US1535174A - Art of feeding powdered coal to blast furnaces - Google Patents

Description

April 28, 1925.

A. G. M GREGOR ART OF FEEDING POWDERED COAL TO BLAST Filed Sept. 29, 1920 FURNACES 2 Sheets-Sheet 1 April 28, 1925. 1,535,174

A. G. MOGREGOR ART OF FEEDING POWDERED COAL TO BLAST FURNACES Filed p 29. 1920 2 Sheets-Sheet 2 4 power is required.

ara'r rain,

. ALEXANDER e'r mcennson, or WARREN, ARIZONA.

ear or rnlnmne rownnnnn COAL TO BLAST FURNACES.

mam flied September 29, 1920. Serial No. 413,595;

To all "wizom it may concern: j Be it known that I, ALEXAN ER G. M0-

" GREGOR, a citizen ofthe United States, residing at'Warren, in thejc'ounty of Cochise and 5 State-ofArizona, have invented or discovered certain new and useful Improvements in the Art of Feeding Powdered Goal 'to 'Blast Furnaces, of which the following is a specification, referencebeing had therein to the accompanyingdrawings.

This invention relates to an improvement in the art of feeding powdered coal to blast furnaces, and has for", its'object. a method which, as ,compared with'the methods at 15. present in use, will be more economicalin the use of power, will require less space around the-furnace, and be more readily installed, "and which will provide a more flexible and reliable means for distributing the coal to each and every tuyere' of the furnace than the method now in'use.

The.method at present most generally in use for feeding the coal into the tuyeres of 1 blast furnaces is by feeding the powdered,

coal from the supply hopper by a screw conveyor. This screw conveyor is arranged so as to distribute the coal into from one to six or eight individualpipes, each leading to an air injector The air in ectorproducesa; suction, drawlng the coal into 1t, and discharges the mixture of coal: and air into'the furnace tuyere.

As the pressure of the blast air entering the furnaces is from 2 to 3 pounds per square inch, it. is usual, in practicing the present method, to use air at a pressure of some 10 pounds greater thanthe blast air at the furnaces, for operating theinjector, and-to prov-ide this air at higher pressure considerable As the usual blast furnace may have from 40 to 140 tuyeres, a number of coal hopperswith their feed screws and injectors would be required, and would make a complicated and bothersome installation" which must be placed as close to the furnace as possible where the space is limited, and where it would interfere more or less with the other 1 equipment and operations. about the furnace. Such systems are not always reliable in delivering-the desired amount of coal to each tuyere. 1 I In accordance with the present invention the powdered coal is delivered and distributed to eachtuyereof a blast furnace by means of an 'aircirculating and distributing system, similar to the systems which are now being used in plants where coalis distributed to a number of heating furnaces in thesame building or plant. In practising'the present invention powdered coal is fed into the suction air pipe of a centrifugal fan blower. In. the fan the coal and air are intimately mixed and discharged, under a" pressure of approximately 6 ozs. per square inch, the discharge being into a fuel pipe main which, through suitable branches, supplies a mixture of air and coal to the various furnace burners.v 5

Sufficient velocity is maintained in the main to prevent the coal from settling and.

clogging it. To accomplish this, the main is preferably in the form of a loop communicating with a return pipe and carries more air and fuel than is delivered to the furnaces, so that a certain amount of the fuelladen air in the main passes by all the branch pipes and is returned to the fuel and air supply for the fan.

' Automatic means may be provided for regulating the-amount of coalfed into the r system, so that the proper. mixture of pow dered coal and air will be maintained in the main. and its branches, regardless of' the amount being actually consumed by the furnace. Such a means and system is described in U. S. Patent No. 1,206,112, issued to A. A. Holbeck, November 28, 1916.

In accordance with the present invention 1 a fuel supply mam, containing a mixture of coal and air underi sufiicient pressure, 'extends around on both sides of the blast furnace, similar to the bustle pipe which furfor delivering coal into the fuel mains through branch pipes, and into the tuyeres of a blast furnace 1n the manner suggested.

going But as the pressure of the blast in the tuyeres' of a copper blast furnace, for instance, is usually maintained at some pressure'between 24 ozs. and40 ozsg per square inch, the fanwhich delivers the mixture of fan from the blast furnace main.

coal and air would have to maintain a pressure at least 6 ozs. higher than the blast pressure, so that the mixture of air and coal delivered by the fan would flow through the main and branchesat a high velocity and into the tuyeres against the furnace blast.

ticles of coal impinging against the'interior' parts of the fan at the high velocity.

In the present invention this difiiculty is overcome by taking the suction air for the In this way the fan is only required to boost the furnace main pressure about 6 02s., and'it willnot be required to run any faster than fans are now running in connection with the ordinary low pressure air coal distributing-systems, and the wear on the fan will be no greater In the accompanying drawings,which, it will be understood, are-more or less diagrammatic, Fig. 1 is an elevation illustrating an apparatus by which the invention may be carried into effect, and Fig. 2-is a plan view of the same.

Referring to the drawings, 12 denotes a blast furnace ha-ving tuyeres 13, through which the powdered coal is to be fed into the furnace by means of air under pressure passing through pipes 14, the outlets of which join the outlets'of the fuel pipes 15, the air pipes 14 communicating with the main air blast pipe 16 through the bustle pipes 16 and the fuel pipes 15 communicating with the fuel feed pipe .17. The powdered fuel is discharged from the fuel inlet pipe 18 to a collector or separator 19 which empties into a bin 20 having at its bottom an outlet 21 through which the powdered coal is discharged into a pipe 22 in'which is located a screw conveyor 23 which feeds the fuel into the pipe 240cmmunicatin'g with a booster blower fan 25 which, in turn, communicates with the fuel feed pipe 17. The air and powdered coal are thoroughly mixed by the fan 25.

The main air blast: pipe 16is provided with a branch pipe 26'opening into an air flow meter 27 through which the air passes into a pipe 28 communicating with the-pipe 24, so that air' from the main air blast pipe @16 is delivered to the fan at a pressure of say 3 pounds to the square inch, or the blast furnace pressure; and this pressure is augmented by the fan 25 by only about 6 ounces to develop the necessary pressure for feeding the powdered fuel into the furnace through the fuelfeed pipe-17.

- against the bin pressure.

Surrounding the furnace 12 is a looped fuel header pipe 29 into which the powdered fuel is discharged from the feed pipe 17, and: with which the fuel pipes 15 communicate, the said header pipe being merely a continuation of said feed pipe. Preferably communicating with the said header pipe The branch pipe 26 is preferably provided with a damper or valve 31 by which the air supply from the main air pipe may be cut off when desired,

The speed of motor 39 and screw feeder 23 which it drives is regulated by means of the rheostat 32, which is controlled by the piston 36 in the air flow meter 27, the said piston being connected by the rod 37 with the lever 3-1 pivoted on a support 35, said lever being in turn connected with the-rheostat regulating lever 33; so that if the amount of fuel and air delivered to the furnace is increased more air will be drawn in through the flow meter and the speed of screw feeder will be automatically increasedQ In the same way, if the air and coal admitted to the furnace is reduced, the speed of the screw feeding the coal will be reduced, thus keeping the ratio of coal to air in the mixture constant. The motor 39 is electrically connected with the rheostat 32 by conductors 38-. i

From the foregoing it will be understood that the normal air pressure, when the fan 25 is not running, is practically the same'in the fuel inlet pipe 17 as in the main air blast pipe 16, and that an increased pressure of fan 25, in order to properly feed the fuel into the furnace.

The coal will preferably be delivered to the bin 20 by .an air transport system through the-pipe 18 and collector 19 for the reason that the bin 20 willbe under a pressure equal to the main air blast pressure, and to avoid interruption in the operation',-the coal would have to be delivered The collector or separator 19 is vented to' the pipe 26 througl'i the pipe 42 which allows the air in thereturn pipe 30 to be delivered to pipe 26; and also'allows whatever air is required in .de: 'livering the coal to the bin 20 by the air transport system, tobe delivered to the fan.

The additional air required by the fan is tom, etc., as usual. V

It; will be understood that, if thought desirab'le, check valves may be installed in the ment described tuyere pipes between the tuyeres and the bustle pipes to prevent the coal from being blown back into the bustle pipes in case the tuyeres become clogged. It will also be understood that the powdered coal may be fed into-the discharge of the fan instead of into the suction, as indicated by the drawings. i It is preferred that the return pipe discharge through the separator 19, so as to collect the surplus powdered fuel which is then discharged into the bin 20, although 'the surplus air could be discharged into the atmosphere; but by discharging the air in the return pipe into a pipe or chamber having connection with the blast main, or to the suction of the fan which has apprexi- .v mately the blast pressure in it, the air is again used and the power required to compress it up to the blast pressure originally is not wasted. The invention is not to be understood being limited to. the details of the particular apparatus herein shown and described and which somewhat conventionally illustrates an apparatus by which the invention may be carried into effect, as the means by which the invention may be practiced may be varied widely, as will be understood by those skilled in the art.

Some of the advantages of the arrangemay be mentioned as follows:

. Much less power is required for forcing the fuelinto the tuyeres than is used in the injector scheme now inuse for delivering powdered coal into blast furnace tuyeres.

As a more eflicient means than a centrifugal fan blower is generally used for delivering the blast air undef' pressure to blast furnaces, 5 by providing a fan to boost this pressure, by only a few ounces, as described, less power on the whole will be required than if a fan were used to draw the coal and air in at atmospheric pressure and compress it up to 6 ozs; higher than the main air blast pressure. This would be similar to the systems now in use for heating furnaces except the fan would be called upon to develop much more pressure, and the wear of the fan on account of the highervelo'city of the rotating part would be greater.

In practice, the blast air pressure varies from time to time, due to pulsation, variation in the speed of the prime mover, and

a variation in the amount of air delivered. to the furnace or furnaces, and if'the compressed air for delivering the coal to the blast furnace tuyeres iscompressed by an independent mean-s, there will also be variations in its pressure, due to variation in the, speed of the motor driving it and due to variations in the amount of air being used.

By using a fan running at a constantspeed, which receives its suction from the air blast main and merely boosts this pressure up a few ounces, to furnish the air for feeding the coal into the furnace tuyeres, it will be apparent that a very simple means is provided in the present invention for maintaining a practically constant difi'erence in pressure between the fuel air and the blast air.

In accordance with the present invention all moving mechanism may be remote from the furnace, where it will not be injured by, or be in the way of the operations about the furnace.

While the sketches and description herein relate more or less to copper blast furnaces, it will be understood that the invention is also applicable to lead and iron and other blast furnaces. I

As hereinbefore stated, to prevent the powdered coal from settling in and thus clogging the fuel feed pipe 1'7, more air and coal are fed into said pipe than is delivered into the furnace and the surplus is returned to the separator 19 through the pipe 30.

Owing to the fact that the closed fuel bin 20 into which the fuel is fed through the pipe 18 by air pressure, is in communication with the'main air blast pipe 16 through the pipes 26 and 42, a pressure higher than atmospheric pressure, and approximately equal to the pressure in sai'd'main blastpipe,

will be maintained in said bin. Thus as no air pressure in the system will be vented to the atmosphere there is no loss of pressure which would haveto be replaced by additional power. Y I

Having thus described my invention I claim and desire to secure by Letters 1. The herein-described method of delivering powdered fuel to a blast-furnace, consisting in introducing the said fuel into the furnace through a fuel pipe or passageway communicating with the main air blast pipe orpassa'geway, and increasing the air pressure in the saidfuel pipe or passageway to a sufiicient extent to enable the fuel to be forced into the furnace against the air pres sure developed therein from the said-main air blast pipe.

2. An apparatus "bination with 'a furnace provided with tuyeres, ofa main blast furnace pipe, branch air pipes communicating with said main blast pipe and leading to the furnace tuyeres, a fuel supply pipe carrying a mixture of air and powdered fuel and also comfor delivering powdered, fuel to a blast furnace, comprislng a main municating with said tuyeres through branch pipes, and means for creating an air' fuel to a blast furnace, comprising a main air blast piper leading to the furnace, a fuel feed pipe communicating with the said main air blast pipe so as to reeeive'air under pressure from said main air blast pipe, and a booster fan communicating with the said main air blast pipe and with the said fuel feed pipe and serving to increase the air pressure in said fuel feed above that received from said main air blast pipe.

5. An apparatus for delivering powdered fuel to a blast furnace, comprising a main air blast pipe leading to the furnace, a fuel feed pipe communicating with the said main air blast pipe so as to receive air under pressure from said main air blast pipe, a booster fan communicating with the said -main air blast pipe and with the said fuel feed pipe, and servingto increase the air pressure in the said fuel feed above that reeeived from said main air blast pipe, and apipe for returning the surplus fuel from the pipes at the furnace to the fuel bin or the fuel entrance part of the apparatus.

furnace blast pressure and adapted to carry 6. An apparatus for delivering powdered coal to a blast furnace comprising a main air blast pipe, a fuel feed pipe, means for causing said fuel pipe to deliver fuel to a furnace under a pressure higher than the more air and fuel thanis discharged into the furnace, a closed fuel supply bin, means for creating a pressure in said bin higher than atmospheric pressure, and a' return or circulating pipe communicating with said fuel feed pipe and said bin so that the surplus fuel may be returned to the source of supply.

7. An apparatus for delivering powdered coal to a blast furnace comprising a main air blast pipe, a fuel feed pipe, means for causing said fuel pipe to deliver fuel to a furnace under a pressure higher than the furnace blast pressure and adapted to carry more air and fuel than is discharged into the furnace, a closed fuel supply bin, means for connecting said bin with said main air blast pipe and thereby creating a pressure in said bin approximately equal to the pressure in said main air blast pipe, and a return or circulating pipe communicating with said fuel feed pipe and said bin so that the surplus fuel may be returned to the source of supply In testimony whereof I affix my signature.

ALEXANDER GRANT McGR-EGOR.

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