Method and system for long-distance conveying and utilization of coal slime

Abstract

The invention discloses a method and system for long-distance conveying and utilization of coal slime, and the method comprises the following steps: S1, adding water and an optional coal slurry additive into the coal slime, and fully stirring to obtain low-concentration coal slurry with the coal slime concentration not higher than 55%; s2, pressurizing the obtained low-concentration coal slurry through a coal slurry pump, and conveying the pressurized low-concentration coal slurry to a destination close to a coal water slurry gasification device through a coal slurry conveying pipeline; and S3, feeding the low-concentration coal slurry reaching the destination and the solid coal powder into a coal mill together to prepare the coal water slurry so as to obtain qualified coal water slurry for gasification, and feeding the coal water slurry into a gasification device for utilization. The coal-water slurry for gasification with proper concentration is prepared in a manner of firstly diluting and then supplementing coal to adjust the coal concentration in the product, so that coal slime can be conveniently transported according to the requirement of actual utilization distance, the coal-water slurry for gasification with relatively high combustion value can be prepared, and the economy of coal slime utilization is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of clean coal, and in particular to a method and system for cleanly conveying and utilizing coal slime. Background Art

[0002] my country is rich in coal resources. With the rapid development of the national economy in recent decades, my country's coal production and consumption have continued to rank first in the world. Coal slime is a by-product of the coal washing process, and its output is about 10%-20% of the raw coal entering the washing process. In recent years, with the continuous increase in the proportion of raw coal selected in my country and the change in coal mining methods, the output of coal slime has also increased significantly. Coal slime has fine particles, such as particle size D95 is usually less than 1mm, high moisture content, high viscosity, and is not easy to store and transport. Moreover, it will be lost when it encounters water and will fly when it dries. It is one of the main sources of pollution in mining areas. How to efficiently utilize coal slime resources and solve the environmental pollution problems it brings is a common concern of coal mines and coal preparation plants across the country.

[0003] Before the 1980s, civil use was the main outlet for coal slime. However, with the sharp increase in coal slime production, the increase in coal prices and the requirement for comprehensive utilization of coal resources, boiler combustion has become its main utilization method. The coal slime produced in the coal preparation process is generally recovered by centrifugal dehydration, filter pressing and other methods, and the filtrate water is returned to the coal preparation system for recycling. The water content of coal slime is usually around 30%, and the calorific value is low (ash content is 10%-50%). When it is added to the boiler for combustion, it causes the exhaust gas temperature to rise and the boiler efficiency to decrease. Compared with coal, the characteristics of coal slime determine that there are more difficulties in its transportation, storage and utilization, which is also one of the important problems facing the coal industry.

[0004] Transforming coal or coal slime into coal slurry and transporting it through pipelines is another feasible way to transport coal over long distances, in addition to transportation by rail, road and water. In certain scenarios, the use of pipelines to transport coal has the advantages of relatively low investment, small impact on the environment, small impact on climate, and low transportation cost. It is a safe, efficient, technologically advanced, energy-saving, land-saving, clean and environmentally friendly way of transporting coal. Generally, the higher the concentration of coal slurry, the greater its corresponding viscosity and the worse its rheological properties. In order to ensure the stability of coal slurry during long-distance pipeline transportation and reduce transportation energy consumption, it is necessary to control the concentration of the transported coal slurry not to be too high. Therefore, after the coal slurry is transported to the destination, it needs to be equipped with complex dehydration or concentration process before it can be used.

[0005] Coal gasification is an important way to utilize coal cleanly and efficiently, and is an indispensable leading technology for modern coal chemical technology. Currently, advanced coal gasification technologies include water-coal slurry gasification technology and dry coal powder gasification technology. Among them, water-coal slurry gasification technology is to prepare coal and water into a water-coal slurry with a concentration of about 60% as a gasification raw material. The water-coal slurry enters the gasifier and reacts with oxygen under high temperature and high pressure to produce synthesis gas for downstream use.

[0006] If the coal slime can be simply processed and transported to the coal chemical park in a clean and efficient manner for use as gasification raw material, the raw material cost of the coal chemical plant can be effectively reduced, while reducing carbon dioxide emissions during the utilization of coal slime. Summary of the invention

[0007] The purpose of the present invention is to provide a method and system for long-distance transportation and utilization of coal slime, so as to solve the problem in the prior art that it is difficult to achieve long-distance clean utilization of coal slime.

[0008] In order to achieve one aspect of the above-mentioned purpose, the method for long-distance transportation and utilization of coal slime provided by the present invention adopts the following technical scheme:

[0009] Step S1, adding water and optional coal slurry additives to the coal slurry and fully stirring to obtain a low-concentration coal slurry with a coal slurry concentration of no more than 55%;

[0010] Step S2, pressurizing the obtained low-concentration coal slurry through a coal slurry pump and delivering it to a destination near a water-coal slurry gasification device through a coal slurry delivery pipeline;

[0011] Step S3, sending the low-concentration coal slurry that has reached the destination together with the solid coal powder into a coal mill to prepare water-coal slurry, so as to obtain qualified water-coal slurry for gasification and send it to a gasification device for use.

[0012] According to the method of the present invention, preferably, after step S1 and before step S2, the method further comprises the step of placing the prepared low-concentration coal slurry in a coal slurry storage tank with a stirring device to prevent sedimentation.

[0013] According to the method of the present invention, preferably, step S2 comprises:

[0014] Step S21, the obtained low-concentration coal slurry is pressurized by a diaphragm pump and then transported to a destination through a pipeline; and

[0015] Step S22, after being transported to the destination, the low-concentration coal slurry first enters a buffer storage tank with a stirring paddle, and then is pumped into the coal mill through a centrifugal pump.

[0016] According to the method of the present invention, preferably, the coal slime is selected from the coal slime with a water content of less than 35% and a particle size D90 of less than 1 mm after filter pressing or centrifugal dehydration in a coal washing plant.

[0017] According to the method of the present invention, preferably, the coal slurry additive is selected from one or more of lignin, naphthalenesulfonic acid formaldehyde polymer, lignin sulfonate and polycarboxylate.

[0018] According to the method of the present invention, preferably, in step S1, the mass concentration of coal slime in the coal slime slurry is 38-55%, preferably 40-50%, such as 45%; studies have found that too low a concentration will affect the stability of the coal slurry.

[0019] According to the method of the present invention, preferably, in step S3, the coal mill is a wet rod mill, and solid coal powder is added to the low-concentration coal slurry while it enters the wet rod mill for co-grinding to obtain water-coal slurry for gasification.

[0020] According to the method of the present invention, preferably, the mass concentration of coal in the water-coal slurry for gasification is 55-68%, preferably 58-65%, such as 60% or 62%.

[0021] According to the method of the present invention, preferably, in step S21, the low-concentration coal slurry is transported through a pipeline by the diaphragm pump to a destination at a distance of more than 0.5 km, preferably 1-300 km, such as a destination at a distance of 3, 10, 50, 100, 200 or 250 km.

[0022] In order to achieve another aspect of the above-mentioned invention object, the coal slime utilization system provided by the present invention adopts the following technical scheme:

[0023] A coal slime utilization system, comprising:

[0024] A coal slurry agitator and a coal slurry bin, a first water tank and a coal slurry additive storage tank respectively connected to the coal slurry agitator, wherein the coal slurry agitator is used to fully stir the coal slurry, water and optional coal slurry additives received from the coal slurry bin, the first water tank and the coal slurry additive storage tank respectively to prepare a low-concentration coal slurry;

[0025] A coal slurry storage tank, a coal slurry pump and a buffer storage tank connected in sequence, wherein the coal slurry storage tank is connected to the coal slurry agitator to receive the low-concentration coal slurry, and the buffer storage tank is used to receive the low-concentration coal slurry delivered from the coal slurry pump;

[0026] A coal mill and a delivery pump, a coal bunker and a second water tank respectively connected to the coal mill, wherein the delivery pump is used to deliver the low-concentration coal slurry from the buffer storage tank, and the coal mill is used to prepare a water-coal slurry for gasification by using the received low-concentration coal slurry, coal powder and optional water; and

[0027] The water-coal slurry gasification device is used to prepare synthesis gas by gasification reaction using the gasified water-coal slurry from the coal mill as raw material.

[0028] In the present invention, "optionally" added substances should be understood as the substances may or may not be added.

[0029] In the present invention, the concentrations or percentages involved are all mass concentrations or mass percentages unless otherwise specified.

[0030] Compared with the prior art, the present invention has the following advantages:

[0031] By applying the technical solution of the present invention, the coal slime is first diluted with water to prepare a low-concentration, low-viscosity coal slime slurry, which is convenient for clean and low-energy pipeline transportation, and then the coal is added and mixed and ground to prepare a water-coal slurry for gasification and send it to the water-coal slurry gasification device for use. The above preparation method prepares a water-coal slurry for gasification of appropriate concentration by first diluting and then adding dry coal to adjust the coal concentration in the product. It is not only convenient to realize the clean and low-energy transportation of coal slime according to the needs of the actual utilization distance, but also eliminates the complex process of dehydrating and concentrating the coal slime again at the utilization terminal, and can prepare coal slime into water-coal slurry for gasification as a coal chemical raw material, which improves the economic efficiency of coal slime utilization and reduces carbon emissions during coal slime utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A schematic diagram of an embodiment of a coal slime utilization system of the present invention;

[0033] Among them, 01-coal slime bin; 02-first water tank; 03-coal slurry additive; 04-coal slurry agitator; 05-coal slurry storage tank; 06-coal slurry pump; 07-coal bin; 08-coal mill; 09-buffer storage tank; 10-conveyance pump; 11-coal slurry conveying pipeline; 12-water-coal slurry gasification device; 13-second water tank. DETAILED DESCRIPTION

[0034] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0035] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so as to describe the embodiments of the present invention described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0036] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0037] As mentioned in the background technology section, although many of the methods for utilizing fine coal slime in the prior art are to prepare it into water-coal slurry for clean utilization, they are basically on-site utilization or short-distance utilization of coal slime, and it is difficult to achieve long-distance transportation or storage of coal slime, and thus achieve long-distance clean utilization. In order to improve this defect of the prior art, the present invention provides a method for long-distance transportation and utilization of coal slime, which includes: step S1, adding water and optional coal slurry additives to the coal slime and fully stirring to obtain a low-concentration coal slime slurry with a coal slime concentration not higher than 55%; step S2, pressurizing the obtained low-concentration coal slime slurry through a coal slurry pump and sending it to a destination near a water-coal slurry gasification device through a pipeline; step S3, mixing the low-concentration coal slime slurry that has arrived at the destination with solid coal powder and entering a coal mill for water-coal slurry preparation to obtain qualified gasification water-coal slurry and sending it to the water-coal slurry gasification device for utilization.

[0038] In the above method of the present invention, water or water and coal slurry additives are first added to the coal slurry to dilute and prepare a low-concentration coal slurry, so as to facilitate long-distance pipeline transportation, and then coal is added or coal and water are added to mix to prepare a mixed coal slurry, and finally the gasification water-coal slurry is obtained by grinding. The above method of the present invention prepares a gasification water-coal slurry of appropriate concentration by first diluting and then adding coal to adjust the coal slurry concentration in the product, which is not only convenient for clean and efficient transportation of coal slurry according to the actual utilization distance, but also can prepare qualified gasification water-coal slurry raw materials, thereby improving the economic efficiency of coal slurry utilization.

[0039] In the above method of the present invention, step S1 can dilute the block or paste-like coal slime into a low-concentration, low-viscosity and high-fluidity coal slime slurry with good fluidity by adding water, thereby facilitating long-distance pipeline transportation. Of course, if the utilization location does not require long-distance transportation of the coal slime, step S2 can be performed directly. In order to further improve the long-distance clean utilization of coal slime, in a preferred embodiment of the present application, the above step S2 includes: step S21, the low-concentration coal slime is pressurized by a diaphragm pump and then transported to the destination through a pipeline; step S22, after being transported to the destination, the low-concentration coal slime first enters a buffer storage tank with a stirring paddle, and then is pumped into a coal mill by a centrifugal pump.

[0040] In step S1, the low-concentration coal slurry obtained by dilution with water is low in concentration and relatively low in viscosity (for example, the viscosity at 25°C is not higher than 300 cP), which is conducive to long-distance pipeline transportation. In a preferred embodiment, the mass concentration of coal slurry in the coal slurry obtained after dilution with water (that is, the mass proportion of coal slurry used in the obtained low-concentration coal slurry) is 38-55%, such as 40%, 45% or 50%. After property analysis, the coal slurry in this concentration range is more suitable for long-distance (≥500 meters) pipeline transportation.

[0041] In step S1, the coal slurry is simply mixed and stirred with water and optional additives, thereby improving the reliability of long-distance clean transportation of the coal slurry. In order to further improve the stability of the coal slurry properties and the continuity of the transportation amount during the actual transportation of the coal slurry, in a preferred embodiment, after step S1 and before step S2, the method further includes the step of placing the coal slurry in a coal slurry storage tank with a stirring device to prevent sedimentation.

[0042] In actual operation, when diluting in step S1, according to the actual coal slime bonding strength, it is selected to perform preliminary stirring or strong stirring in a stirring barrel or agitator, as long as the concentration of the diluted coal slime is reduced to a fluidity that can be transported. From the perspective of reducing process steps and reducing energy consumption, in order to prevent uneven concentration of coal slime during transportation, resulting in poor transportation or unstable properties, it is stored in a coal slime storage tank with a stirring device, so as to maintain the concentration uniformity and flow stability of the diluted coal slime.

[0043] The concentration of the diluted coal slurry affects its transportation efficiency and transportation energy consumption. Considering the transportation efficiency and the economic performance of the utilization of the coal sludge, it is not the case that the longer the distance the coal sludge is transported, the better. The transportation distance needs to be determined based on the location of the coal preparation plant and the coal chemical project. In a preferred embodiment of the present application, the above step S21 includes: using a coal slurry pump to transport the coal slurry through a coal slurry conveying pipeline to a destination location with a distance of 0.5-600 kilometers. Controlling the transportation distance of the conveying pipeline within the above kilometer range can not only improve the current problem that coal sludge is difficult to achieve long-distance clean utilization, but also will not reduce the economic performance of coal sludge recycling.

[0044] In the method of the present invention, dilution with water in step S1 can reduce the viscosity of the coal slurry and improve its transportability. In order to further reduce the viscosity of the coal slurry and improve its stability, in a preferred embodiment, in step S1, a coal slurry additive can be added while diluting the coal slurry with water. The specific coal slurry additive used is a common additive for preparing water-coal slurry available on the market, such as a dispersant, a stabilizer or a mixture thereof, including but not limited to one or more of lignin, naphthalenesulfonic acid formaldehyde polymer, lignin sulfonate and polycarboxylate. The specific type or amount of addition can be reasonably selected according to the properties of the coal slurry and the transportation distance.

[0045] In step S3, according to the requirements of coal particle size, concentration, viscosity, etc. for gasification water-coal slurry, a suitable device can be selected from existing grinding equipment for grinding. In a preferred embodiment, in step S3, the coal mill is a wet rod mill, and solid coal powder is added to the coal slurry while it enters the wet rod mill for grinding together to obtain gasification water-coal slurry; the use of a wet rod mill for grinding has the advantages of low energy consumption, fine grinding, and uniform discharge.

[0046] In the method of the present invention, the viscosity of the coal slurry is reduced by diluting it to improve fluidity, and then in order to make the utilization of coal slurry feasible or improve the economic performance of utilization, and reduce carbon dioxide emissions during utilization, the mass concentration of the coal slurry is increased by adding coal and grinding and slurrying to prepare it into a water-coal slurry that can be used for gasification, which not only solves the problem of long-distance clean transportation of coal slurry, but also improves the economic efficiency of its utilization by using coal slurry as a gasification raw material. The mass concentration of coal in the specific gasification water-coal slurry can be reasonably adjusted according to actual needs, and is not limited to the concentration of coal slurry. In actual production, those skilled in the art understand that according to the specific concentration, flow rate and amount of coal entering the coal mill of the coal slurry, a certain amount of water or even additives can be appropriately adjusted to adjust the concentration of the final gasification water-coal slurry. Considering the feasibility of coal slurry transportation and the economic efficiency of gasification, the mass concentration of coal (that is, dry coal slurry + dry coal) in the gasification water-coal slurry of the present invention is preferably 55-68%, such as 58%, 60%, 64% or 66%.

[0047] In the above preparation method, the coal slime can be any type of coal slime waste generated during the coal selection and washing process, including but not limited to coal slime with a water content of less than 35% and a particle size of less than 1 mm after filter pressing or centrifugal dehydration in a coal washing plant. The natural fine particle characteristics of this type of coal slime can be made into slurry without grinding and stirring, which is suitable for large-scale and economical utilization. In the present invention, by selecting the above coal slime as a raw material, not only the problem of environmental pollution in the process of coal slime utilization is solved, but also the transportation energy consumption is reduced, the carbon dioxide emission is reduced, and the energy utilization rate and utilization cleanliness are improved.

[0048] like Figure 1 As shown, the present invention also provides a coal slime utilization system, comprising:

[0049] A coal slurry agitator 04 and a coal slurry bin 01, a first water tank 02 and a coal slurry additive storage tank 03 respectively connected to the coal slurry agitator 04, wherein the coal slurry agitator 04 is used to fully stir the coal slurry, water and optional coal slurry additives received from the coal slurry bin 01, the first water tank 02 and the coal slurry additive storage tank 03 to prepare a low-concentration water-coal slurry;

[0050] A coal slurry storage tank 05, a coal slurry pump 06 and a buffer storage tank 09 connected in sequence, wherein the coal slurry storage tank 05 is connected to the coal slurry agitator 04 to receive the low-concentration water-coal slurry, and the buffer storage tank 09 is used to receive the low-concentration water-coal slurry delivered from the coal slurry pump 06;

[0051] A coal mill 08 and a delivery pump 10, a coal bunker 07 and a second water tank 11 respectively connected to the coal mill 08, wherein the delivery pump 10 is used to deliver the low-concentration water-coal slurry from the buffer storage tank 09, and the coal mill 08 is used to prepare the gasification water-coal slurry by using the received low-concentration water-coal slurry, coal powder and optional water; and

[0052] The water-coal slurry gasification device 12 is used to prepare synthesis gas by gasification reaction using the gasified water-coal slurry from the coal mill 08 as a raw material.

[0053] Through the coal sludge utilization system of the present invention, the coal sludge is fully stirred with water and optional coal sludge additives by the coal slurry agitator 04 to prepare a low-concentration coal sludge slurry, and then enters the coal slurry storage tank 05 with stirring and is transported to the buffer storage tank 09 with stirring through the coal slurry pump 06 (such as a diaphragm pump) through the coal slurry conveying pipeline 11 over a long distance, and then is sent to the pulverizer 08 through the conveying pump 10 (such as a centrifugal pump) to prepare gasification water-coal slurry with coal powder and optional water. Finally, the prepared gasification water-coal slurry is sent to the water-coal slurry gasification device 12 for utilization.

[0054] In one embodiment, the conveying distance of the coal slurry is estimated by a simulation device, for example, the conveying distance is estimated in a circulating pipeline according to the flow rate, circulation time and stability of the coal slurry.

[0055] The present invention will be further described below with reference to specific embodiments.

[0056] Example 1

[0057] like Figure 1 As shown, coal slime with a water content of 26% and a particle size D90 less than 1 mm from a coal washing plant is conveyed into a coal slurry agitator 04 through a belt, and is fully stirred together with the water in the first water tank 02 and the additive (lignin) in the additive storage tank 03. The concentration of the coal slime slurry after stirring is 52% (the mass proportion of the coal slime used in the coal slime slurry, the same below).

[0058] The stirred coal slurry flows by gravity through a pipeline into a coal slurry storage tank 05 with an agitator, and then a diaphragm pump 06 is used to transport the coal slurry in the coal slurry storage tank 05 through a conveying pipeline over a long distance to a coal slurry buffer storage tank 09 near the destination. The coal slurry is transported 3 km away and remains stable without abnormalities.

[0059] Then, the low-concentration coal slurry in the buffer storage tank 09 is pumped into the wet rod mill 08 through the centrifugal pump 10, and the coal slurry transported into the rod mill 08 is ground together with the coal from the coal bunker 07 to finally form a water-coal slurry with a concentration of 61% (the mass concentration of coal (dry basis) in the water-coal slurry, the same below) and sent to the water-coal slurry gasification device 12 for gasification to produce synthesis gas. It has been observed that the water-coal slurry gasification device can operate stably for more than 30 days, and the conversion rate of coal therein is basically the same as that of the water-coal slurry prepared by using coal.

[0060] Example 2

[0061] like Figure 1 As shown, coal slime with a moisture content of 31% and a particle size D90 less than 1 mm from a coal washing plant is conveyed to a coal slurry agitator 04 through a belt and is fully agitated with the water in the first water tank 02. The concentration of the coal slime after agitation is 45%.

[0062] The stirred coal slurry flows by gravity through a pipeline into a coal slurry storage tank 05 with an agitator, and then a diaphragm pump 06 is used to transport the coal slurry in the coal slurry storage tank 05 through a conveying pipeline over a long distance to a coal slurry buffer storage tank 09 near the destination. The coal slurry is transported 50 km away and remains stable without abnormalities.

[0063] Then, the low-concentration coal slurry in the buffer storage tank 09 is pumped into the wet rod mill 08 through the centrifugal pump 10. The coal slurry transported into the rod mill 08 is ground together with the coal from the coal bunker 07 and the water in the second water tank 13, and finally a water-coal slurry with a concentration of 60% is prepared and sent to the water-coal slurry gasification device 12 for gasification to produce synthesis gas. It has been observed that the water-coal slurry gasification device can operate stably for more than 30 days, and the conversion rate of coal therein is substantially equivalent to that of the water-coal slurry prepared using coal.

[0064] Example 3

[0065] like Figure 1 As shown, coal slime with a water content of 28% and a particle size D90 less than 1 mm from a coal washing plant is conveyed into a coal slurry agitator 04 through a belt, and is fully agitated with the water in the first water tank 02 and the additive (lignin sulfonate) in the additive storage tank 03. The concentration of the coal slime after agitation is 38%.

[0066] The stirred coal slurry flows by gravity through a pipeline into a coal slurry storage tank 05 with an agitator, and then a diaphragm pump 06 is used to transport the coal slurry in the coal slurry storage tank 05 through a conveying pipeline over a long distance to a coal slurry buffer storage tank 09 near the destination. The coal slurry is transported 0.5 km and remains stable without abnormalities.

[0067] Then, the low-concentration coal slurry in the buffer storage tank 09 is pumped into the wet rod mill 08 through the centrifugal pump 10, and the coal slurry transported into the rod mill 08 is ground together with the coal from the coal bunker 07 to finally form a water-coal slurry with a concentration of 55% and sent to the water-coal slurry gasification device 12 for gasification to produce synthesis gas. It has been observed that the water-coal slurry gasification device can operate stably for more than 30 days, and the conversion rate of coal therein is substantially equivalent to that of the water-coal slurry prepared from coal.

[0068] Example 4

[0069] like Figure 1 As shown, coal slime with a water content of 32% and a particle size D90 less than 1 mm from a coal washing plant is conveyed into a coal slurry agitator 04 through a belt, and is fully agitated with the water in the first water tank 02 and the additive (naphthalenesulfonic acid formaldehyde polymer) in the additive storage tank 03. The concentration of the coal slime after agitation is 40%.

[0070] The stirred coal slurry flows by gravity into the coal slurry storage tank 05 with an agitator through a pipeline, and then the diaphragm pump 06 is used to transport the coal slurry in the coal slurry storage tank 05 through a conveying pipeline for a long distance to the coal slurry buffer storage tank 09 near the destination. According to experimental simulation, the viscosity of the coal slurry during the transportation process is 100cp, and the pipeline transportation speed is 1.5 m / s. A coal slurry booster pump station is added at 100km and 200km in the middle of the conveying pipeline respectively. The coal slurry is transported for 300km and is still stable and normal. Finally, the coal slurry can be sent from the storage tank 05 to the storage tank 09.

[0071] Then, the low-concentration coal slurry in the buffer storage tank 09 is pumped into the wet rod mill 08 through the centrifugal pump 10, and the coal slurry transported into the rod mill 08 is ground together with the coal from the coal bunker 07 to finally form a water-coal slurry with a concentration of 62% and sent to the water-coal slurry gasification device 12 for gasification to produce synthesis gas. It has been observed that the water-coal slurry gasification device can operate stably for more than 30 days, and the conversion rate of coal therein is substantially equivalent to that of the water-coal slurry prepared from coal.

[0072] Comparative Example 1

[0073] The difference from Example 1 is that the coal slurry concentration is 30%. The simulation evaluation shows that its stability is poor and the stable transportation distance is correspondingly shortened.

[0074] Comparative Example 2

[0075] The difference from Example 2 is that the water-coal slurry with a concentration of 60% is directly transported, and the stable transportation distance is much less than 50 km.

[0076] Comparative Example 3

[0077] The raw coal is transported to the homogenizing bin by a scraper conveyor. According to the concentration of the coal slime 01 with a water content of 32% and a particle size of 90% less than 1mm from the coal washing plant, an appropriate amount of water is injected into the homogenizing bin to meet the mass concentration of coal in the slurry of 65% (reaching the coal concentration required for water-coal slurry), and a dispersant is added to stir evenly; then the slurry in the homogenizing bin is transported to the ball mill (200 meters away) through a sealed pipeline by a thick slurry pump for grinding. During this operation, the particle size of the slurry can be adjusted by controlling the discharge amount of the thick slurry pump;

[0078] The output obtained in the above steps is transported from the slurry collecting tank to the separator to remove large particle impurities (particle size greater than 5mm), and then transported to the stirring barrel for strong stirring, and the lignin naphthalene sulfonate additive is added to the stirring barrel to control the viscosity of the water-coal slurry (so that the coal slurry concentration is not less than 65%); finally, the obtained slurry is transported to the enhanced pump by a screw pump for strong shearing, and then transported to the storage tank for aging to obtain a finished water-coal slurry with a mass concentration of 65%. The finished water-coal slurry is transported to the destination by tank truck by road or rail for utilization.

[0079] From the description of the above embodiments and comparative examples, it can be seen that the above embodiments of the present invention achieve the following technical effects: by first diluting the coal slime with water to prepare a low-concentration coal slime slurry, it is convenient to realize long-distance pipeline transportation. Pipeline transportation is more energy-efficient than road or rail transportation, and has less impact on the environment. Then, the low-concentration coal slime slurry is prepared into a qualified coal slurry for gasification by adding coal and water for mixing and grinding. The above preparation method prepares a gasification water-coal slurry of appropriate concentration by first diluting and then adding coal to adjust the coal concentration in the product. It is not only convenient to realize the transportation of coal slime according to the actual utilization distance, but also can prepare a gasification water-coal slurry with a relatively high calorific value, thereby improving the economic efficiency of coal slime utilization.

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for long-distance transportation and utilization of coal slime, the method comprising the following steps: Step S1, adding water and optional coal slurry additives to the coal slurry and fully stirring to obtain a low-concentration coal slurry with a coal slurry concentration of no more than 55%; Step S2, pressurizing the obtained low-concentration coal slurry through a coal slurry pump and delivering it to a destination near a water-coal slurry gasification device through a coal slurry delivery pipeline; Step S3, sending the low-concentration coal slurry that has reached the destination together with the coal into a coal mill to prepare water-coal slurry, so as to obtain qualified water-coal slurry for gasification and send it to a gasification device for use.

2. The method according to claim 1, characterized in that After step S1 and before step S2, the method further comprises the step of placing the prepared low-concentration coal slurry in a coal slurry storage tank with a stirring device to prevent sedimentation.

3. The method according to claim 1, characterized in that Step S2 includes: Step S21, the obtained low-concentration coal slurry is pressurized by a diaphragm pump and then transported to a destination through a coal slurry transport pipeline; and Step S22, after being transported to the destination, the low-concentration coal slurry first enters a buffer storage tank with a stirring paddle, and then is pumped into the coal mill through a centrifugal pump.

4. The method according to claim 1, characterized in that: The coal slime is selected from coal slime with a water content of less than 35% and a particle size D90 of less than 1 mm after filter pressing or centrifugal dehydration in a coal washing plant.

5. The method according to claim 1, characterized in that The coal slurry additive is selected from one or more of lignin, naphthalenesulfonic acid formaldehyde polymer, lignin sulfonate and polycarboxylate.

6. The method according to claim 1, characterized in that In step S1, the mass concentration of the coal slime in the low-concentration coal slime slurry is 38-55%, preferably 40-50%.

7. The method according to claim 1, characterized in that In step S3, the coal mill is a wet rod mill, and solid coal powder is added to the low-concentration coal slurry while it enters the wet rod mill for co-grinding to obtain water-coal slurry for gasification.

8. The method according to claim 1, characterized in that The mass concentration of coal in the water-coal slurry for gasification is 55-68%, preferably 58-65%.

9. The method according to claim 3, characterized in that: In step S21, the low-concentration coal slurry is transported through a pipeline by using the diaphragm pump to a destination at a distance of more than 0.5 kilometers, preferably 1-300 kilometers.

10. A coal slime utilization system, comprising: A coal slurry agitator and a coal slurry bin, a first water tank and a coal slurry additive storage tank respectively connected to the coal slurry agitator, wherein the coal slurry agitator is used to fully stir the coal slurry, water and optional coal slurry additives received from the coal slurry bin, the first water tank and the coal slurry additive storage tank respectively to prepare a low-concentration coal slurry; A coal slurry storage tank, a coal slurry pump and a buffer storage tank connected in sequence, wherein the coal slurry storage tank is connected to the coal slurry agitator to receive the low-concentration coal slurry, and the buffer storage tank is used to receive the low-concentration coal slurry delivered from the coal slurry pump; A coal mill and a delivery pump, a coal bunker and a second water tank respectively connected to the coal mill, wherein the delivery pump is used to deliver the low-concentration coal slurry from the buffer storage tank, and the coal mill is used to prepare a water-coal slurry for gasification by using the received low-concentration coal slurry, coal powder and optional water; and The water-coal slurry gasification device is used to prepare synthesis gas by gasification reaction using the gasified water-coal slurry from the coal mill as raw material.

Images