Fluidization bulk density

The ratio of tapped to poured (or perhaps fluidized) bulk density. 

Related Calculations. Another approach that can be used to assess whether intermixing will occur is to compare the fluidized bulk densities of the two adjacent layers (e.g., upper 450 mm of sand and lower 100 mm of anthracite). 

Dye provided limited process conditions, but based on a catalyst feed rate of 1.33 Ib/hr and an average catalyst residence time of 1.5 hours, the production rate can be estimated from the volume of the reaction zone. Assuming a fluidized bulk density of about 12 Ibs/ft, the reaction zone would contain about 7,000 lbs of polyethylene. A production rate of approximately 4,700 Ib/hr would be needed to accoxmt for a 1.5 hr catalyst residence time. Polymerization temperature was 210°F and ethylene pressure was 450 psi. 

There are limits as to the ethylene partial pressure that may be used to increase reactor production rates. For example, an increase in ethylene partial pressure above a certain amount may significantly reduce polymer particle morphology, leading to low resin settled bulk density (post reactor) and low fluidized bulk density within the reactor. Low resin bulk density will reduce conveying rates of granular polyethylene as the resin is transferred to another production step. Lower fluidized bulk density will reduce the amount of granular polyethylene in the reactor, which will reduce catalyst residence time (lower catalyst productivity) at a constant production rate. Limits on comonomer feed rates may also limit the ethylene partial pressure obtainable in order to produce polyethylene with... 

Bulk density can be used to troubleshoot catalyst flow problems. A too-high ABD can restrict fluidization, and a too-low ABD can result in excessive catalyst loss. Normally, the ABD of the equilibrium catalyst is higher than the fresh catalyst ABD due to thermal and hydrothermal changes in pore structure that occur in the unit. 

Apparent Bulk Density—ABD. The density of the catalyst at which it is shipped either in bulk volume or bags. It is density of the catalyst at minimum fluidization velocity. 

In some cases, especially for very fine powders, researchers have looked at other properties to explain or classify product behavior. For example, Gel dart et al. (1984) have found that the ratio of tapped to aerated bulk density provides a good indication of the likely fluidization characteristics of fine and cohesive powders. 

Perhaps the greatest difficulty in predicting fluidization performance via the Geldart (1973) classification is deciding on a single diameter to represent the complete material, especially if the product possesses a wide particle size distribution. This is supported to some extent by the more recent bulk density approach proposed by Geldart et al. (1984). 

Firstly, as described previously, characterize the bulk solid to be conveyed by undertaking particle size, particle density, loose-poured bulk density, fluidization and deaeration tests. 

When evaluating a material for the purpose of establishing dense-phase and long-distance suitability, it is important to undertake all the necessary tests (e.g., particle sizing, particle and bulk densities, fluidization and deaeration). Also, if possible, it is useful to compare such results with those obtained on previously conveyed similar materials (e.g., fly ash). However, it should be noted that such an evaluation only is a qualitative one and it is not possible to predict say, minimum air flows or pipeline pressure drop based on such data (i.e., pilot-scale tests normally are required to confirm minimum velocities, friction factors, etc., especially over long distances and for large-diameter pipes). 

Inlet temperature is 898 K, operating pressure is 1.2 atm, charge rate is 20 lbmol of ethylbenzene and 400 lbmols of steam. Under fluidizing conditions bulk density of the bed is 25 lb/cuft. Conditions are adiabatic. 

Taking the density, thermal conductivity and latent heat of fusion of the peas to be 1050 kg m , l.OWm K and 250kjkg respectively and the bulk density within the fluidized bed as 525kgm , the Plank/ Nagaoka model can be used to estimate the time required for the product outlet temperature to reach -20°C. 

Assuming a catalyst density at flowing conditions in the standpipe of about 90% of the catalyst bulk density, the amount of excess gas above minimum fluidization that is entrained with the catalyst into the standpipe may be calculated. Sufficient aeration should be added to sustain minimum fluidization along the length of the standpipe. 

Typical fluid-bed processor elements can be seen in Figure 1. The fluidizing gas enters the bed at the bottom through an air distributor. The gas passes up through the bed of solids, causing it to fluidize. This gas/solid mixture behaves much like liquid of similar bulk density. Above the fluidized bed, a freeboard section (expansion chamber) is provided to slow down the... 

If the coating and core bulk densities are similar, coatings of 100-150% (based on starting weight) may be applied. Fluidization is also affected by the air distribution plate configuration and the partition height. The finer the particles to be coated are, the less will be the open area in the downbed section of the orifice plate and the smaller the gap between the partition and orifice plate. 

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