US1866769A - Art of drying liquid materials - Google Patents

Description

July 12, 1932. G. D. HARRIS ART OF DRYING LIQUID MATERIALS Original Filed June 22, 1925 l\\ ooo oo o o ooo ooo odoo \Nl v A o@ Lv x o oook 0&0 ooo ooo ooo NAW @bwl 0T E i g@ of lll Patented July 12, 1932 PATENT OFFICE ABT F DRYING LIQUID MATERIALS Application filed .Tune 22, 1923, Serial No. 647,000. Renewed November 6, 1929.

This invention pertains to the art of drying liquid materials, including methods and apparatus, eliminated from` the solid particles under conditions which exclude bacteria from the presence of the material undergoing treatment and wherein the temperature of the product is constant, or substantially so.

According to the invention, liquid material is atomized at relatively low pressure and by the aid of drying gases supplied in a steril, or substantially steril, condition, from a selected number of flues or chambers of the apparatus, and such atomized liquid is subjected to the action of said gases which flow by thermosiphonic action in a circulatory path within the apparatus and from which path atmospheric air is excluded. The circulation of the drying gases is obtained by the chilling effect of certain condensers and by the heating effect of boosters located respectively in different sections of the circulatory path within which such gases are directed to liow.

A salient feature of my invention consists in channeling the How of the drying gases and in heating the resulting multiple currents of such gases to different temperatures, whereby the differently heated multiple currents are directed into contact with the atomized liquid material at different points along a theoretical line of flotation of the residual solid product, the latter floating in a delinite path within a chamber the cross section of which increases or expands beyond the point of entry thereinto of the atomized liquid and of the finely divided solids and of the points of entry of the differently heated multiple currents of the drying gases, said finely divided solids deriving its initial impulse from the atomization to which the uid material is subjected.

In my apparatus and mode of procedure, the liquid material, such as milk, is in a divided condition, suspended and floating in the gases of a chamber, and such divided floating material is exposed to the effects of multiple currents of the heated gases, said multiple currents being heated separately and to temperatures which vary from say 212 .t0

wherein the liquid constituent is liqt finely A 96, more or less. The finely divided liquid at the point of entry into the chamber is exposed to the high temperature gases supplied by one of the multiple currents, and as the di` vided material floats within the chamber, it is exposed to the progressively decreasing temperatures of the successive multiple currents liowing upwardly across the path or line of flotation of the divided liquidmaterial. At the point of entry into the chamber, the divided liquid material contains the largest percentage of its aqueous content, and the exposure at the entry of such material to the highest temperature of the multiple current has the effect of rapidly evaporating the aqueous content of the liquid material, and such exposure of the divided material to the progressively decreasing temperatures of the succeeding multiple currents brings about the progressive evaporation of the aqueous content present on the surfaces and within the bodies of the solid particles, whereby the floating divided material is progressively dried without an increase in the temperature ofthe solid particles, the temperature of the product remaining constant, or substantially constant, in the period of its dotation, or from its entry to its deposit.

Preferably, the liquid material is finely divided by atomizing such materialv at the point of entry into the chamber, and the gas to produce atomization is in a sterile condition, such gas being taken from or supplied by atmosphere from one of the multiple channels within the apparatus. The atomization of liquid material is under pressure, with the effect of imparting an impulse to the divided material, impelling such material across the chamber and across the paths of the upwardly flowing multiple currents of the drying gases, hus assuring the exposure of the divided material to the intimate contact therewith of the multiple currents, for the rapid evaporation of the aqueous content of such divided material, the temperature of which is constant or substantially so.

Other functions and advantages of the invention will appear from the following description taken in connection with the drawing, in which the ligure is a vertical sectional eleva-tion of one form of apparatus wherein the direction of flow of the drying gases and of the path of movement of the residual solid product are indicated by arrows.

'Within a housing A is a treating chamber B the roof b of which isinclined. At one end of the housing is a partition c forming a chamber or flue C, within which is a condenser D shown herein as a coil or coils with suitable provision for feeding thereto a cooli'ng medium and with a valve or valves for controlling the supply of such medium to the condenser, the feeding mechanism not being shown.

At the bottom of the housing is a flue or chamber E, and erected vertically within chamber B is a series of partitions f which produce a series 'of flow channels F in communication with the chamber E. These partitions f extend upwardly from the bottom of the housing, it being preferred to vary the height of said partitions and thus produce flow channels F which decrease in height from P one end of chamber B toward the condenser D. The gases flowing into the channels F are directed by baffles g which may be movable to act as valves, and at the top of some of the flow channels Iare other deflectors or hoods h which overhang the channels and are so related to the partitions f as to attain a series of hot air outlets i from the flow channels into chamber B below the path of movement of the residual solid product floating Within the chamber B.

G is an atomizer herein shown as a nozzle with a liquid feed pipe y' leading from a tank or other source of supply as G and with an air feed pipe lc leading from a tank Gr2 to which sterilized air is supplied by a pipe Z connected to one of the fiow channels F or to chamber B. A pump or other circulating device H is connected to feed pipe j for supplying sterilized air under relatively low pres sure to the nozzle G for atomizing the liquid material so as vto mechanically divide such material and project the same into the chamber at a point above the outlets z' from the flow channels. An initial impulse is thus given to the atomizedliquid material with a view to projecting the same across the chamber in a substantially definite path indicated as an arc by dots and arrows. l

Within the flow channels F are radiators or boosters I, the same being shown as coils to which steam is supplied, suitable provision being made as by valves for controlling the feed .of steam to the coils. These radiators or boosters Within the flow channels are of varying heating capacity and thus constilute a heating apparatus of differential capacity. The coils within the first and second channels F are of greater capacity than the coils in the third channel, and so on through the series, withthe radiators progressively decreasing in capacity in proportion to the decreased height of the flow channels, whereb the currents of drying gases flowing upwar ly within the flow channels are heated to different temperatures. Thus the gases flowing within the longer channels adjacent the atomizer are heated to higher temperatures, say 212 Fahr., whereas the gases flowing within the shorter channels are heated to lower temperatures, say 96 Fahr., the gases in the channels intermediate the longer and shorter channels being heated by the radiators to progressively decreasing temperatures between the selected maximum and minimum temperatures.

The radiators I within the flow channels are of different heating capacities so that said series of radiators collectively constitute a differential heating means or a differential -radiator. ln this connection it is to be observed that such dierential radiator or differential heating means functions as a means for heating to different temperatures multile currents of drying gases, and, further, that the heat units in such multiple currents are apportioned to the moisture content of the floating residual particles of material, as a result of which the product is at a substantially constant temperature and the heat units are supplied by the radiators to the multiple currents of drying gases in ratio of moisture diffusion, the temperature of the multiple air currents decreasing from the initial stage of product treatment to the final stage or stages of such product treatment.

According to my invention the circulation within the chamber is occasioned by chilling and heating the drying gases in different zones remote to the chamber into which is blown the atomized material, which successive chilling and heating of the gases sets up a flow the velocity of which is less than the speed of the atomized material at the point of entrance into the chamber. Again, the compressed air utilized for injecting the liquid material is expanded within the chamber, reducing the velocity of the infiowing air, but such air velocity imparts to the atomized material a certain velocity sufficient to carry or float the atomized material across the chamber, such floating residual product being exposed to the drying effect of the multiple currents of upwardly flowing air heated to different temperatures, as hereinbefore described.

Below the inclined roof b is a lifting coil J extending parallel to said roof and termi-I nating close to the inlet to the condensing chamber C, suitable means being provided for feeding a heating medium to said coil and for controlling the feed of said heating medium to the coil.

The drying atmosphere flowing upwardly within the chamber B and downwardly within the condensing chamber C carries as a constituent thereof the aqueous content evaporated from the finely divided liquid material. In the downfiow ofthe atmosphere within chamber C, the aqueous content is condensed by contact with the cold surfaces of the condenser D, the atmosphere being cooled and chilled, and the water of condensation is discharged from chamber C and condenser D by a suitable pipe or a trap.

In operation, a cooling medium of a selected character is supplied to the condenser, steam is supplied to the radiators and the lifting coil, and the pump is set into operation.

The gases in the vicinity of the condenser are chilled, whereas the gases around the radiators are heated to varying temperatures, and owing to these conditions a tranquil flow of the drying gases is set up within chamber B from which outside atmospheric air is eX- cluded except such as is admitted during the atomization of the liquid material. The gases How downwardly within chamber C, and upwardly within the flow channels F, and thus the gases are set into motion through channel E and within the chamber B. The liquid is supplied by the atomizer in a finely divided mist or spray to the chamber within which it fioats in suspension, and upon the admission of the spray it is met with an upflowing current of heated gases from the longer flues F, and is subjected to the action of the decreasingly heated gases from the remainder of the flow channels, the result of which is, mainly,

to envelop the particles or globules of solid material in heated steril gases and thus effect the evaporation of moisture. The atomized material derives an impulse as a result of the atomization which carries the solid particles in a definite path across the chamber and above the outlets from the flow channels, during which movement the solid particles are progressively dried by the upflowing currents of gas from the channels, and at this 'period of the treatment the temperature of the channeled gas is progressively decreased in a definite ratio to the decreasing moisture content of the solid residual particles, whereby the product temperature remains practically constant during the movement within the chamber1 whereas the gas temperature is conditioned to suit the product with a view to the effective elimination of moisture from the prodf uct. The ascending currents of gases from the flow channels are below the path of the product in a manner to so act upon the solid particles as to contribute to the mechanical suspension thereof Within the gases of the chamber, and thus the solid particles are exposed to the gases under conditions which permit the gradual or progressive descent of such particles under the force of gravity until the particles in a thoroughly dry condition will collect or accumulate within the chamber adjacent the condenser.

vgoing treatment.

It will be noted that the atomized liquid when first admitted meets a current of gases at the maximum temperature, thus effecting the rapid evaporation of moisture from the material and reducing the temperature of the residual particles, water, vapor and drying gases, by reason of such rapid evaporation. In the evaporation of the atomized Inaterial the gases become at least partly saturated with moisture and in order to lift the more or less moisture laden gases above the path of the product I provide the lifting coil below the roof of the chamber, which coil radiates heat units intosuch moist gases and induces or accelerates the fiow of the moist air into the condensing fiue C. The contact of the downfiowing air with the cold surfaces of the condenser tends to condense the moisture present in the gases and to deposit the same in the condition of dew upon the condenser, whence the moisture is discharged in a suitable manner.

y invention is to be used for different liquid materials for obtaining a dry product from such liquids, but its especial utility is the treatment of whole milk, i. e. milk including the fatty contents of milk, for the reason that there is no appreciable temperature variation in the product while under- Having thus fully described the invention, what I claim as new and desire to secure by Letters Patent is:

l. In the art of evaporating liquids containing solids, the process which consists in atomizing a liquid containing solids -into drying gases present within a closed'chamber so that the atomized particles are frce to float in a determined path and to gravitate toward a common place of deposit within said chamber, circulating the drying gases through said chamber, dividing the infiowing gases into multiple currents fiowing upwardly toward the path of fiotationv of the atomized particles, and heating suchV upwardly fiowing multiple currents of gases to temperatures which decrease from the point of entry of the atomized liquid. y

2. In the art of evaporating liquid materials containing solids, the process which consists in atomizing a liquid material into drying gases so as to project the atomized particles in a determined `path within the chamber and to expose suoli atomized particles tothe drying effect of .such gases, circulating the gases through the chamber, dividing the gases into multiple currents and directing such multiple currents across the path of flotation, and heating the divided currents of drying gases to temperatures de creasing along the path of fiotation of the atomized particles.

3. In `the art of evaporating liquid -materials containing solids, the process which consists in setting up a tranquil flow through a closed chamber of drying gases, channeling the path of flotation -of the finely divided the flow of suchlgases as they enter the chammaterial, said separate currents being heated ber into multiple currents, injecting a liquid to different temperatures and traversing the material containing solids into the gases in path of flotation successively in the order of finely divided particles in a path across the decreasing temperatures. multiple currents and evaporating moisture 8. In the art of evaporating liquid material from such finely divided particles, and heatcontaining solids in a body of drying air, ing such multiple currents to temperatures utilizing a portion of said air to deliver 1n which decrease progressively from the entry a forwardly moving direction and in an of the liquid and solids into the chamber. atomized state the said material into said 4. In the art of evaporating liquid matebody of air, generating at levels below that rials containing solids, the process which conof said atomized material forwardly and upsists in setting up a tranquil fiow through wardly moving successively placed currents a closed chamber of drying gases, injecting of said air of progressively decreasing tema liquid material containing solids into the perature to mingle with, and aid in the flotagases and projecting in a iinely divided contion of, and progressively dry, said atomized dition the particles free to ioat in a determaterial, and providing beyond the region mined path across the chamber, dividing the of iiotation a downwardly flowing current of gases into multiple currents flowing across cooled air supplied from said upwardly movthe path of flotation of the divided particles, ing air and in turn supplying the air for and heating such multiple currents to temsaid upwardly moying currents.

peratures which decrease progressively from 9. In the art of evaporating liquid matethe entry of the particles into the chamber. rial containing solids in abody of drying air,

5. In an apparatus for evaporating liquid moving in a forwardly directed course in an materials containing solids, the combination atomized state the said material into the said of a chamber having means to set up a flow body of air, and generating at levels below of drying gases therethrough, means for inthat of said atomized material forwardly and jecting a liquid material containing solids upwardly moving successively placed curinto said chamber so that thev particles in' a rents of said air of progressively decreasing finely divided condition are floatable in a temperatures to mingle with, and aid in the determined path, a series of channels posiflotation of, and progressively dry, said tioned within the chamber adjacent the path atomized material. of flotation of the particles and operating 10. Amilk evaporator comprising a chamto divide the gases into multiple currents ber, means for projecting thereinto liquid adapted to intersect the path of flotation of milk in a finely divided condition, a plurality the atomized particles, and means for heating of mea-ns for separately channeling air and the multiple currents to temperatures decreasdischarging the same into said chamber, and ing successively from the point of entry 0f separate heating means for the air flowing the liquid material into the chamber. within the respective channeling means, said 6. In an apparatus for evaporating liquid separate heating means being of such promaterials, the combination of a closed chamgressively varying capacities as to heat the ber equipped with means for setting up the air to temperatures progressively decreasing flow therethrough of drying gases, means for from the point of entry of said liquid milk. discharging in afinely divided condition into 11. In the art of drying atomized milk the gases a liquid material with residual traversing a chamber, the process which consolids, the cross section of said chamber insists in exposing suspended milk particles to creasing awa-y IOIH the entry 0f Said liquid multiple currents of drying gases, the direcmaterial, heating means in the upper part tion of flow of which multiple currents are of said expanded chamber, channeling means in paths crosswise of the travel of the atomin a lower part of said chamber and connectized milk particles and the temperatures of ed therewith for dividing the gases. into mulwhich Currents S0 decrease from the point tiple currents adapted t0 flow upwardly Witliof entry of such atomized milk particles that in the chamber, and a. plurality of individual the temperature of the milk particles will be radiators of different capacities positioned Substantially constant during the period of within the channeling means for heating the such exposure.

multiple currents of the gases discharge into 12. An apparatus for evaporating liquid the chamber to .temperatures progressively material comprising a chamber, a plurality decreasing from the entry of the liquid maof partitions of varying height arranged terial. transversely in said chamber adjacent one 7. In the art of evaporating a liquid mateend thereof land forming a plurality of pasrial containing solids, the process which consageways between adjacent partitions, a consists in providing a chamber, projecting liqduit communicating with the upper portion uid material in a. finely divided condition of said chamber adjacent the other end therewithin said chamber, and conducting sepaof, and with said passageways at the lower r' rate currents of drying gases in paths across portion of said chamber, means in Said conduit for reducing the huniidity of gases iowing therethrough, means in said passageways for heating the gases prior to introduction into the chamber and means at the end of the cb amber containing the partitions for introducing a liquid into said chamber above the partitions, the heating means in the passageways from the passageway nearest the end of the chamber at which the liquid is introduced to the passageway farthest away being of progressively lesser heating capacity.

13. An apparatus Jfor evaporating liquid material comprising a chamber, a plurality of vertical partitions of 4varying height arranged in said chamber adjacent one end thereof and forming a plurality of passageways between adjacent partitions, those of greatest height being nearest the end of the chamber, a conduit communicating with the upper portion of said chamber at the other end thereof, and with said passageways at the lower port-ion of said chamber, means in said conduit for reducing the humidity of gases flowing therethrough, means in said passagewa-ys for heating the gases prior to introduction into the chamber and means for introducing a stream of gascarrying a liquid into said chamber above said partitions, the heating means in the passageways between the partitions of greatest height having higher heating eifect than the heating means in the passageways formed between the partitions of lesser height. 14. An apparatus for evaporating liquid material comprising a chamber, a plurality of vertical partitions extending upwardly and arranged transversely in said chamber adjacent one end thereof and forming a plurality of passageways between adjacent par-v titi ons, a conduit communicating with the upper portion of said chamber adjacent the other endl thereof. and with Said passageways at the lower portion of said chamber, means in said conduit for reducing` the humidity of gases flowing therethrough, means in said passageways for heating the gases prior to introduction into the chamber and means for withdrawing heated gas from one of said passageways and injecting it into the chamber together with the liquid to be evaporated above the partitions at the end ofthe chamber containing the partitions, the heating means `in the passageways from the passageway nearest the end of the chamber at which the liquid is introduced to the passageway farthest away being of progressively lesser heating capacity.

15. An apparatus for. evaporating liquids comprising a horizontally arranged chamber of gradually increasing cross section, means for introducing atomized liquid into the chamber at the point of smallest cross section, means for introducingr a plurality of streams of drying gas into said chamber at a plurality of points lengthwise thereof and means for separately heating each of said streams so as to maintain the temperature of the material substantially constant.

16. An apparatus for evaporating liquids comprising a substantially horizontally arranged chamber of gradually increasing cross section, means for introducing atomized liquid into the chamber at the point of smallest cross section, means for introducing a plurality of streams of drying gas into' said chamber at a plurality of points lengthwise thereof and means for separately heating each of said streams, the means for heating the streams introduced into the chamber adjacent the portion of the chamber of smallest cross section having a greater heating effect than the means :tor heating the other streams so as to maintain the temperature of the material substantially constant.

17. A method of drying liquid material containing solids comprising floating the material in finely divided form in a substantially horizontally flowing stream of drying gas, supplying upwardly llowing heated gas to said material from a plurality of points below and spaced along the path of said stream, and graduating the temperature of thc upwardly flowing gas to maintain the temperature of the material substantially constant.

18. An apparatus for evaporating liquid material comprising a chamber, a plurality of partitions arranged transversely in said chamber adjacent one end thereof and extending upwardly from the floor of said chamber and terminating at varying distances from the roof of said chamber, said partitions serving to form a plurality of passageways, means for introducing a gas containing the material to be evaporated into said chamber above the partitions, a conduit communicating with the upper portion of said chamber at the other end thereof and communicating with the passageways adjacent the floor of Said. chamber, means in said conduit for reducing the humidity of gases passing therethrough, means in said passageways for heating gases prior to introducing them into the chamber, and valve means arranged at the lower port-ion of each of said passageways to regulate the amount of gas passing through Said passageways, the heating means in the passageways from the passageway nearest the end of the chamber at which the liquid is introduced to the passageway farthest away being of progressively lesser heating capacity.

19. A method of drying liquid materials comprising floating finely divided material in a horizontal path in a. drying gas, supplying in an upward direction, heated gas to said material from below, and heating progressive portions of said upwardly directed gas in the direction of flow of the horizontal gas to progressively decreasing temperatures so that the tempera-ture of the material will remain substantially constant.

20. In the art of drying atomized milk traversing a chamber, the process which consists in atomizing milk with a gas, exposing suspended milk particles to multiple currents of drying gases, the direction of flow of which multiple currents are in paths crosswise of the travel of the atomized milk particles and the temperatures of which currents so decrease from the pointof entry of such atomized milk particles that the temperature of the milk particles will be substantially constant during the period of such exposure, separating the dried milk from the gas and recycling the gas for atomizing the milk and to the multiple currents of drying gas. l

21. A method of drying liquid materials comprising floating nely divided material in a horizontal path in a drying gas, supplying in an upward direction, heated gas to said material from below, and heating progressive portions of said upwardly directed gas in the direction of flow of the horizontal gas to progressively decreasing temperatures so that the temperature of the material will remain substantially constant, separating the dried milk from the gas, and recycling the gas as the drying gas moving in the horizontal path and as the gas supplied in the up-` ward direction.

` In testimony whereof I have hereto signed my name this 19th day of June, 1923.

GORDON D. HARRIS.

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