US3738796A

US3738796A - Apparatus and method for dehydrating wet particulate matter and for disposing of waste products therefrom

Info

Publication number: US3738796A
Application number: US00180702A
Authority: US
Inventors: W Arnold
Original assignee: Individual
Current assignee: Individual
Priority date: 1971-09-15
Filing date: 1971-09-15
Publication date: 1973-06-12
Anticipated expiration: 1990-06-12

Abstract

Apparatus and method for two-stage dehydration of wet particulate matter (such as green forage chops) and disposition of waste products produced during the second stage of dehydration, such as gases, smoke and charred particles, comprise: a first furnace for firing a first dryer in which the chops are partially dried; a first dryer fan for drawing the chops through the first dryer and for disposing of hot moist air; a second furnace for firing a second dryer in which the chops are finally dried and wherein the waste products are produced, the second dryer having a smaller air-handling capacity than the first dryer; transfer means for delivering the partially-dried chops from the first dryer to the second dryer and including either a first cyclone separator connected to the first dryer fan or a material discharge hood disposed between the first dryer and the first dryer fan and a conveyor connected to the discharge hood; a second dryer fan for drawing the chops through the second dryer; a second cyclone separator connected to the second dryer fan for separating the finally-dried chops from the aforesaid waste products; and means, including a conduit and booster fan, for delivering the aforesaid waste products from the second cyclone separator to the first furnace wherein they are consumed.

Description

llnited States Patent 1 Arnold [76 Inventor: William A. Arnold, 2415 S. 65th St.,

W. Allis, Wis. 53214 [22] Filed: Sept. 15, 1971 [21] Appl. No.: 180,702

' [52] U.S. Cl. 432/106, 432/15, 432/58,

34/10, 34/136, 34/140 [51] Int. Cl. F26b 7/00, F27b 7/00 [58] Field of Search 263/32 R, 21 A, 21 B;

[56] References Cited UNITED STATES PATENTS 2,997,286 8/1961 Friese 432/15 2,987,306 6/1961 Petersen 432/15 2,770,052 11/1956 Morrison 432/15 2,822,153 2/l958 Arnold 432/106 3,603,568 9/1971. Ritzmann.... 432/58 3,238,634 3/1966 Goins 34/10 999,492 8/1911 Ellis 263/32 R 3,387,380 6/1968 Pritts, Jr 263/32 R Primary Examiner-John J. Camby Assistant Examiner-Henry C. Yuen Attorney-James E. Nilles and Thomas F. Kirby 11 3,738,790 [4 1 June 12, 1973 [57] ABSTRACT Apparatus and method for two-stage dehydration of wet particulate matter (such as green forage chops) and disposition of waste products produced during the second stage of dehydration, such as gases, smoke and charred particles, comprise: a first furnace for firing a first dryer in which the chops are partially dried; a first dryer fan for drawing the chops through the first dryer and for disposing of hot moist air; a second furnace for firing a second dryer in which the chops are finally dried and wherein the waste products are produced, the second dryer having a smaller air-handling capacity than the first dryer; transfer means for delivering the partially-dried chops from the first dryer to the second dryer and including either a first cyclone separator connected to the first dryer fan or a material discharge hood disposed between the first dryer and the first dryer fan and a'conveyor connected to the discharge hood; a second dryer fan for drawing the chops through the second dryer; a second cyclone separator connected to the second dryer fan for separating the finally-dried chops from the aforesaid waste products; and

means, including a conduit and booster fan, for delivering the aforesaid waste products from the second cyclone separator to the first furnace wherein they are consumed.

14 Claims, 6 Drawing Figures PAIENIED Jun 1 2191s smzennr FIG.1

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to apparatus and methods for two-stage dehydration of wet particulate matter, such as forage material or chops, and for disposing of waste products, such as gases, smoke and charred particulate material, produced during the second stage of dehydration.

2. Description of the Prior Art In agriculture, for example, it is the practice to harvest forage crops, such as alfalfa or the like, and to dry the leaves and stems (in chopped or unchopped form) by means of dehydration apparatus which removes all but about 8 percent of the moistureand leavesa concentrated, uniform feed product. Some prior art dehydration apparatus comprises an oil or gas-fired furnace which exhausts hot air (typically up to about 2,000 F.) into a dryer which comprises a rotating sealed drum through which the matter to be dried is passed. The material in the drum continually gives off moisture and,

discharge end of the drum, removes hot, moist gases and also advances the matter through the drum and dis- 'charges it into a first cyclone separator. The stems,- which are moister and heavier than the leaves and require more drying time, automatically move more slowly through the drum. A second fan transports the dried matter from the first cyclone separator to a second cyclone separator, cooling and further drying it in the process. The dried cooled matter is removed from the second separator and is then ground or pelleted, bagged and stored. A foreign material separator is provided at the outlet end of the first cyclone separator to remove debris such as stones and tramp metal. Vents at the top of the first and second cyclone separators allow hot, moist gases, fine particulate matter and other waste products extracted by the dryer fan and the cyclone or cooler fan, respectively, to be discharged to atmosphere. I I

While such priorart dehydration apparatus is generally satisfactory for its intended purpose, the exhaust to atmosphere from the cyclone separators is a source of objectionable odors, fine particulate matter, and sometimes smoke. and other gases produced in the dryer which may violate pollution codes or otherwise be offens ive. Formerly, these odors and fines could only be eliminated by means of inefficient after-burners or high-cost heat exchangers. It is desirable, therefore, to provide improved dehydration apparatus and methods which eliminate the aforesaid problems and have other advantages.

SUMMARY OF THE INVENTION supplied with heat from the second furnace, transfer partially dried matter from the first dryer to the second dryer, a second dryer fan connected to the discharge end of the second dryer, means including a second cyclone separator connected to the second dryer fan for separating finally-dried matter from waste products, such as gases, smoke and charred particles, and means including a conduit connected between the second cyclone separator and the furnace means for delivering the waste products to the furnace means for combustion. In accordance with a second embodiment of the invention, a discharge hood is connected between the discharge end of the first dryer and the first dryer fan and the transfer means comprise a conveyor connected between the hood and the second dryer.

The method in accordance with the invention comprises the steps Of: supplying wet particulate matter to the first dryer and partially drying it; drawing the matter through the first dryer by means of the first dryer fan and exhausting water vapor extracted; transporting the partially-dried matter from the first dryer and supplying it to the second dryer by means of either the first cyclone separator or by the conveyor; drawing the partially-dried matter through the second dryer wherein it is finally dried and delivering the finally-dried matter to the second dryer cyclone by means of the second dryer fan; separating the finally-dried material from the waste products produced in the second dryer in the second dryer cyclone; discharging the finally-dried material from the second dryer cyclone for further processing; and supplying all of the escaping waste products produced in the second dryer and in other stages of processing to the furnace means for incineration.

Other aspects of the invention provide improved apparatus and methods (I) for dehydrating wet particulate matter and for disposing of waste products produced during dehydration; (2) which employ two furnace-fired dryers operating in tandem and wherein waste products produced in the second dryer, such as gases, smoke and charred particles, are consumed in the furnace means; (3) which are applicable to treat many kinds of wet particulate matter and which substantially reduce or eliminate polluting by-products produced during treatment; (4) which do not require the use of inefficient after-burners or high-cost heat exchangers; (5) wherein the furnace means use a minimum amount of fuel and wherein fuel requirements are supplemented by combustible waste products thereby means including a first cyclone separator for supplying reducing fuel costs; (6) wherein the first dryer makes maximum use of heat supplied thereto because matter therein is only partially dried, which means low o'utlet temperatures of the exhaust gases from the first dryer for maximum thermal efficiency; (7)'wherein operation of the first dryer is at temperatures as high as possible commensurate with the wet matter thereby achieving minimum or no scorching of the matter during the first drying stage and minimum or no production of objectionable charred fines, smoke and odors; (8) wherein final drying in the second dryer is carried out at relatively lower temperatures to achieve minimal scorching or other damage during the second stage of drying; and (9) wherein any fines produced by the first dryer are recoverable and useful.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view in schematic form of one embodiment of two-stage hydration apparatus in accordance with the invention;

FIG. 2 is an elevational view of a portion of the apparatus shown in FIG. 1 and principally shows a first furnace, a first dryer, a first cyclone separator and a portion of a second cyclone separator;

FIG. 3 is a view taken along lines 33 of FIG. 3 and principally shows the first dryer, a supply feeder therefor, and the first cyclone separator;

FIG. 4 is an elevational view taken along lines 44 of FIG. 1 and shows the second cyclone separator;

FIG. 5 is a top plan view of portions of a second embodiment of apparatus in accordance with the invention and shows a discharge hood and conveyor; and

FIG. 6 is a cross-sectional view of the discharge hood taken along lines 66 of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1, 2 and 3 of the drawing, there is shown a first embodiment of a dehydration apparatus in accordance with the present invention which is used to dry wet particulate matter, such as freshly-harvested chopped alfalfa (hereinafter referred to as chops). The first embodiment comprises furnace means including a first furnace 10 having a burner assembly 12 and a combustion chamber 14. The burner assembly 12 is understood to operate on either gas, coal, oil or other suitable fuel which is burned in combustion chamber 14 to supply a quantity of heated air in the temperature range of about l,0O0 to 2,000 F. to a first dryer 16. Burner assembly 12 is controlled by a thermostat 18 which senses air temperature at the discharge outlet of first dryer 16 and regulates burner 12 accordingly, as regards fuel and air, to maintain a constant desired temperature at the discharge outlet of the first dryer. Burner assembly 12 and combustion chamber 14 are designed so that exhaust products therefrom are kept at a minimum and they burn clean.

First dryer 16 is shown in the drawings as a rotatable drum type dryer but it is to be understood that dryer 16 could be any type of enclosed dryer such as, for example, a flash-type dryer or a conveyor-type dryer wherein a conveyor is used to move material through a fixed enclosure.

First dryer 16 may be of the single pass or multiple pass type. However, as FIG. 2 shows, first dryer 16 takes the form of a multiple pass type. First dryer 16 comprises a rotatable drum 20, suitable bearing means 22 for supporting the drum for rotation, and an electric motor 24, a power shaft 26, a chain drive 28, and a rotation gear 30 for rotating the drum. Drum is provided on its interior with a series of interconnected passages 32 through which the chops pass in traveling from a wet feed inlet 34 of the drum to a discharge outlet 36. In the embodiment shown, it is understood that the chops pass through a distance approximately three times the overall length of the drum. Chops are supplied to inlet 34 of first dryer 16 by means of a conveyor 37 which is supplied from a chopper 38, shown in FIG. 3. Chopper 38 and conveyor 37 are powered, for example, by a drive belt 40, shown in FIG. 3, which is ultimately driven by motor 24, shown in FIG. 2, through suitable power take-off means.

Outlet 36 of first dryer 16 is connected to a first dryer fan 42 which creates an air flow and serves as a means to draw the chops through the passageways 32 in drum 20, as well as to draw hot, moist air from the dryer. First dryer fan 42 is driven, for example, by an electric motor 43. A discharge outlet 44 of first dryer fan 42 is connected through a conduit 46 to an upper inlet 48 of a first cyclone separator 50. Chops and hot, moist air drawn from dryer 16 by first dryer fan 42 are expelled into cyclone separator 50. The hot, moist air is discharged to atmosphere through a vent 52 at the top end of cyclone 50 and the chops fall to the bottom of cyclone separator 50 from whence they are discharged by gravity through a conduit 54. It is to be understood that the chops are only partially dried in first dryer 16 and, consequently, the only waste product produced is hot, moist air which is discharged to atmosphere as hereinbefore explained. In practice, it is contemplated that about to percent of the moisture be removed from the chops in passing through first dryer 16 and the temperature of the chops in the first dryer averages, for example, about F. in the case of alfalfa and, consequently, no charring or burning or smoke is produced.

As FIG. 1 further shows, the furnace means for dehydration apparatus in accordance with the first embodiment comprises a second furnace 56 having a burner assembly 58 and a combustion chamber 60. Structurally, second furnace 56 is similar to first furnace 10; however, second furnace 56 is smaller and adapted to provide hot air heated only to a range of about 500 to 1,000 F. to a second dryer 62. Second furnace 56 is controlled by a thermostat 64 similar to thermostat 18 hereinbefore described. In practice, both thermostats and both furnaces are adjusted so that the system is balanced to provide a desired percentage of drying in each of the dryers. It is to be understood that second furnace 56 also burns clean and provides no substantial waste products to atmosphere.

Second furnace 56 is adapted to supply hot air to second dryer 62 which is similar in construction and operation to first dryer 16, except as hereinafter explained. Dryer 62, which like dryer 16 could be any suitable type of enclosed dryer, could also be of the single pass or multiple-pass type, but is shown in the drawings to comprise a rotatable drum 63 having an air-handling capacity which is substantially smaller than the airhandling capacity of drum 20 of dryer 16. .For example, drum 63 of dryer 62 may be considered to have an airhandling capacity of about only one-third to one-half of that of drum 20 of first dryer 16. Drum 20 of second dryer 62 has a feed inlet 66 to which is connected the discharge end of conduit 54 from cyclone separator 50 and partially-dried chops are supplied to dryer 62 by gravity feed. Partially-dried chops enter dryer 62 at substantially the same temperature at whichthey left first dryer 16, i.e., about 150 F. in the case of alfalfa. In the course of passage through second dryer 62, for example, all but about 2 to I5 percent of the moisture is removed from the chops. In addition, charring of some of the chops occurs because the chops are no longer as wet as when passing through first dryer l6 and, consequently, waste products such as smoke, gases and charred particles may be produced in second dryer 62.

Second dryer 62 is provided with a discharge outlet 70 to which a second dryer fan 72 is connected. Second dryer fan 72, which is driven by an electric motor 72, may be similar in construction and operation to first dryer fan 42, hereinbefore described, and serves as a means to move the chops through second dryer 62 and also to remove the waste products produced in second dryer 62. Second dryer fan 72 has a discharge outlet 75 connected to a second cyclone separator 76 and discharges the finally-dried chops, as well as all waste products, thereinto.

Referring to FIGS. 1', 2 and 4, second cyclone separator 76 is provided near its top with a discharge vent 78 which is connected through an enclosed conduit or pipe 80 to combustion chamber 14 of first furnace 10. Second cyclone separator 76 is also provided with a discharge outlet 82 at its lower end, as FIG. 4 shows. The finally-dried chops settle to the bottom of second cyclone separator 76 and pass through discharge outlet 82 by gravity into a hammermill 84 or other device for further processing or final disposition. However, the waste products produced in second dryer 62 are discharged through discharge vent 78 in second cyclone separator 76 and through conduit 80 to combustion chamber 14 of first furnace wherein they are consumed. As FIG. 2 shows, conduit 80 has a booster fan 86, driven by an electric motor 88, connected to it just upstream of the point where it is connected to combustion chamber 14 of furnace 10. Booster fan 86 causes dispersion of waste products entering combustion chamber 14, especially solid particles present in the waste products, and thereby assures complete combustion. As FIGS. 1, 2 and 4 show, conduit 80 is also provided with an auxiliary waste material inlet duct 90, possibly having a control damper 92 therein (shown in FIG. 1), through which other waste products may be introduced. For example, auxiliary inlet duct 90 maybe connected to an outlet 94 on hammermill 84 (shown in FIG. 4) to receive waste material, such as fines and dust, which are produced in the hammer mill. These waste materials are also then consumed by furnace 10 and do not contaminate the atmosphere. It is to be understood that burner 12 of furnace 10 is adjusted so as r to allow for entry of such makeup air as is necessary to ensure complete combustion of all products entering combustion chamber 14 through conduit 80, either from cyclone separator 76 or auxiliary inlet duct 90 or both. I

Referring to FIGS. 5 and 6, there is shown an alternative or second embodiment of dehydration apparatus in accordance with the present invention wherein partially-dried chops from discharge outlet 36 of first dryer 16 are delivered to inlet opening 66 of second dryer62 by conveyor means 100, instead of by means of first cyclone separator 50. As FIG. 5 shows, conveyor means 100 comprises a discharge hood 102 which is located between discharge outlet 36 of first dryer l6 and first dryer fan 42. Partially-dried chops from first dryer 16 are drawn into and deposited in discharge hood 102 by r the action of first dryer fan 42. Hot, moist vapor drawn from first dryer 16 is discharged through cyclone separator 50'to atmosphere through vent 46 on first dryer fan 42, shown in FIG. 5. In the process, some fines and rator 50 can be removed. In some instances, such material may be sufficiently dry and can be transported directly to hammermill 84 without having to undergo the second stage of drying in dryer 62. The partially-dried chops are transported or conveyed from discharge hood 102 to inlet opening 66 of second dryer 62 by means of a mechanical conveyor 104 which comprises a housing 106 and a rotary auger 108, for example, which is driven by an electric motor 110.

The dehydration apparatus, in accordance with the first embodiment of the invention, operates as follows. Wet chops are introduced at inlet 34 of first dryer 16, pass therethrough and are extracted by first dryer fan 42 through outlet 36 of the first dryer and are delivered to first cyclone separator wherein the partially-dried chops fall to the bottom of the separator and the hot, moist vapors are discharged through outlet52 of the first cyclone separator. However, in accordance with the invention, the partially-dried chops pass by gravity through conduit 54 to inlet 66 of second dryer 62. The partially-dried chops are drawn through second dryer 62 for the final drying process by second dryer fan 72. Second dryer fan 72 withdraws the finally-dried chops and waste products through discharge outlet of second dryer 62 and discharges the finally-dried chops and the waste products into second cyclone separator 76. The finally-dried chops fall to the bottom of second cyclone separator 76 and pass through discharge opening 82 thereof to a hammermill 84 wherein they are further processed. If preferred at this stage, the finally-dried chops could be delivered to processing equipment other than to a hammermill 84. Waste products separated from the finally-dried chops in second cyclone separator 76 pass through conduit and are delivered to the combustion chamber of first furnace 10 wherein they are consumed. Other waste products produced during various stages of handling and processing of the partially-dried or fully-dried chops are delivered through auxiliary conduit to conduit 80 for con sumption in furnace 10.

As hereinbefore explained, temperatures within first dryer 16 are as high as possible commensurate with the wet material being supplied to the dryer so as to extract the desired percentage of moisture without causing burning or charring of the material. Finish or final drying in second dryer 62 is carried out at relatively low temperatures which effect the required percentage of finish drying with a minimum of scorching and burning. Since first furnace 10 is operating at relatively high temperature, all waste products introduced into it will als introduced through auxiliary conduit 90. As is apparent, supplying of additional combustible'materials to first furnace 10 slightly reduces the amount of gas, oil or other regular fuel required for burner 12. As regards second furnace 56, it-is to be understood that it receives only fresh combustion air and fuel such as gas or oil and it is thermostatically controlled so as to assure a uniform moisture content in the finished product produced in second dryer 62. It is to be further understood that first furnace 10 and first dryer 16 are of greater capacity than second furnace 56 and second dryer 62, respectively, because of the discharge of waste products for combustion into first furnace l0 and the need to insure complete incineration.

Dehydration apparatus in accordance with the second embodiment of the invention operates as follows. Partially-dried material from first dryer 16 is drawn into discharge hood 102 by means of first dryer fan 42 and deposited in the bottom of the discharge hood. The hot, moist vapors produced in first dryer 16 and some fines and some partially-dried material are discharged by first dryer fan 42 through conduit 46 to cyclone separator 50. At this point, the partially-dried chops may be removed from cyclone separator 50 through outlet 55 for final disposition. Partially-dried material is deliv-' ered or transported from discharge hood 102 through conveyor 104 to inlet 66 of second dryer 62 by driven auger 108. it is to be understood that drying operations in first dryer l6 and second dryer 62 are carried out in substantially the same manner as hereinbefore explained in connection with the description of operation of the first embodiment of the invention. The principal advantage of using conveyor means 100 in accordance with the second embodiment of the invention is that dried chops collected in discharge hood 102 and passing through conveyor 104 may be exposed to ambient air, not experienced when passing through first cyclone separator 50 in the first embodiment of the invention. Consequently, the exposure of the partially-dried chops to ambient air permits a soaking period or allows for equalization of moisture in the partially-dried chops before they enter second dryer 62. This soaking period may or may not be of particular advantage depending upon the material being processed.

While the present invention is hereinbefore described with alfalfa chops as an example of the wet particulate matter being processed, it is to be understood that the invention could be employed with other wet particulate materials produced in agricultural operations or in various types of manufacturing operations wherein materials other than feed products are prothe invention disclosed herein show the furnace means as comprising two separate furnaces, l and 56, it is to be understood that a single furnace having means to supply the desired amount of heat to each of the dryers l6 and 62 could be employed. In such an arrangement, for example, first furnace could be provided with a heat take-off for supplying dryer 62 with heated air which is tempered to the desired temperature range with ambient air by means of suitable thermostaticallycontrolled dampers.

In summary, the apparatus and method for two-stage dehydration of wet particulate matter and disposition of waste products produced during the second stage of dehydration contemplates furnace means such as a first furnace 10 for firing first dryer 16 in which the wet matter is partially dried; first dryer fan 42 for drawing the matter through first dryer 16 and for disposing of hot, moist air; furnace means such as a second furnace 56 smaller than furnace 10 for firing second dryer 62 smaller than dryer 16 in which the partially-dried matter is finally dried and wherein the waste products are produced; transfer means for delivering the partiallydried matter from first dryer 16 to second dryer 62 and including either first cyclone separator 50 connected to first dryer fan 42 or discharge hood 102 connected to first dryer fan 42 and conveyor 104 connected to discharge hood 102; second dryer fan 72 for drawing the matter through second dryer 62; second cyclone separator 76 connected to second dryer fan 72 for separating the finally-dried material from the waste products; and means, including conduit 80 and booster fan 86,

for delivering the waste products from second cyclone 6 1. Apparatus for drying wet particulate matter and for disposing of waste products produced during drying comprising:

a first dryer for partially dryer said matter,

means for moving said matter through said first dryer,

a second dryer for finally drying partially-dried matter received from said first dryer, said second dryer producing combustible waste products during the final drying of said matter as a result of processing of said matter therein,

means for moving said matter through said second dryer, said first and second dryers being enclosed type dryers and wherein said second dryer is of smaller air handling capacity than said first dryer, said second dryer having an air handling capacity in the range of about one-third to one-half of said first dryer,

transfer means for transferring said partially-dried matter from said first dryer to said second dryer,

furnace means for supplying heat to said first and second dryers,

separating means for separating said finally dried matter from said waste products, and means for delivering said waste products to said furnace means wherein they are consumed.

2. Apparatus according to claim 1 wherein said furnace means maintains air inlet temperatures within said first and second dryers of about l,000 to 2,000 F. and of about 500 to l,000 F., respectively.

3. Apparatus for drying wet particulate matter and for disposing of waste products produced during drying comprising:

a first dryer for partially drying said matter,

first means for moving said matter through said first dryer,

a first dryer fan for disposing of moisture released in said first dryer,

a second dryer for finally drying partially-dried matter received from said first dryer, said second dryer producing combustible waste products during the final drying of said matter,

second means for moving said matter through said second dryer,

said first and second dryers being enclosed-type dryers and wherein said second dryer is of smaller airhandling capacity than said first dryer, said second dryer having an air-handling capacity in the range of about one-third to one-half of said first dryer,

furnace means for supplying heat to said first and second dryers,

said furnace means maintaining inlet air temperatures in said first and second dryers of about l,O00 to 2,000 F. and of about 500 to 1,000 F., respectively,

separating means for separating said finally-dried matter from said waste products and for delivering the latter to said furnace means wherein they are consumed, and

a second dryer fan for delivering said waste products from said second dryer to said separating means.

4. Apparatus according to claim 3 wherein said furnace means comprises first and second furnaces for said first and second dryers, respectively.

5. Apparatus according to claim 3 wherein said separating means includes a cyclone separator connected to receive said finally-dried matter and said waste products from said second dryer and a conduit connected to said cyclone separator for delivering said waste products to said furnace means.

6. Apparatus according to claim 5 wherein said first A means for moving said matter through said first dryer comprises said first dryer fan.

7.'A pparatus according to claim 6 wherein said transfer means comprises a second cyclone separator connected between said first dryer fan and said second dryer. l

8; Apparatus according to claim 6 wherein said transfer means comprises a discharge hood connected between said first dryer and said first dryer fan and further comprises conveyor means connected between said discharge hood and said second dryer.

9. Apparatus according to claim 8 including a cyclone separator for receiving fines and some matter from the discharge outlet of said first dryer fan.

10. Apparatusaccording to claim 6 wherein said second means for moving said matter through said second dryer comprises said second dryer fan.

11. A method of drying wet particulate matter and of disposing of waste products produced during drying comprising the steps of:

providing a source of heat by burning combustible fuel in a furnace means, partially drying said matter in a first dryer heated by said furnace means by maintaining inlet air temperatures in said first dryer in the range from about l,000 to 2,000 F. so as to extract from about 80 percent to 90 percent of the moisture to be removed from said matter,

removing moisture from said first dryer and discharging it to atmosphere,

removing the partially-dried matter from the first dryer and transporting it to a second dryer which is heated by said furnace means and has a smaller air-handling capacity than said first dryer,

finally drying said partially-dried matter in said second dryer by maintaining inlet air temperatures in said second dryer in the range from about 500 to 1,000 F. so as to extract all but about 2 per cent to 15 per cent of the remaining moisture from said matter and producing combustible waste products in so doing,

removing the finallydried matter and waste products from said second dryer and separating them, and conducting the waste products to said furnace means wherein they are consumed.

12. A method according to claim 11 including the step of adding makeup air to said furnace means.

13. A method according to claim 12 including the step of tempering the heated air supplied to said second dryer with ambient air so as to maintain air temperature in said second dryer in the said range.

14. A method according to claim 11 including the step of transporting the partially-dried matter from said first dryer to said second dryer to allow for equalization of the moisture in the partially-dried matter.

Claims

1. Apparatus for drying wet particulate matter and for disposing of waste products produced during drying comprising: a first dryer for partially dryer said matter, means for moving said matter through said first dryer, a second dryer for finally drying partially-dried matter received from said first dryer, said second dryer producing combustible waste products during the final drying of said matter as a result of processing of said matter therein, means for moving said matter through said second dryer, said first and second dryers being enclosed type dryers and wherein said second dryer is of smaller air handling capacity than said first dryer, said second dryer having an air handling capacity in the range of about one-third to one-half of said first dryer, transfer means for transferring said partially-dried matter from said first dryer to said second dryer, furnace means for supplying heat to said first and second dryers, separating means for separating said finally dried matter from said waste products, and means for delivering said waste products to said furnace means wherein they are consumed.

2. Apparatus according to claim 1 wherein said furnace means maintains air inlet temperatures within said first and second dryers of about 1,000* to 2,000* F. and of about 500* to 1,000* F., respectively.

3. Apparatus for drying wet particulate matter and for disposing of waste products produced during drying comprising: a first dryer for partially drying said matter, first means for moving said matter through said first dryer, a first dryer fan for disposing of moisture released in said first dryer, a second dryer for finally drying partially-dried matter received from said first dryer, said second dryer producing combustible waste products during the final drying of said matter, second means for moving said matter through said second dryer, said first and second dryers being enclosed-type dryers and wherein said second dryer is of smaller air-handling capacity than said first dryer, said second dryer having an air-handling capacity in the range of about one-third to one-half of said first dryer, transfer means for transferring said partially-dried matter from said first dryer to said second dryer, furnace means for supplying heat to said first and second dryers, said furnace means maintaining inlet air temperatures in said first and second dryers of about 1,000* to 2,000* F. and of about 500* to 1,000* F., respectively, separating means for separating said finally-dried matter from said waste products and for delivering the latter to said furnace means wherein they are consumed, and a second dryer fan for delivering said waste products from said second dryer to said separating means.

6. Apparatus according to claim 5 wherein said first means for moving said matter through said first dryer comprises said first dryer fan.

7. Apparatus according to claim 6 wherein said transfer means comprises a second cyclone separator connected between said first dryer fan and said second dryer.

8. Apparatus according to claim 6 wherein said transfer means comprises a discharge hood connected between said first dryer and said first dryer fan and further comprises conveyor means connected between said discharge hood and said second dryer.

10. Apparatus according to claim 6 wherein said second means for moving said matter through said second dryer comprises said second dryer fan.

11. A method of drying wet particulate matter and of disposing of waste products produced during drying comprising the steps of: providing a source of heat by burning combustible fuel in a furnace means, partially drying said matter in a first dryer heated by said furnace means by maintaining inlet air temperatures in said first dryer in the range from about 1,000* to 2,000* F. so as to extract from about 80 percent to 90 percent of the moisture to be removed from said matter, removing moisture from said first dryer and discharging it to atmosphere, removing the partially-dried matter from the first dryer and transporting it to a second dryer which is heated by said furnace means and has a smaller air-handling capacity than said first dryer, finally drying said partially-dried matter in said second dryer by maintaining inlet air temperatures in said second dryer in the range from about 500* to 1,000* F. so as to extract all but about 2 per cent to 15 per cent of the remaining moisture from said matter and producing combustible waste products in so doing, removing the finally-dried matter and waste products from said second dryer and separating them, and conducting the waste products to said furnace means wherein they are consumed.