High-chlorine coal deep deashing and dechlorination process and system

Abstract

The application discloses a high-chlorine coal deep descaling and dechlorination process and system, and the process comprises the following steps: S1, pre-screening of high-chlorine coal raw coal; S2, the third particle size level raw coal is separated by using a five-stage jig, the second particle size level raw coal is separated by using a two-stage jig, and the first particle size level raw coal enters a slime water barrel; after centrifugal dehydration of jig clean coal, dechlorination clean coal is obtained, jig gangue is discharged, and after centrifugal dehydration of jig medium coal, dechlorination medium coal is obtained; S3, the product in the slime water barrel is first separated into fine particles and coarse particles by using a classification cyclone, the fine particles enter flotation, and the coarse particles enter a liquid-solid fluidized bed for dechlorination; S4, all the dechlorination clean coal and the dechlorination medium coal are subjected to desulfurization treatment respectively, and final clean coal products and medium coal products are obtained. Through improvement of the descaling and dechlorination process of high-chlorine coal, the application can realize efficient descaling and dechlorination of high-chlorine coal, improves the sustainability and economic benefits of the use of high-chlorine coal, and has important significance for the coal industry.

Description

Technical Field

[0001] This invention relates to the field of coal processing technology, and in particular to a deep deashing and dechlorination process and system for high-chlorine coal. Background Technology

[0002] Coal has long been considered one of the world's major energy resources, widely used in power generation, industrial manufacturing, heating, and various other fields. However, some coal mined from certain mines has a high chlorine content, leading to severe fouling and corrosion problems when burned in boilers, significantly limiting its utilization. Chlorine is one of the important harmful trace elements in coal; high-chlorine coal easily produces HCl when it comes into contact with water, which corrodes process equipment, causing economic losses and environmental impacts. During the pyrolysis, combustion, and gasification of coal, chlorine in the coal undergoes complex chemical changes and is transferred into the flue gas, forming various chlorine-containing substances such as HCl, Cl2, and inorganic salts. This not only causes serious environmental pollution and endangers human health, but the volatilization of chlorine also causes fouling, slagging, and corrosion problems on boilers and tail-end heating surfaces, posing significant safety hazards to equipment.

[0003] Therefore, it is now necessary to conduct research on key technologies for washing and dechlorinating high-chlorine coal, and propose a process scheme for washing, deashing, and dechlorinating high-chlorine coal suitable for industrial production. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a deep deashing and dechlorination process and system for high-chlorine coal, which addresses the shortcomings of the prior art.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a deep deashing and dechlorination process for high-chlorine coal, comprising the following steps:

[0006] S1. High-chlorine coal is pre-screened. The raw coal product on the screen is crushed and then enters the grading screen together with the raw coal product under the screen to be graded into the first particle size grade, the second particle size grade, and the third particle size grade. The particle size of the first particle size grade, the second particle size grade, and the third particle size grade increases sequentially.

[0007] S2 and the third-size raw coal are separated by a five-stage jig, the second-size raw coal is separated by a two-stage jig, and the first-size raw coal enters the coal slurry bucket.

[0008] The jigged clean coal obtained from the five-stage jig and the two-stage jig both enter the clean coal vibrating screen for dewatering. The oversize product from the clean coal vibrating screen is centrifuged by the first clean coal centrifuge to obtain dechlorinated clean coal, and the undersize product enters the coal slurry water tank.

[0009] The jigging gangue obtained from the five-stage jig and the two-stage jig is discharged, and the jigging middlings are all fed into the middlings vibrating screen for dewatering. The oversize product of the middlings vibrating screen is centrifuged by the first middlings centrifuge to obtain dechlorinated middlings, and the undersize product is fed into the coal slurry water tank.

[0010] S3. The product in the coal slurry bucket is first separated into fine and coarse particles by a classifying hydrocyclone. The fine particles enter the flotation, and the obtained flotation clean coal is collected into dechlorination clean coal after pressure filtration. The flotation tailings are collected into dechlorination middlings after pressure filtration.

[0011] Coarse particles enter a liquid-solid fluidized bed for dechlorination. The solid products obtained from the overflow of the liquid-solid fluidized bed after dewatering are collected into dechlorinated clean coal, and the solid products obtained from the underflow after dewatering are collected into dechlorinated middlings.

[0012] S4. All dechlorinated clean coal and dechlorinated middlings are subjected to desulfurization treatment to obtain the final clean coal product and middlings product.

[0013] Preferably, in step S1, the screening particle size of the high-chlorine coal pre-screening is 10mm, and the raw coal product on the screen is crushed to below 10mm.

[0014] The particle size ranges of the first, second, and third particle size grades of raw coal are -0.2 mm, 0.2-5 mm, and 5-10 mm, respectively.

[0015] Preferably, the two-stage jig includes a main jigging section and a secondary jigging section. The jigged gangue obtained from the underflow of the main jigging section is discharged and the overflow enters the secondary jigging section. The underflow of the secondary jigging section yields jigged middlings and the overflow yields jigged clean coal.

[0016] The five-stage jig consists of a main jigging stage and four secondary jigging stages. The jigged gangue obtained from the underflow of the main jigging stage is discharged and the overflow enters the secondary jigging stages. The overflow of each secondary jigging stage enters the next secondary jigging stage in sequence. The underflow of the four secondary jigging stages is collected to obtain jigged middlings, and the overflow of the last secondary jigging stage is obtained to obtain jigged clean coal.

[0017] Preferably, the screening particle sizes of the clean coal vibrating screen and the middlings vibrating screen are 0.2-5mm and 5-10mm, respectively.

[0018] Preferably, the fine particles obtained by the classifying hydrocyclone have a particle size of -0.5 mm and the coarse particles have a particle size of +0.5 mm.

[0019] Preferably, the overflow of the liquid-solid fluidized bed is dewatered by a clean coal dewatering screen and then by a second clean coal centrifuge, and the resulting solid products are collected in the dechlorinated clean coal; the underflow is dewatered by a middlings dewatering screen and then by a second middlings centrifuge, and the resulting solid products are collected in the dechlorinated middlings.

[0020] Preferably, in step S3, a flotation machine is used for flotation, and the flotation collector is kerosene and the frother is 2-octanol.

[0021] Preferably, the desulfurization treatment process for dechlorinated clean coal and dechlorinated middlings coal is the same, both including the following steps:

[0022] 1) Add dechlorinated clean coal or dechlorinated middlings to water, stir evenly to prepare a coal slurry with a solid-liquid ratio of 0.25-5 kg / L, add H2O2 solution and desulfurization enhancer, control the mass concentration of H2O2 in the coal slurry to 0.5-2%, and add the desulfurization enhancer at a mass of 0.15-2.5% of the coal addition amount, and stir for 15-90 min;

[0023] 2) The coal slurry is treated with ultrasound for 0.5-3 hours at a temperature of 25-35℃; the ultrasonic power is 400-650W and the frequency is 50-250kHz.

[0024] 3) After the treatment is completed, the solid product is filtered, washed with water, and dried to obtain the desulfurized coal product, which is the final clean coal product or middlings product.

[0025] Preferably, the desulfurization enhancer is prepared by the following method:

[0026] 1-1) Take 0.72-2.88g of citric acid, 0.26-0.90g of urea, 0.27-1.06g of acridine orange, and 0.30-1.20g of ferric sulfate and add them to a mixed solution consisting of 50-200mL of ethanol and 75-300mL of deionized water. Disperse the mixture by sonication for 15-60min to obtain the precursor solution.

[0027] 1-2) Transfer the precursor solution to a polytetrafluoroethylene-lined reactor and react at 180-200℃ for 6-12 hours. After the reaction is completed, cool to room temperature and filter the product through a 0.22μm microporous membrane. Then, dialyze the product in deionized water for 12-48 hours using a dialysis bag with a molecular weight cutoff of 800D. After dialysis, take the solution from the dialysis bag and freeze-dry it to obtain the desulfurization enhancer.

[0028] The present invention also provides a deep deashing and dechlorination system for high-chlorine coal, which uses the process described above to process high-chlorine coal for deashing and dechlorination.

[0029] The beneficial effects of this invention are:

[0030] This invention provides a deep deashing and dechlorination process and system for high-chlorine coal. By improving the deashing and dechlorination process of high-chlorine coal, it can achieve efficient deashing and dechlorination of high-chlorine coal, unify the dechlorination and deashing of high-chlorine coal, improve the production efficiency of the entire coal dechlorination process, improve the sustainability and economic benefits of the use of high-chlorine coal, meet the ever-growing coal demand, and is of great significance to the coal industry.

[0031] This invention has found that the dechlorination effect varies significantly when using jigs with different numbers of stages for raw coal of different particle sizes. Therefore, five-stage jigs and two-stage jigs can be used to treat raw coal by particle size to improve the dechlorination effect.

[0032] This invention overcomes the problem of sulfur enrichment in clean coal and middlings caused by the jigging washing process by adding a desulfurization section after coal dechlorination, thus achieving efficient re-desulfurization treatment of dechlorinated coal. In combination with jigging, it can improve the quality of coal products and ultimately achieve efficient deashing, dechlorination and desulfurization of coal.

[0033] This invention improves the conventional H2O2 oxidation desulfurization process by employing a desulfurization synergist with strong oxidizing power and acoustic sensitivity, combined with ultrasonic action in conjunction with H2O2 oxidation desulfurization, which significantly enhances sulfur removal efficiency. Under ultrasonic excitation, the desulfurization synergist of this invention can transfer energy to the ground-state oxygen of water molecules, thereby generating singlet oxygen with strong oxidizing power. 1 Substances such as O2 and hydroxyl radicals (·OH) can oxidize inorganic and organic sulfur in the H2O2 system to form soluble sulfur salts, thereby removing sulfur from coal; and the desulfurization enhancer can also play a certain catalytic enhancement role in the oxidation of H2O2. Attached Figure Description

[0034] Figure 1 This is a flowchart of the deep deashing and dechlorination process for high-chlorine coal according to the present invention;

[0035] Figure 2 This is a schematic diagram illustrating the principle and structure of the two-stage jig of the present invention;

[0036] Figure 3 This is a schematic diagram of the principle structure of the five-stage jig of the present invention;

[0037] Figure 4 The test results show the effect of particle size and number of jigging stages on the chlorine removal rate of jigging water.

[0038] Figure 5 The results are the composition analysis of raw coal and the composition analysis of ash in clean coal after jigging and dechlorination.

[0039] Figure 6XRD patterns of ash content in raw coal and clean coal after jigging and dechlorination at different temperatures;

[0040] Figure 7 The infrared absorption spectrum of the desulfurization enhancer prepared in Example 1 of the present invention;

[0041] Figure 8 The oxidation performance test results are for the desulfurization enhancer prepared in Example 1 of the present invention. Detailed Implementation

[0042] The present invention will be further described in detail below with reference to embodiments, so that those skilled in the art can implement it based on the description.

[0043] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0044] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples are commercially available. For examples where specific conditions are not specified, conventional conditions or conditions recommended by the manufacturer are followed. For reagents or instruments whose manufacturers are not specified, they are all commercially available products.

[0045] Reference Figure 1 This invention provides a deep deashing and dechlorination process for high-chlorine coal, comprising the following steps:

[0046] S1. High-chlorine coal is pre-screened. The raw coal product on the screen is crushed and then enters the grading screen together with the raw coal product under the screen to be graded into the first particle size grade, the second particle size grade, and the third particle size grade. The particle size of the first particle size grade, the second particle size grade, and the third particle size grade increases sequentially.

[0047] In a preferred embodiment, the screening particle size of the high-chlorine coal pre-screening is 10 mm, and the raw coal product on the screen is crushed to below 10 mm; the particle size ranges of the first particle size grade raw coal, the second particle size grade raw coal, and the third particle size grade raw coal are -0.2 mm, 0.2-5 mm, and 5-10 mm, respectively.

[0048] S2 and the third-size raw coal are separated by a five-stage jig, the second-size raw coal is separated by a two-stage jig, and the first-size raw coal enters the coal slurry tank.

[0049] The jigged clean coal obtained from the five-stage jig and the two-stage jig both enter the clean coal vibrating screen for dewatering. The oversize product from the clean coal vibrating screen is centrifuged by the first clean coal centrifuge to obtain dechlorinated clean coal, and the undersize product enters the coal slurry water tank.

[0050] The jigging gangue obtained from the five-stage jig and the two-stage jig is discharged, and the jigging middlings are all fed into the middlings vibrating screen for dewatering. The oversize product of the middlings vibrating screen is centrifuged by the first middlings centrifuge to obtain dechlorinated middlings, and the undersize product is fed into the coal slurry water tank.

[0051] Reference Figure 2 The two-stage jig includes a main jigging section and a secondary jigging section. The jigged gangue obtained from the underflow of the main jigging section is discharged and the overflow enters the secondary jigging section. The underflow of the secondary jigging section yields jigged middlings and the overflow yields jigged refined coal.

[0052] Reference Figure 3 The five-stage jig includes a main jigging stage and four secondary jigging stages. The jigged gangue obtained from the underflow of the main jigging stage is discharged and the overflow enters the secondary jigging stages. The overflow of each secondary jigging stage enters the next secondary jigging stage in sequence. The underflow of the four secondary jigging stages is collected to obtain jigged middlings, and the overflow of the last secondary jigging stage is obtained to obtain jigged clean coal.

[0053] In a preferred embodiment, the screening particle sizes of the clean coal vibrating screen and the middlings vibrating screen are 0.2-5mm and 5-10mm, respectively.

[0054] Based on the high water solubility of chlorine, this invention employs a jigging process to separate high-chlorine coal, allowing water-soluble chlorine compounds to enter the water, and then removing the chlorine from the coal through solid-liquid separation, thereby achieving efficient dechlorination while deashing.

[0055] The applicant's research revealed that the dechlorination effect varies significantly depending on the number of jigging stages used for raw coal of different particle sizes. For raw coal with a particle size of -5mm (i.e., below 5mm), the dechlorination effect is not sensitive to the number of jigging stages; there is little difference between using two-stage, three-stage, four-stage, and five-stage jigging. To improve efficiency, two-stage jigging is preferred. For raw coal with a particle size of 5-10mm, five-stage jigging significantly outperforms one- to four-stage jigging. Therefore, five-stage jigging is the preferred process for this particle size range.

[0056] S3. The product in the coal slurry bucket is first separated into fine and coarse particles by a classifying hydrocyclone. The fine particles enter the flotation process, and the obtained flotation clean coal is filtered by a clean coal filter press and then collected into dechlorination clean coal. The flotation tailings are filtered by a tailings filter press and then collected into dechlorination middlings.

[0057] Coarse particles enter a liquid-solid fluidized bed for dechlorination. The overflow from the liquid-solid fluidized bed is dewatered by a clean coal dewatering screen and then by a second clean coal centrifuge. The resulting solid products are collected in the dechlorinated clean coal. The underflow is dewatered by a middlings dewatering screen and then by a second middlings centrifuge. The resulting solid products are collected in the dechlorinated middlings.

[0058] In a preferred embodiment, the fine particles obtained by the classifying hydrocyclone have a particle size of -0.5 mm, and the coarse particles have a particle size of +0.5 mm.

[0059] In a preferred embodiment, flotation is performed using a flotation machine in step S3, with kerosene as the flotation collector and 2-octanol as the frother.

[0060] In a preferred embodiment, the screening particle sizes of the clean coal dewatering screen and the middlings dewatering screen are 0.2-5 mm and 5-10 mm, respectively.

[0061] S4. All dechlorinated clean coal and dechlorinated middlings are subjected to desulfurization treatment to obtain the final clean coal product and middlings product.

[0062] The applicant discovered through research that although the chlorine content in the clean coal or middlings product is significantly reduced after the raw coal is jigged and washed, the sulfur content increases significantly. Therefore, in this invention, a desulfurization process is added to the dechlorinated clean coal and dechlorinated middlings to reduce the sulfur content in the product.

[0063] In this invention, the desulfurization treatment processes for dechlorinated clean coal and dechlorinated middlings coal are the same, both including the following steps:

[0064] 1) Add dechlorinated clean coal or dechlorinated middlings to water, stir evenly to prepare a coal slurry with a solid-liquid ratio of 0.25-5 kg / L, add H2O2 solution and desulfurization enhancer, control the mass concentration of H2O2 in the coal slurry to 0.5-2%, and add the desulfurization enhancer at a mass of 0.15-2.5% of the coal addition amount, and stir for 15-90 min;

[0065] 2) The coal slurry is treated with ultrasound for 0.5-3 hours at a temperature of 25-35℃; the ultrasonic power is 400-650W and the frequency is 50-250kHz.

[0066] 3) After the treatment is completed, the solid product is filtered, washed with water, and dried to obtain the desulfurized coal product, which is the final clean coal product or middlings product.

[0067] In a preferred embodiment, the desulfurization enhancer is prepared by the following method:

[0068] 1-1) Take 0.72-2.88g of citric acid, 0.26-0.90g of urea, 0.27-1.06g of acridine orange, and 0.30-1.20g of ferric sulfate and add them to a mixed solution consisting of 50-200mL of ethanol and 75-300mL of deionized water. Disperse the mixture by sonication for 15-60min to obtain the precursor solution.

[0069] 1-2) Transfer the precursor solution to a polytetrafluoroethylene-lined reactor and react at 180-200℃ for 6-12 hours. After the reaction is completed, cool to room temperature and filter the product through a 0.22μm microporous membrane. Then, dialyze the product in deionized water for 12-48 hours using a dialysis bag with a molecular weight cutoff of 800D. After dialysis, take the solution from the dialysis bag and freeze-dry it to obtain the desulfurization enhancer.

[0070] H2O2 oxidation is a conventional method for removing sulfur from coal. It primarily utilizes the oxidizing power of H2O2 to convert inorganic or organic sulfur into soluble sulfur, which is then removed through solid-liquid separation (Yuan Yongguo, Wang Rui, Mu Xiaogang. Study on the method and mechanism of ultrasonic-assisted H2O2 removal of organic sulfur from coking coal [J]. Coal Conversion, 2021. DOI:10.19726 / j.cnki.ebcc.202105011.). However, conventional H2O2 oxidation has a low efficiency in removing sulfur. This invention improves upon the conventional H2O2 oxidation method by adding a desulfurization synergist with strong oxidizing power and acoustic sensitivity to the H2O2 oxidation system, and supplementing it with ultrasonic action, which significantly enhances the sulfur removal efficiency.

[0071] The desulfurization synergist of this invention is an iron-doped carbon dot that inherits the acoustic sensitivity of the precursor material acridine orange and exhibits strong oxidizing ability under ultrasonic excitation, thereby achieving sulfur removal. This desulfurization synergist has at least the following effects:

[0072] 1. Under ultrasonic excitation, the desulfurization enhancer can transfer energy to the ground-state oxygen of water molecules, thereby generating singlet oxygen with strong oxidizing power. 1 In the H2O2 system, substances such as O2 and hydroxyl radicals (·OH) can oxidize inorganic and organic sulfur to form soluble sulfur salts, thereby removing sulfur from coal.

[0073] 2. The desulfurization enhancer can catalyze and enhance the oxidation of H2O2. This is attributed to the sp2 and sp3 hybrid carbon interface structure of the carbon points and the variable valence state of Fe, which can promote electron transfer, increase electron density, and improve reaction efficiency, thereby enhancing the oxidation of S by H2O2.

[0074] In this invention, the assistance of ultrasound can, on the one hand, stimulate iron-doped carbon dots to provide strong oxidation capacity, and on the other hand, it can also disperse the system, so that the desulfurization enhancer and H2O2 can fully contact the coal system particles, thereby further improving the desulfurization effect.

[0075] The present invention also provides a deep deashing and dechlorination system for high-chlorine coal, which uses the above-described process to deash and dechlorinate high-chlorine coal.

[0076] It is understood that this invention is not only applicable to the dechlorination of high-chlorine coal, but also, through the following adaptive improvements, is expected to be applicable to the removal of impurities from other water-soluble high-sodium, high-potassium, high-calcium, and other high-alkali coals.

[0077] The above is the general concept of the present invention. Based on this, detailed experimental test examples, embodiments and comparative examples are provided below to further illustrate the present invention.

[0078] Test Case

[0079] 1. Relationship between jigging dechlorination effect and number of jigging stages for raw coal with different particle sizes

[0080] Test methods

[0081] Four different particle sizes (-0.2mm, 0.2-2mm, 2-5mm, 5-10mm) of raw coal were placed in an oven, which was set to 80℃ and dried for 10 hours.

[0082] 100.00±0.1g of raw coal of four different particle sizes were taken respectively, and deionized water with a water-to-coal ratio of 4:1 was added to prepare coal slurry. The slurry was then jigged at 25℃ (using jigging stages 1, 2, 3, 4, and 5, respectively). After treatment, the gangue was discharged, and the jigged clean coal and jigged middlings were filtered separately. The volume V of the filtrate was measured. y and the chlorine content C in the filtrate y Calculate the chlorine removal rate η of the water washing jigging process;

[0083]

[0084] Where M0 represents the mass of the raw coal and C0 represents the chlorine content in the raw coal, both of which are measured in advance.

[0085] The main process parameters for water washing jigging are as follows: Jig model: 2LTC / 6109 / 8T; Jigging area: 5.76㎡; Stroke coefficient: 0.52-0.35; Processing capacity: 25T / h;

[0086] The ash content of the raw coal is 26.24%, with CI content of 15.667% and S content of 25.99%.

[0087] The chlorine content in raw coal was measured according to the standard GB / T 3558-2014 "Determination of Chlorine in Coal"; the chlorine content in the filtrate was measured using IC (ion chromatography).

[0088] Measurement results as follows Figure 4 As shown in the figure, particle sizes of 0.2mm, 2.0mm, 5.0mm, and 10.0mm represent -0.2mm, 0.2-2mm, 2-5mm, and 5-10mm particle sizes, respectively.

[0089] It can be seen that in the first jigging stage, the removal rate of different particle sizes is around 80%; in the second jigging stage, the removal rate of 2-5mm particles remains unchanged, while the removal rates of -0.2mm, 0.2-2mm, and 5-10mm particles are slightly lower than in the first jigging stage; in the third jigging stage, the removal rates of different particle sizes are basically the same as in the second jigging stage; in the fourth jigging stage, the removal rate of 0.2-2mm particles remains basically unchanged, while the removal rates of the other particle sizes are slightly higher than in the third jigging stage; in the fifth jigging stage, the removal rate of 5-10mm particles increases significantly, reaching around 95%, while the changes in the other three particle sizes remain basically unchanged.

[0090] Analysis of causes: For coal particles with a diameter of -0.2mm: the removal rate does not vary significantly with different numbers of jigging stages in the washing process, mostly remaining above 70%, and even exceeding 80%. This is likely because 0.2mm coal particles have a relatively large surface area, making them more likely to interact with impurities in the water, resulting in a relatively high removal rate. With longer jigging stages, the removal rate increases slightly, possibly due to the longer contact time allowing more impurities to be washed out.

[0091] For coal particles in the 0.2-2mm and 2-5mm sizes: the removal rate showed relatively small changes under different washing jigging stages, but increased with increasing washing time. However, the increase was relatively small. This may be because the surface area of ​​2.0mm and 5.0mm coal particles is relatively small, resulting in a smaller contact area with impurities in the water, thus leading to a slower increase in removal rate.

[0092] For 5-10mm coal particles: the removal rate is low when the number of jigging stages in the washing process is small, but it increases significantly with increasing washing time, especially reaching 95% with a larger number of jigging stages. This is likely because 10.0mm coal particles have a smaller surface area, resulting in a smaller contact area with impurities in the water. When the number of jigging stages is short, impurities are difficult to completely remove. However, the removal rate increases more rapidly with time, as more time allows more impurities to interact with and be washed out of the coal particles.

[0093] The removal efficiency of coal particles of different sizes under different washing and jigging stages is affected by the particle surface area. Smaller coal particles have a larger surface area, so their removal efficiency is higher and less variable; while larger coal particles require a larger number of washing and jigging stages to achieve a higher removal efficiency. Therefore, in the process, the number of washing and jigging stages is relatively increased for larger coal particles to ensure the removal efficiency.

[0094] Based on the above results, different dechlorination effects can be obtained by using different numbers of jigging stages for coal of different particle sizes. Furthermore, for coal with a particle size of 5-10mm, a 5-stage jigging process is preferred, and for coal with a particle size of 0.2-5mm, a 2-stage jigging process is preferred. Since jigging is not effective for treating fine coal slime, for coal with a particle size of -0.2mm, a flotation combined with a liquid-solid fluidized bed process is preferred.

[0095] 2. Composition analysis of raw coal and ash composition analysis of clean coal after jigging and dechlorination.

[0096] Raw coal and the jigged clean coal obtained in step 1 were fed into a muffle furnace and heated to 500°C in air at a rate of less than 10°C / min. The mixture was then kept at this temperature and calcined for 1 hour to obtain the ash content of the raw coal and the clean coal. The content of each element in the ash content of the raw coal and the clean coal was then measured by XRF, referring to the standard GB / T1574-2007 "Methods for Analysis of Coal Ash Composition".

[0097] Measurement results as follows Figure 5 As shown, it can be seen that as the number of jigging stages increases from 1 to 5, the content of each component in the ash of the clean coal remains basically unchanged: the content of CaO and NaO is about 12%, the content of MgO and AlO is about 8%, the content of SiO, FeO, and Cl is about 5%, and the content of S is as high as about 50%.

[0098] The composition of raw coal differs slightly from that of washed coal. CaO content is around 35%, NaO and MgO around 7%, AlO, SiO, and FeO around 5%, SO2 around 25%, and Cl around 15%. The trend is a significant increase in S content, a slight increase in NaO, MgO, AlO, SiO, and FeO content, and a significant decrease in CaO and Cl content.

[0099] Cause analysis:

[0100] CaO and Cl are readily soluble in water. They dissolve during the washing process and are washed out with the water, thus reducing their content. In addition, during the washing process, some components in the water may react with them to produce water-soluble compounds, which are also washed out with the water, thus reducing their content.

[0101] Conversely, the increased content of NaO, MgO, AlIO, FeO, and SiO is due to the presence of salts containing metals such as Na, Mg, and Al in the raw coal. These salts are easily soluble in water, thus increasing their content during the jigging washing process. The increased sulfur content is because some sulfur in the raw coal exists in organic form. During the jigging washing process, these organic sulfur compounds are converted into water-soluble sulfur compounds (SO2). However, since calcium initially accounts for a large proportion and is removed more than other elements during washing, the percentage of other elements increases, leading to an increase in the relative percentage of SO2.

[0102] The above analysis shows that water washing and jigging can effectively remove chlorine, but it will lead to an increase in the relative content of sulfur, so a desulfurization treatment step needs to be added in the subsequent process.

[0103] 3. XRD pattern analysis of ash content in raw coal and jigged dechlorinated coal at different temperatures

[0104] The raw coal and the cleaned coal after jigging and dechlorination were calcined at different temperatures according to the method in step 2, and then the composition of the ash was measured. The ash XRD patterns are shown below. Figure 6 As shown in (a) and (b): (a) is the ash content of raw coal, and (b) is the ash content of clean coal after jigging and dechlorination.

[0105] It can be seen that for raw coal, the ash produced at a muffle furnace temperature of 550℃ mainly consists of NaCl, CaCO3, and CaSO4. However, when the temperature rises to 700℃ and 815℃, the main phase is only CaCO3 or CaO. NaCl is almost completely released before 815℃. It is also noteworthy that at 700℃, the main component is CaCO3, while at 815℃, the main component of the ash is CaO, indicating that the decomposition of CaCO3 may occur between 700℃ and 815℃.

[0106] For coal after jigging and dechlorination, when the furnace temperature is 550℃, the main components are only CaCO3, CaO and CaSO4, indicating that water washing has effectively washed away NaCl and achieved chlorine removal.

[0107] Examples and Comparative Examples

[0108] Example 1

[0109] A deep deashing and dechlorination process for high-chlorine coal includes the following steps:

[0110] S1. High-chlorine coal is pre-screened. The raw coal product on the screen is crushed and then enters the grading screen together with the raw coal product under the screen to be graded into the first particle size grade, the second particle size grade, and the third particle size grade. The particle size of the first particle size grade, the second particle size grade, and the third particle size grade increases sequentially.

[0111] In a preferred embodiment, the screening particle size of the high-chlorine coal pre-screening is 10 mm, and the raw coal product on the screen is crushed to below 10 mm; the particle size ranges of the first particle size grade raw coal, the second particle size grade raw coal, and the third particle size grade raw coal are -0.2 mm, 0.2-5 mm, and 5-10 mm, respectively.

[0112] S2 and the third-size raw coal are separated by a five-stage jig, the second-size raw coal is separated by a two-stage jig, and the first-size raw coal enters the coal slurry bucket.

[0113] The jigged clean coal obtained from the five-stage jig and the two-stage jig both enter the clean coal vibrating screen (screening particle size is 0.25mm) for dewatering. The oversize product of the clean coal vibrating screen is centrifuged by the first clean coal centrifuge to obtain dechlorinated clean coal, and the undersize product enters the coal slurry water tank.

[0114] The jigging gangue obtained from the five-stage jig and the two-stage jig is discharged, and the jigging middlings are all fed into the middlings vibrating screen (screening particle size is 4mm) for dewatering. The oversize product of the middlings vibrating screen is centrifuged by the first middlings centrifuge to obtain dechlorinated middlings, and the undersize product is fed into the coal slurry water tank.

[0115] The two-stage jig includes a main jigging section and a secondary jigging section. The jigged gangue obtained from the underflow of the main jigging section is discharged and the overflow enters the secondary jigging section. The underflow of the secondary jigging section yields jigged middlings and the overflow yields jigged refined coal.

[0116] The five-stage jig consists of a main jigging stage and four secondary jigging stages. The jigged gangue obtained from the underflow of the main jigging stage is discharged and the overflow enters the secondary jigging stages. The overflow of each secondary jigging stage enters the next secondary jigging stage in sequence. The underflow of the four secondary jigging stages is collected to obtain jigged middlings, and the overflow of the last secondary jigging stage is obtained to obtain jigged clean coal.

[0117] The main jigging process parameters for the two-stage jig are: frequency cycle: 1.5s; water flow time: 0.6m / min. The main jigging process parameters for the five-stage jig are: frequency cycle: 1.5s; water flow time: 0.6m / min.

[0118] S3. The product in the coal slurry bucket is first separated into fine particles (-0.5mm) by a classifying hydrocyclone. The fine particles enter the flotation process, and the obtained flotation clean coal is filtered by a clean coal filter press and then collected into dechlorination clean coal. The flotation tailings are filtered by a tailings filter press and then collected into dechlorination middlings.

[0119] Coarse particles (+0.5mm) enter a liquid-solid fluidized bed for dechlorination. The overflow from the liquid-solid fluidized bed is dewatered by a clean coal dewatering screen (screening size 0.25mm) and then by a second clean coal centrifuge. The resulting solid products are collected in the dechlorinated clean coal. The underflow is dewatered by a middlings dewatering screen (screening size 4mm) and then by a second middlings centrifuge. The resulting solid products are collected in the dechlorinated middlings.

[0120] In step S3, a flotation machine is used for flotation. The flotation collector is kerosene, added at a rate of 0.5 kg / t, and the frother is 2-octanol, added at a rate of 100 g / t. The flotation throughput is 65 m³ / t. 3 / h, the flotation machine model selected is XJK-5.8 (effective volume 5.8m³). 3 Processing capacity 7m 3 The stirring power is 22kw, and the rotation speed is 240r / min; the scraper rotation speed is 25r / min, and the power is 1.5kw.

[0121] S4. All dechlorinated clean coal and dechlorinated middlings are subjected to desulfurization treatment to obtain the final clean coal product and middlings product.

[0122] In this invention, the desulfurization treatment processes for dechlorinated clean coal and dechlorinated middlings coal are the same, both including the following steps:

[0123] 1) Add dechlorinated clean coal or dechlorinated middlings to water, stir evenly to prepare a coal slurry with a solid-liquid ratio of 1 kg / L, add H2O2 solution (mass fraction of 25%) and desulfurization enhancer, control the mass concentration of H2O2 in the coal slurry to 0.8%, and add the desulfurization enhancer at a mass of 0.45% of the coal addition amount, and stir for 25 min;

[0124] 2) The coal slurry was treated with ultrasound for 1 hour at a temperature of 30°C; the ultrasonic power was 550W and the frequency was 120kHz.

[0125] 3) After the treatment is completed, the solid product is filtered, washed with water, and dried to obtain the desulfurized coal product, which is the final clean coal product or middlings product.

[0126] In this embodiment, the desulfurization enhancer is prepared by the following method:

[0127] 1-1) Take 1.44g citric acid, 0.45g urea, 0.53g acridine orange and 0.60g ferric sulfate and add them to a mixed solution consisting of 100mL ethanol and 150mL deionized water. Disperse the mixture by sonication for 30min to obtain the precursor solution.

[0128] 1-2) The precursor solution was transferred to a polytetrafluoroethylene-lined reactor and reacted at 190°C for 8 hours. After the reaction was completed, the mixture was cooled to room temperature. The product was filtered through a 0.22 μm microporous membrane and then dialyzed in deionized water for 24 hours using a dialysis bag with a molecular weight cutoff of 800D. After dialysis, the solution in the dialysis bag was taken and freeze-dried to obtain the desulfurization enhancer.

[0129] Example 2

[0130] This embodiment is basically the same as Embodiment 1, except that:

[0131] The desulfurization treatment of both dechlorinated clean coal and dechlorinated middlings includes the following steps:

[0132] 1) Add dechlorinated clean coal or dechlorinated middlings to water, stir evenly to prepare a coal slurry with a solid-liquid ratio of 1 kg / L, add H2O2 solution (mass fraction of 25%) and desulfurization enhancer, control the mass concentration of H2O2 in the coal slurry to 1%, and add the desulfurization enhancer at a mass of 0.45% of the coal addition amount, and stir for 25 min;

[0133] 2) The coal slurry was treated with ultrasound for 1 hour at a temperature of 30°C; the ultrasonic power was 550W and the frequency was 120kHz.

[0134] 3) After the treatment is completed, the solid product is filtered, washed with water, and dried to obtain the desulfurized coal product, which is the final clean coal product or middlings product.

[0135] Example 3

[0136] This embodiment is basically the same as Embodiment 1, except that:

[0137] The desulfurization treatment of both dechlorinated clean coal and dechlorinated middlings includes the following steps:

[0138] 1) Add dechlorinated clean coal or dechlorinated middlings to water, stir evenly to prepare a coal slurry with a solid-liquid ratio of 1 kg / L, add H2O2 solution (mass fraction of 25%) and desulfurization enhancer, control the mass concentration of H2O2 in the coal slurry to 0.8%, and add the desulfurization enhancer at a mass of 0.55% of the coal addition amount, and stir for 25 min;

[0139] 2) The coal slurry was treated with ultrasound for 1 hour at a temperature of 30°C; the ultrasonic power was 550W and the frequency was 120kHz.

[0140] 3) After the treatment is completed, the solid product is filtered, washed with water, and dried to obtain the desulfurized coal product, which is the final clean coal product or middlings product.

[0141] Comparative Example 1

[0142] This example is basically the same as Example 1, except that:

[0143] In step S1, both the second-size and third-size raw coal are processed using a two-stage jig.

[0144] Comparative Example 2

[0145] This example is basically the same as Example 1, except that:

[0146] In this example, the desulfurization processes for dechlorinated clean coal and dechlorinated middlings are the same, both including the following steps:

[0147] 1) Add dechlorinated clean coal or dechlorinated middlings to water, stir evenly to prepare a coal slurry with a solid-liquid ratio of 1 kg / L, add H2O2 solution (mass fraction of 25%), control the mass concentration of H2O2 in the coal slurry to 0.8%, and stir for 25 min;

[0148] 2) The coal slurry was treated with ultrasound for 1 hour at a temperature of 30°C; the ultrasonic power was 550W and the frequency was 120kHz.

[0149] 3) After the treatment is completed, the solid product is filtered, washed with water, and dried to obtain the desulfurized coal product, which is the final clean coal product or middlings product.

[0150] Comparative Example 3

[0151] This example is basically the same as Example 1, except that:

[0152] In this example, the desulfurization enhancer was prepared by the following method:

[0153] 1-1) Take 1.44g of citric acid, 0.45g of urea and 0.53g of acridine orange and add them to a mixed solution consisting of 100mL of ethanol and 150mL of deionized water. Disperse the mixture by sonication for 30min to obtain the precursor solution.

[0154] 1-2) The precursor solution was transferred to a polytetrafluoroethylene-lined reactor and reacted at 190°C for 8 hours. After the reaction was completed, the mixture was cooled to room temperature. The product was filtered through a 0.22 μm microporous membrane and then dialyzed in deionized water for 24 hours using a dialysis bag with a molecular weight cutoff of 800D. After dialysis, the solution in the dialysis bag was taken and freeze-dried to obtain the desulfurization enhancer.

[0155] Sorting index test

[0156] Referring to the methods for determining ash, chlorine, and sulfur content described above, the ash, chlorine, and sulfur content of the clean coal and middlings products obtained in Examples 1-3 and Comparative Examples 1-3 were measured.

[0157] In the examples and comparative examples, the raw coal used was the same (and from the same source as the coal in the previous test examples, all from Shaerhu Lake in Xinjiang). The ash content of the raw coal was 26.24%, with Cl content of 15.667% and S content of 25.99%. The removal rates of Cl and S were then calculated using the following simplified algorithm, denoted as η. Cl and η S The calculation formula is as follows:

[0158]

[0159] Wherein, C0 represents the Cl or S content in raw coal, and C1 represents the Cl or S content in refined coal products / mid-coal products.

[0160] The measurement results are shown in Table 1 below:

[0161] Table 1

[0162]

[0163] As can be seen from the test results in Table 1, the processes in Examples 1-3 can achieve efficient deashing, dechlorination, and desulfurization of coal. The comparison between Comparative Example 1 and Example 1 shows that jigging with different numbers of stages based on particle size can effectively improve dechlorination efficiency. The comparison between Comparative Example 2 and Example 1 shows that the desulfurization enhancer can significantly improve the sulfur removal effect. The comparison between Comparative Example 3 and Example 1 shows that the doping of iron in the desulfurization enhancer helps to improve its sulfur removal rate.

[0164] Performance Characterization

[0165] 1. Taking Example 1 as an example, the desulfurization synergist prepared therein was characterized by infrared absorption spectroscopy. The infrared absorption spectrum is as follows: Figure 7 As shown, the surface of the desulfurization synergist is rich in functional groups: amino, hydroxyl, carboxyl, etc.; 1620, 545cm -1 The characteristic peak at this location originates from ferrite bonds, proving the successful doping of Fe.

[0166] 2. Testing the oxidation performance of the desulfurization enhancer prepared in Example 1.

[0167] 0.2 mg of the desulfurization synergist prepared in Example 1 was added to 1 mL of deionized water and ultrasonically dispersed for 5 min to obtain a dispersion. The singlet oxygen content generated in the dispersion at different time points under ultrasonic treatment (ultrasonic power of 550 W, frequency of 120 kHz) (CDs+UT) and without ultrasonic treatment (CDs+NOUT) was measured (using the singlet oxygen fluorescent probe SOSG). The test results are as follows. Figure 8 As shown in the figure. The test results confirm that this desulfurization enhancer can efficiently generate singlet oxygen under ultrasonic excitation.

[0168] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details.

Claims

1. A deep deashing and dechlorination process for high-chlorine coal, characterized in that, Includes the following steps: S1. High-chlorine coal is pre-screened. The raw coal product on the screen is crushed and then enters the grading screen together with the raw coal product under the screen to be graded into the first particle size grade, the second particle size grade, and the third particle size grade. The particle size of the first particle size grade, the second particle size grade, and the third particle size grade increases sequentially. S2 and the third-size raw coal are separated by a five-stage jig, the second-size raw coal is separated by a two-stage jig, and the first-size raw coal enters the coal slurry tank. The jigged clean coal obtained from the five-stage jig and the two-stage jig both enter the clean coal vibrating screen for dewatering. The oversize product from the clean coal vibrating screen is centrifuged by the first clean coal centrifuge to obtain dechlorinated clean coal, and the undersize product enters the coal slurry water tank. The jigging gangue obtained from the five-stage jig and the two-stage jig is discharged, and the jigging middlings are all fed into the middlings vibrating screen for dewatering. The oversize product of the middlings vibrating screen is centrifuged by the first middlings centrifuge to obtain dechlorinated middlings, and the undersize product is fed into the coal slurry water tank. S3. The product in the coal slurry bucket is first separated into fine and coarse particles by a classifying hydrocyclone. The fine particles enter the flotation, and the obtained flotation clean coal is collected into dechlorination clean coal after pressure filtration. The flotation tailings are collected into dechlorination middlings after pressure filtration. Coarse particles enter a liquid-solid fluidized bed for dechlorination. The solid products obtained from the overflow of the liquid-solid fluidized bed after dewatering are collected into dechlorinated clean coal, and the solid products obtained from the underflow after dewatering are collected into dechlorinated middlings. S4. All dechlorinated clean coal and dechlorinated middlings are subjected to desulfurization treatment to obtain the final clean coal product and middlings product.

2. The deep deashing and dechlorination process for high-chlorine coal according to claim 1, characterized in that, In step S1, the screening particle size of the high-chlorine coal raw coal pre-screening is 10mm, and the raw coal product on the screen is crushed to below 10mm. The particle size ranges of the first, second, and third particle size grades of raw coal are -0.2 mm, 0.2-5 mm, and 5-10 mm, respectively.

3. The deep deashing and dechlorination process for high-chlorine coal according to claim 1, characterized in that, The two-stage jig consists of a main jigging section and a secondary jigging section. The jigged gangue obtained from the underflow of the main jigging section is discharged, and the overflow enters the secondary jigging section. The underflow of the secondary jigging section yields jigged middlings, and the overflow yields jigged refined coal. The five-stage jig consists of a main jigging stage and four secondary jigging stages. The jigged gangue obtained from the underflow of the main jigging stage is discharged and the overflow enters the secondary jigging stages. The overflow of each secondary jigging stage enters the next secondary jigging stage in sequence. The underflow of the four secondary jigging stages is collected to obtain jigged middlings, and the overflow of the last secondary jigging stage is obtained to obtain jigged clean coal.

4. The deep deashing and dechlorination process for high-chlorine coal according to claim 1, characterized in that, The screening particle sizes for clean coal vibrating screens and middlings vibrating screens are 0.2-5mm and 5-10mm, respectively.

5. The deep deashing and dechlorination process for high-chlorine coal according to claim 1, characterized in that, The fine particles obtained by the classifying hydrocyclone have a particle size of -0.5 mm, and the coarse particles have a particle size of +0.5 mm.

6. The deep deashing and dechlorination process for high-chlorine coal according to claim 1, characterized in that, The overflow from the liquid-solid fluidized bed is dewatered by a clean coal dewatering screen and then by a second clean coal centrifuge. The resulting solid products are collected in the dechlorinated clean coal. The underflow is dewatered by a middlings dewatering screen and then by a second middlings centrifuge. The resulting solid products are collected in the dechlorinated middlings.

7. The deep deashing and dechlorination process for high-chlorine coal according to claim 1, characterized in that, In step S3, a flotation machine is used for flotation, with kerosene as the flotation collector and 2-octanol as the frother.

8. The deep deashing and dechlorination process for high-chlorine coal according to claim 1, characterized in that, The desulfurization processes for dechlorinated clean coal and dechlorinated middlings are the same, both including the following steps: 1) Add dechlorinated clean coal or dechlorinated middlings to water, stir evenly to prepare a coal slurry with a solid-liquid ratio of 0.25-5 kg / L, add H2O2 solution and desulfurization enhancer, control the mass concentration of H2O2 in the coal slurry to 0.5-2%, and add the desulfurization enhancer at a mass of 0.15-2.5% of the coal addition amount, and stir for 15-90 min; 2) The coal slurry is treated with ultrasound for 0.5-3 hours at a temperature of 25-35℃; the ultrasonic power is 400-650W and the frequency is 50-250kHz. 3) After the treatment is completed, the solid product is filtered, washed with water, and dried to obtain the desulfurized coal product, which is the final clean coal product or middlings product.

9. The deep deashing and dechlorination process for high-chlorine coal according to claim 8, characterized in that, The desulfurization enhancer is prepared by the following method: 1-1) Take 0.72-2.88g of citric acid, 0.26-0.90g of urea, 0.27-1.06g of acridine orange, and 0.30-1.20g of ferric sulfate and add them to a mixed solution consisting of 50-200mL of ethanol and 75-300mL of deionized water. Disperse the mixture by sonication for 15-60min to obtain the precursor solution. 1-2) Transfer the precursor solution to a polytetrafluoroethylene-lined reactor and react at 180-200℃ for 6-12 hours. After the reaction is completed, cool to room temperature and filter the product through a 0.22μm microporous membrane. Then, dialyze the product in deionized water for 12-48 hours using a dialysis bag with a molecular weight cutoff of 800D. After dialysis, take the solution from the dialysis bag and freeze-dry it to obtain the desulfurization enhancer.

10. A deep deashing and dechlorination system for high-chlorine coal, wherein the high-chlorine coal is deashed and dechlorinated using the process described in any one of claims 1-9.

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