Catalyst diameter

The effect of mass velocity on the conversion rate was studied by using a tube of fixed diameter that was filled with a sample of a given catalyst diameter to give beds with volumes of either 10 or 20 cm3. At a constant ratio of catalyst weight to reactant feed, this method of varying the bed volume has the effect of varying the mass velocity through the bed. 

Figure 5.3-8. Details of the chum-turbulent flow regime of BSCR according to Inga [1], (db)0-gas bubble size at atmospheric conditions in the absence of solid particles, (d, )ps- bubble size at the operating pressure and catalyst concentration. Column height = 2.8 m, internal diameter = 0.316 m. P < 8 bars. Organic media, catalyst diameter < 100 pm.

Reactor Diameter (ft) Range of Bed Height (ft) Catalyst Diameter (in.)... 

At high liquid mass velocities, good contacting effectiveness can be obtained even for reactor/catalyst diameter ratios as low as 1.4/1. 

Denoting the friction coefficient between mat and substrate by p., vibrational acceleration by a, catalyst density by pr, catalyst diameter and length by d and , respectively, and back pressure by pb, Eq. (34) yields... 

Tab. 4. Oxidation of DPS on commercial particles of vanadium catalyst. Diameter of reactor 5 cm...

Let us demonstrate Fig. 1.8 with an example. A process for steam reforming naphtha is carried out at HjO/HC - 10, SOO C, and 40 atm total pressure. A Ni/AIjOj catalyst, diameter 4 mm, 0 0.6, was tested in a pilot unit and gave 75% conversion at a GHSV of 5000 hr. For pressure drop reasons, the process designer wants to double the size of the particle but keep all conditions the same. Will this change the conversion ... 

Catalyst diameter 1 to 5 mm. Gas with fixed catalyst bed residence time <1 s favored if the life of the catalyst is >3 months select fluidized (Section 16.11.6.27) or slurry reactors (Section... 

Shell-and-tube exchanger with reactants and catalyst inside the tubes, 250 to 400 m /m. Tube diameter <50 mm. Gas with fixed bed of catalyst use high mass gas velocity to improve heat transfer kg/s m > 1.35. To ensure good gas distribution and negligible backmixing, Pe > 2 height/catalyst particle diameter H/D > 100 and D/D < 0.10. Gas velocity 3 to 10 m/s residence time 0.6 to 2 s. Heat transfer coefficient U = 0.05 kW/m K. For fast reactions, catalyst pore diffusion mass transfer may control if catalyst diameter is >1.5 mm. Liquids with fixed bed of catalyst to minimize backmixing, Pe> use UD > 200 and D/D <0.10. Liquid velocity 1 to 2 m/s residence time 2 to 6 s. Heat transfer coefficient U = 0.5 kW/m -K. 

For adiabatic operation with exothermic reactions, limit the height of the bed to keep temperature increase < 50 °C. Tube diameter < 50 mm to minimize extremes in radial temperature gradient. For fast reactions, catalyst pore diffusion mass transfer may control if the catalyst diameter >1.5 mm. 

Liquid with catalytic solid catalyst diameter, < 0.1 mm surface area solid 500 nf/nf. 

Gas-liquid with catalyst solid catalyst diameter, 50-1200 surface area solid 500... 

Gas plus catalyst soUd Usually BFB. For fast reactions, gas film diffusion may control and catalyst pore diffusion mass transfer may control if catalyst diameter >1.5 mm. Heat transfer heat transfer coefficient wall to fluidized bed is 20-40 X gas-wall at the same superficial velocity, h = 0.15-0.3 kW/m K. Nu = 0.5-2. Heat transfer from the bed to the walls U = 0.45 to 1.1 kW/m °C. from bed to immersed tubes U = 0.2 to 0.4 kW/m °C from solids to gas in the bed U = 0.017 to 0.055 kW/m °C. Fluidized bed usually expands 10-25 %. Backmix type reactor which increases the volume of the reactor and usually gives a loss in selectivity. Usually characterized as backmix operation or more realistically as a series of CSTR if the height/diameter > 2 Usually 1 CSTR for each H/D= 1. If the reactor operates in the bubble region, then much of the gas short circuits the catalyst so the overall apparent rate constant is lower by a factor of 10. 

The reactor consists of a quartz tube (length = 62 cm, ID = 20 mm) placed in an oven for thermal insulation and reaction light-off. The monolithic honeycomb catalyst (diameter = 19 mm, variable length) is placed 230 mm downstream of the reactor inlet. For increased insulation, the part of the reactor tube, in which the catalyst is positioned, is wrapped with a 1-cm-thick layer of quartz wool. Uncoated monoliths up- and downstream of the catalyst are employed as heat shields (front heat shield (FHS) and back heat shield (BHS), respectively). The FHS also serves as support for the probe applied in the samphng technique. To prevent a gas by-pass between monoliths and quartz tube, the heat shields and the catalyst are wrapped with... 

---