Solid material fluidization radio frequency sterilization apparatus and method

Abstract

The present application relates to a kind of solid material fluidization radio frequency sterilization equipment and method, belong to radio frequency sterilization drying field, including material fluidization system, radio frequency processing system and send exhaust circulating system.Material fluidization system is by paddle screw agitator, gas is sprayed into stirring shaft, so that solid material is uniformly suspended and shows flow state, increase the contact area of radio frequency energy and material, promote heat transfer.Radio frequency processing system utilizes radio frequency electrode plate to generate radio frequency energy to sterilize material, solid-gas separation device separates powder and gas, ensure that microorganism is effectively inhibited.Send exhaust circulating system introduces gas by air inlet device to maintain material flow state, exhaust device discharges treatment gas, and circulating air duct realizes the recycling of gas.The equipment has the characteristics of high efficiency energy saving, no chemical residue etc., can realize the rapid, uniform sterilization of solid food, improve the sterilization efficiency of solid food, and is suitable for efficient sterilization treatment in large-scale production.

Description

Technical Field

[0001] The invention relates to a fluidized radio frequency sterilization device and method for solid materials, belonging to the technical field of radio frequency sterilization and drying. Background Art

[0002] Currently, solid-state food sterilization technology faces numerous challenges. Traditional sterilization methods, such as dry heat and irradiation, have significant limitations. Dry heat typically requires high temperatures (approximately 160°C) and, due to low mass transfer efficiency and prolonged heating times, can easily lead to nutrient degradation and food quality degradation, while also limiting its sterilization effectiveness. Irradiation, due to potential safety risks, can easily provoke consumer resistance.

[0003] In contrast, radiofrequency sterilization technology uses the thermal effect of electromagnetic fields to act on microbial cell membranes, disrupting their structure and thereby inhibiting or killing microorganisms. Due to the high moisture content in microorganisms, they can absorb radiofrequency energy more effectively than low-moisture materials, thus achieving a good sterilization effect even when the material temperature is kept low (approximately 100°C). Therefore, radiofrequency sterilization, with its advantages such as deep penetration, high heat transfer efficiency, lack of chemical residues, and suitability for batch processing, has become an ideal alternative to effectively kill contaminating microorganisms in food.

[0004] However, existing RF sterilization technology still faces several technical bottlenecks, such as edge effects and thermal drift, which lead to non-uniform heating, prolonged processing time, and reduced sterilization efficiency. Furthermore, when applied to solid foods, it can easily lead to material agglomeration. These challenges urgently require further optimization to improve the feasibility and efficiency of RF sterilization technology in actual production. Summary of the Invention

[0005] In order to solve the above-mentioned problems, the present invention provides a fluidized radio frequency sterilization device and method for solid materials. The technical solution is as follows:

[0006] As one aspect of the present invention, a fluidized radio frequency sterilization device for solid materials is provided.

[0007] It includes: a material fluidization system, a radio frequency processing system and an air supply and exhaust circulation system. The radio frequency processing system is arranged above the material fluidization system and is connected to the material fluidization system to perform radio frequency sterilization on the fluidized solid material. The radio frequency processing system includes a solid-gas separation device and a radio frequency processing chamber. The solid-gas separation device is arranged above the radio frequency processing chamber. The air supply and exhaust circulation system includes an air inlet device, an exhaust device and a circulating air duct. The gas storage chamber is used to store inert gas.

[0008] One end of the air inlet device is connected to the gas storage chamber and one end of the circulating air duct respectively, and the other end of the air inlet device is connected to the air inlet of the material fluidization system to fluidize the solid material. One end of the exhaust device is connected to the clean air outlet of the solid-gas separation device through a safety valve, and the other end of the exhaust device is connected to the other end of the circulating air duct and connected to the air through the exhaust damper.

[0009] Furthermore, the material fluidization system includes a paddle screw agitator, which includes a spiral ribbon, a stirring shaft and a spiral ribbon bracket. The spiral ribbon is fixed to the stirring shaft through the spiral ribbon bracket. The stirring shaft is hollow and connected to the air inlet device. A number of air outlet holes are provided on the stirring shaft. A material discharge structure is provided at the bottom center of the material fluidization system.

[0010] Furthermore, the spiral ribbon is a forward and reverse rotating spiral ribbon.

[0011] Furthermore, the RF processing system is provided with a number of parallel RF plates, which are arranged alternately with positive and negative RF plates. The RF plates on both sides close to the outer wall are negative plates. The RF plates are fixed in the RF processing system through insulating material brackets, and a RF processing cavity is formed between the RF plates.

[0012] Furthermore, a number of small holes are evenly opened on the radio frequency plate.

[0013] Furthermore, the solid-gas separation device includes but is not limited to a pulse processor and a dust removal bag, and the pulse processor is arranged directly above the suspension bridge of the dust removal bag.

[0014] Furthermore, the air intake device includes an air intake duct, in which an air intake damper, a gas filter and a blower are sequentially arranged along the air flow transmission direction. The gas filter is arranged at the inlet of the blower, and the outlet of the blower is connected to the air inlet of the material fluidization system through the air intake duct. The connection between the circulating air duct and the air intake duct is located between the air intake damper and the gas filter.

[0015] Furthermore, the exhaust device includes an exhaust duct, which is provided with a safety valve, a silencer, an induced draft fan and an exhaust damper in sequence along the gas transmission direction, and the connection between the circulating air duct and the exhaust duct is located between the exhaust damper and the induced draft fan.

[0016] As another aspect of the present invention, a method for fluidized radio frequency sterilization of solid materials is provided, which is applied to the above-mentioned fluidized radio frequency sterilization equipment for solid materials, comprising:

[0017] The solid material is moved axially by the material fluidization system, and gas is introduced through the air inlet device and ejected from the air outlet of the stirring shaft, so that the solid material enters the radio frequency processing system and becomes fluidized. The gas can be air or an inert gas in the gas storage chamber.

[0018] The radio frequency energy generated between the radio frequency processing chambers in the radio frequency processing system is used to sterilize the fluid solid material;

[0019] The sterilized solid material and gas are separated by a solid-gas separation device, and the gas is discharged through an exhaust device to obtain the sterilized solid material. The discharged gas can be directly discharged into the atmosphere or re-enter the air inlet duct through a circulating air duct.

[0020] Beneficial effects of the present invention:

[0021] The present invention utilizes a material fluidization system to uniformly suspend solid materials in a fluidized state within the radio frequency processing chamber, thereby increasing the contact area between radio frequency energy and the solid materials, promoting heat transfer and uniformity, and improving sterilization efficiency. This allows sterilization to be achieved in a relatively short period of time, avoiding the destruction of the nutritional components of the solid materials by excessive heating time, and protecting the natural flavor and functional components of the food. Furthermore, radio frequency sterilization can maintain temperature uniformity inside and outside the powdered food, preventing crusting. Combined with the uniform distribution of powdered food brought about by the material fluidization system, the moisture contained in the powdered food can be rapidly evaporated during the radio frequency sterilization process, accelerating the drying speed, improving the drying efficiency, and effectively preventing overheating and hardening. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 This is a schematic structural diagram of a solid material fluidized radio frequency sterilization device provided by an embodiment of the present invention;

[0024] Figure 2 It is a left side view of the material fluidization system and radio frequency processing system provided by an embodiment of the present invention;

[0025] Figure 3 Schematic diagram of the structure of the material fluidization system and radio frequency processing system provided by an embodiment of the present invention;

[0026] Figure 4 This is another left side view of the material fluidization system and radio frequency processing system provided by an embodiment of the present invention;

[0027] Figure 5 is a front view of a material fluidization system and a radio frequency processing system provided by an embodiment of the present invention;

[0028] Figure 6 is a bottom view of a material fluidization system provided by an embodiment of the present invention;

[0029] Figure 7 1 is a structural diagram of a paddle-type spiral agitator provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0030] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0031] Example 1:

[0032] The embodiment of the present invention provides a solid material fluidized radio frequency sterilization device, see Figures 1 to 6 , including: a material fluidization system 1, a radio frequency processing system 2 and a supply and exhaust air circulation system, the radio frequency processing system 2 is arranged above the material fluidization system 1 and is connected to the material fluidization system 1 to perform radio frequency sterilization on the fluidized solid material, the radio frequency processing system 2 includes a solid-gas separation device 21 and a radio frequency processing chamber 22, the solid-gas separation device 21 is arranged above the radio frequency processing chamber 22, the supply and exhaust air circulation system includes an air inlet device 3, an exhaust device 4 and a circulating air duct 5, and a gas storage chamber 6 is used to store inert gas, and the gas storage chamber 6 can be a gas bottle;

[0033] One end of the air inlet device 3 is connected to the gas storage chamber 6 and one end of the circulating air duct 5, respectively, for gases such as nitrogen and carbon dioxide. The other end of the air inlet device 3 is connected to the air inlet 11 of the material fluidization system 1 to fluidize the solid material. One end of the exhaust device 4 is connected to the clean air outlet 213 of the solid-gas separation device 21 via a safety valve 41. The other end of the exhaust device 4 is connected to the other end of the circulating air duct 5 and is also connected to the air via an exhaust damper 42. Because dust clouds form when the pressure of the environment in which the dust is located is higher than 0.8 MPa, which is prone to explosion, appropriate pressure relief is provided through the safety valve 41 so that the food powder will not explode within 1.2 MPa, thereby ensuring the safety of the solid material fluidization radio frequency sterilization equipment. In addition, a gas valve is provided on the connecting pipe between the gas storage chamber 6 and the air inlet device 3, and the gas output of the inert gas can be adjusted through the gas valve according to actual needs.

[0034] Specifically, the air intake device 3 includes an air intake duct 32, and the air intake duct 32 is sequentially provided with an air intake damper 31, a gas filter 33 and a blower 34 along the air flow transmission direction. The gas filter 33 is arranged at the inlet of the blower 34, and the outlet of the blower 34 is connected to the air inlet 11 of the material fluidization system 1 through the air intake duct 32. The connection between the circulating air duct 5 and the air intake duct 32 is located between the air intake damper 31 and the gas filter 33.

[0035] The gas filter 33 can filter and purify gas such as inert gas before it enters the blower 34, ensuring the cleanliness of the gas entering the material fluidization system 1, thereby avoiding contamination of solid materials and reducing environmental pollution after the gas is discharged.

[0036] Furthermore, if Figure 7 As shown, the material fluidization system 1 includes a paddle-type spiral agitator 12, which includes a spiral ribbon 121, an agitator shaft 122, and a spiral ribbon bracket 123. The spiral ribbon 121 is fixed to the agitator shaft 122 via the spiral ribbon bracket 123. The agitator shaft 122 is hollow and connected to the air inlet device 3. The agitator shaft 122 is provided with a plurality of air outlet holes 124. A material discharge structure 13 is provided at the bottom center of the material fluidization system 1. In this embodiment of the present invention, the spiral ribbon is specifically a forward and reverse rotating spiral ribbon.

[0037] The water content of the solid material targeted by the embodiment of the present invention is mainly between 5% and 15%. During specific implementation, the motor 14 drives the stirring shaft 122 to rotate, driving the forward and reverse rotating spiral belt to rotate so that the solid material moves axially. At the same time, the gas passes through the gas filter 33 and the blower 34 and is sent into the hollow cavity of the stirring shaft 122 through the air inlet 11 through the pipeline, and is ejected from the air outlet 124 on the stirring shaft 122, so that the solid material is evenly suspended in the radio frequency treatment chamber 22 and presents a fluid state, thereby increasing the contact area between the radio frequency energy and the solid material, promoting heat transfer, and improving the sterilization efficiency. At the same time, the forward and reverse rotating spiral belt can timely make the material that falls into the bottom of the paddle spiral stirrer move axially during the rotation process, and blow it up again through the wind blown out of the air outlet 124, so that it is evenly suspended in the radio frequency treatment chamber for radio frequency sterilization, so as to further ensure the sterilization effect. In addition, the outlet angle of the air outlet 124 can be set according to actual needs, such as the height or width of the RF processing chamber, to further improve the uniformity of the distribution of powdered food in the RF processing chamber.

[0038] Specifically, if Figure 6 As shown, the unloading structure 13 includes a switch 131, a main bearing 132 and a unloading door 133. The processed solid material is unloaded through the unloading structure. During unloading, the fan device is closed, the switch 131 is turned on to drive the main bearing shaft 132 to move, the unloading door 133 is opened, and the forward and reverse rotating spiral ribbons of the paddle spiral agitator 12 are used to push the powder material toward the middle unloading door 133, so that the processed solid material can be discharged efficiently and orderly.

[0039] RF processing system 2 Figures 1 to 4As shown, it includes at least five layers of parallel RF plates 221, and the positive and negative RF plates 221 are alternately arranged. The RF plates 221 on both sides close to the outer wall are oppositely arranged negative plates to ensure RF safety. The RF plates 221 are fixed in the RF processing system 2 by insulating material brackets. The insulating material brackets can be tetrafluoroethylene brackets. RF processing chambers 22 are formed between the RF plates 221 to sterilize solid materials. In addition, the RF processing system 2 is also provided with an observation port 23 at the RF processing chamber 22 to facilitate daily maintenance and inspection of the RF plates 221.

[0040] The solid-gas ratio in the RF treatment system 2 is usually set to 1-10 kg / m 3 The specific value can be further set according to the actual situation such as the height of the RF plate 221 and the type of solid material. The setting of this value should be based on the standard of spraying the powdered food to the top of the RF processing chamber 22 at the highest.

[0041] After the solid material passes through the paddle spiral agitator 12 and turns upward with the air flow into the RF processing chamber 22 of the RF processing system 2, it is heated and sterilized. The RF generator forms an electric field between the two plates. The RF output power can be 13.56MHz, 27.12MHz, and 40.68MHz, so that the RF output power and the plate spacing can be adjusted according to the dielectric constant of different solid materials. The dielectric constant of common powdered foods is currently 2.10-19.72. Therefore, according to the penetration depth formula, the penetration depth is 6.57-62.15m, and the adjustable spacing of the RF plates can be set to 0.15-0.2m, which can effectively sterilize the solid food in the cavity.

[0042] Because the solid material is fluidized by the material fluidization system 1 and can be evenly suspended in a fluid state between the RF processing chambers, the electromagnetic field can evenly act on the powdered food, uniformly heating it. This increases the contact area between the RF energy and the solid material, promotes heat transfer, improves sterilization efficiency, and can achieve sterilization in a shorter time, avoiding the damage to the nutritional components of the solid material caused by excessive heating time, thereby protecting the natural flavor and functional components of the food. In addition, RF sterilization can maintain temperature uniformity inside and outside the powdered food, preventing crusting. Combined with the effect of uniform distribution of the powdered food brought about by the forward and reverse rotating spiral ribbons and the gas ejected from the air outlet, the moisture contained in the powdered food can be quickly evaporated during the RF sterilization process, accelerating the drying speed, improving the drying efficiency, and effectively preventing overheating and hardening. In another embodiment, a plurality of small holes are evenly opened on the RF plate 221, and the solid material can flow between different RF processing chambers 22 through the small holes opened on the RF plate 221, further increasing the uniformity of the fluidization and RF treatment of the solid material.

[0043] The solid-gas separation device 21 in the radio frequency processing system 2 is as follows Figures 1 to 5 As shown, the RF processing system 2 includes a pulse processor 211 and a dust bag 212 for preventing dust leakage. The pulse processor 211 is located directly above the drawbridge of the dust bag 212. In this embodiment of the present invention, there are at least four pulse processors 211 and at least 20 sets of dust bags 212, specifically 20 to 30 sets in this embodiment of the present invention. Furthermore, the RF processing system 2 is provided with a clean air outlet 213, a blowpipe 214, a venturi 215, and an inspection door 216. The inspection door 216 facilitates routine maintenance and inspection of the RF plates.

[0044] After radio frequency sterilization, the solid material further enters the solid-gas separation device 21 with the turning of the air flow. The solid material accumulates on the outer surface of the dust bag 212, and the gas is discharged through the clean air outlet 213. The pulse processor 211 performs pulse cleaning on the dust bag 212, which can effectively clear the layers, avoid the solid material from attaching after leaving the surface of the dust bag 212 and avoid dust leakage, so that the dust bag 212 can completely clean the solid material and complete the solid-gas separation.

[0045] Exhaust device 4 includes an exhaust duct 43, which is sequentially equipped with a safety valve 41, a muffler 45, an induced draft fan 44, and an exhaust damper 42 along the gas transmission direction. The connection between the circulating air duct 5 and the exhaust duct 43 is located between the exhaust damper 42 and the induced draft fan 44. The filtered gas discharged from the clean gas outlet 213 is discharged into the atmosphere through the muffler 45 and induced draft fan 44 or recycled through the circulating air duct 5. The muffler 45 is used to reduce or eliminate sound generated by noise sources, helping to improve the working environment and equipment noise pollution. Simultaneous activation of the induced draft fan 44 and the blower 34 reduces energy consumption, promotes rapid gas circulation, and improves equipment operating efficiency.

[0046] In an embodiment of the present invention, the reflux ratio of the gas through the circulating air duct 5 is generally between 0.1 and 0.4, and can be set according to actual needs. For example, in an embodiment of the present invention, 10% of the gas is discharged to the atmosphere through the exhaust damper 42, and 90% of the gas enters the gas filter 33 through the circulating air duct 5 and is filtered again before flowing back to the air inlet device 3, which can not only effectively save energy but also avoid secondary pollution.

[0047] In summary, the actual working process of the solid material fluidized radio frequency sterilization equipment provided by the embodiment of the present invention is as follows:

[0048] Firstly, the air or inert gas or the mixture of inert gas and air enters the air blower 34 after passing through the gas filter 33, and the gas in the air blower 34 enters the hollow cavity of the stirring shaft 122 through the air inlet 11 of the material fluidization system 1, and the paddle screw stirrer 12 drives the forward and reverse rotation screw belt on the stirring shaft 122 to make the solid material move axially, and the gas is sprayed out of the hollow cavity of the stirring shaft 122 through the air outlet hole 124 on the stirring shaft 122, so that the solid material enters the radio frequency processing cavity 21 in the radio frequency processing system 2 along with the gas flow and presents a flow state, and the sterilization treatment is carried out in the radio frequency processing cavity 21, and the sterilized solid material is intercepted by the pulse processor 211 and the dust cloth bag 212, and falls into the bottom of the material fluidization system 1, at this time, the air inlet device 3 is closed, and the stirring shaft 122 keeps running to drive the solid material to the middle of the discharging structure, and the solid material collection is completed after the opening of the discharging door 133 by the opening of the main bearing shaft 132 by the switch 131, and the gas passes through the clean gas outlet 213 of the fluidized radio frequency device, and is discharged through the silencer 45 and the air blower 44, and the discharged gas can be directly discharged into the atmosphere, or enters the air inlet pipe 32 again through the circulating air duct 5.

[0049] Embodiment 2:

[0050] Another embodiment of the present application provides a solid material fluidized radio frequency sterilization method, which is applied to the above-mentioned fluidized radio frequency sterilization device, and comprises the following steps.

[0051] S100, the solid material in the material fluidization system moves axially, and the gas is introduced through the air inlet device and sprayed out of the air outlet hole of the stirring shaft, so that the solid material enters the radio frequency processing system and presents a flow state, wherein the gas can be air or inert gas in the gas storage chamber;

[0052] S200, the radio frequency energy generated between the radio frequency processing cavities in the radio frequency processing system is used to sterilize the solid material in the flow state;

[0053] S300, the sterilized solid material and the gas are separated by the solid-gas separation device, and the gas is discharged by the air exhaust device, so as to obtain the sterilized solid material, and the discharged gas can be directly discharged into the atmosphere, or enters the air inlet pipe again through the circulating air duct.

[0054] The solid material fluidization radiofrequency sterilization method provided in the embodiment of the present invention uses the forward and reverse rotating spiral ribbons in the paddle spiral stirrer to make the solid material move axially, and at the same time, gas is ejected from the air outlet on the stirring shaft, so that the solid material is evenly suspended in the radiofrequency processing chamber and presents a fluid state, which increases the contact area between the radiofrequency energy and the solid material, promotes heat transfer, improves the sterilization efficiency, can achieve sterilization in a shorter time, avoids the damage to the nutritional components of the solid material caused by excessive heating time, and protects the natural flavor and functional components of the food. In addition, radiofrequency sterilization can maintain the temperature uniformity inside and outside the powdered food, avoid crusting, and combine the effect of uniform distribution of the powdered food brought by the forward and reverse rotating spiral ribbons and the gas ejected from the air outlet. During the radiofrequency sterilization process, the moisture contained in the powdered food can be quickly evaporated, accelerating the drying speed, improving the drying efficiency, and effectively preventing overheating and hardening. Some steps in the embodiment of the present invention can be implemented using software, and the corresponding software program can be stored in a readable storage medium, such as a CD or hard disk.

[0055] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A solid material fluidized radio frequency sterilization device, characterized in that: include: A material fluidization system, a radio frequency processing system, and an air supply and exhaust circulation system. The radio frequency processing system is arranged above the material fluidization system and is connected to the material fluidization system to perform radio frequency sterilization on the fluidized solid material. The radio frequency processing system includes a solid-gas separation device and a radio frequency processing chamber. The solid-gas separation device is arranged above the radio frequency processing chamber. The air supply and exhaust circulation system includes an air inlet device, an air exhaust device, and a circulating air duct. The gas storage chamber is used to store inert gas. One end of the air inlet device is connected to the gas storage chamber and one end of the circulating air duct respectively, and the other end of the air inlet device is connected to the air inlet of the material fluidization system to fluidize the solid material. One end of the exhaust device is connected to the clean air outlet of the solid-gas separation device through a safety valve, and the other end of the exhaust device is connected to the other end of the circulating air duct and connected to the air through an exhaust damper. The material fluidization system includes a paddle-type spiral stirrer, which includes a spiral ribbon, a stirring shaft, and a spiral ribbon bracket. The spiral ribbon is fixed to the stirring shaft through the spiral ribbon bracket. The stirring shaft is hollow and connected to the air inlet device. A plurality of air outlet holes are provided on the stirring shaft. A material discharge structure is provided at the bottom center of the material fluidization system. The RF processing system is provided with a plurality of parallel RF plates, the RF plates are arranged alternately in positive and negative directions, the RF plates on both sides close to the outer wall are negative plates, and the RF plates are fixed to the RF processing system by insulating material brackets, and a RF processing cavity is formed between the RF plates; The air intake device includes an air intake duct, which is sequentially provided with an air intake damper, a gas filter and a blower along the air flow transmission direction. The gas filter is provided at the inlet of the blower, and the outlet of the blower is connected to the air inlet of the material fluidization system through the air intake duct. The connection between the circulating air duct and the air intake duct is located between the air intake damper and the gas filter. The exhaust device includes an exhaust duct, and the exhaust duct is sequentially provided with the safety valve, silencer, induced draft fan and exhaust damper along the gas transmission direction. The connection between the circulating air duct and the exhaust duct is located between the exhaust damper and the induced draft fan.

2. The solid material fluidized radio frequency sterilization equipment according to claim 1, characterized in that: The spiral ribbon is a forward and reverse rotating spiral ribbon.

3. The solid material fluidized radio frequency sterilization equipment according to claim 1, characterized in that: A plurality of small holes are evenly arranged on the radio frequency plate.

4. The solid material fluidized radio frequency sterilization equipment according to claim 1, characterized in that: The solid-gas separation device includes a pulse processor and a dust removal bag, and the pulse processor is arranged directly above the suspension bridge of the dust removal bag.

5. A method for fluidizing radio frequency sterilization of solid materials, applied to a fluidizing radio frequency sterilization device for solid materials according to any one of claims 1 to 4, characterized in that: include: The solid food is moved axially by the material fluidization system, and gas is introduced through the air inlet device and ejected from the air outlet of the stirring shaft, so that the solid food enters the radio frequency processing system and becomes fluidized, wherein the gas is air or an inert gas in the gas storage chamber; Sterilize the fluid solid food by using the radio frequency energy generated between the radio frequency processing chambers in the radio frequency processing system; The sterilized solid food and gas are separated by a solid-gas separation device, and the gas is discharged through an exhaust device to obtain the sterilized solid food. The discharged gas can be directly discharged into the atmosphere or re-enter the air inlet duct through a circulating air duct.

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