Coal heating and carrier gas heat recovery coupling system and method in coal drying process

Abstract

The invention belongs to the technical field of low-rank coal drying and dry distillation, and particularly relates to a coal heating and carrier gas heat recovery coupling system and method in the coal drying process, and the system comprises a coal preheating storage bin, a sealed coal conveying device, a steam rotary drum, a bag-type dust collector and a carrier gas circulating fan. The dry carrier gas inlet is connected with the first carrier gas treatment device through a dry carrier gas pipeline, a circulating fan is arranged on the dry carrier gas pipeline, the bag-type dust collector is connected with the first carrier gas treatment device through a clean wet carrier gas pipeline, and a carrier gas cooling regulator is arranged on the secondary carrier gas pipeline; the first carrier gas treatment device is a hot air generation device, and the second carrier gas treatment device is a hot water generation device. The system has the advantages that coal preheating and coal drying dehydration are achieved, meanwhile, a large number of cold public works used for carrier gas circulating cooling are omitted, middle-low-grade waste heat in wet carrier gas is recycled to the maximum degree, energy consumption of the whole system is reduced, and stability and operation efficiency of the system are improved.

Description

Technical Field

[0001] This invention belongs to the field of low-rank coal drying and carbonization technology, and particularly relates to a coupled system and method for coal heating and carrier gas heat recovery during coal drying. Background Technology

[0002] Low-rank coal, as an important component of the coal resource spectrum, has attracted widespread attention in the energy and chemical industries in recent years due to its huge reserves, relatively favorable occurrence conditions, and relatively low mining costs. Statistics show that global geological resources of low-rank coal amount to approximately 4 trillion tons, accounting for about 40% of the world's total coal resources, demonstrating its strategic position and development potential in the energy structure. In my country, coal resources are abundant in various types, but after long-term large-scale mining, the exploitable space for high-quality coal resources such as bituminous coal and anthracite is becoming increasingly limited, and the pressure of resource sustainability is gradually emerging. In contrast, my country's low-rank coal reserves are considerable, but due to its lower degree of coalification, high moisture content, and generally low calorific value, it still faces many technical bottlenecks in efficient conversion and clean utilization, and large-scale development and utilization are still in the exploratory and demonstration stage.

[0003] Low-rank coal drying is a common pretreatment technology in the utilization of low-rank coal. It is generally applied before coal gasification and coal pyrolysis (external heating and rotary kiln) processes. By reducing the moisture content of raw coal, it reduces the heat load of the main process, thereby increasing production capacity. Currently, the commonly used technology for pulverized coal drying is the indirect heating rotary drum, which uses steam as a heat source to provide heat for pulverized coal drying and introduces carrier gas during the coal rotary drying process to carry away the evaporated water vapor. This process is relatively mature and stable, capable of processing low-rank coal powder of 0-30mm and controlling the moisture content of the coal to below 8% through drying. However, this process has the following problems that restrict its further promotion: 1) The coal drying process uses steam as the only heat source, resulting in large steam consumption and high costs; 2) The carrier gas introduced during the coal drying process carries a large amount of low-grade heat, which needs to be cooled and dehydrated through cold utilities before being reheated and reintroduced into the steam rotary drum. This results in the ineffective recovery and utilization of the carrier gas heat, and further consumption of cold and hot utilities to achieve a closed-loop circulation of the carrier gas system, significantly increasing the process operating costs. Therefore, it is necessary to propose new process technologies based on the existing processes to achieve energy conservation, consumption reduction, and cascade utilization of heat in the coal drying process.

[0004] Chinese invention patent CN103822441A discloses a coal drying method using a low-inert gas circulation system. This process employs a scrubbing tower to wash, cool, and dehumidify the dried exhaust gas after dust removal, before recycling it, thus increasing the safety of the coal drying system. Simultaneously, the method utilizes negative pressure flash evaporation technology to achieve clean water recovery from the dried exhaust gas and resolve the "white dragon" phenomenon in the exhaust gas. However, this process does not achieve heat recovery from the carrier gas, resulting in a still relatively high overall operating cost for the drying process.

[0005] Chinese invention patent CN119819093A discloses a novel carrier gas circulating dehumidification and drying process system. This system includes a carrier gas heater, a dryer, a cyclone dust collector, a bag filter dust collector, a membrane dehumidifier, an adsorption dehumidifier, and a regeneration heater. By combining the membrane dehumidifier and the adsorption dehumidifier, humidity is removed from the circulating carrier gas. The dehumidification process does not require cooling, increasing the energy utilization rate of the circulating carrier gas to over 85%, while reducing exhaust emissions to below 15%, making it more energy-efficient, low-carbon, and environmentally friendly. It can be widely applied in the field of carrier gas circulating drying. However, the membrane separation dehydration process in this method is costly, the stability of its operation needs further verification, and the issue of carrier gas heat recovery remains unresolved. Summary of the Invention

[0006] The purpose of this invention is to provide a coupled system and method for coal heating and carrier gas heat recovery during coal drying, overcoming the shortcomings of the prior art. This system achieves coal preheating and coal drying and dehydration while eliminating a large amount of cold utilities used for carrier gas circulation cooling, maximizing the recovery of medium and low grade waste heat in the wet carrier gas. The recovered heat is used to heat the dehydrated dry carrier gas itself, and the remaining heat generates medium and low temperature hot water, part of which is used to preheat the raw coal, and the remaining hot water is used to heat other units. This helps to reduce the energy consumption of the entire system and improve stability and operating efficiency.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A coupled system for coal heating and carrier gas heat recovery during coal drying includes a coal preheating storage silo, a sealed coal conveying device, a steam rotary drum, a bag filter, and a carrier gas circulating fan. The coal preheating storage silo is connected to the steam rotary drum via the sealed coal conveying device. The steam rotary drum is equipped with a dry coal outlet, a dry carrier gas inlet, a wet carrier gas outlet, a steam inlet, and a condensate outlet. The wet carrier gas outlet is connected to the bag filter via a wet carrier gas pipeline. The dry carrier gas inlet is connected to a first carrier gas treatment device via a dry carrier gas pipeline. A circulating fan is installed on the dry carrier gas pipeline. The bag filter is connected to the first carrier gas treatment device via a clean and wet carrier gas pipeline. The first carrier gas treatment device and a second carrier gas treatment device are connected via a primary carrier gas pipeline and a secondary carrier gas pipeline, respectively. A carrier gas cooling regulator is installed on the secondary carrier gas pipeline. A dust content detection instrument is installed on the clean and wet carrier gas pipeline. The first carrier gas treatment device is a hot air generator, and the second carrier gas treatment device is a hot water generator.

[0008] Furthermore, the first carrier gas treatment device includes a first low-pressure working fluid pipeline, a first high-pressure working fluid pipeline, a first condenser, a first evaporator, and a first compressor. A first condenser is provided between the inlet of the first low-pressure working fluid pipeline and the outlet of the first high-pressure working fluid pipeline, and a first evaporator is provided between the outlet of the first low-pressure working fluid pipeline and the inlet of the first high-pressure working fluid pipeline. A first pressure reducing valve is provided on the first low-pressure working fluid pipeline, and a first compressor is provided on the first high-pressure working fluid pipeline. The first low-pressure working fluid pipeline, the first high-pressure working fluid pipeline, the first condenser, and the first evaporator form a closed loop. The first condenser is also connected to a secondary carrier gas pipeline and a dry carrier gas pipeline, and the first evaporator is also connected to a clean and wet carrier gas pipeline, a primary carrier gas pipeline, and a first condensate pipeline.

[0009] Furthermore, the second carrier gas treatment device includes a second low-pressure working fluid pipeline, a second high-pressure working fluid pipeline, a second condenser, a second evaporator, and a second compressor. A second condenser is installed between the inlet of the second low-pressure working fluid pipeline and the outlet of the second high-pressure working fluid pipeline. A second evaporator is installed between the outlet of the second low-pressure working fluid pipeline and the inlet of the second high-pressure working fluid pipeline. A second pressure reducing valve is installed on the second low-pressure working fluid pipeline, and a second compressor is installed on the second high-pressure working fluid pipeline. The second low-pressure working fluid pipeline, the second high-pressure working fluid pipeline, the second condenser, and the second evaporator form a closed loop. The second condenser is also connected to a hot water supply pipeline and a heated hot water pipeline, respectively. The second evaporator is also connected to a primary carrier gas pipeline, a secondary carrier gas pipeline, and a second condensate water pipeline, respectively.

[0010] Furthermore, the carrier gas cooling regulator is a tubular heat exchanger.

[0011] Furthermore, the first condensate pipe and the second condensate pipe are connected together, and then connected to the main condensate pipe for water purification and treatment system.

[0012] Furthermore, the coal preheating storage silo is equipped with a hot water heat exchange coil, which is connected to a hot water heating pipeline.

[0013] Furthermore, the outer surfaces of all pipes in the system are insulated.

[0014] Furthermore, the first compressor and the second compressor are gear pumps or screw pumps; the bag filter is an electrostatic bag filter; and the sealed coal conveying device is a screw conveyor.

[0015] Furthermore, the temperature inside the coal preheating storage silo is raised from 0-30℃ and 5%-40% moisture content to 60-95℃. After passing through a sealed coal conveying device, it enters a steam rotary drum. Inside the drum, it indirectly exchanges heat with low-pressure steam. The evaporated water vapor is carried away by dry carrier gas at 90-130℃ through the wet carrier gas pipeline. The moisture content of the dried coal is reduced to 5%-15% before being discharged. The wet carrier gas in the pipeline, with a temperature of 70-95℃ and a moisture content of 10%-30%, enters a bag filter dust collector to remove some of the dust it carries, becoming clean wet carrier gas. The clean wet carrier gas then sequentially enters the first carrier gas treatment device and the second carrier gas treatment device through the clean wet carrier gas pipeline. The device realizes the process of dehydration and cooling, and heating and preheating; the temperature of the carrier gas in the clean and wet carrier gas pipeline is 80~95℃, the temperature in the first-stage carrier gas pipeline of the first carrier gas treatment device is 55~65℃, the temperature in the first condensate pipeline is 55℃~65℃, the temperature in the second-stage carrier gas pipeline is 35~45℃, the temperature in the dry carrier gas pipeline is 90~130℃, and the water content is 0%~15%; the temperature in the second condensate pipeline of the first carrier gas treatment device is 35℃~45℃, the temperature in the hot water inlet pipeline is 65~75℃, and the temperature in the heated hot water pipeline is 90~110℃; the temperature of the hot water return water discharged from the coal preheating storage silo is 65~75℃.

[0016] Furthermore, the carrier gas is any one of nitrogen, carbon dioxide, or air, or a mixture of any two or three gases.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1) While achieving coal preheating and coal drying and dehydration, this system eliminates a large number of cold utility projects used for carrier gas circulation cooling, recovers the medium and low grade waste heat in the wet carrier gas to the maximum extent, and uses the recovered heat to heat the dry carrier gas itself after dehydration. The remaining heat generates medium and low temperature hot water, part of which is used to preheat the raw coal, and the remaining hot water is used to heat other units, thereby reducing the energy consumption of the entire system and improving the stability and operating efficiency of the system. 2) The dry carrier gas in the system, with a temperature of 90~130℃, enters the steam rotary drum and directly contacts the coal seam to remove the moisture from the coal drying process. The temperature of the dried wet carrier gas is 70~95℃ and the moisture content is 10%~30%. After entering the bag filter, the wet carrier gas removes some of the dust it carries. After dust removal, the carrier gas then enters the first carrier gas treatment device and the second carrier gas treatment device in sequence to realize the cycle process of dehydration and cooling and heating and preheating. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the process flow structure of an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the first carrier gas treatment device in an embodiment of the present invention; Figure 3This is a schematic diagram of the structure of the second carrier gas treatment device in an embodiment of the present invention; Figure 1 In the middle: 1-Coal preheating storage silo, 2-Sealed coal conveying device, 3-Steam rotary drum, 4-Bag filter dust collector, 5-Carrier gas dust content measuring instrument, 6-First carrier gas treatment device, 7-Carrier gas cooling regulator, 8-Second carrier gas treatment device, 9-Carrier gas circulating fan, 10-Dry carrier gas pipeline, 11-First low-pressure working fluid pipeline, 12-First high-pressure working fluid pipeline, 13-First condenser, 14-First evaporator, 15-First compressor 16-First pressure reducing valve, 17-First condensate pipeline, 18-Wet carrier gas pipeline, 19-Clean and wet carrier gas pipeline, 20-First-stage carrier gas pipeline, 21-Second low-pressure working fluid pipeline, 22-Second high-pressure working fluid pipeline, 23-Second condenser, 24-Second evaporator, 25-Second compressor, 26-Second pressure reducing valve, 27-Second condensate pipeline, 28-Second-stage carrier gas pipeline, 29-Hot water supply pipeline, 30-Heating hot water pipeline. Detailed Implementation

[0019] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the specific embodiments used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the specific embodiments described below are some embodiments of the present invention. For those skilled in the art, other specific embodiments can be obtained based on these specific embodiments without creative effort.

[0021] See Figure 1This is a schematic diagram of an embodiment of a coupled system for coal heating and carrier gas heat recovery during coal drying according to the present invention. It includes a coal preheating storage bin 1, a sealed coal conveying device 2, a steam rotary drum 3, a bag filter 4, and a carrier gas circulating fan 9. The coal preheating storage bin 1 is equipped with a hot water heat exchange coil connected to a heating hot water pipeline 30. The coal preheating storage bin 1 is connected to the steam rotary drum 3 via the sealed coal conveying device 2. The steam rotary drum 3 has a dry coal outlet, a dry carrier gas inlet, a wet carrier gas outlet, a steam inlet, and a condensate outlet. The wet carrier gas outlet is connected to a wet carrier gas pipe. The system is connected to the bag filter 4 via a dry carrier gas inlet (18). The dry carrier gas inlet is connected to the first carrier gas treatment device 6 via a dry carrier gas pipeline 10. A circulating fan 9 is installed on the dry carrier gas pipeline 10. The bag filter 4 is connected to the first carrier gas treatment device 6 via a clean / wet carrier gas pipeline 19. The first carrier gas treatment device 6 and the second carrier gas treatment device 8 are connected via a primary carrier gas pipeline 20 and a secondary carrier gas pipeline 28, respectively. A carrier gas cooling regulator 7, a tubular heat exchanger, is installed on the secondary carrier gas pipeline 28 to regulate the heat balance during the entire carrier gas circulation process. A dust content detection instrument 5 is installed on the clean / wet carrier gas pipeline 19. The first carrier gas treatment device 6 is a hot air generator, and the second carrier gas treatment device 8 is a hot water generator.

[0022] See Figure 2 The first carrier gas treatment device 6 includes a first low-pressure working fluid pipeline 11, a first high-pressure working fluid pipeline 12, a first condenser 13, a first evaporator 14, and a first compressor 15. The first condenser 13 is provided between the inlet of the first low-pressure working fluid pipeline 11 and the outlet of the first high-pressure working fluid pipeline 12. The first evaporator 14 is provided between the outlet of the first low-pressure working fluid pipeline 11 and the inlet of the first high-pressure working fluid pipeline 12. A first pressure reducing valve 16 is provided on the first low-pressure working fluid pipeline 11. The first compressor 15 is provided on the first high-pressure working fluid pipeline 12. The first low-pressure working fluid pipeline 11, the first high-pressure working fluid pipeline 12, the first condenser 13, and the first evaporator 14 form a closed loop, realizing the process of absorbing heat through a relatively high-temperature medium and then releasing heat through a relatively low-temperature medium. The first condenser 13 is also connected to the secondary carrier gas pipeline 28 and the dry carrier gas pipeline 10, respectively. The first evaporator 14 is also connected to the clean and wet carrier gas pipeline 19, the primary carrier gas pipeline 20 and the first condensate pipeline 17, respectively.

[0023] See Figure 3The second carrier gas treatment device 8 includes a second low-pressure working fluid pipeline 21, a second high-pressure working fluid pipeline 22, a second condenser 23, a second evaporator 24, and a second compressor 25. The second condenser 23 is located between the inlet of the second low-pressure working fluid pipeline 21 and the outlet of the second high-pressure working fluid pipeline 22, and the second evaporator 24 is located between the outlet of the second low-pressure working fluid pipeline 21 and the inlet of the second high-pressure working fluid pipeline 22. A second pressure reducing valve 26 is installed on the second low-pressure working fluid pipeline 21, and a second compressor 25 is installed on the second high-pressure working fluid pipeline 22. The second low-pressure working fluid pipeline 21, the second high-pressure working fluid pipeline 22, the second condenser 23, and the second evaporator 24 form a closed loop, realizing the process of absorbing heat through a relatively high-temperature medium and then releasing heat through a relatively low-temperature medium. The second condenser 23 is also connected to a hot water supply pipeline 29 and a heated hot water pipeline 30, respectively. The second evaporator 24 is also connected to a primary carrier gas pipeline 20, a secondary carrier gas pipeline 28, and a second condensate pipeline 27, respectively. The first condensate pipe 17 and the second condensate pipe 27 can be connected together and then connected to the main condensate pipe for water purification and treatment system.

[0024] In this embodiment, the first compressor 15 and the second compressor 25 are gear pumps or screw pumps, with an output pressure of 2~5 kPa and a flow rate of 500~2000 Nm³. 3 / h; Bag filter 4 is an electrostatic bag filter; Sealed coal conveying device 2 is a screw conveyor. To reduce heat loss, insulation treatment can be applied to the outer surface of each pipeline in the system.

[0025] In the operation of this embodiment of the invention, the temperature inside the coal preheating storage bin 1 is raised from 0~30℃ and the raw coal with a moisture content of 5%~40% to 60~95℃. After passing through the sealed coal conveying device 2, it enters the steam rotary drum 3. After indirect heat exchange with low-pressure steam inside the steam rotary drum 3, the evaporated water vapor is carried away by dry carrier gas at 90~130℃ through the wet carrier gas pipeline 18. The moisture content of the dried coal is reduced to 5%~15% before being discharged, preferably 8%. The wet carrier gas in the wet carrier gas pipeline 18, with a temperature of 70~95℃ and a moisture content of 10%~30%, enters the bag filter dust collector 4 to remove some of the dust it carries, becoming clean wet carrier gas. The clean wet carrier gas then enters the first carrier gas treatment device 6 and the second carrier gas treatment device 8 sequentially through the clean wet carrier gas pipeline 19, realizing the process of dehydration, cooling, and preheating. The carrier gas temperature in gas pipeline 19 is 80~95℃; the temperature in the primary carrier gas pipeline 20 of the first carrier gas treatment device 6 is 55~65℃; the temperature in the first condensate pipeline 17 is 55℃~65℃; the temperature in the secondary carrier gas pipeline 28 is 35~45℃; the carrier gas temperature in the dry carrier gas pipeline 10 is 90~130℃, and the water content is 0%~15%; the temperature in the second condensate pipeline 27 of the first carrier gas treatment device 6 is 35℃~45℃; the temperature in the hot water supply pipeline 29 is 65~75℃; the temperature in the heated hot water pipeline 30 is 90~110℃. After heating, the total hot water is divided into two paths: one path goes to other devices to provide a heat source for them; the other path enters the coal preheating storage silo 1 to provide a heat source for coal preheating; the return water temperature of the hot water discharged from the coal preheating storage silo 1 is 65~75℃.

[0026] The carrier gas is any one of nitrogen, carbon dioxide, or air, or a mixture of any two or three gases.

[0027] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A coupled system for coal heating and carrier gas heat recovery during coal drying, comprising a coal preheating storage silo, a sealed coal conveying device, a steam rotary drum, a bag filter, and a carrier gas circulating fan, wherein the coal preheating storage silo is connected to the steam rotary drum via the sealed coal conveying device, the steam rotary drum is provided with a dry coal outlet, a dry carrier gas inlet, a wet carrier gas outlet, a steam inlet, and a condensate outlet, and the wet carrier gas outlet is connected to the bag filter via a wet carrier gas pipeline, characterized in that... The dry carrier gas inlet is connected to the first carrier gas treatment device via a dry carrier gas pipeline. A circulating fan is installed on the dry carrier gas pipeline. The bag filter is connected to the first carrier gas treatment device via a clean and wet carrier gas pipeline. The first carrier gas treatment device and the second carrier gas treatment device are connected via a primary carrier gas pipeline and a secondary carrier gas pipeline, respectively. A carrier gas cooling regulator is installed on the secondary carrier gas pipeline. A dust content detection instrument is installed on the clean and wet carrier gas pipeline. The first carrier gas treatment device is a hot air generator, and the second carrier gas treatment device is a hot water generator.

2. The coupled system for coal heating and carrier gas heat recovery during coal drying as described in claim 1, characterized in that, The first carrier gas treatment device includes a first low-pressure working fluid pipeline, a first high-pressure working fluid pipeline, a first condenser, a first evaporator, and a first compressor. The first condenser is located between the inlet of the first low-pressure working fluid pipeline and the outlet of the first high-pressure working fluid pipeline. The first evaporator is located between the outlet of the first low-pressure working fluid pipeline and the inlet of the first high-pressure working fluid pipeline. A first pressure reducing valve is located on the first low-pressure working fluid pipeline. A first compressor is located on the first high-pressure working fluid pipeline. The first low-pressure working fluid pipeline, the first high-pressure working fluid pipeline, the first condenser, and the first evaporator form a closed loop. The first condenser is also connected to a secondary carrier gas pipeline and a dry carrier gas pipeline. The first evaporator is also connected to a clean and wet carrier gas pipeline, a primary carrier gas pipeline, and a first condensate pipeline.

3. The coupled system for coal heating and carrier gas heat recovery during coal drying as described in claim 1, characterized in that, The second carrier gas treatment device includes a second low-pressure working fluid pipeline, a second high-pressure working fluid pipeline, a second condenser, a second evaporator, and a second compressor. A second condenser is located between the inlet of the second low-pressure working fluid pipeline and the outlet of the second high-pressure working fluid pipeline. A second evaporator is located between the outlet of the second low-pressure working fluid pipeline and the inlet of the second high-pressure working fluid pipeline. A second pressure reducing valve is located on the second low-pressure working fluid pipeline, and a second compressor is located on the second high-pressure working fluid pipeline. The second low-pressure working fluid pipeline, the second high-pressure working fluid pipeline, the second condenser, and the second evaporator form a closed loop. The second condenser is also connected to a hot water supply pipeline and a heated hot water pipeline, respectively. The second evaporator is also connected to a primary carrier gas pipeline, a secondary carrier gas pipeline, and a second condensate water pipeline, respectively.

4. The coupled system for coal heating and carrier gas heat recovery during coal drying as described in claim 1, characterized in that, The carrier gas cooling regulator is a tubular heat exchanger, and the heat exchange medium is cold water or hot water.

5. The coupled system for coal heating and carrier gas heat recovery during coal drying as described in claim 1, characterized in that, The first condensate pipe and the second condensate pipe are connected, and after being combined, they are connected to the main condensate pipe to the water purification and treatment system.

6. The coupled system for coal heating and carrier gas heat recovery during coal drying as described in claim 1, characterized in that, The coal preheating storage silo is equipped with a hot water heat exchange coil, which is connected to a heated hot water pipeline. The hot water return water is returned to the second carrier gas treatment device.

7. The coupled system for coal heating and carrier gas heat recovery during coal drying as described in claim 1, characterized in that, The outer surfaces of all pipes in the system are insulated.

8. The coupled system for coal heating and carrier gas heat recovery during coal drying as described in claim 1, characterized in that, The first and second compressors are gear pumps or screw pumps; the bag filter is an electrostatic bag filter; and the sealed coal conveying device is a screw conveyor.

9. A method for coupling coal heating and carrier gas heat recovery during coal drying according to any one of claims 1-8, characterized in that, The temperature inside the coal preheating storage silo is raised from 0~30℃ and 5%~40% moisture content to 60~95℃. After passing through a sealed coal conveying device, it enters a steam rotary drum. Inside the steam rotary drum, it indirectly exchanges heat with low-pressure steam. The evaporated water vapor is carried away by dry carrier gas at 90~130℃ from the wet carrier gas pipeline. The moisture content of the dried coal is reduced to 5%~15% before it is discharged. The wet carrier gas with a temperature of 70~95℃ and a moisture content of 10%~30% enters the bag filter and removes some of the dust it carries to become clean wet carrier gas. The clean wet carrier gas enters the first carrier gas treatment device and the second carrier gas treatment device in sequence through the clean wet carrier gas pipeline to achieve the process of dehydration and cooling and heating and preheating. The temperature of the carrier gas in the clean and wet carrier gas pipeline is 80~95℃, the temperature in the primary carrier gas pipeline of the first carrier gas treatment device is 55~65℃, the temperature in the first condensate pipeline is 55℃~65℃, the temperature in the secondary carrier gas pipeline is 35~45℃, and the temperature of the carrier gas in the dry carrier gas pipeline is 90~130℃ with a moisture content of 0%~15%. In the first carrier gas treatment device, the temperature in the second condensate pipeline is 35℃~45℃, the temperature in the hot water supply pipeline is 65~75℃, and the temperature in the heated hot water pipeline is 90~110℃; the temperature of the hot water return water discharged from the coal preheating storage silo is 65~75℃.

10. The method for coupling coal heating and carrier gas heat recovery during coal drying as described in claim 7, characterized in that, The carrier gas is any one of nitrogen, carbon dioxide, or air, or a mixture of any two or three gases.

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