US2654159A

US2654159A - Method for treating mixture containing materials and apparatus therefor

Info

Publication number: US2654159A
Application number: US140340A
Authority: US
Inventors: Braback Jorgen
Original assignee: Volund AS
Current assignee: Volund AS
Priority date: 1944-06-01
Filing date: 1950-01-24
Publication date: 1953-10-06
Anticipated expiration: 1970-10-06

Description

Hi HHH 2 Sheets-Sheet l BRABAEK MATERIALS AND APPARATUS THEREFOR METHOD FOR TREATING MIXTURE CONTAINING Nit- Oct. 6, 1953 Filed Jan. 24, 1950 m VENTOR dd? as BRA BA c/r Anew/5y 1953 J BRABAEgRE C 2,654,159

METHOD FOR TREATING MIXT ONTAINING MATERIALS AND APPARATU T EREFOR Filed Jan. 24, 1950 2 Sheets-Sheet 2 I 2/ h l AU MR\\\\\\\\\\\\\\\\\\\\\\\ \\\\\\\\\\\\\\N IN V EN TOR. R at 5194 an EK A 7TORNE) Fig. 4 is a perspective view of a section of the drying zone showing details of construction;

Fig. 5 is an enlarged diagrammatic view showing the relationship of the elements forming the drying zone; and

Fig; 6 is a perspective view, partly-broken away, of another embodiment of the invention.

Referring to the drawings, and particularl to Fig. l, the material to be treated is discharged from a hopper 2 onto a moving support, which in the embodiment illustrated is aiconveyor belt ll, passing over a pair of drums l. Press rollers 3 riding on belt l spread the material in a thin layer on belt d which moves-continuously in the direction indicated by the arrow 5?. Positioned over the belt is a casing 5, which isprovided with a top air inlet, and is also provided with a series of air-guiding members (i which form inlet and outlet passages for the air supplied to the drying I zone, as will be described more in detail hereinafter. The conveyor belt 4 is suitably heated by a number of gas burners it placed below the belt.

The material, having passed through the drying zone, is scraped off the belt, as by a scraper which passes a conveyor belt 9 moving in the direction indicated by the arrow it. On this conveyor belt 33 the material received from the lower end it of hopper i3 is submitted to an afterdrying treatment with air which is supplied through an inlet passage 8 and flows in the direction indicated by the arrow is into an outlet H. The material is removed from conveyor 9 by a scraper or rotating brush or other convenient device (not shown) to a crosswise conveyor '2, which carries the dry material out of the plant. Each of the various conveyors may be run at a speed selected in accordance with the particular operating conditions encountered.

Referring particularly to Figs. 2, 3 and e, the

air-guiding members 6 are secured, as by angle.

irons 22, to the sides of an air channel 23 mounted in casing 5 and extending to the bottom of and enclosing the spaces between each air-guiding member t. Themembers 6 are, in the embodiment illustrated, substantially U-shaped in crosssection and the walls thereof terminate in triangular end sections 2%, the bases of which are parallel to the conveyor belt i. The air is drawn into casing 5 and around the members 8 by any convenient suction device as indicated by the arrows in Fig. 5, the air entering through the top of easing 5 flows downwardly over air channel 23 and is drawn from each side of channel 23 into the spaces 25 formed by thewalls of each member 5. The air is then drawn downwardly and through the relatively thin space formed between the bases of the triangular sections 24 and the belt i. The air. then flows upwardly in the spaces ..5 between members 6 and is drawn away through the interior of air channel 23.

Referring particularly to Fig. 5, it will be observed that the bases 2'5 of the triangular portions 24 lie parallel to the surface of belt 4 on which is supported a thin layer of material 28 and that the length D of the bases 21 is of a substantiall greater order of magnitude than the distance H between the upper surface of belt 4 and the lower surface of the bases 2?. It is a feature of the invention that a substantially laminar, as distinguished from a turbulent, flow of air across the surface of the material 28 is obtained. It has been found that such laminar flow can be obtained and a substantial increase in eficiency realized by making the ratio of H to D at least 118, and the ratio is advantageously set within the range of 1:8 to 1:20. In practice, of course, the thin layer of material '28 reduces the distance H to a slightly smaller value, e. g. it. However, sincethe thickness of layer 28 is relatively insignificant as compared with H, H and. it can, in practice, be considered as having substantially the same value. The thickness of the material on the carrying surface is in most cases, for example, between about 0.05 mm. and 0.5 mm. In the drawings the thickness of layer 28 is, for purposes of illustration, necessarily exaggerated.

' It is desirable to provide some convenient mechawith respect to belt l whereby l nism to permit the casing e to be raised or lowered U (or it) may be adjusted to any desired value.

While the invention has been described above in connection with an embodiment involving a continuous horizontal belt as the supporting surface for the layer of material being treated, the supporting surface may also be provided by the surface of a rotating drum.

Referring particularly to Fig. 8, a drum 33 is rotatably mounted on hollow stub shafts 32 and shaft 32 being supported in bearing 3d and shaft 33 passing through a gear box 33 in which suitable gearing provides a driving connection between the shaft and a motor 38. Arranged over a substantial portion of the surface of drum 3!] is an air case 6%] connected to an exhaust blower 5.2 having an outlet i l. Extending between the side walls 5%} of 'air case is are a series of air-guiding members 8 similar in construction to the air-guiding members ii, except that the former are arranged along a circular path so as to conform to the curvat" e of drum 39. As in the embodiment shown in Fig. l, the bases of the triangular end portions of members as are spaced from the surface of drum it in such manner that the ratio HzD is at least 1:8 as described hereinabove. Each of the side walls 46 is provided with apertures 52 which communicate with the channels 52 between the walls of each air-guiding member 18. Apertures 513 thus permit air to be drawn by the action of blower 52 into both ends of channels $2.

The drum is conveniently heated by steam which is introduced into shaft through inlet 55. The steam condensate is withdrawn through shaft 38 and an outlet 5i connected to any convenient suction device (not shown). In-.

teriorly of drum 36 a flexible tube (not shown)- may be connected to shaft to permit the condensate to be withdrawn from the lower portion of drum 353.

The material to be treated iii; is maintained in a trough 62 mounted across the surface of drum, 3:; between the ends of air case and is applied to drum 39 by means of a feed roll til rotatably mounted in trough The dehydrated material which has passed through the drying zone is; removed by a knife mounted in bearings t8 below feed roll 52 and connected with an adjusting device ill, by means of which the angle of contact of the knife with drum 383 can be varied. A catch plate '52 below knife 3 deflects the material scraped off the drum into a convenient container.

In operation the material 58 is spread in a thin layer on the surface of drum as by the action of feed roll 64. By reason of the rotation of 6f the m'alt'erial 60-on drum 30in the rim 1 Q -iing zone below-the 1cwr surface 6 ther 'i upwardly between-members 48 an 7 ft ionof blower-42 is-drawn thr6ugh apertures 50 i intoeach endof channels iz etween ithelwalls In accordance with my process, I can rapidly and efficiently dehydrate or desiccate all types of materials by exposing a thin layer of the materials on a heated moving surface to an extended laminar flow of air. The process may be carried out with a wide range of temperature conditions, the temperature of the air being substantially lower than the temperature of the supporting surface. The air is conveniently at room temperature e. g. -30 0. although it may be heated somewhat if desired. The temperature of the supporting surface, preferably at least 60 0., is advantageously between 100 and 140 C. The velocity of the air drawn across the surface of the material may vary depending upon operating conditions. Generally speaking, the velocity of the air is between and 100 feet per second.

The efficiency attainable by my improved apparatus may be illustrated by practical experiments wherein it has been shown that the base on which the drying material rests might be heated to 110-140" C. without the material being heated to more than '50-60, i. e., a temperature difference of 60-80 is obtainable, whereas in known apparatus temperature differences of only -50 could be obtained, other factors being equal.

Since my process is intended to remove only the moisture and not the solid or viscous material, it is sometimes advantageous to subject material to a pre-drying step or, in the case of solutions, a pre-evaporation step until the viscosity and cohesion to the material is sufiicient to prevent particles of the material from being carried away by the air current.

It will further be understood that one or more special treatments may in whole or in part be given the material in the drying zone. Thus, the raw material may during its passage through the drying zone be chemically or physically treated e. g. by oxidation, by irradiation with ultra-violet light, or by the addition of other substances, e. g. vitamins. If, for instance, the raw material consists of glands or blood, this material may be sterilized by exposure to ultraviolet rays during the passage through the drying zone, whereby a perfect sterilization will be possible when the material is lying in a very thin, filmy layer.

In the treatment of starch it may be especially advantageous to place immediately before the drying zone or in the first part of the latter a heating zone in which the raw material may be made to dextrinate before it enters the drying zone. In continuous operation the raw material may be caramelized or the starch converted into dextrine after the preliminary heating step.

Further, a cooling zone may be placed immediately beyond the drying zone which will be advantageous when it is a question of drying gelatine and certain kinds of glue which are kept semi-fluid by the drying heat and which prior e -sreraiieflisn e scapees process is-fotlz, special -im pcrtance in the 1 dsieeaubn er air kinds offinelycut green fods 'place'a ea tne tbnteyd in a de'r arid' gardh predat {such as lucerene; clover,

aves. 'Theplantslmay be z-before they have atltherr lee-possible to re- 'their -niost adiiiig the 'r-ying Thee=material I suflicientlypasty consistency to make it form a filmy layer. so

- den'se t'lia-t a sterilizing or vitaminizing irradiation may be effectively applied. All heretofore known desiccation methods for such products have had the drawback that the desiccation has not been uniform because of the thick and thin parts of the plant have been unequally affected or because the desiccation economy has required too high temperatures, too long a period of treatment or the use of unsuitable material, e. g. a product harvested too late, exposed to weather or otherwise depreciated in value.

Finally, the method according to the invention may be used in the treatment of products which after drying are to be exposed to especially high temperature, such as raw cement slurry. In that case the raw material is first applied to the external surface of the moving of a drum of the type shown in Fig. 6, and after drying, the material is scraped off and placed in the interior of the drum which by suitable means is heated to a temperature suitable for the burning of cement, and the hot air or gases resulting are used for the drying of the material on the surface of the drum. These gases may also be used for an after-drying of the material scraped off the outside of the drum and taken through the drum in a relatively thick or porous layer, the said air or gases being, if necessary, first passed through a drying or purifying cyclone. Before these gases are taken to the after-drying zone they may be further heated, as by passing them through a heater or by adding to them hot exhaust gases, e. g. the waste gases from the engine operating the plant. Thereby part of the waste heat of the engine may be utilized. Obviously, the temperatures employed in treating cement are much higher than those mentioned above in connection with the treatment of heat-sensitive materials such as food stuffs.

In the production of cement according to this method a particular heat economy is effected, inasmuch as both the inside and outside of the moving base are utilized and at the same time the same heat supply may be used both internally and externally, first assisting in the burning of the cement and then in the drying of the slurry.

This application is a continuation-in-part of my co-pending application Serial No. 700,364 filed October 1, 1946, now abandoned.

What I claim and desire to secure by Letters Patent:

A method of treating moisture-containing fluid materials to remove at least a portion of the moisture therefrom which comprises spreading the material to be treated in a thin layer having a thickness 0.05 mm. to 0.5 mm., moving said layer unidirectionally through a drying zone, heating -the underside of said layer to a temperature substantially above the ambient temperature, passing a plurality of streams of non-saturated air at the ambient temperature across the top surface of the layer of material and parallel thereto in said drying zone at a velocity of 25 to 100 feet per second, each 01' said plurality of streams being caused to undergo laminar flow across said surface for a predetermined distance substantially less than the distance transversed by said layer in said drying zone, each stream being confined in flowing across said surface {or said predetermined distance and having a height above said surface which bears the ratio to said predetermined distance of 1:81 to 1:20, and removing eachv of said air streams from contact with said surface after having transversed said predetermined distance.

JjDRGEN BRABAEK.

References Cited in the file of this patent UNI'I'ED STATES PATENTS Number Name Date Edwards Apr. 24, 1900 Hockley May 6, 1930 Brabaek Nov. 7, 1933 Stuntz Apr. 25, 1939 Brabak May 23, 1939 Hess et a1. Jan. 6, 1942 King Feb. 2, 1943 Wayland June 29, 1943