US2675090A - Apparatus for cleaning hot gases and blower therefor - Google Patents

Description

April 13, 1954. G. F. LANDGRAF APPARATUS FOR CLEANING HOT GASES AND BLOWER THEREFOR 2 Sheets-Sheet 1 Filed June 15. 1951 INVENTOR. George E Lana'graf h nd.

Mo HA +fuw- H/s ATTORNE Y5 April 13, 1954 e. F. LANDGRAF APPARATUS FOR CLEANING HOT GASES AND BLOWER THEREFOR 2 Sheets-Sheet 2 Filed June 15, 1951 INVENTOR George ELandgraf HIS ATTORNEYS BY mflnch a/AM mm 6m Patented Apr. 13, 1954 APPARATUS FOR CLEANING HOT GASES AND BLOWER THEREFOR George F. Landgraf, Pittsburgh, Pa", assignor to Trion, 1110., McKees Rocks, 2a., a. corporation of Pennsylvania Application June 15, 1951, Serial No. 231,832

3 Claims.

There is an increasing demand by the public and by public authorities that gases produced during manufacturing processes be cleaned prior to discharge into the air of various inert solid materials which are carried by those gases, for example, ashes, soot, dust, chemical lay-products, etc. Heretofore industrial gases have been cleaned by use of electrostatic precipitators which, broadly speaking, are of two types. In one type a series of plates are spaced parallel to each other across a passageway for the gases, the plates extending in the direction of gas flow through the passageway. Wires are suspended in the passageway between the plates, the wires extending parallel to each other and to the plates, and at right angles to the direction of gas flow through the device. The wires and plates are charged opposite to each other or the plates are grounded and the wires are charged so that there is a very high potential difference between the plates and the wires (in the order of '70 or 100 kilovolts). When the gases flow between the wires and the plates, the solid particles in the gases are ionized by the corona discharge from the wires so that the particles acquire a charge the same as that on the wire. The particles thus charged are attracted to the plates to which they cling. At intervals the particles which are picked up by the plates are removed from the plates by vibrating the plates.

The second type of electrostatic 'precipitator which has been used for cleaning gases in industrial processes and for'cleaning air in homes) comprises two units, an ionizing unit and a collecting unit through both of which the gases or air to be cleaned pass. The ionizing unit comprises a series of electrodes spaced across the passageway for the gas or air. These electrodes are oppositely charged to a high potential difference. They are not, however, charged to the values employed in the precipitator first described. The ionizing gas or air then passes to a collecting unit which comprises 'a series of plates spaced parallel to each other across the air or gas passageway. The collecting plates extend in the direction of the gas 'flowand are alternately charged to apotential difference approximately one-half that used in the ionizing unit. As the gas or air flows from the ionizing unit into thecollecting unit, the ionizing particles in the gas or air are attracted to the collecting plates and adhere thereto. At intervals the plates are cleaned by washing or "violently sh'aking them.

While both forms of electrostatic filters as described above are quiteeificient'in cleaning air or gas, it has heretofore been possible only to use them for industrial gases which were at a relatively low temperature. It has not been possible to clean hot gases and by hot I mean gases which are in the neighborhood of 450 F. or above. Hot gases heat the plates of the precipitators and cause them to buckle. Buckling changes the distance between the plates and seriously affects the electrostatic field which has been established between the plates and which is carefully adjusted relative to the distance between the plates. If the plates buckle under the influence of hot gases so that they are brought closer together the current will are over between the plates and destroy them. The higher temperatures also increase the problems of electrical insulation for the plates and electrodes. For example, porcelain becomes conductive at 450" F. Finally, the phenomenon of electrostatic precipitation is not fully understood where the temperatures involved are above 450 F.

I have invented simple effective means for cooling hot gases to a temperature where they can pass through an electrostatic filter without danger to the filter. My invention not only cools the gases but utilizes the heat energyof the gases to blow them through the cleaner and through the conduit through which they are passing. If desired, my cooling mechanism can be used without an electrostatic filter as a blower for forcing hot gases through a conduit. It, therefore, can be used to assist or to replace the induced draft fans now used on industrial furnaces. I have also found that my cooling means improves the operation of an electrostatic filter. Therefore, my cleaner which embodies anelectrostatic filter and a gas cooling mechanism not only success fully cleans hot gases but also operates more effioiently than electrostatic cleaners heretofore used on cool and dry gas.

In the accompanying drawings, I have illustrated a present preferredembodiment of my invention, in which- Figure l is a front view of my apparatus for cleaning hot gases;

Figure 2 is a side view along the lines LII-II of Figure 1;

Figure 3 is a partial front view'of my apparatus showing it in a different operative position from that shown in Figure l;

Figure 4 is a vertical longitudinal section of a portion of the apparatusshown in Figure 'l; and Figure 5 is a section alongthe lines V-V in Figure 4.

Referring to Figure *lymy apparatus comprises a conduit 6 which carries the hot gases from the place where they are generated to a chamber 1 above which is a second chamber 8 which houses an electrostatic cleaner or filter 9 (shown in dotted lines in Figure 1). The gases pass from the chamber 1 to the chamber 8 through an inlet throat H) which directs the gases through the filter 9. The gases pass from the filter 9into a chamber 8A from which they pass to a conduit 6A which leads to a stack (not shown) or to atmosphere.

The electrostatic filter 9 will not be described in detail because a conventional form of electrostatic air or gas filter can be used. The filter can comprise plates spaced from each other across a passageway with ionizing wires between them, or the filter can be a two-stage filter with separate ionizing and collecting units such as are shown in Penney Patents Nos. 2,129,783 and 2,255,677.

As shown in Figure 1, the conduit 6 has in advance of the air cleaner 9, a mechanism designated generally by the reference number N, which mechanism cools the hot gases in the conduit 6 before they reach the filter 9. Referring to Figure 4 where the mechanism is shown on a larger scale than in Figure 1, it comprises a helical coil of pipe l2 which is concentrically positioned in the conduit 6 by three bars |3. The end M of the coil |2 which is first contacted by the gases as they flow through the conduit is bent towards the axis of the coil and looped so that an extension I5 of the pipe extends along the axis of the coil |2 terminating beyond the,

opposite end of the coil with a nozzle It. The other end I] of the coil I2 is connected to a source of water (not shown), the flow of which into the coil l2 may be controlled by a valve I8. The cooling apparatus also comprises a Venturithroat I 9 which is positioned in the conduit 6 in relation to the nozzle It so that gas or steam ejected by the nozzle it will create a suction in the throat it which in turn will draw gas through the conduit 6 past the coil it.

The mechanism operates as follows: Valve I8 is opened to permit water to fiow through the coil l2. Hot gases in the conduit E5 strike the coil l2 and immediately turn the water in the coil into steam which flows out of nozzle l6 under high pressure as a powerful steam jet. In effect, the coil l2 acts as a flash boiler. The steam jet blowing through the Venturi throat l9 creates a vacuum in the throat and a consequent flow of hot gases through the conduit 5 past the coil l2 and into chamber 1. Obviously, the heat absorbed in turning the water into steam will reduce the temperature of the gases. The steam jet also humidifies the gases and this moisture in the gases improves the cleaning efficiency of the electrostatic air cleaner 9.

Figures 1, 2 and 3 show an additional part of my apparatus for cleaning hot gases, namely, an arrangement for removing from the apparatus material which is gathered on the plates ofthe electrostatic filter. The arrangement includes a butterfly valve in the conduit 6 for turning off the fiow of gases at the inlet side .of the cleaner 9 and doors 2| which close the chamber 8 on the outlet side of the cleaner. I also provide mechanism for closing the valve 29 and the doors 2|. A gear box 22 is driven by a chain or belt drive 23, which in turn is driven by a motor (not shown). The gear box 22 carries a crank 24 which opens and closes the doors 2| by means the lever system 25 which is illustrated in Fig- 4 ures 1 and 3. The doors 2| and the levers 25 are shown in the open position in Figure 1 and in the closed position in Figure 3. A chain or belt drive 26 connects the gear box 22 to a pulley 27 which turns a shaft 28. The shaft 28 turns the valve 20 through the pinion gears 29.

At predetermined intervals depending upon the amount of material gathering on the collecting plates of the filter, the motor which drives the gear box 22 is actuated to close the valve 20 and the doors 2|, the doors in their closed position resting on a stop 3|. After the valve 20 and the doors 2| 'have been closed, the collecting plates of the filter are vigorously vibrated to shake ofi, the material which has gathered on them. This can be done by manually striking them with a hammer or by using a conventional pneumatic or electric vibrator operatively connected to the supporting frame of the plates. The material which is shaken off the plates passes down into a hopper 32'from which it can be removed through a door 33.

My hot gas cleaner can be arranged for continuous operation by arranging two or more cleaners, as just described in parallel. While one opened and'another cleaner can be shut down for cleaning of its plates.

From the foregoing it is apparent that I have invented a simple arid effective apparatus for cleaning 'hot gases. I can use an electrostatic filter which has not heretofore been possible with hot gases because I cool the hot gases before they strike the plates. The mechanism for cooling the gases is in itself extremely simple and it performs functions in addition to the cooling of the gases. 'It acts as a blower to force gases through the cleaner and humidifies the air and thereby improves the efiiciency of the electrostatic filter. The cooling mechanism is of importance by itself in that it can be used as a blower to assist 'or replace fans heretofore used. These fans are expensive to operate and to maintain because their blades are subjected to the hot gases and therefore are made out of special expensive alloys. In spite of these alloys the blades fail and must be replaced.

While Iv have described a present preferred embodiment of my invention, it is to be understood that it may be otherwise embodied within the scope of the following claims.

I claim:

1. Apparatus for cleaning hot gases comprising an electrostatic filter, a conduit through which the gases may flow to the filter, a helically coiled pipe concentrically positioned in said conduit having one end adapted for connection to a source of water, the other end of the pipe having a straight extension which extends axially of the'coil, and a Venturi throat in the conduit spaced from the coil in the direction of gas fiow, the end of said straight extension being positioned in the throat whereby a jet of steam from said extension will create a suction in the venturi and draw gases through the conduit and force them through the filter.

2. In apparatus for handling hot gases, a blowerfor the gases comprising a conduit through which the gases may flow, a flash boiler in the conduit and adapted to be, heated by the hot gases, and a Venturi throat also in the conduit, said boiler having connections to a source of water, and a steam outlet positioned in said throat whereby steam emitted by the outlet will tend to create a vacuum in the venturi and thereby draw gases through the conduit, said flash boiler comprising a helically coiled pipe, the coil extending concentrically within the conduit along the path of the flow of gases and adapted to be contacted by the gases, a length of pipe extending lengthwise through the coil and being connected to the front end of the coil (in the direction of gas flow) and having a nozzle at its other end which extends into said Venturi tln'oat.

3. In apparatus for cleaning hot gases having an electrostatic filter and a conduit through which the gases flow to the filter, means for cool- 15 ing the gases and for moving the hot gases through the conduit, said means comprising a flash boiler in the conduit and in contact with the hot gases which flow through the conduit, a Venturi throat in the conduit between the boiler and the filter, a nozzle connected to the boiler for ejecting steam into said venturi and means adapted to connect said boiler to a source of water.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 173,981 May Feb. 22, 1876 1,329,817 Wolcott Feb. 3, 1920 1,329,825 Bradley Feb. 3, 1920 1,966,859 Heinrich July 17, 1934 2,152,251 Gay Mar. 28, 1939

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