JP2007263385A - Boiler feed water treatment device, boiler device, and operation method of boiler feed water treatment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reliably deoxygenate even if a feed water temperature fluctuates without installing an oxygen scavenger excessively or installing a deoxygenation device having a high deoxygenation function, and a boiler apparatus operated by such a method I will provide a.
A boiler apparatus includes a water supply tank 20 to which makeup water is supplied from a raw water tank 10, means 30 for deoxidizing water in the water supply tank, a boiler body 40 to which water after deoxygenation is supplied, And a pipe L5 for returning drain condensed after being evaporated in the boiler body to the water supply tank. The water in the water supply tank 20 is heated with water vapor sent from the boiler body 20 through the pipe L6. A solenoid valve 50 is provided in the pipe L6. The water supply tank 20 is provided with a temperature sensor 60 to measure the water temperature of the water supply in the tank. The control device 70 controls the electromagnetic valve 50 based on the water temperature measured by the temperature sensor 60 and maintains the temperature of the water in the water supply tank 20 at a predetermined temperature.
[Selection] Figure 1

Description

  The present invention relates to boiler feed water treatment and the like, and more particularly, to a boiler feed water treatment apparatus that can supply makeup water that has been suitably deoxygenated even when the temperature of the feed water fluctuates, a boiler apparatus operating method, and a boiler apparatus.

  Currently used boiler water is softened water obtained by removing hardness components (Ca, Mg, etc.) from raw water (city water, industrial water, etc.). The boiler water is further subjected to deoxygenation treatment to remove dissolved oxygen in the water in order to prevent corrosion of the boiler tube and the like. As the deoxygenation treatment, mechanical treatment using a deaerator and chemical treatment adding an oxygen scavenger to makeup water are performed.

  Examples of the mechanical treatment include methods such as nitrogen degassing, vacuum degassing, and membrane separation. Examples of the oxygen scavenger used for the chemical treatment include hydrazine, sulfite, saccharides and the like.

  By the way, in recent years, in order to save energy and save water, the number of cases where the drain generated in the boiler is returned to the water supply tank and reused is increasing. Since the amount of this return drain is constantly fluctuating depending on the state of use of steam at the demand point, the feed water temperature fluctuates accordingly. Moreover, the water temperature of boiler feed water also fluctuates due to fluctuations in outside air temperature.

  By the way, the dissolved oxygen concentration of makeup water becomes higher as the water temperature is lower. Therefore, in the case of a boiler in which the temperature of the makeup water fluctuates, the addition amount of the oxygen scavenger and the operating conditions of the oxygen absorber are set so that the oxygen scavenging process can be performed in accordance with the lowest water temperature. For this reason, when using an oxygen scavenger, the amount of oxygen scavenger added becomes excessive as the water temperature of the makeup water increases. Then, excessive oxygen scavenger decomposes thermally and corrosion of the steam piping occurs, which may cause deterioration of water quality. Moreover, when using a deoxygenation apparatus, the apparatus which has a high deoxygenation function will be used. Then, when the feed water temperature becomes high and the dissolved oxygen concentration becomes low, this deoxygenation function becomes useless, and there arises a problem that the cost increases and the maintenance frequency increases.

  The present invention has been made in view of the above-described problems, and can be reliably removed even if the feed water temperature fluctuates without installing an excessive amount of an oxygen scavenger or installing an oxygen scavenging device having a high oxygen scavenging function. It is an object of the present invention to provide a method of oxygen and a boiler device operated by such a method.

  The boiler water supply apparatus of the present invention is a boiler water supply treatment apparatus comprising a system for supplying water to a boiler, and means for deoxidizing the water, and further, heating means for heating the water, and the heating Control means for controlling the means to maintain the temperature of the water at a predetermined temperature.

  According to the present invention, since water heated and maintained at a predetermined temperature is supplied to the boiler body, the dissolved oxygen concentration of the water supplied to the boiler body can be set to a substantially constant low value. For this reason, when performing a deoxygenation process chemically, it suffices to supply a certain amount of an oxygen scavenger suitable for this dissolved oxygen concentration, and avoid the situation of excessive addition of the oxygen scavenger. it can. Moreover, when performing a mechanical deoxygenation process, it is not necessary to install the deoxygenation apparatus which has a too high deoxygenation capability.

  In this invention, it is preferable that the water supply tank which stores the said water is provided in the upstream of the said deoxygenation means of the said water supply system, and the said heating means heats the water in this water supply tank.

  In this case, since the water in the water supply tank is heated, the temperature control stability is high. If the steam generated in the boiler is introduced into the water supply tank as the heating means, it is not necessary to newly provide the heating means.

  The boiler apparatus of the present invention includes a water supply tank to which makeup water is supplied from a raw water supply source, a means for deoxygenating water in the water supply tank, a boiler body to which water after deoxidation is supplied, and the boiler body And a pipe for returning the drain condensed by the steam generated in step 1 to the water supply tank, the means for heating the water in the water supply tank, and the temperature of the water heated in the means at a predetermined temperature. And means for maintaining.

  According to the present invention, since the means for heating the water in the water supply tank and maintaining it at a predetermined temperature is provided, the dissolved oxygen concentration of the water in the water supply tank can be set to a substantially constant low value. For this reason, the conditions for the deoxygenation treatment can be determined based on this low dissolved oxygen concentration, and deoxygenation can be performed under certain conditions while preventing a situation such as the addition of an excessive oxygen scavenger. And since there is no fear of deoxygenation, the progress of the corrosion of the boiler tube by dissolved oxygen can be sufficiently delayed.

  The operation method of the boiler feedwater treatment device of the present invention is a method for operating a boiler feedwater treatment device comprising a system for supplying water to a boiler and means for deoxidizing the water, and heating the water A step of maintaining a constant temperature; and a step of removing dissolved oxygen from water maintained at a constant temperature by the step.

  According to the present invention, since dissolved oxygen is removed from water that is heated and maintained at a constant temperature, the conditions for deoxidation hand treatment can be determined based on the dissolved oxygen concentration at that temperature, Deoxygenation is possible

  In this invention, it is preferable that the said heating process heats the water in the water supply tank which stores the said water provided in the upstream of the said deoxidation means.

  In this case, if the water in the water supply tank is heated so that the steam generated in the boiler is introduced into the water supply tank as the heating means, it is not necessary to newly provide the heating means.

In the present invention, the types of boiler devices include a round boiler, a water tube boiler, a once-through boiler, a special boiler, and the like. These boilers may be any of low pressure, medium pressure, and high pressure boilers.
The water in the raw water tank may be softened water, pure water, or a mixed water thereof.

  Furthermore, as the deoxygenation treatment means, either a mechanical treatment means using a deaerator or a chemical treatment means for adding a deoxidizer to the makeup water may be used. Examples of the mechanical treatment means include nitrogen degassing, vacuum degassing, membrane separation, and combinations thereof. Examples of the oxygen scavenger used in the chemical treatment means include hydrazine, sulfite, and saccharide.

Examples of the heating means include a heat exchanger, steam blowing, and a heater.
Moreover, a thermometer can be mentioned as a temperature sensor. As a temperature of makeup water, it can be 8-25 ° C, for example. Moreover, as a temperature of the water heated by the heating means, it can be 40-70 degreeC, for example.

  As is clear from the above description, according to the present invention, water heated and maintained at a predetermined temperature is supplied to the boiler body, so that the dissolved oxygen concentration can be set to a substantially constant low value. . For this reason, the conditions for the deoxygenation treatment can be determined based on this low dissolved oxygen concentration, and deoxygenation can always be performed under optimum constant conditions. In addition, the progress of corrosion of the boiler tube by dissolved oxygen can be delayed.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram for explaining a configuration of a boiler apparatus according to an embodiment of the present invention.
The boiler device includes a raw water tank 10, a water supply tank 20 to which makeup water is supplied from the raw water tank 10, a chemical supply device (deoxygenation processing means) 30 for adding an oxygen scavenger to the water in the water supply tank 20, a deoxygenation It consists mainly of a boiler body 40 to which water is supplied later, and a pipe L5 for returning the drain condensed by steam generated in the boiler body 40 to the water supply tank.

First, the configuration of the entire boiler apparatus will be briefly described.
The raw water tank 10 stores raw water (city water, groundwater, industrial water, etc.) that has been softened by a water softener (not shown). This raw water is supplied to the water supply tank 20 through the pipe L1. The raw water supplied to the water supply tank 20 is supplied to the boiler body 40 through the pipe L2. A chemical liquid supply line L3 extending from the chemical liquid tank 31 of the chemical liquid supply device 30 is connected to the pipe L2 from the side. The chemical solution supply line L3 is provided with a liquid feed pump 32 and a chemical solution tank 31 on its original side. The chemical tank 31 stores an oxygen scavenger such as sodium sulfite or hydrazine. When the liquid feed pump 32 is activated, the chemical liquid is fed into the pipe L2 through the chemical liquid supply line L3, and the chemical liquid is added.

  The water to which the oxygen scavenger is added is supplied to the boiler body 40 through the pipe L2. The steam generated in the boiler body 40 is fed to the demand point through the pipe L4, and the steam drain (condensate) is collected into the feed water tank 20 through the pipe L5.

  Another pipe L6 branches off from the pipe L4 extending from the boiler body 40. The tip of the pipe L6 is connected to the water supply tank 20, and water vapor is introduced into the water supply tank 20 to heat the water in the tank. Moreover, the solenoid valve 50 is provided in the pipe L6.

  The water supply tank 20 is provided with a temperature sensor 60 and measures the temperature of the water supply in the tank. The temperature sensor 60 and the electromagnetic valve 50 are electrically connected to the control device 70. The control device 70 controls the electromagnetic valve 50 based on the water temperature measured by the temperature sensor 60.

Next, the operation of this boiler apparatus will be described.
Drain is supplied to the water supply tank 20 through the pipe L5, and the water temperature in the tank rises. However, the amount of drain that returns to the water supply tank 20 varies depending on the state of use of steam at the demand point, and the water temperature in the water supply tank 20 also varies accordingly. Therefore, in the present invention, the temperature of the feed water in the feed tank 20 is measured by the temperature sensor 60. When the water temperature falls below the preset water temperature, the controller 70 controls the electromagnetic valve 50 to introduce steam from the boiler body 40 into the feed water tank 20 through the pipe L6. The temperature of the water supply in the tank 20 is raised. In addition, when the boiler main body 40 is cold, such as at the start of boiler operation, the water temperature can be increased using a separate heating means (for example, heat from an electric heater or heat exchanger).

  When the temperature of the water stored in the water supply tank 20 reaches the set temperature or higher due to the steam thus introduced, the solenoid valve 50 is closed to stop the introduction of the steam. By repeating these operations, the water temperature in the water supply tank 20 can be maintained substantially constant.

  Specifically, the temperature of the water stored in the water supply tank 20 is set to 60 ° C., for example. And if the water temperature of the feed water measured with the temperature sensor 60 falls below 60 degreeC, the control apparatus 70 will open the solenoid valve 50, will supply vapor | steam to the feed water tank 20 through the piping L6 from the boiler main body 40, and supply water. Warm up. And if the temperature of the feed water measured with the temperature sensor 60 will be 60 degreeC or more, the control apparatus 70 will close the solenoid valve 50, and will stop supply of the vapor | steam from the boiler main body 40. FIG.

  When the water temperature in the water supply tank 20 is maintained at a constant temperature in this way, the temperature of the water supplied to the boiler body 40 through the pipe L2 is maintained at a constant temperature, and the dissolved oxygen concentration of the water supply is also constant. Therefore, the chemical solution supply device 30 may always supply the optimum amount of oxygen scavenger necessary for removing the dissolved oxygen maintained at a constant amount from the chemical solution tank 31. Thereby, while preventing the situation which supplies an oxygen absorber excessively, deoxygenation of boiler feed water can be performed reliably.

In this example, the set temperature of the water supply in the water supply tank 20 can be set with a certain width (for example, 55 to 60 ° C.).
Further, as a heating means for the makeup water, a heating means such as heat from an electric heater or a heat exchanger can be used without using the steam of the boiler body 40.
Furthermore, the removal of dissolved oxygen may be performed by mechanical treatment such as nitrogen degassing, vacuum degassing, membrane degassing, etc. in addition to chemical treatment using a deoxidizing agent.

<Example>
A small reflux boiler was used as the boiler body 40 in FIG. The operation conditions of the boiler are: water supply speed: 1.1 t / h, pressure: 0.7 MPa, steam generation amount: 1 t / h, blow rate: 10%, drain water temperature: 75 ° C., and operation time is 24 hours. did. Raw water is softened industrial water (pH 8.0, 0.8 mS / m, M alkalinity: 35 mg / L, Cl concentration: 10 mg / L, Ca + Mg concentration: 1 mg / L, SiO ₂ concentration: 43 mg / L) It was used.

  Based on the water temperature measured by the temperature sensor 60 of the water supply tank 20, the solenoid valve 50 is controlled by the control device 70 so that the water temperature becomes 60 ° C., and the operation of the boiler body 40 is started.

  Table 1 shows the temperature of the feed water and the dissolved oxygen concentration in the feed water tank 20 in this example. From this table, it is understood that the water temperature is maintained at around 60 ° C. by the above-described temperature control, although there is some variation (58 to 65 ° C.). As a result, the dissolved oxygen concentration is also maintained at 4.3 to 4.9 mg / L.

<Comparative example>
In the boiler apparatus used in Example 1, the boiler operation was performed under the same conditions except that the solenoid valve 50 was normally closed, and the water temperature and dissolved oxygen concentration in the water supply tank were measured in the same manner.

  Table 2 shows the temperature of the feed water in the sub tank and the dissolved oxygen concentration in this comparative example. From this table, from 10:00 am to 18:00 pm, the water temperature is maintained at 40-50 ° C., and the dissolved oxygen concentration is maintained at a relatively low value of 5.6-6.4 mg / L. After 19:00, the water temperature rapidly decreases, and the dissolved oxygen concentration increases accordingly, reaching 10.3 mg / L at 24:00.

  Next, as a confirmation of the deoxygenation effect, in the above example, the carbon steel test piece installed at a height of 150 mm from the lower part of the boiler, and the economizer (not shown) installed in the pipe were installed at the entrance. The corrosion rate (test period 7 days) of a test piece (50 mm × 50 mm × 1 mm) made of carbon steel (SS41) was measured.

  On the other hand, in the above comparative example, as shown in Table 2, based on the fact that the dissolved oxygen concentration reaches 10.3 mg / L at the maximum, the necessary amount when the dissolved oxygen concentration is 10.3 mg / L. An oxygen scavenger was supplied from the chemical tank 31 of the chemical supply apparatus 30 to the pipe L2. In this example, 10% by weight of sodium sulfite was supplied to the pipe L2 at a flow rate of 990 ml / h. And the test made from carbon steel (SS41) installed in the entrance of the carbon steel test piece installed in the height of 150 mm from the boiler lower part and the economizer (not shown) installed in piping similarly to an Example. The corrosion rate (test period 7 days) of the piece (50 mm × 50 mm × 1 mm) was measured.

  Table 3 shows the measurement results of the corrosion rates of Examples and Comparative Examples. From Table 3, in the test piece installed in the lower part of the boiler, the corrosion rate in the example is reduced to about 1/5 of the comparative example, and in the test piece installed in the economizer, it is reduced to about 1/3. I understand.

It is a figure for demonstrating the structure of the boiler apparatus which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Raw water tank 20 Water supply tank 30 Chemical liquid supply apparatus 31 Chemical liquid tank 32 Liquid feed pump 40 Boiler main body 50 Electromagnetic valve 60 Temperature sensor 70 Control apparatus L1, L2, L3, L4, L5, L6 Piping

Claims (5)

A boiler water supply treatment apparatus comprising a system for supplying water to a boiler and means for deoxidizing the water,
And heating means for heating the water;
Control means for controlling the heating means to maintain the temperature of the water at a predetermined temperature;
A boiler feed water treatment apparatus comprising:   The water supply tank which stores the said water in the upstream of the said deoxygenation means of the said water supply system is provided, The said heating means heats the water in this water supply tank, The 1st aspect is characterized by the above-mentioned. Boiler feed water treatment equipment. A water supply tank to which makeup water is supplied from a raw water supply source;
Means for deoxygenating the water in the water supply tank;
Boiler body supplied with water after deoxidation,
Piping for returning the drain condensed by steam generated in the boiler body to the water supply tank;
A boiler device comprising:
Means for heating the water in the water supply tank;
Means for maintaining the temperature of the water heated in the means at a predetermined temperature;
A boiler device further comprising: An operation method of a boiler water supply treatment apparatus comprising a system for supplying water to a boiler, and means for deoxygenating the water,
Heating the water to maintain a constant temperature;
Removing dissolved oxygen from water maintained at a constant temperature by the step;
An operation method of a boiler feedwater treatment apparatus, comprising:   The operation method of the boiler feed water treatment apparatus according to claim 4, wherein the heating step heats water in a feed water tank that stores the water provided on the upstream side of the deoxygenation means.

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