Electrical utility companies are looking into the possible use of atmos$-$

pheric fluidized bed coal combustors $($AFBC$)$ as a clean, efficient way to

produce high$-$pressure steam. One design of AFBC consists of a very large

$(4m25m)$ but shallow $(1\mathrm{.}5m)$ fluidized bed traversed with hundreds of

$5-cm$ heat exchange tubes. The bed material is to consist of decomposed

limestone$,$ ash, and burning coal, and will be kept at $840C.$

Many problems, such as nonuniform gas feed, changing solid compo$-$

sition as it slowly moves across the combustor, channeling of bed material

between the various tube bundles, and so on$,$ are anticipated with such a

unit. All this recommends preliminary studies in a relatively cheap cold

model.

For a cold scale model of this monstrous unit, suggest what solids,

fluidizing gas, exchanger tube size, and bed height to use.

Data

For the AFBC bed solids: $\frac{?}{\text{b}\text{a}\text{r}}({)}_s=2500k\frac{g}{m^3}\frac{,}{b}ar(d{)}_p=2mm$

For the gas passing through the bed at $840C$ :

${}_g=0\mathrm{.}37k\frac{g}{m^3},=4\mathrm{.}3{10}^{-5}k\frac{g}{m}*s$