1. Energy Technology and Thermal Process Chemistry, Umeå University, SE-901 87 Umeå, Sweden
2. Energy Technology Centre, Box 726, SE-941 28 Piteå, Sweden
3. Division of Energy Engineering, Luleå Technical University, SE-987 78 Luleå, Sweden
4. Department of Analytical Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden