali solution can be regenerated and reused, but there is no effective method for the regeneration of the alkali loss caused by the alkali-soluble organic matter and sulfide. SUMMARY

[0005] The purpose of the present application is to overcome the problem of ineffective regeneration of the alkali solution for chemical ash removal of coal in the prior art. The alkali-soluble organic matter is derived from the reaction of coal with alkali, and has a complex structure, most of which belongs to humic acid substances. The alkali-soluble sulfide is generated by the reaction of sulfur-containing minerals in coal with alkali, such as sodium persulfate. According to research, physical and chemical methods such as solvent extraction and hydrogen peroxide oxidation cannot effectively remove the alkali-soluble organic matter and sulfide while avoiding the introduction of impurities, which poses a great challenge to the regeneration and reuse of the alkali solution. In order to effectively regenerate the alkali loss caused by the alkali-soluble organic matter and sulfide, the inventors of the present application have conducted a lot of research. After years of research, the inventors accidentally found that the reactivity of the alkali solution is enhanced at high temperature, which can destroy the solubility of the organic matter and sulfide in the alkali solution. On the basis of this discovery, the inventors of the present application further put forward a method for regenerating alkali in the alkali solution for coal ash removal, and a method for coal ash removal.

[0006] The first aspect of the present application provides a method for regenerating alkali in the alkali solution for coal ash removal, the regeneration method comprising: mixing the alkali solution for coal ash removal with a reagent to perform a first reaction, and optionally filtering to obtain a reaction liquid;

[0007] The obtained reaction liquid is heated to 250-350℃, and held for 0.1-6h, and optionally cooled, watered and filtered to obtain a regenerated alkali solution.

[0008] The second aspect of the present application provides a method for regenerating alkali in the alkali solution for coal ash removal, the regeneration method comprising: heating the alkali solution for coal ash removal to 250-350℃, holding for 0.1-6h, cooling and watering, and optionally filtering to obtain a treatment liquid;

[0009] The medicament is added into the treatment liquid, a second reaction is carried out, and the regenerated lye is obtained through optional filtration.

[0010] The third aspect of the present application provides a method for regenerating lye for removing ash from coal, the method comprising the following steps:

[0011] The fourth reaction is carried out after cooling and water replenishment, and the regenerated lye is obtained through optional filtration.

[0012] The fourth aspect of the present application provides a method for removing ash from coal, the method comprising:

[0013] (1) crushing coal to less than 3 mm, adding lye to remove ash by alkali method, and obtaining lye for removing ash and coal after alkali ash removal through solid-liquid separation;

[0014] (2) removing ash from the coal after alkali ash removal by acid method to obtain acid ash removal liquid and ash-removed coal;

[0015] (3) regenerating the lye for removing ash according to the regeneration method provided in the preceding aspects of the present application to obtain regenerated lye;

[0016] (4) using the regenerated lye obtained to remove ash by alkali method in step (1).

[0017] Through the above technical solution, the present application can destroy the solubility of organic matter and sulfide in lye by heating, remove the organic matter and sulfide in lye while removing the dissolved silicate and aluminate in lye, regenerate lye for removing ash from coal, reduce lye consumption, and improve the economy of removing ash from coal. DETAILED DESCRIPTION

[0018] The endpoints of the ranges and any values disclosed in this document are not limited to the precise values recited as the exact dimensions are not critical to the present application. The endpoints of the ranges and any numerical values should be interpreted as approximately including values near the reported values. These ranges and values are approximate values that can depend on several factors, and one of ordinary skill in the art can readily determine the optimal value or range without undue experimentation.

[0019] The first aspect of the present application provides a method for regenerating lye for removing ash from coal, the method comprising the following steps:

[0020] S1, mixing lye for removing ash from coal with a medicament, carrying out a first reaction, and obtaining a reaction liquid through optional filtration;

[0021] S2, heating the reaction solution obtained in step S1 to 250-350℃, and keeping the temperature for 0.1-6h, and then cooling, adding water and filtering to obtain regenerated lye, and realizing the regeneration of the lye for coal desulfurization.

[0022] In step S1 of the present application, the first reaction is carried out at a temperature of 5-99℃ for 0.1-6h; preferably, the first reaction is carried out at a temperature of 20-95℃ for 0.1-3h.

[0023] In step S2 of the present application, the reaction solution obtained in step S1 is heated to 250-350℃, and kept at the temperature for 0.1-6h. At a lower temperature, a longer treatment time is usually required, and the treatment time can be shortened at a higher temperature. For example, the treatment is carried out at 250℃ for 6h, and at 350℃ for 0.1h.

[0024] The alkali-soluble organic matter is derived from the reaction of coal and alkali, and has a complex structure, and is mostly humic acid substances. The alkali-soluble sulfide is generated by the reaction of sulfur-containing minerals and alkali, such as sodium persulfate. According to research, physical and chemical methods such as extraction with various solvents and hydrogen peroxide oxidation method cannot effectively remove the alkali-soluble organic matter and sulfide while avoiding the introduction of impurities, which poses a great challenge to the regeneration and reuse of lye. The inventors of the present application accidentally found that the reactivity of lye is enhanced at high temperature, which can destroy the solubility of organic matter and sulfide in lye. After heating treatment, the coal desulfurization lye can effectively remove the organic matter and sulfide after cooling and water addition and filtration, and regenerated lye is obtained.

[0025] In the present application, the coal desulfurization lye in step S1 refers to the alkaline desulfurization solution generated by chemical desulfurization of coal. The coal desulfurization lye mainly contains alkali-soluble silicon-aluminum mineral components, such as sodium silicate and sodium aluminate, and different amounts of alkali-soluble organic matter and sulfide related to the properties of coal.

[0026] According to the present application, the reagent in step S1 is selected from at least one of calcium agent and magnesium agent.

[0027] The calcium agent is a compound containing calcium element and a reagent prepared from a compound containing calcium element. In order to more efficiently recover and extract the alkali-soluble silicon-aluminum mineral components and recycle the alkali in the desulfurization lye, preferably, the calcium agent is selected from at least one of calcium oxide, calcium hydroxide and lime milk.

[0028] The magnesium agent is a compound containing magnesium element and a reagent prepared from a compound containing magnesium element. In order to more efficiently recover and extract the alkali-soluble silicon-aluminum mineral components and recycle the alkali in the desulfurization lye, preferably, the magnesium agent is selected from at least one of magnesium oxide, magnesium hydroxide and magnesium hydroxide emulsion.

[0029] In step S1 of the present application, the reagent added in the coal ash-removing alkali liquor can be a calcium reagent, a magnesium reagent, or a mixture of the calcium reagent and the magnesium reagent. The present application does not have specific limitations on the addition ratio of the calcium reagent and the magnesium reagent in the reagent, as long as the amount of the added reagent meets the requirement of ash removal of the alkali liquor.

[0030] According to the embodiments of the present application, the first reaction mainly refers to the caustic reaction of sodium silicate and sodium aluminate with the calcium reagent and / or the magnesium reagent. In this process, sodium ions are regenerated into sodium hydroxide.

[0031] In some embodiments, the coal ash-removing alkali liquor is mixed with the calcium reagent, the alkali lost in the ash dissolution in the alkali liquor is regenerated and reused through the first reaction, and an aluminum-calcium-silicon mixture precipitate can be generated after the addition of the calcium reagent. The aluminum-calcium-silicon mixture is a complex mixture containing aluminum, calcium, and silicon, such as calcium hydroxide, calcium aluminate compounds, calcium silicate compounds, and calcium aluminum garnet, etc. The amount of the calcium reagent can be calculated according to the stoichiometry of the desired reaction product. Preferably, based on the total amount of the aluminum-calcium-silicon mixture, the Al content calculated as aluminum oxide in the aluminum-calcium-silicon mixture is 10-70 wt%, the Ca content calculated as calcium oxide in the aluminum-calcium-silicon mixture is 30-80 wt%, and the Si content calculated as silicon dioxide in the aluminum-calcium-silicon mixture is 1-60 wt%.

[0032] In other embodiments, the coal ash-removing alkali liquor is mixed with the magnesium reagent, the alkali lost in the ash dissolution in the alkali liquor is regenerated and reused through the first reaction, and an aluminum-magnesium-silicon mixture precipitate can be generated after the addition of the magnesium reagent. The aluminum-magnesium-silicon mixture is a complex mixture containing aluminum, magnesium, and silicon, such as magnesium hydroxide, aluminum-magnesium mixture, magnesium silicate mixture, and magnesium aluminum garnet, etc. The amount of the magnesium reagent can be calculated according to the stoichiometry of the desired reaction product. Preferably, based on the total amount of the aluminum-magnesium-silicon mixture, the Al content calculated as aluminum oxide in the aluminum-magnesium-silicon mixture is 10-80 wt%, the Mg content calculated as magnesium oxide in the aluminum-magnesium-silicon mixture is 20-80 wt%, and the Si content calculated as silicon dioxide in the aluminum-magnesium-silicon mixture is 1-70 wt%.

[0033] In yet other embodiments, the coal ash-removing alkali liquor is mixed with a mixture of the calcium reagent and the magnesium reagent, preferably the ratio of the calcium reagent to the magnesium reagent is 50-80:20-50, such as 50:50, 60:40, 70:30, etc., the alkali lost in the dissolution of the silicon-aluminum mineral components in the alkali liquor is regenerated and reused through the first reaction, and an aluminum-calcium-silicon mixture and an aluminum-magnesium-silicon mixture precipitate can be generated after the addition of the mixture of the calcium reagent and the magnesium reagent. The amount of the mixture of the calcium reagent and the magnesium reagent is also calculated according to the stoichiometry of the desired reaction product. Since the calcium reagent and the magnesium reagent can be replaced in equimolar, that is, in order to simplify the calculation, the sum of the calcium reagent and the magnesium reagent can be regarded as a whole, for example, the magnesium reagent is converted into the calcium reagent, and then the use amount of the two is calculated by the calculation method of adding the calcium reagent alone, and then the use amount of the calcium reagent and the magnesium reagent is calculated respectively according to the ratio of the two.

[0034] In the present application, step S2 removes the alkali-soluble organic matter and sulfides in the lye by heating the reaction liquid obtained in step S1 to 250-350°C for a holding treatment, thereby reducing the loss of alkali caused by alkali-soluble organic matter and sulfides. After the ash-removing lye is subjected to the heating treatment, it is cooled and filtered after water is added, so that the alkali-soluble organic matter and sulfides can be removed, thereby better achieving the regeneration of the lye. This method is an unexpected discovery of the inventors in a large number of studies. The reactivity of the lye is enhanced at high temperatures, which can destroy the solubility of the organic matter and sulfides in the lye, thereby achieving efficient removal of the organic matter and sulfides and the regeneration of the alkali of the ash-removing lye for coal.

[0035] In the present application, the optional filtration in this step S1 means that the filtration step can be included or not included.

[0036] In some embodiments, the filtration step is included, i.e., step S1 is: mixing the ash-removing lye for coal with the reagent, performing a reaction, and filtering to obtain a reaction liquid. The reaction liquid of this embodiment does not contain precipitates.

[0037] In other embodiments, the filtration step is not included, i.e., step S1 is: mixing the ash-removing lye for coal with the reagent, performing a reaction, and not filtering to obtain a reaction liquid. The reaction liquid of this embodiment contains precipitates. Although both of the above two embodiments can achieve effective regeneration of the ash-removing lye, considering that step S2 will heat the ash-removing lye, and when heated to 250-350°C, the precipitates such as aluminum-calcium-silicon mixture and aluminum-magnesium-silicon mixture in the lye are easy to scab in the reactor, therefore, it is preferred to filter after the first reaction in step S1, to remove the generated precipitates, and then perform the heating treatment.

[0038] If step S1 does not perform the filtration, step S2 preferably performs the filtration to remove the precipitates such as aluminum-calcium-silicon mixture and aluminum-magnesium-silicon mixture, so as to avoid the increase of ash in the coal when the lye is reused.

[0039] Since the organic matter and sulfides in the lye are less than the coal, and have little effect on the performance of low-ash coal and coal-based carbon materials, if step S1 performs the filtration after the reaction, and step S2 does not add water and does not perform the filtration after the heating treatment, but retains the precipitates in the regenerated lye, the precipitates can be directly recycled for the alkali ash-removing of the coal.

[0040] The present application first removes the dissolved silicon-aluminum mineral components in the coal descaling alkali liquor, i.e. ash, by adding a medicament, which is called descaling, and then removes the organic matter and sulfide in the reaction solution by heating treatment, so that the silicon-aluminum removal rate of the regenerated alkali liquor is more than 80%, the organic matter removal rate is more than 80%, and the sulfide removal rate is more than 80% through the two-step method; preferably, the silicon-aluminum removal rate of the regenerated alkali liquor is more than 95%, the organic matter removal rate is more than 95%, and the sulfide removal rate is more than 95%.

[0041] In the present application, the silicon-aluminum removal rate refers to the removal rate of the dissolved silicon-aluminum mineral components in the coal descaling alkali liquor, also called the descaling rate or ash removal rate.

[0042] The present application provides a method for regenerating coal descaling alkali liquor, which comprises the following steps:

[0043] Step 1, heating the coal descaling alkali liquor to 250-350℃, keeping the temperature for 0.1-6h, cooling and adding water, and optionally filtering to obtain a treatment solution;

[0044] Step 2, adding a medicament to the treatment solution obtained in step 1 to perform a second reaction, and optionally filtering to obtain a regenerated alkali liquor, thereby realizing the regeneration of the coal descaling alkali liquor.

[0045] In step 1 of the present application, the coal descaling alkali liquor is heated to 250-350℃, and kept at the temperature for 0.1-6h to obtain a treatment solution. At a lower temperature, a longer treatment time is usually required, and the treatment time can be shortened as the temperature increases. For example, the treatment is performed at 250℃ for 6h, and at 350℃ for 0.1h.

[0046] The alkali-soluble organic matter is derived from the reaction of coal and alkali, and has a complex structure, which is mostly humic acid. The alkali-soluble sulfide is mainly generated by the reaction of sulfur-containing minerals in coal and alkali, such as sodium persulfate. According to research, physical and chemical methods such as solvent extraction and hydrogen peroxide oxidation method cannot effectively remove the alkali-soluble organic matter and sulfide without introducing impurities, which poses a great challenge to the regeneration and reuse of alkali liquor. The present inventors have found by accident that the reactivity of alkali liquor is enhanced at high temperature, which can destroy the solubility of organic matter and sulfide in alkali liquor. After heating treatment of alkali liquor, cooling and adding water and filtering, the organic matter and sulfide can be removed to obtain regenerated alkali liquor.

[0047] In the present application, the coal descaling alkali liquor of step 1 refers to the alkali descaling liquor produced by chemical descaling of coal. The coal descaling alkali liquor mainly contains alkali-soluble silicate and aluminate, and different amounts of alkali-soluble organic matter and sulfide associated with the properties of coal. According to the present application, the coal descaling alkali liquor of step 1 is heated and cooled with water added, and the precipitate can be removed by filtration to obtain a treatment liquor. Alternatively, the treatment liquor can be obtained without removing the precipitate by filtration.

[0048] According to the present application, the agent in step 2 is selected from at least one of calcium agent and magnesium agent.

[0049] The calcium agent is a compound containing calcium element and an agent prepared from a compound containing calcium element. In order to more efficiently recover and extract alkali-soluble silicate and aluminate, and to recover and reuse the alkali in the alkali liquor, preferably, the calcium agent is selected from at least one of calcium oxide, calcium hydroxide and lime milk.

[0050] The magnesium agent is a compound containing magnesium element and an agent prepared from a compound containing magnesium element. In order to more efficiently recover and extract aluminum, and to recover and reuse the alkali in the alkali liquor, preferably, the magnesium agent is selected from at least one of magnesium oxide, magnesium hydroxide and magnesium hydroxide emulsion.

[0051] In step 2 of the present application, the agent added to the treatment liquor obtained in step 1 can be a calcium agent, a magnesium agent, or a mixture of calcium agent and magnesium agent. The present application does not have specific limitations on the addition ratio of calcium agent and magnesium agent in the agent, as long as the amount of the added agent meets the requirements of alkali descaling. In some embodiments, the coal descaling alkali liquor is mixed with a calcium agent, and the alkali lost due to the dissolution of ash in the alkali liquor is regenerated and reused through a second reaction. After the addition of the calcium agent, an aluminum-calcium-silicon mixture precipitate can be formed. In other embodiments, the coal descaling alkali liquor is mixed with a magnesium agent, and the alkali lost due to the dissolution of ash in the alkali liquor is regenerated and reused through a causticization reaction. After the addition of the magnesium agent, an aluminum-magnesium-silicon mixture precipitate can be formed. In yet other embodiments, the coal descaling alkali liquor is mixed with a mixture of calcium agent and magnesium agent, and the ratio of calcium agent to magnesium agent is preferably 50-80:20-50, such as 50:50, 60:40, 70:30, etc. The alkali lost due to the dissolution of ash in the alkali liquor is regenerated and reused through a causticization reaction. After the addition of the mixture of calcium agent and magnesium agent, an aluminum-calcium-silicon mixture and an aluminum-magnesium-silicon mixture precipitate can be formed. The specific reaction is similar to that in step S1, which is not described here again. After the completion of the second reaction, filtration can be performed or not performed to obtain a regenerated alkali liquor. Preferably, filtration is performed to remove the aluminum-calcium-silicon mixture and the aluminum-magnesium-silicon mixture precipitates, so as to avoid the increase of ash in coal and the influence on the performance of low-ash coal and coal-based carbon materials when the alkali liquor is reused.

[0052] In step 2 of the present application, the second reaction has a temperature of 5-99℃ and a time of 0.1-6h; preferably, the second reaction has a temperature of 20-95℃ and a time of 0.1-3h.

[0053] In the present application, by heating the coal descaling alkali liquor to 250-350℃, the alkali-soluble organic matter and sulfide in the alkali liquor are removed, and the loss of alkali caused by the alkali-soluble organic matter and sulfide is reduced. This method is accidentally discovered by the inventor in a large number of studies. The reactivity of the alkali liquor is enhanced at high temperature, and the solubility of the organic matter and sulfide in the alkali liquor can be destroyed. After the descaling alkali liquor is treated by heating, it is cooled and filtered after water is added, so that the organic matter and sulfide can be removed, and the regeneration of the alkali liquor can be better achieved.

[0054] In the present application, the organic matter and sulfide in the coal descaling alkali liquor are first removed by heating treatment, and then the alkali-soluble silicon-aluminum mineral components in the coal descaling alkali liquor are removed by adding a reagent. Through the two-step method, the silicon-aluminum removal rate of the regenerated alkali liquor is more than 80%, the organic matter removal rate is more than 80%, and the sulfide removal rate is more than 80%, so that the effective regeneration of the descaling alkali liquor is achieved; preferably, the silicon-aluminum removal rate of the regenerated alkali liquor is more than 95%, the organic matter removal rate is more than 95%, and the sulfide removal rate is more than 95%.

[0055] The third aspect of the present application provides a regeneration method of a coal descaling alkali liquor, which comprises the following steps:

[0056] Step I: adding a reagent to the coal descaling alkali liquor and heating to 250-350℃ and keeping the temperature for 0.1-6h, and performing a third reaction while heating;

[0057] Step II: cooling and adding water, performing a fourth reaction, and optionally filtering to obtain a regenerated alkali liquor, so as to achieve the regeneration of the coal descaling alkali liquor.

[0058] In the present application, the regeneration method provided in the third aspect is different from the regeneration method provided in the second aspect in that the third reaction with the reagent is performed while the coal descaling alkali liquor is heated. The third reaction is different from the first reaction, and under the heating condition, the third reaction can generate a mixture containing calcium sodium silicate compound, magnesium sodium silicate compound, etc.

[0059] In the present application, the third reaction has a temperature of 250-350℃, preferably 280-320℃, and a time of 0.1-6h, preferably 2-4h.

[0060] The reagent in step I is selected from at least one of a calcium agent and a magnesium agent. The specific reagent is the same as that in step S1, which is not described here again.

[0061] In step II, after cooling and water replenishment, a fourth reaction is carried out at a temperature of 5-99°C for 0.1-6h; preferably, the temperature of the reaction is 20-95°C and the time is 0.1-3h. Under this reaction condition, the mixture containing sodium calcium silicate compound and sodium magnesium silicate compound generated in the third reaction can be hydrolyzed to obtain precipitates containing aluminum calcium silicon mixture and aluminum magnesium silicon mixture. After the reaction is completed, filtration can be carried out or not carried out to obtain regenerated lye. Preferably, filtration is carried out to remove the precipitated organic matter and sulfide, as well as the aluminum calcium silicon mixture and aluminum magnesium silicon mixture precipitates, so as to avoid increasing the ash content in the coal and affecting the performance of low-ash coal and coal-based carbon materials when the lye is reused.

[0062] The fourth aspect of the present application provides a method for removing ash from coal, which comprises the following steps:

[0063] (1) crushing the coal to less than 3mm, adding lye to remove ash by alkali method, and filtering to obtain ash-removed lye and coal after alkali ash removal (alkali-treated coal);

[0064] (2) removing ash from the coal after alkali ash removal obtained in step (1) by acid method to obtain acid ash removal liquid and ash-removed coal (acid-treated coal, i.e. low-ash coal);

[0065] (3) regenerating the ash-removed lye obtained in step (1) to obtain regenerated lye; the regeneration is carried out by using the aforementioned regeneration method of lye for removing ash from coal, and the specific regeneration steps are not described here;

[0066] (4) using the regenerated lye obtained in step (3) for alkali ash removal in step (1).

[0067] According to the method of the present application, in step (1), the coal is crushed and sieved to less than 3mm, for example, 2mm, 1.5mm, 1mm, 0.5mm, etc. Crushing the coal in this step can ensure that the mineral components in the coal can fully contact and react with the lye during alkali ash removal, so as to remove the ash in the coal. In principle, the smaller the size of the crushed coal, the more conducive to ash removal. However, considering that filtration separation is required after ash removal, in order to better separate the coal, the size of the coal is preferably less than 1mm.

[0068] According to the method of the present application, in step (1), the alkali solution used for alkali deslagging is preferably sodium hydroxide or potassium hydroxide, and the concentration of the alkali is 5-99wt%. The alkali deslagging method of the present application can use the conventional acid-alkali method alkali coal reaction conditions in the art, and the reaction temperature of the alkali coal system in the prior art is generally 100-250℃. For example, CN201710999565.9 discloses a process for preparing ultra-pure coal from anthracite by physical-chemical method, CN201710999573.3 discloses a process for preparing ultra-pure coal from anthracite by chemical method, and CN200380102494.4 discloses a method for removing mineral matter from coal.

[0069] According to the method of the present application, in step (1), the alkali solution used for alkali deslagging is preferably sodium hydroxide or potassium hydroxide, and the concentration of the alkali is 5-99wt%. The alkali deslagging method of the present application can use the conventional acid-alkali method alkali coal reaction conditions in the art, and the reaction temperature of the alkali coal system in the prior art is generally 100-250℃. For example, CN201710999565.9 discloses a process for preparing ultra-pure coal from anthracite by physical-chemical method, CN201710999573.3 discloses a process for preparing ultra-pure coal from anthracite by chemical method, and CN200380102494.4 discloses a method for removing mineral matter from coal.

[0070] According to the method of the present application, in step (2), the coal after alkali deslagging obtained in step (1) (alkali-treated coal) is further subjected to acid washing deslagging. The acid that can be used in this step is sulfuric acid, hydrochloric acid or nitric acid, etc. The concentration of the acid is preferably 1-50wt%, more preferably 3-30wt%, and further preferably 5-20wt%. The reaction conditions of the acid deslagging process can be selected according to the prior art, for example, CN201710999565.9 discloses a process for preparing ultra-pure coal from anthracite by physical-chemical method, CN201710999573.3 discloses a process for preparing ultra-pure coal from anthracite by chemical method, and CN200380102494.4 discloses a method for removing mineral matter from coal.

[0071] According to the method of the present application, in step (3), the coal deslagging alkali solution can be regenerated according to the process conditions required for coal deslagging, and the technical solutions provided in the first aspect, the second aspect and the third aspect of the present application can be used to remove the dissolved silicon-aluminum mineral components, organic matter and sulfides, etc.

[0072] According to the method of the present application, the regenerated alkali solution obtained in step (3) is used in step (1) for alkali deslagging. Through the coal deslagging alkali solution regeneration method provided by the present application, the dissolved silicon-aluminum mineral components, organic matter and sulfides, etc. in the coal deslagging alkali solution can be efficiently removed, the alkali regeneration of the coal deslagging alkali solution is achieved, the alkali consumption of the deslagging process is reduced, and the economic efficiency of the coal deslagging is improved.

[0073] The present application will be described in detail below through examples. Unless otherwise specified, the reagents involved in the examples of the present application are all commercially available and can be purchased through commercial channels.

[0074] In the following examples, the concentrations of aluminum and silicon in the coal descaling alkali solution are detected by ICP.

[0075] The composition of the descaling precipitate is detected by XRF.

[0076] The removal rate of aluminum and silicon (%) = (C Al再生 +C Si再生 ) / (C Al碱液 +C Si碱液 ) x 100%

[0077] Wherein, C Al再生 is the concentration of aluminum in the regenerated alkali solution;

[0078] C Si再生 is the concentration of silicon in the regenerated alkali solution;

[0079] C Al碱液 is the original concentration of aluminum in the coal descaling alkali solution;

[0080] C Si碱液 is the original concentration of silicon in the coal descaling alkali solution.

[0081] The concentration of organic matter in the alkali solution is measured by TOC.

[0082] The removal rate of organic matter (%) = (1-C c再生 / C c碱液 ) x 100%

[0083] Wherein, C c再生 is the concentration of total carbon in the regenerated alkali solution;

[0084] C c碱液 is the original concentration of total carbon in the coal descaling alkali solution.

[0085] The concentration of sulfide in the alkali solution is measured by trace sulfur analyzer.

[0086] The removal rate of sulfide (%) = (1-C s再生 / C s碱液 ) x 100%

[0087] Wherein, C s再生 is the concentration of total sulfur in the regenerated alkali solution;

[0088] C s碱液 is the original concentration of total sulfur in the coal descaling alkali solution.

[0089] The industrial analysis results of the coal samples A and B used are shown in Table 1 below. ad , A ad , V ad and FC ad are the moisture content, ash content, volatile matter content and fixed carbon content of the air-dried coal, respectively.

[0090] Table 1 Industrial analysis of coal sample

[0091]

[0092] Example 1

[0093] (1) Preparation of waste lye

[0094] Take coal sample A 400g, mix with potassium hydroxide 700g and water 400ml, after kneading reaction at 120℃ for 3 hours, carry out coal alkali ash removal. Dilute with 1L water after cooling, then filter and wash to obtain coal after alkali ash removal and coal ash removal lye. Add 10wt% dilute hydrochloric acid to the coal after alkali ash removal according to the ratio of acid to coal 1.5:1, leach at 60℃ for 30 minutes, filter and wash to obtain ultra-pure coal with ash content of 0.62wt%.

[0095] (2) Regeneration of lye by adding reagent

[0096] Add calcium hydroxide (add 50g / L, i.e. 50g of calcium hydroxide to 1L of ash removal lye) to the coal ash removal lye 2L obtained in step (1), react at 75℃ for 1 hour, filter to obtain aluminum-calcium-silicon mixture and ash removal regenerated lye; the aluminum content in the obtained aluminum-calcium-silicon mixture is 29wt% in terms of aluminum oxide, the calcium content is 56wt% in terms of calcium oxide, and the silicon content is 15wt% in terms of silicon dioxide. It is detected that after the addition of calcium hydroxide to the coal ash removal lye obtained in step (1) for regeneration, the removal rate of silicon and aluminum is 96%.

[0097] (3) Regeneration of lye by heating

[0098] Heat the ash removal regenerated lye obtained in step (2) to 300℃, keep warm for 1 hour, add water to cool, filter to remove the precipitate, and obtain the regenerated lye by heating.

[0099] It is detected that the removal rate of organic matter is 95% and the removal rate of sulfide is 96%. The regenerated lye by heating is concentrated and used for coal alkali ash removal in step (1).

[0100] Example 2

[0101] Prepare the waste lye according to step (1) of Example 1; regenerate the lye by removing silicon and aluminum according to step (2) of Example 1; the difference from Example 1 is that the regeneration of lye by heating in step (3) is as follows:

[0102] (3) Heat the ash removal regenerated lye obtained in step (2) to 250℃, keep warm for 6 hours. Add water to cool to obtain the regenerated lye by heating.

[0103] The detection results show that the removal rate of organic matter is 83% and the removal rate of sulfide is 85%. The regenerated alkali liquor is directly used in the coal alkali ash removal in step (1) without filtering out the precipitate after concentration.

[0104] Example 3

[0105] The preparation of waste alkali liquor is carried out according to step (1) of Example 1; the silicon and aluminum removal regeneration of alkali liquor is carried out according to step (2) of Example 1; and the difference from Example 1 is that the heating regeneration of alkali liquor in step (3) is carried out as follows:

[0106] (3) The ash removal regenerated alkali liquor obtained in step (2) is heated to 280°C and kept for 4 hours. After cooling by adding water, the precipitate is filtered out to obtain the heating regenerated alkali liquor.

[0107] The detection results show that the removal rate of organic matter is 86% and the removal rate of sulfide is 88%. The heating regenerated alkali liquor is concentrated and then used in the coal alkali ash removal in step (1).

[0108] Example 4

[0109] The preparation of ash removal alkali liquor is carried out according to step (1) of Example 1; the ash removal regeneration of alkali liquor is carried out according to step (2) of Example 1; and the difference from Example 1 is that the heating regeneration of alkali liquor in step (3) is carried out as follows:

[0110] (3) The ash removal regenerated alkali liquor obtained in step (2) is heated to 320°C and kept for 0.5 hours. After cooling by adding water, the precipitate is filtered out to obtain the heating regenerated alkali liquor.

[0111] The detection results show that the removal rate of organic matter is 95% and the removal rate of sulfide is 96%. The heating regenerated alkali liquor is concentrated and then used in the coal alkali ash removal in step (1).

[0112] Example 5

[0113] The preparation of waste alkali liquor is carried out according to step (1) of Example 1; the ash removal regeneration of alkali liquor is carried out according to step (2) of Example 1; and the difference from Example 1 is that the heating regeneration of alkali liquor in step (3) is carried out as follows:

[0114] (3) The ash removal regenerated alkali liquor obtained in step (2) is heated to 350°C and kept for 0.2 hours. After cooling by adding water, the precipitate is filtered out to obtain the heating regenerated alkali liquor.

[0115] The detection results show that the removal rate of organic matter is 97% and the removal rate of sulfide is 98%. The heating regenerated alkali liquor is concentrated and then used in the coal alkali ash removal in step (1).

[0116] Example 6

[0117] (1) Preparation of waste alkali liquor

[0118] Coal sample B 100g was mixed with sodium hydroxide 80g and water 320ml, and then stirred and reacted in an autoclave at 220°C for 3 hours. After cooling and filtration and washing, the coal after alkali deslagging and the coal deslagging alkali liquor were obtained. 10wt% dilute nitric acid was added to the filter cake at an acid to coal ratio of 0.4:1, and leaching was carried out at 75°C for 30 minutes, and filtration and washing were carried out to obtain ultra-pure coal with ash content of 0.19wt%.

[0119] (2) Regeneration of the alkali liquor by adding a reagent

[0120] To the coal deslagging alkali liquor 0.5L obtained in step (1), magnesium hydroxide was added (10g / L, i.e. 10g of magnesium hydroxide was added to 1L of the deslagging alkali liquor), and reaction was carried out at 35°C for 3 hours, and filtration was carried out to obtain an aluminum-magnesium-silicon mixture and deslagging regenerated alkali liquor. The Al content in the aluminum-magnesium-silicon mixture obtained was 35wt% in terms of aluminum oxide, the Mg content was 43wt% in terms of magnesium oxide, and the Si content was 22wt% in terms of silicon dioxide. It was detected that after the addition of magnesium hydroxide to the coal deslagging alkali liquor obtained in step (1) for deslagging regeneration, the removal rate of silicon and aluminum was 96%.

[0121] (3) Regeneration of the alkali liquor by heating

[0122] The deslagging regenerated alkali liquor obtained in step (2) was heated to 300°C, and heat treatment was carried out for 1 hour. After cooling by adding water, the precipitate was removed by filtration to obtain the regenerated alkali liquor by heating.

[0123] It was detected that the removal rate of organic matter was 95%, and the removal rate of sulfides was 96%. The regenerated alkali liquor by heating was concentrated and used for the alkali deslagging of coal in step (1).

[0124] Example 7

[0125] The preparation of waste alkali liquor was carried out according to step (1) of Example 6, the deslagging regeneration of the alkali liquor was carried out according to step (2) of Example 6, and the deslagging regeneration of the alkali liquor was carried out according to step (3) of Example 6. The difference from Example 6 was that in step (2), magnesium hydroxide was added (the amount of addition was 50g / L, i.e. 50g of magnesium hydroxide was added to 1L of the deslagging alkali liquor), and reaction was carried out at 95°C for 0.5 hours.

[0126] It was detected that the removal rate of silicon and aluminum was 99%, the removal rate of organic matter was 95%, and the removal rate of sulfides was 96%. The regenerated alkali liquor by heating was concentrated and used for the alkali deslagging of coal in step (1).

[0127] Example 8

[0128] The preparation of waste lye was carried out according to the procedure (1) of Example 6; the ash removal regeneration of lye was carried out according to the procedure (2) of Example 6, and the ash removal regeneration of lye was carried out according to the procedure (3) of Example 6, with the exception that the procedure (2) of Example 6 was different:

[0129] (2) Calcium hydroxide was added to the ash removal lye obtained in step (1) (the amount of addition was 10 g / L, i.e. 10 g of calcium hydroxide was added to 1 L of ash removal lye), and the reaction was carried out at 75°C for 1 hour.

[0130] It was detected that the removal rates of silicon and aluminum, organic matter and sulfide were 96%, 95% and 96% respectively. The heated regenerated lye was concentrated and used in the ash removal of coal in step (1).

[0131] Example 9

[0132] The procedures (1), (2) and (3) of Example 6 were carried out, with the exception that the procedure (2) of Example 6 was different:

[0133] (2) Magnesium hydroxide was added to the ash removal lye obtained in step (1) (the amount of addition was 10 g / L, i.e. 10 g of magnesium hydroxide was added to 1 L of ash removal lye), and the reaction was carried out at 75°C for 3 hours. Without filtration, the heating regeneration of lye was directly carried out, and scabbing phenomenon occurred.

[0134] It was detected that the removal rates of silicon and aluminum, organic matter and sulfide were 96%, 95% and 96% respectively. The heated regenerated lye was concentrated and used in the ash removal of coal in step (1).

[0135] Example 10

[0136] (1) The preparation of waste lye was carried out according to the procedure (1) of Example 6;

[0137] With the exception that the procedures (2) and (3) of Example 6 were different:

[0138] (2) Heating regeneration of lye

[0139] The ash removal lye of coal obtained in step (1) was heated to 300°C, and the heat preservation treatment was carried out for 1 hour. After cooling and water replenishment, the precipitate was removed by filtration, and the treated liquid was obtained.

[0140] (3) Chemical regeneration of lye

[0141] Calcium hydroxide was added to the treated liquid obtained in step (2) (the amount of addition was 10 g / L, i.e. 10 g of calcium hydroxide was added to 1 L of ash removal lye), and the reaction was carried out at 75°C for 1 hour. After filtration, aluminum-magnesium-silicon mixture and ash removal regenerated lye were obtained.

[0142] The detection results show that the removal rates of silicon and aluminum, organic matter and sulfide are 96%, 95% and 96% respectively. After filtration, the regenerated lye is concentrated and used in the coal alkali ash removal in step (1).

[0143] Example 11

[0144] (1) Preparation of waste lye according to step (1) of Example 1

[0145] The difference from Example 1 is in steps (2) and (3):

[0146] (2) Regeneration of lye by adding reagent and heating

[0147] In 2 L of coal ash removal lye obtained in step (1), 50 g of magnesium hydroxide is added (50 g of magnesium hydroxide is added per 1 L of ash removal lye), and the mixture is heated to 300°C and kept for 1 hour. The reagent and dissolved aluminum and silicon mineral components perform a third reaction, and a heating treatment and third reaction regeneration liquid is obtained.

[0148] (3) Regeneration of lye by cooling and water replenishment

[0149] The heating treatment and third reaction regeneration liquid obtained in step (2) is replenished with water and subjected to a fourth reaction at 75°C for 1 hour. After filtration, an aluminum-magnesium-silicon mixture and ash removal regeneration lye are obtained.

[0150] The detection results show that the removal rates of silicon and aluminum, organic matter and sulfide are 96%, 95% and 96% respectively. After filtration, the regenerated lye is concentrated and used in the coal alkali ash removal in step (1).

[0151] Example 12

[0152] Preparation of waste lye according to step (1) of Example 11; regeneration of lye according to steps (2) and (3) of Example 1. The difference is that calcium hydroxide is added in step (2).

[0153] The detection results show that the removal rates of silicon and aluminum, organic matter and sulfide are 96%, 95% and 96% respectively. After filtration, the regenerated lye is concentrated and used in the coal alkali ash removal in step (1).

[0154] As can be seen from the examples 1 to 5, after the coal ash removal by the alkali method, the alkali solution is lost due to the dissolved ash, and is also lost due to the dissolved alkali-soluble organic matter and sulfide. By adding the calcium / magnesium agent to react with the aluminum and silicon dissolved in the alkali solution to generate aluminum-silicon calcium / magnesium precipitate, the silicon-aluminum removal and regeneration of the alkali solution can be achieved. After further heating treatment to destroy the solubility of the organic matter and sulfide, the alkali regeneration of the coal ash removal alkali solution can be achieved. As can be seen from the examples, in the alkali solution heating regeneration step, with the increase of the temperature and the extension of the treatment time, the removal rate of the organic matter and sulfide can be improved. The temperature has a significant effect on the removal rate, and the treatment time can be shortened at a higher temperature, and the removal rate is significantly improved.

[0155] As can be seen from the examples 6, 7 and 8, in the example 6, the magnesium hydroxide is added in the step (2) (the addition amount is 10 g / L, i.e. 10 g of magnesium hydroxide is added into 1 L of ash removal alkali solution), in the example 7, the magnesium hydroxide is added in the step (2) (the addition amount is 50 g / L, i.e. 50 g of magnesium hydroxide is added into 1 L of ash removal alkali solution), and in the example 8, the calcium hydroxide is added in the step (2) (the addition amount is 10 g / L, i.e. 10 g of calcium hydroxide is added into 1 L of ash removal alkali solution). The effect of the silicon-aluminum removal rate mainly reflects in the addition amount, and the more the addition amount, the higher the silicon-aluminum removal rate. The type of the calcium agent or magnesium agent has a relatively small effect.

[0156] As can be seen from the examples 6 and 9, after the ash removal and regeneration, without filtration, the heating regeneration of the alkali solution is directly performed, and the silicon-aluminum removal rate and the organic matter removal rate change little, but after a long time of regeneration, a small amount of ash is scabbed in the reactor.

[0157] As can be seen from the examples 6 and 10, after changing the order of the alkali solution heating regeneration and the agent addition regeneration, the silicon-aluminum removal rate and the organic matter removal rate change little.

[0158] As can be seen from the examples 11 and 12, the coal ash removal alkali solution is regenerated by heating treatment with the addition of the agent, and the cooling and water supplement regeneration, and by using different agents, the dissolved silicon-aluminum components, organic matter and sulfide in the alkali solution can be efficiently removed, and the alkali regeneration in the coal ash removal alkali solution can be achieved.

[0159] The alkali regeneration method of the coal ash removal alkali solution provided by the application avoids the consumption of the alkali solution due to the gradual accumulation of the soluble aluminum-silicon mineral components, organic matter and sulfide of the coal in the recycling process. The alkali is the main consumption agent for the coal ash removal, and the regeneration of the coal ash removal alkali solution significantly improves the economy of the coal ash removal.

[0160] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including that each technical feature is combined in any other suitable manner. These simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A method for alkali regeneration of coal ash removal alkaline solution, characterized in that, The regeneration method includes: The coal ash removal alkaline solution is mixed with the reagent to carry out the first reaction, filtered, and the reaction solution is obtained. The obtained reaction solution is heated to 250-350℃, kept at that temperature for 0.1-6 h, cooled, replenished with water, and filtered to obtain a regenerated alkali solution. The regenerated alkaline solution has a silicon and aluminum removal rate of over 80%, an organic matter removal rate of over 80%, and a sulfide removal rate of over 80%.

2. The regeneration method according to claim 1, wherein, The temperature of the first reaction is 5-99℃, and the time is 0.1-6h.

3. The regeneration method according to claim 2, wherein, The temperature of the first reaction is 20-95℃, and the time is 0.1-3h.

4. A method for alkali regeneration of coal ash removal alkaline solution, characterized in that, The regeneration method includes: The coal ash removal alkaline solution is heated to 250-350℃, kept at that temperature for 0.1-6 hours, cooled and replenished with water, and then filtered to obtain the treated solution. A reagent is added to the treatment solution to carry out a second reaction, followed by filtration to obtain a regenerated alkali solution. The regenerated alkaline solution has a silicon and aluminum removal rate of over 80%, an organic matter removal rate of over 80%, and a sulfide removal rate of over 80%.

5. The regeneration method according to claim 4, wherein, The second reaction is carried out at a temperature of 5-99℃ for a time of 0.1-6 hours.

6. The regeneration method according to claim 5, wherein, The temperature of the second reaction is 20-95℃, and the time is 0.1-3h.

7. A method for alkali regeneration of coal ash removal alkaline solution, characterized in that, The regeneration method includes: Add the reagent to the coal ash removal alkaline solution, heat to 250-350℃, keep warm for 0.1-6 h, and carry out the third reaction; Cool and add water, carry out the fourth reaction, filter, and obtain regenerated alkali solution; The regenerated alkaline solution has a silicon and aluminum removal rate of over 80%, an organic matter removal rate of over 80%, and a sulfide removal rate of over 80%.

8. The regeneration method according to claim 7, wherein, The third reaction is carried out at a temperature of 250-350℃ for a time of 0.1-6 hours. And / or, the fourth reaction is carried out at a temperature of 5-99°C for a time of 0.1-6 hours.

9. The regeneration method according to claim 8, wherein, The third reaction is carried out at a temperature of 280-320℃ for 2-4 hours. And / or, the fourth reaction is carried out at a temperature of 20-95°C for a time of 0.1-3 hours.

10. The regeneration method according to any one of claims 1, 4, and 7, wherein, The agent is selected from at least one of calcium and magnesium agents.

11. The regeneration method according to claim 10, wherein, The calcium agent is selected from at least one of calcium oxide, calcium hydroxide, and lime milk; And / or, the magnesium agent is selected from at least one of magnesium oxide, magnesium hydroxide, and magnesium hydroxide emulsion.

12. The regeneration method according to any one of claims 1, 4, and 7, wherein, The amount of the reagent is calculated based on the stoichiometry of the reaction product, which is an aluminum-calcium-silicon mixture and / or an aluminum-magnesium-silicon mixture.

13. The regeneration method according to claim 12, wherein, The aluminum-calcium-silicon mixture includes at least one of calcium hydroxide, calcium aluminate compound, calcium silicate compound, and grossular garnet; And / or, the aluminum-magnesium-silicon mixture includes at least one of magnesium hydroxide, magnesium aluminate compound, magnesium silicate compound, and pyrope garnet.

14. The regeneration method according to claim 12, wherein, Based on the total amount of the aluminum-calcium-silicon mixture, the aluminum-calcium-silicon mixture contains 10-70 wt% Al (calculated as alumina), 30-80 wt% Ca (calcium oxide), and 1-60 wt% Si (calculated as silicon dioxide). And / or, based on the total amount of the aluminum-magnesium-silicon mixture, the aluminum-magnesium-silicon mixture contains 10-80 wt% Al based on alumina, 20-80 wt% Mg based on magnesium oxide, and 1-70 wt% Si based on silicon dioxide.

15. The regeneration method according to any one of claims 1, 4, and 7, wherein, The regenerated alkaline solution has a silicon and aluminum removal rate of over 95%, an organic matter removal rate of over 95%, and a sulfide removal rate of over 95%.

16. A method for removing ash from coal, characterized in that, The method includes: Step (1) Crush the coal to less than 3mm, add alkaline solution for alkaline ash removal, and obtain ash removal alkaline solution and coal after alkaline ash removal through solid-liquid separation; Step (2) The coal after alkaline ash removal is subjected to acid ash removal to obtain acid ash removal liquid and deashed coal; Step (3) The ash removal alkali solution is regenerated according to the regeneration method described in any one of claims 1-15 to obtain regenerated alkali solution; Step (4) uses the obtained regenerated alkaline solution for alkaline descaling in step (1); The regenerated alkaline solution has a silicon and aluminum removal rate of over 80%, an organic matter removal rate of over 80%, and a sulfide removal rate of over 80%.

17. The method for removing ash from coal according to claim 16, wherein, In step (1), the alkaline solution is sodium hydroxide or potassium hydroxide, and the concentration of the alkaline solution is 5-95 wt%. And / or, the alkaline descaling process is carried out at a temperature of 100-250℃ for a time of 0.1-6h; And / or, in step (2), the acid used for pickling and descaling is sulfuric acid, hydrochloric acid, or nitric acid, and the concentration of the acid is 1-50 wt%; And / or, the acid pickling and ash removal temperature is 5-99℃, and the time is 0.1-3h.

18. The method for removing ash from coal according to claim 17, wherein, The concentration of the alkaline solution is 10-90 wt%; And / or, in step (2), the concentration of the acid is 3-30 wt%.

19. The method for removing ash from coal according to claim 18, wherein, The concentration of the alkaline solution is 20-85 wt%; And / or, in step (2), the concentration of the acid is 5-20 wt%.

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