US2787840A - Drum type spray dryer - Google Patents

Description

April 9, 1957 R FED( 2,787,840 A DRUM TYPE SPRAY DRYER Filed June 17, 1954 DRUM TYPE SPRAY DRYER Robert lFeix, Frankfurt sam Main, Germany Application 4June 17 '1954, Serial No. 437,479

3 Claims. (Cl. 34-57) This invention relates to spray drying, and more particularly to methods and apparatus especially adapted for spray drying powdered fruit, powdered vegetable, pul Verulent chemicals andtheilike.

lt is an object of this invention to ,provide a yspray ldryer capable .of continuous operation.

.Another object of .the invention is to provide .an improved, 'drum type spray drying apparatus designed 'for continuous operation and effecting a substantially immediate drying of the wet material, at relatively verylow temperatures.

A still further object of the invention is tto provide a method and apparatus for spray drying foodstuffs sufliciently rapidly as to avoid any detrimental influence on color, aroma or vitamin content of the foodstuffs.

Other objects, and the manner in which .the same are attained, will become apparent Aas this speciication proceeds.

ln the manufacture of dried products, the starting material quite often is a wet material which owing to various causes, is rendered plastic 'in the course of the drying procedure and thus becomes dicu'lt to treatin the drying apparatus. This plasticity .may b e caused, for example, by the low melting temperature of some kind of sugar which may be present, because of slow crystallization etc.y A Vtemporary plasticity, however, imperdes the conveyance of the `Inaterial in the dryer. While it lis true that dryers, even ot the spray `drying type, have been proposed heretofore which can 'handle material of the `kind described above, these prior devices sutler from the drawback that they must be stopped for discharge purposes, thus involving loss of time and interruption of the operation. This stoppage, moreover, has a detrimental influence on the dried material a good part of which, quite frequently, sticks to the walls to remain there until it is removed therefrom mechanically, and

more often than not manually, which results in a lengthened exposure to the drying temperature of 80lO0 C. and 'in a detrimental change in the properties of the material. Powdered fruit and vegetable products, as well as many chemicals, are particularly susceptible to being damaged in this manner.

The invention contemplates a drum type spray dryer designed for continuous and uniform operation wherein the 4material is protected during treatment and drying is etected substantially immediately and at such lowl temperatures as from 45 to 50 C., thus involving a material saving in the heat supply. Evaporation takes place, as it did heretofore, in a warm air eddy current which does not require the high temperatures used in other dryers, including roller dryers. Drying is effected im mediately, i. e. in about half a second, so any change in color or aroma, or any detrimental influence on vitamins etc. is avoided. The invention contemplates further that the drying zone is followed by a cooling zone wherein the material under treatment is rendered pulverulent to prepare it for an equally continuous discharge from the drying apparatus. This cooling zone permits converting States Patent ice even thosefproducts whichon drying have becomeprlastic, Yinto a more or less easi1y-pulverizable ,stateso .they .can be conveyed lurtlzier vby means of ldischarge devices, .in .a continuous operation. This is .important also where- Crystallization problems are concerned inasmuch as a rapfid and continuous operation is a prerequisite for retaining the aroma, the added sugar and the vitamins in powdered fruit, for example. Givena slow rotation of Vthedrying drum ata rate of from .about l4 to about l5 revolutions per hour, the complete operationtakes onlya few vminutes or at ,most 1A: hour, most if not all of the ,actual drying in the air current taking up but Yfractions of 4a second. The cooling zone may be equipped with a water o rar Cooling system, and even an interior air cooling system maybe employed it the material has passed Abeyond vthe spraying range.

For carrying out the method according to the invention, a drum typedryer is contemplated which is provided with inlet conduits forthe wet Amaterial vand the warm air which conduits may extend through the axle journal Ao'f the rotary drum. VIn the interior of the .closed rotary drum, these combined conduits terminate in a unit comprising a spraying lnozzlefor the wet material and surlrounding the same, an inlet for the warm air, which vunit is ecoentrically disposed in the cylindrical drying chamber inside the drum. This arrangement yields `the largest possible spraying cone, i. e. the largest possible eitective drying space.

,1 mounts for rotation, the drying drum 2 which .carries a ring gear 3 driven ybya drive gear 4. When .the idrive vapplies `on .the periphery, as shown in the drawing, asaving in power results; however, a direct drive of the axle is also possible with a closed drum. The drum 2 may also be equipped With stationary walls and an open drum cylinder revolving therebetween. In view of the cooling system required, however, a closed cylinder is preferred. The drum 2, as shown in the drawing, is provided with circumferential rails 5 by means ot which it is supported on bearing rolls 6. Where the walls of the drum revolve, as shown in the drawing, the warm air supply conduit 7 and the wet material supply conduit 8 surrounded thereby, extend into the interior of the drum through the axle journal or shaft A of the drum. Both supply conduits proceed from the point of entry into the drum interior, along a curved path to the inlet openings 9 and 10 which are disposed eccentrically to the shaft A of the drum, opening 9 being provided in the form of a spraying nozzle or disk designed to spray the Wet material into the warm air eddy current, in the direction of the drum diameter so the material under treatment is thrown against the wall of the drum, over the range of the spraying cone 14.

Intermediate the wall of the drum and the unit comprising spraying nozzle 9 and warm air supply 10, an arched stationery partition 11 is arranged which is located near the wall of the drum and is designed to control the air eddies. This partition serves the purpose of separating the drying chamber proper with its supply of warm air, from the cooling chamber. Any powder particles which in small quantity, may stick to this partition, are removed from time to time by a stripping `device so they will drop on the wall of the drum to be removed With the bulk of the dried material. The cooling zone situated behind the partition may be equipped with any known type of cooling system. Cooling by a few degrees only is suicient to obtain the effect desired. As shown in the drawing, the stripping device may be provided in the form of stripping members 12 which are mounted on the partition 11. Both the partition 11 and the stripping members 12 are stationary and do not take part in the revolution of the drum 2; as shown in the drawing, the partition 11 may be mounted on the conduits 7 and 8 which are also stationary and do not rotate with the drum. The stripping members 12 are designed to convey the dried material to a lock or discharge opening 13 (Fig. 1) through which it is removed from the apparatus. The wet air is drawn ott" through an exhaust pipe 15, to be passed through a wet air filter (not shown) if desired.

The4 spray drying method according to the invention proceeds as follows. The wet material is conveyed under pressure, through the conduit 8 to the nozzle 9, while at the same time Warm airis passed through the conduit 7 to the opening 10. The wet material sprayed from the spraying nozzle 9 is met by the warm air eddy current and is distributed over the spraying range 14 to be dried substantially immediately, the quantity of dried material adhering to the wall of the drum depending on the tendency of the material under treatment to be rendered plastic under the conditions of treatment. Revolution of the drum, however, causes the dried material to pass rapidly into the cooling zone located in back of the partition 11 where it is rendered pulverizable. The stripping members 12 push the dried material, the bulk of which is a powder, against the front wall toward the discharge opening 13. The wet air is drawn off through the exhaust pipe 15.

If stationary front walls are provided for the drum 2. the supply conduits for the wet material and the heated air can be introduced therethrough directly, eccentrically to the axis of the drum.

I wish it to be understood that I do not desire to be limited to the exact details of construction, design, operation and procedure shown and described as modifications within the scope of the appended claims may occur to a person skilled in the art which involve no departure from 4 the spirit of the invention nor any sacrifice of the advantages thereof.

I claim:

1. Spray drying apparatus comprising a rotary drum, means for rotating said drum, exit means in the wall of the drum for removal of material, a supply conduit for wet material extending into said drum, a supply conduit for heated gas concentric with the wet material supply conduit, both conduits terminating in openings eccentric to the axis of the drum, and a stationary partition located in proximity to the drum wall and on the side nearest the conduit openings, said partition subdividiug the interior of the drum into a drying chamber and a cooling chamber.

2. Spray drying apparatus comprising a rotary drum, means for rotating said drum, exit means in the wall of the drum for removal of material, a supply conduit for wet material extending into said drum and having a spraying nozzle on its opening, a supply conduit for heated gas concentric with the wet material supply conduit, the terminal openings of both conduits being eccentric to the axis of the drum, and a stationary partition located in proximity to the` drum wall and on the side nearest the conduit openings, said partition subdividing the interior of the drum into a drying chamber and a cooling chamber.

3. Spray drying apparatus comprising a rotary drum, means for rotating said drum, exit means in the wall of the drum for removal of material, a supply conduit for wet material extending into said drum and having a spraying nozzle on its opening, a supply conduit for heated gas concentric with the wet material supply conduit and terminating in a heated gas outlet surrounding said spray ing nozzle, the terminal openings of both conduits being eccentric to the axis of the drum, and a stationary parti tion located in proximity to the drum wall and on the side nearest the conduit openings, said partition subdividing the interior of the drum into a drying chamber and a cooling chamber.

References Cited in the file of this patent UNITED STATES PATENTS 2,080,059 Peebles May 11, 1937 2,452,983 Birdseye Nov. 2, 1948 2,465,963 Beardslee Mar. 29, 1949 2,521,442 Birdseye Sept. 5, 1950 2,600,945 Vincent June 17, 1952

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