Development of a to-scale fluid mixing visualization process for analysis of cold-flow mixing

Abstract

Torrefaction is a process by which low energy density biomass is converted to a higher energy density biofuel, called char. Small-scale torrefaction systems are a promising technology for developing countries where large amounts of biomass go underutilized due to inaccessibility and transportation costs. A by-product of torrefaction is volatile gas, thus, a system may be built to harness this otherwise wasted energy and use it to power the treatment of biomass. An efficient fuel-mixer and combustor system which recycles this volatile gas is central to the overall torrefaction system efficiency. In order to analyze the mixing efficiency in a swirl-type mixer such as the design proposed for the small-scale torrefaction system, a project was designed to visualize mixing in an annular mixer. A to-scale cold-mixing system was constructed from two cylinders, three pump systems, as well as an imaging system using a retrofitted green laser. The final model is a tested and proven system for flow imaging of two cold flows within a to-scale fuel-mixer.