Influence of Different Pretreatment Methods on Biomass Gasification and Production of Fischer-tropsch Crude Integrated with a Pulp and Paper Mill

In this paper, the influence on the system performance of different biomass pretreatment methods beforegasification and subsequent production of Fischer-Tropsch crude is considered. Entrained flow gasificationat high pressure is a well proven technology for coal as feedstock with the benefit of producing apractically tar free raw gas with a close to complete carbon conversion. The short residence time in thistype of gasifier requires a fuel, which is relatively dry and has a small particle size, to be pressurized fromambient conditions up to 20-50 bar. The small particle size can be acquired by grinding but this is highlyenergy intensive and feeding is challenging. Torrefaction is a thermal pretreatment method carried out ataround 300 \ub0C which makes the biomass easier to grind, thus requiring less electricity, and makes thematerial less fibrous, while on the other hand requiring heat for the process. Pyrolysis is a process carriedout at around 500 \ub0C which lets the biomass decompose into a gaseous, a liquid and a solid part. Thesolid part can be grinded and fed into the gasifier together with the liquid and gaseous phases. This willfurther facilitate the feeding but with a further increased heat demand compared to torrefaction. Thedifferent pretreatment methods and their impact on the overall biorefinery energy system have beenstudied and evaluated using process integration methodology. The results show that the excess heat froman FT process with a biomass input of 300 MW(HHV) can replace the solid fuel boiler in a large chemical pulpand paper mill. With the preconditions given for this study, thermal pretreatment of the biomass can bebeneficial in terms of system thermal efficiency