JP2007085599A - Heat exchanger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat exchanger comprising a device capable of efficiently preventing corrosion of the whole heat exchanger with a simple constitution. <P>SOLUTION: This heat exchanger includes a heat exchanger main body 20 including a main body barrel 11, a plurality of cooling tubes 13, a supporting plate 16, a water chamber cover 17 forming a water chamber, and tube plates 15 supporting both end portions of the cooling tubes 13, an external DC power source device 40 capable of supplying DC current, an insoluble electrode 30 mounted on a cooling water inflow water chamber cover 17a in a state of being electrically insulated, and a reference electrode 31 for detecting electric potential. A positive electrode of a DC current output circuit of the external DC power source device 40 is connected with the insoluble electrode 30, a negative electrode of the DC current output circuit of the external DC power source device 40 is connected with the tube plates 15 and the supporting plate 16, and protection current is supplied to the cooling water inflow water chamber cover 17, the tube plates 15 and the cooling tubes 13 through sea water. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a heat exchanger that uses seawater as cooling water, such as a condenser that cools and condenses steam used in a thermal power plant, and more particularly to a heat exchanger that has an anticorrosion function using an external power supply system.

  It is well known that heat exchangers that use seawater as a cooling medium are used in many places including power plants and chemical factories. In a thermal power plant, steam generated by a boiler is used to drive a steam turbine, and power is generated by a generator connected to the steam turbine. The steam exhausted from the steam turbine is cooled and condensed by a condenser, and condensed water is recovered. I have to. Since boilers and steam turbines used in thermal power plants are large and the amount of steam exhausted from the steam turbine is large, seawater is used to cool the exhaust steam. Seawater is also used as cooling water in the fresh water cooler that cools the axial cooling water.

  In a thermal power plant, a surface condenser is generally used as a condenser. The surface condenser has an exhaust inlet portion at the upper part of the main body cylinder, and has a plurality of cooling pipes inside the main body cylinder. A cooling water inflow water chamber for sending seawater as cooling water to the cooling pipe and a cooling water outflow water chamber for collecting seawater discharged from the cooling pipe and discharging it to the outside are provided on both sides of the main body barrel. Both ends of the cooling pipe are supported by a tube sheet, and the tube sheet is fixed between the main body body and the water chamber. Further, the cooling pipe is supported by several support plates at the middle part of the pipe.

  Since the condenser uses seawater as cooling water, the material is easily corroded. For this reason, traditionally, an anticorrosion method and a method of forming an iron oxide film and suppressing the corrosion with an iron oxide film have been adopted to protect the tube plate and water chamber from local battery action and corrosion due to contact with different metals. Yes. FIG. 2 is a diagram showing a part of a schematic configuration of a condenser 1 including a conventional general anticorrosion device. The condenser 1 shown in FIG. 2 employs a method of preventing corrosion of the material by electrocorrosion prevention (external power supply method), and an anode 4 installed in a part of the cover 3 forming the water chamber 2 is connected to a DC power source. Connected to the positive electrode of the DC current output circuit of the device 5, connected the negative electrode of the DC current output circuit of the DC power supply device 5 to the tube plate 6, and supplied anticorrosion current from the external DC power supply device 5 to the water chamber 2 through seawater. This protects the inner wall of the water chamber 2 and the tube sheet 6 from corrosion. The detection of the anticorrosion potential is performed using the reference electrode 7 attached in the water chamber 2.

With regard to cathodic protection by the external power supply method, as the quality of seawater deteriorates, even if the anticorrosion current is small at the beginning of energization, the anticorrosion current increases for a while and exceeds the maximum output current value of the device. In order to solve this problem, a method has been proposed in which energization is stopped when a predetermined time has elapsed since the start of energization of the anticorrosion current, and the procedure of resuming energization of the anticorrosion current after the elapse of the predetermined time since the energization was stopped. (For example, refer to Patent Document 1).
JP-A-11-92980

  Even if the technique described in Patent Document 1 requires a corrosion protection current that exceeds the capacity of the cathodic protection device, it temporarily stops energization, and then resumes energization, thereby regaining the capacity of the cathodic protection device. It is possible to maintain the anticorrosion control potential of the seawater cooling water system equipment in the inside, so that it is not necessary to newly install a large-capacity cathodic protection device.

  Incidentally, the corrosion of the condenser does not occur only in the water chamber and the tube sheet, but also occurs in the cooling pipe. However, in the condenser provided with the technique described in Patent Document 1 and the conventional external power supply type anticorrosion method as shown in FIG. 2, the anticorrosion is applied because the negative electrode of the external power supply device is connected to the tube plate. The range is usually the wall of the water chamber and the surface of the tube plate. It is said that the cooling pipe is about 10 times the diameter of the pipe from the inlet of the pipe, and the middle part of the cooling pipe is not protected by electrocorrosion. In order to prevent corrosion of the entire condenser, it is necessary to prevent corrosion of the cooling pipe, and development of a condenser having a simple configuration and a function capable of efficiently preventing corrosion of the entire condenser is awaited. The same applies to heat exchangers including fresh water coolers.

  The objective of this invention is providing the heat exchanger provided with the apparatus which can carry out the corrosion prevention of the whole heat exchanger efficiently with simple structure.

The present invention includes a main body cylinder, a plurality of cooling pipes installed in the main body cylinder, a support plate that supports an intermediate portion of the cooling pipe, and seawater that is cooling water provided in one end portion of the main body cylinder. A cooling water inflow water chamber cover that forms a cooling water inflow water chamber to be supplied, and a cooling water outflow water chamber that is provided at the other end of the main body body and discharges seawater as cooling water flowing out from the cooling pipe to the outside. A cooling water outflow water chamber cover, supporting both ends of the cooling pipe, and located between the main body trunk and the cooling water inflow water chamber cover and between the main body trunk and the cooling water outflow water chamber cover, A heat exchanger main body including a main body cylinder, the cooling water inflow water chamber, and a pair of tube plates that divide the main body cylinder and the cooling water outflow water chamber;
An external DC power supply capable of supplying DC current;
An insoluble electrode attached in an electrically insulated state to the cooling water inflow water chamber cover on the side facing the cooling pipe;
A reference electrode connected to the external DC power supply device installed in the cooling water inflow water chamber and detecting a potential,
The positive electrode of the direct current output circuit of the external direct current power supply device is connected to the insoluble electrode, and the negative electrode of the direct current output circuit of the external direct current power supply device is connected to the main body trunk and the cooling water inflow water chamber cover that are anticorrosive objects. The tube plate located between the main body and the cooling water inflow water chamber cover via seawater, and the tube plate connected between the support plate and the support plate And a heat exchanger for supplying an anticorrosion current to the cooling pipe.

  The heat exchanger according to claim 1, wherein the heat exchanger body is a condenser for cooling and condensing exhaust steam exhausted from a steam turbine.

  The heat exchanger of the present invention includes a heat exchanger body and an external DC power supply device, and is attached in a state where the positive electrode of the DC current output circuit of the external DC power supply device is electrically insulated from the cooling water inflow chamber cover. Connected to the insoluble electrode, and the negative electrode of the direct current output circuit of the external direct current power supply device is connected to the tube plate and the support plate that are to be protected against corrosion and are located between the main body trunk and the cooling water inflow water chamber cover. Since the anti-corrosion current is supplied to the cooling water inflow water chamber cover, the tube plate located between the main body trunk and the cooling water inflow water chamber cover, and the cooling pipe, the entire heat exchanger can be efficiently constructed with a simple configuration. Can be anticorrosive. In particular, unlike a heat exchanger that employs a conventional external power supply system, the entire cooling pipe can be protected from corrosion.

  FIG. 1 is a diagram showing a part of a schematic configuration of a condenser 10 as an embodiment of the present invention. The condenser 10 of the present invention is a surface condenser, and mainly includes a condenser body 20 and a power supply device 40. The surface condenser main body 20 includes a main body barrel 11, a plurality of cooling pipes 13, a support plate 16 that supports an intermediate portion of the cooling pipe, a water chamber cover 17 that forms a water chamber, and a tube plate that supports both ends of the cooling pipe. 15 and the like.

  The main body cylinder 11 has an exhaust inlet portion 12 connected to an exhaust steam port (not shown) of the steam turbine at an upper portion, and has a number of cooling pipes 13 for cooling the exhaust steam exhausted from the steam turbine. A cooling water inflow water chamber 14a for supplying seawater as cooling water to the cooling pipe 13 is collected on both sides of the main body cylinder 11, and seawater as cooling water discharged from the cooling pipe 13 is collected and discharged to the outside. A cooling water outflow water chamber 14b (not shown) is provided.

  The cooling tube 13 is an aluminum brass tube, and both ends thereof are horizontally supported by a pair of tube plates 15 (15a, 15b (not shown)), and a support plate 16 (16a, 16b, 16c,. ). Since the tube plate 15 is made of a copper alloy and functions as a partition wall that separates the main body cylinder 11 and the water chamber 14, seawater does not flow from the connection portion to the main body cylinder 11 when connecting the tube plate 15 and the cooling pipe 13. To be fixed. In addition, the tube sheet 15 is formed between the main body cylinder 11 and the water chamber 14 so that air does not leak from the connection portion with the main body cylinder 11 and seawater does not leak outside from the connection portion with the water chamber 14. Fixed between.

  The water chamber cover 17 that forms the water chamber 14 is made of a steel plate with a rubber lining on the inner surface, and the cooling water inflow water chamber cover 17a that forms the cooling water inflow water chamber 14a into which the cooling water flows is provided with cooling water. The cooling water is discharged to the outside through a pipe 18 for introducing (seawater) and a cooling water outflow water chamber cover 17b (not shown) that forms a cooling water outflow water chamber 14b (not shown) through which the cooling water flows out. A conduit (not shown) is provided. Further, insoluble electrodes 30a and 30b for providing anti-corrosion are attached to the side opposite to the cooling water pipe of the cooling water inflow water chamber cover 17 so as to be electrically insulated from the cooling water inflow water chamber cover 17a. Further, in the water chamber 14a, a reference electrode 31 is attached in a state of being electrically insulated from the water chamber 14a in order to detect the anticorrosion potential in the condenser body 20.

  The power supply device 40 is a device that applies an anticorrosion current (DC current) to the condenser body 20 via the electrodes, and the positive terminal of the DC current output circuit is electrically insulated from the cooling water inflow chamber cover 17a. Are connected to the insoluble electrodes 30a and 30b. The reference electrode 31 is also connected to the power supply device 40 and detects the anticorrosion potential in the condenser body 20. On the other hand, the negative electrode terminal of the direct current output circuit of the power supply device 40 is connected to the tube plate 15a and the support plate 16 (16a, 16b, 16c...) That are anticorrosion objects. The feature of the condenser 10 of the present invention is that, unlike the conventional condenser, the negative electrode of the DC current output circuit of the power supply device 40 is used not only for the tube plate 15a but also for the support plate 16 (16a, 16b, 16c...)).

  When the condenser 10 of the present invention configured as described above is subjected to anticorrosion, the power supply device 40 is turned on, and from the insoluble electrodes 30a and 30b (anode) connected to the positive terminal of the DC current output circuit, The anticorrosion current is supplied to the tube plate 15a, the cooling pipe 13, and the cooling water inflow water chamber 14a via the. Since the support plate 16 (16a, 16b, 16c ...) of the cooling pipe 13 is electrically connected to the cooling pipe 13, the support plate 16 (16a, 16b, 16c ...) is passed through the cooling pipe 13. Anticorrosion current is supplied. The potentials of the tube plate 15a, the cooling tube 13, and the water chamber 14a are detected by the verification electrode 31, and the power supply device 40 controls the potential so that it becomes the set potential.

  In a condenser employing a conventional external power supply system, the negative electrode of the DC current output circuit of the external power supply device is connected to the tube plate and not connected to the cooling pipe. It was not supplied. On the other hand, in the condenser of the present invention, since the support plate is connected to the negative electrode of the DC current output circuit of the power supply device, the anticorrosion current is sufficiently supplied to the cooling pipe via the support plate. As a result, the condenser of the present invention as a whole, including the cooling pipe, is efficiently electrically protected. In addition, the condenser of the present invention is injected for forming a protective film on the cooling pipe by an iron ion implantation apparatus by connecting the entire cooling pipe or a target portion to the cathode of the DC current output circuit of the power supply apparatus. The iron hydroxide particles charged positively as colloidal particles or the iron hydroxide particles positively charged can be attached to the entire cooling pipe or a target portion to form a film of iron hydroxide.

  As described above, the feature of the present invention is to connect the negative electrode of the DC current output circuit of the external power supply device not only to the tube plate but also to the support plate, unlike the condenser adopting the conventional external power supply method. A sufficient anticorrosion current is also supplied to the cooling pipe via the support plate, and as a result, the entire condenser including the cooling pipe is efficiently electrically protected. Therefore, the present invention is not limited to a condenser, but a cooler or heat exchanger that uses seawater having a strong corrosive environment as a cooling medium, for example, fresh water that cools axial cooling water with seawater. The basic configuration of the cooler and the like is the same as that of the condenser, and the present invention can also be applied to these.

It is a figure which shows a part of schematic structure of the condenser 10 as one Embodiment of this invention. It is a figure which shows a part of schematic structure of the condenser 1 provided with the conventional general cathodic protection apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Condenser 11 Main body trunk 13 Cooling pipe 14a Cooling water inflow water chamber 15a Tube plate 16 Support plate 17a Cooling water inflow water chamber cover 20 Condenser main body 30 Insoluble electrode 31 Reference electrode 40 Power supply device

Claims (2)

A main body cylinder, a plurality of cooling pipes installed in the main body cylinder, a support plate that supports an intermediate portion of the cooling pipe, and cooling water that is provided at one end of the main body cylinder and supplies seawater as cooling water to the cooling pipe Cooling water inflow water chamber cover that forms an inflow water chamber, cooling water outflow water chamber that forms a cooling water outflow water chamber that is provided at the other end of the main body and discharges seawater as cooling water flowing out from the cooling pipe to the outside A cover, supporting both ends of the cooling pipe, and positioned between the main body cylinder and the cooling water inflow water chamber cover and between the main body cylinder and the cooling water outflow water chamber cover; A heat exchanger main body including a cooling water inflow water chamber and a pair of tube plates that partition the main body trunk and the cooling water outflow water chamber;
An external DC power supply capable of supplying DC current;
An insoluble electrode attached in an electrically insulated state to the cooling water inflow water chamber cover on the side facing the cooling pipe;
A reference electrode connected to the external DC power supply device installed in the cooling water inflow water chamber and detecting a potential,
The positive electrode of the direct current output circuit of the external direct current power supply device is connected to the insoluble electrode, and the negative electrode of the direct current output circuit of the external direct current power supply device is connected to the main body trunk and the cooling water inflow water chamber cover that are anticorrosive objects. The tube plate located between the main body and the cooling water inflow water chamber cover via seawater, and the tube plate connected between the support plate and the support plate And a heat exchanger for supplying an anticorrosion current to the cooling pipe.   The heat exchanger according to claim 1, wherein the heat exchanger body is a condenser for cooling and condensing exhaust steam exhausted from a steam turbine.

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