JP6592980B2 - Oxygen scavenger and oxygen scavenging method - Google Patents

Description

  The present invention relates to an oxygen scavenger and a oxygen scavenging method. More specifically, the present invention relates to a deoxygenating agent to be added to boiler feedwater and a deoxygenating method to add a deoxygenating agent to boiler feedwater.

  2. Description of the Related Art Conventionally, a technique for adding an oxygen scavenger to boiler feed water supplied to a boiler is known in order to prevent corrosion of piping and the like in the boiler system. As such an oxygen scavenger, for example, a liquid in which an oxygen scavenging component such as ascorbic acid or erythorbic acid that reacts with dissolved oxygen in boiler feed water is dissolved (see, for example, Patent Document 1).

Japanese Patent No. 5513413

  By the way, when the concentration of the oxygen scavenger component in the oxygen scavenger is low, the amount added to the boiler feedwater tends to increase, so the capacity of the oxygen scavenger injection pump is increased and the frequency of transport and replenishment of the oxygen scavenger increases. As a result, the cost increases. On the other hand, when the concentration of the oxygen scavenger component in the oxygen scavenger is increased, the oxygen scavenger component is likely to precipitate, and the liquid stability of the oxygen scavenger is lowered.

  This invention is made | formed in view of the said subject, and it aims at providing the deoxidizer added to boiler feed water which is excellent in liquid stability although the density | concentration of a deoxidation component is high.

  The present invention is an oxygen scavenger to be added to boiler feed water, comprising an ascorbic acid compound of more than 12% by mass and 20% by mass or less, an erythorbic acid compound of 1% by mass to 8% by mass, and water. The total content of the ascorbic acid compound and the erythorbic acid compound relates to an oxygen scavenger that is more than 20% by mass.

  Moreover, it is preferable that the boiler water supply is water supply to a multitubular once-through boiler.

  The present invention also relates to a deoxygenation method in which 20 to 320 mg of the deoxidizer is added to 1 L of boiler feed water.

  ADVANTAGE OF THE INVENTION According to this invention, although the density | concentration of a deoxidation component is high, the deoxidation agent added to boiler feed water which is excellent in liquid stability can be provided.

It is a schematic diagram which shows the structure of the boiler apparatus using the oxygen absorber which concerns on one Embodiment of this invention.

Hereinafter, an embodiment of the present invention will be described.
First, a boiler apparatus 1 using an oxygen scavenger according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing the configuration of the boiler device 1. The boiler device 1 in this embodiment includes a boiler 2, a hard water softening device 3, a water supply tank 4, and an oxygen scavenger addition device 5.
The boiler device 1 also includes a water supply line L1, a fuel supply line L2, a blow line L3, a steam discharge line L4, a steam delivery line L5, a precipitation line L6, and an oxygen scavenger addition line L7. . The “line” in the present specification is a general term for lines capable of flowing a fluid such as a flow path, a path, and a pipeline.

The boiler 2 generates steam to be supplied to steam use equipment (not shown). The boiler 2 includes a boiler body 21, a burner 27, a combustion chamber 26, a feed water pump 6 as boiler feed water supply means, and a steam / water separator 7. The boiler body 21 forms a pressure vessel including a plurality of water pipes 22, an upper header 23, and a lower header 24.
The boiler 2 is a multitubular once-through boiler. In addition, those used at a gauge pressure of 1 MPa or less and having a heat transfer area of 10 m ² or less are referred to as small once-through boilers (Occupational Safety and Health Law Enforcement Ordinance No. 1 No. 4).

  The water supply line L <b> 1 is a line that supplies the boiler water supply W <b> 1 to the boiler body 21. The upstream end of the water supply line L1 is connected to a supply source (not shown) of the boiler water supply W1. The downstream end of the water supply line L <b> 1 is connected to the lower header 24 of the boiler body 21. In the water supply line L1, the water softening device 3, the water supply tank 4, the connection part J1, and the water supply pump 6 are arranged in order from the supply source to the boiler 2.

  The hard water softening device 3 generates soft water by replacing hardness components contained in raw water such as tap water, ground water, and industrial water with sodium ions (or potassium ions). The water softening device 3 has a cation exchange resin bed 3a. The cation exchange resin bed 3a performs water softening treatment of the boiler feed water W1 supplied to the boiler body 21. The water softening device 3 supplies treated water (soft water) obtained by softening the raw water W0 with the cation exchange resin bed 3a toward the boiler 2 as boiler feed water W1.

The feed water tank 4 stores the treated water softened by the hard water softening device 3 as boiler feed water W1. The boiler feed water W1 stored in the feed water tank 4 is supplied to the boiler body 21 by the feed water pump 6.
The feed water pump 6 sucks the boiler feed water W1 from the feed water tank 4, and sends the boiler feed water W1 flowing through the feed water line L1 toward the boiler body 21.

  The downstream end of the oxygen scavenger addition line L7 is connected to the connection J1. An oxygen scavenger addition device 5 as a oxygen scavenger supply means is connected to the upstream end of the oxygen scavenger addition line L7. The oxygen scavenger addition device 5 is a device for adding (supplying) an oxygen scavenger to the boiler feed water W1. The oxygen absorber added to the boiler feed water W1 from the oxygen absorber adding device 5 will be described in detail later.

  The oxygen scavenger addition device 5 is electrically connected to a control device (not shown). The timing and amount of addition of the drug from the oxygen scavenger addition device 5 to the connection portion J1 of the water supply line L1 are controlled by a drive signal transmitted from the control device.

  The boiler body 21 is composed of a group of water pipes erected in the vertical direction between the upper and lower headers, and constitutes the main part of the outer shape of the boiler 2. In the boiler body 21, the boiler feed water W1 supplied through the feed water line L1 is stored as boiler water W2. The boiler water W2 includes water that once accumulates in the boiler body 21 as the boiler water W2 and then taken out as steam and returns to the boiler body 21. For example, the boiler water W <b> 2 includes separated water W <b> 3 that is separated by a steam / water separator 7 described later and returned to the boiler body 21.

  Inside the boiler body 21, boiler water W2 is stored. The boiler body 21 includes a plurality of water pipes 22, an upper header 23, and a lower header 24. The plurality of water pipes 22 are arranged extending in the vertical direction of the boiler body 21. The upper header 23 is disposed on the upper portion of the boiler body 21. The upper header 23 is configured by, for example, an annular container. The upper header 23 is connected to upper ends of a plurality of water pipes 22. The upper header 23 is connected to one end of a steam extraction line L4 described later.

  The lower header 24 is disposed below the boiler body 21. The lower header 24 is constituted by, for example, an annular container. The lower header 24 is connected to lower ends of the plurality of water pipes 22. One end of the side wall of the lower header 24 is connected to the end of the water supply line L1. The other end of the side wall of the lower header 24 is connected to the end of the precipitation line L6. The combustion chamber 26 is configured by a space surrounded by a plurality of water pipes 22.

  The burner 27 heats the inside of the boiler body 21 by burning. The burner 27 is disposed in the central portion on the upper side of the boiler body 21. The burner 27 includes a fuel injection nozzle and an air supply nozzle (both not shown). The burner 27 injects fuel from the fuel injection nozzle toward the combustion chamber 26 of the boiler body 21 and supplies air from the air supply nozzle into the boiler body 21 to burn the fuel.

  The fuel supply line L <b> 2 is a line that supplies the fuel F burned by the burner 27 to the burner 27. The upstream end of the fuel supply line L2 is connected to a fuel F supply source (not shown). The downstream end of the fuel supply line L2 is connected to the burner 27. A fuel supply valve 81 is disposed in the fuel supply line L2. The fuel supply valve 81 is a valve that adjusts the amount of fuel supplied to the burner 27.

  The steam extraction line L4 is a line for taking out the wet steam SM1 generated in the water pipe 22 from the upper header 23 and introducing it into the steam separator 7. The upstream end of the steam extraction line L4 is connected to the upper surface of the upper header 23 of the boiler body 21. The downstream end portion of the steam extraction line L4 is connected to the upper side of the side portion of the steam / water separator 7.

  The steam separator 7 is a device that separates the wet steam SM1 introduced from the upper header 23 through the steam extraction line L4 into dry steam SM2 and moisture (hereinafter also referred to as “separated water W3”). As described above, the separated water W3 separated by the steam separator 7 is also a part of the boiler water W2.

  The steam delivery line L5 is a line that delivers dry steam SM2 separated by the steam separator 7 toward a steam header (not shown). The dry steam SM2 is supplied to a steam use facility (not shown) through a steam header.

  The precipitation line L6 is a line for flowing the separated water W3 separated by the steam separator 7 toward the lower header 24 of the boiler body 21. The upstream end of the precipitation line L6 is connected to the lower part of the steam separator 7. The downstream end of the precipitation line L6 is connected to the lower header 24. Moreover, the connection part J2 is arrange | positioned at the precipitation line L6.

  The upstream end of the blow line L3 is connected to the connecting part J2. The blow line L3 is a line for discharging the separated water W3 (boiler water W2) flowing through the precipitation line L6 (precipitation pipe) to the outside of the boiler 2 through the connection portion J2. A blow valve 82 is provided in the blow line L3. By opening the blow valve 82, the separated water W3 (boiler water W2) flowing through the precipitation line L6 (precipitation pipe) is discharged to the outside.

Subsequently, an oxygen scavenger according to an embodiment of the present invention will be described.
The oxygen scavenger according to the present embodiment contains an ascorbic acid compound, an erythorbic acid compound, and water.

Ascorbic acid compounds include ascorbic acid and ascorbic acid salts. Examples of salts of ascorbic acid include alkali metal salts such as sodium ascorbate and potassium ascorbate, alkaline earth metal salts such as calcium ascorbate, organic salts such as ammonium salts, diethanolamine salts and triethanolamine salts, and the like. be able to.
The oxygen scavenger according to this embodiment preferably contains at least one of ascorbic acid and an alkali metal salt of ascorbic acid as the ascorbic acid compound from the viewpoint of solubility in water.

  The ascorbic acid compound reacts with dissolved oxygen in the boiler feed water, thereby reducing the dissolved oxygen concentration in the boiler feed water and preventing corrosion of the piping of the boiler device. For example, ascorbic acid reacts with oxygen and is oxidized to produce dehydroascorbic acid.

  The oxygen scavenger contains more than 12% by mass and 20% by mass or less of an ascorbic acid compound. When the oxygen scavenger contains 12% by mass or less of the ascorbic acid compound, the required amount of oxygen scavenger added to the boiler feed water increases. On the other hand, when the oxygen scavenger contains more than 20% by mass of the ascorbic acid compound, the liquid stability of the oxygen scavenger decreases because the ascorbic acid compound is difficult to dissolve in water.

Examples of erythorbic acid compounds include erythorbic acid and erythorbic acid salts. Examples of erythorbic acid salts include alkali metal salts such as sodium erythorbate and potassium erythorbate, alkaline earth metal salts such as calcium erythorbate, organic amine salts such as ammonium salts, diethanolamine salts, and triethanolamine salts. be able to.
The oxygen scavenger according to this embodiment preferably contains at least one of erythorbic acid and an alkali metal salt of erythorbic acid as the erythorbic acid compound from the viewpoint of solubility in water.

  Erythorbic acid is a diastereomer of ascorbic acid. Like the ascorbic acid compound, the erythorbic acid compound reacts with dissolved oxygen in the boiler feed water, thereby reducing the dissolved oxygen concentration in the boiler feed water and preventing corrosion of the piping of the boiler apparatus. For example, erythorbic acid reacts with oxygen and is oxidized to produce dehydroerythorbic acid (dehydroisoascorbic acid).

  The oxygen scavenger contains 1% by mass or more and 8% by mass or less of the erythorbic acid compound. When the oxygen scavenger contains less than 1% by mass of the erythorbic acid compound, the required amount of oxygen scavenger added to the boiler feed water increases. On the other hand, when the oxygen scavenger contains more than 8% by mass of the erythorbic acid compound, the liquid stability of the oxygen scavenger decreases because the erythorbic acid compound is difficult to dissolve in water.

  The total content of ascorbic acid compound and erythorbic acid compound in the oxygen scavenger is more than 20% by mass. Since the total content of the ascorbic acid compound and the erythorbic acid compound is more than 20% by mass, the oxygen absorber can reduce the amount added to the boiler feed water, and the capacity of the oxygen absorber injection pump can be reduced. The cost for transporting and replenishing the oxygen scavenger can be reduced. In addition, the upper limit of the total content of ascorbic acid compound and erythorbic acid compound in the oxygen scavenger is 28% by mass. When the total content of the ascorbic acid compound and the erythorbic acid compound exceeds this upper limit value, the liquid stability of the oxygen scavenger is lowered. The lower limit of the total content of ascorbic acid compound and erythorbic acid compound is preferably 21% by mass.

  The contents of the ascorbic acid compound and the erythorbic acid compound in the oxygen scavenger are the contents when the ascorbic acid compound and the erythorbic acid compound are converted into ascorbic acid and erythorbic acid, respectively. For example, when the oxygen scavenger contains sodium ascorbate as the ascorbic acid compound, the content is obtained by converting the sodium salt of ascorbic acid into a free acid.

  The oxygen scavenger according to this embodiment may contain a scale inhibitor, a pH adjuster, and the like as necessary in addition to the ascorbic acid compound and the erythorbic acid compound. Examples of the scale inhibitor include carboxylic acid polymers, acrylic acid polymers, phosphonic acid chelating agents, carboxylic acid chelating agents, and the like. Moreover, as a pH adjuster, sodium hydroxide, potassium hydroxide, etc. which can prevent the fall of pH in a boiler type | system | group are mentioned.

  In addition, ascorbic acid compounds and erythorbic acid compounds are highly safe compounds that are also used as food additives. Therefore, the oxygen scavenger according to the present embodiment is highly safe for the human body and excellent in handleability.

  Next, the deoxygenation method according to this embodiment will be described. In the deoxygenation method according to the present embodiment, 20 to 320 mg of the above deoxidizer is added to 1 L of boiler feed water. More specifically, in FIG. 1, 20 to 320 mg of oxygen scavenger is added from the oxygen scavenger addition device 5 to the connector J1 while 1 L of boiler feed water W1 flows through the connector J1 of the water supply line L1.

  When the amount of the oxygen scavenger added to 1 L of boiler feed water is less than 20 mg, the dissolved oxygen concentration in the boiler feed water tends not to be sufficiently reduced. On the other hand, when the amount of the oxygen scavenger added to 1 L of boiler feed water exceeds 320 mg, the capacity of the oxygen scavenger injection pump, the cost for transporting and replenishing the oxygen scavenger, etc. tend to increase.

According to the oxygen scavenger and the oxygen scavenging method according to the present embodiment, the following effects are exhibited.
(1) In this embodiment, the oxygen scavenger added to the boiler feedwater is more than 12 mass% and 20 mass% or less ascorbic acid compound, 1 mass% or more and 8 mass% or less erythorbic acid compound, and water. It was supposed to contain. Moreover, the total content of the ascorbic acid compound and the erythorbic acid compound in the oxygen scavenger was over 20% by mass.
Thereby, although the density | concentration of a deoxidation component is high, the deoxidation agent added to boiler feed water which is excellent in liquid stability can be provided.

(2) In this embodiment, the boiler feed water to which the oxygen scavenger is added is the feed water to the multi-pipe once-through boiler.
The multi-pipe once-through boiler is prone to corrosion because the lower header 24 and the lower part of the water pipe 22 are likely to be in a low concentration state (low pH state) at the time of start-up or low combustion load. For example, in low pH boiler water having a pH of less than 11, since the corrosion is accelerated when the dissolved oxygen concentration is high, deoxygenation of boiler feed water is important. Therefore, the oxygen scavenger according to the present embodiment can be preferably used for such a multitubular flow through.

(3) In the deoxygenation method according to the present embodiment, 20 to 320 mg of the above deoxidizer is added to 1 L of boiler feed water.
Thereby, the dissolved oxygen concentration of boiler feed water can be reduced effectively, suppressing the usage-amount of an oxygen scavenger.

Although the oxygen scavenger and the oxygen scavenging method according to one embodiment of the present invention have been described above, the present invention is not limited to the above-described embodiment, and can be changed as appropriate.
In this embodiment, the oxygen scavenger is added to the feed water to the multi-tube once-through boiler, but the boiler feed water to which the oxygen scavenger according to the present invention is added is used to feed water to the multi-tube once-through boiler. It is not limited.

  Next, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.

[Examples and Comparative Examples]
Ascorbic acid and / or erythorbic acid as a deoxygenating component was dissolved in pure water (25 ° C.) so as to have the content shown in Table 1, thereby adjusting each oxygen scavenger of Examples and Comparative Examples. .

[Solubility of deoxygenated components]
For each of the oxygen scavengers in the examples and comparative examples, the solubility of the oxygen scavenging component was evaluated. The evaluation of the solubility of the deoxygenated component is “◎” when the deoxygenated component is purely added and immediately dissolved, and when the deoxygenated component is dissolved by 90 minutes after adding pure water. “O” was assigned, and “X” was given when the deoxygenated component was not dissolved after 90 minutes from the addition of pure water. The results are shown in Table 1.

[Liquid stability]
The liquid stability was evaluated for each oxygen scavenger of Examples and Comparative Examples. The liquid stability was evaluated by leaving each oxygen scavenger in a 25 ° C. environment for 30 days. In the evaluation of liquid stability, the evaluation result was “◯” when precipitation or turbidity did not occur after standing, and the evaluation result was “X” when precipitation or turbidity occurred after standing. The results are shown in Table 1.

  From comparison between Examples 1-4 and Comparative Examples 3 and 4, it was found that the oxygen scavengers of Examples 1-4 were higher in liquid stability than the oxygen scavenger of Comparative Example 4. From these results, the content of ascorbic acid and erythorbic acid in the oxygen scavenger is more than 12% by mass and 20% by mass or less and 1% by mass or more and 8% by mass or less, respectively. It was confirmed that it could be improved.

  As is clear from the comparison between Comparative Example 2 and Comparative Example 3, when only ascorbic acid is contained in the oxygen scavenger, the upper limit of the content of ascorbic acid is about 20% by mass. In contrast, the oxygen scavengers (Examples 1 to 4) according to the present invention are mixed with ascorbic acid and erythorbic acid to optimize the respective contents, and the concentration of the oxygen scavenging component is the same as that of the conventional oxygen scavenger. It is higher than the oxygen agent (Comparative Examples 1 and 2).

DESCRIPTION OF SYMBOLS 1 ... Boiler apparatus 2 ... Boiler 21 ... Boiler main body 22 ... Water pipe 23 ... Upper header 24 ... Lower header 26 ... Combustion chamber 27 ... Burner 3 ... Hard water softening device 3a ... Cation exchange resin bed 4 ... Water supply tank 5 ... Deoxygenating agent Addition device 6 ... Water supply pump 7 ... Air / water separator 81 ... Fuel supply valve 82 ... Blow valve L1 ... Water supply line L2 ... Fuel supply line L3 ... Blow line L4 ... Steam discharge line L5 ... Steam delivery line L6 ... Precipitation line L7 ... Oxygen scavenger addition line J1, J2 ... Connection part W0 ... Raw water W1 ... Boiler feed water W3 ... Separation water W2 ... Boiler water SM1 ... Wet steam SM2 ... Dry steam F ... Fuel

Claims (3)

A liquid oxygen scavenger added to boiler feed water,
An ascorbic acid compound of more than 12% by mass and 20% by mass or less;
1% by mass or more and 8% by mass or less of an erythorbic acid compound;
Containing water,
A liquid oxygen scavenger in which the total content of ascorbic acid compound and erythorbic acid compound is more than 20% by mass.   The oxygen scavenger according to claim 1, wherein the boiler feed water is feed water to a multi-tube once-through boiler.   A deoxygenation method in which 20 to 320 mg of the oxygen scavenger according to claim 1 or 2 is added to 1 L of boiler feed water.

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