Conical distributor plate

The gas bypassing results obtained from tracer gas injection studies for a flat and a conical distributor plate are shown in Fig. 4. Theflow ratio, FR, is defined as the total gas flow supplied through the draft tube gas supply and the concentric solids feeder divided by the total gas flow supplied through the downcomer gas supply. The A and Y are the actual amounts of gas passing up the draft tube and the downcomer, respectively, determined from the tracer gas injection studies. If FR equals A Y. there is no gas bypassing. If FR is less than A Y. some of the flow supplied through the downcomer gas supply passes into the draft tube. If FR is larger than A/7, the reverse is true. 

Figure 5. Gas bypassing characteristics of conical distributor plates of different design configurations (No. 3 and No. 7 flows).

Aeration of the downcomer can also be provided with a conical distributor plate (No. 3 flow) with greatly increased solids circulation rate as shown in Fig. 8. At lower downcomer aeration, the solids circulation rate is essentially similar to that without downcomer aeration at a distributor plate location ofL = 21.7 cm. At higher downcomer aeration, however, a substantial increase in solids circulation rate is realized with the same total gas flow rate. Apparently, a minimum aeration in the downcomer is required in order to increase substantially the solids circulation rate. For polyethylene beads, this critical aeration rate is at a downcomer superficial... 

Effect of Distributor Plate Design. Both conical distributor plates of included angles of 60° and 90° were used. They do not seem to affect the solids circulation rate as shown in Fig. 10. Proper location of the distributor plate and the gas nozzle, however, substantially increased the solids circulation rate. 

Except for the conical distributor plate, no simple gas bypassing relationship exists. No rigorous theoretical model has thus far been proposed. The quantitative gas bypassing information is usually determined experimentally. Qualitatively, the gas bypasses from the draft tube side into the downcomer side for small draft-tube-to-downcomer area ratios and vice versa. Gas bypasses exclusively from the downcomer side to the draft tube side when the distance between... 

Figure 4. Summary of gas bypassing data for a conical and a flat distributor plate.

Effect of Distance between the Distributor Plate and the Draft Tube Inlet Figure 4 clearly indicates that the gas bypassing phenomenon depends not only on the design parameters but also on the operating conditions. For the conical plate at a distance from the draft tube inlet of L = 21.7 cm, gas bypasses from the draft tube side to the downcomer side at a high flow ratio and reverses the direction at a low flow ratio. When the conical plate was moved closer to the draft tube inlet atL = 14.1 cm, the gas bypassing direction was exclusively from the downcomer side to the draft tube side. 

The fluidised bed reactor is a vertical pressure vessel with a total height of up to 40 m. A fluidised bed of polymer particles in gaseous ethylene is maintained by a recycle compressor. The ethylene recycling gas enters the reactor through a distributor plate at the bottom to achieve an even gas flow over the entire cross-section and to hold the particles when the gas flow is turned off. In the characteristically conical upper part of the reactor, the gas velocity decreases with the increasing diameter of the reactor to keep the particles in the fluidised bed. The gas leaves the reactor at the top. It is cleaned from entrained particles by a eyelone, the reaction heat is removed by a recycle gas cooler and the gas is then routed back to the bottom reactor inlet. 

A slightly conical process chamber with a tubular partition placed in the center of it, at some distance from the distributor plate ... 

The air-life fermentor consists of two concentric columns. The outer column has a conical bottom section with a perforated plate acting as a gas distributor. The inner column is positioned over this plate. Compressed air, enriched with CO2, is used to lift a suspension of mineral and bacterial culture in medium through this inner column. The suspension then falls to the reservoir and is air-lifted up the column again. The air-lift fermentor provides a good supply of oxygen and is able to keep high pulp densities (25%) of ore fully suspended in the medium. An illustrative example is provided by the work of Helle and Onken (47). Pachucas operate in a similar fashion to the air-lift fermentor, but there is no inner column. Air enters at the conical base of the reactor, aerates the medium, and suspends and circulates the mineral particles. Pachucas are useful reactors for building up culture stocks. 

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