Bed flow

The pressure is higher at the bottom of the sohds draw-off pipe due to the relative flow of gas counter to the sohds flow. The gas may either be flowing downward more slowly than the solids or upward. The standpipe may be fluidized, or the solids may be in moving packed bed flow with no expansion. Gas is introduced at the bottom (best for group B) or at about 3-m intervals along the standpipe (best for group A). The increasing pressure causes gas inside and between... 

Pressure Drop Some models regard trickle bed flow as analogous to gas/liquia flow in pipe lines. Various flow regimes may exist like those typified in Fig. 23-25/ but in a vertical direction. The two-phase APcl is related to the pressure drops of the individual phases on the assumptions that they are flowing alone. The relation proposed by Larkin et al. (AJChE Journal, 7, 231 [1961]) is APaj 5.0784... 

Heated air to regenerate bed flows through rhis area of continuously rotating desiccant bed... 

Moulijn et al. (33) studied the reactions of some linear alkynes over a W08-Si02 catalyst in a fixed-bed flow reactor. Besides metathesis, cyclotrimerization to benzene derivatives occurred. Thus, propyne yielded, in addition to metathesis products, a mixture of trimethylbenzenes. From this an indication of the mechanism of the metathesis of alkynes can be obtained. 

In Fig. 1, a comparison can be observed for the prediction by the honeycomb reactor model developed with the parameters directly obtained from the kinetic study over the packed-bed flow reactor [6] and from the extruded honeycomb reactor for the 10 and 100 CPSI honeycomb reactors. The model with both parameters well describes the performance of both reactors although the parameters estimated from the honeycomb reactor more closely predict the experiment data than the parameters estimated from the kinetic study over the packed-bed reactor. The model with the parameters from the packed-bed reactor predicts slightly higher conversion of NO and lower emission of NHj as the reaction temperature decreases. The discrepancy also varies with respect to the reactor space velocity. 

The kinetic parameters estimated by the experimental data obtained frmn the honeycomb reactor along with the packed bed flow reactor as listed in Table 1 reveal that all the kinetic parameters estimated from both reactors are similar to each other. This indicates that the honeycomb reactor model developed in the present study can directly employ intrinsic kinetic parameters estimated from the kinetic study over the packed-bed flow reactor. It will significantly reduce the efibrt for predicting the performance of monolith and estimating the parameters for the design of the commercial SCR reactor along with the reaction kinetics. 

Fig. 1. Prediction of the model for 10 and 100 CPSI honeycomb reactors extruded with the ViOs/sulfated Xi02 catalyst. (—, prediction with the parameters estimated from the experimental data over a packed-bed flow reactor —, prediction with the parameters estimated from the experimental data over a honeycomb reactor).

Smelter, 1989 with single bed, flow reversal used in second stage with S02 cone. 0-1% ... 

One major difference between pneumatic transport and hydraulic transport is that the gas-solid interaction for pneumatic transport is generally much smaller than the particle-particle and particle-wall interaction. There are two primary modes of pneumatic transport dense phase and dilute phase. In the former, the transport occurs below the saltation velocity (which is roughly equivalent to the minimum deposit velocity) in plug flow, dune flow, or sliding bed flow. Dilute phase transport occurs above the saltation velocity in suspended flow. The saltation velocity is not the same as the entrainment or pickup velocity, however, which is approximately 50% greater than the saltation velocity. The pressure gradient-velocity relationship is similar to the one for hydraulic transport, as shown in... 

Questions as to the validity of the theory supporting Horio s development are based on deficiencies of the CAFM to fully describe circulating fluidized bed flow and the lack of justification for the premise that the five characteristics comprise all that is of interest in a circulating fluidized bed. In particular, the assumption of pressure drop minimization, although convenient, is not justified physically. 

The catalytic test of propane ODH reaction was performed in the 350-600°C range in a quartz fixed bed flow reactor with on line GC analysis. The free volume of the reactor after the catalyst bed was filled with quartz particles to minimize the homogeneous reactions. All the testing set was placed in a thermostat with heated lines to the gas chromatographs at about 100°C to prevent water condensation. The feed gas composition was C3H8/02/N2 = 20/10/70 vol.% at total gas flow 50 cm3 min-1. Catalyst fractions of 0.2-0.315 mm particle size and of 80 mg weight were loaded into the reactor. Before the reaction, the catalyst samples in the reactor were kept under airflow at 600°C for lh. 

C. Packed Bed CFD Simulation Issues 1. Packed Bed Flow Regimes... 

Fig. 8. CH4 conversion as a function of the number of CH4/O2 pulses for partial oxidation of CH4 catalyzed by Ni/La203. Reaction conditions temperature, 873 K catalyst, 20 mg of 20 wt% Ni/La203 loaded in a fixed-bed flow reactor feed gas, 0.9 mL CH4/02 (molar ratio 2/1) in each pulse carrier gas, helium (flow rate, 100 mL min-1) (134).

Fig. 11. CO formation rates determined from reactant conversions and product selectivities in a fixed-bed flow reactor for C02 reforming of CH4. The catalysts were nickel supported on La203, y-Al203, or CaO. Each catalyst contained 17 wt% Ni. Before reaction, the catalyst was reduced in flowing H2 at 773 K for at least 5 h and then at 1023 K for 2 h. Reaction conditions pressure, 1.0 atm temperature, 1023 K feed gas molar ratio, CH4/C02/He = 2/2/6 GHSV, 1,800,000 mL (g catalyst)-1 h-1 (227).

The catalyst is a fixed bed. Flows of gas and liquid are cocurrent downwards. Liquid feed is at a such a low rate that it is distributed over the packing as a thin film and flows by gravity, helped along by the drag of the gas. This mode is suited to reactions that need only short reaction times, measured in seconds, short enough to forestall undesirable side reactions such as carbon formation. In the simplest arrangement the liquid distributor is a... 

We have examined the rate constants for disproportionation and isomerization for a variety of zeolites, using a commercial-type feed containing 70% m-xylene and 30% o-xylene in a fixed-bed flow reactor. The results, listed in Table I, show the exceptionally low disproportionation/isomerization selectivity of ZSM-5 relative to synthetic faujasite. Synthetic mordenite and ZSM-4 have intermediate selectivities. 

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