JPS60187383A - Process for preventing sticking of organism - Google Patents

Abstract

PURPOSE:To obtain highly reliable effect for preventing sticking organisms by closing tightly stand-by lines, stopping flow of water completely, thus blocking the supply of food and oxygen. CONSTITUTION:For example, in a system consisting of plural lines of installation, valves 11, 12 are opened and valves 13, 14 are closed, and carbureters 5-2 is reserved as a stand-by equipment. Then, sea water is filled between the valves 13, 14. The system is allowed to stand under this condition for a specified period. Thereafter, the valves 13, 14 are opened, and the line is exchanged with another line of the system. By this method, the supply of food and oxygen are blocked and sticking of organisms is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preventing marine organisms from adhering to equipment such as pipes, waterways, and heat exchangers that carry seawater.

Seawater is used as raw material for water production plants, heated water for vaporizing liquefied gas,
It is also widely used as cooling water in various plants.

An example of a seawater line in liquefied gas vaporization is shown in FIG. In FIG. 1, a screen facility 1 removes foreign substances such as garbage and jellyfish from the seawater. Next, the seawater is pumped up by pump 2 and header 5
distributed by the liquefied gas vaporizer 5 through the supply pipe 4
is supplied to The used seawater is collected by a downstream header 7 via a discharge pipe 6, and is discharged to the outside of the system by a discharge main pipe 8.

Mussels, barnacles, and other sessile organisms live in seawater and can grow in these systems, blocking pipes and causing equipment damage and corrosion.

Conventionally, in order to prevent biofouling, chlorine was injected before or after the pump 2 in Figure 1 to inhibit the growth of living organisms. In many cases, the injection of chlorine has to be stopped. To counter this, countermeasures have been taken, such as installing a fine-mesh strainer in the supply pipe 4 and applying a biofouling prevention method to the surfaces of the pipes and equipment. However, although the former method can remove small inflowing foreign substances, it cannot remove larvae such as shellfish, and cannot prevent organisms from adhering to downstream equipment and piping.

In addition, although the latter can prevent biofouling on the coated surface,
Because it requires repainting once every 1 to 2 years, it is difficult to use on relatively small-diameter piping and small equipment. In addition, measures to prevent biofouling using ultraviolet rays, ultrasonic waves, and electric shock are being studied, but they have not yet been put into practical use due to cost and effectiveness issues.

The present inventors have investigated a method that is relatively simple, inexpensive, and highly effective in preventing biofouling in order to prevent problems caused by biofouling in various plants that use seawater. As a result of investigating the basic conditions and the actual plant configuration, we arrived at the present invention.

That is, the present invention is a system consisting of pipes, waterways, equipment, etc. of a plant that uses seawater as a raw material or heat medium, has multiple lines including backups with the same function, and is capable of alternate operation. The present invention relates to a method for preventing biofouling, characterized in that a separable seawater line is filled with seawater or fresh water and held for a certain period of time, and the holding period and a period in which seawater is passed are provided alternately.

In systems using seawater, there are often two or more lines with the same equipment, and one or more of them
Seawater is stopped as a backup. A feature of the present invention is that biofouling prevention treatment is performed on this stopped series.

For multiple lines, the 11th cycle of water flow→stop (processing)→water flow is repeated. Further, the bioadhesion prevention treatment is performed in a closed system while the system is in a stopped state. Incidentally, in conventional methods, treatments such as chlorination, strainer treatment, and antifouling coating were all performed in an open system while water was flowing.

The method of the present invention can be applied to water supply plants that use seawater as a raw material, liquefied gas vaporization plants that use seawater as a heat medium, thermal power plants, nuclear power plants, cooling systems for marine equipment, and many others.

Next, a case in which an embodiment of the method of the present invention is applied to the seawater line for vaporizing liquefied gas shown in FIG. 1 will be described with reference to FIG. 2. In FIG. 2, seawater is pumped up by the pump 2, distributed by the header 6, passed through the vaporizer 5-IK through the supply pipe 4-1, and then passed through the discharge pipe 6-1, the downstream header 7, and the discharge main pipe 8. It is then released into the river. Here, valve 11.1
2 is open. Valves 13, 14 are closed and the carburetor 5-
2 is reserved. The space between valves 1'5 to 14 is filled with seawater, and this state is maintained for a predetermined period of time until the valve 1' is opened.
3.14 is opened to allow seawater to flow into the vaporizer 5-2, and at the same time, the valve 11.12 is closed to make the vaporizer 5-1 a standby. The spare valves 11 and 12 are kept filled with seawater, and after a predetermined period of time, the series is switched again. Repeat this operation alternately.

In addition, in FIG. 2, 4-2 means a supply pipe, and 6-2 means a discharge pipe.

FIG. 3 shows an example of a switching operation cycle in the case shown in FIG. 2. FIG. 3(A) shows an example in the case of two streams (one stream is treated as a reserve), and FIG. 3(B) shows an example in the case of five streams (all one stream is treated as a reserve). In FIGS. 3(A) and 3(B), the solid line indicates the seawater flow period, and the dotted line indicates the seawater retention period.

The marine organisms that cause adhesion problems are mainly Fujitbo and mussels, but they are also affected by plankton (animal and vegetable) that floats in the seawater and flows with the seawater, as well as other microscopic organisms. They live by preying on dead carcasses and debris. Therefore, for these lifestyles, it is necessary to have an adequate flow of water so that food and the oxygen necessary for breathing are constantly supplied. In the present invention, by sealing the preliminary system, completely stopping the water flow, and cutting off the supply of food and oxygen, attached organisms in the system and floating larvae such as barnacles that try to attach are killed. or weaken it to the point where attachment growth becomes difficult. The period of water flow required for this purpose is about one week to one month, depending on the species. On the other hand, when switching the series and starting to flow seawater, the longer the period of time, the more biofouling will occur, so it is recommended that the period of water flow be less than 3 months and the period of full water storage be 2 weeks or more, and alternate operation will be performed. A highly effective biofouling prevention effect can be obtained. In addition,
In Fig. 3 (A), sea water was passed for 2 months and sea water was maintained for 2 months, and in Fig. 5 (B), sea water was passed for 2 months and sea water was held for 1 month.

The effects of the case shown in FIG. 2 above are as follows.

(11) Biofouling between the valves 11 and 12 and between the valves 13 to 140 in FIG. 2 and the resulting damage can be prevented.

(2) Necessary equipment includes series switching valves (11, 12, 15, 14 in Figure 2), but these are often already installed in the plants that are the subject of this invention. These may be used as they are, or the placement locations may be considered so that the effects of the present invention can be applied as widely as possible.

In addition, the operation is extremely easy as the operation can be automated by simply switching the valve, and it can be automated as an electric valve or the like.

(3) Since no chemicals are used, there are no power costs, and operating costs are low.

Note that the effect does not extend to the screen equipment 1, pump 2, header 3.7, and discharge main pipe shown in Figure 2, but these are relatively large pipes and fC9, so they should be located in locations where they can be easily maintained from the outside. Therefore, there is a considerable effect of preventing biofouling mainly through antifouling paints and cleaning, so there are great benefits when combined with the present invention.

Next, another embodiment of the method of the present invention is shown in FIG. This example is also an example applied to the seawater line for vaporizing liquefied gas shown in FIG. 1, similar to the example shown in FIG. 2 above. In FIG. 4, seawater is pumped up by a pump 2, distributed by a header 5, passed through a supply pipe 4-1 to a vaporizer 5-1, then passed through a discharge pipe 6-1, a downstream header 7, and a discharge header. It is discharged via pipe 8. Here, valves 16 and 17 are open and air bleed valve 1
5. Close the drain valve 20.

On the other hand, in other series, valves 18 and 19 are closed and the carburetor 5-
2 is reserved. In this preliminary series, the air bleed valve 14 and the drain bleed valve 21 are closed, and the space between the valves 18 to 190 is filled with seawater.

Here, the biofouling prevention operation between the valves 18 and 19 is performed as follows.

(11 Open the air bleed valve 14 and the drain bleed valve 21 to remove most of the seawater between valves 18 and 19 from the system.

(2) Close the drain valve 21.

(3) Fresh water is supplied from the fresh water supply means 15 through the fresh water line 11t1'' between the valves 18 and 19, so that the valves are almost completely filled with water.

(4) Close the air bleed valve 14 to retain fresh water.

(5) Replace the vaporizer after holding it for a certain period of time. That is, valves 18 and 19 are opened to supply seawater to the vaporizer 5-2. The fresh water is then pushed out of the system. Also valve 16.
17 is closed.

Next, fresh water is supplied between the spare valves 16 and 17 by operations similar to those in (11 to (4) above) and held for a certain period of time.

In this way, in the case of Figure 4, the period for retaining fresh water,
The operation is carried out by alternating the periods during which seawater is passed through.

In addition, in FIG. 4, 4-2 means a supply pipe, 6-2 means a discharge pipe, 9 and jo mean a drain line, and 12 means a fresh water line.

An example of the switching operation cycle in the case of FIG. 4 is shown in FIG. Figure 5 (A) shows the case of 2 series (1 series is treated as preliminary)
, FIG. 5(B) shows an example in the case of three streams (one stream is treated as a reserve). In FIGS. 5(A) and 5(B), the solid line indicates the seawater flow period, the dotted line indicates the freshwater retention period, * indicates the seawater extraction point, and O indicates the freshwater supply point.

With some exceptions, it is difficult for marine organisms to survive in freshwater. The opposite is true for freshwater organisms. The reason for this is not necessarily clear, but in the case of marine organisms, the difference in osmotic pressure between the inside and outside of the cell membrane of organisms that are in contact with fresh water creates an abnormal layer of intracellular pressure NI (the opposite in the case of freshwater creatures). This may be the cause of.

Murasaki mussels, fujibo, etc. that are associated with attachment problems are
Growth under freshwater conditions is difficult, and if kept in freshwater conditions for more than 3 days, attached organisms will die.

On the other hand, the growth of biofouling inside piping while seawater is flowing increases as the water flow period increases, so switching between water flow and treatment once every 2 weeks to 2 months will improve reliability. High biofouling prevention effect can be obtained. In addition, in Fig. 5 (A), seawater flow is carried out for 1 month, fresh water is maintained for 1 month, seawater is removed for 2 hours, and fresh water is supplied for 2 hours. The water was drained for 2 hours, and fresh water was supplied for 2 hours.

The effects of the case shown in FIG. 4 above are as follows.

(1) Biofouling between the valves 16 and 17 and between the valves 18 and 19 in FIG. 4 and the resulting damage can be prevented.

(2) The required equipment is mainly relatively inexpensive equipment such as piping, valves, and tanks, and there is no special equipment and operation is easy.

(3) Pulp operation procedures are constant and can be easily automated using electric valves.

(4) Since no chemicals are used, there is no need to worry about environmental problems. In addition, the fresh water can be used for small business purposes or at the level of clean river water, so treatment costs are low. In particular, the amount of fresh water is small because the seawater flowing through the water is not diluted with fresh water, but is replaced in a limited volume such as a sealed one.

Note that the effect does not extend to the screen equipment 1, pump 2, header 3.7, and discharge main pipe 8 in Figure 4, but these are relatively large pipes or are located in locations that are easy to maintain from the outside. Therefore, there is a considerable effect of preventing biofouling mainly through antifouling paints and cleaning, so the benefits of combining it with the present invention are large.

Moreover, in the case of FIG. 4, if the amount of fresh water required for the treatment is small and there is enough supply, seawater may be pushed out with fresh water instead of handling seawater. (The air bleed valve can be omitted and the operation can be simplified.) Conversely, when the amount of fresh water supplied is insufficient, instead of pushing out the fresh water with seawater when switching trains, drain the drain and remove the used water. After dropping it into a freshwater tank, close the drain valve, fill it with seawater little by little, and switch the series to reuse the freshwater. (Even if about half of the seawater is mixed in, the same effect as Habo can be obtained.) Examples are shown below.

Example Using clean seawater from the Pacific coast, seawater was passed through seven series of tar-epoxy lined steel pipes each having an inner diameter of 50 mm at a flow rate of 15 m/8θC under the following conditions.

(1) Continuous water flow (2) Water flow and seawater retention repeated every day 3) Repeated every 5 days 4) Repeated every 2 weeks 5) Repeated every 1 month 6) Repeated 3 Repeatedly every 6 months (7) Repeatedly every 6 months The results after running water for 2 years under each of the above conditions are shown in Table 1.

Table 1: The amount of deposits inside the pipe per unit length (dry base) is shown as a relative value when condition (1) is set to 1i100.

[Brief explanation of drawings]

FIG. 1 shows an example of a seawater line in conventional liquefied gas vaporization, and FIG. 2 shows a flow in which an embodiment of the method of the present invention is applied to the seawater line of FIG. 1. Figure 5 (A),
(B) shows an example of a switching operation cycle in the case of FIG. FIG. 4 shows a flow in which another embodiment of the method of the present invention is applied to the seawater line of FIG. 1. Figure 5 (A),
(B) shows an example of a switching operation cycle in the case of FIG. Sub-agent 1) Meiji agent Ryo Hagiwara - (to)

Claims (1)

[Claims] Seawater that can be separated by alternate operation in a system consisting of pipes, waterways, equipment, etc. of a plant that uses seawater as a raw material or heat medium, has multiple lines including spares with the same function, and can be operated alternately. A method for preventing biofouling, characterized in that a stopped train is filled with seawater or fresh water and held for a certain period of time, and the holding period and a period of flowing seawater are provided alternately.