Research Scientist Petteri Kangas will
present his dissertation on modelling the super-equilibria in thermal biomass
conversion in Åbo Akademi on 28 May, 2015.
Black liquor from
kraft pulp mills, bark and forest residues covers over a fifth of domestic
energy demand in Finland. These bioenergy processes seldom operate flawless and
thus different kind of emissions, particles and tars are observed in the
processes. In addition the precipitations and corrosion are eroding process
equipment. These problems are often caused by the non-equilibrium state of
chemical process: certain compounds are accumulating into the process and thus a
super-equilibrium state is formed.
A new computational method is
presented in this study for describing these super-equilibrium states during the
thermal biomass conversion processes. This method allows concurrent calculation
of dominant chemical reactions, heat generation of process, and relevant state
properties. This work is based on the novel constrained free energy method (CFE)
developed at VTT. The method has been previously utilised in the fields of paper
making, metallurgy and chemical industry. This study presents a new application
area in energy production for the CFE-methodology.
In the study, it is
shown that presented methodology is well applicable for the high temperature
processes such as combustion of black liquor and wood, biomass gasification, and
nitric oxide emissions. Here a local super-equilibrium state is a valid
assumption and limited number of reactions is used for defining constraint
chemical state. It is shown that constraints can be defined based on the
industrial measurements, experimental models and reaction kinetics models.
Limitations for the presented methodology were found in low temperature
processes such as torrefaction and pyrolysis, or if the number of constraints
were too large.
Process engineering and studies related to combustion,
gasification and biofuel are possible applications areas for the methodology in
the future. The calculation method can be seen as a good alternative for
traditional mechanistic and phenomenological models by combining the benefits of
both in a single elegant solution.
Petteri Kangas will present his dissertation
Modelling the super-equilibria in thermal biomass conversion - Applications and
limitations of the constrained free energy method on 28 May, 2015 at 12 at Åbo
Akademi (address: Piispankatu 8, Turku).