JP7328682B2 - How to operate a vacuum dryer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a vacuum dryer, and more particularly to a vacuum dryer that vacuum-dries a sample housed in a vacuum chamber.

As a vacuum dryer, the sample placed in a container such as petri dish or vat placed on the sample placing shelf in the vacuum chamber is kept at a preset temperature, and the inside of the vacuum chamber is decompressed by a vacuum pump through an exhaust passage. In some cases, the sample is vacuum-dried in a short period of time, and in some cases, a cooling trap that collects and freezes the vapor evaporated in the vacuum chamber is provided in the exhaust passage (see, for example, Patent Document 1). .).

With such a vacuum dryer, for example, even if there is a vacuum leak from the door packing of the vacuum chamber, the sample can be vacuum-dried as usual as long as the vacuum pump is operating. Until then, it was common to operate the vacuum pump continuously.

JP-A-2008-45802

However, continuous operation of the vacuum pump during drying causes continuous noise and increases costs. Furthermore, when an oil rotary pump, for example, is used as the vacuum pump, the oil components diffuse from the oil rotary pump into the vacuum chamber, and the dried sample may smell of oil. , was a problem when the sample was food.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a vacuum dryer capable of reducing noise from a vacuum pump, reducing costs, and preventing sample contamination.

In order to achieve the above object, the method of operating a vacuum dryer of the present invention comprises: a vacuum chamber containing a sample to be dried; a vacuum pump for reducing the pressure in the vacuum chamber through an exhaust passage; and a cooling trap for heating and drying the sample under vacuum, wherein the sample in the vacuum chamber is heated to a set temperature and the cold trap is cooled to a set temperature. After operating the vacuum pump in the state, a valve provided between the cooling trap and the vacuum pump in the exhaust passage is opened, and the gas in the vacuum chamber is discharged through the cooling trap and the valve. An exhaust step is performed in which the sample is evacuated from the exhaust passage by means of the vacuum pump, and after the pressure in the vacuum chamber is reduced to a set pressure in the exhaust step, the valve is closed and the vacuum pump is stopped to evaporate the vapor from the sample. is collected by the cooling trap, and in the vacuum pump stopping step, the pressure in the vacuum chamber, the temperature of the cooling trap, and the temperature of the exhaust passage are measured, and the vacuum chamber When the internal pressure rises, the temperature of the cold trap drops, and the temperature of the exhaust passage is below a set temperature, condensate blocks the exhaust passage between the vacuum chamber and the cold trap. After determining that the condensate has been removed, the vacuum pump is operated, and then the valve is opened to suck and move the condensate toward the cooling trap.

According to the vacuum dryer and the method of operating the vacuum dryer of the present invention, a valve that opens and closes while the vacuum pump is operating is provided between the cooling trap in the exhaust passage and the vacuum pump, and the sample in the vacuum chamber is set. After heating to the desired temperature and cooling the cooling trap to the set temperature, the vacuum pump is operated, the valve is opened, and the gas in the vacuum chamber is exhausted from the exhaust passage through the cooling trap and the valve by the vacuum pump. After the vacuum chamber is decompressed to the set pressure in the evacuation process, the vacuum pump is stopped after closing the valve, and the vacuum pump stop process is performed to collect the vapor evaporated from the sample with a cooling trap. As a result, the noise from the vacuum pump can be reduced, and the cost can be reduced. In addition, it is possible to prevent contaminants from the vacuum pump from diffusing toward the upstream side of the exhaust passage, so there is no risk of contamination of the sample.

Furthermore, in the vacuum pump stop step, the pressure in the vacuum chamber, the temperature of the cooling trap, and the temperature of the exhaust passage are measured, the pressure in the vacuum chamber increases, the temperature of the cooling trap decreases, and the exhaust When the temperature of the passage is below the set temperature, it is determined that the space between the vacuum chamber of the exhaust passage and the cooling trap is blocked by condensate, and after operating the vacuum pump, the valve is opened to allow the condensate to flow into the cooling trap. It is possible to prevent the exhaust passage from being clogged by providing the blocking release step of sucking and moving toward the exhaust passage.

BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing which shows the example of one form of the vacuum dryer of this invention.

The vacuum dryer 11 includes a vacuum chamber 12 for storing a sample to be dried, a vacuum pump 14 for reducing the pressure in the vacuum chamber 12 via an exhaust passage 13, a cooling trap 15 provided in the exhaust passage 13, and an exhaust passage 13. A solenoid valve 16 (valve) provided between the cooling trap 15 and the vacuum pump 14 is provided.

The vacuum chamber 12 is detachably provided with a plurality of sample mounting shelves 12 a therein, and is provided with an electric heater (not shown) for heating the inside of the vacuum chamber 12 . The cold trap 15 is connected to the vacuum chamber 12 through the exhaust passage 13, collects the vapor generated in the vacuum chamber 12, cools it, liquefies it, and recovers it. The solenoid valve 16 is opened and closed according to a signal from a control unit (not shown) while the vacuum pump 14 is operating.

When vacuum-drying a sample with the vacuum dryer 11 as described above, first, the sample in the vacuum chamber 12 is heated to the set temperature, and the cooling trap 15 is cooled to the set temperature. is operated, the solenoid valve 16 is opened, and the gas in the vacuum chamber 12 is evacuated from the exhaust passage 13 through the cooling trap 15 and the solenoid valve 16 by the vacuum pump 14 .

Next, when the vacuum chamber 12 is decompressed to the set pressure in the exhaust process and the temperature of the cooling trap 15 starts to rise, the solenoid valve 16 is closed and the vacuum pump 14 is stopped to cool the vapor evaporated from the sample. A step of stopping the vacuum pump for capturing by the trap 15 is performed. At this time, if the room temperature is lower than the temperature of the vapor evaporated from the sample and the temperature of the exhaust passage 13 is low, the vapor will condense somewhere in the exhaust passage 13 from the vacuum chamber 12 to the cooling trap 15 and the pipe will be closed. It could get blocked.

Therefore, in the vacuum pump stop process, the pressure in the vacuum chamber 12, the temperature of the cooling trap 15, and the temperature of the exhaust passage 13 are measured, the pressure in the vacuum chamber 12 increases, and the temperature of the cooling trap 15 decreases. When the temperature of the exhaust passage 13 is equal to or lower than the set temperature, the controller determines that the space between the vacuum chamber 12 and the cooling trap 15 in the exhaust passage 13 is blocked by condensate, and operates the vacuum pump 14. After that, the solenoid valve 16 is opened to suck and move the condensate toward the cooling trap 15 to perform a deblocking process.

When the clogging process is completed and the clogging is eliminated, a large amount of steam accumulated in the vacuum chamber 12 flows into the cooling trap 15, and the temperature of the cooling trap 15 rises sharply, but the temperature of the cooling trap 15 rises. This increases the refrigeration capacity, causing the vapor to quickly condense and freeze. As the amount of steam decreases, the vacuum dryer 11 returns to its stable operating state before blockage occurred. After the vacuum dryer 11 reaches a stable operating state, the electromagnetic valve 16 is closed, the vacuum pump 14 is stopped, and the vacuum pump stop step of collecting the vapor evaporated from the sample with the cooling trap 15 is resumed.

According to experiments, in one drying experiment, the exhaust passage 13 was clogged twice, and the above clogging release step was performed. Even if the blocking release step was performed, the total drying time was not extended, and the sample was not contaminated by the vacuum pump 14 . The cooling trap 15 could not process the water vapor that flowed in at once, and its temperature rose sharply, but after a certain period of time had passed, it returned to normal operation. In the experiment, when the drying time was about 6 hours, the first blockage was performed for about 1 minute, and the second blockage was performed for about 10 seconds. was able to resolve.

In this embodiment, as described above, the electromagnetic valve 16 that opens and closes while the vacuum pump 14 is operating is provided between the cooling trap 15 in the exhaust passage 13 and the vacuum pump 14, and the exhaust process is performed. At the stage where the pressure inside the vacuum chamber 12 is reduced to the set pressure and the temperature of the cooling trap 15 begins to rise, the electromagnetic valve 16 is closed, the vacuum pump 14 is stopped, and the vapor evaporated from the sample is captured by the cooling trap 15. By performing the step of stopping the vacuum pump to collect the vacuum, the noise from the vacuum pump 14 can be reduced and the cost can be reduced. In addition, it is possible to prevent the contaminants from the vacuum pump 14 from diffusing toward the upstream of the exhaust passage 13, so that there is no risk of contamination of the sample.

Furthermore, in the vacuum pump stop process, the pressure inside the vacuum chamber 12, the temperature of the cooling trap 15, and the temperature of the exhaust passage 13 are measured, the pressure inside the vacuum chamber 12 increases, and the temperature of the cooling trap 15 decreases. When the temperature of the exhaust passage 13 is equal to or lower than the set temperature, the controller determines that the space between the vacuum chamber 12 and the cooling trap 15 in the exhaust passage 13 is blocked by condensate, and operates the vacuum pump 14. After that, the blockage of the exhaust passage 13 can be prevented by performing the blocking release step of opening the solenoid valve 16 to suck and move the condensate toward the cooling trap.

It should be noted that the valve of the present invention is not limited to the solenoid valve as in the above embodiment, and may be a manual valve, a pneumatic valve, or the like.

DESCRIPTION OF SYMBOLS 11... Vacuum dryer, 12... Vacuum chamber, 12a... Sample mounting shelf, 13... Exhaust passage, 14... Vacuum pump, 15... Cooling trap, 16... Solenoid valve

Claims (1)

A vacuum chamber containing a sample to be dried, a vacuum pump for reducing the pressure in the vacuum chamber through an exhaust passage, and a cooling trap provided in the exhaust passage are provided to heat and dry the sample under vacuum. In the method for operating a vacuum dryer, the sample in the vacuum chamber is heated to a set temperature and the cooling trap is cooled to the set temperature, and after operating the vacuum pump, the cooling of the exhaust passage is performed. performing an exhaust step of opening a valve provided between the trap and the vacuum pump to exhaust the gas in the vacuum chamber from the exhaust passage through the cooling trap and the valve by the vacuum pump; After the inside of the vacuum chamber is decompressed to the set pressure, the valve is closed, the vacuum pump is stopped, and vapor evaporated from the sample is collected by the cooling trap , performing a vacuum pump stop step,
In the vacuum pump stopping step, the pressure in the vacuum chamber, the temperature of the cooling trap, and the temperature of the exhaust passage are measured, and the pressure in the vacuum chamber increases and the temperature of the cooling trap decreases. and determining that a space between the vacuum chamber and the cooling trap in the exhaust passage is clogged with condensate when the temperature of the exhaust passage is equal to or lower than the set temperature, and after operating the vacuum pump, A method of operating a vacuum dryer , comprising opening a valve to perform a blocking release step of sucking and moving the condensate toward the cooling trap.

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