Excess Gas Flow Research Articles

Large particle fluidisation

The fluidization characteristics of large particles (1000–2000 μm) have been studied using bed depths up to 30 cm in equipment having a cross-section 61 × 61 cm. Results are compared with data obtained earlier using a two-dimensional bed. The size of bubble eruptions, together with bubble frequencies and concentrations at the bed surface, were measured from cine film. Visible bubble flow rates were calculated using these data and found to be about 55 per cent of the excess gas flow. Empirical equations are presented relating these parameters with bed height and gas flow rate. The velocities of single bubbles measured using an inductance probe and simultaneous cine photography, agreed well with the Davies—Taylor equation. An unusual bubble formation mechanism gave rise to horizontally aligned swarms of bubbles. These appear to be peculiar to large particle systems and result in large vertical oscillations of the bed surface and severe vibration. Another unusual feature of this large particle system was that non-coalescing bubbles were observed to expand rapidly as they rose through the two-dimensional bed.

A flow-through gas adsorption balance

The balance described is intended for isothermal studies of moderately fast gas-solid interactions, such as adsorption, in which the heat of reaction is not negligible. The sample of solid is contained in a chamber which is integral with a hollow balance beam. The gas flow rate through the chamber is adjusted to minimize the resistance to heat and mass transfer in the boundary layer. The excess gas flow acts as a heat sink. The deflection of the beam under load changes is sensed by a frequency modulation capacitance system. Load changes of 15-250 mg give full scale deflection on a chart recorder and direct calibration and range reset by riders are available at any time. The balance has been used extensively in measurements of gas adsorption and diffusion in porous solids.