Integration of Membrane Separation Technology in Hydrogen Production from Gasified Black Liquor with CO2 Capture
Examensarbete för masterexamen
The countries which ratified the Kyoto protocol have committed to reduce their emissions of carbon dioxide and five other greenhouse gases, or engage in emissions trading if they maintain or increase emissions of these gases. In this context, the production of CO2 free fuels should become a major concern. With successful fuel cell development, hydrogen could be a fuel for the future. A previous project has studied the feasibility to integrate hydrogen production from gasified black liquor with a pulp mill. The pulp mill used is the Eco-cyclic pulp mill (KAM), a model mill developed in a Swedish national research programme using the best available technology in commercial use. The use of membrane separation technology instead of conventional separation technology in the hydrogen production process has been studied in this work. Three processes have been modeled with Hysys, a general-purpose simulation software. Energy balance, CO2-emissions reduction potential and economic benefits were estimated for the three processes. The results obtained were compared with the results of the process using conventional separation technology and with the results of the KAM pulp mill without hydrogen production. The results show that the use of membranes in the hydrogen production unit integrated with the pulp mill has several advantages over conventional separation technology. It increases the hydrogen production yield with 25 %, it reduces the quantity of biomass to import and more district heating is produced. However, the electric power consumption increases by 17 to 38 % depending on the process. Only the KAM pulp mill with a Tomlinson boiler and no hydrogen production can export electrical power and biomass. Hydrogen produced by one KAM pulp mill and used in fuel cell vehicles, could replace 14 % of the gasoline currently used in the car transportation sector in Sweden. Integration of membrane separation technology achieves a CO2-emissions reduction of 3,6 % on a national basis for one KAM pulp mill with integrated hydrogen production. A sensitivity analysis was made with two hydrogen prices 7,16 €/GJ and 13,43 €/GJ. Operating margins were calculated for all the processes and it shows that in both cases operating margins for membrane-based processes are higher than those achieved by the process using conventional separation technology and the KAM pulp mill with Tomlinson boiler. The allowable extra investment cost for membrane based processes compared to the process based on conventional technology was estimated at 125M€ if a payback period of three year is assumed, CO2 capture is possible and the hydrogen sales price is high.
Energi , Kemiteknik , Energy , Chemical Engineering