FR3041087A1 - COOLING TOWER WITHOUT VESICULAR DRIVE - Google Patents

Abstract

The cooling tower comprises a heat exchange body 14, a distribution system 16 of a liquid on the heat exchange body, a means 26 for generating a gas flow in the direction of the heat exchange body, and a drop separator 18 disposed downstream of the heat exchange body 14 and capable of separating distributed liquid droplets which are entrained by the flow of gas. The tower further comprises an absorption filtering means disposed downstream of the gas-permeable droplet separator and adapted to absorb droplets of distributed liquid entrained by the gas flow.

Description

Cooling tower without vesicular drive

The present invention relates to the field of cooling towers of a liquid which are also known as "cooling towers".

A cooling tower can efficiently and economically evacuate to an external environment heat generated by industrial processes or air conditioning systems.

It is known cooling towers called "open circuit" in which the liquid to be cooled is sprayed by a distribution means directly on a heat exchange surface formed by an exchange body mounted inside an envelope of the tower. A flow of air, which is pulsed by a motor-fan unit attached to the casing, passes through the exchange body to evaporate a portion of the liquid to cool and remove the calories of the liquid. This air flow is then released into the atmosphere. The walls of the envelope thus define an inner chamber defining the air circuit and in which the evaporative runoff is carried out. The cooled liquid is collected in a pond before being returned to the industrial process or the air conditioning system to be cooled.

It is also known cooling towers called "closed circuit" comprising a heat exchanger through which a primary circuit in which circulates the liquid to be cooled and a secondary circuit in which circulates a heat transfer liquid. In this type of design, the liquid that is cooled inside the tower is the coolant. The cooling principle of this heat transfer liquid inside the tower is identical to that of an open circuit cooling tower.

It is still known other types of cooling towers called "hybrid" may be open or closed circuit and in which the liquid to be cooled or the coolant passes through an anti-plume battery before being sprayed at the body of the body. heat exchange. Before being released into the atmosphere, the air flow pulsed by the fan unit passes through the anti-trap battery so as to heat it and substantially reduce the condensation of water vapor at the exit of the tower.

Whatever the type of tower, the principle of evaporative cooling results in the creation of a vesicular drive. The term "vesicle entrainment" is understood to mean the droplets or particles of the liquid to be cooled which are entrained in the atmosphere by the flow of air circulating inside the tower. This vesicular drive is less than 0.01% of the flow of liquid to cool circulating in the tower.

However, unlike evaporated water, these droplets entrained to the ambient environment have the same composition as the liquid to be cooled and are therefore likely to carry bacteria such as Legionella.

The present invention aims to remedy this disadvantage.

More particularly, the present invention aims to provide a cooling tower for operation without vesicular drive.

In one embodiment, the cooling tower comprises a heat exchange body, a system for dispensing a liquid to be cooled on the heat exchange body, a means for generating a flow of gas towards the body. heat exchange, and a drop separator disposed downstream of the heat exchange body and adapted to separate droplets of distributed liquid which are entrained by the gas flow.

The tower further comprises an absorption filtering means which is disposed downstream of the droplet separator, and which is permeable to gases and adapted to absorb droplets of distributed liquid entrained by the gas flow.

Thus, the cooling tower comprises two separate retaining means, namely the droplet separator and the absorption means, capable of acting one after the other to prevent the emission of droplets of liquid to be cooled towards the bottom. ambient.

In a conventional cooling tower, the droplet separator is the last obstacle to the emission of droplets of liquid sprayed to the environment. The implantation of the absorption filtering means downstream of the droplet separator, considering the flow direction of the flow of gas inside the tower, makes it possible to mechanically retain the residual liquid droplets which are entrained by the flow of water. gas at the outlet of the droplet separator. The operation of the tower is achieved without a vesicle drive. The residual liquid droplets are absorbed by the filtering means. These droplets do not flow along the filtering means.

Advantageously, the absorption filtering means covers the whole of an outlet opening of the gas flow of said tower.

Preferably, the absorption filtering means is located away from the droplet separator.

In one embodiment, the filtering means is made of at least one material absorbing droplets of liquid dispensed. The filtering means may comprise cellulose fibers. The filtering means may consist of a plurality of corrugated sheets and made of cellulose fibers.

The tower may comprise an envelope inside which are completely mounted the heat exchange body, the droplet separator and the filtering means.

In one embodiment, the means for generating the gas flow comprises at least one motor-fan unit. Alternatively, for example when the cooling tower is large, it may be possible to obtain the generation of a flow of air thanks to the shape of the envelope of the tower which is in this case designed to exploit the density difference between the incoming air and the warmer air already present inside. Under these conditions, the means for generating the air flow is formed by the tower's own shape. This is called a natural draft trick.

In one embodiment, the liquid distribution system is disposed upstream of the droplet separator. The invention also relates to a method of cooling a liquid inside a cooling tower comprising a step of spraying the liquid to be cooled on a heat exchange body of the tower which is traversed by a gas flow. and a step of separating droplets from the pulverized liquid which are entrained by the gas flow. The method further comprises, after the separation step, a step of filtering residual liquid droplets entrained by said gas flow so as to reject said flow in the atmosphere without vesicular entrainment. The filtering step is carried out by absorption of the residual liquid droplets.

The present invention will be better understood from the study of the detailed description of an embodiment taken by way of non-limiting example and illustrated by the accompanying drawing schematically showing a cooling tower according to an exemplary embodiment.

In the single figure, there is illustrated the general architecture of a cooling tower, referenced as a whole, and shown in a supposed vertical position. The cooling tower 10 may be a so-called "open circuit" or "closed circuit" tower.

The tower 10 comprises a casing 12 with vertical side walls and defining an internal enclosure, a heat exchange body 14, a distribution system 16 of a liquid F to be cooled and a separator 18 of drops. The exchange body 14, the distribution system 16 and the drop separator 18 are housed inside the internal enclosure delimited by the envelope 12.

As will be described in more detail below, the tower 10 further comprises an absorption filtering means 20 enabling operation without vesicular drive.

The distribution system 16 of the liquid F to be cooled comprises a plurality of supply pipes 22 (only one being visible in the figure) and a plurality of nozzles or dispersers 24 mounted on each of these pipes. The dispensing system 16 is disposed inside the casing 12 between the exchange body 14 and the drop separator 18 so as to spray the liquid to be cooled on said exchange body 14.

The heat exchange body 14 is fixed on the walls of the envelope 12. The exchange body 14 forms wet exchange surfaces for cooling the liquid which is sprayed by the distribution system 16. The body of exchange 14 may for example be of "film" type on which the sprayed liquid flows in forming a film. In this case, the exchange body 14 may comprise a stack of walls, for example in the form of elements made of thermoformed synthetic material known as "packings". Alternatively, the exchange body 14 may be of the "drops" type on which the sprayed liquid explodes in successive droplets on superimposed slats.

The tower 10 also comprises a fan unit 26 fixed outside the casing 12 and for generating inside it an upward flow of air, shown schematically by the arrows referenced 28, 30 and 32. The air flow successively passes through the heat exchange body 14, the drop separator 18 and the filtering means 20 by absorption. Considering the direction of flow of the air flow, the exchange body 14 is mounted upstream of the separator 18 of drops which is itself mounted upstream of the filtering means 20 by absorption. The flow of air from the fan unit 26 allows cooling and partial evaporation of the sprayed liquid on the exchange body 14.

In the exemplary embodiment illustrated, the fan unit 26 is mounted on the casing 12 in the lower part of the tower. Alternatively, it is possible to provide mounting of the fan or groups at the top of the tower, for example at the upper end of the casing 12 and outside the enclosure defined by this envelope.

The tower 10 further comprises a basin 34 in which the liquid projected onto the exchange body 14 is recovered by gravity. The basin 34 is situated at the lower end of the envelope 12. A pipe (not referenced) extends from the basin 34 and is equipped with a pump to allow the circulation of the collected liquid out of the tower.

The drop separator 18 is fixed on the walls of the casing 12 by being disposed vertically above the exchange body 14 and the distribution system 16. The separator 18 makes it possible to limit the entrainment of sprayed liquid droplets. of the tower 10 by the air flow that is generated by the motor-fan unit 26. The separator 18 forms an obstacle allowing the separation of the drops of sprayed liquid that are conveyed by the air flow. The separator 18 comprises a set of baffles which, by changing the direction of the air flow, makes it possible to separate the droplets of sprayed liquid from this stream. The separator 18 comprises for example a plurality of blades or stacked sheets, made for example of synthetic material, to form this set of baffles.

As indicated above, the absorption filtering means 20 makes it possible to obtain operation of the tower 10 without vesicular drive. The filtering means 20 is mounted downstream of the separator 18 of drops by considering the direction of flow of the air flow inside the tower 10. In the illustrated embodiment, the filtering means 20 is located vertically. above and away from the separator 18 of drops so as to obtain a better filtering efficiency. Indeed, the vertical spacing of the filtering means 20 with respect to the drop separator 18 makes it possible to avoid a direct transfer of the drops of liquid from the separator to the filtering means. As an indication, the vertical distance separating the filtering means 20 and the separator 18 may for example be between one and fifteen cm.

The filtering means 20 is gas permeable and capable of absorbing residual liquid droplets entrained by the airflow that have not been separated from this upstream stream by the drop separator 18. Indeed, before the exit of the air flow from the tower 10, the flow still loaded by the residual droplets is passed through the filter means 20 which is adapted to retain these droplets. A mechanical filtering is thus carried out so as to trap the droplets of the liquid conveyed by the air stream and which have not been eliminated beforehand by the separator 18. Generally, the diameter of these droplets or drops is between a few hundred of micrometers and a millimeter.

The filtering means 20 is mounted inside the casing 12 so as to cover the entire opening of the tower provided for the outlet of the air flow. The filtering means 20 is fixed on the walls of the envelope 12. The filtering means 20 is in the form of one or more panels juxtaposed so as to obtain a continuity of filtration between the separator 18 and the opening The filtering means 20 extends transversely with respect to the walls of the casing 12. The filtering means 20 is made of at least one material capable of absorbing the droplets of liquid dispensed, for example from cellulose fibers. The filtering means 20 may consist of a plurality of corrugated sheets and made of cellulose fibers. The use of an absorption means made of cellulose makes it possible to obtain good filtration efficiency and high longevity. As an indication, it is possible to use panels marketed under the "Star Cool" dominance of Gigola & Riccardi. As an indication also, the thickness of the filtering means 20 may for example be between 75 and 100 millimeters. Alternatively, the filtering means 20 may be made of another material capable of absorbing droplets of distributed liquid, which is not obtained from cellulose.

The filtering means 20 ensures by absorption the retention of the residual droplets of liquid carried by the air flow downstream of the separator 18. This gives the tower operation without vesicle entrainment. In addition, even with an accumulation of liquid droplets inside the filtering means 20, the filtration efficiency is not reduced given the speed of the pulsed air flow, generally less than 4 meters / second. . In order to optimize the lifetime of the filtering means, however, it can be provided for drying steps of this means by operating the tower without spraying liquid. The invention has been illustrated on the basis of a cooling tower that can be "open circuit" or "closed circuit". The cooling tower could also be a hybrid tower. In this case, the filtering means is placed downstream of the anti-plume battery by considering the flow direction of the air flow inside the tower.

Claims (10)

Cooling tower comprising a heat exchange body (14), a distribution system (16) for a liquid on the heat exchange body, means for generating (26) a flow of gas in the direction of of the heat exchange body, and a separator (18) of drops disposed downstream of the heat exchange body (14) and adapted to separate droplets of distributed liquid which are entrained by the gas flow, characterized in that it further comprises an absorption filtering means (20) disposed downstream of the gas-permeable droplet separator and adapted to absorb droplets of distributed liquid entrained by the gas flow. The tower of claim 1, wherein the absorption filtering means (20) covers an entire outlet opening of the gas flow of said tower. The lathe according to claim 1 or 2, wherein the absorption filter means (20) is located remote from the drop separator (18). 4. A lathe according to any one of the preceding claims, wherein the filtering means (20) is made of at least one absorbent material. The lathe of claim 4, wherein the filtering means (20) comprises cellulose fibers. The lathe according to claim 5, wherein the filter means (20) is comprised of a plurality of corrugated sheets and made of cellulose fibers. Tower according to any one of the preceding claims, comprising a casing inside which the heat exchange body (14), the drop separator (18) and the filtering means (20) are entirely mounted. absorption. 8. Tower according to any one of the preceding claims, wherein the means (26) for generating the gas flow comprises at least one motor-fan unit. Tower according to any one of the preceding claims, wherein the distribution system (16) is arranged upstream of the separator (18) of drops. 10. A method of cooling a liquid inside a cooling tower comprising a step of spraying the liquid to be cooled on a heat exchange body of the tower which is traversed by a gas flow, and a step separating droplets of pulverized liquid which are entrained by the gas flow, characterized in that it further comprises, after the separation step, a step of filtering residual liquid droplets entrained by said gas flow by absorption said droplets so as to reject said flow out of the tower without vesicular entrainment.