US1889160A - Blast furnace - Google Patents

Description

Nov. 29, 1932. H. A. STRAIN ET AL.

BLAST FURNACE Filed Jan. 2l, 1950 Patented Nov. 29, 1932 UNiren STATES PATENT OFFICE :BLAST FURNACE VAppinanon mea January 21, 1930. serial No. 422,387.

This invention relates to improvements in the construction of blast furnaces and aims 'to provide a furnace of such design as to increasethe varea of a horizontal plane between the base of the usual charging bell and the stock `line section of the furnace; and to effect a more homogeneous mixture of coars-e and fine materials than can be secured by the furnaces of standard design. The invention will be fully apparent from the following specification when read in connection with y the accompanying' drawing in which Fig. l is a longitudinal vertical section through a blast furnace embodying our invention;

Fig. 2 is an enlarged vertical section taken through the stock line portion of the furnace.

Referring in detail to the drawing, a Arepresents the base of the furnace above which is located the usual hearth section A, bosh sec` tion B and inwall section C. Above the inwall section, the furnace is formed with our improved design of stock line section D. This stock line section is of substantially inverted frusto-conical form so as to provide an increased area in the horizontal plane between the base of the large charging bell G- and the stock line of the furnace. As shown in detail in Fig. vEZ, the stock line section of the furnace is formed by incorporating therein a multiplicity of superposed members al. Each of these members is provided with an upwardly and outwardly diverging chamber wall portion d. It is vthus' apparent that the 5 stock line section includes a number of superposed members, each having a central longitudinal chamber therein which is of larger dia-meter than the chamber of the member next below. These members l have out- 0 wardly extending web portions Z2 which are incorporated or bonded to the brickwork or other masonry construction d3 forming the outer structure of the furnace in the zone of the stock line.

The furnace is provided with the usual blast bustle pipe E and tuyeres F with the usual supporting columns H and the usual off-take J.

The chief feature of novelty of our invention, it is therefore seen, relates to the vertical cross sectional contour of the upper part of the furnace whereby we secure a diverging stock line.

Heretofore this stock line section has usually been built with parallel, vertical walls and particular attention has beenpaid to the diameter at the stock line with respect to the diameter of thecharging bell.

Our invention deviates from` the prior standard practice bythe provision of a construction wherein the diameter in a horizontal plane between the base of the charging bell and the stock line is materially increased. By such increased diameter and a flaring or diverging of the wall of the stock line we secure a more homogeneous mixture of the coarse and fine material in the column of stock charged to the furnace.

' Increasing the area below the base of the r charging bell aids in reducing flue dust losses. i The provision of an upwardly diverging stock line which is effective to secure a homogeneous mixing of the coarse and ne materials increases furnace efficiency and also reduces the undesirable channeling of gases through the 7 furnace.

Modern blast furnaces are of a large size, frequently attaining a height of 110 feet and diameter of from twenty to twenty eight feet in the largest parts. It is desirable to in- Vcrease the size of furnaces up to certain points with the object of increasing output and reducing the cost of the product. lVith increased size of furnaces'new problems arise, 'one of whichv relates to the provision of 8-5 proper means to effect a thorough mixing of the coarse and fine materia-ls, another of which is to reduce flue dust losses.

The flue dust is a by-product carried over from the top of the furnace into suitable dust catchers by the outgoing gases. lt contains quantities of line ore, stone and coke dust and to recover these Values the flue dust is sometimes sintered, or briquetted, or otherwise 5 treated and recharged to the blast furnace. lt 9 is more advantageous, however, to convert as much of the burden material into iron as possible with a minimum production of flue dust. In some smelters flue dust actually constitutes a waste product because the cost of handling the same is so great as to offset the value of material recovered. Clearly where the flue dust is not retreated, our novel arrangement, which minimizes the fine dust losses, possesses an appreciable advantage over standard prior practice. In several of the present day steel plants some of the blast furnaces are of such size that ninety five thousand cubic feet of air is blown without objectionable movement through the materials in the stack. Such furnaces can produce approximately one thousand tons of pigr iron per day and they generate approximately live million five hundred thousand cubic feet of gas per hour. Be-` cause of this large volume of gas, the prior furnaces have a high velocity of gas flow through the area lying between the charging bell and the stock line. This causes they furnace to blowout large quantities of so-called flue dust. Even where this dust is recharged to the furnace either in a sintered or in a raw, wetted state the handling and preparation thereof adds materially to the cost of furnace operation. And cutting down or saving on the output of Hue dust tends to lessen the cost per ton of the iron. Our improved furnace with an upwardly and outwardly converging stock line materially lessens the velocity of the gas and the amount of outgoing flue dust. Y

In the former furnaces having'a stock line with cylindrical or substantially parallel walls, we have observed by actual eXperiment that, when the charging bell is lowered, there is an appreciable segregation of the coarse material and the fine material. The coarse rolls in toward the center and the fine tends to stay near the periphery. This is due to the radial unevenness of the stock column, said column being high along the walls and low below the center of the charging bell. This segregation is undesirable because it effects an irregular stock porosity and provides too easy a path for the ascending gases in the center of a mass within the furnace. As the ascending gas is the direct agent for the reduction of ores, it is quite clear that in prior furnaces this channeling or chimneying effect through a restricted part of the charge reduces the efficiency of the furnace. With our improved furnace having a diverging stock line thesegregation of materials of different sizes is largely overcome. Due to the increased diameter at the stock level certain of the larger pieces lodge along the walls of the furnace and as this material descends toward the smaller diameter or throat portion of the stock line such larger pieces push the finer material resulting in a sliding or rolling toward the center. This forced pushing of the fine material caused by the inclination of the stock line walls toward the throat section improves the homogeneity of the stock column throughout the entire cross sectional area.

With this improved distribution of the coarse and fine material of the burden, the stock porosity is improved and this permits an increased contact between the descending solids and the ascending gases, thus preventing the objectionable channeling or chimneying effect.

The invention described herein has been actually reduced to practice and the comparisons mentioned between the operation and efficiency of furnaces-'of prior design and the furnaces of our invention are based on our actual observations and studies of the different types. We have also determined that with a furnace having a diverging stock line such as described, the top gas temperatures were materially reduced and the movement of the furnace stock was smoother and the operation of the furnace as a whole was more uniform.

While we have described quite specifically the embodiment of the invention illustrated it is to be understood that we are not limited thereto since various modifications may be made without departure from the invention as defined in the appended claim.

What we claim is:

A blast furnace having a. lower inwall portion sloping inwardly and upwardly, an upper stock line section sloping outwardly and upwardly, the plane of junction between the inwall section andthe stock line section being of lesser furnace interior cross sectional area than planes thereabove, said plane of junction being located below the stock line, a bell located at a point materially above the plane of minimum furnace area and adapted to discharge material directly against the outwardlyk flaring walls of said stock line section whereby the material is directed inwardly and downwardly, said stock line section being lined with a multiplicity of superimposed members, each provided with an upwardly and outwardly diverging wall portion and having a web portion bonded to the brick work construction forming the outer structure of the furnace, and gas oiftalres connected to the upper portion of the furnace and communicating with the space above the entire upper surface of the stock.

In witness whereof, we have hereunto signed our names.

HARRY A. STRAIN. GEORGE E. STEUDEL.

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