JP2013110995A - Heat sterilization device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an abrupt temperature drop during cooling and delay of temperature control.SOLUTION: The heat sterilization device has a sterilization tank 1 for holding a material to be sterilized, a jet water circulation path 11 that has a heat exchanger 3 halfway and circulates circulation jet water between the sterilization tank 1 and the path, a temperature detector 7 for detecting the temperature of the circulation jet water, and a cooling water amount control valve 6 for controlling a cooling water amount sent for cooling the circulation jet water by the heat exchanger. In the heat sterilization device for controlling the opening of the cooling water amount control valve 6 to lessen a difference between an actual temperature of the circulation jet water and a target temperature when the material to be sterilized is cooled, an operation amount of the cooling water amount control valve 6 for the difference between the actual temperature of the circulation jet water and the target temperature is set to a relatively small amount when the temperature of the circulation jet water is high at the initial stage of cooling step, and an operation amount of the cooling water amount control valve 6 for the difference between the actual temperature of the circulation jet water and the target temperature is set to a relatively large amount when the temperature of the circulation jet water is low at the final stage of cooling step.

Description

  The present invention performs sterilization by heating an object to be sterilized (packaged food) contained in a sterilization tank, and after heat sterilization, the circulating jet water is cooled and sprayed onto the object to be sterilized while being cooled. The present invention relates to a heat sterilization apparatus for cooling a sterilized product.

  As described in Japanese Patent No. 4229420, an object to be sterilized sealed in a sterilization tank is accommodated, and heated circulating jet water is sprayed toward the object to be sterilized in the sterilization tank. Heat sterilizers that sterilize by heating a sterilized product and maintaining it at a sterilization temperature for a predetermined time are widely used. In this heat sterilization apparatus, one end is connected to the bottom of the sterilization tank, and the other end is provided with a circulation pipe connected to an injection nozzle provided in the sterilization tank. The circulating jet water sprayed on the article to be sterilized in the sterilization tank is taken out from the bottom of the sterilization tank to the circulation pipe and is circulated again to be sprayed from the spray nozzle toward the article to be sterilized.

  The operation process of the heat sterilizer includes a heating process in which heated circulating jet water is sprayed onto the article to be sterilized in the sterilizing tank to heat the article to be sterilized, and the circulating jet water in the sterilizing tank is cooled after the heating process. There is a cooling process in which the object to be sterilized is sprayed to cool the object to be sterilized. When cooling the circulating jet water, the temperature may be lowered by mixing normal temperature water in the circulating jet water, but a heat exchanger is installed in the jet water circulation path to lower the circulating jet water temperature by heat exchange. By doing so, water required for cooling can be reduced. In this case, a cooling water circulation path with a cooling tower is installed on the other side of the heat exchanger so that the cooling water is circulated between the heat exchanger and the cooling tower. The circulating jet water can be cooled by discharging it to the outside air.

  If a sudden temperature change is performed during the heating process or the cooling process, the difference between the pressure in the sterilization tank and the pressure in the package becomes large, and the package is damaged due to the difference in expansion. Further, even if it takes more time than necessary by making the change in temperature moderate, the processing time becomes longer and the working efficiency becomes worse. Therefore, it is necessary to control the temperature and pressure to be appropriate. Usually, the elapsed time from the start of operation and the target temperature at that time are set, and heating and cooling are performed while adjusting the temperature so that the detected actual temperature approaches the target temperature.

  Temperature control when heating the circulating jet water can be performed by increasing or decreasing the amount of steam supplied for heating. If the temperature of the supplied steam is constant, temperature control can be easily performed. The temperature of the circulating jet water at the time of cooling is adjusted by installing a bypass pipe for bypassing the heat exchanger in the cooling water circulation path and adjusting the flow rate in the bypass pipe. When the flow rate in the bypass pipe is changed, the flow rate of the cooling water sent from the cooling tower to the heat exchanger changes, and the temperature of the circulating jet water can be controlled by changing the amount of heat taken by the cooling water in the heat exchanger. If the amount of cooling water flowing through the bypass pipe and flowing into the heat exchanger is reduced, the amount of heat absorbed from the circulating jet water by the heat exchanger is reduced, and the temperature drop of the circulating jet water is reduced. Conversely, if the flow rate of the bypass pipe is reduced, the amount of cooling water flowing through the heat exchanger portion increases, so the amount of heat absorbed from the circulating jet water increases, and the temperature drop amount of the circulating jet water increases.

  Circulating jet water temperature control calculates the difference between the target temperature set based on the elapsed time and the actual temperature obtained by actual measurement, and adjusts the opening of the cooling water flow control valve so that there is no difference. Adjust with PID control. By adjusting the opening of the cooling water volume control valve based on the difference from the target temperature, it should be possible to perform cooling along the target temperature line, but in reality, a sudden temperature drop occurs at high temperatures. However, the temperature may not change as expected, for example, it takes time to approach the target temperature at low temperatures.

Japanese Patent No. 4229420

  The problem to be solved by the present invention is that, in the heat sterilization apparatus that cools the sterilized product by lowering the temperature of the circulating jet water during cooling, rapid temperature reduction and temperature adjustment are delayed. It is in providing the heat sterilizer which can prevent.

  The invention described in claim 1 is a sterilization tank for storing an object to be sterilized, a jet water circulation path for circulating circulating jet water between the sterilization tank having a heat exchanger in the middle, and a temperature for detecting the temperature of the circulating jet water. It has a cooling water volume control valve that controls the amount of cooling water sent to cool the circulating jet water with a detector and heat exchanger, and sterilizes by heating the object to be sterilized in the sterilization tank. This is a heat sterilizer that cools the object, and when the object to be sterilized is cooled, the opening of the cooling water amount control valve is controlled so that the difference between the actual temperature of the circulating jet water and the target temperature is small. In the heat sterilizer that adjusts the temperature of the circulating jet water by adjusting the amount of cooling water sent to the heat exchanger, the actual temperature of the circulating jet water and the target temperature are Operating amount of cooling water flow control valve for difference Relatively small amount, when the circulating water jet temperature cooling step telophase, the operation amount of the cooling water amount control valve for the difference between the actual temperature and the target temperature of the circulating water jets is relatively large amounts.

  In the heat sterilization apparatus according to claim 2, a cooling water circulation path for circulating cooling water between the heat exchanger and the cooling tower is installed on the cooling water side of the heat exchanger, and the cooling water circulation path Is characterized in that a bypass pipe for bypassing the heat exchanger is installed and the amount of cooling water sent to the heat exchanger is adjusted by controlling the flow rate in the bypass pipe.

  When the temperature of the circulating jet water at the initial stage of the cooling process is high, the temperature difference between the circulating jet water and the cooling water is large. Therefore, if the amount of cooling water sent to the heat exchanger is changed, the temperature of the circulating jet water is changed. Changes greatly. Conversely, at low temperatures after the cooling process has progressed, the temperature difference between the circulating jet water and the cooling water is small, so even if the amount of cooling water sent to the heat exchanger is changed by the same amount, the temperature of the circulating jet water The amount of change is small. Change the amount of change in the cooling water volume control valve opening for the difference between the target at high temperature and low temperature, decrease the amount of cooling water supply at high temperatures, and increase the amount of cooling water supply at low temperatures Thus, it is possible to perform cooling according to the target at the time of cooling.

  By carrying out the present invention, it is possible to prevent the circulating jet water temperature from rapidly decreasing at a high temperature in the initial stage of the cooling process, and the temperature change of the circulating jet water from being delayed at a low temperature at the end of the cooling process.

Flow diagram of a heat sterilizer embodying the present invention

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a flow diagram of a heat sterilizer embodying the present invention. The heat sterilization apparatus accommodates the article to be sterilized 2 in a cylindrical sterilization tank 1 and sterilizes the article to be sterilized 2 by spraying heated water onto the article to be sterilized 2. One end of the jet water circulation path 11 is connected to the bottom of the sterilization tank 1, and the other end of the jet water circulation path 11 is connected to an injection nozzle 13 provided in the sterilization tank 1. A jet water circulation pump 4 and a heat exchanger 3 are provided in the middle of the jet water circulation path 11, and water taken out from the bottom of the sterilization tank 1 is pressurized by the jet water circulation pump 4 and injected into the sterilized object 2 in the sterilization tank 1. Make sure you do.

  The heat exchanger 3 takes heat from the circulating jet water during the cooling process of the heat sterilizer, and cools the circulating jet water by exchanging heat between the two fluids. On one side of the heat exchanger, circulating jet water circulating between the sterilization tank 1 passes, and on the other side cooling water for releasing heat taken from the circulating jet water passes. A cooling tower 8 for cooling the cooling water is provided on the cooling water side, and a cooling water circulation path 9 for circulating the cooling water between the heat exchanger 3 and the cooling tower 8 is provided. A cooling water circulation pump 10 for circulating the cooling water and a bypass pipe 5 connecting the front and rear of the heat exchanger 3 are installed in the middle of the cooling water circulation path 9. A possible cooling water amount control valve 6 is provided.

  An operation control device 12 for controlling the operation of the heat sterilizer is provided, and the operation control device 12 is connected to each device of the heat sterilizer. The operation of the heat sterilizer includes a heating process for heating and sterilizing the article to be sterilized 2 and a cooling process for cooling the article to be sterilized 2 after the heating process is completed. Both heating and cooling of the object to be sterilized 2 are performed by operating the jet water circulation pump 4 to take out the circulating jet water from the sterilization tank 1 to the jet water circulation path and inject it into the article to be sterilized 2 through the jet water circulation path and the injection nozzle 13. To do.

  In the heating step, steam is supplied to the bottom of the sterilization tank to heat the circulating jet water. The circulating jet water heated at the bottom in the sterilization tank passes through the jet water circulation path 11 by operating the jet water circulation pump 4 and is jetted from the spray nozzle 13 toward the article to be sterilized 2 to heat the article to be sterilized 2. To do. The object to be sterilized 2 is sterilized by heating the object to be sterilized 2 to a predetermined sterilization temperature and maintaining the sterilization temperature for a predetermined time.

When the object to be sterilized is heated in the heating process, the object to be sterilized is hermetically sealed, so that the internal pressure is increased by heating. At this time, the pressure in the object to be sterilized becomes higher than the pressure in the sterilization tank, and if the difference becomes large, the object to be sterilized may be damaged. Therefore, the operation control device 12 adjusts the amount of steam supplied to the sterilization tank 1 and heats it while adjusting the pressure in the sterilization tank and the temperature of the object to be sterilized.
At the time of heating, the elapsed time from the start of operation and the temperature and pressure in the sterilization tank at that time are set, and the steam supply amount is adjusted so as to be a set value.

  When the heating process ends, the process proceeds to a cooling process for cooling the article 2 to be sterilized. Also in the cooling step, the elapsed time and the temperature and pressure in the sterilization tank at that time are set, and the cooling rate is adjusted so that the set value is obtained. In the operation control device 12, the cooling water circulation pump 10 is operated during cooling, and the cooling water is circulated between the heat exchanger 3 and the cooling tower 8. If the circulating jet water of the jet water circulation path 11 is sent to the heat exchanger 3 in this state, heat exchange occurs between the circulating jet water and the cooling water, and the heat of the circulating jet water moves to the cooling water. Since the temperature of the circulating jet water is reduced by heat exchange, when the circulating jet water is injected from the jet nozzle 13 to the article to be sterilized 2, the temperature of the article to be sterilized 2 is lowered.

  Since the cooling water circulates between the heat exchanger 3 and the cooling tower 8, the heat taken from the circulating jet water by the heat exchanger 3 moves to the cooling tower 8, and heat is released into the atmosphere through the cooling tower 8. . The cooling water whose temperature has been reduced by the cooling tower goes to the heat exchanger 3 again. Since the circulating jet water whose temperature has decreased in the heat exchanger 3 has increased in temperature by cooling the article 2 to be sterilized in the sterilization tank 1, the circulating jet water whose temperature has increased in the heat exchanger 3 and Heat exchange is performed again between the cooling water whose temperature has decreased, and heat is transferred from the circulating jet water to the cooling water, thereby cooling the article 2 to be sterilized.

  In the cooling process, if the amount of cooling water sent to the heat exchanger 3 is large, the amount of heat absorbed from the circulating jet water increases, and if the amount of cooling water is small, the amount of heat absorbed from the circulating jet water decreases. The amount of cooling water sent to the heat exchanger 3 can be adjusted by controlling the opening degree of the cooling water amount control valve 6 in the bypass pipe 5. When the opening degree of the cooling water amount control valve 6 is increased, the amount of cooling water passing through the bypass pipe 5 increases, and the amount of cooling water passing through the heat exchanger 3 decreases accordingly. And if the amount of water for cooling which flows through a heat exchanger decreases, the temperature fall of circulating jet water will decrease. Conversely, if the opening degree of the cooling water amount control valve 6 is reduced and the flow rate in the bypass pipe 5 is reduced, the amount of cooling water flowing through the heat exchanger increases, so the temperature drop of the circulating jet water increases.

  In the operation control device 12, the actual temperature of the circulating jet water is detected by the temperature detection device 7 provided in the jet water circulation path 11, and the cooling water amount control is performed so that the target temperature is set corresponding to the elapsed time. The opening of the valve 6 is adjusted to control the cooling water temperature. When controlling the circulating jet water to the target temperature, the difference between the actual temperature detected by the temperature detection device 7 and the target temperature set at that time is calculated, and PID control is performed based on the difference. In the PID control, as the difference between the target temperature and the actual temperature is larger, the opening degree change amount in the cooling water amount control valve 6 is increased, and when the difference is smaller, the opening degree change amount in the cooling water amount control valve 6 is changed. The amount of change in the opening degree of the cooling water amount control valve 6 is set to be different between the actual temperature and the target temperature even when the temperature is high at the beginning of the cooling process and at the low temperature at the end of the cooling process. deep.

  When the temperature of the circulating jet water is high at the initial stage of the cooling process, there is a large difference between the temperature of the circulating jet water and the temperature of the cooling water. Therefore, even if the flow rate of the cooling water sent to the heat exchanger 3 is slightly changed, the temperature of the circulating jet water that changes in the heat exchanger 3 becomes relatively large. On the contrary, when the temperature of the circulating jet water is low at the end of the cooling process, the temperature difference between the circulating jet water and the cooling water becomes small. Therefore, even if the flow rate of the cooling water sent to the heat exchanger 3 is changed by the same amount, the temperature of the circulating jet water that changes in the heat exchanger 3 becomes relatively small. Therefore, when the temperature of the circulating jet water at the initial stage of the cooling process is high, the opening change amount of the cooling water amount control valve 6 is set to be smaller than the difference between the actual temperature and the target temperature. Conversely, when the circulating jet water temperature at the end of the cooling process is low, the opening change amount of the cooling water amount control valve 6 is set to be larger than the difference between the actual temperature and the target temperature.

  If the difference from the target value is the same in the case of normal PID control, the operation amount will be the same. Therefore, when the temperature of the circulating jet water is high, the temperature change of the circulating jet water becomes larger than expected, When the temperature of the circulating jet water is low, the temperature change of the circulating jet water becomes smaller than expected when the temperature of the circulating jet water is low. . However, by carrying out the present invention, it becomes possible to cool along the target temperature throughout the entire cooling process, so that it does not take a long time until a rapid temperature change or the target temperature is reached.

  The present invention is not limited to the embodiments described above, and many modifications can be made by those having ordinary knowledge in the art within the technical idea of the present invention.

DESCRIPTION OF SYMBOLS 1 Sterilization tank 2 Object to be sterilized 3 Heat exchanger 4 Jet water circulation pump 5 Bypass pipe 6 Cooling water amount control valve 7 Temperature detection device 8 Cooling tower 9 Cooling water circulation path 10 Cooling water circulation pump 11 Jet water circulation path 12 Operation control device 13 Injection nozzle

Claims (2)

A sterilization tank that contains the object to be sterilized, a jet water circulation path that circulates the circulating jet water between the sterilization tank with a heat exchanger in the middle, a temperature detection device that detects the temperature of the circulating jet water, and a circulating jet in the heat exchanger Has a cooling water control valve that controls the amount of cooling water sent to cool the water,
It is a heat sterilization apparatus that performs sterilization by heating the object to be sterilized in the sterilization tank, and then cools the object to be sterilized,
When cooling the object to be sterilized, the opening of the cooling water amount control valve is controlled so that the difference between the actual temperature of the circulating jet water and the target temperature is small, and the amount of cooling water sent to the heat exchanger is adjusted. In the heat sterilizer that adjusts the water temperature,
At the high temperature of the circulating jet water at the beginning of the cooling process, the amount of operation of the cooling water flow control valve is relatively small with respect to the difference between the actual temperature of the circulating jet water and the target temperature, and at the low temperature of the circulating jet water at the end of the cooling process, the circulating jet water The heat sterilizer is characterized in that the amount of operation of the cooling water amount control valve with respect to the difference between the actual temperature and the target temperature is relatively large. The heat sterilization apparatus according to claim 1, wherein a cooling water circulation path for circulating cooling water between the heat exchanger and the cooling tower is installed on the cooling water side of the heat exchanger, and the cooling water circulation path has a heat exchanger. A heat sterilizer characterized by adjusting a cooling water amount to be sent to a heat exchanger by installing a bypass pipe that bypasses the flow path and controlling a flow rate in the bypass pipe.

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