CA1213208A - Method of cleaning humid air contaminated with vapour - Google Patents
Method of cleaning humid air contaminated with vapourInfo
- Publication number
- CA1213208A CA1213208A CA000428533A CA428533A CA1213208A CA 1213208 A CA1213208 A CA 1213208A CA 000428533 A CA000428533 A CA 000428533A CA 428533 A CA428533 A CA 428533A CA 1213208 A CA1213208 A CA 1213208A
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- air
- water
- vapour
- cooling
- heat
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Abstract
ABSTRACT:
"A method of cleaning humid air contaminated with vapour"
A method of cleaning humid air contaminated with vapour, such as ventilation air from a rolling mill or the like, comprises the steps of cooling the air in one or more stages to a temperature below the condensation temperature of the contaminating vapour in the air, and below the dew point of water. The condensate is collected in such a way that the condensed vapour is substantially separated from the condensed water. The condensed vapour may then be re-used. The water, which may still be contaminated with a small proportion of the condensed vapour, is returned to the air to re-humidify the air. In a preferred embodiment the cooling is conducted in two stages, the initial stage condensing substantially only the vapour, and the second stage condensing the water together with a relatively small propor-tion of the vapour still remaining in the air. The condensate may be separated into two phases in a separation tank.
"A method of cleaning humid air contaminated with vapour"
A method of cleaning humid air contaminated with vapour, such as ventilation air from a rolling mill or the like, comprises the steps of cooling the air in one or more stages to a temperature below the condensation temperature of the contaminating vapour in the air, and below the dew point of water. The condensate is collected in such a way that the condensed vapour is substantially separated from the condensed water. The condensed vapour may then be re-used. The water, which may still be contaminated with a small proportion of the condensed vapour, is returned to the air to re-humidify the air. In a preferred embodiment the cooling is conducted in two stages, the initial stage condensing substantially only the vapour, and the second stage condensing the water together with a relatively small propor-tion of the vapour still remaining in the air. The condensate may be separated into two phases in a separation tank.
Description
Lo "Q method of cleaning humid air contaminated with vapor".
TIE PRESENT INVENTION rotates to a method of cleaning air, which may be humid air, which is contaminated with vapor, such as oil vapor. The invention also relates to an apparatus for carrying out such a method.
It if often necessary to clean air which is contaminated with vapors, and that air will have a certain humidity, depending upon the ambient atmospheric humidity at the time.
In n rolling mill In which steel is rolled or converted, the rollers which come into contact with the hot ingots or metal billets to be rolled have to be cooled. This cooling is often carried out by spraying an oil-based liquid onto the rollers. Large quantities of oil are evaporated during the cooling process as result of absorbing heat from the rollers or even from the ingots or metal billets, and the resultant vapor is entrained in the I ventilating air. For environmental reasons, this air has to be cleaned to a certain maximum acceptable level of contamination before it is released to the atmosphere or reused. The quantities of air involved can be very large, for example or the order of 50000 cubic metros per hour.
It is Jo be understood that the contaminated air contains, in addition to the oil vapor mentioned above, a quantity of water in the form of atmospheric humidity. The quantity of water contained in the air at any one time depends upon the ambient level of atmospheric humidity If an attempt is made to glean the air simply by cooling the air so as to condense the oil vapor, it has been found that large quantities of water will also condense, for example of the order of 40 cubic metros per 24 hours when Lowe cubic metros per hour of air is treated. The reason for this is that the air has to be cooled to a comparatively low temperature in order to 3û
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condense a substantial proportion of the oil or vapor in the air, and of course a substantial proportion of the oil vapor must be condensed to obtain de-contaminated air that is suitable for release into the atmosphere.
Thus, the result of the substantial cooling of the air is condensation of a mixture of oil and water. While a large proportion of the condensed oil can be separated comparatively easily from the water for reuse, a certain quantity of the condensed oil will remain in suspension in the condensed water. It is very expensive and time consuming to separate the oil completely from the water. The quantity of oil that remains in the water after an economically satisfactory separation of the oil and water has been carried out is so large that the water is not suitable for release into a municipal sewer without further cleaning of the water.
It will be appreciated, therefore, -what the cleaning of substantial quantities of humid air contaminated with oil vapor presents a severe problem that is difficult to solve in an economically satisfactory way.
Whilst the prior art process provides air thaw is suitably de-contaminated, the prior art method produces large quantities of water that are con-laminated and that must therefore be disposed off appropriately.
The present invention seeks to reduce or overcome the above-described difficulties of the prior art.
According to one aspect of this invention there is provided a method of cleaning humid air contaminated with vapor, said method comprising the step of cooling the air in one or more stages to a temperature below the condensation temperature of the contaminating vapor in the air and below the dew point of water to effect condensation of the vapor and water and collecting the condensate in such a way that the condensed vapor is 3û substantially separated from the condensed water, and subsequently no-introducing the water, which may stiff be contaminated with a small portion of the condensed vapor, to the air to remodify the air.
Preferably the cooling is effected by cooling the air initially to a temperature below the condensation point of the vapor but above the dew point of water, so that substantially only the vapor is condensed, and subsequently cooling the air to a temperature below the dew point of water, .
L32{j~3 so that water and further quantities of the contaminating vapor condensed.
Conveniently the condensate obtained during the said subsequent cooling stage is allowed to separate into an aqueous fraction and a condensed vapor fraction, and the aqueous fraction is the water that is no-introduced to the air.
Advantageously the ventilating air is cooled to at least about -10 degrees centigrade during the cooling process.
Preferably the cleaned air is heated before the water is reintroduced to the air.
Conveniently heat pumps or the like are utilized initially to cool the air by extracting heat from the air, and then to heat the air by no-introducing that heat to the air.
According to another aspic t of the invention there is provided an apparatus for cleaning humid air contaminated with vapor, said apparatus comprising one or more cooling stages adapted to cool the air to a temperature below the condensation temperature of the contaminating vapor in the air and below the dew point of water to effect condensation of the vapor and water, means for collecting the condensate formed in the said stage or stages in such a way that the condensed vapor is substantially separated from the condensed water, and means for subsequently no-introducing the water, which may be contaminated with a small proportion of the condensed vapor, to the air to remodify the air.
Preferably the apparatus comprises at least two successive cooling I stages, a first cooling stage or stages being adapted to cool the air to a temperature below the condensation point of said vapor and above the dew point of water, a subsequent cooling stage or stages being adapted to cool the air to a temperature below the dew point of water.
Conveniently said means for collecting the condensate comprise means for collecting the condensate from said first stage or stages and directing thaw condensate to a first receptacle and means for collecting the ~13~2Q~3 condensate from said subsequent stage or stages and directing thaw con-dentate to a second receptacle.
In one embodiment the second receptacle comprises a receptacle having a relatively large volume such that the condensate directed to the vessel only flows slowly through the vessel to enable the condensate to separate into an aqueous fraction and a condensed vapor fraction.
Preferably said receptacle is divided into two compartments by means of a vertical partition, the compartments communicating in the lowermost region of the receptacle the means supplying condensate to the receptacle terminating in a first said compartment, there being an overflow outlet from the second said compartment to permit the flow of the aqueous phase to a further receptacle.
Conveniently means are provided for detecting the level of fluid within said further receptacle, and a control device is provided, responsive to the level of fluid within the receptacle, for controlling a pump, said pump being provided in a circuit to pump fluid from said further receptacle to a 2û moistener or humidifier which may operate to return the moisture to the air before it leaves the apparatus.
Preferably said cooling stage or at least one of said cooling stages is provided with coolant from a refrigeration plant, heat pump or the like.
Conveniently heating means are provided for heating the air after it has been cooled and before the water is returned to the air.
Advantageously said heating means incorporate at least one heating stage which is provided with heclt from said refrigeration plant, heat pump or the like.
Preferably means are provided for controlling the quantity of heat supplied to said heating stage in response to the level of fluid within said further receptacle.
Conveniently said cooling stage or stages and said heating means :
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comprise at least one cooling heat exchanger and at least one heating heat exchanger, and means for pumping heat exchange medium between the said heat exchangers, the arrangement being such that the hoe t exchange medium is utilized in the cooling heat exchange or exchangers to cool the air initially, the heat exchange medium thus being heated, and tile heated heat exchange medium is then transferred to the heating heat exchanger which subsequently heats the air with a consequent cooling of the heat exchange medium the then cooled heat exchange medium being returned to the cooling heat exchanger or exchangers.
In order that the invention may be more readily understood, and so that further features thereof may be appreciated, the invention will now be described by way of example with reference to the accompanying drawing which is a flow diagram of an apparatus for carrying out a method in IS accordance with the present invention.
In the apparatus illustrated in the accompanying drawing a plurality of heat exchangers 11, 12, 13, I 15 and 16 are arranged serially along a conduit defining a flow path that is followed by a stream of air that is to be de-contaminated. The inlet part 17 of the conduit is shown at the left hand side of the drawing, and the outlet part 18 of the conduit is shown at the right hand side of the drawing The apparatus effectively comprises four cooling stages l-IV which cool the air flowing from the inlet 17 towards the outlet 18 and two heating stages V-VI which subsequently heat the air before it passes to the outlet 18.
A closed circuit is provided for the flow of a heat exchange medium from the heat exchanger I I, through a pump (indicated by a circle containing an arrow head, which is the conventiollal sign for a pump uiilsed throughout the accompanying drawing) to the heat exchanger 15. The heat exchanging medium passes from the heat exchanger 15 to the heat ox-changer 12, and then back to the heat exchanger 11. A refrigeration plant or heat pump 19 is provided to supply a cooling heat exchange fluid to the heat exchangers 13 and 14. The main outlet of the refrigeration plant 19 supplies a flow of coolant directly to the heat exchanger 14, and part of the heat exchange fluid emerging from that heat exchanger is returned directly . . .
3~8 to the refrigeration plant 19, whilst another part of that flow is directed through the heat exchanger 13. The refrigeration plant or heat pump 19 is also associated with a heated heat exchange fluid circuit which causes heated heat exchange fluid to flow through the heat exchanger 16.
The portions of the conduit between the heat exchangers 11 end 12, and 12 and 13 each have their lower regions configured to form a funnel, and the lowermost parts of the funnels extend into drain conduits which combine and terminate within a receptacle 20. The receptacle 20 is divided into two interior chambers 21, 22 by means of a whir and the drain conduit terminates within the chamber 21~ A float arrangement is associated with the chamber 22 and is adapted to control a valve such that when the level of the fluid within the chamber 22 reaches a predetermined level the valve may be opened to permit the fluid to flow away through a drain conduit 23.
A valve controlled outlet is provided at the base of the chamber 21, and a sight glass is provided on the exterior of the receptacle 20 to enable the nature of the contents of the chamber 21 to be observed.
The conduit portions between the heat exchangers Andy 14, and 15 and 16 also have lower regions defining funnels which are connected two downwardly extending conduits which combine to form a single drain conduit that enters into a second relatively large receptacle I The receptacle 24 has a downwardly extending partition so that the receptacle is divided into two compartments 25, 26 that communicate adjacent the base of the receptacle 24. The single drain conduit enters into the compartment 25 mentioned above. An overflow outlet is provided extending -from the compartment 25 to q further receptacle 27. This further receptacle 27 is provided with a sight glass and has a valve controlled towel outlet and a valve controlled outlet located at an intermediate level.
An overflow outlet 28 is also provided` from the compartment 26 which extends to a further receptacle 29. A float actuated control is associated with the receptacle 29 which is adapted to actuate a pump to pump fluid from the receptacle 29 through a conduit 31 to an evaporator aye located within the conduit through which the air flows, after the last heat exchanger. A return conduit 32 is also provided. The float actuated control also actuates valves present in the heated heat exchange medium .. .. .. , . .... , _ .
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circuit located between the refrigeration plant or heat pump 19 and the heat exchanger 16.
The lowermost part of the conduit portion between the heat exchangers 15 and 16 is also shaped like a funnel" the outlet of which is connected to the single drain conduit mentioned above.
In operation of the device air, which may be humid, which is contaminated with oil vapor or some other vapor is caused to flow through the conduit that defines said flow path and enters the apparatus through the inlet 17 in the direction indicated by the arrow. The air typically has a temperature of ~35 degrees centigrade. The air passes through the first heat exchanger i I, and the air is cooled to approximately 20 degrees centigrade. The heat from the air is transferred to the heat exchange medium flowing through the heat exchanger 11 and the thus heated heat exchange medium is driven by the pump to the heat exchanger 15. The air then passes through the second heat exchanger 12, where it is further cooled to a temperature of + 13 degrees centigrade. The heat exchanger 12 receives its heat exchange medium at a very tow temperature from the heat exchanger 15 as will be described hereinafter, and the heat exchange medium flows from the heat exchanger 12 to the heat exchanger 11.
The temperatures of 20 degrees centigrade and 13 degrees centigrade are below the condensing point of the oil vapor that is contaminating the air, but these temperatures are above the dew point of water. Thus, in the first two cooling stages I and 11 substantially only oil is condensed. The condensing oil droplets fall into the funnels defined in the lower regions of the conduit and flow downwardly through the pipes into the chamber 21 at the right hand side of the receptacle 20. When this chamber has been filled up the oil will flow over the whir into the chamber 22. When the level of the oil within the chamber 22, as detected by the float, is sufficient the valve is opened and the oil is drained off through the conduit 23 for reuse.
If any water is condensed within the first two cooling stages I and 11, the water will collect at the lower part of the chamber 21. If any water is seen within this chamber through the sight glass the water can be drained out approprkltely and such water may, for example, be introduced to the receptacle 29.
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The air then passes through the heat exchangers 13 and 14 which further cool the air in two stages to a temperature of I degree centigrade and then to a temperature of -10 degrees centigrade. These temperatures are below the dew point of water, and in these stages water will be condensed. However, these low temperatures ensure that substantially all the oil vapor present in the air is condensed and thus, as the air leaves the cooling stage IV, the air is substantially pure, containing, -for example, only 60 my of oil per cubic moire. The condensed water and oil flows downwardly into the compartment 25 of the receptacle 24. The receptacle lo has a very large volume relative to the flow of water so that, within the receptacle 24, there are only very slow flow rates. Consequently there will be a period of time during which the oil and water may separate out. Thus, in the compartment 25 the water will tend to gravitate to the lower part of the compartment, whereas the lighter oil will remain in the upper part of the compartment. The water in the lower part of the compartment flows underneath the partition into the compartment 26 whilst the oil flows through the overflow conduit into the receptacle 27. If any water is still entrained with the oil, the water will be given an opportunity to settle out in the receptacle 27 and if any water is observed in the sight glass the water 2û may be drained out through the lowermost drain in the receptacle 27, that water being returned, for example, to the receptacle 29. When a sufficient level of oil has accumulated within the receptacle 27, as seen through the sight glass, the oil may be drained out through the intermediate level outlet and may be returned to the rolling mill for reuse.
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the air passes through the heat exchanger 15, which is supplied, as has been mentioned, with heated heat exchange medium From the heat exchanger I I . The air is thus heated to + 12 degrees centigrade and the heat exchange medium is cooled to a very low temperature. It is this very tow temperature heat exchange medium that is supplied to the heat exchange aye and then to the heat exchanger 11. Any fluid droplets still in the air may fall into the funnel before the air enters the heat exchanger 16 where it is raised to a temperature of +32 degrees centigrade. The droplets in the funnel are drained into compartment 25 of the receptacle 24.
Meanwhile, within the receptacle 24, the water flowing into the compartment 26 may still contain a certain quantity of oil, for example of ; .
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L321~3 .
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the order of 50 grams per cubic moire. Thus this water is not suitable for direct release into a municipal sewage disposal system. The water is thus drained off through the overflow drain 28 into the receptacle 29, and, under the control of the float operated control device 30, the fluid from the receptacle 29 is pumped up to the humidifier aye, where the water with the small amount of oil entrained therein is absorbed by the dry clean ventilating air which has been heated by the heat exchanger 16 to a temperature of ~32 degrees centigrade. Thus the air flowing to the outlet 18 has approximately the same relative humidity as the air initially introduced to the described apparatus through the inlet 17, and the air flowing through the outlet 18 stiff has entrained therein a small quantity of oil vapor, this being the oil vapor reintroduced to the air at the humidifier aye, together with the oil that remained in the air throughout the entire cleaning process. However this small quantity of oil vapor is not detrimental to the environment and is thus quite acceptable.
It should be mentioned that the float operated control device 30 associated with the receptacle 29 detects the level of water in the receptacle and controls the heat supply to the heat exchanger 16 in such a way that the heat supply increases when the level of water in the receptacle 29 is rising, so that the moisture absorbing capacity of the air increases.
Equally the heat supply to the heat exchanger 16 decreases when the water level in the receptacle 29 is falling. This ensures, in an easy way, that the condensed water will always be absorbed by the air leaving the described apparatus with a minimum wastage of heat.
The present invention provides significantly improved results when compared with the prior art discussed above. If air containing oil vapor is cooled to a temperature of 10 degrees centigrade the air may still contain about 25û milligram oil per cubic moire. Even if, in the prior art arrangement, the temperature have been lowered to 0 degree centigrade, the air would still contain about 130 degree my of oil per cubic moire.
However, in utilizing the present invention and cooling the air to a temperature of -10 degrees centigrade the ventilating air subsequently only contains about 60 my of oil per cubic moire, which is a very low value.
admittedly this value is increased slightly when oil is reintroduced to the air stream at the humidifier aye, but the final figure is still very low when . .
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compared with the prior art.
It is to be appreciated trot the apparatus described above wilt operate with a minimum consumption of power, since the apparatus is internally efficient. Effectively a refrigeration plant or heat pump is utilized to extract heat from the air as it enters the apparatus and to no-introduce that heat to the air before it leaves the apparatus. Thus the refrigeration plant or heat pump must merely transfer heat from one part of the apparatus to another part of the apparatus, although, due to heat loss lo and the inevitable slight inefficiency of the apparatus, some make-up heat will have to be provided.
Whilst only one embodiment of an apparatus according to the invention and only one specific example of the application of the apparatus have been described it is to be understood that many modifications may be effected without departing from the scope of the invention.
The cooling stage IV in which the temperature reduced to -10 degrees centigrade may be constituted by two identical cooling stages mounted in parallel. The reason for this is that, at a temperature of -lo degrees centigrade, ice may form within the cooling stage, thus restricting the flow of air. If there are two identical cooling stages connected in parallel, one cooling stage may be utiiised while the ice in the other cooling stage melts and drains away or while the ice is physically removed, and then the flow of air, and coolant, may be switched over to the other stage.
It is to be understood that the cooling temperatures specified with regard to the various cooling stages can be modified depending upon the specific nature of the air to be purifies and the available cooling power. It isalso to be understood that the separation of oil or any other cooling or lubricating liquid from the water can be performed in many different ways so that, for example, only owns cooling stage will be needed. It is, however, very convenient to use at least two cooling stages having different temperatures so that the great proportion of the cooling or lubricating liquid can be condensed in one stage (or a group of stages) and the water can be condensed in a second stage (or a group of stages) as described above, because this will considerably facilitate the recovery of the cooling or . ' .
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Lubricating liquid.
It is to be understood that the supply of cooling and heating power, respectively to the separate stages, may also be provided in many ways. In S this connection, heat pumps may be used to take up the waste heat appearing in the system. The number of cooling and heating stages may also be varied within wide limits, as required. During the winter months it has been found that only one heating stage is normally required, and this stage can be supplied with heat from any of the preceding stages. In the summer, however, normally a second heating stage is required which must be supplied with external heat, to make it possible for the ventilating air leaving the apparatus to absorb the water from the humidifier 1 aye.
TIE PRESENT INVENTION rotates to a method of cleaning air, which may be humid air, which is contaminated with vapor, such as oil vapor. The invention also relates to an apparatus for carrying out such a method.
It if often necessary to clean air which is contaminated with vapors, and that air will have a certain humidity, depending upon the ambient atmospheric humidity at the time.
In n rolling mill In which steel is rolled or converted, the rollers which come into contact with the hot ingots or metal billets to be rolled have to be cooled. This cooling is often carried out by spraying an oil-based liquid onto the rollers. Large quantities of oil are evaporated during the cooling process as result of absorbing heat from the rollers or even from the ingots or metal billets, and the resultant vapor is entrained in the I ventilating air. For environmental reasons, this air has to be cleaned to a certain maximum acceptable level of contamination before it is released to the atmosphere or reused. The quantities of air involved can be very large, for example or the order of 50000 cubic metros per hour.
It is Jo be understood that the contaminated air contains, in addition to the oil vapor mentioned above, a quantity of water in the form of atmospheric humidity. The quantity of water contained in the air at any one time depends upon the ambient level of atmospheric humidity If an attempt is made to glean the air simply by cooling the air so as to condense the oil vapor, it has been found that large quantities of water will also condense, for example of the order of 40 cubic metros per 24 hours when Lowe cubic metros per hour of air is treated. The reason for this is that the air has to be cooled to a comparatively low temperature in order to 3û
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condense a substantial proportion of the oil or vapor in the air, and of course a substantial proportion of the oil vapor must be condensed to obtain de-contaminated air that is suitable for release into the atmosphere.
Thus, the result of the substantial cooling of the air is condensation of a mixture of oil and water. While a large proportion of the condensed oil can be separated comparatively easily from the water for reuse, a certain quantity of the condensed oil will remain in suspension in the condensed water. It is very expensive and time consuming to separate the oil completely from the water. The quantity of oil that remains in the water after an economically satisfactory separation of the oil and water has been carried out is so large that the water is not suitable for release into a municipal sewer without further cleaning of the water.
It will be appreciated, therefore, -what the cleaning of substantial quantities of humid air contaminated with oil vapor presents a severe problem that is difficult to solve in an economically satisfactory way.
Whilst the prior art process provides air thaw is suitably de-contaminated, the prior art method produces large quantities of water that are con-laminated and that must therefore be disposed off appropriately.
The present invention seeks to reduce or overcome the above-described difficulties of the prior art.
According to one aspect of this invention there is provided a method of cleaning humid air contaminated with vapor, said method comprising the step of cooling the air in one or more stages to a temperature below the condensation temperature of the contaminating vapor in the air and below the dew point of water to effect condensation of the vapor and water and collecting the condensate in such a way that the condensed vapor is 3û substantially separated from the condensed water, and subsequently no-introducing the water, which may stiff be contaminated with a small portion of the condensed vapor, to the air to remodify the air.
Preferably the cooling is effected by cooling the air initially to a temperature below the condensation point of the vapor but above the dew point of water, so that substantially only the vapor is condensed, and subsequently cooling the air to a temperature below the dew point of water, .
L32{j~3 so that water and further quantities of the contaminating vapor condensed.
Conveniently the condensate obtained during the said subsequent cooling stage is allowed to separate into an aqueous fraction and a condensed vapor fraction, and the aqueous fraction is the water that is no-introduced to the air.
Advantageously the ventilating air is cooled to at least about -10 degrees centigrade during the cooling process.
Preferably the cleaned air is heated before the water is reintroduced to the air.
Conveniently heat pumps or the like are utilized initially to cool the air by extracting heat from the air, and then to heat the air by no-introducing that heat to the air.
According to another aspic t of the invention there is provided an apparatus for cleaning humid air contaminated with vapor, said apparatus comprising one or more cooling stages adapted to cool the air to a temperature below the condensation temperature of the contaminating vapor in the air and below the dew point of water to effect condensation of the vapor and water, means for collecting the condensate formed in the said stage or stages in such a way that the condensed vapor is substantially separated from the condensed water, and means for subsequently no-introducing the water, which may be contaminated with a small proportion of the condensed vapor, to the air to remodify the air.
Preferably the apparatus comprises at least two successive cooling I stages, a first cooling stage or stages being adapted to cool the air to a temperature below the condensation point of said vapor and above the dew point of water, a subsequent cooling stage or stages being adapted to cool the air to a temperature below the dew point of water.
Conveniently said means for collecting the condensate comprise means for collecting the condensate from said first stage or stages and directing thaw condensate to a first receptacle and means for collecting the ~13~2Q~3 condensate from said subsequent stage or stages and directing thaw con-dentate to a second receptacle.
In one embodiment the second receptacle comprises a receptacle having a relatively large volume such that the condensate directed to the vessel only flows slowly through the vessel to enable the condensate to separate into an aqueous fraction and a condensed vapor fraction.
Preferably said receptacle is divided into two compartments by means of a vertical partition, the compartments communicating in the lowermost region of the receptacle the means supplying condensate to the receptacle terminating in a first said compartment, there being an overflow outlet from the second said compartment to permit the flow of the aqueous phase to a further receptacle.
Conveniently means are provided for detecting the level of fluid within said further receptacle, and a control device is provided, responsive to the level of fluid within the receptacle, for controlling a pump, said pump being provided in a circuit to pump fluid from said further receptacle to a 2û moistener or humidifier which may operate to return the moisture to the air before it leaves the apparatus.
Preferably said cooling stage or at least one of said cooling stages is provided with coolant from a refrigeration plant, heat pump or the like.
Conveniently heating means are provided for heating the air after it has been cooled and before the water is returned to the air.
Advantageously said heating means incorporate at least one heating stage which is provided with heclt from said refrigeration plant, heat pump or the like.
Preferably means are provided for controlling the quantity of heat supplied to said heating stage in response to the level of fluid within said further receptacle.
Conveniently said cooling stage or stages and said heating means :
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comprise at least one cooling heat exchanger and at least one heating heat exchanger, and means for pumping heat exchange medium between the said heat exchangers, the arrangement being such that the hoe t exchange medium is utilized in the cooling heat exchange or exchangers to cool the air initially, the heat exchange medium thus being heated, and tile heated heat exchange medium is then transferred to the heating heat exchanger which subsequently heats the air with a consequent cooling of the heat exchange medium the then cooled heat exchange medium being returned to the cooling heat exchanger or exchangers.
In order that the invention may be more readily understood, and so that further features thereof may be appreciated, the invention will now be described by way of example with reference to the accompanying drawing which is a flow diagram of an apparatus for carrying out a method in IS accordance with the present invention.
In the apparatus illustrated in the accompanying drawing a plurality of heat exchangers 11, 12, 13, I 15 and 16 are arranged serially along a conduit defining a flow path that is followed by a stream of air that is to be de-contaminated. The inlet part 17 of the conduit is shown at the left hand side of the drawing, and the outlet part 18 of the conduit is shown at the right hand side of the drawing The apparatus effectively comprises four cooling stages l-IV which cool the air flowing from the inlet 17 towards the outlet 18 and two heating stages V-VI which subsequently heat the air before it passes to the outlet 18.
A closed circuit is provided for the flow of a heat exchange medium from the heat exchanger I I, through a pump (indicated by a circle containing an arrow head, which is the conventiollal sign for a pump uiilsed throughout the accompanying drawing) to the heat exchanger 15. The heat exchanging medium passes from the heat exchanger 15 to the heat ox-changer 12, and then back to the heat exchanger 11. A refrigeration plant or heat pump 19 is provided to supply a cooling heat exchange fluid to the heat exchangers 13 and 14. The main outlet of the refrigeration plant 19 supplies a flow of coolant directly to the heat exchanger 14, and part of the heat exchange fluid emerging from that heat exchanger is returned directly . . .
3~8 to the refrigeration plant 19, whilst another part of that flow is directed through the heat exchanger 13. The refrigeration plant or heat pump 19 is also associated with a heated heat exchange fluid circuit which causes heated heat exchange fluid to flow through the heat exchanger 16.
The portions of the conduit between the heat exchangers 11 end 12, and 12 and 13 each have their lower regions configured to form a funnel, and the lowermost parts of the funnels extend into drain conduits which combine and terminate within a receptacle 20. The receptacle 20 is divided into two interior chambers 21, 22 by means of a whir and the drain conduit terminates within the chamber 21~ A float arrangement is associated with the chamber 22 and is adapted to control a valve such that when the level of the fluid within the chamber 22 reaches a predetermined level the valve may be opened to permit the fluid to flow away through a drain conduit 23.
A valve controlled outlet is provided at the base of the chamber 21, and a sight glass is provided on the exterior of the receptacle 20 to enable the nature of the contents of the chamber 21 to be observed.
The conduit portions between the heat exchangers Andy 14, and 15 and 16 also have lower regions defining funnels which are connected two downwardly extending conduits which combine to form a single drain conduit that enters into a second relatively large receptacle I The receptacle 24 has a downwardly extending partition so that the receptacle is divided into two compartments 25, 26 that communicate adjacent the base of the receptacle 24. The single drain conduit enters into the compartment 25 mentioned above. An overflow outlet is provided extending -from the compartment 25 to q further receptacle 27. This further receptacle 27 is provided with a sight glass and has a valve controlled towel outlet and a valve controlled outlet located at an intermediate level.
An overflow outlet 28 is also provided` from the compartment 26 which extends to a further receptacle 29. A float actuated control is associated with the receptacle 29 which is adapted to actuate a pump to pump fluid from the receptacle 29 through a conduit 31 to an evaporator aye located within the conduit through which the air flows, after the last heat exchanger. A return conduit 32 is also provided. The float actuated control also actuates valves present in the heated heat exchange medium .. .. .. , . .... , _ .
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circuit located between the refrigeration plant or heat pump 19 and the heat exchanger 16.
The lowermost part of the conduit portion between the heat exchangers 15 and 16 is also shaped like a funnel" the outlet of which is connected to the single drain conduit mentioned above.
In operation of the device air, which may be humid, which is contaminated with oil vapor or some other vapor is caused to flow through the conduit that defines said flow path and enters the apparatus through the inlet 17 in the direction indicated by the arrow. The air typically has a temperature of ~35 degrees centigrade. The air passes through the first heat exchanger i I, and the air is cooled to approximately 20 degrees centigrade. The heat from the air is transferred to the heat exchange medium flowing through the heat exchanger 11 and the thus heated heat exchange medium is driven by the pump to the heat exchanger 15. The air then passes through the second heat exchanger 12, where it is further cooled to a temperature of + 13 degrees centigrade. The heat exchanger 12 receives its heat exchange medium at a very tow temperature from the heat exchanger 15 as will be described hereinafter, and the heat exchange medium flows from the heat exchanger 12 to the heat exchanger 11.
The temperatures of 20 degrees centigrade and 13 degrees centigrade are below the condensing point of the oil vapor that is contaminating the air, but these temperatures are above the dew point of water. Thus, in the first two cooling stages I and 11 substantially only oil is condensed. The condensing oil droplets fall into the funnels defined in the lower regions of the conduit and flow downwardly through the pipes into the chamber 21 at the right hand side of the receptacle 20. When this chamber has been filled up the oil will flow over the whir into the chamber 22. When the level of the oil within the chamber 22, as detected by the float, is sufficient the valve is opened and the oil is drained off through the conduit 23 for reuse.
If any water is condensed within the first two cooling stages I and 11, the water will collect at the lower part of the chamber 21. If any water is seen within this chamber through the sight glass the water can be drained out approprkltely and such water may, for example, be introduced to the receptacle 29.
' 1 ~3L3~
The air then passes through the heat exchangers 13 and 14 which further cool the air in two stages to a temperature of I degree centigrade and then to a temperature of -10 degrees centigrade. These temperatures are below the dew point of water, and in these stages water will be condensed. However, these low temperatures ensure that substantially all the oil vapor present in the air is condensed and thus, as the air leaves the cooling stage IV, the air is substantially pure, containing, -for example, only 60 my of oil per cubic moire. The condensed water and oil flows downwardly into the compartment 25 of the receptacle 24. The receptacle lo has a very large volume relative to the flow of water so that, within the receptacle 24, there are only very slow flow rates. Consequently there will be a period of time during which the oil and water may separate out. Thus, in the compartment 25 the water will tend to gravitate to the lower part of the compartment, whereas the lighter oil will remain in the upper part of the compartment. The water in the lower part of the compartment flows underneath the partition into the compartment 26 whilst the oil flows through the overflow conduit into the receptacle 27. If any water is still entrained with the oil, the water will be given an opportunity to settle out in the receptacle 27 and if any water is observed in the sight glass the water 2û may be drained out through the lowermost drain in the receptacle 27, that water being returned, for example, to the receptacle 29. When a sufficient level of oil has accumulated within the receptacle 27, as seen through the sight glass, the oil may be drained out through the intermediate level outlet and may be returned to the rolling mill for reuse.
I
the air passes through the heat exchanger 15, which is supplied, as has been mentioned, with heated heat exchange medium From the heat exchanger I I . The air is thus heated to + 12 degrees centigrade and the heat exchange medium is cooled to a very low temperature. It is this very tow temperature heat exchange medium that is supplied to the heat exchange aye and then to the heat exchanger 11. Any fluid droplets still in the air may fall into the funnel before the air enters the heat exchanger 16 where it is raised to a temperature of +32 degrees centigrade. The droplets in the funnel are drained into compartment 25 of the receptacle 24.
Meanwhile, within the receptacle 24, the water flowing into the compartment 26 may still contain a certain quantity of oil, for example of ; .
, .
L321~3 .
I
the order of 50 grams per cubic moire. Thus this water is not suitable for direct release into a municipal sewage disposal system. The water is thus drained off through the overflow drain 28 into the receptacle 29, and, under the control of the float operated control device 30, the fluid from the receptacle 29 is pumped up to the humidifier aye, where the water with the small amount of oil entrained therein is absorbed by the dry clean ventilating air which has been heated by the heat exchanger 16 to a temperature of ~32 degrees centigrade. Thus the air flowing to the outlet 18 has approximately the same relative humidity as the air initially introduced to the described apparatus through the inlet 17, and the air flowing through the outlet 18 stiff has entrained therein a small quantity of oil vapor, this being the oil vapor reintroduced to the air at the humidifier aye, together with the oil that remained in the air throughout the entire cleaning process. However this small quantity of oil vapor is not detrimental to the environment and is thus quite acceptable.
It should be mentioned that the float operated control device 30 associated with the receptacle 29 detects the level of water in the receptacle and controls the heat supply to the heat exchanger 16 in such a way that the heat supply increases when the level of water in the receptacle 29 is rising, so that the moisture absorbing capacity of the air increases.
Equally the heat supply to the heat exchanger 16 decreases when the water level in the receptacle 29 is falling. This ensures, in an easy way, that the condensed water will always be absorbed by the air leaving the described apparatus with a minimum wastage of heat.
The present invention provides significantly improved results when compared with the prior art discussed above. If air containing oil vapor is cooled to a temperature of 10 degrees centigrade the air may still contain about 25û milligram oil per cubic moire. Even if, in the prior art arrangement, the temperature have been lowered to 0 degree centigrade, the air would still contain about 130 degree my of oil per cubic moire.
However, in utilizing the present invention and cooling the air to a temperature of -10 degrees centigrade the ventilating air subsequently only contains about 60 my of oil per cubic moire, which is a very low value.
admittedly this value is increased slightly when oil is reintroduced to the air stream at the humidifier aye, but the final figure is still very low when . .
. ,, ~Z~3~
compared with the prior art.
It is to be appreciated trot the apparatus described above wilt operate with a minimum consumption of power, since the apparatus is internally efficient. Effectively a refrigeration plant or heat pump is utilized to extract heat from the air as it enters the apparatus and to no-introduce that heat to the air before it leaves the apparatus. Thus the refrigeration plant or heat pump must merely transfer heat from one part of the apparatus to another part of the apparatus, although, due to heat loss lo and the inevitable slight inefficiency of the apparatus, some make-up heat will have to be provided.
Whilst only one embodiment of an apparatus according to the invention and only one specific example of the application of the apparatus have been described it is to be understood that many modifications may be effected without departing from the scope of the invention.
The cooling stage IV in which the temperature reduced to -10 degrees centigrade may be constituted by two identical cooling stages mounted in parallel. The reason for this is that, at a temperature of -lo degrees centigrade, ice may form within the cooling stage, thus restricting the flow of air. If there are two identical cooling stages connected in parallel, one cooling stage may be utiiised while the ice in the other cooling stage melts and drains away or while the ice is physically removed, and then the flow of air, and coolant, may be switched over to the other stage.
It is to be understood that the cooling temperatures specified with regard to the various cooling stages can be modified depending upon the specific nature of the air to be purifies and the available cooling power. It isalso to be understood that the separation of oil or any other cooling or lubricating liquid from the water can be performed in many different ways so that, for example, only owns cooling stage will be needed. It is, however, very convenient to use at least two cooling stages having different temperatures so that the great proportion of the cooling or lubricating liquid can be condensed in one stage (or a group of stages) and the water can be condensed in a second stage (or a group of stages) as described above, because this will considerably facilitate the recovery of the cooling or . ' .
, I:
I
Lubricating liquid.
It is to be understood that the supply of cooling and heating power, respectively to the separate stages, may also be provided in many ways. In S this connection, heat pumps may be used to take up the waste heat appearing in the system. The number of cooling and heating stages may also be varied within wide limits, as required. During the winter months it has been found that only one heating stage is normally required, and this stage can be supplied with heat from any of the preceding stages. In the summer, however, normally a second heating stage is required which must be supplied with external heat, to make it possible for the ventilating air leaving the apparatus to absorb the water from the humidifier 1 aye.
Claims (17)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of cleaning humid air contaminated with vapour, said method comprising the step of cooling the air in one or more stages to a temperature below the condensation temperature of the contaminating vapour in the air and below the dew point of water, to effect condensation of the vapour and water and collecting the condensate in such a way that the condensed vapour is substantially separated from the condensed water, and subsequently re-introducing the water, which may still be contaminated with a small proportion of the condensed vapour, to the air to re-humidify the air.
2. A method according to claim 1, wherein the cooling is effected by cooling the air initially to a temperature below the condensation point of the vapour but above the dew point of water, so that substantially only the vapour is condensed, and subsequently cooling the air to a temperature below the dew point of water, so that water and further quantities of the contaminating vapour condensed.
3. A method according to claim 2, wherein the condensate obtained during the said subsequent cooling stage is allowed to separate into an aqueous fraction and a condensed vapour fraction, and the aqueous fraction is the water that is re-introduced to the air.
4. A method according to any one of the preceding claims, wherein the ventilating air is cooled to at least about -10 degrees centigrade during the cooling process.
5. A method according to any one of Claims 1-3 wherein the cleaned air is heated before the water is re-introduced to the air.
6. A method according to any one of Claims 1-3.wherein heat pumps or the like are utilised initially to cool the air by extracting heat from the air, and then to heat the air by re-introducing that heat to the air.
7. An apparatus for cleaning humid air contaminated with vapour, said apparatus comprising one or more cooling stages adapted to cool the air to a temperature below the condensation temperature of the contaminating vapour in the air and below the dew point of water to effect condensation of the vapour and water, means for collecting the condensate formed in the said stage or stages in such a way that the condensed vapour is substantially separated from the condensed water, and means for subsequently re-introducing the water, which may be contaminated with a small proportion of the condensed vapour, to the air to re-humidify the air.
8. An apparatus according to claim 7, comprising at least two successive cooling stages, a first cooling stage or stages being adapted to cool the air to a temperature below the condensation point of said vapour and above the dew point of water, a subsequent cooling stage or stages being adapted to cool the air to a temperature below the dew point of water.
9. An apparatus according to claim 8, wherein said means for collecting the condensate comprise means for collecting the condensate from said first stage or stages and directing that condensate to a first receptacle and means for collecting the condensate from said subsequent stage or stages and directing that condensate to a second receptacle.
10. An apparatus according to claim 9, wherein the second receptacle comprises a receptacle having a relatively large volume such that the condensate directed to the vessel only flows slowly through the vessel to enable the condensate to separate into an aqueous fraction and a condensed vapour fraction.
11. An apparatus according to claim 10, wherein said second receptacle is divided into two compartments by means of a vertical partition, the compartments communicating in the lowemost region of the receptacle the means supplying condensate to the receptacle terminating in a first said compartment, there being an overflow outlet from the second said compartment to permit the flow of the aqueous phase to a further receptacle.
12. An apparatus according to claim 11 wherein means are provided for detecting the level of fluid within said further receptacle, and a control device is provided, responsive to the level of fluid within the receptacle, for controlling a pump, said pump being provided in a circuit to pump fluid from said further receptacle to a moistener or humidifier which may operate to return the moisture to the air before it leaves the apparatus.
13. An apparatus according to claim 7 wherein said cooling stage or at least one of said cooling stages is provided with coolant from a refrigeration plant, heat pump or the like.
14. An apparatus according to claim 13 wherein said means are provided for heating the air after it has been cooled and before the water is returned to the air.
15. An apparatus according to claim 14 wherein said heating means incorporated at least one heating stage which is provided with heat from said refrigeration plant, heat pump or the like.
16. An apparatus according to claim 12 wherein heating means are provided for heating the air after it has been cooled and before the water is returned to the air, said heating means incorporating at least one heating stage which is provided with heat from said refrigeration plant, heat pump or the like, means being provided for controlling the quantity of heat supplied to said heating stage in response to the level of fluid within said further receptacle.
17. An apparatus according to claim 14, 15 or 16, wherein said cooling stage or stages and said heating means comprise at least one cooling heat exchanger and at least one heating heat exchanger, and means for pumping heat exchange medium between the said heat exchangers, the arrangement being such that the heat exchange medium is utilized in the cooling heat exchange or exchangers to cool the air initially, the heat exchange medium thus being heated, and the heated heat exchange medium is then transferred to the heating heat exchanger which subsequently heats the air with a consequent cooling of the heat exchange medium, the then cooled heat exchange medium being returned to the cooling heat exchanger or exchangers.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000428533A CA1213208A (en) | 1983-05-19 | 1983-05-19 | Method of cleaning humid air contaminated with vapour |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000428533A CA1213208A (en) | 1983-05-19 | 1983-05-19 | Method of cleaning humid air contaminated with vapour |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1213208A true CA1213208A (en) | 1986-10-28 |
Family
ID=4125285
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000428533A Expired CA1213208A (en) | 1983-05-19 | 1983-05-19 | Method of cleaning humid air contaminated with vapour |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1213208A (en) |
-
1983
- 1983-05-19 CA CA000428533A patent/CA1213208A/en not_active Expired
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