Future CO₂ Removal From Pulp Mills - Process Integration Consequences

Earlier work has shown that capturing the CO₂ from flue gases in the recovery boiler at a pulp mill can be a cost effective way of reducing mill CO₂ emissions. However, the CO₂ capture cost is very dependent on the fuel price. In this paper, the potential for reducing the need for external fuel and thereby the possibility to reduce the cost for capturing the CO₂ is investigated. The reduction is achieved using thermal process integration. In alternative 1, the mill processes are integrated and a steam surplus made available for CO₂ capture, but still there is a need for external fuel. In alternative 2, the integration is taken one step further and the reboiler is fed with MP steam and the waste heat from the absorption unit is used for generation of LP steam needed at the mill. The avoidance costs are in both cases lower than before the process integration. The avoidance cost in alternative 1 varies between 25.4 and 30.7 EUR/tonne CO₂ depending on the energy market parameters. For alternative 2, the cost varies between 22.5 and 27.2 EUR/tonne CO₂. With tough CO₂ reduction targets and corresponding high CO₂ emission costs, the annual earnings can be substantial, 18.6 MEUR with alternative 1 and 21.2 MEUR with alternative 2