Heat transfer and flow characterization studies in a moving and stirred bed vacuum pyrolysis reactor handling polydispersed softwood bark feedstock

In this work, the heat transfer and flow characteristics have been studied in a pilot scale moving and stirred bed vacuum pyrolysis reactor fed with polydispersed softwood bark feedstock. Thermo-physical properties such as particle density, particle thermal conductivity and specific heat of softwood bark and therein derived softwood char have been experimentally measured and are reported for the first time. A new comprehensive unified approach using Linear Packing Theory and Unit Cell Model, is proposed for calculation of the effective thermal conductivity (ETC) of polydispersed packed beds. This approach has been validated on binary and ternary beds and has been applied to higher order beds of softwood bark and softwood char. The ETC of polydispersed beds of softwood bark and softwood char have been predicted as a function of particle size distribution. Using the polydispersed fluorescent tracers and residence time distribution technique, the flow characteristics of polydispersed particle of softwood bark have been studied in a pilot scale reactor. Single parameter dispersed plug flow model and identical CSTRs-in-series models have been successfully used to fit the experimental data.