FIELD OF THE INVENTION
The present invention provides a three drum feeder system for extracting and feeding of bagasse and other cellulose fuels of similar character. Three drum feeder is an improved version of Bagasse drum feeder and it can handle milled and diffused bagasse, without choking. It also eliminates the screw feeder used down below the single drum feeder for feed control.
BACKGROUND OF THE DISCLOSURE
The waste materials from many commercial processes are burned to dispose off the materials and to produce heat which can be economically used in the process or to produce power. The process of producing sugar from sugar cane is a typical commercial process where the waste materials produced therein i. e. bagasse, can be economically burned. Bagasse has a low heat value and a high moisture content when compared with commercial solid or liquid fuels, such as coal or fuel oil. Moreover, the bagasse is fibrous, and with its high moisture content, is particularly difficult to feed with the desired degree of uniformity.
A bagasse feeder is known to have been provided in the art comprising of a single roller provided with saw tooth blades and supported on a shaft. The said roller is disposed in a body to cover the roller from all sides. Further, the roller with the body is attached with a feeding chute at the upper part and an outlet at the lower part for supply and discharge of the bagasse to the boiler furnace However, said feeder is associated with the following disadvantages:jamming of the feeder due to honey comb effect of bagasse.Actually, agricultural product like bagasse has natural tendency of sticking to each other causing honey comb effect thereby causing jamming of the feeder. Consumption of more electrical power for a particular capacity during its operation.It cannot regulate compression and pressure on bagasse.
Reference is made to US 2796198 wherein an apparatus for feeding bagasse is disclosed. A furnace-stoker-feeder system comprises of a rotary feed drum mounted on a generally horizontal axis and having a drum surface spaced below the cutter edge and located with relation to the cutter edge so that the cutter edge overlies the mid region of the top of the drum.
Reference is made to a three drum feeders of FSE energy ( http://fseenergy.com/products/3-drum-feeders). The 3-drum feeder works as a monitored mechanical feeding device. First, it 2
utilizes a multiple drum approach to ensure a consistent texture and quantity, then it employs mechanical paddles to distribute bagasse onto the grate for a more uniform and efficient combustion.
Reference is made to triple drum feeders (http://www.thermalenergysystems.com/teskit.html) as disclosed by TES. TES tripple drum feeder has focused on eliminating chokages and smoothening fuel flow. The two small drums at the top of the feeder, meter the fuel. A large toothed drum, running at a much higher peripheral speed, provides a carding action to ensure a steady flow of discrete particles to the spreader. However, it is different from the present invention as 1/ the bottom drum diameter is bigger than upper drum. 2/ Bottom drum kept at centre of feeder. 3/ Spikes of the drum are flat type. 4/ Housing type casing. 5/ Discharge opening is almost at centre of bottom drum.
Reference is made to Continuous bagasse feeding system by Avant-Garde (www.avantgarde-india.com/.../Continuous%20Bagasse%20Feeding%20System.pdf) wherein single drum type feeder system is described.Single drum feeder is used in extracting the bagasse from a silo and feeding the bagasse to boiler using pneumatic spreaders. The drum centre in a single drum feeder usually has an offset with silo centre to prevent column load acting directly on the drum. This feature creates a gap in the feeder discharge point due to which controllability of bagasse flow is affected. When fibre size of bagasse is less, the same gets bypassed in the gap which further affects controllability. When fibre size is too high, the feeder discharges the bagasse in lump form. To break these lumps, a screw conveyor is used after single drum feeder prior to feeding into the boiler.
Conventional feeders used in bagasse feeding system extracts the bagasse from silo and feed to boiler through screw feeder and pneumatic spreader. The screw feeder is required to break and loosen the bagasse which gets compacted during extraction from silo by feeders. The feeders have limitation of the vertical bagasse column in silo to avoid jamming of bagasse during extraction.
Thus to overcome the problems associated with the prior arts and to eliminate the screw feeder in the system, a new three drum feeder system has been developed by the inventors.
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DETAILED DESCRIPTION OF THE INVENTION
Three drum feeder is improved version of Bagasse single drum feeder and it can handle milled bagasse, without choking. This can eliminate the screw feeder used down below the single drum feeder for feed control.
The design capacity of feeder is 14500 kgs/ hr at 4.3 rpm for upper twin drums and 8.6 rpm for lower drum. The high speed lower drum is able to break and loosen the compressed bagasse during extraction at upper twin drums.
In this feeder, the upper twin drums ( 4 and 5) are provided to extract the bagasse from the silo and control the flow of bagasse. The bagasse flow is varied / controlled by varying the speed of drive motor (15).
A lower drum (6) having spikes, run at higher speed than upper drums to break and loosen the bagasse which is compressed during extraction by the upper drums, and also facilitates free flow of bagasse to furnace, through chute and spreader. Upper and lower drums are driven through sprockets & chain arrangement, coupled to the drive unit of gearbox ( 16) and electric motor (15)
The feeder casings are made of 8mm thick carbon steel plate and lined with 3mm thick stainless steel plate for corrosion resistance and free flow of bagasse. The casings are made in three segments Upper (1), Middle (2) and bottom casings (3) with split flanges. Also the middle casing (2) is provided with front split with bolted connection to facilitate approach to twin drums in-situ.
The spikes are welded to the entire surface of upper (4 and 5) and lower drums ( 6) and it is arranged at an inclination with respect to its rotation for better extraction. Solid shafts are used and both ends are supported by casing using suitable plummer blocks.
The upper drums ( 4 and 5) are identical in size and located with required gap between them to ensure the rated flow of bagasse. They rotate nearly at half the speed of the lower drum by common chain drive with reduction sprockets.
The gap between upper drums (4 and 5) and lower drum (6) shall be strictly maintained to attain 4
the rated discharge capacity and free from choking.
The upper drums ( 4 and 5) rotate in opposite direction to each other, towards inner centre line and bagasse is extracted from the silo and discharge through centre gap. The lower drum further feeds it to the furnace through chute.
The chain (19) and sprocket (7, 8, 9 and 10) arrangement is made to get the different direction of rotation of drums, the speed ratio and chain tightness.
The lower drum (6) non-driven end is connected with small diameter sprocket (9) and driven end of the shaft is connected with gear box through gear coupling (13) and further connected with drive motor through flexible coupling (14).
This feeder is provided with “L” Pipe arrangement (20) to prevent free flow of bagasse during initial filling of bagasse. The same shall be removed prior to switching on / operating the feeder.
The drive arrangement consists of 7.5 KW AC motor, suitable for operation with variable frequency control with planetary gear unit. The gear box output shaft and the feeder drive shaft are connected through couplings.
Silo outlet opening (inside dimensions) is 910mm x 650mm (this size is always lower than feeder inlet size) to ensure the relief of bagasse when it enters the feeder.
Figure 1: Schematic diagram of three drum feeder.
Figure 2: Parts of three drum feeder system.
Figure 3: Three drum feeder assembly.
Figure 4: Drum size and spacing arrangement. Spacing between the top drums is designed to have desired capacity of bagasse at maximum speed. The diagonal gap between top and bottom drum is designed to prevent accumulation. Bottom drum rotates at double speed of top drum and designed to prevent bagasse accumulation in-between top and bottom drums. The bottom drum has slight offset with top to facilitate discharge in the direction of rotation.
Figure 5: Shroud arrangement on drums. Specially designed shroud profile on top of each drum 5
for preventing bagasse entry on sides to avoid choking and trips.
Figure 6: Chain drive arrangement. Special configuration of Chain and sprocket arrangement to ensure that drive chain is in tension for effective load transfer.
Figure 7: Initial filling provision. Specially designed stopper pipe to prevent bagasse escape from silo to chute during initial filling.
Figure 8: Curved casing adjacent to top drum. Casing on top drum sides were profiled to match drum profile. This smooth curve prevent excessive accumulation of bagasse and associated trips.
Figure 9: Spike design. Spikes are used to extract the material and feed them to the chute.Spikes are fixed at an angle so that the tangential force available on them is more for easy extraction. The spike is designed with triangle shape so that it can resist more force during extraction due to its section modulus.
ADVANTAGES OF PRESENT INVENTION
1/ Upper twin drum extracts the bagasse from silo and feed to lower drum.
2/ Lower drum breaks and loosens the compressed bagasse during extraction and feed to the boiler through pneumatic spreader.
3/ This three drum feeder can be used for both milled and diffused bagasse.

We claim:
1. A three drum feeder system comprising:
a pair of upper drums (4,5) having plurality of spikes (21) on its entire external surface and
a lower drum (6) having plurality of spikes on its entire external surface, the said upper
drums (4, 5) being rotatably mounted in a casing (1 & 2) with their respective axis being
substantially parallel to each other in a horizontal plane and said lower drum (6) being
rotatably mounted in said casing below the the upper drums (43);
the said upper drums (43) and the lower drum (6) being mechanically coupled to a prime
mover, each of the said upper drums (4,5) being configured to rotate in a direction
opposite to each other such that the left upper drum (4) is configured to rotate in clockwise
direction, the right upper drum (5) is configured to rotate in anticlockwise direction and
the said lower drum (6) is configured to rotate in clockwise direction when looked from
driven end;
the said spikes (21) being arranged on the upper drums (4, 5) in such a manner that when
rotated, the spikes of one drum (4) do not interfere with spikes of other drum (5).
2. The feeder system as claimed in claim 1, wherein the casing of feeder system consists of
three segments namely upper casing (I), middle casing (2) and bottom casing (3).
3. The feeder system as claimed in claim 1, wherein the upper drums (4, 5) are identical in
size and spatially disposed with 300 mm - 550 mm spacing between them.
4. The feeder system as claimed in claim 1, wherein the prime mover comprises a sprockets
and chain arrangement mechanically coupled to the drive unit of gearbox (16), further
mechanically coupled to an electric motor (15).
5. The feeder system as claimed in claim 5, wherein the electric motor (15) is an alternating
current motor with power rating from 3.7 KW to 7.5 KW (please confirm range).
6. The feeder system as claimed in claim 1, wherein the casing of the feeder system is
provided internally with 3 mm thickness SA240Gr409/304 (SS409/304) liner.
7. The feeder system as claimed in claim 1, wherein the upper drums (4, 5) have a diameter
from 200 mm to 550 mm and the lower drum (6) has diameter from 200 mm to 550 mm.
8. The feeder system as claimed in claim 1, wherein the upper drums (43) rotate at nearly
half the speed of the lower drum (6).
9. The feeder system as claimed in claim 1, wherein spikes (2 1) have a triangular shape.
10. The feeder system as claimed in claim 1, wherein the feeder is provided with "L" pipe
arrangement (20) to prevent free flow of bagasse into the feeder system.