JPS606694B2 - Antifouling method for seawater equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an antifouling method for seawater equipment that prevents equipment using seawater from being soiled by animals and plants in the seawater.

In seawater introduction pipes and equipment and plants that use seawater as cooling water, phenomena such as seawater organisms adhering to or growing in the seawater passageways increase passageway resistance and heat transfer resistance, and in severe cases. may block the passage itself. For this reason, structures that serve as seawater passages have traditionally been coated with antifouling paints containing compounds such as mercury, arsenic, and copper, and toxic substances such as chlorine and sodium hypochlorite have been injected into the seawater. Other methods have been used to kill seawater microorganisms, such as electrolyzing seawater itself as an electrolyte and utilizing the toxicity of chlorine and chlorate ions generated at the cathode. Since these methods use poisonous substances to kill animal and plant microorganisms living in seawater, they remain in the wastewater after use, and the entire sea area near the drainage outlet is contaminated by the poisonous substances. It is dangerous and not environmentally friendly. In addition, there are many problems in terms of safety and health when handling these harmful substances. Due to these circumstances, antifouling (preventing the fouling of seawater channels due to the adhesion, proliferation, and growth of animal and plant microorganisms in seawater...hereinafter simply referred to as antifouling) is being developed using ultrasonic energy. A method is being considered.

For example, methods include applying ultrasonic vibrations to the structure itself to prevent the adhesion of microorganisms, or directly irradiating seawater in the water chamber of a heat exchanger with antifouling methods. However, with current technology, the former method has drawbacks such as the effective range is limited to the vicinity of the ultrasonic transducer, and a large number of transducers and power are required to decontaminate a large area. However, in the latter method, simply irradiating ultrasonic waves into a large water chamber will not work because of the directivity of ultrasonic waves (the propagation of ultrasonic waves in water has the property of traveling in a straight line, just like light). It is difficult to transmit the energy necessary for antifouling to the entire water chamber and all heat exchanger tubes. Installing a large number of vibrators to compensate for this has disadvantages, such as being uneconomical, as in the above case. The present invention has been made in view of the above circumstances, and involves irradiating seawater introduced into seawater-using equipment with high-density ultrasonic energy, and applying ultrasonic waves to the parts of the equipment itself into which seawater is introduced that come in contact with seawater. The present invention aims to provide a method of antifouling seawater equipment that can significantly improve the antifouling effect by applying vibration.

The present inventor has developed a method for applying ultrasonic waves of relatively high frequency to seawater that is introduced into seawater introduction pipes, seawater cooling piping, heat exchangers that use seawater as cooling water, and equipment that uses seawater such as plant equipment in a state with high energy density. When irradiated, seawater microorganisms, especially their larvae (
The seawater (which grows, multiplies and causes problems) dies or loses its growth potential, so just introducing this seawater has a considerable antifouling effect, but if the equipment itself is also subjected to ultrasonic vibrations, It has been found that the antifouling effect is significantly improved because the surviving larvae are unable to attach to the wall surface and the adhesion and accumulation of foreign substances other than microorganisms contained in seawater are prevented.

The effect of ultrasound on underwater microorganisms varies depending on the ultrasound frequency, and the mortality rate (irradiation between two inkstone sands) when underwater microorganisms (nauplii larvae of the vertical mackerel) were irradiated with ultrasound at various frequencies was as follows: . Frequency (KHz
) Mortality rate (%) 14 2 28 33 50 45 100 80 200 98 Here, when applying ultrasonic vibration to equipment to prevent the adhesion of marine microorganisms, unlike the above, low frequency The larger the size, the more effective it is, so 28-50K
HZ level is good.

This is because "if the frequency is too low, it will cause cavitation erosion, as well as fatigue of the constituent metal materials and loosening of bolts, nuts, etc.". First Embodiment 3 In FIG. A low ultrasonic vibrator 4 is provided, and seawater 5 is introduced from the inlet side of the introduction pipe 2.

Then, since the seawater passage is narrow in the mounting part 4 of the vibrator 3,
Seawater passing through this area will be exposed to ultrasonic waves with extremely high energy density. Thereafter, the seawater 5 is introduced into the water storage tank through the valve 6, but since the tank 1 itself is given ultrasonic vibration by the vibrator 4 with a relatively low frequency, the seawater 5 in the water storage tank 1 is introduced into the water storage tank. will be affected indirectly. The seawater in the tank is discharged from the drain pipe 7 to the outside via the valve 8. FIG. 2 shows details of the vibrator attached to the introduction tube, in which the vibrator 3 is in direct contact with seawater and can impart high-density ultrasonic energy to the seawater. However, as an example of the above method, a seawater inlet pipe with an inner diameter of 5 ribs was made of 200K barium titanate.
Attach two Hz oscillators to the outside of the water storage tank with a capacity of 2. Attach four 2-Hz Hz oscillators made of ferrite to the center of the side wall so that it is 0.5 Hz at the position of the seawater inlet pipe. Experiments were conducted continuously for two weeks under the following test conditions by pouring seawater into the tank, and the antifouling effect was examined by the amount of seawater organisms that adhered to the side walls of the tank.

Test condition Wind Drives only the oscillator in the inlet pipe.

Song Drives only the vibrator of the water storage tank.

{C} Drive both vibrators. Plate Stop all vibrators.

The table in Figure 3 shows the above test results. The one that drives the child has an effect of about 20%, and even more.
This method has an antifouling effect of 50% or more, and it has been found that this method can provide extremely useful antifouling.

Second Embodiment FIG. 4 shows the present invention applied to a heat exchanger that uses seawater as cooling water. In the figure, 11 is a water chamber, 12 is a seawater introduction pipe, and 13 is a frequency 100KH2 ultrasonic vibrator, 14 is an ultrasonic vibrator for water chamber (frequency 50K
H2), 1 5 is an ultrasonic vibrator for tube sheets (frequency 2 class HZ
), 16 is a heat transfer tube, 17 is an overflow inlet, and 18 is a hot water outlet.

The seawater 89 introduced from the inlet side of the introduction pipe 12 is transferred to the introduction pipe 1.
2, and after being irradiated with high-density ultrasonic energy by the vibrator 13, it enters the water chamber 11 of the heat exchanger. In the heat exchanger, ultrasonic vibrators 14 and 15 drive the water chamber and the tube plate to apply extremely small vibrations, and the seawater flows through the heat exchanger tube 1.
6 and is discharged from the outlet 20 of the water chamber 11. As an example of the above method, two barium titanate vibrators are installed in the introduction tube, two ferrite vibrators are installed in the water chamber, and two ferrite vibrators with nickel horns attached to the tube plate are installed, and the temperature reaches 2. Said first through the seawater of ○
The heat exchanger was operated for a certain period of time in the same way as in the example,
We investigated changes in heat transfer resistance of the mating tube (copper alloy) and the adhesion of seawater organisms to the water chamber.

The test conditions at this time were the following six conditions, and each was operated continuously for three weeks. Test conditions are poor. Only the vibrator in the introduction tube is driven.

(B} Only the vibrator in the water chamber is driven.

) Only the vibrator of the tube plate is driven.

(D} Drive the vibrator in the water chamber and tube plate.

tE) Drive all oscillators. 'F} Stop all oscillators.

The table in Figure 5 shows the above test results, and as in the case of the first embodiment, the test using the 'E} method had less foreign matter adhering to the heat transfer tubes and the rate of decrease in heat transfer resistance was extremely high. There is also less seawater organisms attached to the water chamber, and an excellent antifouling effect is recognized.

On the other hand, {another, 'C} and Dish's method are more effective than (F}'s method, but {E-'s method is far less effective and requires high-density ultrasonic energy to be introduced into the seawater. It can be seen that irradiation is extremely important to increase the antifouling effect.The above series of experiments shows that it is effective if the ultrasonic energy density irradiated to the introduced seawater is 300 mbar or more. Also, although it is necessary to drive the inlet tube's vibrator continuously, the vibrator in the water chamber and tube plate can be driven intermittently in pulses, that is, at intervals of several minutes, but it is not sufficiently effective. Admitted.

As explained above, the present invention irradiates high-density ultrasonic energy to seawater introduced into seawater-using equipment, and applies ultrasonic vibrations to the parts of the equipment itself into which seawater is introduced that come into contact with seawater. The gist is: Therefore, according to the present invention, a sufficient antifouling effect on seawater equipment can be expected,
In addition, since the ultrasonic transducer can be attached to the outside of the equipment, even when applying it to existing equipment, it can be easily implemented without stopping the operation of the equipment or changing the structure. Even in the event of a failure of the ultrasonic transducer, it is possible to carry out maintenance without interrupting the operation of the device, and other remarkable effects can be achieved.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of a water storage tank for explaining the first embodiment of the present invention, Fig. 2 is a sectional view of the main part of the introduction pipe of the tank, and Fig. 3 is a table showing test results using the tank. , FIG. 4 is a block diagram of a heat exchanger for explaining a second embodiment of the present invention, and FIG. 5 is a table showing test results using the same heat exchanger. 1...Water storage tank, 2...Seawater introduction pipe, 3
, 4... Ultrasonic vibrator, 11... Water chamber, 1
2... Seawater introduction pipe, 13, 14, 15... Ultrasonic vibrator, 16... Heat exchanger tube. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1 Set the seawater to be introduced into the seawater equipment at 100KHz in advance.
In addition to irradiating high-density ultrasonic energy at a high frequency of about 50 kHz or higher, ultrasonic vibrations of a low frequency of about 50 KHz or less are applied to the parts of the equipment itself into which seawater is introduced that come into contact with the seawater. Antifouling method for seawater equipment.