US2280073A - Method and apparatus for dehydrating liquid products - Google Patents

Description

April 21, 1942. J. M. HALL 1 2,280,073

" METHOD AND APPARATUS FOR DEHYDRATING LIQUID PRODUCTS Fi led Ma -15, 1959 4 2 Sheets-Sheet 1 I} v' y 78 :I i j 7% 4s g ii April 21, 1942. J. M.HALL; 2,280,073 METHOD AND APPARATUS FOR DEHY DRATI NG LIQUID PRODU CTS I Filed May 15, 1959 2 Sheets-Sheet 2 'gj a the fan and associated Patented Apr. 21 1942 I Ma'r'uon ES PAT AND APPARATUS FOR ING LI QUID PRODUCTS v Joseph M. Hall, Chicago, Ill.

nnurnaa'r- Application May 15, 1939, Serial No. 273,641 (Cl. 159-4) v 6 Glaims. This invention relates to concentration and dehydration of liquid products.

. One of the objects of the invention is the provision of a. new and improved concentrating and dehydratlngapparatus having novel means for desiccating liquid products of various types.

Another object of the invention is the provision of a new and improved system forconcentrating and dehydrating liquid products that employs a minimum number of vacuum pans or chambers.

A further object of the invention is the provision of a new and improved method and apparatus for concentrating and dehydrating liquid tlnuous process.

products on a large production'scale in a conused for concentrating other liquid products that may be subjected to a similar treatment.

In the treatment of milk and other food products, it is necessary, and is the custom at the present time with most of thelarger producers, to thoroughly clean and sterilize each portion of the apparatus that contacts the milk at least once each 24 hours in order to insure against contamination and the growth of injurious bacteria. One of the principal objects of the present invention is the construction of an apparatus that may be easily, quickly and inexpensively cleaned. By employing large evaporating cham- A still further object of the invention is the provision of a new and improved apparatus for concentrating and desiccating liquid products having a minimum number of parts and those.

parts so constructed that they may be washed or cleansed with a minimum of labor and exense Another object of the invention is the. provision of a new and improved apparatus for concentrating and desiccating liquid products that is inexpensive to manufacture, simple in construction, easily assembled, that maybe operated at a minimum of expense, and one that employs air as the dehydrating medium.

Other and further objects and advantages of the invention will appear from the following de- I scription, taken in connection with the accompanying drawings, in which- Figs. 1 and 1a, taken together, show aside elevation of 'the apparatus shown diagrammatically and with parts inflsection and parts broken away: h

Fig. 2 is a top plan view of the upper portion of" the dehydrator or desiccator Fig. 3 is a side elevation of the dryerand air separator taken 90 from that shown in i Fig. {is a top plan viewof Fig. 3; Fig; 5 is a top plan view of of the evaporator;.and

Fig. 6 is a perspective view of a portion of parts; with parts broken away. i l

In order to disclose one embodiment'of'the invention, the structure will be described as an apparatus for, and system of, evaporating and desiccatlng milk and like products. It is understood, however, that this is by way of example only and that the system or apparatus may be 55 the upper portion bers of the centrifugal separator type instead of the tubular vacuum chambers usually employed, the cleaning operation is immensely simplified and the parts readily and easily cleansed.

In the apparatus herein disclosed, the liquid product to-be treated is moved in one direction through the apparatus and the evaporating or dehydrating fluid is moved through the apparatus in a closed circuit in the opposite direction.

' Referring now to the drawings, Figs. 1 and 1a,

taken together show, more or less diagrammatically, one embodiment of the'invention. The entire evaporating and desiccating apparatus is designated by the reference character l0 and the apparatus for handling the liquid product comprises a reservoir II for containing the liquid product'to be dehydrated, a vacuum pan or chamber l2, a separator IS, a vacuum pump I 4 and a condenser l5 for partially evaporating the moisture from the liquid. This apparatus also comprises an evaporator chamber I6 for concentrating the product, a desiccator chamber IT for dehydrating or desiccating the product and a cooler l8 and air separator IQ for cooling and collecting the powder.

The heating medium or fluid is air and the mechanism for handling the air comprises an air conduit 20, a fan or blower 2| and an "air conduit. 22 within which is located the fu'rnacebr heater 23. The conduit 22 delivers heated air into the dehydrating or desiccating chamber IL. The mechanism also comprises a return conduit 24 and a furnace or heater 25 for heating the air in theconduit 24 The conduit 2 delivers the heated air into the evaporating chamber 16. An

air passage 31 conducts the air from the evap- EINT OFFICE f in its lower end forming Y28 and 291 liquid product carried over a of the liquid product. an extension to which a the headers 3| and 32, respectively. Suitable tubes 33 have their upper and lower ends rigidly secured in the partitions These tubular members are in communicationwith the headers 3| and 32 and milk orother'liquid'product from the reservoir H is adapted to fill the lower header 32- and partially fill the tubes 33. A pipe 30 between the reservoir valve 30a controls the flow of the liquid product.

The level of the liquid products in the tubes may be above that in the reservoir ll because of the partial vacuum in the header 3'! and tubes caused to rise therein by atmospheric pressure. The header 3| is in communication with the separator I3 through a conduit 34 and a deflector 35 is provided on the inner end of thhe conduit 34 for directing the 'from the vacuum chamber by the vapor generated therein downwardly into the lower portion of the separator l3. A suitablegauge'36 may be mounted on the-conduit 34 for indicating the pressure in the conduit, header and separator. The outer casing 21 of the vacuum chamber l2 forms a jacket about the tubes 33 and this casing is in com- 33. The liquid will be 'munication with an air passage or conduit 31 which conducts heated air from'the evaporator l6, as will presently appear.

The separator l3 comprises an upper enlarged section 38 and a lower reduced section 39, the lower portion of which contains more or less The uppersection 38 has this tube is in' communication with the jacket of the steam condenser l which in turn is in comv munication with the vacuum pump l4 through a passage 42. The condenser l5 has a coil 43 therein for conducting cool water to-and from the condenser for condensing the vapor that is withdrawn from the liquid product while in the vacuum pan or chamber l2 and separator l3. The water condensed may be discharged from the vacuum pumps into the waste or it may be 7 utilized in other portions of the plant.

The header 32 is provided with an outlet passage 44 which is also 7 lower section-39 of in communication with the the separator by a conduit 45. The heated air entering the jacket of the vacuum chamber l2 through the passage 31 will impart its heat to the millg contained in the tubes 33 and since the milk in 'the tubes is under a partial vacuum, the milk will be boiled and the moisture, in the form of vapor, withdrawn by the vacuum pump H. The evaporation of the moisture in the milk will in turn reduce, the tem-' perature of the air in the jacket 21- below its saturation point. As a consequence, a certain amount of the moisture in the air willbe precipitated and the liquid may passoutward through the tube 46 either as a-'waste or it may be utilized for other purposes about the plant.

The milk or liquid product in the passage 44 is transferred by the pump'41 to a sprayhead 48 in the evaporator Hithrough the pipe 40. The

spray head 48, Figs. la and 6, is suspended byaspindle 49 axially of the evaporator chamber l6. The spindle 49 is-provided with suitable journals and'isadapted to be rotated in anyconventional manner'as by means of the motor 5|; The armature shaft of the motor constitutes aspindle whichis surrounded by a tapered cone-shaped shield 52 that positions the same. 49 is hollow" and is adapted to convey tube 4| is attached and The spindle the liquid product to The spray head 48 comprises a plurality of arms 53 which extend radially outwardly in a substantially horizontal plane. These arms are hollow and have nozzle openings 54 which discharge the liquid product outwardly in a sprayv as the arms rotate. These arms extend through a deflector 55 which is atapered air conduit 56 which is in communication with the air-passage 31, as will-presently appear.

The deflector 55 is flared'at its lower end and has its side curved in cross-section so as to defiect the air entering through the air conduit 24 downwardly and outwardly, as will presently appear. I

The evaporator I6 is in the form of a cyclone separator having an enlarged cylindrical body portion 51, a lowerconical portion 58 and a top or upper, somewhat conical, portion 59. Theupper portion 59 has a depending downwardly tapered portion or extension 6| extendingabout the spindle 49 which is in the axis of the evaporator. The lower ends of the tapered portion 6| is curved downwardly and outwardly as at 62 to form withthe curved'portion of the member 55 a passagefor directing the air downwardly and outwardly within the evaporator across the nozzles 54. Y

The conduit 24 extendsfrom the dehydrator l1 through the heater 25 to a point above the evaporator IB and terminates in a snail 63 above the downwardly extending portion 6| in order that air passing through the conduit 24 and through 'the snail 63 will begiven a rotary movement so that it will enter the evaporator in a rotating spiral form. A thermometer 66 is provided for indicating the temperature of the air in the lower portion of the evaporator.

Suitable means are provided for withdrawing the air axially from the evaporator. In the form of the construction shown, the spray head 48 is so constructed that it forms an exhaust fan for this purpose. As shown inFig. 6, the arms 53 are made in the form of fan blades so that they will exhaust the air from the evaporator and discharge the same into the passage 31.

It will thus be seen that the liquid product,

after it has had part of its moisture removed in heater 25, a considerable portion ofthe moisture will be evaporated andthe air removed from the evaporator will be conducted'over to the vacuum chamber I2 for heating the liquid product contained therein, as described above. The concentrate collected in the-bottom ofthe evaporator I6 is withdrawn through a conduit 64 by means of. the pump 65'. and is delivered to the 'dessicator I1.

The dehydrator or desiccator I1 is similar in construction to the evaporator l6 and comprises an, upper cylindrical section 69, a lower tapered section 1| and an upper ordome-like section 12 which has an axial opening" 13 therein. The dome section 12 has a dependingconical member '14 which tapers downwardly and is flared out- I wardly at its lower end as; at15. Theconduit 22 for conducting heatedair to' the dehydrator I is provided with a snail 16 whichis attached'to the upper section 12 and extends about the opening 13 so that air passing along'the conduit22 the spray head 48, from the pipe 40.

located directly beneath ina' spray into the head 8| extends spindle is adapted tobe rotated by a motor the arms 83.-

will be caused to rotate and move downwardly throughthe opening 13'.

Suitable. means are provided for conducting the air delivered by the conduit 22 from the dehydrating chamber ll axially'thereof. The conduit 24 through which the air is exhausted is provided at its outer end with a downwardly extending tapered section ll which extends through the snail l8 and terminates adjacent to the curved portion 15 of the .airtdeflector 1.4. Secured to.

of the conduit 24,

v axially of the opening 18, isa tapered shield I8 axially through the shield 18.

82 mounted above the spindle. The spray head 8| is similar to the spray head 48 jandis pro- -vided with a plurality ofarms 88 that-are at- .-for circulating the air 7 10 :chamber or pan l2. An air intake valve 88 is" and depending downwardly from, the upper wall and the-spindle .18 cfaspray dicates the temperature of the said conduit. The fan 2| is meadows mometer 828 indicates airinthe passage 81. 1 ditis used as the heating medium and itisf circulated in a closed system. The mechanism charges the air'lnto the conduit 22 and,causee tachedto the spindle 19 and have longitudinal liquid product passing along the pipe 64 from the passages therethrough' in communication with an axial passage in the spindle 19 so that the evaporator IE will pass downwardly through the spindle I9 and be discharged in a spray through The arms 83 pass outwardly through a deflector 18 which has its outer surface curved downwardly and outwardly as shown at 8,4 for directing air entering from the conduit 22 outwardly across the nozzles for dehydrating the liquid product discharged by said nozzles. In order to exhaust the air from the dehydrator, the arms 88 are in the form of fan blades as shown at 53 in Fig. 6. 1 4 Since the spray head arrangement is substantially the same as that shown in Fig. in, it is not thought necessary to further scribe the same. v The fan blades or arms 83 exhaust'the air the chamber throu illustrate or. de-

from the dehydrator l1 and discharge the same upwardly throughthe tapered member 11 into I the conduit 24. The air entering through the i conduit 22 is of suchtemperature that the pare ticles of the liquid product are dehydrated and due to the centrifugal action of the mass'within the. dehydrator chamber, the air. is separated and its path of movement will now be described. I 1 Starting with the fan 2|. the air hdrawn into the fan 2| through the air con uit -28 whichnil it! communication with the jacket of the provided in the'air conduit 20 for admitting fresh air as occasion may-be required A barometer 84 the pressure ofthe and is operated by a motor 88. The fan diethe same to flow along the .conduit into the H of the heater and a baille III which extends down from. the top .wall thereof in a'plane substantially midway between the battles and II.

The chamber 81 is provided at one end'with aiuel feeding device |82pwhich supplies fuel such as oil or gass to the combustion chamber and the products of combustion are discharged from gh a pipe I03 -at opposite ends of the chamber.

' a heating chamber m is mounted abovethe combustion chamber and thisheatingchambercomprises the perforated heads J88 and I88. in

the perforations of which are'secu'red dues or tubes I01 heated by the gases of combustion.

The air from, the fan 2| passes through these from the dehydrated particles and is withdrawn bythe fan 88 as described above.

In order to reduce turbulence in the lower portion of the dehydrator II, 'a double cone-shaped member 85 is mounted therein so that the rotat ing air, as it descends, will rotate about the upper portion of the double cone thereby throwing the solid particles out against the walls of the dehydrator which will slide down the inclination of these walls. These particles will slide downwardly and be discharged by a power operated valve 88 into a passage 81 leading to a snail 88 of a. combined cooler and centrifugal air separator, l8. The valve 88 is of the usual power operated type and is adapted, to be oper ated by a suitable motor 89.. The outer end of the passage 81 is closed by a valve 9| which is adapted to be opened or partially opened to,

. introduce fresh air for cooling the product down to storage temperature, which in the case of milk powder may be around 100 F. Thepowder may be removed through power operated valve 88 operated by motor 88 which permits the powder to fall by gravity into the container I88. This air is utilized for conveying the mixture of air and or heater 23. The air passing around the snail I8 is given a rotary movement and passes downtubes and is heated as it passes through the same.

- The air passing through the superheater is discharged into the outer end of the pipe 22 and into the snail I8. A thermometer I88, is provided in the coriduit section 22 for indicating the temperature of the air passing from the furnace wardly through the opening?" across the nozzles of the arms 83 for dehydrating the spray of the liquid product discharged by those nozzles. The concave surface ofvthe shield or deflector i8 directs-the air outwardly toward the peripherytofwth'e dehydrator and the centrifugal movement of this column 01 air throws the dehydrated particles of the product outwardly against the interior wall of the dehydrator and these particles slide downwardly-into the lower portion of .the dehydrator and are removed through the valvelli as previously described. Y

The incoming air. rotates in a. wide-spiral as indicated by the arrows Hi9 about the vertical axistof the dehydrator and this spiral gradually narrows toward the lower portion of the dehydrator and rotating about the upper section of the cone in a small spiral moves upwardly in a spiral of small diameter and is-exhausted adapted to remove any of dehydrated material to the separator is and for cooling the-material. A thermometer 92 attached to the dehydrator I1. is employed for indicating the temperature of the air therein and a therby the fan formed by the header 8| and is dis charged through the shield section 11 into the return conduit 24 through a filter in whichis thesolid particles carried along with the all.

The air, in dehydrating the liquid products, has its temperature greatlyreduced and before air is introduced into the evaporator I8 for tor l6.

' nozzles 54 ther tially the the heated air 'ly' into the evaporator v v spiral, it comes'in contact with. the finely divided -cles. the bottom of the evaporator and be removed by i concentrating the 1 liquid product; it is passed through the heater for increasing its tempera ture The he'ater 25 is similar in construction to the heater 23 and comprises thecombustion chamber H2 abovewhich is. located the'heating chamber H3 as in the previous constructions.

particles of the liquid product discharged by the and evaporates a considerable por-' tion of the moisture, contained in these parti- The concentrated liquid will flow down to the pump as described above. The temperature of the air will be greatly reduced in the evaporator 16' due to its imparting heat to the liquid particles in concentrating the liquid,

The air will be withdrawn by the header 48 which functionsas a'ian'and is dis'charged'into the air passage 31 at greatly reduced temperature'. This air passes along the. passage 31 into the jacket of the vacuum chamber or pan l2 and passes further describe the same.

it rotates, it passes downwardly among the tubes 33 heating the same ber 12 for boiling the liquid for evaporating the fresh liquid product 'supv plied to the evaporatorfrom the container or reservoir 1 I. The air, after passing through the vacuum chamber. has its temperature still furreduced and mcisture'removed therefrom by condensation, It is discharged into. the air conduit 20 which completes the circuit.

In order that the system shall operate econom-' ically, it is desirable that the air be recirculated and the temperatures maintained in the different parts of the system .besubstantially constant. It is also necessary, in order to operate efficiently,

that .there be a substantially constant relationbetween the amount of liquid treated and the temperature ofthe airjin the various parts. of.

the system in treating any particular'product.

It has been 'found that the following, .which is givenby way of example only, gives satisfactory results for dehydrating or desiccating skim milk.

In a plant having acapacity of fifteen pounds of milk powder per minute and in which the evaporator chamber is probably fifteen feet .in -greatest:diameter and ten feethigh and the dehydrator chamber is probably seventeen .feet in greatest diameter and probably eighteen feet high. the following operating conditions were observed: l I g i The air enters the fan 2| at substantially 125 1 F; and 8500 cubic feet of airper minute is passed through the fan. The air passes from the superheater at a temperatureof- 400.F-. and afterit passes through the dehydrator l1. into the-"conduit 24, its temperature is around-200 F. While in'the dehydrator, it has evaporated about thirty pounds of water inproducing fifteen pounds of 6 powder. With that additional amount r moisture in sucha volume of air,th'e saturation point of the air would be around 140? so-that the air that is beingdischarged at 200' is above the saturation point. In passing through the superof the liquid at pan to. around 130 .62.5 lbs.

amount of water from the milk, about 92.5 lbs.

I for heater 25, the temperature of the air is raised to 540'F.and is discharged into the evaporating chamber I6 at that temperature. In the evaporating chamber, somewhere about 62.5 lbs. of water is evaporated per minute. The air leaving the evaporator chamber isaround .160" F. and is saturated at that temperature. This saturated air passes into the vacuum pan or chainproduct introduced therein from the supply reservoir. A partial vacuum of around 27.5 inches is maintained in this vacuum chamber which results in a boiling around F. with a consequent condensation of the moisture from the air. This absorption of heat by the liquid reduces the temperature of the air passing through the vacuum F. with a consequent condensation of the moisture therein and the fresh air introduced through the valve 93 will further reduce the'temperature to around F. The amount of liquid suppied to the vacuum chamber or pan ,is around 170 lbs. skimmed milk per minute and the amount of moisture evaporated, from this milk in the vacuum chamber is around per minute. In evaporating this of moisture is condensed and removed from this air thus reducing its temperature 'to around While the above data is given in more or less detail, it is understood that the same is by way of example only and that the invention may vary within wide limits and that the scope of the invention is not to be limited beyond the terms of the claims appended hereto.

It is thought from the foregoing, taken in connection with the accompanying drawings, that the constructionand operation of my device will be apparent to those skilled in the art that changes in size, shape. proportion and details may be made without departing from the spirit and scope of the appended claims.

, I claim as my invention:

1. An apparatus for dehydrating milk and other -liquid products comprising a desiccating chamber, an evaporating chamber, a vacuum pan having heat exchange surfaces, a conduit for conducting air from the-vacuum pan to said'desiccating chamber, a second conduit for conducting air from said desiccator chambe'n'a passage for conducting air from said evaporating chamber to said vacuum pan and across said heat exchange surfaces, heating means heating the air flowing in said conduits, throughsaidchambers and across said heat exchange surfaces,- means fordischarging said air into said chambers in a rotary movement, means causing said product to pass through said pan and'chambers in a direction counter to the movement of the air through the same, means for spraying the product into said airwithin said '2. In an apparatus for desiccating liquid products, a plurality 'of centrifugal air, separators,

means for circulatinga stream of air through said separators inv a predetermined order. in series, means for conducting a liquid product to said separatorsand for spraying said product into said separators inseries in the reverse order, means for heating the air to a predetermined high temperature just prior .to its introduction into'oneof said separators fordesiccatin'g the product, means for heating theair discharged from said one separator to a temperature far to said evaporating its introductioninto another of said separators for removing moisture from said sprayed product for concentrating the product, and means for preheating said product and removing moisture from said air preparatory to reusing thetair in the apparatus, said last-named meanscomprlsing a vacuum chamber throughwhich the air discharged from said last-named separator is conducted, a reservoir for the fresh liquid product, and means for conducting said fresh liquid product.to saidvacuum chamber from said reservoir and for conducting the same from said reservoir to said second-named means.

3. In a system of dehydrating a liquidrproduct, a vacuum chamber in the form of a heat exchanger, an enlarged evaporating chamber, a

uid product first to to said evaporating said vacuum chamber, then chamber and then to said decentrating said downwardly moving spiral only of said medium in said evaporating chamber for still further conproduct and then conducting the liquidconcentrate from said evaporating chamber to said dehydrating chamber and spraying the same into the downwardly moving spiral only of said drying medium in said dehydrating material chamber, and finally removing the desiccated from said dehydrating chamber. ,5. Almethod of desiccating a liquid product in a continuous operation which comprises circulating the same stream oi air continuously in a closed circuit through a-third, a second and a first space in series in the order named, concentrating a liquid product by first bringing the same into heat exchange relation with said dehydrating chamber, means for conveying a liqhydrating chamber, a rotary spray -for said evapl spraying said liquid product in said evaporator and dehydrator, means for circulating the same air in a closed circuit through said chambers without replenishing the air supply. first to said vacuum chamber and then to said dehydrating chamber and then to said evaporating chamber,

means for heating the air during its passage between the evaporating and dehydrating chambers to a predetermined temperature, means for heating the air in its passage from the dehydrating chamber to the evaporating chamber to a temperature above said predetermined temperature, means for dischars'ing said air across said sprays for evaporating moisture from the sprayed particles, and means for conducting said air through said vacuum chamber in heat exchange relation to the fresh liquid uum chamber. e I

4. A method of concentrating and deslceating a liquid product in a gaseous drying medium moving in a closed circuit which comprises passing all product in said vac-' stream of air in said first space while said product is under subatmospheric pressure, then spraying the concentrate into said stream of air within said second space, then spraying the concentrate' from the second space into the stream of air in said third space, causing said stream of air to movev spirally within said third and then said second spaceat high velocity, and heating said stream of air just prior to each spraying process, the heating of said air being much greater immediately prior to the spraying operation in the e the spraying operation in the third space. a

6. A method of evaporating and dehydrating -a liquid product which comprises heating a current of air to a temperature around 400 F., causing the same to flow in a spiral form in a closed dehydrating chamber, conducting the air from said chamber, heating the same to around 540' F.

and discharging the heated air into an evaporatof said medium through a heater, then causing the same to. move spirallydownwardly into and upwardly out of a dehydrating chamber, again heating said medium above that of the flrst heating and causing the same to flow spirally downwardly into and upwardly out of an evaporating chamber, then conducting all of said medium discharged from said but to a high temperature ing chamber, causing the air to rotate in said evaporating chamber, conducting said air from the evaporating chamber through a heat exchanger chamber for reducing the temperature and moisture content thereof, recycling the air through said dehydrating chamber, said evapcrating chamber and through said heat exchanger chamber, in series, in the order named, causing a liquid product to ilow through said heat exchanger chamber in heat exchange relation with said air passing therethrough for concentration, conducting the concentrate of said product from said last-named chamber to said evaporating chamber and spraying the same into the spirally moving air there n. conducting the concentrate to said dehydrating chamber and spraying the same into the spirally moving air therea in, and finally collecting the dehydrated mate- Joann: u. HALL.

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