A TCD-based technique for experimental study of mass transfer in a gas–solid fluidized bed with liquid injection

• A TCD-based technique was developed for studying mass transfer in a fluidized bed.
• Trends in vapor release fraction were obtained from TCD concentration curves.
• The method could be applied to studies of mass transfer in other reaction systems.

A technique using the measurement of gas phase concentrations for the study of mass transfer in gas–solid fluidized beds has been developed. This method uses thermal conductivity detectors (TCDs) to measure local concentrations of a gaseous species as it evolves from a continuously sprayed binary liquid into the system. The binary liquid, a mixture of paraffin wax and n-heptane, was chosen to be a low temperature analogue of bitumen, which is thermally converted into lighter liquid products using the FLUID COKING™ process. In both the commercialized process and the low temperature analogue, the volatile fraction of the liquid feed is released into the gas phase, while the heavy components remain in the bed and eventually solidify. The n-heptane vapor concentration was continuously measured using three TCDs, sampling from different locations in a 4-m tall, 0.4 m × 0.1 m fluidization column. By varying operating conditions such as the superficial gas velocity, bed temperature, and air-to-liquid ratio, the present work successfully demonstrated the ability to measure changes in mass transfer conditions in a fluidized bed continuously and accurately with fast response.

Typical TCD response curves during liquid injection into a fluidized bed.Figure optionsDownload as PowerPoint slide