Right choice for biomass drying
KUVO belt dryer
successfully on-stream at
Finnish NSE Biofuels
The Metso-supplied KUVO belt dryer for the drying of biomass started up successfully
in March 2009 at NSE Biofuels Oy Ltd, a joint venture between Stora Enso and Neste Oil
operating at Stora Enso’s Varkaus mill in Finland. Since the spring the plant has been
generating dry biomass and syngas from wood residues: birch and softwood bark from
Stora Enso’s wood handling system, purchased chips, and harvest residues. The plant also
reduces greenhouse gas emissions, as wood-based gas from the plant will replace oil in
the pulp mill’s lime kiln.
Text Ari Havu and Hannele Björkbacka
Proven dryer technology
utilizing waste heat
The KUVO belt dryer represents state-ofthe-art belt dryer technology. The even
material distribution on the dryer belt
and air flow controllability guarantee an
excellent drying result. The air flow can be
controlled according to the product dry
content and heating air temperature. Power consumption is therefore always as low
as possible. For drying energy, the KUVO
belt dryer uses low-pressure steam from
the mill’s power plant and has a drying
capacity of 8.3 tons of evaporated water
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RESULTS PULP & PAPER
(From right to left) Juha Nissilä, Veikko Jokela,
Esa Rosvall and Sauli Ekola from the NSE Biofuels
team with Metso’s Tauno Koivunen examining
the biomass, which after drying and gasification
will replace oil in the pulp mill’s lime kiln.
Capacity
8.3 t/h evaporated water
Area
~ 150 m2
Drying
temperature
~ 100 ºC air
Heat source
Low-pressure steam
-> Water/glycol
Material
Bark, wood residues
Dry content in
35 – 55 %
Dry content out 85 %
Material flow
per hour. Condensate is recirculated to the
power plant. The KUVO belt dryer can utilize several secondary heat sources such as
waste heat (water), hot air or low-pressure
steam, as in the case of NSE Biofuels, and
no primary energy is needed.
Double-layer drying saves energy
The wet material is distributed in an even
layer onto the drying belt. The drying air
enters the dryer via heat exchangers and
flows through the material layer, absorbing
water from the material. The moistened air
exits the dryer through the extractor fan.
30 – 80 loose -m3/h
The semi-dry material discharged from the
dryer is fed back into the system on top of
the first material layer. This arrangement
ensures optimal utilization of the drying
capacity of air resulting in savings in heat
energy consumption. The dryer capacity
and dry content of the product can be controlled by adjusting the speed of the drying
belt and the rate of the drying air flow. The
biomass reaches 85 % dry content in the
dryer (Figure 1.)
Efficient drying-air generation
Due to winter conditions, the heating
REPORTING RESULTS
Wet product in
Semi-dry product out
Semi-dry product in
Dry product out
Air in
Heat exchanger
Fan
Air out
Belt washing
Power boiler
Wood
residues
Water
Condensate
Bark storage
Water-to-air
heat exchanger
5
3
1
Low-pressure steam
Steam-to-water
heat exchanger
Biomass bin
6
Syngas
1.
2.
3.
4.
5.
6.
7.
8.
9.
KUVO
belt dryer
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4
9
2
8
Figure 1. KUVO belt dryer, double-layer drying.
energy of steam is transmitted to a water/
glycol system to ensure the supply of 100 °C
drying air to the KUVO belt dryer. The drying
air is produced with efficient copper air heat
exchangers and two axial fans (Figure 2).
To minimize the power consumption of
the fans, special attention has been paid to
the air heat exchangers in order to attain a
minimum pressure drop.
Good references and reliable supplier
“NSE Biofuels selected Metso’s KUVO belt
dryer for their biomass handling from several options because KUVO’s heat integration and capacity met the requirements of
Figure 2. The efficient copper air heat
exchangers are used to produce the drying air.
Lime kiln
Gasification
Figure 3. The process flow
sheet for NSE Biofuels. The
dried biomass is used either in
power boiler or in gasification
process for the lime kiln.
the mill’s operational environment (Figure 3).
In addition, the large number of KUVO belt
dryers supplied globally for the drying of
various materials and the fact that Metso
was the supplier convinced NSE Biofuels
that the project would be a success ,” stated
Veikko Jokela, Research Advisor at Stora
Enso, Pulp Supply, Pulp Competence Centre.
Based on this and the successful start-up, it
was easy for Sauli Ekola, Project Manager
at NSE Biofuels to say: “We are extremely
pleased with Metso’s delivery, which was
implemented smoothly and on schedule.
The KUVO belt dryer represents reliable,
easy-to-operate and environment-friendly
technology, and has proven to be the right
choice for drying biomass at our plant.”
Biomass utilization, a
growing energy source
The KUVO belt dryer supplied to NSE
Biofuels is a fine example of Metso’s wide
range of products and solutions for the
growing biomass utilization market. In
2008, Metso and SWISS COMBI –W. Kunz
dryTec A.G. entered into a full product
license agreement for the KUVO belt dryer.
The license agreement is valid for drying
biomass in the pulp and paper industry
and in power generation globally.
Figure 4. The scope of the delivery to NSE Biofuels
consisted of a 150 m2 KUVO belt dryer, a biomass
feed bin and a heating system with installation. The
modularity of the dryer ensures easy installation
and connection to downstream processes. The
dryer was installed in an existing building in
Varkaus and erection started in November 2008.
The dryer came on stream in March 2009, as
planned. The belt dryer’s maintenance requirement
is minimal and its functioning is fully automatic.
Ari Havu, General Manager
Biofuel Handling
ari.havu@metso.com
Tel. +358 40 825 5421
RESULTS PULP & PAPER
2/2009
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