Pyrolysis and Gasification in a Bench-Scale High-Pressure Fluidized-Bed Reactor

Abstract

A bench-scale high-pressure fluidized-bed reactor designed for pyrolysis, gasification, and combustion experiments (up to 1000 °C, 40 bar) has been constructed and commissioned. The system is intended to generate fuel reactivity data rapidly and cheaply, under realistic experimental conditions; it is relatively simple to construct and capable of operation by a single researcher. The reactor body (Incoloy Alloy 800HT, 34 mm i.d., 504 mm long) serves as the resistance heater and is designed to withstand the reaction pressure, obviating use of a “cold” pressure casing. The reactor is lined with a loosely fitting quartz tube to limit corrosion and catalytic effects. Sample (up to 2000 mg) is held between two air actuated valves and injected batchwise (“single-slug”) through a water-cooled probe. The design of the reactor allows determination of tar/oil and char yields. Exhaust gases are passed through a dryer before entering the analytical stage. The present report focuses on equipment design and preliminary data from pyrolysis and gasification experiments with Daw Mill coal (UK) at up to 1000 °C and 30 bar. Extents of gasification were calculated by subtraction of total volatile yields in CO2 from mass loss during pyrolysis in helium, performed under otherwise identical conditions. Combustion reactivities of chars were determined in an atmospheric pressure TGA instrument. A number of design adjustments have been described, enabling total volatile yields from the FB reactor to match those from a high-pressure wire-mesh reactor. As expected, tar yields from the fluidized-bed reactor were significantly lower than those from the wire-mesh instrument, due to longer residence times of volatiles in the bed of solids and the reactor freeboard.