US2663557A - Washer for blast furnace gases - Google Patents

Description

Dec. 22, 1953 w. L. DAWBARN WASHER FOR BLAST FURNACE GASES 2 Sheets-Sheet 1 Filed .June 23 1950 INVENTOR. MEI/vs ZEN xDmveneu Ass/VT Dec. 22, 1953 w. L. DAWB'ARN 2,663,557

I WASHER FOR BLAST FURNACE GASE$ Filed June 25, 1950 2 Sheets-Sheet 2 INVENTOR. MIR/N6 lewA/ox'Dnn/qne/v Patented Dec. 22, 1953 WASHER FOR BLAST FURNACE GASES Waring Lennox Dawbarn, Winchester, Mass., as-

signor to Arthur D. Little, Inc., Cambridge, Mass, a corporation of Massachusetts Application June 23, 1950, Serial No. 169,835

4 Claims.

This invention relates to the controlling of liquid levels in ga washers and the like, particularly in gas washers associated with blast furhaces for Washing the blast furnace exit gases. It is of particular utility in connection with the operation of blast furnaces under high top pressure, as disclosed in the Avery Patent 2,131,031, although not limited to such use.

Th exit gases from a blast furnace are customarily led first to a dust catcher and then to a gas washer, which together serve to remove the bulk of the suspended solids from the exit gases. The usual gas washer comprises a vertically disposed chamber into which the gases emerging from the dust catcher are led at a point spaced above the Water level in the bottom of the washer, a gas exit near the top of the chamber, means for spraying water into the rising stream of gas, a hopper in the chamber bottom for collecting a body of water and contained dust particles resulting from the spraying or washing, and an overflow pipe arranged to maintain the body of water at a more or less constant level governed by the point of overflow of said pipe.

This conventional overflow arrangement is sometimes inadequate for use with furnaces operated under normal top pressures, because slips and rolls in the furnace are at times of suflicient magnitude to cause sudden increase in pressure within the gas washer-before the action of the bleeder valves becomes fully eiiective-such that substantially all of the water in the bottom of the washer is blown out through the overflow pipe and some gases escape into the atmosphere. This diificulty is much more prevalent in furnaces operated under high top pressures, because the gas pressure in the washer varies over a considerably greater range than in normal top pressure operation.

The escape of gases from the gas washer through the overflow pipe creates a serious hazard to the operating personnel, particularly in relatively closed areas around the washer, due to the poisonous nature (principally from carbon monoxide) of the escaping gases. In addition there is of course the loss of time in restoring operations to normal.

In accordance with the present invention, means are provided for maintaining a body of liquid in the hopper at the bottom of the gas washer, regardless of gas pressure fluctuations within the washer, so that escape of gases from the bottom of the washer through the overflow pipes is efiectively prevented. This is accomplished by means presently to be described, which comprise a reservoir or reservoirs of water adapted to discharge their contents into the hopper of the gas washer whenever the water level therein descends to undesirably low levels.

This invention in its preferred forms will now be described in more detail and with reference to the accompanying drawings, wherein:

Fig. 1 is a front elevation of one embodiment of this invention;

Fig. 2 is a top view thereof;

Fig. 3 is a side elevation of the structure shown in Fig. 1;

Fig. 4 is a cross-sectional view taken along line 4-4 of Fig. 1;

Fig. 5 is a front elevation of a modified form of the structure shown in Fig. 1;

Fig. 6 is a cross-sectional view taken along line 6-6 of Fig. 5; and

Fig. 7 is a cross-sectional view taken along line 1'l of Fig. 5.

In Figs. 1 to 4 inclusive, the numeral I0 represents a gas washer chamber supported by legs I l and provided with a liquid-collecting hopper ii at the bottom thereof, an overflow pipe I4 leading from near the bottom of hopper l2 and having an outlet opening 15, a drain valve l6 at the bottom of the hopper, a gas inlet conduit l8 which supplies dirty gas to be washed and which leads from the dust catcher (not shown), means (not shown) for discharging a spray of water into the gas ascending within chamber I 0, said lat ter means being supplied by suitable water lines such as line [9, a closure structure 20 at the top of chamber It! provided with a bleeder or relief valve 22 and an outlet conduit 24 for conducting the washed gas to subsequent processing. All of the foregoing arrangement is conventional gas washer structure.

In accordance with the present invention, I provide such a conventional gas washer with one or more reservoirs 30, which communicate with the interior of hopper l2 through openings or port 32. These reservoirs extend upwardly substantially the entire length of the washer chamber ID, and are unrestrictedly open to the atmosphere at their tops 34. When more than one opening is provided, these openings are-preferably arranged at different levels, as shown in Figs. 1, 3, 4, 5 and 7, for reasons explained hereinafter. These openings are all at various distances below the normal water level, which in the embodiment shown in the accompanying drawings is at approximately the top of the hopper [2 where it joins the main chamber of the gas washer-i. e. at line 36. These reservoirs have,

in the aggregate, sufficient cross-sectional area to provide a large enough volume of water for introduction into the hopper so that complete draining of the hopper, on sudden increases in gas pressure, will be prevented, as explained in greater detail hereinafter. It is generally convenient to arrange the reservoirs fiat against the washer body, as shown, in order to utilize the warmth of the washer to prevent freezing of the water columns. However, in areas where no freezing danger exists, or where heat is supplied by other means to the reservoirs (see Fig. 5), this is unnecessary, and the reservoirs may have for example a circular cross-section. While it is not necessary that the reservoirs. touc'hthe gas washer chamber at all, it is preferable, for structural support, that they do.

In operations where the furnace is under normal top pressure, control of the water level may be had by the simple overflow pipe arrangement M, which discharges through opening [5 any water accumulating above the normal liquid level at 36. It is however preferable-end in the case of high top pressure operations essential-that some other overflow arrangement be provided. For that purpose, pipe l4 may be rendered inoperative by valve ll, and another overflow pipe 40 provided, having a liquid-level-controlled valve 42 operably connected from control box 24 by connection 46. This control of valve 42 is carried out in the conventional manner for operating any liquid-level-controlled valve, so that as the water level at 36 rises the valve opens wider to discharge more water and bring the level down to normalor as the water level falls below level 38 the valve closes enough to reduce the flow of liquid through pipe 40 sufiiciently to permit the water level to rise to normal.

During the high-top-pressure operations for which this invention is particularly designed, the water level in reservoirs 30 will be much further above the normal level in the gas washer at 33 than during normal top pressure operations. Thus, with a top'pressure of about 12 p. s. i. gauge the column of water in the reservoirs will be about 25 feet above. the level at 36. This water level in the reservoirs is indicated at 50. The pressure in the gas. washer chamber i is substantially the same as that in the furnace top, being uninterruptedly in communicationtherewith through the dust catcher. This pressure is reduced to atmospheric by suitable throttling valves beyond the gas washer, as represented diagrammatically by valve 26 or in any other convenient manner. These throttling valves serve to maintain the desired top pressure within the blast furnace. 1

The embodiment shown in Figs. 5, 6 and 7 is the same (other than for the omission of a few conventional parts not necessary to the description which follows) as that of Figs. 1 to 4 inclusive, except for a modification in the form of the reservoirs. By this arrangement, the reservoirs are capable of furnishing a larger volume of water should that be desirable. To do this, the reservoirs comprise one or more tanks 52 each having conduits 55 leading to openings 32 in hopper l2. These conduits 54 are sufl'icient in number and aggregate cross-sectional. area to provide the desired rapidity of drainage of water from tanks 52 into hopper l2. From the top of each of tanks 52, pipes 56 extend upwardly substantially the full height of the gas washer, with an unrestricted opening 34 at the top of each pipe. The position of the water level in the reservoirs will of course 'depe nd upon the gas pressure within the gas washer. It may be at some point within tanks 52, or at a higher point somewhere in pipes 56 as indicated by the numeral 50.

As already indicated, the reservoir structure may be more or less flattened against the walls of the gas washer, or more or less separated there from, according to convenience in construction. If because of such separation there should be danger of freezing, heat may be supplied to the water in the reservoir by' any convenient means, e. g. by blowing in waste steam. This may be done for example by leading such steam into tank 52 (Figs. 5 and '7.) through line 58, from which. it emerges, through holes 59 in that line, into the water in the tank.

During normal furnace operation, the liquid level in the gas washer will remain at or close to whatever predetermined point (e. g. has been established for the particular apparatus and operation in question. This level will be maintained during normal operation by the liquid-level-control of valve 62. The height of water in the reservoirs (as indicated at 59) will depend of course upon the gas pressure within the gas washer. Whenever there occurs a sudden increase in the gas pressure within the washer, due for example to slips or rolls within the furnace, this sudden augmented pressure tends to blow the water in hopper l2 out through pipe to before valve :32 can be closed. (Note that bleeder valve 2:2 is set to open only at extraordinarily high pressures, for the purpose of preventing the rupturing of the gas washer in the event of plugging in or after line 24.) When the water level in hopper I2 thus descends below the highest one of the openings 32, the water in the reservoir above that opening will promptly discharge into hopper l2 and gas will be expelled up through that reservoir and on through top opening 34 thereofwhich is at a safe distance away from the operating personnel. If the sudden increase in pressure and drop in water level are still not effectively compensated, the descending water level will uncover a lower one of the openings 32, and so on until the excess pressure is relieved and the emergency has passed. The water level then rises fairly rapidly to its normal levels in the gas washer and in the reservoirs due to accumulation of the falling spray. This rise may be augmented, if desired, by an independent supply led in at any convenient pointe. g. via pipe 60 controlled by valve 52, as shown in Fig. 1. This latter showing is merely diagrammatic; the valve 62' would be located at, or its operation controlled from, any suitable and convenient place.

When. operating for example at 12 p. s. 1. gauge top pressure in the furnace, with a gas washer of about 20 feet inside diameter and about feet in vertical distance between the hopper top and the lower edge of the top structure 20, and a hopper about 20 feet in height, a reservoir capacity of about 2000 gallons is generally satisfactory, although in some cases and especially with higher top pressures at larger capacity is preferable-for example such as may be provided by a larger number of the reservoirs 30 or by tanks 52.

At cast times, or whenever else the furnace top pressure is reduced to substantially atmospheric, the water level in the reservoirs will fall to approximately equalize that in the gas washer. In the case of the foregoing illustration, with :3. normal water level at 35, this would cause a rise of water level in the gas washer of no more than about 10 inches--due to the large cross-sectional area of the washer chamber--even if the overflow line 40 were closed for any reason. Ordinarily this rise in level would quickly be taken care of by the operation of valve ,2 seeking to return the water level to its predetermined normal position.

I claim:

1. In a washer for blast furnace gases the combination with a vertically extending closed gas Washer chamber adapted to maintain a superatmospheric pressure therein under normal conditions of operation, means for conducting compressed gases to be washed into said chamber, means for introducing a spray of water into the upper part of said chamber, a hopper at the bottom of said chamber for collecting the water of said spray, means for conducting Washed compressed gases out of said chamber, of overflow means leading from the lower part of said hopper and being provided with valve means controlled by the liquid level in said hopper, reservoir means in thermal contact with the walls of said washer and extending upwardly above the plane of said normal liquid level and being adapted to contain a supply of water the level of which is normally maintained above said normal liquid level by said superatrnospheric pressure, an opening at the bottom of said reservoir means providing unrestricted flow of water between said reservoir means and said hopper and opening into the hopper below the normal liquid level of the body of water therein, and unrestricted opening at the top of said reservoir means communicating with the atmosphere and positioned adjacent the upper end of said gas Washer chamber, said reservoir 6 means being of substantial capacity whereby, upon sudden surges of pressure within said washer tending to force the water out of said hopper through said overflow means before said valve means can be closed, the water content of said hopper is promptly replenished by discharge of water from said reservoir means into said hopper.

2. Apparatus in accordance with claim 1 wherein said reservoir means is flattened against the walls of said gas washer chamber throughout the major portion of the length of said reservoir means.

3. Apparatus in accordance with claim 1 wherein said reservoir means comprises a tank spaced from said opening at the bottom.

4. Apparatus in accordance with claim 1 wherein said reservoir means is provided with a plurality of openings at the bottom thereof providing unrestricted flow of water between said reservoir means and hopper, said openings being positioned at a plurality of distances below said normal liquid level.

WARING LEN N OX DAWBAR-N.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 867,553 Bradley Oct. 1, 1907 953,040 Kruger Mar. 29, 1910 1,423,696 Stevens July 25, 1922 1,466,348 Weinel Aug. 28, 1923 1,718,988 Stewart July 2, 1929 2,585,779 Janecek et a1 Feb. 12, 1952

Images