US3593430A

US3593430A - Crop dehydrator

Info

Publication number: US3593430A
Application number: US773188A
Authority: US
Inventors: Stanley P Thompson
Original assignee: Individual
Current assignee: Beloit Technologies Inc
Priority date: 1968-11-04
Filing date: 1968-11-04
Publication date: 1971-07-20
Anticipated expiration: 1988-07-20

Abstract

A dehydrator including an elongated drum mounted for rotation about its longitudinal axis. A frustoconical furnace sidewall cooperates with a ring burner to provide hot combustion gases for dehydrating material in the drum. Vanes in the drum are bent at varying angles to enhance even distribution of the material across the drum and cleats are also provided to reduce the slippage of material from some of the vanes.

Description

United States Patent [72] Inventor Stanley P. Thompson Box 7, St. Marys, Kans. 66536 [21] Appl. No. 773,188 [22] Filed Nov. 4, 1968 [45] Patented July 20,1971

[54] CROP DEHYDRATOR 8 Claims, 9 Drawing Figs.

[52] US. Cl 114/108, 263/33 [51] Int. Cl F26b 11/02 [50] Field of Search 34/109, 124,125, 137,431/37, 89; 263/19 A, 33; 236/15 C [56] References Cited v UNITED STATES PATENTS 263,584 8/1882 Rice 34/137 1,154,207 9/1915 Roberts.... 263/15 1,987,242 l/1935 Madsen.... 34/137 2,292,243 8/1942 Schwartz 236/15 Primary Examiner Frederick L. Matteson Assistant ExaminerTheophil W. Streule Attorney-Don M. Bradley ABSTRACT: A dehydrator including an elongated drum mounted for rotation about its longitudinal axis. A frustoconical furnace sidewall cooperates with a ring burner to provide hot combustion gases for dehydrating material in the drum. Vanes in the drum are bent at varying angles to enhance even distribution of the material across the drum and cleats are also provided to reduce the slippage of material from some of the vanes.

I PATENTEU JULZO I971 SHEEI 1 OF 2 A ORNEYfi CROP DEHYDRATOR This invention relates to material-processing apparatus and, more particularly, to a dehydrator for hay and other products.

It is a very important object of this invention to provide a dehydrator having a furnace equipped with a combustion chamber of novel shape for enhancing the transfer of heat into the dehydrator drum and for minimizing deleterious effects from the heat on the furnace wall.

Still another object of this invention is to provide a dehydrator furnace having improved gas flow characteristics in that expansion of gases resulting from combustion is accommodated by a progressively enlarged combustion chamber in the direction of flow of the gases.

A further object of the invention is to provide a dehydrator furnace making maximum use for the preheating of air, of heat which would otherwise be lost from the system. In this connection, it is also anobject of the invention to provide novel structure for creating airflow patterns calculated to produce enhanced combustion upon introduction of air into the furnace.

In the achievement of the foregoing objects, it is also an object of the invention to provide a novel dehydrator furnace combining a ring burner with a conical-combustion chamber to derive increased efficiency and uniformity in operation of the dehydrator system.

Still another very important object of this invention is the provision of a dehydrator having flights of vanes strategically positioned and shaped to distribute the material as uniformly as. possible across the entire cross section of the drum to cause maximum transfer of heat from the hot gases of combustion to the material as the latter travels through the rotating drum.

ln carrying out the preceding object, it isalso another object of the invention to provide vanes configured to permit automatic separation of relatively light or leafy material from heavier or stemmy material so that the lighter particles may be carried out. of' the drum by the airstream in advance of the heavier particles which require further time in' the drum to achieve a uniformly dried product.

A. yetfurther object of this invention is the provision of a novel control for the dehydrator furnace fuel supply so that the output of the furnace may be controlled by the operator at the inlet end of the system, even though the fuel supply is coupled through a controller for automatic adjustment responsive to heat requirements-sensed at the. outlet end of the dehydra tor drum.

Another object of this invention is the provision of an annular flame retainer provided in the refractory lining of the combustion chamber to insure stabilization of the flame from the ring burner and also to minimize-the level of the noise resulting from operation of the system.

These and other important objects of the invention will be further explained or will be apparent from the drawings, specification and claims.

In-thedrawings:

FIG. 1 is afragmentary, side elevational viewon aireduced scale and partially schematic of a dehydrator system incorporating the principles of this invention, parts being broken away and appearing incross section to reveal details of construction;

FIG., 2 is a vertical, cross-sectional view through the dehydrator drum transversely thereof;

FIG. 3 is a fragmentary, vertical, cross-sectional view through the drum longitudinally thereof, the flighting appearing in elevation;

FIG. 4-is a vertical, cross-sectional view through the furnace, the air blowerappearing in elevation;

FIG. 4a is an enlarged, detailed view of a portion of FIG. 4 showing the mounting of the ring burner in the furnace and illustrating the annular flame retainer'in the refractory lining of the combustion chamber;

FIG. S-is a vertical, cross-sectionalview taken along line 5-5 of F IG; 4;

FIG. 6 is an enlarged, fragmentary front elevational view of the ring burner;

FIG. 7 is a cross-sectional view taken along line 7-7 of FIG. I; and

FIG. 8 is a cross-sectional view taken along line 8-8 of FIG. 7.

Referring initially to FIG. 1' of the drawings, the dehydrator of this invention includes an elongated, cylindrical drum 10 having a sidewall 12 and an outlet end wall 14. A furnace l6 communicates with the inlet end of drum 10 and a fan broadly designated 18 is interposed in a material discharge conduit 20 which communicates with the outlet end of drum 10 through a discharge opening 22 best seen in FIG. 7. A material inlet conveyor 24 is provided adjacent furnace 16 at the inlet end of drum 10 for the purpose of introducing the material to be dehydrated into the drum. The latter is mounted for rotation about its longitudinal axis on roller means 26 and is powered by drive means (not shown) to effect rotation of the drum in the direction of the arrow in FIG. 2.

Furnace 16 includes a blower 28 for providing air to be mixed with the fuel which is introduced into furnace 16 through a fuel line 30. The hot gases of combustion are directed into the interior of drum 10 for drying the material as the latter progresses through the drum. To this end, blower or fan 18 serves to draw the gases through the drum so that the dried material is drawn toward outlet opening 22 and into conduit 20. It will be understood that conduit 20 may communicate with a cyclone separator or the like (not shown) so that the dehydrated material may be separated from the airstream for further processing as may be desireable or required.

In the drying of hay or other materials it is particularly important that as much surface area of the material particles as possible be exposed to the drying influence of the hot gases passing through the drum. To this end, the interior of drum I0 is provided throughout its length with a flighting adapted to engage the material upon rotation of the drum and to distribute" the material as uniformly as possible across the entire hollow cross section of the drum. Manifestly, upon lifting of the material to a given position as the drum rotates, the material is dropped for gravitation toward the bottom of the drum. The material is thereupon again lifted by the flighting for subsequent distribution to permit gravitation of the particles of material through the hot stream of gases and toward the bottom of the drum whereupon the process continues successively until the material is sufficiently dehydrated to be carried to the discharge end of the drum by the hot gases.

The flighting to accomplish the foregoing operation on the material in the drum includes a plurality of vanes secured in annular rows to the inner surface of the cylindrical drum wall 12. Each row of vanes includes a series of differently shaped vanes. Thus, a vane 32 comprises a substantially flat panel 34 having one end thereof secured as by welding or the like to the inner surface of wall l2. The panel 34 extends radially inwardly of the drum and terminates in a lip 36 at the marginal edge of panel 34' remote from wall 12.

The next successive vane 38 in the row proceeding in a counterclockwise direction is spaced circumferentially from vane 32 and comprises a panel 40 having one marginal edge thereof secured as by welding or the like to the inner surface of sidewall 12 similar to the attachment of panel 34 to the drum. It should be-noted, however, that the panel 40 is provided with a line of bend 42 in spaced relationship from wall 12 and from the innermost end of the panel. Thus, the panel comprises a portion extending radially inwardly of the drum and a second portion deviates at an angle from the direction of the first portion as illustrated clearly in'FlG. 2. The outermost end of panel 40 is provided with a lip 44 similar to lip 36 of panel 34.

The next successive vane 46 of the series of vanes is similar to vane 38 in that it is provided with a line of bend 48 intermediate its ends. However, the angle of bend of the portions of the vane 46 is such that the vane is straighter than vane 38. Again, vane 46 is provided with a lip 50 at its innermost end.

Although the specific arrangement of the different vanes in the series depicted has been found desirable, other arrangements for the vanes will also produce advantageous results.

Referring to FIGS. 2 and 3, it may be seen that each row 52 of vanes may be identical to the adjacent rows but it has been found to be desirable that each successive row longitudinally of the drum be rotated with respect to the preceding row. Thus, a vane 32 is not directly adjacent an identical vane 32 of the adjacent row. Rather, it is adjacent a vane 38 or a vane 46. Similarly, the vanes 42 and 46 are disposed beside dissimilar vanes of the adjacent row.

Certain of the vanes are provided intermediate their lengths with cleats 54 which may be formed of key stock material welded to the leading surface of the vane. The cleats 54 serve to retard the slippage of the material along the surface of the vane for a purpose to be more fully explained hereinafter.

A longitudinally extending shaft 56 is disposed axially of drum and is secured to the latter by a plurality of hangers 58. Each hanger 58 includes an arcuate portion 60 having one end thereof secured to the outer surface of shaft 56 by welding or the like and an integral straight portion 62 having its outermost end with to the inner surface of drum 10. It will be understood that as many hangers 58 are provided as are necessary for securing the shaft in its proper position. Further, the provision of the arcuate portion 60 disposed in a wrappedaround manner adjacent the outer surface of shaft 56 insures that the latter is maintained in its proper axial position even when the hangers 58 and shaft 56 are exposed to the extreme temperatures caused in drum 10 by the hot dehydrating gases provided by furnace 16. It should be noted that the straight portions 62 of hangers 58 extend tangentially of shaft 56 so that heating of the hangers 58 merely causes a rotation of shafts 56 without moving the latter from its axial position.

Shaft 56 mounts a plurality of vanes 64 extending radially outwardly from the shaft. The vanes 64 are connected with brace members 66 as illustrated best in FIG. 2. Further, each vane 64 is provided with a cleat 68 on its leading and its trailing surface to reduce the slippage of material on the vane. Shaft 56 rotates with the drum 10 thereby rotating the vanes 64.

Referring now particularly to FIGS. 1 and 4--6, furnace 16 includes a frustoconical, tubular sidewall 70 provided with a liner 72 of refractory material defining a frustoconical combustion chamber 74. The latter is provided with an annular offset 76 adjacent its smaller, inlet end presenting an annular shoulder 78. Liner 72 is preferably cast for economy of fabrication. A plurality of hanger elements 80 extending into material 72 serve to mount an annular, tubular ring-type burner 82 in concentric relationship with the inlet opening of the combustion chamber 74 as illustrated in FIGS. 4 and 4a. The inlet end of the furnace is closed by a plate 84 having a circular opening 86 axially aligned with the combustion chamber 74. The fuel line 30 communicates with the ring burner 82 and the latter is provided with a plurality of spaced orifices 88 as illustrated best in FIG. 6.

A jacket or shroud 90 circumscribes wall 70 of furnace 16 throughout a substantial portion of the length thereof and is mounted in outwardly spaced concentric relationship therewith by spacers 92 spanning the distance between jacket 90 and wall 70. A conduit 94 extends generally tangentially to jacket 90 and is in communication therewith and with blower 28. The outlet side of the latter is in communication with a closed circular vessel 96 having an annular sidewall 98 and end walls 100, one of the latter having an opening 102 aligned with opening 86 in the furnace end wall 84. The communication between the blower 28 and vessel 96 is through an inlet 104 which extends tangentially of the sidewall 98 of vessel 96 as illustrated in FIGS. 4 and 5.

A control for the supply of fuel to furnace 16 includes a line 106 which is adapted to be coupled with a source of pressurized fluid such as the main fuel line 30. Line 106 is equipped with a pressure regulator 108 and a micrometer flow control valve 110. Line 106 communicates with a control line 112 which, in turn, flows through a temperature responsive flow controller 114. The latter has a temperature-sensing element 116 extending into the discharge conduit 20 at the outlet end ofdrum 10 as illustrated in FIG. 1. Thus, element 116 senses the temperature of the hot gases as the latter discharge through conduit 20. Element 116 then operates controller 114 to adjust the pressure flowing through line 112 responsive to the temperature of the gases in conduit 20.

Line 1 12 is also operably connected with the diaphragm ofa throttling valve 118 interposed in the main fuel supply 30 upstream of the ring burner 82. Valve 118 is constructed so that the valve setting controlling the flow of fuel through line 30 is manually adjustable even though the valve setting is responsive to the pressure in line 112. In other words, the particular setting of valve 118 governing the flow of fuel through line 30 corresponding with a particular pressure of fluid in line 112 may be manually regulated or varied.

In operation, fuel emanating from the orifices 88 in ring burner 82 is ignited in the combustion chamber 74. Drum 10 is powered to rotate on its longitudinal axis and blower 28 is operated to provide air to the furnace as is necessary for proper combustion of the fuel in the combustion chamber. The fan or blower 18 is also operated to insure a flow of gases longitudinally through drum 10 from the inlet end thereof to the discharge so that the dehydrated material which enters drum 10 through conveyor 24 moves progressively through the drum and out discharge conduit 20. The shoulder 78 near the burner 82 serves as a flame retainer by virtue of the turbulence and reduction of velocity in the combustible mixture as the same traverses through the combustion chamber from left to right as viewed in FIG. 4. Accordingly, a generally annular ring of flame or combustion proceeds from ofiset 76 in the direction of enlargement of the combustion chamber. The taper of the combustion chamber accommodates the increase in volume of the gases from combustion as they progress through the combustion chamber so that the gases flow through the furnace at a relatively uniform velocity despite such volume increase. A portion of the heat from combustion travels through the furnace wall and serves to preheat the air for combustion which enters the annular orifice defined by the mouth of the shroud or jacket proximal the outlet end of the furnace. Since the inlet to blower 28 extends substantially tangentially to the annular chamber defined by the wall 70 and jacket 90, the air tends to follow a generally swirling path of travel around wall 70 on its way to the blower. This insures maximum possible heat interchange between the air and the furnace wall 70 to preheat the air for increasing the efficiency of operation of the system. Further, the air which is discharged by blower 28 travels in a circular pattern in vessel 96 to enter the combustion chamber in a spiraling or swirling motion as it travels through the aligned

openings

102 and 86 adjacent ring burner 82.

This spiraling and swirling motion increases the turbulence of the air as the latter combines with the fuel emanating from the orifices 88 in burner 82 to enhance the mixing of fuel and preheated air for greater combustion efficiency.

Shoulder 78 tends to hold the flame in its proper position within the combustion chamber to eliminate the noise attendant upon a vacillating or transitory flame location and also to prevent the flame from becoming extinguished during variations in the fuel flow through the burner.

The taper of the inner surface of the combustion chamber in the direction shown tends to reflect a component of the heat of combustion toward the drum entrance. This has the twofold advantage of transferring the heat in the direction where it is desired for dehydrating the material in the drum and also for reducing the possibility of burnout of the combustion chamber lining. The latter permits the economy of operation of furnace 16 with a substantially thinner lining than would otherwise be possible.

The rotating drum constantly moves the vanes in a counterclockwise direction as viewed in FIG. 2 so that the material in the drum is picked up by the vanes as they rotate along their lowermost positions within the drum. The material is retained on the vanes as the same is lifted thereby until the v'ane reaches a position along its path of travel where the vane drops the material for gravitation across the drum toward the bottom of the drum. The different shapes of the fingers insure that the material release point for the various fingers is reached at different positions of rotation of the drum. Thus, a substantially uniform curtain of material in relatively small clumps is alternately picked up and then released by the successive fingers for gravitation across the drum.

The central vanes 64, however, prevent the material from gravitating to the bottom of the drum when it is first dropped by the vanes 32, 38 and 46. The vanes 64 retard the travel of the material to the bottom of the drum by catching the material at an intermediate point along its path of travel. After the material is caught by the vanes 64, the latter carry the material over for subsequent release to gravitate to the bottom of drum 10. This subsequent release of the material occurs at a point in time subsequent to the release of the material by the corresponding vanes 32, 38 and 46. The shortened paths of gravitation of the material insures that the gas flow through the drum does not have sufficient time to act on the material while falling to move the material through the drum at too fast a rate for proper drying.

The

cleats

54 and 68 on the respective vanes further tend to dribble the material from the vanes rather than releasing the same in a clump when the vane reaches a position for discharging material. This also serves to enhance the distribution of the material uniformly across the drum for maximum exposure of the material to the hot gases of combustion for dehydrating the material.

Not to be overlooked is the effect of the rows of vanes which are disposed in series and in offset relationship longitudinally of the drum. This arrangement for the vanes which are secured to the inner surface of the cylindrical sidewall 12 re tards against the material from bunching as the material moves longitudinally through the drum.

Referring now particularly to FIGS. 1, 7 and 8, it may be seen that the end wall 14 at the discharge end of the drum is provided with a plurality of inwardly extending, radially disposed members 120 having lips 122 extending along the innermost marginal edges thereof and in the direction of advancement of the drum during operation. The members 120 terminate at the peripheral margin of opening 22 in wall 14. The members 120 and their respective lips 122 thus serve as positive discharge scoops which tend to receive the dehydrated material and to conduct the same toward the discharge opening 22. it has been found desirable to provide cleats 124 intermediate the ends of the members 120, again to dribble the material toward the outlet opening 22 rather than to permit the material to slide as a bunch toward the outlet opening when the position of the member is reached which would otherwise permit slippage of the material by gravity along the member.

Controller 114 may be ofa type which produces an increase in the pressure of fluid in line 112 responsive to the sensing by element 116 of a reduction of the temperature in conduit 20 below a predetermined desired temperature. The increase of pressure in line 112 acts upon the diaphragm of valve 118 to cause the valve member of the latter to move to a position to increase the flow of fuel to the burner. This results in an increase in the heat output of the furnace to raise the temperature in the system. Controller 114 and line 112 operate to maintain the temperature in the system correlated to the load on the system or amount and kind of material passing through the drum. It will be understood that line 112 may exhaust to atmosphere after passing through controller 114 as is conventional in fluid control systems of the type described.

A decrease of the pressure in line 112 responsive to a temperature in conduit 20 above that required for the particular load on the system will have the opposite effect causing a diminution in the fuel supply to thereby lower the temperature emanating from furnace 16.

Manually adjustable valve 118 provides the advantage of normally automatic operation of the system under the control of the temperature responsive controller 114. However, when it is desired to alter the temperature of operation of the system it is not necessary to readjust or to replace the controller 114. The dehydrator operator quickly and easily accomplishes this by manually adjusting valve 118 to increase or decrease the flow of fuel to the burner. Manifestly, any manual adjustment of valve 118 merely changes the reference point from which controller 114 continues to automatically monitor and regulate the flow of fuel to the system.

The automatic monitoring of this system is extremely important. The response of the heat output from the furnace to changes in heat requirements is much faster than is possible with systems provided with manual controls. Changes in the heat of operation of the system are inversely proportional to the changes in fuel supply to the burner. That is to say, the closer the fuel supply follows the heat requirements dictated by the load, the more uniform will be the temperature of operation of the system.

The nature of the material handled by a dehydrator system of this type dictates that the load on the system will not be uniform. For example, the material may be bunched, will vary in moisture content, and may fluctuate radically in the proportion of leafy or fine material comprising the load. Accordingly, the operating temperature in the system will necessarily vary upwardly and downwardly from a selected operating mean temperature. The amplitudes of such inevitable variations are kept relatively small in the system of this invention, however, since the remedial changes in heat input from the furnace closely follow the load variations.

Referring now to FIG. 1, it may be seen that the system includes a damper 126 in the outlet of blower 28 and controlled by a gas-operated actuator 128 which is operably coupled with the fuel line 30 by a line 130. Another damper 132 is interposed in the outlet of fan 18. An actuator 134 is coupled to line 30 by a conduit 136 (shown but fragmentarily in FIG. 1). Actuator 132 is similar to actuator 128, but is of the delay type so that it operates damper 132 only after a delay of a predetermined time interval following a change of pressure in conduit 136.

Actuator 128 is proportioned to maintain the proper setting for damper 126 to provide the correct amount of air to furnace 16 at all times. Thus, as the fuel flow in line 30 increases or decreases, damper 126 is opened or closed to provide the correct amount of air for maximum combustion of the fuel in the furnace.

Damper 132 at the outlet end of the dehydrator also is moved in response to changes in the flow of fuel in line 30. The greater the fuel flow, the wider damper 132 is opened by actuator 134. This permits a faster flow of the gases through the dehydrator drum to pneumatically convey the particles of material through the dehydrator at a faster rate.

Conversely, when the flow of fuel gas in line 30 is lessened as the heat requirements for the load in the system diminish, damper 132 is moved toward a closed position to reduce the rate at which the material is conveyed by the gases through the drum.

Actuator 134 is constructed so that it operates in response to changes in the fuel pressure in line 30. This insures that the rate at which the material is conveyed through the system does not change immediately upon the sensing of a change in the heat required for the load. Rather, the rate of movement of the material occurs after furnace 16 has had an opportunity to adjust its heat output to accommodate the load changes. This means that the material movement rate is correlated to the furnace heat output and contributes to the production of a uniformly dried product from the system.

I claim:

1. In a dehydrator including an elongated drum having a material inlet at one end of the drum and an outlet at the other end thereof, and means mounting the drum for rotation about its longitudinal axis, the combination with said drum of a furnace for providing hot gases to the drum, said furnace comprising:

a frustoconical, tubular combustion chamber communicating with the inlet end of the drum, said chamber being disposed with the end thereof having the greatest diameter adjacent said drum inlet; and

a ring burner in the combustion chamber at the end thereof remote from said drum inlet,

the sidewall of said chamber having a uniform, substantially continuous taper in a direction toward the drum inlet to reflect a portion of the heat from said combustion out of the chamber and into the drum through said inlet.

2. The invention of claim 1, wherein said burner includes an elongated tube shaped into a ring, the axis of said ring being in general alignment with the longitudinal axis of said combustion chamber, and a plurality of ports in the tube for egress of fuel for combustion.

3. The invention of claim 2, wherein is provided an annular offset in the inner surface of said sidewall downstream of said burner for retaining the zone of initiation of the flame of said combustion in the region of said annular offset during operation of said furnace means.

4. The invention of claim 1, wherein is included inlet means for providing air to said combustion chamber, said air inlet means including a tubular shroud extending around the sidewall of said chamber in outwardly spaced relationship from the latter and communicating with the chamber, the inlet end of said shroud being remote from the zone of communication between the shroud and the chamber whereby heat emanating through the sidewall may preheat the air traveling through the shroud.

5. The invention of claim 4, wherein said air inlet means includes a closed vessel having a pair of spaced-apart end walls and an annular sidewall, there being an opening in one of said end walls communicating the vessel with the chamber, and conduit means extending between the shroud and the vessel and including an inlet for the vessel extending tangentially to said annular sidewall to impart a swirling of the air in the vessel to enhance turbulence of the air as the latter enters the combustion chamber.

6. The invention of claim 5, wherein is provided blower means interposed in said conduit means, and wherein is provided a discharge for said air from the shroud and upstream of the blower means, said discharge extending generally tangentially from said shroud to enhance the swirling of the air around the sidewall of the combustion chamber as the air is drawn through the shroud.

7. In a dehydrator including an elongated drum having an inlet end and an outlet, a furnace for providing hot gases to the inlet end of said drum, said furnace including an inlet damper means interposed in the furnace air supply structure, and a fuel supply line coupled with the furnace and adapted to be coupled with a source of fuel under pressure, a control for said dehydrator comprising:

a conduit in fluid communication with said supply line and vented to atmosphere;

temperature controlled valve means interposed in said conduit and including temperature responsive actuator means for the valve means and disposed to control the valve means for regulating the fluid pressure in the conduitresponsive to the temperature at the outlet end of said drum;

a valve interposed in said fuel supply line for regulating the flow of fuel to the furnace;

means responsive to the pressure of fluid in the conduit and operably coupled with said valve and with the inlet damper means for automatically operating the valve and inlet damper to regulate the fuel and air supply responsive to the temperature at said outlet end,

fan means operably coupled with the outlet end of said drum for creating artificial currents of gases through the drum to convey the material to said outlet;

outlet damper means operably associated with the fan means for regulating the velocit of said currents; and actuator means operably couple with the outlet damper means and said fuel supply line and responsive to the fuel flow in the latter to automatically regulate said outlet damper to control the rate of conveying of the material through the drum responsive to the fuel supply to said furnace, said actuator means including time delay means to permit movement of said outlet damper means only after a predetermined time increment following a change in the flow of fuel through said line, whereby to effect uniform drying of the product.

8. In a furnace for use in providing a stream of combustion gases, structure for providing air for combustion to the chamber, said structure comprising:

a closed, cylindrical vessel having a pair of spaced apart end walls and an annular sidewall, the vessel being disposed at the inlet end of said chamber, there being an opening in the endwall adjacent the chamber communicating the vessel with the chamber;

a tubular shroud extending around the sidewall of the chamber in outwardly spaced relationship from the latter and having an outlet opening through the shroud at the end thereof proximal the vessel, the spacing between the shroud and the outer surface of the chamber permitting flow of air between said chamber surface and the shroud to preheat the air;

a discharge conduit communicating with the shroud opening and extending generally tangentially outwardly therefrom;

inlet structure for the vessel including an inlet conduit extending generally tangentially from the annular sidewall and communicating therethrough; and

blower means interposed between the discharge and inlet conduits whereby air is drawn in a swirling path around the chamber and is discharged in a swirling path into the vessel for swirling flow through the opening into the combustion chamber.

Claims

1. In a dehydrator including an elongated drum having a material inlet at one end of the drum and an outlet at the other end thereof, and means mounting the drum for rotation about its longitudinal axis, the combination with said drum of a furnace for providing hot gases to the drum, said furnace comprising: a frustoconical, tubular combustion chamber communicating with the inlet end of the drum, said chamber being disposed with the end thereof having the greatest diameter adjacent said drum inlet; and a ring burner in the combustion chamber at the end thereof remote from said drum inlet, the sidewall of said chamber having a uniform, substantially continuous taper in a direction toward the drum inlet to reflect a portion of the heat from said combustion out of the chamber and into the drum through said inlet.

7. In a dehydrator including an elongated drum having an inlet end and an outlet, a furnace for providing hot gases to the inlet end of said drum, said furnace including an inlet damper means interposed in the furnace air supply structure, and a fuel supply line coupled with the furnace and adapted to be coupled with a source of fuel under pressure, a control for said dehydrator comprising: a conduit in fluid communication with said supply line and vented to atmosphere; temperature controlled valve means interposed in said conduit and including temperature responsive actuator means for the valve means and disposed to control the valve means for regulating the fluid pressure in the conduit responsive to the temperature at the outlet end of said drum; a valve interposed in said fuel supply line for regulating the flow of fuel to the furnace; means responsive to the pressure of fluid in the conduit and operably coupled with said valve and with the inlet damper means for automatically operating the valve and inlet damper to regulate the fuel and air supply responsive to the temperature at said outlet end, fan means operably coupled with the outlet end of said drum for creating artificial currents of gases through the drum to convey the material to said outlet; outlet damper means operably associated with the fan means for regulating the velocity of said currents; and actuator means operably coupled with the outlet damper means and said fuel supply line and responsive to the fuel flow in the latter to automatically regulate said outlet damper to control the rate of conveying of the material through the drum responsive to the fuel supply to said furnace, said actuator means including time delay means to permit movement of said outlet damper means only after a predetermined time increment following a change in the flow of fuel through said line, whereby to effect uniform drying of the product.

8. In a furnace for use in providing a stream of combustion gases, structure for providing air for combustion to the chamber, said structure comprising: a closed, cylindrical vessel having a pair of spaced apart end walls and an annular sidewall, the vessel being disposed at the inlet end of said chamber, there being an opening in the endwall adjacent the chamber communicating the vessel with the chamber; a tubular shroud extending around the sidewall of the chamber in outwardly spaced relationship from the latter and having an outlet opening through the shroud at the end thereof proximal the vessel, the spacing between the shroud and the outer surface of the chamber permitting flow of air between said chamber surface and the shroud to preheat the air; a discharge conduit communicating with the shroud opening and extending generally tangentially outwardly therefrom; inlet structure for the vessel including an inlet conduit extending generally tangentially from the annular sidewall and communicating therethrough; and blower means interposed between the discharge and inlet conduits whereby air is drawn in a swirling path around the chamber and is discharged in a swirling path into the vessel for swirling flow through thE opening into the combustion chamber.