JPH02272202A - Vacuum evaporator - Google Patents

Abstract

PURPOSE:To perform a vacuum evaporation in a simple construction without requiring a complex control in such a constitution where the heating medium in the temperature regulating valve expands and contracts to open and close the main valve opening of said temperature regulating valve to regulate the flow of the heating fluid so as to adjust the secondary side temperature of the temperature regulating valve or the temperature of the heated fluid in the heat exchanger to a desired level. CONSTITUTION:The temperature regulating valve 4 detects by its sensing part 16 the temperature of the heated fluid which is to be controlled, and regulates the flow rate of steam from the primary side line 28 to the secondary side by causing its bellows to be actuated by the pressure change on account of the expansion of the thermally expandable fluid sealed therein. The secondary side of the temperature regulating valve 4 is always maintained in the negative pressure by the operation of a vacuum pump 12, and its steam temperature is also maintained below 100 deg.C. When the temperature of the heated fluid is below the set temperature, the temperature regulating valve 4 opens to supply the steam from the primary side to the heat exchanger. When the temperature of the heated fluid which exchanged heat becomes higher than the set temperature, the temperature regulating valve 4 closes to control the supply of the steam. By repeating such process, the temperature of the heated fluid is maintained at the set level.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention provides a vacuum steam system that constantly generates and supplies stable vacuum steam in order to safely and efficiently heat-treat objects to be heated at temperatures below IOO'C. Regarding the generator.

Heat treatment is widely performed in various manufacturing factories, but such heat treatment often involves heating the object to a high temperature of 100°C or higher, and steam from the boiler is directly used, that is, positive pressure is used. This is done using a system heating device.

However, in some chemical and food factories, for reasons of work safety and product quality, the heating process is carried out at a relatively low temperature of 100°C or less, that is, using negative pressure heating equipment. There are cases.

<Prior Art> Conventionally, there is a vacuum steam generator described in Japanese Unexamined Patent Publication No. 19202/1983. This is a device that has an automatic control valve on the primary side of the heat exchanger and a vacuum pump on the secondary side.The temperature of the heated object is detected by a temperature detector, and the signal is input to the PtD controller. However, the automatic control valve is controlled by PID so that the deviation between the detected temperature and the set temperature of the object to be heated, which is preset in the PID controller, is O.

<Problems to be Solved by the Invention> However, in the above-described apparatus, a temperature change of the object to be heated occurs on the exit side of the heat exchanger. This may be caused by a change in temperature due to a change in the pressure of the heating fluid, a change in the flow rate of the object to be heated, or a change in the temperature of the object to be heated. These causes can occur when only a temperature change occurs due to a change in the pressure of the heated fluid, when only a change in the flow rate of the heated object or a change in the temperature of the heated object occurs, and when a change in the pressure of the heated fluid occurs. There are cases where the accompanying temperature change and the flow rate change or temperature change of the heated object occur simultaneously.

These fluctuations are corrected by a PID controller, but the PID controller is optimal for correcting temperature changes due to pressure changes in the heating fluid.
The ID constant, the optimum PID constant for correcting the flow rate change or temperature change of the heated object, and the optimum PID constant for correcting both the temperature change due to the pressure change of the heating fluid and the flow rate or temperature change of the heated object. However, if a PID controller were used to handle all of these cases, the control would become complicated.

Furthermore, the above control system is very expensive.

Therefore, the technical problem of the present invention is to provide a device that generates vacuum steam with a simple structure without requiring complicated control such as PIDli1 control.

Means for Solving the Problems> The technical means of the present invention taken to solve the above problems is to adjust the heat medium on the primary side of the heat exchanger by a mechanism that detects the temperature of the object to be controlled. A temperature regulating valve is installed to maintain a constant temperature of the controlled object by opening and closing the valve port.
The temperature is detected by detecting the temperature on the secondary side of the temperature regulating valve or the temperature of the heated fluid in the heat exchanger, and a vacuum pump is connected to the secondary side of the heat exchanger.

Effect> By suctioning with a vacuum pump, the pressure on the secondary side of the temperature control valve becomes a negative pressure state, and steam is supplied from the negative side.

The temperature detection part of the temperature adjustment valve detects the temperature on the secondary side of the temperature adjustment valve,
Alternatively, since the heat exchanger is installed to detect the temperature of the heated fluid, the heating medium in the temperature regulating valve expands and contracts, opening and closing the main valve port of the temperature regulating valve, thereby increasing the temperature of the heated fluid. The flow rate is adjusted so that the temperature on the secondary side of the temperature regulating valve or the temperature of the heated fluid in the heat exchanger reaches the desired set temperature.

<Example> An example showing a specific example of the above technical means will be described. (See FIGS. 1 and 2) A temperature control valve 4 is disposed on the primary side of the header 2, and a pipe 14 is taken out from the top of the header 2 and connected to a heat exchanger 10 via a stop valve 8. The secondary side of the heat exchanger 10 is connected to a suction section 20 of a vacuum pump 12 via a pipe 18. The heat exchanger 10 is provided with an inlet pipe 30 and an outlet pipe 32 for the fluid to be heated, and a temperature sensing portion 16 of the temperature regulating valve 4 is attached to detect the temperature of the fluid to be heated. In this embodiment, a temperature sensing section 16 is installed to control the temperature of the fluid to be heated. 16 may be inserted. A piping 22 is taken out from the lower end of the header 2 and a steam trap 24 is placed therein, and its secondary side is connected to the suction part 20 of the vacuum pump 12 via a piping 26. Temperature adjustment valve 4
The primary side piping 28 is a positive pressure steam system, and everything after the secondary side is a negative pressure steam system.

The structure of the temperature regulating valve 4 consists of a valve body part 6a and an actuator part 6b. Although not shown, the valve body portion 6a has a valve port through which fluid passes, and a valve body that opens and closes the valve port. It has a built-in bellows that is operated via a rod. The bellows is biased in one direction by a spring, and an arbitrary set temperature can be selected by adjusting the biasing force. The temperature sensing section 16 and the actuator section 6
A bellows (not shown) in b is connected with a flexible tube 17, and a thermal expansion fluid such as ether is sealed inside the flexible tube 17. The temperature of the object to be heated is detected by the temperature sensing part 16, and the bellows is driven by the pressure change due to the expansion of the enclosed thermal expansion fluid, and the valve body opens and closes the valve port via the valve stem, - The amount of steam passing from the next side piping 28 toward the secondary side is adjusted.

Next, the vacuum pump 12 will be explained according to FIG.

A suction pipe 46 with a temperature sensor 44 is connected to the tank 40 and the pump 42, and a discharge pipe 48 is provided on the secondary side of the pump 42. This pump 42 is a conventional centrifugal pump. A part of the ejector 50 is provided in the discharge pipe 48 to form the suction part 20, and the ejector 50 returns to the tank 40 via piping again. Cooling water piping 5 is installed in the tank 40.
2 is connected, and an electric valve 54 is provided to interlock with the temperature sensor 44. Further, the discharge pipe 48 is provided with an electric valve 56 for pressure feeding, which is linked with an electrode rod 58 built in the tank 40 .

The fluid in the tank 40 is sucked into the pump 42 from the suction pipe 46, pumped to the discharge pipe 48 and the ejector part 50, and returned to the tank for circulation. At this time, a portion of the ejector generates a saturation pressure relative to the temperature of the fluid flowing therein.

Therefore, by setting the temperature sensor 44 provided in the suction pipe 46 to an arbitrary temperature, the electric valve 54 opens and closes, allowing cooling water to enter the tank and maintain the tank at the desired fluid temperature, resulting in saturation at the set temperature. Pressure can be generated in the esector. That is, by lowering the temperature of the fluid in the tank to 100° C. or lower, a pressure lower than atmospheric pressure can be generated in a portion of the ejector.

Due to the vacuum area generated in the ejector part 50, the suction part 20
Fluids such as condensate and steam are suctioned from the tank 40 and sent under pressure to the tank 40. When the liquid level in the tank 40 reaches a high level, the electrode 58 detects this, and the pressure-feeding electric valve 56 opens to force-feed the fluid to a distant location. When the water level in the tank reaches a predetermined low level, the electric valve 56 closes.

Next, the operation of the entire device will be explained. The secondary side of the temperature control valve 4 is always maintained at a negative pressure by the operation of the vacuum pump 12, and the temperature of the steam is also maintained at 100° C. or lower. Since the temperature regulating valve 4 is set at a desired set temperature, when the temperature of the object to be heated is lower than the set temperature, the temperature regulating valve 4 is opened to supply steam on the primary side to the heat exchanger. When the temperature of the heated object becomes higher than the set temperature after heat exchange, the temperature regulating valve 4 operates in the closing direction to suppress the supply of steam. By doing this continuously, the temperature of the object to be heated is maintained at the set value.

As mentioned above, the vacuum pump 12 can generate any vacuum pressure, so by setting its set pressure, that is, the temperature of the generated steam, a little lower than the target temperature of the object to be heated, the temperature adjustment valve 4 can be adjusted. The mouth can operate at a stable, most efficient balance point without excessive opening and closing.

The steam trap 24 quickly removes condensate generated within the header 2, thereby improving the dryness of the steam and improving the thermal conductivity of the heat exchanger.

<Effects of the Invention> According to the present invention, stable vacuum steam can be generated and supplied using a very inexpensive device without using complicated and expensive control equipment.

Furthermore, anyone can use it without requiring knowledge of advanced control technology.

[Brief explanation of drawings]

FIG. 1 is a system diagram of a vacuum steam generating apparatus showing a specific embodiment of the present invention, and FIG. 2 is a schematic diagram of an ejector-type vacuum pump used in the apparatus of the present invention. : Header: Vacuum pump: Temperature sensing part: Tank: Ejector part 4: Temperature adjustment valve 10: Heat exchanger 24 Ni steam trap 42: Pump 44: Temperature sensor

Claims (1)

[Claims] 1. A temperature adjustment valve is placed on the primary side of the heat exchanger to maintain the temperature of the controlled object at a constant level by opening and closing the valve opening by adjusting the heat medium using a mechanism that detects the temperature of the controlled object. A vacuum steam generator that detects the temperature on the secondary side of a temperature regulating valve or the temperature of the heated fluid in a heat exchanger and connects a vacuum pump to the secondary side of the heat exchanger. .