A dehydration system and a dehydration method for dehydrated onion production

Abstract

The application discloses a dehydration system and method for dehydrated onions, and belongs to the technical field of onion processing. The system comprises, in sequence, a blanching pool, a cold water pool, a medium-temperature drying box, a high-temperature drying box and a cold air box, and adopts an upwardly-inclined metal conveying mesh belt to shorten the equipment footprint; the blanching and cooling stations are matched with a mesh-tube auger conveyor to realize synchronous conveying and draining. A plurality of groups of dispersed, rotating and soft scattering roller shafts are arranged in the drying and cooling boxes respectively, a partitioned air supply structure is arranged at the bottom, and a flexible mesh capable of being shaken and cleaned is arranged at the front end of the box. The application adopts a segmented gradient drying process, removes surface free water at medium temperature, removes internal bound water at high temperature, and cooperates with normal-temperature flexible cooling and scattering to solve the problems of uneven drying, material clumping, high breakage rate and easy odor generation in traditional single-stage drying. The application has compact structure, low energy consumption and convenient maintenance, can effectively improve the completeness and quality consistency of the dehydrated onion products, and is suitable for continuous and large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of dehydrated onion production technology, specifically a dehydration system and dehydration method for dehydrated onion production. Background Technology

[0002] Dehydrated onions are a commonly used dehydrated seasoning ingredient in the food processing industry, with a large market demand. Currently, industrial production generally uses continuous mesh belt drying equipment to complete the dehydration process. Existing traditional dehydration equipment mostly adopts a fully horizontal conveyor structure and a single-stage constant temperature drying mode. The overall equipment layout is lengthy, with high plant space occupancy and poor compactness, which is not conducive to the intensive layout of production lines. At the same time, single constant temperature drying cannot adapt to the moisture evaporation characteristics of onions at different stages of dehydration, which easily leads to the problem of rapid drying and caking of the material surface and retention of internal moisture, resulting in uneven drying and poor drying consistency in the finished product, making it difficult to guarantee the overall drying quality.

[0003] After the drying process is completed, the materials are often directly piled up for collection. At high temperatures, the onion shreds still have adhesive properties, which makes it easy for the materials to clump together and form lumps, seriously affecting the appearance of the finished product and its subsequent performance. Existing equipment generally lacks an independent low-temperature slow cooling and dispersing structure, which cannot fundamentally solve the problem of clumping in the finished product.

[0004] Furthermore, the existing equipment design has many shortcomings. After blanching and cooling, the onion material retains a large amount of free moisture on its surface. Conventional conveying structures lack simultaneous drainage, resulting in a significant amount of moisture being directly introduced into the drying chamber, increasing drying energy consumption and load. During the drying process, the material easily piles up and sticks together; the lack of multi-stage dispersing rollers for layered spreading leads to poor ventilation and numerous drying dead zones. The drying chamber lacks a flexible protective structure, allowing lightweight onion shreds to be easily carried away by the hot air, resulting in a high material loss rate. Traditional direct-blowing hot air structures have a strong airflow impact, easily causing onion shreds to break and crumble, resulting in low product integrity and a high breakage rate.

[0005] Therefore, there is a need to develop new dehydration systems and methods for dehydrated onion production to meet this demand. Summary of the Invention

[0006] To address the above technical problems, this invention provides a dehydration system and method for dehydrating onions. By using an upward-sloping conveying structure, the system shortens the equipment layout length and saves factory space. Combined with medium-temperature and high-temperature segmented gradient drying, it improves the uniformity of dehydration. Furthermore, an independent cold air slow cooling station is added, along with a dispersing structure, to effectively eliminate the problem of material clumping. At the same time, it is equipped with a multi-stage roller spreading, flexible anti-escape, and integrated conveying and draining structure, which significantly improves the overall production quality and efficiency of dehydrated onions.

[0007] To solve the above technical problems, the technical solution adopted by the present invention is as follows: a dehydration system for dehydrated onion production, comprising a blanching tank, a cold water tank, a medium-temperature drying chamber, a high-temperature drying chamber, and a cold air box arranged sequentially from front to back. A first auger conveyor is fixedly connected to the bottom of the blanching tank, with its discharge end located at the top of the cold water tank. A second auger conveyor is fixedly connected to the bottom of the cold water tank, with its discharge end located at the front end of the medium-temperature drying chamber. A metal conveyor belt is connected to the lower interior of the medium-temperature drying chamber, and the metal conveyor belt is inclined upwards at its tail. The end of the metal conveyor belt in the medium-temperature drying chamber is located at the front end of the interior of the high-temperature drying chamber. The end of the metal conveyor belt is located at the front end of the cold air box; the bottom of the medium-temperature drying box is connected to several medium-temperature air ducts, the bottom of the high-temperature drying box is connected to several high-temperature air ducts, and the bottom of the cold air box is connected to several low-temperature air ducts. The tops of the medium-temperature air ducts, high-temperature air ducts, and low-temperature air ducts are all connected to several air nozzles; a first dispersing roller is rotatably connected inside the medium-temperature drying box, a left rotating roller, a right rotating roller, and a second dispersing roller are rotatably connected inside the high-temperature drying box, and a set of dispersing rollers is rotatably connected inside the cold air box. The first dispersing roller, the left rotating roller, the right rotating roller, the second dispersing roller, and the dispersing roller are all located above the metal conveyor belt; a flexible mesh is fixedly connected to the front end of both the high-temperature drying box and the cold air box.

[0008] Furthermore, the outer shells of the first auger conveyor and the second auger conveyor are both divided into an upper shell and a lower shell. A mesh cylinder is fixedly connected inside the first auger conveyor and the second auger conveyor. An auger motor is fixedly connected to the side of the first auger conveyor and the second auger conveyor. The rotating shaft of the auger motor is fixedly connected to the auger.

[0009] Furthermore, several upper connecting plates are fixedly connected to both sides of the upper shell, and several lower connecting plates are fixedly connected to both sides of the lower shell. The upper and lower connecting plates are matched in position and fixedly connected by bolts and nuts. An auger inlet is fixedly connected to the front end of the upper shell, and an auger outlet is fixedly connected to the end of the lower shell. A drain pipe is fixedly connected to the front end of the lower shell, and a first valve is provided on the drain pipe. The mesh cylinder has notches at the auger inlet and auger outlet.

[0010] Furthermore, several support rollers are rotatably connected inside the medium-temperature drying box, the high-temperature drying box, and the cold air box. The metal conveyor belt is connected to the support rollers. Conveyor motors are fixedly connected to the outer walls of the medium-temperature drying box, the high-temperature drying box, and the cold air box. The rotating shaft of each conveyor motor is fixedly connected to the roller at the beginning of the corresponding metal conveyor belt.

[0011] Furthermore, the left end of the first dispersing roller shaft is fixedly connected with a left-handed blade, the right end is fixedly connected with a right-handed blade, and it also includes a first dispersing motor. The first dispersing motor is fixedly connected to the side wall of the medium-temperature drying oven, the rotating shaft of the first dispersing motor is fixedly connected to the first dispersing roller shaft, and the second dispersing roller shaft is configured in the same way as the first dispersing roller shaft.

[0012] Furthermore, the left-hand rotating blade is fixedly connected to the left rotating roller shaft, and the right-hand rotating blade is fixedly connected to the right rotating roller shaft. The left-hand rotating motor and the right-hand rotating motor are fixedly connected to the side wall of the high-temperature drying oven. The rotating shaft of the left-hand rotating motor passes through the side wall of the high-temperature drying oven and is fixedly connected to the left rotating roller shaft. The rotating shaft of the right-hand rotating motor passes through the side wall of the high-temperature drying oven and is fixedly connected to the right rotating roller shaft.

[0013] Furthermore, the upper part of the scalding pool and the cold water pool are fixedly connected to a water inlet pipe, and the bottom is connected to a water outlet pipe, with a second valve installed on the water outlet pipe.

[0014] Furthermore, an upper connecting rod is fixedly connected to the upper end of the flexible net, and a lower connecting rod is fixedly connected to the lower end. Both ends of the upper and lower connecting rods are fixedly connected to the side wall of the high-temperature drying oven. An electric cylinder is fixedly connected to the side wall of the high-temperature drying oven. The electric cylinder is located below the flexible net, and a shaking rod is fixedly connected to the output end of the electric cylinder. The connection relationship and accessories of the flexible net in the cold air box are consistent with the connection relationship and accessories in the high-temperature drying oven.

[0015] Furthermore, a dispersing plate is fixedly connected to the dispersing roller shaft. The dispersing plate is made of soft rubber material. A dispersing motor is fixedly connected to the side of the cold air box. The rotating shaft of the dispersing motor passes through the side wall of the cold air box and is fixedly connected to the dispersing roller shaft.

[0016] Furthermore, the dehydration method for dehydrated onion production includes the following steps:

[0017] Step 1: Raw material pretreatment: Fresh onions are peeled, washed, and cut into onion shreds, which are then sent into a blanching tank. The blanching tank maintains a hot water environment of 88-92℃, and the onion shreds are blanched for 40-60 seconds to inactivate enzymes. After blanching, the onion shreds are conveyed upward by the first auger conveyor and fall into the cold water tank.

[0018] Step 2: Rapid cooling and draining: The onion slices are cooled in a cold water tank at 10-15℃ for 1-2 minutes to inhibit the volatilization of sulfides caused by residual heat; the cooled onion slices are then conveyed by a second auger conveyor, during which a mesh cylinder is used to drain the water.

[0019] Step 3: Medium temperature drying: Control the drying temperature at 45-52℃ in the medium temperature drying oven. Output low-disturbance flexible hot air through medium temperature air ducts and nozzles to continuously remove moisture. The first dispersing roller shaft, together with the left-hand and right-hand rotating blades, flattens and disperses the material to prevent the onion shreds from piling up and clumping, and continuously removes the free moisture on the surface of the material.

[0020] Step 4: High-temperature drying: The material is sent into a high-temperature drying chamber, where the temperature is controlled at 60-72℃. Gentle hot air is output from the high-temperature air duct. The left and right rotating rollers guide and spread the material in opposite directions, and the second dispersing roller disperses the material again. With the help of a flexible net, the material is prevented from falling and sticking. The bound water inside the onion is removed smoothly. The temperature is controlled not to exceed 72℃ throughout the process to avoid local overheating that could cause the sulfide thermal decomposition and produce a foul odor.

[0021] Step 5: Gentle Cooling at Normal Temperature: The dried onion shreds are sent into a cold air box. The air temperature inside the cold air box is controlled at 20-28℃. A normal temperature airflow is introduced through the low temperature air duct. The dispersing roller gently disperses the dried onion shreds with the help of a soft dispersing plate to reduce the material breakage rate and make the material cool down evenly. The electric cylinder drives the shaking rod to intermittently knock on the flexible net to clean the adhering material.

[0022] Step 6: Finished Product Discharge: After cooling, the dehydrated onions are continuously discharged, and the moisture content of the finished product is controlled to be ≤8%.

[0023] The method employs a segmented heating stage during the drying process and a low-speed, flexible air delivery method to reduce the degree of breakage of onion shreds and minimize the release of malodorous sulfides from cell tearing.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] 1. This invention uses a metal conveyor belt with its tail angled upwards, which is different from the traditional horizontal layout. It can shorten the horizontal length occupied by the equipment, effectively save factory space, improve site utilization, facilitate the intensive layout of production lines, and adapt to large-scale continuous production in workshops of different specifications.

[0026] 2. This invention features independent medium-temperature and high-temperature drying chambers to achieve segmented, gradient drying. Based on the moisture migration characteristics of onions at different stages of dehydration, corresponding temperature conditions are matched. The medium-temperature stage gently removes free moisture from the surface of the material, preventing the onion skin from drying out quickly and sealing internal moisture channels. The high-temperature stage continuously removes bound water from the material's interior, effectively improving the defects of uneven drying caused by single constant-temperature drying, such as external dryness and internal dampness, thus enhancing drying uniformity and product quality consistency.

[0027] 3. This invention adds an independent cold air box as a slow cooling station. The onion shreds after high temperature drying enter the cold air box for uniform cooling, reducing the adhesion of the material surface. Combined with the dispersing roller with a soft dispersing plate, the material is gently dispersed. This improves the problem of easy clumping and caking of high temperature materials when collected directly from the source, ensuring that the finished product is loose and improving the appearance of the finished product.

[0028] 4. The present invention provides a auger conveyor with a mesh cylinder for the blanching tank and cold water tank. The material conveying process is completed simultaneously with the draining process, which reduces the amount of free water carried into the drying chamber, reduces the load on the drying system, saves drying energy consumption, and realizes the integration of material conveying and draining, making the connection between each process more compact.

[0029] 5. In this invention, multiple sets of dispersing rollers are arranged in the medium-temperature drying box and the high-temperature drying box, and left-handed and right-handed blades are configured. During the conveying process, the onion shreds are continuously flattened, guided and dispersed to avoid the accumulation of materials and the formation of drying dead corners. The drying box body adopts bottom air duct and air nozzle to deliver air, and the airflow disturbance is gentle, reducing the breakage of onion shreds caused by airflow impact, reducing the amount of debris generated and improving the integrity of the finished product.

[0030] 6. The high-temperature drying oven and the front end of the cold air box of this invention are equipped with a flexible net and a shaking rod driven by an electric cylinder. On the one hand, it prevents the light onion shreds from being carried away by the hot air and reduces material loss; on the other hand, it cleans the material adhering to the flexible net by intermittent shaking, avoids long-term material accumulation, ensures that the equipment can operate stably and continuously for a long time, and reduces the frequency of manual cleaning.

[0031] 7. The auger conveyor of the present invention is divided into an upper shell and a lower shell, which are assembled and fixed by connecting plate bolts. During maintenance, the upper and lower shells can be quickly separated, making it convenient to directly and thoroughly clean the onion debris and mucus impurities attached to the surface of the internal mesh cylinder. It is less likely to cause blockage, and the equipment is easy to disassemble and maintain, which is conducive to long-term continuous production. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the structure of the present invention.

[0033] Figure 2 This is a schematic diagram of the auger connection relationship of the present invention.

[0034] Figure 3 This is a schematic diagram of the connection relationship of the mesh cylinders in this invention.

[0035] Figure 4 This is a schematic diagram of the structure of the medium-temperature drying oven of the present invention.

[0036] Figure 5 This is a schematic diagram of the internal structure of the high-temperature drying oven of the present invention.

[0037] Figure 6 This is a schematic diagram of the internal structure of the cold air box of the present invention.

[0038] Figure 7 This is a schematic diagram of the connection relationship of the metal conveyor belt of the present invention.

[0039] Figure 8 This is a schematic diagram of the dispersing roller structure of the present invention.

[0040] Figure 9 This is a schematic diagram of the left-hand rotating roller structure of the present invention.

[0041] Figure 10 This is a schematic diagram of the right-hand rotating roller structure of the present invention.

[0042] Figure 11 This is a schematic diagram of the blanching pool structure of the present invention.

[0043] Figure 12 This is a schematic diagram of the connection relationship of the electric cylinder of the present invention.

[0044] Figure 13 This is a schematic diagram of the flexible mesh structure of the present invention.

[0045] Figure 14 This is a schematic diagram of the dispersing roller structure of the present invention.

[0046] The components include: 1. Blanching tank; 2. Cold water tank; 3. Medium-temperature drying oven; 4. High-temperature drying oven; 5. Cold air box; 6. First auger conveyor; 7. Auger; 8. Auger motor; 9. Second auger conveyor; 10. Metal conveyor belt; 11. First dispersing roller; 12. Medium-temperature air duct; 13. Air nozzle; 14. Flexible net; 15. Electric cylinder; 16. Left rotating roller; 17. Right rotating roller; 18. Second dispersing roller; 19. High-temperature air duct; 20. Dispersing roller; 21. Low-temperature air duct; 22. Mesh cylinder; 23. 24. Upper shell, 25. Lower shell, 26. Upper connecting plate, 27. Lower connecting plate, 28. Drain pipe, 29. First valve, 20. Screwdriver inlet, 30. Screwdriver outlet, 31. Second valve, 32. Vibrating rod, 33. Conveyor motor, 34. Support roller, 35. First dispersing motor, 36. Left-handed blade, 37. Right-handed blade, 38. Left-handed motor, 39. Right-handed motor, 40. Water inlet pipe, 41. Water outlet pipe, 42. Upper connecting rod, 43. Lower connecting rod, 44. Dispersing motor, 45. Dispersing plate. Detailed Implementation

[0047] The present invention will be further described below with reference to specific embodiments.

[0048] Example 1

[0049] This embodiment provides a dehydration system and method for dehydrating onions, employing... Figures 1-14The aforementioned dehydration system, equipped with optimal production process parameters, enables continuous and high-quality production of dehydrated onions. The specific equipment assembly and production process are as follows.

[0050] 1. Specific assembly structure of the equipment

[0051] The equipment is assembled in sequence along the front and back direction, including a blanching tank, a cold water tank, a medium-temperature drying box, a high-temperature drying box, and a cold air box. Each workstation is arranged in a straight line. The tail of the metal conveyor belt is inclined upward at an angle of 15°. Compared with the traditional horizontally arranged equipment, the horizontal footprint is shortened by 18%, and the utilization rate of factory space is significantly improved.

[0052] Both the blanching tank and the cold water tank are equipped with a top-inlet, bottom-outlet water circulation structure. The upper inlet pipe continuously replenishes water, while the bottom outlet pipe is equipped with a second valve to achieve timed discharge of wastewater, ensuring water cleanliness. A first auger conveyor is fixed to the bottom of the blanching tank, and a second auger conveyor is fixed to the bottom of the cold water tank. The two auger conveyors have identical structures; their outer shells are assembled by connecting plates on both sides and sealed with bolts and nuts, making disassembly and assembly convenient. An internal stainless steel mesh cylinder with a 2mm aperture is embedded, allowing for simultaneous drainage during material transport. The auger motor drives the internal auger to rotate at a uniform speed of 12 r / min. A drain pipe with a first valve is installed at the front end of the lower shell to promptly drain accumulated water, preventing moisture from being carried into the drying station.

[0053] The medium-temperature drying oven, high-temperature drying oven, and cold air box are all equipped with stainless steel conveyor belts with a 5mm mesh diameter. These belts are independently driven by external conveyor motors and smoothly transmitted via internal support rollers, with a uniform conveying speed of 0.8m / min. The bottom of the medium-temperature drying oven has 8 sets of medium-temperature air ducts, the high-temperature drying oven has 10 sets of high-temperature air ducts, and the cold air box has 8 sets of low-temperature air ducts. Each set of air ducts has a circular flexible air nozzle arrayed at the top, employing a bottom-up, low-velocity airflow mode, with the air velocity controlled at 0.6m / s to prevent high-speed airflow from impacting and breaking the onion shreds.

[0054] The medium-temperature drying oven is equipped with a first dispersing roller, with left-handed and right-handed blades fixed at both ends. Driven by a first dispersing motor, it rotates at a uniform speed of 15 r / min, achieving bidirectional flattening and dispersion of the material. Inside the high-temperature drying oven, a left-handed rotating roller, a right-handed rotating roller, and a second dispersing roller are arranged sequentially from front to back. The left-handed roller is equipped with left-handed blades, and the right-handed roller is equipped with right-handed blades. Driven independently by left-handed and right-handed motors respectively, they rotate in opposite directions to guide the material, with a speed of 18 r / min for each. The parameters of the second dispersing roller are the same as those of the first dispersing roller, achieving secondary fine dispersion of the material.

[0055] Both the high-temperature drying oven and the front of the cold air box are equipped with high-density nylon flexible mesh with a mesh size of 1mm, effectively preventing lightweight onion shreds from scattering. The upper and lower ends of the flexible mesh are fixed by connecting rods, and an electric cylinder and shaking rod are installed below. The electric cylinder extends and retracts at a frequency of 5 times / min, intermittently striking the flexible mesh to automatically clean adhering materials and prevent material accumulation and blockage. Inside the cold air box, there is a dispersing roller, with a soft rubber dispersing plate of 8mm thickness fixed to the outer circumference of the roller. It is driven by a dispersing motor to rotate at a low speed of 10r / min, realizing the flexible dispersing of materials and reducing the breakage rate.

[0056] 2. Specific dehydration production process

[0057] The specific steps for producing dehydrated onions using the above system are as follows:

[0058] Step 1: Raw material pretreatment. Select fresh, high-quality onions that are free from rot and pests. After manual peeling and high-pressure washing, cut them into uniform onion strips with a thickness of 3mm using a slicing device. Feed the onion strips evenly into the blanching tank, maintain the blanching water temperature at 90℃, and blanch for 50 seconds to completely deactivate the oxidases and sulfidases inside the onions, preventing browning and off-flavors in subsequent processing. After blanching, the onion strips are smoothly conveyed upwards by the first auger conveyor and automatically fall into the cold water tank.

[0059] Step 2: Rapid cooling and draining. The cold water tank maintains a constant temperature of 12°C. The onion slices are immersed in the ice water for rapid cooling for 1.5 minutes to quickly stop the residual heat reaction, inhibit the volatilization of sulfides, and lock in the original flavor of the onions. After cooling, the onion slices fall into the second auger conveyor. During the conveying process wrapped in the mesh cylinder, the surface free water is quickly drained. The draining time is 20 seconds. After draining, the moisture content of the material is reduced to about 45%, which greatly reduces the subsequent drying load.

[0060] Step 3: Medium-temperature gradient pre-drying. The drained onion shreds are conveyed into a medium-temperature drying chamber via a metal conveyor belt. The temperature inside the chamber is precisely controlled at 48°C. Low-disturbance, flexible hot air is output through the bottom medium-temperature air duct and nozzles to continuously remove free moisture from the surface of the material. At the same time, the first dispersing roller continues to rotate, and the bidirectional blades flatten and disperse the stacked onion shreds, completely eliminating dead corners in the material stacking and ensuring uniform dehydration of the material surface. The drying time is 25 minutes. After treatment, the surface moisture content of the material is reduced to 20%, and there is no surface drying and sealing phenomenon.

[0061] Step 4: High-Temperature Deep Dehydration. The pre-dried onion shreds are automatically fed into a high-temperature drying chamber, where the temperature is controlled at 65℃ and does not exceed 72℃ throughout the process to prevent the decomposition of sulfides and the generation of foul odors. Gentle hot air is output from the high-temperature air duct to remove the bound water inside the onion shreds layer by layer. At the same time, the left and right rotating rollers rotate in opposite directions to guide and spread the gathered material to both sides, and the second dispersing roller further refines and disperses the material to ensure uniform ventilation. With the help of the front flexible mesh to prevent the material from scattering, falling and sticking, drying continues for 30 minutes to complete the deep dehydration.

[0062] Step 5: Gentle Cooling and Dispersing at Normal Temperature. The onion shreds, dried at high temperature, are sent into a cold air box at a constant temperature of 25°C. Clean air at normal temperature is introduced through low-temperature air ducts to cool the material evenly from all directions. At the same time, the dispersing roller drives the rubber dispersing plate to rotate at low speed, gently tapping and dispersing the clumps of onion shreds without hard squeezing or crushing. The electric cylinder intermittently drives the shaking rod to strike the flexible mesh, cleaning the fine material adhering to the mesh surface. The cooling and dispersing process takes 20 minutes, and the material temperature drops to room temperature, and the material becomes loose and free of clumps.

[0063] Step 6: Finished Product Inspection. After cooling, the dehydrated onions are continuously discharged. The finished product moisture content is consistently controlled between 6.5% and 8%, meeting the industry's high-quality finished product standards. The material has high integrity, no clumping, and no off-odors.

[0064] 3. Implementation Results

[0065] The dehydrated onions produced in this embodiment are uniform in color and intact in shape, without blackening or browning. The broken product rate is ≤1.2%, far lower than the broken product rate of over 5% in traditional processes. The finished product has no foul odor or off-odor, retains a high degree of original flavor, and the material is loose and does not clump, with a 100% moisture content compliance rate. At the same time, the equipment has strong stability during continuous operation, requiring no frequent shutdowns for cleaning. Compared with traditional equipment, production energy consumption is reduced by 15%, and production efficiency is increased by 20%.

[0066] Comparative Example 1 (Traditional single-stage constant temperature drying process)

[0067] The traditional horizontal mesh belt drying equipment is used, with a single constant temperature of 65℃ for the whole process of drying. There is no segmented temperature control, no pre-drainage structure, and no cold air dispersing station. The other raw material pretreatment, blanching, and cooling steps are the same as in Example 1.

[0068] Production results show that: after drying with traditional process, the onion shreds have obvious external dryness and internal moisture, and the finished product is uneven in dryness and moisture content, with the largest difference in moisture content reaching 4%; the material clumps and caking after drying, with a breakage rate as high as 5.8%; continuous high-temperature drying causes the sulfide decomposition of some materials, resulting in a slight odor, and the finished product qualification rate is only 82%. In addition, the equipment has high energy consumption, requires frequent manual cleaning of accumulated materials, and has low production efficiency.

[0069] Example 2 (Example of Parameter Range Limit Verification)

[0070] This embodiment uses the same equipment structure as Embodiment 1, and adjusts the process parameters to the extreme values ​​within the range defined by this invention to verify the adaptability and stability of the equipment and process.

[0071] 1. Process parameters: blanching temperature 88℃, blanching time 60s; cold water cooling temperature 10℃, cooling time 2min; medium temperature drying temperature 52℃, drying time 22min; high temperature drying temperature 72℃, drying time 28min; cold air cooling temperature 28℃, cooling time 18min, and other structural parameters such as air supply speed and equipment speed remain unchanged.

[0072] 2. Implementation Results: The moisture content of the finished product was stable at 7.2% to 8.0%, with a compliance rate of 100%; the material had no surface drying, no internal water residue, no clumping, no excessive breakage, and a breakage rate of ≤1.5%. There were no off-odors or browning defects. The equipment operated continuously and stably without material blockage or accumulation, which could meet the needs of large-scale production under extreme parameters, verifying the rationality and reliability of the process parameter range of the present invention.

[0073] Example 3 (Low-parameter adaptation example)

[0074] The equipment structure remains unchanged, and production is carried out using the lower limit process parameters: blanching temperature 92℃, blanching time 40s; cold water cooling temperature 15℃, cooling time 1min; medium temperature drying temperature 45℃, drying time 28min; high temperature drying temperature 60℃, drying time 32min; cold air cooling temperature 20℃, cooling time 22min.

[0075] Production results show that the finished product has a moisture content of 6.2% to 7.5%, excellent quality, high material integrity, good looseness, and no quality defects. This further proves that the technical solution of this invention has a wide range of adaptability and strong versatility. The parameters can be flexibly adjusted according to production needs to adapt to different production capacities and quality requirements.

[0076] In summary, this invention, through its synergistic design of segmented gradient drying, integrated conveying and dewatering, multi-stage flexible dispersion, and slow cooling and dispersing with cold air, completely solves the technical pain points of traditional dehydrated onion production, such as uneven drying and wetting, clumping and hardening, high breakage rate, obvious odor, and high energy consumption. The equipment has a compact layout, is easy to maintain, and operates stably, which can significantly improve the quality and efficiency of dehydrated onion production and has extremely high industrialization and promotion value.

Claims

1. A dehydration system for producing dehydrated onions, characterized by: The equipment includes a blanching tank (1), a cold water tank (2), a medium-temperature drying box (3), a high-temperature drying box (4), and a cold air box (5) arranged sequentially from front to back. The bottom of the blanching tank (1) is fixedly connected to a first auger conveyor (6), the discharge end of the first auger conveyor (6) is located at the top of the cold water tank (2), and the bottom of the cold water tank (2) is fixedly connected to a second auger conveyor (9), the discharge end of the second auger conveyor (9) is located at the front end of the medium-temperature drying box (3). The lower end of the interior of the medium-temperature drying oven (3) is connected to a metal conveyor belt (10), the high-temperature drying oven (4) and the cold air box (5), and the tail of the metal conveyor belt (10) is inclined upward. The end of the metal conveyor belt (10) in the medium-temperature drying oven (3) is located at the front end of the interior of the high-temperature drying oven (4), and the end of the metal conveyor belt (10) in the high-temperature drying oven (4) is located at the front end of the interior of the cold air box (5). The bottom of the medium-temperature drying box (3) is connected to several medium-temperature air ducts (12), the bottom of the high-temperature drying box (4) is connected to several high-temperature air ducts (19), the bottom of the cold air box (5) is connected to several low-temperature air ducts (21), and the top of the medium-temperature air ducts (12), high-temperature air ducts (19) and low-temperature air ducts (21) are all connected to several air nozzles (13). The medium-temperature drying box (3) is rotatably connected to a set of first dispersing rollers (11). The high-temperature drying box (4) is rotatably connected to a left rotating roller (16), a right rotating roller (17), and a second dispersing roller (18) in sequence. The cold air box (5) is rotatably connected to a set of dispersing rollers (20). The first dispersing roller (11), the left rotating roller (16), the right rotating roller (17), the second dispersing roller (18), and the dispersing roller (20) are all located above the metal conveyor belt (10). The front ends of the high-temperature drying box (4) and the cold air box (5) are both fixedly connected with flexible nets (14).

2. The dehydration system for producing dehydrated onions according to claim 1, characterized by: The outer shells of the first auger conveyor (6) and the second auger conveyor (9) are both divided into an upper shell (23) and a lower shell (24). A mesh cylinder (22) is fixedly connected inside the first auger conveyor (6) and the second auger conveyor (9). An auger (7) is rotatably connected inside the mesh cylinder (22). An auger motor (8) is fixedly connected to the side of the first auger conveyor (6) and the second auger conveyor (9). The rotating shaft of the auger motor (8) is fixedly connected to the auger (7).

3. The dehydration system for producing dehydrated onions according to claim 2, characterized in that: The upper shell (23) is fixedly connected to several upper connecting plates (25) on both sides, and the lower shell (24) is fixedly connected to several lower connecting plates (26) on both sides. The upper connecting plates (25) and lower connecting plates (26) are matched in position and fixedly connected by bolts and nuts. The front end of the upper shell (23) is fixedly connected to an auger inlet (29), and the end of the lower shell (24) is fixedly connected to an auger outlet (30). The front end of the lower shell (24) is fixedly connected to a drain pipe (27). A first valve (28) is provided on the drain pipe (27). The mesh cylinder (22) has notches at the auger inlet (29) and the auger outlet (30).

4. The dehydration system for producing dehydrated onions according to claim 1, characterized by: The medium-temperature drying box (3), the high-temperature drying box (4) and the cold air box (5) are each rotatably connected with several support rollers (34). The metal conveyor belt (10) is connected to the support rollers (34). The outer walls of the medium-temperature drying box (3), the high-temperature drying box (4) and the cold air box (5) are all fixedly connected with conveyor motors (33). The rotating shaft of each conveyor motor (33) is fixedly connected to the roller (34) at the beginning of the corresponding metal conveyor belt (10).

5. The dehydration system for producing dehydrated onions according to claim 1, characterized by: The left end of the first dispersing roller (11) is fixedly connected with a left-handed blade (36) and the right end is fixedly connected with a right-handed blade (37). It also includes a first dispersing motor (35), which is fixedly connected to the side wall of the medium-temperature drying oven (3). The rotating shaft of the first dispersing motor (35) is fixedly connected to the first dispersing roller (11). The second dispersing roller (18) is configured in the same way as the first dispersing roller (11).

6. The dehydration system for producing dehydrated onions according to claim 1, characterized by: The left-hand rotating blade (36) is fixedly connected to the left rotating roller shaft (16), and the right-hand rotating blade (37) is fixedly connected to the right rotating roller shaft (17). The left-hand rotating motor (38) and the right-hand rotating motor (39) are fixedly connected to the side wall of the high-temperature drying box (4). The rotating shaft of the left-hand rotating motor (38) passes through the side wall of the high-temperature drying box (4) and is fixedly connected to the left rotating roller shaft (16). The rotating shaft of the right-hand rotating motor (39) passes through the side wall of the high-temperature drying box (4) and is fixedly connected to the right rotating roller shaft (17).

7. The dehydration system for producing dehydrated onions according to claim 1, characterized by: The upper part of the scalding pool (1) and the cold water pool (2) are fixedly connected to the water inlet pipe (40) and the bottom is connected to the water outlet pipe (41). The water outlet pipe (41) is equipped with a second valve (31).

8. The dehydration system for dehydrated onion production according to claim 1, characterized in that: The upper end of the flexible net (14) is fixedly connected to an upper connecting rod (42), and the lower end is fixedly connected to a lower connecting rod (43). Both ends of the upper connecting rod (42) and the lower connecting rod (43) are fixedly connected to the side wall of the high-temperature drying box (4). An electric cylinder (15) is fixedly connected to the side wall of the high-temperature drying box (4). The electric cylinder (15) is located below the flexible net (14). A shaking rod (32) is fixedly connected to the output end of the electric cylinder (15). The connection relationship and accessories of the flexible net (14) in the cold air box (5) are consistent with the connection relationship and accessories in the high-temperature drying box (4).

9. The dehydration system for dehydrated onion production according to claim 1, characterized in that: A dispersing plate (45) is fixedly connected to the dispersing roller shaft (20). The dispersing plate (45) is made of soft rubber material. A dispersing motor (44) is fixedly connected to the side of the cold air box (5). The rotating shaft of the dispersing motor (44) passes through the side wall of the cold air box (5) and is fixedly connected to the dispersing roller shaft (20).

10. A dehydration method for producing dehydrated onions according to any one of claims 1-9, characterized in that, Includes the following steps: Step 1: Raw material pretreatment: Fresh onions are peeled, washed and cut into onion shreds and sent into the blanching tank (1). The blanching tank maintains a hot water environment of 88-92℃ and the onion shreds are blanched for 40-60 seconds to inactivate enzymes. After blanching, the onion shreds are conveyed upward by the first auger conveyor (6) and fall into the cold water tank (2). Step 2: Rapid cooling and draining: The onion shreds are cooled in a cold water pool (2) with ice water at 10-15℃ for 1-2 minutes to suppress the volatilization of sulfides caused by residual heat; the cooled onion shreds are conveyed by the second auger conveyor (9), and the draining is achieved by the mesh cylinder (22) during the auger conveying process; Step 3: Medium temperature drying: The drying temperature is controlled at 45-52℃ in the medium temperature drying box (3). Low-disturbance flexible hot air is output through the medium temperature air duct (12) and air nozzle (13) to continuously remove moisture. The first dispersing roller (11) cooperates with the left-hand rotating blade (36) and the right-hand rotating blade (37) to flatten and disperse the material, prevent the onion shreds from piling up and clumping, and continuously remove the free moisture on the surface of the material. Step 4: High-temperature drying: The material is sent into the high-temperature drying box (4), and the temperature inside the box is controlled at 60-72℃. The high-temperature air duct (19) outputs gentle hot air; the left rotating roller (16) and the right rotating roller (17) guide and spread the material in opposite directions, and the second dispersing roller (18) disperses the material again. With the help of the flexible net (14), the material is prevented from falling and adhering, and the bound water inside the onion is removed smoothly. The temperature is controlled not to exceed 72℃ throughout the process to avoid local overheating that causes sulfide thermal decomposition and produces odor. Step 5: Gentle Cooling at Normal Temperature: The dried onion shreds are sent into the cold air box (5). The airflow temperature inside the cold air box is controlled at 20-28℃. The low-temperature air duct (21) introduces normal temperature airflow. The dispersing roller (20) gently disperses the dried onion shreds with the help of the soft dispersing plate (45) to reduce the material breakage rate and at the same time make the material cool down evenly. The electric cylinder (15) drives the shaking rod (32) to intermittently knock on the flexible net (14) to clean the adhering material. Step 6: Finished Product Discharge: After cooling, the dehydrated onions are continuously discharged, and the moisture content of the finished product is controlled to be ≤8%. The method employs a segmented heating stage during the drying process and a low-speed, flexible air delivery method to reduce the degree of breakage of onion shreds and minimize the release of malodorous sulfides from cell tearing.

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