US2468738A - Method of blowing in blast furances - Google Patents

Description

May 3, 1949. w. w. DURFEE. ET AL METHOD OF BLOWING IN" BLAST FURNACES 2 Sheets-Sheet 1 Filed Jan. 15, 1947 Wa/ te'l' M Du/fee Thar (Ittorneg y 1949. w. w., D URFEE 'EF'AL 2, ,7

METHOD OF BLOWING IN BLAST FURNACES I Filed Jan. 15, 1947 2 Sheets-Sheet 2 Smaentor Wa/Ler M Du/fee 0/70 Ja m P F0 I Then (Ittorneg Patented May 3, 19 2,468,7 38

NITED: STATE-Se PATENT oF pcg-a Walter W. Durfee and'John P. Fley,- Lorain,0hio,

assignors to; National. Tube Company, a corporation of New Jersey Application-January 15; 1947; Serial No. 722,174 I 4 Claims -(Cl. 75-'41) 1 2 The present invention relates' torblastl.furnacea:z any: known manneigiand thereafter "blowing: air a operation and particularly toan -improvedmethod'rs. intothe: tap .holerorv. iron. notch; of the furnac for b]owingjna,b1ast.fumace under a pressuresufficient to preventa fiowno Among the obiectsof theinvention is the D iron 113 6 furnace and for-a period-10 vision of an improved method'for blowing in a enough to heat up the bottomvandnhearth uniblast furnace, characterized byease of operation-w formly. and to melt the residual iron found thereand a reduction ofithe time necessary to' bring in. :Before making the first tap of iron. from thesr: the furnace into operation. The method displays furnace and following-an extendedperiod of such-=7 particular advantages whenz'employedin blowing. blowing..in, a blast of 1 air. .may be admitted, if in a banked blast furnace. l-lrdes'ired, through the tuyres to heat -up thebosh Because of fluctuating .iron' demands,theneed and stack and bring about a further melting-10f for repairs to thelfurnaces, andother ';enfor'ced-- ironwhich now flows easily-through the heated 1 shutdown of the furnace, it is at times necessary arth, gradually becomingmore highly heated to blow in furnaces which have been either live and ui d g p a 1 v r f' lt n ironbanked or deadbanked. In dead banking a blast 41117119 tt furnace, the air blast is replaced'by a blast relaz he blast to be empl yed t ou h the tap-hole tively free of oxygen, for example, by blast fur ay be cold air, hot y e e e a d: nace gas or by gas rich in 'carbonxdioxide; nitroe y e in e es e iundillliied' O y e gen, or the like, that quickly extinguishes the he time interval betweenlighting the furnace 1- fire. In the live bankin 'of blast furnaces, some'20e d making the-first tap: obviously'depe ds 011' hours before the last cast is made a coke blanka y factors, such asthe amount-of residualis formed in thelupperaportion of th furnace by iron in the hearth; the net volume of blast adcharging only coke thereinto. Alternatively, a mittedthrought et p the-nature OL burden richer incoke than normal can-be charged ume of blast. admitted-through t e' y at :such time. In 'live'banking, the tuyeres an'dtheaccumulated volume: of iron and cinder in these blow pipe are sealed off and th stack ffe t i furnace. A blast similar to-that-admitted to the relied upon to-maintain diminished combustion. t p' e can be used in the cinder notch. Howwhich is suflicient to prevent-extinguishing of the v s d na ily is n t n ssary f r diffi ulty fire. in iron flow'at thecinder notch is rarely experi In the prior methods of blowing in'a blast fur- 0 41. nace which has b either (leader The invention will be more readily understood it has been customary t light especially prepared reference t0 the y ng drawings in and easily ignitable portionsof theburdemfollow ing which'the'furnace'has'been blown in with Figure 1 is a schematic view in vertical cross--, blast of air or with oxygen .enriche'dair, admitted 3 .Sectiondihrollgh a portion fa banked blast fur-- through the tuyresr Such methods have not nace-in the vicinity of the tuyeres and iron notchgr been altogether successful because by :their use,- ure 2 s a S milar View of such furnace even after long periods: of blowing, it has-been q ipped withthe blowing: in'apparaiius O Our difiicult t bt i free running iron i t t -g invention after-the furnace has been'operated inhole or iron notch. It was therefore necessary fl with 0111 method; and to employ oxygen lenses and othermeans to cut Figure a ViBW'Of a P I' the pp at out the chilled iron at the iron notch and melt it employed in practicin th m h the view be sufilciently to bring about its flow; Suchoperaihg taken 8along theiline in Figu e 2. tions at the iron notch are hazardous to th'e:oper- The blast furnace Shown schematically in ators, who are exposed to the heat'encl flames Figures and providediwith a bustle pipe-4' thrown back from the solid iron by the oxygen Which extends around y h -t elances, as well as to the suddenfiow. of hot iron? t a t th o h t e'tui e-smcks 8 which arewhen a break throughfoccurs: Usually such sup; pp d thereinto and thence to the tuyres 6, 0f-- plementary heating of the iron'notch; with pr s; which one is shown. The furnace-is also pro- 7 vious methods of blowing in, have to'be repeated- .Vided-With an I10i70h'9 Which is u a y many times before a good'flow of iron is obtained: p ged as with clay, not Shown; when the furand the furnace blown i with normal blast nace-is in the banked condition indicated in Fig- Briefly, the method of the present "invention ure 1. The. contents of thefurnacewhenit isin comprises lightingthe coke in the vicinity- Of'--.th&--: such' banked condition consist-of a burden' l0, ironnotch -of a=dead-orslive -banked furnaceinos which i a m e- 0 n i n ore. In Figures 1 and 2 the lumps of coke are indicated by the large shapes designated 12, the lumps of iron ore are designated by the small rounded hatched shapes denoted l4, and the lumps of limestone are shown as triangular shapes 16. In the banked condition, whether dead or live, all or substantially all combustion in the vicinity of the hearth below the level of the iron notch 9 has ceased and the residual iron in the hearth solidifies after a time into a solid mass 13.

Blowing in of the furnace shown in Figure 1 in accordance with the invention may conveniently be effected by the use of the apparatus shown connected thereto in Figure 2. Such apparatus consists of the pipe 20 having a valve 22 therein tapped into the tuyere stock 8, as shown, to lead a portion of the blast gas into the iron notch. Pipe 20 is connected to a vertical pipe 26 through the elbow 24 and thence through a series of double elbow connections to the pipe 52 which is inserted into the iron notch 9 after the clay plug has been removed therefrom. Such double elbow connections, which are shown at 30, an, and 40 between the pipes 26 and 32, 32 and 35, and 36 and 42, respectively, allow a relative freedom of axial movement of pipe 42 so that it may be inserted in the iron notch and withdrawn therefrom while remaining connected to the source of blast. Chain 56, which is shown attached at the elbow joint 40, allows the quick withdrawal of pipe 42 from the iron notch by means such as a winch, not shown, when the flow of iron begins at the notch. The described supplementary blowing means for the iron notch is equipped with a pressure gauge, as at 2B, and with an inlet pipe 38 tapped thereinto, pipe 38 being provided with a valve and being connected to a source of oxygen, not shown, to allow the enrichment of the blast with oxygen as desired.

The following specific example, which is illustrative only, demonstrates one manner in which the method of the invention may be carried out. In this instance, the furnace to be blown in had been live banked for about sixty days. The supplementary iron notch blowing apparatus shown in Figure 2 was connected to a tuyere stock in the manner indicated, all tuyres were clayed up, and the peep sights were opened. A hot blast enriched with oxygen was thereupon admitted through the iron notch through pipe 42 and was continued for five hours. The initial static pressure of such blast was about two pounds per square inch, the estimated average volume of hot blast blown through the iron notch through the iron notch blowing apparatus, in which all pipes were four inch size, was 3,000 cubic feet per minute. The enriching oxygen was supplied through pipe 38 at the rate of 350 cubic feet per minute. The temperature of the hot blast in the bustle pipe Was 1100 F., the temperature of such blast as it entered the iron notch being estimated at 600 F. After the initial five-hour period, three tuyeres in the front of the furnace were opened and a total of about 18,000 cubic feet of hot blast per minute blown through them for an additional five-hour period. The hot enriched blast through pipes 20 and so forth into pipe 52 and thence into the iron notch was maintained, the pressure in such pipes building up slowly to about four pounds per square inch during the ten hours of blowing through the iron notch. Within the onehalf hour period following the initial blowing through the iron notch and the five hours of combined blowing, the pressure, as indicated by gauge 28, increased rather quickly to about ten pounds per square inch, indicating the presence of a substantial body of molten iron at the iron notch zone. Thereupon pipe 42 was quickly withdrawn from the iron notch by chain 56 and a quarter ladle of free running iron and slag was immediately obtained from the notch. After claying up the iron notch in the usual manner normal operating blast on all tuyres was provided and normal operation of the blast furnace resumed.

A consideration of Figure 2 will make clearer the manner in which the blowing in method of the present invention operates. As above indicated, one of the initial steps in the blowing in of a banked furnace is the lighting of the un consumed burden in the vicinity of the iron notch. It will be apparent, therefore, that such lighted burden when acted upon directly by a blast, and particularly by a hot oxygen enriched blast, will relatively quickly raise the burden, portions of the other furnace contents, and parts of the furnace adjacent thereto to a high temperature. Such high temperature zone is indicated in Figure 2 by the dotted outline 54.

In such high temperature zone the metal refining process of the blast furnace is thus resumed in miniature, the iron ore being reduced to iron which descends in the form of molten iron drops 58 onto the hearth, and the molten Slag resulting therefrom, shown as drops 50, likewise trickling through the burden onto the hearth. The blast in the iron notch has the further effect of gradually melting the solidified mass is of iron in the hearth. As shown in Fi ure 2, which represents the condition of the furnace after a substantial period of blowing at the iron notch, a pool of molten iron is formed at 46, and an adjacent zone M of semi-molten iron. There will, of course, also be present adjacent the notch a layer of molten slag, designated 52, which floats on top of the molten iron.

By blowing in a furnace in accordance with the present invention, it is possible to accomplish such operation with none of the hazards to the workmen or the dimcult cleanups of chilled iron heretofore encountered when blowing in a blast furnace. The uniformity of heating at the iron notch accomplished by our invention makes it possible to blow in a furnace from fully banked condition to normal operation in a total time of less than about twelve hours. Although the invention has been described is connection with the blowing in of a banked furnace, it may be employed to advantage in initially blowing in a furnace with a clean burden.

Although we have described and illustrated preferred embodiments of the method of blowing in a blast furnace in accordance with the invention and a preferred embodiment of the apparatus for carrying out such method, it is to be understood that the invention is not confined thereto but that it is defined within the scope of the following claims.

We claim:

1. The method of blowing in a banked blast furnace comprising sealing the tuyres, lighting the burden in the vicinity of the iron notch, blowing a substantial quantity of oxygen containing blast gas through the iron notch for a substantial length of time, thereupon unsealing the tuyres in the vicinity of the iron notch and blowing oxygen-containing blast gas additionally through such tuyres while maintaining the blast through the iron notch, and after a substantial quantity of molten iron has been obtained on the hearth in the vicinity of the iron notch, unsealing the remainder of the tuyeres and resuming normal furnace blast therethrough.

2. The method of blowing in a banked blast furnace comprising sealing the tuyres, lighting the furnace burden in the vicinity of the iron notch, blowing through the iron notch a substantial quantity of hot blast air for a substantial length of time, thereupon unsealing tuyres in the vicinity of the iron notch and blowing a substantial quantity of blast air therethrough while maintaining the blast at the iron notch, continuing such combined blowing operations until a substantial quantity of molten iron is obtained on the hearth, and then unsealing the remainder of tuyres and resuming normal furnace operations by introducing blast air therethrough.

3. The method of blowing in a banked blast furnace comprising sealing the tuyeres, lighting the furnace burden in the vicinity of the iron notch, blowing through the iron notch a substantial quantity of hot blast air enriched with an appreciable percentage of oxygen for a substantial length of time, thereupon unsealing tuyres in the vicinity of the iron notch and introducing substantial quantities of hot blast air therethrough, continuing the blast at the iron notch, such combined blowing operations being continued until a substantial quantity of molten iron is obtained on the hearth, discontinuing the iron notch blast, drawing off the molten iron, unsealing the remainder of the tuyres, and resuming normal operation by blowing blast gas through the tuyres.

4. The method of blowing in a banked blast furnace comprising sealing the tuyeres, lighting the furnace burden in the vicinity of the iron notch, blowing through the iron notch hot blast air at a rate on the order of 3000 cubic feet per minute and at an initial static pressure of about two pounds per square inch, the blast air entering the iron notch at a temperature on the order of 600 F. and being enriched by approximately 350 cubic feet per minute of oxygen, continuing such blast at the iron notch for a period on the order of five hours, thereafter opening a relatively small number of tuyres adjacent the iron notch and introducing hot blast air therethrough in a total quantity on the order of 18,000 cubic feet per minute for an additional period on the order of fiVe hours, while maintaining the iron notch blast simultaneously therewith until a substantial quantity of molten iron is obtained on the hearth as indicated by a rise in back pressure of the iron notch blast, thereupon discontinuing such blast, drawing off the molten iron, unsealing the remainder of the tuyeres, and resuming the blast through all tuyres to normal furnace operation.

WALTER W. DURFEE. JOHN P. FOLEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,507,740 Kirby Sept. 9, 1924 1,654,300 McGee et a1 Dec. 27, 1927 2,301,973 Riddle Nov. 17, 1942 OTHER REFERENCES Stahl und Eisen, vol. 45, pages 609-614, April 23, 1925.

Proceedings of the Blast Furnace and Raw Materials Committee (A. I. M. E.), vol. 1, 1941, pages 59 and 60.

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