LAUSR

Abstract Biogenic residues upgraded by torrefaction are well suited for co-firing in existing thermal power plants due to their increased net calorific value, their improved grindability and their good characteristics regarding storage and transport. In this work, torrefied and pelletized biomass (coniferous wood sawdust) and hard coal (Columbian Calenturitas) were co-combusted in a 1 MWth pulverized coal-fired furnace. The mixture of both fuels (torrefied biomass and hard coal) was co-grinded at two ratios with a thermal share of biomass of 3.8% and 7.3% using the same coal mill. For comparison purpose, experiments on pure hard coal combustion (only coal) were carried out, too. Despite torrefaction, the throughput of the mill was sharply reduced at higher biomass shares and the average grain size of pulverized fuel was increased. However, both fuel blends were co-combusted without any difficulty. Compared to mono-combustion of the hard coal, no significant differences were detected, neither in the flue gas emissions nor in the char burnout. Gas measurements in the flame profile show higher levels of released volatile matter close to the burner, resulting in a higher oxygen demand.