Low-rank coal drying and grading utilization method and system

Abstract

The invention discloses a low-rank coal drying and grading utilization method and system, and the method comprises the steps: carrying out drying treatment on low-rank raw coal to obtain upgraded coal; carrying out solid-solid separation treatment on the upgraded coal to obtain a dry coal product and dry coal powder less than or equal to 0.5 mm; the dry pulverized coal is introduced into an airflow classifier to be subjected to classification treatment, and dry fine pulverized coal larger than 74 micrometers and dry superfine pulverized coal smaller than 74 micrometers are obtained; blending the dried fine coal powder and undried raw coal according to different proportions to obtain a coal product with a specific heat value; and mixing the dried superfine pulverized coal with pulverized coal smaller than 400 [mu] m, and adding water and an additive to prepare a coal water slurry product. The heat value of coal can be effectively increased, and the problem that fine coal powder is difficult to treat and utilize is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of clean utilization of coal, and in particular to a method and system for drying and grading low-rank coal. Background Art

[0002] As one of the world's major energy resources, coal is widely used in the fields of electricity, metallurgy, and chemical industry. However, due to the high moisture content of low-rank coal, which can usually reach 15% to 30% or even higher, its calorific value is low, and it is difficult to burn and utilize it efficiently if used directly.

[0003] Coal drying can significantly reduce the moisture content of low-rank coal, improve its calorific value, optimize combustion performance, and facilitate efficient utilization, making it more suitable for industrial applications such as coal-fired power generation or blast furnace injection. In order to improve the energy utilization value of low-rank coal, drying has become one of the key technologies.

[0004] However, low-rank coal has a low degree of coalification, a high grindability coefficient, and is relatively soft, which easily produces a large amount of fine coal powder. If not handled in time, it is easy to spontaneously combust during the drying process, and there is even a risk of dust explosion. At present, fine coal powder is usually recovered by nitrogen filling, canning, etc., and then sent to the nearest power plant for coal-fired power generation. This treatment method is costly. If there is no power plant nearby, the whereabouts of these fine coal powders is a difficult problem to solve, resulting in waste of resources and environmental pollution. Therefore, how to efficiently recover and reasonably utilize these fine coal powders during the drying process has become an important technical challenge for improving the quality of low-rank coal.

[0005] In addition, the traditional water-coal slurry preparation process usually requires multiple processes such as crushing, grinding, grading, and additive mixing of raw coal. The process flow is complicated and energy-intensive. In addition, the traditional water-coal slurry preparation process is mainly rod milling. If bimodal or multimodal grading is required, additional fine mills and ultrafine mills are required. The particle size distribution of coal powder is strictly required, and the particle size control is difficult. In particular, the preparation cost of ultrafine coal powder is high, which limits the widespread application of water-coal slurry technology. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method and system for drying and grading low-rank coal in view of the above-mentioned deficiencies in the prior art, which can effectively improve the calorific value of coal and solve the problem that fine coal powder is difficult to handle and utilize.

[0007] The technical solution of the present invention to solve the above technical problems is:

[0008] According to one aspect of the present invention, a method for drying and grading low-rank coal is provided, comprising:

[0009] Drying low-rank raw coal to obtain upgraded coal;

[0010] The upgraded coal is subjected to solid-solid separation treatment to obtain a dry coal product and a particle size of ≤

[0011] 0.5mm dry coal powder;

[0012] Passing the dried coal powder into an air flow classifier for classification treatment to obtain dried fine coal powder with a particle size greater than 74 μm and dried ultrafine coal powder with a particle size less than 74 μm;

[0013] The dried fine coal powder is mixed with undried raw coal in different proportions to obtain a coal product with a specific calorific value;

[0014] The dry ultrafine coal powder is mixed with coal powder with a particle size of less than 400μm, and then water and additives are added to make a water-coal slurry product.

[0015] Optionally, before drying the low-rank raw coal, the method further includes: pre-treating the low-rank raw coal to reduce its particle size to below 50 mm.

[0016] Optionally, the drying process is carried out at a temperature of 150 to 200° C. and for a time of 10 to 30 minutes.

[0017] Optionally, the air flow velocity in the air flow classifier is 15-20 m / s, the classifying wheel rotation speed is 1000-3000 rpm, and the feed rate is 100-200 kg / h.

[0018] Optionally, the mass proportion of the dry ultrafine coal powder is 25-50%, and the concentration of the water-coal slurry is 55-65%.

[0019] According to one aspect of the present invention, a low-rank coal drying and classification utilization system is provided, comprising a drying device, a separation device, an airflow classifier, a blending device and a water-coal slurry preparation device, wherein:

[0020] The drying device is used to dry low-rank raw coal to obtain upgraded coal;

[0021] The separation device is connected to the drying device, and is used to receive the upgraded coal and perform solid-solid separation treatment on it to obtain dried coal and dried coal powder with a particle size of ≤0.5 mm;

[0022] The airflow classifier is connected to the separation device and is used to receive the dry coal powder and classify it to obtain dry fine coal powder with a particle size greater than 74 μm and dry ultrafine coal powder with a particle size less than 74 μm;

[0023] The blending device is connected to the airflow classifier and is used to receive the dry fine coal powder and blend it with undried raw coal in different proportions to obtain a coal product with a specific calorific value;

[0024] The water-coal slurry preparation device is connected to the airflow classifier and is used to receive the dry ultrafine coal powder and mix it with coal powder with a particle size of less than 400 μm to prepare a water-coal slurry product.

[0025] Optionally, the system further comprises a pretreatment device, which is connected to the drying device and is used for pretreatment of the low-rank raw coal before drying the low-rank raw coal to reduce its particle size to below 50 mm.

[0026] Optionally, the separation device includes a unloading silo, a cyclone dust collector, a bag dust collector, and an induced draft fan, wherein: the unloading silo is connected to the drying device, and the induced draft fan is connected to the unloading silo through the cyclone separator and the bag dust collector, and the air in the unloading silo is extracted by the induced draft fan to generate negative pressure, and the fine coal powder in the upgraded coal is captured in the cyclone dust collector and the bag dust collector for separation to obtain the dry coal and the dry coal powder.

[0027] Optionally, the system further comprises a crusher, which is connected to the water-coal slurry preparation device and is used to prepare coal powder with a particle size of less than 400 μm.

[0028] Optionally, the water-coal slurry preparation device is a tank agitator.

[0029] Beneficial effects:

[0030] The present invention provides a method and system for drying and grading low-rank coal, which forms a complete low-rank coal drying and grading process by drying low-rank coal, recovering fine coal powder, and utilizing it in different grades and qualities. The drying process can reduce the moisture content of low-rank coal by 5-15%, effectively improve the calorific value of coal, and increase the calorific value to 4750-5800 Kcal / kg, thereby improving the quality of coal and obtaining upgraded coal products. These high-calorific value upgraded coal products can significantly improve the combustion efficiency and can be directly used for power generation, blast furnace injection or other energy purposes. The fine coal powder is captured and recovered by using negative pressure dust removal technology, the risk of spontaneous combustion is reduced, and safe production is ensured. The recovered fine coal powder is graded and utilized to obtain coal products with specific calorific value and High-value-added high-concentration water-coal slurry, these coal products with specific calorific values ​​can be used in industrial applications that meet different calorific value requirements, high-concentration water-coal slurry can be directly used for coal gasification and the preparation of chemicals such as alcohols and olefins, thereby solving the problem that fine coal powder is difficult to handle and utilize, realizing the graded and quality-based utilization of coal, efficient and clean utilization, resource recycling, reducing resource waste and environmental pollution, and improving the comprehensive utilization efficiency and utilization value of low-quality coal. At the same time, it can also simplify the steps of the traditional water-coal slurry preparation process. The addition of dry ultrafine coal powder can optimize the particle size distribution scheme of water-coal slurry, which can increase the concentration of water-coal slurry by 2-3%, reduce the complexity, energy consumption and cost of water-coal slurry preparation, expand the application field of water-coal slurry, and have significant economic and environmental benefits. The overall solution of this method not only solves the problem of low efficiency and high pollution of direct combustion of low-rank coal, but also provides an innovative solution for the efficient and clean utilization of coal resources, with broad application prospects and promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of a method and system for drying and grading low-rank coal in an embodiment of the present invention.

[0032] In the figure: 1- hopper; 2- drying device; 3- unloading silo; 4- cyclone dust collector;

[0033] 5-Bag filter; 6-Induced draft fan; 7-Airflow classifier; 8-Hammer crusher; 9-Tank mixer; 10-Low-rank raw coal; 11-Dry coal product; 12-Air containing coal powder; 13-Dry coal powder with particle size ≤ 0.5mm; 14-Dry fine coal powder larger than 74μm; 15-Dry ultrafine coal powder smaller than 74μm; 16-Coal for water-coal slurry gasification; 17-Less than 400

[0034] μm coal powder; 18-water coal slurry product. DETAILED DESCRIPTION

[0035] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0036] In view of the fact that low-rank coal in the prior art has high water content and low calorific value, it is difficult to burn and utilize it efficiently, and the drying of coal will lead to problems such as difficulty in handling and utilizing fine coal powder. At the same time, the traditional water-coal slurry preparation process has problems such as complex process flow and high energy consumption. The present invention provides a method for drying and grading low-rank coal, including:

[0037] Drying low-rank raw coal to obtain upgraded coal;

[0038] The upgraded coal is subjected to solid-solid separation treatment to obtain a dry coal product with a high calorific value and dry coal powder with a particle size of ≤0.5 mm;

[0039] Passing the dried coal powder into an air flow classifier for classification treatment to obtain dried fine coal powder with a particle size greater than 74 μm and dried ultrafine coal powder with a particle size less than 74 μm;

[0040] The dried fine coal powder is mixed with undried raw coal in different proportions to obtain a coal product with a specific calorific value;

[0041] The dry ultrafine coal powder is mixed with coal powder with a particle size of less than 400μm, and then water and additives are added to make a water-coal slurry product.

[0042] Accordingly, the present invention also provides a low-rank coal drying and classification utilization system, comprising a drying device, a separation device, an airflow classifier, a blending device and a water-coal slurry preparation device, wherein:

[0043] The drying device is used to dry low-rank raw coal to obtain upgraded coal;

[0044] The separation device is connected to the drying device, and is used to receive the upgraded coal and perform solid-solid separation treatment on it to obtain a high calorific value dry coal product and dry coal powder with a particle size of ≤0.5 mm;

[0045] The airflow classifier is connected to the separation device and is used to receive the fine coal powder and classify it to obtain dry fine coal powder with a particle size greater than 74 μm and dry ultrafine coal powder with a particle size less than 74 μm;

[0046] The blending device is connected to the airflow classifier and is used to receive the dry fine coal powder and blend it with undried raw coal in different proportions to obtain a coal product with a specific calorific value;

[0047] The water-coal slurry preparation device is connected to the airflow classifier and is used to receive the dry ultrafine coal powder and mix it with coal powder with a particle size of less than 400 μm to prepare a water-coal slurry product.

[0048] Example 1

[0049] like Figure 1 As shown, this embodiment discloses a method for drying and grading low-rank coal, comprising:

[0050] Step S1, drying the low-rank raw coal 10 to obtain upgraded coal.

[0051] In some embodiments, the low-rank raw coal 10 is preferably a non-sticky coal with low ash, low sulfur and high moisture content, wherein the ash content A ar 2~7%, volatile matter V daf 26~33%, total water content M t The sulfur content is 26-32%. t,d <1.0%, calorific value Q net,ar It is 4400~4900Kcal / kg.

[0052] In some embodiments, the temperature of the drying process is 150-200°C and the time is 10-30 minutes. The drying process can be drum drying, fluidized bed drying, etc. In addition, the drying device used for the drying process is equipped with sensors for detecting parameters such as temperature, humidity, and airflow, and has an automatic control system that can monitor the drying process in real time and automatically control the drying process through system settings. The temperature, time, and hot air flow rate of the drying process are automatically adjusted according to the data fed back by the sensor to improve the uniformity of drying and reduce the moisture fluctuation to ±1%.

[0053] After drying, the moisture content of the coal can be reduced from 26-32% to 10-20%, and the calorific value is 4750-5800 Kcal / kg. After step S2, a dry coal product is obtained, which can be used in coal-fired power generation or blast furnace injection.

[0054] In some embodiments, before drying the low-rank raw coal, the method further comprises:

[0055] Step S0, pre-treating the low-rank coal raw coal 10, the pre-treatment includes but is not limited to crushing, screening and the like, so that its particle size is reduced to below 50 mm, that is, step S1 preferably selects the low-rank coal raw coal 10 with a particle size below 50 mm for drying.

[0056] Step S2, performing solid-solid separation treatment on the dried coal to obtain a dried coal product 11 with a high calorific value and dried coal powder 13 with a particle size of ≤0.5 mm.

[0057] In some embodiments, the upgraded coal is subjected to a solid-solid separation process, specifically:

[0058] First, the upgraded coal obtained in step S1 is discharged into the discharge silo 3, and the air in the discharge silo 3 is extracted by the strong induced draft fan 6 to generate negative pressure, and the fine coal powder in the upgraded coal (i.e., the coal powder-containing air 12) is captured and separated in the cyclone dust collector 4 and the bag dust collector 5, thereby obtaining the dry coal product 11 and the dry coal powder, which can prevent the coal powder from escaping into the air and avoid the coal powder from spontaneous combustion. The dry coal powder recovered by the present invention accounts for about 5-10% of the total amount of raw coal.

[0059] Specifically, an external vortex is formed in the cyclone dust collector 4, and the dust suspended in the external vortex moves to the wall of the device under the action of centrifugal force, and moves to the lower part of the bag dust collector 5 with the external vortex, and is discharged from the dust discharge hole. The gas pre-treated by the cyclone dust collector 4 enters the bag dust collector 5, and the fine particles of coal powder are intercepted by the filter bag of the bag dust collector 5. The purified gas flows out from the inside of the filter bag and enters the upper induced draft fan 6 for discharge.

[0060] While completing the drying and fine coal powder capture, the natural cooling of the dried coal can be accelerated, and the temperature of the dried coal product 11 at the discharge outlet of the discharge silo 3 can be reduced to 40-50° C., ensuring the safety of coal transportation and storage.

[0061] Step S3, passing the dry coal powder into the airflow classifier 7 for classification treatment, further optimizing the particle size distribution of the fine coal powder, and obtaining dry fine coal powder 14 with a particle size greater than 74 μm and dry ultrafine coal powder 15 with a particle size less than 74 μm.

[0062] In some embodiments, the air flow velocity in the air flow classifier 7 is 15-20 m / s, the classifying wheel speed is 1000-3000 rpm, and the feed rate is 100-200 kg / h. Ash content of dry ultrafine coal powder A ar 3~10%, volatile matter V daf 25~31%, total water content M t 10~15%, sulfur content S t,d <1.0%, calorific value Q net,ar It is 5300~5800Kcal / kg.

[0063] Step S4, blending the dry fine coal powder and the undried raw coal in different proportions to obtain a coal product with a specific calorific value, which is used for industrial applications that meet different calorific value requirements. Specifically, the dry fine coal powder and the undried raw coal are blended according to a weighted average calculation method, and the blending ratio is calculated according to the target calorific value of the coal product. The blending ratio of the dry fine coal powder to the undried raw coal is in the range of 1:9 to 9:1, and a coal product with a specific calorific value is obtained, and the calorific value is 4500 to 5700 Kcal / kg;

[0064] After the dry ultrafine coal powder is mixed with the coal powder 17 with a particle size less than 400 μm, water and additives are added to further prepare a water-coal slurry product 18.

[0065] Specifically, the coal powder 17 with a particle size less than 400 μm can be produced in the following manner: the water-coal slurry gasification coal 16 with a particle size distribution in the range of 5 to 50 mm can be sent to a hammer crusher 8 for crushing. The rotation speed of the hammer crusher 8 is set between 500 and 1000 rpm, and the screen aperture is 0.3 to 0.4 mm, so that the coal powder 17 with a particle size less than 400 μm can be produced.

[0066] The coal powder 17 smaller than 400 μm and the dry ultrafine coal powder 15 smaller than 74 μm obtained by the above classification are directly sent to the tank mixer 9 for dry water-coal slurry preparation. Water and additives are added and stirred evenly to obtain a high value-added water-coal slurry product 18, wherein the mass proportion of the dry ultrafine coal powder is 25-50%, and the concentration of the water-coal slurry is 55-65%. These water-coal slurries can be used for coal gasification and the preparation of chemicals such as alcohols and olefins.

[0067] Compared with the traditional coal-water slurry preparation process, the present method simplifies the complicated grinding and classification steps in the traditional coal-water slurry process, and can reduce the complexity, energy consumption and cost of coal-water slurry preparation.

[0068] The low-rank coal drying and graded utilization method of the present embodiment, through the above continuous steps, carries out drying treatment, fine coal powder recovery and graded and quality-based utilization of the low-rank coal, so as to form a complete low-rank coal drying and graded utilization process, wherein the moisture content of the low-rank coal can be reduced by 5-15% through drying treatment, and the calorific value of the coal can be effectively increased to 4750-5800Kcal / kg, thereby improving the quality of the coal and obtaining an upgraded coal product. These high-calorific value upgraded coal products can significantly improve the combustion efficiency and can be directly used for power generation, blast furnace injection or other energy purposes; the fine coal powder is captured and recovered by adopting negative pressure dust removal technology, the risk of spontaneous combustion is reduced, and safe production is ensured, and the recovered fine coal powder is graded and utilized to obtain a specific calorific value coal product. Products and high-value-added high-concentration water-coal slurry. These coal products with specific calorific values ​​can be used in industrial applications that meet different calorific value requirements. High-concentration water-coal slurry can be directly used for coal gasification and the preparation of chemicals such as alcohols and olefins, thereby solving the problem that fine coal powder is difficult to handle and utilize, realizing the graded and quality-based utilization of coal, efficient and clean utilization, and resource recycling, reducing resource waste and environmental pollution, and improving the comprehensive utilization efficiency and utilization value of low-quality coal. At the same time, it can also simplify the steps of the traditional water-coal slurry preparation process. The addition of dry ultrafine coal powder can optimize the particle size distribution scheme of water-coal slurry, which can increase the concentration of water-coal slurry by 2-3%, reduce the complexity, energy consumption and cost of water-coal slurry preparation, expand the application field of water-coal slurry, and have significant economic and environmental benefits. The overall scheme of this method not only solves the problem of low efficiency and high pollution of direct combustion of low-rank coal, but also provides an innovative solution for the efficient and clean utilization of coal resources, with broad application prospects and promotion value.

[0069] Example 2

[0070] like Figure 1 As shown, this embodiment discloses a low-rank coal drying and classification utilization system, which is used for the low-rank coal drying and classification utilization method described above. The system includes a drying device 2, a separation device, an airflow classifier 7, a blending device (not shown in the figure) and a water-coal slurry preparation device, wherein:

[0071] The drying device 2 is used to dry the low-rank raw coal 10 to obtain upgraded coal;

[0072] The separation device is connected to the drying device 2, and is used to receive the upgraded coal and perform solid-solid separation treatment on it to obtain a dried coal product 11 and dried coal powder 13 with a particle size of ≤0.5 mm;

[0073] The airflow classifier 7 is connected to the separation device, and is used to receive the dry coal powder and classify it to obtain dry fine coal powder 14 with a particle size greater than 74 μm and dry ultrafine coal powder 15 with a particle size less than 74 μm;

[0074] The blending device is connected to the airflow classifier 7 and is used to receive the dry fine coal powder and blend it with undried raw coal in different proportions to obtain a coal product with a specific calorific value;

[0075] The coal-water slurry preparation device is connected to the airflow classifier 7 and is used to receive the dry ultrafine coal powder and mix it with coal powder 17 with a particle size of less than 400 μm to form a coal-water slurry product 18.

[0076] In some embodiments, the drying device 2 may be a drum drying device, a fluidized bed drying device, etc. In addition, the drying device 2 is equipped with sensors for detecting parameters such as temperature, humidity, and airflow, and has an automatic control system, which can monitor the drying process in real time, and automatically control the drying process through system settings, and automatically adjust the temperature, time, and hot air flow rate of the drying process according to the data fed back by the sensors, so as to improve the drying uniformity and reduce the moisture fluctuation to ±1%.

[0077] In some embodiments, the water-coal slurry preparation device is a tank agitator 9.

[0078] In some embodiments, the system further includes a pretreatment device (not shown in the figure), which is connected to the drying device 2 through the hopper 1, and is used to pretreatment the low-rank raw coal 10 before drying the low-rank raw coal 10, so that its particle size is reduced to less than 50 mm. The pretreated fine coal with a particle size of 50 mm is passed through the hopper 1 to the drying device 2 for drying.

[0079] In some embodiments, the pretreatment device includes but is not limited to a crushing device and a screening device.

[0080] In some embodiments, the separation device includes a discharge silo 3, a cyclone dust collector 4, a bag dust collector 5, and an induced draft fan 6, wherein:

[0081] The unloading silo 3 is connected to the drying device 2, and the induced draft fan 6 is connected to the unloading silo 3 through the cyclone separator 4 and the bag dust collector 5. The induced draft fan 6 draws air in the unloading silo to generate negative pressure, and the fine coal powder in the upgraded coal (i.e., the coal powder-containing air 12) is captured and separated into the cyclone dust collector 4 and the bag dust collector 5 to obtain the dried coal product 11 and the dried coal powder.

[0082] In some embodiments, the system further comprises a crusher, which is connected to the coal water slurry preparation device and is used to prepare coal powder 17 with a particle size of less than 400 μm and pass it into the coal water slurry preparation device.

[0083] In some embodiments, the crusher is a hammer crusher 8.

[0084] Example 3

[0085] like Figure 1 As shown, this embodiment discloses a method for drying and grading low-rank coal using the above-mentioned low-rank coal drying and grading system, the steps comprising:

[0086] Step S1, feed the low-rank raw coal 10 into a drum dryer for drying to obtain upgraded coal. The low-rank raw coal 10 uses low-ash, high-moisture, non-sticky coal as shown in Table 1, the feed rate is set to 100 kg / h, the drying temperature is set to 200°C, and the drying time is set to 20 minutes. The total moisture content of the upgraded coal obtained after drying is 15.53%, and the calorific value is 5470 Kcal / kg.

[0087] Table 1

[0088]

[0089] Step S2, unloading the upgraded coal into the unloading silo 3, extracting the air in the unloading silo 3 through the induced draft fan 6 to generate negative pressure, capturing the fine coal powder in the upgraded coal into the cyclone dust collector 4 and the bag dust collector 5 for separation, and obtaining a dry coal product 11 and dry coal powder 13 with a particle size of ≤0.5 mm, wherein the dry coal powder accounts for about 5% of the total amount. The dry coal product is discharged from the unloading outlet of the unloading silo 3 at a temperature of about 45°C and is sent to the power plant for coal-fired power generation or blast furnace injection.

[0090] Step S3, the dried coal powder is passed into the airflow classifier 7 for classification, the airflow velocity is set to 20m / s, the classifier wheel speed is set to 2500rpm, and the feed rate is set to 100kg / h, to obtain dried fine coal powder 14 with a particle size greater than 74μm and dried ultrafine coal powder 15 with a particle size less than 74μm. Among them, the ash content of the dried ultrafine coal powder is A ar The volatile matter V is 4.15%. daf 27.45%, full moisture M t The sulfur content is 14.14%. t,d 0.23%, calorific value Q net,ar It is 5580Kcal / kg.

[0091] Step S4, mixing the dried fine coal powder and the undried raw coal (calorific value of 4700 Kcal / kg) in a weight ratio of 2:3 to obtain a coal product with a calorific value of 5000 Kcal / kg;

[0092] Coal 16 for water-coal slurry gasification (medium-high volatile bituminous coal A1S1 for fluidized bed gasification) with a particle size distribution in the range of 20 to 50 mm is selected and crushed using a hammer crusher 8, wherein the rotation speed of the hammer crusher 8 is set to 1000 rpm and the screen aperture is 0.4 mm, to obtain coal powder with a particle size less than 400 μm; the dry ultrafine coal powder is mixed with the coal powder 17 with a particle size less than 400 μm, wherein the dry ultrafine coal powder accounts for 25%, and the coal powder 17 with a particle size less than 400 μm obtained by crushing the raw coal accounts for 75%, and after adding water and additives and stirring evenly, a water-coal slurry product with fluidity Class A is obtained, and the test concentration is 58.9%.

[0093] Example 4

[0094] like Figure 1 As shown, this embodiment discloses a method for drying and grading low-rank coal using the above-mentioned low-rank coal drying and grading system, the steps comprising:

[0095] Step S1, feed the low-rank raw coal 10 into a drum dryer for drying to obtain upgraded coal. The low-rank raw coal 10 uses low-ash, high-moisture, non-sticky coal as shown in Table 2, the feed rate is set to 150kg / h, the drying temperature is set to 150°C, and the drying time is set to 12min. The total moisture content of the upgraded coal obtained after drying is 17.6%, and the calorific value is 5320Kcal / kg.

[0096] Table 2

[0097]

[0098] Step S2, the upgraded coal is sent to the unloading silo 3, the air in the unloading silo is extracted by the induced draft fan 6 to generate negative pressure, and the fine coal powder in the upgraded coal is captured in the cyclone dust collector 4 and the bag dust collector 5 for separation, so as to obtain a dry coal product 11 and dry coal powder 13 with a particle size of ≤0.5mm, wherein the dry coal powder accounts for about 7% of the total amount. The dry coal product is discharged from the unloading outlet of the unloading silo 3 with a temperature of about 50°C and is sent to the power plant for coal-fired power generation or blast furnace injection.

[0099] Step S3, the dried coal powder is passed into the airflow classifier 7 for classification, the airflow velocity is set to 20m / s, the classifier wheel speed is set to 2500rpm, and the feed rate is set to 100kg / h, to obtain dried fine coal powder 14 with a particle size greater than 74μm and dried ultrafine coal powder 15 with a particle size less than 74μm. Among them, the ash content of the dried ultrafine coal powder is A ar 5.07%, volatile matter V daf The total water content is 27.04%. t The sulfur content is 16.15%. t,d 0.13%, calorific value Q net,arIt is 5450Kcal / kg.

[0100] Step S4, blending the dried fine coal powder and the undried raw coal (calorific value of 4759 Kcal / kg) in a weight ratio of 7:3 to obtain a coal product with a calorific value of 5200 Kcal / kg;

[0101] Coal 16 for water-coal slurry gasification (medium-high volatile bituminous coal A1S1 for fluidized bed gasification) with a particle size distribution in the range of 10 to 50 mm is selected and crushed using a hammer crusher 8, wherein the rotation speed of the hammer crusher 8 is set to 500 rpm and the screen aperture is 0.4 mm, to obtain coal powder 17 with a particle size less than 400 μm; the dry ultrafine coal powder is mixed with the coal powder with a particle size less than 400 μm, wherein the dry ultrafine coal powder accounts for 35%, and the coal powder 17 with a particle size less than 400 μm obtained by crushing the raw coal accounts for 65%, and after adding water and additives and stirring evenly, a water-coal slurry product with fluidity Class A is obtained, and the test concentration is 59.7%.

[0102] Example 5

[0103] like Figure 1 As shown, this embodiment discloses a method for drying and grading low-rank coal using the above-mentioned low-rank coal drying and grading system, the steps comprising:

[0104] Step S1, feed the low-rank raw coal 10 into a drum dryer for drying to obtain upgraded coal. The low-rank raw coal 10 uses low-ash, high-moisture, non-sticky coal as shown in Table 3, the feed rate is set to 100 kg / h, the drying temperature is set to 200°C, and the drying time is set to 15 min. The total moisture content of the upgraded coal obtained after drying is 20%, and the calorific value is 5200 Kcal / kg.

[0105] Table 3

[0106]

[0107] Step S2, the upgraded coal is sent to the unloading silo 3, the air in the unloading silo 3 is extracted by the induced draft fan 6 to generate negative pressure, and the fine coal powder in the upgraded coal is captured in the cyclone dust collector 4 and the bag dust collector 5 for separation, so as to obtain a dry coal product 11 and dry coal powder 13 with a particle size of ≤0.5mm, wherein the dry coal powder accounts for about 8% of the total amount. The dry coal product is discharged from the unloading outlet of the unloading silo 3 with a temperature of about 43°C and is sent to the power plant for coal-fired power generation or blast furnace injection.

[0108] Step S3, the dried coal powder is passed into the airflow classifier 7 for classification, the airflow velocity is set to 20m / s, the classifier wheel speed is set to 2500rpm, and the feed rate is set to 100kg / h, to obtain dried fine coal powder 14 with a particle size greater than 74μm and dried ultrafine coal powder 15 with a particle size less than 74μm. Among them, the ash content of the dried ultrafine coal powder is A ar The volatile matter V is 3.22%. daf The total water content is 28.34%. t The sulfur content is 18.25%. t,d 0.47%, calorific value Q net,ar It is 5320Kcal / kg.

[0109] Step S4, mixing the dried fine coal powder and the undried raw coal (calorific value of 4559 Kcal / kg) in a weight ratio of 3:2 to obtain a coal product with a calorific value of 5000 Kcal / kg;

[0110] Coal 16 for water-coal slurry gasification (medium-high volatile bituminous coal A1S1 for fluidized bed gasification) with a particle size distribution in the range of 20 to 50 mm is selected and crushed using a hammer crusher 8, wherein the rotation speed of the hammer crusher 8 is set to 800 rpm and the screen aperture is 0.4 mm, to obtain coal powder 17 with a particle size less than 400 μm; the dry ultrafine coal powder is mixed with the coal powder 17 with a particle size less than 400 μm, wherein the dry ultrafine coal powder accounts for 50%, and the coal powder 17 with a particle size less than 400 μm obtained by crushing the raw coal accounts for 50%, and after adding water and additives and stirring evenly, a water-coal slurry product with fluidity Class A is obtained, and the test concentration is 59.1%.

[0111] Example 6

[0112] like Figure 1 As shown, this embodiment discloses a method for drying and grading low-rank coal using the above-mentioned low-rank coal drying and grading system, the steps comprising:

[0113] Step S1, feed the low-rank raw coal 10 into a drum dryer for drying to obtain upgraded coal. The low-rank raw coal 10 uses low-ash, high-moisture, non-sticky coal as shown in Table 4, the feed rate is set to 120kg / h, the drying temperature is set to 160°C, and the drying time is set to 30min. The total moisture content of the upgraded coal obtained after drying is 15.27%, and the calorific value is 5654Kcal / kg.

[0114] Table 4

[0115]

[0116] Step S2, the upgraded coal is sent to the unloading silo 3, the air in the unloading silo 3 is extracted by the induced draft fan 6 to generate negative pressure, and the fine coal powder in the upgraded coal is captured in the cyclone dust collector and the bag dust collector for separation, so as to obtain a dry coal product 11 and dry coal powder 13 with a particle size of ≤0.5mm, wherein the dry coal powder accounts for about 6% of the total amount. The dry coal product is discharged from the unloading outlet of the unloading silo 3 with a temperature of about 46°C and is sent to the power plant for coal-fired power generation or blast furnace injection.

[0117] Step S3, the dried coal powder is passed into the airflow classifier 7 for classification, the airflow velocity is set to 15m / s, the classifier wheel speed is set to 1000rpm, and the feed rate is set to 200kg / h, to obtain dried fine coal powder with a particle size greater than 74μm and dried ultrafine coal powder with a particle size less than 74μm. Among them, the ash content of the dried ultrafine coal powder is A ar 5.78%, volatile matter V daf The total water content is 27.56%. t The sulfur content is 14.11%. t,d 0.30%, calorific value Q net,ar It is 5740Kcal / kg.

[0118] Step S4, mixing the dried fine coal powder and the undried raw coal (calorific value of 4889 Kcal / kg) in a weight ratio of 4:1 to obtain a coal product with a calorific value of 5500 Kcal / kg;

[0119] Coal 16 for water-coal slurry gasification (medium-high volatile bituminous coal A1S1 for fluidized bed gasification) with a particle size distribution in the range of 20 to 40 mm is selected and crushed using a hammer crusher, wherein the speed of the hammer crusher 8 is set to 600 rpm and the screen aperture is 0.3 mm, to obtain coal powder 17 with a particle size less than 400 μm; the dry ultrafine coal powder is mixed with the coal powder 17 with a particle size less than 400 μm, wherein the dry ultrafine coal powder accounts for 30%, and the coal powder 17 with a particle size less than 400 μm obtained by crushing the raw coal accounts for 70%, and after adding water and additives and stirring evenly, a water-coal slurry product with fluidity Class A is obtained, and the test concentration is 59.0%.

[0120] Example 7

[0121] like Figure 1 As shown, this embodiment discloses a method for drying and grading low-rank coal using the above-mentioned low-rank coal drying and grading system, the steps comprising:

[0122] Step S1, feed the low-rank raw coal 10 into a drum dryer for drying to obtain upgraded coal. The low-rank raw coal 10 uses low-ash, high-moisture, non-sticky coal as shown in Table 5, the feed rate is set to 140kg / h, the drying temperature is set to 180°C, and the drying time is set to 10min. The total moisture content of the upgraded coal obtained after drying is 16%, and the calorific value is 5500Kcal / kg.

[0123] Table 5

[0124]

[0125] Step S2, the upgraded coal is sent to the unloading silo 3, the air in the unloading silo is extracted by the induced draft fan 6 to generate negative pressure, and the fine coal powder in the upgraded coal is captured in the cyclone dust collector 4 and the bag dust collector 5 for separation, so as to obtain a dry coal product 11 and dry coal powder 13 with a particle size of ≤0.5mm, wherein the dry coal powder accounts for about 12% of the total amount. The dry coal product is discharged from the unloading outlet of the unloading silo 3 with a temperature of about 40°C and is sent to the power plant for coal-fired power generation or blast furnace injection.

[0126] Step S3, the dried coal powder is passed into the airflow classifier 7 for classification, the airflow velocity is set to 18m / s, the classifier wheel speed is set to 3000rpm, and the feed rate is set to 150kg / h, to obtain dried fine coal powder 14 with a particle size greater than 74μm and dried ultrafine coal powder 15 with a particle size less than 74μm. Among them, the ash content of the dried ultrafine coal powder is A ar 3.88%, volatile matter V daf 26.95%, full water content M t The sulfur content is 15%. t,d 0.51%, calorific value Q net,ar It is 5600Kcal / kg.

[0127] Step S4, mixing the dried fine coal powder and the undried raw coal (calorific value of 4406 Kcal / kg) in a weight ratio of 9:1 to obtain a coal product with a calorific value of 5500 Kcal / kg;

[0128] Coal 16 for water-coal slurry gasification (medium-high volatile bituminous coal A1S1 for fluidized bed gasification) with a particle size distribution in the range of 5 to 10 mm is selected and crushed using a hammer crusher 8, wherein the speed of the hammer crusher 8 is set to 700 rpm and the mesh aperture is 0.3 mm, to obtain coal powder 17 with a particle size of less than 400 μm; dry ultrafine coal powder is mixed with coal powder with a particle size of less than 400 μm, wherein the dry ultrafine coal powder accounts for 40% and the coal powder 17 with a particle size of less than 400 μm obtained by crushing the raw coal accounts for 60%, and after adding water and additives and stirring evenly, a water-coal slurry product with fluidity A is obtained, and the test concentration is 59.2%

[0129] Comparative Example 1

[0130] Compared with Example 7, this comparative example has the following differences:

[0131] Coal 16 for water-coal slurry gasification (medium-high volatile bituminous coal A1S1 for fluidized bed gasification) with a particle size distribution in the range of 50 to 70 mm is selected and crushed using a hammer crusher 8, wherein the rotation speed of the hammer crusher 8 is set to 700 rpm and the sieve aperture is 0.3 mm, to obtain coal powder 17 with a particle size less than 400 μm; the dry ultrafine coal powder is mixed with the coal powder with a particle size less than 400 μm, wherein the dry ultrafine coal powder accounts for 40%, and the coal powder 17 with a particle size less than 400 μm obtained by crushing the raw coal accounts for 60%, and after adding water and additives and stirring evenly, a water-coal slurry product with fluidity grade B is obtained, and the test concentration is 58.5%.

[0132] Compared with Example 7, the water-coal slurry product prepared by the method of this comparative example has poor fluidity and low concentration.

[0133] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method for drying and grading low-rank coal, characterized in that: include: Drying low-rank raw coal to obtain upgraded coal; The upgraded coal is subjected to solid-solid separation treatment to obtain a dry coal product and dry coal powder with a particle size of ≤0.5 mm; Passing the dried coal powder into an air flow classifier for classification treatment to obtain dried fine coal powder with a particle size greater than 74 μm and dried ultrafine coal powder with a particle size less than 74 μm; The dried fine coal powder is mixed with undried raw coal in different proportions to obtain a coal product with a specific calorific value; The dry ultrafine coal powder is mixed with coal powder with a particle size of less than 400μm, and then water and additives are added to make a water-coal slurry product.

2. The method for drying and grading low-rank coal according to claim 1, characterized in that: Before drying the low-rank raw coal, the method further comprises: The low-rank raw coal is pretreated to reduce its particle size to below 50mm.

3. The method for drying and grading low-rank coal according to claim 1 or 2, characterized in that: The drying process is carried out at a temperature of 150 to 200° C. and for a time of 10 to 30 minutes.

4. The method for drying and grading low-rank coal according to claim 1 or 2, characterized in that: The air flow velocity in the air flow classifier is 15-20 m / s, the classifying wheel rotation speed is 1000-3000 rpm, and the feed speed is 100-200 kg / h.

5. The method for drying and grading low-rank coal according to claim 1 or 2, characterized in that: The mass proportion of the dry ultrafine coal powder is 25-50%, and the concentration of the water-coal slurry is 55-65%.

6. A low-rank coal drying and classification utilization system, characterized in that: The invention comprises a drying device (2), a separation device, an air flow classifier (7), a blending device and a water-coal slurry preparation device, wherein: The drying device is used to dry low-rank raw coal to obtain upgraded coal; The separation device is connected to the drying device, and is used to receive the upgraded coal and perform solid-solid separation treatment on it to obtain dried coal and dried coal powder with a particle size of ≤0.5 mm; The airflow classifier is connected to the separation device and is used to receive the dry coal powder and classify it to obtain dry fine coal powder with a particle size greater than 74 μm and dry ultrafine coal powder with a particle size less than 74 μm; The blending device is connected to the airflow classifier and is used to receive the dry fine coal powder and blend it with undried raw coal in different proportions to obtain a coal product with a specific calorific value; The water-coal slurry preparation device is connected to the airflow classifier and is used to receive the dry ultrafine coal powder and mix it with coal powder with a particle size of less than 400 μm to prepare a water-coal slurry product.

7. The low-rank coal drying and classification utilization system according to claim 6, characterized in that: Also includes a pre-processing device, The pretreatment device is connected to the drying device and is used to pretreatment the low-rank raw coal before drying it, so that its particle size is reduced to below 50 mm.

8. The low-rank coal drying and classification utilization system according to claim 6 or 7, characterized in that: The separation device comprises a discharge silo (3), a cyclone dust collector (4), a bag dust collector (5), and an induced draft fan (6), wherein: The unloading silo is connected to the drying device, and the induced draft fan is connected to the unloading silo through the cyclone separator and the bag dust collector. The air in the discharge silo is extracted by an induced draft fan to generate negative pressure, and the fine coal powder in the upgraded coal is captured and separated in a cyclone dust collector and a bag dust collector to obtain the dry coal and the dry coal powder.

9. The low-rank coal drying and classification utilization system according to claim 8, characterized in that: Also includes crusher, The crusher is connected to the water-coal slurry preparation device and is used to prepare coal powder with a particle size of less than 400 μm.

10. The low-rank coal drying and classification utilization system according to claim 9, characterized in that: The water-coal slurry preparation device is a tank agitator (9).

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