US1941606A - Metallurgical apparatus - Google Patents

Description

Jan. 2, 1934. .c R. KUZELL 1,941,605

METALLURGICAL APPARATUS Filed Nov. 19, 1929.

INVENTOR C: harfes R. Kuze HISATTORNEYS Patented Jan. 2, 1934 UNITED'STATES PATENT OFFICE METALLURGICAL APPARATUS Application November 19, 1929 Serial No. 408,247

13 Claim.

This invention relates to metallurgical apparatus and has for an object the provision of an improved receptacle for receiving molten baths l od of lining molten bath receptacles with basic materials. In one of its more limited aspects, the invention contemplates the provision of an improved basic lined copper converter.

In processes involving the treatment of mol- 16 ten baths at high temperatures, it is customary to employ receptacles for the baths which comprise sheet metal shells lined with refractory materials. The nature of the refractory material employed is determined by the nature of the 20 process and the composition or character of the bath. Thus, in some instances, acid refractories such as silica are employed, while in other instances, basic refractories such as magneslte are employed. The form in which the refractory material is applied to the inner surface of the receptacle depends largely upon the character of the material and to some extent upon the nature of the process to be carried out. The character of a refractory material may be such that it may be employed in providing a monolithic lining for use in a particular process, or its character may be such that it can only be successfully employed in the form of bricks which have been subjected to high temperatures and/or pressures. Frequent replacement of linings is necessary in many cases because of rapid destruction and disintegration resulting from high temperatures, corrosion and other causes. Monolithic linings, as a general rule, may be provided at a lower cost than brick linings, and it is therefore advisable when possible to use refractory material which is capable of forming satisfactory monolithic linings or to so form a monolithic lining from ordinarily unsuitable material that satisfactory service may be obtained.

According to some present practices, molten bath receptacles employed in processes requiring the use of basic linings are lined with bricks. It is generally believed that such linings must be 30 formed of bricks of properly heat treated material and that a monolithic lining cannot be successfully employed. The use of basic materials in brick form is, in some instances, satisfactory from the operating standpoint, but patching of brick linings and replacement of burned out portions is usually a difficult and costly procedure.

In replacing a portion of a brick lining, it is generally necessary to remove a considerable portion of the lining adjacent theburned out portion to provide smooth, flat contact surfaces. This involves the destruction and removal of a considerable amount of substantially unimpaired lining and enforced idleness of the receptacle for a relatively long period. Furthermore, bricks are relatively costly and, in some instances, the line5 ing replacement cost constitutes a major operating cost.

Various factors contribute to the destruction and disintegration of linings. Thus, in copper smelting operations, basic converter linings are injured by the heat of the charge, by changes in temperature, and by the corrosive action of the slag and matte. The action of an improper slag is probably the more harmful, and the character of the slag must therefore be carefully controlled. Slags containing large amounts of silica attack basic linings, and, consequently, slags containing relatively small amounts of silica are used in copper converting operations employing converters lined with expensive basic go' brick such, for example, as magnesite brick in order to avoid destruction of the lining. It is probable that the corrosive eifect of high-silica slags as compared with low-silica slags may be attributed largely to the fact that in the case of 95 high-silica slags little or no magnetite is formed and deposited on the lining while low-silica slags are conducive to the production of magnetite which is deposited on the linings and provides protective coatings therefor.

While the use of a slag having a low silica content prolongs the life of a converter lining, such slags also produce certain harmful effects. Low-silica slags retain more copper than highsilica slags, the amount of copper carried by the slag being inversely proportional to the amount of silica contained therein. Considerable difficulty is experienced in handling low-silica slags in ladles and in introducing such slags into retreatment furnaces. Retreatment of low-silica slags also involves some difliculties. It is dimcult to extract copper from such slags, andthere is a tendency for magnetite contained therein to separate .out and build accretions on the hearth of the retreatment furnace.

The present invention contemplates the pro vision of a method of lining molten bath receptacles to obtain monolithic linings which are satisfactory in service and which are less costly and more easily repaired than brick linings. 110

The invention further contemplates the provision of a copper converter provided with a basicrlining which may be replaced at a cost which will permit the use of relatively highsilica slag to avoid copper losses and to minimize handling and retreatment difilcuities.

According to the present invention, granulated basic refractory material is mixed with a suitable binder in the wet state and rammed or tamped into place between the receptacle wall and a suitable form to provide a wall of proper thickness. When the lining material has been rammed or tamped into place, the form is removed and the wet lining is subjected to heat at a low temperature for a sufilciently long period to drive oil the major portion of the water contained therein. The lining is subsequently heated until it reaches a temperature approximating that to which it will be subjected in service to a temperature which is high enough that the charging of a bath of normal temperature will not cause material damage. It isunnecessary to bring the entire lining up to the maximum temperature. Good results can be obtained if only that portion of the lining immediately adjacent the inner surface is thus heated.

In order that the best results may be obtained in forming the refractory lining material of the invention, it is important that the particle sizes be carefully proportioned. The most satisfactory material comprises a mixture of relatively fine particles and relatively coarse particles. The coarse particles should form the major portion of the mixture. The fine particles should be sufilciently small to form a compact mass which is substantially impervious to, or capable of affording satisfactory resistance to penetration by, the molten mineral bath in conjunction with which the lining is to be used. The relative amounts of fine and coarse material 'to be used in each case will depend upon the character and sizes of the coarse grains. Suflicient fine material to fill the voids between the coarse particles should be used. It is desirable, though.

not necessary, to provide just suflicient fine ma.-

. terial to fill the voids and permit at least one point of contact of each coarse particle with every adjacent coarse particle.

The fine material may consist substantially entirely of particles ranging from substantially colloidal particles to -mesh, and the coarse material may consist substantially entirely of particles ranging from 20-mesh to one-half inch or larger. In general, it is advisable to use mixtures of which thirteen to twenty per cent of the particles are sufllciently small to pass an 80-mesh screen. A large proportion of the remaining particles should be too large to pass a 20-mesh screen. About eighty per cent of the minus 80-mesh material should pass a 200-mesh screen. The proportion of particles between ZO-mesh and 80-mesh in size should be minimized. In'fact, it is desirable to eliminate such sized particles. While any suitable mixture of grain sizes may be used, the best results may be obtained when no intermediate sizes are used and when thirteen to twenty per cent of the particles pass an 80- mesh screen and the remaining particles are too large to pass a 20-mesh screen. Material in which ten to fifteen percent of the particles are too large to pass a 3-mesh screen is very satisfactory.

Particle sizes have been given in terms of the Tyler series. Percentages by weight are given throughout the specification.

The mixtures of particles of different sizes may be formed in any desired manner. A number of difierent sizes may be separately formed and classified and subsequently mixedin the proper proportions, or crushing and grinding may be so conducted that very coarse material may be reduced to provide a mixture containing approximately the correct sizes and proportions in a single operation. The composition of the resulting mixture may be corrected by additions of separately classified particles of the proper sizes. Satisfactory coarse and fine products may be obtained by subjecting the raw or initial materials to types of treatment designed to produce particles having maximum sizes corresponding to the maximum sizes desired. In each case the grinding or crushing operations utilized will produce a mixture containing the maximum and minimum sizes as well as a. variety of intermediate sizes. If the resulting products are not satisfactory separate additions and/or removal of particles of particular sizes may be made.

Any suitable solid or liquid substance may be 1 used as a bonding agent. The binder may comprise a plastic mass of finely divided solid particles. When a binder comprising solid particles is used, the binder may provide a portion of the fine material required for the lining mixture.

The binder should be selected to avoid the incorporation of large amounts of fiuxing materials in the lining. The following binders have been found to be satisfactory when used with granu- The lining mixture should contain sufilcient water or other fluid that a plastic mass capable of being tamped to form a dense structure is pro- 1 vided. A water or fluid content of about 3 to 5% by weight is ordinarily satisfactory.

1 Owing to the fact that in crushing or grinding refractory materials an infinite variety of particle shapes may be produced, it is substantially l2 impossible to predict that any mixture of particles of different sizes will result in the production of a perfect lining. Mixtures of particles within the size limits hereinbefore set forth produce satisfactory linings, and the most satisfactory mixture for any particular material or for any particular purpose may be determined readily by meansof a. few simple tests. For example, small amounts of several different mixtures may be formed into bricks which may be subjected 13 to conditions similar to those to which the lining will be subjected, and a comparison of the effects on the different bricks will indicate the mixture which is the more suitable.

Magnesite linings formed in accordance with I the method of the present invention are particularly suitable for use in copper converters, and when so used give satisfactory service at a lower cost than brick linings of similar materials. California magnesite may be used advantageously. 1 Two commercial forms of magnesite, dead burned magnesite and periclase, have been found to be satisfactory for forming linings in accordance with the method of the invention. A number of magnesite linings which served satisfsc- 1' 1,941,eoc I torily in copper converters showed matte and slag penetration varying from about one-half inch to about one and three-quarter inches.

Linings of the invention have been successfully used in copper converters, twelve feet in diameter, of the type illustrated in the accompanying drawing, in which Fig. 1 is a sectional side elevation of a wellknown type 'of copper converter provided with a monolithic lining; and

Fig. 2 is a section taken substantially along line 2--2 of Fig. 1.

The converter comprises a substantially cylindrical receptacle having sheet metal side walls 10 and a sheet metal bottom wall 11. The side walls and bottom of the receptacle are provided with a monolithic lining 12. A tuyre pipe 13 extends through the side wall 10 and the lining 12 and provides means of communication between the interior of the receptacle and a source of supply of air under pressure (not shown). A layer or lining 17 of heat insulating bricks is disposed between the sheet metal side wall 10 and the monolithic lining and extends around the receplacle in the vicinity of the tuyere pipe. A substantially conical cap 14. provided with an opening 15 in its side wall and having a monolithic lining, 16 is removably mounted on the receptacle.

When the converter is to be-lined, the cap is removed to permit the insertion of forms. The bot.om is first provided with a layer of a suitable refractory mixture of the desired thickness which is tamped to provide a dense structure. When the bottom has been lined, forms having substantially vertical walls areplaced within the receptacle with their vertical walls spaced the proper distances from the vertical side walls of the receptacle. The lining mixture is then placed between the form and the side walls in successive horizontal layers of suitable thickness. Each layer is thoroughly tamped and packed before the next succeeding layer is added. Thebest results have been obtained when the material has, been inserted in layers varying from three to seven inches in thickness. Layers of greater thickness are diflicult to tamp properly and their use might result in segregation of the coarse particles. The insulating and protecting bricks are placed in position in layers periodically as the lining mixture is inserted. The tuyere pipes are inserted when the lining has been built to the proper height. The lining mixture is iamped and packed around the sides and above the twere pipes. During the tamping, bars or heavy pipes may be inserted within the tuyeie pipes to prevent distortion. The force used in tamping need only be sufllcient to insure thorough packing and the production of a dense mass. v The cap is separately lined while inverted. The cap may be lined with the lining mixture of the invention or any other suitable refractory. The caps are not subjected to excessive wear and the cost of their linings is not of great importance. The joint between the cap lining and the shell lining when the cap is'attached may be plastered with the lining mixture of the invention or any suitable plastic mass of refractory material.

When the lining has been completed a slow wood fire is started in the receptacle and heating is conducted in this manner until the lining has been well dried. This requires from about eight to forty-eight hours depending probably upon the heat generated, the thickness of the lining, and the amount of moisture in the lining. when The converter should be put in service before any considerable drop in the temperature of the lining takes place. The usual procedure with respect to copper converters may be followed in putting the converter into service. A coating of magnetite may be provided or not as desired. Better service will be obtained if copper is not made within forty-eight hours after the converter is put into operation.

The monolithic linings of the present invention are not only satisfactory in service when new, but they may also be quickly and cheaply repaired when portions thereof are damaged. In patching a damaged monolithic lining it is only necessary to cut away a sufficient amount of the old lining to provide a rough surface for bonding purposes and apply a suitable amount of the lining mixture to build the damaged portion to the required thickness.

It is advisable to dry and burn patches in the same manner as new linings prior to putting the receptacles back in service.

Linings formed in accordance with the present invention are considerably cheaper than linings formed from refractory bricks according to the heretofore customary practices. Granular material can be obtained more cheaply than bricks at any desired location. The linings of the invention can be installed at a lower cost than brick linings. The installation of brick linings re quires highly skilled labor while the installation of the linings of the invention may be made by relatively cheap common labor.

The relatively lower cost of monolithic basic linings of the invention permits the use of a more siliceous slag in copper converters even though the siliceous slag attacks the lining. The use of a siliceous slag is not only advantageous because of the lesser amount of copper carried thereby, but it is more advantageous because a relatively high-silica slag is easier to handle in ladles, easier to introduce into retreatment furnaces, and retreatment is more complete not only with respect to the copper extracted but also with'respect to the Segr ation of the more or less infusible and refractory magnetite which, 1

in the case of less siliceous converter slags, separates out in the retreatment furnaces and builds accretions on the hearth. Thus, the use of the linings of the invention permits not only saving in lining costs but a saving in the cost of retreatment and a higher recovery of copper as well.

I claim:

1. Refractory lining material comprising a mixture of granular magnesite and a solid binder in which about thirteen to twenty per cent of the particles are minus 80-mesh and about eighty per cent of the minus 80-mesh particles are minus ZOO-mesh.

2. Refractory lining material comprising a bonded mixture of granular magnesite and a solid binder in which about eighty to eighty-seven per cent of the particles are plus 80-mesh and in which about eighty per cent of the remaining particles are minus ZOO-mesh.

'3. A molten bath receptacle having a monolithic refractory lining in which about thirteen to twenty percent of the bonded particles are minus BO-mesh, about eighty to eighty-seven percent are plus 20-mesh and about ten to fliteen percent are plus 3-mesh, and in which about eighty percent of the minus -mesh particles are minus 200-mesh.

4. Lining material comprising a mixture of granular magnesite and a binder in which about thirteen to twenty percent of the particles are minus BO-mesh and the major portion 0! the remaining particles are plus 20-mesh, the binder being present in the mixture in an amount equal to about 0.5 to 10.0 percent by weight of the mixture.

5. Lining material comprising a mixture of granular magnesite and ilreclay in which about thirteen to twenty percent of the particles are minus 80-mesh and the major portion of the remaining particles are plus 20-mesh, the fireclay being present in the mixture in an amount equal to about 2.0 to 5.0 percent by weight of the mixture.

6. Lining material comprising a mixture of granular magnesite and bauxite in which about thirteen to twenty percent of the particles are minus 80-mesh and the major portion of the remaining particles are plus 20-mesh, the bauxite being present in the mixture in an amount equal to about 2.0 to 10.0 percent by weight of the mixture.

7. Lining material comprising a mixture of granular magnesite and molasses in which about thirteen to twenty percent oi. the particles are minus 80-mesh and the major portion of the remaining particles are plus 20-mesh, the molasses being present in the mixture in an amount equal to about 0.5 to 5.0 percent by weight of the mixture.

8. A copper converter having a monolithic lining comprising magnesite and a binder and in which about thirteen to twenty percent of the bonded particles are minus 80-mesh, the remaining particles are plus 80-mesh, and about eighty percent of the minus 80-mesh particles are minus 200-mesh.

9. A molten bath receptacle having a monolithic lining made from a mixture comprising magnesite and .a binder in which about thirteen to twenty percent of the bonded particles are minus 80-mesh, the remaining particles are plus 80-mesh, and the major proportion of the minus 80-mesh particles are minus 200-mesh, the binder 80 being present in the mixture in an amount equal to about 0.5 to 10.0 percent by weight oi. the mixture.

10. A molten bath receptacle having a monolithic lining made from a mixture comprising magnesite and a flreclay in which about thirteen to twenty percent 01' the bonded particles are minus 80-mesh, the remaining particles are plus BO-mesh, and. the major proportion of the minus 80-mesh particles are minus 200-mesh, the fireclay being present in the mixture in an amount equal to about 2.0 to 5.0 percent by weight of the mixture.

11. A molten bath receptacle having a monolithic lining made from a mixture comprising magnesite and bauxite in which about thirteen to twenty percent of the bonded particles are minus 80-mesh, the remaining particles are plus 80- mesh, and the major proportion of the minus 80- mesh particles are minus ZOO-mesh, the bauxite being present in the mixture in an amount equal to about 2.0 to 10.0 percent by weight of the mixture.

12. A molten bath receptacle having a monolithic lining made from a mixture comprising magnesite and molasses in which about thirteen to twenty percent 0! the bonded particles are minus 80-mesh, the remaining particles are plus 80-mesh, and the major proportion of the minus 80-mesh particles are minus zoo-mesh, the molasses being present in the mixture in an amount equal to about 0.5 to 5.0 percent by weight of the mixture.

13. Refractory lining material comprising a mixture of granular magnesite and a binder in 11 which about thirteen to twenty percent of the particles are minus 80-mesh and the major proportion of the minus 80-mesh particles are minus. 200-mesh.

CHARLES R. KUZELL.

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