US1948697A - Manufacture of metals - Google Patents

Description

Feb. 27, 1934. H A, BRASSERT 1,948,697

KANUFACTURE oF METALS Filedvuuly 27. 1931 2 sheets-sheet 1 ym #den Feb. 27, 1934. f

' H. A. BRAssERT 1,948,697

MANUFACTUHE OF METALS Filed July 27. 1931 2 Sheets-Sheet 2 Patented Feb. 27, 1934 Herman A. Brassert,

poration of Illinois Chicago, Ill., assignor 1 H. A. Brassert & Company,

Chicago, Iii., a cor- Appiicauon July 27, 1931. serial `V No. l553,249 e claims. (favs- 17) This inventionv relates to the manufacture` of metals and especially of iron and steel, and more particularly to the production of a purer grade of metal than is usually obtained by the present 1 methods.

It is a well known fact that iron or steel made 'directly from virgin material, that is from the metal` ironinthe ore, without permitting the to be reoxidized or to saturate itself with foreign substances, is of asuperior quality. In the last furnace the iron ore is" first reduced and then that portion of'it which happens to descend in ythe areasclose to the tuyres is reoxidized in the presence ofpreponderant amounts of oxygen and CO2 in the tuyre areas. Such iron oxides y Iare again reduced asthey `come in'contact with the incandescent carbon of the coke lying in the hearth. Whether allof the oxides are reduced depends on the temperature of the hearth, the reactivity of the coke and the time element. At any rate, the effect of the tuyre blast on the reduced iron ory molten iron sponge trickling down past the tuyres is detrimental to -the quality of the iron', not only in that it is exposed to oxidatiombut also to the absorption from the blast of hydrogen and nitrogen. I

In the blast furnace process, as now on, this cannot be prevented as the enormous blast volume required to burn the ,heavy coke charge penetrates a considerable distance into the coke bedwithout its oxygen being completely converted into CO. The slow reactivity of metallur'gical coke aggravatesths phenomenon. Char- A coal with its high reactivity reduces this oxidizing has decreased the relative size of the annular oxi- Vdizing zone in the tuyre area. However, this increase in hearth diameters has brought with ,it/ disadvantages, as for instance a substantial decrease'in the productive capacity of blast fur- `nacesper square foot of hearth area, due to the large inert center areas present in such furnaces.`

Also there are heavy iiue dust losses ,due to the increased volumes of blast required to cover the Ienormous circumferences of such hearths. The latter-objection lcan be overcome by decreasing the nitrogen content of the-blast through oxygen enrichment. This, however, would further aggravate the phase of iron oxidation -which is so objectionable and which should .be prevented as much as possible. f

It is an object of the present invention to pro# vide a new and improved method for the manufacture of a purer grade of metaLthan is usually ,55 obtained by present methods. 1

carried phase. The gradual increase of hearth diameters v It isl a `further object to provide a method whereby reduction and melting can be carried out in a reducing gas phase throughout.

It is also an object to provide a' method for the production of iron or steel whereby the intraduction of sulphur into the metal'from coke fuel is reduced to a minimum or entirely eliminated. .y 7 y Other and furthercbjects will appear as the description proceeds. f

My invention provides a method whereby reduction and melting can be carried out. in a reducing gas phase throughout. This cannot be accomplished if coke isused as a fuel. Coke is too slow to react with the blast, consequently there will always be an oxidizing zone in front of the tuyeres when coke is used. vThe larger the .coke andfthe denser, harder and slower burning it is, the deeper this zone will penetrate toward the center. I propose, therefore, to do away with the method of reducing and melting,

as carried out in the present blast furnace, and

to substitute a more reactive fuel than coke fors carrying out my process. I propose to substantially eliminate the oxidizing zone in the tuyre area. v

This I accomplish by substituting for the present blast furnace hearth and bosh a chamber of'such dimensionsas to provide an annular combustion space around the descending mate- 85 rials. This annular combustion chamber should be of such depth that combustion can be completed to such an'extent externally to the mass of materials that no free carbon remains. Into this chamber I feed fuel and combustion air in such proportions that the resulting flame is of a reducing character so that the melting materials will not be re-oxidized in contact with either oxygenorCOa...

I Vhave shown a preferred embodiment of a furnace adapted for carrying out'my invention lin the accompanying drawings, in which- Figure 1 is a vertical section through the furnace;

Figure 2 is a horizontal section taken through 100 the lower line of tuyres; and A Figure 3\is a plan view of the hearth portion partly in section, through the 'upper' linef of tuyres. I l 1 In the drawings, the stack potion 11 is shown 105 as provided with a metal shell 12 and a refractory lining i3, which is provided with water cooled bosh plates 14 which maybe of usual construction. It will be understood that any usual type of charging bell may be located atvthev up- 110 per`end of the stack portion, which will also be provided with offtakes for carrying olf the products of combustion.

The stack portion is supported on theannular water cooled metal ring 15. The hearth portion 16 is provided with a base 17 which may be formed of any usual refractory brick or other similar material, and which is enclosed in a water cooled metal jacket 18. The hearth is shown as covered with a lining 19 of refractory material which may be any of the types of material used in open hearth and similar furnaces. A tapping The central portion 23 of the hearth is raised.

and this, together with the layer of refractory material 19 on the central portion, causes this portion to extendvto a level above that of the lower line of tuyres 24. These tuyres are fedA with air through pipes 25 leading from bustle pipe 26,l and with fuel through pipes 27 fed from fuel header 28. As clearly shown in Figure 2, these tuyres 24 are located on approximately tangential lines so that the flame from the tuyres is directed down on the annular bath of metal and slag rather than toward the raised central portion of the hearth. This causes a circular movement of the heated gases and enables the ame to be in contact With the bath-over an extended space without burning out the refractory central portion. This refractory. central portion 23 may be provided with suitable-cooling means, suchas the pipes 29, to assist in maintaining it.

The upper curved Wall portion 30 of the hearth section is shown as made up of a plurality of segments 31, as best shown in Figure 3. These segments are individually removable, being supported at their upper ends against the water cooled ring 15 and at their lower ends by the water cooled ange 32 of the water cooled jacket 18 of the vertical walls.` These segments 31 are provided with a plurality of water cooled pipes 33, and their inner faces are formed by refractory brick 34.

- The upper series of tuyres 35 extend through the curved portions, certain segments 36 being especially designed and provided with 'tuyre openings. The tuyres 35 are fed with air through pipes v 37 from the bustle pipe 26, and with fuel Vthrough pipe 38 from header 28. As clearly shown in Figure 3, these'tuyres 35 are preferably placed slightly oi of an exact radial line so as to insure a circulatory movement of the gases and yet they are not placed tangentially as the lower tuyres, as it is desired to direct the flame from the upper tuyres against the central column of descending material.

A third set of tuyres 39 discharge through small openings 40 into the upper portion of the domed section of the hearth. These tuyres 39 are supplied through pipe 41 from the bustle pipe 42. These tuyres arenormally supplied with burned gases or other inert gases which will not burn, and which gases form a protective layer adjacent the inner surface of the domed hearth wall to protect this surface against erosion by the of higher temperature.

heated products of combustion from the two lower sets of tuyres.

j It is well known that the temperatures required than are used or necessary. in present blast furnace practice.

In fact the carrying out of my invention to its fullest extent has become possible through the recentl development of means of economically producing high blast temperatures, such means consisting of zoned checkerwork, as described in Patents No. 1,771,282, July 22, 1930, and N0. 1,771,286, July 22, 1930. Preferably I heat the air to 1800 F. and as much more as possible before admitting it to the tuyres. 'Ihe high blast temperatures compensate for the loss of fiame temperature caused by carrying a reducing llame. The fuel used for the purpose of obtaining and maintaining a reducing phase in the melting zone is preferably powdered coal, which may be injected by itself or as an addition to other fuels, such as natural gas, coke oven gas,

blast furnace gas, producer gas or oil.

As a means for better control of my process, I

may also use a blast enriched with oxygen preferably to about twice its natural content. This can be done very economically by modern methods, and has the advantage of considerably increasing the llame temperature. This permits me to carry a flame with a still greater excess of carbon producing a phase of stronger reducing power, which will accelerate the reduction of the ores without retarding the melting process. It will also result in a still finer grade of iron being made, as my iron is protected from the direct action of the enriched blast.

A further important advantage of the use of fuels of this character lies in the fact that the sulphur which is normally 'introduced into the metal from the usual coke fuel charge, is not brought into the process. This sulphur is injurious to the iron andits removal adds to refining costs so that its elimination at its source is highly desirable.

To follow the process through, when using ore, I charge it into the top of the furnace. It descends through the shaft in contact with the.

CO ascendingfrom the reducing gas phase below, whichv gives 01T its heat to the descending materials and reduces same by. indirect reduction. I add some carbon to the ore charge to cause some direct reduction totake place in zones By the time the materials reach thel lower section of the stack they have .been reduced to iron sponge and are entering the melting zone completely surrounded by a CO gas phase in the presense of excess carbon. Under these conditions the melting iron is not exposed to any oxidizing inuences. Because the -combustionzone isseparate and independent of the melting column, its temperature can be regulated and can be maintained uniformly at a point most advantageous to the production of high grade metal. This is not the case in the blast furnace where the materials descend directly into the combustion zone in a more or less irregular manner.

While I' preferably use a combustion chamber of annular shape, other forms, such as ellipti- Cal Or rectangular, can be employed for the same purpose. Incase of iron ores being used, I may charge'tliemv in their natural state or dried or sintered or briquetted, or I may mix cmshed lump ,ores with'nes and briquettes. With varying character of ores, various methods will be found desirable. In any case, my invention provides a means of producing iron or steel from ores, scrap Aor sponge iron which neither become reoxidized with the blast nor saturated with carbon as happens in the present blast furnaces. The saturation of iron with carbon in the blast furnace necessitates a subsequent oxidation process in the Bessemer converter or open hearth furnace, which again exposes the metal to vitia` tion with oxides. By my method the amount of carbon which the metal absorbs can be kept under control and can be limited to small amounts and the carbon can be reduced by the addition of iron ore, either in the hearth or preferably at the top, as lumpsof sumcient size that they will arrive in the molten bath containing the iron oxide required to bring down the carbon in the metalto' the desired point. It is a well known fact that the removal of carbon by iron oxide addedfto the bath results in a liner grade of steel than if the carbon is removed by an air blast, as in the Bessemer process.

The form of. construction shown in the drawings is to be understood to be illustrative only,

as my improved method may be lcarried out in furnaces differing materially from'that shown, and I contemplate such changes and modificallame being maintained at a temperature sufficient to melt the reduced ore inthe lower portion of the column of material, supporting the column of material out of contact with the melted metal, and passing reduced gases from the ilame upthrough the yupper portion of the column whereby the ore in the column is reduced.

2. The method of producing pure metal, which comprises treating' a column of descending ore by surrounding the lower portion of the column with a reducing flame adjacent and spaced from vthe column of material, the reducing iiame' beving created by the injection of fuel and air, the flame being maintained at a temperature sunlcient to melt the reduced ore in the lower portion of the column of material, supporting the column of `material out of contact with the melted metal, treating the molten metal with a relining llame, and passing reducing gases from the flame up through the upper portion of the col-` umn whereby' the .ore in the column is reduced. HERMAN A. BRASSERT.

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