US2161011A - Manufacture of cement - Google Patents

Description

June 1939- c; H BREE'RWOOD ET AL 2, 6

I I MANUFACTURE OF CEMENT Filed Sept. 10, 1957 CRUDE. ROCK TUBE MILL 4 .7

[CARBON :LOTATION I FINISHED CARBoN CONCENTRATES M 1 N v IROUGHER SILIcEous FLOTATION] ICLEANER CALcITE FLoTATIoNl Co'NcENTRATEs v TAILINGS FINISHED TAILINGS FINISHED CALcI'rE A CONCENTRATES I,

' [CLEANER SlLIcEous FLoTATIoN] FINISHED TAILINGs SILIcEous OR CONCENTRATES MIDDLINGS (WASTE) INVENTOR'J CHARLES H. BREERWOOD.

. V v Y JOHN-C. WILLIAMS ATTORNEY! Patented June 6, 1939 I UNITED STATES 2,161,011 MANUFACTURE or CEMENT Charles H. Breerwood,

Narberth, and John 0.

Williams, Catasauqua, Pa., assignors to Separation Process Company, a corporation of Delaware Application September 10, i937, Serial No. 163,305

6 Claims.

This invention relates to the froth flotation treatment of cement raw materials and more particularly to\ the reduction of the proportions of siliceous minerals, especially silicates of alumina, in argillaceous limestones, marls and chalks,-

whereby the beneficiated materials may be used as the ultimate mixtures, or major proportions of raw material mixtures, to produce modern cements of predetermined compound compositions. 1 It has especially to do with the utilization of froth flotation in successive operations in which a pulp of a material is subjected to froth flotation in the presence of a fattyacid, or a collecting reagent in which a fatty acid is an es- 1; sential ingredient, to concentrate at least fine particle size fractions of the oxide mineral calcite, the tailings of this operation being subjected to froth flotation in the presence of a reagent of a class giving in solution the long-chain groupin the positive ion, to concentrate the excessive proportion of the siliceous mineral or minerals. The latter concentrates are the waste or by-product minerals of the process, and the tailings ofthis operation are utilized with the calcite concentrates as the ultimate raw material mixture, or the major proportion thereof..

It is among the purposes'of the invention, and particularly in view of the low commercial value of Portland cement, to beneficiate inferior raw materials by effecting the desired reductions of J the proportion of a siliceous mineral or minerals, with a minimum weight loss of useful minerals; with a minimum cost of grinding, and with a minimum consumption of the positive ion reagents, used for effecting the concentration of siliceous mineralsand which will be fully identified hereinafter, as these reagents are inherently considerablymore expensive than the fatty acids. Depending upon the natural chemical and mineralogical composition and the degree of recrystallization, the calcite concentrates in combination with the tailings of the siliceous mineral concentration, may constitute the ultimate raw material mixture, properly corrected as to the proportions and ratios of the four essential constituents, or will form the major proportion of a mixture to be completely corrected by the ad'- dition of a quantity of. another material, as when the natural material is deficient in an essential constituent to a degree that its recovery by flotation would involve an unnecessary and uneconomical waste of useful minerals, or when the material is above composition in its pro-. portion of calcite, but excessive in a siliceous mineral'and must be beneficiated whereby it may be used as a component of a mixture in which a siliceous material, such as -a sandstone, sand, clay or a shale is the other.

The inferior natural raw materials contem 1;.) plated herein are of almost infinite variety by reference both to mineralogical and physical com- 1 position, i. e. degree of recrystallization. As Portland cements are produced by combining oxides of silicon, iron, aluminum and calcium, the mineral sources of these oxides are of little practical effect-in the clinkering reactions provided mixture and contact is complete, but thenatural mineral constituents have a very decided bearing upon the processing steps that may be adopted to eliminate excessive quantities of one or more minerals, i. e. quantities that will result in a mixture, or mixture component, corrected chemically within desirable or permissible limits.

The principal mineral constituents, of the materialswith which this invention is concerned, are calcite; silica in crystalline and cryptocrystalline forms, usually quartz, flint and/or chalcedony; alumina, which always occurs in practical quantities in the form of silicates of alumina, principally the various micas, but also as kaolin,'kaolinite, the feldspar minerals, etc.; iron as oxides, the hydroxide, limonite and/or pyrite. Magnesia, an undesirable adulterant, is usually present principally as dolomite, but also as magnesian alumino silicates, e. g., phlog'opite mica, talc, and/or brucite. Carbon, 'in a form commonly called graphitic is frequently present and although it has no apparent effect upon the clinkering reactions, it is highly undesirable in a flotation pulp and adversely effects flotation 1 concentration, as will be described more fully hereinafter. A wide variety of other minerals in minor quantities are usually present, but the proportions involved are usually too small 'to warrant consideration.

Throughout the specification and claims the terms ,silica, silicate and "siliceous are specifically limited to and are to be construed in accordance with the following definitions: Silica refers-to crystalline and crypto-crystalline silicon dioxide (SiOz) only. Silicate" refers to any mineral salt of silicic acids, particularly compounds containing alumina, magnesia or both. Siliceous? is generic and refers to either or both silica and silicate minerals as defined above.

Natural crystallization of these mineral con- 'stituents, with the possible exception of the carbonaceous matter, occurs throughout extreme ranges, from large visible crystals down to materials of such incomplete orfine crystallization that grinding must be carried out to an extreme degree of fineness to release the physical bonds,

or at least to free a sufllcient proportion of the mineral or minerals occurring in excess, that the necessary elimination can be accomplished. An 7 example of the latter will be found hereinafter,

- in which the extreme fineness of the crys'talliza-' particle siz'efractions below 20 microns.

Each of the materials described above may be beneficiated by the present method, and although an. ancillary step or steps may be desirable or required to produce satisfactory results under specific conditions, to be described hereinafter, the essential steps of the method are substantially identical under all conditions. Ordinarily, the objectives of the process are to reduce the proportions of the alumina in the natural material, frequently to reduce the alumina together with magnesia and especially magnesian silicates, and in rare cases to eliminate in part at least, crystalline silica, especially fine sand grains from marls and so-called"sand limestones".

With a few exceptions, the limestones, marls and chalks, available for cement manufacture, contain alumina in too great abundance for use in producingcements capable of satisfying the requirements of present specifications of the Federal and several State governments, for cements of low-heat. of hydration, particularly specifications which fix a maximum limit for the proportion of tri-calcium aluminate at or near by additions of iron oxide, to combine with a part of the alumina, and particularly where the calcite content of the material is high enough to permit further correction of the ultimate composition by additions of high grade silica, such as sandstone, where such correctives are available. Additions of iron oxides are not satisfactory or complete solutions of the problem, not only because of their effect on the color of the concrete but principally because of the reduction of the silica ratio. Further, it is now generally believed that sub stantial proportions of tetra-calcium alumina ferrite decrease the resistance of concrete to attack by sulphates in marine and ground waters. One present specification limits the sum of tetracalcium alumino ferrite and tri-calcium aluminate in the-finished cement to 10% and another specification sets a limit at 12%, and it will be evident that few natural materials can be utilized, by additions of iron oxides, to produce compositions within these low limits. It should also be borne in mind that tetra-calcium alumino ferrite has little if any hydraulic value, and regardless of the beneficial effects of iron as a flux or catalyst in burning, this compound is an adulterant.

Magnesia, at least in quantities above a maximum limit, as established by various specifications, is an undesirable constituent of a cement raw material mixture. Only a negligible propor-. tion reacts in burning in the range of Portland cement clinker, and although if the liquid phase of the clinker is solidified before complete. crystallization takes place, a part of the magnesia is suspended in solid solution in the glass", the remainder is present in the clinker as periclase. This compound is a principal contributor to delayed expansion and ultimate disintegration of concrete.

In general, the practice of the invention comprises at least two radically distinct types of 7 arc er:

- silicates of alumina were accomplished in the the presence of a fatty acid reagent, the preferred types of which will be described hereinafter, either to concentrate the major proportion of the calcite in the frothor to concentrate at least the finer calcite in the froth and thereby substantially reduce the proportion of colloidal and near-colloidal particles, as well as fine particles of slow settling rates in water, in the tailings of the fatty acid flotation. Generally, the concentration of the major proportion of .the calcite is the preferred practice when the natural crystallization is so incomplete that the ,pulp is largely a fine slime, or contains an abundance of slimes, either naturally or when the materials must be ground to extreme fineness to free a sumcient proportion of the mineral or minerals present in excess, to permit the desired elimination. This practice makes it possible'to efiect substantial economies inthe consumption of the positive ion reagents, one of the principal pur of the invention, because the tailings of the fatty acid flotation are the-feed of the second flotation operation, and, first, this feed is only a minor proportion of the weight of the original flotation pulp, and, second the proportion of fine slimes, which complicate any flotation operation, has been substantially reduced, thereby making it practical to carry out the second operation with I i: L1;

considerably reduced positive ion reagent consumption. The alternative, of con .entrating the.

finer calcite in the froth, is the preferred procedure at this step when the natural crystallization is coarser and the necessary proportion of the mineral or minerals occurring in excess is freed by less extreme grinding and in the resulting pulp the colloidal and near-colloidal slimes constitute only a minor proportion. Accordingly,

the reduction in proportion of these fine slimes provides for economy in the concentration of. siliceous matter from the remainder of the pulp.

It will be realized from the foregoingthat the second fiotation operation is to concentrate the excessive proportion of the siliceous matter as a minirnumv oi the weight of the remainder of the original pulp. It is usually desirable to-recover the available crystalline silica, such as quartz, for use as an essential constituent of the mixture. The tailings of this operation then include the major proportion of the free quartz, in addition to the remainder of the calcite, iron compounds and the unbroken or composite rock particles.

One of the most important steps of the present method is the preliminary reduction of the natural materials by grinding. This step is not may have to be further reduced to make them suitable for burning, or to normal grinding as a preliminary to flotation separation by other processes and for the recovery of other minerals. In normal preliminary grinding prior to froth flotation concentration, the objective is to reduce the mineral bonds to a degree that a maxi mum recovery of high grade concentrate canbe obtained. In the present method, however, the minerals are preferably reduced only to a degree that will permit the necessary elimination by flotation, for chemical and economicalreasons, and especially when the materials are fine grained. At such a degree of grinding, it will be evident that a substantial proportion of the particles in the pulp, and especially the coarser particles are unbroken, i. e., they are comprised of two or more distinct minerals.

2,161,011 The chemical purposes of thisprocedure have,

' 1 fineness, that'the minerals from which the four crystallization. economy, to limit the quantity of flotation cell essential oxides are derived be thoroughly mixed and in intimate contact, for uniformity and completeness of the reactions. Provided the mineral particles arev sufliciently fine, the proportion of unbroken or composite mineral particles, above described, are especially desirable as the mineral bonds assure contact of different constituents. It will also be realized that it is not necessarily desirable to attempt to obtain high grade calcite concentrates, provided the grade obtained is sufficiently highv to effect the desired composition corrections, but that it is desirable to subtract the minimum weight of the total materials as a siliceous concentrate, so that'the natural blend and contact of'the original materials, and which jhasbeen improved by the mixing effect of grinding,'has been disturbed only to a degree that the desired ultimate chemical correction can be made.

As grinding is one of the most expensive operations in the manufacture of cement, it will be evident that substantially complete grinding of fine grained materials is economically impractical, and even in cases where the crystallization is relatively coarse, it willbe obvious that mineral eliminations should be made without wasting power by unnecessarily reducing the quantity to be discarded. I I The proportion of the total lime-bearing material to be treated by froth flotation depends upon both its mineralogical and chemical composition, especially the deviation from the desired composition, and the size ranges of natural It is desirable, for purposes of feed to the proportion of the total quantity which will permit correction of the mixture, when the calcite concentrates, the flotation tailings of the siliceous flotation and theremainder or the untreated part are mixed in proper proportions.

Any such division is preferably made on a basis of particle size, rather than a mere division of the ground materials, to improve the results of the flotation operations and to economize in equipment and reagents. Thus, if the crystals are relatively coarse, and a sufficient proportion of the siliceous matter or mineral is free in the coarser fractions resulting from a limited degree'of grinding, the next step is to classify the ground materials to segregate a chemically perthe fine particles of all constituents, which are especially suitable for burning.

When the constituent minerals are dispersed in a wide range of sizes, such that after moderate grinding, bond breakage in the coarser fractions is too incomplete to permit effective separations, the ground materials are preferably classified into slimes, intermediate and coarse fractions. The intermediate size fractions are treated by froth flotation and the calcite concentrates and the tailings of the siliceous flotation are combined with quantities of the slimes and coarse fractions, the latter usually being first re-ground.

Usually, the material to be eliminated in part is micaceous, and although natural crystallization may be relatively coarse, the ease with which mic'a is released by grinding, as compared with a the harder minerals, tends to concentrate a a greater proportion of mica in the finer particle size fractions. Even in such cases, the proportion of the flotation cell feed may be limited by preliminaryclassification, but the finer fractions are subjected to flotation, and their calcite concentrates and the siliceous flotation tailings are utilized in combination with the untreated coarse fractions.- It is to be understood that although the term "coarse has been used to describe these materials, the ground materials are largely slimes, as the term is used in the art of flotation, or the proportion of slimes is far too great to make it practical to discard them, and

the improvement in composition of the coarser fractions ordinarily is not complete and the recombinations described above are necessary to make the ultimate correction.

However, the more common materials available, especially in the eastern cement producing districts, and which may be beneficiated for use in the production of cement of the types described, require flotation treatment preferably of the entire supply. ,These materials are argillaceous limestones in which re-crystallization is so incomplete that extremely fine grinding must be resorted to to free a suflicient proportion of the micaceous matt'erfparticularly sericite, to make it possible to effect the desired corrections. The average materials are excessive in alumina and total silica and deficient in calcite and usually crystalline silica. This, together with the wide distribution of the constituent minerals throughout extreme ranges of particle size makes it necessary to grind the total quantity to such fineness that theresulting materials are "slimes. .The actual or principal flotation separations are made in the particle size fractions below 20 microns, in the two examples to be given hereinafter, and as at this degree of fineness, hydraulic classification is unnecessary, preferably the entire supply of ground materials are subjected to flotation. However, the process is economical and total weight of the siliceous matteris collected and from a minor part of the original pulp, as the flotation concentrates. 'ings contain large proportions of unbroken rock particles, which ,for reasons previously discussed, are especially desirable to promote uniform and complete reactions in burning.

The flotation operation in which the calcite is concentrated may be carried out in the presence of common fatty acid collecting reagents, such as oleic acid and fish oil fatty acids, provided the pulp is relatively coarse, the proportion of siliceous mineralsis not increased substantially in the fine particle size fractions, and the pulp water is relatively warm. However, for the purposes described, particularly for the concentration of the fine fractions of the calcite, these re- The flotation tailagents are unsatisfactory especially at normal pulp temperatures because dispersion is incomplete and the consequent over-oiling causes partial heavy flocculation, with the result that the concentrates are of low grade. Although a single stage of calcite flotation may be sufficient to concentrate the finest fractions of the calcite, when this procedure is appropriate for reasons previously described, the best results are obtained in light stage oiling circuits, and such circuits are essential to produce effective results in concentrating the major proportion of the weight of the calcite, particularly in fine pulps. Accordingly, the preferred collectors are those which can be introduced as dilute solutions or aqueous emulsions, to obtain rapid and complete dispersion, and also to permit accurate control of the small quantities introduced at each oiled stage.

The more common fatty acid emulsions are not wholly satisfactory for the present purposes. Those stabilized by amine soaps produce heavy froths of low grade, difficult to clean by flotation and difficult to thicken. Those stabilized by sodium soaps and sulphonated alcohols produce excessive froths, and the concentrates produced by the latter are of low grade.

The aqueous emulsions found to be especially satisfactory are those stabilized by minimum quantities of sulphonated oils, as more fully described in the co-pending application of Ried.

. Serial No. 163,306, flied September 10, 1937,-and

with mineral oil as described in the latter applicentration of the excessive proportion of siliceous matter, is carried out in a manner generalcation of Ried. This'collecting reagent is more fully described in the co-pending application of Vogel-Jorgensen, Serial No. 151,203, filed June 30,

The calcite collecting reagents referred to above and those contemplated by the present invention are of the anionic type.--

The second flotation operation, for the conly similar to that described in our co-pending application SerialNo. 163,304, flied September 10, 1937, in the presence of a positive ion reagent, the surface-active portion of which is a positive ion such as. those of the class discovered by Lenher and described in his Patent No. 2,132,902 for A flotation process. The reagents found to be effective are those. which in solution give a positively charged ion containing an aliphatic hydrocarbon group of at least 8 carbon atoms, preferably quaternary ammonium compounds containing a hydrocarbon group of from 12 to 18 carbon atoms wherein the aforesaid constituents in solution give a positively charged ion, preferably the negative ion in solution being a halogen.

Of the foregoing class, two have been found to be especially satisfactory for the present purposes. and in the order of preference are, first,

dodecyl amine hydrochloride, and second, a mixture of hydrochlorides of the higher primary aliphatic amines in which the alkyl groups correspond in carbon content and composition to the fatty acids occurring naturally in coconut oil. The latter reagent was used as the collector in the; examples to be given hereinafter and will be referred to for brevity as 0-2.

We have discovered, and it is an important feature of the practice of the invention, that although these reagents have capacity to collect or concentrate acidic minerals, and all of the prin cipal constituent minerals in pulps of the class described, including the oxide mineral, calcite, that they may be employed to efi'ect a plurality of differential concentrations, when the operations are controlled, as will be illustrated by the examples to be described hereinafter.

We have succeeded in effecting differential concentrations in the following order, first, the aluminum and magnesian micas, second, the feldspar minerals, and third, crystalline silica, particularly quartz, without concentrating a substantial proportion of the remaining free calcite grains in the froth. The practical significance of this discovery will be understood if it is remembered that the more common materials are excessive in alumina, and usually excessive in silica, and when present in substantial proportions magnesia 'is an undesirable adulterant. Thus, a very limited concentration of the total weight of the remainder of the pulp, subjected to the second flotation operation, effects the desired reduction of alumina, and as it occurs as a silicate, the total silica is necessarily reduced, in the recovered materials. Particularly when magnesian mica is present, this concentration effects desirable reductions in alumina, silica and magnesia, talc, being a silicate is also concentrated, retaining in the tailings the calcite and the usually desirable crystalline silica. Iron oxides tend to concentrate but as the collecting power of the positive ion reagents is relatively low with respect to the oxides of iron, as well as calcite, froth cleaning by flotation, without the addition of collecting reagents, is effective in increasing the recovery in the flotation tailings. The unbroken r'ock particles are not as amenable to concentration, in the presence of these reagents, as the crystalline silica and can accordingly also be retained in these tailings.

The differential separations are effected by conditioning a pulp of the fatty acid flotation tailings with very limited quantities of the collecting reagent, and in light stage oiling" circuits in which the total quantity is introduced in small increments. It will be understood that the term oiled" is used to identify the flotation cell circuit, as the positive ion reagents are not oils. Especially in the treatment of flne pulps, the positive ion reagent is preferably diluted in a substantial volume of water to obtain accuracy in the control of each quantity introduced, and to effect rapid and complete dispersion in the relatively enormous volume of the pulp. Failureto control the quantities and dispersion of the re.- agent results in partial over-oiling and consequent partial heavy flocculation in which useful minerals are included. Expressed in another way, the concentrates are of low grade, unnecessary weight losses of the desirable minerals occur, the

desired composition correction may not be com pleted, and the consumption of reagent makes the operation uneconomical.

Further, lower weight losses of the flner particles the useful minerals of both flotation operations are usually obtained if the air volumes entering the pulp through the flotation cells are reduced below normal. The purpose in controlling the air, volume in concentrating the siliceous matter is primarily totake advantage of the peculiar settling characteristics of mica particles. The shapes of the mica particles give them a much slower settling rate in water, the rate being about equal to particles of other minmica with a negligible quantity of reagent.

The use of very small quantities of the positive ion reagents under careful control in introducing and dispersing them in the pulp, as above described, results in the formation of siliceous concentrates of only a minor proportion of the total weight of the flotation cell feed of the second or siliceous flotation. It will be recalled that this feed represents only a minor proportion of the original flotation feed. Accordingly, these features make the present method economically competitive with older processes, despite the fact that the positive ion reagents cost several times as much as the fatty acids, per pound. Calcite pulps, of the class contemplated herein, are slightly alkaline, the normal alkalinity usually being within the range pH 7.4 to 7.8, and as the reagents described are efiective in alkaline pulps below about pH 8.5, no reagents need be employed to modify the natural alkalinity.

Further, the action of these reagents is not adversely affected by the use of depressing and dispersing agents, at least those of the types to be referred to hereinafter, when necessary to meet specific conditions. The limited quantities used permit the accurate control of froth volumes, at each stage, essential for the best results in light stage oiling circuits, by suitable additions of common frothing agents, such as cresy'lic acid, but preferably a frothing agent comprising a mixture of branched and straight chain aliphatic monohydric alcohols boiling between about 152 C. and about 162 C. obtainable along with methanol by the catalytic hydrogenization of carbon oxides, hereinafter referred to for brevity as (F 1,1- I

The practice of the invention can best be'explained by reference-to examples, which will serve as guides for the treatment of other inferior cement raw materials. The material selected for the two, following examples is especially suitable for purposes-of illustration, as it is especially difficult to'beneficiate, and was generally believed to be not amenable to froth flotation concentration. The principal diificulties have to do with the extremely fine state of natural crystallization and the wide distribution or dispersion of colloidal or near colloidal graphitic carbon.

The material is typical of-the finer grained argillaceous vlimestones of the Lehigh Valley cement producing district of Pennsylvania. It is classifiablegeologically as Jacksonburg limestone of the Ordovician age, and is intermediate in composition between limestone and shale, the color and general appearance more nearly resembling slate, but calcite is the most abundant mineral. The other principal minerals are quartz; mica, mostly of ,the sericite variety, dolomite, and. iron, principally as the hydroxide, limonite. Petrographic examinations of thin sections of the rock reveal distinct layers of fine calcite grains alternating with thin layers of fine scaley and fibrous sericite. There are occasional elongate lenses and elongated isolated grains of quartz. Thequartz is widely distributed, usually as fine grains of a few microns or tens of microns in diameter. The carbonaceous matter is dispersed throughout the rock in intimate contact with the various other constituents, and constitutes about one half of one percentof the total mineral weight.

Petrographic examination of this rack, after grinding to 98% minus the 325 mesh sieve, reveals that even in the particle size fractions below 20 microns, mineral bond breakage is incomplete, and that the coarser fractions are largely unbroken rock particles, i. e., the individual particles are composites of calcite, quartz and/or sericite. There is,-however, a somewhat increased proportion of the mica in the finer fractions, in the form of free particles, and it is from the fractions below 20 microns that the principal concentrations are made. naceousinclusions and coatings of the calcite grains are frequent, and abundant on the quartz-- silica and the alumina are too high and the pro-.

portions of calcite and pure silica (quartz) are too Carbolow. The concentration and elimination of a part of the mica will effect the correction of both the total silica and alumina, and increase the proportion of the calcite and quartz in the re- This will be understood when volving substantial weight losses of the especially desirable fine calcite and quartz. Further, it has the effect of adsorbing or otherwise consuming relatively large quantities of the fatty acid and positive ion reagents. The carbonaceous matter should therefore either be substantially completely removed, as illustrated hereinafter in the first example, or depressed and rendered substantially harmless, by the use of a depressing .agent, such as a lignin sulphonate, preferably calcium lignin sulphonate, as described in the second example, the latter practice being preferred for reasons to be explained in detail later.

For a better understanding of the complete practice of,the invention and as further illustrated by-the first of the following examples, reference is made to the accompanying drawing, in which the figure is a flow diagram showing the method of treating the limestone described specifically above, materials substantially equivalent thereto, and which will serve as a guide in the treatment of the other types, previously referred to, of, materials of the class argillaceous limestonesfmarls and chalks.

This material, being fine grained, required fine grinding to free a sufiicient proportion of the mica, which in this material tends to increase in the finer particle size fractions, as a resultof grinding. These characteristics made it prefer-' able to subject the' entire supply to the two principal flotation operations, and to concentrate the major proportion of the calcite by-froth flotation.- For satisfactory reductions of total silica and alumina, an extreme degree of grinding was not essential, in view of the procedure about to be total weight. It will be realized that the entire pulp was a slime as the term is used in the art of flotation, and that colloidal and nearcolloidal slimes were abundant.

- The objectives of the two following examples were to illustrate how a plurality of separations can be made with a minimum of reagents and equipment, whereby recombinations can be effected to produce ultimate mixtures of desired types. References made hereinafter to total silica" mean the sum of silica present as quartz and the proportion .of silica in the silicate minerals, principally 'sericlte, and it should be borne in mind that this material is deficient incrystalline silica to an extent that the recovered quartz is preferably augmented by the addition of high grade silica to the ultimate mixture or mixtures.

First example The first example is intended to illustrate a procedure in which the carbonaceous matter was first concentrated, as a preliminary step. The flotation operations were carried out as lock 'tests at pH 7.8.

' inated. I

Although this is not the preferred procedure in the presence of carbon, it is illustrated in this example to show that when the desired ultimate composition permits, these concentrates may be utilized, although the proportion of alumina is relatively high. Had the alternative step of depressing the carbon, to be described in the second ex; ample, been followed-in this case, it would have been desirable to conditlonthe pulp for about 3 minutes in the presence of'about 1 lb. per ton of a lignin sulphonate, preferably calcium lignin suiphonate, as more fully described in Breerwood PatentNo. 2,130,574.

The subsequent flotation operations would further have been improved by the use of a total of about 2 pounds of calcium lignin sulphonate, whereby the additionalquantity would serve as a disperser to reduce the natural flocculation of the remaining fine constituents, a condition usually'characteristic of pulps of these types. The agent, an effective disperser of the constituents of pulps of this class is described in the copending application of Breerwood, Serial No. 163,303,.flled September 10, 1937, but some of the commondispersing agents are ineffective, and others appear to promote flocculation.- However,

no dispersing agentwas used in this example, to

demonstrate that eflectii/e results are obtainable, particularly by light stage oiling and with dilute collectors. p I

The tailings of the carbon concentration were then subjected to rougher flotation to concentrate the calcite in-the presence of an aqueous emulsion of oleic acid of an oil in water ratioof 1:9,

the emulsion being dispersed temporarily for the purposes of the test by passing the. mixture and complete dispersion in the pulp and to permit accurate control of the quantities used, for reasons previouslymentioned. It was added to the cell in small increments in the equivalent of lightstage oiling until a total of 0.44 lb.- per ton had been introduced, the concentration of the calcite The tailings of the rougher calcite flotationv amounted to only 32.3% of the original weight of the flotation pulp. These tailings were then submitted to rougher froth flotation in the presence of additional frothing agent, F-l, and in the presence of positive ion reagent 0-2, both being added in small increments, in the equivalent of light stage oiling, until a total of 0.36 lb. additional frother.and 0.12 lb. collector per ton of original feed had been introduced. Rougher mica'concentration was completed in 5 minutes.

The siliceous-concentrates were then cleaned by froth flotation without using additional reagents. The tailings of the cleaning operation are included in the table of analyses for purposes of description, but it will be understood that in normal practical operation they would be returned,.in closed circuit, to rougher mica flotation to reduce further the proportion of. mica, and to increase the weight of the useful materials comprising the final tailings, i, e., the rougher tailings of positive ion flotation.

The cleaner concentrates of this operation are the-waste products of the process, as they include the excessive proportions of the alumina I and silica, as will appear from their composition,

set forth in the table. It is especially to be noted that they represent only 7.1%. of the total weight of original material, and that the mica constitutes at least 73% of the siliceous material, assuming that the combined silica is at the lowest theoretical ratio for sericite mica, but as nearly as can be estimated petrographically, the mica constituted to of these discarded concentrates, even though mineral bond breakage inthese concentrates was incomplete, due to in-- complete original grinding.

The rougher tailings are a useful product of the process, as they include the uncoated and/or incompletely surface-coated calcite, quartz and the iron compounds, the recovery; of the latter -P t Analyses as percent ercen No. Product weight Bio: F8203 A120: 0800;

Feed-.-) 13.00 h 2.74 5.92 72.28

1 08113011.--. 7.1 18.60- ass 9.92 55.11

2 omen/Mane.--" 0.0 I 4.00 1.11 2.09 ram. :4 Mlc8.c0ilc 7.4 40.28 2. 57 10. 70 10.23

4 Mica cl. tails 7.1 46.58 2.32 ll.88 20.88

' 5 Bougber tails-.. 17.3 17.74 3.34 5.08 case 0 2+5. 75.4 7.82 2.74 3.47 81.50 7 2+4+t 85.5 11.04 272 41s 78.30 s 1+2+4+5 02.0 11.77 2.84 ms 70.30.

It will be seen from the analysis that the original material is so deficient in crystalline silica, with reference to any normal ultimate cement.

raw material mixture, that the recovery of a sufllcient proportion to satisfy a final requirement would involve an uneconomical and unnecessary weight'lossof the useful constituents particularly calcite, in which the original material was also deficient, and the recovery of the required silica, in the form of quartz would require excessive grinding and flotation costs. The material was, accordingly, so processed that the reduction of silicates would make it possible to make the ultimate correction by small additions of natural high grade silica minerals, such as sand or sandstone, usually available at low cost.

'The products numbered 6, l and 8 are com binations of various of the numbered products of the separation operations, excepting the waste products, the mica concentrates, product No. 3, to show how in addition to the separated products, recombinations can be made to produce various types of cemen'ts, and to limitweight losses of useful products, all of these mixtures requiring in this instance, additions of varying quantities of high grade silica.

The reduction .in alumina was the principal purpose and the proportion of alumina in each of the foregoing products is especially to be noted.

' Second example The purposes of this example were to illustrate the alternative procedure of depressing the carbonaceous matter and the recovery of a greater weight of micaceous concentrates, but with a considerable reduction in the consumption of the positive ion reagent, principally by omitting the carbonaceous concentration of the first example. As the procedure was generally the same as that of the first example, a separate flow diagram is not included in the drawing.

The material treated, although of lower calcite grade, was similar and from the same source. It

was ground to the same degree of fineness, for

to render the carbonaceous matter harmless in pulps of this type, and the quantity is preferably increased to about 2 lbs. to reduce natural flocculation to improve subsequent flotation conditions. During the conditioning period 0.21 lb. of commercial No. 3 fuel oil, 0.03 lb. of frotherE-l, and 0.5 lb. of oleic acid (not emulsified) were added to the pulp, per tonof solids.

The pulp was then subjected to froth flotation to concentrate the major proportion of the calcite, additional frother and oleic acid being added in small increments, in the equivalent of light stage oiling, until a total of 0.09 lb. of frother and 1.65 lbs. of 'oleic acid had been introduced.

Rougher calcite concentration was completed in 1 7 minutes.

' The calcite concentrates were then cleaned by froth flotation without using additional reagents, flotation being completed in 3.5 minutes. These concentrates were a finished product and their composition is given in the following table. The cleaner tailings were returned, asin closed circuit, to rougher calcite flotation.

The rougher calcite flotation tailings constituted,42.3% of the total weight of the original material, an increase in weight, as compared with those of the previous example, "principally attributable to the retention in the feed of the weight of the constituents that would have been concentrated had the carbon been removed.

These tailings were submitted to flotation in the presence of an'addition of 0.018 lb. of frot'her F 1, and in the presence of 0.07 lb. of positive ion reagent C-2 per ton of original feed, to concentrate the mica. Flotation was completed in 8 minutes. These concentrates were then cleaned by froth flotation in the presence of additions of 0.004 lb. offrother F-l and 0.03 lb. of reagentC-2, per ton of original feed. Cleaner concentration was completed in 8 minutes. The waste products of the process included the excess mica. .The composition of these concentrates is also given in the table. The analysis of the cleaner tailings is'also included in the table, but it is again to be noted that in practical operation they would be returned in closed circuit to the rougher siliceous flotation operation.

The tailings of the rougher siliceous flotation are a useful product to be recovered and combined with other products, as will be described hereinafter.

The principal flotation results are as follows:

The concentration of mica is especially significant, particularly in view of the reduction in total consumption of the positive ion reagent to slightly less than that required to complete this step in the previous example, and although the weight of these concentrates was, about three times as great, but with a somewhat lower proportion of mica. These concentrates, however, included 57.1% of the total alumina available in the original material, even thoughmfneral bond It willbe seen thattwo recombinations may be made to produce various types of cements, when the combined products are further corrected by additions of the necessary quantities of high grade silica. These recombinations may be products Nos. 1 and 4 or products Nos. 1: 3 and 4, the

latter being preferred in view of inceased weight recovery and slightly higher silica ratio. It will anionic calcite collecting reagent, sufficient to ration of an ultimate cement raw material mixture, inferior cement raw materials of the class concentrate at least the finer particles of the calcite, subjecting a pulp of the tailings of calcite flotation to froth flotation in the presence of an amount of a reagent, the surface-active portion of which is a positive ion having differential selec tive collecting capacity for siliceousminerals and calcite of the naturally occurring raw materials, sufficient to collect said excess of siliceous mineral, but insufficient in amount to collect all of the normally floatable portion of the siliceous constituents, to concentrate a minimum of the weight of said pulp in the froth, whereby the excess of siliceous mineral is carried off in said froth and the proportion of calcite isincreased in the remaining materials.

2. In a method of beneflciating, for the prepaof argillaceous limestones, marls and chalks, including an amount of at least one siliceous mineral in excess of that desired in the ultimate mixture, to reduce the percentage of said siliceous mineral; the improvement which comprises. subjecting a pulp of the ground material to froth flotation in the presence of an amount of an anionic calcite collecting reagent sufficient to concentrate a substantial proportion of the calcite, subjecting a pulp of the taflings of calcite flotation to froth flotation in the presence of. an amount of areagent, the surface-active portion of which is a positive ion having differential selective collecting capacity for siliceous minerals and calcite of the naturally occurring raw materials, sufficient to collect said excess of siliceous mineral,

' but insuflicient to collect all of the siliceous matter and insuflicient to collect a substantial proportion of the calcite in said pulp, to concentrate a minimum of the weight of said pulp in the froth wherebythe excess of siliceous mineralis carried off in said froth and the proportion of calcite is increased in the remaining materials.

'3. In a method of beneficiating, for the preparation of an ultimate cement raw material mixture, inferior cement raw materials of the class of argillaceous limestones, marls and chalks, which contain silica and an amount of at least one silicate mineral in excess of that desired in the ultimate mixture, to reduce the percentage of said silicate mineral; the improvement which comprises subjecting a pulp of the ground material to froth flotation in the presence of an amount of an anionic calcite collecting reagent, s'ufflcient to collect at least theflner particles of the calcite, subjecting a pulp of the tailings of calcat'e mineral, but insufficient in amount to collect a substantial proportion of the silica, to concentrate a minimum of the weight of said pulp in the froth, whereby the excess of silicate mineral is carried off in said froth and the proportion of silica is increased in the tailings of said pulp.

4. In a method of beneflciating, for the preparation bf an ultimate cement raw material mixture, inferior cement rawmat erials of the class of argillaceous limestone, marls and chalks,. which contain silica and an amount of micaceousjmatter in excess of that desired in the ultimate mixture, to reduce the percentage of said micaceous matter; the improvement which comprises subjecting a pulp of the ground material to froth flotation in the presence of an amount of an anionic calcite collecting reagent suflicient to concentrate at least the finer particles of the cal-- cite, subjecting a pulp of the tailings of calcite flotation to froth flotation in the presence of an amount of a reagent, the surface-active portion of which is a positive ion having differential selective collecting capacity for siliceous minerals and calcite of the naturally occurring raw materials, sufficient to collect said excess of micaceous matter, but insufficient in amount to collect a substantial proportion of silica, to concentrate a minimum of the weight of said pulp in the froth, whereby the excess of micaceous matter is carried off in said froth and the proportion of silica is increased in the tailings of said pulp.

5. In a method of beneficiating, for the preparation of an ultimate cement raw material mixture, inferior cement raw materials of the class of argillaceous limestones, marls and chalks, which contain silica and an amountof at least one sili-' cate mineral in excess of that desired in the ultimate mixture, to reduce the percentage of said silicate mineral; the improvement which comprises subjecting a pulp of the material ground to contain an abundance of flne slimes to froth flotation in the presence of an amount of an cate mineral, but insufficient in amount to collect substantial proportions of silica and calcite, to concentrate a minimum of the weight of said pulp in the froth, whereby the excess of silicate.

mineral iscarried off in said froth and the proportions of silica and calcite are increased in the tailings of said pulp.

6. In a method of beneflciating, for the preparation of an ultimate cement raw material mixture, inferior cement raw materials of the class of argillaceous-limestones, marls and chalks,'which contain silica and an amount of at least one silicate mineral in excess of that desired in the ultimate mixture, to reduce the percentage of said silicate mineral; the improvement which comprises subjecting a pulp oi the ground material to froth flotation in a stage oiling circuit in the presence of amounts of an anionic calcitecollect-K ing reagent, the total amount of reagent so added being sufficient to collect'the major proportion of ings of calcite flotation to froth flotation in the presence of an amount of a reagent, the surfaceactive portion or which is a positive ion having diiIerentia-l selective collecting capacity for siliceous minerals and calcite oi' the naturally occurring raw materials, sufllcient to collect said excess of silicate mineral, but insuilicient in amount to collect a substantial proportion of the silica, to concentrate a minimum oi the weight or said pulp inthe i'rcth. whereby the excess of silicate mineral is carried 08 in said i'roth and the proportion of silica is increased in the tailin'zs of said P lp.

JOHN C.

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