Black liquor gasification with calcium looping for carbon-negative pulp and paper industry

Although considered one of the major energy-intensive industries (EIIs), the pulp and paper industry has also the potential for energy production from an industrial waste, black liquor. This study proposes black liquor gasification (BLG) coupled with calcium looping (CaL) as a CO₂ capture route for the pulp and paper industry. BLG with H₂ production (BLG-CaL-H₂), BLG with gas turbine combined cycle (BLG-CaL-GT) or with solid oxide fuel cell (BLG-CaL-SOFC) were considered. The dependence of carbon capture and storage (CCS) cost on the natural gas, limestone, electricity imported and H₂ sale prices aside the expenditures related with BLG-CaL were evaluated. The CCS route, based on CaL retrofitted to the pulp and paper plant, was found to have a lower cost of CO₂ avoided (39.0 €/tCO₂) when compared with BLG-CaL (48.8–57.1 €/tCO₂). Between the BLG-CaL scenarios, BLG-CaL-H₂ presented the lowest cost of CO₂ avoided (48.8 €/tCO₂) but the highest energy penalty. Based on the thermodynamic performance, it was shown that CaL retrofit and BLG-CaL-SOFC presented the best overall performance, turning the electricity importer reference plant into electricity exporter. The economic sensitivity showed that the capital requirement of BLG-CaL has a strong effect on the cost of CO₂ avoided for all alternatives. The H₂ production is also strongly affected by the H₂ sale price while BLG-CaL-SOFC and BLG-CaL-GT are strongly dependent on natural gas price.