Ash removal method for pulverized coal

Abstract

The invention provides a coal dust deashing method, and belongs to the technical field of coal cleaning and processing. According to the method, the anthracite is subjected to first acidolysis by adopting hydrochloric acid, so that carbonate minerals and metal oxides such as Fe2O3 and CaO in the anthracite are directionally removed; then destroying a silicate crystal structure in the anthracite by adopting a hydrofluoric acid solution so as to deeply desiliconize; and finally, hydrochloric acid is adopted for second acidolysis, insoluble fluorides such as CaF2 generated in the hydrofluoric acid desiliconization stage are dissolved, efficient deashing of anthracite is achieved, and the ash content of finally obtained deashed coal is smaller than or equal to 0.2 wt%. The method has the advantages of extremely high anthracite ash removal efficiency and low cost, is suitable for efficiently cleaning anthracite to prepare subsequent products, and does not cause secondary pollution.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of clean coal processing, and particularly relates to a method for removing ash from pulverized coal. BACKGROUND

[0002] As high-grade coal resources, anthracite in coal is rich in silico-aluminate (such as quartz, kaolinite) and metal oxides (Fe2O3 and CaO, etc.) in ash. Although traditional physical ash removal techniques such as flotation and centrifugal separation can remove part of the large-particle silico-aluminate minerals, the removal efficiency is insufficient for fine minerals with a particle size of less than 10 μm. Research data show that the ash content of anthracite treated by traditional physical methods is still as high as 8 wt% or more, and the mechanical force in physical ash removal can easily cause the collapse of the pore structure of the coal matrix, resulting in a loss of specific surface area of more than 40%, which seriously limits the application of the ash-removed coal in high-end fields such as carbon-based energy storage materials and high-performance adsorbent materials.

[0003] To solve the above technical defects and improve the ash removal efficiency, chemical acid washing is usually used for coal ash removal. Commonly used acid washing reagents include hydrochloric acid and hydrofluoric acid. The dissolution rate of hydrochloric acid for metal oxides in coal can reach 90%, but the removal rate for silico-aluminate is less than 60%. Although hydrofluoric acid can effectively destroy the crystal structure of silico-aluminate and remove silico-aluminate efficiently, it is difficult to remove metal oxides. Moreover, CaF2 and other insoluble fluorides generated by the reaction between hydrofluoric acid and coal can easily adhere to the surface of coal, causing secondary pollution. SUMMARY

[0004] The present application aims to provide a method for removing ash from pulverized coal. The anthracite is sequentially subjected to first acidolysis, desilication and second acidolysis to reduce the ash content in the anthracite without causing secondary pollution by insoluble fluorides.

[0005] To achieve the object of the present application, the present application provides the following technical solutions:

[0006] A method for removing ash from pulverized coal, comprising the following steps:

[0007] The pulverized coal is sequentially subjected to first acidolysis, desilication and second acidolysis to obtain ash-removed coal; the pulverized coal is anthracite;

[0008] The reagent used in the first acidolysis and the second acidolysis is hydrochloric acid, and the reagent used in the desilication is a hydrofluoric acid solution; the molar concentration of the hydrochloric acid is 5-7 mol / L, and the concentration of the hydrofluoric acid solution is 35-45 wt%.

[0009] Preferably, the ash content of the anthracite is 17-25 wt%.

[0010] Preferably, the mass of the anthracite and the volume of the hydrochloric acid are in a ratio of 1:5-10; the mass of the anthracite and the volume of the hydrofluoric acid solution are in a ratio of 1:5-10.

[0011] Preferably, the first acidolysis, desilication and second acidolysis are carried out under water bath conditions; the temperature of the water bath is 55-65℃.

[0012] Preferably, the time of the first acidolysis, desilication and second acidolysis is 2-5h respectively.

[0013] Preferably, the first acidolysis, desilication and second acidolysis further respectively comprise sequentially carrying out solid-liquid separation and solid-phase water washing.

[0014] Preferably, the second acidolysis further comprises drying after the solid-phase water washing.

[0015] The temperature of the drying is 45-55℃, and the time is 10-14h.

[0016] Preferably, the ash content of the deashed coal is ≤0.2wt%.

[0017] The application provides a deashing method of coal powder, characterized by comprising the following steps: sequentially carrying out first acidolysis, desilication and second acidolysis on the coal powder to obtain deashed coal; the coal powder is anthracite; the reagent used in the first acidolysis and second acidolysis is hydrochloric acid; the reagent used in the desilication is a hydrofluoric acid solution; the molar concentration of the hydrochloric acid is 5-7mol / L, and the concentration of the hydrofluoric acid solution is 35-45wt%. The application adopts hydrochloric acid to carry out first acidolysis on coal ash, directionally removes carbonate minerals and metal oxides such as Fe2O3 and CaO in anthracite; then adopts a hydrofluoric acid solution to damage the silicate crystal structure in anthracite, thereby deeply desilicating; finally, adopts hydrochloric acid to carry out second acidolysis, dissolves CaF2 and other insoluble fluorides generated in the hydrofluoric acid desilication stage, realizes efficient deashing of anthracite, and the ash content of the finally obtained deashed coal is ≤0.2wt%. The application has the advantages of high deashing efficiency of anthracite ash and low cost, is suitable for efficient and clean preparation of subsequent products from anthracite, and does not cause secondary pollution. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the application or the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can also be obtained by those skilled in the art without creative effort.

[0019] Figure 1 The flow chart of the deashing method of anthracite in the embodiments of the application;

[0020] Figure 2 The ash content of the de-ashed coal obtained in Example 1 and Comparative Examples 1-3 of the present application is shown in the following table. DETAILED DESCRIPTION

[0021] The present application provides a method for de-ashing coal powder, comprising the following steps:

[0022] The coal powder is sequentially subjected to first acidolysis, desilication and second acidolysis to obtain de-ashed coal; the coal powder is anthracite coal;

[0023] The reagent used in the first acidolysis and the second acidolysis is hydrochloric acid; the reagent used in the desilication is hydrofluoric acid solution; the molar concentration of the hydrochloric acid is 5-7 mol / L, and the concentration of the hydrofluoric acid solution is 35-45 wt%.

[0024] In the present application, all raw materials are commercially available products well known to those skilled in the art, unless otherwise specified.

[0025] In the present application, the ash content of the anthracite coal is 17-25 wt%; the content of oxides in the ash can be Al2O346.2385%, SiO246.0857%, SO32.1878%, TiO21.83%, Fe2O30.9991%, CaO 0.8005%, Na2O 0.7036%, P2O50.6318%, MgO 0.2806%, K2O 0.1071%, SrO 0.0791% and ZrO20.0561%.

[0026] In the present application, the concentration of the hydrochloric acid is 5-7 mol / L, and in specific embodiments, it can be 5.5 or 6 mol / L; the concentration of the hydrofluoric acid solution is 35-45 wt%, and in specific embodiments, it can be 38 or 40 wt%.

[0027] In the present application, the mass ratio of the anthracite coal to the hydrochloric acid is 1:5-10, and in specific embodiments, it can be 1:6 or 1:9; the mass ratio of the anthracite coal to the hydrofluoric acid solution is 1:5-10, and in specific embodiments, it can be 1:6 or 1:9.

[0028] In the present application, the first acidolysis, desilication and second acidolysis are carried out under water bath conditions; the temperature of the water bath is 55-65℃; the stirring speed in the water bath is 600-800 r / min; the time for the first acidolysis, desilication and second acidolysis is 2-5 h, and in specific embodiments, it can be 3 or 4 h.

[0029] In the present invention, the first acid hydrolysis, desiliconization treatment and second acid hydrolysis further include sequential solid-liquid separation and solid-phase water washing; the present invention does not specifically limit the method of solid-liquid separation, and a method well known to those skilled in the art can be used; in a specific embodiment, the solid-phase water washing is carried out in a centrifuge; the rotation speed of the centrifuge is 10,000 to 15,000 r / min.

[0030] In the present invention, the second acid-hydrolyzed solid phase is washed with water and then dried; the drying temperature is 45 to 55° C. and the drying time is 10 to 14 hours.

[0031] The present invention uses the high reactivity of concentrated hydrochloric acid to preferentially dissolve calcium carbonate and metal oxides through the first acid hydrolysis, removing 70-80 wt% of the soluble ash. The reaction during the first acid hydrolysis is as follows:

[0032] CaCO3+2HCl→CaCl2+CO2↑+H2O;

[0033] Fe2O3+6HCl→2FeCl3+3H2O;

[0034] After the first acid hydrolysis, the residue is desiliconized using a hydrofluoric acid solution. Fluoride ions specifically attack silicon-oxygen bonds, decomposing 15-20 wt% of the aluminosilicate ash. The reactions during the desiliconization process are shown below (using SiO2 as an example):

[0035] SiO2+6HF→H2SiF6+2H2O;

[0036] 2HF+CaO→CaF2+H2O;

[0037] After desiliconization, hydrochloric acid is used for secondary acid hydrolysis, which can not only dissolve the CaF2 generated in the hydrofluoric acid desiliconization stage, but also remove the residual fluoride ions, ensuring that the final deashed coal meets environmental protection standards. The reaction during the second acid hydrolysis process is as follows:

[0038] CaF2+2HCl→CaCl2+2HF↑.

[0039] In the present invention, the ash content of the deashed coal is ≤0.2 wt %. In a specific embodiment, it can be 0.18 or 0.12 wt %.

[0040] In order to further illustrate the present invention, the coal pulverized deashing method provided by the present invention is described in detail below with reference to the accompanying drawings and examples, but they should not be construed as limiting the scope of protection of the present invention.

[0041] Example 1

[0042] according to Figure 1 The process shown is to deash anthracite, and the specific steps are:

[0043] Take 5g anthracite powder (ash content 18.54wt%) into 50mL 6mol / L hydrochloric acid, under the condition of constant temperature water bath stirring at 60℃ for 4h, after washing with deionized water for 3-5 times and filtering, add 50mL 40wt% hydrofluoric acid solution into the solid anthracite, under the condition of constant temperature water bath stirring at 60℃ for 4h, after washing with deionized water for 3-5 times and filtering, add 50mL 6mol / L hydrochloric acid, under the condition of constant temperature water bath stirring at 60℃ for 3h, wash with deionized water until the filtrate is neutral, dry the obtained solid anthracite at 50℃ for 12h, and obtain the de-ashed coal.

[0044] Comparative Example 1

[0045] Take 5g anthracite powder into 50mL 6mol / L hydrochloric acid, under the condition of constant temperature water bath stirring at 60℃ for 4h, wash with deionized water until the filtrate is neutral, dry the obtained solid anthracite at 50℃ for 12h, and obtain the de-ashed coal.

[0046] Comparative Example 2

[0047] Take 5g anthracite powder into 50mL 6mol / L hydrochloric acid, under the condition of constant temperature water bath stirring at 60℃ for 4h, after washing with deionized water for 3-5 times and filtering, add 50mL 40wt% hydrofluoric acid solution into the solid anthracite, under the condition of constant temperature water bath stirring at 60℃ for 4h, wash with deionized water until the filtrate is neutral, dry the obtained solid anthracite at 50℃ for 12h, and obtain the de-ashed coal.

[0048] Comparative Example 3

[0049] Take 5g anthracite powder into 50mL 40wt% hydrofluoric acid solution, under the condition of constant temperature water bath stirring at 60℃ for 4h, wash with deionized water until the filtrate is neutral, dry the obtained solid anthracite at 50℃ for 12h, and obtain the de-ashed coal.

[0050] Comparative Example 4

[0051] Take 5g anthracite powder into 50mL 40wt% hydrofluoric acid solution, under the condition of constant temperature water bath stirring at 60℃ for 4h, after washing with deionized water for 3-5 times and filtering, add 50mL 6mol / L hydrochloric acid into the solid anthracite, under the condition of constant temperature water bath stirring at 60℃ for 4h, under the condition of constant temperature water bath stirring at 60℃ for 3h, wash with deionized water until the filtrate is neutral, dry the obtained solid anthracite at 50℃ for 12h, and obtain the de-ashed coal, and the ash content of the de-ashed coal is measured as 0.65wt%.

[0052] Comparative Example 5

[0053] Take 5g anthracite powder (ash content 18.54wt%) into 50mL 3mol / L hydrochloric acid, under the condition of constant temperature water bath stirring at 60℃ for 4h, after washing with deionized water for 3-5 times and filtering, add 50mL 10wt% hydrofluoric acid solution into the solid anthracite, under the condition of constant temperature water bath stirring at 60℃ for 4h, after washing with deionized water for 3-5 times and filtering, add 50mL 6mol / L hydrochloric acid, under the condition of constant temperature water bath stirring at 60℃ for 3h, after washing with deionized water until the filtrate is neutral, dry the obtained solid anthracite at 50℃ for 12h, to obtain the deashed coal, and measure the ash content of the deashed coal as 10wt%.

[0054] Figure 2 The ash content of the deashed coal obtained in Example 1 and Comparative Examples 1-3 is shown in the following table. Figure 2 It can be seen that the ash content of the anthracite can be removed to below 0.2wt% by the present application.

[0055] Although the above embodiment has described the present application in detail, it is only a part of the embodiments of the present application, not all the embodiments, and other embodiments can be obtained according to the present embodiment without creativity, which all belong to the protection scope of the present application.

Claims

1. A method for deashing coal powder, characterized in that: The following steps are involved: The pulverized coal is subjected to a first acid hydrolysis, a desiliconization, and a second acid hydrolysis in sequence to obtain deashed coal; the pulverized coal is anthracite; The reagents used in the first acidolysis and the second acidolysis are hydrochloric acid; the reagent used in the desiliconization is hydrofluoric acid solution; The molar concentration of the hydrochloric acid is 5-7 mol / L, and the concentration of the hydrofluoric acid solution is 35-45 wt %.

2. The deashing method according to claim 1, wherein The anthracite has an ash content of 17-25 wt%.

3. The deashing method according to claim 1 or 2, characterized in that The mass ratio of the anthracite to the hydrochloric acid is 1:5-10; the mass ratio of the anthracite to the hydrofluoric acid solution is 1:5-10.

4. The deliming method according to claim 1, wherein The first acidolysis, desiliconization and second acidolysis are carried out in a water bath; the temperature of the water bath is 55-65°C.

5. The deliming method according to claim 1 or 4, characterized in that The time for the first acid hydrolysis, desiliconization and second acid hydrolysis is 2 to 5 hours respectively.

6. The deliming method according to claim 1, characterized in that The first acid hydrolysis, desiliconization and second acid hydrolysis further include: sequentially performing solid-liquid separation and solid-phase water washing.

7. The deliming method according to claim 6, characterized in that The second acid-hydrolyzed solid phase is washed with water and then dried; The drying temperature is 45-55° C. and the drying time is 10-14 hours.

8. The deliming method according to claim 1, characterized in that The ash content of the deashed coal is ≤0.2 wt%.

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