JP3839915B2 - Refrigerant cooling device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a refrigerant cooling apparatus, and more particularly, to an apparatus for cooling a refrigerant used as a cooling source for a low temperature reaction such as fine chemical in the chemical industry by heat exchange in a heat exchanger using a low temperature liquefied gas as a cooling source. .
[0002]
[Prior art]
When removing reaction heat generated by a chemical reaction, a refrigerant generally called brine, such as methanol, ethanol, ketone, amine, silicone oil, and organic halide, is circulated and used. Various low-temperature liquefied gases such as liquid nitrogen and liquid air are used as a cooling source for cooling such a refrigerant to a low temperature range that is difficult with a normal refrigerator, for example, −50 ° C. or lower. The refrigerant is cooled to a predetermined temperature by exchanging heat between the refrigerant and the refrigerant using a heat exchanger.
[0003]
Conventionally, as the heat exchanger, a tank & coil method and a thermostatic chamber method were often used so that the refrigerant would not freeze in the heat exchanger part. From an easy point etc., the double tube type heat exchanger has come to be used.
[0004]
When the refrigerant is cooled by the low-temperature liquefied gas using the double pipe heat exchanger, it is necessary to prevent the refrigerant from freezing in the refrigerant flow path of the heat exchanger. That is, if freezing of the refrigerant occurs even in the refrigerant flow path, the viscosity of the refrigerant increases and the flow velocity decreases, and frozen matter adheres to the heat transfer surface of the heat exchanger, increasing the flow path resistance. Furthermore, freezing of the refrigerant is promoted. Thus, if the flow resistance of the refrigerant flow path increases due to the freezing of the refrigerant, the heat transfer coefficient decreases and the heat exchange capability is impaired, so that the low temperature liquefied gas is not vaporized in the heat exchanger and heat exchange is performed. There was a risk of the liquid being blown out from the vessel.
[0005]
For this reason, for example, in the refrigerant cooling device described in Japanese Utility Model Laid-Open No. 6-22880, the refrigerant temperature is detected at a plurality of locations in the refrigerant flow path, and the low-temperature liquefied gas supply amount to the heat exchanger is detected according to the detected temperature. By controlling this, freezing of the refrigerant in the refrigerant flow path is prevented.
[0006]
[Problems to be solved by the invention]
On the other hand, plate type heat exchangers with a large number of plates stacked and fluid flow between each plate are smaller and have higher performance than the tank & coil method, thermostatic bath method, double tube heat exchanger, etc. Therefore, it is desired to use this plate heat exchanger also for the refrigerant cooling device.
[0007]
However, in the case of a plate-type heat exchanger, it is difficult to accurately measure the temperature in the middle of the flow path, so it is not possible to employ a control method that detects the refrigerant temperature at a plurality of locations in the refrigerant flow path. It was.
[0008]
Accordingly, an object of the present invention is to provide a refrigerant cooling device that can reliably prevent the freezing of the refrigerant in the refrigerant flow path of the heat exchanger and can use the brazing plate heat exchanger. .
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the refrigerant cooling device of the present invention is a refrigerant cooling device that cools the low-temperature circulating refrigerant by exchanging heat between the low-temperature circulating refrigerant that cools the low- temperature reaction tank and the low-temperature liquefied gas in a heat exchanger. The heat exchanger is a brazing plate heat exchanger, and the refrigerant cooling device is configured to circulate the low-temperature circulating refrigerant between the low-temperature reaction tank and the brazing plate-type heat exchanger by a pump, The low-temperature liquefied gas is supplied to the brazing plate heat exchanger from the low-temperature liquefied gas storage tank, and the low-temperature liquefied gas route is supplied to the brazing plate heat exchanger through the low-temperature liquefied gas route. A flow rate adjusting valve for adjusting the amount and a shut-off valve for shutting off the supply of the low-temperature liquefied gas, and the brazing plate type heat An evaporative gas temperature detecting unit for detecting the temperature of the evaporative gas derived from the brazing plate heat exchanger is provided in the heat exchanger outlet flow channel through which the evaporated gas vaporized in the liquefied gas flow channel in the exchanger flows. The refrigerant circulation path includes a refrigerant temperature detection unit that detects a refrigerant temperature at a refrigerant outlet of the brazing plate heat exchanger, and a refrigerant at each of a refrigerant inlet and a refrigerant outlet of the brazing plate heat exchanger. And a bypass path and a bypass valve for returning the low-temperature circulating refrigerant discharged from the pump to the low-temperature reaction tank without introducing it into the brazing plate heat exchanger. The refrigerant temperature detected by the refrigerant temperature detector is input to the first temperature indicating controller, and the first temperature indicating controller is set in advance. The evaporative gas temperature detection is performed by controlling the supply amount of the low-temperature liquefied gas supplied to the brazing plate heat exchanger by adjusting the opening of the flow rate adjusting valve based on the set temperature value and the detected refrigerant temperature. The evaporative gas temperature detected by the unit is input to the second temperature indicating controller, and the second temperature indicating controller controls the shut-off valve based on a preset temperature setting value and the detected evaporating gas temperature. The refrigerant pressure at the refrigerant inlet and the refrigerant outlet detected by the refrigerant pressure detector is input to the differential pressure switch, and the supply of the low-temperature liquefied gas to the heat exchanger is cut off. The switch operates the shut-off valve on the basis of the difference between the detected pressures of the refrigerant pressure detector and a preset differential pressure setting value to supply the low-temperature liquefied gas to the brazing plate heat exchanger The second temperature indicating controller and the differential pressure switch control the opening degree of the bypass valve in accordance with the detected evaporative gas temperature or refrigerant differential pressure .
[0010]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a system diagram showing an embodiment of the refrigerant cooling device of the present invention. This refrigerant cooling apparatus is for cooling a low-temperature circulating refrigerant for cooling the low-temperature reaction tank 1 to a predetermined temperature, for example, methylene chloride by heat exchange with a low-temperature liquefied gas, for example, liquid nitrogen, The low-temperature liquefied gas storage tank 2 for storing the low-temperature liquefied gas, the brazing plate heat exchanger (hereinafter referred to as “heat exchanger”) 3 for exchanging heat between the low-temperature liquefied gas and the circulating refrigerant, and the pump 4 The refrigerant circulation path 5 circulates the circulating refrigerant between the low-temperature reaction tank 1 and the heat exchanger 3, and the low-temperature liquefied gas path 6 that supplies the low-temperature liquefied gas from the low-temperature liquefied gas storage tank 2 to the heat exchanger 3. .
[0011]
The low-temperature liquefied gas path 6 is provided with a flow rate adjusting valve 7 for adjusting the supply amount (flow rate) of the low-temperature liquefied gas to the heat exchanger 3 and a shut-off valve 8 for cutting off the supply of the low-temperature liquefied gas. ing. Further, an evaporative gas temperature detection unit for detecting the temperature of the evaporative gas derived from the heat exchanger 3 is provided in the heat exchanger outlet flow channel 6b through which the evaporated gas vaporized in the liquefied gas flow channel 6a in the heat exchanger 3 flows. (Temperature sensor) 9 is provided.
[0012]
The refrigerant circulation path 5 includes a refrigerant temperature detection unit (temperature sensor) 10 that detects the refrigerant temperature of the refrigerant outlet 3a of the heat exchanger 3, and a refrigerant inlet 3b and a refrigerant outlet 3a of the heat exchanger 3. Refrigerant pressure detectors (pressure sensors) 11 and 12 for detecting the pressure of the refrigerant are provided, and the low-temperature circulating refrigerant discharged from the pump 4 is introduced into the low-temperature reaction tank 1 without being introduced into the heat exchanger 3. A bypass path 13 and a bypass valve 14 for returning are provided.
[0013]
The refrigerant temperature detected by the refrigerant temperature detection unit 10 is input to a first temperature indicating controller (TIC1) 15, which uses the preset temperature set value and the detected refrigerant temperature. Based on this, the opening degree of the flow rate adjusting valve 7 is adjusted, and the supply amount of the low-temperature liquefied gas supplied to the heat exchanger 3 is controlled.
[0014]
The evaporative gas temperature detected by the evaporative gas temperature detection unit 9 is input to the second temperature indicating controller (TIC2) 16, and the second temperature indicating controller 16 detects the evaporative gas detected in advance and the preset temperature set value. Based on the temperature, the shut-off valve 8 is operated to cut off the supply of the low-temperature liquefied gas to the heat exchanger 3.
[0015]
Further, the refrigerant pressure detected by the refrigerant pressure detectors 11 and 12 is input to a differential pressure switch (PS) 17, and the differential pressure switch 17 detects the difference between the detected pressures of the refrigerant pressure detectors 11 and 12, that is, both paths. As with the second temperature indicating controller 16, the shutoff valve 8 is operated based on the differential pressure of the refrigerant flowing through and the preset differential pressure set value, and the low-temperature liquefied gas is supplied to the heat exchanger 3. Shut off the supply.
[0016]
The second temperature indicating controller 16 and the differential pressure switch 17 also control the opening degree of the bypass valve 14 according to the detected evaporative gas temperature and the refrigerant differential pressure.
[0017]
In the above-described refrigerant cooling device, the low-temperature liquefied gas supplied from the low-temperature liquefied gas storage tank 2 is transferred to the liquefied gas flow path 6a in the heat exchanger 3 via the shut-off valve 8 and the flow rate adjusting valve 7 of the low-temperature liquefied gas path 6. The low-temperature circulating refrigerant introduced and cooled from the refrigerant circulation path 5 to the refrigerant flow path 5a in the heat exchanger 3 is vaporized to become evaporated gas and flows out from the heat exchanger outlet flow path 6b. On the other hand, the low-temperature circulating refrigerant heated in the low-temperature reaction tank 1 is introduced into the heat exchanger 3 by the pump 4, cooled in the refrigerant flow path 5 a, and then returned to the low-temperature reaction tank 1 again.
[0018]
In a normal operation state, the opening degree of the flow rate adjustment valve 7 is adjusted according to the refrigerant temperature of the refrigerant outlet part 3a detected by the refrigerant temperature detection part 10, and the supply amount of the low-temperature liquefied gas to the heat exchanger 3 is controlled. The That is, the supply amount of the low-temperature liquefied gas is decreased when the refrigerant temperature at the refrigerant outlet portion 3a falls below a preset temperature, and the supply amount of the low-temperature liquefied gas is increased when the refrigerant temperature rises above the set temperature. Thereby, it is possible to sufficiently cope with the fluctuation of the normal heat load in the low temperature reaction tank 1.
[0019]
Note that a refrigerant temperature detection unit is provided in the refrigerant inlet 3b instead of the refrigerant outlet 3a, and the same control can be performed even if the refrigerant temperature flowing into the heat exchanger 3 is detected. You may make it detect the refrigerant | coolant temperature of both the exit parts 3a.
[0020]
Further, when the refrigerant temperature is controlled in the vicinity of the freezing point, the viscosity of the low-temperature circulating refrigerant flowing into the heat exchanger 3 increases and the refrigerant fluidity decreases. Thereby, the flow path resistance in the refrigerant flow path 5a of the heat exchanger 3 increases, and the differential pressure between the refrigerant inlet part 3b and the refrigerant outlet part 3a gradually increases. The degree of increase in the differential pressure varies depending on various conditions such as the type of the low-temperature circulating refrigerant and the state of the refrigerant flow path 5a. However, when the differential pressure during normal operation is 1.3 to 1.4 kgf / cm ² , 2 kgf When the differential pressure increases to more than / cm ² , the refrigerant often begins to freeze rapidly.
[0021]
Accordingly, when the set value of the differential pressure switch 17 is set to 1.7 kgf / cm ² , for example, and the differential pressure rises to 1.7 kgf / cm ² , the differential pressure switch 17 is activated to close the shutoff valve 8. What is necessary is just to set so that supply of the low-temperature liquefied gas to the heat exchanger 3 may be shut off. As a result, the temperature of the low-temperature circulating refrigerant does not further decrease, and the low-temperature circulating refrigerant can be prevented from freezing in the refrigerant flow path 5a.
[0022]
In addition, as described above, when the viscosity of the low-temperature circulating refrigerant flowing into the heat exchanger 3 increases, the heat exchange capability in the heat exchanger 3 decreases, so that the low-temperature liquefied gas that performs heat exchange with the low-temperature circulating refrigerant is sufficiently supplied. Can not be heated. Thereby, the temperature of the evaporative gas flowing out from the liquefied gas flow path 6a of the heat exchanger 3 to the heat exchanger outlet flow path 6b gradually decreases. The degree of this temperature drop varies depending on various conditions such as the type of the low-temperature circulating refrigerant and the type of the low-temperature liquefied gas, as in the case of the differential pressure. For example, the low-temperature circulating refrigerant is methylene chloride and the low-temperature liquefied gas is liquid nitrogen. In some cases, when the evaporating gas temperature in the heat exchanger outlet channel 6b becomes −150 ° C. or lower, the low-temperature circulating refrigerant may freeze in the refrigerant channel 5a. Therefore, in this case, it may be set such that when the evaporative gas temperature detected by the evaporative gas temperature detection unit 9 reaches −150 ° C., the second temperature indicating controller 16 is activated and the shutoff valve 8 is closed.
[0023]
The return of the shut-off valve 8 can be automatically performed according to the operating state of the low temperature reaction tank 1 or may be performed manually. Further, the flow rate adjusting valve 7 may be fully closed by a signal from the second temperature indicating controller 16 or the differential pressure switch 17 without providing the shutoff valve 8.
[0024]
Further, in the present embodiment, when there is a possibility that the low-temperature circulating refrigerant freezes as described above, the bypass valve 14 is opened by a signal from the second temperature indicating controller 16 or the differential pressure switch 17. As a result, even if the low-temperature circulation refrigerant freezes in the heat exchanger 3 and the refrigerant flow path 5a is closed, the circulation path for the low-temperature circulation refrigerant is secured, so that a load may be applied to the pump 4. Thus, it is possible to prevent the pressure in the refrigerant inlet 3b side flow path from rising abnormally or the pump 4 from being damaged.
[0025]
Thus, not only the temperature of the low-temperature circulating refrigerant flowing through the refrigerant circulation path 5 is detected to adjust the supply amount of the low-temperature liquefied gas to the heat exchanger 3, but also the refrigerant at the refrigerant inlet portion 3b and the refrigerant outlet portion 3a. The freezing of the low-temperature circulating refrigerant can be detected in advance by detecting the differential pressure and the temperature of the evaporative gas flowing out of the heat exchanger 3, and the freezing of the low-temperature circulating refrigerant can be detected by shutting off the supply of the low-temperature liquefied gas. Can be reliably prevented.
[0026]
In addition, since each of the inlet portions and the inlet portions of the heat exchanger 3 are provided with detection means such as a temperature sensor and a pressure sensor, it is possible to deal with heat exchangers of various structures, and it is difficult to apply in the past. Plate heat exchangers, especially brazing plate heat exchangers that are brazed and brazed to each plate, making it possible to significantly improve heat exchange efficiency. The entire apparatus can be reduced in size and efficiency, and the manufacturing cost can be reduced.
[0027]
【The invention's effect】
As described above, according to the refrigerant cooling device of the present invention, since the brazing plate heat exchanger having excellent heat exchange efficiency can be used, the entire device can be reduced in size and cost.
[Brief description of the drawings]
FIG. 1 is a system diagram of a refrigerant cooling device showing an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Low temperature reaction tank, 2 ... Low temperature liquefied gas storage tank, 3 ... Heat exchanger, 3a ... Refrigerant outlet part, 3b ... Refrigerant inlet part, 4 ... Pump, 5 ... Refrigerant circulation path, 6 ... Low temperature liquefied gas path, 6a ... Liquefied gas flow path, 6b ... Heat exchanger outlet flow path, 7 ... Flow rate adjusting valve, 8 ... Shut-off valve, 9 ... Evaporative gas temperature detection unit, 10 ... Refrigerant temperature detection unit, 11, 12 ... Refrigerant pressure detection unit, 13 ... Bypass path, 14 ... Bypass valve, 15 ... First temperature indicating controller, 16 ... Second temperature indicating controller, 17 ... Differential pressure switch

Claims (1)

In the refrigerant cooling device for cooling the low-temperature circulating refrigerant by exchanging heat between the low-temperature circulating refrigerant for cooling the low- temperature reaction tank and the low-temperature liquefied gas in a heat exchanger, the heat exchanger is a brazing plate heat exchanger, The refrigerant cooling device includes a refrigerant circulation path for circulating the low-temperature circulating refrigerant to the low-temperature reaction tank and the brazing plate heat exchanger by a pump, and the low-temperature liquefied gas from the low-temperature liquefied gas storage tank to the brazing plate-type heat. A low-temperature liquefied gas path for supplying to the exchanger, and the low-temperature liquefied gas path includes a flow rate adjusting valve for adjusting a low-temperature liquefied gas supply amount to the brazing plate heat exchanger, and the low-temperature liquefied gas. And a shutoff valve for shutting off the supply of gas, evaporative gas vaporized in the liquefied gas flow path in the brazing plate heat exchanger flows The exchanger outlet flow path is provided with an evaporative gas temperature detection unit for detecting the temperature of the evaporative gas derived from the brazing plate heat exchanger, and the refrigerant circulation path is provided with the brazing plate heat exchanger. A refrigerant temperature detector for detecting the refrigerant temperature at the refrigerant outlet, a refrigerant pressure detector for detecting the pressure of each refrigerant at the refrigerant inlet and the refrigerant outlet of the brazing plate heat exchanger, and the pump A bypass path and a bypass valve are provided for returning the discharged low-temperature circulating refrigerant to the low-temperature reaction tank without introducing it into the brazing plate heat exchanger, and the refrigerant temperature detected by the refrigerant temperature detector is The first temperature indicating controller is input to the first temperature indicating controller based on the preset temperature setting value and the detected refrigerant temperature. The amount of the low-temperature liquefied gas supplied to the brazing plate heat exchanger is controlled by adjusting the opening of the amount adjustment valve, and the evaporative gas temperature detected by the evaporative gas temperature detector is the second temperature indication Input to the controller, and the second temperature indicating controller operates the shut-off valve based on a preset temperature set value and the detected evaporative gas temperature to supply the low-temperature liquefied gas to the heat exchanger. The refrigerant pressure at the refrigerant inlet portion and the refrigerant outlet portion detected by the refrigerant pressure detection unit is shut off and input to the differential pressure switch, and the differential pressure switch is a difference between the detected pressure difference of the refrigerant pressure detection unit and the refrigerant pressure detection unit. , Based on a preset differential pressure set value, the shut-off valve is operated to shut off the supply of low-temperature liquefied gas to the brazing plate heat exchanger, and the second temperature indicating controller and the differential pressure Sui The switch controls the opening degree of the bypass valve according to the detected evaporative gas temperature and the refrigerant differential pressure .

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