Efficient dechlorination method for Xinjiang high-chlorine coal

Abstract

The invention belongs to the field of coal processing, and particularly relates to an efficient dechlorination method for Xinjiang high-chlorine coal, which comprises the following steps: 1) crushing the high-chlorine coal into a coal sample with the particle size of less than 0.2-10 mm, carrying out 2.45 GHz microwave radiation pretreatment for 2-5 minutes, and mixing the coal sample with deionized water according to the mass ratio of the coal sample to distilled water of 2-4 to obtain a mixed solution; (2) putting the mixed solution into a constant-temperature water bath kettle, and stirring for 5-120 minutes at the temperature of 5-40 DEG C; and 3) separating the mixed liquid and drying to obtain the upgraded coamer.According to the method, deionized water is selected for eluting water-soluble chlorine in the high-chlorine coal, and the dechlorination rate can reach 84% or above. The method is safe, low in cost, easy to operate and good in dechlorination effect, has industrial popularization potential and provides an efficient and feasible method for stokehole dechlorination of the Xinjiang high-chlorine coal.

Description

Technical Field

[0001] This invention belongs to the field of coal processing, specifically relating to an efficient dechlorination method for high-chlorine coal in Xinjiang, applicable to the effective dechlorination and upgrading of high-chlorine coal mainly composed of soluble chlorine minerals. Background Technology

[0002] High-chlorine coal refers to a special type of coal with a chlorine content greater than 0.3%, mainly distributed in the Turpan and Hami regions of Xinjiang, my country. Its predicted reserves are nearly 100 billion tons. It possesses low ash content, a good ignition point, and good combustion characteristics, making it a highly promising energy resource. However, due to historical reasons for coal formation and the unique natural geographical location of the region, the chlorine content of Xinjiang high-chlorine coal is significantly higher than average, exceeding 0.3% (with some exceeding 1%), far exceeding the chlorine content range of other coal types in my country (0.01%~0.20%). Furthermore, the chlorine in the coal mainly exists in the form of inorganic soluble chlorine, accounting for approximately 92% of the total chlorine content in raw coal. During the thermal conversion process of high-chlorine coal, chlorine is released from the coal to generate corrosive gases (mainly HCl), exacerbating equipment corrosion, affecting the long-term stable operation of the process system, and severely restricting the development and utilization of high-chlorine coal.

[0003] Existing dechlorination technologies mainly focus on dechlorination treatment of flue gas after raw coal combustion, with relatively few methods for dechlorination at the source. Furthermore, Xinjiang's high-chlorine coal differs from other coal types; its chlorine-containing components are primarily soluble inorganic chlorides, and efficient dechlorination can be achieved by adjusting water washing parameters. Chinese patent CN 117414942 A discloses a method for dechlorination based on different preset washing machine durations according to coal sample particle size classification. However, this method's jig is ineffective for dechlorinating large-particle coal (>10 mm), and excessively long washing times generate excessive coal slime, affecting subsequent dewatering. Chinese patent CN112625771 A discloses a water washing dechlorination method for chlorinated coal, proposing the addition of organic solvents as additives to the washing liquid to improve the washing rate. Although this increases the dechlorination rate to 45%~86%, the addition of additives, high water consumption, complex water treatment, and high treatment costs prevent its application in large-scale industrial production.

[0004] Therefore, based on the characteristics of chlorine in high-chlorine coal in Xinjiang, which is mainly composed of inorganic soluble chlorine, and long-term experimental research, this invention proposes a more efficient and lower-cost method for removing water-soluble chlorine through microwave radiation pretreatment and water washing parameter adjustment, providing a technical reference for the industrialization of source dechlorination of high-chlorine coal. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a highly efficient dechlorination method for high-chlorine coal from Xinjiang. This method is suitable for removing chlorine-containing media from high-chlorine coal in Xinjiang, which is primarily composed of soluble chlorine minerals. It solves the problems of poor dechlorination efficiency, high water consumption, and high dechlorination costs associated with current raw coal furnace dechlorination methods. The detailed technical solution of this invention is as follows, including the following steps: 1) The raw coal is crushed and screened, and coal samples of different particle sizes are screened out and then subjected to microwave pretreatment; 2) Mix the sieved coal samples with water in a certain proportion to prepare a coal-water mixture; 3) Based on the desorption characteristics of chlorine in coal during the water washing process, effective dechlorination is achieved by stirring at low speed (20 r / min) for a certain period of time at a set temperature; 4) After the coal-water mixture is processed in step 3), it is separated, filtered, and dried to obtain dechlorinated coal.

[0006] Among the above-mentioned efficient dechlorination methods for high-chlorine coal in Xinjiang: In step 1), the particle sizes of the coal samples obtained by crushing and screening are <10 mm, <5 mm, <2 mm, and <0.2 mm, which are in line with the actual industrial applications. In step 1), the microwave pretreatment of the coal sample uses a microwave frequency of 2.45 GHz, a power of 400-700 W, and a pretreatment time of 2-5 min. The water used for mixing the coal in step 2) is deionized water; In step 2), the mass ratio of water to high-chlorine coal in the coal-water mixture is 2-4. In step 3), the temperature range of the coal-water mixture is 5~40℃, the stirring speed is about 20 r / min, and the stirring time is 5~120 min. In step 5), the drying temperature used is 80°C.

[0007] This invention discloses a method for efficient dechlorination of high-chlorine coal in Xinjiang, with a chlorine removal rate of >84%. When the particle size is <2 mm, the synergistic effect of a water-coal ratio of 4:1 and 40℃ can make the dechlorination rate exceed 95%.

[0008] The present invention discloses a highly efficient dechlorination and dealkali removal method for high-chlorine coal in Xinjiang. Compared with existing technologies, this method offers the following advantages: During the pure water washing process, water molecules penetrate the coal matrix through osmosis and react with chloride ions in the coal to form hydrated chloride ions (Cl⁻·nH₂O), which are easily removed from the coal sample. Simultaneously, the mechanical stirring and water flow impact during the washing process further promote the desorption and diffusion of chloride ions from the coal sample surface and pores, ultimately resulting in efficient dechlorination through the washing liquid discharge system. This mechanism achieves significant dechlorination without the need for chemical additives, relying solely on physical action. It features low water consumption, short washing time, low requirements on coal particle size, and significant dechlorination effect (dechlorination rate can reach over 84%). It also boasts advantages such as simple operation, low equipment requirements, low cost, and environmental friendliness, making it easily applicable for large-scale industrial applications. Attached Figure Description

[0009] Figure 1 XRD patterns of ash content in raw coal and washed coal samples.

[0010] Figure 2 SEM-EDS images of raw coal and washed coal samples. Detailed Implementation

[0011] The present invention will now be described through specific embodiments. Unless otherwise specified, all technical means used in this invention are methods well known to those skilled in the art. Furthermore, the embodiments should be understood as illustrative, not limiting, of the scope of the invention; the essence and scope of the invention are defined only by the claims. For those skilled in the art, various changes or modifications to these embodiments, without departing from the essence and scope of the invention, also fall within the protection scope of this invention.

[0012] The following examples use high-chlorine coal from Hami region, Xinjiang: According to GB / T 3558-2014, the method for determining chlorine content in coal, the chlorine content was determined using the Eschka mixture fusion-IC test. The chlorine content in the filtrate after water washing and dechlorination treatment was determined using IC. Examples of some experiments and results conducted by the inventors during actual research are provided to further illustrate the invention. All examples were repeated three times, and the data are averages. Example 1

[0013] (1) Grind and screen the high-chlorine coal to a particle size of <2 mm, and microwave pretreat it for 5 min at a microwave frequency of 2.45 GHz and a power of 700 W. (2) The sieved coal sample is mixed with distilled water and stirred continuously at 20 r / min at 25℃ for 5 min to prepare a mixture; wherein the mass ratio of the coal sample to the distilled water is 1:4. (3) Separate the above mixture to obtain dechlorination liquid and wet coal.

[0014] (4) Place the wet coal in a drying device at 80°C to dry it, and cool the dried product to room temperature to obtain upgraded coal. Example 2

[0015] (1) Grind and screen the high-chlorine coal to a particle size of <5 mm, and pre-treat it with microwave for 5 min at a microwave frequency of 2.45 GHz and a power of 700 W. (2) The sieved coal sample is mixed with distilled water and stirred continuously at 20 r / min at 25℃ for 5 min to prepare a mixture; wherein the mass ratio of the coal sample to the distilled water is 1:4. (3) Separate the above mixture to obtain dechlorination liquid and wet coal.

[0016] (4) Place the wet coal in a drying device at 80°C to dry it, and cool the dried product to room temperature to obtain upgraded coal. Example 3

[0017] (1) Grind and screen the high-chlorine coal to a particle size of <10 mm, and microwave pretreat it for 5 min at a microwave frequency of 2.45 GHz and a power of 700 W. (2) The sieved coal sample is mixed with distilled water and stirred continuously at 20 r / min at 25℃ for 5 min to prepare a mixture; wherein the mass ratio of the coal sample to the distilled water is 1:4. (3) Separate the above mixture to obtain dechlorination liquid and wet coal.

[0018] (4) Place the wet coal in a drying device at 80°C to dry it, and cool the dried product to room temperature to obtain upgraded coal. Example 4

[0019] (1) Grind and screen the high-chlorine coal to a particle size of <0.2 mm, and microwave pretreat it for 5 min at a microwave frequency of 2.45 GHz and a power of 700 W; (2) The sieved coal sample is mixed with distilled water and stirred continuously at 20 r / min at 25℃ for 120 min to prepare a mixture; wherein the mass ratio of the coal sample to the distilled water is 1:4. (3) Separate the above mixture to obtain dechlorination liquid and wet coal.

[0020] (4) Place the wet coal in a drying device at 80°C to dry it, and cool the dried product to room temperature to obtain upgraded coal. Example 5

[0021] (1) Grind and screen the high-chlorine coal to a particle size of <2 mm, and microwave pretreat it for 5 min at a microwave frequency of 2.45 GHz and a power of 700 W. (2) The sieved coal sample is mixed with distilled water and stirred continuously at 20 r / min at 25℃ for 120 min to prepare a mixture; wherein the mass ratio of the coal sample to the distilled water is 1:2. (3) The above mixture is separated to obtain washing liquid and wet coal.

[0022] (4) Place the wet coal in a drying device at 80°C to dry it, and cool the dried product to room temperature to obtain upgraded coal. Example 6

[0023] (1) Grind and screen the high-chlorine coal to a particle size of <2 mm, and pre-treat it with microwave for 2 min at a microwave frequency of 2.45 GHz and a power of 700 W. (2) The sieved coal sample is mixed with distilled water and stirred continuously at 20 r / min at 25℃ for 120 min to prepare a mixture; wherein the mass ratio of the coal sample to the distilled water is 1:3. (3) The above mixture is separated to obtain washing liquid and wet coal.

[0024] (4) Place the wet coal in a drying device at 80°C to dry it, and cool the dried product to room temperature to obtain upgraded coal. Example 7

[0025] (1) Grind and screen the high-chlorine coal to a particle size of <2 mm, and pre-treat it with microwave for 3 min at a microwave frequency of 2.45 GHz and a power of 700 W. (2) The sieved coal sample is mixed with distilled water and stirred continuously at 20 r / min at 25℃ for 120 min to prepare a mixture; wherein the mass ratio of the coal sample to the distilled water is 1:4. (3) The above mixture is separated to obtain washing liquid and wet coal.

[0026] (4) Place the wet coal in a drying device at 80°C to dry it, and cool the dried product to room temperature to obtain upgraded coal. Example 8

[0027] (1) Grind and screen the high-chlorine coal to a particle size of <2 mm, and microwave pretreat it for 4 min at a microwave frequency of 2.45 GHz and a power of 700 W. (2) The sieved coal sample is mixed with distilled water and stirred continuously at 20 r / min at 25℃ for 30 min to prepare a mixture; wherein the mass ratio of the coal sample to the distilled water is 1:4. (3) The above mixture is separated to obtain washing liquid and wet coal.

[0028] (4) Place the wet coal in a drying device at 80°C to dry it, and cool the dried product to room temperature to obtain upgraded coal. Example 9

[0029] (1) Grind and screen the high-chlorine coal to a particle size of <2 mm, and microwave pretreat it for 5 min at a microwave frequency of 2.45 GHz and a power of 700 W. (2) The sieved coal sample is mixed with distilled water and stirred continuously at 5°C for 120 min at a stirring speed of 20 r / min to prepare a mixture; wherein the mass ratio of the coal sample to the distilled water is 1:4. (3) The above mixture is separated to obtain washing liquid and wet coal.

[0030] (4) Place the wet coal in a drying device at 80°C to dry it, and cool the dried product to room temperature to obtain upgraded coal. Example 10

[0031] (1) Grind and screen the high-chlorine coal to a particle size of <2 mm, and microwave pretreat it for 5 min at a microwave frequency of 2.45 GHz and a power of 700 W. (2) The sieved coal sample is mixed with distilled water and stirred continuously at 40°C for 120 min at a stirring speed of 20 r / min to prepare a mixture; wherein the mass ratio of the coal sample to the distilled water is 1:4. (3) The above mixture is separated to obtain washing liquid and wet coal.

[0032] (4) Place the wet coal in a drying device at 80°C to dry it, and cool the dried product to room temperature to obtain upgraded coal.

[0033] Test Instance Chlorine removal rate test in coal. The determination method is as follows: The chlorine content in coal is determined according to the method of "Determination of Chlorine in Coal" (GB / T 3558-2014). The chloride ion content of the leaching filtrate is determined by IC (ion chromatography), and the chlorine removal rate in high-chlorine coal is calculated. After water washing pretreatment, the total chlorine removal efficiency of high-chlorine coal is above 84%. If the treatment temperature is increased to 40℃, the dechlorination rate can reach above 96%. The residual chlorine content in the coal after water washing is 0.25%, and can be as low as 0.05%.

[0034] After being crushed, the coal samples were treated with microwave irradiation, which vaporized the bound water in the coal and created microcracks, increasing the porosity of the coal structure and reducing the diffusion resistance of chloride ions during subsequent water washing. The high-chlorine coal samples from Examples 1 and 5, before and after treatment, were placed in a muffle furnace and heated to 500°C for 1 hour. The phase composition of their ash was then determined using XRD, and the results are as follows: Figure 1 As shown. According to Figure 1 The XRD phase spectra of the high-chlorinated coal and Example 5 are shown. The characteristic peaks of NaCl and CaCO3 in the high-chlorinated coal are obvious, and characteristic peaks of SiO2 and CaSO4 are also observed. After water washing, the diffraction peaks of NaCl and CaSO4 in the coal sample disappear, while the diffraction peak of CaCO3 increases. This is because a large amount of chlorides (such as NaCl) desorb and dissolve from the coal during the water washing process, resulting in a relative increase in the CaCO3 content. In summary, water washing can effectively remove substances such as NaCl and CaSO4 from high-chlorinated coal. SEM-EDS testing was also performed on the coal sample treated in Example 5, and the results are shown below. Figure 2 As shown in Figures a and a-1, these are SEM images of high-chlorine coal before and after water washing. The surface of the raw coal is smooth. After water washing, its microstructure changes, the surface structure of the coal sample collapses, and micropores appear. Combined with XRD analysis, it can be seen that this is mainly because water washing removes some minerals from the coal sample.

[0035] Those skilled in the art will readily understand that the above description is only a part of the embodiments of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for efficient dechlorination of high-chlorine coal in Xinjiang, characterized in that... Includes the following steps: 1) The raw coal was crushed and screened into coal samples with a particle size of <0.2-10 mm, and then microwave pretreated (frequency 2.45 GHz, power 700 W, time 2-5 min). 2) Mix the sieved coal samples with deionized water at a mass ratio of 2-4:1 to obtain a coal-water mixture; 3) Stir the coal-water mixture obtained in step 2) at 5-40℃ and 20 r / min for 5-120 min; 4) After the coal-water mixture is separated and filtered following step 3), it is dried at 80°C to obtain dechlorinated coal.

2. The efficient dechlorination method for high-chlorine coal in Xinjiang according to claim 1, characterized in that: In step 1), the particle sizes of the raw coal crushed and screened coal samples are <10 mm, <5 mm, <2 mm, and <0.2 mm, respectively.

3. The efficient dechlorination method for high-chlorine coal in Xinjiang according to claim 1, characterized in that: In step 1), the crushed coal sample is subjected to microwave pretreatment for 2-5 minutes at a microwave frequency of 2.45 GHz and a power of 400-700 W.

4. The efficient dechlorination method for high-chlorine coal in Xinjiang according to claim 1, characterized in that: In step 2), the mass ratio of water to high-chlorine coal is 2-4:1, and the water used for coal washing is deionized water.

5. The efficient dechlorination method for high-chlorine coal in Xinjiang according to claim 1, characterized in that: In step 3), the coal-water mixture is stirred, with a stirring speed of 20 r / min, a stirring time of 5~120 min, and a temperature of 5~40℃.

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