Methods for removing ash from solid carbon-containing materials

Abstract

A method for removing ash from solid carbonaceous materials, characterized in that it comprises: S1) Mixing an alkaline submelting salt medium and a solid carbonaceous material to be treated under kneading, heating, such that alkali and ash of the solid carbonaceous material to be treated react in the alkaline submelting salt medium, then carrying out a solid-liquid separation of the mixed slurry produced from the reaction to obtain a first solid product and an alkali treatment solution, wherein the mass fraction of the alkali in the alkaline submelting salt medium is 50% or more;and wherein the mass ratio of the alkali to the solid carbonaceous material to be treated is between 0.1 and 2:1,S2) using an acid solution to perform an acid washing treatment on the first solid product and repeating a solid-liquid separation to obtain a second solid product and an acid washing solution, wherein the acid washing treatment with the acid solution is performed n times in countercurrent contact with the first solid product, where n is equal to or greater than 2.;

Description

TECHNICAL FIELDThe present invention relates to the technical field of ash removal from the solid carbonaceous materials, and more particularly to a method for ash removal in the solid carbonaceous materials.PRIOR ARTSolid carbonaceous materials refer to the solid materials containing a large amount of carbon, and include chemical materials such as solid fuels, activated carbon, asphalt, etc., the solid fuels referring to the combustible solid materials which can generate heat or electricity and generally contain carbon or hydrocarbons, the natural solid fuels are such as wood, peat, brown coal, coal, anthracene, oil slate, etc., and the solid fuels obtained by processing are such as charcoal, coke, briquettes and coal balls, etc. The solid carbonaceous materials generally contain ash and, in use, the amount of ash content directly affects the performance of the solid carbonaceous materials.Here, coal can be taken as an example, the categorization of coals into china may be complex, and the coals have substantially inferior quality and relatively high ash content, the coal quality gradually deteriorates after the long-year degradation. The commercial coal has a high ash content, that is, an average ash content between 20 wt % to 24 wt %, and the average ash content of the coal used for power generation reaches 28 wt %. Among the major use of coals, when the ash content of coals used for power generation is reduced by 1 wt %, the heating value can be increased by 200-360J / g, and the standard coal consumption for power generation is reduced by 2-5 g per kwh. When the ash content of the coke coal is decreased by 1 wt%, the coke coal consumption for iron making is reduced by 2.66 wt%, and the utilization coefficient of the blast furnace for iron making can be increased by 3.99%. The process for producing synthetic ammonia can save 20 wt% coal when the washed and selected anthracene coal is used. Value-added applications for coal include oil-replaced coal and coal-based carbon materials which have severe constraints on ash content in coals. For the "coal-water slurry" referred to as the oil-replaced coal, it is specified in the People's Republic of China national standards that the Grade I product must have an ash content of less than 6 wt%. With respect to the carbon-based carbon materials, the recommended standards for the ash content in the coal are as follows: the ash content in the activated carbon is less than 2% by weight, the ash content in the coal ingot and in the carbon electrodes is less than 6% by weight, and the ash content in the electrode paste is less than 8% by weight. The coal having an ash content of less than 1-3 wt% is generally referred to as ultra-pure coal which can be used for the production of a fine coal-water slurry burned as a substitute for oil, the coal-water slurry has a high heating value, thereby the renovating and improvement of the boiler is not required, and the emissions are in accordance with environmental protection rules and regulations. Moreover, the ultra-pure coal can also be used in internal combustion engines and combustion gas turbines and in power plants such as aircraft turbines.The refining methods of coal, especially for the production of refined coal with high value consumption and low ash content, consist mainly of the chemical methods and the physical methods. The chemical methods refer to the processes of performing chemical reactions between the chemical agents and the components in coal; the physical methods consist mainly of an oil agglomeration process and a flotation floc process, both of which serve to finely grind the feed coal to enable monomer separation by utilizing the difference in lipophilicity and hydrophobicity of organics and inorganic minerals in coal; the lipophilic fine organics are agglomerated by means of the bridging liquid and the shear force of neutral oils such as hydrocarbons so that the hydrophilic mineral particles are dispersed in water, and then subjected to separation by means of the sieving, centrifugation or flotation method. The physical methods are relatively simple and practicable, but have poor adaptability and low ash removal efficiency, while the chemical methods have high adaptability and high ash removal efficiency. The chemical methods currently used are mainly comprised of hydrofluoric acid method, conventional acid-alkali method, molten alkali leach method and chemical coal method. The conventional acid-alkali method is the most widely used method, the basic principle of which is that an alkali reacts with minerals of coal under certain conditions, then the inorganic compounds formed are washed with an acid, and a filtering and washing process is carried out to separate the organic components of coal. Although the conventional acid-alkali method has a high adaptability and a high ash removal efficiency, it generally requires operation at a high temperature of 150-250° C. under a high pressure, and the mass ratio of the caustic solution to the coal may be 3-10 or more. The water consumption is high throughout the process, the reaction conditions are relatively severe, the amount of alkali consumed is large, the processing capacity of coal is small, so that the difficulty and cost of recovering alkali thereafter are increased.The publication by WANG, Z.Y.; et al. (Removal of mineral matter from coal by alkali treatment, Fuel Proc. Techn. 1986, Vol. 13, pp 279-289, ISSN 0378-3820) discloses a method for removing minerals from coal by alkali treatment and discloses in particular the following content: 5 grams of coal and 55 ml of NaOH (at a concentration of 1, 4, 10 and 20 M) were heated in a 100 ml teflon crucible; the crucible was surrounded by a stainless steel jacket whereby the system could be pressurized during the reaction to the vapor pressure of the slurry. After a predetermined reaction time, the crucible was rapidly cooled in ice water.CONTENT OF THE PRESENT INVENTIONEmbodiments of the present invention provide a method for removing ash in the solid carbonaceous materials. The reaction conditions are mild and the ash can be removed in a more efficient manner, thereby reducing the amount of alkali and water used and increasing the processing capacity of the solid carbonaceous materials, thereby reducing the difficulty and cost of recovering alkali.In order to achieve the above objects, the following technical solutions are applied in the present invention:Embodiments of the present invention provide a method for removing ash in the solid carbonaceous materials, the method comprising:S 1) mixing an alkaline sub-melting salt medium and a solid carbonaceous material to be treated, heating so that alkali and ash of the solid carbonaceous material to be treated react in the alkaline sub-melting salt medium, then performing solid-liquid separation of the mixed slurry generated from the reaction to obtain a first solid product and an alkali treatment solution, wherein the mass proportion of the alkali in the alkaline sub-melting salt medium is 50% or more;S 2) using an acid solution to perform an acid washing treatment on the first solid product, and performing solid-liquid separation again to obtain a second solid product and an acid washing solution.Optionally, the mass ratio of the alkali to the solid carbonaceous materials to be treated is from 0.1 to 2:1.Optionally, the alkaline submelting salt medium is mixed with the solid carbonaceous materials to be treated with kneading.Optionally, the reaction is carried out at a temperature in the range of 100-200°C and a normal pressure for 0.5-9h.Optionally, the ash removal process further comprises cooling the reacted mixed slurry by dilution with water before subjecting the reacted mixed slurry to solid-liquid separation.Optionally, the temperature after the cooling process is in a range of 10-99°C.Optionally, the cooling time may be 3h or less.Optionally, the n times of acid washing treatments are carried out with the acid solution in countercurrent contact with the first solid product, where n is equal to or greater than 2.Optionally, the n times of acid washing treatments are performed with the acid solution in counter-current contact with the first solid product, the acid washing treatment specifically comprising: a solid product obtained after the i-1th acid washing treatment is subjected to an acid washing treatment using an acid washing solution obtained after the i-th acid washing treatment, and the first solid product is subjected to an acid washing treatment using an acid washing solution obtained after the second acid washing treatment, wherein i is a natural number and 2≤i≤n.Optionally, the yield of the second solid product is equal to or greater than 95%.Optionally, the mass ratio of the ash in the second solid product is 1% or less.Optionally, the mass ratio of the ash in the second solid product is 0.2% or less.The embodiments of the present invention provide a method for removing ash in the solid carbonaceous materials; by using a high reaction activity of the sub-melting salt medium, the alkali can destroy or decompose the mineral components in a more effective manner, and then the destroyed or decomposed mineral components can be dissolved and extracted by the acidic washing treatment to enable the removal of ash. Since the submelting salt medium generates vapor pressure lower than atmospheric pressure and has high reaction activity, the whole reaction can be carried out under normal pressure, the reaction conditions are milder and the ash can be removed more efficiently than the acid-alkali method used in the related art, so that the amount of alkali and water used is reduced and the processing capacity of the solid carbonaceous materials is increased, thereby reducing the difficulty and cost of recovering alkali.BRIEF DESCRIPTION OF THE DRAWINGSIn order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly presents the accompanying drawings necessary for describing the embodiments. It is obvious that the accompanying drawings in the following description show only some embodiments of the present invention, and a person skilled in the art can derive from these accompanying drawings still other drawings without any curative work. FIG. 1 shows a schematic flow diagram of a method for removing ash in the solid carbonaceous materials provided by an embodiment of the present invention; FIG. 2 is a schematic flow chart of performing the n-times acid washing treatment using the acid solution in counter-current contact with the first solid product provided by an embodiment of the present invention.EMBODIMENTSThe following content will clearly and fully describe the technical solution in the embodiments of the present invention with reference to the accompanying drawings of the embodiments of the present invention. It should be understood that the embodiments described herein are merely some of the embodiments of the present invention, rather than enumeration of all embodiments of the present invention. Based on the embodiments of the present invention, a person skilled in the art without any creative work would derive all other embodiments of the present invention, each of which falls within the scope of the present invention.Referring to FIG. 1, embodiments of the present invention provide a method for removing ash in the solid carbonaceous materials, the method comprising:S 1) mixing an alkaline sub-melting salt medium and a solid carbonaceous material to be treated, heating so that alkali and ash of the solid carbonaceous material to be treated react in the alkaline sub-melting salt medium, then performing solid-liquid separation of the mixed slurry generated from the reaction to obtain a first solid product and an alkali treatment solution, wherein the mass proportion of the alkali in the alkaline sub-melting salt medium is 50% or more;S 2) using an acid solution to perform an acid washing treatment on the first solid product, and performing solid-liquid separation again to obtain a second solid product and an acid washing solution.Ash in a solid carbonaceous material refers to the residue of the solid carbonaceous material after calcination. The solid carbonaceous material undergoes a series of physical and chemical changes at high temperatures, where the organic constituents evaporate and are discharged while the inorganic constituents (inorganic salts and oxides) remain, such residues being referred to as ash.Ash consists of oxides or salts of various mineral elements mainly consisting of Si, Al, Ca, Mg, K, Na, P, S, Fe, as well as lithium (Li), gallium (Ga), uranium (Ur), mercury (Hg), other rare earth metals and dispersed elements as well as noble metals.The submelting salt medium is sodium hydroxide or potassium hydroxide in a proportion by mass of 50% or more. By way of example, the mass ratio of alkali to water may be 1:1, 1.5:1, 2:1, 3:1 or 4:1. The sub-melting salt medium can provide an alkali metal ionization medium having a high concentration of the negative oxygen ions with high activity, is located between the molten salt medium and the electrolytic solution medium, has excellent physical and chemical properties such as low vapor pressure, high boiling point and desirable fluidity, as well as high activity factor, excellent reaction activity and adjustable separation function, so that the sub-melting salt medium can realize decomposition and conversion of mineral components with high efficiency. According to the above properties of the sub-melting salt, the vapor pressure generated in the present invention is lower than a normal pressure, and the highly active reaction can be carried out under the atmospheric pressure.The embodiments of the present invention provide a method for removing ash in the solid carbonaceous materials; by using a high reaction activity of the sub-melting salt medium, the alkali can destroy or decompose the mineral components in a more effective manner, and then the destroyed or decomposed mineral components can be dissolved and extracted by the acidic washing treatment to enable the removal of ash. Since the submelting salt medium generates vapor pressure lower than atmospheric pressure and has high reaction activity, the whole reaction can be carried out under normal pressure, the reaction conditions are milder and the ash can be removed more efficiently than the acid-alkali method used in the related art, so that the amount of alkali and water used is reduced and the processing capacity of the solid carbonaceous materials is increased, thereby reducing the difficulty and cost of recovering alkali.Prior to mixing an alkaline sub-melting salt medium and a solid carbonaceous material to be treated, the method further comprises: crushing the solid carbonaceous material to be treated into particles having a particle size of less than 5 mm, preferably less than 1 mm.The present invention does not contain any restrictions with respect to the type and ash content of the solid carbonaceous material to be treated, the technical solution is applicable to the deashing of various solid carbonaceous materials. In the specification, the solid carbonaceous material is a broad term that may include: coal, coal direct liquefaction residues, heavy residual oil, coke, petroleum coke, oil sand, shale oil, carbonaceous industrial wastes or tails, biomass, synthetic plastics, synthetic polymers, scrap tires, municipal solid wastes, bitumen, and / or mixtures thereof.Using the example of coal, the alkali / coal ratio can be adjusted flexibly depending on the type of coal and the ash content.For example, a lower alkali / coal ratio may be selected with respect to the low ash coal, such as 0.4:1; and a high alkali / coal ratio may be selected with respect to the high ash coal, such as 1.5:1.The mass ratio of the alkali to the solid carbonaceous materials to be treated is therefore optionally 0.1-2:1.In one embodiment of the present invention, the mass proportion of the alkali in the alkaline sub-melting salt medium is 50% or more. By way of example, the mass ratio of the alkali to water may be 1:1, 1.5:1, 2:1, 3:1 or 4:1. In this way, the sub-melting salt medium can be formed to improve the efficiency of removal of ash.In another embodiment of the present invention, the submelting salt medium of the liquor is mixed with the solid carbonaceous materials to be treated with kneading.When the submelting salt medium is mixed with the solid carbonaceous material to be treated and subjected to a reaction, the materials are viscous at elevated temperature. The kneading is a process of uniformly mixing the paste-like and viscous materials using the mechanical stirring. It is common to use a pair of complementary rotating Σ blades to produce a shear action so that the viscous materials react rapidly in a semi-dry state or in a rubbery form to achieve uniform mixing and good agitation. As compared with the stirring operation in the usual sense, kneading is more suitable for mixing high viscosity materials to more uniformly mix the materials and thereby improve the efficiency of removal of ash; moreover, the kneading operation can reduce the pulverization phenomenon of the materials caused by the stirring when the materials are excessively pulverized, the cost for the subsequent solid-liquid separation is increased, and the yield of the product is adversely affected.In the present invention, the reaction temperature, pressure and time are not specifically defined. In one embodiment of the present invention, the reaction is carried out at a temperature in a range of 100-200°C, preferably 105-150°C, and a normal pressure for 0.5-9h, preferably 2-6h.The atmospheric pressure is an atmospheric pressure, i.e., the gas pressure generated in the atmosphere in our daily life is 101.325Pa. Each location has an actual atmospheric pressure which does not necessarily coincide with the standard atmospheric pressure due to the different geographical location, flight altitude and temperature, therefore the atmospheric pressure can be regarded as approximately standard atmospheric pressure.In an embodiment of the present invention, the reaction temperature is 50-100°C lower than that in the conventional acid-alkali method, the reaction pressure is at a normal pressure, the reaction conditions are mild, and the deasch efficiency is high, and the reaction time can be shortened.Note that in practical applications after completion of step S 1), the obtained mixed slurry is in a high-temperature viscous state, and the operation difficulty is increased when the solid-liquid separation is directly performed. However, the operating difficulty can be further increased if a temperature lowering treatment is carried out before the solid-liquid separation, because thereby the solids having a certain hardness and strength can be produced by coagulation of the mixed slurry. Therefore, it is preferable that the ash removal method further comprises cooling the reacted mixed slurry by dilution with water before subjecting the reacted mixed slurry to solid-liquid separation. In this way, by diluting the reacted mixed slurry, on the one hand, the temperature of the reacted mixed slurry can be lowered and industrial separation can be economically performed; on the other hand, the mixed slurry after dilution can maintain a flowable state by adding water, thus preventing the mixed slurry from coagulating to solids.The temperature after cooling is not limited as long as it is favorable to carry out the solid-liquid separation. In one embodiment of the present invention, the temperature after cooling is in a range of 10-99°C, preferably 30-60°C.It should be further explained that in practical use, after cooling the reacted mixed slurry to 10-99°C, the system is in a metastable state; if the mixed slurry is at rest for a long time, it will cause precipitation of the water-soluble alkali metal salts; therefore, it is preferred that the cooling time is 3h or less, more preferably 1h or less. Such an arrangement enables timely solid-liquid separation of the materials after cooling, and precipitation of the residues caused by instability of the system can thereby be avoided, thereby not impairing the efficiency of removal of ash. If the treatment is not carried out in time for some reason, the cooled residues must first be broken, or the system is heated again to the viscous state, then it is diluted by adding water.It is further preferred that the cooling time is less than or equal to 30 minutes.In addition, the cooling time is 10-15 min.The solid-liquid separation can be carried out by filtration.In another embodiment of the present invention, after the solid-liquid separation and before the acid washing treatment with an acid solution for the first solid product, the method further comprises: washing the first solid product with water. A portion of the water-soluble alkali metal salts may be washed away.The specific type of the acid washing treatment is not limited here, the first solid product may be subjected to acid washing treatments using the acid solution one or more times.In one embodiment of the present invention, n times of acid washing treatment is carried out with the acid solution in countercurrent contact with the first solid product, where n is equal to or greater than 2.The acid washing treatment specifically includes: a solid product obtained after the i-1th acid washing treatment is subjected to an acid washing treatment using an acid washing solution obtained after the i-th acid washing treatment, and the first solid product is subjected to an acid washing treatment using an acid washing solution obtained after the second acid washing treatment, where i is a natural number and 2≤i≤n.In an embodiment of the present invention, the counter-current contact is assumed such that the solid products having the lowest ash content are subjected to an acid washing treatment by means of the acid washing solution having the lowest ash content. Such solid products having the gradually higher ash content are subjected to an acid washing treatment by means of the acid washing solution having an increased ash content one after another; such an arrangement can maximize the acid washing effect and further reduce the ash content in the solid carbonaceous material.In practice, referring to FIG. 2, the first solid product may be introduced into a first acid washing tank, the first solid product is subjected to a first acid washing treatment using an acid washing solution generated in a second acid washing tank to obtain a solid product and an acid washing solution; wherein the solid product produced after the first acid washing treatment is introduced into the second acid washing tank, and the solid product in the second acid washing tank is subjected to a second acid washing treatment using an acid washing solution produced in a third acid washing tank to obtain a solid product and an acid washing solution again, and so on, the solid product produced in the n-1th acid washing tank is introduced into the n-th acid washing tank, the acid washing treatment is performed with the acid solution there to obtain a second solid product and an acid washing solution, the solid product in the n-1th acid washing tank is subjected to an acid washing treatment using the acid washing solution produced in an n-th acid washing tank.In the above process, the first product can be contacted with acid solution stepwise countercurrently and further improve the deash effect.The present invention does not provide a limitation on the mass ratio of the acid in the acid solution to the solid carbonaceous material to be treated, because after the alkali reacts with the mineral components in the solid carbonaceous material to be treated, the mineral components can be destroyed or decomposed, and very few mineral components are introduced into the alkali treatment liquid by solid-liquid separation, thereby subjecting the first solid product to an acid washing treatment by adding the acid solution, to thereby dissolve the destroyed or decomposed mineral components in the acid solution, so that the ash is removed. Thus, the amount of acid added in the acid solution can be adjusted flexibly depending on the kind and ash content of the solid carbonaceous material to be treated, and for example, a lower acid / coal ratio can be selected with respect to the coal having a low ash content, such as 0.4:1; while a high acid / coal ratio can be selected with respect to the coal having a high ash content, such as 1.5:1.Thus, optionally, the mass ratio of the acid in the acid solution to the solid carbonaceous material to be treated is between 0.1-2:1.The acid in the acid solution may be nitric acid, hydrochloric acid or sulfuric acid.The present invention is not limited to the mass proportion of the acid in the acid solution.In one embodiment of the present invention, the mass fraction of the acid in the acid solution is in a range of 3-30%, preferably 5-20%.The method for removing ash in the solid carbonaceous materials further includes: washing the second solid product with water; and drying the second solid product to remove the residual acid solution in the second solid product during the solid-liquid separation re-process performed to obtain the second solid product and the acid washing solution.The solid-liquid separation can be performed by a filtration method.The temperature and time of each acid washing treatment are not particularly limited.In another embodiment of the present invention, each of the acid washing treatments is performed at a temperature of 10-99° C. for 5-180 minutes. Either the too high temperatures or the too long acid wash time may cause ash to precipitate, which is not advantageous for ash removal.Through experiments, it was found that the yield of the second solid product can reach 95-99% or more using this method for removing ash. The mass ratio of the ash in the second solid product is 1% or less. The present process can improve the properties of solid carbonaceous materials, so the processed coal can meet the ultra-pure coal requirements, thus increasing the utility value of the coal. When the processed coal is used for combustion, the heating value is significantly improved and the environmental pollution of ash is avoided.Preferably, the mass ratio of the ash in the second solid product is 0.2% or less.Recovery of both the water wash solution and the acid solution and brine can be carried out according to mature prior art techniques. For example, the water washing solution after the caustification treatment can be recycled for reuse in the step (1), and the acid was recovered and reused by roasting the acid washing solution.The embodiments of the present invention will be described below in more detail with reference to comparative examples and embodiments. The comparative examples and embodiments are only examples proposed for describing the present invention. It should be understood by those skilled in the art that the scope of the present invention is not limited by the comparative examples and examples.For coal samples A and B, the results of the industrial analysis are shown in the following Table 1.A. A6,3034,2524,6334,82B. B2,335,1220,5771,98where M is ad the proportion by mass of moisture, A is ad the proportion by mass of ash, V is ad the proportion by mass of volatile constituents and F is Cad the proportion by mass of solid carbon. The coal samples are comminuted to particles having a particle size of less than 5 mm and partly less than 1 mm.Embodiment 1400 The g of coal sample A was taken out and mixed with 700 g of sodium hydroxide and 400 ml of water (the mass ratio of sodium hydroxide was 63.6%, the alkali / coal ratio was 7:4, the mass ratio of alkali to coal sample A was 11:4), the mixture was subjected to kneading reaction at 105° C. in a closed environment under atmospheric pressure for 9 hours. 1L of water was added to dilute and cool the mixture, after 1 hour, the mixture was subjected to a filtering and washing process to obtain a first solid product (i.e., alkaline coal). 10 wt % of diluted hydrochloric acid was added to the alkaline coal according to an acid / coal ratio of 1.3:1, the alkaline coal was subjected to an acid washing treatment at a temperature of 60° C. for 30 minutes, the filtering and washing process was performed, and the filter cake was subjected to drying to obtain a second solid product (i.e., ultra-pure coal). The yield of ultra-pure coal was 97.1%, and the mass ratio of ash in the ultra-pure coal was 0.35% by weight.Embodiment 2400 The g of coal sample A was taken out and mixed with 600 g of sodium hydroxide and 300 ml of water (the mass ratio of sodium hydroxide was 66.7%, the alkali / coal ratio was 3:2, the mass ratio of alkali to coal sample A was 9:4), and the mixture was subjected to kneading reaction at 150° C. in a closed environment under atmospheric pressure for 5 hours. 1L of water was added to dilute and cool the mixture, after 30 minutes, the mixture was subjected to a filtering and washing process to obtain a first solid product (i.e., alkaline coal). 20% by weight of dilute sulfuric acid was added to the alkaline coal according to an acid / coal ratio of 1.1:1 in a counter-current manner, the alkaline coal was subjected to an acid washing treatment at a temperature of 99° C. for 60 minutes per treatment three times, the filtering and washing process was performed, and the filter cake was subjected to drying to obtain a second solid product (i.e., ultra-pure coal). The yield of ultra-pure coal was 97.7%, and the mass ratio of ash in the ultra-pure coal was 0.43% by weight.Embodiment 3400 The g of Coal Sample A was taken out and mixed with 600 g of potassium hydroxide and 200 ml of water (the mass ratio of potassium hydroxide was 75%, the alkali / coal ratio was 3:2, the mass ratio of alkali to Coal Sample A was 8:4), and the mixture was subjected to kneading reaction at 175° C. in a closed environment under atmospheric pressure for 2 hours. 1L of water was added to dilute and cool the mixture, and after 15 minutes, the mixture was subjected to a filtering and washing process to obtain a first solid product (i.e., alkaline coal). 15 wt % of diluted nitric acid was added to the alkaline coal according to an acid / coal ratio of 0.9:1 in counter-current manner, the alkaline coal was subjected four times to an acid washing treatment at a temperature of 75 °C for 5 minutes per treatment, the filtering and washing process was performed, and the filter cake was subjected to drying to obtain a second solid product (i.e., ultra-pure coal). The yield of ultra-pure coal was 98.0 %, and the mass ratio of ash in the ultra-pure coal was 0.78 wt %.Embodiment 4400 The g of coal sample B was taken out and mixed with 160 g of sodium hydroxide and 100 ml of water (the mass ratio of sodium hydroxide was 61.5%, the alkali / coal ratio was 0.4:1, the mass ratio of alkali to coal sample B was 2.6:4), and the mixture was subjected to kneading reaction at 120° C. in a closed environment under atmospheric pressure for 6 hours. 1L of water was added to dilute and cool the mixture, and after 30 minutes, the mixture was subjected to a filtering and washing process to obtain a first solid product (i.e., alkaline coal). 10 wt % of diluted hydrochloric acid was added to the alkaline coal in an acid / coal ratio of 0.4:1 in counter-current manner, the alkaline coal was subjected five times to an acid washing treatment at a temperature of 20° C. for 100 minutes per treatment, the filtering and washing process was performed, and the filter cake was subjected to drying to obtain a second solid product (i.e., ultra-pure coal). The yield of ultra-pure coal was 99.1%, and the mass ratio of ash in the ultra-pure coal was 0.13 wt %.Embodiment 5400 The g of coal sample B was taken out and mixed with 40 g of sodium hydroxide and 40 ml of water (the mass ratio of sodium hydroxide was 50%, the alkali / coal ratio was 0.1:1, the mass ratio of alkali to coal sample B was 0.8:4), and the mixture was subjected to kneading reaction at 200° C. in a closed environment under atmospheric pressure for 0.5 hours. 1L of water was added to dilute and cool the mixture, and after 30 minutes, the mixture was subjected to a filtering and washing process to obtain a first solid product (i.e., alkaline coal). 10 wt % of diluted hydrochloric acid was added to the alkaline coal in an acid / coal ratio of 0.4:1 in counter-current manner, the alkaline coal was subjected to an acid washing treatment at a temperature of 10° C. for 180 minutes per treatment three times, the filtering and washing process was performed, and the filter cake was subjected to drying to obtain a second solid product (i.e., ultra-pure coal). The yield of ultra-pure coal was 99.3%, and the mass ratio of ash in the ultra-pure coal was 0.28% by weight.Embodiment 6400 The g of coal sample A was taken out and mixed with 700 g of sodium hydroxide and 400 ml of water (the mass ratio of sodium hydroxide was 63.6%, the alkali / coal ratio was 7:4, the mass ratio of alkali to coal sample A was 11:4), the mixture was subjected to kneading reaction at 100° C. in a closed environment under atmospheric pressure for 9 hours. 1L of water was added to dilute and cool the mixture, and after 1 hour, the mixture was subjected to a filtration and washing process to obtain a first solid product (i.e., alkaline coal). 10 wt % of diluted hydrochloric acid was added to the alkaline coal in an acid / coal ratio of 1.3:1 in a counter-current manner, the alkaline coal was subjected to an acid washing treatment at a temperature of 99° C. for 30 minutes per treatment three times, the filtering and washing process was performed, and the filter cake was subjected to drying to obtain a second solid product (i.e., ultra-pure coal). The yield of ultra-pure coal was 97.2%, and the mass ratio of ash in the ultra-pure coal was 0.12% by weight.Embodiment 7400 G of coal sample A was taken and mixed with 700 g of sodium hydroxide and 400 ml of water (the mass ratio of sodium hydroxide was 63.6%, the alkali / coal ratio was 7:4, the mass ratio of alkali to coal sample A was 11:4), the mixture remained still at 100° C. in a closed environment under atmospheric pressure for 9 hours. 1L of water was added to dilute and cool the mixture, the mixture was subjected to a filtering and washing process after 1 hour to obtain a first solid product (i.e., alkaline coal). 10 wt % of diluted hydrochloric acid was added to the alkaline coal in an acid / coal ratio of 1.3:1 in a counter-current manner, the alkaline coal was subjected to three times of an acid washing treatment at a temperature of 99° C. for 30 minutes in each treatment, the filtering and washing process was performed, and the filter cake was subjected to drying to obtain a second solid product (i.e., ultra-pure coal). The yield of ultra-pure coal was 97.1%, and the mass ratio of ash in the ultra-pure coal was 0.98 wt %.Comparative Example 1100 The g of coal sample A was taken out and mixed with 200 g of sodium hydroxide and 800 ml of water (the mass ratio of sodium hydroxide was 20%, the alkali / coal ratio was 2:1, the mass ratio of alkali to coal sample A was 10:1), and the mixture was subjected to reaction under stirring at 250° C. under the corresponding saturated steam pressure (about 40 atmospheric pressure) for 6 hours. The mixture was subjected to a filtration and washing process to obtain an alkaline coal. 10 wt % of diluted hydrochloric acid was added to the alkaline coal in an acid / coal ratio of 1.3:1, then leaching was performed at 60° C. for 30 minutes, a filtering and washing process was performed, and the filter cake was subjected to drying to obtain the ultra-pure coal. The yield of ultra-pure coal was 57.9 wt %, and the mass ratio of ash in the ultra-pure coal was 5.67 wt %.Comparative Example 2100 The g of coal sample A was taken out and mixed with 400 g of sodium hydroxide and 600 ml of water (the mass ratio of sodium hydroxide was 40%, the alkali / coal ratio was 4:1, the mass ratio of alkali to coal sample A was 10:1), and the mixture was subjected to reaction under stirring at 250° C. under the corresponding saturated steam pressure (about 40 atmospheric pressure) for 6 hours. The mixture was subjected to a filtration and washing process to obtain an alkaline coal. 10 wt% of diluted hydrochloric acid was added to the alkaline coal at an acid / coal ratio of 1.3:1, then leaching was carried out at 60°C for 30 minutes, a filtering and washing process was carried out, and the filter cake was subjected to drying to obtain the ultra-pure coal. The yield of ultra-pure coal was 65.1 wt %, and the mass ratio of ash in the ultra-pure coal was 3.53 wt %.Comparative Example 3100 The g of coal sample B was taken out and mixed with 80 g of sodium hydroxide and 320 ml of water (the mass ratio of sodium hydroxide was 20%, the alkali / coal ratio was 4:5, the mass ratio of alkali to coal sample B was 4:1), and the mixture was subjected to reaction under stirring at 220° C. under the corresponding saturated steam pressure (about 20 atmospheric pressure) for 6 hours. The mixture was subjected to a filtration and washing process to obtain an alkaline coal. 10 wt% of diluted hydrochloric acid was added to the alkaline coal at an acid / coal ratio of 0.4:1, then leaching was carried out at 75 °C for 30 minutes, the filtering and washing procedure was carried out, and the filter cake was subjected to drying to obtain the ultra-pure coal. The yield of ultra-pure coal was 79.7%, and the mass ratio of ash in the ultra-pure coal was 1.39% by weight.As can be seen from Working Examples 1 to 6 and Comparative Examples 1 to 3, in the high ash coal sample A and the low ash coal sample B, the mass proportion of alkali is 50% or more, the reaction can be carried out under normal pressure, and the activity is increased, the addition amount of alkali can be reduced by more than 50%, and the amount of water used is reduced, the reaction temperature of the alkaline coal can be lowered by 50 to 100° C., and the finally produced ultra-pure coal has a high yield and a significantly reduced ash content. As can be seen from the comparison result of Example 6 and Example 1, the alkaline coal was subjected to an acidic washing treatment in a multistage counter-current contacting, the removal effect of ash can be further improved, and the mass ratio of the ash in the obtained ultra-pure coal can be 0.2% or less. Further, in the alkali coal reaction in Examples 1-6, a kneading process having a reduced amount of pulverized coal and an improved yield of ultra-pure coal as well as an improved removal effect of ash is performed as compared with the stirring process in Comparative Examples 1-3; moreover, the kneading process is advantageous for the removal of ash as the shutdown and reaction process in Example 7.The above content merely represents the specific embodiments of the present application, but the scope of the present invention is not limited thereto. Any modification or replacement readily conceivable by those skilled in the art without departing from the inventive concept of the present invention falls within the scope of the present application. The scope of the present invention is therefore subject to the scope of the claims.

Claims

A method for removing ash in solid carbonaceous materials, characterized by comprising: S1) mixing an alkaline sub-melting salt medium and a solid carbonaceous material to be treated with kneading, heating so that alkali and ash of the solid carbonaceous material to be treated react in the alkaline sub-melting salt medium, then performing solid-liquid separation of the mixed slurry generated from the reaction to obtain a first solid product and an alkali treatment solution, wherein the mass proportion of the alkali in the alkaline sub-melting salt medium is 50% or more; and wherein the mass ratio of the alkali to the solid carbonaceous material to be treated is from 0.1 to 2:1, S2) using an acid solution to perform an acid washing treatment on the first solid product, and performing a solid-liquid separation again to obtain a second solid product and an acid washing solution, wherein the acid washing treatment is performed with the acid solution n times in counter-current contact with the first solid product, where n is equal to or greater than 2.The process for the removal of ash in solid carbonaceous materials according to claim 1, characterized in that the reaction is carried out at a temperature in the range of 100-200°C and a normal pressure for 0.5-9h.The method for removing ash in solid carbonaceous materials according to claim 1 or 2, characterized in that the method for removing ash further comprises cooling the reacted mixed slurry by dilution with water before subjecting the reacted mixed slurry to solid-liquid separation.The method for removing ash in solid carbonaceous materials according to claim 3, characterized in that the temperature after the cooling process is in a range of 10-99°C.The method for removing ash in solid carbonaceous materials according to claim 4, characterized in that the cooling time is 3h or less.The method for removing ash in solid carbonaceous materials according to claim 1, characterized in that the acid washing treatment is performed with the acid solution n times in counter-current contact with the first solid product, wherein the acid washing treatment comprises: a solid product obtained after the i-1th acid washing treatment is subjected to an acid washing treatment using an acid washing solution obtained after the i-th acid washing treatment, and the first solid product is subjected to an acid washing treatment using an acid washing solution obtained after the second acid washing treatment, wherein i is a natural number and 2≤i≤n.The method for removing ash in solid carbonaceous materials according to claim 1, characterized in that the yield of the second solid product is equal to or greater than 95%.The method for removing ash in solid carbonaceous materials according to claim 1 or 7, characterized in that the mass proportion of the ash in the second solid product is 1% or less.The method for removing ash in solid carbonaceous materials according to claim 8, characterized in that the mass proportion of the ash in the second solid product is 0.2% or less.

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