A TEC’s Mjolnir mill:
The future of
alternative fuels
preparation & burning
By
Pedro Montes de Oca
and
Jonathan Forinton
Agenda
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Background
Mjolnir Features
Plant Flowsheet
Test and industrial results
Link to pyroprocess
Solid waste as a fuel alternative
It is possible to substitute common fuels like coal 100% with
municipal waste. This is being done in Europe in some plants.
The thermal energy content of municipal waste is interesting at
approx. 15…21 MJ/kg depending on the preparation process.
Municipal solid waste breaks down and forms methane which is
21x more potent than CO2 for global warming.
During the fuels preparation process, enhanced recycling can be
integrated.
MSW make-up
MSW is relatively similar in different parts of America
The % organics and % water depends on the economic profile of the
neighbourhood.
Thermal fraction with
calorific value: 17-21 MJ/kg
Recyclables
Minerals, dirt
General Block Diagram for alternative fuels
Standard Alternative Fuel Preparation Technology
collection
processing
Operation Guidlines &
Adjustment
storage
transport
Process Design &
Evaluation
dosing
Combustion
Technology
ATEC production and process technology for utilization of alternative fuels
There are 2 sections for an alternative fuels plant:
1) Mechanical handling, processing and dosing
2) Implementation in the cement kiln
Where Mjolnir product is injected
Combustion Gas Temperature
Main burner:
> 2000°C
CC-burner:
< 2000°C
Kiln inlet burner: < 1200°C
Calciner burner: < 900°C
CALCINER
TAD 4
Particle size
Main burner: < 20 mm
Other burner: < 80 mm
COMBUSTION
CHAMBER
TAD 3
Calciner Burner
TAD 2
TAD 1
MIXING
CHAMBER
Quench
Kiln Inlet Burner
Bypass
Main Burner
Different sizing is discharged from different points
Light fraction for kiln burner heavy fraction for calciner burner
Industrial Size Test Mill at Sommariva, Italy
The mill is set up similar to a vertical roller mill system
Foundation is light because moving parts are light
Building footprint approx . L10 x W5 x H6 m
Mjolnir Test Mill- Main Technical Data
Mill size
2.5
Weight
52‘000
Kg
Drive Unit
2 x 300
kW
~ 580
min-1
Rotor Speed
Capacity
6 t/h <15mm
15 t/h <50mm
Feeding
2 x Conveyor screws
Discharge
2 x Conveyor screws
Industrial Size Test Mill at Sommariva, Italy
The mill allows for a gas
throughput, like a vertical roller
mill.
This means we can effect drying
and grinding in 1 step
The ultra-fines are dedusted and
can be separately handled and
dosed to kiln system
Flowsheet
Feed belt conveyor
Bin with screw
conveyors
Exhaust
Condenser
Middle
Gate
ID Fan
Bag Filter
Outlet Gate 1
Outlet Gate 2
Outlet screw conveyor1
Outlet screw conveyor2
Different sizing is discharged from different points
Even metals can be quite reliably separated by density
Industrial Size Test Mill at Sommariva, Italy
2 Feed belts bring material into each
of the 2 shredding chambers
Mjolnir Design Features
Common feed bin with 2 screw
conveyors to each of the 2 mill
chambers
Rejects manual outlet gate
Product outlet screens
Mjolnir View inside the mills
Mjolnir Features of the grinding tools
Incoming material < 150 mm
Easy to maintain (NO KNIVES)
Separated from FE and non FE materials
The chains are individually adjustable in height and position at the shaft head
depending on the input material which has to be grinded.
The change in position can be done in a quick time, if it should come to a
request to change the input material.
The same applies if the chains have to be replaced due to wear.
Mjolnir 3D Model
Mjolnir inside the test mill
above, the outlet screens and on
the right side the manual outlet gate
left, the chains after the testing
period
Mjolnir Advantages
1) Size reduction from 150mm to 5mm in one grinding step
2) Saves one step of shredding
3) Easy to operate
4) Easy to maintain
5) No knives to keep sharp
6) Drying effect during operation
7) Separation of FE and non FE – materials
8) Different output fuel particle sizes for main burner and
calciner possible
Feed  Product
Feed pre-selection
No larger carpets
No tyres
Reduce large solid beams
Proper Pyro-Control with FFB Feeder
FFB - Fuel Feeder Burner:
The hopper feeds to the burner pipe directly
An outer pipe carries coal as 10% control fuel
Tertiary air ducted tangentially to control flame
FFB - Fuel Feeder Burner:
Unlike rotary units, this unit:
is easy to operate and maintain
is easy to take off-line during operation
provides air seal by the fuel material itsself so no moving parts can get stuck
Mjolnir
The future of alternative fuels preparation !
One grinding step does everything
Do nt worry about feeding in hard foreign objects
Throw the resultant fuel directly to burners
Correct dosing and injection methods
Control pyro-process