A drying apparatus and method for high-moisture low-rank coal

Abstract

This invention provides a drying apparatus and method for high-moisture-content, low-rank coal. The drying apparatus includes a fixed fluidized bed, a roller screen, and a heat source device. The fixed fluidized bed comprises a shell, an air distribution plate, a gas heating assembly, and a main fan. The air distribution plate divides the shell cavity into a drying chamber and a gas chamber from top to bottom. The roller screen is located inside the drying chamber and is spaced above the air distribution plate. The shell has an inlet and an outlet that communicate with the drying chamber. The inlet and outlet are spaced apart along the length of the shell. The inlet is located at the front end of the air distribution plate and above the roller screen, while the outlet is located at the end of the air distribution plate. The gas heating assembly, the main fan, and the gas chamber are connected sequentially. The heat source device heats the screen shaft and the screen plate connected to the screen shaft of the roller screen. This invention achieves separate drying of materials with different particle sizes while simultaneously drying the oversize and undersize materials, improving drying efficiency and coal quality.

Description

Technical Field

[0001] This invention belongs to the field of coal drying technology, and particularly relates to a drying apparatus and method for high-moisture, low-rank coal. Background Technology

[0002] Currently, lignite is gradually becoming one of the main raw materials for power plants. However, its high moisture content (40% by weight is water) results in relatively low power generation efficiency, making lignite drying an important process in the coal preparation industry. Lignite drying has several important implications: The calorific value of lignite is typically 3000 kcal or less, which is relatively low. Drying can significantly increase its calorific value, sometimes reaching 4000 to 5000 kcal, thereby improving its efficiency and utilization as fuel. Due to its high moisture content, dried lignite is lighter, reducing energy consumption and costs during transportation. Furthermore, lignite drying helps to further improve combustion efficiency, reduce air pollution, and lower environmental pollution levels, contributing to energy conservation, emission reduction, and the development of an environmentally friendly industry.

[0003] Fluidized bed drying is a common type of machinery used for drying coal. It utilizes a perforated air distribution plate at the bottom of the bed to introduce drying air, causing the material to be dried above the bed to suspend and boil under the action of the drying air, thus achieving full contact between the material and the drying air for drying. However, for lignite with high moisture content, existing fluidized bed drying methods suffer from low heat exchange efficiency and long drying times. Furthermore, due to the limited drying thermal efficiency of existing fluidized beds, the calorific value of the dried lignite is generally low. Summary of the Invention

[0004] Based on the problems existing in the prior art, the present invention provides a drying device and method for high-moisture-content low-rank coal, which solves the technical problems of low fluidized bed heat exchange efficiency and long drying time for high-moisture-content lignite or bituminous coal.

[0005] To achieve the above objectives, the present invention adopts the following technical solution.

[0006] According to one aspect of the present invention, a drying apparatus for high-moisture-content low-rank coal is provided, comprising a fixed fluidized bed, a roller screen, and a heat source device. The fixed fluidized bed includes a shell, an air distribution plate, a gas heating assembly, and a main fan. The air distribution plate is provided in the inner cavity of the shell, dividing the inner cavity of the shell into a drying chamber and a gas chamber from top to bottom. The roller screen is located in the drying chamber and is spaced above the air distribution plate. The shell has an inlet and an outlet respectively communicating with the drying chamber. The inlet and outlet are spaced apart along the length of the shell. The inlet is located at the front end of the air distribution plate and above the roller screen, and the outlet is located at the end of the air distribution plate. The gas heating assembly, the main fan, and the gas chamber are connected in sequence. The heat source device is used to heat the screen shaft and screen plate of the roller screen.

[0007] Optionally, the heat source provided by the heat source device is high-temperature steam, the screen shaft is a hollow shaft, and the two ends of the hollow shaft have a first steam inlet and a first steam outlet, respectively. The heat source outlet of the heat source device is connected to the first steam inlet.

[0008] Optionally, the gas heating assembly includes a gas heater, which has a heating gas inlet, a heating gas outlet, a second steam inlet, and a second steam outlet; the heating gas inlet, the heating gas outlet, and the inlet of the main blower are connected in sequence; the first steam outlet, the second steam inlet, the second steam outlet, and the heat source inlet of the heat source device are connected in sequence.

[0009] Optionally, the drying device for high-moisture, low-rank coal also includes a dust collector, a tail gas induced draft fan, and a chimney. The gas heating assembly also includes a gas preheater. The top of the shell is provided with an exhaust port communicating with the drying chamber. The gas preheater has an external gas inlet, an external gas outlet, a waste steam inlet, and a waste steam outlet. Further, the exhaust port is connected to the inlet of the dust collector, and the gas outlet, waste steam inlet, waste steam outlet, tail gas induced draft fan, and chimney of the dust collector are sequentially connected. The coal outlet of the dust collector is connected to the coal bunker, and the external gas inlet, external gas outlet, and heating gas inlet are sequentially connected.

[0010] Optionally, the roller screen includes a feeding section and a drying section connected to the feeding section. The feeding section and the drying section are arranged along the direction from the feed inlet to the discharge outlet, wherein the feeding section is inclined and arranged at an obtuse angle to the feed outlet.

[0011] Optionally, an airlock rotary feeder is provided at the feed inlet, a first airlock unloader is provided at the discharge outlet, and a second airlock unloader is provided between the end of the roller screen and the side wall of the shell.

[0012] Optionally, a scraper conveyor is installed on the air distribution plate.

[0013] Optionally, the air chamber is equipped with an air regulating panel.

[0014] According to another aspect of the present invention, a method for drying high-moisture-content low-rank coal is provided, comprising a drying apparatus for high-moisture-content low-rank coal using any of the above-mentioned methods, including:

[0015] Step S1: Start the heat source device to heat the screen shaft and screen plate of the roller screen;

[0016] Step S2: Start the gas heating assembly and main fan to deliver hot gas into the gas chamber;

[0017] Step S3: The material is fed into the drying chamber of the fixed fluidized bed through the feed inlet;

[0018] Step S4: The material is screened by the roller screen, wherein the material smaller than or equal to the preset size falls onto the air distribution plate and is dried by the hot gas and conveyed to the discharge port, and the material larger than the preset size on the roller screen is dried by the screen shaft, screen plate and hot gas and conveyed to the discharge port.

[0019] Compared with the prior art, the technical solution of the drying device and method for high moisture content low-rank coal of the present invention has the following beneficial effects: The present invention uses a roller screen to separate the material into oversize and undersize materials. The oversize material is agitated, tumbled, conveyed and dried by the screen shaft, screen plate and hot gas. The undersize material is fluidized, conveyed and dried by the air distribution plate and hot gas. While achieving separate drying of materials with different particle sizes, it also achieves simultaneous drying of oversize and undersize materials, which greatly improves drying efficiency, reduces drying time and improves coal quality.

[0020] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and will become apparent from the description or may be learned by practice of the invention. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A schematic diagram of the structure of a drying device for high-moisture-content, low-rank coal provided in an embodiment of the present invention;

[0023] Figure 2 A schematic diagram of the left side of the drying device for high-moisture-content low-rank coal provided in an embodiment of the present invention;

[0024] Figure 3 A top view schematic diagram of the drying device for high-moisture-content low-rank coal provided in an embodiment of the present invention;

[0025] Figure 4 A process flow diagram of a drying apparatus for high-moisture, low-rank coal provided in an embodiment of the present invention.

[0026] Explanation of the reference numerals in the attached figures:

[0027] 1. Shell; 2. Air distribution plate; 3. Roller screen; 4. Main fan; 5. Airlock rotary feeder; 6. First airlock unloader; 7. Second airlock unloader; 8. Scraper conveyor; 9. Air regulating plate; 10. Outer casing. Detailed Implementation

[0028] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0029] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. It should be understood that when we say an element is “connected” or “coupled” to another element, it can be directly connected or coupled to the other element, or there may be intermediate elements. Furthermore, “connected” or “coupled” as used herein can include wireless connections or couplings. The term “and / or” as used herein includes any and all combinations of one or more of the associated listed items.

[0030] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0031] To facilitate understanding of the embodiments of the present invention, the following will provide further explanation and description with reference to the accompanying drawings and several specific embodiments. These embodiments do not constitute a limitation on the embodiments of the present invention.

[0032] The high-moisture, low-rank coal involved in this invention generally refers to low-rank coal, which has a low calorific value on an ash-free basis. The low-rank coal in this invention is characterized by a total organic matter content of carbon, hydrogen, and oxygen of over 95%. Low-rank coal mainly includes lignite and bituminous coal. Low-rank coal is a solid combustible mineral formed gradually from ancient plants buried underground through complex biochemical and physicochemical changes. Lignite is a type of low-rank coal, characterized by high moisture content and a low degree of metamorphism. Bituminous coal, compared to lignite, has a higher degree of metamorphism but still falls under the category of low-rank coal. Bituminous coal is further subdivided into sub-bituminous coal, among which sub-bituminous coal is a transitional coal between bituminous and lignite, with a lower calorific value (19306-26749 kJ / kg). Anthracite and semi-anthracite are high- and low-rank coals with low volatile matter yield, high fixed carbon content, high density, high hardness, high ignition point, and no smoke during combustion. Anthracite is further divided into No. 01 anthracite (old anthracite), No. 02 anthracite (typical anthracite), and No. 03 anthracite (young anthracite). Due to their low volatile matter yield and high fixed carbon content, anthracite and semi-anthracite are generally not suitable for the high-moisture-content low-rank coal drying process of this invention. Because the high-moisture-content low-rank coal drying process of this invention employs a two-stage drying process (drying materials of different particle sizes separately, and drying oversize and undersize materials simultaneously), it is prone to spontaneous combustion or a decrease in calorific value, leading to the deterioration of anthracite and semi-anthracite. Even existing fluidized bed drying processes for anthracite and semi-anthracite use low-temperature drying and fluidized bed drying processes.

[0033] A drying device for high-moisture, low-rank coal according to the present invention includes a fixed fluidized bed, a roller screen, and a heat source device. The fixed fluidized bed includes a shell, an air distribution plate, a gas heating assembly, and a main fan. The air distribution plate is provided in the inner cavity of the shell, dividing the inner cavity of the shell into a drying chamber and a gas chamber from top to bottom. The roller screen is located in the drying chamber and is spaced above the air distribution plate. The shell has an inlet and an outlet that are respectively connected to the drying chamber. The inlet and outlet are spaced apart along the length of the shell. The inlet is located at the front end of the air distribution plate and above the roller screen, and the outlet is located at the end of the air distribution plate. The gas heating assembly, the main fan, and the gas chamber are connected in sequence. The heat source device heats the screen shaft and screen plate of the roller screen.

[0034] Optionally, the heat source provided by the heat source device is high-temperature steam, the screen shaft is a hollow shaft, and the two ends of the hollow shaft have a first steam inlet and a first steam outlet, respectively. The heat source outlet of the heat source device is connected to the first steam inlet.

[0035] Optionally, the gas heating assembly includes a gas heater, which has a heating gas inlet, a heating gas outlet, a second steam inlet, and a second steam outlet; the heating gas inlet, the heating gas outlet, and the inlet of the main blower are connected in sequence; the first steam outlet, the second steam inlet, the second steam outlet, and the heat source inlet of the heat source device are connected in sequence.

[0036] Optionally, the drying device for high-moisture, low-rank coal also includes a dust collector, a tail gas induced draft fan, and a chimney. The gas heating assembly also includes a gas preheater. The top of the shell is provided with an exhaust port communicating with the drying chamber. The gas preheater has an external gas inlet, an external gas outlet, a waste steam inlet, and a waste steam outlet. The exhaust port is connected to the inlet of the dust collector. The gas outlet, waste steam inlet, waste steam outlet, tail gas induced draft fan, and chimney of the dust collector are connected in sequence. The coal outlet of the dust collector is connected to the coal bunker. The external gas inlet, external gas outlet, and heating gas inlet are connected in sequence.

[0037] Optionally, the roller screen includes a feeding section and a drying section connected to the feeding section. The feeding section and the drying section are arranged along the direction from the feed inlet to the discharge outlet, wherein the feeding section is inclined and arranged at an obtuse angle to the feed outlet.

[0038] Optionally, an airlock rotary feeder is provided at the feed inlet, a first airlock unloader is provided at the discharge outlet, and a second airlock unloader is provided between the end of the roller screen and the side wall of the shell.

[0039] Optionally, a scraper conveyor is installed on the air distribution plate.

[0040] Optionally, the air chamber is equipped with an air regulating panel.

[0041] According to another aspect of the present invention, a method for drying high-moisture-content low-rank coal is provided, employing the drying apparatus for high-moisture-content low-rank coal as described above, comprising the following steps:

[0042] Step S1: Start the heat source device to heat the screen shaft and screen plate of the roller screen;

[0043] Step S2: Start the gas heating assembly and main fan to deliver hot gas into the gas chamber;

[0044] Step S3: The material is fed into the drying chamber of the fixed fluidized bed through the feed inlet;

[0045] Step S4: The material is screened by a roller screen. Material smaller than or equal to the preset size falls onto the air distribution plate and is fluidized and dried by hot gas. It is then conveyed to the discharge port by a scraper conveyor above the air distribution plate. Material larger than the preset size on the roller screen is dried by the screen shaft, screen plate and hot gas and then conveyed to the discharge port.

[0046] The present invention will now be further described and illustrated with reference to the accompanying drawings.

[0047] See Figures 1 to 3 As shown, this embodiment of the invention provides a drying device for high-moisture, low-rank coal, which includes a fixed fluidized bed, a roller screen 3, and a heat source device. The fixed fluidized bed includes a shell 1, an air distribution plate 2, a gas heating assembly, and a main blower 4. The air distribution plate 2 is provided in the inner cavity of the shell 1, which divides the inner cavity of the shell 1 from top to bottom into a drying chamber and a gas chamber (the upper part is the drying chamber, and the lower part is the gas chamber). The roller screen 3 is located in the drying chamber and is spaced above the air distribution plate 2. The shell 1 has an inlet and an outlet that are respectively connected to the drying chamber. The inlet and outlet are spaced apart along the length of the shell 1. The inlet is located at the front end of the air distribution plate 2 and above the roller screen 3, and the outlet is located at the end of the air distribution plate 2. The gas heating assembly, the main blower 4, and the gas chamber are connected in sequence. The heat source device is used to heat the screen shaft and screen plate of the roller screen 3. The material is screened according to the particle size distribution law of the roller screen 3. For example, the screen plate gap is 6mm. Wet coal enters the drying device from the feed inlet through the coal conveying system. The wet coal falls on the roller screen 3. Fine coal with a particle size of less than or equal to 6mm will be gradually screened onto the air distribution plate 2 at the bottom of the dryer. The fluidizing medium is hot air or other inert gas. For example, hot air (hot air temperature is between 100℃ and 180℃) heated by the gas heating component is introduced into the air chamber. The hot air passes through the air distribution plate 2 with a certain perforation rate to fluidize and dry the fine coal with a particle size of less than or equal to 6mm. The hot air directly contacts the fine coal for heat exchange. The air after heat exchange carries the moisture evaporated from the fine coal through the roller screen 3 to continue drying the lump coal with a particle size greater than 6mm (the particle size of the lump coal is not greater than 50mm) on the roller screen 3. At the same time, the screen shaft and screen plate of the roller screen 3 are heated by the heat source device to conduct heat exchange to the lump coal, thereby realizing the drying and dehydration of the lump coal.

[0048] By applying the technical solution provided in the above embodiments of the present invention, the material is screened into oversize and undersize by the roller screen 3. The oversize is agitated, tumbled, conveyed and dried by the screen shaft, screen plate and hot gas, while the undersize is fluidized, conveyed and dried by the air distribution plate 2 and hot gas. This achieves separate drying of materials of different particle sizes, and also realizes simultaneous drying of oversize and undersize, which greatly improves drying efficiency, reduces drying time and improves coal quality.

[0049] In some embodiments, the heat source provided by the heat source device is high-temperature steam, and the screen shaft is a hollow shaft with a first steam inlet and a first steam outlet at each end. The heat source outlet of the heat source device is connected to the first steam inlet. The high-temperature steam is introduced into the screen shaft to heat the screen shaft and screen plates, thereby conducting heat exchange between the gaps in the screen plates and on the screen plates. The high-temperature steam can be steam, flue gas, other waste heat, or new energy sources such as steam generated from abandoned electricity, produced by power plants, metallurgy, chemical plants, etc. The temperature of the high-temperature steam is between 120°C and 200°C. Of course, the heat source can also be hot water or other energy sources that generate heat.

[0050] See Figure 4 As shown, in some embodiments, the gas heating assembly includes a gas heater having a heating gas inlet, a heating gas outlet, a second steam inlet, and a second steam outlet; the heating gas inlet, the heating gas outlet, and the inlet of the main blower 4 are sequentially connected; the first steam outlet, the second steam inlet, the second steam outlet, and the heat source inlet of the heat source device are sequentially connected. For example, the temperature of the hot air used for drying after being heated by the gas heater 5 is 100°C to 180°C. The hot air enters the main blower 4 through the heating gas outlet and then enters the gas chamber through the main blower 4; high-temperature steam enters the screen shaft of the roller screen 3 through the first steam inlet via a pipe, heating the screen shaft and screen plate; water vapor flowing out from the first steam outlet flows into the gas heater through the first steam outlet to continue heating the air; finally, the high-temperature water vapor is converted into condensate and returns to the heat source device (power plant or boiler) through the second steam outlet.

[0051] See Figure 4As shown, in some embodiments, the drying device for high-moisture, low-rank coal further includes a dust collector, a tail gas induced draft fan, and a chimney. The gas heating assembly also includes a gas preheater. The top of the shell 1 is provided with an exhaust port communicating with the drying chamber. The gas preheater has an external gas inlet, an external gas outlet, a waste steam inlet, and a waste steam outlet. The exhaust port is connected to the inlet of the dust collector. The gas outlet, waste steam inlet, waste steam outlet, tail gas induced draft fan, and chimney of the dust collector are connected in sequence. The coal outlet of the dust collector is connected to the coal bunker. The external gas inlet, external gas outlet, and heating gas inlet are connected in sequence. For example, ambient air enters the gas preheater through the external gas inlet and is heated to 10℃-30℃. The heated air then sequentially passes through the external gas outlet and the heating gas inlet into the air heater, where it exchanges heat with high-temperature water vapor. The heated air is then heated to 100℃-180℃, flows through the main fan 4 for further pressurization, and enters the air chamber. The hot air passes through the air distribution plate 2 with a certain perforation rate to fluidize and dry the fine coal. The hot air directly contacts the fine coal for heat exchange. The air, carrying the moisture evaporated from the fine coal, passes through the roller screen 3 to continue drying the lump coal on the roller screen 3. Simultaneously, it is heated by the screen shaft and screen plate on the roller screen 3. The heated air then enters the dilute phase zone at the top of the drying chamber, where it cools to 40℃-60℃. At 0℃ and relative humidity of 40%-60%, carrying moisture evaporated from wet coal and extremely fine coal dust, this exhaust gas, commonly referred to as waste gas, enters the dust collector (e.g., a bag filter) through the exhaust port and dust collector inlet. Inside the dust collector, fine coal dust is separated and collected through the coal outlet. The high-humidity, low-temperature waste gas then enters the gas preheater through the gas outlet and waste gas inlet of the dust collector, exchanging heat with the cooler ambient air. In the gas preheater, some of the water vapor condenses into water by releasing its latent heat of vaporization, while the remaining water vapor, along with the waste gas, is extracted by the exhaust fan through the waste gas outlet and discharged into the atmosphere through the chimney. Filtration by the dust collector ensures that the high-humidity air discharged into the atmosphere meets environmental protection regulations. For the above structure and process flow, please refer to [link / reference needed]. Figure 4 As shown.

[0052] Overview Figure 4The process flow is as follows: The main body of the drying unit consists of a fixed fluidized bed and a roller screen, which is connected to a wet coal inlet, a dry coal outlet, and an exhaust steam outlet (an outlet for the mixed gas of moisture evaporated from the wet coal and extremely fine coal powder). Hot air from the gas heater is delivered to the main body of the drying unit via a main fan for drying. The wet steam from the main body of the drying unit is heated by the gas heater. Dry steam from the heat source unit is used to regulate the process and drying purpose of the main body of the drying unit. The mixed gas (exhaust steam) of moisture evaporated from the wet coal and extremely fine coal powder is dedusted by a dust collector, preheated by a gas preheater, and mixed with air. The heated clean gas (the mixed gas obtained by mixing air with the heated gas after dedusting by the dust collector) is then supplied to the gas heater. The remaining exhaust gas (part of the water vapor and exhaust steam) is discharged through a chimney via an exhaust gas fan. The condensate drainage process between the gas heater and the heat source device is as follows: the water vapor flowing out from the first steam outlet flows into the gas heater through the first steam outlet to continue heating the air, and finally the high-temperature water vapor is converted into condensate and returns to the heat source device (power plant or boiler) through the second steam outlet.

[0053] See Figure 1 As shown, in some embodiments, the roller screen 3 includes a feeding section and a drying section connected to the feeding section. The feeding section and the drying section are arranged along the direction from the feed inlet to the discharge outlet. The feeding section is inclined and at an obtuse angle to the feed outlet, so that the material can fall at a certain inclined angle and avoid material accumulation.

[0054] In some embodiments, an airlock rotary feeder 5 is provided at the feed inlet, a first airlock unloader 6 is provided at the discharge outlet, and a second airlock unloader 7 is provided between the end of the roller screen 3 and the side wall of the shell 1. Wet coal enters the drying device through the airlock rotary feeder 5 and falls onto the roller screen 3. As the roller screen 3 rotates continuously, fine coal with a particle size of less than or equal to 6 mm will fall onto the air distribution plate 2, while lump coal with a particle size greater than 6 mm continues to move along the roller screen 3 towards the other end of the shell 1. Because high-temperature steam is continuously introduced through the hollow screen shaft to heat the screen shaft and the heat-conducting screen plate, the lump coal is continuously heated on the roller screen 3 by the hot air passing through the air distribution plate 2 and the roller screen 3. During the movement of the lump coal on the roller screen 3, it is continuously tumbled, increasing the gap between the lump coal and making it more effective for the hot air to heat the lump coal. After drying, the lump coal falls into the second airlock unloader 7. The second airlock unloader 7 ensures that the hot air inside the shell 1 does not leak from the lump coal drop point; the hot air can only pass through the screen openings of the roller screen 3 to dry the lump coal. The fine coal falling onto the air distribution plate 2 is continuously fluidized and dried by the hot air passing through the air distribution plate 2. The dried fine coal mixes with the lump coal falling from the second airlock unloader 7 and enters the first airlock unloader 6 together. The rotation of the first airlock unloader 6 causes the dried coal to fall onto the conveyor belt outside the drying device. The first airlock unloader 6 not only isolates the drying device from the external environment but also ensures that the dried coal is transported from inside the drying device to outside the dryer.

[0055] See Figure 1 As shown, in some embodiments, a scraper conveyor 8 is installed on the air distribution plate 2. The fine coal falling onto the air distribution plate 2 is continuously fluidized and dried by the hot air passing through the air distribution plate 2. By installing a scraper conveyor 8 with circulating disturbance above the air distribution plate 2, both efficient drying of fine coal particles and rapid conveying of fine coal particles to the outlet of the drying device are achieved. Due to the continuous disturbance of the fine coal particles by the scraper conveyor 8, defects such as agglomeration, channeling, and short-circuiting of fine coal particles during the fluidized drying process are also prevented.

[0056] See Figure 1 As shown, in some embodiments, an air regulating plate 9 is installed in the air chamber, and air is evenly distributed to the air distribution plate 2 through the air regulating plate 9. There are multiple air regulating plates 9, which are spaced apart from each other and evenly distributed in the air chamber along the length of the air chamber, dividing the air chamber into multiple equal-pressure air chambers. The windward area and airflow direction of the air regulating plate 9 are adjusted by adjusting the tilt angle of the air regulating plate 9, thereby adjusting the pressure in each air chamber.

[0057] See Figures 1 to 3 As shown, in some embodiments, the drying device for high-moisture-content low-rank coal also includes an outer casing 10, which covers the exterior of the housing 1 and the main blower 4, and protects the internal devices by providing the outer casing 10.

[0058] In this embodiment, the heat source used in the drying device for high-moisture, low-rank coal is high-temperature steam. This steam can be generated from exhaust gas from a power plant, from pulverized coal steam boilers that burn fine coal powder collected by bag filters, or from waste water heated by renewable energy sources. The high-temperature steam primarily heats clean air from the environment via a gas heater. The heated air temperature for drying is between 100°C and 180°C. The high-temperature steam is introduced into the hollow screen shaft of the roller screen 3, heating the screen shaft and screen plates. The screen plates then heat the gaps between the screen plates, the lump coal on the screen plates, and the flowing fluidized air. The water vapor flowing out from the hollow screen shaft of the roller screen 3 enters the gas heater to further heat the air. Finally, the high-temperature water vapor is converted into condensate and returned to the power plant or boiler.

[0059] Ambient air is drawn into the gas preheater by the main blower to exchange heat with the dried exhaust gas, raising the ambient air temperature by 10-30℃. The heated air is then drawn into the gas heater by the main blower 4 to exchange heat with the high-temperature water vapor inside. The air is heated to 100℃-180℃, flows through the main blower 4 for further pressurization, and enters the air chamber from one end of the casing 1. An air regulating plate 9 is installed in the air chamber; by adjusting the air regulating plate 9, air can be evenly distributed to the air distribution plate 2. The hot air passes through the air distribution plate 2 with a certain perforation rate to fluidize and dry the fine coal particles with a particle size of less than 6mm in the fluidized bed. The hot air directly contacts the fine coal for heat exchange. The air after heat exchange, carrying the moisture evaporated from the fine coal, passes through the roller screen 3 to further dry the particles with a particle size of 6mm on the screen. Lump coal between 25mm and 1m in diameter is dried and simultaneously heated by the screen plates on the roller screen 3. The air after heat exchange enters the dilute phase zone at the top of the dryer, where it cools to 40-60℃ with a relative humidity of 40-60%, carrying moisture evaporated from the wet coal and extremely fine coal dust, commonly referred to as exhaust steam. The exhaust steam is drawn into a bag filter by a fan, where fine coal dust is separated and collected. The high-humidity, low-temperature exhaust steam is then drawn into a gas preheater to exchange heat with the even lower ambient air. In the gas preheater, some of the water vapor releases its latent heat of vaporization and condenses into water. Some of the water vapor, along with the exhaust steam, is discharged into the atmosphere through a chimney by a fan. The filtration by the bag filter ensures that the high-humidity air discharged into the atmosphere meets environmental protection standards.

[0060] In this process, wet coal enters the shell 1 through the airlock rotary feeder 5 and falls onto the roller screen 3. As the roller screen 3 rotates continuously, fine coal with a particle size of less than 6mm is screened onto the air distribution plate 2, while lump coal with a particle size of more than 6mm but less than 25mm continues to move along the roller screen 3 towards the other end of the shell 1. Because high-temperature steam continuously heats the hollow rollers and screen plates, the lump coal on the roller screen 3 is constantly heated by the hot air introduced from the fluidized bed, the rollers, and the screen plates. During its movement on the roller screen 3, the lump coal is continuously tumbled, increasing the gaps between the lump coal particles and further enhancing the heating effect of the hot air. After drying, the lump coal falls into the second airlock unloader 7. The second airlock unloader 7 ensures that the hot air in the fluidized bed does not leak from the lump coal discharge point, forcing the hot air to pass through the gaps in the roller screen 3 to dry the lump coal. The 9-11 rollers at the very front of the roller screen 3 can be designed to fall at a certain angle. Fine coal particles with a diameter of less than 6mm falling into the fluidized bed are continuously fluidized and dried by hot air passing through the air distribution plate 2. A scraper conveyor 8, mounted on the air distribution plate, continuously pushes the fine coal from the feed end to the dried discharge end. The constant disturbance of the fine coal by the scraper conveyor 8 avoids defects in the fluidized drying process. The dried fine coal mixes with lump coal falling from the second airlock unloader 7 and enters the first airlock unloader 6. The rotating unloader then discharges the dried coal onto a conveyor belt outside the dryer. The first airlock unloader 6 isolates the fluidized bed from the environment while ensuring the dried coal is transported from inside the dryer to outside.

[0061] According to another aspect of the present invention, a method for drying high-moisture-content low-rank coal is provided, comprising a drying apparatus for high-moisture-content low-rank coal using any of the above embodiments, including:

[0062] Step S1: Activate the heat source device to heat the screen shaft and screen plate of the roller screen 3, including:

[0063] The heat source device delivers high-temperature steam through a steam pipeline to the hollow screen shaft of the roller screen 3. This screen shaft has conductive fins, and the high-temperature steam heats the screen shaft and the conductive fins through conduction. The high-temperature steam can be steam, flue gas, other waste heat, or new energy sources such as steam generated from abandoned power plants, metallurgical plants, chemical plants, etc. The temperature of the high-temperature steam is between 120℃ and 200℃.

[0064] Step S2, start the gas heating assembly and main fan 4 to deliver hot gas into the gas chamber, including:

[0065] The gas is heated by a gas heating component, and the temperature of the heated dry gas is between 100°C and 180°C. The gas can be air or other inert gas.

[0066] The hot gas is transported to the air chamber by the main fan 4.

[0067] The gas heating component includes a gas preheater and a gas heater. The gas preheater heats the external gas to 10-30°C and then delivers it to the gas heater, where the gas heater heats the gas to 100°C-180°C.

[0068] In some embodiments, a heat source is provided to the gas heater via a heat source device to heat the gas entering the air heater. The gas heater and the roller screen 3 can be heated by the same heat source device, or they can be heated by separate heat source devices.

[0069] In some embodiments, after the high-temperature steam passes through the screen shaft of the roller screen 3 for heat exchange, it can flow into the gas heater through a pipe to heat the air.

[0070] Step S3 involves feeding the material into the drying chamber of the fixed fluidized bed through the feed inlet, including:

[0071] The material to be dried (such as lignite) is fed into the drying chamber from the feed port at the top of the shell 1 through the coal conveying system and falls onto the roller screen 3.

[0072] Step S4 involves screening the material using a roller screen 3. Material smaller than or equal to a preset size falls onto the air distribution plate 2, is dried by hot gas, and then conveyed to the discharge port. Material larger than the preset size on the roller screen is dried using the screen shaft and hot gas and then conveyed to the discharge port. This includes:

[0073] As the roller screen 3 rotates, materials with a particle size smaller than or equal to a preset size (e.g., 6 mm) fall onto the air distribution plate 2, while materials with a particle size larger than the preset size remain on the roller screen 3.

[0074] The material on the air distribution plate 2 is fluidized and dried by hot gas passing through the air distribution plate 2, and the material on the air distribution plate 2 moves along the air distribution plate 2 towards the discharge port. During the fluidization and drying, the material on the air distribution plate 2 is disturbed by the scraper conveyor 8.

[0075] While the material on the roller screen 3 is transmitted and heated by the screen shaft and the conduction fins, the material on the roller screen 3 is also heated and dried by the hot gas rising after fluidized drying. The material on the roller screen 3 moves along the roller screen 3 towards the discharge port.

[0076] Collect the dried material output from the discharge port.

[0077] In some embodiments, the drying method for high-moisture, low-rank coal further includes exhaust gas purification treatment. The exhaust steam, after passing through the roller screen 3 and undergoing heat exchange, is introduced into a dust collector through the exhaust port. After the dust collector separates and collects particulate materials, the high-moisture, low-temperature exhaust steam is further transported to a gas preheater to exchange heat with external gas at a lower temperature. In the gas preheater, some of the water vapor releases its latent heat of vaporization and condenses into water. Some of the water vapor, together with the exhaust steam, is extracted by the exhaust gas fan and discharged through the chimney.

[0078] The gas, after passing through the roller screen 3 and undergoing heat exchange, enters the dilute phase zone at the top of the drying chamber. Here, the gas cools to 40-60℃, with a relative humidity of 40-60%, and carries moisture evaporated from the wet coal and extremely fine coal dust; this is commonly referred to as exhaust steam. See also... Figure 4 As shown in the specific embodiment, 20 tons of lignite with a particle size of 0-13mm and a moisture content of 17.88% were subjected to a drying test in a high-moisture, low-rank coal drying device. The test lignite entered the drying device through the feed inlet at the top of the shell 1 via the coal conveying system. The lignite fell onto the screen shaft with a roller screen 3. The fine-grained lignite below -6mm was gradually screened off to the lower part of the drying chamber. High-temperature steam of about 152°C was passed through the hollow screen shaft. The steam heated the screen shaft and screen plate through conduction. The screen shaft and screen plate then conducted heat to the lumps on the screen, and the hot air rising through the air distribution plate 2 also heated the lumps. At the same time, a large volume of hot air of about 103.6°C was introduced into the lower air chamber of the drying device to directly contact the fine-grained coal for fluidized bed drying. The temperature inside the fluidized bed was about 35.9°C. A circulating scraper conveyor 8 was installed above the air distribution plate 2. Under the action of the scraper conveyor 8, the fine-grained coal was quickly conveyed to the discharge port of the drying device. During the continuous feeding of lump coal with a particle size of 6mm or larger from the front end of shell 1 to the rear end of shell 1 on roller screen 3, heat exchange occurs both through conduction by the screen shaft and screen plate and through convective heat exchange by the hot air flowing out of the air distribution plate, ultimately achieving the drying and dehydration of the lump coal. Since the drying temperature, the rotation speed of the roller screen, and the speed of the agitator scraper are all adjustable, simultaneous dehydration of fine coal and lump coal is achieved. After drying, the mixture of fine coal and lump coal at 34.5℃ and 14.30% moisture content falls from the discharge port and is transported to the coal bunker. A very small portion of fine material enters the dust collector with the 36.8℃ airflow, and the fine material separated by the dust collector is recovered as product. Relevant experimental data are shown in Table 1, and the calculated results are shown in Table 2. Table 1 is the original experimental data record table, and Table 2 is the drying performance calculation table based on the experimental data in Table 1.

[0079]

[0080]

[0081] Table 1

[0082] 1 Coal input amount tons / H 20 2 Lignite Moisture ％ 17.88 3 Coal moisture ％ 14.30 4 Water removal rate ％ 3.58 5 Water removal ton 0.84 6 Heating hot air temperature ℃ 103.6 7 Exhaust temperature ℃ 36.8 8 Ambient temperature ℃ 0 9 Feed temperature ℃ 0 10 discharge temperature ℃ 34.5 11 Hot air releases heat inside the drying device 10,000 KJ 364.41 12 Total heat required for dry coal 10,000 KJ 1162.65 13 Hot air volume (mass) ㎏ / H 212589

[0083] Table 2

[0084] In summary, the embodiments of the present invention provide a drying apparatus and method for high-moisture-content, low-rank coal, which have the following beneficial effects:

[0085] (1) By using a roller screen consisting of a hollow screen shaft with a screen plate in the upper part and a fixed fluidized bed with a disturbance device in the lower part of the drying device, two different coal particles can be dried simultaneously through two different paths. This not only achieves efficient dehydration of high-moisture-content low-rank coal, but also makes full use of hot air to dry coal of mixed particle sizes, thereby improving coal quality.

[0086] (2) Since the drying temperature, the rotation speed of the roller screen and the speed of the agitator scraper are all adjustable, the simultaneous dewatering of fine coal and lump coal is achieved while meeting the needs for adjusting different dewatering rates.

[0087] (3) Both fine coal and lump coal fall from the end of the drying device and are transported to the coal bunker. A very small portion of fine materials enter the dust collector with the airflow. The fine materials separated by the dust collector are recycled as products. The high-humidity and low-temperature exhaust gas can be used by the gas preheater to exchange heat with the lower ambient air. There are no pollutant emissions during the drying process. Furthermore, the high-level steam can be recycled as a heat source, which is energy-saving and environmentally friendly.

[0088] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of one embodiment, and the modules or processes shown in the drawings are not necessarily essential for implementing the present invention.

[0089] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for apparatus or system embodiments, since they are basically similar to method embodiments, the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments. The apparatus and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0090] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A drying apparatus for high-moisture-content, low-rank coal, characterized in that, It includes a fixed fluidized bed, a roller screen, a heat source device, a dust collector, a tail gas induced draft fan, and a chimney. The fixed fluidized bed includes a shell, an air distribution plate, a gas heating component, and a main fan. The air distribution plate is provided in the inner cavity of the shell, and the air distribution plate divides the inner cavity of the shell into a drying chamber and a gas chamber from top to bottom. The roller screen is located in the drying chamber and is spaced above the air distribution plate. The housing has an inlet and an outlet that are respectively connected to the drying chamber. The inlet and the outlet are spaced apart along the length of the housing. The inlet is located at the front end of the air distribution plate and above the roller screen, and the outlet is located at the end of the air distribution plate. The gas heating assembly, the main blower, and the gas chamber are connected in sequence. The heat source device is used to heat the screen shaft of the roller screen and the screen plate connected to the screen shaft. The gas heating assembly includes a gas heater, which has a heating gas inlet, a heating gas outlet, a second steam inlet, and a second steam outlet. The heating gas inlet, the heating gas outlet, and the inlet of the main blower are connected in sequence. The heat source provided by the heat source device is high-temperature steam, the screen shaft is a hollow shaft, and the two ends of the hollow shaft have a first steam inlet and a first steam outlet, respectively. The heat source outlet of the heat source device is connected to the first steam inlet. The first steam outlet, the second steam inlet, the second steam outlet and the heat source inlet of the heat source device are connected in sequence; the gas heating assembly also includes a gas preheater, the top of the shell is provided with an exhaust port communicating with the drying chamber, and the gas preheater has an external gas inlet, an external gas outlet, an exhaust steam inlet and an exhaust steam outlet; The air chamber is equipped with an air regulating plate; there are several air regulating plates, which are spaced apart from each other and evenly distributed in the air chamber along the length of the air chamber, dividing the air chamber into several equal pressure air chambers.

2. The drying apparatus for high-moisture-content, low-rank coal according to claim 1, characterized in that, The exhaust port is connected to the inlet of the dust collector, and the gas outlet of the dust collector, the exhaust steam inlet, the exhaust steam outlet, the tail gas induced draft fan and the chimney are connected in sequence. The coal outlet of the dust collector is connected to the coal bunker, and the external gas inlet, the external gas outlet and the heating gas inlet are connected in sequence.

3. The drying apparatus for high-moisture-content, low-rank coal according to claim 1, characterized in that, The roller screen includes a feeding section and a drying section connected to the feeding section. The feeding section and the drying section are arranged along the direction from the feed inlet to the discharge outlet, wherein the feeding section is inclined and forms an obtuse angle with the drying section.

4. The drying apparatus for high-moisture-content, low-rank coal according to claim 1, characterized in that, An airlock rotary feeder is provided at the feed inlet, a first airlock unloader is provided at the discharge outlet, and a second airlock unloader is provided between the end of the roller screen and the side wall of the shell.

5. The drying apparatus for high-moisture-content, low-rank coal according to claim 1, characterized in that, A scraper conveyor is installed on the air distribution plate.

6. A method for drying high-moisture-content, low-rank coal, using the drying apparatus for high-moisture-content, low-rank coal as described in any one of claims 1-5, comprising the following steps: Step S1: Start the heat source device to heat the screen shaft and screen plate of the roller screen; Step S2: Start the gas heating assembly and main fan to deliver hot gas into the gas chamber; Step S3: The material is fed into the drying chamber of the fixed fluidized bed through the feed inlet; Step S4: The material is screened by the roller screen, wherein the material smaller than or equal to the preset size falls onto the air distribution plate and is dried by the hot gas and conveyed to the discharge port, and the material larger than the preset size on the roller screen is dried by the screen shaft, screen plate and hot gas and conveyed to the discharge port.

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