Energy conversion performance of black liquor gasification to hydrogen production using direct causticization with CO2 capture

This paper estimates potential hydrogen production via dry black liquor gasification system with direct causticization integrated with a reference pulp mill. The advantage of using direct causticization is elimination of energy intensive lime kiln. Pressure swing adsorption is integrated in the carbon capture process for hydrogen upgrading. The energy conversion performance of the integrated system is compared with other bio-fuel alternatives and evaluated based on system performance indicators. The results indicated a significant hydrogen production potential (about 141 MW) with an energy ratio of about 0.74 from the reference black liquor capacity (about 243.5 MW) and extra biomass import (about 50 MW) to compensate total energy deficit. About 867,000 tonnes of CO2 abatement per year is estimated i.e. combining CO2 capture and CO2 offset from hydrogen replacing motor gasoline. The hydrogen production offers a substantial motor fuel replacement especially in regions with large pulp and paper industry e.g. about 63% of domestic gasoline replacement in Sweden.