WO2005066420A1

WO2005066420A1 - System and method to prevent the impingement of marine organisms at the intake of power plants

Info

Publication number: WO2005066420A1
Application number: PCT/KR2004/003442
Authority: WO
Inventors: Jae-Hac Lee; Dong-Sung Kim; Woo-Jin Lee; Seung-Baek Lee
Original assignee: Korea Ocean Research And Development Institute
Priority date: 2004-01-03
Filing date: 2004-12-24
Publication date: 2005-07-21
Also published as: JP4237228B2; KR20050071831A; KR100558267B1; JP2007513275A

Abstract

Provided are a system and method for preventing the inflow of marine organisms into seawater intakes of power stations. The system includes a marine organism lifting apparatus for lifting the marine organisms and a marine organism discharging apparatus. The marine organism lifting apparatus includes a plurality of brush traveling screens installed at an inclination of a predetermined angle with respect to the seawater intakes to wholly or partially screen the seawater intakes and engaged in upper and lower sprocket wheels so that the widths of the brush traveling screens are matched to those of the seawater intakes, each brush traveling screen including a caterpillar traveling chain guided by an upper chain guiding rail and a plurality of brushes installed at the caterpillar traveling chain to lift marine organisms jammed or laid between the brushes; and a scraper installed at the upper sprocket wheel and formed with a plurality of grooves and blades to scrape the marine organisms jammed or laid between the brushes. The marine organism discharging apparatus includes a conveyor for moving the marine organisms scraped by the scraper using a screw; and a collecting box for collecting the marine organisms moved by the conveyor. Therefore, lifting of various types of marine organisms is easy, a remarkably increased treatment capacity ensures complete removal of large quantities of marine organisms, a pressure drop of seawater can be minimized, and system optimization is possible.

Description

SYSTEM AND METHOD TO PREVENT THE IMPINGEMENT OF MARINE ORGANISMS AT THE INTAKE OF POWER PLANTS

TECHNICAL FIELD The present invention relates to a system and method for preventing the inflow of marine organisms into seawater intakes of power stations where a huge amount of seawater is used for circulating cooling water. More particularly, the present invention relates to a system and method for efficiently preventing the mass influx of various types of marine organisms, such as jellyfish, Euphausiids, fish, and seaweeds, into the seawater intakes, which frequently causes power derating and even shutdowns.

BACKGROUND ART Various conventional apparatuses such as bar screens, trash rakes, traveling water screens (TWSs), and drum screens are currently installed to stop or remove foreign substances such as marine organisms. However, the removal capability of these conventional apparatuses is very low, in particular against the mass inflow of marine organisms in a specific period of time which leads to frequent derating or power shutdowns, thereby resulting in enormous financial losses. Since the conventional apparatuses are faced directly with the seawater of the intakes, marine organisms in large populations in nearshore areas could have been identified. The influx in large quantities into the seawater intakes of power stations has occurred in a specific period of time, e.g., a season, a marine ecosystem cycle, and a typhoon season, which can be confirmed from various documents acquired from the power stations that have failed to stop or remove the marine organisms. In more detail, with respect to the bar screens currently installed, bars are disposed at a predetermined spacing. Since a general bar spacing is about 200 nm to prevent a pressure drop, the bar screens serve only as simple protectors for equipment to be used in a next process, and thus, have substantial limitations in preventing massively entered or small-sized foreign substances. Trash rakes have a bar spacing of about 50 mm and are used to remove marine plants or trash raked by bars. Due to the very slow movement speed of the rakes, the treatment of large volume of marine organisms is impossible.

RECORD COPY - TRANSLATION (Rule 12.4) Meanwhile, to decrease the load of expensive traveling water screens, a trash rake with a detachable wire mesh was developed (Korean Utility Model Registration No.

20-323134, published on August 14, 2003). However, the pressure drop coefficient of the wire mesh is high, while the movement speed of the rake is still slow. Therefore, accumulation of marine organisms in the trash rake may damage the trash rake itself. With respect to the traveling water screens, several screen baskets where a wire mesh is secured to a supporting frame are continuously attached to a rotating chain, as disclosed in Korean Patent Laid-Open Publication No. 2003-0015423, entitled "Apparatus for Fixing Screen Mesh of Traveling Water Screen ", published on February 25, 2003. A screen mesh fixing apparatus as disclosed in Korean Patent Laid-Open Publication No. 2003-0015423 is designed to have strong resistance to mechanical damages. This shows that marine organisms accumulated in large quantities in a screen mesh (wire mesh) increase the load of a traveling water screen, and thus, damage to the screen mesh and a screen mesh fixing apparatus is frequently caused. Furthermore, a recent trend is that a square screen mesh with a mesh size of 3 mm x 3 mm is substituted for a square screen mesh with a mesh size of 10mm x 10mm. However, since a screen mesh with a smaller mesh size has large resistance against fluid flow, pressure loss increases, thereby leading to a higher likelihood of damage to a screen mesh and a screen mesh fixing apparatus. A conventional traveling water screen has average, fast, and maximum traveling speeds of 3 m/min, 6 /min, and 10 m/min, respectively. The treatment capacity of the traveling water screen is remarkably low, thus leads to failure to remove large quantities of marine organisms. In this respect, Korean Utility Model Registration No. 0323140 ("Directly Driven Traveling Water Screen", published on August 14, 2003) discloses a directly driven traveling water screen with a high traveling speed. According to the Utility Model document, the traveling water screen can be driven at a high linear travel speed of 22m/min or more. However, a much higher traveling speed is required considering the inflow amount of seaweed in the Gori nuclear power station (Gori, Korea) and the Ulsan thermal power station (Ulsan, Korea) in a typhoon season. In addition, drum screens have been used in the Uljin nuclear power station (Uljin, Korea) and the Ulsan thermal power station (Ulsan, Korea), instead of traveling water screens. Drum screens have such a structure where a wire mesh is secured to a drum and have similar functions and performances to traveling water screens. For example, in the Uljin nuclear power station, drum screens are operated at two circumferential linear velocities of 2.5 m/min and 10 m/min, which are insufficient to treat large quantities of marine organisms, thereby leading to frequent power shutdowns.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view illustrating a system for preventing the inflow of marine organisms into seawater intakes of a power station according to an exemplary embodiment of the present invention; FIG. 2 is a side view of the system of FIG. 1 ; FIG. 3 is a side view of another example of a marine organism floating apparatus shown in FIG. 2; FIG. 4 is a sectional view taken along a line IV-IV of a brush traveling screen of a marine organism lifting apparatus shown in FIG. 2; FIG. 5 is a sectional view of another example of the brush traveling screen of FIG.

4; FIG. 6 is a sectional view of still another example of the brush traveling screen of FIG. 4; FIG. 7 is an enlarged view of a part "A" of FIG. 2; and FIG. 8 is an enlarged rear view of FIG. 7.

DETAILED DESCRIPTION OF THE INVENTION Technical Goal of the Invention The present invention provides a system and method for preventing the inflow of marine organisms into seawater intakes of power stations, wherein brushes are used to remove various marine organisms and a high marine organism treatment capacity ensures the complete removal of a large volume of marine organisms. The high marine organism treatment capacity can be accomplished by generating fewer loads at the brushes attached to a chain and reducing a driving resistance by sprocket wheels and an upper guiding rail, thereby ensuring high-speed traveling. The present invention also provides a system and method for preventing the inflow of marine organisms into seawater intakes of power stations, wherein brushes are easily permeated by seawater, thereby reducing a pressure drop of seawater. Furthermore, due to floating of marine organisms by air bubbles or water stream, the brush traveling screens can be installed highly, whereby lower portions of the seawater intakes are open without being screened by the brush traveling screens to minimize the pressure drop of seawater. The present invention also provides a system and method for preventing the inflow of marine organisms into seawater intakes of power stations, which can be optimized by appropriately designing a marine organism floating apparatus and a marine organism lifting apparatus and by selecting appropriate brushes, according to the types and inflow amounts of marine organisms in a specific period of time.

Disclosure of the Invention According to an aspect of the present invention, there is provided a system for preventing the inflow of marine organisms, including jellyfish, into seawater intakes of a power station, the system being installed at the seawater intakes of the power station and including a marine organism lifting apparatus for lifting the marine organisms and a marine organism discharging apparatus for discharging the marine organisms lifted by the marine organism lifting apparatus, wherein the marine organism lifting apparatus includes: a plurality of brush traveling screens installed at an inclination of a predetermined angle with respect to the seawater intakes to wholly or partially screen the seawater intakes and engaged in upper and lower sprocket wheels so that the widths of the brush traveling screens are matched to those of the seawater intakes, each brush traveling screen including a caterpillar traveling chain guided by an upper chain guiding rail and a plurality of brushes installed at the caterpillar traveling chain to lift marine organisms jammed or laid between the brushes; and a scraper installed at the upper sprocket wheel and formed with a plurality of grooves and blades to scrape the marine organisms jammed or laid between the brushes. The marine organism discharging apparatus includes a conveyor for moving the marine organisms scraped by the scraper using a screw; and a collecting box for collecting the marine organisms moved by the conveyor. To prevent the flow of seawater toward sides of the brush traveling screens of the marine organism lifting apparatus, a guiding plate may be installed at both sides of each brush traveling screen of the marine organism lifting apparatus so that the seawater is guided toward the brush traveling screens and flows into the seawater intakes. To ensure a broad application of the system, the brushes of the brush traveling screens may be formed in a triangular sectional shape, in a reverse-triangular sectional shape, or in a semicircular sectional shape, and installed detachably from the traveling chain, to selectively use appropriate brushes considering the sizes, types, and inflow amounts of the marine organisms in a specific period of time. The system may further include a marine organism floating apparatus installed at the seabed in front of the marine organism lifting apparatus to float the marine organisms to the brush traveling screens of the marine organism lifting apparatus screening upper parts of the seawater intakes, wherein the marine organism floating apparatus includes: an air bubble forming unit composed of at least one array of pipes receiving air and a plurality of nozzles installed at the pipes to generate air bubbles; a water stream generating unit for generating water stream using a seawater pressure difference by a pump or a propeller; or a combination thereof. According to another aspect of the present invention, there is provided a method of preventing the inflow of marine organisms into seawater intakes of a power station using a marine organism inflow prevention system including a marine organism floating apparatus for floating the marine organisms, a marine organism lifting apparatus for lifting the marine organisms using an inclined caterpillar, and a marine organism discharging apparatus for discharging the lifted marine organisms; the method including: floating the marine organisms to a predetermined height using air bubbles or water stream to decrease a pressure drop of seawater that enters the seawater intakes; lifting the marine organisms floated by the air bubbles or water stream to the surface of seawater using the caterpillar; and discharging the lifted marine organisms to facilitate transfer of the marine organisms.

Effect of the Invention As apparent from the above description, according to the system and method for preventing the inflow of marine organisms into seawater intakes of power stations, various types of marine organisms are easily lifted and pressure drop of seawater can be minimized. Furthermore, the system has a treatment capacity sufficient to completely remove large quantities of marine organisms and can be optimized according to the types and inflow amounts of marine organisms, etc.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a system and method for preventing the inflow of marine organisms into seawater intakes of power stations according to exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. First, referring to FIGS. 1 and 2, a system for preventing the inflow of marine organisms into seawater intakes of a power station according to an exemplary embodiment of the present invention is installed in front of a seawater intake 1 of a power station and is used to remove marine organisms such as jellyfish 2. The system of the present invention consists essentially of a marine organism lifting apparatus 10 and a marine organism discharging apparatus 20. The system of the present invention may further include a marine organism floating apparatus 30. The marine organism lifting apparatus 10 may wholly screen the seawater intake 1. It is preferable that the marine organism lifting apparatus 10 screens an upper part of the seawater intake 1 to reduce the pressure drop of seawater that enters the seawater intake 1 . In this case, the marine organism floating apparatus 30 may be installed so that marine organisms are floated to the marine organism lifting apparatus 10. The marine organism lifting apparatus 10 serves to lift marine organisms such as the jellyfish 2 that may enter the seawater intake 1 and includes a brush traveling screen 1 1 and a scraper 12. Referring to FIG. 2, the brush traveling screen 1 1 is installed at an inclination of a predetermined angle with respect to the seawater intake 1 to screen an upper part of the seawater intake 1 and engaged in upper and lower sprocket wheels 13 and 14 so that the width of the brush traveling screen 11 is matched to that of the seawater intake 1 . There are a plurality of brush traveling screens with the above structure. Referring to FIGS. 4 through 6, the brush traveling screen 11 includes a caterpillar traveling chain 15 guided by an upper chain guiding rail (not shown) and a plurality of brushes 16 installed at the caterpillar traveling chain 15 to lift marine organisms jammed or laid between the brushes 16. The brush traveling screen 11 is installed to a depth sufficient to lift marine organisms floated by air or water stream generated by the marine organism floating apparatus 30 as will be described later. The scraper 12 is installed at a part "A" of FIG. 2. Referring to FIGS. 7 and 8, the scraper 12 is installed at the upper sprocket wheel 13 of the brush traveling screen

11 and is formed with a plurality of grooves and blades. The scraper 12 is a device capable of directly scraping marine organisms jammed or laid between the brushes 16. The scraper 12 is installed at the upper sprocket wheel 13 with a head shaft 13a that is positioned at an opposite side of the lower sprocket wheel 14 with a tail shaft 14a, as shown in FIG. 2. Therefore, the scraper 12 can completely separate marine organisms from the brushes 16 by a direct contact method, instead of an unreliable method such as back-washing. Meanwhile, as shown in FIGS. 1 and 2, the marine organism discharging apparatus 20 is an apparatus discharging marine organisms lifted by the marine organism lifting apparatus 10. The marine organism discharging apparatus 20 includes a conveyor 22 for moving marine organisms scraped by the scraper 12 using a screw 21 and a collecting box 23 for collecting the marine organisms moved by the conveyor 22. Further, a guiding plate 3 may be installed at both sides of the brush traveling screen 11 of the marine organism lifting apparatus 10 so that seawater can flow into the seawater intake 1 via the brush traveling screen 11 to prevent the flow of seawater toward sides of the brush traveling screen 11 , as shown in FIGS. 1 and 2. Meanwhile, the system according to the exemplary embodiment of the present invention as shown in FIG. 2 includes the marine organism floating apparatus 30. The marine organism floating apparatus 30 is installed at the seabed in front of the marine organism lifting apparatus 10 and serves to lift marine organisms that may enter the seawater intake 1 to the brush traveling screen 11 of the marine organism lifting apparatus 10 screening an upper part of the seawater intake 1. Referring to FIG. 2, the marine organism floating apparatus 30 may include an air bubble forming unit 33 composed of at least one array of pipes 31 receiving air and a plurality of nozzles 32 installed at the pipes 31 to generate air bubbles. Alternatively, referring to FIG. 3, the marine organism floating apparatus 30 may include a water stream generating unit 34 for generating water stream using a seawater pressure difference by a pump (not shown) or a propeller (not shown). In addition, although not shown, the air bubble forming unit 33 of the FIG. 2 and the water stream generating unit 34 of FIG. 3 may be installed at the same time. With respect to the air bubble forming unit 33 installed at the seabed in front of the seawater intake 1 , the pipes 31 are disposed perpendicular to the flow direction of seawater and three through ten pipes may be installed with about 500 mm spacing.

Therefore, marine organisms such as jellyfish and Euphausiids contained in seawater can hold sufficient air, and thus, can rise toward the surface of seawater. In particular, the jellyfish 2 move remarkably slowly relative to seawater and can easily change the movement direction according to the flow direction of the seawater. In this respect, it is preferable to use the water stream generating unit 34 of FIG. 3, instead of the air bubble forming unit 33 of FIG. 2. The distance from the seawater intake 1 and the number of the pipes 31 and the nozzles 32 of the air bubble forming unit 33 and the water stream generating unit 34 can be optimally adjusted considering the function and installation depth of the air bubble forming unit 33 and the water stream generating unit 34 and the flow rate of seawater to maximize the floating effect of marine organisms. Furthermore, provided that sufficiently small marine organisms can be lifted, the spacing of the brushes 16 of the brush traveling screen 11 may increase, the area of the seawater intake 1 not screened by the brush traveling screen 11 may increase, or the depth of the brush traveling screen 11 from the surface of seawater may decrease, whereby the pressure drop of seawater that enters the seawater intake 1 can be reduced. Also, the arrangement of the brushes 16, the installation position of the brush traveling screen 11 , or the like can be optimally designed according to the sizes and types of marine organisms and the necessary amount of seawater. Meanwhile, the brushes 16 of the brush traveling screen 11 may have various sectional shapes according to the sizes or types of marine organisms. Referring to FIGS. 4 through 6, the brushes 16 are formed in a semicircular sectional shape (FIG. 4), in a reverse-triangular sectional shape (FIG. 5), or in a triangular sectional shape (FIG. 6). Preferably, the brushes 16 are installed detachably from the traveling chain 15 to selectively use appropriate brushes considering the types and inflow amounts of marine organisms that may enter the seawater intake 1 in a specific period of time. A method of preventing the inflow of marine organisms into seawater intakes of a power station is performed using the above-described system of the present invention. The marine organism inflow prevention method includes floating marine organisms to a predetermined height using air bubbles or water stream to decrease the pressure drop of seawater that enters seawater intakes; lifting the marine organisms floated by the air bubbles or the water stream to the surface of seawater using an inclined caterpillar; and discharging the lifted marine organisms. According to the marine organism inflow prevention system and method of the present invention, less load is generated at the brushes 16 attached to the chain 15. Furthermore, since a chain guiding rail (not shown) may be installed only on an upper surface of the brush traveling screen 11 between the head shaft 13a at which the upper sprocket wheel 13 is installed and the tail shaft 14a at which the lower sprocket wheel 14, the driving resistance of the brush traveling screen 1 1 can be decreased, thereby increasing a linear travel speed of the brushes 16 (theoretically, 60-80 m/min). Therefore, the brush traveling screen 1 1 of the present invention can have a remarkably increased marine organism treatment capability, as compared to a conventional traveling water screen (linear travel speed of 22m/min) and a conventional drum screen (linear travel speed of 10m/min). While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. For example, the shape of a marine organism floating apparatus, the shape of brushes, and a marine organism discharging apparatus using a screw have been illustrated with reference to the accompanying drawings but may be changed without departing from the spirit of the present invention. Therefore, the invention for which protection is sought is not defined by the detained description thereof but by the spirit and scope of the following claims.

Claims

1. A system for preventing the inflow of marine organisms, comprising jellyfish, into seawater intakes of a power station, the system being installed at the seawater intakes of the power station and comprising a marine organism lifting apparatus for lifting the marine organisms and a marine organism discharging apparatus for discharging the marine organisms lifted by the marine organism lifting apparatus, wherein the marine organism lifting apparatus comprises: a plurality of brush traveling screens installed at an inclination of a predetermined angle with respect to the seawater intakes to wholly or partially screen the seawater intakes and engaged in upper and lower sprocket wheels so that the widths of the brush traveling screens are matched to those of the seawater intakes, each brush traveling screen comprising a caterpillar traveling chain guided by an upper chain guiding rail and a plurality of brushes installed at the caterpillar traveling chain to lift marine organisms jammed or laid between the brushes; and a scraper installed at the upper sprocket wheel and formed with a plurality of grooves and blades to scrape the marine organisms jammed or laid between the brushes.

2. The system of claim 1 , wherein the marine organism discharging apparatus comprises: a conveyor for moving the marine organisms scraped by the scraper using a screw; and a collecting box for collecting the marine organisms moved by the conveyor.

3. The system of claim 1 , wherein a guiding plate is installed at both sides of each brush traveling screen of the marine organism lifting apparatus so that seawater is guided toward the brush traveling screens and flows into the seawater intakes.

4. The system of claim 1 , wherein the brushes of the brush traveling screens are formed in a triangular sectional shape, in a reverse-triangular sectional shape, or in a semicircular sectional shape, and are installed detachably from the traveling chain, to selectively use appropriate brushes considering the sizes, types, and inflow amounts of the marine organisms in a specific period of time.

5. The system of claim 1 , further comprising a marine organism floating apparatus installed at the seabed in front of the marine organism lifting apparatus to float the marine organisms to the brush traveling screens of the marine organism lifting apparatus screening upper parts of the seawater intakes, wherein the marine organism floating apparatus comprises: an air bubble forming unit composed of at least one array of pipes receiving air and a plurality of nozzles installed at the pipes to generate air bubbles; a water stream generating unit for generating water stream using a seawater pressure difference by a pump or a propeller; or a combination thereof.

6. The system of claim 5, wherein spacing of the brush traveling screens, areas of the seawater intakes not screened by the brush traveling screens, and installation depths of the brush traveling screens from the surface of seawater are optimized so that the pressure drop of seawater that enters the seawater intakes is reduced.

7. A method of preventing the inflow of marine organisms into seawater intakes of a power station using a marine organism inflow prevention system comprising a marine organism floating apparatus for floating the marine organisms, a marine organism lifting apparatus for lifting the marine organisms using an inclined caterpillar, and a marine organism discharging apparatus for discharging the lifted marine organisms, the method comprising: floating the marine organisms to a predetermined height using air bubbles or water stream to decrease a pressure drop of seawater that enters the seawater intakes; lifting the marine organisms floated by the air bubbles or water stream to the surface of seawater using the caterpillar; and discharging the lifted marine organisms to facilitate transfer of the marine organisms.