Potential for increased electricity production at an integrated pulp and paper mill with black liquor gasification

Paper in proceeding, 2001

A number of ongoing efforts aim at reducing greenhouse gas emissions from industrial energy systems. This can be achieved through increased biofuel usage. Biofuels are however a limited resource, and their usage must therefore be as efficient as possible. The objective of this study was to identify pulp and paper mill powerhouse configurations with maximal electricity production from a given limited amount of biofuel (black liquor and conventional wood fuels). The configurations investigated include black liquor gasification and conventional Tomlinson recovery boiler systems. The study is based upon a detailed model of the mill's chemical recovery island and a simplified model of the remainder of the mill. In order to satisfy the mill's heat balance, extra biofuel must be imported for most of the configurations considered. The configuration with the highest on-site electricity production (96 MW) includes biofuel gasification and firing in a gas turbine combined cycle unit. However, if biofuel is assumed a limited resource, importing biomass to the mill implies that less biofuel is available for other competing users. The net global electric power production is shown to decrease from 96 MW to 41 MW for the same powerhouse configuration when performance is evaluated in a global perspective.