Minor effect—Bed pressure

Industrial catalyst bed pressures are typically 1.1 to 1.4 bar. They are highest in T catalyst beds and lowest in last beds - due to dissipation of mechanical energy as gas passes through the beds. 

The effect of bed pressure on intercept % SO2 oxidized is shown in Fig. 18.4. It is small, especially after 3 catalyst beds. 

1 through 18.4 specify the same pressure in all 3 catalyst beds. This specification is not necessary - the Appendix S worksheet can specify individual bed pressures. It is, however, convenient for graphing. 

The difference between the results is tiny, especially after 3 beds. 

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Leading characteristics of five main kinds of reactors are described following. Stirred tanks, fixed beds, slurries, and three-phase fluidized beds are used. Catalyst particle sizes are a compromise between pressure drop, ease of separation from the fluids, and ease of fluidization. For particles above about 0.04 mm dia, diffusion of liquid into the pores and, consequently, accessibility of the internal surface of the catalyst have a minor effect on the overall conversion rate, so that catalysts with small specific surfaces, of the order of 1 m2/g, are adequate with liquid systems. Except in trickle beds the gas phase is the discontinuous one. Except in some operations of bubble towers, the catalyst remains in the vessel, although minor amounts of catalyst entrainment may occur. 

Assuming the cross-sectional area of the column is unchanging with bed level, e.g., the bed is untapered, then, neglecting minor bed entrance, bed exit, and wall friction effects, the pressure drop, — Ap, due to the liquid motion is equivalent to the frictional pressure drop, — Apf, due to flow through the bed of particles. A typical plot of — Apf as a function of liquid velocity is shown in Fig. 2. 

DA also causes the release of NE from nerve terminals, which contributes to its effects on the heart. DA usually increases systolic blood pressure and pulse pressure and either has no effect on diastolic blood pressure or increases it slightly. Total peripheral resistance usually is unchanged when low or intermediate doses of DA are given, probably because of reduced regional arterial resistance in some vascular beds (e.g., mesenteric and renal) with minor increases in others. At high concentrations, DA activates vascular receptors, leading to more... 

The reactivity of limestones with respect to the reaction with sulfur dioxide varies markedly. For example, for a given fluidised bed combustor, the Ca S stoichiometric ratio required to achieve a 90 % reduction in sulfur emission at atmospheric pressure, varies from 2 to 5. The reasons for such a variation are not understood, but are likely to include decrepitation, catalytic effects of minor components such as iron, and the structure of the limestone and lime [12.12]. Laboratory test methods have been developed for predicting the performance of sorbents [12.13,12.14]. 

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