Hydrogen for oil refining via biomass indirect steam gasification: energy and environmental targets

Artikel i vetenskaplig tidskrift, 2013

The energy and CO2 consequences of substitution of a fossil-fuel-based hydrogen production unit with a biomass-based process in a large European refinery are studied in this study. In the base case, the biomass-based process consists in atmospheric, steam-blown indirect gasification of air-dried woody biomass followed by necessary upgrading steps. The effect of gradually substituting the current refinery hydrogen production unit with this process on global energy and CO2 targets is estimated first. Few process concepts are studied in further detail by looking at different degrees of heat integration with the remaining refinery units and possible polygeneration opportunities. The proposed process concepts are compared in terms of energy and exergy performances and potential reduction in refinery CO2 emission also taking into account the effect of marginal electricity. Compared to the base case, an increase by up to 8 % points in energy efficiency and 9 % points in exergy efficiency can be obtained by exploiting process integration opportunities. According to energy efficiency, steam production appears the best way to use excess heat available in the process while electricity generation through a heat recovery steam cycle appears the best option according to exergy efficiency results. All investigated cases yield to significant reduction in CO2 emissions at the refinery. It appears in particular that maximal emission reduction is obtained by producing extra steam to cover the demand of other refinery units if high efficiency marginal electricity scenarios are considered.