Gas Flow Distribution

The axial gas flow distribution in the annulus in a spouted bed under the condition Hsp = Hm can be derived by considering the boundary condition of U = Umf at zs = Hm, 

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H. Weltans and co-workers. Optimisation of Catalytic Converter Gas Flow Distribution by CFD Prediction, SAE 930780, Society of Automotive Engineers, Warrendale, Pa., 1993. 

Poor gas flow distribution High level of lines in hopper Improper control settings Rapping system degradation Process gas conditions PM fines electrical resistivity... 

Figure 9.14. Gas flow distribution in the bed based on the two-phase model.

Predicting Gas Flow Distribution Between the Phases in FBC. In FBC s Role in the World Energy Mix. Ed. L. Rubow. New York ASME. 

The flow field and EB/GDL must be matched for optimum performance and durability. Designing for the most uniform gas flow distributions and effective water management should translate into the most... 

Gas distributors are also an important component of packed bed columns and influence phase distribution. The design issue is to ensure a uniform gas flow distribution through the reactor or a necessary gas flow ratio relative to the liquid phase. The liquid-gas ratio is only important if the process requires a chemical reaction of the liquid phase induced by the gas phase. The packing, on the other hand, is responsible for the pressure drop profile and, hence, the downstream gas-phase distribution. 

A. Operation Near Atmospheric Pressure. The simplest approach to hydrogen header control at very low pressure uses large water-sealed vents designed to maintain a fairly precise back-pressiure with little or no fluctuation. Figure 11.35 shows such a vent. Section 9.1.10.1 gives design details for this type of system as a pressure-relief device with little heed to gas flow distribution. For more precise control, it is important to distribute the gas as small bubbles over a wider area of the water seal (10-20 nun deep) in order to provide minimum pressure drop and fluctuation in flow. 

Fig. 31. Flue gas flow distribution (a) correct discharge design and (b) absence discharge...

As presented in the previous paragraphs, mass transport processes are relevant for different scales, from the processes inside the electrode up to the gas flow distribution in a complete stack. When performing experimental analysis of mass transport, the choice of cell/stack hardware will determine which transport processes will be included in the experiment. Some possible hardware designs (c.f. Fig. 5) are listed here ... 

Particle velocimetry measurements for the analysis of the gas flow distribution [20]... 

To improve the consistency of density of the discharged material To secure mass flow at reduced wall inclinations To expand the flow channel To improve the extraction pattern To reduce overpressures on feeders To save headroom/secure more storage capacity To counter segregation To blend the contents on discharge To improve counter-current gas flow distribution To prevent blockages by lumps or agglomerates In the body of the hopper... 

H. Weltens, H. Bressler, F. Terres, H. Neumaier, H. Neumaier, and D. Rammoser. Optimisation of catalytic converter gas flow distribution by cfd prediction. SAE Technical Paper, 930780, 1993. 

Due to its monolithic structure, the catalyst can be represented by a single monolith channel (Fig. 22.1) if a uniform gas flow distribution over the whole catalyst frontal area is assumed [15-18]. This is nearly the case for the major part of operation, justifying a simplihed ID consideration instead of a 2D model. 

Valenzuela JA, Glicksman LR. Gas flow distribution in a bubbling fluidized bed. Presented at AIChE 74th... 

Olowson PA, Almstedt AE. Influence of pressure and fluidization velocity on the bubble behaviour and gas flow distribution in a fluidized bed. Chem Eng Sci 45 1733-1741, 1990. 

The gas flow distribution through the catalyst is the most critical feature in the design of an adiabatic bed. Obviously, when the residence times of equal amounts of synthesis gas in contact with the catalyst are significantly different, they pass through different profiles of conversion and temperature along the bed. Those portions of gas that spend a shorter time in contact with the catalyst than the optimum cannot be compensated, in terms of total conversion, by the other portions which stay longer, because of equilibrium constraints. 

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