JPH0160552B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to providing an iron ion implantation monitoring device. Copper alloy tubes are used in heat exchangers using seawater, and iron ion implantation is an effective method for preventing erosion of the tubes. In other words, the corrosion resistance of copper alloy members is generally influenced by the protective film formed on the surface, but it is the iron-based protective film that plays a particularly important role in improving corrosion resistance. In particular, for corrosion protection inside cooling pipes, when used in conjunction with conventional cathodic protection methods, corrosion protection effects can be expected not only on the pipe ends but also on the entire inner surface of the pipe, and the required corrosion protection current for cathodic protection can be reduced. This type of combination tends to be widely implemented because it can also be used to measure As a method for implanting iron ions to form an iron-based protective film, ferrous sulfate or an iron electrolytic bath is used. However, when implementing these anti-corrosion methods, it is important to maintain and manage the protective film, and a means to clearly confirm the anti-corrosion status and continue appropriate supply is required. Conventionally, the corrosion protection status in the iron ion supply method was confirmed by supplying iron ions for a certain period of time, then pulling out the cooling pipe and cutting a part of it, or by taking out a test piece that had been placed in a water chamber in advance and forming an anticorrosion protective film on the surface. Since the method involves observing the state of the substance and analyzing its components, the determination is subject to time constraints and requires a great deal of time and effort. Therefore, based on the empirical relationship between the polarization resistance value of the anti-corrosion protective coating formed on the surface of the copper alloy member and the coating condition as shown in the table below,

[Table] The state of the anti-corrosion coating on copper alloy members can be managed by simply measuring the above polarization resistance value during plant operation. The cathode (copper alloy member) potential and the cathode (copper alloy member) potential when the anticorrosive current is supplied are input to the arithmetic circuit that stores the anticorrosive current distribution ratio to the copper alloy member and the area to be protected in advance. However, a method has been proposed in which the coating (polarization) resistance value per unit area is calculated and the state of the anticorrosion coating is determined based on the above relationship. However, although this seems reasonable and reasonable at first glance, it has a serious error factor. In other words, as mentioned above, the film resistance value measured using the current circuit of the cathodic protection device changes depending on external conditions such as the temperature and quality of the seawater that constitutes part of the circuit, regardless of the state of formation of the film. Therefore, the film evaluation is not always appropriate. The present invention has been made in view of the above circumstances, and provides a new means for correcting such inappropriate factors. In other words, the present invention detects the formation state of the protective film using detection electrodes installed in the water chamber and the intake channel, and displays it electrically as an external alarm to indicate the appropriate injection time. exchanger water chamber,
A single or multiple detection electrodes are installed in the tube plate and cooling pipes and in the seawater intake channel before iron ion injection, and changes in polarization resistance due to a film and dirt on the electrode surface due to iron ions formed on the detection electrode on the heat exchanger side and water intake. This is a device that electrically compares the magnitude of change in polarization resistance due to contamination of the road detection electrode and externally indicates appropriate iron ion implantation according to the amount of change. FIG. 1 schematically shows the apparatus of the present invention, in which a detection electrode 2 is installed in a water chamber and a detection electrode 3 is installed in a water channel, and each insulated wire is connected to an iron ion monitoring device 1. The signal from the monitoring device 1 can be displayed on the panel or in the central electrical control room, and can also be used as a control signal for the ferrous sulfate injection device 7 and the iron electrolytic cell 8 installed at the site. The detection electrodes 2 and 3 are made of the same material as the tube plate or cooling pipe of the heat exchanger, and the shapes of the electrodes attached to each are the same. Incidentally, the detection electrodes 2 and 3 may be used alone or in plurality, and each of them is wired together in the connection box 4. In the figure, 5 is the heat exchanger water chamber, 6 is the circulating water pump, and 9
indicate seawater intake channels. Further, FIG. 2 schematically shows the measuring section of the apparatus of the present invention described above. A rectangular wave generator 10 applies voltage to both ends of a bridge circuit consisting of each detection electrode 2, 3 and two resistors, and the remaining two terminals of the bridge circuit are connected to an amplifier 11 to form a detection electrode. Amplifier 11 amplifies the detected voltage, which varies depending on the degree of coating formed by iron ions. In other words, the same current flows through the detection electrode 2 in the water chamber and the detection electrode 3 in the water channel, but the polarization resistance increases due to the formation of a film by iron ions on the detection electrode 2 in the water chamber, so the amount of polarization increases and the polarization at both ends increases. The voltage increases from the detection electrode 3 in the water channel, and the output voltage of the bridge circuit increases. Since the magnitude of the detection voltage needs to have a certain standard width depending on the state of film formation, adjusting devices 12 and 13 are attached. That is, 12 is the adjustment of the reference value and excess value, and 13 is the adjustment of the reference value and insufficient value. The amplified voltage is input to a comparison circuit 14 to compare the magnitude of each detection electrode current. The comparison circuit 14 includes a regulator 1 that changes the reference value.
5, a correction circuit 16 for correcting the flow velocity conditions at each electrode installation location, and an arithmetic circuit 17 for calculating the average value of a plurality of detection electrodes. The external display method is by using lamps, meters, bells, etc. on the device panel, and is indicated by 18 in the figure.
19 and 20 are display devices indicating excessive injection, appropriate injection, and insufficient injection. In addition, alarm terminals and computer terminals are installed inside the device to enable external management control by sending symbols to the central control electrical room. Note that 21 in the figure indicates a power supply circuit. FIG. 3 shows changes in the detected voltage, and is an estimated diagram showing appropriate standards, excessive values, and insufficient values. According to the device of the present invention described above, the surfaces of the detection electrode 2 in the water chamber and the detection electrode 3 in the waterway have different deposits depending on the installation environment. That is, the iron coating adheres to the surface of the electrode 2 in the water chamber into which iron ions are implanted, but does not adhere to the surface of the electrode 3 in the water channel. In the present invention, the iron protective coating is evaluated based on the magnitude of the surface resistance of the tube sheet and tube end based on actual measurements of the condenser during cathodic protection. The surface resistance is less than 1Ω-m2 for new pipes and when the protective film is insufficient, and for a proper protective film it is 1Ω- ^m2 or less.
~20Ω-m ² , and the excess protective film is 20Ω-m ² or more. One way to manage and control iron ion implantation is to automatically measure the surface resistance of tube sheets and tube ends and display its magnitude, but in this case, water temperature fluctuates seasonally. Change in conductivity due to,
The surface resistance also changes due to water pollution in summer and changes in the amount of cooling water, regardless of the state of formation of the protective film. Therefore, the magnitude of the surface resistance becomes inaccurate, which is not practical. Another method is to install the detection electrode inside the water chamber, but in this case as well, as with the surface resistance method, various conditions are added, making the method inaccurate and thus impractical. However, in the present invention, the detection electrode is installed in the same water channel as the cooling water used for the heat exchanger before the iron ion injection point, and the amount of iron ions attached to the surface of the detection electrode in the water chamber is compared for each electrode. However, since this is a method of electrically detecting changes in the amount of adhesion, the water quality conditions of the detection electrodes installed are the same, and the elements of water temperature, water quality, and conductivity can be omitted. This makes it possible to detect accurate values. As a result, the following effects are produced. (1) Conventionally, ferrous sulfate was injected manually, but now it is possible to automatically determine when to inject ferrous sulfate based on the state of the protective film formed. (2) When using an iron electrolytic cell, the amount of iron ions generated can be automatically controlled depending on the state of the protective film formed. Further, examples of usage of the device of the present invention are as follows. (1) Controls iron ion implantation lines for condensers and coolers in thermal power plants. (2) Iron ion implantation management and control of coolers in petrochemical and oil refineries. (3) Iron ion implantation management and control for marine condensers and coolers. (4) Management and control of the amount of iron ions generated in the iron electrolyzer.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the device of the present invention, FIG. 2 is a schematic diagram of the measuring section of the device, and FIG. 3 is a diagram of changes in detected current. 2, 3...detection electrode, 1...iron ion monitoring device, 4
... Connection box, 5... Heat exchanger water chamber, 6... Circulating water pump, 7... Ferrous sulfate injection device, 8... Iron electrolytic cell, 9
... seawater intake channel, 10 ... square wave generator, 11 ... amplifier, 12, 13 ... adjustment device, 14 ... comparison circuit,
15... Adjuster, 16... Correction circuit, 17... Arithmetic circuit, 18, 19, 20... Display device, 21... Power supply circuit.

Claims (1)

[Claims] 1. A single or multiple detection electrode is provided in the water chamber, tube plate, and cooling pipe of a heat exchanger, etc., and in the seawater intake channel before iron ion injection, and the iron ions formed on the heat exchanger side detection electrode are used to detect the electrode surface. By electrically comparing the change in polarization resistance due to the film and dirt with the magnitude of the change in polarization resistance due to dirt on the intake channel detection electrode, it is possible to externally display appropriate iron ion implantation according to the amount of change. Features: Iron ion implantation monitoring device used in combination with conventional cathodic protection methods to prevent erosion by iron ion implantation.