Food dryer and control method thereof

Abstract

The invention provides a food dryer and a control method thereof, and belongs to the technical field of food processing equipment. The food dryer comprises a rack and a drying roller rotatably installed on the rack, one end of the drying roller is provided with a feeding shell fixed to the rack, the outlet end of the feeding shell extends into the drying roller, and the feeding shell is provided with a hot air inlet and a material inlet which are communicated with a heat supply device. And a first lifting conveyor communicated with the material inlet is mounted outside the rack. The feeding shell extends into the drying roller, so that hot air preheats wet materials entering the drying roller preferentially, and adhesion and blockage of fed materials are effectively prevented; the vibrating screen classifier is directly connected to the discharging end, so that drying and screening are integrated; dried tail gas is introduced into the feeding bin through the gas collecting box to preheat wet materials, and waste heat recovery is achieved. According to the invention, the continuity and the automation level of food drying operation are obviously improved, the energy consumption and the labor cost are reduced, and the product quality is improved.

Description

Technical Field

[0001] This application relates to the field of drying equipment technology, and in particular to a food dryer and its control method. Background Technology

[0002] In the industrialized food production process, drying is one of the key steps in extending the shelf life of food and improving product quality. It is widely used in the processing of dehydrated vegetables, dried fruits, grains, nuts, and other materials. Currently, rotary drum dryers have become the mainstream equipment in the food drying field due to their advantages such as large processing capacity, uniform heating of materials, and continuous operation. Their working principle is that the material comes into contact with hot air inside a rotating drum, achieving moisture evaporation through heat exchange.

[0003] However, in practical applications, existing rotary drum food dryers still face some technical bottlenecks, hindering the improvement of production efficiency and the stability of product quality. Firstly, in the feeding stage, traditional feeding structures are often quite simple. The wet material to be dried enters the high-temperature drum directly, easily causing surface adhesion near the feed inlet due to rapid moisture evaporation, leading to clumping or blockage. This not only impedes normal material entry but also affects the uniformity of airflow distribution within the drying chamber, resulting in localized overheating or uneven drying. Secondly, the dried material often contains impurities such as debris, dust, and unbroken lumps, requiring additional screening equipment for post-processing. Furthermore, the large amount of high-temperature, high-humidity exhaust gas generated during the drying process is usually directly emitted, with a significant amount of waste heat not being effectively utilized, resulting in energy waste and contradicting the current industrial development direction of green manufacturing and energy conservation and emission reduction. In addition, in the front-end conveying stage for feeding the dryer, for spherical or easily rolling granular materials, traditional flat belt conveyors tend to cause the material to roll to both sides, resulting in uneven feeding and affecting the stability of subsequent drying processes.

[0004] Therefore, overcoming the aforementioned technical bottlenecks and developing a food drying equipment that features smooth feeding, integrates drying and screening, and provides uniform and stable material supply is of great significance for improving the overall technical level of the food processing industry. Summary of the Invention

[0005] This application provides a food dryer and its control method, which can achieve stable and efficient screening and drying of materials. It features a compact structure, integrated functions, energy efficiency, and stable operation.

[0006] To achieve the above objectives, the embodiments of this application adopt the following technical solution: A continuous processing equipment for food materials includes a frame, on which a drying drum is rotatably mounted. A feeding device is provided at one end of the drying drum, the feeding device including a feeding shell fixed to the frame, the outlet end of which extends into the interior of the drying drum. A hot air inlet is provided on the feeding shell for communication with the output port of a heating device. A material inlet is also provided on the feeding shell. A first lifting conveyor, communicating with the material inlet, is installed outside the frame for lifting and conveying the material to be processed into the feeding shell.

[0007] With the above structure, hot air first enters the feeding shell area to preheat the incoming wet material, causing the surface moisture to evaporate quickly. This effectively prevents the material from sticking and clumping due to the instantaneous high temperature and humidity when entering the drying drum, ensuring the smooth flow of the feeding channel.

[0008] Furthermore, to enable online screening of the dried material, a discharge device is installed at the other end of the drying drum. This discharge device is connected to the inlet of a vibrating screen installed outside the frame. The screen box of the vibrating screen is equipped with an impurity discharge outlet and a finished product discharge outlet, both communicating with its internal cavity. The inlet of the impurity discharge outlet is flush with the upper area of ​​the screen mesh, used to discharge the oversize material; the inlet of the finished product discharge outlet is located below the screen mesh, used to collect and discharge the undersize material. The other end of the finished product discharge outlet is connected to a second lifting conveyor, used to transport the screened finished material to the next process.

[0009] Furthermore, in order to achieve uniform and stable front-end material supply, a belt conveyor is connected to the feed inlet of the first lifting conveyor.

[0010] As a preferred conveying structure, belt conveyors have multiple sets of V-shaped idlers spaced apart beneath the conveyor belt. These V-shaped idlers support the bearing surface of the conveyor belt, forming a trough-shaped structure with a concave center and raised sides. This structure allows materials to automatically converge towards the center during conveying, effectively preventing spherical or easily rolling particles from rolling to the sides, thus forming a continuous and stable material flow.

[0011] Furthermore, a feed hopper is fixedly installed above the belt conveyor to receive materials from the front-end pre-processing equipment. A support frame is provided at the bottom of the feed hopper, and the mounting frame of the belt conveyor is fixed to the support frame to form a compact feeding unit.

[0012] Preferably, the feed hopper is funnel-shaped, wider at the top and narrower at the bottom, with its lower outlet positioned directly opposite the centerline of the conveyor belt to ensure that the material falls accurately into the central area of ​​the conveyor belt.

[0013] To recover and utilize the waste heat from the drying exhaust gas and reduce system energy consumption, a gas collection box is installed at the end of the discharge device. The upper part of the gas collection box is connected to the internal space of the feeding hopper via a gas conveying pipe. The hot and humid exhaust gas that has completed heat exchange inside the drying drum is collected in the gas collection box and introduced into the feeding hopper through a pipe. It passes through the wet material falling into the feeding hopper from bottom to top, preheating the material and realizing the cascade utilization of energy.

[0014] As an improvement, the first lifting conveyor is connected to the material inlet of the feed housing via a transition box, on which a material regulating plate is rotatably mounted. This regulating plate controls the material flow rate and automatically closes the channel by gravity when the machine stops, preventing hot airflow from flowing back into the drying drum.

[0015] Furthermore, to promote the orderly movement of materials within the drying drum, spiral guide blades are fixedly installed on the inner wall of the drying drum.

[0016] The present invention also discloses a control method for the above-mentioned continuous processing equipment for food materials, comprising the following steps: Step 1: System Start-up: The control system sequentially starts the vibrating screen, the drive unit of the drying drum, the first lifting conveyor, the second lifting conveyor, and the belt conveyor, while simultaneously turning on the heating device and the induced draft device connected to the air collection box; Step 2: Parameter Presetting: Based on the characteristics of the material to be processed, set the rotational speed of the drying drum, the hot air temperature, the running speed of the belt conveyor, and the air volume parameters of the induced draft device on the control system's operating interface; Step 3, Uniform Material Distribution: The wet material to be processed is fed into the feed hopper and falls onto the belt conveyor running below. Under the action of the trough conveyor belt formed by the V-shaped idlers, the material automatically centers to form a uniform material layer and is steadily transported to the feed inlet of the first lifting conveyor. Step 4, Quantitative Feeding: The first lifting conveyor lifts the material and feeds it into the feeding shell through the transition box and material inlet. During this process, the material flow rate into the drying drum can be controlled by adjusting the opening of the material regulating plate. Step 5: Drying: Inside the rotating drying drum, the material moves continuously forward under the push of the spiral guide blades, and fully contacts and exchanges heat with the high-temperature hot air entering from the hot air inlet to achieve dehydration and drying; Step Six: Waste Heat Recovery: The wet and hot exhaust gas generated during the drying process is collected in the gas collection box by the discharge device. Under the action of the induced draft device, it is sent into the feeding hopper through the gas conveying pipeline to preheat the wet material in the feeding hopper, thus completing the waste heat recovery. Step 7, Screening and Separation: After the dried material is discharged from the discharge device, it directly enters the vibrating screen for screening. Impurities generated during screening are discharged from the impurity discharge outlet, and qualified finished product particles fall through the screen and enter the second lifting conveyor through the finished product discharge outlet. Step 8, Finished Product Conveying: The second lifting conveyor lifts the screened finished product material and transports it to the subsequent packaging or storage process, completing the entire processing flow.

[0017] As can be seen from the above technical solutions, the embodiments of this application have at least the following beneficial effects: 1. The food dryer and its control method provided in this application embodiment solve the problem of feed adhesion and blockage. By extending the outlet end of the feed shell into the drying drum and setting an independent hot air inlet on the feed shell, the hot air prioritizes heating the feed area. The wet material is preheated before entering the main drying zone, and the surface moisture evaporates rapidly. This avoids the adhesion phenomenon caused by direct contact between cold and wet material and the high-temperature drum wall, ensuring smooth feeding and improving the reliability of system operation.

[0018] 2. By directly connecting the vibrating screen to the discharge end of the drying drum, the drying and screening processes are seamlessly connected, eliminating the intermediate material transfer link, simplifying the process flow, reducing the equipment footprint, realizing integrated drying and screening, and avoiding heat loss and material damage during the transfer process, thereby improving product yield and quality.

[0019] 3. The drying exhaust gas is introduced into the feed hopper through a gas collection box and gas conveying pipeline to preheat the wet material, achieving efficient recovery and utilization of waste heat. This not only recovers the sensible heat in the exhaust gas, but also utilizes the latent heat released by water vapor condensation, significantly reducing overall energy consumption and demonstrating significant energy-saving and environmental protection benefits.

[0020] 4. The V-shaped idlers form a trough structure on the conveyor belt, which allows the material to automatically converge towards the center during the conveying process, forming a stable and uniform material flow. This avoids the lateral rolling and accumulation of spherical or easily rolling particles, ensuring a continuous and stable material flow into the drying system. This lays the foundation for precise control of the drying process and optimizes the uniformity of material supply.

[0021] 5. The vibrating screener performs online screening of the dried material, promptly removing impurities such as debris and lumps, ensuring the purity and particle size uniformity of the final product, and improving product quality.

[0022] 6. The control system coordinates the control of each component and presets process parameters based on material characteristics, ensuring a continuous, stable, and controllable drying process. Simultaneously, the optional temperature feedback adjustment function dynamically adjusts the feeding speed according to the discharge temperature, ensuring consistent drying results and reducing the uncertainty and labor intensity of manual operation.

[0023] It should be understood that the descriptions of technical features, technical solutions, beneficial effects, or similar language in the embodiments of this application do not imply that all features and advantages can be achieved in any single embodiment. Rather, it is understood that the description of a feature or beneficial effect means that a specific technical feature, technical solution, or beneficial effect is included in at least one embodiment. Therefore, the descriptions of technical features, technical solutions, or beneficial effects in this specification do not necessarily refer to the same embodiment. Furthermore, the technical features, technical solutions, and beneficial effects described in this embodiment can be combined in any suitable manner. Those skilled in the art will understand that embodiments can be implemented without one or more specific technical features, technical solutions, or beneficial effects of a particular embodiment. In other embodiments, additional technical features and beneficial effects may be identified in specific embodiments that do not embody all embodiments. Attached Figure Description

[0024] Figure 1 A schematic diagram of a food dryer provided in an embodiment of this application; Figure 2 A rear view of a food dryer provided in an embodiment of this application; Figure 3 A side view of a food dryer provided in an embodiment of this application; Figure 4 for Figure 3 Sectional view at point AA; Figure 5 This is a flowchart of the control method for a food dryer.

[0025] Reference numerals: 100, frame; 200, drying drum; 300, feed housing; 310, hot air inlet; 320, material inlet; 400, first lifting conveyor; 500, discharge housing; 600, vibrating screen; 610, screen box; 611, impurity discharge outlet; 612, finished product discharge outlet; 700, second lifting conveyor; 800, belt conveyor; 810, V-shaped idler; 900, feed hopper; 1000, support frame; 2000, air collection box; 3000, gas conveying pipeline; 4000, transition box; 5000, adjusting plate; 6000, hollow box; 7000, baffle plate. Detailed Implementation

[0026] The terms "first," "second," and "third," etc., used in this application specification and accompanying drawings are used to distinguish different objects, not to limit a specific order.

[0027] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0028] Example 1 Please see Figures 1 to 4 This embodiment provides a food dryer, which is mainly used for the continuous drying of dehydrated vegetables, fruit granules and other materials.

[0029] like Figure 1 As shown, the equipment includes a frame 100 welded from structural steel, serving as the foundation support for the entire equipment. A drum drying mechanism is mounted on the frame 100, comprising a rotatable drying drum 200. The drying drum 200 is a long cylindrical structure, rolled and welded from Q235 carbon steel plate. Spiral guide blades, made of wear-resistant steel plate, are fixedly installed on its inner wall by welding, propelling the material forward as the drying drum 200 rotates. The exterior of the drying drum 200 is covered with an aluminum silicate fiber insulation layer to reduce heat loss during operation.

[0030] A feeding device is installed at the left end (feed end) of the drying drum 200. For example... Figure 2 As shown, the feeding device includes a fixed feeding housing 300, which is fixed to the left end of the frame 100 by a bracket. The feeding housing 300 is cylindrical in shape and made of 304 stainless steel plate, meeting food hygiene requirements. The right end (outlet end) of the feeding housing 300 extends into the interior of the drying drum 200, and a labyrinth-type dynamic seal structure is provided between them to prevent air leakage. A hot air inlet 310 is provided on the upper side wall of the feeding housing 300, which is connected to the output port of a hot air furnace through a high-temperature resistant pipe. In this embodiment, a gas-fired hot air furnace can be selected, which has the advantages of high thermal efficiency and rapid heating. A material inlet 320 is also provided on the top side wall of the feeding housing 300 for feeding materials.

[0031] On the left exterior of the frame 100, a first lifting conveyor 400, a bucket elevator, is installed. Its discharge port is connected to the material inlet 320 of the feed housing 300 through a square transition box 4000. The transition box 4000 is also made of 304 stainless steel plate, and a baffle plate 7000 is installed inside it via hinges. The baffle plate 7000 hangs down naturally under gravity. It is pushed open when material passes through and automatically closes the channel when there is no material, thus preventing hot air backflow.

[0032] To achieve uniform material feeding, a belt conveyor 800 is connected to the feed inlet of the first lifting conveyor 400. For example... Figure 3 As shown, the belt conveyor 800 includes a frame 100, drive rollers and driven rollers mounted at both ends of the frame 100, and a conveyor belt wrapped around the rollers. The conveyor belt is made of food-grade polyurethane (PU) material, which is wear-resistant, oil-resistant, and easy to clean. Below the conveyor belt, multiple sets of V-shaped idlers 810 are spaced apart along the conveying direction. Each set of V-shaped idlers 810 consists of three rollers: the rollers on both sides are inclined upwards, and the roller in the middle is horizontal, collectively supporting the bearing surface of the conveyor belt into a trough-shaped structure that is low in the middle and high at both ends. This structure allows materials to automatically converge towards the center during conveying, preventing them from rolling off.

[0033] A feed hopper 900 is fixedly installed above the belt conveyor 800. The feed hopper 900 is welded from 304 stainless steel plates and is shaped like a frustum of a square pyramid, wider at the top and narrower at the bottom. Its upper opening is open for receiving materials, and its lower opening is a rectangular discharge port, directly facing the center line of the conveyor belt. A support frame is welded around the lower part of the feed hopper 900, and the frame 100 of the belt conveyor 800 is fixedly installed on the support frame, forming an independent feeding unit.

[0034] A discharge device is provided at the right end (discharge end) of the drying drum 200. The discharge device includes a discharge housing 500 fixed to the right end of the frame 100. The left end of the discharge housing 500 also extends into the drying drum 200 and is dynamically sealed to it. The lower part of the discharge housing 500 is provided with a discharge port, which is directly connected to the feed port of a vibrating screen. The vibrating screen is a rectangular vibrating screen, and a layer of stainless steel woven screen is installed inside its screen box 610. The mesh size of the screen is selected according to the material requirements. For example, a 10-mesh screen can be selected for dried carrot cubes. An impurity discharge port 611 is provided at the upper right end of the screen box 610. The inlet of the impurity discharge port 611 is flush with the upper area of ​​the screen and is used to discharge large impurities and clumps of raw material on the screen. A finished product discharge port 612 is provided at the bottom of the screen box 610. The finished product discharge port 612 is located below the screen and is used to collect qualified finished products under the screen. The feed inlet of the second lifting conveyor 700 is connected below the finished product discharge outlet 612, which is used to lift the finished product material to the next process.

[0035] Specifically, in this embodiment, a gas collecting box 2000 is provided at the right end of the discharge housing 500. The gas collecting box 2000 is a sealed box, the inlet of which is connected to the interior of the discharge housing 500, and is used to collect the hot and humid exhaust gas discharged from the drying drum 200. The top of the gas collecting box 2000 is connected to the upper side wall of the feed hopper 900 through a stainless steel pipe, and an induced draft fan is installed on the pipe. In this embodiment, a centrifugal fan is selected as the induced draft fan, and the air volume is adjustable. The outlet of the pipe extends into the interior of the feed hopper 900 and bends downward, so that hot air can be blown from top to bottom onto the material falling into the feed hopper 900.

[0036] The working principle of this embodiment is as follows: After the equipment is started, the high-temperature hot air generated by the hot air furnace enters the feed housing 300 through the hot air inlet 310 and is continuously blown into the rotating drying drum 200. At the same time, the vibrating screen, drying drum 200, first lifting conveyor 400, second lifting conveyor 700, belt conveyor 800 and induced draft fan are started in succession.

[0037] The operator or the previous process puts wet material into the feed hopper 900, and the material falls onto the running conveyor belt through the discharge port. As the conveyor belt forms a trough shape under the action of the V-shaped idler rollers 810, the material automatically centers itself, forming a stable and uniform material layer, which is then smoothly transported to the feed port of the first lifting conveyor.

[0038] The first lifting conveyor 400 lifts the material and sends it into the feed housing 300 through the transition box 4000 and the material inlet 320. During this process, the baffle 7000 is pushed open by the material. After the material enters the feed housing 300, it is immediately preheated by the high-temperature hot air entering from the hot air inlet 310, and the surface moisture evaporates rapidly. Then it is pushed into the drying drum 200.

[0039] Inside the drying drum 200, the material is continuously tumbling forward under the push of the spiral guide blades and comes into full contact with the high-temperature hot air, causing the moisture to evaporate continuously and achieving dehydration and drying.

[0040] The dried material is discharged from the discharge shell 500 and falls directly into the vibrating screen below for screening. After screening, qualified finished particles fall under the screen and enter the second lifting conveyor 700 through the finished product discharge port 612, and are transported to the packaging section; impurities on the screen are discharged from the impurity discharge port 611.

[0041] During this process, the hot, humid exhaust gas generated during drying is collected in the gas collection box 2000 via the discharge shell 500. Under the suction of the induced draft fan, it is sent into the feed hopper 900 through the pipeline, passing through the falling wet material from bottom to top, preheating the material. After preheating, the exhaust gas temperature decreases and the humidity increases, eventually escaping from the top of the feed hopper 900, completing the waste heat recovery cycle.

[0042] Example 2 This embodiment, based on Embodiment 1 above, discloses a control method for the food dryer. The method relies on a central control system, which includes a programmable logic controller (PLC) and a human-machine interface (HMI).

[0043] This method includes the following steps, and a flowchart can be found here. Figure 5 : Step 1: System Startup: The operator presses the start button on the HMI, and the PLC outputs instructions sequentially according to the preset program. First, the PLC outputs a signal to start the vibrating motor of the vibrating screen; after a 5-second delay, the PLC starts the drive motor of the drying drum 200 and simultaneously turns on the burner and fan of the hot air furnace to begin heating; after another 10-second delay, the PLC starts the induced draft fan and sets its frequency converter to an initial frequency of 30Hz; finally, the PLC starts the drive motors of the belt conveyor 800 and the first lifting conveyor 400 and the second lifting conveyor 700, and the system enters the material waiting operation state.

[0044] Step 2, Parameter Preset: On the HMI, the operator sets the rotation speed of the drying drum 200 to 6 rpm, the hot air temperature to 90°C, the motor frequency of the belt conveyor 800 to 20Hz (corresponding to a low initial feeding speed), and the frequency of the induced draft fan inverter to 35Hz, based on the characteristics of the material to be dried (such as apple pieces with a moisture content of 80%).

[0045] Step 3, Uniform Material Distribution and Feeding: After the settings are completed, the material begins to be fed into the feeding hopper 900 and automatically enters the aforementioned conveying, lifting, and feeding process.

[0046] Step 4: Drying process: The material enters the drying drum 200 to begin drying. Simultaneously, a temperature sensor installed near the discharge housing 500 monitors the temperature of the discharged material in real time and feeds back a 4-20mA analog signal to the PLC.

[0047] Step 5: Dynamic Adjustment: The PLC runs a PID control program with the discharge temperature as the controlled variable and the motor frequency of the belt conveyor 800 as the control variable. The target discharge temperature is set to 50°C. When the detected discharge temperature is higher than 55°C, it indicates that the material residence time in the drum is too long or the flow rate is too low. The PLC automatically increases the motor frequency of the belt conveyor 800 by 2Hz to accelerate the feeding speed. When the discharge temperature is lower than 45°C, it indicates that the feeding is too fast. The PLC automatically decreases the motor frequency by 2Hz to slow down the feeding speed. Through this dynamic adjustment, the discharge temperature is stabilized within the range of 50°C ± 3°C, ensuring consistent drying results.

[0048] Step Six: Waste Heat Recovery and Screening Conveying: During the drying process, waste heat recovery, screening, and finished product conveying are continuously and automatically operated until all materials are processed.

[0049] Step 7: System Shutdown: After the material processing is completed, the operator presses the stop button. The PLC first stops the belt conveyor 800, the first lifting conveyor 400 and the second lifting conveyor 700. After a 5-minute delay, it stops the hot air furnace and the induced draft fan. After another 10-minute delay, it stops the drive motor of the drying drum 200 after the material is emptied. Finally, it stops the vibrating screen, completing the entire shutdown process.

[0050] Example 3 This embodiment mainly provides supplementary explanations on the material selection, connection method, and function of key components in the equipment to meet the requirement of sufficient disclosure. This embodiment is for reference when mass production and is not intended to be the only limitation. Other alternative materials are also within the scope of protection of this invention.

[0051] As mentioned earlier, all components that come into direct contact with materials, such as the feed housing 300, discharge housing 500, transition box 4000, feed hopper 900, pipelines, and the screen box 610 of the vibrating screen, are made of food-grade 304 austenitic stainless steel. This material has excellent corrosion resistance, will not react with food materials, has a smooth surface that is easy to clean, and meets the requirements of GB 9684-2011 "National Food Safety Standard for Stainless Steel Products". The stainless steel plates are mainly joined using argon arc welding, followed by pickling and passivation treatment to restore the surface's corrosion resistance.

[0052] The drying drum 200's body is made of Q235 carbon steel, as it serves as a structural component and needs to withstand significant loads and torques, without directly contacting the materials (the inner wall is coated). After welding, the drum body undergoes overall annealing to eliminate internal stress and ensure machining accuracy. The spiral guide blades on the inner wall are made of wear-resistant NM400 steel and are fixed to the inner wall of the drum using intermittent welding, ensuring connection strength while preventing stress concentration that could lead to drum deformation. The external insulation layer of the drum body uses aluminum silicate fiber felt, which has low thermal conductivity and can withstand temperatures above 1000°C. It is fixed with stainless steel wire mesh and clamps, and the outermost layer is wrapped with a 0.5mm thick stainless steel sheet as a protective layer.

[0053] The conveyor belt is made of food-grade polyurethane (PU) material, which has excellent wear resistance and tensile strength, and is non-toxic and odorless, meeting FDA food contact material standards. The V-shaped idler roller 810 is made of high-molecular-weight polyethylene material, which has good self-lubrication, flexible rotation, low noise, and corrosion resistance.

[0054] The baffle plate 7000 is made of polypropylene (PP) board, which is lightweight, heat-resistant and corrosion-resistant. It is hinged in the transition box 4000 by stainless steel hinges, and the structure is simple and reliable.

[0055] The PLC and HMI in the control system are connected via an industrial Ethernet cable. The PLC's output module controls the contactors of each motor through intermediate relays, thus starting and stopping the motors. The temperature sensor is a PT100 platinum resistance thermometer, which is highly accurate and stable. A temperature transmitter converts the resistance signal into a 4-20mA standard signal, which is then sent to the PLC's analog input module. A frequency converter is used to control the motor speeds of the belt conveyor 800 and the induced draft fan, achieving stepless speed regulation. In this embodiment, a Siemens G120C series frequency converter is selected.

[0056] In summary, the food dryer and its control method provided by this invention systematically solve the problems of feeding blockage, single function, high energy consumption, and uneven feeding in the prior art through structural innovation and control optimization, and realize efficient, energy-saving, continuous and automated food drying operation.

[0057] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions within the technical scope disclosed in this application should be covered within the scope of protection of this application.

Claims

1. A food dryer, comprising a frame (100) and a drying drum (200) rotatably mounted on the frame (100), characterized in that... One end of the drying drum (200) is provided with a feed housing (300) fixed on the frame (100). The outlet end of the feed housing (300) extends into the interior of the drying drum (200). The feed housing (300) is provided with a hot air inlet (310) for communication with a heating device. The feed housing (300) is also provided with a material inlet (320). A first lifting conveyor (400) communicating with the material inlet (320) is installed on the outside of the frame (100).

2. The food dryer according to claim 1, characterized in that... The other end of the drying drum (200) is provided with a discharge shell (500), which is connected to the inlet of the vibrating screen (600) installed outside the frame (100). The screen box (610) of the vibrating screen (600) is provided with an impurity discharge port (611) and a finished product discharge port (612) connected to its inner cavity. The impurity discharge port (611) is located in the area above the screen, and the finished product discharge port (612) is located below the screen. The finished product discharge port (612) is connected to a second lifting conveyor (700).

3. The food dryer according to claim 2, characterized in that... The first lifting conveyor (400) is connected to a belt conveyor (800) at its feed inlet. Multiple sets of V-shaped idlers (810) are provided under the conveyor belt of the belt conveyor (800). The V-shaped idlers (810) support the bearing surface of the conveyor belt in a trough-shaped structure that is low in the middle and high on both sides.

4. The food dryer according to claim 3, characterized in that... A feed bin (900) is fixedly installed above the belt conveyor (800), and a support frame (1000) is provided at the lower part of the feed bin (900). The mounting frame (100) of the belt conveyor (800) is fixed on the support frame (1000), and the discharge port of the feed bin (900) is located directly above the belt conveyor.

5. The food dryer according to claim 4, characterized in that... The end of the discharge housing (500) is provided with a gas collection box (2000), which is connected to the internal space of the feed hopper (900) through a gas conveying pipe (3000). An exhaust fan is installed on the gas conveying pipe (3000).

6. The food dryer according to claim 4, characterized in that... The first lifting conveyor (400) is connected to the material inlet (320) through a transition box (4000), and an adjustment plate (5000) for adjusting the material flow and preventing backflow of air is rotatably installed on the transition box (4000).

7. The food dryer according to claim 2, characterized in that... Spiral guide blades for guiding materials to move forward are fixedly installed on the inner wall of the drying drum (200).

8. The food dryer according to claim 1, characterized in that... The first lifting conveyor (400) is connected to the feed inlet through a hollow box (6000), and a baffle plate (7000) is hinged on the hollow box (6000).

9. A control method for a food dryer as described in any one of claims 1-8, characterized in that... This includes the following steps: System startup: Start the vibrating screen (600), drying drum (200), first lifting conveyor (400), second lifting conveyor (700), belt conveyor (800), heating device, and induced draft device connected to the air collection box (2000); Preset parameters: Set the rotational speed of the drying drum (200), the hot air temperature, and the running speed of the belt conveyor (800); Uniform feeding: The material falls from the feed hopper (900) to the belt conveyor (800), forms a stable material flow on the trough conveyor belt formed by the V-shaped idlers (810), and is conveyed to the first lifting conveyor (400); Feeding and drying: The material is fed into the feeding shell (300) by the first lifting conveyor (400), and after being preheated by hot air, the material enters the drying drum (200) to achieve drying; Waste heat recovery: The wet and hot exhaust gas generated during drying is sent into the feed hopper (900) by the induced draft device through the gas collection box (2000) and gas conveying pipeline (3000) to preheat the wet material in the feed hopper (900); Screening output: After drying, the material enters the vibrating screen (600) for screening, and the finished particles enter the second lifting conveyor (700) for output through the finished product outlet (612).

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