Tubular PBRs

This gas-phase reaction is carried out over a zeolite catalyst and follows an elementary rate law. The catalyst is packed in a tubular PBR that is 2 m in diameter and 22 m in length. Pure methanol Is fed at a molar flow rate of 950 mol/s, a pressure of 1500 kPa, a concentration of 0.4 mol/ dm, and 490°C. The conversion and pressure at the exit are 0.5 and 375 kPa, respectively. Flow throughout the bed is known to be such that the mrbulem contribution in the Eigun equation (i,e., G ) can be neglected. The tubular PBR is to be replaced with a spherical PBR containing an equal amount of identical catalyst. The spherical PBR measures 5.2 m hi diameter and has screens placed 2 dm from each end (i.e., L= L lA dm). 

Where B is a function of the mass flow rate, feed properties, and catalyst properties—all of which arc constant for pan (a). Note that all equations up to now apply to a tubular PBR and spherical PBR. To find B and ko we must model the tubular PBR on POLYMATH by entering the above equations in addition to... 

The shell/tube configuration of tubular PBRs depends on the nature of the catalytic reaction. For highly endothermic reactions such as catalytic steam reforming, the reactor geometry is similar to that of a fired furnace in which the catalyst-packed tubes are heated by the energy released by the combustion of a fuel on the shell side. Catalytic steam reforming involves the conversion of a hydrocarbon to a hydrogen-rich mixture in the presence of steam ... 

The design and operational requirements explained for tubular PBRs are also valid for PBRs in which the catalyst bed is packed in one vessel as described schematically in Figure 1.6a [4]. This reactor configuration is preferred when the reaction is carried out at adiabatic conditions. However, as demonstrated in Figure 1.6b and c [4], bed temperature can be changed by heat addition to/removal from the bed for obtaining a temperature... 

Tubular PBR Large illumination surface area Scale-up challenges... 

Instead of placing the tubes horizontally as in the tubular PBR, the tubes can be placed vertically as shown in Figure 6. This kind of PBR is called a bubble-column reactor because the air is pumped from the bottom of each tube and forms bubbles [36]. As depicted on the right side of Figure 6, the output of a tubular column is connected with the input of the next tubular column. 

If similar calculations are performed for the tubular packed-bed reactor (PBR), one finds that for the same catalyst weight the conversion and pressure at the exit are... 

Dibular Reactors (FFR/PBR). When the heat flow varies along the length of the reactor, such as would be the case in a tubular flow reactor, we must integrate the heat flux equation along the length of the reactor to obtain the total heat added to the reactor. 

In ihe three idealized types of reactors just discussed (the perfectly mixed batch reactor, the plug-fiow tubular reactor (PFR). and the perfectly mixed con-tinuous-siirred tank reactor (CSTR), the design equations (i.e.. mole balances) were dei doped based on reactor volume. The deris ation of the design equation for a packed-bed catalytic reactor (PBR) will be carried out in a manner analogous to the development of the tubular design equation. To accomplish this derivation. we simply replace the volume coordinate in Equation (MO) with (he catalyst weight coordinate H (Figure - 4). 

There is a wide variety of PBR technologies available, including tubular, cylindrical, and flat-panel systems (some examples are given in Fig. 2). This... 

The above-mentioned systems are generally considered low technology, but remain those of choice by most hatcheries because of their ease of use and maintenance, general reliability and low capital cost (or, in the case of bags, low replacement cost). However, these systems are typically characterised by low cell densities and productivities, i.e. for aquaculture strains often below 100 mg DW microalgae Ud compared to small volume cultures, or other PBR systems with significantly higher SA V (Table 4.3 and Tredici et aL, 2009). Examples of PBRs include tubular (serpentine. 

The most popular PBRs include tubular systems, helical PBRs, plastic bag systems, well systems, pyramid PBRs, airlift PBRs, annular PBRs, colunui PBRs, bubble-colunm PBRs, vertical column PBRs, flat-Plate PBRs, stirred-tank PBRs, rectangular tanks, immobilized bioreactors, and hybrid systems. 

By combining a two-phase flow simulator and the photosynthesis model, Sato et al. [92,93] explored the amount of carbon fixation and the growth curve of microalgae. A similar approach was applied to simulate a tubular recycled PBR for macro-algal cell suspension cultures [49]. This model predicts a critical ceU density at which photosynthetic biomass production switches from a rate-limited process to a CO2 delivery-limited process. Rate-limited growth proceeds only to this critical cell... 

Packed-bed reactors are tubular reactors filled with catalyst particles. In PBRs it is the weight of catalyst W that is important, rather than the reactor volume. The derivation of the dilTerential and integral forms of the design equations for packed-bed reactors are analogous to tho.se for a PFR [cf. Equations (2-15) and (2-16)). That is. substituting Equation (2-12) for Equation (1-15) gives... 

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