US2865731A - Iron ore briquette with paper pulp binder - Google Patents

Description

2,365,233 Patented Dec. 23, 1953 IRON ORE BRIQUETTE WITH PAPER PULP BENDER I John H. 'Crowe, Lakeland, Fiat, assignor to Minerals & Chemicals Corporation of America, a corporation of Maryland No Drawing. Application June 25, 1954 Serial No. 439,453

13 Claims. (Cl. 75-3) and it is with the briquetting of such concentrates that the present invention is primarily concerned, although it is not restricted thereto. Other iron oxide fines as, for example, flue dust from blast furnaces or powderedv taconite concentrates can also be agglomerated according to my invention.

Essentially all of the methods of agglomerating iron ore fines in present day usage rely on high temperature heat treatment to toughen the product. It is one object of the present invention to provide a means of furnishing iron ore briquettes tough enough to stand up satisfactorily under the rough handling they must undergo before they are finally in the blast furnace, without the use of an expensive high temperature heat treatment.

Some methods of agglomerating ironore fines employ inorganic binders, which are undesirable in a number of respects, chief among which are (1) The fact that such binders usually result in a tight, dense mass, thus entailing a sacrifice of porosity; a certain amount of porosity is necessary to permit saturation by the reducing gas in the furnace.

. (2) The fact that such binders-do not burn and thus do not contribute to the reducing atmosphere but,instead, simply add to the burden of the waste slag.

3) The fact that such binders sometimes require relatively long periods of time in which to set.

It is a further object of the present invention to provide an iron ore briquette which does not possess these undesirable characteristics.

j Another object is to provide an iron ore briquette which possesses great strength in the green state and which is .'held together by a binder that burns, thereby contributing to the reducing atmosphere of the blast furnace and increasing the porosity of the briquette while in said furnace.

Other objects and advantages of my invention will become apparent to one skilled in the art from the following disclosure of said invention.

I have discovered that cellulose fibers make an excellent binder for use in briquetting finely divided iron ores. When a thick aqueous pulp of such fibers is dispersed throughout a batch of the said ore fines, in a suitable proportion, and briquettes are made from the resulting mixture, the briquettes are extremely tough, even when freshly made (green). After the moisture has been dried from these briquettes they are ideal for blast furnace feed as evidenced by the results of laboratory tests for strength, porosity and heat resistance, which are hereinafter described (it is not essential that the briquettes be completely dried prior to being fed to the furnace, how

ever; they can be fed after only partial drying or even in the green state).

The best known material in the cellulose fiber category, and the one of most utility for the present invention, is wood pulp. Any wood pulp prepared as though for subsequent paper manufacture (regardless of the pulping process), sufiices as a binder in the method of my invention (this includes repulped paper). Other cellulose fiber pulps (e. g., the rag pulp employed for making fine paper) are very satisfactory as binders also, but the cheapness and ready availability of wood pulp make it the preferred one.

The essence of the present invention, then, lies in the fact that cellulose fibers make an excellent binder when uniformly distributed throughout an iron ore briquette.

The quantity of cellulose fibers in our novel iron ore briquette may vary over a wide range, it being only necessary that a suflicient amount be employed to give the desired binding effect. The optimumarnount for maximum toughness is dependent upon the type iron ore fines to be agglomerated, and the particular cellulose fibers employed. I have found that 12 to 18 pounds of cellulose fibers per ton of iron ore fines give excellent results; however, amounts up to or more of the cellulose fines based on the weight of the bonded briquette can be utilized within the scope of this invention. These briquettes can be readily turned out with mixing and briquetting equipment in common usage today, as for example, a pan mixer in conjunction with a roll type press. Following are descriptions of certain laboratory tests which will contribute to a fuller understanding of this invention. At the same time, it is to be understood that the descriptions of specific operations in these examples do not imply limitation of the invention thereto, since there are many modifications of method falling within the scope of said invention.

Example I Newspaper was pulped with water in a blender and the wet pulp then partially dewatered on a screen. The partially dewatered pulp was kneaded into a batch of finely divided hematite flotation concentrates with a laboratory mixer. The amount of pulp added was such that the ratio of pulp (dry basis) to ore (dry basis) in the final mixture was 18 pounds per ton. The ore, as used, was slightly damp, containing 14.8% moisture (total weight basis).

Small cylindrically shaped briquettes, one and one-half inches in diameter and about one-half inch thick and weighing about 45 gm. each (after drying), were formed from the plastic ore mass. A mold-and-piston type hydraulic hand press was employed for this operation; pressures used did not exceed about 5600 p. s. i.

To find out how tough the green briquettes were, two of the freshly made ones were tumbled and the resulting fragments screened. The tumbling device was a steel drum of about three foot diameter with internal lifting flights. Tumbling was accomplished by rotating this drum rather slowly aboutits axis, with the briquettes in side, for a period of one minute. The results of this test give an indication of briquettes resistance to impact.

It was found that the fraction of tumbled material retained on'a Tyler standard IO-mesh screen amounted to 98% by weight of the initial briquettes and that, of this, 88% would not pass a Tyler 1-inch screen. These re- 'sults showed an unusually high resistance to impact, a

characteristic not found in green iron oxide briquettes when other binders are used.

Some of the greenbriquettes were dried in an oven at a temperature of about 250 F. for two hours, and three of these were given the tumbling test. The results: 94.3% of the product turned out to be plus-IO-mesh in size and about 87% of this fraction was plus-l-inch. These results indicate a high degree of toughness, equal or superior to that of briquettes with other binders. Similar oven-dried briquettes of the same ore with no binder have been found to tumble to 54.5% plus-10-mesh.

A reliable porosity test comprises soaking a briquette in water for five minutes, after which itsgain in weight is determined. Very little or no gain, of course, means that the briquette is unsatisfactory in porosity. One of the above-mentioned oven-dried briquettes was given this test, during which it took up 12.9% of its weight of water. This amount of gain, as one skilled in the art knows, is evidence of excellent porosity.

Example II One of the briquettes was compressed between steel plates, with the hand press, until it had been mashed to about half of its initial thickness. Although it cracked during the ordeal, it remained in one piece. This was a striking demonstration of the excellent holding ability of cellulose fibers. Briquettes with conventional binders tend to crumble under compression, some doing it at extremely low pressures.

Example 111 A batch of briquettes was prepared in the same way as those of Example I, except that pulped toilet tissue was substituted for the pulped newspaper. Some of these were oven-dried, as those of Example I had been, and some were dried in the air at room temperature for one week.

Tumbling results on the oven-dried ones were: 95.8%

'plus-lO-mesh, of which all was also plus-l-inch; and on the air dried ones: 91.5% plus-l-mesh.

A porosity test of one of the oven-dried briquettes showed 11.8% absorption.

In addition to the typesof paper used in the examples, kraft paper, paper towels and bond paper 'were pulped and tested as binders. Also, paper pulps of all kinds (mechanical, sulfate, sulfite and soda) were obtained from paper mills and tested. All pulps investigated proved effective.

One of the briquettes (filter paper) was tested for heat resistance by heating it up to 2000 F. in such a way that plenty of time was allowed for the paper to burn out. It

remained intact throughout this treatment, thus indicating that the present briquettes would not disintegrate prematurely in the furnace. I

The above examples show that cheap and readily available cellulose fiber pulp makes an excellent binder for the briquetting of finely divided iron oxide materials and more particularly, that such a binder imparts unusual green strength to the finished briquette; that said briquettes require no high temperature induratingtreatment; that they are adequately tough, porous and heat resistant; that they are possessed of excellent plasticity (i. e.,

4 they deform rather than disintegrate under compression). Also, as above mentioned, the present binder is one that burns, thereby contributing to the reducing atmosphere of the furnace (and producing no slag).

I claim:

1. In a process for briquetting finely divided iron oxide material, the step which comprises incorporating cellulose fibers into the iron oxide material, as a binder, prior to the briquette forming operation.

2. The method of briquetting finely divided iron oxide material which comprises mixing the said material with a thick aqueous pulp of cellulose fibers and briquetting the resulting mixture.

3. The method of claim 2 wherein the iron oxide mate rial is hematite flotation concentrates.

4. The method of claim 3 wherein the pulp of cellulose fibers is paper pulp.

5. The method of claim 3 wherein the pulp of cellulose fibers is repulped paper.

6. The method of claim 3 wherein the briquettes are dried at about 250 F.

7. An agglomerate comprising essentially finely divided iron oxide material and cellulose fibers present in amount suflicient to bind the particles of iron oxide material together.

8. An improved briquette comprising essentially finely divided iron oxide material with cellulose fibers distributed throughout in amount sufficient to bind the particles of iron oxide material together.

9. The improved briquette of claim 8, in which the proportion of cellulose fibers is between about 10 and about 25 pounds per ton of the iron oxide material.

10. The briquette of claim 8 in which the cellulose fibers comprise paper pulp.

11. The briquette of claim 8 in which the cellulose fibers comprise repulped paper.

12. The briquette of claim 8 in which the iron oxide material consists of hematite flotation concentrates.

13. An improved briquette comprising essentially hematite flotation concentrates with paper pulp distributed throughout in amount between about 12 and about 18 pounds per ton of the concentrates, the paper pulp acting as a binder.

References Cited in the file of this patent UNITED STATES PATENTS 841,718 Robeson Jan. 22, 1907 854,527 Pollacsek May 21, 1907 987.554 Coggeshall Mar. 21, 1911 1,002,453 Ronay Sept. 5, 1911 1,024,428 Valentine Apr. 23, 1912 1,154,980 Exbrayat Sept; 28, 1915 1,158,366 Bibb Oct. 26, 1915 1,168,401 Kippe Jan. 18, 1916 1,576,248 Robeson Mar. 9, 1926 1,614,369 Kippe Jan. 11, 1927 2,127,632 Najarian Aug. 23, 1938 2,533,027 Maust et a1 Dec. 5, 1950v FOREIGN PATENTS 24,845 Great Britain of 1908 24,846 Great Britain of 1908 OTHER REFERENCES Handbook of Briquetting, vol. 1, by Franke, 1917, page

Claims (1)

1. 2. THE METHOD OF BRIQUETTING FINELY DIVIDED IRON OXIDE MATERIAL WHICH COMPRISES MIXING THE SAID MATERIAL WITH A THICK AQUEOUS PULP OF CELLULOSE FIBERS AND BRIQUETTING THE RESULTING MIXTURE.