Waste heat recovery system for a dryer, dryer and method

Abstract

This invention provides a waste heat recovery system, dryer, and method for a dryer, relating to the field of wet material drying technology. It includes a waste heat recovery device and a first heat exchanger. The waste heat recovery device has a high-temperature flue gas inlet and a high-temperature medium outlet. The high-temperature flue gas inlet is adapted to be connected to the exhaust port of the dryer to allow the introduction of high-temperature flue gas. The medium within the waste heat recovery device can exchange heat with the high-temperature flue gas to raise its temperature. The first heat exchanger has a low-temperature side and a high-temperature side. The low-temperature side of the first heat exchanger is adapted to introduce combustion air, and the low-temperature side outlet of the first heat exchanger is adapted to be connected to the combustion air inlet of the dryer. The high-temperature side inlet of the first heat exchanger is connected to the high-temperature medium outlet to allow the introduction of a high-temperature medium. The high-temperature medium on the high-temperature side of the first heat exchanger can exchange heat with the combustion air on the low-temperature side of the first heat exchanger. This invention can recover waste heat from the high-temperature flue gas of the dryer to preheat the combustion air and reduce energy consumption.

Description

Technical Field

[0001] This invention relates to the field of wet material drying technology, and more particularly to a waste heat recovery system, dryer, and method for a dryer. Background Technology

[0002] In the drying process of wet materials in the chemical and metallurgical industries such as potash fertilizer, rotary drum dryers are often used to dry the wet materials. Related technologies for rotary drum dryers (see...) Figure 1 The process involves burning natural gas and combustion air in a hot blast stove to generate high-temperature flue gas. This high-temperature flue gas is then used to heat wet materials in a rotating drum and remove moisture from the materials. The dried hot materials are then cooled by air in a cooling section and discharged from the outlet. The wet and dusty flue gas is directly discharged after dust removal. Under this treatment method, a large amount of residual heat in the flue gas is not fully utilized, resulting in the wasteful emission of natural gas.

[0003] Therefore, there is an urgent need to design a system that can recover and utilize the waste heat from the flue gas of the dryer. Summary of the Invention

[0004] The present invention aims to at least partially solve one of the technical problems in the related art.

[0005] Therefore, one embodiment of the present invention provides a waste heat recovery system for a dryer, which can recover waste heat from the high-temperature flue gas of the dryer to preheat the combustion air and reduce energy consumption.

[0006] Another embodiment of the present invention provides a dryer.

[0007] Another aspect of the present invention provides a method for waste heat recovery in a dryer.

[0008] According to an embodiment of the present invention, a waste heat recovery system for a dryer includes a waste heat recovery device and a first heat exchanger. The waste heat recovery device is provided with a high-temperature flue gas inlet and a high-temperature medium outlet. The high-temperature flue gas inlet is adapted to be connected to the exhaust port of the dryer to allow the introduction of high-temperature flue gas. The medium in the waste heat recovery device is capable of exchanging heat with the high-temperature flue gas to increase its temperature. The first heat exchanger has a low-temperature side and a high-temperature side. The low-temperature side of the first heat exchanger is adapted to be supplied with combustion air. The low-temperature side outlet of the first heat exchanger is adapted to be connected to the combustion air inlet of the dryer. The high-temperature side inlet of the first heat exchanger is connected to the high-temperature medium outlet to allow the introduction of a high-temperature medium. The high-temperature medium in the high-temperature side of the first heat exchanger is capable of exchanging heat with the combustion air in the low-temperature side of the first heat exchanger.

[0009] According to an embodiment of the present invention, a waste heat recovery system for a dryer allows a medium within a waste heat recovery device to exchange heat with high-temperature flue gas, absorbing the heat energy from the flue gas to obtain a high-temperature medium. This high-temperature medium then enters a first heat exchanger to exchange heat with combustion air introduced into the first heat exchanger, thereby preheating the combustion air and reducing the heat energy required for combustion of the combustion air and natural gas in the dryer's hot air furnace. This fully recovers waste heat from the flue gas without affecting the original drying process, reducing natural gas consumption. Therefore, compared to related technologies, the present invention can recover waste heat from the high-temperature flue gas of the dryer to preheat the combustion air and reduce energy consumption.

[0010] Furthermore, the waste heat recovery device is one of a spray waste heat recovery tower and a gas-water heat exchanger.

[0011] In some embodiments, the waste heat recovery system further includes a heat pump unit and a second heat exchanger. The heat pump unit includes an evaporator and a condenser. The high-temperature medium outlet is also connected to the evaporator inlet to introduce the high-temperature medium into the evaporator. The high-temperature medium in the evaporator can exchange heat with the circulating working fluid in the condenser. The second heat exchanger has a low-temperature side and a high-temperature side. The low-temperature side outlet of the first heat exchanger, the low-temperature side of the second heat exchanger, and the combustion air inlet of the dryer are connected in sequence. The high-temperature side of the second heat exchanger is connected in series with the condenser to introduce the circulating working fluid. The circulating working fluid in the high-temperature side of the second heat exchanger can exchange heat with the combustion air in the low-temperature side of the second heat exchanger.

[0012] In some embodiments, the waste heat recovery device is further provided with a first low-temperature medium inlet and a second low-temperature medium inlet, the high-temperature side outlet of the first heat exchanger is connected to the first low-temperature medium inlet, and the evaporator outlet is connected to the second low-temperature medium inlet.

[0013] In some embodiments, the waste heat recovery device further includes a low-temperature flue gas outlet, and the second low-temperature medium inlet is located between the low-temperature flue gas outlet and the first low-temperature medium inlet in the upward direction of the flue gas flow.

[0014] In some embodiments, the waste heat recovery device is a spray waste heat recovery tower, which includes a tower body, a first nozzle and a second nozzle. The tower body has a receiving cavity and is provided with a high-temperature flue gas inlet and a high-temperature medium outlet communicating with the receiving cavity. The first nozzle and the second nozzle are both located in the receiving cavity and are used to spray spray liquid to cool the high-temperature flue gas. The first nozzle is connected to the first low-temperature medium inlet, and the second nozzle is connected to the second low-temperature medium inlet.

[0015] In some embodiments, there are multiple first nozzles and second nozzles, which are arranged at intervals in the receiving cavity.

[0016] In some embodiments, the first nozzle is located between the high-temperature flue gas inlet and the second nozzle in the upward direction of the flue gas flow, the flue gas flow direction is consistent with the vertical direction, and the spray waste heat recovery tower further includes a flue gas baffle, the flue gas baffle is provided below at least one of the first nozzle and the second nozzle, and the flue gas baffle is located in the receiving cavity.

[0017] In some embodiments, the flue gas baffle extends along the vertical direction, and there are multiple flue gas baffles arranged at intervals along a first direction, which is orthogonal to the vertical direction;

[0018] The distance between any two adjacent flue gas baffles is s, and s is 1cm to 10cm.

[0019] A dryer according to an embodiment of the present invention includes a hot air furnace, a rotary drum, and a waste heat recovery system. The hot air furnace is provided with a combustion air inlet, the rotary drum is used to hold materials and is provided with a flue gas outlet, the hot air furnace is connected to the rotary drum and is used to introduce combustion flue gas into the rotary drum to dry the materials inside the rotary drum; the waste heat recovery system is the waste heat recovery system described in any of the above embodiments, the high-temperature flue gas inlet of the waste heat recovery device of the waste heat recovery system is adapted to be connected to the flue gas outlet, and the low-temperature side outlet of the first heat exchanger of the waste heat recovery system is adapted to be connected to the combustion air inlet.

[0020] According to an embodiment of the present invention, the waste heat recovery system of the dryer is designed to recover the waste heat in the high-temperature flue gas of the dryer, so as to use the recovered heat energy to preheat the combustion air, thereby reducing the heat energy required for the combustion of the combustion air and natural gas in the hot air furnace of the dryer. Without affecting the original process operation of the drying process, the waste heat of the flue gas is fully recovered, and the energy consumption is low. Therefore, compared with related technologies, the dryer using this waste heat recovery system can save natural gas consumption and reduce the operating cost of the drying process.

[0021] In some embodiments, the dryer further includes a dust collector, the inlet of which is connected to the exhaust port, and the outlet of which is connected to the high-temperature flue gas inlet of the waste heat recovery device.

[0022] According to an embodiment of the present invention, a waste heat recovery method for a dryer, based on the waste heat recovery system described in any of the above embodiments, includes the following steps: Waste heat recovery involves passing the high-temperature flue gas discharged from the exhaust port of the dryer into a waste heat recovery device. The medium inside the waste heat recovery device exchanges heat with the high-temperature flue gas to obtain low-temperature flue gas and a high-temperature medium. The waste heat recovery device then discharges the low-temperature flue gas. First-stage preheating involves introducing combustion air into the low-temperature side of the first heat exchanger and allowing at least a portion of the high-temperature medium to enter the high-temperature side of the first heat exchanger. The high-temperature medium exchanges heat with the combustion air to obtain a first low-temperature medium and heated combustion air. Waste heat is utilized by introducing the heated combustion air into the dryer.

[0023] The technical advantages of the waste heat recovery method for a dryer according to the embodiments of the present invention are the same as those of the waste heat recovery system for a dryer described above, and will not be repeated here.

[0024] In some embodiments, after the primary preheating operation, the waste heat recovery method further includes the step of: Secondary preheating involves introducing the heated combustion air into the low-temperature side of the second heater, and allowing at least a portion of the high-temperature medium to enter the evaporator of the heat pump unit. The high-temperature medium exchanges heat with the circulating working fluid in the condenser of the heat pump unit to obtain a second low-temperature medium and a heated circulating working fluid. The heated circulating working fluid then enters the high-temperature side of the second heater to exchange heat with the heated combustion air, further heating the combustion air.

[0025] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of a rotary drum dryer in related technologies.

[0027] Figure 2 This is a schematic diagram of a waste heat recovery system for a dryer according to an embodiment of the present invention.

[0028] Figure 3 This is a schematic diagram of the structure of a spray waste heat recovery tower in a waste heat recovery system for a dryer according to an embodiment of the present invention.

[0029] Figure 4 This is a schematic diagram of the structure of a dryer according to an embodiment of the present invention.

[0030] Figure 5 This is a schematic flowchart of a waste heat recovery method for a dryer according to an embodiment of the present invention.

[0031] Figure label: 10. Dryer; 100. Hot air furnace; 200. Rotary drum; 300. Waste heat recovery system; 400. Dust collector; 1. Waste heat recovery device; 11. High-temperature flue gas inlet; 12. High-temperature medium outlet; 121. Conveying main pipe; 122. First conveying branch pipe; 123. Second conveying branch pipe; 13. First low-temperature medium inlet; 14. Second low-temperature medium inlet; 15. Low-temperature flue gas outlet; 16. Tower body; 161. Receiving cavity; 17. First nozzle; 18. Second nozzle; 19. Flue gas baffle; 2. First heat exchanger; 21. Low-temperature side outlet of the first heat exchanger; 22. High-temperature side inlet of the first heat exchanger; 23. Low-temperature side inlet of the first heat exchanger; 24. High-temperature side outlet of the first heat exchanger; 3. Heat pump unit; 31. Evaporator; 32. Condenser; 4. Second heat exchanger; 41. High-temperature side inlet of the second heat exchanger; 5. Combustion air inlet; 51. Natural gas inlet; 6. Exhaust vent; 61. Drying section; 611. Wet material inlet; 62. Cooling section; 621. Dry material outlet; 622. Cooling air inlet. Detailed Implementation

[0032] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0033] like Figure 2 As shown, an embodiment of the present invention provides a waste heat recovery system for a dryer, comprising a waste heat recovery device 1 and a first heat exchanger 2. The waste heat recovery device 1 is provided with a high-temperature flue gas inlet 11 and a high-temperature medium outlet 12. The high-temperature flue gas inlet 11 is adapted to be connected to the exhaust port 6 of the dryer 10 to allow the introduction of high-temperature flue gas. The medium inside the waste heat recovery device 1 can exchange heat with the high-temperature flue gas to raise its temperature. The first heat exchanger 2 has a low-temperature side and a high-temperature side. The low-temperature side of the first heat exchanger 2 is adapted to be supplied with combustion air. The low-temperature side outlet 21 of the first heat exchanger is adapted to be connected to the combustion air inlet 5 of the dryer 10. The high-temperature side inlet 22 of the first heat exchanger is connected to the high-temperature medium outlet 12 to allow the introduction of high-temperature medium. The high-temperature medium inside the high-temperature side of the first heat exchanger 2 can exchange heat with the combustion air inside the low-temperature side of the first heat exchanger 2.

[0034] According to an embodiment of the present invention, the waste heat recovery system for a dryer allows the medium in the waste heat recovery device 1 to exchange heat with high-temperature flue gas, thereby absorbing the heat energy in the high-temperature flue gas to obtain a high-temperature medium. The high-temperature medium then enters the first heat exchanger 2 to exchange heat with the combustion air introduced into the first heat exchanger 2, thereby preheating the combustion air and reducing the heat energy required for combustion of the combustion air and natural gas in the hot air furnace 100 of the dryer 10. This fully recovers the waste heat of the flue gas without affecting the original process operation of the drying process, thus reducing natural gas consumption. Therefore, compared with related technologies, the present invention can recover the waste heat in the high-temperature flue gas of the dryer 10 to preheat the combustion air and reduce energy consumption.

[0035] Specifically, the high-temperature flue gas inlet 11 may be equipped with a fan to provide power for conveying the high-temperature flue gas into the waste heat recovery device 1. The low-temperature side inlet 23 of the first heat exchanger may be equipped with a fan to blow combustion air into the low-temperature side of the first heat exchanger 2. A transfer pump may be installed between the high-temperature side inlet 22 of the first heat exchanger and the high-temperature medium outlet 12 to transport the high-temperature medium to the high-temperature side of the first heat exchanger 2. The first heat exchanger 2 is not limited to an air heater.

[0036] Furthermore, the waste heat recovery device 1 is one of a spray waste heat recovery tower and a gas-water heat exchanger.

[0037] It is understandable that when the high temperature flue gas has a high moisture content, a spray waste heat recovery tower can be used to perform total heat exchange on the high temperature flue gas. When the high temperature flue gas has a low moisture content, a steam-water heat exchanger can be used, that is, a gas-water heat exchanger can be used as an air heater for sensible heat exchange.

[0038] Specifically, when the waste heat recovery device 1 is a spray waste heat recovery tower, the medium inside the waste heat recovery device 1 is the spray liquid, and when the waste heat recovery device 1 is a gas-water heat exchanger, the medium inside the waste heat recovery device 1 is the water in the heat exchange pipeline.

[0039] It should be noted that the flue gas produced after the natural gas and combustion air are mixed and burned has a large amount of residual heat after the material is dried. However, the relevant technology treats the dried flue gas by directly discharging it after dust removal. Under this treatment method, a large amount of residual heat in the flue gas is not fully utilized, which easily leads to the waste of natural gas.

[0040] Taking the equipment parameters of a certain drying process as an example, the dryer 10 requires 50,000 Nm of air. 3 The average annual air temperature is 5℃, and the flue gas temperature is assumed to be 100℃. Considering only the sensible heat of the flue gas, the natural gas consumption is approximately 173 Nm³. 3Based on a natural gas price of 3 yuan per cubic meter and an annual working time of 330 days, the annual natural gas consumption is approximately 4.13 million yuan. Therefore, there is a huge potential for energy saving and cost reduction.

[0041] Therefore, by applying the waste heat recovery system 300 of the present invention, the waste heat of flue gas can be fully recovered without affecting the process operation, thereby saving natural gas consumption and reducing the operating cost of the drying process.

[0042] like Figure 2 As shown, in some embodiments, the waste heat recovery system 300 further includes a heat pump unit 3 and a second heat exchanger 4. The heat pump unit 3 includes an evaporator 31 and a condenser 32. The high-temperature medium outlet 12 is also connected to the inlet of the evaporator 31 to introduce the high-temperature medium into the evaporator 31. The high-temperature medium in the evaporator 31 can exchange heat with the circulating working fluid in the condenser 32. The second heat exchanger 4 has a low-temperature side and a high-temperature side. The low-temperature side outlet 21 of the first heat exchanger, the low-temperature side of the second heat exchanger 4, and the combustion air inlet 5 of the dryer 10 are connected in sequence. The high-temperature side of the second heat exchanger 4 is connected in series with the condenser 32 to introduce the circulating working fluid. The circulating working fluid in the high-temperature side of the second heat exchanger 4 can exchange heat with the combustion air in the low-temperature side of the second heat exchanger 4.

[0043] Understandably, when a high-temperature medium is introduced into the evaporator 31 of the heat pump unit 3, the medium can be further heated by the heat pump unit 3 and exchange heat with the circulating working fluid in the condenser 32 of the heat pump unit 3, thus heating the circulating working fluid. The heated circulating working fluid can then enter the high-temperature side of the second heat exchanger 4. Simultaneously, the combustion air heated by the first heat exchanger 2 will re-enter the low-temperature side of the second heat exchanger 4. The combustion air on the low-temperature side of the second heat exchanger 4 can exchange heat with the circulating working fluid on the high-temperature side of the second heat exchanger 4 to be heated, thus undergoing secondary preheating. Specifically, when the high-temperature medium is a high-temperature spray liquid or high-temperature water, the heat pump unit 3 can heat the water to above 80°C, significantly increasing the temperature of the preheated combustion air.

[0044] Therefore, by combining the heat pump unit 3 and the second heat exchanger 4, the high-temperature medium's thermal energy can be efficiently utilized, further improving the utilization efficiency of waste heat recovery from high-temperature flue gas.

[0045] Specifically, a transfer pump can be installed between the inlet of evaporator 31 and the high-temperature medium outlet 12. A transfer pump can also be installed between the outlet of condenser 32 and the high-temperature side inlet 41 of the second heat exchanger. The high-temperature medium outlet 12 can be connected to a transfer header 121, which has a first outlet and a second outlet. The first outlet is connected to the high-temperature side inlet 22 of the first heat exchanger via a first transfer branch pipe 122, and the second outlet is connected to the inlet of evaporator 31 via a second transfer branch pipe 123. The second heat exchanger 4 is not limited to an air heater.

[0046] like Figure 2 As shown, in some embodiments, the waste heat recovery device 1 is further provided with a first low-temperature medium inlet 13 and a second low-temperature medium inlet 14. The high-temperature side outlet 24 of the first heat exchanger is connected to the first low-temperature medium inlet 13, and the outlet of the evaporator 31 is connected to the second low-temperature medium inlet 14, so that the first low-temperature medium obtained after heat exchange in the first heat exchanger 2 and the second low-temperature medium obtained after heat exchange in the evaporator 31 are both returned to the waste heat recovery device 1 to continue to participate in the waste heat recovery of high-temperature flue gas, thereby improving the energy utilization rate of the waste heat recovery system 300.

[0047] like Figure 2 As shown, in some embodiments, the waste heat recovery device 1 is further provided with a low-temperature flue gas outlet 15, and the second low-temperature medium inlet 14 is located between the low-temperature flue gas outlet 15 and the first low-temperature medium inlet 13 in the flue gas flow direction. That is, the second low-temperature medium inlet 14 is closer to the low-temperature flue gas outlet 15 than the first low-temperature medium inlet 13. In other words, the first low-temperature medium inlet 13 is closer to the high-temperature flue gas inlet 11 than the second low-temperature medium inlet 14.

[0048] It is understandable that the heat exchange efficiency of the heat pump unit 3 and the second heat exchanger 4 is higher than that of the first heat exchanger 2. Therefore, the temperature of the first low-temperature medium at the first low-temperature medium inlet 13 is higher than that of the second low-temperature medium at the second low-temperature medium inlet 14. The above structure is beneficial to further improve the efficiency of heat recovery from high-temperature flue gas.

[0049] like Figure 2 and Figure 3 As shown, in some embodiments, the waste heat recovery device 1 is a spray waste heat recovery tower. The spray waste heat recovery tower includes a tower body 16, a first nozzle 17 and a second nozzle 18. The tower body 16 has a receiving cavity 161 and is provided with a high-temperature flue gas inlet 11 and a high-temperature medium outlet 12 communicating with the receiving cavity 161. The first nozzle 17 and the second nozzle 18 are both located in the receiving cavity 161 and are used to spray spray liquid to cool the high-temperature flue gas. The first nozzle 17 is connected to the first low-temperature medium inlet 13 and the second nozzle 18 is connected to the second low-temperature medium inlet 14.

[0050] It is understandable that by adopting the spray waste heat recovery tower structure, the total heat exchange of high-temperature flue gas with high moisture content can be achieved. Specifically, the first nozzle 17 sprays the first low-temperature medium (or first spray liquid) returning from the first heat exchanger 2 and the second nozzle 18 sprays the second low-temperature medium (or second spray liquid) returning from the evaporator 31 into the containment cavity 161 to cool down the high-temperature flue gas.

[0051] Specifically, both the tower body 16 and the receiving cavity 161 can extend vertically. The high-temperature flue gas inlet 11 and the high-temperature medium outlet 12 can both be located near the bottom of the tower body 16. The low-temperature flue gas outlet 15 can be located at the top of the tower body 16.

[0052] like Figure 3 As shown, in some embodiments, there are multiple first nozzles 17 and second nozzles 18, which are arranged at intervals in the receiving cavity 161 so that the spray liquid (including the first spray liquid and the second spray liquid) can exchange heat evenly with the high-temperature flue gas, thereby improving the recovery effect of the heat energy of the high-temperature flue gas.

[0053] Preferably, a plurality of first nozzles 17 are arranged at equal intervals in the receiving cavity 161, and a plurality of second nozzles 18 are arranged at equal intervals in the receiving cavity 161.

[0054] like Figure 3 As shown, in some embodiments, the first nozzle 17 is located between the high-temperature flue gas inlet 11 and the second nozzle 18 in the upward direction of the flue gas flow. The flue gas flow direction is consistent with the vertical direction, that is, in the upward direction of the flue gas flow, the high-temperature flue gas inlet 11, the first nozzle 17, and the second nozzle 18 are arranged sequentially. The spray waste heat recovery tower also includes a flue gas baffle 19, which is provided below at least one of the first nozzle 17 and the second nozzle 18, and the flue gas baffle 19 is located in the receiving cavity 161.

[0055] Understandably, by adopting the above structural design, the first spray liquid sprayed by the first nozzle 17 can cool the high-temperature flue gas once, and the second spray liquid sprayed by the second nozzle 18 can cool the high-temperature flue gas a second time, so as to achieve full recovery of the waste heat of the high-temperature flue gas and reduce the temperature of the exhaust flue gas. The flue gas baffle 19 can increase the contact area between the high-temperature flue gas and the spray liquid, further improving the cooling effect of the high-temperature flue gas and improving the heat recovery efficiency.

[0056] Specifically, a flue gas baffle 19 is provided below the first nozzle 17; or, a flue gas baffle 19 is provided below the second nozzle 18; or, a flue gas baffle 19 is provided below each of the first nozzle 17 and the second nozzle 18.

[0057] For example, as shown in the figure, along the direction from bottom to top, the high-temperature flue gas inlet 11, the first low-temperature medium inlet 13, the second low-temperature medium inlet 14, and the low-temperature flue gas outlet 15 are arranged in sequence.

[0058] like Figure 3 As shown, in some embodiments, the flue gas baffle 19 extends in the vertical direction, and there are multiple flue gas baffles 19 arranged at intervals along a first direction, which is orthogonal to the vertical direction.

[0059] The distance between any two adjacent flue gas baffles 19 is s, and s is 1cm to 10cm. For example, s can be 1cm, 2cm, 4cm, 5cm, 6cm, 8cm, 10cm, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0060] It is understandable that the flue gas baffle 19 is designed as a vertical flue gas baffle, and the spacing between the vertical flue gas baffles is 1cm to 10cm, which facilitates both heat and mass exchange and prevents the flue gas passage from being blocked by dust in the high-temperature flue gas. The flue gas passage is the gap formed between any two adjacent flue gas baffles 19.

[0061] It should be noted that the materials of the fan, transfer pump and related transfer pipes in the above-mentioned waste heat recovery system 300 can all be high-temperature resistant and corrosion resistant materials.

[0062] like Figure 4 As shown, a dryer 10 according to an embodiment of the present invention includes a hot air furnace 100, a rotary drum 200, and a waste heat recovery system 300. The hot air furnace 100 is provided with a combustion air inlet 5. The rotary drum 200 is used to hold materials and is provided with a flue gas outlet 6. The hot air furnace 100 is connected to the rotary drum 200 and is used to introduce combustion flue gas into the rotary drum 200 to dry the materials inside the rotary drum 200. The waste heat recovery system 300 is the waste heat recovery system 300 of any of the above embodiments. The high temperature flue gas inlet 11 of the waste heat recovery device 1 of the waste heat recovery system 300 is adapted to be connected to the flue gas outlet 6. The low temperature side outlet 21 of the first heat exchanger of the waste heat recovery system 300 is adapted to be connected to the combustion air inlet 5.

[0063] According to an embodiment of the present invention, the waste heat recovery system 300 of the dryer 10 is designed to recover the waste heat in the high-temperature flue gas of the dryer 10, so as to use the recovered heat energy to preheat the combustion air, thereby reducing the structure of the structure required for the combustion of the combustion air and natural gas in the hot air furnace 100 of the dryer 10. Under the premise of not affecting the original process operation of the drying process, the waste heat of the flue gas is fully recovered and the energy consumption is low. Therefore, compared with related technologies, the dryer 10 using this waste heat recovery system 300 can save natural gas consumption and reduce the operating cost of the drying process.

[0064] Specifically, the hot blast stove 100 may be equipped with a natural gas inlet 51, which is suitable for connection to an external natural gas source to allow natural gas to be supplied to the hot blast stove 100. The natural gas and preheated combustion air can be combusted in the hot blast stove 100 to generate flue gas. The rotary drum 200 may include a drying section 61 and a cooling section 62. The drying section 61 may be equipped with a wet material inlet 611 and connected to the hot blast stove 100 so that flue gas enters the drying section 61 to dry the wet material. The cooling section 62 may be equipped with a dry material outlet 621, a cooling air inlet 622, and a flue gas outlet 6. Cooling air can enter the cooling section 62 to cool the material, and the cooled material can be discharged from the dry material outlet 621.

[0065] like Figure 4 As shown, in some embodiments, the dryer 10 further includes a dust collector 400, the air inlet of which is connected to the exhaust port 6, and the air outlet of the dust collector 400 is connected to the high-temperature flue gas inlet 11 of the waste heat recovery device 1, so as to remove dust from the flue gas discharged from the exhaust port 6 by the dust collector 400.

[0066] like Figure 5 As shown, an embodiment of the present invention provides a waste heat recovery method for a dryer, based on the waste heat recovery system 300 of any of the above embodiments. The waste heat recovery method includes the following steps: Step S1, waste heat recovery: the high-temperature flue gas discharged from the exhaust port 6 of the dryer 10 is passed into the waste heat recovery device 1. The medium in the waste heat recovery device 1 exchanges heat with the high-temperature flue gas to obtain low-temperature flue gas and high-temperature medium. The waste heat recovery device 1 discharges low-temperature flue gas. Step S2, primary preheating: combustion air is introduced into the low-temperature side of the first heat exchanger 2, and at least part of the high-temperature medium enters the high-temperature side of the first heat exchanger 2. The high-temperature medium exchanges heat with the combustion air to obtain the first low-temperature medium and the heated combustion air. Step S3: Waste heat utilization, the heated combustion air is introduced into the dryer 10.

[0067] The technical advantages of the waste heat recovery method for dryer 10 according to the present invention are the same as the technical advantages of the waste heat recovery system for dryer described above, and will not be repeated here.

[0068] like Figure 5 As shown, in some embodiments, after step S2, the waste heat recovery method further includes the following step: Step S2', secondary preheating: The heated combustion air is introduced into the low-temperature side of the second heater, and at least part of the high-temperature medium enters the evaporator 31 of the heat pump unit 3. The high-temperature medium exchanges heat with the circulating working fluid in the condenser 32 of the heat pump unit 3, resulting in a second low-temperature medium and heated circulating working fluid. The heated circulating working fluid enters the high-temperature side of the second heater and exchanges heat with the heated combustion air again, raising the temperature of the combustion air. The temperature of the second low-temperature medium is lower than the temperature of the first low-temperature medium.

[0069] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0070] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0071] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0072] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0073] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0074] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A waste heat recovery system for a dryer characterized by, include: A waste heat recovery device is provided, wherein the waste heat recovery device is provided with a high-temperature flue gas inlet and a high-temperature medium outlet, the high-temperature flue gas inlet is adapted to be connected to the exhaust port of the dryer so as to introduce high-temperature flue gas, and the medium inside the waste heat recovery device can exchange heat with the high-temperature flue gas to raise its temperature. The first heat exchanger has a low-temperature side and a high-temperature side. The low-temperature side of the first heat exchanger is adapted to be vented with combustion air. The low-temperature side outlet of the first heat exchanger is adapted to be connected to the combustion air inlet of the dryer. The high-temperature side inlet of the first heat exchanger is connected to the high-temperature medium outlet so as to vent with a high-temperature medium. The high-temperature medium in the high-temperature side of the first heat exchanger can exchange heat with the combustion air in the low-temperature side of the first heat exchanger.

2. The waste heat recovery system for a dryer according to claim 1, characterized by, Also includes: A heat pump unit, comprising an evaporator and a condenser, wherein the high-temperature medium outlet is also connected to the evaporator inlet to allow the high-temperature medium to be introduced into the evaporator, and the high-temperature medium in the evaporator can exchange heat with the circulating working fluid in the condenser. The second heat exchanger has a low-temperature side and a high-temperature side. The low-temperature side outlet of the first heat exchanger, the low-temperature side of the second heat exchanger, and the combustion air inlet of the dryer are connected in sequence. The high-temperature side of the second heat exchanger is connected in series with the condenser to allow the introduction of a circulating working fluid. The circulating working fluid in the high-temperature side of the second heat exchanger can exchange heat with the combustion air in the low-temperature side of the second heat exchanger.

3. The waste heat recovery system for a dryer according to claim 2, characterized in that, The waste heat recovery device is further provided with a first low-temperature medium inlet and a second low-temperature medium inlet. The high-temperature side outlet of the first heat exchanger is connected to the first low-temperature medium inlet, and the outlet of the evaporator is connected to the second low-temperature medium inlet.

4. The waste heat recovery system for a dryer according to claim 3, characterized in that, The waste heat recovery device is also provided with a low-temperature flue gas outlet, and the second low-temperature medium inlet is located between the low-temperature flue gas outlet and the first low-temperature medium inlet in the flue gas flow direction.

5. The waste heat recovery system for a dryer according to claim 3 or 4, characterized in that, The waste heat recovery device is a spray waste heat recovery tower, which includes: The tower body has a receiving cavity and is provided with a high-temperature flue gas inlet and a high-temperature medium outlet communicating with the receiving cavity; A first nozzle and a second nozzle are both disposed in the receiving cavity and used to spray spray liquid to cool the high-temperature flue gas. The first nozzle is connected to the first low-temperature medium inlet, and the second nozzle is connected to the second low-temperature medium inlet. Both the first nozzle and the second nozzle are multiple and are arranged at intervals in the receiving cavity.

6. The waste heat recovery system for a dryer according to claim 5, characterized in that, The first nozzle is located between the high-temperature flue gas inlet and the second nozzle in the upward direction of the flue gas flow. The flue gas flow direction is consistent with the vertical direction. The spray waste heat recovery tower also includes a flue gas baffle. The flue gas baffle is provided below at least one of the first nozzle and the second nozzle. The flue gas baffle is located in the receiving cavity.

7. The waste heat recovery system for a dryer according to claim 6, characterized in that, The flue gas baffle extends along the vertical direction, and there are multiple flue gas baffles arranged at intervals along a first direction, which is orthogonal to the vertical direction; The distance between any two adjacent flue gas baffles is s, and s is 1cm to 10cm.

8. A dryer, characterized in that, include: A hot air furnace and a rotary drum, wherein the hot air furnace is provided with a combustion air inlet, the rotary drum is used to hold materials and is provided with a flue gas outlet, the hot air furnace is connected to the rotary drum and is used to introduce combustion flue gas into the rotary drum to dry the materials inside the rotary drum; A waste heat recovery system, wherein the waste heat recovery system is the waste heat recovery system according to any one of claims 1-7, wherein the high-temperature flue gas inlet of the waste heat recovery device of the waste heat recovery system is adapted to be connected to the exhaust port, and the low-temperature side outlet of the first heat exchanger of the waste heat recovery system is adapted to be connected to the combustion air inlet.

9. A method for waste heat recovery in a dryer, based on a waste heat recovery system as described in any one of claims 1-7, characterized in that, The waste heat recovery method includes the following steps: Waste heat recovery involves passing the high-temperature flue gas discharged from the exhaust port of the dryer into a waste heat recovery device. The medium inside the waste heat recovery device exchanges heat with the high-temperature flue gas to obtain low-temperature flue gas and a high-temperature medium. The waste heat recovery device then discharges the low-temperature flue gas. First-stage preheating involves introducing combustion air into the low-temperature side of the first heat exchanger and allowing at least a portion of the high-temperature medium to enter the high-temperature side of the first heat exchanger. The high-temperature medium exchanges heat with the combustion air to obtain a first low-temperature medium and heated combustion air. Waste heat is utilized by introducing the heated combustion air into the dryer.

10. The waste heat recovery method for a dryer according to claim 9, characterized in that, Following the primary preheating process, the waste heat recovery method further includes the following steps: Secondary preheating involves introducing the heated combustion air into the low-temperature side of the second heater, and allowing at least a portion of the high-temperature medium to enter the evaporator of the heat pump unit. The high-temperature medium exchanges heat with the circulating working fluid in the condenser of the heat pump unit to obtain a second low-temperature medium and a heated circulating working fluid. The heated circulating working fluid then enters the high-temperature side of the second heater to exchange heat with the heated combustion air, further heating the combustion air.

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