Waste Management

 

 

 

[6] http://www.untha.com/en/shredders/industrial-shredders/xr2000/3000_p41

[5] Keller, E. (Hrsg): Abfallwirtschaft und Recycling-
Probleme und Praxis. Essex: Verlag Girardet 1977

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[4] http://www.emswasterecycle.com/products/trommels-t1200-t5000/

[3] Waste Management book by B. Bilitewski, G. Hardtle, K. Marek –
page 351

[2] http://www.steinertglobal.com/de/en/products/magnetic-separation/steinert-suspension-magnets/

[1] https://www.eggersmann-recyclingtechnology.com/en/brt-hartner/products/bag-opener-bos/

References

 

 

 

As per the seasonal variation we will get highest 337 Mg/day of
waste. The throughput of the selected shredder would be 50 t/h for MSW. The
maximum speed would be 22 rpm.

[Source: UNTHA shredding technology GmbH 2018]

·        
Internal pushing system: continuous waste
feeding

·        
Predefined fraction size

·        
Minimum noise emission

·        
Less-wear: Reduces maintenance cost

·        
Low energy cost

The characteristics of the chosen machine are as follows:

                                                [Source:
UNTHA shredding technology GmbH 2018]

                                                                                Figure
6: Shredder

 

 

 

 

 

 

 

 

 

 

 

 

 

After waste is fed into the shredder, it is pressed against rotor
which contain cutters to reduce the size of waste. The shredded waste then
falls through a screen of size 40 mm and taken to subsequent processes. To meet
these requirements, we have selected the model by UNTHA Shredding technology.

A shredder is used to reduce the overall particle size of the
waste. It is required to include this equipment before the waste is taken to
digester and composting unit to comply with their system requirements and
enable undisturbed downstream operations. There are two types of system
available namely ripper and cutter system. The latter is chosen in this case
because it can shred the input waste stream down to a particle size of less
than 40 mm.

2.4.5 Shredder

 

                [Source: Keller, E. (Hrsg): Abfallwirtschaft und
Recycling- Probleme und Praxis. Essex:
Verlag Girardet 1977]

                                                Figure
5: Schematic drawing of an air classifier

 

 

 

 

 

 

 

 

 

 

It is used to separate the light fractions from the heavy
fractions based on the particle density. In air classifier the incoming waste
are separated into two parts based on the size, shape and weight of the
materials. The lighter materials are blown away and the heavier materials will
go to the next phase. Our aim is to separate recyclable materials like paper,
foil, plastic dust and plastic film.

2.4.4 Air Classifier

 

As per the seasonal variation we will get highest 337 Mg/day of
waste. The throughput of the selected trammel screen would be 50 t/h for MSW.
The maximum speed would be 20 rpm.

 

[Source: EMS Turnkey Waste Recycling Solutions
2018]

·        
Heavy loads can be handled

·        
Minimal setup time

·        
Low maintenance

·        
Various mesh and plate sizes

The characteristics of the chosen machine are as follows:

 

                                                                                                  [Source: EMS Turnkey Waste Recycling
Solutions 2018]

Figure 3: Schematic Diagram of Trommel Screen [3]                         Figure 4: Trommel
Screen [4]

 

 

 

 

 

 

 

 

 

 

 

 

Screening is used to separate the finer fractions from the larger
fractions. The equipment to be used is a trommel screen because it is very
flexible in terms of its placement in a waste management facility. For example,
it can be used for screening both at the start of a pretreatment process as
well as at the end of its process train. In this plant it is used to separate
particles in bio waste that are less than 40mm from larger fractions, wherein
the finer fractions are fed directly into the digester. The retained larger waste
will proceed to the next step. The selection of this equipment is such that the
screen size can be changed based on the system requirements. In bio waste and
garden waste there will be a lot finer fractions. Thus, screening will also help
to reduce the load on shredder as most of the waste would already have been
separated by trommel, leaving only larger fraction for the following stage.

2.4.3 Trommel Screen

As per the seasonal variation we will get highest 337 Mg/day of
waste. The throughput of the selected magnetic separator would be 50 t/h for
MSW. And it has a cut height of up to 1m.

 

[Source: Steinert GmbH 2015]

·        
Self-cleaning

·        
Permanent magnets

The characteristics of the chosen machine are as follows:

 

                                Figure
2: Overhead magnetic separator [Source: Steinert GmbH 2015]

 

 

 

 

 

 

 

 

 

Ferrous metals could
be present in both bio waste and garden waste. The presence of ferrous
materials in digester and composting unit may reduce the production and cause
barrier in the system. Also having this inside the waste is not a good choice
as the ferrous material could damage the shredder. So to remove this impurity
we will be using a magnetic separator. While the waste will be passing through
conveyor belts, the overhead magnetic separator would help to remove the
unwanted ferrous materials. For this we have chosen an overhead magnetic
separator from STEINERT GmbH, who will help installing it in the plant.

2.4.2 Magnetic Separator

As per the seasonal variation we will get maximum 337 Mg/day of
waste. The throughput of the selected bag opener would be 50 t/h for MSW. The maximum
speed would be 18 rpm.

                                                Figure
2: Bag Opener  [Source: Eggersmann GmbH
2018]

 

 

 

 

 

 

 

 

 

 

 

 

[Source: Eggersmann GmbH 2018]

·        
Machine operates silently.

·        
Wear resistant and extremely robust

·        
In case of blockages there will be automatic
switch-off

·        
Requirement of maintenance and servicing is
less

·        
Able to open bags inside bag

·        
100% efficient in opening and emptying plastic
bags

The characteristics of the chosen machine are as follows:

Although it is not permitted to use plastic bags for throwing the
bio waste in most of the European countries, people are still doing this.
Moreover, it is not allowed to use manpower directly in waste management plant.
Keeping these concerns in mind we are installing a bag opener to increase the automation
as well as efficiency of the plant. We have chosen Eggersmann
GmbH as our potential partner who will help us in installing the bag opener
facility.

2.4.1 Bag Opener

In this process we are using equipment which will be installed by
our partnered companies. Among different companies we tried to choose the best suitable
machines for this plant. Detailed specifications of the machines are given in
the following.

2.4 Pretreatment equipment:

                                                                Table
1: Design of the storage area

 

Storage for bio waste

Storage for garden waste

Length
x Width (m x m)

36 x 12

4 x 12

Height
(m)

4

4

Total
Capacity (m3)

1728

192

 

We are considering the storage for 2 days of waste for that we
need a storage of twice the volume of bio waste and garden waste per day. The
following table showing the dimensions of the storage areas:

We will have separate storage unit for both bio waste and garden
waste. It will help to avoid any unexpected mixture of waste. The storage unit
will be designed based on the highest volume per day. According to the seasonal
variation maximum volume of bio waste and garden waste are 830 m3/day
and 26 m3/day respectively.

Storage is the first part of the pretreatment unit where all the
incoming bio waste and garden waste will be stored. At first, there will be
weighing stations where the weight of the incoming waste will be calculated. Total
weight of the vehicle including the waste will be calculated first then the
weight of the empty vehicle will be noted to calculate the actual weight of the
incoming waste. This calculation is helps to compare the incoming waste and the
final production of biogas and compost.

2.3 Storage

In the pretreatment unit first there will be a storage unit where
the incoming waste will be stored. From there it will proceed directly into the
bag opener machine where the bags will be opened. After opening the bags, the
waste will go through specific conveyor belts and there will be an upper head
magnetic separator which will remove the ferrous materials. Followed by a
trommel screen to separate the finer fractions from the larger fractions. On
top of the trommel screen the larger particles will be retained. Through
conveyor belts they will go to air classifier where the lighter particles will
be removed and at the end of the process there will be a shredder to minimize
the size of the remaining waste to make it finer. Pretreatment process ends
here and it will proceed to next step.

               

 

 

 

2.2 Process Flow:

For one treatment line there would be
only one line for the total pretreatment system. For two treatment line there
would two lines. For two lines there is in need of same machines twice. So it
needs more space as well as more equipment cost. Considering the cost, energy,
maintenance and space requirement we are selecting “One treatment line” for
this plant.

2)     
Separate treatment line

1)     
One treatment line for both waste

Bio waste and garden waste will be
available for pretreatment. There are two solutions available for the
pretreatment line. Among them one option is needed to select for the mechanical
pretreatment. The options are:

There will be two types of waste
available according to the contract, one is bio waste and another is garden
waste. After pretreatment bio waste will proceed to the digester and garden
waste will go directly to the composting unit. They both have impurities and
which will be removed by mechanical pretreatment unit. Bio waste and garden
waste both contains impurities e.g. paper, ferrous materials, aluminum foil
etc. Different types of machines will be used in the pretreatment unit to
efficiently remove all the impurities

3)     
Size reduction

2)     
Classification

1)     
Separation

2.1 Mechanical Pretreatment:
Mechanical pretreatment is performed to separate impurities from the incoming
waste. The performance of biological treatment is very much dependent on the
type of pretreatment. Previously, there were different types of machines which
were available for industries like mine industries and those machines were
modified and used for the purpose of waste treatment. Now with the help of
advanced technologies several machines are available. The whole mechanical
pretreatment can be divided into several parts as the following

2 Pretreatment

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