Gas separation: processes – With control responsive to sensed condition – Gas flow rate sensed
Reexamination Certificate
1999-10-05
2001-10-02
Spitzer, Robert H. (Department: 1724)
Gas separation: processes
With control responsive to sensed condition
Gas flow rate sensed
C095S052000, C096S004000, C096S008000
Reexamination Certificate
active
06296683
ABSTRACT:
The invention relates to a dryer for compressed air, fitted with a filter bowl, a) presenting an inlet for damp compressed air, an outlet for dried compressed air, an inlet for scavenging air and an outlet for scavenging air, and b) in which is accommodated a membrane filter, fitted preferably with a bundle of hollow fibre membranes, on one side of said filter is stroked by the compressed air flow, while the scavenging air flows on the other side, particularly in the direction opposite to that of the compressed air. The filter bowl lets selectively water steam flow through and comprises a feeder pipe through which the compressed air, which is dried since it comes from the outlet, is introduced in a depressed state into the scavenging air inlet.
Such a dryer for compressed air is known from the U.S. printed patent specification 5,002,590. In the case of using compressed air, for example in industrial engineering or in medicine technology, the humidity in the network and at the places of consumption is a quality problem. Therefore, an important task is always the drying of the compressed air.
For this membrane filters are used, which selectively let water steam flow through. In the filter bowl, a bundle of highly selective hollow fibre membranes is fitted, through which compressed air flows. The damp compressed air is preferably filtered, so that dirt particles, oil mist and condensate, still present in the damp compressed air, are kept back, thus the hollow fibre membranes do not become clogged. Through the hollow fibre membranes, water steam diffuses to the outside. At the outlet for dried compressed air, a small partial flow of compressed air is branched off and used after the expansion as scavenging air. The scavenging air is led in counterflow to the compressed air via the outside of the hollow fibres. On account of the difference in the water steam concentration, a continuous conveyance of the water molecules is achieved from the compressed air into the scavenging air.
This procedure occurs continuously. The scavenging air continuously dries the entering damp compressed air. Only water molecules are able to penetrate the membranes of the hollow fibres. The composition of the dried compressed air remains unchanged. As result one has clean, dry compressed air.
Unfavourably, however, is the constant need of scavenging air. The scavenging air is, in accordance with the state of the art, branched off immediately from the compressed air; a part of the compressed air is thus constantly lost for the scavenging. Particularly the energy, put into the scavenging air, needed for the compression, is lost without purpose, because the branched off partial flow of the compressed air is expanded before it is fed into the scavenging air inlet.
This is where the invention starts. It is the problem of the invention to state a dryer for compressed air for the above mentioned kind, where the compressed air within the dryer is used more economically and where a larger part of the compressed air is available for a device, operated by compressed air.
Departing from the dryer of the above-mentioned kind, this problem is solved thus, that the feeder pipe is designed with closing means, the closed position of which depends on the consumption of compressed air.
According to the state of the art, scavenging air flows continuously through the filter bowl, irrespective of the case, whether or not compressed air is actually taken from the compressed air outlet or from the useful air outlet. In this way a noticeable part of the compressed air, made available, is lost. This invention proposes savings for this.
The invention follows essentially two paths: On the one hand it proposes to control the branched off compressed air flow, which is fed into the scavenging air inlet in such a way, that scavenging air is actually only then available, when compressed air is extracted from a device, operated by compressed air. For this the scavenging air flow is switched off in those rest periods, in which the device, operated by compressed air, is not used or it is at least regulated down in so far, that clearly less compressed air is used for the dehumidification. However, a control, depending on the extracted flow of compressed air is also possible by making more or less scavenging air available, when more or less compressed air is extracted for a series connected device, operated by compressed air.
On the other hand, this invention proposes to only take scavenging air behind a device, operated by compressed air, this means at its air outlet and to feed the scavenging air from there to the scavenging air inlet, as the case may be through the interposition of an air flow distributor and/or a fan.
In a particularly preferred embodiment, the closing means have its own drive, especially an electric, an electromagnetic, a hydraulic or pneumatic drive. Preferably the closing means are embodied as solenoid valve or as a device, operated by compressed air. On account of its own drive the closing means can be controlled, for example via an operating connection of a device, operated by compressed air, via a flow feeler fitted at the outlet on the way to a consumer or something of the kind.
As particular preferred it has proved to extract the scavenging air at the air outlet of a device, operated by compressed air. This device and the appropriate procedure have the advantage that no compressed air is lost for the scavenging, on the contrary, the complete compressed air, present at the outlet, is used for at least one device, operated by compressed air. Only behind the device, operated by compressed air, the scavenging air is actually extracted, especially the feeder pipe branches off, which supplies the scavenging air inlet with air. In the case of this embodiment the main pipe for the compressed air, which, according to the state of the art, supplies the device, operated with compressed air, and the feeder pipe run initially parallel and, as the case may be, only separate behind the device, operated by compressed air.
The last mentioned procedure complies with a serial arrangement of consumers, i.e. it complies with the device, operated by compressed air and with the scavenging air inlet as well as with the scavenging air outlet. According to the state of the art, in the contrary, a parallel arrangement is known, i.e. the splitting up of the compressed air flow immediately behind the outlet for dried compressed air and the supply of a main flow through a main pipe to the consumer as well as a branched off flow as scavenging air into the scavenging air inlet.
The series connection presumes, in accordance with the invention, that the consumer, operated by compressed air, does not pollute the compressed air itself, especially that it does not mix it with water. In addition, other impurities, such as for example oil or pollutants, would be harmful. Therefore it must be seen to, that the consumer, operated by compressed air, through which the compressed air flows before it finds use as scavenging air, is sealed accordingly and is carried out cleanly.
Although, in the case of the described serial arrangement, it is on principle possible to feed the complete air flow, which has flowed through the consumer, operated by compressed air, into the scavenging air inlet, a splitting of this air flow is preferred. For this a volume distributor is planned, which guides a partial flow to the scavenging air inlet, whilst another partial flow is discharged into the surroundings. This volume control can be controlled in such a way, that, depending on the compressed air consumption of the consumer, operated by compressed air, a more or less large share of the scavenging air is made available for the scavenging air inlet.
In the case of the series connection, in accordance with the invention in hand, the loss of pressure in the filter bowl and between scavenging air inlet and scavenging air outlet can unfavourably become apparent. In order to compensate for it, a number of ways are possible. First of all the scavenging air inlet, the cross-section
BEKO Technologies GmbH
Cornaby K. S.
Spitzer Robert H.
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