JPH01139998A - Control of performance of condenser tube made of copper alloy - Google Patents

Abstract

PURPOSE:To eliminate the damage due to corrosion and an increase in the fuel cost accompanying lowered heat transfer performance by keeping a specified polarization resistance value so it will not fall below it and starting the cleaning operation of sponge balls when it reaches the lower limit of a set cleanness buffer width of the cleanness and stopping the cleaning operation of sponge balls when it reaches the upper limit of the set cleanness buffer width of the cleanness. CONSTITUTION:In the control of the performance of a condenser made of a copper alloy its operation is based on cleanness, and the buffer width set up for a standard value (85%) of cleanness is specified to be within + or -15% of the value in the upper and lower ranges and the upper limit of the buffer width to be 95%. And, the control operation for ON-OFF of a sponge ball cleaning device within this buffer width is executed. Furthermore, the ON-OF control operation is made so as to keep the polarization resistance value of the condenser not lower than 3000OMEGA.cm<2>, and in the case in which the polarization resistance value is below 3000OMEGA.cm<2>, the operation of the sponge ball cleaning is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a method for managing the performance of a condenser tube made of a copper alloy, and in particular to a method for managing the performance of a condenser tube based on measured polarization resistance and cleanliness. This invention relates to a method for effectively operating such a system and maintaining the condition of the inner surface of a pipe with more precision when iron ion implantation for forming an anti-corrosion film is not possible or restricted. .

(Prior art and its problems) Conventionally, condensers for thermal power plants, chemical factories, ships, etc. have been made of brass with aluminum, arsenic, or other silicon added to it as a condenser tube, which is a heat transfer tube. So-called special brass tubes and copper alloy tubes such as cupronickel made of copper, nickel, and iron are widely used, but in these condensers, seawater, river seawater, river water, etc. are used as cooling water.
By allowing it to flow through the condenser pipe, heat exchange takes place between the high temperature fluid (steam) in contact with the outer surface of the condenser pipe and the cooling water that is made to flow within the condenser pipe. This has led to various problems. In other words, because cooling water such as seawater flows through the condenser pipes, it takes a long time.

Depending on the use of the cooling water, various substances depending on the quality of the cooling water,
For example, sludge such as earth and sand, iron rust, corrosion products, slime, etc. adhere to the inner surface, which reduces the heat transmission coefficient (heat transfer performance) and deteriorates the thermal efficiency of the condenser.

For this reason, the management of copper alloy condenser pipes in condensers that use seawater, etc. as cooling water has traditionally been carried out to (a) prevent corrosion caused by the cooling water, and (b) prevent various suspended particles. This has been done to prevent deterioration in heat transfer performance due to the adhesion of corrosion products and the accumulation of corrosion products.

That is, for the former, injection of ferrous sulfate as iron ions is used, and for the latter, sponge balls (S B
) has been found to be extremely effective.
These measures are being adopted as appropriate.

By the way, anticorrosion performance can be significantly improved by a film made of ferric hydroxide (anticorrosion film) formed by iron ions generated by the addition of ferrous sulfate, etc., but at the same time, heat transfer performance may be reduced. On the other hand, heat transfer performance can be improved by sponge ball cleaning, but if the anti-corrosion coating is removed too much, the anti-corrosion performance will decrease and corrosion may occur, resulting in instability. It is widely acknowledged that there are problems with poor trajectory.

For this reason, conventionally, in order to satisfy both of these performances,
Based on laboratory tests and actual operating results, we operate the condenser under preset ferrous sulfate injection conditions and sponge ball cleaning conditions, and then make adjustments gradually based on the results of periodic inspections. However, the quality of water used as cooling water, such as seawater, is not necessarily constant (therefore, continuing operation under preset conditions will affect the inner surface condition of the pipes in terms of corrosion resistance and heat transfer properties). It could not be said to be suitable for maintaining the optimum condition.

Therefore, the present inventors first applied the patent application No. 60-26769.
As No. 9, etc., the corrosion resistance and antifouling property (heat conductivity) of the copper alloy condenser tube installed in the condenser are evaluated by the polarization resistance value and cleanliness, respectively. Directly and continuously detects the change in its cleanliness over time, detects the change in cleanliness over time, directly measures the heat transfer performance of the condenser tube, and determines both of these characteristics. The values are plotted on the Y-axis and Y-axis in Figure 1, and the iron installed in the condenser is plotted in the shaded area in the diagram, which is preset according to the cooling water quality, in order to maintain the optimal performance range. We proposed a performance management system that operates an ion implanter and a sponge ball (SB) cleaning device.

In short, such a performance management system for condenser tubes increases the polarization resistance value by iron ion implantation, and increases the cleanliness by sponge ball cleaning.
This system could be advantageously employed in condensers of plants equipped with antifouling equipment.

However, due to current water treatment regulations regarding cooling water such as seawater, there are plants that are unable to implant iron ions, or are only allowed to implant iron ions at extremely low concentrations, and are restricted in the amount of iron ions that can be implanted. 1. The number of such plants is likely to increase in the future. Therefore, when the above performance management system is applied to such a plant, in reality, only the cleanliness of the Y-axis can be managed, and the polarization resistance value of the Y-axis can be controlled. It is difficult to say that it can be adequately managed.

Under such conditions, if the operation is performed with priority given to cleanliness among the conditions that give the area shown by the diagonal lines in Fig. 1, the first
While following the trajectory shown in the figure, such as a-43, -) a2 . Note that here, point a is the value at the time of initial corrosion protection film formation. In addition, the decrease in cleanliness is due to the introduction of earth and sand, the adhesion of slime, the formation of corrosion products, the adhesion of manganese oxides, and the like. On the other hand, an operation that prioritizes or maintains the polarization resistance value causes a significant drop in cleanliness, and is therefore not applicable to the above-mentioned performance management system.

In any case, 3. +3t ...→a6 When operating in the pattern shown above, severe local erosion is likely to occur in the condenser pipes, so for plants under the restricted water treatment conditions described above, There is a need to establish a driving pattern different from the conventional one.

(Solution Means) The present invention has been made in order to solve the problems inherent therein against the background of the above-mentioned circumstances, and as a result of intensive research by the present inventors, it has been found that seawater, river seawater,
In copper alloy condenser pipes that use river water, etc. as cooling water, (
a) The passage of sponge balls (SB) causes erosion; (b) The number of SBs passing through and the cleaning interval affect the depth of erosion; the larger the number of SBs passing and the shorter the cleaning interval, the more the erosion If the depth increases, (c) the total number of SB passes is the same,
Knowledge that the depth of erosion is shallower when the cleaning interval is longer and the number of 38 pieces that pass in one cleaning is greater than when the cleaning interval is short and the number of 38 pieces that pass in one cleaning is smaller. It has been completed by obtaining the following.

That is, the present invention provides a method for maintaining and managing the performance of a copper alloy condenser pipe that is attached to a condenser and allows seawater, river seawater, river water, etc. to flow through the pipe as cooling water. While measuring the polarization resistance value and cleanliness of the water pipe, ±15% above and below the set cleanliness standard value.
% and the upper limit does not exceed 95%, and the measured polarization resistance value does not fall below 3000 Ω・elf''. The sponge ball cleaning operation for the inner surface of the condenser tube is started when the measured value reaches the lower limit of the cleanliness buffer width, and the sponge ball cleaning operation is started when the upper limit of the cleanliness buffer width is reached. The present invention provides a performance management method for a copper alloy condenser tube, characterized by stopping the pipe and maintaining the stopped state until the measured cleanliness value reaches the lower limit of the cleanliness buffer width.

(Specific explanation of the configuration) By the way, in the initial stage of operation of a condenser, the corrosion resistance of the copper alloy pipe as a condenser pipe installed in such a condenser against cooling water such as seawater is determined by the passage of cooling water. It is known that when an anti-corrosion film is formed in the initial stage, the improvement is markedly improved, and such an anti-corrosion film can be formed simply by passing cooling water such as seawater, or preferably by adding iron ions to the cooling water. injection, actually the addition of water-soluble iron compounds such as ferrous sulfate,
Advantageously formed by melting, and by such injection operations, a coating having a polarization resistance value of generally 5000 Ω·(Jll” or more, preferably 10000 Ω·02 or more) is formed as an effective anticorrosion coating. Therefore, even in the present invention, such an effective anti-corrosion film is advantageously first formed on the inner surface of the condenser tube at the initial stage of operation. In general, cleanliness as a heat transfer property of pipes is maintained at 95% or more compared to new pipes by performing SB cleaning or the like as appropriate.

In the present invention, after appropriately forming an effective anti-corrosion film on the inner surface of the condenser tube at the initial stage of operation as described above, the polarization resistance value and cleanliness (heat transfer characteristics) of the condenser tube are determined.
While detecting this, normal operation is carried out, and at that time, according to the present invention, the following performance management operation is carried out based on cleanliness standards.

Here, the polarization resistance value (R:
Ω・cfiI"), as disclosed in Japanese Patent Application No. 60-267699 proposed earlier by the present inventors,
This is defined by the following equation (1).

R= (Eo/ro)t(2yc"a'/ρ
)... (1) However, E6 = difference between cathodic protection potential and natural potential (mV):
Normally, it is set to about 200mV. = Current per condenser tube at the above potential setting (m
A) a - Inner radius of condenser tube (cra) ρ = Specific resistance of cooling water (Ω・am) In addition, cleanliness (C ) is the standard heat transfer coefficient (K,
) and the actual heat transfer coefficient (K1), which is calculated using the following equation (2).

c= (Kt /Ko)xloo (%)... (2
) Here, the reference thermal conductivity (Ko) is determined by the following equation (3).

K0=ct x/V... (3) However,
C,=constant determined by the material and thickness of the condenser tube ■=average flow velocity in the condenser tube Also, the actual heat transfer coefficient (K,) is calculated by the following equation (4).

K1- (wx rXCpX(tz L+))/(A
s×θ, )... (4) However, W = Cooling water flow rate r = Cooling pipe path C, = Cooling water specific heat t2 - Cooling water outlet temperature R, = Cooling inlet temperature A, = Cooling area θ0 = Heat counter Furthermore, the average temperature difference θ1 in the equation (4) is calculated using the following equation (5).

θ@ = (tz-11)/re((t s-t +)/(
't s-t z))... (5) However, 1. = Hot well temperature Note that it is also possible to use the degree of vacuum of the condensate section outside the condenser tube attached to the condenser as a measure (guideline) regarding heat transfer performance in place of the cleanliness. It is also possible to substitute the degree of decrease in the degree of vacuum as the value of cleanliness. In any case, changes in cleanliness and heat transfer performance can be ascertained using thermometers, vacuum gauges, flow meters, etc. that are normally attached to equipment.

According to the present invention, a reference value of the cleanliness of the condenser tube installed in the condenser is set in advance. This cleanliness standard value is a value that allows the equipment (condenser) to fully demonstrate the specified performance even if the condenser pipe is dirty with deposits, and is usually used for new pipes. A value of 75 to 90%, often about 85%, of the cleanliness (heat transfer performance value) is adopted.

The present invention provides a predetermined buffer width above and below the cleanliness reference value, and at the lower limit, the sponge ball (SB) cleaning device is turned on and the SB cleaning operation is started. On the other hand, as the SB cleaning operation progresses, the cleanliness increases, and when the upper limit of the buffer width is reached, the SB cleaning device is turned off, the SB cleaning operation is stopped, and the stopped state is The test was continued and held until the measured cleanliness value reached the lower limit of the buffer width.

That is, the present invention operates based on cleanliness in performance management of copper alloy condenser pipes, and at that time, S
A predetermined buffer width is provided between ON and OFF of the B cleaning device, and in the method of the invention, the Y axis (polarization resistance value) shown in FIG. 1 is not managed, and the X
Only the axis (?ff cleanliness) is managed. and,
In the ON-OFF control method of the SB cleaning device using the set value of tu cleanliness (here 85%) as shown in Fig. 1, the interval between cleaning is short and the number of particles passing through in one cleaning is 38. In contrast to the SB cleaning pattern with fewer SB cleaning patterns, by providing a buffer zone above and below the set value, the cleaning interval becomes longer and the SB cleaning pattern passes through in one cleaning.
This makes it possible to operate with the SB cleaning pattern, which increases the number of cleaning devices. In short, the present invention, for example,
As shown in the figure, when the width of the buffer zone is ±5% with respect to the cleanliness set value (85%), the SB cleaning device is activated (ON) when the width falls below 80% of the lower limit value.
), and exceeds the set value, and exceeds the upper limit of 90
%, the SB cleaning device is turned off and this pattern is repeated.

In addition, in the present invention, the buffer width set with respect to the standard value of cleanliness must be within 115% above and below the standard value.

If this buffer width becomes too wide, it will take a long time for performance recovery due to SB cleaning, the number of cleanings will increase, and the period of poor performance will become longer, resulting in lower condenser operation. This causes disadvantageous problems in terms of cost. In addition, the buffer width is generally ±5 relative to the reference value.
It is preferable that the value is set at a value of approximately % or more, and thereby the ON-OFF control of the SB cleaning device using the effective buffer width according to the present invention can be advantageously performed. The standard value of cleanliness is 80% (75%).
%), the 0N-OFF control range is 95 to 6
5% (90-60%), which is considerably lower than the standard value, but such a lower limit is an acceptable value for a short period of time in terms of condenser performance. .

Further, in the present invention, the upper limit of the buffer width is 95%.
It is necessary to do so. However, even if the number of SB cleaning increases as the cleanliness increases, the cleanliness does not increase proportionally, and on the other hand, the corrosion depth increases with the number of SB cleaning. Therefore, if this upper limit exceeds 95%, it will be disadvantageous from the viewpoint of the balance between corrosion and heat transfer performance.

Furthermore, in the present invention, when performing ON-OFF control of the SB cleaning device within a predetermined buffer width according to the cleanliness standard as described above, the polarization resistance value of the condenser tube is 3000Ω·cII.
+2 should not be lowered and such 0N-
If the OFF control operation is performed and the measured polarization resistance value becomes lower than 3000Ω・cm2,
Regardless of the cleanliness level, the SB cleaning operation will be stopped. If this polarization resistance value becomes too low,
This is because there is a possibility that severe local ulceration may be induced.

In addition, in the present invention, in the above operation, -
If the number of SBs passing through each condenser pipe is 50 or more, or if the continuous cleaning time is 5 hours or more, the SB cleaning operation will increase the progress of corrosion. It is desirable to stop the SB cleaning operation, and it is also desirable not to perform the SB cleaning operation more than once a day or more than four times a week. Unfortunately, S too many times
This is because the cleaning operation B increases the progress of corrosion.

In addition, the SB (sponge ball) cleaning according to the present invention uses a sponge ball similar to that conventionally used, which generally has a diameter about two fins larger than the inner diameter of the condenser pipe. A suitable number of them are allowed to flow into and pass through the condenser pipe together with cooling water such as seawater, thereby cleaning the inner surface of the pipe.

(Examples) Below, some examples according to the present invention will be shown together with comparative examples to clarify the present invention more specifically. Needless to say, this is not something that can be accepted.

In addition to the following examples and the above-mentioned specific description, the present invention includes various changes, modifications, and changes based on the knowledge of those skilled in the art, as long as they do not depart from the spirit of the present invention. It should be understood that improvements may be made.

Outer diameter: 25.4 mm, wall thickness: 1.245 mm, length: 15
00 dragon aluminum brass tube (JIS-H3300-C
6871; Seamless Brass Pipe for Condenser) was used as a condenser tube sample and set in the same condenser model as in Japanese Patent Application No. 60-267699, and the polarization resistance and cleanliness of each test tube were determined. While monitoring according to formulas (1) and (2) above, under the driving pattern shown in Table 1 below,
It was operated under the following seawater quality and duration. In addition,
The SB (sponge ball) passed through the pipe is 2
A medium-hard one (manufactured by Tabloge) with a diameter of 611 was used. In addition, for samples 11h2 to 5, during operation, the number of SB passages per tube was 50 or more, or
If the operating time of the B cleaning device exceeds 5 hours, the SB cleaning operation will be stopped, and the SB cleaning operation will not be performed more than once a day or more than 4 times a week.

Part 1: Surface seawater quality: Inside the pipe? In order to increase the reduction in R cleanliness, silica sand with a particle size of 5 μm or less was mixed into normal natural seawater (untreated with chlorine) for 2 hours a day. The concentration of silica sand was 500 ppm. In addition, during the time when the silica sand was being mixed, the system was operated at a flow rate of 0.5 m/sec for 5 hours a day to promote slime adhesion. At other times, natural seawater was passed through at a rate of 2 m/s. The operation pattern shown in Table 1 above was aimed at a time period where the flow velocity was 2 m/s.

Period: Under the above conditions, water was passed almost continuously for 7 months from March to October.

As a result, the number and number of SB passages, amount of slime adhesion, ultimate resistance value, cleanliness, and corrosion depth as shown in Table 2 below were obtained. As is clear from this result, samples 11h2 and 11h2, whose performance was controlled using the operating pattern according to the present invention,
3.4, especially 1lh3 was found to have good corrosion resistance and heat conductivity of 2.

However, Samples 1 and 5 as comparative examples had a large corrosion depth and were not practical.
In sample N17, which had a large decrease in cleanliness, and in which operation was not performed based on the measured values of polarization resistance and cleanliness, compared to any of the samples on floors 2 to 4 according to the present invention,
The cleanliness, heat transfer performance, and corrosion depth were poor.

Table 2 (Effects of the Invention) As is clear from the above explanation, the present invention evaluates the corrosion resistance and heat transfer performance of the inner surface of the condenser tube based on the measured polarization resistance value and cleanliness, and The system is designed to maintain the performance or condition of the sponge ball (SB cleaning equipment) and is operated according to the cleanliness standard, and at that time, the on-off (O
This allows the surface condition of the inner surface of the condenser tube to maintain corrosion resistance and conductivity even under conditions where iron ion injection into the cooling water is severely restricted. This makes it possible to maintain the optimum state from a thermal standpoint, effectively solving problems such as damage caused by corrosion and increased fuel costs due to decreased heat transfer performance. This is where the present invention has great industrial significance.

The operating system according to the present invention is suitable for plants without iron ion implantation (excluding initial anticorrosive film formation) or plants where the amount of iron ion implanted exceeds its effective limit, for example, continuously at an implantation concentration of 1Qppb or less. This means that it can be advantageously employed in plants where iron ions are implanted or in which the formation of an anticorrosive film by iron ion implantation is poor.

[Brief explanation of the drawing]

FIG. 1 is a graph showing an example of performance management of a condenser tube based on polarization resistance value and cleanliness, and FIG. 2 is a graph showing an example of cleanliness buffer width according to the present invention. Applicant Sumitomo Light Metal Industries Co., Ltd. No. 1 Cause 2 Ward 1 Judo (@mu)

Claims (1)

[Claims] A method for maintaining and managing the performance of a copper alloy condenser tube that is attached to a condenser and allows seawater, river seawater, river water, etc. to flow as cooling water in the tube, and to polarize the condenser tube. While measuring the resistance value and cleanliness, a cleanliness buffer width is provided above and below the set cleanliness standard value at a rate not exceeding ±15% and so that the upper limit does not exceed 95%, and the above measurement. The polarization resistance value is 3000Ω・cm^2
starts a sponge ball cleaning operation on the inner surface of the condenser tube when the measured cleanliness reaches the lower limit of the cleanliness buffer width, while A copper alloy condensate characterized in that the sponge ball cleaning operation is stopped when the upper limit of the width is reached, and the stopped state is maintained until the measured cleanliness value reaches the lower limit of the cleanliness buffer width. How to manage the performance of organs.