JPS63302299A - Method and facility for controlling corrosionproofing and mechanical cleaning of heat transfer tube - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) This invention measures the polarization resistance and activates or intensifies chemical or electrical means to improve corrosion protection when the resistance limit is exceeded. and/or deactivating or weakening said means and/or after measuring the heat transfer coefficient from the steam to the coolant, starting a cleaning cycle of the cleaning body if it is below a limit value and stopping it if it is above a limit value. or to a method for controlling corrosion protection and/or mechanical cleaning by means of a cleaning body of heat exchanger tubes, in particular power plant cooling tubes, by strengthening and weakening the cleaning circulation.

The invention further provides at least one device for measuring the polarization resistance for checking the passive layer or other protective layer on the inner wall of a tube or tube group, and for forming a protective layer in the inlet region of the heat exchanger. metering devices to mix in substances that promote oxidation or electrical cathodic protection devices to prevent erosion of the inner pipe walls and/or devices to measure the heat transfer rate from the steam to the coolant and cooling of the cleaning body to remove deposits on the inner pipe walls. Mechanical protection and/or cleaning of heat exchanger tubes, especially power plant cooling pipes, and a control system that determines the charging frequency, charging time, and charging strength of each device. Concerning equipment for controlling cleanliness.

(Prior art) A similar type of equipment without a corrosion protection part is disclosed, for example, in European patent application no.
It is known from No. 0459. In this installation, the heat account of all condensers is measured using measurement technology and compared with the ideal state. When a difference is detected between the two conditions, a cleaning cycle of the cleaning body is initiated and continues until a sufficient approach to the ideal condition is achieved. There, measurements are taken at the inlet and outlet of the condenser and at the steam room. One of these measurements within the steam chamber is a heat, quantity measurement on the steam side of a single cooling pipe.

It was found that batch detection of condensers was not sufficient to obtain a more accurate clue as to the actual degree of contamination. In particular, stains are often non-uniform, making bulk detection methods unsuitable. Therefore, attempts have already been made to subdivide the tube nest of the condenser into parts and create a heat account for each part (Special Publications Publication No. 5).
No. 7-14193, % Application No. 55-89708). There, a calorimeter is installed outside the cooling pipe in each area, and the inlet temperature and outlet temperature are measured at the same time at the inlet and outlet of the condenser. Based on the subdivided measurement of the degree of contamination via the tube nests, various metering devices associated with the measurement area are operated, which supply the cleaning material substantially area by area.

Chemical treatments are known that can eliminate 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 can also be used to prevent erosion of the tubing. Of particular importance is the chemical conditioning of the water, which contributes to being protected from corrosive effects if the condenser tubes are of certain materials that feature a passive layer or surface layer for good corrosion resistance.

However, if the surface layer is too thick, it is of course harmful to heat transfer.
In this respect, the thickness of the surface layer must be kept to the minimum necessary for corrosion protection. This is particularly true when adding iron ions, which form an iron-rich surface layer on the inner pipe wall.

Measuring the surface state KFi In particular, it is useful to measure the polarization resistance, which can be carried out on individual tubes.

As a result, the electrical conduction resistance from the coolant into the tube material is measured. Up to now, chemical conditioning or cathodic protection of the coolant and mechanical cleaning using cleaning bodies have been carried out separately.

(Problem to be solved by the invention) Detecting the area of the condenser using a measurement engineering method as described above has not yielded results because the flow velocity of the cooling pipe equipped with the calorimeter is unknown. Ta. For example, if the tube in which the heat transfer is to be measured is located in an unfavorable region, the coolant will only flow slowly through the tube and will be warmed up relatively strongly. Therefore, if the calorimeter displays a bad value even though there is no problem with the heat transfer state of the tube, it will be K. If, on the other hand, the flow passes through the tube to be measured very quickly, large heat transfers occur that give rise to the measurement signal, even though this tube may already contain deposits that require cleaning.

The object of the invention is therefore to improve a method of the type mentioned at the outset for determining the actual state of the individual cooling pipes and subsequently operating the installation. The purpose of the equipment is to provide a suitable measurement method for more accurately quantifying the properties of the tubes within the heat exchanger during operation.

(Means for Solving the Problem) The above objective is solved by measuring the polarization resistance and/or heat transfer coefficient of a predetermined number of tubes distributed evenly over substantially the entire tube nest surface, and measuring the polarization resistance and/or heat transfer coefficient of the tubes with the highest risk of corrosion. Corrosion protection enhancement measures can be applied zone by region or all at once depending on the results of strong pipes, and/or cleaning circulation can be controlled depending on the results of pipes with poor heat transfer coefficients.

Regarding the equipment, in order to achieve the above object, the present invention arranges each measuring device in a plurality of tubes (12) preferably evenly distributed over the entire surface of the tube nest, and controls the device useful for corrosion prevention to maintain a constant polarization resistance by a control system. Depending on the result, it can be turned on area by area or all at once depending on the most unfavorable fixed result, and the purifying body circulation device can be turned on by the control system according to the measured value of the worst heat transfer coefficient. I suggest that.

(Function/Effect) Unlike the prior art, the present invention measures all parameters directly on each individual tube of the heat exchanger, quantifies the heat transfer coefficient, and compares it with a predetermined target value or reference value. Teach me things. The new state of the cooling pipe is measured as a reference value, and based on this reference value, subsequent contamination can be determined by a so-called contamination factor or cleanliness. Alternatively, for kettles using a special cleaning body after acid treatment, the reference value can also be the measured value obtained after mechanical cleaning and a fundamental cleaning of the pipe, which can be carried out by hand, for example during rework. . lastly,
A theoretically calculable value that can be quantified based on pipe dimensions and material data can also be used as a reference value.

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

The conventionally used heat indicator is secured to the outer surface of the cooling tube, for example by adhesive or by a fixture.

When equipping the condenser part with pipes that are inside the condenser part, these pipes, after the manufacture of this condenser part, must be fitted with pipes, since the spacing of adjacent pipes no longer allows sufficient passage for human hands or tools.
It can no longer be approached. For this reason, repairs, seat inspections, etc. cannot be performed. The invention now takes a turn.

Instead, the invention proposes to shut down one of the adjacent tubes of the cooling tube, whose heat f is being measured, and to flow steam to bring the limb to the temperature of the steam. To stop the operation, use the stopper.
In other words, when inspecting a cooling pipe that has developed a tendency to leak, it is carried out using methods that are already in use at present to eliminate this obstruction. In this case, the actual temperature sensor is sufficiently pushed away by the two tube plates, so that the temperature at the point where the steam temperature is reached during continuous operation is reliably detected.

The measurement of the flow rate is preferably carried out intermittently, i.e. not using a turbine impeller, pitot probe, etc., and preferably the distance between the two measuring points, pipe inlet and pipe outlet, and the free coolant component at one measuring point. It is calculated by quoting the time elapsed to reach the other measurement point. The amount of free coolant may be a foreign body or fluid in the form of a floating measuring sphere whose diameter is smaller than the internal diameter of the entire tube, which may be added in small amounts in the area of the first measuring point or in place of the first measuring point. It is either a liquid substance or a gas. This fluid may be an ink, a salt solution with a different electrical conductivity than the coolant, or any other optically detectable substance whose turbidity or reflectivity can affect, for example, a photoelectric barrier. The measuring balls can also be inserted in the inlet region of the condenser, as long as their number is so large that a certain probability of passing through the tube to be measured exists. In particular, it is possible to load the measuring sphere together with the cleaning body, as long as the measuring sphere is suitably coded and can be detected as such by a single measuring device. This is done by mixing capacitively or inductively detectable metal particles, etc. In this case, a detector can be used to confirm the passage of the beginning and end of the tube.

Particularly suitable as a detector for measuring the passage of a fluid introduced at the pipe inlet and which differs physically and/or chemically from the coolant are two electrodes arranged one behind the other or opposite each other in the direction of flow. This is used to measure the conductive resistance of the coolant as a steady state value. When a fluid passes through such a detector, for example with better or worse conductivity, the conductive resistance changes for a short time, which is used for the measurement. With a detector of this kind it is also possible to detect the passage of the aforementioned measuring spheres or of ordinary cleaning bodies. This is because they change the conductor resistance between the two electrodes at the moment of passage due to liquid displacement or flow effects.

The advantage of such a detector as a component of the invention is, in particular, that the same electrodes that are also a component of the blade detector can be used for measuring the polarization resistance. In this way, the expenditure required for the detector of the cooling pipe to be measured is significantly reduced. The cooling pipe itself can be used as an electrode if a second electrode is housed in a cylinder installed next to the cooling pipe or in a so-called insert inserted into the cooling pipe, insulated from the cooling pipe. can.

Of course, in such a tube or insert there are also remaining detectors, i.e. temperature detectors, capacitive, inductive or optical measuring devices, and also, depending on the equipment of the entire measuring system, one
It can be stored at both the pipe inlet and the pipe outlet of the pipe to be measured in one condenser.

As already mentioned above, one of the possible implementations includes supports that serve as detector supports axially in front and behind the tube sheet at the tube inlet and tube outlet, respectively. Such a support can be temporarily fixed to the condenser tubes, or retention can be achieved using a plug used to measure the steam temperature to shut down one of the adjacent cooling pipes. With this type of retention, the tubesheet remains completely untouched and the entire installation of the condenser side measurement module becomes significantly W15g.

In this way, the risk of leakage is avoided, especially between the steam and coolant compartments of the condenser. The support, especially at the tube inlet, must be constructed such that the probability that clean bodies will flow into the tube still does not change the flow conditions in the tube. These conditions will be explained later on the basis of the illustrated embodiment.

The out-of-service pipe in which the steam temperature measurement takes place can be used particularly advantageously to lead all measuring terminals on one condenser side to the other condenser side, and Only a single duct is required for the entire room. The inlet chamber of the condenser is specifically designed for this purpose. Therefore, in at least one of the chambers, the measuring conductor is well protected from the action of the fluid, and the risk of damage is largely avoided in this area.

In general, the present invention relates both to the chemical conditioning of cooling water and to a cathodic protection device for cooling pipes, which additionally controls the circulation of the clean body depending on the rate of heat transfer from the steam to the coolant. It can be confirmed that the combination of the equipment and the two condenser optimization methods is related.

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

The circuit diagram shown in FIG. 1 schematically shows two measuring devices and nine associated controllers and a controller for processing the measured values. For example, the inside of a normal condenser 1 that condenses steam in a power plant (an inlet chamber 2, an outlet chamber 3, and a tube nest 6 of cooling pipes between them)
The coolant can flow through the cooling pipe via the inlet 4 and the outlet 5. At the end of the tube a tube plate 7.8 separates the steam chamber from the coolant chamber. The supply and discharge of steam to and from the cooling pipe through the steam chamber is not shown.

In general, the coolant does not pass through the tube nest 6 uniformly, but rather in high-speed areas, low-speed areas, areas where there is a high probability of clean body flowing in,
There are small areas, especially dirty areas, etc. In order to detect representative values of individual regions, a cooling pipe 12 to be measured, the corrosion state and heat transfer coefficient of which are detected continuously or at intervals, is placed alongside the non-measured cooling pipe 11 at a predetermined location. It is a provision.

In the case of a condenser with a rectangular cross-section, which is common today, for example, nine pipes are measured, and the pipes are stacked one on top of the other in 3,000 sides, so that each three pipes are distributed substantially evenly over the entire surface of the tube bank 6. It is arranged as follows. Since this arrangement is repeated for six tubes, only a single cooling tube 12 to be measured is shown in FIG. 1 by way of example only.

Each of the cooling pipes 12 to be measured is associated with a cooling pipe 15 which is out of operation, which will be explained in more detail later. The cooling pipe 13 whose operation has been stopped is closed with plugs 14 on both sides.

At each inlet side and each outlet side of the tube to be measured 12, a cylindrical support 18, 19, which respectively contains the necessary detectors at these points, is inserted into the tube to be measured 12 as a kind of insert.

Temperature detectors 20.21 are attached to this for measuring the coolant inlet temperature and outlet temperature at these points on both sides, and the amount of absorbed heat is detected together with the flow rate. Knowing the steam temperature is essential for this. This is measured by a temperature detector 28 in the tube 13 which has been shut down. Five temperature measurements are input to the controller where they are utilized for further processing.

In the illustrated embodiment, the flow rate per unit volume is measured as follows. On the inlet side of the tube 12 to be measured, in the region of the cylindrical support 18, there is a charge 22 through which chemicals can be sprayed from the tank into the flowing coolant by means of a metering pump 26.

The interstitial material instantaneously matches the velocity of the flowing coolant and is thus conveyed through the tube 12 as a relatively complete liquid enclave. 2 inside the cylindrical support 19 on the outlet side of the tube to be measured 12
The electrodes 23 are arranged one after the other.

When the sprayed substance, for example a salt solution, passes through the electrode 23, the electrical current changes briefly and is used to detect the charge material at this point. Since the time of charging is known in the charging section 22 and the cross-sectional area of the tube to be measured 12 has been detected in advance, the time from when the substance flows out from the charging section 22 until it passes through the electrode 23 is The volumetric flow rate can be calculated from the time between. The volumetric flow rate is determined by the cross-sectional area of the cooling pipe to be measured.
It is equal to the quotient resulting from the product of the length between the electrodes 23 and the measurement time during which the sprayed substance traverses the cooling pipe 12 to be measured. Therefore, the metering pump 26 is connected to the attached controller for the charging time and the electrode 23 for the final time measurement. The tube dimensions are permanently stored in the attached flow rate controller.

From the above quantities, that is, the flow rate per unit volume of the coolant, the temperature difference, the specific density, the heat capacity, and the steam temperature, detecting the heat transfer coefficient at which the steam is transferred to the coolant through the wall of the pipe 12 to be measured. Can be done.

Such measurements are carried out after radical cleaning of the metal with an abrasive cleaner until smooth, pickling or hand cleaning.
Since this can be done on new cooling pipes that are not yet contaminated, a reference value can be obtained through this first measurement and used as a measure of each deterioration due to contamination. The deviation from that is
Since the dimensions and material data are known and the heat transfer coefficient can be calculated, it can also be used as the basis for theoretical values for pure metal tubes. With this reference value, it is possible to determine the fouling factor or the cleanliness, which respectively represents a general characteristic value for the thermotechnical state of the cooling pipe.

As already mentioned at the outset, the individual cooling pipes 11 can be cleaned by adding cleaning bodies, for example sponge rubber balls, at regular intervals or in succession, possibly with varying concentrations, to the coolant and, after passing through the cooling pipes, at the outlet. Capture again in area 5. A too intensive treatment of the inner walls of the individual cooling pipes 11 with a cleaning agent has a negative effect, especially in the case of alloys which are K-treated to provide a surface layer for corrosion protection. If the tube walls are generally smooth, the circulation of the cleaning body does not significantly improve the heat transfer, and in this case the surface layers are affected, increasing the risk of corrosion.

In order to ensure that this critical limit is approached, the illustrated condenser is equipped according to the invention with a measuring device for detecting the polarization resistance. For this purpose, a measuring electrode 24,
In the feed tube leading to the charging section 22, there is a reference electrode 23 which serves as a working electrode together with the tube wall of the tube to be measured 12 and makes it possible to measure the polarization resistance of this tube. The evaluation of the measured values takes place in the attached controller. Polarization resistance as a measure of surface condition is expressed in 9 ohms per unit area. The experience values are sufficiently known and from this it is possible to set target values for each usage condition.

The surface layer can be strengthened by chemical treatment of the coolant entering the condenser, for example by charging iron sulfate in the case of copper alloy cooling tubes. Alternatively, protection against erosion of the pipework in the inlet and outlet areas of the cooling pipes can also be achieved by using so-called sacrificial anodes or active cathodic protection, even though the surface layer is damaged or eroded.

The measured values obtained from the measured amount of heat and polarization resistance are not only displayed on the original controller, but also used to activate the cleaning equipment and anticorrosion system. Based on measurements and empirical values, the duration and strength of the purifying circulation of the purifying body are adjusted. This cleaning may impair the effectiveness of the surface layer, but this can be compensated by appropriate chemical treatments or activation of cathodic protection. The process can also be made dependent on the measured value of the polarization resistance, ie terminated when a sufficiently stable surface layer exists to exclude harmful corrosion.

By combining condenser cleaning and corrosion protection, especially when measuring iron sulfate, with the present invention, it is possible to constantly monitor the condition of the condenser and immediately adapt to changes in operating conditions for optimal operation of the condenser. Become. Since the heat transfer and polarization resistance of the individual cooling pipes are specifically measured with the proposal of the invention, the measurement quality is no longer compromised. This makes it possible to detect the distribution of dirt and corrosion and, if necessary, to take targeted countermeasures in specific areas of the tubesheet.

A variation in the arrangement of the detector on one side of the tube nest is shown in Figure 2.

Instead of a cylindrical support, in the illustrated embodiment a plate-like support 31 is provided with a single electrode 32 on the inlet side. The second electrode necessary to form the detector is provided in the form of the tube 12 to be measured.

The illustrated electrode 32 fills only about 6/4 of the circumference of the appropriate hole in the support 32, rather than the entire circumference, allowing a temperature sensor (not shown) to be housed without difficulty in the free surrounding area. .

The plate-like support 31 has stopped operating (the stopper 5 that closes W13
It is held at 4. The plug 54 has an elastic wall area that can be collapsed using the anchor bolt 35, creating a liquid-tight fixed seat inside the out-of-service tube 13. The anchor fixing part is firm enough to fix the plate-shaped support 31 to the plate-shaped support 31 without movement.

Therefore, the plate-shaped support 31 has a relatively large area and is thin (Example 1) so that the probability of the inflow of clean bodies in the area of the plate-shaped support 31 is not influenced. In other words, the cleaning body should always take the same path into the cooling pipe as predicted by the law of statistical chance, regardless of the presence of the plate-shaped support 31-.

The plate-shaped support 51 shown in FIG. 2 can be easily used together with the support 19 shown in FIG. 1 on either the inlet or outlet side of the cooling pipe. The important thing is that each detector is mutually aligned, and the only difference is that the distance between the detector for volume flow detection and another detector is known.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a facility for controlling corrosion protection and cleaning of heat exchanger tubes using a detector insert, and includes a cross-sectional view partially enlarging a schematically illustrated condenser. FIG. 2 is a cross-sectional view of an enlarged portion of FIG. 1 to clarify the use of the detector support in combination with the cooling pipe to be measured. [Explanation of symbols] 11, 12.13-... Cooling pipe.

Claims (1)

[Claims] 1) Measuring the polarization resistance and activating or intensifying chemical or electrical means to improve corrosion protection when the resistance falls below a resistance limit;
deactivating or weakening said means if a resistance limit value is exceeded, and/or starting a cleaning cycle of the cleaning body if the resistance limit value is below the limit value after measuring the heat transfer coefficient from the steam to the coolant;
and in a method of controlling corrosion protection of heat transfer tubes, in particular power plant cooling tubes and/or mechanical cleaning carried out by means of a cleaning body, by shutting down or intensifying and weakening the cleaning circulation when a limit value is exceeded, substantially over the entire tube nest surface. measuring the polarization resistance and/or heat transfer coefficient for a predetermined number of tubes evenly distributed in the area, and depending on the fixed results for the tubes with the highest risk of corrosion, applying corrosion protection improvement means zone by zone or all at once; and/or a method characterized in that the cleaning circulation is controlled according to the measurement result of the tube with the worst heat transfer coefficient. 2) switching before this signal for the duration of a predetermined wake time between the signal after exceeding or falling below the limit value and the signal after deactivating or weakening the corrosion protection enhancing means and/or the cleaning circulation; The method according to claim 1, characterized in that the state is maintained. 3) Detecting the heat transfer coefficient of an individual tube by measuring the coolant inlet temperature, outlet temperature, flow rate, and measuring the steam temperature for a tube without coolant flow adjacent to the measured tube. A method according to claim 1 or 2, characterized in that: 4) Add a solid or fluid that can be confirmed to be chemically or physically different from the coolant to measure the flow rate of the coolant at the pipe inlet, and record the presence of the solid or fluid at the pipe outlet. The method according to claim 3, wherein the measured time from addition to presence measurement is related to the distance from the addition point to the presence measurement point. 5) at least one device for measuring polarization resistance in order to check the passive layer or other protective layer on the inner wall of the tube or tube group and in the inlet region of the heat exchanger to promote the formation of the protective layer; A metering device to mix the substances or an electric cathodic protection device to prevent erosion of the pipe walls and/or a device to measure the heat transfer rate from the vapor to the coolant and a cleaning body placed in the coolant to remove deposits on the pipe walls. A device for charging and circulating;
In equipment that controls corrosion protection of heat transfer tubes, especially power plant cooling pipes, and/or mechanical cleaning performed by a cleaning body, each measuring device is equipped with a control system that determines the input frequency, input time, and input strength of each device. The device is arranged in the tubes (12), preferably evenly distributed over the tube surface, and the device serving for corrosion protection is controlled by the control system depending on the measurement result of the polarization resistance, region by region or the most unfavorable measurement result. A facility characterized in that it can be turned on all at once according to the heat transfer coefficient, and that the purifying body circulation device can be turned on according to the measured value of the worst heat transfer coefficient by a control system. 6) Each heat transfer coefficient measuring device has one temperature detector (20, 21) each measuring the temperature rise of the coolant at the pipe inlet and the pipe outlet.
), a temperature detector (28) for measuring the steam temperature in the adjacent pipe (13) whose operation has been stopped, and a flow meter for quantifying the amount of coolant flowing through the pipe (12). Equipment described in scope item 5. 7) The equipment according to claim 6, characterized in that the flow meter measures discontinuously. 8) The flow meter records solids or fluids intermittently with a time measuring device and a detector that records solids or records physical and/or chemical changes in the coolant at the charge (22) at the tube inlet and at the tube outlet. 8. Installation according to claim 7, characterized in that the time measuring device detects the time between the charging signal and the detector signal. 9) The flow meter consists of a time measuring device, a detector at the beginning of the tube, and a detector at the end of the tube, and the coolant can be detected by the detector.
Equipment according to claim 7, characterized in that it can optionally be provided with a measuring sphere of a diameter smaller than the inner diameter of the tube (12), and the time measuring device detects the time between the detector signals. . 10) Each detector consists of two electrodes (23) arranged at a distance from each other and connected to a power source, the time signal being generated by the conductivity change caused by the measuring bulb at the moment the fluid passes between the electrodes. Claim 8 characterized in that
Equipment as described in paragraph or paragraph 9. 11) Patent claims characterized in that each measuring sphere is detectable, in particular by at least one metal body or otherwise capacitively or inductively, and each detector consists of a measuring capacitor or a measuring coil. The equipment described in item 8 or 9 of the scope. 12) The equipment according to claim 11, characterized in that the measuring bulb circulates simultaneously with the cleaning body. 13) Equipment according to claim 10, characterized in that the electrode (23) is a component of a polarization resistance measuring device. 14) Claim 10 or 13, characterized in that one of the electrodes is the tube (12) itself.
Equipment described in Section. 15) The temperature detector (20), charging section (22) or detector at each tube inlet and tube outlet is connected to a cylindrical support (18, 1), respectively.
9) The equipment according to any one of claims 6 to 14, characterized in that the equipment is housed in a container. 16) Installation according to claim 15, characterized in that the cylindrical support (18, 19) is inserted as a kind of insert into each tube (12). 17) The temperature sensor (20), charging section (22) or detector at each tube inlet and tube outlet is adjusted in position by a holder before or after each tube (12), and the holder (32) is operated. 15. Installation according to any one of claims 6 to 14, characterized in that it is bolted in a stopped adjacent pipe (13). 18) The adjacent pipe (13), which has stopped operating, is connected to one condensate chamber (3).
) serving to lead the conductors (30) of each measuring device into the other condensation chamber, the conductor ducts of all measuring conductors being provided in the wall of the other condensation chamber. 6-1
Equipment described in any of Section 7. 19) Equipment according to claim 9 or 10, characterized in that each detector consists of a photoelectric barrier, the dark part of which is passed through a measuring sphere or a turbid substance for signal generation.