Torrefied Biomass and its Handling Aspects – A State-of-the-art Review

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Torrefied Biomass and its Handling Aspects

– A State-of-the-art Review

Victoria E. Hancock, Ioannis Dafnomilis, Dingena L. Schott, Gabriel Lodewijks

Delft University of Technology

Faculty of Mechanical, Maritime and Materials Engineering, Department of Maritime and Transport Technology,

Section of Transport Engineering and Logistics

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Contents

Introduction and research objective

Biomass characteristics and Terminal Logistics

Handling aspects

Requirements and Design aspects

Conclusions

1.

2.

3.

4.

5.

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1. Introduction

•

increasing relevance of

biomass use for bioenergy

production

(+)

renewable and abundant

energy source

(-) problematic transport, storage and handling of raw

biomass

•  low bulk density, high moisture content

•  heterogeneous and fibrous consistency

•  bridging tendency

64.3 % 35.7 %

Renewable energy production in EU28 countries (2013) [1]

bioenergy other

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1. Research objective

•  various pretreatments to improve properties of raw biomass

•  Torrefaction seen as promising thermal method

Ø  product with coal-like properties

Ø  used e.g. in the form of pellets or briquettes

•

What about transport, storage and handling?

Ø  research status on logistics and transport systems from

port terminal to end user

Ø  biomass and coal infrastructure

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2. Biomass

untreated biomass

•

7-60 % moisture content, 40-250 kg m

bulk density

•

low calorific values and energy density

•

fibrous, irregular shapes, low flowability

cuttings Shrubs shells

Virgin wood Crop wastes Treated wood wastes

[2] www.biomasspelletplant.com [3] www.biomass-energy.org [2]

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2. Biomass treatment methods

•  mechanical, chemical or thermal

treatment

Ø

changing form and structure

v 

Densification

uniform size and shape, 7-10 % moisture, up to 10 times higher bulk density

v 

Torrefaction

increased energy density, 1-5% moisture, brittle and hydrophobic nature

[4]

[5]

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2. Biomass Logistics

•

specific demands for biomass handling, transportation and

storage

Ø

prevention of degradation and

extensive dust generation

Ø

avoidance of moisture uptake

•

material properties influence choice of handling equipment

•

biomass supply chain:

v 

transhipment

v 

transportation and transfer

v 

storage

v 

reclaiming

[6]

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2. Biomass Logistics

•

Solid bulk transhipment

Ø  Grabs, Pneumatic systems,

Self unloaders

•

Transportation and transfer

Ø  Belt conveyors, Pouch conveyors,

Pipe conveyors, Bucket elevators, Screw conveyors, Transfer station

•

Storage

Ø  Silos, Bunkers, Bins, Flat storage,

Dome storage

[7]

[8]

[9]

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2. Biomass Logistics

•

Reclaiming systems

Ø  Push floor, Keith walking floor, Sliding

frame, Hydraulic rotor discharger, Screw reclaimer, Tubefeeder,

Underpile chain reclaimer, Kamengo feeder, Feedex reclaimer, Hopper

•

Loading systems & inland transportation

Ø  Truck and Rail loading station,

Drax rail wagon, Floating crane, Choke spout, Boom feeder

Ø  Trucks, Train, Ships/Vessel/Barge

[10]

[11]

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3. Handling aspects of torrefied biomass

•

Modification of biomass through torrefaction

Ø  more homogenous solid product, low moisture content

Ø  increased heating value and grindability

Ø  shows hydrophobic nature

Ø  low bulk density (180-300 kg m-3) can be greatly

increased by compressing the torrefied biomass

Ø  same durability as regular wood pellets

Ø  angle of repose similar to hard coal

Material Moisture Content (%) Bulk Density (kg m-3₎ Calorific Value (MJ kg-1₎ Angle of Repose (°) Wood pellets Torrefied Pellets Hard coal 7-10 1-5 10-15 650-750 750-850 800-850 15-16 20-24 23-35 34-40 38-44 27-45 [12]

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3. Handling aspects - material properties

•

handling of bulk solids influenced by:

v  physical material properties

v  handling equipment in contact with material

v  interaction of bulk solid material and handling equipment

•

Interacting material properties

Ø  mechanical durability: moisture content, particle size

distribution

Ø  particle density: particle size, moisture content

Ø  angle of repose and particle size distribution, moisture

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4. Coal infrastructure

•

general elements shared by both bulk and biomass supply

chain

•

operations at a coal handling Dry Bulk Import Terminal:

Transport

Transshipment Transfer Storage

Sea-going vessel Coal

Unloading

Transport

operations Transfer points

Storing Loading Distributing modality (Ship/Train/Truck) Stock pile (open) Silo (closed) Reclaiming Transfer direct direct

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4. Equipment Design Aspects

•

design of bulk material handling equipment is influenced

by many factors

Ø

type of handled commodity

Handling Functions

Types of Equipment/

Handling Facility Relevant Material Properties

Transshipment Ship unloader, ship loader Particle Size, Bulk Density

Transport

Open & Closed Conveyors: Belt Conveyor, Screw

Conveyor, Pipe conveyor

Particle Size, Bulk Density, Angle of Repose, Wall Friction Angle, Internal Friction

Transfer Transfer chutes, Feeders: Belt

Feeder, Apron Feeder Wall Friction Angle, Internal Friction

Storage Silos, Hoppers Open-area Stockyards

Particle size; Bulk Density; Flow Properties: Effective Angle of Internal Friction, Internal Friction, Unconfined Yield Strength, Wall Friction Angle Angle of Repose

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4. Equipment Design Aspects

•

conveyor

Ø  belt speed

•

transfer chute

Ø  velocity, cut off angle

Ψ Q = qvρb = 3.6Avkρb [14] [15]

•

silo

Ø

bulk density,

unconfined

yield strength

[12] Tumuluru et al., 2011; Wu, 2012; Chen et al., 2015; Sinnott & Towler, 2013

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5. Conclusions

•

research concentrates mainly on torrefaction process

•

fewer studies on handling characteristics of torrefied

products in the supply chain

Ø

physical and chemical material properties

Ø

lack of studies regarding the mechanical behaviour

•

extensive research of torrefied biomass under varying

transport and storage conditions

•

further research on aspects such as dust generation,

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Thank you for your attention!

Victoria E. Hancock, Ioannis Dafnomilis, Dingena L. Schott, Gabriel Lodewijks

Faculty of Mechanical, Maritime and Materials Engineering, Department of Maritime and Transport Technology, Section of

Transport Engineering and Logistics, Delft University of Technology