JPH04191A - Method for cleaning the inner surface of heat transfer tubes in a heat exchanger - Google Patents

Abstract

PURPOSE:To surely and effectively clean many heat transfer tubes without loss of the operation of a heat exchanger by making flow down particles made of aquatic plant having a specific weight substantially equal to that of liquid flowing in the tubes of a multitube type heat exchanger, and jetting gas from the inlet end of the tube in two-phase solid/liquid stream flowing down in the tube to form three-phase flow of solid/gas/liquid. CONSTITUTION:A particle supply unit 8 is integrally provided at a particle supply nozzle 10 provided in a coolant inlet tube 9, and an optimum amount of particles are supplied to a water chamber 4 in response to the contaminating state in a heat transfer tube. The particles are made of plant living in the water having the same properties as those of coolant, have properties which are returned to the end of underwater plant when a predetermined period is elapsed after they are fed down in the tube, and substantially the same specific weight as that of water. The amount of the jetted gas supplied through a gas conduit 15 to a cleaning head 114 formed of a plurality of gas jetting nozzles 13 is controlled by a cleaning gas flowrate control system 16 in response to the contaminating state of the inner surface of a heat transfer tube 3. The interior of the tube 3 is cleaned by using three-phase solid/gas/liquid flow of the particles, gas and water.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for cleaning the inner surface of a heat exchanger tube in a heat exchanger, and particularly to a method for cleaning the inner surface of a heat exchanger tube in a multi-tubular heat exchanger such as a condenser in a power generation plant. The present invention relates to a method for cleaning the inner surface of a heat exchanger tube to remove slime, scale, etc. adhering to the inner surface.

[Conventional technology]

Conventionally, heat exchanger tubes used as coolers include:
Bacteria, algae, and fungi multiply due to the formation of scales such as limescale and rust, and the rise in water temperature, and when these are mixed with dust, slime and the like are formed. If these adhere to the wall surface inside the tube, problems such as a decrease in heat exchange capacity and the formation of corrosion holes in the heat exchanger tube occur. In particular, in the case of a condenser, etc., the efficiency of the steam turbine decreases and the output of the generator decreases, resulting in huge losses.

As a countermeasure to these problems, scale and slime are currently removed using chemical cleaning agents, but since the waste liquid after cleaning poses a water pollution problem, neutralization treatment is required. In particular, in the case of heat exchangers that use seawater, since the amount of cooling water is large, methods that do not use chemicals are being adopted even if there is no leakage of chemicals due to concerns that the marine ecosystem will change. .

As a cleaning method that does not use chemicals, sponge balls are floated in heat exchange water and cleaned while flowing through the heat exchanger tubes, but it is difficult to measure the wear and tear of the sponge balls and maintain operational management for replenishment. The drawback was that it was annoying. Further, as seen in Japanese Patent Application Laid-Open No. 59-10381, a method of mixing and circulating resin particles in cooling water has a sufficient cleaning effect on initial slime formation and scale adhesion. However, for slime and scale that have grown to a certain extent, there is a drawback that the collision of the particles with the wall surface becomes weaker, and the cleaning effect may suddenly decrease.

Furthermore, as in Japanese Patent Laid-Open No. 61-252498, a method has been proposed in which gas is released into the liquid in the form of bubbles at the inlet end of a heat transfer tube, and ultrasonic waves are oscillated in this gas-liquid mixed flow. , a large amount of money is required to install an ultrasonic transmitter, etc. At this time, if you try to clean with only gas-liquid two-phase flow, the cleaning effect of bubble flow will be limited and it will be difficult to obtain sufficient performance in areas with heavy dirt, slime generation, and summer when growth is large. There was a drawback. Moreover, JP-A-593
As seen in Japanese Patent No. 0000, an apparatus has been proposed that attempts to clean a tube using a three-phase flow of water, sand, and air. This seems to have a very great cleaning effect, but because the particles are made of sand, which has a higher specific gravity than water, the cleaning is carried out vigorously locally, potentially damaging parts of the tube.

[Problem to be solved by the invention]

An object of the present invention is to be able to reliably and effectively clean each of a large number of heat exchanger tubes without impairing the operation of the heat exchanger.
Moreover, it is an object of the present invention to provide a method for cleaning the inner surface of a heat exchanger tube, which reduces the cost of a cleaning device and does not affect the environment.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a multi-tubular heat exchanger in which a liquid flows inside the heat transfer tubes, in which particles made of underwater plants whose specific gravity is approximately equal to that of water in the liquid flowing inside the tubes. Flowing down, and blowing out gas at the inlet end of the heat transfer tube into the solid-liquid two-phase flow flowing down inside the tube to create a solid-gas-liquid three-phase flow, deposits inside the tube can be removed and dust can be removed. This prevents the adhesion of bacteria, etc.

In addition, in order to protect the natural environment and reduce the cost of cleaning equipment, the particles made from the underwater plants are removed from the ends of the original underwater plants after a certain period of time after flowing into the heat transfer tube. This is a particle with characteristics that allow it to return to its normal state.

Furthermore, in order to perform cleaning effectively, the present invention stores a cleaning head consisting of a plurality of gas jetting nozzles in an ice chamber on the cooling water inlet side of the heat exchanger, and blows out the gas supplied to each cleaning head. The amount is controlled according to the state of dirt inside the pipe.

[Effect]

Since the method of the present invention does not use chemicals, it does not pose a pollution problem. Moreover, since solid-gas-liquid three-phase flow of particles, gas, and water is used to remove deposits inside the pipe and prevent the adhesion of dust and bacteria, the turbulence of the fluid inside the pipe becomes strong.
Since the particles collide with the wall with a large amount of energy, the cleaning effect is greatly improved. Furthermore, since the particles are made from underwater plants with a specific gravity almost equal to that of water, they are easy to handle without settling in narrow spaces or places with slow flow, and can be easily handled using a multi-tube heat exchanger. In the case of heat exchanger tubes, particles are mixed into each heat exchanger tube, and since uniform and reliable cleaning can be performed, it is possible to prevent damage to the heat exchanger tubes due to excessive local cleaning.

In addition, the particles made from underwater plants used have the property of returning to the original fragments of underwater plants after a certain period of time after flowing down the heat transfer tube, so they are useful not only for protecting the natural environment but also for other purposes. Since it is discarded together with the waste water after cleaning, there is no need to provide particle collection or circulation system equipment, making it possible to reduce the cost of the overall cleaning equipment.

Furthermore, the present invention can control the amount of gas ejected depending on the dirt condition inside the tube, so the flow velocity and turbulence inside the tube can be controlled, thereby controlling the strength of cleaning, so that the inside surface of the heat transfer tube can always be optimized. It becomes possible to maintain In other words, it is possible to remove deposits inside the tube without destroying the anticorrosion coating of the heat exchanger tube, or
Adhesion can be prevented efficiently.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is a system diagram in which the present invention is applied to a condenser of a power generation plant.

A large number of heat transfer tubes 3 are arranged inside the condenser body 1 by a tube plate 2.
is supported, and the cooling water filled in the cooling water inlet side water chamber 4 connected to the main body 1 on the inlet side of the heat exchanger tube 3 passes through the inside of the heat exchanger tube 3 and reaches the outlet of the heat exchanger tube 3. The outlet side water chamber 5 of the cooling water is connected to the main body 1 on the side. On the other hand, the steam flowing in from the steam port 6 at the upper part of the main body 1 is condensed by exchanging heat with the cooling water in the heat exchanger tube 3, and becomes condensed water, which is formed in the condenser outlet pipe 7 provided at the lower part of the main body 1. drained from the water.

In addition, a particle supply nozzle 1 provided in the cooling water inlet pipe 9
0 is connected with a particle supply device 8 consisting of a particle supply valve 11, a particle supply pump 12, and a particle supply tank 43, and supplies the optimum amount of particles to the water chamber according to the dirt condition inside the heat transfer tube. It is designed to be supplied to 4. These particles are made from plants that live in water of the same quality as the cooling water, and after flowing through the heat transfer tube,
It is suitable that the particles have the property of returning to the original fragments of underwater plants after a certain period of time, and moreover, it is desirable that the specific gravity of the particles is approximately the same as the specific gravity of water. In addition, the mixing ratio of particles and water in the water chamber 4 is preferably about 3 to 30%, and the particle diameter is 1 to 5 mm in diameter. good.

Further, the main body 1 includes a cleaning gas flow rate control system that controls the jetting flow rate of gas supplied through the gas conduit 15 to the cleaning head 14 consisting of a plurality of gas jetting nozzles 13 in accordance with the dirt state of the inner surface of the heat transfer tube 3. 16 are provided. The control system 16 includes a compressor 17, a gas supply tank 18, a control valve 19, a vacuum level detector 21, and a flow rate control device 20. At this time, the degree of vacuum detector 21 indirectly detects dirt on the inner surface of the heat exchanger tube.

In the present invention, the main body 1 includes a gas reservoir 24 that collects gas that has leaked into the heat transfer tube 3 without being ejected, a gas reservoir 25 that collects gas that has flowed down inside the heat transfer tube 3, and a gas reservoir 25 that collects gas that has flowed down inside the heat transfer tube 3. Venting pump 26 for extracting accumulating gas
．． 27 and extraction piping 28, 29 are provided, so that gas does not accumulate in the system and cause trouble.

In this way, the condenser of the present invention uses the particle supply device 8 that supplies particles made from underwater plants and the cleaning gas flow rate control system 16 to control the flow of particles, gas, and water inside the heat transfer tubes 3. Since cleaning is performed using a solid-gas-liquid three-phase flow, the turbulence of the fluid inside the heat transfer tube is strong, and the energy with which the particles collide with the wall surface is large, making it possible to create a system with a large cleaning effect.

In addition, by making the specific gravity of the particles almost equal to the specific gravity of water, the particles are evenly mixed into the heat exchanger tubes and reliable cleaning can be performed, so damage to the heat exchanger tubes due to localized excessive cleaning can be prevented. Furthermore, after flowing down the heat transfer tube, these particles are discharged from the cooling water outlet and flowed into the sea, and after a certain period of time, they return to the original fragments of underwater plants. In addition to protecting the environment, there is no need to install equipment for particle recovery or particle recirculation, making it possible to reduce the cost of the overall cleaning equipment.

In addition, the cleaning gas flow rate control system 16 can control the amount of gas ejected according to the state of contamination inside the pipe, so the flow rate and degree of turbulence of the fluid inside the pipe can be controlled, thereby controlling the strength of cleaning. , it is possible to always maintain the inner surface of the heat exchanger tube in an optimal state.

This situation will be explained in more detail using FIG. 2. This figure is an explanatory diagram showing the solid-gas-liquid three-phase flow inside the heat exchanger tube 3 when the amount of gas ejected is changed.

Assuming that the particles are mixed uniformly in the water, when the gas flow rate is increased, the flow inside the heat transfer tube becomes wavy flow 34 → bubble flow 35 → slag flow 36 → froth flow 37 → annular flow 38 → spray flow 39 The cleaning intensity increases in this order. In other words, assuming that the amount of cooling water is constant, as the gas flow rate is increased, the flow velocity and degree of turbulence will increase, so the energy with which the particles collide with the wall surface will increase, and the cleaning effect will increase.

In this way, the fact that cleaning intensity can be controlled by the magnitude of the gas flow rate means that if the gas flow rate is increased in an actual plant when the generation and growth of slime increases, such as in the summer,
The inner surface of the heat exchanger tube 3 can always be kept clean.

The condenser of the present invention includes a particle supply device 8 and a gas extraction system 3.
0 etc., automatic operation is possible and a decrease in the efficiency of the power generation plant can be suppressed.

In addition, since the device of the present invention does not have any moving parts underwater,
This reduces troubles and improves equipment reliability.

[Effects of the Invention] According to the present invention, it is possible to remove the deposits on the inner surface of the heat exchanger tube and prevent the deposits without causing any pollution problems.
This can be done effectively even while driving. Furthermore, since cleaning can be carried out while grasping the contamination state of the heat exchanger tubes, optimal cleaning can be performed without fear of damage to the heat exchanger tubes due to excessive cleaning. Furthermore, since the device returns to the natural regeneration cycle after a certain period of time after a single particle is discharged from the equipment, equipment such as particle collection and particle recirculation systems can be omitted, making it possible to reduce the cost of cleaning equipment. .

[Brief explanation of drawings]

FIG. 1 is a system diagram showing an embodiment of the present invention, and FIG. 2 is an explanatory diagram of the cleaning state of the present invention. 1... Condenser main body, 3... Heat exchanger tube, 4. Death: Himuro, 8: Particle supply device, 10: Particle supply nozzle,
13... Gas jet nozzle, 14... Cleaning head, 1
6...Cleaning gas flow rate control system, 19...Control valve, 2
1...Vacuum level detector, 30.31...Gas extraction system.

Claims (1)

[Claims] 1. In a multi-tubular heat exchanger in which a liquid flows through heat transfer tubes, particles made of underwater plants having a specific gravity approximately equal to that of water flow down into the liquid flowing within the heat transfer tubes. By ejecting gas at the inlet end of the heat transfer tube into the solid-liquid two-phase flow flowing down inside the heat transfer tube to create a solid-gas-liquid three-phase flow, deposits inside the tube can be removed and dust, bacteria, etc. can be removed. A method for cleaning the inner surface of a heat exchanger tube in a heat exchanger, characterized in that the method aims to prevent 2. In claim 1, the heat exchanger is characterized in that the particles made from underwater plants return to the original fragments of underwater plants after a certain period of time after flowing down in the heat transfer tube. A method for cleaning the inner surface of a heat transfer tube in a heat exchanger. 3. In claim 1, a cleaning head consisting of a plurality of gas jetting nozzles is housed in a water chamber on the cooling water inlet side of the heat exchanger, and the jetting flow rate of the gas supplied to each cleaning head is adjusted to the state of contamination in the pipe. A method for cleaning the inner surface of heat exchanger tubes in a heat exchanger. 4. In claim 1, a particle supply nozzle for supplying the particles is provided in the cooling water inlet side piping of the heat exchanger, and a heat source for controlling the amount of particles supplied to the particle supply nozzle according to the state of contamination in the pipe. A method for cleaning the inner surface of heat transfer tubes in an exchanger.