US2329403A - Cleaning of cereal grains - Google Patents

Description

Patented Sept. 14, 1943y g CLEAnINGoF CEREA'L GRAINS Y Y Leland H. LoguarDenver, Colo., assignor'toMin-fv, A' f 1 t f A ing Process and Patent Company, Ilenvcxz,

Colon a corporation of Delaware t Appliatin raeiiruairy 41o, 1941,:seria1No; 373,313 reclama ,-(ciao3- 951)M This invention relates to the cleaningand beneciation ofv grains and the likel and is illustrated herein asfapplied tothe treatment of cereal grains for the removal of chaff, dirt, smut, insect eggs, insects andthe like from grain vprior to milling. c

The process` also may be applied tothetreatment offcereal grains priorto'nilling for the removal of the hull or outer skin,y which, jin reality, is the true bran and hasflittle, if any, food value. n

A 'further application of the present invention to the treatment of grains is a selective sepafra` tionA of the vgrains vor kernels into vfrac'tion's,one offwhich would be most suitable forseed "pur-A poses, Whileanother fraction wouldbeseparatei vide'ka simple, inexpensive Land Vex'pe`clitioi`1sfprovcess for removing' contaminating f matterffror'n cereal grains'. .Y Another object of the inventionisftof rovide Aio a method for increasing' the food valueper-un'it of Weight of cereal grainsby removingiltlfiere'iroin the outer hull value.

or bran 4contient' of negligible food A further .object of' the invention is to provide a treatment for vgrading cereal grains'laccording to variations in the protein content thereof.` ,K

Other objects reside in novel stepsY and treat-l ments, all of which will appear more fully in Vthe course of the following descriptionj According to the present invention', thenfriei clusive of the bran content, ywill differ fromfth'e' grain kernels'in siz'e, shape and specific'v gravity so that itis possible-to lget'ja sufcientlyjclean separation to satisfyordina-ry r"eq*uireinfantsl hydraulic classification.4 As ya consequence;A the materials taken for treatrne"n t`y may @be condi-4 tioned for the Aseparation :according 'to difieren; tial wetting properties, but it yisfalso possibleto render thematerial better suited for"certai"l arations by the use of suitable dispersing rel -ents' and a, variety of separating methods may ployed in conjunction therewith.

A typicall separation involvingl the treatment of cereal grains primarily for the removal ofbran, but also veffective for removal ofdirt andhother contaminating matter'will now be describedin "Ihe grain delivered to an elevator or the like is iirs't fed in dry condition to ay screening oper; ationvfor* the removal of coarse foreign matter, such as Wood chips", wire, bolts andrthelike.

'The Yscreened product of"'this operation is` collectedfand'f'ed yto 'a revolving cylinder or the like,

such asaylarge ytrunniony ball mill, which'allows f only a low'pulp leveltc be carried. In"this`mi ll, the grain is mixed with sufficientV water to make a lsemi-fluid massand where reagents are to be used -in theftreatment, they preferably are vin-j troducedinto themill to -attain'thefdesired de-f4 f gree of mixing; f y Reagents wellysuited` to acty as dispersants in the prsent treatmentfare sodaash and sodium'L silicate,y although othery reagents' possessing similarl propertiesv which ywill not vhave a .deleterious effecten the grain mayv be "used in place thereof; The amount of reagent required in the treatment will "vary, according tothe nature ofthe subsequent treatment andthe condition ofthe-ma'- terial, but' from'one-tenth pound to' ive pounds of reagent` per ton of grain will give satisfactory results.y y'

Either'the wetting medium, usually water, o1' the reagent of the treatment tend to loosen and k.remove the outer skin from the grain'kernel and the combined presence ofr these'agents' inthe mill serves to soak the individual kernels and'loo'sens the outer'skin,'causing it to become detached from the kernels; Y f l The tumbling,r action and the continual movement of kernels against one` another also assists in loosening' and separating this outer skin. The

ficient to insurev loosening andvfreeing the major percentage of thefbran coverings fromithe `kernels, initial testing is' desirable to determineth'e treatment time. From two tothre'e minutes will serve,y as a Vlower limit,l while up to ftwentyftovtwenty-tive minutes lconstitutes the uppery vlimit of the treatmenttime. v 1

"After `treatmentinfthefmill, the discharging mass is diluted and passed tothe subsequent sep-L aratiori stage of ithefoperation." TheeXtent oi dilution *may be varied and [usually ythree to' four parts water to one part grain will insure good results,

In this example, the treatment at the separation stage consists. inieeding the dilute mass The bran particles, together Withthe contaminating matter, are maintained in a dispersed` conv dition under the action `of the reagent and kept from forming iiocs which might tend to sinkdue to their dispersed condition, remain at the surface and pass across the tailings discharge.

Other types of hydraulic classification may be employed in place of table concentration. Jigs and' hindered settling classiers are cited as other types of equipment which may be used.

Another use of the present invention is to grade the constituents of a cereal grain according` to variations in its protein content. In such an operation, the grain which preferably is a precleaned product, is introduced into the tumble mill in the presence of the wetting medium and 1 `subjected to a conditioning operation of not to and also are kept from depositing on thegrain surfaces with which they come in contact, as

might otherwise occur if they `were not respond. Y

ing to the action of the reagent. V

As a consequence, this matter because of its lighter specific gravity forms` an overlying stratum and remains in a state of semi-suspena sion in the Water `or wetting medium flowing across the deck of the tableand is carried thereby over what is normally considered the tailing side.` As a` resultk of this series o f treatments, the grain discharged at the. concentrates end of the table is in a substantially clean condition and free from any appreciable quantity of its koriginal bran content.` The b ran removal also servesto effectively separatel contaminants of mineral, vegetable `and animalroriginf, anda,s a consequence., thenal grain concentrate isa substantially pure product possessing high foodvalue. y

` vWhile the treatment hereinbeiore described is Well suited for the treatment of what may be broadlyclassifled as cereal grains', ithasy particular application to the treatment of wheahbarley,- rye, corn and oats. f

The wetting;A medium of the treatment preferably consists of-water, but `may be any other liquid or solution possessing the desiredwetting qualities which will not lhavea contaminating or injurious effect on the grains. g Y

In another treatment, it was desired to retain thevbran i-n the grain and merely subject the grain to a cleaning operation for the removal of contaminants. v Y l As an extended period of conditioning ith the reagent will loosen the skin, it its necessary in such an operation to hold the rconditioning time to a minimum, as well 'as to avoid a pro--U nounced'attrition action. Therefore, the mass subjectedk to the agitation in the tumblingl `action is passed through the treatment in from two to three minutes, Which serves to provide the de.-

sired differential wetting action.

In thisl connection, it will be understood that the liquid content in the conditioning operation may be increased, and thereafter less additional dilution will be necessary to properly prepare the material for the hydraulic classification.

Furthermore, While it is preferable to initially condition the material in a tumble mill, any other form of=mixing which will serve to bring the reagent into contact with the solids content to be removed by the classification may be substituted therefor. Fory example, a conditioning tank provided with rotary ragitators may be used. f

yAfter the conditioning treatment, the product is diluted as required and subjected to the final separation by feeding it to a concentrating table Where the grain tending tosink because of its wetted condition passes across the concentrates discharge While Chau. insects.. dirt and the like.

` different wetting characteristics which' permit Y sink or might become entrapped withfthe rof the aforesaid operations.

exceed four minutes. The grain of high protein content which; has the best food value wets rst, while the low protein content which has the best seed value wets last. The discharge of the conditioning treatment is diluted sufiiciently to form a free-flowing pulp and subjected to stratifying classification.

Due` to the diiierences in the wetting properties. the high protein content -will sink and be held in the riiiies` to pass to the concentrates discharge, while the lowv protein content forms anv overlying stratum which moves across the rimes to the tailings discharge where it may be collected as a second valuableconstituent of the operation.

It will be understood that all the.` foregoing treatments will not depend upon the use ot a reagent, as the materials to be separated possess a satisfactory recovery by the use of hydraulic classification. However, the use of a dispersing agent serves to keep certain fractions of the contaminant matter from depositing on grain surfaces and from gathering in docs which might temi` to content.

The accompanying flow sheet represents an operation well suited to attain the objects of any In thistroatment grain after an initial screening operation t@ removeoversize foreign matter, passes into a com ditioning stage to obtain the differential wet. ting and, if continued for a suiiicient interval, to remove the outer. skins from the grain kernels.

Following this conditioning operation,r the grain is subjected to hindered settling in an air-free liquid.` The grain, or grain of high protein content, sinks in the liquid, while chaff, foreign matter and other contaminants pass to the surface and are removed.

f The cleaned grain is then subjected to the l action of a centrifuge and passed to a drier from which it is discharged as a dried and cleaned final product. f y

Air-.free liquid. as used in thefdescription and claims is intended to designate a liquid con taining no gas other than the normal amount of oxygen present by reason of sui-faceabsorp tion'. It is also possible to use the same treatment operations in conjunction with an agglomerating separation by the use of suitable agglomeratq ing agents. Features of the agglomerating action described but not claimed herein have been Lmade y `the subjects matter of claims in my co-.pending application of even date, Serial No. 378,317, en-

titled Agglomeration of cereal grains. y n

kChanges and modifications may be availed of within the spirit and scope of the invention as defined in the hereunto appended claims.

What I claim and desire to secure by Letters Patent is: f .i

graim l. In a process of separating grain kernels from the outer skins of their natural formation, the steps of treating cerealgrain in an aqueous carrier vehicle, and during said treatment agitating the grain submerged in Isaid vehicle for an interval sufficient to loosen the outer skins and differentially Wet the grain kernels and said skins without substantially reducing the grain kernels, subjecting said skins upon loosening to the influence of a dispersing reagent, causing said loosened skins While subject to the dispersing influences of the reagent to collect in suspension at or near the surface of the liquid in overlying relation to said grain kernels by subjecting the submerged solids to a vibrating table treatment capable of exerting a suspending influence on said skins,A and recovering the solids so separated at separate points of discharge from the treatment.

2. In a process of separating grain kernels from the outer skins of their natural formation, the steps of treatingcereal grain in an aqueous carrier vehicle, and during said treatment agitating the grain submerged in said vehicle for an interval suilicient to loosen the outer skins and differentially wet the grain kernels and said skins without substantially reducing the grain kernels, subjecting said skins upon loosening to the influence of a dispersing reagent, causing said loosened skins while subject to the dispersing influences of the reagent to collect in suspension at or ynear the surface of the liquid in s overlying relation to said grain kernels by subjecting the submerged solids to a ligging treatment capable of exerting a, suspending influence to attrition in a tumbling action for an interval sufficient to loosen theouter skins and differentially wet the grain kernels and said skins, subjecting said skins after loosening to the iniiuence of a dispersing reagent, then causing said loosened skins While subject to the dispersing influences of the reagent to collect in suspension at or near the surface of the liquid in overlying relation to said grain kernels by subjecting the submerged solids to a classification treatment capable of yexerting a suspending influence on said skins, and recovering the solids so separated at separate points of discharge from the treatment.

4. In a process of separating grain kernels from the outer skins of their natural formation, the steps of treating cereal grainy in an aqueous carrier Vehicle, and during 'said treatment maintaining the grain submerged in said vehicle, initially subjecting the immersed ygrain to attrition in a tumbling action for an interval sufficient toL loosen the outer'skins and differentially Wet the grain kernels and said skins, diluting the product of the attrition action, subjecting said skins after loosening to the inuence of a dispersing reagent, then causing said loosened skins while subject to the dispersing innuences of the reagent to collect in suspension at 0r near the surface of the liquid in overlying relation to said grain kernels by subjecting the submerged solids to a classiiication treatment capable of exerting a suspending influencel on said skins, and recovering the solids so separated at separate points of discharge from the treatment.

5. In a process of separating grain kernels from the outer skins of their natural formation, the steps of treating cereal grain in an aqueous. carrier vehicle, and during said treatment maintaining the grain submerged in'said vehicle, initially mixing the cereal grain with ay suflicient quantity of the carrier vehicle to make a semiiiuid mass, subjecting the semi-iiuid mass to attrition in a tumbling action for an interval sufncient to loos/en the outer skins and diierentially Wet the grain kernels and said skins, dilutingy the product of the attrition action, subjecting said skins after loosening t0 the influence of a dispersing reagent, then causing said loosened skins while subject to the dispersing influences of the reagent to collect in suspension at or near the surface of the liquid in overlying relation to said grain kernels by subjecting the submerged solids to a classification treatment capable of exerting la suspending influence on said skins, and recovering the solids so separated at separate points of discharge from the treatment.

6. A treatment according to claim 5 in which the semi-fluid mass is subjected to attrition for an interval of from two to twenty-five minutes.

LELAND H. LOGUE.

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