US3522034A - Supplying fuel as part of the blast furnace charge - Google Patents

Description

United States Patent 3,522,034 SUPPLYING FUEL AS PART OF THE BLAST FURNACE CHARGE Ervin G. Bailey, Bethlehem Township, Pa. (3502 Chipman Road, Easton, Pa. 18042) Filed June 30, 1969, Sell. N0. 837,575 Int. Cl. C211! 5/00 US. Cl. 75-42 2 Claims ABSTRACT OF THE DISCLOSURE All or part of the coke requirements of an iron ore reduction blast furnace operation are supplied by coking coal within the blast furnace, rather than in a coke oven, thereby dispensing, to that extent, with the coke oven investment, maintenance, and operating expense, and applying B.t.u.s now lost with the release of coal volatiles in the coke oven, to heating the incoming blast furnace charge. While the coal is coked in the upper part of the furnace it is enclosed in gas pervious containers which allow the volatiles to escape While preventing reaction of the carbon with the furnace gases. The container melts in the lower portion of the furnace allowing the coke to perform its normal functions in this portion of the furnace.

This invention relates to iron reduction blast furnace operation.

One of the objectives of my prior Pat. No. 3,346,367 was to provide blast furnace operation wherein escaping top gases contained less CO and H content to be later recovered in stoves.

This was accomplished by introducing secondary air into the upper zone of the furnace and confining reaction of the secondary air to the burning of CO and H which was ascending through the upper zone, so as to prevent consumption of fuel while it was descending through the upper zone and preserve as much of the heat energy of the fuel as possible for release in the form of CO in a lower zone to generate there the high CO gaseous content required to reduce iron ore.

Blast furnace operation in accordance with this present invention continues to accomplish that objective, but, additionally, takes cognizance of thefact that the preparation of coke itself entails loss of B.t.u.s in the coke oven before the blast furnace operation ever starts.

It is hence an object of this invention to supplement the invention of my prior patent by releasing within the blast furnace, not only B.t.u.s theretofore lost in escaping top gas, but also B.t.u.s now lost from the fuel in coke ovens in the course of coking fuel preparatory to its use in the blast furnace.

In short, this invention transfers the coking operation from the conventional coke oven into the blast furnace. It feeds into the blast furnace the material heretofore fed into the coke oven, namely, coal. It converts the raw (i.e., uncoked, though it may be briquetted) coal into coke within the blast furnace 'by driving off the coal volatiles in an upper zone of the furnace where they react with secondary air introduced above the level of the reducing zone so that these volatiles burn within the blast furnace along with any CO or H content in the gases ascending from the reducing zone. To perform the coking operation in the upper zone of the furnace without consuming the solid carbon of the coal, suitable means are provided to shield or shroud the coal, during the coking opeartion, from the gases ascending through the upper or coking zone in a manner similar to the shrouding of the coke in my previous Pat. No. 3,346,367. However, to secure the operation of this invention, where the shrouding is a container and contains, as it here does, coal to be coked, instead of pre-formed coke, it is essential to vent the container so that the coal volatiles, as they are released, expand and discharge out of the container to burn in the surrounding ascending gas stream. This is done by making the containers gas pervious. Differential higher pressure within the containers caused by the expanding volatiles, prevents the ascending gases from contacting the coal or coke within the containers.

In addition, the containers of the coal being coked are composed of metal, which will carry the burden of the descending charge. They can be made from metal such as steel, iron, or other meltable material which alloys with iron from the ore. The shrouding material should, as in the case of my Pat. No. 3,346,367, have a melting point of about 2800 F. They may be made in cylindrical, spherical, cubical or other rectilinear form from tubing, stampings or castings. The wall thickness should vary with size, but may be about 12 gage steel or cast iron of corresponding thickness. The containers are filled with the coal, preferably as single briquettes of a shape and volume corresponding to the internal shape and volume of the container, with the covers being attached by mechanical means such as interlocking lugs, or by tack or spot welding or by other suitable means, in each case leaving vent openings for the escape of volatile gases therefrom. The container, if spherical, may be constituted of two hemispherical cups of a chosen size containing for example anywhere from /2 of a pound to something over 2 pounds of coal in the form of a spherical briquette. The vents can be apertures in the container walls or may be cracks between the cover and the rest of the container or between welds.

As can be understood, a briquette, which is substantially the same in size and shape as the internal volume of the container, exerts considerable pressure on the container walls which resist its expansion when the coal swells as it is subjected to the increasing heat gradient downwardly in the upper zone of the furnace. The resulting compressive forces tend to make good strong coke which will carry the burden when the containers are melted away.

The metal containers are sufficiently rigid to carry the furnace burden in the upper zone, then after the hard coke is formed, this coke will carry its share of the burden after the metal containers are melted away in the lower zone, where the coke performs the same functions as in the standard blast furnace.

In the accompanying drawings, FIG. 1 is a diagrammatic view of a blast furnace indicating at the bottom the tap 10 for molten iron, above that the slag tap 12 and above that inlet connections 14 for introducing a com,- bustion sustaining gas, for example, oxygen enriched hot air, into the bosh. At 16 there are shown inlets for the introduction of pre-heated secondary air. The portion of the furnace above the inlets 16 will be referred to as an upper heating zone, and the portion of the furnace above the molten slag will be referred to as the lower reducing zone.

FIG. 2 is a flow sheet indicating in register with the various levels of the furnace shown in FIG. 1, the reactions and occurrences during a combined upper level coking and lower level ore reduction operation in accordance with this invention.

The shrouded coal is introduced into the top of the furnace as part of the charge which includes ore pellets and sinter. Any CD or H rising as part of the ascending gases as a result of the oxygen blast into the bosh inlets 14 which enter the upper zone of the furnace and burn, along with the hydrocarbon and other volatiles driven off from the coal out of the containers, in reaction with the secondary air so that the top gases contain a very high C01 and H 0 content relative to their content of CO and H When the top gas is practically free from any combustible gases, and at loW temperature as a result of heat exchange with the incoming charge, heat recovery in the usual stoves becomes unnecessary, thereby further saving equipment and operating costs.

The volatiles are driven off from the coal, starting at about 700 F., and completed at about 2200 F.

As the shrouded coal descends below the inlets 16 freed of its volatiles and now coked, the containers are melted off the coke until by the time the then formed coke reaches the lower portion of the furnace, its surfaces are exposed so that the solid carbon therein reacts with the incoming blast at 14 to maintain the reducing conditions for reducing the ore, as in the standard blast furnace. The blast can be heated by separately fired heaters, using coal, oil or gas, with oxygen enrichment, if desired.

Insofar as the shrouded coal input at the top of the blast furnace replaces preformed coke input, it represents a corresponding saving in coke oven investment and expense of coke oven operation and maintenance. While it is contemplated that, in some cases, the entire fuel requirement of the blast furnace may be satisfied only in part by shrouded coal, with the remainder being the presently used pre-formed coke, any decreasse in coke demand for steel making will be more than Welcome because of the limited remaining life of many coke ovens which would otherwise soon have to be rebuilt or replaced.

Moreover, it is contemplated that some coals, not now rated as coking coal, and hence less costly, may be used in Whole or in part in the containers of this invention, and be satisfactorily coked therein because of the higher pressure conditions in the blast furnace than in conventional coke ovens.

Numerical values given in the above description are for illustrative purposes only, and may be varied dependent upon prevailing conditions.

What is claimed is:

1. The method of supplying some or all of the coke requirements for an iron ore reduction operation performed in a blast furnace having an upper heating zone and a lower reducing zone comprising:

feeding coal into the top of said furnace enclosed within gas pervious rigid meltable containers, as part of the descending charge, to shield the coal from gases ascending from said lower reducing zone through said upper zone,

heating said coal in said containers to drive the volatile content of said coal out of said gas pervious containers into the ascending gas stream and convert the coal, at the pressure prevailing in said upper zone, into coke,

injecting a combustion-sustaining gas adjacent the bottom of the upper zone of said furnace to burn, in the furnace, the coal volatiles driven out of said containers as the coal is coked and add heat to said upper zone, and

after said coal is converted to coke in said containers and descends as coke into said lower zone, melting said containers to expose the coke to the hot gases ascending through said lower zone to maintain a reducing atmosphere in said lower zone.

2. The method as claimed in claim 1, wherein the coal is in the form of briquettes having substantially the same size and shape as the internal volume of said containers to subject said coal to resistance against expansion when it tends to swell as it is subjected to the increasing heat gradient downwardly of said furnace, thereby making a strong coke.

References Cited UNITED STATES PATENTS 406,210 7/1889 Graif et al. 42 X 869,043 10/1907 Arden 75 42 1,148,782 8/1915 Kilbourn. 2,767,080 10/1956 Wiberg 75--42 X 2,805,146 9/1957 Howard. 3,346,367 10/1967 Bailey 7542 FOREIGN PATENTS 676,962 8/1952 Great Britain.

HENRY W. TARRING II, Primary Examiner Patent No. a 522 3 D t d July 28, 1970 Inventor(g) E. G. Bailey It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the heading after the inventors name and resident address insert --assignor to Bailey Inventions, Inc.

a corporation of Pennsylvania-.

Signed and sealed this 25th day of May 1971 (SEAL) Attest:

EDWARD M.FLETGHER,JR. WILLIAM E. SCHUYLER, JR. Attesting Officer Commissioner of Patents

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