The rational scale-up of gas fluidized bed reactors from laboratory units to commercial size requires an understanding of the grid support plate. This is particularly true in fluid bed reactors because, in many cases, most of the reaction occurs at or near the grid.

Three aspects of grid behaviour have been studied experimentally;​ namely, the momentum, heat, and mass transfer from a grid jet to a large fluid bed of fresh cracking catalyst.

First, an investigation was made into the axial distribution of longitudinal momentum for air jets issuing from vertical long nozzles into an 11 in. diameter and 3 ft. deep bed close to the minimum fluidizing velocity. The test nozzle diameter was varied from 1/4 to 1 1/2 in. and the nozzle velocity from 50 to 300 ft./sec., which is within the range of industrial practice. A modified theory of Abramovich was compared with the experimental results. A statistical analysis of the axial data for initial jet velocities between 150 and 300 ft./sec. led to the following relationship:​

[equation]

where No is the Nozzle number. Also, similar experiments were made to measure the axial distribution of longitudinal momentum for grid jets issuing from single and multi-hole grid plates of various thicknesses. In addition, the axial dissipation of vertical air jets loaded with cracking catalyst and issuing into air and into the fluid bed were studied. Furthermore, the shape of the hydrodynamic boundary of an air jet dissipating into a fluid bed was compared to that given by the modified theory of Abramovich.

Second, heat transfer from a vertical long nozzle grid jet within a 2 ft. diameter and 4 ft. deep fluidized bed was studied. In this case, the test nozzle diameter was varied from 1/4 to 1 in. and the nozzle velocity from 50 to 250 ft./sec. The axial temperature data have been related to a Froude, a Nozzle, and a Reynolds number in a general correlation as follows:​

[equation]

Moreover, a simple jet quenching model was proposed that allows the jet quenching time to be calculated. Within the more important jet quenching zone, the radial profiles were described by a curve of the form:​

[equation]

Finally, the thermal boundary of the jet mixing region was defined.

Third, mass transfer from a vertical grid air jet within the 2 ft. diameter fluid bed was studied. In these experiments, the nozzle diameter varied from 1/4 to 3/4 in. and the nozzle velocity from 50 to 300 ft./sec. Five mole percent of carbon dioxide in air was used as the jet gas. Gas samples were analyzed by means of a gas chromatograph equipped with a thermal conductivity detector. The axial concentration data were also related to a Froude, a Nozzle, and a Reynolds number in a general correlation:​

A simple mass dissipation model was proposed which enabled the mass dissipation times for a grid jet to be computed. Within the jet region 3 < No < 7, the radial distributions of concentration were described by a curve having the form:​

[equation]

Finally, the concentration boundary of the jet mixing region was defined and compared with the hydrodynamic and thermal boundarie