2.2 The automated paper soaking unit (APSU) accessory
This accessory has been especially designed to make waste paper ready
for charging into HEVSTOW. As paper is made almost entirely of
cellulose, with very low content of nitrogen, phosphorous, and other
nutrients, APSU enables stacks of waste paper sheets to be automatically
soaked in cow-dung slurry. This not only provides the needed nutrients
but also softens the paper matrix, making it amenable to rapid feeding
by the earthworm. It (Figure 1) consists of a hopper that spreads the
paper waste evenly in thin layers over a conveyor belt, which transports
it to a surface inclined at an angle of 15o. The inclined surface is
fitted with a set of overhead sprinklers and an array of taps to spread
a thin layer of cowdung slurry over the inclined surface. This not only
ensures proper soaking, reinforced with the help of a set of overhead
sprinklers, but also facilitates transportation and deposition of the
paper waste into the collection module placed at the bottom of the 2 m
long inclined surface. The paper soaked in cow-dung slurry is collected
and transferred to the vermicomposting unit. The excess slurry is
collected and recycled to the overhead tank, used to store and supply
cow-dung slurry to the sprinkler system.
Among the distinguishing features of the design is the feed arrangement
which consists of a hopper fitted with a vibrator and a mechanism to
move it to-and-fro. This to-and-fro movement along with the vibration
helps in evenly spreading the paper waste over the conveyor belt. The
overhead sprinklers along with the array of taps fitted on the inclined
surface ensure proper soaking and transport of paper waste into the
collection vessel. The excess cow-dung slurry is collected underneath
and is recycled to the overheard storage tank. The flow chart of the
system is depicted in Figure 1.
Each APSU, shown in figure 2, typically included a hopper Amounted over a conveyor belt B of 0.6 m in length, a 2 m long
metal sheet C placed at the end of the conveyor belt. The metal
sheet C is placed such that it has an inclination of 15o. An
array of taps D is positioned on the top of the inclined
surface C . These taps apply a thin layer of cow-dung slurry
over the inclined surface. As the cow-dung slurry flows down the
inclined surface C , under the force of gravity, it carries the
paper waste, transported from the conveyor belt B , to the
collection module E . The proper soaking of the paper waste is
ensured by a set of overhead sprinklers F . The collection
module is fitted with a mesh G under which a collection tank is
placed to collect the excess slurry. The collected slurry is then
recycled to the overhead tank which is 56 used to store and supply the
cow-dung slurry to APSU. The height of a typical paper soaking unit is
1.1 m.
The hopper (A ; 0.4 m* 0.4 m* 0.4 m) is mounted on a set of
rods; it can slide freely over these rods. A set of levers is used to
couple the movement of the conveyor belt and the hopper. Thus, only a
single motor is required to drive both the hopper and the conveyor belt.
In order to regulate the flow of paper waste, the hopper is provided a
set of shutters which are adjusted to provide a clearance of 5mm between
the conveyor belt and the hopper. The thin layer of Paper waste is then
conveyed onto the inclined metal sheet fitted with the sprinkler system.
The sprinkler system is designed to minimize the energy required to run
the unit. The gravity driven flow of cow-dung slurry over the inclined
sheet provides a thin film of fluid over which the paper waste is easily
transported down the slope. The over head sprinklers ensure that the
paper waste is properly soaked before it floats out of the unit and into
the collection module. A collection module is provided at the end of the
inclined surface to facilitate collection and recycle of excess cow-dung
slurry to the overhead tank.
A collection module is provided at the end of the inclined surface to
facilitate collection and recycle of excess cow-dung slurry to the
overhead tank.
The functions of the main components are defined as follows:
- Side-wise moveable hopperThe hopper is designed to spread thin layers of paper waste onto the
inclined surface. It moves sideways to aid equal distribution of paper
waste on the conveyor belt placed below. Hopper can hold up to 5 to 7
kg of paper waste at a time.
- Conveyor beltBelow the hopper is the conveyor belt, which is attached to the
mechanical handle to rotate the belt. When conveyor belt is rotated
the paper waste falls on the inclined surface.
- Inclined surfaceThis is specially designed to hold thin sheets of paper waste. The
paper waste slides downwards due to gravity as it is getting soaked in
the cow dung slurry.
- Sprinkler system and the cow dung slurry pumpCow dung slurry is loaded into a slurry tank and as the pump runs the
slurry is sprayed on the inclined surface which has paper waste,
through the sprinklers attached on the inclined surface.
- Mesh and collection vesselAs the soaked paper slides down the slurry drains into the collection
vessel placed below. The collection vessel has a drain which is
attached to the slurry tank through which the excess slurry is sent to
the slurry tank and reused. The mesh filters out the soaked paper
waste which can be sent to the vermicomposting unit for further
processing.2.2.1 Distinguishing features of the APSU design
- The unit ensures proper soaking of paper waste in cow dung slurry,
thus accelerating the vermicomposting process.
- The design can be easily scaled up or down to suit the desired plant
capacity.
- The paper can be easy fed into the hopper either manually or with the
help of an automated loading system.
- A system of levers is used to couple the movement of the conveyor and
the hopper to cut down the energy requirement.
- The unit exploits the gravity driven slurry flow over an inclined
surface to reduce energy requirement.
- The excess slurry is collected and recycled to the overhead tank,
leaving no waste.
- Being only 1.1 m in height, the unit enables easy loading and
operation.
- The automated process saves the labor required to separate waste paper
sheets prior to soaking, thus making the overall process more
efficient and economical.