Comparison of electric energy production of several models for black liquor gasification combined cycle power plant

Black liquor is the major share of energy in the pulp and paper mill. It is traditionally combusted in the recovery boilers, which represents chemicals and energy recovery. The recovery boiler is coupled with steam turbine, where the high-pressure steam (9.5 MPa, 490 grad C) produced by combusting of black liquor expands to medium pressure (MP, 12 bar) and low pressure (LP, 5.5 bar) steam. By expanding high pressure steam in the steam turbine, the electric energy is produced. Black liquor gasification with integrated combined cycle (IGCC) can potentially replace recovery boilers as it represents advantages in energy and heat production. In the gasifier operated at 3 MPa and 950 grad C synthesis gas is produced. In this work, several system layouts of cogeneration unit with synthesis gas combustion are modelled. For every model the same fuel input (1600 tpd dry black liquor, 75 % wt dry content) and the same steam delivery to technology (813 tpd of MP and 1869 tpd of LP steam) are the basis for energetic and economic performance comparison. (authors)