Solid biofuels from torrefied biomass

Solid biofuels from torrefied biomass Production of Solid Sustainable Energy Carriers from Biomass by Means of Torrefaction – The SECTOR project Wolf...
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Solid biofuels from torrefied biomass Production of Solid Sustainable Energy Carriers from Biomass by Means of Torrefaction – The SECTOR project

Wolfgang Stelte, Ph.D. Center for Biomass and Biorefinery Danish Technological Institute – DTI

Danish Technological Institute -DTI  Private, self-owned and not-for-profit institution  Development and dissemination of research- and technologicallybased knowledge for the Danish and international business sectors

Center for Biomass & Biorefinery  Biomass logistics and storage : Safety, cost reduction, supply chain modeling and optimization  Characterization: Chemical analysis, heating value, combustion properties, ash content, impurities  Pre-treatment: Mechanical, thermal, enzymatic pre-treatment of biomass  High value side streams: Materials, nutrients, food, feed, fertilizer  Liquid, solid, gaseous biofuels  Industry consulting  R&D Projects with industry and universities

Pellet related activities at DTI Pelletizing process: Laboratory and pilot scale facilities

Lab scale: Single pellet press - Parameter screening and optimization, friction and quality test (100 g material) Bench scale: Kahl press, flat die (50 kg/h) Pilot and production scale facilities: Andritz presses (250-2000 kg/h)

Pellet related activities at DTI Storage and handling and safety of pellets

Research activities and consulting in the following areas:  Monitoring of critical parameters: Risk evaluation, hazard reduction and fire prevention  Self heating, oxygen depletion and off-gassing during transport & storage  Safety in silos and during shipping, ATEX, dust Prevention

Pellet related activities at DTI Standardization and quality analysis Offering commercial analysis Wide range of standard methods (EN/ISO) Development of new test methods

Biomass Analysis: Ash, heavy metals, sulfur, chlorine, C, H, N, Ash melting and slagging, etc. Pellet quality: Mechanical durability, heating value, density, etc. Consulting pellet producers: Standardization and certification

SECTOR Project Production of Solid Sustainable Energy Carriers from Biomass by Means of Torrefaction – SECTOR 

Collaborative project financed by European Commission

Project start:



42 months

Total budget:

10 Mio. Euro


21 from 9 EU-countries



SECTOR Project SECTOR Project

Pellets from torrefied biomass Advantages of torrefaction and pelletization  Torrefaction is a mild roasting of biomass in an inert atmosphere    

Removal of water and volatiles from biomass  Increased heating value Increased C/O ratio: better combustion / fuel properties Fibers are converted into a brittle material  Easy to grind (coal mill) Dry product with hydrophobic characteristics  Biomass with coal like properties

 Pelletization  Increase density and reduce dust formation  Lowering transportation and handling costs  Standardized size and automated feeding

Pellets from torrefied biomass Possible problems when pelletizing torrefied biomass  High friction in press channel 

High energy uptake of pellet mill up to 150 kWh/t (usually 50-60 kWh/t for wood pellets)

Heat generation in pellet mill (risk of fire / dust explosion)

Lower capacity

More wear on the pellet mill parts

 Pellet quality

Issues are closely linked to - Biomass feedstock


- Torrefaction parameters

Self heating

- Pelletization parameters


- Can be different case by case


Storage of torrefied pellets


Requires knowledge and further studies

Pellets from torrefied biomass Single pellet press tool: Fast and only few grams of material needed Set-up allows variation of: Temperature, pressure, particle size, moisture, and additive addition

Determination of: Compression energy, friction and quality analysis of pellets

Earlier tests have shown correlation between friction and energy consumption of industrial scale pellet press

Pellets from torrefied biomass Example: Pelletization of torrefied pine tree  Friction increase when pelletizing torrefied pine tree Increase of friction for torrefied biomass Pellet mill: Energy requirements increase Capacity gets lower More heat development in press

Pellets from torrefied biomass  What can we do to improve the pelletizing properties?  Increase moisture content  Increase die temperature  Add a lubricant to reduce friction  Additives  Change press channel dimensions  Torrefaction parameters  Temperature  Reaction time

 …

We have looked on a few of them Some examples

Pellets from torrefied biomass Example: Pelletization of torrefied pine tree  Increase of die temperature 125 - 190 °C

Friction is reduced by 50%

No effect on the untreated pine tree

Pellets from torrefied biomass Example: Pelletization of torrefied pine tree  5 % water addition

Friction is reduced by 50%

Pellets from torrefied biomass Example: Pelletization of torrefied pine tree  2% rape seed oil

Friction is reduced by 70 % But… Negative impact on pellet strength

Pellets from torrefied biomass Parametric study – which parameters are the important ones Design of experiments - Torrefaction degree expressed as mass yield (90.5% - 71.1%) -

Temperature 250 to 300 °C

- Moisture content (0 to 10%) - Die temperature (125-180˚C) - Particle size( small / big)

Pellets from torrefied biomass Parametric study – which parameters are the important ones Key results: - Main parameters affecting friction and pellet durability are: torrefaction degree, moisture content and die temperature - High torrefaction degree increases friction and decreases pellet strength - Water addition and increasing temperature counteracts this effect

 Mathematical modeling of the interaction between the parameters and their dependency is in progress and will be published soon

Pellets from torrefied biomass Successful Pilot and production scale trials - Partners in SECTOR project have successfully produced several tons of torrefied pellets - Large scale production facilities in SECTOR project -

Energy center of The Netherlands (ECN) National Renewable Energy Center, Spain (CENER) Umeå University & Swedish Agricultural University (SLU), Sweden Topell, The Netherlands

- Feedstock: Pine, spruce, poplar, willow, forest residues, straw,… - Material are used in logistics, storage and combustion trials right now  Successful demonstration of the technology

Briquetting of torrefied biomass


240 °C

260 °C

280 °C

Briquetting of torrefied biomass Feeding tank

Conditioning of raw material : Water addition

Briquetting press: outlet

Cooling conveyor Production trials with Industry partner C.F. Nielsen Briquette press manufacturer

Briquetting of torrefied biomass Results from production trials Raw material

Spruce (fresh)

240 C

260 C

280 C

Density (raw material) Moisture Particle size min Particle size max

kg/m3 % mm mm

153 13,4 1x1 10x5

181 5,2 0,1x0,1 5x2

157 4,3 0,1x0,1 5x2

162 4,8 0,1x0,1 5x2

Process Power consumption Die Temperature Strokes per min Strokes number Capacity (measured)

A C 1/min n kg/h

70 160 269 13 600

85 165 269 9 660

85 200 269 16 600

80 205 269 17 600

Product Diameter Length Volume Weight Density (briquette)

mm mm cm3 g kg/m3

59 155 424 446 1053

59 115 314 318 1012

60 162 450 456 1013

59,5 159 442 444 1005

Briquetting of torrefied biomass 

Continuous briquetting of torrefied spruce without stoppages

Briquette quality is good but slightly decreasing for higher torrefaction temperatures

Water addition can improve the briquette strength, there is an optimum moisture content  further tests required to confirm

Unit Density is around 1000 kg/m3 but can most likely be improved by adjusting die diameter and length and by adding additives. Latest developments shows densities up to 1300 kg/m3 for small tests.

Briquette surface is porous, flake like structures – Latest developments shows improvements  Process needs further optimization to obtain a sealed surface of the briquette  Best results when briquettes remain under heat and pressure for longer time  Baking of the briquette

Friction increases with degree of torrefaction (Temperature increase), however Capacity and Power consumption of press remains stable

Market situation for torrefied fuels Barriers for commercialization of torrefied pellets  Technology is ready but, manufacturers and buyers are risk averse to new technologies  Producers are willing to implement torrefaction technology and produce torrefied biomass, but before investing in a full size commercial plant they need long term off take contracts from bankable customers

 Buyers are not un-willing to buy, but first they need to prove that promises concerning torrefied biomass use are met, including quality and volume guarantees, and on operational issues.

 Classic “Chicken and Egg” problem  One has to make the first move

 Thank you for your attention! For more information please contact:

Wolfgang Stelte Consultant, Ph.D. Biomass & Biorefinery

Gregersensvej 2 DK- 2630 Taastrup Denmark

Danish Technological Institute Energy and Climate

Tel. +45 7220 2000 Fax +45 7220 2019

Mobile: +45 7220 1072 [email protected]

"The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement n° 282826."

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