IE43525B1 - Apparatus for cleaning and/or cooling a gas flow - Google Patents

Abstract

1521226 Gas washer V J JARVENPAA 11 Aug 1976 [18 Aug 1975] 33411/76 Heading B1R A gas washer comprises a tubular body having an entry part 10 for gas 11 to be washed or cooled, a pipe 13 for introducing wash liquid, an end wall with an aperture 29 therein, an internal radial blower 15 for separating liquid drops from the gas flow, an external radial blower 19 outside the body and coacting therewith via a duct 18 and distributor vanes 14 for dispersing liquid from tube 13, which liquid then flows down the walls of entry part 10, making contact with the gas, the gas then being dewatered by blower 15 and sucked through duct 18 by blower 19.

Description

The present invention concerns apparatus for cleaning a gas flow by removing gaseous and/or solid impurities present in the flow and/or for cooling the gas flow, in which apparatus the gas flow is brought into contact with a washing liquid.

It is well known that gas flows frequently contain impurities in the form of gaseous contaminants as well as of solid particles, which have to be removed before the fluid flow is discharged or reused. In practice the situation is also often encountered in which a gas flow contains so much solid components that it is advisable to remove them before the gas enters a washer.

There are numerous wet washer designs for gas flows, whereof the commonly employed so-called beds may be mentioned, through which the gas flow has to pass either so that the washing liquid enters as a counterflow or so that the washing liquid is jetted along with the gas flow.

Such designs are considered rather good, but the drawbacks are clogging of the filler bed, and structures requiring much space. 2.

Commonly used are also the so-called diffuser washers, wherein by reducing the width of the flow tube or duct the gas flow is accelerated to a high velocity and at the same time the washing liquid is fed into the gas flow, whereby good contact of the gas flow with the washing liquid is obtained. Such designs require large amounts of power; in addition they are expensive as regards the apparatus costs.

So-called S-waves are also used as wet washers, wherein the washing liquid and the gas flow both enter an S-shaped tube passage, whereby the gas and the washing liquid are contacted with each other. One of the embodiments of this type is such that therein the gas flow to be purified is brought into contact with a fcaming washing liquid and the gas has to pass through a foam bed, whereupon follows drop separation which is as complete as possible.

One step in very wet washer is the separation of droplets from the gas flow because in connection with the washing droplets are invariably formed, which have to be removed from the gas flow. The number of such droplets formed is naturally greater the more complete the contact of the gas and the washing liquid has been. On the other hand, of course, a large number of droplets is desirable since the impurities present in the gas flow are expressly bound to these droplets. The drop separator is therefore connected after the wet washer at an appropriate point, usually before the blower. In the capacity of drop separators one has employed various kinds of traps, grilles which rapidly change the flow, or certain kinds of groove designs. Filter mats are also used as droplet separators.

All these kinds of designs have the drawback that the liquid droplets may clog the drop separator, which in its turn causes escape of the impurities or at least insufficient droplet separation. It is also known in prior art 3. 135 Ρ. 5 to use drop separators wherein the gas flow becomes so slow that the droplets are separated e.g. on the walls of the column. Cyclone separators have also been used for droplet separation. All above-mentioned washerdroplet separator designs have large dimensions; on the other hand they constitute one separate problem solution as regards the washer and a second separate solution with reference to the droplet separator.

The present invention provides apparatus wherein a gas flow is brought into contact with a washing liquid for cleaning and/or cooling the gas flow, comprising tubular body for receiving the gas flow and means for placing the gas in contact with the washing liquid in the interior of the tubular body, the tubular body having an inlet through which the gas flow enters and an end wall spaced from the inlet and formed with an aperture, an internal radial blower situated in the tubular body adjacent the said end wall for separating droplets from the wetted gas flow in the tubular body, an external radial blower situated outside the tubular body adjacent the end wall the external blower being coaxial with and having a diameter greater than that of the internal blower, both blowers having central suction regions, the common axis of both blowers being substantially perpendicular to the end wall, a connecting duct passing through the aperture in the end wall and communicating fluid-tightly with the said central suction regions thereof, so that gas from which droplets have been removed by the internal blower flows from it through the connecting duct to the external blower to be radially discharged thereby.

The apparatus of the invention is appropriate for mounting in a cyclone, in which case the gas entering the cyclone is mainly purified before it comes into contact with the washing liquid. A preferred design, wherein the smaller diameter blower operating as a drop separator 4. and the larger diameter blower producing the gas flow are combined as a unit rotating on one shaft, serves above all to ensure that the droplet separation is complete and that the gas has been dried of its contents of washing liquid before it enters the larger diameter blower. The apparatus can be of small size and yet have the ability to handle even very large gas quantities if need be.

The invention is described in detail below, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic elevational view of apparatus for cleaning and/or cooling a gas flow; Figure 2 shows a section along the line II-II in Figure 1; Figure 3 shows a section along the line III-III in Figure 1; Figure 4 shows a section along the line IV-IV in Figure 1; Figure 5 shows a section along the line V-V in Figure 1; Figure 6 shows a section along the line VI-VI in Figure 1.

The gas flow 11 enters from below a tubular body or entry part 10, whose lower end is open and which has an aperture 29 in its closed upper end, (The entry part 10 is most appropriately the central tube of a cyclone separator, but generally considered it may be any tubular body throttled by an aperture at one end.) The washing liquid is conducted into the entry part 10 by a flow pipe 13, the discharge aperture of which lies close to a set of distributor vanes 14. . 53S The distributor vanes 14 are fixed to an end plate 16 closing the upstream side of a blower drop separator 15. The plate 16 in its turn is attached to the lower edge of the vanes 15a of the blower drop separator 15, and the upper edges of the vanes 15a are affixed to a plate ring 17. The central aperture of the plate ring 17 communicates with a connecting duct or tube 18, whose lower end is fixed to the plate ring 17. The upper end of the connecting tube 18 is affixed to a plate ring 20 attached to the lower edges of the vanes 19a of a blower 19. Thus the upper end of the connecting tube 18 communicates with the blower 19.

The upper edges of the vanes 19a of the blower 19 are affixed to a rear plate 21 of the blower 19.

The blower 19 has a diameter larger than that of the blower drop separator 15. The blower 19 is disposed outside the aperture 29 in the closed end of the entry part 10, whereas the drop separator 15 is placed inside the entry part 10 and preferably close to the aperture 29.

The tube 18 connecting the blower 19 and the drop separator 15 has a diameter slightly smaller than that of the aperture 29 and is fitted to pass tightly through the aperture 29.

The above-described structure, wherein the drop separator 15 and the blower 19 consist of respective blower impellers whose suction sides face each other, the connecting tube 18 being the common suction tube for the drop separator 15 and the blower 19, has in its entirety been combined on one rotating shaft 22, which is driven by a motor 23 via a belt transmission 24, 25, 26. (It is understood that the rotation of the shaft 22 may be accomplished by other transmission mechanisms known in themselves.) The bearing arrangements of the shaft 22 are indicated by reference numerals 27 and 28. 6. 43535 The gas flow 11 has to pass at first from below into the tubular entry part 10 and then through the vanes 15a of the blower drop separator 15 into the connecting tube 18 and through the connecting tube 18 into the impeller of the blower 19 and out through the vanes 19a of the blower 19. The outflowing gas has been indicated by 12 in Figure 1. The gas flow 11 acquires a flow direction from the blower drop separator 15 towards the blower 19 and out through the blower 19 as a result of the fact that the blower 19 has a diameter larger than that of the drop separator 15. The washing liquid passes along the flow pipe 13 to the distributor vanes 14, whereby the rotation caused by the shaft 22 flings the washing liquid from the vanes 14 towards the walls of the tubular entry part 10. The gas flow 11 is hereby forced to pass through a powerful washing liquid spray, and it is thoroughly wetted.

Since the washing liquid runs down along the wall of the entry part 10 and falls from it as drops of liquid, the entering gas flow 11 also comes into contact with the washing liquid owing to this cause, whereby the wetting of the gas flow 11 is increased.

The substantially completely wetted gas flow 11 subsequently enters the drop separator 15 and, at a normal rotation speed for a gas flow blower, the vanes 15a cause a centrifugal force acting on the liquid droplets of such a magnitude that it surpasses the atmospheric pressure several times over, and hereby the gaseous fluid flow 11 is purified of its liquid droplets up to the saturation limit. This saturation limit, in its turn, depends on the temperature and on the gas pressure of the washing liquid. It is thus understood that the vanes 15a of the drop separator 15 fling the liquid droplets outwardly onto the wall of the entry part 10, and the gas flow 12 leaving the vanes 19a of the blower 19 has not only been washed clean of impurities but has also been dried to be free of 7. washing liquid. All this has been accomplished by means of a rotating unit combined on one shaft 22. In addition there has been imparted to the gas flow 11 a sufficient flow velocity and differential pressure, which has been produced either before or after the washer in the pipe system.

Recovery of the washing liquid as it flows out from the entry part 10 may take place either in a way known in itself in prior art, or more advantageously in that the washing liquid flow pipe 13 and the distributor vanes 14 together by a suitable fitting design cause a suction effect, as in a centrifugal pump, by the aid of which the washing liquid is returned into a closed circulation after passing through settling cells (not depicted). This latter way enables a closed circulation of the washing liquid to be obtained without any separate pump designs, which also are often expensive.

The above embodiment is presented primarily to illustrate the principles of operation, and for each particular case the appropriate embodiment will be based on these principles. The apparatus according to the invention is appropriate, above all, in application to a cyclone separator, where the coarsest component of the fluid flow have already settled out from the gas flow prior to washing. But the apparatus of the invention is equally well mountable e.g. on top of evaporator columns.

There are also numerous modifications which can be made within the scope of the invention as defined in the appended claims; for instance, the mouth of the washing liquid flow pipe 13 may constitute a spray nozzle, which thus is equivalent to the distributor vanes 14. A nozzle of this kind has to be concentric with the shaft 22 and the rotating blower drop separator 15. However, a design of this kind does not achieve a sufficiently efficient liquid spray, caused by the distributor vanes 14, up to the wall of the tubular entry part 10. 8.

The diameter of the impeller vanes in the drop separator, compared with that of the blower vanes, may be varied as required and as desired in each instance. The diameter of the distributor vanes may vary in order to achieve desired results. The design may also be applied in view of cooling the liquid flowing in the flow pipe, in which case the consumption of cooled or cooling liquid will be minimal as a result of the efficient drop separation.

Claims (7)

1. Apparatus wherein a gas flow is brought into contact with a washing liquid for cleaning and/or cooling the gas flow, comprising tubular body for receiving the gas flow and means for placing the gas in contact with the washing liquid in the interior of the tubular body, the tubular body having an inlet through which the gas flow enters and an end wall spaced from the inlet and formed with an aperture, an internal radial blower situated in the tubular body adjacent the said end wall for separating droplets from the wetted gas flow in the tubular body, an external radial blower situated outside the tubular body adjacent the end wall, the external blower being coaxial with and having a diameter greater than that of the internal blower, both blowers having central suction regions, the common axis of both blowers being substantially perpendicular to the end wall, a connecting duct passing through the aperture in the end wall and communicating f1uid-tightly with the said central suction regions thereof, so that gas from which droplets have been removed by the internal blower flows from it through the connecting duct to the external blower to be radially discharged thereby.

2. Apparatus as claimed in claim 1, wherein the internal blower has an end plate remote from the connecting duct, a washing liquid flow pipe leading into the tubular body and terminating adjacent to the end plate for discharging washing liquid against the end plate. 9. 43523

3. Apparatus as claimed in claim 2, wherein the washing liquid flow pipe is provided with a spray nozzle.

4. Apparatus as claimed in claim 2, wherein a plurality of distributor vanes are fixed to and project from the end plate for distributing washing liquid into the interior of the tubular body.

5. Apparatus as claimed in claim 4, wherein the blowers, the connecting duct, and the distributor vanes all are fixed to each other to form a single unit having a common axis, a single shaft being fixed to the unit and extending along the common axis thereof, coaxially therewith, and drive means being operatively connected to the shaft so as to rotate the unit about its common axis.

6. Apparatus as claimed in claim 4, wherein the washing liquid flow pipe and the distributor vanes cooperate in the manner of a centrifugal pump, for sucking the washing liquid through the said pipe towards the end plate, means being provided for forming a path along which washing liquid flows from the tubular body back to the flow pipe under the effect of the suction.

7. Apparatus for cleaning and/or cooling a gas flow, substantially as described herein with reference to, and as shown in, the accompanying drawings.