Cooling tower

Abstract

A cooling tower is disclosed comprising: a chamber defined by a peripheral wall and a top wall, wherein the top wall defines an outlet of the cooling tower; a gas inlet formed in the peripheral wall for introducing a gas into the chamber; one or more spray nozzles configured to spray a liquid to be cooled into the chamber; a fluid outlet for allowing cooled liquid to exit the chamber; and one or more demisters arranged within the chamber. The demisters are arranged such that fluid moving from within the chamber to the outlet passes through the one or more demisters substantially radially inwardly, towards a centerline of the cooling tower, before it reaches the outlet. A method of cooling a liquid in the cooling tower and a method of cleaning the cooling tower are also disclosed.

Description

[0001] HE Ref: 276880 p7 / tl0

[0002] COOLING TOWER

[0003] Technical Field

[0004] The present disclosure relates to a cooling tower, a method of cooling liquid using the cooling tower, and a method of cleaning the cooling tower.

[0005] Background

[0006] Cooling towers are widely used in industry for cooling fluids. Some cooling towers are essentially passive, in which airflow in the atmosphere around the tower acts to draw air in near a base of the tower which is then heated inside the tower. The warmed air rises up through the tower an out from the top. There are “wet” cooling towers, where the air comes into contact directly with a fluid to be cooled. There are “dry” cooling towers where the air passes over a heat exchanger through which the liquid to be cooled is flowing.

[0007] In the field of hydrometallurgy, electrolytes or acidic solutions containing slurries or metals need to be cooled. For example, it is known to separate zinc from an electrolytic solution containing zinc ions and sulfuric acid. In the separation process, the temperature of the electrolyte generally rises and this then needs to be cooled.

[0008] WO 2007 / 096457 A2 discloses a cooling tower wherein cooling air is passes via a fan into the tower near the base of the tower. The cooling air enters the tower generally horizontally and swirls around inside the tower. Nozzles are provided near an upper end of the tower and these spray a liquid to be cooled into the tower so that the droplets of liquid mix with the air and are cooled by evaporation.

[0009] Eight demisters are arranged near a top end of the cooling tower, arranged such that fluid passing through the demisters is moving horizontally out from the top of the tower. The demisters remove water droplets suspended in the air, along with any impurities contained in said droplets. The demisters therefore substantially purify the fluid passing therethrough, such that there are limited overall emissions of impurities (which may be toxic in some cases) from the cooling tower.

[0010] During use, impurities from the liquid can build up on the wall of the chamber and can build up in the demisters. This causes a need for relatively frequent cleaning and is often the main limiting factor in determining the maintenance cycle. That is, these are the parts of the cooling tower that need most-frequent maintenance, which may be once per month, for example. To perform this maintenance cleaning, the demisters must be sprayed with a pressure hose to wash off the buildup of impurities. The wall and floor of the chamber must also be sprayed with a pressure hose, which typically requires removal of the demisters in order to allow a maintenance worker to access the inside of the chamber.

[0011] Summary

[0012] According to a first aspect, there is provided a cooling tower comprising: a chamber defined by a peripheral wall and a top wall, wherein the top wall defines an outlet of HE Ref: 276880 p7 / tl0 the cooling tower; a gas inlet formed in the peripheral wall for introducing a gas into the chamber; one or more spray nozzles configured to spray a liquid to be cooled into the chamber; a fluid outlet for allowing cooled liquid to exit the chamber; and one or more demisters arranged within the chamber, such that fluid moving from within the chamber to the outlet passes through the one or more demisters substantially radially inwardly, towards a centerline of the cooling tower, before it reaches the outlet.

[0013] The liquid is cooled by the gas from the gas inlet. The liquid is cooled primarily by evaporation. The gas therefore mixes with the liquid to form a mixed fluid that then passes through the demisters. The demisters are for removing the cooled liquid from the mixed fluid, such that the gas exiting the cooling tower via the outlet is substantially free from liquid. The liquid may be toxic or otherwise environmentally-unfriendly.

[0014] A platform may be located within the chamber, wherein at least one of the one or more demisters is arranged such that a first end of the demister is connected to the platform and an opposed second end of the demister is connected to the top wall. The platform may therefore provide a convenient mounting location for the demisters. The platform may also provide a place for a maintenance worker to stand while maintaining the cooling tower.

[0015] The fluid outlet may be located in a base of the cooling tower. The base may be integrally formed the rest of the cooling tower. That is, the base may be connected to or integrally formed with the peripheral wall. Alternatively, the peripheral wall of the cooling tower may be installed upon a pre-existing base on-site. For example, the peripheral wall may be mounted onto a concrete platform.

[0016] Alternatively, the fluid outlet may be an overflow fluid outlet located in the peripheral wall of the tower. In this latter case, in use, a pool of cooled liquid will exist in the lower part of the tower and, as additional liquid is sprayed into the chamber and cooled, the overflow flows into the overflow fluid outlet.

[0017] The cooling tower may comprise a fan, a compressor, a blower, and / or a compressed gas source connected to the gas inlet for forcing gas, preferably air, into the chamber. This may increase the cooling capacity of the tower by increasing the airflow into the cooling tower, rather than relying e.g. on natural airflow and / or convection.

[0018] For at least one of the or each demister, the demister may be located radially inward from the peripheral wall such that a gap exists in the radial direction between a radially outer edge of the demister and the peripheral wall. In use, fluid in the chamber may have a larger velocity in the horizontal direction compared to the vertical direction. As such, fluid in the gap may pass in the horizontal direction through the demisters, which thereby make use of this larger horizontal component of the fluid’s velocity. Optionally, several or even all of the one or more demisters may be located in this manner.

[0019] The arrangement of the demisters may make use of the larger horizontal velocity component of the fluid in the chamber, and ensures more / faster fluid flow through the demisters, increasing the capacity of the cooling tower.

[0020] For each demister of the or each demister, the demister may comprise a plurality of spaced-apart corrugated sheets of material. HE Ref: 276880 p7 / tl0

[0021] The corrugated sheets of material force fluid moving through the demister, between the sheets, to take a curved or serpentine path. The changes of direction in this path cause the fluid velocity to drop and this allows droplets of liquid that are entrained in the fluid flow to drop out of the fluid flow and either drop out of the demister directly or to adhere to the sheets and then flow out of the demister. In this manner, the demister removed liquid from the fluid flowing through the demister. This liquid may be returned to the chamber.

[0022] At least one of the or each demister may define a predetermined flow direction for fluid to flow through the demister. One or more of the corrugated sheets may further comprise one or more hook portions, wherein each hook portion extends in a direction opposite to the predetermined flow direction, such that a dead end is formed in the flow direction where the hook portion joins to the sheet.

[0023] The hook portion(s) may increase the demisting action of the demister by forcing a portion of the fluid flowing through the demister to come to a complete stop at or near the dead end.

[0024] At least one of the or each demister may be arranged parallel to a centerline of the cooling tower that extends from the base to the top wall. When the cooling tower is installed such that the top wall is vertically above the peripheral wall, the centerline will be a vertical centerline of the cooling tower.

[0025] This may allow fluid flowing through the demister to flow entirely or substantially- entirely in the horizontal direction. This orientation may therefore make use of the higher flow velocity of fluid in the chamber in the horizontal direction.

[0026] Alternatively, for at least one of the one or more demisters, the demister may be arranged at an angle to a centerline of the cooling tower that extends from the base to the top wall, such that a base end of the demister that is closer to the base of the cooling tower is closer to said centerline than an opposed top end of the demister that is closer to the top wall. Optionally, several or even all of the one or more demisters may be arranged in this manner.

[0027] The angle may be greater than zero degrees and less than20 degrees, preferably less than 15 degrees. That is, the at least one of the or each demister may lean outward compared to the centerline of the tower. This arrangement may make for easier insertion and removal of the demister(s) from the tower, e.g. during maintenance. For example, where demisters are removed by a crane extending in through the outlet, it may be easier to remove the demister(s) if it is angled upwards to some extent. The demister(s) may also thereby be held in place relative to the platform via gravity.

[0028] The outlet in the top wall may be vertically oriented such that gas exiting the tower exits in the vertical direction. This may provide a simple means for allowing gas the exit the cooling tower, for example, by providing the outlet as a hole in the top wall. Having gas leave the cooling tower in the vertical direction may avoid a circulation pattern in which warmed air exiting the cooling tower flows downwards towards the inlet. Such circulation can undesirably reduce the cooling efficiency of the tower by increasing the temperature of the medium (i.e. gas) that is used to cool the liquid in the tower. HE Ref: 276880 p7 / tl0

[0029] The platform may be connected to the top wall by one or more struts and / or beams. The one or more struts and / or beams may be configured to receive the or each demister in order to mount the or each demister in the cooling tower.

[0030] That is, the struts and / or beams may together provide one or more frames to receive the one or more demisters in.

[0031] Alternatively or additionally, the platform may be connected to the peripheral wall by one or more struts and / or beams. A strut is a component that is configured to resist longitudinal compression and may, in some cases, resist longitudinal extension (tension). A beam is a component that is configured to primarily resist loads laterally across the beam’s axis. In some cases, the same item may function as either a beam or a strut, depending on its use case.

[0032] The cooling tower may be configured for use in hydrometallurgy. For example, the components may be made of suitable materials to avoid corrosion and / or heat damage caused by the liquid that is to be cooled in the cooling tower. The choice of suitable materials will depend on the specific use case for a given tower, e.g. whether the liquid to be cooled is highly basic, or is highly acidic, or is especially hot when entering the tower.

[0033] According to a second aspect, there is provided a method of cooling a liquid in the cooling tower according to the first aspect. The method comprises: passing gas, optionally air, through the gas inlet into the chamber, spraying liquid to be cooled from the one or more spray nozzles into the chamber, such that gas from the gas inlet cools the liquid and mixes with the liquid to form a mixed fluid, and passing the mixed fluid through the one or more demisters to reduce or eliminate liquid from the mixed fluid.

[0034] The gas cools the liquid and then liquid entrained in the gas is removed by the demisters. The removed liquid may be recirculated back into the chamber for further cooling. Removal of the liquid by the demisters may be especially important in cases where the liquid is toxic or otherwise environmentally unfriendly.

[0035] According to a third aspect, there is provided a method of cleaning the cooling tower according to the first aspect. The method comprises: spraying the one or more demisters with a high-pressure stream of liquid; and / or removing one or more of the one or more demisters to allow access to the chamber and spraying a wall of the chamber with a high-pressure stream of liquid. Optionally the liquid is water. Optionally the stream of liquid includes a cleaning agent. The wall that is cleaned in this manner may be the peripheral wall, the top wall, or both the peripheral wall and the top wall.

[0036] The platform may provide a convenient place for a maintenance worker to stand relative to the demister(s). That is, the worker can stand directly in front of the demister and, for example, spray it with a pressure hose from there. Similarly, when a demister is removed from its position between the platform and the top wall, the worker on the platform can then see directly into the chamber and, from the platform, can spray the chamber to clean out residue therein.

[0037] Brief Description of the Drawings HE Ref: 276880 p7 / tl0

[0038] Figure 1 shows a perspective view of a known cooling tower;

[0039] Figure 2 shows a cutaway perspective view of the known cooling tower of Figure 1 ;

[0040] Figure 3 shows a cross-sectional schematic view of a cooling tower;

[0041] Figure 4 shows a cutaway perspective view of a cooling tower;

[0042] Figure 5 shows a cutaway perspective view of a demister;

[0043] Figure 6 shows a top section of a cooling tower.

[0044] Detailed Description

[0045] Figures 1 and 2 show a known design of cooling tower 10. The cooling tower 10 comprises a wall 12 that defines a chamber 13. The wall 12 typically defines a generally cylindrical chamber 13. A gas inlet 14 is provided near a base of the cooling tower 10 and a fan 15 is used to draw gas, typically air from the atmosphere surrounding the cooling tower 10, into the chamber 13. An upper part 16 of the cooling tower 10 has a plurality of demisters 18a,b that are arranged such that fluid exits the cooling tower 10 in a generally horizontal direction, radially outward from a centerline Y of the coling tower 10, after having passed through the demisters 18a,b which are arranged circumferentially around the cooling tower 10. A pipe 20 is provided to convey liquid to be cooled to the upper part 16 of the cooling tower and thence to a plurality of spray nozzles 24 located inside the chamber 13. The nozzles 24 are located at a vertical level below the demisters 18 and are oriented generally downwards at an angle, such that liquid is broadly sprayed towards a middle of the chamber 13.

[0046] In use, a liquid to be cooled is pumped through the liquid pipe 20 to the spray nozzles 24. The liquid sprays out into the chamber 13, moving generally downwards, and mixes with a gas flow (which may be air from the atmosphere) that is rising up from the gas inlet 14. This generates turbulent flow as the liquid and gas mix together and the gas cools the liquid. Some of the liquid evaporates into the gas flow and some is suspended as droplets in the gas flow, creating a mixed fluid. The mixed fluid flows through the demisters 18a, b, moving in a generally horizontal direction that is generally radially outward from the vertical centerline Y of the cooling tower 10.

[0047] Demisters 18a,b typically comprise a plurality of spaced-apart corrugated sheets, where the corrugations on adjacent sheets are aligned with one another. This forces a fluid passing through the demister to take a serpentine path which substantially drops the velocity of the fluid. This drop in velocity causes the suspended droplets to separate from the fluid flow and to form on the sheets. The droplets may then flow out of the demister.

[0048] Figure 3 depicts a new design of cooling tower 100. The cooling tower 100 comprises a peripheral wall 112 that defines a chamber 113 of the cooling tower. The peripheral wall 112 may define a cylindrical chamber 113, but other shapes are envisaged such as chambers having a square, rectangular, hexagonal, or oval cross-sectional shape. A top wall 122 of the chamber 113 defines a top of the chamber 113. The top wall 122 has an outlet 123 therein for allowing fluid to flow out of the chamber 113. The outlet HE Ref: 276880 p7 / tl0

[0049] 123 may be any shape, including, for example, circular, hexagonal, or square. A base 125 of the chamber 113 defines a bottom of the chamber 113. The base 125 of the chamber 125 comprises a liquid outlet 126 for allowing liquid to flow out of the chamber 113. The base 125 may be part of the cooling tower 100, Alternatively, the cooling tower peripheral wall 112 and top wall 122 may be built upon an already-existing space (e.g. a concrete platform) on-site such that the pre-existing space thereby closes the bottom side of the cooling tower and consequently acts as the base of the cooling tower 100 once constructed. When assembled, the cooling tower 100 is arranged vertically such that a centerline X of the cooling tower that extends from the base 125 to the top wall 122 is vertical, i.e. , with respect to gravity.

[0050] The peripheral wall 112 may be made from any suitable material. The top wall 122 may be made of any suitable material. Some suitable materials include fiberglass, aluminium, (stainless) steel, and combinations thereof. The base 125 may be a separate material and may, for example, be concrete that the peripheral wall 112 of the cooling tower 100 is installed upon. Alternatively, the base 125 may be made of the same material as the peripheral wall 112.

[0051] A gas inlet 114 is provided through the peripheral wall 112, near the base 125 of the cooling tower 100 and a fan 115 is provided for drawing gas, typically air, into the chamber 1 13. The air is used to cool a liquid to be cooled, as described below. While only one gas inlet 114 is shown, more than one gas inlet may be provided near the base of the cooling tower 100.

[0052] A platform 119 is provided inside the chamber 113 towards an upper end of the chamber 113. That is, the platform 119 is at a vertical position within the chamber 113 that is between the base 125 and the top wall 122, and is typically located closer to the top wall 122 than to the base 125. Put another way, the platform is located in the upper half of the cooling tower 100.

[0053] The platform 119 is spaced apart from the peripheral wall 112, but may be connected thereto, e.g., via struts and / or beams. Alternatively or additionally, the platform 119 may be connected to the top wall 122, e.g. via struts and / or beams. One or more demisters 118 are provided around the platform 119, generally extending between the platform 119 and the top wall 122. In one example, eight demisters 118 are provided circumferentially around the platform 119. In other examples, anywhere from two to ten demisters 118 are provided. These exemplary demisters 118 extend substantially the whole distance between the platform 119 to the top wall 122. If present, the struts that connect the platform 118 to the top wall 122 may also provide mounting points for the demisters 118. That is, the struts / beams may generally define a frame for each demister to be mounted in. The platform 119 is solid such that fluid cannot pass through the platform 119 itself.

[0054] The one or more demisters 118 are located radially inward from the peripheral wall 112 of the cooling tower 100. The one or more demisters 118 are arranged such that fluid exiting the outlet 123 must first pass through the one or more demisters 118. That is, each demister is arranged within the chamber such that fluid moving from within the chamber 113 to the outlet 123 passes through the demister substantially radially inwardly, towards the centerline X of the cooling tower, before it reaches the outlet 123. HE Ref: 276880 p7 / tl0

[0055] One or more spray nozzles 124 are provided inside the chamber 113. These are typically arranged at or below a level of the platform 119, but may be located higher provided their spray does not directly impinge upon the one or more demisters 118. The spray nozzles 124 are configured to spray a liquid to be cooled into the chamber 113. The liquid to be cooled is not particularly limited and may be any liquid, including, for example, water, acids, acidic solutions, electrolyte, or neutral solution. The liquid may be provided at any temperature. Typically, the cooling tower 100 may be for cooling a liquid having a temperature of between 25°C and 95°C. The temperature of cooled liquid exiting via the liquid outlet 123 may be between 15°C and 75°C. The temperature of gas entering the gas inlet 114 may ambient atmospheric temperature and so may typically be between -35°C and 45°C. The temperature of gas exiting the outlet 123 may be between 0°C and 65°C.

[0056] In use, a flow of gas A1 is drawn into the chamber 113 via the inlet 114 near the base 125 of the chamber 113. This flow of gas is typically air taken from the atmosphere surrounding the cooling tower 100, but in principle may be any gas including gas, for example, from a compressed source such as a compressed-gas tank or compressor.

[0057] The flow of gas A1 is generally horizontal when it enters the chamber 113. The gas inlet 114 may be arranged such that a horizontally extending centerline of the gas inlet does not intersect the vertical centerline X of the tower. That is, the inlet may not point directly towards a centerline of the cooling tower 100. In this manner, the gas inlet 114 may inject gas into the chamber 113 such that the gas is moving circumferentially within the chamber 113. A flow of liquid to be cooled B1 is sprayed into the chamber 113 from the nozzles 124. The downward-falling flow of liquid to be cooled B1 mixes with the flow of gas A1 to form a turbulent flow of mixed fluid A2 inside the chamber 113. Where the mixed fluid flow becomes turbulent, its velocity in the horizontal direction (i.e. , in a plane perpendicular to the centerline X) increases.

[0058] In the turbulent flow A2, the liquid to be cooled is cooled by the gas, primarily by evaporation but also by conduction and convection. The intense airflow and turbulence helps break up water droplets emitted from the nozzles 124 into yet-smaller droplets, which further enhances the cooling efficiency of the tower. The cooled liquid eventually drops of the base 125 of the cooling tower 100 and the flow of cooled liquid B2 exits the cooling tower 100 via the liquid outlet 126. In Figure 3, the liquid outlet 126 is shown as a vertically-oriented outlet formed in the base 125 of the chamber 113. In alternative designs, the liquid outlet 126 may be generally horizontally oriented and formed in the peripheral wall 112 of the cooling tower 100, at a location near the base 125 of the cooling tower 100, i.e. arranged as an overflow outlet.

[0059] The liquid exiting the outlet 126 may be recycled through the cooling tower 100 again, if desired. That is, this portion of liquid may be run through the tower again by being directly sent to one of the nozzles 124, or the liquid may be mixed with the (hotter) flow of liquid to be cooled that is being delivered generally to the nozzles 124.

[0060] The turbulent flow A2 rises up towards the one or more demisters 118. As stated, the turbulence of the flow leads to increase the velocity in the horizontal direction. The fluid, which is a mixture of the gas (e.g., air), evaporated liquid, and liquid droplets forms a fluid flow A3 that passes through the demisters in a generally horizontal HE Ref: 276880 p7 / tl0 direction, radially inwards towards the centerline X of the cooling tower 100. Thus, the particular orientation of the demisters 118 allows them to make use of the high horizontal velocity of the turbulent flow as it moves to exit the cooling tower 100.

[0061] Where there are multiple demisters 118, any given portion of fluid will typically only pass through one of the demisters 118 before exiting the cooling tower 100, but the demisters 118 are arranged such that all or substantially all of the fluid exiting the chamber 113 must pass through at least one of the demisters 118.

[0062] Demisters 118 comprise a plurality of spaced-apart corrugated sheets, where the corrugations on adjacent sheets are aligned with one another. This shape forces the fluid passing through the demister to take a serpentine path which substantially drops the velocity of the fluid. This drop in velocity causes the suspended droplets to separate from the fluid flow and to form on the sheets. The droplets may then flow out of the demister 118.

[0063] Each of the demisters 118 is arranged such that fluid flowing through the demister is flowing generally horizontally. When droplets drop out of the airflow in a demister that is oriented in this way, the droplets drop under the action of gravity generally perpendicular to the flow direction. This helps avoid the droplets from slowing the flow of further fluid entering the demister. By contrast, in vertically-oriented demisters, where the fluid is flowing generally vertically upwards through the demister, droplets that drop out of the airflow are falling down under the action of gravity in the opposite direction to the airflow. This can undesirably reduce the fluid velocity of fluid coming in behind said droplets and also increases the chance of droplets becoming re-entrained in the airflow. Horizontally-oriented demisters may have double the efficiency compared to an equivalent vertically-oriented demister. That is, it may demist twice as much mixed fluid per unit time compared to a vertically-oriented demister.

[0064] After having passed through the one or more demisters 118, the fluid flow A4 changes direction and moves vertically upward and exits the cooling tower 100 via the outlet 123. At this stage, having passed through the one or more demisters 118, the fluid is almost-entirely or entirely gas that has been warmed via contact with the liquid to be cooled. The gas exits to the atmosphere.

[0065] In the known cooling tower 10 shown in Figures 1 and 2, the demisters 18 are located radially outward compared to the wall 12 of the cooling tower 10. This means that the effective-footprint of the cooling tower 10 is larger than the footprint measured at the ground, around the circumference of the wall 12. Further, fluid exits the cooling tower 10 in a generally horizontal direction. In the cooling tower 100 of Figures 3 and 4, fluid exits the cooling tower 100 in a generally vertical direction, but nonetheless passes the demisters 118 generally in the horizontal direction, thus retaining the aforementioned higher-efficiency of horizontal demisters compared to vertical demisters.

[0066] By contrast, the cooling tower 100 depicted in Figures 3 and 4 may have an effective footprint that is defined entirely by the wall 12 (plus a small amount to accommodate the gas inlet 114). As such, multiple cooling towers 100 may be placed closer together than in the known cooling towers 10. HE Ref: 276880 p7 / tl0

[0067] As one example, four cooling towers 10 according to the design of Figures 1 and 2 arranged in a square, each having a 6m diameter cylindrical chamber 13, require 22m x 22m ground space at the installation site, in order to accommodate the larger upper parts 16 of the two cooling towers 10 and to provide sufficient spacing therebetween. By contrast, four cooling towers 100 according to the new design arranged in a square, each having 6m diameter chamber, may require only 12m x 12m ground space at the installation site. Thus, the new design may offer significant space savings for a given cooling capacity, both for individual cooling towers and for multi-tower installations.

[0068] The smaller overall size of the cooling tower 100 according to the new design (due to the lack of the aforesaid large upper part 16) may also offer reduced material costs and simpler construction for equivalent cooling capacity.

[0069] It has further been found that the generally-horizontal outflow of warm gas from the cooling tower 10 can lead to a circulation of air outside the cooling tower 10 such that the air drawn in at the inlet 14 is warmer than it would otherwise be. This reduces the efficiency of the cooling provided by the tower 10.

[0070] As the fluid flow A4 from the cooling tower 100 depicted in Figures 3 and 4 is ejected in the vertical direction, there may be significantly less of the aforesaid undesirable circulation of air outside the tower, and consequently significantly less warming of the gas (air) entering the inlet 114 in this new design of cooling tower 100.

[0071] Figure 5 shows a perspective view of a demister 118 that may be used in the cooling tower 100. The demister 18 comprises a plurality of spaced-apart sheets 40,42, typically arranged in a frame that holds the sheets in the proper spaced-apart relation to one another. Two sheets 40,42 are shown in Figure 5, but typically a single demister will comprise ten to fifty (10-50) such sheets. Each demister 118 is formed of a plurality of sheets and has a generally rectangular form overall that may be defined by the frame. The sheets 40,42 each have a corrugated profile and are arranged generally parallel to one another such that the sheets 40,42 define a plurality of serpentine flow paths through the demister 118. Slits are defined between each pair of adjacent sheets. In the example of Figure 5, the slits extend vertically when the demister 18 is installed in the cooling tower 100. In another example, not shown, the sheets may be arranged such that the slits extend horizontally when the demister 18 is installed in the cooling tower 100. In both cases, the airflow through the demister is primarily in the horizontal plane. In the latter case, there will be a small amount of deflection of fluid in the vertical plane due to the corrugation of the sheets. However, the overall direction of fluid flow from one side of the demister to the other side is horizontal.

[0072] The demisters 118 may preferably be arranged such that the slits extend in the vertical direction when the demister is installed, so that drops may freely fall to the bottom of the demister under the action of gravity. The fluid flow A3 is depicted by an arrow in Figure 5.

[0073] The fluid entering the demister 118 contains gas, evaporated liquid, and suspended liquid droplets coming from the chamber 113. As the fluid flows between the corrugated sheets 40,42, the fluid is forced to change direction and loses velocity in doing so. This causes the droplets to hit the sheets 40,42 and stick to them via surface tension. This also causes suspended droplets to fall out of the airflow, towards a base of the dem ister HE Ref: 276880 p7 / tl0

[0074] 118. The droplets then drop and / or flow down the sheets 40,42 and, depending on the arrangement of the demister 118, may either be collected and recirculated back into the chamber 113 or may drop directly back into the chamber 118, i.e. droplets falling off the bottom of each sheet 40,42.

[0075] Each demister sheet 40,42 may have one or more hook portions 40a, 40b, 42a, 42b facing into the fluid flow A3. Each hook portion may be a section of wall that faces into the direction of the fluid flow A3, such that fluid flowing into a hook portion reaches a dead end. Droplets of liquid may preferentially collect in the hook portions 40a, 40b, 42a, 42b.

[0076] The demisters 118 shown in Figures 3 and 4 are arranged vertically in the cooling tower such that the top of a given demister 118, where it connects to the top wall 122 is directly vertically above the base of that demister 118, where it connects to the platform 119.

[0077] Figure 6 shows an alternative design of the cooling tower 100 in which the demisters 118 are arranged at an angle to the vertical direction. In this design, the demisters 118 cumulatively define a frustoconical shape, where the narrower end of the frustocone is closer to the base 125 and the wider end of the frustocone is closer to (or directly adjacent to) the top wall 122. Put another way, each demister 118 may be said to be “leaning out” from the platform 119. The fluid flow A3 may still flow through these demisters substantially in the horizontal plane. Thus, this design also makes use of the higher horizontal velocity of the fluid flow in the chamber 113.

[0078] To perform maintenance on the cooling tower 100, a worker may climb from the top wall 122 down to the platform 119, at which point the worker is generally surrounded by the demisters 118. From this position, the worker may spray the demisters 118 with a pressure hose to clean them. From this position, the worker may remove one or several of the demisters 118 (optionally with the assistance of a crane) in order to see into the chamber 113. The worker may then spray the wall of the chamber 113 with the pressure hose to clean the wall. It is substantially easier and safer for a worker to access the demisters 118 in this way, from the platform 119, compared to the accessing the demisters of WO 2007 / 096457 A2, where the demisters are accessed from above, i.e. from the platform above the demisters.

[0079] A curtain, not shown, may be provided on the radially inner face of the peripheral wall 112 or hanging radially inward from the wall such that the liquid does not come into contact the wall directly, but instead contacts the curtain. The curtain may be a replaceable item. The curtain may be non-load-bearing. The curtain may be made of a material that is more resistant to corrosion by the liquid compared to a material of the wall. Suitable materials for the curtain may be selected depending on the planned use of the cooling tower 100, i.e. what liquid is to be cooled by the cooling tower.

Claims

HE Ref: 276880 p7 / tl0CLAIMS1. A cooling tower comprising: a chamber defined by a peripheral wall and a top wall, wherein the top wall defines an outlet of the cooling tower; a gas inlet formed in the peripheral wall for introducing a gas into the chamber; one or more spray nozzles configured to spray a liquid to be cooled into the chamber; a fluid outlet for allowing cooled liquid to exit the chamber; and one or more demisters arranged within the chamber, such that fluid moving from within the chamber to the outlet passes through the one or more demisters substantially radially inwardly, towards a centerline of the cooling tower, before it reaches the outlet.

2. The cooling tower according to claim 1 , comprising a platform located within the chamber, wherein at least one of the one or more demisters is arranged such that a first end of the demister is connected to the platform and an opposed second end of the demister is connected to the top wall.

3. The cooling tower according to claim 2, wherein the platform is connected to the top wall by one or more struts and / or beams, optionally wherein at least some of the one or more struts and / or beams are configured to receive the or each demister in order to mount the or each demister in the cooling tower.

4. The cooling tower according to claim 2 or 3, wherein the platform is connected to the peripheral wall by one or more struts and / or beams.

5. The cooling tower according to any preceding claim, wherein the fluid outlet is located in a base of the cooling tower; or wherein the fluid outlet is an overflow fluid outlet located in the peripheral wall of the tower.

6. The cooling tower according to any preceding claim, comprising a fan, a compressor, a blower, and / or a compressed gas source connected to the gas inlet for forcing gas, preferably air, into the chamber.

7. The cooling tower according to any preceding claim wherein, for at least one of the or each demister, the demister is located radially inward from the peripheral wall such that a gap exists in the radial direction between a radially outer edge of the demister and the peripheral wall.

8. The cooling tower according to any preceding claim, wherein for at least one of the or each demister, the demister comprises a plurality of spaced-apart corrugated sheets of material.HE Ref: 276880 p7 / tl09. The cooling tower according to claim 8, wherein the or each demister defines a predetermined flow direction for fluid to flow through the demister, and wherein one or more of the corrugated sheets further comprises one or more hook portions that extend in a direction opposite to the predetermined flow direction, such that a dead end is formed in the flow direction where each hook portion joins to the sheet.

10. The cooling tower according to any preceding claim, wherein at least one of the or each demister is arranged parallel to a centerline of the cooling tower that extends from the base to the top wall.11 . The cooling tower according to any of claims 1-9, wherein for at least one of the one or more demisters, the demister is arranged at an angle to a centerline of the cooling tower that extends from the base to the top wall, such that a base end of the demister that is closer to the base of the cooling tower is closer to said centerline than an opposed top end of the demister that is closer to the top wall, optionally wherein the angle is greater than 0 degrees and less than 20 degrees, preferably less than 15 degrees.

12. The cooling tower according to any preceding claim, wherein the outlet in the top wall is oriented such that gas exiting the tower exits in a direction parallel to a centerline of the cooling tower.

13. The cooling tower according to any preceding claim, wherein the cooling tower is for use in hydrometallurgy.

14. A method of cooling a liquid in the cooling tower according to any one of claims 1-13, the method comprising: passing gas, optionally air, through the gas inlet into the chamber, spraying liquid to be cooled from the one or more spray nozzles into the chamber, such that gas from the gas inlet cools the liquid and mixes with the liquid to form a mixed fluid, and passing the mixed fluid through the one or more demisters to reduce or eliminate liquid from the mixed fluid.

15. A method of cleaning the cooling tower according to any one of claims 1 -13, the method comprising: spraying the one or more demisters with a stream of liquid; and / or removing one or more of the one or more demisters to allow access to the chamber and spraying a wall of the chamber with a stream of liquid, optionally the stream of liquid includes a cleaning agent, and / or the liquid is sprayed at high pressure, and / or the liquid is water.

Images