NL1032531C2 - Method and system for controlling biological fouling on a bin cooler placed in a compartment; assembly of a bin cooler and such a system; vessel provided with such an assembly; and method for installing such a system. - Google Patents

Description

Title: Method and system for controlling biological fouling on a bin cooler placed in a compartment; assembly of a bin cooler and such a system; vessel provided with such an assembly; and method for installing such a system.

The invention relates to a method and a system for controlling biological fouling, respectively, on a bin cooler placed in a compartment according to the preamble of claim 1 and claim 11. The invention furthermore relates to an assembly of a bin cooler and the like system, as well as on a vessel provided with such an assembly. The invention further relates to a method for installing such a system.

Such a method and such a system are known from practice.

Bin coolers are increasingly being used in the maritime industry, with the benefits to be found in particular in the absence of a seawater circulation system. A bin cooler is a heat exchanger that is used, for example, on sea-going vessels, for example to cool the cooling water of marine engines. Tank coolers are also used for heat exchange with cooling liquid for other parts of an installation to be cooled. For the purpose of cooling, heat exchange takes place between the cooling liquid and the surrounding (sea) water. A bin cooler is installed in a compartment (bin) of, for example, a ship. A maritime environment is present in the interior of the compartment. In the case of a ship, this is achieved through openings in the ship's skin. The maritime environment in the well ensures external cooling of the cooling fluid circulating in a closed system. Parts of the bin cooler are therefore exposed to different types of (sea) water.

There is therefore a risk of biological (maritime) fouling on the bin cooler, such as fouling of mussels, barnacles, grasses, crustaceans, seaweed, algae and the like. The growth of a bin cooler with one or more of such organisms has a negative influence on the cooling capacity of the bin cooler. This will ultimately lead to a situation where a costly cleaning operation is necessary, which may require an unwanted docking of the ship in a ship.

In the known method and device, biological fouling is combated by arranging one or more copper anodes in the bin near the cooling elements of the bin cooler. These copper anodes are arranged in an electrically isolated manner relative to grounding parts of the well in the well. The copper anodes are forcefully dissolved with the aid of a current source. This releases positive copper ions that mix in the seawater and are carried along with the seawater flow along parts of the bin cooler. A toxic environment is created by the dissolved copper ions, which impedes the biological (on) growth.

The electric currents generated by the current source are, inter alia, discharged to surfaces of the well and of the cooling elements, which then function as cathode surfaces. In order to reduce the potential differences in the well, in the known method and device use is made of one or more steel cathode plates arranged at a small distance along the copper anodes. These steel cathode plates are welded or bolted to grounding parts of the confined space.

A drawback of the known method and device is that said method of combating biological fouling entails an increased risk of scale formation on various parts of the bin cooler and the bin. This can be explained as follows.

At the cathode surfaces, such as those of the metal cathode plates, an alkaline environment is created by the electrochemical reaction, whereby, among other things, lime formation is promoted according to the reactions:

OH- + HCO-3-COCO 2 + H 2 O

CO32- + Ca2 + -> CaCOe (Calcium carbonate)

Several studies have been conducted into the chemistry of this so-called "calcareous deposits formation" in seawater, and these have shown that this is an extremely complex matter. Magnesium salts, for example, also form part of the formed lime layer.

The solubility of calcium carbonate decreases with higher temperatures, whereby the combination of warm coolers and an alkaline environment caused by the applied method of combating biological fouling greatly increases the risk of lime formation.

Calcium build-up on the metal cathode plates increases the electrical resistance between the copper anodes and these plates, and the known system automatically sends out a higher voltage to maintain a set current. This also increases the potential difference between the cooling elements and the seawater, as a result of which there is also an increased risk of lime formation on the cooling elements. In practice, lime layers of more than 2 centimeters are achieved. It is further apparent from the literature that calcium carbonates can form a significant layer at temperatures above 60 degrees Celsius, certainly when this takes place in combination with poor flow.

It will be clear that such limescale build-up can lead to a reduced efficiency of bin coolers, non-adequately cooled machines and unforeseen repairs and dockings.

4

It is an object of the invention to provide a solution according to which not only biological fouling but also the build-up of lime layers on a bin cooler is effectively combated.

To this end, according to the invention, a method according to the preamble of claim 1 is characterized in that the method further comprises a descaling step alternating the copper-dissolving step, during which descaling step the metal-containing element which is electrically insulated from ground parts of the compartment in the compartment is arranged via a second current connection to an anodic potential, wherein the metal-containing element is descaled as a result of an anodic reaction occurring on the metal-containing element and wherein the copper-containing element acts as a cathode. To that end, according to the invention, a system according to the preamble of claim 11 is characterized in that in operation the metal-containing element is arranged in an electrically insulated manner with respect to grounding parts of the compartment in the compartment and that the control unit is further arranged for interchanging between the copper-dissolving operating state and a descaling operating state of the system and for setting the metal-containing element to an anodic potential in the descaling operating state of the system via a second current connection of the system, in which descaling operating state the metal-containing element is descaled as a result of an anodic reaction occurring acts as a cathode on the metal-containing element and the copper-containing element.

By adjusting the metal-containing element to an anodic potential, metal (M) of the metal-containing element dissolves according to the anodic reaction: M - * Mn + + ne_. For example, if the metal-containing element is steel, this formula would look like this: 2Fe -> 2Fe2 + + 4e. Because the metal (for example, iron 30 Fe) of the metal-containing element dissolves on the surface and forms an oxide, this detaches and increases in volume to be carried along by the water flow together with the deposited lime layer. The metal-containing element becomes sacrificial in a certain sense and can be replaced over time, for example simultaneously with the replacement of the copper-containing element during, for example, a regular docking turn of a vessel. By mutually switching between the copper-dissolving operating state and the descaling operating state, both biological fouling and build-up of lime layers are effectively combated.

The invention is further embodied in an assembly according to claim 13, in a vessel according to claim 14 and in a method according to claim 15 for installing a system.

Specific embodiments of the invention are laid down in the subclaims.

In the following, the invention is further elucidated with reference to the schematic figures in the accompanying drawing.

Figure 1 shows diagrammatically in cross-section an example of an embodiment of a system according to the invention applied to a bin cooler.

Figure 2 schematically shows an example of set current intensities used in an embodiment of a method according to the invention during copper dissolving and descaling process steps.

Referring first to FIG. 1. In FIG. 1 shows a bin cooler 1 which is arranged in a compartment 2, in this case in a bin 2 of a vessel. The walls of the tank 2 are formed by the ship's skin 3 and bulkheads 4. The tank cooler 1 comprises cooling pipes 5 through which cooling liquid flows. Arrows A and B indicate the places where the coolant enters and exits the hopper. In the ship's hull 3 there are inflow and outflow openings 6 for (sea) water. Arrows C and D indicate the places where the 6 seawater enters and exits through the openings 6 and the tank 2 respectively. Heat exchange takes place at the cooling pipes 5 between the cooling liquid and the sea water.

The bin cooler 1 is provided with a system for combating biological growth on the bin cooler. This system comprises a control unit 7. Two copper-containing rods 8 are arranged in the hopper 2. Each of these copper-containing rods 8 is connected by means of brackets 10 to supports 21 connected to the walls 3, 4 of the hopper 2. Insulation material 9 ensures that each rod 8 is electrically insulated relative to ground parts 21, 3 and 4. of the hopper 2. It is noted that instead of the two bars 8 other numbers and forms of copper-containing elements can also be used. Such elements may also be oriented in the channel 2 in other ways, suspended and electrically insulated from ground parts of the channel 2.

The system further comprises a first current connection 11 which has an electrical connection to a direct current source not shown, as well as electrical connections to the copper-containing rods 8. The control unit 7 is arranged for setting the copper-containing rods 8 in a copper-dissolving operating state 20 of the system via the first current connection 11. In this copper-dissolving operating state, positive copper ions 17 are released from the rods 8. The released positive copper ions mix in the seawater and are entrained with the seawater flow through the well 2. Through the dissolved copper ions a toxic environment is created in the well 2. This toxic environment hinders the biological (initial) growth in the bin 2 and on the bin cooler 2.

Three steel strips 18 are further arranged in the hopper 2. These strips 18 are supported by the carriers 21, wherein insulating material 19 ensures that each strip 18 is arranged in an electrically insulated manner with respect to grounding parts 21, 3 and 4 of the hopper 2. In the example shown, the two bars 8 and the three strips 18 are arranged such that a strip 18 is located on either side of each bar 8. It is noted that instead of the three strips 18 other numbers and shapes of metal-containing elements can also be used. Such elements may also be oriented in the hopper 2 in other ways, suspended and electrically insulated from ground parts of the hopper 2. During the copper-dissolving operating condition of the system mentioned, the metal-containing elements 18 arranged in the hopper 2 function as cathodes.

The system further comprises a second power connection 12 which has an electrical connection to a power source (not shown), as well as electrical connections to the steel strips 18. The system also comprises a third current connection 14 which serves to establish a ground connection to ground parts 3, 4, 21 of the well 2. The control unit 7 is adapted to switch between said copper-dissolving operating state and a descaling operating state of the system and for setting the steel strips 18 to an anodic potential via the second current connection 12 in the descaling operating state. The said switching between said operating states can be realized, for example, by mutually reversing electrical control connected to a direct current source by the control unit 7. connections of the first power connection 11 and the second power connection 12.

In said descaling operating condition, the steel strips 18 descale from the steel strips 18 as a result of an anodic reaction occurring, viz. The anodic reaction: 2Fe -> 2Fe2 + + 4e. More generally, instead of one or more steel strips 18 more metallic elements are used. In that case, metal (M) 30 of the metallic elements goes into solution according to the anodic reaction: Μ - * Mn + + ne-. Because the metal (for example, iron Fe) of the metal-containing element dissolves at the surface and forms an oxide, this detaches and increases in volume to be carried along with the deposited lime layer through the water flow.

During said descaling operating condition, the copper-containing rods 8 each function as cathodes. The following cathodic reaction then occurs on the copper-containing rods 8: O 2 + 2 H 2 O + 4 - - 40H When the steel strips 18 are set to an anodic potential during said descaling operating condition, the insulating material 19 prevents an uncontrolled electrical connection between the steel strips 18 and the earthing parts 21, 3 and 4 of the bin 2.

In order to prevent the formation of salt bridges between parts of the steel strips 18 and / or the earthing parts 3, 4, 21 and / or the copper-containing rods 8, it has been found that it is advantageous if the steel strips and the copper-containing rods are such in relation to to each other and relative to the grounding parts, the length of the shortest "electrical" distances between a steel strip and an earthing part, between a steel strip and a copper-containing rod and between a grounding part and a copper-containing rod is at least 20 millimeters.

Reference is now made to Figure 2, which figure shows an example of current intensities I applied by the control unit 7, shown in Amps, as a function of the time T, represented in minutes, in an embodiment of a method according to the invention.

In Figure 2 a positive current I indicates the current of the electric direct current through the copper-containing rods set during an copper-dissolving operation of the system. A negative current I indicates the current of the electric direct current through the descaling operation of the system on an anodic potential 30 adjusted steel strips 18.

9

In the example shown in Figure 2, the current intensity I is set to a constant value during each of consecutive consecutive time intervals, the set constant value always shifting step by step upon transition from such a time interval to a subsequent such time interval. In the example shown, the respective set constant values are II = +1.5 Amps, 12 = +0.5 Amps, 13 = +2.5 Amps and 14 = -2.5 Amps. After this II is also referred to as high current, 12 low current and 13 extra high current. In the example, the duration of the time intervals in which the values II, 12 and 14 are set is always 15 minutes and the duration of the time intervals in which the value 13 is set is always 30 minutes.

In the example, in a copper-dissolving operating period of 705 minutes, first the high and low current intensities II and 12 are alternately set a number of times and then the extra high current intensity 13 is set. The high amperage II is considered to be sufficiently high to generate sufficient ionic copper to prevent maritime fouling, for example, to prevent a barnacle from getting stuck. Because with a lower current intensity less calcium build-up takes place, the high current intensity II is alternated with the low current intensity 12. The duration of the time intervals in which the low current intensity 12 is set (in the example 15 minutes) is adjusted to the minimum time required for example for a barnacle to fix itself. Due to the alternation of the high and low current intensities, for example, barnacles do not get a chance to settle, while limescale buildup is combated. Compared to a situation in which no low current 12 is used in addition to the high current II, the use of the low current 12 further offers the advantage that the quantity of copper discharged is reduced, so that the copper-containing rods 8 need to be replaced less quickly.

10

More generally, it is advantageous that during the copper-dissolving step the copper-containing rods 8 are set to an anodic potential such that during the copper-dissolving step, periods with high current intensities II occurring through the copper-containing rods 8 and 5 periods with the copper-containing rods 8 occurring low currents 12 alternate.

Suitable values for the latter high current intensities II can be determined in dependence on the total cooling surface of the bin cooler. For example, in some circumstances a high amperage II of approximately 3.0 Ampere may be suitable for a total cooling surface of the bin cooler of approximately 100 square meters, while in comparable circumstances a high amperage II of approximately 0.3 Ampere may be suitable for a total cooling surface of approximately the bin cooler of approximately 10 square meters. It has been found that the latter low current intensities 12 are preferably between 20% and 40% of the high current intensities II.

In the example, the copper-dissolving operating period is closed with a set extra high current 13 during a time interval of 30 minutes ("boost period"). At the end of this boost period, the descaling operating period starts, during which the negative current 14 is set for 15 minutes. An advantage of applying the boost period prior to the descaling operating period is that, during the boost period, the maritime growth is again extra strongly prevented that in the descaling operation period in which no buyer is dissolved, the maritime growth could occur too quickly. develop.

More generally, it is advantageous that during the copper-dissolving step the copper-containing rods 8 are set to an anodic potential such that the copper-dissolving step comprises a boost period 30 with extra high 11 current intensities 13 occurring by the copper-containing rods 8 relative to said high current intensities . It has been found that the latter extra-high current intensities 13 are preferably between 130% and 200% of the high current intensities II. Furthermore, it is then advantageous for the descaling step to be connected to one of the periods with high current intensities occurring by the copper-containing rods 8 or to the boost period, preferably to the last-mentioned boost period. It has been found that the negative current intensities 14 used during the descaling step are preferably between minus 130% and minus 200% of the high current intensities II.

At the end of the descaling operating period, the copper-dissolving operating period starts again, preferably with a set high-current II, as in the example, or with a set extra-high current 13. An advantage of using the high or the extra-high current immediately following the end of the descaling operating period, maritime accretion is thus strengthened as a counterweight to the preceding descaling operational period in which no buyer was dissolved and maritime accretion could have developed too quickly. The duration of the time intervals in which the current intensity 14 is set (in the example 15 minutes) is also tuned to the minimum period required for, for example, a barnacle to settle.

The control unit of a system according to the invention, such as the control unit 7 of the system described with reference to Figure 1, can be adapted to perform methods according to the invention which have been described above with reference to Figure 2.

Furthermore, it is important that the bin cooler 1 or the grounding parts 3, 4, 21 of the bin 2 are protected against corrosion. To this end, it is important that properly applied preservation is supplemented with cathodic protection. The system for combating biological fouling described so far can also be adapted to control the potential difference between the (sea) water and the bin cooler or the grounding parts to set values in operation for the purpose of said cathodic protection. The latter control then also prevents said potential difference from becoming too large, in which case an increased risk of lime formation on the bin cooler or the bin would arise.

For this purpose it is shown in FIG. 1 provided with a reference cell 20 which in operation measures the said potential difference and the control unit 7 is arranged to prevent a set maximum permissible potential difference between the (sea) water and the bin cooler or the like.

10 the grounding parts are not exceeded. In the example of FIG. 1, the reference cell 20 is mounted on a baffle 4 of the well 2. The reference cell 20 is connected via a communicative connection 15 to the control unit 7. The system comprises a controlled circuit which, each time the potential difference measured by the reference cell 20, reaches the set maximum or 15 threatens to exceed or fall below a set minimum, temporarily conducts current to the earthing parts 21, 3 and 4 of the well 2, or interrupts it, so that the potential difference between the (sea) water and the stock cooler or the earthing parts is optimized and the set maximum potential difference is not exceeded. This temporary current 20 is taken from the circuit which electrically connects the steel strips 18 and the copper-containing plates 8, in the example shown via the first and second current connections 11 and 12. The controlled circuit may, for example, be a switch accommodated in the control unit 7. 22 which, depending on the potential difference measured by the reference cell 20, establishes or cancels a connection between the second current connection 12 and the third (grounding) current connection 14.

The reference cell 20 can further comprise a temperature sensor, so that measured temperatures can be transmitted to the control unit 7. 13 temperature sensors connected to the control unit 7 can also be provided at other places in the well 2, for example integrated in the copper-containing rods 8. Temperatures measured by such temperature sensors can, for example, be stored in an electronic memory for recording, so that it can subsequently be checked which temperatures have prevailed at locations in the tank 2. The measured temperatures can also be used by the control unit for controlling the set current intensities and / or the above-mentioned set value of the potential difference between the (sea) water and the bin cooler or the walls of the bin as a function of the temperatures. In this way, the temperature dependence of the risk of scale formation can then be taken into account. For example, it is known that the risk of lime formation increases significantly at temperatures above 60 degrees Celsius, while it is also known that the chance of maritime growth at these types of temperatures decreases significantly.

It is noted that the above-mentioned examples of embodiments do not limit the invention and that various alternatives are possible within the scope of the appended claims. The control unit can thus comprise various control components, of which individual control components or groups of control components in a common housing or in a plurality of housings, whether directly or indirectly or not, are communicatively connected to each other. Furthermore, many variations are possible in for instance the number of the different set current intensities, in the values of the different set current intensities and in the duration of the different time intervals in which the different current intensities are applied. Furthermore, it is possible to use boost periods more or less often during the copper-dissolving operating conditions. Such and similar alternatives are understood to fall within the scope of the invention as defined in the appended claims.

1032531

Claims (15)

Method for controlling biological fouling on a bin cooler (1) placed in a compartment (2), comprising a copper-opising step, wherein, for combating biological fouling as a result of (sea) water present in the compartment, a copper-containing 5 element (8) arranged in an electrically isolated manner with respect to ground parts (3, 4, 21) of the compartment in the compartment via a first current connection (11) is set to an anodic potential, whereby positive copper ions (17) are free coming from the copper-containing element (8) and wherein a metal-containing element (18) arranged in the compartment acts as a cathode, characterized in that the method further comprises a descaling step alternating the copper-dissolving step, during which descaling step the metal-containing element ( 18) which is arranged in an electrically isolated manner relative to grounding parts (3, 4, 21) of the compartment in the compartment via a second 1 The current connection (12) is set to an anodic potential, the metal-containing element (18) being descaled as a result of an anodic reaction occurring on the metal-containing element and the copper-containing element (8) acting as a cathode. Method according to claim 1, further comprising measuring a potential difference between the (sea) water and the bin cooler (1) or the earthing parts (3, 4, 21), taking electrical control off in a controlled manner in dependence on the measured potential difference current from a circuit circuit (11, 12) electrically connecting the copper-containing element (8) and the metal-containing element (18) to each other, as well as conducting the collected current to the grounding parts in a controlled manner. 1032531 3. Method as claimed in claim 1 or 2, wherein during the copper-dissolving step the copper-containing element (8) is set to an anodic potential such that during the copper-dissolving step periods with high current intensities (II) occurring by the copper-containing element and periods with through it alternating low current intensities (12) occurring in the copper-containing element. The method of claim 3, wherein said low current strengths (12) are between 20% and 40% of the high current strengths (II). 5. Method according to claim 3 or 4, wherein during the copper-dissolving step the copper-containing element (8) is set to an anodic potential such that the copper-dissolving step comprises a boost period with extra high current intensities (13) occurring by the copper-containing element relative to the high currents (II). Method according to claim 5, wherein said extra high current intensities (13) occurring during the boost period are between 130% and 200% of the high current intensities (II). A method according to any one of claims 3 to 6, wherein the descaling step connects to one of the periods with high current intensities (II) occurring by the copper-containing element (8). 25 A method according to claim 5 or 6, wherein the descaling step connects to the boost period. A method according to any one of claims 3 to 8, wherein one of the periods of high current (II) occurring by the copper-containing element (8) is connected to the descaling step. The method according to any of claims 5, 6 or 8, wherein the boost period follows the descaling step. A system for controlling biological fouling on a bin cooler (1) placed in a compartment (2), which system comprises a control unit 10 (7) which is adapted for the copper-dissolving operating state of the system via a first power connection ( 11) adjusting the system to an anodic potential of a copper-containing element (8) which is arranged in an electrically insulated manner with respect to ground parts (3, 4, 21) of the compartment in the compartment, in which copper-dissolving operating condition, for controlling of biological fouling as a result of (sea) water present in the compartment, positive copper ions being released from the copper-containing element (8) and a metal-containing element (18) arranged in the compartment functions as a cathode, characterized in that, during operation, the metal-containing metal element (18) is arranged in an electrically isolated manner relative to grounding parts (3, 4, 21) of the compartment in the compartment and that the r hedgehog unit (7) is furthermore arranged for switching between the copper-dissolving operating state and a descaling operating state of the system and for setting the metal-containing element to an anodic potential of the metal-containing element via a second current connection (12) of the system via a second current connection (12) of the system ( 18), in which descaling operating condition the metal-containing element is descaled as a result of an anodic reaction to the metal-containing element and the copper-containing element (8) acting as a cathode. System according to claim 11, further comprising a reference cell (20) communicatively connected to the control unit (7) for measuring a potential difference between the (sea) water and the bin cooler (1) or the grounding parts (3, 4, 21) , as well as a controlled circuit (22) for extracting electrical current from a circuit circuit (11, 12) electrically connecting the copper-containing element (8) and the metal-containing element (18) in dependence on a potential difference measured by the reference cell and for guiding the collected current to the grounding parts. 10 Assembly of a bin cooler (1) and a system according to claim 11 or 12. 14. Vessel provided with an assembly according to claim 13. 15 A method for installing a system according to claim 11 or 12, wherein the metal-containing element (18) is placed in the compartment in an electrically isolated manner with respect to the grounding parts (3, 4, 21) of the compartment (2) and the second current connection (12) is connected to the metal-containing element. 1032531