US2766108A

US2766108A - Method of deactivating sponge iron

Info

Publication number: US2766108A
Application number: US519253A
Authority: US
Inventors: John E Eberhardt; Hugh S Graham; Richard G Gold
Original assignee: Bethlehem Steel Corp
Current assignee: Bethlehem Steel Corp
Priority date: 1955-06-30
Filing date: 1955-06-30
Publication date: 1956-10-09
Anticipated expiration: 1973-10-09

Description

United States Patent Ofifice 2,766,108 Patented Oct. 9, 1956 John E. Eberhardt, Bethlehem, Hugh S. Graham, Hellertown, and Richard G. Gold, Coopersburg, Pa., assignors to Bethlehem Steel Company, a corporation of Pennsylvania No Drawing. Application June 30, 1955, Serial No. 519,258

8 Claims. (Cl. 75--.5)

This invention relates to improvements in the deactivation of sponge iron and particularly to the deactivation of compacted sponge iron.

By sponge iron, as is well known, is meant metallic iron which has been chemically reduced from its oxide without fusion. The particular sponge iron with which this invention is concerned is sponge iron which has been compressed or compacted into solid pieces which are better adapted for use in certain metallurgical processes than the powdered form of sponge iron.

In a process of producing sponge iron which is at present being practiced, finely divided iron ore is treated with hydrogen or other reducing gas by means of the well known fiuidization process in a heated reactor. The reduced iron which leaves the reactor in powder form is, while still in a protective atmosphere to prevent oxidation, fed between rolls which compress or compact the iron into a continuous strip, preferably about one-quarter inch in thickness. This strip then passes through a breaker, which breaks the material into fragments or chips of a usable size, say in the neighborhood of two by three inches.

One fiaw in this process, as heretofore known, however, was that the compacted material could not be stored to await further use. It was found that when the chips were stored in piles, the underneath layers of chips commenced to reoxidize, and this reoxidation continued until the material had reverted practically to the state of oxidation in which it was prior to the reducing treatment. In this state the material could not be put to its intended use.

We have discovered a method of treating the sponge iron chips which puts them in a condition allowing them to be stored in piles for an indefinite time without occur rence of reoxidation. This method consists primarily in allowing a slight, initial oxidation of the chips to take place, and meanwhile subjecting them to a draft of cooling air. This cooling step arrests the oxidation before the chips have heated up more than about 300 to 400 degrees F., and thereafter further oxidation does not occur. The slight initial oxidation that has taken place does not affect the utility of the material.

In the practice of our invention, the sponge iron chips are discharged from the compacting apparatus into the atmosphere. At this point the chips are at a temperature of from 100 F. to 400 F. The chips are immediately delivered to an apparatus which is capable of subjecting them to a gentle tumbling action. For example, the chips may be fed into a rotating drum, or they may be fed onto the first step of a clinker cooler such as is well known in the cement industry and which slowly pushes the material forward and down over a series of steps, tumbling the chips a number of times during their travel to the end of the cooler.

If the chips are treated in a drum, a continuous stream of air will be blown through the drum, subjecting all surfaces of the chips to the oxidizing and cooling action of the air.

Ona clinker cooler, the bed of the cooler may be perfQrated and air be drawn down through the perforations, oxidizing and cooling the chips in the process.

Whichever apparatus is used, the air is blown over the chips at a velocity snificient to arrest the oxidation of the chips before their temperature has risen by more than three or four hundred degrees above what it was at the beginning of the cooling step.

As an example of what we have done, we have treated chips of iron made by reducing Swedish ore on a clinker cooler, the area of the bed of which was approximately 36 square feet. Air was blown past the chips on the cooler at a rate of approximately 5,000 C. F. M. and the time required for the chips to travel the length of the cooler was about 11 to 13 minutes. A slight initial oxidation of the chips occurred, causing a rise in their temperature of to 300 degrees F., after which oxidation ceased and their temperature dropped, eventually reach ing nearly atmospheric temperature before they were discharged from the clinker cooler. The material was then stored in piles, and no further oxidation took place.

We are not aware of the exact reason for the effect our treatment has on the sponge iron chips. It may be that the very thin and harmless film of oxide formed on the chips renders them impervious to further oxidation. Whatever the explanation, our treatment has made it possible to store for indefinite periods material which heretofore could not be stored without reoxidizing.

The term deactivating" or deactivation as used in the following claims means the treatment of the material in question to render it non-oxidizable in air at atmospheric temperatures.

We claim:

1. A method of deactivating compacted sponge iron comprising subjecting the sponge iron, immediately upon its discharge into air, to the action of-a stream of air to cool the sponge iron and prevent its temperature from rising more than 400 F.

2. A method of deactivating compacted sponge iron comprising delivering the sponge iron into open air, permitting a slight initial oxidation of the sponge iron and then cooling the sponge iron in a stream of air to arrest said oxidation and prevent the temperature of the sponge iron from rising more than 400 F. above its temperature at the time of its delivery into open air.

3. A method of deactivating compacted sponge iron comprising breaking said sponge iron into pieces and subjecting said pieces to a tumbling action while at the same time blowing cooling air over said pieces to prevent the temperature of said pieces from rising more than 400 F. during said tumbling action.

4. A method of deactivating compacted sponge iron comprising delivering said sponge iron into open air and permitting an initial oxidation of said sponge iron accompanied by a temperature rise of not more than 400 F., and blowing a stream of cooling air on said sponge iron to arrest said oxidation and cause the temperature of the sponge iron to be reduced.

5. A method of deactivating sponge iron comprising compacting the freshly reduced iron into strips in a new oxidizing atmosphere, discharging the compacted sponge iron into open air and immediately subjecting the sponge iron to the cooling action of a stream of air blown directly thereon, whereby oxidation of the surface of the sponge iron is arrested before the temperature of the sponge iron has risen more than 400 F. above its temperature at the time of its discharge into open air.

-6. A method according to claim 1 wherein the compacted sponge iron is at a temperature of 100 F. to 400 F. upon its discharge into air.

7. A method according to claim 2 wherein the com- 3 4 pacted sponge iron is at a temperature of from 100 F. to References Cited in the file of this patent 400 F. at the time of its delivery into ope air. UNITED STATES PATENTS 8. A method accordmg to elazm 3 wherem the pleces 1,695,041 Elman Dec 11, 1948 of compacted sponge iron are at a temperature of from 100 F. to 400 F. when they are first subjected to the 5 2'501128 tumbling action.

Kerr Mar. 21, 1950

Claims

1. A METHOD OF DEACTIVATING COMPACTED SPONGE IRON COMPRISING SUBJECTING THE SPONGE IRON, IMMEDIATELY UPON ITS DISCHARGE INTO AIR, TO THE ACTION OF A STREAM OF AIR TO COOL THE SPONGE IRON AND PREVENT ITS TEMPERATURE FROM RISING MORE THAN 400* F.