Bo Bodenstein number

Figure 3.12 Residence time distribution in a micro reactor which is tightened by different means. ( ) Glued reactor without catalyst coating (X) glued reactor with catalyst coating ( ) reactor with graphite joints. Calculated curves for tubular reactors with the Bodenstein number Bo = 33 (solid line) and Bo = 70 (dashed line).

In order to evaluate the efficacy of the expanded bed technique the plate height (HETP), plate number (N), resolution (Rs), Bodenstein number (Bo), particle Peclet number (Pep) and axial dispersion coefficient (DJ have been calculated and compared with the corresponding values of a traditional HPLC column. N can be expressed by... 

Other factors limiting the overall rate can be external or internal mass transfer, or axial dispersion in a fixed-bed reactor. Pertinent dimensionless numbers are the Biot number Bi, the Damkohler number of the second kind Dan, or the Bodenstein number Bo (Eqs. (5.46)—(5.48)]. 

Characterizing the distribution according to the dispersion model yields a dimensionless number describing the degree of axial mixing within the bed. The Bodenstein number Bo relates convective transport of liquid to dispersion according to Eq. (9). 

In Fig. 5, the liquid phase axial dispersion coefficient Daxi and the Bodenstein number Bo calculated from this relationship according to Eqs. (9), (10) and (13) are plotted for a range of linear velocities used in fluidized bed adsorption. The physical parameters of the commercial Streamline SP adsorbents (average particle size 247 pm, average particle density 1143 kg/m3, terminal settling velocity 0.0044 m/s, n = 4.7 as described by Chang and Chase [37]) were... 

Axial Convective Diffusion. The variation in width, length and direction of individual channels formed by the interstices of the packing give rise to a dispersion which can be characterized by the dimensionless Bodenstein number. Bo, which is a similar number as the Peclet number but with the particle diameter as characteristic dimension... 

For single phase and two-phase flow through randomly packed beds the Bodenstein number is a function of the Reynolds number. A global correlation between Bo and Re, established by Gierman (2) on the basis of published data, is shown in Figure 4. 

The longitudinal dispersion for flow through a packed bed is correlated with the dimensionless axial Bodenstein number Bo, defined as Bo = dpu/Dapj. At the low linear velocities typical for the operation of the LFR, Bo tends to approach a constant value of approximately 0.4, as found by Gierman [12]. Hence, Eq. (10) can be written as... 

For the conditions in Example 14-1, we see that the number of tanks calculated from the Bodenstein number. Bo (i.e., Pe,), Equation (14-42), is 4.75, which is very close to the value of 4.35 calculated from Equation (14-12). Consequently, for reactions other then first-order, one would solve successively for the exit concentration and conversion from each tank in series for both a battery of four tanks in series and of five tanks in series in order to bound the expected values. 

Fig. 2 Model calculation for the CO decomposition. Model parameters Mean residence time, state of mixedness (described with Bodenstein number Bo) and temperature, Oj concentration 2 Vol% and H2O concentration 15 Vol%, Kinetic data see Table I...

An alternative model for real flows is the dispersion model with the model parameters Bodenstein number (Bo) and mean residence time t, The Bodenstein number which is defined as Bo = uL/D characterises the degree of backmixing during flow. The parameter D is called the axial dispersion coefficient, u is a velocity and L a length. The RTD of the dispersed plug flow model ranges from PFR at one extreme (Bo = °) to PSR at the other (Bo = 0). The transfer function for the dispersion model with closed-closed boundaries is [10] ... 

Dimensionless parameters represent ratios of different mass transport and reaction phenomena. One example is the Bodenstein number (Bo, sometimes called the axial Peclet number), which is the ratio of convection rate to axial dispersion ... 

Bo = - k- ax Dal = x/tT Dali = tm/tT pP — ud 1 e x Re = c AtJEj ° RT% Qr — -L. J Dm Sh = krt CX dVk<7 DnV T Dm Bodenstein number Capillary number first Damkohler number second Damkohler number axial Peclet number Reynolds number (channel) particle Reynolds number heat production potential Schmidt number Sherwood number (channel) Sherwood number (particle)... 

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