US2216815A

US2216815A - Dehydrating system

Info

Publication number: US2216815A
Application number: US201977A
Authority: US
Inventors: Joseph M Hall
Original assignee: Individual
Current assignee: Individual
Priority date: 1938-04-14
Filing date: 1938-04-14
Publication date: 1940-10-08
Anticipated expiration: 1957-10-08

Description

Oct. 8, 1940. J. M. HALL DEHYDRATING SYSTEM Filed April 14, 1938 5 Shegts-Sheet l JFuJ/Q LZOP:

.fasze v/i M [fall M M O 8, 1940- J. M. HALL DEHYDRATING SYSTEM Filed April 14, 19:58 5 she ts-sheet 2 ilial Oct. 8, 1940. J. M. HALL DEHYDRATING SYSTEM Filed April 14, 1938 5 Sheets-Sheet 3 Oct. 8, 1940. J. M. HALL DEHYDRATING SYSTEM Filed April 14, 1958 5 Shee tsSheet 4 fose v/i lfffal 1940- J. M. HALL DEHYDRATING SYSTEM Filed April 14, 1938 5 Sheets-Sheet 5 flu/anion- Joseph/1117a Patented Oct. 8, 1940 UNITED STATES PATENT OFFICE z,21e,s1s

nnmmaa'rmo SYSTEM Joseph M. Hall, Chicago, III. I

Application April 14, 1938, Serial No. 201,971

11 Claims.

This invention relates to dehydratingor desiccating systems and more particularly to the type of apparatus in which a substantially closed heating medium circulating system is employed.

a One of the objects of the invention is the provision of a new and improved dehydrating device in which the waste heat is reduced to a minimum.

Another object of the invention is the proviw sion of a new and improved system of concentrating and desiccating liquid products and of collecting the dehydrated product.

A further object of the invention is the provision of a new and improved dehydrating appais ratus having novel means for reusing the heating medium during the operation of the apparatus. I a

A still further object of the invention is the provision of new and improved dehydrating chamber and means for removing the'desiccated material therefrom. v

Another object of the invention is the provision of a new and improved system or method of dehydrating material, together with a novel 25 method of collecting or causing the desiccated material to be deposited in a collector or depository.

A further object of the invention is the provision of a new and improved dehydrating appa- 30 ratus that is simple in construction, eirlcient in operation, comparatively inexpensive to install and that is composed of few moving parts.

Other and further objects and advantages of the invention will appear from thefollowing description, taken in connection with the accompanying drawings, in which- I Fig. 1 is a side elevation of the apparatu shown more or less diagrammatically; f

Fig. 2 is a vertical section through the dehydrator chamber, with parts broken away;

Fig. 3 is a section on the line 3-3 of Fig. 2 showing the parts on an enlarged scale;

Fig. 4 is a plan view of the dehydrator chamber;

Fig. 5 is a section on the line 5-5 of Fig. 2;

Fig. 6 is a vertical section of the primary boiler or evaporator;

Fig. 7 is a vertical section of the secondary boiler or evaporator;

Fig. 8 is a vertical section of the secondary boiler r evaporator taken at right angles to that shown in Fig. 7; and

Fig. 9 is a vertical section through the spray head.

In dehydrating products on a commercial scale, it is common practice to use artificial heat for evaporating the moisture and ordinarily a great number of thermal units are discharged into the air in the form of sensible or, in some instances, latent heat or heat of vaporization. Such a process is expensive and in many instances all but prohibitive, especially where the moisture is evaporated at atmospheric pressure and the vapor discharged directly into the air.

The present invention seeks to remedy these 10 difliculties by the provision of means whereby the moisture in the product is evaporated at sub-atmospheric pressure and the latent heat of vaporization utilized to further evaporate moisture from the product preparatory to dehydratmg or desiccating the product.

Furthermore, the present invention contemplates recirculating portions of the heated air so as to utilize to as great an extent as possible the heat applied to the air, thereby effecting an economy in the use of fuel.

A portion only of the air may be recirculated because the moisture absorbed in the dehydrator chamber is not all condensed in the boilers and for that reason fresh air is continually introduced into the system for dehydrating or desiccating the product in the dehydrating chamber, as will presently appear.

Referring now to Fig. 1 of the drawings, the reference character I0 designates the apparatus in general which comprises a furnace II, an air heater I2, a principal or primary boiler or evap orator I3, an auxiliary or secondary boiler or evaporator I4, a liquid reservoir IS, a condenser I6, a vacuum pump I1, a dehydrating chamber I8, a spray head or nozzle I9 and the centrifugal air separator and collector 2|.

The furnace II is provided in its forward portion with a conventional combustion chamber 22 that is separated from the remainder of the furnace chamber .by a baflie 23. The bafile is provided with an opening 24 and the size of this opening may be varied at will by the insertion or removal of layers of firebrick 25, as desired. I The upper portion of the furnace II has the air heating mechanism I2 mounted therein. This mechanism comprises a plurality of horizontally arranged tubes 26 having their ends in communication with the headers 21 and 28. The header 28 has connected thereto a blower 29 operated by a suitable motor SI for forcing air through the heating tubes 26.

The header 2! has connected thereto a pipe or passage 32 for conducting the heated air to the dehydrating chamber 18, as will presently be described.

The bafile 23 extends upwardly among the tubes 26 and is adapted-to cause the heated gases to pass upwardly around the tubes 26 for heating the air passing through said tubes.

Heat may be supplied to the furnace in any suitable manner. As shown, a conventional oil burner 33 is provided for this purpose. Oil is then supplied to the burner 33 by a pipe 34 in the usual manner.

Suitable doors

35 and 36 are provided in the side of the furnace to permit access to the same.

Suitable means are provided for concentrating the product preparatory to dehydrating the same. In the form oi the device selected to illustrate one embodiment of the invention,'a plurality of boilers or evaporators are employed. As shown, two are used, but it is understood that this is by way of example only as additional boilers may be employed, if desired. These two boilers, for convenience of description, will be referred to as the primary or principal boiler and secondary or auxiliary boiler.

The primary boiler [3 comprises an upper section or vapor chamber 31 and a lower section 38, Fig. 6. The lower section 38 has a header 39 secured below the same and this header is in communication with the upper section 31 through a series of pipes 4| secured in a partition plate 42 between the upper and lower sections. The lower ends of the tubes 4| are secured in a partition plate 43 between the lower section 38 in the header 39. The primary boiler is adapted to be supplied with milk or other liquid or semi-liquid product from the reservoir I5 through a suitable pipe or pasasge 44 which is controlled by a valve 45, 1e. 1.

The upper end of the primary boiler or evaporator I3 is provided with a manhole 46, Fig. 6, having an upwardly extending cylindrical portion 41 provided with an outwardly extending peripheral flange 48. The manhole 46 is provided with a closure 49 hinged as at 5| and is provided with a latch 52 for clamping the same in position.

The parts are so constructed that the closure is air-tight. The closure 49 may, if desired, be provided on its upper portion with a sight opening 53 which is closed by a glass plate 54.

During the operation of the device, the milk or other liquid product is supplied to the primary boiler so that the level will be slightly above the partition 42.

Suitable means are provided for evaporating the liquid in the primary boiler. In the form of the device selected to illustrate one-embodiment of the invention, this is accomplished by passing heated gases from the furnace I I, Fig. 1, through the lower section 01' the primary boiler and simultaneously reducing the pressure in the upper portion of the boiler. As shown, the back wall of the furnace II is provided with an opening in which one end of a conduit 55 is secured, its other end being secured in the wall 56 of the lower section of the boiler l3. The heated gases pass around the tubes 4|, Fig. 6, and impart their heat to the liquid contained in the tubes and these gases are exhausted from the lower section through the wall 56 and through a conduit 51 into the secondary boiler, as will presently be described.

The secondary boiler or evaporator I4, Figs. '7 and 8, is constructed somewhat similar to the primary boiler but with certain exceptions as will now be described.

This boiler comprises an upper section 58, a lower section 59 and a header section 6l. The upper section 58 is provided with a flanged opening 62 having a closure 63 provided with 'a sight opening closed by a glass plate 64 as in the previous construction.

The lower section 59 of this boiler has an inner cylindrical portion 65 and an outer annular chamber 66, surrounding the cylindrical portion 65. The inner section 65 has an outer wall 61 concentric with the wall 68 01' the lower section 59 of the boiler and has end plates 69 and H which are provided with openings in which are secured the pipes 12. The pipes 12 place the upper section 58 of the boiler in communication with the header 6|. The outer annular portion 66 has a partition 60 between it and the upper portion and a partition 10 between itand the header 6|. Tubes place the header 6| in communication with the upper section 58.

The space 13 among the tubes 12 of the inner cylindrical portion 65 of the lower section 01' the boiler I4 is placed in communication with the upper section of the primary boiler l3 through the pipe 14, as shown more clearly in Figs. 1 and 7 of the drawings. The pipe I4 is attached to the upper section 31 of the boiler l3 adjacent its upper end and to the upper portion of the evaporating the liquid condensate contained in,

those tubes. The concentrate from the primary boiler is transferred to the secondary boiler through the pipe 15 and the flow is controlled by a suitable valve 16 in the pipe 15.

In order to materially increase evaporation of the product, during the operation of the device, suitable means are provided for maintaining the pressure within said boilers at sub-atmospheric and in order to insure the flow of the liquid product from the primary to the secondary boiler, means are provided for maintaining the pressure within the secondary boiler below that in the primary boiler as will now be described.

The lower end of the inner or cylindrical portion 65, Fig. '7, of the lower section of the secondary boiler is connected to the vacuum pump H by means of

pipes

11 and 18, Figs. 1 and '7. The pipe" is providedwith a valve 19 which may, if desired, be made automatic to open at a predetermined pressure. The parts are so adjusted that the pressure in the upper section of the primary boiler I3 is below that of the atmosphere but considerably above that in the secondary boiler l4 whereby vapor and the concentrate will be caused to flow from the first to the second boiler. By manipulating the valve 19, the pressure within the inner portion 65 of the lower section of the secondary boiler may be held at any desired and predetermined amount and this in turn will control the pressure within the upper section of the primary boiler I3 through the pipe 14.

The upper section oi. the secondary boiler is connected by a pipe 30 with the condenser l6 and through the condenser to the pump l1 whereby a low pressure is maintained in the upper section 58 of the secondary boiler. The pressure within the upper portion of the primary boiler is maintained higher than that within the cylindrical portion 65 thus allowing the vapor to readily pass over from the primary to the secondary boiler.

The upper section or the secondary boiler is maintained at a lower pressure than the upper section of the primary boiler whereby the concentrate readily passes from the primary to the secondary boiler, where it is further concentrated.

As an example of the working conditions, the pressure within the boiler I3 may be held at twenty inch vacuum by manipulating the valve 19 while the pressure within the secondary boiler I4 exterior of the portion 85 may be held at a vacuum of twenty-eight inches. The temperature of the air from the furnace II entering the primary boiler may, for instance, be around 700 F. while the temperature of the heated gases supplied to the secondary heater I4 may be materially lower due to the absorption of heat by the liquid product causing the latter to boil. The air may leave the second boiler around 180 to 190 degrees. These temperatures are given by way of example only and it is understood they may be varied within wide limits.

After the heated gases supplied from the furnace to the primary boiler through the passage 55 have passed through the primary boiler, 8. GO!)- siderable portion of the heat is imparted to the liquid to be evaporated and then these gases pass through the passage 51 to the outer portion of the lower section of the secondary boiler; The fan or blower 40 exhausts the heated gases, which have their temperature lowered still further in passing through the secondary boiler and will finally emerge into the discharge passage 8| the fan or blower 40 at a greatly reduced temperature.

The combustion gases, on passing from the secondary boiler I4, are conducted through the conduit 82 into the centrifugal fan 40 and from thence they are discharged into the rear end of the firebox 22 through the conduit 8I and a portion of them are caused to be recirculated through the boilers in a partially closed system and a portion discharged through the discharge pipe 83. Since air is being continuously introduced into the system, air or the combustion gases must be continuously discharged therefrom. Consequently, .a portion of these gases is discharged into the atmosphere through a discharge conduit 83 as they circulate through the conduit 8|. The conduit 83 has a suitable'valve 84 for controlling the discharge oi! these gases.

Suitable means are provided for dehydrating or desiccating the concentrated liquid product. In the form of the construction shown, a dehydrator chamber I8 is provided for this purpose. This chamber may be of any suitable form but in the construction shown, it is cylindrical and has an upwardly sloping top wall 85, Fig. 1, which terminates in a horizontal portion 86 through which the liquid product from the second boiler I4 is delivered to the interior of the dehydrator.

The lower portion of the dehydrator tapers inwardly and downwardly as at I10 and has a cone deflector I80 rising upwardly within said tapered portion whereby inner and outer sloping walls are provided for directing the desiccated material downwardly into an air channel or trough, as will presently appear.

The evaporator or dehydrator chamber I8 is provided, on its upper portion, with a distributor mechanism I9 comprising a spray mechanism or atomizer 81 for reducing the concentrated liquid product delivered through the pipe 88 to fine particles and discharging the same into a heated current of air within the dehydrating chamber, as will presently appear.

The spray mechanism 81 comprises acasing 89, Fig. 9, which is rigidly mounted on the top wall of the evaporating chamber I8 and has a complementary section 9| which is hinged thereto as at 92 and a latch mechanism 98 is adapted to secure the two sections together to form a chamber 94 within which a centrifugal blower 95 is adapted to rotate.

The blower 95 is of the usual or any well known construction having the spiral blades 98 for discharging air radially into the space or passage 91 extending about the tan or blower 95. The air is discharged through a passage formed by a par tition I00, into a hollow drum or cylindrical member 98 which is secured to the central portion of the casing 89 and extends downwardly into the dehydrator I8 as is more clearly shown in Fig. 9 01' the drawings. The blower 95 is rigidly attached to a vertical spindle 99 which extends downwardly into the interior of the dehydrating chamber. This spindle is hollow for conducting the liquid product to the header as will presently appear.

The spindle 99 is adapted to be rotated by a motor IN, the rotor 90 of which is rigidly connected to said spindle. The casing I02 for the motor is provided with an air passage or jacket- I03 which extends about the motor for cooling the same. The air enters the passage I03 through an opening I04 which has an adjustable closure 50 and passes around the motor and through the passage I05 into the chamber I08 just above the blower 95 and is then drawn axially into said blower and discharged radially into the passage 91 as described above. From the passage 91, the air is forced along the passage I01 into the drum 98 for cooling the bearings I28 and for preventing back pressure in the head, as will presently appear.

The upper end of the spindle 99 extends into a stationary casing or hollow casting I08 in which a suitable gland I09 is provided for making a liquid-tight joint between the spindle and the casting as shown more clearly in Fig. 9 of the drawings. The upper end of the casting I08 is provided with a screw-threaded cap I II within which is mounted a spring I I2 which seats against an element II3 of the gland. By adjusting the cap III, the tension on the gland element may be varied.

The casting I08 is provided with a lateral extension II4 having a passage II5 closed at its outer end by a plug H6. The lateral extension is provided with a nipple I I1 to which the lower end of the conduit or pipe 88 is adapted to be attached. Mounted within the passage H5 is a control valve II8 for controlling the supply of liquid product to the passage in the spindle 99.

Suitable anti-friction bearings I I9 and I2I may be provided for the spindle 99. The drum 98 is rigidly attached at its upper end to the blower or fan casing 89 and its lower end is closed by a plate I22 having an axial opening I23 therein through which the spindle 99 extends. The plate I22 is secured to a fiange I24 on the cylindrical member 98 as by means of the cap screws I25. 'A sleeve I28 of insulated material is provided for the cylindrical member 98, as shown in Fig. 9 of the drawings, for preventing the liquid product in the bore of the spindle from becoming injuriously affected with the hot air introduced around the sleeve for dehydrating the atomized material, as described below.

Secured in the rabbet in the lower end of the cylindrical-member 98 by the plate I22 is a.casting I21. cess in which is mounted an anti-friction bearing I28 for the lower end of the spindle. A pipe I29, secured in the casting I21, is adapted to supply the necessary amount of lubricant to the bearing I28. The plate I22 and casting I2'I are provided with a plurality of openings I3I through which the air from the blower is discharged.

Mounted on the lower end of the spindle 99 is the spray head I32 which comprises a cone member I33 having its apex attached to the spindle 99 whereby the head rotates with said spindle. The apex of the cone member is provided with air passages I34 for admitting a portion of the air discharged through the passages I3I for preventing back pressure in the cone member I33 when the same is in operation since the high speed rotation of the con-e member tends to create a partial vacuum in this member.

The lower end of the spindle 99 is provided with a cap I35 having downwardly and outwardly extending openings I36 through which the liquid product flowing through the axial opening I36 in the spindle 99 is discharged. This liquid is withdrawn from the boiler I 4 and forced through the pipe 88 and passage I36 by a pump I31, Fig. 1, operated by a motor I38. The pressure of the liquid and centrifugal force of the rotating head is suflicient to cause the liquid product to be deposited on the interior surface of the cone member I33 and due to the speed of this member, the liquid product will be gradually thrown outwardly onto the inner surface of the cone and will spread out in the form of a film which gradually decreases in thickness as the area of the surface expands toward the lower end of the cone member I33. The lower edge of the cone member is provided with a large number of slots I 39 spaced some distance apart. These slots are arranged at 'an angle to vertical planes through the axis of the cone member. The cone member is rotated in the direction of the arrow in Fig. 3, that is, it is rotated in such a direction that the lower ends of the slots' lead the upper ends thereof. Their distance apart and the angular direction of the slots are such that a vertical plane through the axis of the cone and the upper end of the advancing slot will intercept the lower end of the following slot whereby all of the liquid passing downward on the inner surface of the cone member will be intercepted by slots and thrown outwardly from the entire length of the edge of each slot by centrifugal force in the form of a band or ribbon of particles.

The lower portion of the cone member I33 is provided with radially extending flanges or plates HI and I42 spaced apart and. having curved vanes I43 between the same, Figs. 3 and 9. The plates HI and I42 diverge outwardly so that the vanes I43 are wider at their outer ends than at their inner ends. The lower plate I42 terminates outwardly of the lower end of the cone I33 and the opening is closed by a plate I44. When the plate I44 is removed, access may be had to the inner portion of the cone. If desired, the upper and lower plates MI and I42 may be cast integral with the vanes I43 and with the cone I33 as shown in Fig. 9 of the drawings. The lower portion of the cone below the upper ends of the slots I39 extends downwardly below the upper plate I but terminates above the plate I44.

The casting I21 is provided with a re-' The blades I43 curve sharply rearwardly at their inner ends. This is done in order to pre vent. spattering of the product discharged outwardly by centrifugal action of the cone when it comes in contact with the blades. These particles are traveling at the speed of the slots when they are thrown tangentially from the cone. This speed is lower than the vanes I43 so by curving the vanes rearwardly they may pick up these particles and gradually increase their speed, as it were. The band or ribbon of particles discharged from the slots I39 is spread evenly across the inner ends of the blades I43 and the centrifugal force of the particles will cause them to spread across the blade as they approach the outer ends thereof and since these blades increase in width toward their outer ends, the film of the liquid product on each blade will become thinner and thinner as it approaches the blade ends. The liquid material is thrown from each blade in a fine ribbon-like spray. This ribbon-like spray of finely divided particles will be struck broadside by the rotating column of hot air for dehydrating the particles, as will presently appear.

The head I32 may be of any convenient size and rotated at any desirable speed. It has been found that the use of a head of from sixteen to eighteen inches in diameter across the vanes I43 and rotated at a velocity of 3500 revolutions per minute operates satisfactorily to reduce milk concentrate to the desired degree of fineness for geesiiigating the same in the dehydrating cham- Suitable means are provided for delivering a strong blast of heated air across the atomized material discharged radially outwardly from the blades I43. In the form of the construction shown, the pipe 32 leading from the air heater I2 is connected to an air distributor I45 on the top of the dehydrator I8. This distributor is arranged in the form of a snail about the upper end of the spindle 93 and is of gradually diminishing diameter so as to maintain a constant pressure and velocity of the air throughout the length of the snail.

The top of the dehydrator is provided with an opening I46 extending about the spindle 99 and the top wall I" of the air distributor I45 is spaced upwardly from the wall of the dehydrator so as to provide a passage I48 through which air can escape from the snail passage I49 throughout its length. A sleeve I5I extends downwardly from the marginal edge of the opening I46 and has its lower end flared outwardly as shown at I52 for directing the air downwardly and outwardly across the head I32, as shown more clearly in Fig. 2 of the drawings. The diameter of the sleeve I5I is such that the head I32 may be removed by lifting the same upwardly through this sleeve.

A suitable cone-shaped shield I40 is mounted over the head I32 for directing the air outwardly toward the periphery of the head.

The air passing through the conduit 32 may be previously heated to any desired temperature. It is found that for dehydrating milk concentrate that a temperature of around 500 F. gives satisfactory results. The air is delivered under pressure by the blower 29 and escapes across the head I33 inumbrella form. This heated air is caused to rotate by the snail or circular form of the air distributor I45 and the parts are so arranged that the air will be moved in the same direction as the rotation of the 15 duit I61 is provided for this purpose.

head I33 so that the air and mist, or atomized or finely divided particles of liquid product will thoroughly intermingle whereby those particles are completely dehydrated.

The solid particles, after being dehydrated, will pass with the air to the bottom of the dehydrator. The bottom of the dehydrator is provided with a circular channel I53, the outer side waliof which is bent inwardly and rigidly secured to the tapered wall of the dehydrator. The edge of the cone 80 extends into the channel to form a restricted slot which will permit the dehydrated material to slide down these inclined walls into the channel I53 but will be sufliciently restricted to conduct the air along the channel. The channel is of gradually increasing cross-sectional area toward its discharge end.

The desiccated material, while hot, tends to adhere to the trough or channel I53. It has been found that if the air flowing through the trough I53 is reduced in temperature or its velocity increased, or both, that the channel will remain practically clean.

Suitable means are provided for introducing cool air into the channel or trough andalso for increasing the velocity of the air flowing through this channel. In the form of the construction shown Fig. 1, a return pipe or conduit I65 is provided for conducting air from the conduit I51 to the channel I53 as indicated in Figs. 4 and 5. The conduit I65 delivers into the small end of the channel I 53 as shown more clearly in Figs. 4 and 5. A suitable blast valve I66 is provided in the conduit I65 for controlling the amount of air passing from the pipe I51 back to the channel.

Suitable means are also provided for introducing cool air into the return pipe I65. A con- It is in communication with the conduit I65 and has mounted therein a fan I 68 operated by a suitable motor I69. The intake I1I of the fan is adapted to be provided with a suitable air filter I12 so that filtered air may be introduced from the atmosphere into the pipe I61 and in turn into the channel I53. A valve or blast gate I13 is provided for controlling the amount of air delivered by the fan I68 into the passage I61. By properly adjusting the valves I66 and I13, air at the required temperature and velocity may be introduced into the channel I53 for maintaining the same'bompletely free of matter adhering to the walls thereof.

Suitable means are provided for separating the material contained in the air in the conduit I55. The collector 2| is employed for this purpose. The collector 2| is of centrifugal type and has a casing to which the conduit I55, leading from the enlarged end of the channel I53, for delivering air and solid material axially into the separator 2I, is attached. The separator is operated by a suitable motor I56. The separator sucks the air and desiccated material through the conduit I55 and after separating the material from the air, discharges the latter through a conduit I51 into the forward end of the firebox 22 as at I58 as shown more clearly in Fig. 1 of the drawings.

Since the collector 2| is well known in the art and the details of which constitute no part of the present invention, it is not thought necessary to further illustrate or describe the same.

The solid particles, separated from the air, fall by gravity into a hopper I59 which has a rotary discharge valve I6I controlled by a motor I62 in the usual manner.

In the operation of the device, milk or other liquid products to be dehydrated are delivered from the reservoir I5 into the primary boiler I3 where the product is partially evaporated, as above described, by heated air flowing through the conduit 55. The heated gases .pass into the outer annular chamber 66 and from thence into the fan 40 and back to the furnace to be mixed with the heated gases therein. A portion of it escapes into the atmosphere. The vapor from the product in the first boiler is conducted to the inner chamber 65 of the second boiler for assisting in evaporating the liquid product in that chamber. From the second boiler the concentrate is conducted to the atomizer within the dehydrator. Heated air from the air heater I2 is delivered over the atomizer for desiccating the atomized material. The desiccated material, mixed with air, is removed by a current of air to the collector where the dehydrated material is collected and the air conducted to the furnace to aid in combustion of the fuel for heating the air used in the process.

It is thought from the foregoing, taken in connection with the accompanying drawings, that the construction and operation of my device will be apparent to those skilled in the art and 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. In a dehydrating system for liquid products, a primary and a secondary boiler arranged in series, means for heating said primary boiler by heated combustion gases .for evaporating moisture from said products for concentrating the products, means for utilizing said combustion gases from the primary boiler and the vapor produced in the primary boiler for heating the concentrated liquid product in the secondary boiler for further concentrating the same, and means for maintaining the pressure within said secondary boiler below that of the atmosphere and below that within the primary boiler.

2. In a system for dehydrating liquid products, a furnace, a pair of boilers arranged in series, means for supplying liquid products to said boilers, a furnace, means for conducting heated gases from said furnace through said boilers in heat exchange relationship to the liquid product within said boilers for evaporating moisture from said liquid product, means for conducting vapor produced in one of said boilers into the-other boiler for assisting in heating the product contained therein, and means for lowering the pressure in said second boiler below that of the atmosphere and for maintaining said pressure below that in the first boiler whereby the concentrate within the first boiler will fiow into said second boiler and have its boiling point lowered in said second boiler.

3. In a dehydrating apparatus, a furnace, an air heater within said furnace, an evaporator for concentrating a liquid product, means for recirculating heated gases through said furnace and evaporator and for causing heated gases to flow through said heater, a dehydrator, means for supplying the concentrate from said evaporator to said dehydrator, means for conducting heated air from said heater to said dehydrator for dehydrating said product, and means for conducting all of said air from said dehydrator to the combustion chamber of said furnace for causing an increased velocity of the heating fluid through said heater.

4. A dehydrator comprising a chamber, means for conducting heated air to said chamber, means for conducting a liquid product to said chamber, means for atomizing said product and for discharging the samein said dehydrator, a discharge channel extending around the lower end of said chamber in a circular path for said air and dehydrated product, and means for introducing air under pressure into said channel for increasing the velocity of the air therein.

5. A dehydrator comprising a chamber, means for conducting heated air to said chamber, means for conducting a liquid product to said chamber, means for atomizing said product and for discharging the same in said dehydrator, a discharge channel extending around the lower end of said chamber in a circular path for said air and dehydrated product, a centrifugal separator in communication with said channel, and a conduit for conducting air fromthe discharge of said separator to said channel for increasing the velocity of the air passing therethrough.

6. In a dehydrating system for liquid products, a furnace having a combustion chamber, a dehydrator, means for spraying a liquid product within said dehydrator, an air heater heated by said furnace, means for conducting air from said heater to said dehydrator and for discharging the same therein for evaporating moisture from said product, means for conducting said air from said dehydrator to said combustion chamber, evaporator means, means including a conduit for recirculating combustion gases through said combustion chamber and evaporator means, said conduit having an opening for discharging a portion of said gases from said system.

7. In an apparatus for dehydrating liquid products, a furnace having a combustion chamber, an air heater heated by said furnace, evaporator means, means for supplying a liquid product to said means, means for conducting heated gases from said furnace through said evaporator means and back to said furnace for evaporating moisture from said liquid product, a discharge conduit in the means for conducting the heated gases for discharging a portion of said gases therefrom, a dehydrator, means for conducting heated air from said air heater to and through said dehydrator, and discharging the same into said combustion chamber, and means for conducting said air along with said heated gases through said evaporator for evaporating moisture from said liquid product.

8. In an apparatus for dehydrating liquid products, a furnace, a heater for a drying fluid heated by said furnace, a dehydrator, means for discharging a liquid product into the upper end of said dehydrator in finely divided particles, means for forcing said drying fluid through said dehydrator for dehydrating said product, said dehydrator having a collecting channel around its lower end for receiving the dehydrated material and drying fluid, a collector, means for conducting said fluid and dehydrated material from said channel to said collector for separating the dehydrated product from said drying fluid and for collecting said product, a conduit for conducting said drying fluid from said collector, a conduit for conducting a portion of said drying fluid back to said channel for increasing the velocity of the drying fluid passing along said channel, and means for discharging fresh air into said channel for cooling the dehydrated material flowing along the same.

9. A method of dehydrating liquid products which comprises subjecting the products to indirect heat exchange with a heating medium to preliminarily concentrate the same, atomizing the concentrate and discharging the same into a current of hot air for dehydrating the product, separating the product from said hot air, mingling the hot air with the heating medium, and recirculating all of said hot air with said heating medium.

10. A method of continuously concentrating a liquid product which comprises subjecting the product to sub-atmospheric pressure and to a heating fluid of elevated temperature for removing moisture from said product, then lowering the temperature and pressure of the concentrate and conducting said moisture and said heating fluid into separate heat exchange relationship with said concentrate for further concentrating the same.

11, A method of concentratinga liquid product comprising applying heat thereto by means of a gaseous heating medium for reducing moisture contained therein to steam, applying said steam and medium in separate heat exchange relationship with the concentrate to further concentrate the same while reducing the pressure on the concentrate below that on the liquid product, whereby substantial vaporization of said concentrate is obtained.

JOSEPH M. HALL.