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:
  1. 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.
  2. 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.
  3. 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.
  4. 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.
  5. 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