GB1596568A

GB1596568A - Removal of vapour from gases

Info

Publication number: GB1596568A
Application number: GB4155/78A
Authority: GB
Original assignee: DROOGTECH
Current assignee: DROOGTECH
Priority date: 1977-02-10
Filing date: 1978-02-02
Publication date: 1981-08-26
Also published as: SE432531B; NL177388B; BE863533A; DK149039B; NL177388C; DE2803038C2; DK149039C; NL7701403A; FR2380063B3; DE2803038A1; SE7801338L; DK60178A; FR2380063A1

Description

(54) IMPROVEMENTS IN AND RELATING TO THE REMOVAL OF VAPOUR FROM GASES (71) We, DROaGTECHNIEK EN LUCHT BEHANDELING B.V., a Dutch Body Corporate of Westrik 17, Prinsenbeek, Netherlands, do hereby declare the invdntion, for which we pray that a patent may be granted us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to a method and a device for removing a vapour from a hot gas, and more particularly, but not exclusively, for drying compressed air.

According to the invention there is provided a method for removing a vapour from a feed gas having a higher temperature than the ambient air, said method comprising feeding the hot gas through one of two chambers provided with an absorbent for the vapour, said one chamber having been used previously to absorb vapour from the gas whereby the hot feed gas tends to reactivate the adsorbent in the said one chamber, cooling, in a first cooler, the hot gas downstream of the said one chamber whereby a substantial part of the vapour in the hot feed gas condenses out, feeding the cooled feed gas through the other of said chambers whereby the remaining vapour in the feed gas is removed, and after a period of time, reversing the effective positions of the chambers in the feed gas flow path whereby the hot feed gas is first fed through the said other chamber to reactivate same and the cooled feed gas is fed through the said one chamber for removal of remaining vapour from the feed gas, the time during which each respective chamber is reactivated being less than the time during which the other chamber is used for vapour adsorption from the cooled feed gas, and at least during a part of the time remaining between the end of the reactivation and the reversal of the effective positions of the chambers, hot feed gas being fed to the cooler without first passing through the reactivated chamber and a part of the cooled feed gas flow being fed through the reactivated chamber to cool same prior to using the reactivated chamber for adsorption after the reversal of the effective positions of the chambers.

Further according to the invention, there is provided a device for carrying out the above method comprising two chambers each provided with an adsorbent, a feed duct for feeding the hot feed gas, first switching means for directing the hot feed gas, selectively, through one or other of the chambers to reactivate that chamber, a first cooler, second switching means for directing the hot feed gas from the chamber being reactivated to the cooler and for directing cooled feed gas from the cooler to the other of the two chambers for removal of remaining vapour from the cooled feed gas, first valve means selectively operable to connect the feed duct with the first cooler by by-passing the chamber which has been reactivated, and second valve means selectively operable to permit feeding of a part of the feed gas cooled in the cooler to the chamber which has been reactivated whereby to cool same prior to operation of the switching means to direct the hot feed gas to the reactivated chamber.

The invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a circuit diagram of a vapourremoving device according to the invention, the device being shown in a first utilisation condition; and Figure 2 is a circuit diagram corresponding to Figure 1, but showing additional parts of the device in a second utilisation condition of the device.

The device shown in the drawing is, for instance, intended for drying compressed air, and comprises a supply duct 1 connected to a compressing pump or other source of compressed air, not shown, as well as a discharge duct 2 which is to be connected to utilization apparatus and/or storage tank for compressed air. The compressed air fed through the supply duct is hot as a consequence of the compression.

The duct 1 leads to a valve 3 which, in the condition of Figure 1, is opened, and connects the duct 1 with a duct 4 leading to one part of a first four-way switching valve 5.

In the illustrated position shown of this valve 5, the duct 4 is connected to one end 6 of a drying chamber 7, the other end 8 of which is connected to a second four-way switching valve 9, which in the position shown, makes a connection with a duct 10. The duct 10 is connected by means of a non-return valve 11, to an input duct 12 of a cooler 13, which can be cooled by means of a cooling fluid.

The discharge duct 14 of this cooler leads to a water separator 15 having a discharge duct 16 which, by means of a throttle valve 17, communicates with the second part of the four-way switching valve 9, which forms a connection with one- side 18 of a second drying chamber 19, the other side 20 of which communicates with the second part of the first switching valve 5 forming a connection with the discharge duct 2. When both valves 5 and 9 are switched over simultaneously, the chambers 7 and 19 mutually change places, so that only one operative condition will be described.

A connecting duct 21 connects the duct 1 upstream of the valve 3, with the duct 12 and is provided with a valve 22, and an adjustable valve 23 interconnects the ducts 10 and 16. The valves 22 and 23 are closed in the condition now being discussed and will, therefore, be left out of consideration for the moment.

Hot compressed air introduced into the duct 1 is led through the chamber 7 which was used as a dryer during a preceding period. The hot air is able to adsorb a relatively large quantity of moisture, and is used for reactivating adsorbent present in this chamber 7. The less hot air which is now saturated with moisture leaves the chamber 7 and flows towards the cooler 13 in which a substantial part of the adsorbed moisture will condence out. The condensed moisture is subsequently separated in the separator 15, after which the cold air flows towards the chamber 19 in which the final drying takes place by means of adsorbent in this chamber. The dry air is discharged at 2.

The drying in the chamber 19 can continue for a longer time than the time required for reactivation. This fact is made use of for cooling the chamber 7 which was heated by the hot air.

For this purpose, the device is brought into the condition shown in Figure 2. The valve 3 is now closed, and the valve 22 is opened, so that the duct 1 is now connected to the duct 21, and the connection with the duct 4 is interrupted. The hot air can now directly flow towards the cooler 13. The non-return valve 11 prevents air from flowing from the duct 21 back towards the valve 9.

Also the valve 23 is now opened so that, since a certain pressure drop will occur across the throttle 17, a part of the flow from the duct 16 can flow towards the duct 10, which air will flow, then, towards the end 8 of the chamber 7. This cold air now flows oppositely to the preceding reactivation flow sense through the hot chamber 7, so that cooling will take place in countercurrent. The other end 6 is still connected to the duct 4, but the latter is closed from the duct 1 by means of the valve 3. The duct 4 is, however, connected to a branch duct 24 leading towards an auxiliary cooler 25 connected to a water separator 26. The outlet of the separator 26 is connected to a duct 27 with a valve 28 which connects to a part of the duct 16 beyond the throttle 17.

If now the valve 28 is open, the cooling air from the chamber 7 can flow off through the cooler 25 in which its temperature is lowered again and the adsorbed moisture is separated for a substantial part. Subsequently, this air flows, together with the air from the duct 16, towards the chamber 19 which continues to act as a drying chamber. If, at the end of the cooling period, adsorbent in chamber 19 is still sufficiently active, the valves 23 and 28 are closed so that all the air will now directly flow through the chamber 19, whereas the chamber 7 remains outside the flow and is ready for the next drying operation. In order to switch over to the chamber 7, the valve 3 is opened, the valve 22 is closed, and both valves 5 and 9 are switched over. Thereafter the preceding operation is repeated with the chamber 7 acting as a drying chamber, and the adsorbent chamber 19 is reactivated. It is, of course, also possible to switch over immediately at the end of the cooling of the reactivated chamber.

Alternatively, the branch duct 24 can be provided with a valve only and open into the ambient air. The construction shown is, however, more favourable since, then, always the same amount of air will be delivered at the discharge duct 2.

If the air supplied through the duct 1 is very hot, it may be preferable to divert a part thereof directly towards the cooler 13 from the outset, the valve 22 then being slightly closed accordingly in order to obtain the required distribution ratio.

Although the device has been described with reference to its use for drying compressed air, it may also be generally used for removing vapour from other hot gases having a sufficient pressure to enable it to be forced through the different portions of the device; it will, of course, be apparent that the adsorbent should be adapted to the vapour to be remove.

Furthermore several parts of the device may, of course, be modified. For instance the valves 3 and 22 may be replaced by a three-way switching valve, and several valves which are to be actuated simultaneously may be interconnected in a suitable manner.

The switching valves 5 and 9 may be replaced by a correspondingly operating assembly of separate and, if necessary, mutually coupled single valves. Actuation of the various valves and switching valves may be effected automatically under the control of a timing switch or suitable sensors for the condition of the gas to be treated.

The flow senses in the chambers 7 and 19 are only given by way of example, and may be reversed if required.

The method and device described permit substantial energy savings to be obtained in the removal of vapour from a hot gas, which is used to reactivate the adsorbent.

WHAT WE CLAIM IS: 1. A method for removing a vapour from a feed gas having a higher temperature than the ambient air, said method comprising feeding the hot gas through one of two chambers provided with an adsorbent for the vapour, said one chamber having been used previously to adsorb vapour from the gas whereby the hot feed gas tends to reactivate the adsorbent in the said one chamber, cooling in a first cooler, the hot gas down-stream of the said one chamber whereby a substantial part of the vapour in the hot feed gas condenses out, feeding the cooled feed gas through the other of said chambers whereby the remaining vapour in the feed gas is removed, and after a period of time, reversing the effective positions of the chambers in the feed gas flow path whereby the hot feed gas is first fed through the said other chamber to reactivate same and the cooled feed gas is fed through the said one chamber for removal of remaining vapour from the feed gas, the time during which each respective chamber is reactivated being less than the time during which the other chamber is used for vapour adsorption from the cooled feed gas, and at least during a part of the time remaining between the end of the reactivation and the reversal of the effective positions of the chambers, hot feed gas being fed to the cooler without first passing through the reactivated chamber and a part of the cooled feed gas flow being fed through the reactivated chamber to cool same prior to using the reactivated chamber for adsorption after the reversal of the effective positions of the chambers.

2. A method according to claim 1, wherein the flow direction of the hot gas flow through the chamber being reactivated is opposite to the flow direction of the cooled feed gas flow through that chamber when the chamber is being used for vapour adsorption.

3. A method according to claim 1 or claim 2, wherein the flow direction of the hot feed gas flow through the chamber being reactivated is opposite to the flow direction of the cooled feed gas flowing through that chamber to cool same after reactivation and prior to reversal of the effective positions of the chambers.

4. A method according to any one of claims 1 to 3, wherein the feed gas flow used for cooling the reactivated chamber, is cooled in a second cooler after leaving the reactivated chamber and is then passed through the chamber used for adsorption, together with the remainder of the gas cooled in the first cooler.

5. A device for carrying out the method claimed in claim 1, comprising two chambers each - provided with an adsorbent, a feed duct for feeding the hot feed gas, first switching means for directing the hot feed gas, selectively, through one or other of the chambers to reactivate that chamber, a first cooler, second switching means for directing the hot feed gas from the chamber being reactivated to the cooler and for directing cooled feed gas from the cooler to the other of the two chambers for removal of the remaining vapour from the cooled feed gas, first valve means selectively operable to connect the feed duct with the first cooler by by-passing the chamber which has been activated, and second valve means selectively operable to permit feeding of a part of the feed gas cooled in the cooler to the chamber which has been reactivated whereby to cool same prior to operation of the switching means to direct the hot feed gas to the reactivated chamber.

6. A device according to claim 5, wherein the arrangement is such that the flow direction of the hot feed gas flow through the chamber being reactivated is opposite to the flow direction of the cooled feed gas through that chamber when the chamber is being used for vapour adsorption.

7. A device according to claim 5 or claim 6, wherein the arrangement is such that the flow direction of the hot feed gas through the chamber being reactivated is opposite to the flow direction of the cooled feed gas flowing through the chamber to cool same after reactivation and prior to operation of the switching means to direct the hot feed gas to the reactivated chamber.

8. A device according to any one of claims 5 to 7, wherein the second valve means controls the flow of the said part of the cooled feed gas flow through a branch duct of a cooled gas flow duct which leads from the first cooler to the said other chamber for removal of the remaining vapour, said cooled gas flow duct including throttle means downstream of the point at which the branch duct branches from the cooled feed gas flow duct.

9. A device according to any one of claims 5 to 8, further comprising means for feeding the cooled feed gas used for cooling the reactivated chamber to a second cooler and thence to the said chamber which is being used for removal of the vapour.

10. A method according to claim 1 sub

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. of separate and, if necessary, mutually coupled single valves. Actuation of the various valves and switching valves may be effected automatically under the control of a timing switch or suitable sensors for the condition of the gas to be treated. The flow senses in the chambers 7 and 19 are only given by way of example, and may be reversed if required. The method and device described permit substantial energy savings to be obtained in the removal of vapour from a hot gas, which is used to reactivate the adsorbent. WHAT WE CLAIM IS:

1. A method for removing a vapour from a feed gas having a higher temperature than the ambient air, said method comprising feeding the hot gas through one of two chambers provided with an adsorbent for the vapour, said one chamber having been used previously to adsorb vapour from the gas whereby the hot feed gas tends to reactivate the adsorbent in the said one chamber, cooling in a first cooler, the hot gas down-stream of the said one chamber whereby a substantial part of the vapour in the hot feed gas condenses out, feeding the cooled feed gas through the other of said chambers whereby the remaining vapour in the feed gas is removed, and after a period of time, reversing the effective positions of the chambers in the feed gas flow path whereby the hot feed gas is first fed through the said other chamber to reactivate same and the cooled feed gas is fed through the said one chamber for removal of remaining vapour from the feed gas, the time during which each respective chamber is reactivated being less than the time during which the other chamber is used for vapour adsorption from the cooled feed gas, and at least during a part of the time remaining between the end of the reactivation and the reversal of the effective positions of the chambers, hot feed gas being fed to the cooler without first passing through the reactivated chamber and a part of the cooled feed gas flow being fed through the reactivated chamber to cool same prior to using the reactivated chamber for adsorption after the reversal of the effective positions of the chambers.

10. A method according to claim 1 sub

stantially as hereinbefore described with reference to the accompanying diagrammatic drawings.

11. A device according to claim 5 substantially as hereinbefore described with reference to the accompanying diagrammatic drawings.