JP3694399B2 - Membrane deaerator that uses chemical deaeration depending on the feed water temperature - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a membrane deaeration device that uses chemical deaeration together depending on the feed water temperature.
[0002]
[Prior art]
A membrane deaerator is known as an apparatus for removing dissolved oxygen in water. In this device, a vacuum generator is connected to a membrane module containing a gas / liquid separation membrane with a minute hole, and one side of the membrane in the module is depressurized and water is passed to the other side. Deaeration is performed by moving dissolved oxygen to the reduced pressure side.
[0003]
When removing dissolved oxygen using a membrane deaerator, the concentration of dissolved oxygen remaining after treatment varies depending on the water temperature of the water to be treated, and the dissolved oxygen concentration is low when the water temperature is high and high when the water temperature is low. In the case of a system that does not heat the water supply, the water temperature is different between the winter and summer, and if the capacity required for the membrane deaerator is determined by the water temperature in the winter, it will have more capacity than necessary in the summer. If the capacity required for the deaerator is determined, the capacity will be insufficient in winter. In addition, when a membrane deaeration device is installed in the boiler water supply line, it is possible to eliminate seasonal changes in the water supply temperature by heating the water supply with steam generated by the boiler. However, since it cannot be heated with steam when the boiler is started, and heating means other than steam is expensive and is not generally adopted, the water supply cannot always be heated. Change cannot be lost. Therefore, the capacity of the membrane deaerator may be excessive or insufficient depending on the situation.
[0004]
[Problems to be solved by the invention]
The problem to be solved by the present invention is to always keep the dissolved oxygen concentration in the feed water at a low value without excessively increasing the capacity of the membrane deaerator.
[0005]
[Means for Solving the Problems]
A membrane deaerator is provided in the middle of the water supply line for supplying water to the boiler, and a feed water heater for heating the feed water sent to the membrane deaerator using a part of the steam generated in the boiler, the heated water supply A temperature detection device for detecting the temperature, a chemical injection device for injecting an oxygen scavenger into the feed water line downstream from the membrane deaeration device, and a steam introduction control valve for controlling the introduction of steam to the feed water heating device are provided. A signal line is connected to the chemical injection control device that controls the operation of the chemical injection device based on the feed water temperature detected by the temperature detection device, and the temperature detection device and the steam introduction control valve. A feed water heating control device that controls the operation of the steam introduction control valve based on the feed water temperature detected by the temperature detection device is provided.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view showing the arrangement of each device in one embodiment of the present invention, and a membrane module 6 incorporating a gas-liquid separation membrane is provided in the middle of a water supply line 2 for supplying water from a water tank 7 to a boiler 3. ing. The inside of the membrane module 6 is divided into a reduced pressure side and a water flow side by a gas-liquid separation membrane, and a vacuum generator 8 is connected to the reduced pressure side, and the membrane deaerator 1 is constituted by the membrane module 6 and the vacuum generator 8. To do. The number of membrane modules 6 varies depending on the amount of treated water in the membrane deaerator, and usually a plurality of membrane modules 6 are installed, but are simplified in FIG. A temperature detection device 4 is provided in the water supply line 2 between the water tank 7 and the membrane module 6, and a chemical injection device 9 is connected to the water supply line 2 between the membrane module 6 and the boiler 3 by a chemical injection pipe 10. A main steam pipe 15 is connected to the boiler 3, a steam introduction pipe 12 branched from the main steam pipe 15 is provided, and the other end of the steam introduction pipe 12 is connected to a feed water heater 13 that heats feed water in a water tank 7. The steam introduction control valve 11 is provided in the middle of the steam introduction pipe 12. Moreover, the chemical injection control device 5 connected to each of the chemical injection device 9 and the temperature detection device 4 by a signal line, and the feed water heating control device 14 connected to each of the steam introduction control valve 11 and the temperature detection device 4 by a signal line. Is provided.
[0007]
When deaeration treatment is performed, the decompression side of the membrane module 6 is evacuated by operating the vacuum generator 8 and the raw water is sent to the water flow side of the membrane module 6 so that the dissolved water contained in the water on the water flow side is dissolved. Oxygen moves to the decompression side through the gas-liquid separation membrane. The deaerated water treated by the membrane deaerator 1 is sent to the boiler 3 through the feed water line 2, and is converted into steam by the boiler 3 and sent to the steam use side through the main steam pipe 15.
[0008]
The temperature detection device 4 measures the water temperature of the raw water sent to the membrane deaeration device 1 and outputs water temperature information to the chemical injection control device 5 and the feed water heating control device 14.
The chemical injection control device 5 outputs the operation of the chemical injection device 9 when the water temperature detected by the temperature detection device 4 is lower than the chemical injection setting value. Outputs the operation stop. When the operation of the chemical injection device 9 is output, the chemical injection device 9 injects the oxygen scavenger into the water supply line 2 through the chemical injection pipe 10. Even if the deaeration process using the membrane deaerator cannot completely remove dissolved oxygen, it is further removed by the oxygen scavenger injected by the chemical injection device 9 and the dissolved oxygen concentration of the feed water sent to the boiler 3 is extremely high. Low value.
[0009]
Further, the feed water heating control device 14 opens the steam introduction control valve 11 when the water temperature detected by the temperature detection device 4 is less than the set value for starting feed water heating, and controls the steam introduction control when it is equal to or more than the set value for stopping feed water heating. Control to close the valve 11 is performed. A part of the steam sent through the main steam pipe 15 is sent to the feed water heating device 13 by opening the steam introduction control valve 11 to heat the feed water. The upper limit value of the feed water temperature is determined by the material of the membrane module 6. For example, if the upper limit value of the membrane module 6 is 60 ° C., the set value for stopping feed water heating is 60 ° C., and the set value for starting feed water heating is slightly lower than the upper limit value. The wind is set to 55 ° C. If the temperature of the raw water sent to the membrane module 6 is raised to near the upper limit value of the membrane module 6, more dissolved oxygen is removed by the membrane degassing device, and it is sent to the boiler 3 without using a deoxidizer. The dissolved oxygen concentration of the supplied water is extremely low.
[0010]
When the water temperature sent to the membrane module 6 is high, the dissolved oxygen concentration remaining in the water taken out from the membrane module 6 has a low value, and when the water temperature is low, the remaining dissolved oxygen concentration has a high value. By detecting the water temperature, it is possible to know the concentration of dissolved oxygen contained in the deaerated water after the deaeration process is performed by the membrane deaerator. inject. When the water temperature is low, removal of dissolved oxygen by chemicals can prevent the dissolved oxygen concentration from increasing even if the water temperature is low, and it can be dissolved without excessively increasing the capacity of the membrane deaerator. Water with high oxygen concentration is prevented from being supplied. The removal of dissolved oxygen by chemicals is performed only when the remaining dissolved oxygen concentration is high because the water temperature is low, and injection of chemicals is not required when the water temperature is high and the residual dissolved oxygen concentration is low. Therefore, the amount of chemicals used is small.
[0011]
Further, the membrane deaerator efficiently operates by controlling the opening and closing of the steam introduction control valve 11 according to the water temperature detected by the temperature detector 4 and raising the feed water temperature to near the upper limit temperature of the membrane module 6. Since the dissolved oxygen can be removed, the membrane deaerator can have a higher dissolved oxygen removal capacity than that obtained by normal water supply.
[0012]
Although the example which controlled the chemical injection apparatus 9 by ON-OFF was described in the present Example, the chemical injection rate which is the ratio of the chemical injection amount with respect to the amount of water supply is changed proportionally or in steps according to water supply temperature. Also good.
[0013]
【The invention's effect】
By implementing the present invention, the dissolved oxygen in the feed water can always be kept at a low value without excessively increasing the capacity of the membrane deaerator.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing the arrangement of devices in an embodiment of the present invention.
DESCRIPTION OF SYMBOLS 1 Membrane deaeration device 2 Water supply line 3 Boiler 4 Temperature detection device 5 Chemical injection control device 6 Membrane module 7 Water tank 8 Vacuum generator 9 Chemical injection device 10 Chemical injection piping 11 Steam introduction control valve 12 Steam introduction piping 13 Feed water heating device 14 Feed water heating control device 15 Main steam piping

Claims (1)

A membrane deaerator is provided in the middle of the water supply line for supplying water to the boiler, and a feed water heater for heating the feed water sent to the membrane deaerator using a part of the steam generated in the boiler, the heated water supply A temperature detection device for detecting the temperature, a chemical injection device for injecting an oxygen scavenger into the feed water line downstream from the membrane deaeration device, and a steam introduction control valve for controlling the introduction of steam to the feed water heating device are provided. When the feed water temperature detected by the temperature detection device is lower than the preset value for the chemical injection, the operation of the chemical injection device is output. When the feed water temperature detected by the temperature detection device is less than the set value for starting the feed water heating , connected to the chemical injection control device, the temperature detection device and the steam introduction control valve for performing the operation stop output of the injection device with a signal line Open the steam introduction control valve and set the membrane module in the membrane deaerator. Feedwater heater controller film deaerator used in combination degassed with chemicals by feed water temperature, characterized in that a performing rising when the control to close the steam introduction control valve to feed water heating stop set value which is the upper limit of.

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