FIELD OF INVENTION:
The present invention relates to combined apparatus for drying bagasse or any
other similar biomass and condensing steam / vapours.
BACKGROUND AND PRIOR ART:
Definition of important term(s):
Bagasse: Cane residue leaving mill(s) after extraction of juice. The cane may be crushed in a train of mills or if diffusion is practised the prepared cane or bagasse bed coming out of diffuser is pressed in dewatering mill(s).
In sugar industry, the vapours produced from the boiling of sugar solutions in evaporators and pans are condensed by cold water in condensers, which may be of the direct or indirect type. Both types of condensers require considerable quantity of cold water to condense the said vapours which necessitates the recycling of the coolant water. This is done by cooling the warmed water in spray ponds or cooling towers employing significant energy expenditure and losses.
Further, bagasse is a by-product of high value, which can be utilized in many different ways, but in almost all cases cane sugar industry obtain the thermal, electrical or mechanical energy necessary for sugar manufacture by burning bagasse. However, the final bagasse has high water content (about 50%), which both reduces its heating value and is the cause of the largest energy loss in the boilers because the fuel moisture carries the latent heat of vaporization up the stack. Therefore, attempts have been made to reduce its water content.
The present invention incorporates known unit operations such as condensation and drying in its process but combines them in a novel manner in a simple apparatus permitting optimum energy efficiency in and/or extraction from a sugar factory complex.

OBJECT OF THE INVENTION:
It is an object of the invention to provide a simple apparatus, combined for bagasse drying and condensation of waste vapours, by means of which the overall sugar manufacturing process becomes more economical and efficient.
SUMMARY OF THE INVENTION:
The invention incorporates known unit operations such as drying and condensation in its process but combines them in a novel manner permitting optimum energy efficiency in and/or extraction from a sugar factory complex. The invention discloses an apparatus for drying bagasse and condensation of low temperature waste / reject vapours from evaporators and pans in sugar industry. Conventional cooling and condensing equipments and means employed in the industry are wasteful both of the energy and precious water. Also, the apparatus and methods used to dry bagasse have their own limitations due to which their deployment in the industry has been very limited. The capital and maintenance cost associated with both of them is also quite high. The present invention proposes an apparatus of simple construction combined for bagasse drying and condensation of low temperature waste / reject vapours whereby the conventional cooling and condensing equipments like condensers, cooling towers or spray ponds, pumping means, etc. are substantially eliminated resulting in considerable savings of capital, energy and water. Also the limitations associated with prior art bagasse driers are simultaneously overcome.
STATEMENT OF INVENTION:
Accordingly, the invention provides an apparatus for drying bagasse and the like comprising a continuous dryer cum condenser wherein the apparatus has means for indirectly heating bagasse and the like and also means for simultaneous moisture removal from bagasse and the like by passing ambient air through it. The said apparatus comprises an inner shell and an outer shell, and at least one annular drying stage or chamber vertically-disposed there between, wherein one

of the said shells is fixed and the other rotatable; said drying stage or chamber comprising;
a deck plate with slots for air to enter said drying chamber;
an air inlet chamber positioned below said deck plate;
said air inlet chamber having air inlets located in said outer shell;
heating elements arranged in said drying chamber above said air slots;
at least one member associated with said rotatable shell and adapted to move the material to be dried over said deck plate and said heating elements;
air outlets located in said inner shell and opening into a central tunnel;
means for generating air draft;
an inlet for material to be dried;
an outlet for discharging the dried material; and
the or each deck plate and underlying air inlet chamber being provided with a hatch at a predetermined position for material to fall through once it has completed a partial revolution of said drying stage.
There is also provided a method of drying bagasse and the like continuously comprising the steps of
(a) indirectly heating the bagasse using waste vapours from pans and evaporators; and
(b) simultaneously passing air through bagasse to remove moisture therefrom.

BRIEF DESCRIPTION OF THE DRAWINGS:
Fig. 1 shows the cut isometric view of the drier condenser according to an
embodiment of the present invention;
Fig. 2 shows the sectional elevation of the same;
Fig. 3 shows the sectional plan of the same;
Fig. 4 is the schematic section view of a drying stage showing heat transfer area
and air path; and
Fig. 5 is the enlarged view of the circle (B) in Fig. 4.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE DRAWINGS:
The invention will now be described by way of example with reference to the accompanying diagrammatic drawings.
According to the invention there is provided an apparatus comprising at least one vertically disposed, annular drying stage, an inner rotatable shell and an outer fixed shell, means to heat the material, means to pass air through the material, means to move the material being dried around each stage, each stage including an orifice for material to fall to a lower drying stage or to a material removal stage.
The or each drying stage may comprise a stationary slotted deck plate, heating means associated therewith, air inlet means fixed to the outer shell opening into an air inlet chamber below the deck plate and means associated with the rotatable inner shell of the apparatus movable there over so as to move the material being dried over the deck plate and heating elements. The deck plate and the air inlet chamber cone plate of each drying stage is provided with a hatch at a predetermined position for the material to fall through once it has completed a partial revolution of the deck plate of each stage.
Corresponding and like parts are referred to in the following description, and indicated in all the views of the drawings, by the same reference characters.

In the figures, the apparatus 1 comprises of an inner cylindrical shell 2 supported around its bottom perimeter on rollers 3. The inner shell 2 is slowly rotated by suitable rotating means 4, preferably synchronized electric or hydraulic motors or hydraulic rams, attached to the bottom and top perimeter of the shell. In the exemplary embodiment synchronized planetary drives impel rotating discs with pins which get engaged with the sprocket wheel 5 on the top as well as bottom perimeter of the inner shell 2. Any other or additional suitable means may be used to rotate the inner shell.
The shell is divided into vertical stages. Each stage has substantially comb-like members 6 attached to the inner rotating shell 2 and radiating outwards from the centreline of the apparatus 1. The said members 2 form compartments and convey the bagasse across the slotted deck 7 and heating elements 8. They may have a grid structure between them to strengthen the structure. In the exemplary embodiment the members 6 are supported at the other end by rollers 9 moving over a ledge or channel 10 fixed to the outer stationary shell 11. Some of the said members 6 are adapted to toss around the material.
A fixed outer column 11 provides support to the or each stationary slotted deck plate 7 together with air inlet chamber cone plate 12 below it forming the air inlet chamber 13. The air inlet chambers 13 have air inlets 14 located in the fixed outer column 11. The air inlets 14 may be controlled. The size and number of the air inlets 14 is variable. The air inlets 14 of adjacent stages however, are preferably arranged so as not to superimpose. The vertical wall surfaces 15 (shown in Fig. 4 & 5) of the air slots 16 (shown in Fig. 5) in the deck plate 7 are designed to allow the free flow of air through the material without the material easily working through the slots. The vertical wall surfaces 15 of the air slots 16 may, for example, be perforated with perforations of suitable size or louvered or lamella walls provided with openings 17 (shown in Fig. 5) of suitable shape or size. These vertical members 15 thus provide a clearance for the air to enter from below into drying chamber 18. Means (not shown) are also provided for clearing out any

material falling through the air slots 16 into the air chamber 13 below. The heating elements 8 are associated with the slotted screen decks 7 and are arranged in a concentric fashion over the air slots 16 (shown in Fig.5) in the deck plate 7 with the vertical members 15 (shown in Fig. 4 & 5) of the air slots 16 (shown in Fig.5) providing support to the said heating elements 8. The heating elements 8 are preferably welded to the vertical members 15 of the air slots 16. Outlets 19 for air exit into the central vertical tunnel 20 are located in the inner movable shell 2. They are preferably above the level of comb-like members 6. Forced, induced or natural draft may be used for generating air movement. The fixed outer column 11 is also divided into vertical stages so that fixed outer and rotating inner members form a complete stage. The apparatus 1 could comprise of one or more stages depending upon the capacity and degree of drying required.
Each deck plate 7, together with the air inlet chamber cone plate 12 below it, has a segment removed to form a hatch 21 through which material can fall from one level to the next lower level. The decks 7 have their hatches 21 arranged for the material to be dropped on to the next lower deck 7 at a position remote from its hatch 21 so that the material travels almost a full revolution at each stage.
The low temperature waste vapours are supplied through a vapour header 22 and distributed in the heating elements through distribution headers 23. The non-condensables and condensate are removed at a location remote to the vapour inlet. In the exemplary embodiment, the non-condensable gases (NCG) and the condensate is removed by common removal lines 24 from either side of each hatch 21, opening into a separate condensate and NCG removal headers shown at 25 & 26 respectively. Preferably, the vapour distribution headers 23 are positioned at almost half a revolution between the said hatches 21. Since the hatches 21 of each stage are arranged for the material to be dropped on to the next lower stage at a position remote from its hatch 21 so that the material travels almost a full revolution at each stage, the vapour supply header 22 and the condensate and NCG removal headers 25 & 26 take a configuration similar to that of helical strands.

Bagasse containing around 50% moisture content is fed into the top stage by a conveyor 27 through a rotary air-lock valve. The bagasse is heated indirectly by the low temperature waste vapours of around 50-60 deg. C rejected from the evaporators and pans which are distributed into the heating elements 8 through the vapour distribution header 23. The substantial comb-like members 6 associated with the rotating inner shell 2 move the material over the deck plate 7 and the heating elements 8.
The air enters through air inlets 14 in the fixed cylindrical outer shell 11 into the air chamber 13 below the slotted deck plate 7. The air inlets 14 are preferably controlled. The air then enters through the air slots 16 (shown in Fig. 5) in the deck plate 7 opening below the heating elements 8, gets warmed up, passes through the material being dried, removing moisture therefrom. The moist warm air exits through the outlets 19 located on the inner movable shell 2 into the central vertical tunnel 20. The outlets 19 are preferably located on the inner shell 2 above the level of comb-like members 6. In order to restrict the air from flowing through the clearance between the stationary deck plate 7 and the rotating inner shell 2, a seal system 26a (shown in Fig.4) is affixed thereto. In the exemplary embodiment it includes a leather or rubber strip attached to the deck plate and pressing against the inner rotating shell. In the top-most stage such a seal system is replaced preferably by a water seal. The warm moist air exiting into the central tunnel may be utilized as combustion air in the boiler since increased calorific value of dried bagasse reduces excess air required and makes it tolerable to use some moist air.
In this preferred exemplary embodiment induced draft fans 28 are installed at the top of the central vertical tunnel 20. Alternatively, the height of the central vertical tunnel 20 may be increased for employing natural draft and eliminating use of fan power.

After completing the circuit of the upper deck the bagasse falls through the hatch 21 to the next lower level and makes another circuit until it reaches the discharge hatch 21, through which it falls to the next lower deck, and so on until it reaches a bagasse discharge conveyor 29. The bagasse mat is reformed after every transfer from one level to another avoiding the formation of layers. The bagasse is removed using a rotary valve by an air-belt or screw conveyor or other suitable means.
In order to eliminate or substantially reduce the ovalness in the rotating inner cylindrical shell 2, it is supported by spokes 30 attached in the centre to a hollow cylindrical hub 31. One or more such arrangements may be made depending upon the height of the apparatus. It is also supported from outer side with rollers (not shown) affixed towards the inner ends of the deck plate and the air inlet chamber cone plate which press against the inner rotating shell 2.
The pH of the vapours rejected from the evaporators and pans is maintained using suitable means such as spraying of caustic soda in evaporators to prevent corrosion. Suitable means are also provided to prevent risk of fire.
Although the exemplary embodiment of the invention has an inner rotating shell 2 and an outer fixed shell 11, another embodiment of the invention may have a fixed inner shell and a rotating outer shell.
The advantages of the invention are seen to be as follows:
a. Complete or partial elimination of condensers and saving of enormous
quantity of cooling water used therein depending upon the vapour
load.
b. Corresponding complete or partial reduction in the requirement of
spray pond or cooling tower to cool the water warmed in the
condensers.
c. All the water pumping requirements eradicated or drastically reduced.

d. No use of flue gases for drying bagasse, so no integration with boiler
required.
e. No adverse effects of overheating.
f. Separate equipments e.g. cyclones, required to clean the bagasse after
drying with flue gases got rid off.
g. It operates at relatively low temperatures and uses ambient air.
h. Low operating and maintenance cost.
i. The design lends itself to easy transportation and erection,
j. Additional deck(s) can be added later without major alterations,
k. Suitable for outdoor operation and is totally enclosed.
1. It does not occupy much floor space.
In the preceding detailed description, the invention is described with reference to specific exemplary embodiments thereof. Various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention as set forth in the claims. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.
"Comprises / comprising" when used in this specification and claims is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps or components or groups thereof.
List of Reference Numbers:
1. Apparatus of the invention
2. Inner Rotating Shell
3. Rollers of Inner Shell
4. Rotating means
5. Sprocket wheel
6. Comb-like members
7. Slotted Deck Plate

8. Heating Elements
9. Roller of comb-like members
10. Ledge or channel
11. Outer stationary shell/column
12. Air Inlet Chamber Cone Plate
13. Air Inlet Chamber
14. Air Inlets
15. Vertical wall surfaces of air slots
16. Air Slots
17. Openings in vertical wall surfaces of air slots
18. Drying Chamber
19. Air Outlets
20. Central Vertical Tunnel
21. Hatch
22. Vapour Header
23. Vapour Distribution Header
24. Common Condensate & NCG removal line
25. Condensate Header
26. NCG Header
26a. Seal
27. Bagasse Inlet Conveyor
28. Induced Draft Fans
29. Bagasse Discharge conveyor
30. Spokes
31. Hollow cylindrical hub

What is claimed is:
1. An apparatus for the drying of bagasse or the like comprising a continuous dryer cum condenser wherein the apparatus (1) has means for indirectly heating bagasse and the like and also means for simultaneous moisture removal from bagasse and the like by passing ambient air through it.
2. The drier cum condenser apparatus as claimed in claim 1, wherein said apparatus (1) comprises:
an inner shell (2) and an outer shell (11), and at least one annular drying stage or chamber (18) vertically-disposed there between, wherein one of the said shells is fixed (11) and the other rotatable (2); said drying stage or chamber (18) comprising;
a deck plate (7) with slots (16) for air to enter said drying chamber (18);
an air inlet chamber (13) positioned below said deck plate (7);
said air inlet chamber (13) having air inlets (14) located in said outer shell
(11);
heating elements (8) arranged in said drying chamber (18) above said air slots (16);
at least one member (6) associated with said rotatable shell (2) and adapted to move the material to be dried over said deck plate (7) and said heating elements (8);
air outlets (19) located in said inner shell (2) and opening into a central tunnel (20);
means for generating air draft;
an inlet for material to be dried;
an outlet for discharging the dried material; and
the or each deck plate (7) and underlying air inlet chamber (13) being provided with a hatch (21) at a predetermined position for material to fall through once it has completed a partial revolution of said drying stage (18).
3. The apparatus according to claim 2, wherein the said rotatable shell (2) is
supported on rollers or the like (3) and is rotatably driven.

4. The apparatus according to claim 2 or 3, wherein said rotatable shell (2) is driven by one or more planetary drives impelling rotating discs with pins which get engaged with at least one sprocket wheel (5) associated with the shell (2) to be rotated.
5. The apparatus according to claim 2, wherein said air slots (16) in said deck plate (7) have vertical wall surfaces (15) with perforations or clearances to allow air to pass into said drying chamber (18).
6. The apparatus according to claim 2, wherein said air inlet chamber (13) comprises a cone plate (12) attached to said fixed shell (11).
7. The apparatus according to claim 2, wherein said heating elements (8) are arranged in said drying chamber (18) above said deck plate air slots (16) in a concentric manner.
8. The apparatus according to claim 2 or 7, wherein said heating elements (8) are supported by vertical members (15) of said air slots (16).
9. The apparatus according to claim 8, wherein said heating elements (8) are welded to said vertical members (15) of said air slots (16).
10. The apparatus according to claim 2, wherein said members (6) associated with said rotatable shell (2) and adapted to move the material to be dried over said deck plate (7) and said heating elements (8) have substantially a comb-like configuration.
11. The apparatus according to claim 2, wherein some of said members (6) associated with said rotatable shell (2) and adapted to move the material to be dried over said deck plate (7) and said heating elements (8) are also adapted to toss the material while it is being moved.
12. The apparatus according to claim 2 wherein the air inlets in the outer shell are controlled air inlets.
13. The apparatus as claimed in claim 2, wherein the means for generating air draft are natural, forced or induced or combination thereof.
14. The apparatus as claimed in claim 2, wherein the or each deck plate (7) and the air inlet chamber cone plate (12) has hatch (21) arranged for the material

to be dropped on to the next lower deck plate (7) at a position remote from its hatch (21) so that the material travels almost a full revolution at each stage.
15. The apparatus as claimed in claim 2, wherein said inner shell (2) is rotatable and is supported at one or more places by spokes (30) attached at the centre to a hollow cylindrical hub (31).
16. A method of drying bagasse and the like continuously comprising the steps of:

(a) indirectly heating the bagasse using waste vapours from pans and evaporators; and
(b) simultaneously passing air through bagasse to remove moisture therefrom.
17. An apparatus substantially as herein described with reference to the
accompanying drawings.