US3864119A - Method and apparatus for simultaneously producing large and small heat hardened agglomerates of mineral ore - Google Patents

Abstract

A method and apparatus is disclosed for simultaneously producing heat hardened agglomerate balls of two size ranges from finely divided mineral ore. The apparatus includes a first balling device for making balls of ore in a first size range, an indurating furnace assembly for drying, preheating and heat hardening the balls, means for collecting a predetermined quantity of hardened balls of a size within the first size range, and a second balling device. According to the method disclosed the collected hardened balls are delivered to the second balling device and rolled in additional moistened ore to apply a coating thereto until the collected balls grow to a second size range. The coated balls are then fed to the furnace with the balls from the first balling device for drying, preheating and heat hardening the coating of the coated balls simultaneously with the drying, preheating and heat hardening of the first size range balls.

Description

United States Paten Whitaker et al.

Feb. 4, 1 975 [75] Inventors: Orion C. Whitaker, Wauwatosa;

Glenn A. Heian, Franklin, both of Wis.

[73] Assignee: Allis-Chalmers Corporation,

Milwaukee, Wis.

[22]. Filed:' Oct. 1, 1973 [21] Appl. No.: 402,456

52 US. Cl. 75/3 [51] Int. Cl C21b 1/20 [58] Field of Search 75/3-5 [56] References Cited UNITED STATES PATENTS 2,l27,632 8/l938 Najarian 75/3 2,41 l,8'73 12/1946 Firth 7573 3,149,958 9/1964 Ward 75/3 X 3,l88,l95 6/1965 Price 75/3 X 3,333,951 8/1967 Ban 75/3 3,753,682 8/1973 Kohl 75/3 Primary Examiner-Allen B. Curtis Attorney, Agent, or Firm-Arthur M. Streich [57] ABSTRACT livered to the second balling device and rolled in additional moistened ore to apply a coating thereto until the collected balls grow to a second size range. The coated balls are then fed to the furnace with the balls from the first balling device for drying, preheating and heat hardening the coating of the coated balls simultaneously with the drying, preheating and heat hardening of the first size range balls.

2 Claims, 1 Drawing Figure PATENTEUFEB 4mm 1 METHOD AND APPARATUS FOR SIMULTANEOUSLY PRODUCING LARGE AND SMALL HEAT HARDENED AGGLOMERATES OF MINERAL ORE BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to amethod and apparatus for agglomerating finely divided mineral ore and furnacing such agglomerates to produce a hard durable product. In particular the present invention relates to agglomerating and heat hardening such as iron oxide ores for subsequent conversion to the metals iron and steel.

2. Description of the Prior Art U.S. Pats. Nos. 2,750,272; 2,750,273 and 2,750,274 of June 12, 1956, are examples of patents related to heat hardening agglomerates of iron ore on a horizontal traveling grate.

U.S. Pats. Nos. 2,925,336 of Feb. 16, 1960; 3,313,534 of Apr. 11, 1967 are examples of patents related to heat hardening agglomerates of ore utilizing both a horizontal traveling grate and a rotary kiln.

U.S. Pats. Nos. 3,301,659 of Jan. 31, 1967 and 3,319,949 of May 16, 1967 are examples of patents related to rolling an unfired ball of mineral ore in moist ore to produce a coated ball which is then fired'to harden the ball.

U.S. Pat. No. 2,127,632 of Aug. 23, 1938 relates to a ball of-metalliferous material having a nucleus or core which may be sintered ore.

I The present invention is directed to simultaneously producing desired quantities ofheat hardened balls of 1 mineral ore in at least two distinctly different size ranges, with balls of a first size being of a size usually produced according to the practices of the aforesaid prior art, and with balls of the second size also being produced which are substantially larger.

SUMMARY OF THE PRESENT INVENTION The present invention is directed to producing substantial quantities of heat hardened balls of mineral ore, for example iron oxide ore, of standard size which usually falls within a range of three-eighths of an inch to five-eighths of an inch in diameter, for a use such as charging to a blast furnace. The present invention also provides for producing desired quantities of somewhat larger heat hardened balls of perhaps three-fourths to 1% inches in diameter, for use as a coolant charge to a basic oxygen steelmaking furnace and sometimes for charging a blast furnace as well.

When green ball diameters exceed five-eighths of an inch, indurating rates become heat-transfer and moisture-diffusion limited. That is, the indurating process, particularly on a grate, must be substantially slowed down to assure that all moisture is removed in drying before preheating and preheating must be prolonged to assure that requisite preliminary induration occurs in the centers of the balls before they are transferred into I a kiln for final heat hardening.

Further, experience has shown that even if this preheat ing balance is attained, the fire pellets may have underfired cores. Pellet quality is then adversely affected.

The object of the present invention is to simultaneously produce fully heat hardened balls of two sizes. one size of perhaps three-eighths of an inch to fiveeighths of an inch in diameter and a larger size of perhaps three-fourths of an inch to 1% inches in diameter.

According to a preferred embodiment of the present invention green balls of finely divided mineral ore in a first preselected size range, perhaps three-eighths of an inch to five-eighths of an inch, are made in a balling drum. The green balls of the first size are deposited on a horizontal grate conveyer for drying, preferably by a down draft of hot gases, and preheating. The balls are then fired, preferably in a rotary kiln, until hard and abrasion resistant. The hardened first size balls pass a suitable device to collect a selected quantity of the balls from the total produced, and the collected balls are rolled in an additional quantity of finely divided ore to apply a coating thereto until such balls have grown in diameter to a second and larger preselected size range, perhaps three-fourths of an inch to 1% inches. The larger balls are then deposited on top of the bed of smaller balls on the grate for drying and preheating the coating ofthe large balls simultaneously with the drying and preheating of the smaller balls. Both size balls are then tumbled through the rotary kiln for final hardening of the coating of the large balls and final hardening of the smaller balls. The fully hardened balls of both sizes pass over the screening device to remove the large balls for their specialized use, and the smaller balls pass a device to collect the preselected quantity of small balls for continuing the coating operation while the remainder of the small size balls are discharged for eventual use as such as blast furnace feed. The apparatus operating according to the present method therefore continues to simultaneously produce two sizes of heat hardened balls, and delivers each size to its own conveyer.

Other features and objects of the present invention that have been attained will appear from the more detailed description to follow with reference to an embodiment of the present invention shown in the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING The accompanying drawing shows diagrammatically a side elevation, partly in section, of a balling and furnacing system according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing, such as finely divided iron ore along with bentonite is discharged from hopper l at a rate controlled by feeder 2, and mixed and rolled into suitable agglomerates or balls 4 by such as a balling drum 5 which may be of the type shown in US Pats. Nos. 1,994,718 and 2.41 1,873. The balling drum 5 may be arranged to discharge to a vibrating screen 6 having screen deck 7 with openings sized to screen out balls larger than about five-eighths of an inch diameter. Such oversize balls may be broken by means (not shown) and recycled. Balls passing through deck 7 pass over a screen deck 8 having openings to screen out balls smaller than about three-eighths of an inch which, as shown, may be recycled directly to balling drum 5.

Balls passing through deck 7 but not through deck 8, of a size range larger than three-eighths of an inch but not larger than five-eighths of an inch, are transferred by suitable conveying means and feeder 9 to discharge to a gas previous traveling grate l enclosed by a housing 11. The housing 11 has a baffle wall 12 projecting downwardly from the roof of housing 11 to a predetermined distance above the grate 10..The baffle wall 12 divides the space enclosed by housing 11 over grate 10 into a drying chamber 15 and a preheat chamber 16. Windboxes 17 and 18 are arranged beneath chambers 15 and 16. A chute 20 with a hood 21 connects the grate 10 to a rotary kiln 22. The kiln 22 has an axial burner 23. The kiln 22 may be mounted on rollers (not shown) for rotation in a conventional manner. A second chute 26 with a hood 27 that also serves as the firing hood for kiln 22, connects kiln 22 to a cooler 30 which may be an annular grate of the type shown in US. Pat. No. 2,256,017.

The agglomerates or balls 4 which are formed in balling drum are formed into a bed on gr-ate 10, with individual agglomerates at rest relative to each other, and the bed is transported by grate through the housing 11 to the chute 20. At the chute 20 the bed of agglomerates is disrupted and the agglomerates are discharged into kiln 22. The agglomerates 4 are tumbled through the kiln 22 to the chute 26 which discharges the agglomerates as indurated pellets to the cooler 30.

A gas flow through kiln 22 proceeds counterflow to the movement of the agglomerates 4 through kiln 22. The gas flow'results'from air flowing from cooler 30 into kiln 22 and fuel and air admitted to kiln 22 through the axial burner 23. The gas flow proceeds, counterflow to agglomerates 4, from kiln 22 through hood 2] to the preheat chamber 16 where the gases are drawn downwardly through .the bed of agglomerates 4, through grate 10 through windbox 18, and through a conduit 32 by a fan 33. Fan 33 discharges the gases drawn downwardly through the bed of agglomerates 4 in preheat chamber 16, into a conduit 34 that discharges the gases into the drying chamber over grate 10. The gases in chamber 15 are drawn downwardly through the bed of agglomerates 4, through grate 10, through windbox l7, and through a conduit 35 by a fan 36 which discharges the gases up a stack 37.

The agglomerates 4 are discharged from cooler 30 as heat hardened balls are discharged to separating and collecting means comprising a second vibrating screen 40 having a deck 41 with openings sized to pass pellets smaller than about three-fourths of an inch diameter. Initially, as operation of the described plant is started, substantially all of the pellets 4 from cooler 30 will pass through deck 41. Screen 40 may also be provided with a second deck 42 having openings to collect pellets smaller than those passing through deck 41 but which are the larger balls within the first size range to provide a predetermined quantity of balls for a purpose which shall appear as the description of the present invention proceeds. The desired quantity of balls may be colshown in US. Pats. Nos. 2,293,439; 2,436,766 or 3,010,145. By adjusting the rates of feed to pan 52 and its angle of inclination, balls may be produced of a size desired for the practice of the present invention, and such balls are deposited by a second feeder 55, in or preferably on top of the bed on grate 10 which is first formed with balls from balling drum 5, all for a purpose that will appear from the description of the method of operation to follow.

A preferred operation of the apparatus according to the method of the present invention will now be described.

Green balls 4 (i.e., unfired) from the first balling device, drum 5, are screened by screen 6 to provide balls of a first size range of three-eighths of an inch to fiveeighths of an inch diameter and formed into a bed on grate 10. The green balls 4 will be dried in zone 15 preheated in zone 16 and given a final burning while tumbling in kiln 22 to provide heat hardened pellets of such lected by proper sizing of openings in deck 42. For exampl'e, providing a deck 42 with openings of fiveeighths of an inch diameter may screen out and collect enough balls for the intended purpose, but if not deck 42 may be provided with nine-sixteenths of an inch openings, one-half of an inch openings or whatever size may be necessary for deck 42 to screen out and collect balls of the quantity desired.

Heat hardened pellets 4 which pass through deck 42 of screen 40 are discharged to a suitable conveyer 49 for transport to stockpiles. Pellets passing through deck as iron ore. After being cooled in cooler 30 the hardened pellets pass to screen 40. Initially, during start-up operation, substantially all balls will pass through deck 41 of screen 40 and on to deck 42. Screen deck 42 is provided with openings sized to collect from the discharge through deck 41, five-eighths of an inchballs, or if necessary to collect the desired quantity fiveeighths of an inch balls and nine-sixteenths of an inch balls, from the first size range, in order to collect, for example, 1 ton of balls from every 30 to 40 tons passing through deck 41. Most of the balls will therefore pass through deck 42 to conveyer 49. The smaller proportion of balls passing through deck 41 but not through deck 42 are delivered to bin 50. Balls from bin 50 will be rolled in balling pan 52 with finely divided ore from bin 53 to coat the collected balls with ore until they grow in size to a second and larger size range of perhaps about three-fourths of an inch to 1% inches diameter. These larger balls will be placed upon the bed of the smaller first size balls from drum 5 which is formed on grate 10, where the larger balls will be exposed to the hottest gases passing downwardly therethrough. The coating of the larger balls is dried in zone 15 and preheated in zone 16 along with the drying and preheating of the smaller size balls in the first formed bed on grate 10. The halls of both sizes tumble through kiln 22 wherein the coating of the large balls and the smaller balls are indurated to achieve the same desired strength and abrasion resistance. Both size balls pass through cooler 30 and now with the larger pellets present in the mix, deck 4] screens out the coated balls of the desired larger size and discharges them to a conveyer 60 for transport to stockpile and specialized use as for example, a coolant charge to a basic oxygen steelmaking furnace, while the first size range balls pass through deck 41 to deck 42 for continued and continuous collection of balls for coating and production of both the first and second size fully heat hardened agglomerate balls for such uses as blast furnace and steelmaking furnace feeds.

From the foregoing detailed description of the present invention it has been shown how the objects of the present invention have been attained in a preferred manner. However, modification and equivalents of the disclosed concepts such as readily occur to those skilled in the art are intended to be included in the scope of this invention. Thus, the scope of the invention is intended to be limited only by the scope of the claims such as are or may hereafter be, appended hereto.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

l. A method of making finished fired and heat hardened agglomerates of finely divided mineral ore of a first predetermined desired agglomerate size and a lesser quantity per unit of time of a second and larger agglomerate size, in a single facility, the method comprising the steps of:

a. making individual green balls of a first preselected size range from finely divided ore;

b. drying, preheating and heat hardening the first size range balls;

c. a first screening of the heat hardened first size range balls to separate therefrom balls of a preselected size larger than the first preselected desired size range when such balls are present and pass therethrough balls within the first preselected size range;

d. a second screening of the heat hardened balls which have passed through said first screening to remove during the second screening preselected size balls from within the first size range which represent less than one half the number of balls that have passed through the first screening, and pass through the second screening the remaining size balls within said first preselected size range which are then collected for storage as finished fired and hardened agglomerates of said first predetermined desired size;

. rolling the balls removed from the first size range during the second screening step, in additional moistened finely divided ore to apply a coating of ore thereto until the rolling balls grow in diameter to a predetermined larger size to provide the balls of said second predetermined desired agglomerate size; and

depositing the coated balls with green balls of the first size range for drying, preheating and final heat hardening of the coating of the coated balls simultaneously with drying, preheating and final hardening of the balls of the first size range, after which the first said screening step screens out the hardened coated balls which are collected to provide the supply of second desired size agglomerates, and the second screening continues to separate finished fired and hardened agglomerates of the first predetermined size from hardened balls of the size prese lected for coating.

2. A method according to claim 1 in which the prede termined portion of first size range balls removed by the second screening for coating is of the order of one ton of balls removed for coating from every 30 to 40 tons of the total hardened first size agglomerates produeed.

Claims (1)

1. 2. A method according to claim 1 in which the predetermined portion of first size range balls removed by the second screening for coating is of the order of one ton of balls removed for coating from every 30 to 40 tons of the total hardened first size agglomerates produced.

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