GB2199513A - Device for continuous drying of a gas - Google Patents

Abstract

A device for continuous drying of a gas, for instance air, which is compressed beforehand to a determined pressure comprises two drying containers which each contain a moisture absorbing material, a common feed line from the compressor which splits in each case into a branch line running to a container, whereby each branch line is provided with a controllable stop valve and a controllable bleed valve, wherein the bleed and stop valves are accommodated in a single housing, whereby valve operation takes place by means of a single ON-OFF connection.

Description

DEVICE FOR CONTINUOUS DRYING OF A GAS The invention relates to a device for continuous drying of a gas, for instance air, which is compressed beforehand to a determined pressure, the device consisting substantially of two drying containers which each contain a moisture absorbing material, a common feed line from the compressor which splits in each case into a branch line running to a container, whereby each branch line is provided with a controllable stop valve and a controllable bleed valve.

When placing surrounding air and also other gases under pressure it is desirable to dry the gases after compression, because, particulariy when there is fall in temperature and lowering of pressure, condensation can occur in the pressure lines, which can be disadvantageous for the processes performed with that compressed gas.

Moreover, excessive corrosion can occur. In the known devices this drying is carried out continuously by alternatingly setting into operation each of two containers so that the one branch line to the one container has to be closed off each time and.that container has to be vented, while the feed lines to the other container is opened and the bleed opening closed.

This requires four comparatively expensive valves which have to be controlled separately by a relatively complicated control unit. This makes the installation not only expensive but also vulnerable, especially in those regions where few or no skilled personnel are available for maintenance work.

The invention has for its object to overcome the above-mentioned drawback and provides to this end a device which is distinguished in that the bleed and stop valves are accommodated in a single housing, whereby valve operation is carried out by means of a single ON-OFF switch.

As a result of this single valve housing the quite complicated control system is reduced to a simple on-off control system, whereby the maintenance problem is reduced to the minimum.

In the preferred embodiment both stop valves take the form of a single slidable valve body.

In a further development the bleed valve bodies are each accommodated co-axially for sliding in the housing relative to the slide piece.

In order to make the sequence of control of the valves take place correctly the diameter of the bleed valve is smaller than that of the stop valve.

Finally, the ON-OFF control of the valves is preferably pneumatic whereby a control channel in the housing leads to a chamber formed between bleed valve and stop valve.

In order to be able to automatically regenerate the moisture absorbing material a connecting line with throttle opening is arranged between the containers or between the heat exchangers of both containers.

The invention will be further elucidated in the figure description hereinafter with reference to an embodiment.

In the drawing: Fig. la and lb each show a schematic disposition of the device according to the invention, Fig. 2, 3 and 4 each show a lengthwise section of a valve housing according to the invention with valves arranged therein in various operating positions.

The device shown in Fig. la consists of a first drying container 1 and a second drying container 2, in which moisture absorbent material is assumed to be located in random manner. Each container is in addition provided with a heat exchanger 3. The containers are supplied by means of a feed line 4 which runs from a filter 5. The filter is connected to a compressor (not shown) via a connecting piece 6.

Feed line 4 splits into two branch lines 7, 8 which are both provided with a stop valve 9 and 10 respectively and a bleed valve 11 and 12 respectively. The heat exchangers 3 are joined to each other by a connecting line 13 with throttle opening 14. The underside of drying containers 1 and 2 are connected to a discharge system consisting of discharge lines 15 with non-return valves 16, this line leading to a filter 17. The dried and compressed air is discharged into a storage container (not shown) connected to connecting piece 18.

Continuous drying by the above-mentioned device is performed as follows: As a result of opening of stop valve 9 and bleed valve 10 and the closing of stop valve 9 and bleed valve 12 gas will flow as according to the arrows via branch line 8 to the right-hand container 2.

Moisture is removed from this gas by the moisture absorbing material, whereby it will also give up heat, which results in cooler and dryer gas being discharged via lines 15 to filter 17 and connecting piece 18. The treated gas is, as already stated, compressed beforehand by a compressor connected to connecting piece 6 and prefiltered in filter 5.

During this drying treatment the heat exchanger 3 will be heated up as a consequence of the hot gas and the heat will flow via connecting line 13 and throttle opening 14 to the heat exchanger 3 in container 1 and escape from there via bleed valve 11. The reason for this is as follows.

When the moisture absorbing material in container 2 has reached a determined moisture absorption capacity, the gas flow has to be reversed and stoevalve 10 and bleed valve 11 will be closed, while stop valve 9 and bleed valve 12 are both opened. The gas flow will as a result be guided to container 1 and will be dried and cooled as in the manner described above with reference to container 2.

The relatively cold gas flows via heat exchanger 3 and connecting line 13 and throttle opening 14 to the hot heat exchanger in container 2, whereby the already cooled and dry gas from container 1 is heated up once more and is capable of carrying much moisture out of the moisture absorbent material and discharging it via bleed valve 12.

The absorbent material in container 2 is in this way regenerated.

As soon as the moisture absorbent material in container 1 has reached the maximum moisture take-up capacity, the gas flow is once again reversed.

Fig. lb shows an embodiment also provided with two drying containers 1, 2, whereby the same regulating and other auxiliary equipment is used, these being designated with the same reference numerals. The difference lies in the omission of heat exchanger 3 with the associated connecting line 13 with throttle opening 14. These latter are replaced by line 13' with throttle opening 14' which is connected to each of the lines 15 from each container 1,2. In this embodiment a small quantity of dried air is used to regenerate the moisture absorbing material in the container currently not in use in the drying process.

In the above described manner a continuous drying process for gases is achieved.

The invention relates to a regulating valve indicated with the broken line 19 for guiding and controlling the gas flow.

This valve, which is shown in the Figs. 2 - 4 comprises the four previously mentioned valves 9 - 12.

The valve consists of a valve housing 20 that is formed in the centre with an inlet port 21 onto which connects the feed line 4. Shown above in schematic form is the filter 5.

Housing 20 is additionally formed with outlet ports 22, onto which connect the respective branch lines 7 and 8.

Accommodated in housing 20 as a single slidable body 23 are both the stop valves 9 and 10. The closing body consists of a central stem 24 onto which are mounted valve discs 25,26. Each valve disc co-operates with the respective valve seats 27 and 28 of valve housing 20.

Arranged on the sides of the valve discs facing away from each other is a collecting chamber 29 which leads via channels 30 to a collecting chamber 31 provided with the previously mentioned outlet ports 22.

The valve body 23 is formed on the side facing away from the stem 24 with a plunger 32 attached onto the central pin of stem 24, this plunger having a flattened end portion. Accommodated in this flattened end portion is an O-ring 33. Located around the flattened end portion for sliding in housing 20 is a piston 34 provided with O-rings along the peripheral casing and formed with a bore 35 in order to be able to accommodate the flattened end portion of plunger 32. The piston is provided with a control channel 36 which connects the bore 35 to a circular channel 37 in housing 20. This circular channel communicates with a control port 38.

Piston 34 is further formed with a valve disc 39 which co-operates with a port 40 which leads to a chamber 41 provided with a port 42 which is connected to a line forming the venting.

It is noted that the above described valve housing with valves and moving parts arranged therein takes a mirror symmetrical form relative to the central transverse plane.

The operation of the above described assembled valve is as follows.

Starting from the position in Fig. 2, wherebey the slidable valve body 23 lies in the furthest left-hand position, valve disc 26 will be lifted from valve seat 28, which will result in air for drying being able to flow via channels 30 to chambere 31 and via port 22 to the righthand container 2. The left-hand container 1 communicates via conduit 7 with port 22 and chamber 31, as a result of which the gas to be vented can flow to channels 30 which, because of the right-hand position of piston 34, come into communication with port 40 and chamber 41 and venting port 42. In this way container 1 can be vented. The process pressure holds valve disc 25 firmly on valve seat 27 so that no gas can leak away via the left-hand part of valve housing 20.

When port 38 is actuated by means of actuating air, which can be carried out by a simple on-off control, the piston 34 will be moved to the left, see fig. 3 and port 40 will close. The container 1 is hereby closed off and can no longer be vented. As a result the pressure in container 1 will rise via connecting line 13, whereby the extent of the rise depends on the extent of choking via throttle opening 14. After the predetermined time, process pressure will prevail in both containers 1 and 2, and thus in lines 7, 8 and in both the chambers 29 on either side of valve discs 25, 26. The control pressure on ports 38 will as a result be capable of shifting the valve body 23 to the right, thereby assuming that the control pressure on the right-hand port 38 of valve housing 20 is discontinued via the same on-off connection.

As a result of the shifting of valve body 23 to the right, the right-hand part of valve housing 20 is separated from feed line 4 and the left-hand part will be brought into connection with it. The gas for drying will therefore flow via the left part via line 7 to container 1 and undergo a drying treatment. The overpressure in line 8 will in the meantime have shifted the right-hand piston 34 to the left, resulting in valve 39 being lifted from port 40 so that container 2 is connected onto venting port 42 and can therefore be vented.

By turning the on-off switch the gas flow can then be reversed once again without further operations being necessary.

The invention is not limited to the above-described embodiment.

Claims (6)

CLAIMS:

1. Device for continuous drying of a gas, for instance air, which is compressed beforehand to a determined pressure, said device comprising two drying containers which each contain a moisture absorbing material, a common feed line from the compressor which splits in each case into a branch line running to a container, whereby each branch line is provided with a controllable stop valve and a controllable bleed valve, wherein the bleed and stop valves are accommodated in a single housing, whereby valve operation takes place by means of a single ON-OFF connection.

2. Device as claimed in clai#m 1, wherein both stop valves are formed as a single slidable valve body.

3. Device as claimed in claim 1 or 2, wherein the bleed valve bodies are each accommodated co-axially for sliding in the housing relative to the slide piece.

4. Device as claimed in any one of claims 1 to 3 wherein the ON-OFF control of the valves is pneumatic, whereby a control channel in the housing leads to a chamber formed between bleed valve and stop valve.

5. Device as claimed in any one of claims 1 to 4, wherein each drying container is provided with a heat exchanger.

6. Device as claimed in claim 5 wherein a connecting line with a throttle opening is arranged between the heat exchangers of both containers.