US2809106A - Method of sintering iron ore with beehive coke oven refuse - Google Patents

Description

METHOD OF SINTERING IRON ORE WITH BEEHIVE COKE OVEN REFUSE Marshall J. H. Jones, Pittsburgh, Pa., assignor to Jones Coal and Coke Company, Pittsburgh, Pa., a corporation of Pennsylvania No Drawing. Application November 13, 1953, Serial No. 392,041

2 Claims. (Cl. 75-5) This invention relates to a method of sintering and to a solid combustible for use in such a method.

Sintering involves, as is well known, the feeding of a mixture of the material to be sintered and a solid fuel to the pallets of a movable grate sintering apparatus. Commercially only two fuels have been used for that purpose, namely, anthracite coal, referred to for brevity hereinafter as coal, and coke breeze. The use of such fuels in, for instance, the sintering of iron ore to prepare it for blast furnace burden, is attended by certain disadvantages pointed out hereinafter.

It is among the objects of this invention to provide a solid combustible for use in sintering on both moving and stationary grate apparatus which, in comparison with the use of coal and coke breeze as fuels, affords better heat distribution through the sinter bed during its entire travel, avoids hot spots, results in a sinter that is more uniform, chemically and physically, and more satisfactory, provides substantially greater grate life, and affording less in cost of combustible.

Another object is to provide a combustible for sintering materials subjected to that operation that is inexpensive, makes use of waste material heretofore economically inapplicable to any purpose, and afiords improved sintering operations.

Beehive oven coking is probably the oldest mode of making metallurgical coke. The oven construction and mode of operation are so well known in the industry as to require no detailed description. In beehive operation the practice is to recover only the coke of useful size. Inevitably, however, operation of the ovens results in amounts of material, or refuse, that can not be used as metallurgical coke. This refuse is a conglomerate of a wide variety of materials including coke too fine for practical use, raw and semi-distilled coal, wood ash, ash from coal combustion, and possibly some amount of coal tar. Over the years the belief has been that this material could be put to no useful purpose because of its extremely heterogeneous nature. In consequence it has been treated as refuse accumulated in dump piles, called ash, gob, piles.

No means has ever been found for economical recovery of useful materials from such refuse. The consequence has been that enormous tonnages of such refuse have accumulated, and despite the inefliciency of the beehive oven, due to the wastage of all volatiles, the need for metallurgical coke has been such that beehive ovens are still operated so that the refuse piles continue to grow.

Ihave discovered, and it is upon this that the invention is predicated, that there can be recovered from such beehive refuse a material that affords a highly satisfactory sintering combustible, much more satisfactory, in fact, as experience has shown, than coal or coke breeze. I have found that this is accomplished by the simple expedient of screening the refuse to remove from it all material under 4-mesh size. The material containing all of the natural gob constituents of 4-mesh size and smaller is then used as the combustible in the mix fed to sinter ing apparatus.

nited States Patent The use of this screened refuse material may be exerhplified with reference to the sintering of iron ore. Standard practice has been to use anthracite coal of minus inch size, or coke bfeeze through a 6-mesh screen. My new material is of 4-mes'h size and finer. No size reducing operation, such as grinding, is necessary so that the grinding costs necessary in the preparation of coal and coke breeze are avoided, with consequentsaving.

Of greater importance, however, is the fact that coal tends to burn spottily with production of hot spots, While both coal and coke tend to burn from the bed before it has reached the end of its travel. Experience has shown that my new combustible holds the heat to the end of the travel, apparently because the refuse coke present burii's first and heats the residual raw or semi-distilled coal, that is present in the refuse, as the bed progresses, which newly formed coke then burns, and as a result heat is maintained throughout the bed travel. This maintenaiice' of heat results in better heat distribution during the entire sintering operation and produces a physically better sinter, i. e., a sinter that is stronger, contains fewer fines, and is of more uniform cluster than has been the case when using other supplemental fuel.

The maintenance of temperature by the use of this recovered refuse combustible is of particular advantage for blast furnace practice in that there is greater conversion of ferric oxide (FezOs) to magnetite (Fe3O4) than is the case with coal or coke.

The avoidance of hot spots, which may occur with coal or coke breeze as fuel, not only affords the foregoing advantages but also, according to experience, results in longer grate life, judged from experience.

In addition to the foregoing major advantages, my new combustible atfords other desirable factors. Thus the material is less abrasive than coke breeze or coal so that its use results in less Wear of mixing equipment, such as pug mills, and of the feeding equipment.

Moreover, in the use of this new combustible there is a tendency for the off gases to be at a higher temperature than is the case when coal or coke are used. Thus, being of bituminous nature the kindling point is lower than that of anthracite coal or coke breeze and affords instantaneous ignition which accelerates the sintering cycle, and due to the exothermic reaction created actually increases the temperature of the off gases as sintering progresses. Neither anthracite coal nor coke has these attributes to this marked degree. This means not only that the bed is more open for better combustion, with production of a better sinter, but also that it is of especial significance in the use of multiclone dust recovery systems where high temperature is important because for proper operation the ssytem must be kept at a temperature above the dew point to avoid clogging. If the expelled gases are not kept at the proper high tempera tures the maximum amount can not be drawn from the sinter bed, which results in an inferior product. Porosity is necessary in sinter and can be achieved only by maintaining highest possible temperatures during the entire cycle of raw materials sintered into finished product.

Still another advantage of this new combustible is that it is less expensive than anthracite coal or coke breeze. Furthermore, its use involves the gradual removal of the unsightly gob piles that surround beehive oven areas whether or not the ovens are now in operation.

In the use of this new sintering combustible the natu ral constituents of beehive coke oven refuse of 4-mesh size and finer are mixed in standard manner with the material to be sintered, the mixture is fed as usual to the pallets of the sintering apparatus, and the combustible in the mixture is ignited as the pallets leave the feeding station. This combustible ignites more readily than coal or coke, as far as I have found.

Depending on the composition of the screened beehive coke oven refuse, enough is mixed with the material to be sintered to supply the amount of combustible required for sintering. In the case of iron ore this is equivalent to about four percent of combustible carbon in the mixture. The exact amount will depend, as will be realized, upon the sinter material.

The judgment of the sintering department of one of the largest steel companies that has been using this refuse combustible is that it is the best fuel that has been used there, from the standpoints developed above.

Although the invention has been described with particular reference to the sintering of iron ore, it is to be understood that the combustible may be used instead of the fuels previously used for sintering purposes in general, for instance, with taconite, blast furnace dust, clay for expanded block products, concentrates, and the like.

According to the provisions of the patent statutes, I have explained the principle and mode of practicing my invention and have described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

I claim:

1. In a method of sintering, the steps comprising mixing iron ore to be sintered with, as the combustible, beehive coke oven refuse containing all the natural constituent material of 4-mesh size and finer, passing the mix to a moving bed sintering apparatus, and igniting said combustible.

2. A method according to claim 1, said refuse consisting essentially of coke fines, raw and semi-distilled coal, and ash from combustion of wood and coal.

References Cited in the file of this patent UNITED STATES PATENTS 1,205,944 Giesecke Nov. 21, 1916 1,231,831 Yost July 3, 1917 1,565,689 Van Slyke Dec. 15, 1925 2,295,811 Stefiensen Sept. 15, 1942 2,380,056 Lloyd July 10, 1945 2,412,104 Stewart Dec. 3, 1946 2,506,618 Sainderichin May 9, 1950 2,527,311 Kelsey Oct. 24, 1950 2,544,752 Gelbman Mar. 13, 1951 2,631,178 Morton Mar. 10, 1953

Claims (1)

1. IN A METHOD OF SINTERING, THE STEPS COMPRISING MIXING IRON ORE TO BE SINTERED WITH, AS THE COMBUSTIBLE, BEEHIVE COKE OVEN REFUSE CONTAINING ALL THE NATURAL CONSTITUENT MATERIAL OF 4-MESH SIZE AND FINER, PASSING THE MIX TO A MOVING BED SINTERING APPARATUS, AND IGNITING SAID COMBUSTIBLE.