Grate for improving sterilization effect of sterilization pot, grate trolley and combination of grate trolley

Abstract

According to the grate for improving the sterilization effect of the sterilization pot, the grate trolley and the combination of the grate and the grate trolley, holes are formed in the side face and the bottom face of the grate, and the total hole forming area of the side face of the grate accounts for 20%-23%. The utility model discloses a grate trolley for improving the sterilization effect of a sterilization pot. A gap is formed between every two adjacent grate trolleys. By changing the structures of the grate and the grate trolley, the uniformity of heat distribution of the sterilization pot is improved, the sterilization effect of products is improved, the purpose that the sporadic deterioration of the sterilized products is reduced is achieved, and meanwhile the consistency of the sterilization strength, color, taste, flavor and tissue structure of the sterilized products is improved.

Description

Technical Field

[0001] The utility model belongs to the technical field of food processing equipment, and particularly relates to a grate, a grate vehicle and a combination thereof for improving the sterilization effect of a sterilizer. Background Art

[0002] A retort, also known as a sterilizer or autoclave, is a sealed container that heats sealed packages to a specific temperature and maintains it for a specific period of time. It is primarily used in the food and pharmaceutical industries. The sterilization process is essentially a process of heat transfer, which involves heat transfer lag, resulting in temperature differences at different locations within the retort at the same time. If a location within the retort reaches the sterilization temperature 15 minutes after the start of the constant temperature cycle, the product at that location will require 15 minutes less to sterilize than if the product reached the sterilization temperature immediately after the start of the constant temperature cycle. In other words, under the same sterilization conditions, products at different locations will experience inconsistent sterilization intensity, posing a potential safety risk. Therefore, heat uniformity within the retort is crucial. Newly installed retorts and refitted sterilization equipment must undergo heat distribution testing. Only retorts with uniform heat distribution can meet the requirements of the sterilization process.

[0003] In existing autoclaves, during the sterilization process, the grate carts are mostly placed close to each other in the autoclave, and the gap between the carts is narrow, making it difficult for hot water to flow smoothly between the grate carts. This seriously affects the heat transfer process between the heat transfer medium and the product, especially the heat transfer process to the second cart in the middle, which in turn affects the heat distribution uniformity of the autoclave.

[0004] The company uses grates as containers for loading products in the sterilizer, which are made of perforated stainless steel plates. During the sterilization process, the water in the pot flows through these holes to complete the heat transfer process. Therefore, the number of openings and the size of the holes are particularly important. The products are placed in the grates in a horizontal multi-layer manner, and almost completely cover the small holes at the bottom of the grates. Therefore, it is difficult for steam to enter the grate through the small holes at the bottom of the grate, and it mainly enters through the small holes on the sides of the grate and the top grate cover of the grate cart. The total opening area of ​​the grates currently used accounts for about 11%, which is lower than the requirement of the "Test Procedure for Thermal Distribution of Food Thermal Sterilization Equipment" (GB / T 39948-2021) that the total opening area should be no less than 30%. Utility Model Content

[0005] In view of the deficiencies in the prior art, the utility model provides a grate, a grate trolley and a combination thereof for improving the sterilization effect of a sterilizer. By changing the structure of the grate and the grate trolley, the uniformity of heat distribution in the sterilizer is improved, the sterilization effect of the product is improved, and the purpose of reducing the number of sporadic deterioration of the product after sterilization is achieved. At the same time, the consistency of the sterilization strength, color, taste, flavor and organizational structure of the sterilized product is improved.

[0006] The purpose of the utility model is achieved in the following way: a grate for improving the sterilization effect of a sterilizer, holes are opened on the side and bottom of the grate, and the total hole area of ​​the side of the grate accounts for 20%-23%.

[0007] After the grates are stacked, gaps are formed between the sides of the upper and lower grates, and the gaps cannot allow the product to be sterilized to escape from the gaps.

[0008] For cod intestines with a diameter of 1.1-1.2 cm, the gap formed between the sides of the upper and lower layers of the grate is 0.5-1.1 cm.

[0009] The holes on the side of the grate are ≥ three rows of holes, and the centers of the holes are arranged in an equilateral triangle.

[0010] A grate car is provided for improving the sterilization effect of a sterilizer, wherein gaps are provided between adjacent grate cars.

[0011] The grate car side is provided with a stopper. By being provided with the stopper on the grate car side, a gap is provided between adjacent grate cars.

[0012] One side or both sides of the two opposite sides of the grate car are provided with a stopper, so that a gap is provided between adjacent grate cars.

[0013] The grate cart comprises a frame and running wheels. A support frame for placing the grates is provided on the frame. Limiting blocks are provided on the sides of the support frame. Gaps are provided between adjacent grate carts.

[0014] A stopper is provided in front of or behind the running wheel direction of the grate trolley frame. When only the running wheel running direction is provided with the grate trolley in the sterilizing pot, a gap is provided between adjacent grate trolleys.

[0015] A stopper is provided on one side or both sides of the two opposite sides of the grate trolley frame. When a grate trolley is provided on the side of the running direction of the running wheel in the sterilizing pot, a gap is provided between adjacent grate trolleys.

[0016] A combination of a grate and a grate trolley for improving the sterilization effect of a sterilizer, wherein the grate is the grate described above, and the grate trolley is the grate trolley described above.

[0017] Compared with the existing technology, the utility model provides a grate, a grate trolley and a combination thereof for improving the sterilization effect of the sterilization pot. By changing the structure of the grate and the grate trolley, the uniformity of the heat distribution of the sterilization pot is improved, and the sterilization effect of the product is improved, so as to achieve the purpose of reducing the number of spoilage cases per ten thousand tons of product after sterilization, and also improve the consistency of the sterilization strength, color, taste, flavor and organizational structure of the sterilized product. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the existing grate structure.

[0019] Figure 2 It is a structural diagram of the existing grates when they are stacked up and down.

[0020] Figure 3 It is a structural schematic diagram of three existing grate cars that are closely adjacent to each other without any gap.

[0021] Figure 4 It is a structural schematic diagram of the horizontal sterilizing pot of the utility model.

[0022] Figure 5 It is a schematic diagram of the improved grate structure of the utility model.

[0023] Figure 6 It is a schematic structural diagram of the improved grates of the utility model when they are stacked up and down.

[0024] Figure 7 It is a structural diagram of the improved grate car.

[0025] Figure 8 It is a schematic structural diagram of three adjacent grate carts in a pot after improvement of the utility model.

[0026] Figure 9 Schematic diagram of the steam diffusion pipe end plugging and opening structure.

[0027] Figure 10 Schematic diagram of the structure of the front view and top view of the steam diffusion tube, A is the front view and B is the top view.

[0028] Figure numerals: pot body 1, grate car 2, frame 20, walking wheel 21, support frame 22, limit block 23, circulation pump 3, grate 4, gap 5, block 6, hot water spray pipe 7, cold water spray pipe 8, steam diffusion pipe 9, steam hole 10, gripper 11, support frame 12, limit device 13. DETAILED DESCRIPTION

[0029] like Figures 4-10 As shown, a method for improving the sterilization effect of the retort is to increase the area for the heat transfer medium to pass between the upper and lower layers of the grates, and to increase the area for the heat transfer medium to pass between the grate carts;

[0030] The steam holes on the steam diffusion pipe should be horizontal and evenly distributed;

[0031] Make the power of the circulation pump sufficient to ensure that the hot water in the sterilizer circulates once for 3-4 minutes;

[0032] Reduce scale residue in pipes;

[0033] During the heating process before sterilization, when the temperature measuring device determines that the temperature in the pot has reached the sterilization temperature, the time t1 for introducing steam is calculated, and the time t2 for continuing to introduce steam is 10%-15% of t1, and then the constant temperature stage is entered for sterilization.

[0034] The total opening area of ​​the bottom and sides of the grate accounts for more than 30%; the total opening area of ​​the sides of the grate accounts for 20%-23%.

[0035] When the temperature measuring device detects that the temperature in the pot rises to a certain temperature difference of the sterilization temperature, the steam introduction mode is changed from continuous introduction to pulse introduction until the sterilization temperature is reached, and the currently set temperature difference is adjusted to 1°C;

[0036] Take the time t1 required for the duration of the heating stage of each pot and the lowest temperature of the temperature probe to reach the lower limit of the process constant temperature (i.e. sterilization temperature), and take the average value t10 of t1 of different pots. At this time, t2 is 10%-15% of t10. Therefore, the minimum heating time t= (t10+t2) required for similar products to reach the constant temperature (i.e. sterilization temperature) can be limited. During the heating process of similar products, when steam is introduced for heating, the sterilization temperature and the minimum heating time t are used as indicators respectively. Only when both are reached at the same time, the constant temperature stage is entered for sterilization.

[0037] The temperature measuring device may be an existing conventional temperature detection device, such as a temperature detection probe or an automatic temperature recorder probe.

[0038] A horizontal sterilizing pot includes a pot body 1, a grate trolley 2 and a circulation pump 3. A hot water spray pipe 7 is provided above the pot body 1, and a cold water spray pipe 8 and a steam diffusion pipe 9 are provided below. The hot water spray pipe 7, the cold water spray pipe 8 and the steam diffusion pipe 9 are respectively provided with spray holes. The grate trolley 2 is equipped with grates 4. After the grates 4 are stacked up and down, there is a gap 5 between the sides of the upper and lower grates 4. The gap cannot allow the sterilized product on the grates to escape from the gap.

[0039] There is a gap between adjacent grate carts 2.

[0040] By providing a stopper 6 on the side of the grate car 2, a gap is provided between adjacent grate cars.

[0041] The gap is 3cm-6cm.

[0042] One side or both sides of the two relative sides of the grate car 2 are provided with a stopper 6 so as to leave a gap between the adjacent grate cars.

[0043] Specifically, the grate cart 2 includes a frame 20 and running wheels 21. The frame 20 is provided with a support frame 22 for placing the grate. The side of the support frame is provided with a limit block 23, and a gap is provided between adjacent grate carts 2. The side of the support frame is provided with a limit block 23, so that after the grate is placed on the support frame 22, the grate can be prevented from shifting. Preferably, the support frame is a rectangular frame, and the four sides of the rectangular frame are provided with a limit block 23 to prevent the grate from shifting in all directions.

[0044] The front and / or rear of the grate trolley 2 frame running wheel 21 direction are provided with a stopper 6. When two or more grate trolleys are provided in the running wheel running direction in the sterilizing pot, a gap is provided between adjacent grate trolleys.

[0045] When only the front or the rear is provided with the stopper 6, the length of the stopper is 3cm-6cm. For example, it can be 5cm.

[0046] One side or both sides of the two sides relative to the grate trolley 2 frames are provided with a stopper 6. When two or more grate trolleys are provided on the side of the running wheel 21 direction of travel in the sterilizing pot, a gap is provided between adjacent grate trolleys.

[0047] When only one side is provided with the stopper 6, the length of the stopper is 4cm-6cm. For example, it can be 5cm.

[0048] For cod fish intestines with a diameter of 1.1 cm to 1.2 cm, the gap 5 formed between the sides of the upper and lower layers of the grate 4 is 0.5 to 1.1 cm, preferably 1 cm.

[0049] The side of the grate 4 is provided with holes, the holes are ≥ three rows of holes, and the aperture centers are arranged in an equilateral triangle.

[0050] The power of the circulation pump 3 is sufficient to ensure that the hot water in the sterilizer circulates once for 3-4 minutes; the spray holes of the hot water spray pipe 7 should be evenly distributed, and the total cross-sectional area of ​​the spray holes of the hot water spray pipe 7 should be ≤ the cross-sectional area of ​​the outlet pipe of the circulation pump 3; the total cross-sectional area of ​​the spray holes of the cold water spray pipe 8 should be ≤ the cross-sectional area of ​​the inlet pipe of the circulation pump 3; the cold water spray pipe 8 at the bottom of the sterilizer is provided with a filter at the water inlet inside the pot body (this pipe serves as a cold water supply pipe and a water extraction pipe in different sterilization stages); the circulation pump is provided with an operation indicator device, which is a flow meter, an indicator light or an ammeter.

[0051] The spray holes of the steam diffusion pipe 9 should be horizontal and evenly distributed.

[0052] The steam diffusion tube 9 of the horizontal sterilizer extends to the entire length of the bottom of the sterilizer; the number and aperture size of the nozzle holes of the steam diffusion tube 9 meet the requirement that the total opening area (number of holes * area of ​​a single hole) is equal to 1.8-2.0 times the minimum cross-sectional area of ​​the steam inlet pipeline connected to the steam diffusion tube 9. The number and aperture size of the openings can be adjusted according to actual conditions; both ends of the steam diffusion tube 9 are blocked, and holes are evenly distributed on the blockage.

[0053] The heating method of the sterilization pot is to first spray hot water (which can be hot water from the hot water pipeline) through the hot water spray pipe 7 above the pot, and then input steam through the steam diffusion pipe 9 below the pot to heat the water in the pot. While the steam is being introduced, the water heated by the steam is drawn out from the cold water spray pipe 8 below the pot, and after the action of the circulation pump, it re-enters the pot through the hot water spray pipe 7 above the pot for circulation. When the temperature measuring device determines that the temperature in the pot reaches the sterilization temperature, the heating time of the steam is calculated, and the time for continuing to introduce steam is 10%-15% of the heating time, and then enters the constant temperature stage for sterilization.

[0054] Constant Temperature Stage: Circulating pump 3 remains on, and when the temperature inside the pot is lower than the sterilization temperature as measured by the temperature measuring device, steam is introduced. When the temperature inside the pot is equal to the sterilization temperature, steam is stopped to maintain a constant temperature. During the constant temperature stage, the circulating pump remains on to promote uniform temperature at all locations.

[0055] After sterilization is completed, cold water is fed into the cold water spray pipe 8 from the bottom in the pot through the cold water line to cool down, and the hot water spray pipe 7 from the top in the pot is drained simultaneously. Now, drainage can be reused by the hot water recovery pipeline.

[0056] After the constant temperature is over, it will enter the replacement and recovery stage. Cold water is injected from the cold water pipe below, and hot water (above 100℃) is pushed out from the hot water spray pipe above by pressure. It enters the hot water recovery tank through the hot water recovery pipeline and the temperature is maintained at 80-90℃. After treatment, it is injected into the sterilizer through the hot water spray pipe 7 as hot water to perform the next batch of sterilization. When the temperature probe detects that the water temperature in the pot is below 40℃, the replacement ends and the hot water is no longer recovered. Instead, the product is cooled by the existing water in the pot. This stage is the soaking stage. After cooling, drainage begins. The discharged water will be treated and enter the cooling tower for storage and cooling for the next batch of use.

[0057] The utility model provides a grate, a grate trolley and a combination thereof for improving the sterilization effect of a sterilizer. By changing the structure of the grate and the grate trolley, the uniformity of heat distribution in the sterilizer is improved, the sterilization effect of the product is improved, and the purpose of reducing the number of spoilage cases per 10,000 tons of product after sterilization is achieved. The sterilization strength, color, taste, flavor and consistency of the organizational structure of the sterilized product can also be improved.

[0058] The utility model provides a method for improving the sterilization effect of a sterilizer and a horizontal sterilizer, which improves the uniformity of heat distribution in the sterilizer, so that the sterilization effect of products sterilized in the improved sterilizer is more consistent, the sterilization strength, color, taste, flavor, and consistency of the organizational structure of the products are improved, and the number of spoilage cases per 10,000 tons of products is reduced by more than 30%.

[0059] The present invention is described in detail below with reference to specific embodiments. It is necessary to point out that the present embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Technical personnel skilled in the art can make some non-essential improvements and adjustments based on the contents of the present invention.

[0060] Horizontal sterilizer improvement plan:

[0061] By reviewing relevant domestic and international data, and considering equipment safety and the company's actual production situation, we propose a retort improvement plan while minimizing major changes to the retort hardware and maintaining existing production capacity. This plan is divided into the following six parts:

[0062] Part 1 Factors affecting the uniformity of heat distribution in sterilizers

[0063] Part 2: Use a circulation pump with appropriate flow

[0064] The third part is to increase the ratio of the opening area on the side of the grate

[0065] Part 4: Optimizing the layout of steam nozzles in steam diffusion pipes

[0066] Part 5: Reducing scale residue in pipes

[0067] Part 6 introduces the concept of "minimum temperature rise time (mCUT)"

[0068] Part 1 Factors affecting the uniformity of heat distribution in sterilizers

[0069] A retort is a sealed container that heats sealed packages to a specific temperature and maintains it for a specific period of time. The sterilization process involves heat transfer, and with heat transfer comes heat transfer lag, which results in temperature differences. If a location within the retort takes 15 minutes to reach the sterilization temperature, the product at that location will require 15 minutes less sterilization time than products at other locations. This means that under the same sterilization conditions, the sterilization intensity at that location will be much lower than at other locations, posing a potential safety risk. Therefore, measuring the uniformity of heat distribution in retorts is crucial. This testing is particularly important for newly installed retorts and refitted sterilization equipment. Only retorts with uniform heat distribution can meet the requirements of the sterilization process.

[0070] The main factors affecting the heat distribution of the sterilizer are summarized as follows:

[0071] 1. Initial temperature of the product

[0072] The initial product temperature refers to the temperature of the product contents when the retort begins heating. A higher initial product temperature allows the product to reach the sterilization temperature quickly. However, a lower initial product temperature may cause the core temperature of a heat-conductive product, which heats up more slowly, to still be far below the sterilization temperature by the time the retort's ambient temperature reaches the sterilization temperature. These different initial product temperatures upon entering the retort result in different amounts of heat being absorbed to reach the constant temperature (i.e., the sterilization temperature), ultimately affecting the uniformity of heat distribution within the retort.

[0073] 2. How to place the product during sterilization

[0074] The placement of products during sterilization is crucial, as it affects the contact between the products and the heat transfer medium within the retort, and thus the heat transfer efficiency between the medium and the products. The same product placed in one layer versus three layers will experience different sterilization intensities. The more products loaded, the closer the contact between them, which in turn affects heat transfer between the heat transfer medium and the products, leading to "cooked" products, which ultimately affects the uniformity of heat distribution within the retort.

[0075] 3. Steam Diffusion Design

[0076] Steam diffusion is accomplished through a steam diffusion pipe (steam pipe for short). The steam pipe refers to the extension of the steam inlet pipe inside the retort, located at the bottom of the retort, and is usually formed by drilling holes in the steam input pipe.

[0077] Steam is the primary heat source for retorts. Therefore, products located far from the steam outlet experience slower heat transfer, which can lead to insufficient sterilization and the risk of spoilage after entering the market. Products located closer to the steam outlet experience faster heat transfer, potentially leading to overcooking. Uniform heat distribution throughout the retort is a hallmark of uniform steam distribution.

[0078] 4. Type of heat transfer medium for sterilization

[0079] There are many different types of retorts, and the heat transfer media used for sterilization include steam, hot water, superheated water, steam / water mixtures, and steam / water / air mixtures. The retorts currently used by companies primarily complete the sterilization process by introducing steam into 80-90°C hot water, continuously raising the water temperature until it reaches the specified sterilization temperature (>100°C). Water with a temperature exceeding 100°C is called superheated water, indicating that superheated water is currently the heat transfer medium used in the sterilization process. Low-acid flexible packaging products are generally sterilized using superheated water as the heat transfer medium because these products are sensitive to expansion but not pressure, while steam-based sterilization methods can easily cause the product casings to rupture.

[0080] 5. Fluidity of heat transfer medium

[0081] The shortcomings of sterilization using superheated water as a heat transfer medium are also significant. Because water has a lower thermal enthalpy (the heat of 6 kg of superheated water at 121°C is equivalent to the heat of 1 kg of saturated steam), its flow rate is slower than that of steam. The flow rate of hot water determines the heat transfer effect. Therefore, the larger the total open area of ​​the product loading container (such as the grate) in the retort, the more superheated water, acting as the heat transfer medium, flows through the grate, improving heat flow, speeding up heat transfer, and improving heat distribution uniformity. Of course, this also depends on the flow rate and head of the circulating pump.

[0082] Part 2: Use a circulation pump with appropriate flow

[0083] Because superheated water has a low thermal enthalpy, it is particularly important to increase its flow direction and speed to compensate for its low thermal enthalpy.

[0084] 1. Theoretical Basis

[0085] Good flowability of the heat transfer medium (such as superheated water) within the retort is essential for uniform heat distribution, and the circulation pump is the primary device ensuring this fluidity. A review of relevant domestic standards revealed no specific regulations for the power and flow rate of retort circulation pumps. Further discussions with retort manufacturers revealed a gap in domestic standards in this area.

[0086] 2. Data Analysis

[0087] For example, a retort contains approximately 2.7 cubic meters of water. The original circulating pump has a power of 2.2 kW, a head of 28 meters, and a flow rate of 11.7 cubic meters per hour. Therefore, the circulating pump requires approximately 14 minutes to circulate all the water in the retort. In practice, this smoothness is further reduced by obstructions such as grates and product.

[0088] 3. Improvement Plan

[0089] The optimal power of the circulation pump should be able to circulate the water in the retort approximately every 4-5 minutes. Based on the current product loading conditions in the retort, an additional 10% safety margin is added to the 4-5 minute cycle. In theoretical calculations, the water cycle time is set at 3.5 minutes (0.058 hours). Assuming the pump head matches the operating pressure in the retort, the circulation pump flow rate should be at least 46.5 cubic meters per hour (2.7 cubic meters per 0.058 hours).

[0090] In addition, wear or damage to the circulation pump and scale generation in the circulation pipe may affect the sterilizer water circulation system.

[0091] 1. The spray holes of the spray pipe should be evenly distributed, and the total cross-sectional area of ​​the spray holes should not be larger than the cross-sectional area of ​​the pump outlet pipe to ensure that each spray hole has a certain pressure;

[0092] 2. A filter should be installed at the water outlet at the bottom of the pot to prevent debris from entering the water circulation system;

[0093] 3. The circulating pump should have an operation indicator (such as a flow meter, indicator light, ammeter, etc.) to alert the operator.

[0094] The third part is to increase the ratio of the opening area on the side of the grate

[0095] The grate, which serves as the container for product in the retort, is made of perforated stainless steel. During the sterilization process, water flows through these openings, completing the heat transfer process. Therefore, the size and number of openings are particularly important. In theory, we use the concept of "total open area ratio"—the ratio of the cross-sectional area of ​​all openings to the total plate area—to quantitatively calculate the smoothness of water flow within the retort.

[0096] 1. Theoretical Basis

[0097] To ensure adequate water flow within the sterilizer, both my country and the US FDA have established regulations for the total open area percentage of containers (such as grates) used to hold product during sterilization. my country's national standard, "Good Manufacturing Practice for Canned Food Enterprises" (GB / T20938-2007), stipulates that the total open area percentage should be no less than 36%. The "Test Procedure for Heat Distribution in Food Thermal Sterilization Equipment" (GB / T39948-2021) stipulates that when hot water is used as the heat transfer medium for sterilization, the total open area percentage should be no less than 30%. The National Food Processors Association (NFPA) Bulletin 26-L stipulates a minimum requirement: for a 25.4mm (1-inch) hole diameter, the center-to-center distance between adjacent holes should be 50.8mm (2 inches). At this point, the total open area percentage of the total area is approximately 20%-23%. The holes are arranged using the corners of an equilateral triangle as the center of the circle.

[0098] 2. Data Analysis

[0099] like Figure 1-Figure 3 As shown, currently, across the industry, products are arranged in multiple layers horizontally within the grate, almost completely covering the small holes at the bottom of the grate. As a result, hot water has difficulty entering the grate through these holes, and instead primarily enters through the small holes on the sides and the top grate cover of the grate cart, resulting in poor hot water flow within the pot. Therefore, calculating the percentage of total open area at the bottom of the grate is meaningless, and the percentage of total open area on the sides must be recalculated in real production scenarios.

[0100] By measuring the grate and aperture sizes, it was calculated that the total open area of ​​the four sides of a grate accounts for 10.89%, the total open area of ​​a grate cart (8 grates stacked up and down) accounts for (4 sides + the top grate cover) is 11.73%, and the total open area of ​​three grate carts (closely connected without gaps) accounts for (4 sides + the top three grate covers) is 11.91%, all of which are lower than the 20%-23% specified in the National Food Processors Association (NFPA) 26-L Bulletin.

[0101] 1. A grate is 103 cm long, 81.2 cm wide, and 10 cm high. The diameter of the holes is 1.2 cm. The area of ​​one hole is (1.2 / 2). 2 ×π=1.13cm 2 There are 56 small holes on one side with a grip 11 (the grips are holes on opposite sides of the grate that allow fingers to reach in and grab the grate, making it easier to lift the grate). There are 80 small holes on the side without a grip, for a total of 272 small holes (56×2+80×2=272). The grips are 9cm long and 2.6cm high, with a total of 4 grips on the two sides, and the grips also have holes. The general appearance of the grate is shown below. Figure 2 :

[0102] The total area of ​​the four sides of a grate is: 103×10×2+81.2×10×2=3684cm 2 The total opening area of ​​the four sides of a grate is: 272×1.13+9×2.6×4=400.96cm 2 , the proportion of total opening area: 400.96 / 3684×100%=10.89%;

[0103] 2. A grate cart (8 grates stacked up and down) has a side length of 103cm, a width of 81.2cm, and a height of 80cm. The grate cover has 1090 holes, and each grate has 272 holes on its four sides, for a total of 3266 holes (1090 + 272 × 8 = 3266). It also has 32 handles. See below for a general description of a grate cart. Figure 3 :

[0104] The total area of ​​1 grate car with 4 sides and 1 grate cover is:

[0105] The sum of the total area of ​​the four sides of each grate × 8 grates + 1 grate cover area, that is, 3684 × 8 + 103 × 81.2 = 37835.6 cm 2 ;

[0106] The total opening area of ​​1 grate car's 4 sides + 1 grate cover is: the sum of the opening areas of each grate's 4 sides × 8 grates + 1 grate cover opening area, that is, 400.96 × 8 + 1090 × 1.13 = 4439.38 cm 2 ;

[0107] The proportion of total opening area is: 4439.38 / 37835.6×100%=11.73%.

[0108] 3. Three grate carts (closely connected without gaps) have a side length of 309cm, a width of 81.2cm, and a height of 80cm. One grate cover has 1090 small holes and a total of 96 grips. The general situation of the three grate carts (closely connected without gaps) is shown below. Figure 4 :

[0109] The total number of small holes on 3 grate carts (closely connected without gaps) is: the number of small holes in 1 grate cover × 3 grate covers + the number of small holes on the side of each grate with a grip × 48 sides + the number of small holes on the side of each grate without a grip × 16 sides, that is, 1090 × 3 + 56 × 48 + 80 × 16 = 7238;

[0110] The total area of ​​the four sides of three grate carts (closely connected without gaps) + the three grate covers is: the area of ​​one side of each grate with a grip × 48 sides + the area of ​​one side of each grate without a grip × 16 sides + the area of ​​the three grate covers, that is, 103 × 10 × 48 + 81.2 × 10 × 16 + 103 × 81.2 × 3 = 87522.8 cm 2 ;

[0111] The total opening area of ​​the 4 sides of the 3 grate carts (closely connected without gaps) + 3 grate covers is: total number of small holes × area of ​​each small hole + total number of grips × area of ​​each grip, that is, 7238 × 1.13 + 96 × 9 × 2.6 = 10425.34 cm 2 ;

[0112] The proportion of total opening area is: 10425.34 / 87522.8×100%=11.91%.

[0113] 3. Improvement Plan

[0114] 1. The side of the grate is changed from two rows of holes to three rows of holes, and the centers of the holes are arranged in an equilateral triangle.

[0115] 2. Compared with the existing grate, keep the height of the four corner supports of the new grate unchanged, and reduce the height of the four sides of the grate by 1 cm, so that a 1 cm gap is formed between the grates after stacking.

[0116] The schematic diagram of the new grate is as follows Figure 5 : 1cm height is removed from the upper ends of the four sides of the grate, and the height is retained unchanged only at the four corners or a certain length near the four corners to form a support frame 12. The certain length near the four corners is 1 / 20-1 / 8 of the length of each side, or 1cm-5cm, to ensure that the height of the four corner supports of the new grate remains unchanged. The angle on both sides of the support frame 12 is the angle between the two adjacent sides of the connected grate, so that a 1cm gap is formed between the sides of the upper and lower grate layers after the upper and lower grate layers are stacked.

[0117] In this way, one grate can add 136 small holes (56 on the two sides with grips 11 and 80 on the two sides without grips), which can increase the opening area by 136×1.13=153.68cm 2 , alleviating the problem of low heat transfer efficiency caused by too many products placed in the grate.

[0118] The height is set at 1cm mainly to minimize the possibility of products escaping from the grate and falling into the pot during the sterilization process. The specific calculation is as follows:

[0119] Currently, the smallest product in the company is 10g. This product has a casing width of 44mm and a 6-8mm edge width. Using the formula π × d + edge width = casing width, the product diameter is calculated to be between 1.1cm and 1.2cm. Designing the saw cut width (1cm) to be smaller than the smallest product diameter ensures that the product does not escape from the grate during sterilization, minimizing economic losses.

[0120] According to the above dimensions, cut notches on the top of the four sides of the grate, i.e., remove 1mm of height from the top of the four sides of the grate, leaving only a certain length at the four corners to form support frames 12, which can increase the opening area by about 300cm 2 , to alleviate the serious unevenness of the heat distribution test in the middle layer of the grate car.

[0121] Through 1 and 2, one grate can increase the opening area by 453.68cm 2 , increasing the total opening area from the current 10.89% to 23.18%; one grate car can increase the opening area by 3630.48cm 2 , increasing the total opening area from the current 11.73% to 21.33%; 3 grate cars (closely connected without gaps) can increase the opening area by 7201.92cm2 , increasing the proportion of total open area from the current 11.91% to 20.15%, basically meeting the 20%-23% requirement stipulated in the 26-L Bulletin of the National Food Processors Association (NFPA).

[0122] The outer side of the grate is provided with a limiter 13, which can prevent the upper grate from misaligning with the lower grate when the grates are stacked up and down, and also facilitates the alignment of the upper and lower grates when the grates are stacked up and down. In particular, it can be set on the outer side of the four corners of the grate. In this case, the limiter can be V-shaped, right-angled or "∟" shaped.

[0123] 3. If Figure 7 A stopper 6 such as an iron stop is installed on the side of the grate car base without a grip, so that there is a certain gap between the cars after the grate cars enter the pot, which is convenient for enhancing the fluidity of the heat transfer medium between the cars and alleviating the serious unevenness of the heat distribution test of the second car in the middle. Figure 8 :

[0124] Taking the widely used brand A and brand B autoclaves as an example, the corresponding measured lengths of their grate car tracks are as follows:

[0125] Sterilizer brand Length of grate track in pot (cm) The remaining length of the track after 3 grate carts are put into the pot (cm) Brand A 316 13 Brand B 325 16

[0126] As shown in the table above, after three grate carts are fully loaded in a Brand A retort, 13cm of track space remains, while after three grate carts are fully loaded in a Brand B retort, 16cm of track space remains. This provides sufficient track length to accommodate the additional stoppers 6 installed on the grate bases. Installing the stoppers on only one side of two carts, or on both sides of the middle cart, will ensure a gap between adjacent compartments within the retort. The stoppers can be designed to be approximately 5cm (<13 / 2 = 6.5, ensuring safety margin). Based on the improved grate design, installing the stoppers on the grate cart frames increases the total open area of ​​the three carts from 20.15% for seamless, adjacent carts to 21.33% for three separate, non-adjacent carts. Furthermore, the addition of the stoppers enhances the fluidity and velocity of hot water between carts, improving heat transfer and further enhancing heat distribution uniformity.

[0127] According to the above three specific improvement measures in this section, it is recommended to open holes on the side of the grate and install blocks of appropriate length on the grate cart frame, rather than installing blocks on the entire length of the side of the grate cart frame. It is best to install them only in the middle part, so as to increase the fluidity of the heat transfer medium between the carts and improve the uniformity of heat distribution.

[0128] Part 4: Optimizing the layout of steam nozzles in steam diffusion pipes

[0129] Current sterilizers all use steam as a heat source, so the steam supply to the sterilizer must be sufficient at all times to ensure that the sterilizer has sufficient heat and even heat distribution.

[0130] 1. Theoretical Basis

[0131] A steam diffusion tube (steam tube for short) must be installed at the bottom of the horizontal sterilizer and run through the entire length of the sterilizer.

[0132] Considering that high-temperature steam spraying directly on the casing will cause the casing to deform, the steam holes of the steam pipe should be horizontal and evenly distributed.

[0133] 2. Improvement Plan

[0134] ①The steam diffusion pipe of the horizontal sterilizer should extend to the full length of the bottom of the pot so that the steam pipe fully covers all the grate cars, as shown in the schematic diagram. Figure 8 As shown:

[0135] ② The number and diameter of the steam pipe spray holes should meet the requirement that the total opening area (number of holes * area of ​​a single hole) is approximately 1.9 times the minimum cross-sectional area of ​​the steam inlet pipe;

[0136] ③ Considering that direct injection of high-temperature steam into the casings may cause deformation of the casings, the steam holes of the steam pipe should be horizontal and evenly distributed.

[0137] ④ Such as Figure 9 As shown, both ends of the steam pipe are blocked, and four steam holes 10 are drilled respectively.

[0138] The front view and top view of the steam diffusion tube are as follows Figure 10 shown.

[0139] Part 5: Reducing scale residue in pipes

[0140] Thermal sterilization of food is near the end of the food processing process. If uneven heat distribution is discovered during sterilization, or if equipment malfunctions midway through, the resulting losses are immeasurable. The best way to prevent unexpected events during the thermal sterilization process, such as uneven heat distribution, is to establish a preventive maintenance program. Don't wait until the equipment becomes truly "ill" and stops functioning before conducting a "diagnosis" of the retort. For hydrothermal retorts, one of the most important preventive maintenance steps is regular descaling. Scale buildup in pipes impedes hot water circulation within the retort, so reducing this residual scale is crucial.

[0141] 1. Theoretical Basis

[0142] After the equipment has been running for a period of time, scale will form in the pot (related to the water quality and frequency of use), which will seriously affect the sterilization effect and lead to incomplete sterilization. Generally, it needs to be cleaned once every three months. If the water hardness is high and the frequency of use exceeds 8 hours a day, it should be cleaned once a month.

[0143] Scale is mostly composed of alkaline substances such as calcium ions (CaCO3) and magnesium ions (MgCO3). Acids are generally effective for cleaning, but be careful not to use hydrochloric acid, as chloride ions can corrode stainless steel (even 304 and 316 stainless steel). Nitric acid was previously commonly used, but safety and environmental considerations require consideration. Therefore, weaker acids such as oxalic acid, phosphoric acid, and even citric acid are recommended. Currently, many descaling agents are corrosion inhibitors, a mixture of various chemical reagents. They are less corrosive to metals, inexpensive, and effective, but descaling takes longer and is not as fast as acidic descaling. However, they are still less corrosive to metals.

[0144] 2. Improvement Plan

[0145] Make the following suggestions:

[0146] 1. Cleaning method

[0147] ① When cleaning for the first time or when the oil stain is heavy, first circulate 1%-2% caustic soda (sodium hydroxide solution) at 70-85℃ for 15-30 minutes. Then circulate clean water for 5 minutes.

[0148] ② Use 1%-3% weak acid solution at 80-85℃, circulate for 40-60 minutes, then add water and circulate for 5 minutes;

[0149] ③The concentration of washing liquid and time should be adjusted according to the degree of oil stains and scale.

[0150] 2. Cleaning precautions

[0151] ① The soda mixer of the full-water sterilizer is most likely to be scaled, so it is best to remove it and check and clean it again after cleaning;

[0152] ②The filter elements or filters of steam and cold water pipes should be replaced regularly;

[0153] ③ If there is less oil on the pot, you can directly use acidic detergent;

[0154] ④ Keep abreast of and master the latest descaling technologies, such as using an automatic electronic descaling device for descaling. The electronic descaling device uses the main unit to generate an electromagnetic field to treat the water quality, creating a resonance effect that breaks up the original large molecular clusters of water and decomposes them into highly active single molecules or small molecular clusters of water, thereby changing the physical structure and properties of the water, enhancing the polarity of the water molecules, increasing the dipole moment of the water molecules, and improving the water molecules' ability to dissolve scale-forming components such as calcium and magnesium ions and carbonate ions, thereby preventing scale formation. At the same time, under the action of the high-frequency electromagnetic field, the original scale crystals gradually become soft, fall off, and dissolve, thereby achieving the purpose of descaling. Currently, there are electronic descaling devices, pipeline descaling devices and other equipment on the market;

[0155] ⑤ It is recommended to formulate a practical and feasible standard operating procedure for descaling the autoclave after full consultation with the autoclave manufacturer.

[0156] Part 6 introduces the concept of "minimum temperature rise time (mCUT)"

[0157] Ramp-up time refers to the time it takes from the moment steam enters the closed retort until it reaches the designated sterilization temperature. If the steam supply during the ramp-up phase is insufficient, even if the sterilization process enters the constant temperature phase and the ambient temperature reaches the designed constant temperature, the core temperature of the product will take a long time to reach the sterilization temperature. This is like an airplane failing to reach the designated altitude due to insufficient power during takeoff, resulting in mission failure. The introduction of the "minimum cut time (mCUT)" concept allows the retort to accumulate additional heat during the ramp-up phase, which promotes uniform heat distribution.

[0158] 1. Theoretical Basis

[0159] For sterilizers that use hot water as the heat transfer medium, since the thermal enthalpy of hot water is not as high as that of steam, the heat transfer speed during sterilization is not as fast as steam, and the temperature inside the sterilizer is not easy to reach uniformity, so a reasonable heating time needs to be specified.

[0160] 2. Improvement Plan

[0161] Based on the existing sterilization process, it is recommended to introduce the concept of "minimum temperature rise time t (mCUT)" into the product processing procedures and establish it as one of the redline parameters in the sterilization process. After completing the hardware modification of the retort, this includes using a circulation pump with appropriate flow rate, increasing the area ratio of the grate side openings, optimizing the layout of the steam diffusion pipe nozzles, and reducing residual scale in the pipes. By analyzing the results of thermal distribution tests on the retort, during the temperature rise process before sterilization, when the temperature measuring device determines that the temperature inside the pot has reached the sterilization temperature, the steam is introduced for a time t1, and the steam is continued for a time t2 of 10%-15% of t1. After that, the sterilization enters the constant temperature stage. This stage achieves a more effective sterilization effect, reducing the number of spoilage cases per 10,000 tons of product. It also improves the consistency of the sterilization intensity, color, taste, flavor, and texture of the sterilized product.

[0162] To facilitate standard control, we take the duration of each heating phase and the time t1 required for the lowest temperature of the temperature probe to reach the lower limit of the process constant temperature (i.e., sterilization temperature). We then take the average value t10 of t1 across different batches. At this point, t2 is 10%-15% of t10. This allows us to define the minimum heating time t = (t10 + t2) required for similar products to reach the constant temperature (i.e., sterilization temperature) after steam is introduced. Therefore, when heating similar products with steam, the sterilization temperature and the minimum heating time t are used as indicators. Steam heating is stopped only when both are reached simultaneously, ensuring uniform temperature within the retort.

[0163] The reason why we wait until the hardware modification of the sterilizer is completed before considering this part of the improvement measures is that the minimum heating time calculated is the shortest after the heat distribution uniformity of the sterilizer is greatly improved through other methods. In this way, without touching the safety red line of special high-voltage equipment, after the hardware has made the greatest improvement efforts, the heat distribution uniformity of the sterilizer can be further improved from the software perspective, and the overall sterilization process time can be compressed as much as possible, reducing the impact on production capacity.

[0164] Improved results:

[0165] The positive impact of the improved retorts is primarily reflected in four key areas: First, heat distribution is more uniform. 381 retorts after the improvements were tested according to the national standard "Test Procedure for Heat Distribution of Food Thermal Sterilization Equipment" (GB / T 39948-2021), and all met the standards. Second, the number of spoilage cases per 10,000 tons decreased by over 30% year-on-year. Third, the sensory quality of products at different positions within the retort has improved. 225 tasters from 15 factories conducted blind evaluations of over 227 high-temperature meat products sterilized in retorts before and after the improvements. By comparing the color, texture, and flavor of products at different positions within the same retort, the panelists unanimously agreed that the sensory consistency of products at different positions within the retorts was better after the improvements. Fourth, the improved retorts have reduced bag breakage and product dropout, stabilized the pressure within the retort, and reduced vibration during operation, improving safety.

[0166] Deterioration refers to a condition where the product packaging is intact and the contents are completely isolated from the outside world, but the product has become darker, smelly, sour, soft, or bulging. This condition is caused by microorganisms that break down nutrients in the product after sterilization, resulting in abnormalities in the product's inherent quality.

[0167] We use F value to express the sterilization intensity. When the sterilization condition is 108℃ for 30 minutes, the minimum F value in the pot before improvement is 0.87 and the maximum is 2.3. After the improvement, the minimum and maximum are approximately 1.7-2.2.

[0168] Taking the 105g Qingyifang Wangchu chicken sausage (sterilization temperature 108°C) as an example, its optimal color is bright white. Before the improvement, the product near the door and the topmost layer of the grate cart near the end of the pot received the highest sterilization intensity, resulting in a dark white color. The product at the bottom and middle layers near the end of the grate cart received the lowest sterilization intensity, resulting in a bright white color. The color of the remaining products ranged between dark white and bright white. After the improvement, the product near the door and the topmost layer of the grate cart near the end of the pot received the highest sterilization intensity, resulting in a slightly brighter color than dark white. The product at the bottom and middle layers near the end of the grate cart received the lowest sterilization intensity, still a bright white color. The difference between the darkest and lightest products in the retort after the improvement is smaller than before, indicating better consistency.

[0169] The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. It should be pointed out that for those skilled in the art and any technician familiar with this technical field, without departing from the overall concept of the present invention, equivalent replacements or changes based on the technical solution and inventive concept of the present invention, as well as several changes and improvements made, should also be regarded as the scope of protection of the present invention.

Claims

1. A grate for improving the sterilization effect of a retort, with holes opened on the sides and bottom of the grate, characterized in that: The total opening area on the side of the grate accounts for 20%-23%.

2. The grate for improving the sterilization effect of the retort according to claim 1, characterized in that: After the grates are stacked, there is a gap between the sides of the upper and lower grates, and the gap cannot allow the product to be sterilized to escape from the gap.

3. The grate for improving the sterilization effect of the retort according to claim 1, characterized in that: For cod intestines with a diameter of 1.1-1.2 cm, the gap formed between the sides of the upper and lower layers of the grate is 0.5-1.1 cm.

4. The grate for improving the sterilization effect of the retort according to claim 1, characterized in that: The holes on the side of the grate are ≥ three rows of holes, and the centers of the holes are arranged in an equilateral triangle.

5. A grate car for improving the sterilization effect of a retort, characterized by: There is a gap between adjacent grate cars.

6. The grate cart for improving the sterilization effect of the retort according to claim 5, characterized in that: One side or both side surfaces of the two opposite side surfaces of the grate cart are provided with a stopper.

7. The grate cart for improving the sterilization effect of the retort according to claim 5, characterized in that: The grate vehicle comprises a vehicle frame and running wheels. A support frame for placing the grates is provided on the vehicle frame, and a limit block is provided on the side of the support frame.

8. The grate cart for improving the sterilization effect of the retort according to claim 7, characterized in that: A stopper is provided in front of and / or behind the traveling wheel direction of the grate cart frame.

9. The grate cart for improving the sterilization effect of the retort according to claim 7, characterized in that: A stopper is provided on one side or both side surfaces of the two opposite side surfaces of the grate vehicle frame.

10. A combination of a grate and a grate cart for improving the sterilization effect of a retort, characterized by: The grate is the grate described in any one of claims 1 to 4, and the grate cart is the grate cart described in any one of claims 5 to 9.

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