US2290470A - Method of and apparatus for dehydrating liquid products - Google Patents

Description

July 21, 1942. J, M, HALL A "2,290,470

METHOD OF AND APPARATUS FOR DEHYDRATING LIQUID PRODUCTS 2 Sheets-Sheet 1 INVENTOR.

33 40 5'0 ATTORNEYS.

July 21,1942. J. M. HALL 2,290,470

METHOD OF AND APPARATUS FOR DEHYDRATING LIQUID PRODUCTS Filed Feb. '7, 1940 2 Sheets-Sheet 2 IQ} INVENTOR. $5220 4 1U flail BY ATTORNEYS.

Patented July 21, 1942 METHOD OF AND APPARATUS FOR DEHY- DRATING LIQUID PRODUCTS I Joseph M. Hall, Chicago, 111., assignor to Drying & Concentrating Company, a corporation of Delaware Application February 7, 1940, Serial No. 317,726

7 Claims.

This invention relates to a system of desiccating or dehydrating liquid products and one of the principalobjects of the invention is the provision of a new and improved arrangement of the various structures of the system whereby a large amount of air at atmospheric temperature may be mixed with a quantity of heated air for forming the dehydrating medium.

Another object of the invention is the provision of a new and improved dehydrating systemhaving novel means for dehydrating liquid products and novel means for circulating and.

recirculating all, or portions only of the drying medium.

A further object of the invention is the provision of a new and improved means for insuring delivery of the dehydrated product from the dehydrator in a continuous process.

Another object of the invention is the utilization of a large portion of fresh air in the drying medium without first passing it through a heater.

Another object of the invention is the provision of a new and improved system for dehydrating liquid products employing an apparatus that is simple in construction, eflicient and economical in operation, requires a minimum of ing only a portion of the is supplied to the dehydrator and-to mix this heated portion with a copious supply of air under atmospheric conditions immediately prior to the dehydrating operation. By means of this arrangement, an economy in heat units is obtained due to utilizing such a large number of heat units contained in air under atmospheric conditions. A high rate artificial heat, is composed of few parts, and

that is not likely of order.

Other and further objects and advantages of the invention will appear from the following description, taken in connection with the accompanying drawings, in which- Fig. 1 is a diagrammatic view in elevation f to become deranged or get out of evaporation may be obtained at moderately elevated temperatures of the heating medium if the liquid product be atomized and projected into direct contact with the heating medium while it is moving at high velocity.

' In the present invention, the concentration and dehydration are accomplished by projecting theatomized liquid product into spirally moving currents of moderately heated air. The outward and downward movement of the liquid particles through the air, together with their centrifugal movement radially outward in the spirally moving heated current of air insures a constantly changing contact of those particles and air and such everchanging contact is conductive to a high rate of evaporation. With this system, excellent results may be obtained by the use of air heated but a few degrees above the boiling point of water, say from 220 to 225 F. although much higher temperatures may be employed, if desired. The evaporation of the moisture from around the particles prevents the particles frombecoming overheated while they contain moisture.

, But the evaporation 9i the moisture quickly low! a portion of an apparatus for dehydrating liquid 1 products;

Fig. la is a similar view of the remaining portion of the apparatus;

Fig. 2 is a top plan view of a portion of the construction shown in Fig. 1; r

Fig. 3 is a section onthe line 3-3 of Fig. 1;.

Fig. 4 is a cross-section on the line 44 of Fig. 1; and

Fig. 5 is a section on the line 55 'of 1.:

In dehydrating liquid products, it is common practice to remove the moisture from the product by a heating gaseous medium such as air, dry steam or the like. The present invention employs heated air for this purpose. Air under atmospheric conditions is usually. much below its saturation point and consequently it possesses considerable capacity for absorbing moisture.

The present invention seeks to take advantage of this fact in the provision of means for heaters' the temperature of the air so that the dried particles do not come in contact with air at temperatures sufliciently high to injuriously afiect the product. 7 Furthermore, the process is of such short-eduration that the particles aretnot subjected to heat at even at moderately high temperatures for but a'few moments.

Referring now to the drawings, the reference I character Ill designates the apparatus which comprises a tank II for containing the liquid product to be dehydrated; an evaporating chamber or cabinet l2 which, for convenience, may betermed the first-stage evaporator; a second evaporator chamber or cabinet 13 which may be A termed the second-stage evaporator; and a dehydrator chamber or cabinet l4, which may be termed the third-stage evaporator, in which the liquid product is dehydrated. The apparatus also'comprises a fan l5. which introduces air into the system and causes it to flow through the w heat exchanger IS, a second fan l'l, a furnace l8 having the heater l9, and a blower 2| for introducing fresh air into the system at the intake of the dehydrator H, as will presently appear. A collector 22 is also provided for col- 2,aao,-47o introduced through the conduit 45 into the caslecting the dehydrated material discharged from the dehydrator H. The liquid product and the drying medium pass through the second evaporator and the dehydrator in opposite .directions.

Referring now to Fig. 1a, the liquid product contained in'the reservoir or container II is forced by the pump 23 through the conduit 24 into the first-stage evaporator l2 in the usual manner. The first-stage evaporator 2 is of the centrifugal separator type and comprises an up: per cylindrical section 25 and a lower tapered section 26. The lower end 21 of the taperedpor tion 26 has its walls at a more obtuse angle to the axis -.of the chamber than the remaining part of 'the tapered portion for shortening the height of the evaporator, as clearly shown in said figure. The upper part of the cylindrical portion 25 is closed by the top wall 30 which may have its central part depressed to form an annular upwardly extending portion 28 of the main chamand has attached, at its lower end, a plurality of arms having nozzles 32 attachedthereto. At-

tached to the arms 48 is an annular deflector member 33 concave ,on its upper surface. The distributor member 29 is attached to the hollow shaft 3| and is rotated by a motor 34. The arms 40, to which the nozzles 32 are attached, are each provided with a passage 58 in communication with' the passage 60, formed in the hollow shaft 3|, and are shaped .to form fan blades, as shown at 40 in Fig. 4, for'exhausting air from the chamber I2. The liquid product passes downwardly from the conduit 24 through the hollow rotating l6 from theconduit is discharged through a pipe 46 into the atmosphere after ithas imparted heat to the air introduced into the heatexchanger by the fan I5 or it may be used for other heating purposes about the plant.

shaft 3|, through the passages: in the arms 40 and, by the action of centrifugal force, it-is discharged from the nozzles 82 into the evaporator |2 in the form of a spray of finely divided particles.

Suitable means are provided for evaporating a portion of the moisture sprayed into the cabinet or chamber. Inthe form of the construction shown, air is employed as the heating and evapcrating, medium. This air is heated and circulated through the system, including the heat exchanger IS, in 'a manner that will shortly be described.

The heat exchanger l6 comprises an outer casing 35 havinga tapered end 36 in communication with the discharge of the fan IS. The casing is tapered at its opposite end and is in communication with a conduit 31. The casing is provided: at each end with partitions or flue sheets 38 and 39 which are perforated and have tubes or fiues' 4| secured in the perforations, the tubes forming passages for the air through the heat exchanger. The intake 42 of the fan 5 is provided of baffles" 44 extending from opposite sides of the heatexchanger so as to cause the heated air A portion of the air flowing through the heat I exchanger it from the fan l5 may be diverted by an'adjustable .valve 310 into the conduit 41 and the remainder is delivered to a snail 48 which discharges the air in a spiral'form' through the opening 49 into the chamber |2 onto the deflector 33 across the spray of the liquid product. This heated air, moving spirally around the walls of the chamber is exhausted by the fan formed by the distributor 29 through a sleeve'or conduit 5| extending axially upwardly through the snail 48 into the casing 52 from which it is finally discharged through the conduit 53. The intimate contact between the heated air and atomized particles of the liquid product ,within the first stage evaporator |2 evaporates a considerable portion of the moisture and the concentrate falls or flows by gravity to the bottom of said evaporator.

A portion of' the air deflected into the conduit "by. the valve 310 is caused to flow. through the heater l9 of the furnace |8 into the conduit 54 by the fan IT. The furnace l8 comprises the acasing 55 provided with the flue sheets or partitions 56 and 51 which are perforated and have tubes or fiues 58 secured therein throughwhich air from the, fan I! passes to the conduit 54. The top wall 59 of the combustionchamber is provided, at its front end, with passages 6| through which the heated gase pass into the heater |9 about the forward end .portions ,of the tubes 58 for heating the air as it passes through said tubes.

The heater chamber is provided with one or more bailies 62, one being shown, which causes the heated combustion gases to take a zig-zag path therethrough. The rear wall 63 of the combustion chamber is spaced forwardly of the rear wall 64.0f the furnace to form a discharge chamber 65 for the exhaust gases. In order to conserve heat, a portion of these gases may be recirculated ,by a fan 66. This fan exhausts from. I the chamber 65 through a, conduit .61 connected with the intake of the fan and discharge intoa conduit 68. i This conduit returns the heated gases to the combustion chamber through the.

front wall 69 of the furnace. The remainder of the gases in the chamber 65 is discharged into the stack through a conduit 12., A valve I3 is provided for "directing all, or a portion,- of the gas into the conduit 68, as may be desired.

The air, in passing through'the heater I9, is

, heated to a high temperature and is delivered, in-

exhausted from the second evaporator l3 and this heated condition, through the conduit 54 to a snail I5 having ;an outlet intothe dehydrator l4. The conduit 54 may be provided with an air filter 16, if desired. A large volume of fresh air,

nace l8. In the form of the construction selected to illustrate one embodiment of the invention, the blower 2| is employed for this purpose.

The blower 2| draws in fresh air and discharges it through the conduit I8 and through thefilter 18 in said conduit, into the snail I of conventional design, where it is thoroughly mixed with the heated air by the gyratory moan enlarged opening 8|, the walls of which are' integral with the snail I5 and constitute an outlet for said snail. Extending axially downwardly through the opening BI and axially of the dediameter than the opening 8| and which is connected at its upper end to, and supported by, an

enlarged casing 83 which in turn is in communication with a conduit 84 leading to the second evaporator chamber l3. Extending axially downwardly through the casing 83 and sleeve or cylindrical casing 82 is a hollow shaft 85 through which the concentrated liquid product is delivered to the rotating distributor head or member 86 beneath the sleeve or casing 82. The shaft 85 is protected by a sleeve 85a surrounding the same. This shaft. is adapted to be rotated in any suitable manner as by means of the motor 81. Since the distributor member or distributor 88 is similar to the distributor 29 already described, it is not thought necessary to further illustrate or describe the same further than to say that the distributor or distributor member, as in the one previously described, functions-as an atomizer and as an exhaust fan for removing the air or evaporating medium from the chamber l4.

The drying medium passes from the snail I5 'turned at an angle to form the fan blades, as

shown in Figs. 4 and 5. The dry particles ofthe product are thrown by centrifugal force against the walls of the cabinet and fall by gravity to the bottom of the cabinet.

The lower end of the dehydrator I4 is provided with an upstanding conical member 95. The conical member 95 may be integral with the walls of the dehydrator and forms with said walls an annular channel or passage 96. The passage 96 is connected -with an outlet passage 91, Fig. 3, which is tangential to the passage 96.

The air discharged from the dehydrator 18, while its temperature has been lowered, is still far above its saturation point and for that reason is employed in concentrating the liquid product after it leaves the first-stage evaporator. The air passing along the conduit 84. from the dehydrator l4 enters a snail 88 which delivers the air into the second-stage evaporator l3 in a spiral form across the nozzles of the spray head 89 for evaporating moisture from the concentrated liquid product. Since the construction of the evaporator I3 is similar to the evaporator i2 and the parts are similarly arranged and function in a hydrator is a sleeve or cylindrical casing 82 of less like manner, it is not thought necessary to repeat the description of the same at this point.

The air exhausted from the evaporator l3 by the distributor 89 is discharged into the conduit 45 and from thence the air passes through the heat exchanger It for heating fresh airforced through the heat exchanger by the fan 15 as has already been described.

It will thus be seen thatthe liquid product has a portion of its moisture evaporated in the firststage evaporator l2 by fresh air which is heated from the air discharged from the second-stage evaporator and that the concentrate which is discharged from the bottom of the evaporator l2 into a conduit 9| is forced by the pump 92 into the second-stage evaporator B where it is further concentrated in said evaporator by air discharged from the dehydrator M. The concentrate from the evaporator chamber I3 is caused to flow through a conduit 93 by a pump 94 into the dehydrator H where it is sprayed into heated air moving spirally in the dehydrator and-dehydrated or reduced tov a powder which is collected in the lower portion of the dehydrator l4 and the powder removed therefrom to the separator l8. In other words, the liquid advances from the second-stage evaporator evaporator l3 and thence to the dehydrator l4 whereas the air advances in the opposite direction through first the dehydrator l4 and then the second evaporator l3. Fresh air is employed in the first-stage evaporator but this air is heated by the air discharged from the second-stage evaporator.

In the operation of centrifugal separators,

there is usually a partial vacuum formed along .column of air and are in turn thrown outwardly by the centrifugal force of the inner column into the outer rotating column thus starting the cycle all over again.

Suitable means are provided for preventing this recirculation by causing the particles to be discharged from the cabinet as soon as they are deposited in the lower part thereof. As shown,

this is accomplished'by causing a blast of air to be discharged across the outer end of the conduit 91 so asto partially exhaust the air from said conduit by induction. As shown, this is accomplished by a conduit 98 through which a current of fresh air is caused to flow by a fan'99.

The outer'end of the conduit 91, where it is connected to the conduit 98, is so constructed that it discharges into the conduit and in the direction the same.

partial vacuum is created by induction in the conduits 91 and 96.- The air and dehydrated material is delivered by the conduit 98 into a centrifugal air separator 22 of a conventional type. The air is discharged axially from the separator through the conduit l0! and the material is discharged through a power control valve I02 in the lower portion of the separator 22, as is usual in such constructions. Since the separator 22 is of the usual or any well known construction, it is not necessary to describe the details of It will thus be seen that in this system, only a portion of the gaseous drying medium is heated and that the remaining portion of the drying medium is introduced directly from the atmosphere. The product may, if desired, be removed from l2 to the first-stage f either the first or second stage evapcrators through the valves I20 in a more or less concentrated form, as desired.

It-is thought from the foregoing, taken in connection with the accompanying drawings, that the construction and operation of my device will hydrator and for causing the same to travel downward in a spiral path to the lower portion of said dehydrator and then spirally upwardly in a spiral of small diameter for dehydratin the sprayed particles and for separating the same from the air by gravity and centrifugal action, a conduit in tangential communication with the lower portion of said dehydrator, and means for creating a partial vacuum in the conduit whereby I the dried particles in said dehydrator will, while continuing to rotate about the axis of the dehydrator, fall by gravity into the lowermost portion of said dehydrator and be withdrawn tiTingentially therefrom and through said conduit.

2. In a dehydrating system, a dehydrator of the centrifugal type having an upper section circular in cross-section and a lower tapered section,

said lower tapered section having a circular channel in its lower portion for receiving dehydrated particles of said product and a conduit tangent to said channel and in communication therewith, and mean for causing a stream of air to flow along said conduit for creating a partial vacuum therein for assisting in removing the dried particles of said product from said dehydrator.

3. In a system for dehydrating a liquid prodnot, a dehydrator chamber, an air heater for heating a small stream of fresh air to high temperature, means for discharging the heated air into said chamber, means for mixing a large stream of cool fresh air with said heated air and for discharging the mixture into said dehydrator in a downward spiral, means for discharging a liquid product in finely divided particles into said for dehydrating said particles, and means for preheating said first named stream of air, said means comprising a heat exchanger through which all the air discharged from said dehydrator is conducted for preheatingsaid mall stream of air. 4. In a system for dehydrating liquid product comprisin a dehydrator having a dehydrating chamber and a snail chamber above'said dehydrating chamber, means for discharging a liquid product in the form of finely divided'particles into said dehydrating chamber in an annular spray about the axis of said dehydrator adjacent to the top thereof, means for heating air, means for introducing the same at high temperature through the circular periphery of said snail mixture of air within said dehydrator chamber the sprayed particles and then spirally upwardly in the same direction and discharging the same from said dehydrator, for dehydrating said particles.

5. 'A' method of dehydrating a liquid product within a chamber and for removing the same therefrom which comprises discharging the product in said chamber in the form of an annular spray, heating a quantity of fresh air to a high 7 temperature, causing the same to move in a spiral current, introducing a quantity of fresh air at atmospheric temperature to said spiral current to assist its rotation and mix with it, discharging the mixed air through the top of the chamber across the sprayed material, and causing the mixed air'to travel first downwardly in said chamber in an outer spiral path and then upwardly in an inner spiral path through, said annular spray without contacting said spray, for removing the dehydrated particles from the air by centrifugal force.

6. In a dehydrating system, a dehydrator chamber, means for discharging a copious supply of fresh air at atmospheric temperature into said chamber, means for heating a small stream of air and for discharging the same into said copious supply for heating the same just prior to its discharge into said dehydrator chamber, means for causing the mixed air to move spirally downwardly in an outer spiral within said chamber and then spirally upwardly in an inner spiral within the first-named spiral and in contact therewith and in the same rotational direction thereas, means for spraying a liquid product into said outer spiral only for dehydrating said product, an annular passage extending about the lower portion of said chamber to receive the dehydrated productrtherefrom, and means for directing a stream of air into tangential communicatiOn with the annular passage to assist. the dehydrated product to move in the annular passage in the same rotational direction as the spiral currents and to induce the dehydrated product from the annular passage.

'I. A method of evaporating a liquid product within an enlarged chamber by a rotating mass.

of air, which comprises heating only a portion of said mass of air, mixing the heated air with an unheated mass of fresh air preparatory to its entry into said chamber, causing said mass of mixed air to rotate spirally within an enlarged chamber, rotatably spraying a liquid product into the spirally-moving mass of air, and separating said air from ,said product within said chamber by centrifugal action, causing the-last-named air to be discharged from said chamber and utilizing heat therein for preheating the portion of said air that is heated just prior to its entry into saidchamber.-

JOSEPHM. HALL.

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