Influence of dryer type on the performance of a biomass gasification combined cycle co-located with an integrated pulp and paper mill

• Three dryer types, prior to a biomass gasification combined cycle, were evaluated.
• The combined cycle was integrated with a pulp and paper mill.
• Marginal efficiencies differed by up to 8 percentage points depending on dryer type.
• Net annual profit differed by up to EUR 10 million depending on dryer type.
• The annuity factor highly influences the forecasted profitability of the project.

Integration of biomass gasification with a pulp and paper mill is a possible route to create more value-added products. This route facilitates, for example, more advanced electricity generation and production of biomass based transportation fuels or chemical feedstock. Each unit operation in such a process affects overall efficiency as well as possibilities for process integration. In this paper, the impact of different dryer types in a biomass gasification combined cycle (BIGCC) has been evaluated in terms of efficiency and economic performance. The BIGCC was sized so that the excess heat would replace the current steam production from bark and oil. The results show that the dryer type can have a significant impact on economic performance and efficiencies. A BIGCC with an integrated belt dryer, utilizing excess heat to heat the drying air from the mill, can result in electrical efficiencies of up to around 40%, while e.g. a steam dryer can reach 36–37%. Choice of oxidant, air or oxygen, in the gasifier affects both capital and operational cost. Air was proven to be the most cost efficient solution for the cases evaluated in this study. The investment of around 100 to 140 million Euros for a BIGCC facility is profitable for most evaluated cases for an annuity factor of 0.1, while the net annual profit is negative for most cases when the annuity factor was increased to 0.2, even when including financial support for renewable electricity.