A method for pre-desliming of raw coal suitable for coal and heavy oil hydrocracking

Abstract

The application discloses a method for pre-desliming of raw coal suitable for coal and heavy oil hydrocracking, and belongs to the field of deep processing of coal. The lignite with the mass fraction of air dry ash content greater than 15% is crushed and passed through a 200-mesh sieve, and is prepared into coal water slurry with deionized water at a mass ratio of 1:6-1:10; the coal water slurry is treated with hydrochloric acid with a mass fraction of 36%, hydrofluoric acid with a mass fraction of 40% and hydrochloric acid with a mass fraction of 36% in sequence, and is centrifugally cleaned with deionized water after the first two acid treatments. The temperature of each acid treatment is 40-60 DEG C, the stirring speed is 500-1000 r / min, and the treatment time is 3.5 h. Solid-liquid separation is carried out after the second hydrochloric acid treatment, and the obtained solid phase is cleaned with deionized water until the washing liquid is neutral, thereby obtaining pre-deslimed coal with the mass fraction of air dry ash content less than 2%. The method can reduce the ash content and the contents of silicon, iron, aluminum and calcium in the raw coal, and provides low-ash raw material for the coal and heavy oil hydrocracking.

Description

Technical Field

[0001] This invention belongs to the field of raw coal pretreatment technology, specifically relating to a method for pre-ashing of raw coal suitable for co-refining of coal and heavy oil. Background Technology

[0002] With the rapid development of the world economy, the problem of insufficient energy supply is becoming increasingly prominent. my country has abundant coal reserves, making the rational utilization of these resources crucial. Based on the current state of domestic coal, lignite has a low degree of coalification and presents many problems: its moisture content is excessively high, the highest among all types of coal, generally reaching 10%–40%; this high moisture content significantly impacts the utilization efficiency of lignite, resulting in high porosity, high volatile matter, and low calorific value; lignite has an oxygen content as high as 15%–30%, leading to poor chemical reactivity and thermal stability, which is detrimental to effective utilization such as coal liquefaction; the poor thermal stability of lignite also hinders long-distance transportation, reducing its economic value. Therefore, reducing the high moisture content of lignite is a key issue for its development and utilization. However, large-scale industrial application of lignite drying technology in my country is still in its early stages, and the technology is not yet mature enough, lacking experience in pre-dehydration techniques.

[0003] Currently, low-rank coal drying technologies are divided into mechanical drying, evaporative drying, and non-evaporative drying. Mechanical drying involves mechanical hot pressing under certain pressure and temperature, where high pressure or shearing causes irreversible damage to the gel structure and pore system of the coal, removing moisture without evaporation. However, this method requires excessively high pressure and sophisticated equipment manufacturing. Evaporative drying removes water from the coal in a gaseous state. Depending on the drying medium, it can be divided into hot steam drying and hot air / flue gas drying. Key technologies include rotary tube drying, drum drying, steam-air combined drying, fluidized bed drying (WTA), bed mixed drying (BMD), and vibrating bed drying. However, these methods have certain problems. For example, drum drying easily generates smoke and dust, and due to contact with the combustion furnace, the temperature is too high, posing a risk of combustion and explosion. Steam-air combined drying incorporates inert gases, resulting in high pressure drop and wear. Non-evaporative drying removes water from the coal in a liquid state, thus consuming less energy. Non-evaporative dehydration and upgrading technology involves directly or indirectly heating lignite with steam at a certain temperature and pressure, removing moisture in a liquid form. The resulting products include low-moisture coal and coal-water slurry. Since no evaporation heat is consumed during dehydration, it is less prone to spontaneous combustion. The main representative technology is thermal dehydration, but it involves high investment costs, complex wastewater treatment, and potential environmental pollution if not properly treated. Furthermore, non-evaporative dehydration and upgrading technology cannot remove moisture to the maximum extent. Summary of the Invention

[0004] The purpose of this invention is to provide a method for pre-ash removal of raw coal suitable for co-processing of coal and heavy oil. This method mainly solves the problems in existing pretreatment methods for raw coal in co-processing of coal and heavy oil, such as the difficulty in efficiently and stably removing ash from high-ash lignite and the lack of clear and repeatable acid washing process parameters.

[0005] This invention provides a method for pre-deashing raw coal suitable for co-refining of coal and heavy oil, comprising the following steps: Lignite with an air-dried ash content greater than 15% was pulverized and passed through a 200-mesh sieve. The resulting coal powder was mixed with deionized water at a mass ratio of 1:6 to 1:10 to obtain a coal-water slurry. The coal-water slurry was subjected to a first hydrochloric acid treatment using 36% hydrochloric acid by mass. After the treatment, the resulting coal sample was centrifuged and washed with deionized water to obtain a first washed coal sample. The first washed coal sample was then subjected to hydrofluoric acid treatment using 40% hydrofluoric acid by mass. After the treatment, the resulting coal sample was centrifuged and washed with deionized water. The coal was first cleaned to obtain a second cleaned coal sample. This second cleaned coal sample was then subjected to a second hydrochloric acid treatment using 36% hydrochloric acid by mass. After treatment, solid-liquid separation was performed, and the resulting solid phase was washed with deionized water until the washing solution was neutral on pH paper, yielding pre-deashed coal. The treatment temperatures for the first hydrochloric acid treatment, the hydrofluoric acid treatment, and the second hydrochloric acid treatment were all 40–60°C, the stirring rate was 500–1000 r / min, and the treatment time was 3.5 h. The resulting pre-deashed coal had an air-dried ash content of less than 2% by mass.

[0006] Further, the lignite is Inner Mongolia lignite with an air-dried ash content of 25.57% by mass; based on 50g of the Inner Mongolia lignite, the amount of deionized water used to prepare the coal-water slurry is 500mL, the amount of hydrochloric acid with a mass fraction of 36% used for the first hydrochloric acid treatment is 90mL, the amount of hydrofluoric acid with a mass fraction of 40% used for the first hydrochloric acid treatment is 105mL, and the amount of hydrofluoric acid with a mass fraction of 36% used for the second hydrochloric acid treatment is 90mL.

[0007] Further, the lignite is Liaoning lignite with an air-dried ash content of 17.92% by mass; based on 50g of the Liaoning lignite, the amount of deionized water used to prepare the coal-water slurry is 500mL, the amount of hydrochloric acid with a mass fraction of 36% used for the first hydrochloric acid treatment is 64mL, the amount of hydrofluoric acid with a mass fraction of 40% used for the first hydrochloric acid treatment is 73mL, and the amount of hydrofluoric acid with a mass fraction of 36% used for the second hydrochloric acid treatment is 64mL.

[0008] Furthermore, the volume of hydrochloric acid used in the first hydrochloric acid treatment is the same as that used in the second hydrochloric acid treatment.

[0009] Furthermore, the treatment temperatures for the first hydrochloric acid treatment, the hydrofluoric acid treatment, and the second hydrochloric acid treatment are all 60°C.

[0010] Furthermore, the centrifugal cleaning after the first hydrochloric acid treatment and the centrifugal cleaning after the hydrofluoric acid treatment both adopt a centrifugal speed of 3000-5000 r / min, and the centrifugation time is 5-7 min each time; the number of centrifugal cleanings after the first hydrochloric acid treatment and the number of centrifugal cleanings after the hydrofluoric acid treatment are 3-5 times respectively.

[0011] Furthermore, both the centrifugal cleaning after the first hydrochloric acid treatment and the centrifugal cleaning after the hydrofluoric acid treatment were performed at a centrifugal speed of 4000 r / min, with each centrifugation lasting 5 min; the number of centrifugal cleanings after the first hydrochloric acid treatment and the number of centrifugal cleanings after the hydrofluoric acid treatment were 3 times each.

[0012] Furthermore, the solid-liquid separation after the second hydrochloric acid treatment is performed by vacuum filtration; during the vacuum filtration process, the retained solid phase is washed with deionized water until the resulting washing solution is neutral on pH test paper as the washing endpoint.

[0013] Furthermore, for the Inner Mongolia lignite with an air-dried ash content of 25.57%, the treatment temperatures for the first hydrochloric acid treatment, the hydrofluoric acid treatment, and the second hydrochloric acid treatment are all 60°C. After the first hydrochloric acid treatment and the hydrofluoric acid treatment, the lignite is centrifuged three times at a speed of 4000 r / min, with each centrifugation lasting 5 min. After the second hydrochloric acid treatment, vacuum filtration is performed, and during the vacuum filtration process, the retained solid phase is washed with deionized water until the resulting washing solution is neutral on pH test paper. The washed solid phase is dried at 115°C for 1 h, and the air-dried ash content of the obtained pre-de-ashed coal is not higher than 1.85%.

[0014] Furthermore, for the Liaoning lignite with an air-dried ash content of 17.92%, the treatment temperatures for the first hydrochloric acid treatment, the hydrofluoric acid treatment, and the second hydrochloric acid treatment were all 60°C. After the first hydrochloric acid treatment and the hydrofluoric acid treatment, the lignite was centrifuged three times at a speed of 4000 r / min, with each centrifugation lasting 5 min. After the second hydrochloric acid treatment, vacuum filtration was performed, and during the vacuum filtration process, the retained solid phase was washed with deionized water until the resulting cleaning solution was neutral on pH test paper. The washed solid phase was dried at 115°C for 1 h, and the air-dried ash content of the resulting pre-de-ashed coal was not higher than 1.40%.

[0015] The beneficial effects of this invention are as follows: By sequentially performing a first hydrochloric acid treatment, a second hydrofluoric acid treatment, and centrifugal washing between adjacent acid treatment steps, acid-soluble minerals and silicon- and aluminum-containing minerals in high-ash lignite are removed in stages, reducing the impact of residual acid and leaching from the previous treatment stage on the subsequent treatment stage. Simultaneously, the treatment temperature of 40–60°C provides mild reaction conditions, and the residual acid in the pre-deashed coal is reduced through final solid-liquid separation and deionized water washing. Experimental results show that the method of this invention can reduce the air-dried ash content of Inner Mongolia lignite (25.57%) to 1.85% and that of Liaoning lignite (17.92%) to 1.40%, while significantly reducing the content of Si, Al, Fe, and Ca elements in the coal, thereby obtaining pre-deashed coal with an air-dried ash content of less than 2%, providing low-ash feedstock for coal-heavy oil hydrorefining. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort, wherein: Figure 1 X-ray diffraction patterns of raw coal from eastern Inner Mongolia and pre-deashed coal obtained in Example 1; Figure 2 The X-ray diffraction patterns are those of raw coal from Liaoning and pre-deashed coal obtained in Example 2. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention; that is, the described embodiments are merely some embodiments of the invention, and not all embodiments. The components of the embodiments of the invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0018] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0019] It should be noted that relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0020] Inner Mongolia lignite and Liaoning lignite were selected as raw materials. Both types of raw materials were crushed and passed through a 200-mesh sieve. The industrial analysis results of the two types of raw materials are shown in Table 1.

[0021] Table 1. Industrial analysis results of the two raw coal materials As shown in Table 1, the air-dried ash content of Inner Mongolia lignite is 25.57%, and the air-dried ash content of Liaoning lignite is 17.92%. Both types of raw coal are high-ash lignite with an air-dried ash content greater than 15%.

[0022] Example 1 This embodiment uses Inner Mongolian lignite as raw material and includes the following steps: (1) Raw coal crushing and coal-water slurry preparation Crushed and passed through a 200-mesh sieve, 50g of the sieved coal powder was weighed and added to a 1000mL plastic beaker. Then, 500mL of deionized water was added to the plastic beaker and stirred thoroughly to disperse the coal powder in the deionized water, thus obtaining a coal-water slurry.

[0023] (2) First hydrochloric acid treatment Place the plastic beaker containing coal-water slurry in a constant temperature water bath at 60℃, and set the stirring speed to 800 r / min. Add 90 mL of 36% hydrochloric acid to the resulting coal-water slurry. After adding the hydrochloric acid, stir for 3.5 hours to complete the first hydrochloric acid treatment.

[0024] (3) First centrifugal washing After the first hydrochloric acid treatment, the treated material was removed from the constant temperature water bath and the coal sample was centrifuged and cleaned with deionized water.

[0025] The centrifugal washing process involves dispensing the solution into 50mL centrifuge tubes, adding water, dispersing and shaking, then centrifuging at 4000 rpm for 5 minutes, and discarding the supernatant. This process is repeated three times: adding water, dispersing, centrifuging, and discarding the supernatant. The resulting wet precipitated coal sample is collected to obtain the first washed coal sample.

[0026] (4) Hydrofluoric acid treatment Add 500 mL of deionized water to the first cleaned coal sample to prepare a slurry, and place it in a constant temperature water bath at 60℃. Keep the stirring speed at 800 r / min, add 105 mL of hydrofluoric acid with a mass fraction of 40%, and stir for 3.5 h to complete the hydrofluoric acid treatment.

[0027] (5) Second centrifugal washing After hydrofluoric acid treatment, the coal sample obtained after treatment was centrifuged and cleaned with deionized water.

[0028] The centrifugal cleaning process involves dispensing the solution into 50mL centrifuge tubes, adding water, dispersing and shaking, centrifuging at 4000 rpm for 5 minutes, and discarding the supernatant. This process is repeated three times: adding water, dispersing, centrifuging, and discarding the supernatant. The resulting wet precipitated coal sample is collected to obtain the second cleaned coal sample.

[0029] (6) Second hydrochloric acid treatment Add 500 mL of deionized water to the obtained second cleaned coal sample to prepare a slurry, and place it in a constant temperature water bath at 60℃. Keep the stirring speed at 800 r / min, add 90 mL of hydrochloric acid with a mass fraction of 36%, and stir for 3.5 h to complete the second hydrochloric acid treatment.

[0030] (7) Vacuum filtration and cleaning After the second hydrochloric acid treatment is completed, the resulting material is vacuum filtered to separate the solid and liquid phases.

[0031] During vacuum filtration, deionized water is used to wash the solid phase retained by vacuum filtration. During the washing process, pH test paper is used to detect the washing solution obtained after each wash. Washing is stopped when the washing solution turns green on the pH test paper. After vacuum filtration is completed, the washed filter cake is obtained.

[0032] (8) Drying and storage The cleaned filter cake was separated from the filter paper, and the filter cake was placed in a constant temperature drying oven at 115℃ for 1 hour to obtain the pre-deashed coal from eastern Inner Mongolia.

[0033] After drying, the obtained pre-de-ashed coal from eastern Inner Mongolia is stored in sealed bags.

[0034] (9) Industrial analysis results The four industrial components (moisture, ash, volatile matter, and fixed carbon) of raw coal and pre-deashed coal from eastern Inner Mongolia were determined using a JHGF-3 fully automatic industrial analyzer. The test results are shown in Table 2.

[0035] Table 2. Industrial analysis results of raw coal from eastern Inner Mongolia and pre-deashed coal from eastern Inner Mongolia obtained in Example 1. As shown in Table 2, after the pre-ash removal treatment in this embodiment, the air-dried ash content of the lignite from eastern Inner Mongolia decreased from 25.57% to 1.85%, a decrease of 23.72 percentage points; at the same time, the volatile matter content increased from 37.15% to 45.98%, and the fixed carbon content increased from 35.72% to 50.85%.

[0036] (10) X-ray fluorescence spectroscopy analysis results X-ray fluorescence spectroscopy analysis was performed on the raw coal and the obtained pre-deashed coal from eastern Inner Mongolia. The results are shown in Table 3.

[0037] Table 3. X-ray fluorescence spectroscopic analysis results of raw coal from eastern Inner Mongolia and pre-deashed coal from eastern Inner Mongolia obtained in Example 1. As shown in Table 3, after the pre-deashing treatment in this embodiment, the contents of Si, Fe, Al, and Ca in the lignite from eastern Inner Mongolia were significantly reduced. Specifically, the Si content decreased from 8.40 wt% to 0.06 wt%, the Fe content decreased from 3.79 wt% to 0.16 wt%, the Al content decreased from 4.19 wt% to 0.26 wt%, and the Ca content decreased from 3.57 wt% to 0.04 wt%.

[0038] (11) X-ray diffraction analysis results Figure 1 The images show the X-ray diffraction patterns of raw coal from eastern Inner Mongolia and the pre-deashed coal from eastern Inner Mongolia obtained in this example. Figure 1 It can be seen that, compared with the raw coal in eastern Inner Mongolia, the intensity of the diffraction peaks corresponding to minerals in the pre-deashed coal in eastern Inner Mongolia is reduced, and the diffraction peaks corresponding to some minerals disappear, indicating that the minerals in the lignite in eastern Inner Mongolia have been removed.

[0039] Example 2 This embodiment uses Liaoning lignite as raw coal and includes the following steps: (1) Raw coal crushing and coal-water slurry preparation The Liaoning lignite was crushed and passed through a 200-mesh sieve. 50g of the sieved Liaoning coal powder was weighed and added to a 1000mL plastic beaker. Then, 500mL of deionized water was added to the plastic beaker and stirred thoroughly to disperse the Liaoning coal powder in the deionized water, thus obtaining a coal-water slurry.

[0040] (2) First hydrochloric acid treatment The plastic beaker containing the coal-water slurry was placed in a constant temperature water bath at 60℃. The stirring speed was fixed at 800 r / min. 64 mL of 36% hydrochloric acid was added to the resulting coal-water slurry. After adding the hydrochloric acid, the mixture was stirred for 3.5 hours to complete the first hydrochloric acid treatment.

[0041] (3) First centrifugal washing After the first hydrochloric acid treatment, the treated material was removed from the constant temperature water bath and the coal sample was centrifuged and cleaned with deionized water.

[0042] The centrifugal washing process involves dispensing the solution into 50mL centrifuge tubes, adding water, dispersing and shaking, centrifuging at 4000 rpm for 5 minutes, and discarding the supernatant. This process is repeated three times: adding water, dispersing, centrifuging, and discarding the supernatant. The resulting coal sample is collected after centrifugal washing to obtain the first washed wet precipitated coal sample.

[0043] (4) Hydrofluoric acid treatment Add 500 mL of deionized water to the first cleaned coal sample to prepare a slurry, and place it in a constant temperature water bath at 60℃. Keep the stirring speed at 800 r / min, add 73 mL of hydrofluoric acid with a mass fraction of 40%, and stir for 3.5 h to complete the hydrofluoric acid treatment.

[0044] (5) Second centrifugal washing After hydrofluoric acid treatment, the coal sample obtained after treatment was centrifuged and cleaned with deionized water.

[0045] The centrifugal washing process involves dispensing the solution into 50mL centrifuge tubes, adding water, dispersing and shaking, then centrifuging at 4000 rpm for 5 minutes, and discarding the supernatant. This process of "adding water—dispersing—centrifuging—removing supernatant" is repeated three times. The resulting coal sample is collected after centrifugal washing to obtain the second washed wet precipitated coal sample.

[0046] (6) Second hydrochloric acid treatment Add 500 mL of deionized water to the obtained second cleaned coal sample to prepare a slurry, and place it in a constant temperature water bath at 60℃. Keep the stirring speed at 800 r / min, add 64 mL of hydrochloric acid with a mass fraction of 36%, and stir for 3.5 h to complete the second hydrochloric acid treatment.

[0047] (7) Vacuum filtration and cleaning After the second hydrochloric acid treatment is completed, the resulting material is vacuum filtered to separate the solid and liquid phases.

[0048] During vacuum filtration, deionized water is used to wash the solid phase retained by vacuum filtration. During the washing process, pH test paper is used to detect the washing solution obtained after each wash. Washing is stopped when the washing solution turns green on the pH test paper. After vacuum filtration is completed, the washed filter cake is obtained.

[0049] (8) Drying and storage The cleaned filter cake was separated from the filter paper, and the filter cake was placed in a constant temperature drying oven at 115℃ for 1 hour to obtain Liaoning pre-deashed coal.

[0050] After drying, the obtained Liaoning pre-deashed coal is stored in sealed bags.

[0051] (9) Industrial analysis results The four industrial components (moisture, ash, volatile matter, and fixed carbon) of Liaoning raw coal and the obtained Liaoning pre-deashed coal were determined using a JHGF-3 fully automatic industrial analyzer. The test results are shown in Table 4.

[0052] Table 4. Industrial analysis results of Liaoning raw coal and Liaoning pre-deashed coal obtained in Example 2. As shown in Table 4, after the pre-ash removal treatment in this embodiment, the air-dried ash content of Liaoning lignite decreased from 17.92% to 1.40%, a decrease of 16.52 percentage points; at the same time, the volatile matter content increased from 39.65% to 45.61%, and the fixed carbon content increased from 41.52% to 51.91%.

[0053] (10) X-ray fluorescence spectroscopy analysis results X-ray fluorescence spectroscopy analysis was performed on the raw coal from Liaoning and the obtained pre-deashed coal from Liaoning. The results are shown in Table 5.

[0054] Table 5. X-ray fluorescence spectroscopic analysis results of Liaoning raw coal and Liaoning pre-deashed coal obtained in Example 2. As shown in Table 5, after the pre-deashing treatment in this embodiment, the contents of Si, Fe, Al, and Ca in Liaoning lignite were significantly reduced. Specifically, the Si content decreased from 5.89 wt% to 0.04 wt%, the Fe content decreased from 2.66 wt% to 0.11 wt%, the Al content decreased from 2.94 wt% to 0.18 wt%, and the Ca content decreased from 2.50 wt% to 0.03 wt%.

[0055] (11) X-ray diffraction analysis results Figure 2 The images show the X-ray diffraction patterns of raw coal from Liaoning and the pre-deashed coal from Liaoning obtained in this example. Figure 2It can be seen that, compared with the raw coal of Liaoning, the intensity of the diffraction peaks corresponding to minerals in the pre-deashed coal of Liaoning is reduced, and the diffraction peaks corresponding to some minerals disappear, indicating that the minerals in the Liaoning lignite have been removed.

[0056] Comparative Example 1 The lignite from eastern Inner Mongolia shown in Table 1 was used as the control coal sample. The lignite from eastern Inner Mongolia was crushed and passed through a 200-mesh sieve. The resulting lignite powder was not subjected to first hydrochloric acid treatment, hydrofluoric acid treatment, or second hydrochloric acid treatment. The raw lignite from eastern Inner Mongolia was directly subjected to industrial analysis, X-ray fluorescence spectroscopy analysis, and X-ray diffraction analysis.

[0057] The industrial analysis results of raw coal from eastern Inner Mongolia are shown in Table 2, the X-ray fluorescence spectroscopy analysis results are shown in Table 3, and the X-ray diffraction patterns are shown in Table 4. Figure 1 .

[0058] As shown in Tables 2 and 3, the air-dried ash content of the raw coal from eastern Inner Mongolia without pre-deashing treatment is 25.57%, with Si, Fe, Al and Ca contents of 8.40 wt%, 3.79 wt%, 4.19 wt% and 3.57 wt%, respectively.

[0059] Comparing Comparative Example 1 with Example 1, it can be seen that the pre-deashing method of sequentially performing first hydrochloric acid treatment, hydrofluoric acid treatment, and second hydrochloric acid treatment can reduce the ash content and the content of Si, Fe, Al, and Ca in Inner Mongolia lignite.

[0060] Comparative Example 2 The Liaoning lignite shown in Table 1 was used as the control coal sample. The Liaoning lignite was crushed and passed through a 200-mesh sieve. The resulting Liaoning coal powder was not subjected to first hydrochloric acid treatment, hydrofluoric acid treatment, or second hydrochloric acid treatment. The raw Liaoning coal was directly subjected to industrial analysis, X-ray fluorescence spectroscopy analysis, and X-ray diffraction analysis.

[0061] The industrial analysis results of Liaoning raw coal are shown in Table 4, the X-ray fluorescence spectroscopy analysis results are shown in Table 5, and the X-ray diffraction patterns are shown in Table 6. Figure 2 .

[0062] As shown in Tables 4 and 5, the air-dried ash content of Liaoning raw coal without pre-deashing treatment is 17.92%, of which the contents of Si, Fe, Al and Ca are 5.89wt%, 2.66wt%, 2.94wt% and 2.50wt%, respectively.

[0063] Comparing Comparative Example 2 with Example 2, it can be seen that the pre-deashing method of sequentially performing first hydrochloric acid treatment, hydrofluoric acid treatment, and second hydrochloric acid treatment can reduce the ash content, as well as the content of Si, Fe, Al, and Ca in Liaoning lignite.

[0064] Experimental Results Analysis As shown in Tables 2 and 4, after pre-deashing treatment, the air-dried ash content of Inner Mongolia lignite decreased from 25.57% to 1.85%, and the air-dried ash content of Liaoning lignite decreased from 17.92% to 1.40%. The air-dried ash content of both types of pre-deashed coal was less than 2%.

[0065] As shown in Tables 3 and 5, the contents of Si, Fe, Al, and Ca in both Inner Mongolia lignite and Liaoning lignite were significantly reduced after pre-deashing treatment. (Combined with...) Figure 1 and Figure 2 It can be seen that after pre-deashing treatment, the intensity of diffraction peaks corresponding to minerals in the raw coal decreases, and some diffraction peaks corresponding to minerals disappear.

[0066] The above results show that by sequentially performing a first hydrochloric acid treatment, a hydrofluoric acid treatment, and a second hydrochloric acid treatment, and then centrifuging and washing after the first hydrochloric acid treatment and the hydrofluoric acid treatment, the present invention can remove minerals from the high-ash lignite used in the examples, and obtain pre-deashed coal with an air-dried basis ash content of less than 2%.

[0067] It should be noted that the existing comparative examples are only raw coal without pre-deashing treatment, which can only prove that the complete pre-deashing method has a deashing effect compared to untreated raw coal. The existing data cannot alone prove that the second hydrochloric acid treatment, inter-stage centrifugal washing, or specific treatment parameters have unexpected technical effects compared to other acid washing methods.

[0068] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for pre-deashing raw coal suitable for co-refining of coal and heavy oil, comprising the following steps: Lignite with an air-dried ash content greater than 15% was pulverized and passed through a 200-mesh sieve. The resulting coal powder was mixed with deionized water at a mass ratio of 1:6 to 1:10 to obtain a coal-water slurry. The coal-water slurry is subjected to a first hydrochloric acid treatment, wherein the first hydrochloric acid treatment uses hydrochloric acid with a mass fraction of 36%. After the treatment, the coal sample obtained by treatment is centrifuged and washed with deionized water to obtain a first cleaned coal sample. The first cleaned coal sample was treated with hydrofluoric acid, wherein the hydrofluoric acid treatment used hydrofluoric acid with a mass fraction of 40%. After the treatment, the coal sample was centrifuged and cleaned with deionized water to obtain the second cleaned coal sample. The second cleaned coal sample was subjected to a second hydrochloric acid treatment with a mass fraction of 36%. After the treatment, solid-liquid separation was performed, and the obtained solid phase was washed with deionized water until the washing solution was neutral on pH test paper, thus obtaining pre-deashed coal. The first hydrochloric acid treatment, the hydrofluoric acid treatment, and the second hydrochloric acid treatment are all performed at a temperature of 40–60°C, a stirring rate of 500–1000 r / min, and a treatment time of 3.5 h. The resulting pre-deashed coal has an air-dried ash content of less than 2%.

2. The method for pre-deashing raw coal suitable for co-refining of coal and heavy oil according to claim 1, characterized in that, The lignite is Inner Mongolia lignite with an air-dried ash content of 25.57% by mass. For every 50g of the Inner Mongolia lignite, the amount of deionized water used to prepare the coal-water slurry is 500mL, the amount of hydrochloric acid with a mass fraction of 36% used for the first hydrochloric acid treatment is 90mL, the amount of hydrofluoric acid with a mass fraction of 40% used for the first hydrochloric acid treatment is 105mL, and the amount of hydrofluoric acid with a mass fraction of 36% used for the second hydrochloric acid treatment is 90mL.

3. The method for pre-deashing raw coal suitable for co-refining of coal and heavy oil according to claim 1, characterized in that, The lignite is Liaoning lignite with an air-dried ash content of 17.92% by mass. For every 50g of the Liaoning lignite, the amount of deionized water used to prepare the coal-water slurry is 500mL, the amount of hydrochloric acid with a mass fraction of 36% used in the first hydrochloric acid treatment is 64mL, the amount of hydrofluoric acid with a mass fraction of 40% used in the first hydrofluoric acid treatment is 73mL, and the amount of hydrofluoric acid with a mass fraction of 36% used in the second hydrochloric acid treatment is 64mL.

4. The method for pre-deashing raw coal suitable for co-refining of coal and heavy oil according to claim 1, characterized in that, The volume of hydrochloric acid used in the first hydrochloric acid treatment is the same as that used in the second hydrochloric acid treatment.

5. The method for pre-deashing raw coal suitable for co-refining of coal and heavy oil according to claim 1, characterized in that, The treatment temperatures for the first hydrochloric acid treatment, the hydrofluoric acid treatment, and the second hydrochloric acid treatment are all 60°C.

6. The method for pre-deashing raw coal suitable for co-refining of coal and heavy oil according to claim 1, characterized in that, Both the centrifugal cleaning after the first hydrochloric acid treatment and the centrifugal cleaning after the hydrofluoric acid treatment were performed at a centrifugal speed of 3000-5000 r / min, with each centrifugation lasting 5-7 min, and the number of centrifugal cleaning cycles after the first hydrochloric acid treatment and the hydrofluoric acid treatment were 3-5 times respectively.

7. A method for pre-deashing raw coal suitable for co-refining of coal and heavy oil according to claim 6, characterized in that, Both the centrifugal cleaning after the first hydrochloric acid treatment and the centrifugal cleaning after the hydrofluoric acid treatment were performed at a centrifugal speed of 4000 r / min, with each centrifugation lasting 5 min. The number of centrifugal cleaning cycles after the first hydrochloric acid treatment and the hydrofluoric acid treatment were 3 each.

8. The method for pre-deashing raw coal suitable for co-refining of coal and heavy oil according to claim 1, characterized in that, The solid-liquid separation after the second hydrochloric acid treatment is performed by vacuum filtration; during the vacuum filtration process, the retained solid phase is washed with deionized water until the resulting washing solution is neutral on pH test paper as the washing endpoint.

9. A method for pre-deashing raw coal suitable for co-refining of coal and heavy oil according to claim 2, characterized in that, The treatment temperature for the first hydrochloric acid treatment, the hydrofluoric acid treatment, and the second hydrochloric acid treatment is 60°C. After the first hydrochloric acid treatment and the hydrofluoric acid treatment, the samples are centrifuged and washed three times at a speed of 4000 r / min, with each centrifugation lasting 5 min. After the second hydrochloric acid treatment is completed, vacuum filtration is performed, and during the vacuum filtration process, the retained solid phase is washed with deionized water until the resulting washing solution is neutral on pH test paper; the washed solid phase is dried at 115°C for 1 hour, and the air-dried ash content of the obtained pre-deashed coal is not higher than 1.85%.

10. A method for pre-deashing raw coal suitable for co-refining of coal and heavy oil according to claim 3, characterized in that, The treatment temperature for the first hydrochloric acid treatment, the hydrofluoric acid treatment, and the second hydrochloric acid treatment is 60°C. After the first hydrochloric acid treatment and the hydrofluoric acid treatment, the samples are centrifuged and washed three times at a speed of 4000 r / min, with each centrifugation lasting 5 min. After the second hydrochloric acid treatment is completed, vacuum filtration is performed, and during the vacuum filtration process, the retained solid phase is washed with deionized water until the resulting washing solution is neutral on pH test paper; the washed solid phase is dried at 115°C for 1 hour, and the air-dried ash content of the obtained pre-deashed coal is not higher than 1.40%.

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