US2733913A - Blast furnace linings - Google Patents

Description

G- E. MERCER BLAST FURNACE LININGS Filed Oct. 8, 1951 F eb. 7. 1956 E .e N w E a 3354 QMQQS 4 T c 2 4 a m z w L E a w 6 V 5 4 w n n M e a 4 g m N Q N u. 5 m s K a P u e u e A H m 3 e r e c z p A E n P E M c M 4 A e m n u w w e u m m u u a e s u 5 w w A u .m 3 w 4 a n w. wiomwzinwu w 6 N% i 52 ZZ% m 4T 2,733,913 enema Feb. 7, 1956 BLAST FURNACE LININGS George E. Mercer, Mount Lebanon Township, Alleghen County, Pa.

Application October's, 1951, Serial No. 250,383 5 Claims. (Cl. 266-43) A This invention relates generally to linings for furnaces and more particularly to linings for blast furnaces employed to produce pig iron.

A blast furnace forthe production of pig iron is constructed on a foundation or floor and is built up in differerent sections that vary in shape from the bottom to the top of the furnace and which are known as the crucible,

the bosh, the mantle, the lower and upper inwall, the stock line and the bell. The bottom of the furnace comprises a crucible which contains the molten iron and it 'must have refractory walls and floor suitable to contain the molten iron. Immediately above the crucible is what is known as the bosh. The bosh increases in diameter from thetop of the crucible to what is known as the mantle and is the Zone in which the tuyeres are placed for the purpose of introducing gases into the blast furnace. The largest diameter of the blast furnace is at the upper end of the bosh and the lower end of the mantle. The inwall extends from the top of the bosh or mantle upwardly to what is known as the stock line, which is that portion in the top of the furnace employed to receive the raw materials prior to their being melted and descending downit ward to the reducing zone. The inwall section may be divided oif in two parts; the lowerinwall section and the upper inwall section, both of which are substantially the same height. The whole of the inwall section is large in diameter at the mantle and may be cylindrical for a short distance, possibly ten feet, and then it becomes gradually smaller in diameter and the furnace rises for about approximately forty-five feet until the bottom of the stock line is reached. Above the stock line is what is known as the bell which is a conical cover over the center of the furnace on which the raw materials are dumped when loading the furnace.

The principal object of this invention is the provision of different characters of refractory linings for blast furnaces for the purpose of increasing thelife of the blast furnace and also to increase the production .ofthe same.

Linings are ordinarily constructed from forty to sixtyinches thick. These linings are made principally from fireclay brick which will disintegrate at predetermined temperatures owing to the presence of carbon monoxide. When carbon monoxide comes into contact with ferric oxide in the brick and the oxygen transfers from the monoxide to the iron leaving free carbon, the free carbon grows within the refractory structures and causes them to break and destroy the lining of the furnace. This weakening of the furnace lining is due to disintegration. Also, other faults are created such as erosions or the production of scabs such as the growth of a conglomerate on the refractory wall. Faults of this character increase the cokes consumption and decrease the life of the lining, requiring the furnace to be shut down sooner than it should be and be relined before its production can be again increased to normal and reduce the coke consumption.

The present invention contemplates the use of a refractory that is low in ferric oxide or will not take on ferric oxide which, when subjected to carbon monoxide, produces a free carbon that will accumulate and disintegrate and silica and produce a ferric alumina silicate that is impervious to the carbon monoxide.

'Another object is the provision of a blast furnace lining constructed of an alumina refractory that has a very low porosity in combination with a high fusion hard burned mullite lining and a high fusion silicon carbide lining. Each of these refractory materials may be formed into bricks or other suitable lining shapes after which they may be built into the lining to produce a finished blast furnace, which then can be charged and operated without additional treatment.

In accordance with the teachings of this invention an ordinary fire-clay lining requires a special burning prior to operating the same unless the brick is hard burned. A hard burned brick provides a low porosity lining and prevents the ingress of carbon monoxide.

A hard burned fire-clay brick which has been turned to a sufiicient temperature to convert any ferric oxide into a ferro-alumina silicate or any one of the alumina mullite or silicon carbide lining materials are of low porosity and have low ferric oxide and will be more resistant to the ingress of the carbon monoxide. Thus, they will not be attacked by the growth of free carbon within their structures. A blast furnace lining of this character will not disintegrate due to the growth of free carbon. Again, these bricks are of a materially higher order of refractoriness than of an ordinary fire-clay and they produce a lining that will withstand much higher temperatures and are impervious to the attack of the reducing atmosphere of a blast furnace. Thus the thickness of a blast furnace lining may be reduced from sixty inches to approximately twenty-seven inches. This mechanically increases the capacity of the blast furnace, yet the lining itself will last a materially longer time than the sixty inch lining of fire-clay and, thus, provide an increased production of pig iron which is far greater than the increased cost of the lining over an ordinary fire-clay brick lining.

It has been found preferable to construct the blast furnace lining by placing on the bottom of the crucible a floor of alumina brick, whereas the lining in the vertical wall forming the crucible may be constructed from a mullite brick. This mullite brick may be extended up to the bosh or to the mantle and a high fusion alumina brick may be made to line the lower inwall above the bosh and the mantle A high fusion silicon carbide brick is employed to line the upper inwall and the stock line. Reasons for employing a silicon carbide brick in the upper inwall are to provide a brick that is impervious to sudden changes in temperature as well as abrasion and at the same time will not be attacked by the carbon monoxide and to prevent scab formations.

A blast furnace lining may be constructed using a high alumina brick of low porosity in the bottom of the crucible with a high fusion hard burned mullite brick lining the walls of the crucible and the bosh above the same.

Starting at the mantle and upwardly a high fusion alumina brick of low porosity may be employed for the lower inwall and a high fusion silicon carbide brick lining may be employed for the upper inwall section. A similar mullite brick can be used for lining the upper portion of the inwall section. Thus, the lower inwall section and the lower portion of the upper inwall section would form three different zones of different character of brick designed to withstand the temperature and the erosion con- -ditionsat those levels and to withstand the carbon monoxide. The belLzoneat the top,ofthefurnacemdlbts lined with a fire clay brick.

All of these linings are of a materially higher grade refractory than the ordinary @fire-clay brick. However, a 'material improvement may be made .in the fire-clay around 420 C. to 500 C. and-if a.brick istburned:at a

temperature .materially higher, that is, in .the ;order of -a 23 cone, thefusionpointof:suchabrick wil1:rise to al-33 cone. However in most instances the fusionzpointvofa mullite brick is abouta 39 cone andthatof an.-alumina brick with a 14% porosity would:be arounda142cone,

whereas a vitrified alumina1witha'2% to 31% porosity may have v afusion point at a.:42;cone. .The siliconcar bide brick which is burned arounda -26-conedisassociates around .4000" F. or over. Ifthemullite type of brick contains about 64% to 72% .alumina,-it-may.be.-burned at a 35 cone and it will nottmeltvabove a 385COI16. -Refractories of this nature will provide a.-much betterlining than that of a fire-clay and-will not t-besubjected to the disintegration as these refractories :are less porous and will not admit the carbon monoxidegas in sufficient quantities to disintegrate'it. There is nothingin these refractories which would function in the .manner of a catalyst to convert the gasto afree carbon causingit to grow and disintegrate the refractory, whereas the'more porous fire-clay structure, which frequently :has ferric oxide, will admit carbon monoxide, giving rise .to the conversion of the gas to carbon'between 400 C. and 700 C. and allowing the entrapped gas to change chemically and release the carbon to provide the oxygen for tion of the upper inwall which is referred toras merely the upper portion of the upper inwall zone.

High fusion alumina brick of low porosity lines the bottom of the furnace which is also the'bottomof the crucible. A high fusion charred burned mullite brick lines the walls of the crucible and the bosh above said bottom, and a high fusion alumina brick of'lowporosity lines the lower inwall above the bosh and the mantle.

The upper inwall and the stock line-zones may'have different linings in accordance withthis invention. The

- znssma I r p g 4 lower portion of the upper inwall which may be referred .tothesca lon is lined w t Silicon carbide brick- The upper portion of the upper inwall may be lined with either silicon carbide brick or a high fusion hard burned mullite brick.

The stock zone may likewise be lined with different character of brick. The stock line may be lined with either silicon carbide brick.or a fire-clay brick which has been firedunderconditions thatthe ferric oxide will combine with the aluminum and silica to produce a ferric alumina silicate :that is impervious to carbon monoxide gas.

The large bellzqne which ,is above the stock line is ordinarily lined with a fire-clay brick of similar character of that used in;t he.stock line.

I claim:

1. A blast furnace lining comprising a high fusion alumina brick of low porosity covering the bottom of the furnace,,,a high fusion hard -bu1fne d; mullitebrick'lining the crucible .andthe bosh above s 2 1id-bottorn, a high fusion alumina brick of low ;porosity-,lining the lower inwall above the bosh iand mantle, and ;a ,-high fusion silicon carbide ibrick lining the upper inwall and the stock line of the furnace.

,2. The structure of claim lwhich alsoincludes a fireclay brick lining the ;bell;zone;at the top of thefurnace. .3. A :blast furnace lining comprising a high fusion alumina brickof 10W porosity lining the bottom of the furnace, ;a high fusion hard .bllrned mullite brick lining the Walls ,offthecrucible .and'boshabove said bottom, -a highfnsion alumina brick of low; porosity lining the lower inwall abovethe boshandrnantlqa silicon carbide brick lining thelower portion of the upper-inwall, and

,a fire-clay brick lining -the-bellzone-,at thetop of the fur c inwall, the stock line and the bell zone, and a silicon carbide ,brickilining the lowerportion of the upper-inwall.

References Cited in the file of this patent :UNITED STATES PATENTS Laird Jan. .20, 1920 Brassert etal. Sept. '4, 1951 OTHER REFERENCES American Foundryman, May 1947, page 66. Iron Age, June' 10, 1948, page 94.

Steel, Sept.'l 1, 1950, page 105.

IronAge, Sept.'21, 1950, pages-92 to 94. Steel, Nov. 27, 1950, pages'74, 77 and 78.

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