1. Division of Energy Engineering, Luleå University of Technology, S-971 87 Luleå, Sweden, Energy Technology and Thermal Process Chemistry, Umeå University, S-901 87 Umeå, Sweden, Unit for Biomass Technology and Chemistry, Swedish University of Agricultural Sciences, Box 4097, S-904 03, Umeå, Sweden, and Skellefteå Kraft AB. S-93180, Skellefteå, Sweden