Air distributor

P. E. Glascow and A. A. Murica, "Process and Mechanical Design Considerations for ECC Regeneration Air Distributors," presented at Katalistiks... 

Conveying-screen diyers are fabricated with conveyor widths from 0.3- to 4.4-m sections 1.6 to 2.5 m long. Each section consists of a sheet-metal enclosure, insulated sidew s and roof, heating coils, a circulating fan, inlet-air distributor baffles, a fines catch pan under the... 

There are two regions in the regenerator the dense phase and the dilute phase. At the velocities common in the regenerator, 2-4 ft/sec, the bulk of catalyst particles are located in the dense bed immediately above the air distributor. The dilute phase is the region above... 

Figure 4-51. Air distributor— pipe grid design version. (Source Enpro Systems, Channelview, Texas.)...

Figure 4-52. Air distributor— air ring design. (Source Vat-Vamp, Inc., Houston, Texas.)...

Figure 1-11. Examples of air distributors. (Top courtesy of Enpro Systems, Inc.. Channelview, Texas bottom courtesy of VAL-VAMP, Incorporated. Houston. Texas.) Note These distributors are upside down for fabrication...

PSD is an important indicator of the fluidization characteristics of the catalyst, cyclone performance, and the attrition resistance of the catalyst. A drop in fines content indicates the loss of cyclone efficiency. This can be confirmed by the particle size of fines collected downstream of the cyclones. An increase in fines content of the E-cat indicates increased catalyst attrition. This can be due to changes in fresh catalyst binder quality, steam leaks, and/or internal mechanical problems, such as those involving the air distributor or slide vah es. 

Air distributors. Improvements in the metallurgy, refractory lining of the outside branches, and better air nozzle design, combined with reducing L/D of the branch piping, have reduced thermal stresses, particularly during start-ups and upset conditions. 

The main purpose of the regenerator is to produce a clean catalyst, minimize afterbum, and reduce localized sintering of the catalyst. For efficient catalyst regeneration it is very important that the air and the spent catalyst are evenly distributed. Although, in recent years, the design of air distributors has improved significantly, the same cannot... 

A well-designed air distributor system has the following characteristics ... 

Two types of air distributors have been used in the past. In some of the original side-by-side units, both the air and the catalyst fltnvcd through the distributor. In virtually all the air distributors designed today, only air flows through the distributor. 

Design of mechanically robust spent catalyst and air distributors. 

Selective plugging/addition of air distributor jets to match the spent catalyst distribution... 

Other more capital-intensive modifications include installing a dedicated air blower for the spent catalyst riser. The spent catalyst riser often requires a higher back-pressure than the main air blower to deliver the catalyst into the regenerator. Therefore, less total combustion air would be available if one common blower is used to transfer spent catalyst and provide combustion air to the air distributors. 

A schematic diagram of the experimental apparatus is shown in Fig. 1. A rotating fluidized bed composes of a plenum chamber and a porous cylindrical air distributor (ID400xD100mm) made of stainless sintered mesh with 20(xm openings [2-3]. The horizontal cylinder (air distributor) rotates around its axis of symmetry inside the plenum chamber. There is a stationary cylindrical filter (ID140xD100mm, 20(o.m openings) inside the air distributor to retain elutriated fine particle. A binary spray nozzle moimted on the metal filter sprays binder mist into the particle bed. A pulse air-jet nozzle is also placed inside the filter, which cleans up the filter surface in order to prevent clogging. 

In wet granulation experiments, dried Ti02 particles were fed into the cylindrical air distributor (vessel), then the air distributor rotated and fluidization air was supplied. After a predetermined amount of binder liquid was sprayed, drying of products was conducted. 

The simulated FBAC consists of an acrylic main reactor (0.5m-H x 0.5m-W x l.Om-L), an air distributor system, particles feeding system including a feed hopper, a discharging sampler, a bag filter for capture of the elutriated fine particles and, pressure and flow rate measurement systems (Fig. 1). The air distributor system has ten air headers. An individual air header is connected with 5 air nozzles and can regulate the airflow rate. The opening ratio of the distributor is 2.1% and each nozzle has four holes for uniform air supply. To measure the pressure fluctuation at an individual air header, high frequency pressure transmitters were mounted at the approach and the exit headers of the FBAC. 

A schematic of the two-dimensional test apparatus with three draft tubes is shown in Fig. 12. The two-dimensional bed is constructed with transparent Plexiglas plates in the front and aluminum plates at the back with a cross-section of 50.8 cm by 2.54 cm and 244 cm high. The three draft tubes have a cross-sectional area of 2.54 cm by 2.54 cm each and 91 cm high. The three draft tubes divide the bed into four separate downcomers. The two downcomers next to the side walls have a cross-section of 5.9 cm by 2.54 cm while the remaining two downcomers have a cross-section exactly two times, i.e., 11.8 cm by 2.54 cm. If all three draft tubes operate similarly, the bed should have three identical cells, each with a single draft tube. The distance between the draft tube inlet and the air distributor plate was maintained at a constant spacing of 5.1 cm throughout the experiments. 

Figure 3. Thermal chamber. 1. Thermal chamber 2. Desorber 3. Silica gel cartridge 4. Flowmeter 5. Thermo relay 6. Fan 7. Contact thermometer 8. Air distributor 9. Drying column 10. Air distributor 11. Water pump.

Kurita, Y. and Sekiguchi, L, Effect of vortex orifice air distributor on granule growth in conical fluidized bed granulation with bottom entry spray, /. Ghent. Eng. Japan, 33 (2000) 57-66. 

IV. Effects of the characteristic of the fluidized bed, the atomization and the air distributor on the physical properties of granulates, Hungarian. Ind. Chem., 1 (1973c) 475-492. 

Replace a plate air distributor widi multiple air rings... 

Add multiple bed density taps to the regenerator to determine quality of fluidization and identify a damaged or partially plugged air distributor... 

Check the air line from the air blower to the air distributor for excessive pressure drop... 

Repair or revamp the air and/or spent catalyst distribntor(s) maintain ade-qnate air distributor pressure drop... 

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