Counter current flow tubular reactors

Tubular reactors are commonly used in laboratory, pilot plant, and commercial-scale operations. Because of their versatility, they are used for heterogeneous reactions as well as homogeneous reactions. They can be run with cocurrent or counter-current flow patterns. They can be run in isothermal or adiabatic modes and can be used alone, in series, or in parallel. Tubular reactors can be empty, packed with inert materials for mixing, or packed with catalyst for improved reactions. It is often the process that will dictate the design of the reactor, as discussed in this entry. 

Figure 5.19 Temperature profiles for a tubular reactor with jacket cooling (a) Parallel flow, high coolant rate (b) parallel flow, moderate coolant rate (c) counter-current flow, moderate coolant rate. 

FIG. 23-25 Typ es of industrial gas/Hqiiid reactors, (a) Tray tower, (h) Packed, counter current, (c) Packed, parallel current, (d) Falling liquid film, (e) Spray tower, if) Bubble tower, (g) Venturi mixer, h) Static in line mixer, ( ) Tubular flow, (j) Stirred tank, (A,) Centrifugal pump, (/) Two-phase flow in horizontal tubes. 

Gas and liquid reactants can be contacted in fixed-bed tubular reactors according to one of several possible so-called gas-liquid contacting patterns. The three most commonly used contacting patterns are illustrated in Fig. 5. These include trickle-bed reactors (TBRs) with either downward cocurrent (Fig. 5A) or counter-current (Fig. 5B) gas-liquid flow. 

The water cooled tubular reactor (WCTR) represents the optimal solution for the etherification because it is the best compromise between kinetics and thermodynamics [7]. The Snamprogetti (now Saipem) WCTR (Figure 11.5) is a bundle-type heat exchanger with the catalyst in the tube side and the tempered cooling water flowing co-current or counter-current in the shell side. The catalyst is self-supporting in the bottom shell of the reactor, in the tubes and above the upper tube sheet. 

The performance of a PSR will be bench marked against two reference cases (i) a multi-tubular cooled plug flow reactor (PFR) containing only a catalyst and cooled co- or counter currently, and (ii) a combination of a PSA vessel containing a sorbent to separate A, and a multi-tubular cooled PFR containing a catalyst and receiving the A-enriched feed from the PSA. 

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