A TEC’s Mjolnir mill: The future of alternative fuels preparation & burning

By Pedro Montes de Oca andJonathan Forinton

Agenda

• Background• Mjolnir Features• Plant Flowsheet• Test and industrial results• Link to pyroprocess

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.

Solid waste as a fuel alternative

MSW is relatively similar in different parts of America

The % organics and % water depends on the economic profile of the neighbourhood.

MSW make-up

Thermal fraction with calorific value: 17-21 MJ/kg

Recyclables Minerals, dirt

General Block Diagram for alternative fuels

collection storage transport dosingprocessing

Operation Guidlines & Adjustment

Process Design & Evaluation

Combustion Technology

Standard Alternative Fuel Preparation 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 dosing2)Implementation in the cement kiln

Where Mjolnir product is injected

TAD 4

TAD 3 TAD 2 TAD 1

Bypass

Quench

Main Burner

COMBUSTION CHAMBER

CALCINER

MIXINGCHAMBERCalciner Burner

Kiln Inlet Burner

Particle sizeMain burner: < 20 mmOther burner: < 80 mm

Combustion Gas TemperatureMain burner: > 2000°CCC-burner: < 2000°CKiln inlet burner: < 1200°CCalciner burner: < 900°C

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

Rotor Speed ~ 580 min-1

Capacity 6 t/h <15mm15 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

Bag Filter

Condenser

Outlet Gate 1

Middle Gate

Bin with screw conveyors

Outlet Gate 2

ID Fan

Exhaust

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

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.

Incoming material < 150 mm Easy to maintain (NO KNIVES) Separated from FE and non FE materials

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: 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

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

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