JP2691344B2 - Corrosion protection for heat transfer tubes. Mechanical cleaning control method and equipment - Google Patents

Description

Description: FIELD OF THE INVENTION This invention measures polarization resistance and activates or enhances chemical or electrical means to improve corrosion protection below a resistance limit above the resistance limit. And deactivating or weakening said means and / or after measuring the heat transfer coefficient from the steam to the coolant, start a clean circulation of the cleaning body below the limit value and stop it above the limit value, Alternatively, it relates to a method for controlling the mechanical cleaning performed by corrosion protection and / or cleaning bodies of heat transfer tubes, in particular power plant cooling tubes, by strengthening and weakening the clean circulation.

The invention further provides at least one device for measuring the polarization resistance for inspecting a passive layer or other protective layer on the inner wall of a tube of a single tube or a group of tubes and the formation of a protective layer in the inlet area of the heat exchanger. A metering device that mixes substances that promote heat transfer, or an electric cathodic protection device that prevents erosion of the inner wall of the pipe and / or a device that measures the heat transfer coefficient from steam to the coolant, and the cleaning body is cooled to remove the deposit on the inner wall of the pipe. A mechanical system that is equipped with a device for charging and circulating in the agent and a control system that determines the charging frequency, charging time, and charging strength of each device. It relates to equipment for controlling cleaning.

(Prior Art) A similar type of equipment without an anticorrosion part is disclosed in European Patent Application
Known by No. 30459. In this facility, the heat balance of all condensers is detected by measurement engineering and compared with the ideal condition.
When a difference is detected between the two states, the clean circulation of the cleaning body is started and continued until a sufficient approach to the ideal state is achieved. There, measurements are taken at the inlet and outlet of the condenser and the steam room. One of these measurements in the steam chamber is the heat flow measurement on the steam side of a single cooling tube.

It was found that batch detection of the condenser was not enough to obtain a more accurate cue about the actual degree of fouling. Especially, since the stains are often non-uniform, the batch detection method is not suitable. Therefore, it has already been attempted to subdivide the tube nest of the condenser into parts and create a heat balance inside one part (Japanese Patent Laid-Open Publication No. Sho.
57-14193 publication). There, a heat flow meter is also provided outside the cooling pipe and in each region, and the inlet temperature and the outlet temperature are collectively measured at the inlet and outlet of the condenser. On the basis of subdividing and measuring the degree of contamination via the tube nest, various metering devices associated with the measuring area are operated, which supply the cleaning body substantially area by area.

Chemical treatments are known which are capable of combating biological deposits under certain conditions of use. Similar treatments can also be used to reduce hard precipitates. Along with chemical conditioning of the coolant, electrical systems that prevent erosion of tubing can also be used. Of particular importance is the chemical conditioning of the water, which contributes to being protected from corrosive action when the tubes of the condenser are certain materials which require a passive or surface layer for good corrosion resistance. However, if the surface layer is too thick, it is of course detrimental to heat transfer. From this point, the thickness of the surface layer must be kept to the minimum necessary for corrosion protection. This is especially true when adding iron ions which form a surface layer rich in iron on the inner wall of the tube.

For the measurement of the surface state, it is particularly effective to measure the polarization resistance that can be performed for each tube. As a result, the resistance of the coolant to the tube is measured. Heretofore, chemical conditioning of the coolant or cathodic protection and mechanical cleaning with a cleaning body have been carried out separately.

(Problems to be solved by the invention) Detection of the condenser area by the measurement engineering method as described at the beginning did not bring any results because the flow velocity of the cooling pipe equipped with the heat flow meter is unknown. . For example, if the pipe whose heat transfer is to be measured is in an unfavorable area, the coolant will only slowly flow through it and the coolant will be warmed relatively strongly. Therefore, the heat flow meter displays a bad value despite the fact that there is no problem with the heat transfer condition of the tube, ie the cleanliness. On the other hand, if the pipe to be measured flows through very quickly, the data measured by the heat flow meter show good values, even though the pipe may already contain a deposit which requires cleaning.

The object of the present invention is therefore to improve a method of the kind mentioned at the outset, in which the actual state of the individual cooling pipes is measured and subsequently the equipment is put into operation. The purpose of equipment is
The object of the present invention is to provide a suitable measuring means for more accurately determining the properties of the tube in the heat exchanger during operation.

(Means for Solving the Problem) Regarding the method, the solution to the above object is to measure polarization resistance and / or heat transfer coefficient for a predetermined number of tubes substantially evenly distributed over the entire tube nest surface, The measurement is made from the coolant inlet temperature, outlet temperature and flow velocity and steam temperature, and corrosion protection improving means is charged in each region or collectively according to the measurement result of the pipe with the highest risk of corrosion, and / or Alternatively, the clean circulation is controlled according to the measurement result of the tube having the worst heat transfer coefficient.

Regarding the equipment, in order to achieve the above-mentioned object, the present invention arranges each measuring device in a plurality of pipes (12), preferably evenly distributed over the entire tube nest surface, and measures the polarization resistance of the device useful for corrosion prevention by a control system. Proposal to make it possible to make a batch injection depending on the area or according to the most inconvenient measurement result, and to make it possible to put the clean body circulation device according to the worst heat transfer coefficient measurement value by the control system To do.

(Operation / Effect) That is, the present invention is different from the prior art in that all the parameters are measured directly in the individual tubes of the heat exchanger, and the heat transfer coefficient thereof is quantified and compared with a predetermined target value or reference value. teach. As a reference value, the new state of the cooling pipe can be measured, and based on this reference value, subsequent contamination can be determined by the so-called contamination coefficient or cleanliness. Alternatively, it is also possible to use as reference the measured values obtained after a basic cleaning of the pipe, which can be carried out after acid treatment with a special cleaning body or after mechanical cleaning, for example by hand in the process of reconditioning. Finally, a theoretically quantifiable value that can be quantified based on the pipe size and material data can also be used as the reference value.

The inlet temperature, outlet temperature, flow rate or flow rate per unit time, and steam temperature of each pipe to be measured must be measured during continuous operation. While the two temperatures of the coolant are conventionally detected using temperature detectors, the present invention takes a new path in flow velocity measurement and vapor temperature measurement.

Conventionally used heat flow meters are fixedly attached to the outer surface of the cooling pipe, for example, adhered or held by fixing metal fittings.

When equipped with pipes inside the condenser part, these pipes are no longer accessible after the manufacture of this condenser part, as the spacing between adjacent pipes no longer allows sufficient passage for human hands or tools. Can not do it. For this reason, repairs and inspections cannot be performed. The present invention is about to turn.

Instead, the present invention seals one of the pipes (adjacent pipes) adjacent to the cooling pipe whose calorific value is measured so that the coolant does not flow, and causes steam to flow to bring the temperature of the steam to the temperature of the steam. Suggest to do. Shutdowns are performed by means of plugs, that is to say in the cooling pipes which have become leaky, using the methods already in place to eliminate this obstacle during inspection. At that time, the original temperature detector is sufficiently pushed and separated by both tube plates, and the temperature of the portion which becomes the steam temperature during the continuous operation is surely detected.

The flow velocity is preferably measured intermittently, that is, not using a turbine impeller or a Pitot probe, but preferably the distance between the two measurement points of the pipe inlet and the pipe outlet and the free coolant component at one measurement point. This is done by the quotient of the time elapsed from passing through to the other measurement point. The amount of released coolant is smaller than the inner diameter of the entire pipe. Foreign matter in the form of a floating measurement sphere or a fluid, that is, a liquid charged in a trace amount in the range of the first measurement point or in the range that replaces the first measurement point. It is either a substance or a gas. The fluid may be ink, a salt solution having a different electrical conductivity than the coolant, or other optically detectable substance whose turbidity or reflectance can act on a photoelectric barrier or the like. The measuring spheres can then also be loaded in the inlet range of the condenser, as long as the number of measuring spheres is so great that a certain probability of passing through the pipe to be measured appears. In particular, it is possible to load the measuring sphere together with the cleaning body, as long as the measuring sphere is appropriately coded, that is to say that the measuring device can detect it as such. This is simply done by mixing metal particles or the like that can be detected capacitively or inductively. In this case, a detector can be used to confirm passage through the beginning and end of the tube.

Particularly suitable as a detector for measuring the passage of a fluid charged at the pipe inlet and physically and / or chemically different from the coolant are electrodes arranged in front of or behind one another in two flow directions. This is used to measure the conductivity resistance of the coolant as a steady value. As the fluid passes through such a detector, eg with better or worse conductivity, the conductivity resistance changes for a short time, which is used for the measurement.
With this type of detector, it is also possible to detect the passage of the measuring spheres described above or the usual cleaning bodies. This is because they change the resistance of the conductor between the two electrodes at the moment of passage due to liquid exclusion or flow effects.

The advantage of such a detector as a component of the invention is in particular that the same electrode, which is also a component of the detector, can be used for measuring the polarization resistance. In this way, the expenditure required for the measured cooling pipe detector is significantly reduced. The cooling tube can be used as an electrode if it is insulated and stored in a cylinder in which the second electrode is mounted next to the cooling tube or in a so-called insert inserted in the cooling tube. it can.

Of course, the remaining detectors in such tubes or inserts
That is, a temperature detector, a capacitive, inductive or optical measuring device, and further depending on the equipment of the entire measuring mechanism, and also at the inlet and outlet of one condenser to be measured. be able to.

As already mentioned above, one of the possible embodiments comprises a support serving as a detector support at the tube inlet and at the tube outlet, respectively, axially before and after the tube sheet. Such a support can be fixedly attached to the condenser tubesheet, or held in one of the adjacent cooling tubes with a stopper used to measure the vapor temperature to prevent coolant flow. I do. This type of retention leaves the tube sheet untouched and greatly simplifies the installation of the entire condenser side measurement module.

In this way, the risk of leakage is avoided, especially between the steam chamber and the coolant chamber of the condenser. The support must be constructed, especially at the tube inlet, so that the probability of the cleaning body entering the tube does not change the flow conditions in the tube. This condition will be described later with reference to the illustrated embodiment.

The coolant-free pipe in which the steam temperature measurement is carried out can be used particularly advantageously to guide all measuring terminals on one condenser side to the other condenser side. The condensate room only needs a single duct as a whole. The condenser inlet room is specifically planned for this. The measuring conductor is therefore well protected from the action of the fluid in at least one of the chambers, the risk of damage being sufficiently avoided in this range.

In general, the present invention relates to the chemical conditioning of cooling water as well as to the cathode protection device for cooling tubes, which additionally controls the circulation of the cleaning body depending on the heat transfer coefficient from the steam to the coolant. It can be confirmed that it is related to the equipment to be used and the combined use of the two condenser optimization methods.

(Example) Hereinafter, the illustrated example of the present invention will be described in detail.

The circuit diagram shown in FIG. 1 schematically shows two measuring devices and their associated controllers and controllers for processing the measured values. For example, a normal condenser 1 for condensing steam from a power plant has an inlet chamber 2, an outlet chamber 3, and a tube nest 6 of a cooling pipe between them, and the coolant is cooled by the inlet 4 and the outlet 5 through the cooling pipe. Can flow through. At the ends of the tubes, the tube sheets 7, 8 separate the vapor chamber from the coolant chamber. The supply / discharge of steam to / from the cooling pipe through the steam chamber is not shown.

The coolant generally does not flow uniformly through the tube nest 6, but there are a high-speed region, a low-speed region, a region having a high probability of inflow of the cleaning material, a small region, particularly a dirty region. In order to detect the representative numerical value of each area, in parallel with the non-measurement cooling pipe 11, the measured cooling pipe 12 whose corrosion state and heat transfer coefficient are detected continuously or at intervals is provided. It is provided.

In the case of a condenser of rectangular cross section, which is common today, for example, nine tubes are measured, the tubes being stacked one above the other in three planes, each three tubes being distributed substantially evenly over the entire surface of the tube nest 6. It is arranged. Since this arrangement is repeated for each tube, only a single measured cooling tube 12 is shown in FIG. 1 as an example.
Each cooling pipe 12 to be measured is provided with a cooling pipe 13 through which a coolant does not flow, which will be explained exactly later. The cooling pipe 13 in which the coolant does not flow is closed by plugs 14 on both sides.

At each inlet side and each outlet side of the pipe to be measured 12, tubular supports 18 and 19 respectively including detectors required at these locations are inserted into the pipe to be measured 12 as a kind of insert. Temperature detectors 20 and 21 that measure the coolant inlet temperature and the coolant outlet temperature at these points on both sides are attached to this, and the absorbed heat amount is detected together with the flow rate. Knowing the steam temperature is essential for this. This is measured by the temperature detector 28 in the cooling pipe 13 in which no coolant flows. Three temperature measurements are input to the controller, where they are used for further processing.

In the case of the illustrated embodiment, the flow rate per unit volume is measured as follows. A charging part 22 is provided in the region of the tubular support 18 on the inlet side of the measured cooling pipe 12, and a metering pump 26 allows chemical substances to be sprayed from the tank into the flowing coolant through the charging part. The atomized material momentarily becomes the velocity of the flowing coolant,
In this way, the inside of the pipe 12 to be measured is sent as a relatively complete liquid enclave. Two electrodes 23 are arranged one behind the other in the cylindrical support 19 on the outlet side of the measured cooling pipe 12.

When a spray substance, for example a salt solution, passes through the electrode 23, the flow of electricity changes for a short time and is used at this point to detect the charge substance. The charging time is known in the charging section 22,
Further, since the cross-sectional area of the measured cooling pipe 12 is detected in advance, the volume flow rate can be calculated from the time from when the substance flows out of the charging portion 22 to when it passes through the electrode 23.
The volume flow rate is the cross-sectional area of the measured cooling pipe charging part 22, electrode 23
It is equal to the quotient resulting from the product of the length of the gap and the measured time that the spray substance traverses the measured cooling pipe 12. The metering pump 26 is therefore connected to the attached controller because of the time of charging and the electrode 23 for the final time measurement. The pipe dimensions are stored securely in the attached flow rate controller.

From the above amount, that is, the flow rate of the coolant per unit volume, the temperature difference, the specific density, the heat capacity, and the steam temperature, it is possible to detect the heat transfer coefficient at which the steam is transferred to the coolant through the wall of the pipe 12 to be measured. You can Such a measurement can be carried out with a fresh, clean tube after being thoroughly cleaned with an abrasive cleaning body until the metal is smooth, pickled or hand-cleaned. A reference value can be obtained through the measurement of and can be used as a measure of each deterioration due to dirt. The deviation from that can be used as a basis for the theoretical value of the pure metal tube, since the dimension and material data are known and the heat transfer coefficient can be calculated. With this reference value it is possible to detect the fouling factor or cleanliness, which respectively represent a general characteristic value for the thermotechnical condition of the cooling pipe.

At the beginning, as already mentioned, the cleaning of the individual cooling pipes 11 is carried out by adding a cleaning body, for example sponge rubber balls, at regular intervals or continuously, optionally with varying concentrations, to the coolant and after passing through the cooling pipes the outlet. Recapture in area 5 and perform. Excessively intensive treatment of the inner walls of the individual cooling pipes 11 with a cleaning body has a negative effect, in particular in the case of alloys which are intended to provide a surface layer for corrosion protection. If the pipe wall is generally smooth, the circulation of the cleaning body does not improve by heat transfer, and in this case the surface layer is affected and the risk of corrosion increases.

In order to make sure that this danger limit is approached, the illustrated condenser is equipped with a measuring device according to the invention for detecting the polarization resistance. Therefore, the measurement electrode 24 in the cylindrical support 18, and in the feed pipe reaching the charging portion 22, as a working electrode together with the pipe wall of the cooling pipe 12 to be measured, a reference electrode capable of measuring the polarization resistance of this pipe. There are 25. Evaluation of the measured values is also carried out in the attached controller. Polarization resistance as a measure of surface state is expressed in ohms per unit area. The empirical value is well known, and the target value can be set for each usage condition.

The surface layer can be strengthened by chemical treatment of the coolant flowing into the condenser, for example, in the case of a copper alloy cooling pipe, iron sulfate is added. Alternatively, the so-called sacrificial anode or active cathode protection can also be used to achieve erosion protection of the tube base material at the inlet and outlet areas of the cooling tube despite the surface being damaged or eroded. .

The measured value obtained from the measured amount of heat and the polarization resistance is used for activation of the cleaning equipment and anticorrosion system in addition to being displayed by the original controller. The duration and strength of the clean circulation of the cleaning body are adjusted based on the measurement and the empirical value. This cleaning can impair the surface effectiveness, which can be compensated for by appropriate chemical treatment or activation of the cathodic protection. This process can also be made dependent on the measured polarization resistance, i.e. it is terminated when there is a sufficiently stable surface to eliminate harmful corrosion.

By combining the cleaning and anticorrosion of the condenser with the present invention especially when measuring iron sulfate, it is possible to immediately adapt to changes in operating conditions while constantly monitoring the state of the condenser and perform optimal operation of the condenser. Become. As the heat transfer and polarization resistance of the individual cooling tubes are specifically measured by the invention proposal, the measurement quality is no longer exceeded. This makes it possible to detect the distribution of dirt and corrosion, and in some cases it is possible to take targeted countermeasures in a specific area of the tube sheet.

The deformation of the detector on one side of the tube nest is shown in FIG. Instead of the cylindrical support, a plate-like support 31 provided with a single electrode 32 is provided on the inlet side in the illustrated embodiment. The second electrode required to form the detector is provided in the form of the measured cooling pipe 12. The illustrated electrode 32 fills only about 3/4 of the perimeter of the appropriate hole of the support 32, rather than the entire perimeter, allowing a temperature sensor (not shown) to be easily accommodated in the remaining free perimeter. .

The plate-like support 31 is held by a stopper 34 that closes the tube 13 that has stopped operating. The plug 34 has an elastic wall region that can be crushed using the anchor bolt 35, and a liquid-tight fixed seat is formed inside the cooling pipe 13 in which the coolant does not flow. The anchor fixing portion is strong enough to fix the plate-like support 31 to the plate-like support 31 so that the plate-like support 31 does not move.

Therefore, the plate-shaped support 31 has a relatively large area and is thin so that the probability of inflow of the cleaning material in the region of the plate-shaped support 31 is not affected. In other words, the cleaning body should always follow the same route as predicted by the statistical chance law, regardless of the presence of the plate-shaped support 31 and always reaching the inside of the cooling pipe.

The plate-like support 31 shown in FIG. 2 can be easily used together with the support 19 shown in FIG. 1 at both the inlet side and the outlet side of the cooling pipe. All that is essential is that the detectors are tuned to each other and the distance between one detector and another is known for volume flow detection.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of equipment for controlling corrosion prevention and cleaning of a heat transfer tube by using a detector insert, and includes a cross-sectional view showing a partially enlarged schematic view of a condenser. FIG. 2 is a cross-sectional view of the enlarged portion of FIG. 1 to clarify the use of the cooling pipe to be measured and the support for the combined detector. [Explanation of symbols] 11, 12, 13 ... Cooling tubes.

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Claims (18)

(57) [Claims] 1. A method for measuring polarization resistance, activating or enhancing chemical or electrical means for improving corrosion protection below a resistance limit, deactivating or weakening said means above a resistance limit, and / or Alternatively, after measuring the heat transfer coefficient from the steam to the coolant, a clean circulation of the cleaning body is started if it is below the limit value and stopped if it exceeds the limit value, or the clean circulation is strengthened or weakened to increase the heat transfer tube, especially A method of controlling the mechanical cleaning performed by a corrosion protection and / or a cleaning body of a power plant cooling pipe, in which polarization resistance and / or heat transfer coefficient is measured for a predetermined number of pipes substantially evenly distributed over the entire nest surface of the pipe. The heat transfer coefficient is measured from the coolant inlet temperature, outlet temperature, flow velocity and steam temperature, and corrosion protection improving means is set for each region or collectively according to the measurement result of the pipe with the highest risk of corrosion. Method characterized by charged, and / or depending on the measurement result of the worst tube heat transfer coefficient for controlling the cleaning cycle. 2. A method as claimed in claim 1, characterized in that the steam temperature is detected via a pipe in which the coolant does not flow. 3. A fixed or fluid, which can be confirmed to be chemically or physically different from the coolant, is added to measure the flow rate of the coolant at the pipe inlet, and a solid or fluid is added at the pipe outlet. Method according to claim 1, characterized in that the presence is recorded and the measured time from addition to the presence measurement is related to the distance from the addition point to the presence measurement point. 4. At least one device for measuring polarization resistance for checking a passive layer or other protective layer on the inner wall of a tube of a single tube or a group of tubes, and the formation of a protective layer in the inlet area of the heat exchanger. A metering device that admixes the facilitating substance or an electric cathodic protection device that prevents erosion of the inner wall of the pipe and / or a device that measures the heat transfer coefficient from the vapor to the coolant, and the cleaning body is a coolant to remove deposits on the inner wall of the pipe. It is equipped with a device for charging and circulating it inside, and a control system that determines the charging frequency, charging time, and charging strength of each device, and is a mechanical system that performs corrosion prevention and / or cleaning of heat transfer pipes, especially power plant cooling pipes. In a facility for controlling cleaning, each measuring device is arranged in a plurality of tubes (12), preferably evenly distributed over the entire tube nest surface, and in particular, the apparatus for measuring the heat transfer coefficient is a tube inlet and a tube outlet. Measure the temperature of the coolant at A control system is a device that includes one temperature detector (20, 21), a temperature detector (28) for measuring the steam temperature, and a flow meter for quantifying the amount of coolant flowing through the pipe (12), and which is useful for anticorrosion. Depending on the measurement result of the polarization resistance, it is possible to put in each region collectively or according to the most inconvenient measurement result, and the clean body circulation device is controlled by the control system according to the worst heat transfer coefficient measurement value. Equipment that can be input. 5. A temperature detector (28) for measuring steam temperature,
5. Equipment according to claim 4, characterized in that it is installed in a pipe (13) adjacent to the pipe (12) in which the coolant does not flow. 6. Equipment according to claim 4, characterized in that the flow meter measures discontinuously. 7. A flow meter, a time measuring device, a detector for recording solids at the inlet (22) of the pipe inlet and at the pipe outlet or for recording physical and / or chemical changes of the coolant, solids. Or a metering device (26) for intermittently supplying fluid,
7. Equipment according to claim 6, characterized in that the time measuring device detects the time between the charging signal and the detector signal. 8. A measuring sphere having a diameter smaller than the inner diameter of the pipe (12), wherein the flowmeter comprises a time measuring device, a detector at the beginning of the pipe and a detector at the end of the pipe, and the coolant can be detected by the detector. 7. The device according to claim 6, characterized in that the time measuring device detects the time between the detector signals.
Equipment described in paragraph. 9. Each detector is composed of two electrodes (23) arranged at a distance from each other and connected to a power supply, and the time of the change in conductivity caused by a measuring sphere at the moment when a fluid passes between the electrodes. Equipment according to claim 7 or 8, characterized in that a signal is generated. 10. Each measuring sphere can be detected capacitively or inductively by at least one metal body or by any other method, each detector consisting of a measuring capacitor or a measuring coil. The equipment according to claim 7 or 8. 11. The equipment according to claim 10, wherein the measuring sphere circulates at the same time as the cleaning body. 12. Equipment according to claim 9, characterized in that the electrode (23) is a component of a polarization resistance measuring device. 13. The method according to claim 9, wherein one of the electrodes is a tube (12) itself.
Equipment described in paragraph 12. 14. A temperature detector (20) for each pipe inlet and pipe outlet,
The charging part (22) or the detector is respectively a cylindrical support (18,1
The equipment according to any one of claims 5 to 13, characterized in that the equipment is stored in 9). 15. Equipment according to claim 14, characterized in that the tubular support (18, 19) is inserted as a kind of insert into each tube (12). 16. A temperature detector (20) at each pipe inlet and pipe outlet,
The charging part (22) or the detector is adjusted in position by a holder before or after each pipe (12), and the holder (32) is bolted in the pipe (13) where the coolant does not flow. The facility according to any one of claims 5 to 13, which is characterized in that 17. A conduit (13) in which no coolant flows serves to guide the conductors (30) of each measuring device of one condensate chamber (3) to the other condensate chamber, the conductor ducts of all measuring conductors. Is provided on the wall of the other condensate chamber.
The equipment according to any one of Items 16 to 16. 18. Equipment according to claim 8 or 9, characterized in that each detector comprises a photoelectric barrier, the dark part of which is passed through a measuring sphere or a turbid substance for signal generation. .