JP6699234B2 - Boiler water treatment method - Google Patents

Description

  The present invention, when applying a film-forming amine and a feed water pH adjuster during normal operation of a boiler, supplements the treatment effect of the film-forming amine with a boiler agent and/or an oxygen scavenger to make up makeup water and recovery water. The present invention relates to a method for reducing the influence of the property of condensate as much as possible and effectively preventing the corrosion and scale of the boiler even in the case of boiler water with poor water quality.

  The "Boiler Water Supply and Boiler Water Special Committee" established in the General Machinery Subcommittee of the Japan Industrial Standards Committee deliberated on water quality standards and established JISB8223 "Boiler water supply and boiler water quality" in February 1961. Was done.

According to JIS B8223 (2015), the treatment of the water supply system is a volatile substance treatment (AVT(R)) using a volatile deoxidant or a volatile base (amine or ammonia), and a small amount of oxygen is added to adjust the oxygen concentration. Oxygen treatment (OT) to make 20 to 50 μg/L, AVT (LO) to apply volatile substance treatment when oxygen concentration is less than 5 μg/L, volatile substance treatment when oxygen concentration is 5 to 20 μg/L Is applied to AVT(O). In OT, AVT(LO), and AVT(O), the advantage of including oxygen in the water supply lies in the suppression of FAC (flow accelerated corrosion), which has been a problem in recent years.
Among them, it is described that it is desirable to change to AVT(R) when oxygen exceeds the lower limit of 5 μg/L of AVT(O) and copper is present in the system.

  In JP-A-2010-216762, by adding a deoxidizing agent immediately before the use site of copper, the elution of iron in a relatively low temperature region where FAC is likely to occur is suppressed and the deoxidizing agent is added. By doing so, a method for suppressing the elution of copper is disclosed.

  FIG. 1 is a system diagram showing a power generation boiler system described in JP 2010-216762 A.

  This power generation boiler system 1 is for generating high-pressure steam S1 in the boiler device 2 and operating the power generator 10 with this high-pressure steam S1. The boiler device 2, the deaerator 3, the water supply tank 4, and 2 High-pressure boiler system including secondary water supply line 5, primary water supply line 6, pH adjusting agent injecting device 7, decanting agent injecting device 8, and oxygen absorber injecting device 9, power generation device 10, and steam It is composed of a line 11 and a condensate line 12.

  The boiler device 2 has a water tube boiler that generates high-pressure steam S1 as a main part, and an economizer 20 that preheats the boiler feed water W3, a steam generation unit 21 that has a steam drum, and a saturated steam superheated at a constant temperature. It has a super heater (not shown) for making steam. From the boiler apparatus 2, the steam line 11 is used to supply the high-pressure steam S1 for power generation to the steam turbine of the power generation apparatus 10.

  The deaerator 3 is for physically removing the dissolved gas (mainly dissolved oxygen) in the boiler feed water W3 by bringing the boiler feed water W3 into contact with the low-pressure steam S2 to heat it. The boiler feed water W3 in the deaerator 3 is usually heated to about 110 to 120° C. by the low pressure steam S2 generated by the use of the high pressure steam S1 on the power generation device 10 side.

  The water supply tank 4 temporarily stores the condensate water W1 from the condensate line 12 and the makeup water W2 from the makeup water line 13, and supplies the mixed water to the boiler device 2 side as the boiler feed water W3. It is a thing. The condenser line 12 is provided with a condenser 120 and a desalting device (polisher) not shown, and the condensate W1 of the high-pressure steam S1 extracted from the condenser 120 side is desalted. The contact portion of the condenser 120 with the condensate W1 is usually made of a copper-based material (copper or copper alloy) in order to increase the heat transfer coefficient.

  The secondary side water supply line 5 is a water supply line from the outlet of the deaerator 3 to the inlet of the economizer 20 of the boiler device 2, through which the boiler water supply W3 flows. The secondary side water supply line 5 supplies the feed water pump 50 that pressurizes the boiler feed water W3 deaerated by the deaerator 3 to high pressure, and the boiler feed water W3 that is pressurized to high pressure from the power generation device 10 side. It has a high-pressure feed water heater 51 that is heated by the like, and a pipe portion 52 that connects the devices. The high-pressure feed water heater 51 heats the boiler feed water W3 from 110° C. to 200° C., for example. Incidentally, in recent years, no copper-based material has been used in a portion of the secondary side water supply line 5 that is in contact with the boiler water supply W3, and almost all the material is a steel-based material.

  In the piping 52 between the high-pressure feed heater 51 and the economizer 20 of the secondary side water supply line 5 and in front of the economizer 20, the sampling portion P1 of the boiler can M1 and the boiler feed water W3 are sampled at positions where they are gradually separated from the economizer 20. A part P2 and an injection part P3 for the oxygen absorber M2 are provided. The dewatering agent injecting device 8 injects the dewatering agent M1 into the injecting section P1, and the sampling sample P2 takes out the analysis sample of the boiler feed water W3 at this position. P1 may be directly inserted into the boiler drum.

  The primary side water supply line 6 is a water supply line through which the boiler water supply W3 from the water supply tank 4 outlet to the deaerator 3 inlet flows. The primary side water supply line 6 is a pipe connecting the equipment to a low pressure water supply heater 60 that directly or indirectly heats the boiler water supply W3 at the outlet of the water supply tank 4 with steam (derived from the high-pressure steam S1) on the power generator 10 side. And a part 61. In the portion of the primary side water supply line 6 that is in contact with the boiler water supply W3, a copper-based material is usually not used, and almost all the material is a steel-based material. Since the low-pressure feed water preheater 60 before the deaerator 3 has a low boiler feed water W3 temperature and low corrosiveness, a copper-based material may be used.

  An injection part P5 of the pH adjusting agent M3 is provided between the water supply tank 4 of the primary side water supply line 6 and the low-pressure water supply heater 60. From this injection part P5, the pH adjusting agent injection device 7 operates the pH. Conditioning agent M3 is injected. The oxygen scavenger M2 is often injected by the oxygen scavenger injection device 9 before and after the injection part P5 instead of the injection part P3.

  In this power generation boiler system 1, the condensate water W1 and makeup water W2 collected in the condensate line 12 are collected in the water supply tank 4, and the boiler water supply W3 in the water supply tank 4 passes through the primary side water supply line 6. Is supplied to the deaerator 3 and heated in the primary side water supply line 6 to, for example, 50° C. by the low-pressure feed water heater 60, and the pH adjuster M3 and the oxygen scavenger M2 are injected to adjust the pH The 25° C. standard is raised to a constant value (eg pH 9.0). The boiler feed water W3 supplied to the deaerator 3 comes into contact with the low-pressure steam S2 and is deaerated while being heated to, for example, 110° C., and the dissolved oxygen concentration at the outlet of the deaerator 3 is reduced.

  The boiler feed water W3 that has been degassed by the deaerator 3 is heated to, for example, 200° C. by the high-pressure feed water heater 51 after the pressure is raised to a predetermined value by the water feed pump 50, and the economizer of the boiler device 2 is then used. Immediately before 20, the boiler agent M1 was injected, the dissolved oxygen concentration of the boiler water and the like in the boiler apparatus 2 was maintained at almost zero by the oxygen scavenger M2 added in P3 or P5, and the boiler apparatus 2 side The obstruction of boiler water in is eliminated. Then, the high-pressure steam S1 generated in the boiler device 2 is sent to the power generation device 10 via the steam line 11, used for power generation (rotating the steam turbine), and then recovered as the condensed water W1 in the condensate line 12. , Part of the boiler water supply W3. Since part of the steam is consumed in the boiler device 2 and the like, the makeup water W2 is supplemented.

  On the other hand, in place of the conventional treatment using a deoxidizer such as hydrazine, water treatment using a film-forming amine has come to be performed especially in overseas countries. This method is a method of preventing corrosion by adding a long-chain alkylamine such as octadecylamine called a film-forming amine to form a water-repellent film on the metal surface in the steam condensing system pipe.

  For example, Power Plant Chemistry, 2009, vol. 11(2) and the like describe that a long-chain aliphatic amine such as oleylpropanediamine is used to form an adsorption film on a metal surface to suppress boiler corrosion. In this case, since the film-forming amine has no effect of increasing the pH, when the film-forming amine treatment is carried out, ammonia or a basic amine such as a neutralizing amine is used together, or the film-forming amine and the neutralizing property are neutralized. Water treatment chemicals mixed with amines are used to control the pH of feed/condensate and boiler water.

The treatment using a film-forming amine is described in Power Plant Chemistry, 2015, vol. It is said that it has an effect of suppressing FAC (flow accelerated corrosion) as shown in 17 (6) and the like.
Power Plant Chemistry 2015, vol. Table 1 of 17(6) can be applied to a system in which copper is present in the feed water oxygen concentration range of 5 to 20 ppb, but the cation conductivity of the boiler water is limited to 5 μS/cm or less, and It is described that it cannot be applied to boiler water with high conductivity (0.5 or less is a typographical error).

On the other hand, in AVT(R) of JIS B8223 (2015) (using hydrazine as a deoxidizer) and AVT(LO) of less than 5 μg/L of oxygen feed water, the cation conductivity of boiler water is allowed up to 20 μS/cm. This indicates that the combined use of the oxygen scavenger suppresses corrosion in the concentrated boiler water even if a trace amount of chloride and sulfate ions coexist. From this point, it can be said that the deoxidation treatment is more effective for the deterioration of the water quality of the feed water.
Here, the cation conductivity is an index of corrosive ions such as sulfate ions and chloride ions, and the higher the cation conductivity, the higher the corrosiveness of boiler water.

  Also known is a method of adding a canning agent such as a phosphate as a canning agent, and in JP 2010-216762A, an oxygen scavenger and a canning agent are added together. Phosphate treatment has high corrosion resistance to corrosive ions, and compared to volatile substance treatment (AVT(R)), the allowable concentration of chloride ions in boiler water is 2 to 5 times that of phosphate treatment. Highness is described in JIS B8223 (2015).

  Since the cation conductivity of the boiler water is strictly set to 5 μS/cm or less even in the case of the film-forming amine treatment, it is considered that the allowable concentration of chloride ion needs to be set lower than that of the phosphate treatment.

  Therefore, in the treatment of boiler feed water, the film-forming amine treatment has a higher tolerance for the water quality of the boiler water than the conventional combined treatment of the oxygen scavenger and the phosphate with respect to the salt concentration. It is considered low.

JP, 2010-216762, A

JISB8223 (2015) "Water supply of boiler and water quality of boiler" Power Plant Chemistry, 2009, vol. 11 (2) Power Plant Chemistry, 2015, vol. 17 (6)

  The treatment with a film-forming amine and a basic amine such as ammonia or a neutralizing amine as described in Patent Document 1 does not use an oxygen scavenger, so oxygen is present in the system. Therefore, it is considered that when the concentration of impurities in the system increases due to deterioration of makeup water or leakage of condenser, corrosion is likely to proceed. In addition, since no boiler cans such as phosphate are used, there is a risk of scale adhesion due to leakage of the condenser.

  The present invention solves such a problem in the conventional water treatment of boiler water using a film-forming amine and a feed water pH adjuster, and effectively corrodes and scales the boiler even in the case of poor water quality boiler feed water. An object of the present invention is to provide a method for preventing boiler water from being treated.

  As a result of repeated studies to solve the above problems, the present inventors have added a boiler agent and/or an oxygen scavenger together with a film-forming amine and a feed water pH adjusting agent to the boiler feed water to add the boiler feed water. It has been found that the corrosion and scale of can be effectively prevented.

  That is, the gist of the present invention is as follows.

[1] A water treatment method for boiler water, in which a boiler agent and/or an oxygen scavenger is added to the boiler feed water in addition to the film-forming amine and the feed water pH adjuster.

[2] The method for water treatment of boiler water according to [1], wherein the feed water pH adjusting agent contains a neutralizing amine.

[3] The water treatment method for boiler water according to [1] or [2], wherein the cation conductivity of the boiler water exceeds 5 μS/cm.

[4] The water treatment method for boiler water according to [3], wherein the cation conductivity is a value measured based on sulfate ions and chloride ions in the boiler water.

[5] The method for water treatment of boiler water according to any one of [1] to [4], wherein the oxygen scavenger is added between the feed water heater of the boiler system and the economizer inlet.

[6] The water treatment method for boiler water according to any one of [1] to [5], wherein the boiler agent is a phosphate.

According to the present invention, in the water treatment of boiler water in which the film-forming amine and the feed water pH adjusting agent are applied during the normal operation of the boiler, the treatment effect of the film-forming amine is supplemented by a boiler agent and/or an oxygen scavenger. As a result, the influence of the properties of the makeup water and the recovered condensate can be reduced as much as possible, and the corrosion and scale of the boiler can be effectively prevented.
INDUSTRIAL APPLICABILITY The water treatment method for boiler water of the present invention can prevent the corrosion and scale of the boiler even in the case of poor-quality boiler water having a cation conductivity of more than 5 μS/cm. Can be relaxed.

It is a systematic diagram which shows an example of a power generation boiler system.

  Embodiments of the present invention will be described in detail below.

In the present invention, a film-forming amine and a feed water pH adjusting agent (hereinafter sometimes referred to as “pH adjusting agent”), a boiler agent and/or an oxygen absorber are added to the boiler feed water. Preferably, a film-forming amine, a feed water pH adjusting agent, a boiler agent and a deoxidizer are added to the boiler feed water.
In the present invention, "boiler water supply" refers to water until it enters the boiler in the boiler system, and "boiler water" refers to water in the boiler can.

[Boiler water supply]
The boiler to be treated in the present invention is not particularly limited and may be a high pressure boiler system as shown in Fig. 1 or a combination of a plurality of steam turbines and a plurality of boilers.

  As described above, the cation conductivity of the boiler water is regulated by the treatment method, and the cation conductivity of the boiler water needs to be 5 μS/cm or less in the conventional film-forming amine treatment. Boiler water having a cation conductivity of more than 5 μS/cm can be effectively treated by using a water removing agent and/or an oxygen scavenger together with a cationic amine and a pH adjusting agent, and a cation conductivity of 20 μS/cm. Up to about cm is allowed.

  Therefore, the present invention is not limited to the boiler using pure water as supplementary water, but can be applied to a boiler using RO treated water (reverse osmosis membrane permeated water) and soft water as supplementary water.

The cation conductivity of the boiler water is preferably measured based on the sulfate ion and chloride ion in the boiler water.
Further, the cation conductivity shows a measured value at 25°C.

[Film forming amine]
Examples of the film-forming amine added to the boiler feed water include those represented by the following general formula (1), and specifically, long-chain compounds such as octadecylamine and N-octadecenylpropane-1,3-diamine. One or more chain alkylamines can be used.
_{^{R 1 - [NH (R 2}} ) -] n -NH 2 ... (1)
(In the formula, R ¹ represents a long-chain (straight-chain) alkyl group having 12 to 18 carbon atoms, R ² represents an alkyl group having 1 to 4 carbon atoms, and n is an integer of 0 to 7.)

[PH adjuster]
In the present invention, a pH adjusting agent for adjusting the pH of the boiler feed water to about 8.5 to 10.3 is also used.

  As the pH adjuster, ammonia, monoethanolamine (MEA), cyclohexylamine (CHA), morpholine (MOR), diethylethanolamine (DEEA), monoisopropanolamine (MIPA), 3-methoxypropylamine (MOPA), A neutralizing amine (volatile amine) such as 2-amino-2-methyl-1-propanol (AMP) can be used. These may be used alone or in combination of two or more. Further, the pH may be adjusted with ammonia derived from thermal decomposition of the oxygen scavenger, instead of the neutralizing amine.

[Deoxidizer]
As the oxygen scavenger, hydrazine derivatives such as hydrazine and carbohydrazide can be used. Further, as a non-hydrazine-based oxygen scavenger, carbohydrazide, hydroquinone, 1-aminopyrrolidine, 1-amino-4-methylpiperazine, N,N-diethylhydroxylamine, isopropylhydroxylamine, erythorbic acid or a salt thereof, ascorbic acid or The salt can also be used.
These may be used alone or in combination of two or more.

[Cleaning agent]
Examples of the clearing agent include phosphate-based agents such as phosphates such as sodium phosphate, inorganic alkali agents such as potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, etc., and phosphates are preferred. Used.
These may be used alone or in combination of two or more.

  In particular, the phosphoric acid type clearing agent may be used together with a caustic alkali such as sodium hydroxide for the purpose of pH buffering property and compatibility with hardness leakage.

Since the film-forming amine is generally difficult to dissolve in water, it is usually used as a formulation mixed with a surfactant (emulsifier) in order to maintain a stable dissolved state of the film-forming amine in boiler feed water. .
However, the surfactant may cause carry-over of the boiler material. Therefore, in the present invention, it is preferable to use a surfactant that does not accelerate carryover of the can.
Here, not to accelerate the carryover of the clear can agent means that the amount of the carryover of the clear can agent in the boiler to which the surfactant is not added is compared to the amount of the clean can when the surfactant is added. Indicates that the carryover amount of the agent is below the same level.

[Chemical injection location]
The locations where each drug is added are preferably as follows.
It is preferable to add the film-forming amine to a low temperature region (a region where the water temperature is about 10 to 100°C) of the water supply system or the makeup water system before the deaerator (upstream side). Is preferably added to. The film-forming amine and the pH adjusting agent may be mixed together with the surfactant in advance and added to the same location, or the film-forming amine and the pH adjusting agent may be added separately to the same location or in the vicinity thereof.

  It is preferable to add the oxygen scavenger between the feed water heater of the boiler system and the economizer inlet, especially after the FAC generation site such as the high-pressure feed water heater, because dissolved oxygen in the boiler water can be removed to prevent corrosion.

  When the boiler feed water is used for reducing the temperature of superheated steam, it is generally preferable to add the boiler agent after the branch point of the reduced temperature water. This is to prevent the dissolved solid matter in the boiler material from precipitating on the turbine blade.

  When two or more of the above-mentioned agents are added to the same location, they may be mixed in advance and then added separately.

[Medication dosage]
The amount of each drug added is preferably as follows.

  The film-forming amine is preferably added in an amount of 0.01 to 10 ppm, particularly 0.1 to 1 ppm, relative to the makeup water. If the amount added is less than this range, the anticorrosive effect of the film-forming amine cannot be sufficiently obtained, and if it is too large, tacky deposits may occur in the system.

  The oxygen absorber is added in a necessary amount with respect to the oxygen concentration at the outlet of the deaerator and the oxygen concentration of the water supply system when there is no deaerator. For example, it is preferable to add 0.01 to 100 mg/L, especially 0.05 to 50 mg/L to the boiler feed water. If the amount added is less than this range, the antioxidative effect of the oxygen absorber cannot be sufficiently obtained.

  The boiler agent is preferably added so that the pH of the boiler water is 8.5 to 10.8, particularly 8.8 to 9.8. If the amount added is less than this range, the scale preventive effect of the canning agent cannot be sufficiently obtained, and if it is too large, carryover may occur and the vapor quality may deteriorate.

  As described above, the pH adjusting agent is added so that the pH of the boiler feed water is in the range of 8.5 to 10.3.

1 Power generation boiler system (high pressure boiler system)
2 Boiler device (boiler)
3 Deaerator 5 Secondary side water supply line (water supply line)
6 Primary side water supply line (water supply line)
12 Condensate line 20 Economizer 21 Steam generator 51 High-pressure feed water heater (feed water heater)
60 Low pressure water heater (water heater)
S1 High-pressure steam S2 Low-pressure steam M1 Cleaner agent M2 Deoxidizer M3 pH adjuster W1 Condensate W2 Make-up water W3 Boiler feed water

Claims (5)

A water treatment method for boiler water, wherein a boiler agent and/or an oxygen scavenger is added to a boiler feed water having a cation conductivity of more than 5 μS/cm in addition to a film-forming amine and a feed water pH adjuster.   The method for treating boiler water according to claim 1, wherein the feed water pH adjusting agent contains a neutralizing amine. The water treatment method for boiler water according to claim 1 or 2 , wherein the cation conductivity is a value measured based on sulfate ions and chloride ions in the boiler water. In any one of claims 1 to 3, wherein the addition between the oxygen scavenger from the feed water heater of the boiler system economizer inlet, water treatment method of the boiler water. The water treatment method for boiler water according to any one of claims 1 to 4 , wherein the boiler agent is a phosphate.

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