The aim of the project was to verify a new liquid biofuel chain for
heat production, to determine fuel specifications for pyrolysis oil
(PO) in different applications and to carry out long term combustion
tests. Scientific objectives included modification of PO composition
for improved stability by hot gas filtration and production of emulsions
and cleaner combustion by increased understanding of fundamental phenomena
through single droplet experiments.
It is estimated that implementation of liquid biofuel, RES and CHP
directives, CO2 decreasing objectives and certificate trade will generate
many attractive markets for biofuels. The objectives of the project
were compatible, for example, with the above mentioned EU directives,
objectives of EU’s Kyoto Treaty, and with several national and
international research programs. If light mineral fuel oil (LFO) is
replaced with pyrolysis oil, LFO can be used as diesel fuel in traffic.
Use of pyrolysis oil as liquid fuel in a boiler makes effectively
more middle distillates available for traffic use. This for its part
effectively promotes one of the key aims of the biofuel Directive
by increasing fuel supply sources for transport.
Pyrolysis oil has been produced in a partner (Fortum Oil & Gas-presently
Neste Oil) pilot plant, and oil has been used in boiler (Fortum Värme
and Fortum Oil & Gas-presently Neste Oil) and laboratory tests
(IM). Biomass feedstock availability has been reviewed in Italy (ETA)
and Finland (Vapo). Preliminary fuel specifications have been developed
further (VTT). Laboratory facilities have been prepared and used to
study fundamentals of pyrolysis liquid combustion (IM). Emulsions
from PO and light fuel oil have been produced in laboratory to be
tested in combustion (CSGI). An existing process development unit
has been modified to include a hot vapour filter (HVF) (VTT). Both
emulsion and HVF oils should have improved utilisation properties.
Competitiveness of PO production in Finland has been assessed (VTT)
and a techno-economic assessment of the whole bioenergy chain from
biomass sources to pyrolysis oil production, pyrolysis oil emulsion
production, transportation and utilization in small scale boilers
in Tuscany, Italy, has been carried out (ETA).
The pyrolysis process has been shown to be able to produce high yields
of liquid products which can be shipped, stored and utilised more
economically than solid fuel systems in the small to medium size class
(50 kW to 1 MWth). However, to date there have been no long term experiences
with pyrolysis fuel use in this size class due to lack of sufficient
quantities of suitable quality fuel.
Therefore it is envisaged that to be able to enter into heating fuel
markets, the new liquid biofuel, pyrolysis oil (PO), chain has the following
- To be competitive economically;
- To fulfil specifications required by users.
In Finland a strong demand for wood fuels continues, and wood fuel
prices have continued to increase during the years. Logging residues
were selected as the raw material for the pyrolysis liquid production.
In Italy agricultural residues were considered as primary potential
feedstocks for pyrolysis oil production. In Tuscany, used as case
study for the Techno-economic assessment, wood industry residues could
provide also significant amounts of biomass.
In pilot plant performace it was shown that stable process conditions
can be achieved. A high quality product could be obtained by removing
solids using commercial centrifuges. The liquid yield, 65 weight percent,
was less than expected and most likely due to our higher feedstock
particle size than in smaller systems. Further development work is
needed on product cooling, on tar removal from non-condensable gases,
on combustion of coke in transfer pipes, and on online phase separation
in forestry residue pyrolysis.
In laboratory scale combustion a database relative to heating, spraying,
swelling, vaporization, ignition, liquid burning, cenosphere formation
and burning processes, gaseous emissions, ageing, was formed and all
the relevant parameters were recognised and correlated with the fuels
properties. Hard solids such as micro sand, even at levels of 0.03-0.05
weight percent, can cause problems in pumps, nozzles and higher emissions.
The levels of emissions were small except for the amount of dust or
particulate matter. Tar and PAHs were reduced to very low levels.
Technically the medium scale (200 kW-1 MW) combustion system was a
success and could be used for long term heat production. The cost
of the combustion system was however higher than the goal due mainly
to the cost for the industrial pump required but also the increased
In large scale combustion (510 MW boilers) PO should be single phase.
Either the heating value has to be increased or the combustion conditions
have to be modified. The latter could be done by modifying the boiler
and place some bricks at the bottom and to the side of burner to create
a radiating shield. Other possibilities are more refractory, air pre-heater
or pre-combustion chamber.
Based on the results from hot vapour filtration it was concluded that
with the present experimental arrangement HVF of pyrolysis vapours
does not appear feasible.
Plants below 2-3 t/h feed rate are unlikely to be viable. However
the profitability could be enhanced by fully recovering the heat associated
to the char and flue gas produced in the pyrolysis reaction, or by
selling waste heat and by-product char. Extra heat is available from
pyrolysis, when a relatively dry feedstock is used, as assumed in
the Italian case study.
Although a reasonable internal rate of return of 10% was calculated
in the Finnish case study in replacing light fuel oil in boilers,
increase of feedstock price in Finland made economics not so attractive
during the time of assessment.
The project has been supported by the European Commission.
The duration of the project has been 42 months, from 01/01/2003