Efficient microwave vacuum continuous drying equipment

Abstract

The invention relates to the technical field of drying equipment, in particular to efficient microwave vacuum continuous drying equipment which comprises a drying bin, and a feeding pipe and a discharging pipe are arranged on the side walls of the two ends of the drying bin correspondingly. A vacuum sealing module is arranged at the connecting position of the feeding pipe and the drying bin and the connecting position of the discharging pipe and the drying bin, a microwave generating device is arranged on the outer side wall of the drying bin, a material conveying device is arranged in the drying bin, and a waste gas treatment module is arranged outside the drying bin. The vacuum degree of the drying bin can be guaranteed, the drying bin does not need to be vacuumized in a reciprocating mode, it is guaranteed that the whole drying operation environment is continuously carried out, especially when heat-sensitive materials are dried, a stable low-temperature drying environment can be provided, continuous work is effectively protected in the state that the materials are not decomposed or deteriorated, and the drying efficiency is improved. The production efficiency is greatly improved, and meanwhile, the stability of the production quality is ensured.

Description

Technical Field

[0001] This invention relates to the field of drying equipment technology, specifically to a high-efficiency microwave vacuum continuous drying equipment. Background Technology

[0002] Microwave drying differs from traditional drying methods. It achieves drying by directly applying high-frequency electromagnetic wave oscillations to water molecules, with heat conduction occurring in the same direction as moisture diffusion. Compared to traditional drying methods, it offers advantages such as higher drying rates, energy savings, higher production efficiency, more uniform drying, cleaner production, easier automation, and improved product quality. Therefore, it is gaining increasing importance in many products and fields requiring drying.

[0003] In practical industrial applications, microwave drying equipment mainly adopts two technical routes: continuous microwave drying at room temperature and intermittent vacuum microwave drying. Continuous microwave drying at room temperature is similar to connecting multiple microwave ovens in series, with a length that can reach ten to tens of meters. The material to be dried enters from one end of the equipment using a conveyor system, passes through multiple microwave generators in sequence to achieve the required drying standard, and then exits from the other end.

[0004] Intermittent vacuum microwave drying equipment is mostly used for drying heat-sensitive materials. First, the material to be dried is placed in the turntable in the closed cavity of the microwave drying equipment. Then, the entire drying cavity is closed and a vacuum is drawn. When the set vacuum state is reached, the drying equipment is started to dry the material. After the drying requirements are met, the equipment is stopped, air is introduced to break the vacuum state, and the material is taken out and dried in sequence.

[0005] The two commonly used microwave drying technologies each have their own advantages and disadvantages: the room temperature continuous drying route can ensure a continuous drying process with high efficiency, but it also has prominent problems. First, it is not suitable for heat-sensitive materials. Microwave drying heats up quickly and is difficult to control, which can easily cause the temperature to rise above the material's critical temperature, leading to material decomposition or deterioration. Second, relying solely on microwaves for drying at room temperature results in wasted heat energy.

[0006] The vacuum-interval drying method was developed primarily for drying heat-sensitive materials. By lowering the boiling point of water under negative pressure, it minimizes the deterioration and decomposition of the heat-sensitive materials while ensuring effective drying. The biggest problem with this method is its complex operation, requiring constant vacuuming and breaking, resulting in extremely low drying efficiency and making it unsuitable for industrial production. Summary of the Invention

[0007] To address the aforementioned problems, this invention provides a high-efficiency microwave vacuum continuous drying device that can rapidly dry materials at low temperatures. It allows for continuous drying of materials, especially heat-sensitive materials, under vacuum conditions. This continuous operation effectively protects the materials from decomposition and deterioration, greatly improving production efficiency while ensuring stable production quality.

[0008] To achieve the above objectives, the present invention employs the following technical solution: a high-efficiency microwave vacuum continuous drying device, comprising a drying chamber, wherein a feed pipe and a discharge pipe are respectively provided on the side walls at both ends of the drying chamber, and a vacuum sealing module is provided at the connection between the feed pipe and the discharge pipe and the drying chamber; a microwave generating device is provided on the outer side wall of the drying chamber; a material conveying device is provided inside the drying chamber; and a waste gas treatment module is provided outside the drying chamber.

[0009] As a further improvement to the above technical solution:

[0010] The drying chamber is made of cylindrical seamless steel pipe with a diameter of 200-500 mm.

[0011] There are three drying chambers, each with a length of 4 meters. The material conveying devices in adjacent drying chambers convey materials in opposite directions.

[0012] The microwave generator includes a support, a top cover is provided above the support, a sealing gasket is provided between the support and the top cover, and a waveguide is provided above the top cover.

[0013] The number of microwave generating devices is sufficient and they are evenly distributed along the length of the drying chamber. The side wall of the drying chamber is provided with clearance openings corresponding to the positions of the microwave generating devices.

[0014] The sealing gasket is made of polytetrafluoroethylene sheet with a thickness of 5-15 mm.

[0015] The vacuum sealing module includes a transfer tube, with a sealing valve one and a sealing valve two respectively installed at both ends of the transfer tube, and a vacuum extraction valve installed on the side wall of the transfer tube.

[0016] The material conveying device is a polytetrafluoroethylene belt conveyor.

[0017] The exhaust gas treatment module includes an exhaust pipe, one end of which is connected to a drying chamber, and the other end is equipped with a heat exchanger. A vacuum pump is installed at the end of the heat exchanger.

[0018] A filter module is installed between the vacuum pump and the heat exchanger.

[0019] The beneficial effects of this invention are as follows: The high-efficiency microwave vacuum continuous drying equipment includes a drying chamber. A feed pipe and a discharge pipe are respectively installed on the side walls at both ends of the drying chamber. A vacuum sealing module is installed at the connection between the feed pipe and the discharge pipe and the drying chamber. A microwave generator is installed on the outer side wall of the drying chamber. A material conveying device is installed inside the drying chamber. A waste gas treatment module is installed outside the drying chamber. Through the external microwave generator, the vacuum level of the drying chamber can be guaranteed, eliminating the need for repeated vacuuming operations and ensuring continuous operation throughout the drying process. Especially when drying heat-sensitive materials, it can provide a stable low-temperature drying environment, effectively protecting the material from decomposition and deterioration during continuous operation, greatly improving production efficiency while ensuring stable production quality. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the drying chamber in this invention; Figure 2 This is a schematic diagram of the installation structure of the heat exchanger in this invention; Figure 3 This is a side view of the drying chamber in this invention; Figure 4 This is a cross-sectional view of the drying chamber in this invention; Figure 5 This is a schematic diagram of the microwave generator in this invention; Figure 6 This is a diagram showing the distribution of the clearance openings in this invention; Figure 7 This is a schematic diagram of the overall structure of the present invention.

[0021] In the diagram: 1. Drying chamber; 2. Feed pipe; 3. Discharge pipe; 4. Support; 5. Top cover; 6. Sealing gasket; 7. Waveguide; 8. Refractory port; 9. Transfer pipe; 10. Sealing valve one; 11. Sealing valve two; 12. Vacuum extraction valve; 13. Exhaust pipe; 14. Heat exchanger; 15. Vacuum pump. Detailed Implementation

[0022] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0023] See Figure 1-7The high-efficiency microwave vacuum continuous drying equipment of this embodiment includes a drying chamber 1. The drying chamber 1 is the core drying cavity of the equipment and is made of cylindrical seamless steel pipe with a diameter range of 200-500 mm. In order to improve drying efficiency and throughput, the equipment is equipped with three drying chambers 1. Each drying chamber 1 is 4 meters long, and the material conveying devices in two adjacent drying chambers 1 are designed with opposite conveying directions.

[0024] The cylindrical resonant cavity is considered as a cylindrical waveguide and two metal short-circuit plates. The electromagnetic field distribution, resonant frequency, and intrinsic quality factor of the cylindrical resonant cavity in the TEmnl mode are obtained by the field solution method as follows:

[0025]

[0026]

[0027]

[0028]

[0029]

[0030] In the formula, Similarly, we obtain TE. mnl The resonant frequency of the mode and its intrinsic quality factor Q c

[0031]

[0032] Based on the above formula, considering factors such as the quality factor, transmission, and material feeding and discharging, the resonant cavity of this invention is designed using a seamless stainless steel tube with a diameter of 200-500 mm as the cavity body.

[0033] In this embodiment, there are three drying chambers 1 arranged longitudinally, connected end to end in pairs, and the material conveying directions in the two adjacent drying chambers 1 are opposite, forming an S-shape. This effectively reduces the space occupied by the equipment. At the same time, the entire drying process is divided into three parts (the three drying chambers form three resonant cavities). Each of the three resonant cavities is independently sealed, and the number of microwave generators installed on each resonant cavity is different, ensuring variable power control of the microwave generators. Since the moisture content and drying effect requirements of each material are different, the actual design must be calculated and designed separately according to the material characteristics.

[0034] The material drying process involves four stages: preheating, constant speed, deceleration, and final drying. The microwave energy requirements vary at different stages. To minimize energy consumption while ensuring material drying quality, this invention employs magnetron variable power control. Specifically, different power magnetrons are used to provide energy at different stages of drying. The microwave generator is installed in different locations on each drying chamber, such as... Figure 6 As shown, the overall structure is spirally distributed, and the number of microwave generators on the three resonant cavities gradually decreases from top to bottom. Taking the experimental machine of this invention as an example, the three resonant cavities are equipped with 15, 9, and 6 1kW microwave generators, respectively, corresponding to different drying stages of the material. This can effectively save energy and improve the quality of the dried material.

[0035] In this embodiment, the microwave generator operates in a pulsed manner, that is, it operates for 60 seconds and then pauses for 30 seconds. Combined with the distribution of the microwave generator and the distribution of the three-segment resonant cavity, it aims to shorten the drying time and reduce costs.

[0036] The feed pipe 2 and the discharge pipe 3 are respectively installed on the side walls of the two ends of the drying chamber 1. In order to ensure the vacuum environment in the drying chamber 1, a vacuum sealing module is installed at the connection between the feed pipe 2, the discharge pipe 3 and the drying chamber 1. The vacuum sealing module specifically includes a transfer pipe 9, and a sealing valve 10 and a sealing valve 11 are installed at both ends of the transfer pipe 9. At the same time, a vacuum extraction valve 12 is installed on the side wall of the transfer pipe 9. The vacuum sealing and smooth transfer of materials are achieved through the coordinated control of the valves, ensuring that the vacuum state in the drying chamber 1 is not disrupted.

[0037] The microwave generator is installed on the outer wall of the drying chamber 1 to provide the microwave energy required for drying. This distribution method has the advantage of ensuring stable vacuum within the chamber while preventing the magnetron from being affected by the vacuum level, and also facilitating maintenance and replacement. Its specific structure includes a support 4, with a top cover 5 above the support 4. To ensure sealed microwave transmission, a sealing gasket 6 is placed between the support 4 and the top cover 5. A waveguide 7 is connected above the top cover 5. The sealing gasket 6 is made of polytetrafluoroethylene (PTFE) sheet with a thickness ranging from 5 to 15 mm. To ensure uniform drying of the material within the drying chamber 1, multiple microwave generators are installed, evenly distributed along the length of the drying chamber 1. Correspondingly, clearance openings 8 are provided on the side wall of the drying chamber 1, corresponding to the positions of the microwave generators.

[0038] The material conveying device is installed inside the drying chamber 1 to achieve stable material conveying within the drying chamber 1. In this equipment, the material conveying device is a polytetrafluoroethylene belt conveyor. Considering the influence of metal components on microwaves, all belt conveyor parts inside the drying chamber 1 are made of Teflon material to avoid hot spots. Metal components such as the head and tail of the machine are arranged outside the drying chamber, and the two sides of the drying chamber are isolated by shielding nets.

[0039] The exhaust gas treatment module is located outside the drying chamber 1 and is used to treat the exhaust gas generated during the drying process. Specifically, it includes an exhaust pipe 13, one end of which is connected to the drying chamber 1, and the other end is connected to a heat exchanger 14. A vacuum pump 15 is installed at the end of the heat exchanger 14. To prevent impurities in the exhaust gas from entering the vacuum pump 15 and causing damage, a filter module is installed between the vacuum pump 15 and the heat exchanger 14. The filter module uses media such as sponge iron to compensate for corrosion, so as to avoid damage to the vacuum pump 15 caused by acid, alkali and other gases generated by some materials escaping with water vapor during the drying process.

[0040] Operating principle: The material enters the drying chamber 1 through the vacuum sealing module. Upon re-entry, the sealing valve 10 is opened first, and the material enters the transfer pipe 9. At this time, the sealing valve 10 closes, and the vacuum extraction valve 12 is opened to evacuate the transfer pipe 12. Then, the sealing valve 11 is opened, and the material enters the drying chamber 1. It then moves within the three drying chambers 1 through the material conveying device. During the movement, the microwave generator operates to dry the material. After drying, the material is discharged through the vacuum sealing module at the discharge pipe 3.

[0041] During the drying process, the microwave generator adopts a pulsed working mode to perform intermittent operation, ensuring the drying effect while reducing energy consumption. The exhaust gas during the drying process enters the heat exchanger 14 through the exhaust pipe 13. Part of it is discharged after being condensed into liquid, while the part that cannot be condensed into liquid is sucked away by the vacuum pump and enters the filter module for absorption treatment.

[0042] To verify the performance of the device, the first prototype of this invention underwent debugging and comparative testing at a chemical plant, with remarkable results, as shown in the following comparison: Drying materials: Salt, bulk density 1.4, decomposes above 65℃; Results: Wet material moisture content >1.5%, dried material moisture content <0.1%; Process: Fluidized bed drying process; Main parameters of the equipment: three blowers, two of which are 15kW and one is 30kW, and one induced draft fan is 160kW, with a total power of 220kW; Heat source: 140℃ saturated steam in the conventional industrial park is used as the heat source for drying, 240 yuan / ton; Continuous drying capacity: 2 tons / hour; Excluding labor costs: 137 yuan / ton Electricity cost: 0.7 yuan / kWh, 220 0.7 = 154 yuan; Steam cost: 240 yuan 0.5 = 120 yuan; (154+120) / 2=137 yuan / ton; Main parameters of the experimental equipment: 30 1kW magnetrons, 1 2kW dry screw vacuum pump; 20 square meters of shell and tube heat exchangers; three 0.75kW conveying devices; The total capacity is 30 + 2 + 0.75 =34.25kW; Theoretical heat exchange condensation capacity: 9.96kW; Local chilled water price: 1.2 yuan / RT; According to actual calculations, the drying capacity of this equipment is 300 kg / hour; Its cost is: 34.25 0.7 = 23.98 yuan, chilled water cost 9.96 / 3.516 = 2.83 RT; The calculated drying cost is: (23.98 + 2.83) 1.2) 1000 / 300 = 91.25 yuan / ton.

[0043] (137-91.25) / 137=33.34%.

[0044] The above measured data clearly shows that drying materials using the experimental equipment can significantly reduce energy consumption. This only refers to direct energy consumption, because vacuum microwave continuous drying equipment can be easily automated, which can greatly reduce manual operation and equipment maintenance costs.

[0045] It should be noted that in the description of this invention, terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," which indicate direction or positional relationships, are based on the direction or positional relationships shown in the accompanying drawings. These are used merely for ease of description and do not indicate or imply that the device or element 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. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0046] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0047] The term "comprising" or any other similar term is intended to cover non-exclusive inclusion, such that a process, article, or apparatus / device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to those processes, articles, or apparatus / devices.

[0048] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A high-efficiency microwave vacuum continuous drying device, characterized in that, It includes a drying chamber (1), and a feed pipe (2) and a discharge pipe (3) are respectively provided on the side walls at both ends of the drying chamber (1). A vacuum sealing module is provided at the connection between the feed pipe (2) and the discharge pipe (3) and the drying chamber (1). A microwave generator is installed on the outer wall of the drying chamber (1), a material conveying device is installed inside the drying chamber (1), and a waste gas treatment module is installed outside the drying chamber (1).

2. The high-efficiency microwave vacuum continuous drying equipment according to claim 1, characterized in that, The drying chamber (1) is made of cylindrical seamless steel pipe with a diameter of 200-500 mm.

3. The high-efficiency microwave vacuum continuous drying equipment according to claim 2, characterized in that, The number of drying chambers (1) is three, and the length of each drying chamber (1) is 4 meters. The material conveying devices in two adjacent drying chambers (1) convey in opposite directions.

4. The high-efficiency microwave vacuum continuous drying equipment according to claim 1, characterized in that, The microwave generator includes a support (4), a top cover (5) is provided above the support (4), a sealing gasket (6) is provided between the support (4) and the top cover (5), and a waveguide (7) is provided above the top cover (5).

5. The high-efficiency microwave vacuum continuous drying equipment according to claim 4, characterized in that, The number of microwave generating devices is multiple and they are evenly distributed along the length of the drying chamber (1). The side wall of the drying chamber (1) is provided with a clearance opening (8) corresponding to the position of the microwave generating device.

6. The high-efficiency microwave vacuum continuous drying equipment according to claim 4, characterized in that, The sealing gasket (6) is made of polytetrafluoroethylene sheet with a thickness of 5-15 mm.

7. The high-efficiency microwave vacuum continuous drying equipment according to claim 1, characterized in that, The vacuum sealing module includes a transfer tube (9), with a sealing valve one (10) and a sealing valve two (11) respectively installed at both ends of the transfer tube (9), and a vacuum extraction valve (12) installed on the side wall of the transfer tube (9).

8. The high-efficiency microwave vacuum continuous drying equipment according to claim 1, characterized in that, The material conveying device is a polytetrafluoroethylene belt conveyor.

9. The high-efficiency microwave vacuum continuous drying equipment according to claim 1, characterized in that, The exhaust gas treatment module includes an exhaust pipe (13), one end of which is connected to the drying chamber (1), and the other end is provided with a heat exchanger (14), and the end of the heat exchanger (14) is provided with a vacuum pump (15).

10. The high-efficiency microwave vacuum continuous drying equipment according to claim 9, characterized in that, A filter module is provided between the vacuum pump (15) and the heat exchanger (14).

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