PROJECT OVERVIEW

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 general objectives:

• 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 automation.
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 to 30/06/2006.