US3159385A - Combustion by-pass for back-drafting blast furnaces - Google Patents

Description

Dec. 1, 1964 A R. J. FLANAGAN 3,

COMBUSTION BY-PASS FOR BACK-DRAFTING BLAST FURNACES Filed June 3, 1963 L Combustion A ir INVENTOI? RQBERT J. FLA/VAGAN i /1e: W

mm m ey United States Patent F 3 159 385 (JOMBUSTION BY-PASS FOR BACK-DRAFTKNG BLAST FURNACES Robert J. Flanagan, McKeesport, Pa., assignor to United States Steel Corporation, a corporation of New Jersey Filed June 3, 1963, Ser. No. 285,061 4 Claims. (Cl. 263-19) This invention relates to a by-pass for back-drafting blast furnaces and, in particular, to a valved combustionchamber by-pass extending from a point on the hot-blast main adjacent the furnace, to the chimney main.

The need for back-drafting blast furnaces and the objections to the conventional method of so doing are explained in Heist et al. Patent 1,879,230, which discloses an elemental by-pass for the purpose. My invention is an improvement thereon in that I provide a combustion chamber wherein the combustible gases withdrawn from the furnace may be safely burned. I also provide the chamber with a supply of air for combustion and with temperature-control means to prevent excessive heat from resulting which might damage the lining of the chimney main and chimney.

A complete understanding of the invention may be obtained from the following detailed description and explanation which refer to the accompanying drawing illustrating the present preferred embodiment, the single figure of which is a diagrammatic layout showing the arrangement in plan of the air-preheating system of a blast furnace, incorporating my invention.

Referring now in detail to the drawing, the bustle pipe of a blast-furnace (not shown) receives preheated air from hot-blast main 11. The .air is heated in one of stoves 12, 13 and 14 adapted to be connected to the main by hot-blast valves 15. Air \at atmospheric temperature is supplied to the stoves from a cold-blast main 16 under the control of cold-blast valves 17. According to the usual practice, two of the three stoves are on gas, i.e., being fired with blast-furnace gas, while the other is on blast. The stoves on gas have their valves and 17 closed and the products of combustion therein flow to a chimney main 18 through chimney valves 19 which are open. The chimney valves of the stove on blast are closed but its valves 15 and 17 are open. Chimney main 18 extends to chimney 20.

The system described thus far is conventional. My improvement therein consists in the provision of a combustion by-pass 21 extending from a point in the hot-blast main 11 adjacent bustle pipe 10 to the chimney main 18, conveniently the end thereof remote from chimney 20. The by-pass includes a normally closed valve 22 controlling the flow of gases therein.

In greater detail, the by-pass 21 comprises principally a refractory-lined elongated combustion chamber 23 into the frusto-conical entering end of which a refractory-lined inlet pipe 24 from main 11 extends as an inspirator, whereby air for combustion is drawn in through a lateral airsupply pipe 25 having a valve 26 therein. From the other end of chamber 23, a refractory-lined exit pipe 27, in spaced relation thereto, extends to main 18.

A wind box 28 surrounds the adjacent but spaced ends of chamber 23 and pipe 27, land the inlet pipe 29 thereof has a control valve 30 therein. Air admitted through pipe 29 tempers combustion products formed in chamber 3,15,385 Patented Dec. 1,, 1964 23 and reduces their temperature to a value such that they will not damage the lining of pipe 27 or main 13.

Chamber 23 is provided at the end adjacent pipe 25 with an ignitor 31. A thermostat 32 in pipe 27 is connected to a controller 33 which automatically adjusts valve 30 to maintain the temperature of the exit gases below a predetermined maximum.

When it is desired to back draft the furnace, the stove on blast is taken off by closing its valves 15 and 17, placing it in a so-called bottled condition. Valve 22 which is normally closed is opened and the draft of chimney 2t) withdraws residual gases from the furnace, creating a condition of negative pressure therein. These gases are combustible and, on reaching chamber 23 are fired by ignitor or hot tube 31 of known construction, in the presence of combustion air admitted by opening valve 26. The combustion products pass on to pipe 27 but have their temperature reduced to a safe value by cooling air from wind box 28 before entry into the pipe.

When the desired period of back-drafting has elapsed, normal operation may be resumed by a reversal of the operations just described.

It will be evident that my invention provides a backdnafting by-pass in the form of a combustion chamber with means for admitting a controlled amount of combustion air and cooling air in the amount necessary to prevent the temperature of the combustion products going to the chimney from exceeding a predetermined value. More particularly, the invention provides a valved combustion bypass from a point on the hot-blast Inain 11 adjacent the furnace to the chimney main 18.

Although I have disclosed herein the preferred embodiment of my invention, I intend to cover as well any change or modification therein which may be made Without departing from the spirit and scope of the invention.

I claim:

1. The combination with a blast furnace bustle pipe, a plurality of stoves thereadjacent and cold-blast, hot-blast and chimney mains connected to said stoves, of a combustion by-pass comprising an inlet pipe connected to said hot-bl ast main at a point adjacent the bustle pipe, an exit pipe connected to said chimney main, an elongated combustion chamber connected between said inlet and exit pipes, and a combustion-air supply pipe connected to said chamber.

2. The combination defined in claim 1, characterized by said chamber having a frusto-conical entrance end into which said inlet pipe extends in spaced relation.

3. The combination defined in claim 1, characterized by a cooling-air supply pipe communicating with said exit P P 4. The combination defined in claim 3, characterized by a valve in said cooling-air supply pipe, a controller for said valve and a thermostat in said exit pipe downstream from said cooling-air supply pipe, connected to said controller.

References Cited in the file of this patent UNITED STATES PATENTS 803,284 Hartman et a1 Oct. 31, 1905 1,879,230 Heist et a1 Sept. 27, 1932 2,931,635 Braun et a1. Apr. 5, 196.0

Claims (1)

1. THE COMBINATION WITH A BLAST FURNACE BUSTLE PIPE, A PLURALITY OF STOVES THEREADJACENT AND COLD-BLAST, HOT-BLAST AND CHIMNEY MAINS CONNECTED TO SAID STOVES, OF A COMBUSTION BY-PASS COMPRISING AN INLET PIPE CONNECTED TO SAID HOT-BLAST MAIN AT A POINT ADJACENT THE BUSTLE PIPE, AN EXIT PIPE CONNECTED TO SAID CHIMNEY MAIN, AN ELONGATED

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