Mechanical vapor recompression (MVR) heat pump drying system

Abstract

The embodiment of the present application relates to the technical field of material drying, and provides a mechanical vapor recompression (MVR) heat pump drying system.The mechanical vapor recompression (MVR) heat pump drying system provided by the embodiment of the present application comprises a dryer, a steam compressor and an ejector, the first outlet of the dryer is connected with the inlet of the steam compressor, the outlet of the steam compressor is connected with the first inlet of the ejector, and the outlet of the ejector is connected with the first inlet of the dryer, so that a secondary steam heat exchange circulation loop is formed among the dryer, the steam compressor and the ejector.The mechanical vapor recompression (MVR) heat pump drying system provided by the embodiment of the present application is provided with a circulation loop, secondary steam generated in the drying process of the dryer is compressed into high-temperature and high-pressure steam by the steam compressor, and then the high-temperature and high-pressure steam is used as a heat source to enter the dryer to dry materials, so that the secondary steam is recycled, and the energy utilization rate of the drying system is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of material drying, in particular to a mechanical vapor recompression (MVR) heat pump drying system. BACKGROUND

[0002] Material drying is related to chemical industry, pharmaceutical industry, mining, food industry, environmental protection and other fields. It is not only an indispensable basic link in industrial and agricultural production, but also a major energy consumption link. As a process of net energy consumption, drying generally uses air as the medium, primary energy, electric heating and the like as the heat source, and utilizes low-humidity hot air to exchange heat and humidity with wet materials to remove water from the materials. The whole drying process consumes a high amount of energy, reaching 3200-3500 kJ per kilogram of water, and consumes electric energy of 45-90 kW per ton of water. Meanwhile, a large amount of drying tail gas needs to be further treated, which increases the cost of material processing and the complexity of the system.

[0003] According to statistics, the energy utilization rate of commonly used drying equipment in China is only 40%-50%, while the energy utilization rate of foreign drying equipment is more than 70%, and the energy-saving potential is huge.

[0004] MVR is the abbreviation of mechanical vapor recompression. The mechanical vapor recompression (MVR) heat pump technology is a high-efficiency and environmentally friendly energy-saving technology, which is widely used in evaporation crystallization and environmental protection industries, but rarely used in material drying. Therefore, under the trend of energy saving and emission reduction, it is a general trend to apply the mechanical vapor recompression (MVR) heat pump technology to the drying process to reduce the energy consumption of the drying system and improve the energy utilization rate. SUMMARY

[0005] In order to solve the problems of large energy consumption and low energy utilization rate of the drying system in the prior art, the present application provides a mechanical vapor recompression (MVR) heat pump drying system.

[0006] According to one embodiment of the present application, the mechanical vapor recompression (MVR) heat pump drying system comprises a dryer, a steam compressor and an ejector, a first outlet of the dryer is connected with an inlet of the steam compressor, an outlet of the steam compressor is connected with a first inlet of the ejector, and an outlet of the ejector is connected with a first inlet of the dryer, so as to form a secondary steam heat exchange circulation loop among the dryer, the steam compressor and the ejector.

[0007] According to an embodiment of the present application, the secondary steam heat exchange circulation loop further comprises a secondary steam purification device, an inlet of the secondary steam purification device is connected with the first outlet of the dryer, and an outlet of the secondary steam purification device is connected with the inlet of the steam compressor through a first pipeline.

[0008] According to an embodiment of the present application, the mechanical vapor recompression (MVR) heat pump drying system further comprises an exhaust fan, an inlet of the exhaust fan is connected on the first pipeline through a second pipeline, and an outlet of the exhaust fan is used for exhausting the non-condensable gas.

[0009] According to an embodiment of the present application, a first regulating valve is further arranged on the second pipeline.

[0010] According to an embodiment of the present application, the mechanical vapor recompression (MVR) heat pump drying system further comprises a condensate tank, an inlet of the condensate tank is connected with the second outlet of the dryer, and a first outlet of the condensate tank is connected with the second inlet of the ejector pump through a third pipeline.

[0011] According to an embodiment of the present application, a second regulating valve is arranged on the third pipeline.

[0012] According to an embodiment of the present application, the mechanical vapor recompression (MVR) heat pump drying system further comprises a feed conveyor, a first inlet of the feed conveyor is used for receiving the wet material, a second inlet of the feed conveyor is connected with the second outlet of the condensate tank, a first outlet of the feed conveyor is connected with the second inlet of the dryer, and a second outlet of the feed conveyor is used for discharging the condensate.

[0013] According to an embodiment of the present application, the mechanical vapor recompression (MVR) heat pump drying system further comprises a discharge conveyor, an inlet of the discharge conveyor is connected with a third outlet of the dryer, and an outlet of the discharge conveyor is used for discharging the dry material.

[0014] According to an embodiment of the present application, the dryer is any one of a hollow paddle dryer, a disc dryer, a tube bundle dryer or a scraper dryer.

[0015] According to an embodiment of the present application, the steam compressor is any one of a screw water vapor compressor, a Roots water vapor compressor or a centrifugal water vapor compressor.

[0016] The mechanical vapor recompression MVR heat pump drying system provided by the embodiment of the present application has the following advantages: the dryer, the vapor compressor and the ejector pump are arranged into a circulating loop, the secondary vapor generated in the drying process of the dryer is compressed into high-temperature and high-pressure steam by the vapor compressor, the steam is injected into the dryer as a heat source to dry the material by the driving of the ejector pump, the secondary vapor is recycled, no external heat source and circulating cooling water are needed in the whole drying process, the energy utilization rate of the drying system is improved, and the emission of SO2, CO2, dust and drying tail gas is reduced, and the environmental benefits are very considerable. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0018] Figure 1 The structure schematic diagram of the mechanical vapor recompression MVR heat pump drying system provided by the embodiment of the present application.

[0019] Explanation of reference signs:

[0020] 1-dryer; 2-secondary vapor purification device; 3-vapor compressor; 4-ejector pump; 5-exhaust fan; 6-condensate tank; 7-outlet conveyor; 8-inlet conveyor; 11-first pipeline; 12-second pipeline; 13-third pipeline; 21-first regulating valve; 22-second regulating valve. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without any creative effort belong to the protection scope of the present application.

[0022] In the description of the present application, it should be noted that, unless otherwise explicitly specified and limited, the terms "mounting", "connection" and "connection" should be understood in a broad sense, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0023] Further, in the description of the present application, unless otherwise specified, the meaning of "a plurality of", "a plurality of roots", "a plurality of groups" is two or more, and the meaning of "several", "several roots", "several groups" is one or more.

[0024] Reference will now be made to Figure 1 The embodiments provided by the present application are described. It should be understood that the following description is only illustrative of the embodiments of the present application and does not constitute any special limitation on the present application.

[0025] As Figure 1 As shown in one embodiment of the present application, the mechanical vapor recompression MVR heat pump drying system comprises a dryer 1, a vapor compressor 3 and an ejector pump 4, the first outlet of the dryer 1 is connected with the inlet of the vapor compressor 3, the outlet of the vapor compressor 3 is connected with the first inlet of the ejector pump 4, and the outlet of the ejector pump 4 is connected with the first inlet of the dryer 1, so as to form a secondary vapor heat exchange circulation loop among the dryer 1, the vapor compressor 3 and the ejector pump 4.

[0026] Specifically, the wet material is heated in the drying cavity of the dryer 1, the water is evaporated by heating, and the generated secondary vapor is discharged from the first outlet of the dryer 1 into the vapor compressor 3, and is compressed into high-temperature and high-pressure steam by the vapor compressor 3, and then is discharged from the outlet of the vapor compressor 3 and enters the suction chamber of the ejector pump 4 through the first inlet of the ejector pump 4. In the ejector pump 4, the compressed steam mixes with the non-condensable gas in the condensate tank 6 after being injected, and then enters the condensation side of the dryer 1 as a heat source to heat the material. The secondary vapor generated during the heating process of the material enters the vapor compressor 3 again and is compressed into high-temperature and high-pressure steam as a heat source for heating the material in the dryer 1, and the cycle is repeated, so as to form a secondary vapor heat exchange circulation loop among the dryer 1, the vapor compressor 3 and the ejector pump 4. The latent heat of the secondary vapor generated during the drying process of the material is fully utilized, and the whole drying process does not need external heat source, which greatly improves the energy utilization rate of the heat pump drying system.

[0027] Further, the high-temperature and high-pressure steam entering the condensation side of the dryer 1 becomes condensate after heat exchange with the wet material, and is discharged from the second outlet of the dryer 1 to the condensate tank 6. The dry material meeting the water content requirement is discharged from the third outlet of the dryer 1 to the discharge conveyor 7, and then is discharged out of the heat pump drying system.

[0028] Further, in the embodiment of the present application, the dryer 1 can be a disc dryer, a tube bundle dryer, a scraper dryer or a hollow paddle dryer. In one embodiment of the present application, the dryer 1 is a hollow paddle dryer.

[0029] In one embodiment of the present invention, the steam compressor 3 may optionally be a screw steam compressor, a Roots steam compressor, or a centrifugal steam compressor, etc.

[0030] It should be understood that the forms of dryer 1 and steam compressor 3 are merely illustrative, and other alternative types of dryers and steam compressors can also be used in this invention. This depends on the specific application, and the invention is not limited thereto.

[0031] The mechanical vapor recompression (MVR) heat pump drying system provided in this invention can be widely applied to the drying process of materials such as sludge, pharmaceutical residues, coal slime, and salts. This system, by configuring the dryer, steam compressor, and jet pump into a circulating loop, compresses the secondary steam generated during the drying process into high-temperature, high-pressure steam via the steam compressor. This steam is then injected into the dryer as a heat source to dry the material, allowing for the recycling of the secondary steam. The entire drying process requires no external heat source or circulating cooling water. Simultaneously, the jet pump drives the gas circulation within the heat pump drying system, improving the heat exchange efficiency of the dryer and thus enhancing the energy utilization rate of the heat pump drying circulation system provided in this invention.

[0032] like Figure 1 As shown, in one embodiment of the present invention, the mechanical vapor recompression (MVR) heat pump drying system further includes: a condensate tank 6, the inlet of which is connected to the second outlet of the dryer 1, and the first outlet of the condensate tank 6 is connected to the second inlet of the jet pump 4 via a third pipeline 13.

[0033] Specifically, the secondary steam generated during the drying of wet materials in dryer 1 is compressed into high-temperature, high-pressure steam by steam compressor 3, and then discharged into the suction chamber of jet pump 4 through the outlet of steam compressor 3. Simultaneously, the high-temperature condensate generated after heat exchange in dryer 1 and the non-condensable gases formed during the drying process enter condensate tank 6 through the second outlet of dryer 1. The high-temperature condensate in condensate tank 6 is discharged into feed conveyor 8 through the second outlet, serving as a heat source for preheating the wet materials. The non-condensable gases in condensate tank 6 enter the suction chamber of jet pump 4 through the third pipeline 13, mix with the high-temperature, high-pressure steam compressed by steam compressor 3, and then enter the condensation side of dryer 1.

[0034] Furthermore, a second regulating valve 22 is also provided on the third pipeline 13. As the content of non-condensable gas in the heat pump drying system of this embodiment of the invention continues to increase, the content of non-condensable gas entering the dryer 1 can be adjusted by adjusting the second regulating valve 22.

[0035] like Figure 1As shown, in one embodiment of the present invention, the secondary steam heat exchange loop further includes: a secondary steam purification device 2, the inlet of which is connected to the first outlet of the dryer 1, and the outlet of which is connected to the inlet of the steam compressor 3 through the first pipeline 11.

[0036] In one embodiment of the present invention, the mechanical vapor recompression (MVR) heat pump drying system further includes an exhaust fan 5, the inlet of which is connected to the first pipe 11 via a second pipe 12, and the outlet of which is used to discharge non-condensable gases.

[0037] Specifically, the secondary steam generated during the drying of wet materials in dryer 1 first enters a secondary steam purification device 2 for purification. After removing entrained dust and other impurities in the secondary steam purification device 2, the secondary steam enters the steam compressor 3 through the first pipeline 11 and is compressed into high-temperature, high-pressure steam. Further, a second pipeline 12 is connected to the first pipeline 11. Non-condensable gases generated during the drying process in dryer 1, after passing through the secondary steam purification device 2, are discharged through the second pipeline 12 to the exhaust fan 5, which discharges a portion of the non-condensable gases. The discharged non-condensable gases can be further treated or recycled, reducing environmental pollution from waste gas.

[0038] Furthermore, a first regulating valve 21 is also provided on the second pipeline 12. As the content of non-condensable gas in the mechanical vapor recompression (MVR) heat pump drying system of this embodiment of the invention continues to increase, adjusting the first regulating valve 21 can periodically discharge a small amount of non-condensable gas through the exhaust fan 5 connected to the second pipeline 12, so as to achieve dynamic balance in the heat pump drying system.

[0039] like Figure 1 As shown, in one embodiment of the present invention, the mechanical vapor recompression (MVR) heat pump drying system further includes: a feed conveyor 8, the first inlet of which is used to receive wet material, the second inlet of which is connected to the second outlet of the condensate tank 6; the first outlet of which is connected to the second inlet of the dryer 1, and the second outlet of which is used to discharge condensate.

[0040] Specifically, wet material enters the feed conveyor 8 through its first inlet. Inside the feed conveyor 8, the evaporated condensate exchanges heat with the wet material, preheating it. The preheated material then enters the dryer 1 through the first outlet of the feed conveyor 8 for drying. High-temperature condensate from the condensate tank 6 enters the feed conveyor 8 through its second outlet to preheat the wet material and simultaneously recover waste heat from the condensate. The condensate after heat exchange with the wet material is discharged from the heat pump drying system through the second outlet of the feed conveyor 8 for direct reuse or further treatment.

[0041] Further, the second outlet of the feeding conveyor 8 is a hot stream outlet. In an embodiment of the present application, the feeding conveyor 8 is a heat exchange type screw conveyor. It should be understood that the form of the feeding conveyor 8 is only illustrative, and other alternative types of conveyors can also be applied in the present application. This can be determined according to the specific use, and the present application is not limited thereto.

[0042] As shown in the drawings, in an embodiment of the present application, the mechanical vapor recompression MVR heat pump drying system further comprises a discharging conveyor 7, an inlet of the discharging conveyor 7 is connected with the third outlet of the dryer 1, and an outlet of the discharging conveyor 7 is used for discharging the dry material. Figure 1 Specifically, after the material is dried in the dryer 1, the dry material meeting the water content requirement is discharged from the third outlet of the dryer 1 to the discharging conveyor 7, and then discharged out of the heat pump drying system through the outlet of the discharging conveyor 7. Further, in an embodiment of the present application, the discharging conveyor 7 is a screw conveyor. It should be understood that the form of the discharging conveyor 7 is only illustrative, and other alternative types of conveyors can also be applied in the present application. This can be determined according to the specific use, and the present application is not limited thereto.

[0043] The mechanical vapor recompression MVR heat pump drying system provided by the embodiment of the present application has reasonable design and simple structure, and can realize full-process automatic control. Since the heat pump drying system directly recovers the latent heat of the secondary steam generated in the material drying process, the energy consumption in the drying process is effectively reduced, and the emissions of SO2, CO2, dust and drying tail gas are reduced. The present application provides technical support for the development and popularization of the mechanical vapor recompression MVR heat pump drying technology, and has high economic and social benefits.

[0044] The working principle of the mechanical vapor recompression MVR heat pump drying system provided by the embodiment of the present application is described in detail as follows:

[0045]

[0046] ​The wet material enters the feeding conveyor 8 to exchange heat with the evaporated condensate to preheat the wet material. The preheated wet material enters the dryer 1 to be heated and dried, and the secondary steam and a small amount of non-condensable gas generated in the drying process enter the secondary steam purification device 2 through the first outlet of the dryer 1 to be purified to remove the impurities such as dust. The purified secondary steam enters the steam compressor 3 through the first pipeline 11 to be compressed into high-temperature and high-pressure steam, which enters the suction chamber of the ejector pump 4. The high-temperature and high-pressure steam injects and mixes with part of the non-condensable gas in the condensate tank 6 to enter the condensing side of the dryer 1 as a heat source. The high-temperature and high-pressure steam completes heat exchange in the dryer 1 to form high-temperature condensate and entrained non-condensable gas, which enter the condensate tank 6 through the second outlet of the dryer 1. The dryer 1, the secondary steam purification device 2, the steam compressor 3 and the ejector pump 4 form a secondary steam heat exchange circulation loop, so that the secondary steam is recycled and the energy utilization rate of the heat pump drying system is improved.

[0047] When the content of non-condensable gas in the heat pump drying system is relatively high, a small amount of non-condensable gas can be regularly discharged through the exhaust fan 5 by adjusting the first adjusting valve 21 arranged on the second pipeline 12, and the discharged non-condensable gas can be further treated to reduce the pollution of the gas to the environment. Meanwhile, the second adjusting valve 22 is arranged on the third pipeline 13, and the content of non-condensable gas entering the dryer 1 can be adjusted by adjusting the second adjusting valve 22.

[0048] The material with the required moisture content enters the discharge conveyor 7 through the third outlet of the dryer 1, and is then discharged through the outlet of the discharge conveyor 7.

[0049] The high-temperature condensate in the condensate tank 6 enters the feeding conveyor 8 through the second outlet of the condensate tank 6 to preheat the wet material. The condensate after heat exchange is discharged from the second outlet of the feeding conveyor 8, and can be directly reused or further treated. The heat pump drying system provided in the embodiments of the present application can recycle or re-treat the non-condensable gas and condensate discharged from the system, reduce the pollution to the environment, and has very good environmental protection benefits.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features can be replaced by equivalents. Such modifications or replacements do not change the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A mechanical vapor recompression (MVR) heat pump drying system, characterized in that, The system comprises: a dryer, a steam compressor, an ejector pump, a condensate tank and a feeding conveyor, the first outlet of the dryer is connected with the inlet of the steam compressor, the outlet of the steam compressor is connected with the first inlet of the ejector pump, the outlet of the ejector pump is connected with the first inlet of the dryer, so as to form a secondary steam heat exchange circulation loop among the dryer, the steam compressor and the ejector pump; the inlet of the condensate tank is connected with the second outlet of the dryer, the first outlet of the condensate tank is connected with the second inlet of the ejector pump through a third pipeline; the non-condensable gas in the condensate tank enters the suction chamber of the ejector pump through the third pipeline; the first inlet of the feeding conveyor is used for receiving wet materials, the second inlet of the feeding conveyor is connected with the second outlet of the condensate tank, so as to receive high-temperature condensate in the condensate tank; the first outlet of the feeding conveyor is connected with the second inlet of the dryer, and the second outlet of the feeding conveyor is used for discharging condensate; a second regulating valve is arranged on the third pipeline.

2. The mechanical vapor recompression (MVR) heat pump drying system of claim 1, wherein, The secondary steam heat exchange circulation loop further comprises a secondary steam purification device, the inlet of the secondary steam purification device is connected with the first outlet of the dryer, and the outlet of the secondary steam purification device is connected with the inlet of the steam compressor through a first pipeline.

3. The mechanical vapor recompression (MVR) heat pump drying system of claim 2, wherein, An exhaust fan is further included, the inlet of the exhaust fan is connected with the first pipeline through a second pipeline, and the outlet of the exhaust fan is used for discharging non-condensable gas.

4. The mechanical vapor recompression (MVR) heat pump drying system of claim 3, wherein, A first regulating valve is further arranged on the second pipeline.

5. The mechanical vapor recompression (MVR) heat pump drying system of claim 1, wherein, Further comprising: a discharging conveyor, the inlet of the discharging conveyor is connected with the third outlet of the dryer, and the outlet of the discharging conveyor is used for discharging dry materials.

6. The mechanical vapor recompression (MVR) heat pump drying system of claim 1, wherein, The dryer is any one of a hollow paddle dryer, a disc dryer, a tube bundle dryer or a scraper dryer.

7. The mechanical vapor recompression (MVR) heat pump drying system of claim 1, wherein, The steam compressor is any one of a screw water vapor compressor, a Roots water vapor compressor or a centrifugal water vapor compressor.

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