JPH09137909A - Low pressure steam heater by heat medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of cavitation phenomenon and the denaturalizing of a heat medium within a circulation pump by controlling the opening or closing of a valve means so that the pressure in a tank rises higher by a specified value as compared with an saturation pressure with respect to a temperature value detected. SOLUTION: The opening or closing of automatic valves 40 and 43 is controlled by a controller 5 so that the pressure in a tank 21 rises higher by a specified value as compared with a saturation pressure with respect to the temperature of a fluid within the tank 21 as detected by a temperature sensor 45. The pressure in the tank 21 is fed back by a pressure sensor 18 to a controller 5. Hence, the pressure in the tank 21 is maintained by a specified value as compared with a saturation pressure with respect to the temperature of a fluid in the tank 21 sucked by a circulation pump 22 so that a necessary forcing pressure is applied into the circulation pump 22 ceaselessly to eliminate cavitation phenomenon within the circulation pump 22. Thus, the tank 21 is always filled with an inert gas such as nitrogen gas to be kept from contacting from air thereby preventing denaturalizing of the heat medium 27 by oxidization thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating medium for heating an object to be heated by steam of a heating medium, which is used in various heating processes in the petrochemical industry, the synthetic fiber industry, the synthetic resin industry and the like. The present invention relates to a steam heating device.

[0002]

2. Description of the Related Art As an example of a conventional steam heating apparatus using a heat medium, for example, one shown in FIG. 2 has been used. This is a boiler for heat carrier as an evaporator of heat carrier.
The heat medium vapor generated in 1 is supplied to the reaction vessel 2 which is a kind of heat exchanger to heat the object to be heated in the reaction vessel 2, and the condensate of the heat medium vapor condensed by heating is stored in the tank 3. It is made to flow down and is collected in the boiler 1 by the circulation pump 4.

Although various kinds of heat mediums are commercially available and used, those having a lower pressure and a higher temperature are generally used as compared with the steam generated by boiling normal water, and the heating device is highly resistant to heat. It can be heated at a relatively high temperature without pressure design, and is widely used in various heating processes.

[0004]

When the above-described conventional steam heating device using a heat medium is used, there is a problem that the heat medium is oxidized and deteriorated due to contact with the air in the tank. The tank is usually used in an open state so as to be able to cope with fluctuations in the amount of fluid flowing down, but the heat medium deteriorates with the lapse of usage time.

Further, in the case of the above-mentioned conventional heating device, when the temperature of the fluid in the tank becomes high and the saturation pressure corresponding to that temperature becomes equal to or higher than atmospheric pressure, a cavitation phenomenon occurs in the circulation pump. There was a problem. This is because the pushing pressure to the circulation pump is insufficient, bubbles are generated in the high temperature fluid inside the pump, and the bubbles collapse,
It is a phenomenon that causes significant noise and vibration, and causes noise problems and damage to equipment.

Therefore, a technical object of the present invention is to obtain a low-pressure steam heating device using a heating medium, which can prevent the cavitation phenomenon from occurring in the circulation pump and prevent the deterioration of the heating medium.

[0007]

Means for Solving the Problems The technical means of the present invention taken to solve the above-mentioned technical problem is to connect a steam supply pipe of a heat medium to a primary side of a heat exchanger, In the one that collects the condensed heat medium to the collection destination such as an evaporator,
A vacuum pump having an ejector, a tank, and a circulation pump is connected to the secondary side of the heat exchanger, and an inert gas supply pipe for supplying an inert gas such as nitrogen gas into the tank is provided through a valve means. Then, a pressure detecting means for detecting the pressure in the tank is provided, and a temperature detecting means for detecting the temperature of the fluid flowing down to the circulation pump is attached, and the saturated pressure of the fluid with respect to the temperature value detected by the temperature detecting means is determined from the saturated pressure of the fluid. Is also provided with a control unit for controlling the opening / closing of the valve means so that the pressure in the tank increases by a predetermined value.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION By connecting a vacuum pump having an ejector, a tank and a circulation pump on the secondary side of the heat exchanger, the fluid in the tank is supplied to the ejector by the circulation pump to generate suction force. By generating and sucking gas or liquid in the heat exchanger, the inside of the heat exchanger is maintained at a low pressure,
The object to be heated in the heat exchanger can be heated with a predetermined low-pressure steam, that is, low-temperature steam.

By supplying the inert gas so that the tank internal pressure is higher by a predetermined value than the saturation pressure corresponding to the temperature value of the fluid flowing down to the circulation pump, the pushing pressure to the circulation pump is secured, and the high temperature fluid The cavitation phenomenon does not occur even if is sucked into the pump.

By supplying the inert gas into the tank, air does not exist in the tank, and deterioration due to oxidation of the heat medium can be prevented.

[0011]

An embodiment showing a specific example of the above technical means will be described (see FIG. 1). In this embodiment, an example in which the reaction kettle 2 is used as a heat exchanger is shown, and the same members as those in the prior art shown in FIG.

The heat medium boiler 1 serving as an evaporator is connected to the jacket portion 6 of the reaction kettle 2 and the lower portion of the jacket portion 6 is connected to the vacuum pump 7, and the vacuum pump 7 is connected to the tank 3 and the circulation pump 4. The low-pressure steam heating device using the heat medium is configured by connecting to the boiler 1 for heat medium via.

The heating medium boiler 1 and the reaction vessel 2 are connected by a pressure adjusting valve 8, a gas-liquid separator 9 and a heating vapor supply pipe 11 via a pressure sensor 10. The pressure adjusting valve 8 adjusts the steam pressure in the heating steam supply pipe 11 detected by the pressure sensor 10 to a predetermined value, and the gas-liquid separator 9 controls the heat medium in the heating steam supply pipe 11. The vapor and the liquid are separated, and only the separated vapor is supplied to the jacket portion 6 of the reaction kettle 2,
The liquid is discharged from the steam trap 12 provided below the liquid. The gas-liquid separator 9 may be of a collision type, a centrifugal type, a filter type, or the like.

A jacket portion 6 arranged on the outer periphery of the reaction kettle 2.
The lower connection port 13 is connected to the ejector 20 of the vacuum pump 7 by a pipe line 16 in which a steam trap 14 and a bypass valve 15 are provided in parallel. Further, the outlet of the steam trap 12 of the gas-liquid separator 9 is connected to the ejector 20 via the conduit 17.

The vacuum pump 7 is composed of an ejector 20, a tank 21, a circulation pump 22 and a connecting pipe line 23. The ejector 20 is formed of a nozzle portion 25 and a diffuser portion 26.

On the upper part of the tank 21, a pressure sensor 18 as a pressure detecting means for detecting the pressure in the tank 21,
Inert gas supply pipe 4 via automatic valve 40 as valve means
1, a heat medium supply pipe 42, and an inert gas discharge pipe 44 via an automatic valve 43 are attached. A temperature sensor-45 as a temperature detecting means for detecting the fluid temperature in the tank 21 is attached to the lower portion of the tank 21. Although not shown, the temperature sensor 45, the pressure sensor 18, and the automatic valves 40 and 43 are connected to the controller 5 as a control unit.

In this embodiment, the inert gas discharge pipe 44 is used.
I have shown an example that provided, but this is not always necessary,
For example, by supplying a certain amount of inert gas and exhausting a minute amount of gas from a minute orifice or the like, the tank 2
It becomes unnecessary when the inside of 1 is maintained at a predetermined pressure.

From the upper part of the tank 21, the pipe 36 and the automatic valve 4
It is connected via 6 to the suction chamber of the steam ejector 34. The inlet side of the steam ejector 34 is connected to the heat medium boiler 1 through the pipe line 37 and the control valve 39, and the outlet side is connected by a pipe line 38 to a separate heat medium vapor use point or heat Connect with medium boiler-1.

The tank 21 has a heat medium 27 accumulated therein.
A cooling pipe 28 for cooling the cooling device separately from the steam ejector 34 is attached via an automatic valve 29. Automatic valve 2
9 and 46 are also connected to the controller 5 so that the temperature of the heat medium 27 can be maintained at a predetermined value.

The vacuum pump 7 circulates the heat medium 27 in the heat exchange tank 21 through the ejector 20 by the circulation pump 22, and the nozzle portion 25 of the ejector 20 produces a suction force corresponding to the temperature of the heat medium 27. The heat medium is generated and the heat medium is sucked from the jacket portion 6 of the reaction kettle 2, and the inside of the jacket portion 6 is maintained at a predetermined pressure state. The liquid temperature of the heat medium 27 can be lowered by increasing the suction amount of the steam ejector 34 and sucking more re-evaporated vapor in the tank 21, and the cooling fluid from the cooling pipe 28 can be reduced. The liquid temperature can be lowered by increasing it.

A part of the connecting pipe line 23 of the vacuum pump 7 is branched to connect the pipe line 32 so that a part of the circulating heat medium is supplied from the pipe line 33 to the tank 3. Three
5 to connect a part of the circulating heat medium to the heating steam supply pipe 11
It is injected into the primary side of the gas-liquid separator 9 therein. Even when the heat transfer medium whose pressure is adjusted by the pressure adjusting valve 8 by the pipe line 35 becomes superheated steam, a part of the circulating heat transfer medium is injected and heat is exchanged in the gas-liquid separation unit 9 to obtain the saturation temperature. It can be steam.

Next, the operation will be described. Boiler for heat medium-1
The heat medium vapor generated in 1 is supplied to the jacket portion 6 of the reaction vessel 2 after being pressure-adjusted via the pressure adjustment valve 8. The inside of the jacket portion 6 is in a predetermined low pressure state by the suction force of the ejector 20 of the vacuum pump 7, and the heat medium vapor supplied to the jacket portion 6 reaches a predetermined pressure, that is, the vapor temperature, in the reaction vessel. The object to be heated in 2 is heated. The heat medium vapor that has been heated and deprived of heat condenses into a liquid, is sucked by the ejector 20 through the steam trap 14, and reaches the tank 21.

The tank 2 is a predetermined value higher than the saturation pressure with respect to the fluid temperature in the tank 21 detected by the temperature sensor 45.
The controller 5 controls the opening and closing of the automatic valves 40 and 43 so that the pressure in 1 becomes high. The pressure in the tank 21 is fed back to the controller 5 by the pressure sensor-18. The pressure in the tank 21 is maintained higher than the saturation pressure with respect to the temperature of the fluid in the tank 21 sucked by the circulation pump 22 by a predetermined value, so that the circulation pump 22 is constantly applied with a necessary pushing pressure, No cavitation phenomenon occurs in the circulation pump 22. Further, since the tank 21 is constantly filled with an inert gas such as nitrogen gas, it does not come into contact with air, and therefore the heat medium 27 is not oxidized and deteriorated.

When the saturation pressure of the condensation heat medium flowing down from the jacket portion 6 of the reaction kettle 2 changes from a vacuum pressure of atmospheric pressure or less to a positive pressure state equal to or higher than atmospheric pressure, the pressure in the tank 21 changes. When the fluid having a saturation temperature higher than the atmospheric pressure flows into the circulation pump 22 in a state equal to the atmospheric pressure, cavitation occurs. However, as in the present embodiment, the pressure in the tank 21 is set to the saturated pressure of the fluid. Cavitation can be prevented by constantly increasing the value by a predetermined value.

Further, when the saturation pressure of the fluid does not exceed the vacuum pressure, when the pressure in the tank 21 is increased by a predetermined value, the pressure of the inert gas equal to the atmospheric pressure is applied to the inside of the tank 21. It is possible to more reliably prevent air from entering.

The heat medium 27 in the tank 21 is cooled to a predetermined temperature by the steam ejector 34 sucking the re-evaporated vapor, or cooled to a predetermined temperature by the cooling pipe 28 and then ejected by the circulation pump 22. -20, and the heat medium in the jacket portion 6 is sucked again. Since the suction force generated by the ejector 20 is determined by the temperature of the fluid passing through the ejector 20, the suction force of the ejector 20, that is, the degree of decompression, is adjusted by appropriately adjusting the liquid temperature of the heat medium 27 in the tank 21. Can be controlled. By controlling the suction force of the ejector 20,
The pressure state in the jacket portion 6 can be controlled, and the pressure in the jacket portion 6 can be controlled from a negative pressure state below atmospheric pressure to a positive pressure state above atmospheric pressure.

In the case of using, for example, Dowsum under the trade name as the heat medium, when the steam pressure is 0.3 kg in absolute pressure, the steam temperature is about 210 ° C., and 1.1 km is about 260 ° C. The steam temperature can be controlled by controlling the steam pressure.

In this embodiment, the reaction vessel 2 is used as the heat exchanger, but other heat exchangers such as synthetic fibers or synthetic resins, or heat exchangers for food or medical products are used. Can also be used as.

In this embodiment, the circulation pump 22 of the vacuum pump 7 and the circulation pump 4 in the lower part of the boiler 1 are used, but the distance between the vacuum pump 7 and the boiler 1 is large. This is an example of the case where the circulation pump 22
If the heat medium can be pumped to the boiler-1,
The circulation pump 4 is unnecessary.

[0030]

As described above, according to the present invention, the inert gas is supplied into the tank so that the pressure becomes higher than the saturation pressure of the fluid by a predetermined value, thereby ensuring the pushing pressure of the circulation pump. As a result, the cavitation phenomenon does not occur, and the heat medium in the tank does not come into contact with air, so that deterioration due to oxidation can be prevented.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of a low-pressure steam heating device using a heat medium according to the present invention.

FIG. 2 is a configuration diagram showing a conventional steam heating device using a heat medium.

[Explanation of symbols]

 1 Boiler for heat medium 2 Reactor 5 Controller 6 Jacket 7 Vacuum pump 18 Pressure sensor 20 Ejector 21 Tank 22 Circulation pump 34 Steam ejector 40 Automatic valve 41 Inert gas supply pipe 44 Inert gas discharge tube

Claims (1)

[Claims] 1. A secondary side of a heat exchanger in which a steam supply pipe for a heat medium is connected to a primary side of the heat exchanger and the heat medium condensed by the heat exchanger is recovered to a recovery destination such as an evaporator. A vacuum pump having an ejector, a tank and a circulation pump is connected in series to the tank, and an inert gas supply pipe for supplying an inert gas such as nitrogen gas into the tank is provided through a valve means to control the pressure in the tank. In addition to providing a pressure detecting means for detecting, a temperature detecting means for detecting the temperature of the fluid flowing down to the circulation pump is attached, and the inside of the tank is a predetermined value higher than the saturation pressure of the fluid with respect to the temperature value detected by the temperature detecting means. A low-pressure steam heating device using a heat medium, characterized in that a control section for controlling opening / closing of the valve means is provided so that the pressure becomes high.