JPH0774684B2 - Vacuum steam generator - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a vacuum steam generator for supplying vacuum steam for safely and efficiently heat-treating an object to be heated at a temperature of about 100 ° C. or lower.

In various factories, heat treatment is widely performed, but such heat treatment often heats the object to be heated at a high temperature of 100 ° C. or higher, and the steam from the boiler is directly used as a whole pressure system. It was performed using the heating device of.

On the other hand, in a chemical factory or a food factory, there is a case where the object to be heated has to be heated at a relatively low temperature of 100 ° C. or lower in order to maintain product quality and productivity.

Prior Art The applicant of the present invention has developed a vacuum steam generator capable of heating with steam having a temperature of 100 ° C. or less in Japanese Patent Application No. 61-271491.

The apparatus is shown in FIGS. 2 and 3. FIG. 2 is a schematic diagram of an ejector type vacuum pump. The tank 1 and the pump 2 are connected by a suction pipe 3 and a discharge pipe 4 to which a temperature sensor 10 is attached. The ejector section 5 is provided on the discharge pipe 4,
The suction port 6 is formed. A cooling water pipe 7 is connected to the tank 1, and an electric valve 8 is provided to interlock with a temperature sensor 10. A motor-operated valve 9 for pressure feeding is provided between the discharge pipe 4 and the ejector unit 5, and is linked with the electrode rod 11 built in the tank 1.

The fluid in the tank 1 is sucked by the pump 2 from the suction pipe 3 and is pressure-fed to the discharge pipe 4 and the ejector unit 5, and the tank 1 is again fed.
It returns to the inside and circulates. At this time, in the ejector unit 5, a saturated pressure is generated with respect to the temperature of the fluid flowing therein. Therefore, by arbitrarily setting the temperature sensor 10 provided in the suction pipe 3, the motor-operated valve 8 is opened / closed to allow the cooling water to enter the tank to maintain a desired fluid temperature, and as a result, the saturation pressure with respect to the set temperature is set to the ejector section 5 Occurs in. Therefore temperature sensor 10
It is possible to obtain an arbitrary degree of vacuum by adjusting.

A vacuum region generated in the ejector unit 5 sucks fluid such as condensate or steam from the suction port 6 and pressure-feeds it to the tank 1. When the liquid level in the tank 1 reaches a high water level, the electrode rod 11 detects it and the electric motor valve 9 for pressure feeding is opened to pressure-feed the fluid to a distance. Then, when the predetermined low water level is reached, the motor-operated valve 9 is closed.

FIG. 3 shows a vacuum steam generator using the above ejector type vacuum pump. Pressure reducing valve 22 on the primary side of the indirect heating container 21
Then, the ejector type vacuum pump 20 is connected to the secondary side to reduce the pressure of the system. The pressure reducing valve 22 is a special pressure reducing valve, and when the pressure in the indirect heating container 21 becomes lower than the set pressure, the valve that has been closed until then starts opening and supplies the steam on the primary side into the heating container 21. However, when the desired value is reached, it acts again in the valve closing direction to suppress the supply amount of steam. Structurally, the pressure setting spring of the conventional pressure reducing valve is used in a compressed state, but this pressure reducing valve is operated in a tensioned state.

As described above, the vacuum pump 20 can be set to an arbitrary degree of vacuum, so if the desired value of the pressure inside the heating container 21, that is, the setting value of the pressure reducing valve 22, is set to the same value, the inside of the heating container 21 is excessively vacuumed. Keep a constant pressure without making a degree. Therefore, it is not necessary to supply extra steam from the pressure reducing valve 22.

Problems to be Solved by the Present Invention In the above-described conventional vacuum vapor generator, the temperature of the object to be heated is not constant due to fluctuations in the amount of the object to be heated, that is, the load. This is because the amount of steam supplied from the pressure reducing valve, that is, the pressure (or the saturation temperature for that pressure) is constant while being sucked by the ejector vacuum pump, but the temperature of the heated object also changes due to the change in the load amount. This is because it ends up. If the change in the secondary pressure of the pressure reducing valve is within the predetermined range, it can be corrected by mechanically opening and closing the pressure reducing valve port by the self-adjusting function of the pressure reducing valve itself, but there is a limit. Variations or the like cause variations in the temperature of the object to be heated.

Therefore, a technical problem of the present invention is to obtain a vacuum steam generator capable of constantly supplying stable steam even when there is a load change and maintaining the temperature of a heated object at a predetermined value.

Means for Solving the Problems Technical means of the present invention taken to solve the above technical problems are provided with an automatic control valve having an actuator on the primary side of an indirect heating container, and an ejector on the secondary side. The ejector type vacuum pump is formed by connecting the ejector, the tank, and the pump, and a temperature detector for detecting the temperature of a load as an object to be heated passing through the indirect heating container is attached and the temperature detector is adjusted. A temperature reducer for spraying the secondary drain is arranged between the automatic control valve and the indirect heating container while being connected to the actuator of the automatic control valve via a meter. Here, the automatic control valve is a control valve capable of maintaining the secondary pressure at a predetermined vacuum pressure lower than atmospheric pressure.

The pressure that can be created at the nozzle of the ejector vacuum pump is
The saturation pressure is a function of the temperature of the fluid passing through the nozzle.
Therefore, an arbitrary pressure can be generated by controlling the temperature of the fluid passing therethrough.

When the system is sucked by setting an arbitrary pressure with an ejector type vacuum pump, suction is continued until the pressure in the indirect heating container reaches the set pressure of the pump. By setting the set pressure of the automatic control valve to be almost the same as the set pressure of the vacuum pump, the valve is closed when the pressure on the secondary side of the valve is still high, and opens if the pressure falls below the set pressure. Is fed into the heating vessel.

If the temperature of the object to be heated is detected by the temperature detector and the temperature of the object to be heated changes due to fluctuations in the amount of load, etc., the signal is sent to the actuator of the automatic control valve via the controller and the desired temperature is reached. Adjust the steam supply by opening and closing the valve opening of the control valve until.

EFFECTS OF THE INVENTION According to the present invention, the required amount of vacuum vapor can be supplied and the temperature of the object to be heated can be kept constant irrespective of load fluctuations or changes in outside air.

Accurate temperature control can be performed by a temperature detector and an automatic control valve, and it is not necessary to set the precise temperature by adjusting the supply of cooling water by the ejector vacuum pump itself.

Further, according to the apparatus of the present invention, it is more effective when the set temperature of the object to be heated is closer to the ambient temperature of room temperature. With conventional devices, the temperature of the object to be heated rises excessively, and if you want to lower it, you have to rely on natural heat dissipation, but with this device, the supply steam is forcibly narrowed down by the automatic control valve. The response will be very quick.

Example An example showing a specific example of the above technical means will be described (see FIG. 1).

Members corresponding to those in FIGS. 2 and 3 are designated by the same reference numerals, and the structure of the ejector type vacuum pump is the same as that in FIG.

In this embodiment, as the automatic adjusting valve, the adjusting means for adjusting the pressure setting spring of the vacuum reducing valve described in the prior art adopts the automatic adjusting vacuum reducing valve 44 having the actuator 45 for operating the adjusting means. . Pressure reducing valve 44 and indirect heating container
Piping branched from the discharge side piping of vacuum pump 20 by placing header 30 between 21 and attaching desuperheater 31 to the side surface.
At 32, install a valve 35 on the way and contact. Also, take out the piping from the bottom of the header 30 and install a steam trap 33,
The secondary side is connected to the suction port of the vacuum pump 20 by a pipe 34. Reference numerals 46 and 48 are inlet / outlet piping on the load side (object to be heated).

The indirect heating container 21 is provided with a temperature detector 40 for detecting the temperature of the object to be heated, and sends a signal from the temperature detector 40 to the actuator 45 of the pressure reducing valve 44 via the controller 42 (PID control). If the desired temperature is set by the controller 42 and there is a temperature change of the heated object due to the change of the load, the actuator 45 should be set to the temperature of the heated object to correct the change, that is, the difference between the set value and the measured value. The operation signal is given until is close to the set value.
Therefore, even if there is a large temperature change in the object to be heated, the pressure reducing valve 44 adjusts the amount of steam supplied, so that a constant temperature of the object to be heated can be maintained.

The desuperheater 31 is for making the steam to be supplied to the indirect heating container 21 into a steam having a saturation temperature, and is provided with a nozzle (not shown) on the cylindrical body outlet side, and the inside of the header 30 is The nozzle is spraying the drain of the saturation temperature with respect to the secondary side set pressure from the vacuum pump 20.

Generally, the steam decompressed by the pressure reducing valve becomes superheated steam. Superheated steam is a state where the temperature is higher than the saturation temperature for that pressure even if the pressure is a predetermined pressure, so by spraying the saturation temperature drain on the superheated steam, heat is exchanged with each other. The temperature drops to saturated steam. Since the saturation temperature drain is adjusted by the drain from the indirect heating container 21 and further by the vacuum pump 20, it can be always supplied.

If cooling water is used instead of the saturated temperature drain, the superheated steam may be cooled and drained beyond the saturated temperature steam region depending on the supply amount, which is uneconomical.

The saturated temperature drain excessively sprayed in the header 30 is sucked by the vacuum pump 20 through the pipe 34 in the steam trap 33. The amount of spray can be arbitrarily adjusted by the valve 35 according to the amount of superheated steam.

As described above, the present embodiment economically reduces the steam temperature,
It is possible to maintain the temperature of the object to be heated constant regardless of the fluctuation of the load.

[Brief description of drawings]

1 is a system diagram of a vacuum steam generator of the present invention using the ejector type vacuum pump shown in FIG. 2, and FIG. 2 is a schematic diagram of an ejector type vacuum pump used in the device of the present invention.
The figure is a system diagram of a conventional vacuum steam generator using the ejector type vacuum pump shown in FIG. 1: Tank, 2: Pump 3: Suction pipe, 4: Discharge pipe 5: Ejector part, 10: Temperature sensor 20: Vacuum pump, 21: Indirect heating container 30: Header, 31: Desuperheater 40: Temperature detector, 42: Controller 44: Automatic adjustment vacuum regulator 45: Actuator

Claims (1)

[Claims] 1. An indirect heating container in which an automatic control valve having an actuator is provided on the primary side of the indirect heating container, an ejector is connected to the secondary side, and an ejector type vacuum pump is formed by the ejector, a tank and a pump. A temperature detector that detects the temperature of a load as an object to be heated that passes through the inside is attached, and the temperature detector is connected to the actuator of the automatic adjustment valve via a controller, and the automatic adjustment valve and the indirect heating container are connected. A vacuum steam generator characterized in that a temperature reducer for spraying secondary drain is arranged between them.