US2259606A - Drying apparatus - Google Patents

Description

1941- A. c. BEARDSLEE ETAL DRYING APPARATUS F fliled May 19, 1958 INVENTOR ARTHUR C. BEARDSLEE 2 BY GZR/GE W LSON A TTZRNEY Patented Oct. 21, 1941 DRYING APPARATUS Arthur C. Beardslee, Arcade, and George W. Wilson, Watertown, N. Y., assignors to The Borden Company, New York, N. Y., a corporation of New Jersey Application May 19, 1938, Serial No. 208,948

Claims. (Cl. 159-11) The invention relates to the drying of heavy suspensions of solid material in liquid vehicles. More particularly, it relates to improvements in apparatus for drying cereal products, feed, and similar products which are insoluble or only partly soluble.

In drying products of the class described, it is the general practice to employ heated drying rolls or drums arranged horizontally, the material being fed downwardly between the rolls and later stripped therefrom in any convenient manner. The rolls are arranged with their axes in parallelism, and their adjacent surfaces are separated by an amount which varies in accordance with the type of material being dried. Usually dams are provided at the opposite ends of therolls so that the material may accumulate in the reservoir thus formed, providing a continuous supply. In order to dry successfully certain products, such as cereal mixtures, products containing whey and casein or similar products, it has been found necessary to space the rolls so far apart that a considerable quantity of the admixture drops through the opening between them or drips from the rolls. This results in considerable waste which, in the case of certain of these products,- assumes such proportions that the drying operation becomes impracticable.

It is an object of our invention to provide apparatus for drying products of the character described which overcomes this disadvantage'and which embodies other improvements over apparatus known heretofore.

A further object of the invention is to provide means for drying heavy suspensions rapidly and at low cost.

A more particular object is to provide means for drying suspensions of solids in liquids in the use of which excess material dripping from the drying surfaces is not wasted.

A further object is to provide improvements in "The adjacent surfaces of the rolls move downwardly as indicated by the arrows a, a; that is,

as viewed in Fig. 1, the roll at the left rotates clockwise and the roll at the right counterclockwise. At each end of the rolls I there is preferably provided a dam 2 so as to form with the rolls a reservoir for the material being fed between them. A tank 3 containing the supply of material to be dried is arranged in any convenient position for feeding the material into the space between therolls. As shown, the tank is mounted at an elevation above the rolls I so that the suspension may be fed by gravity through the pipe 4. A valve 5 may. be provided to regulate the flow. The accumulated feed stock in the reservoir between the dams 2 is indicated at 6 in Fig. 1. This feed stock flows onto the rolls I, forming a thin layer 1 on each of the rolls. The rolls are heated in any convenient manner to a temperature which should be somewhat v above the boiling point of water. For this purapparatus for drying materials of the class deshown in the lower part of Fig. 1. v

The apparatus consists essentially of a pair of drying rolls or drums I, l arranged for rotation in opposite directions around substantially horipose any heating means known to the art may be employed. The thin cohesive film of moist solids thus formed is peeled from the drying rolls at points which conveniently may be located about from the roll pass 8. For this purpose a pair of knives 9 are arranged adjacent and at an angle to the surfaces of the rolls. As the films leave the rolls they pass downwardly over inclined tables or guides l0 into spiral conveyors II which break up the dried material and carry it to a succeeding station for further processing, packaging, or storing, as may be desired.

An essential feature of our invention resides in the provision of means for reclaiming excess material which otherwise would be wasted. The amount of Waste in drying certain types of material is very considerable. This is true, for example, with cereal products, animal feed, .products containing whey and casein, and similar products, during the manufacture of which heavy suspensions of solid matter in liquids are extending lengthwise of the rolls. The bottom l3 of the trough I2 is preferably inclined, as shown in Fig. 2. At its lower end it is provided with a discharge outlet; l4 leading to a pump i5. A pipe I6 leading from a source of supply of the same feed stock that is being fed to the rolls is arranged so as to discharge a quantity of the feed stock into the upper end of the trough l2. This serves to washout the surplus material accumulating in the trough so that it passes freely out through the conduit H to the pump. A pump thoroughly mixes the solution and forces it through the pipe I! to be returned to the supply tank 3 where it is mixed with the main body of the feed stock.

The feed stock introduced through the pipe i6 may be provided by a separate tank or other source of supply but we prefer that it be drawn from the main tank 3, thus insuring that the mixture in the trough l2 will be of the same composition as that which is being fed to the rolls. J Thus the pipe l6 may be connected to the tank 3 or to the pipe 4 by the pipe l8. A valve l9 provides convenient means for regulating the amount of feed stock which is by-passed into the trough l2. It will be understood that only a sufiicient amount to wash out the material accumulated in the trough l2 need be bypassed through the pipe IS.

A leveling bar is arranged in proximity to the under surface of each of the rolls l, the lower edges of these bars preferably being flanged down:

wardly as at 2|. The purpose of the leveling bars is to smooth out the film of material on the rolls and to dislodge and remove fibrous or other undesirable lumps or particles occurring therein.

A novel feature of our invention resides in arranging the leveling bars above the trough 12 in such a way that the surplus material removed thereby is delivered to the trough. This material is then washed out of the trough together with the material dripping from the rolls, being thoroughly mixed with the separate quantity of feed stock introduced into the upper end of the trough so as to prepareit for reintroduction to the supply tank to be re-applied to the heated surfaces of the rolls. It will be observed that with my arrangement this will be accomplished without altering the composition and without diluting the suspension.

We have found that the drying operation may be performed-very rapidly with the arrangement described inasmuch as the increased amount of feed stock dripping from the rolls at higher speeds of operation does not represent an increased waste, The increased speed of operation is further assisted by the provision of means for further drying the moist film as it leaves the ,rolls. This may be accomplished by directing a stream of warm air or other drying fluid against the film. For this purpose we provide perforated pipes 22 arranged to direct air against both surfaces of the films I. The perforated pipes 22 are connected to any suitable source of supply (not shown) by the conduits 23. A significant feature of our preferred arrangement resides in directing the air against both sides of the film. We have found that it is quite important to direct air against the under side of the film because there is formed, between the film passing down over the guides l0 and the rolls, a pocket 24 in which moist air accumulates. However, we have found that this accumulated moisture is rapidly driven out by means of the air forced through the inner drying pipes 22.

It will be understood that various modifications can be made in the particular arrangement described. For example, the feed stock could be applied to the rolls other than as specifically i1- lustrated. It might be sprayed onto the rolls or run onto the rolls through a suitable conveyor. It will be understood also that our apparatus is advantageous in the manufacture of a wide variety of materials. The invention is particularly advantageous, however, as applied to the drying of heavy suspensions of solids in liquids such as whey or milk. In this category may be named suspensions of any suitable ground material such as seed meal high in protein, e. g. soy bean meal, in whey or skim milk. An example of such a suspension is a mixture of whey, which alone contains 6 per cent. solids, with enough soy bean flour to give a total solids content of 50 per cent. The term suspensions as used herein and in the appended claims is intended as a term of description and not of limitation, and is to be understood as including any materials which are equivalent to those named by way of example. The same is true of other terms and expressions used herein, and we have no intention in the use of such terms and expressions of excluding any equivalents of the invention described, or of portions thereof.

We claim:

1. Apparatus for drying suspensions of solids in liquids comprising adjacent drying rolls arranged for rotation in opposite directions around substantially horizontal parallel axes with the adjacent surfaces thereof moving downwardly, means for heating the surfaces of said rolls, means for feeding suspensions into the rolls, a trough positioned below the adjacent surfaces of the rolls for collecting material dripping therefrom, leveling means positioned above said trough and extending substantially the full length of the drying surfaces for removing excess material from the surfaces of the suspensions on the rolls, and means for feeding a separate quantity of the suspensions into said trough for mixing with said collected material and excess material to produce a material suitable for mixing with the suspensions entering the rolls.

2. Apparatus for drying suspensions of solids in liquids comprising adjacent drying rolls arranged for rotation in opposite directions around substantially horizontal parallel axes with the adjacent surfaces thereof moving downwardly, means for heating the surfaces of said rolls, means for feeding suspensions into the rolls, an inclined trough positioned below the adjacent surfaces of the rolls for collecting material dripping therefrom, means positioned above the trough for removing excess material from the surfaces of the suspensions on the rolls, means for feeding a separate quantity of the suspensions into the upend of said trough to wash said collected materials from the trough, and means for mixing said materials with the suspensions entering the rolls.

3. Apparatus for drying suspensions of solids in liquids comprising adjacent drying rolls arranged for rotation in opposite directions around substantially horizontal parallel axes with the adjacent surfaces thereof moving downwardly, means for heating the surfaces of said rolls, a tank and means associated therewith for discharging suspensions into the rolls, a trough positioned below the adjacent surfaces of the rolls, means connected to said tank for conveying a portion of the suspensions into said trough independently of said discharging means, and means for returning suspensions from said trough to said tank.

suspensions into the rolls, a trough positioned below the adjacent surfaces of the rolls, levelers.

arranged above said trough for cooperation with said rolls, means connected to said tank for conveying a portion or the suspensions into said trough, and means for returning suspensions from said trough to said tank.

5. Apparatus for drying suspensions of solids in liquids which comprises an element'having a drying surface. a reservoir for feed stock consisting of such a suspension, said reservoir being 10- cated at a point removed from the drying surface, a second reservoirarranged to hold feed stock in contact with the drying surface, means for conveying the feed stock from the first reservoir to the second reservoir for application to said surface to form a cohesive film, means for collecting the excess material resulting from the formation of said film, means for by-passing a portion of the feed stock from the first reservoir around the second reservoir to said collecting means for mixing with said excess material, and means for conveying the resulting mixture to the first reservoir.

ARTHUR C. BEARDSLEE. GEORGE W. W'IL SON.

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