Reactor slug flow

We now formalize the definition of piston flow. Denote position in the reactor using a cylindrical coordinate system (r, 6, z) so that the concentration at a point is denoted as a(r, 9, z) For the reactor to be a piston flow reactor (also called plug flow reactor, slug flow reactor, or ideal tubular reactor), three conditions must be satisfied ... 

Hovmand, S., and Davidson, J. F, Slug Flow Reactors, Fluidization, (J. F. Davidson, and D. Harrison, eds.), Academic Press, London (1971)... 

The unmodified alumina-supported cobalt catalyst (catalyst A) was tested in the pilot plant slug-flow reactor under realistic Fischer-Tropsch conditions. The produced wax was... 

Fig. 2. (a) A SEM image of the alumina-supported cobalt catalyst A after a Fischer-Tropsch synthesis test run in the demonstration unit, (b) Relative mean PSD values of the supported catalyst (catalyst B) after an 8 months test tun on the Pilot Plant slug-flow reactor. 

Fluid-fluid systems are widely used for chemical transformations. Examples are halogenations, hydrogenations, and hydroformylations for gas-liquid reactions and nitrations, polymerizations, and cyclization for liquid-liquid systems. In addition, two-phase slug flow reactors can be used to get narrow residence time distribution at low liquid Reynolds numbers as demonstrated in chapter 3. Most of the reactions mentioned above are highly exothermic and heat evacuation is an important issue for efficient temperature control. 

Figure 11.5 The velocity vectors in a G-L slug flow reactor. (From Gunther, A. et al., Langmuir, 21(4), 1547, 2005.)...

Hovmand S, Davidson JF. Slug flow reactors. In Davidson JF, Harrison D, eds. Fluidization. London Academic Press, 1971. 

This class of hybrid components comprises chip micro-reactor devices, as described in Section 4.1.3, connected to conventional tubing. This may be H PLC tubing which sometimes has as small internals as micro channels themselves. The main function of the tubing is to provide longer residence times. Sometimes, flow through the tube produces characteristic flow patterns such as in slug-flow tube reactors. Chip-tube micro reactors are typical examples of multi-scale architecture (assembly of components of hybrid origin). 

OS 33] ]R 16h] ]P 25] For the nitration of single-ring aromatics in a capillary-flow reactor, internal circulation, exhibiting an inner downwards and an outer upwards flow, in the aqueous slug of a two-phase flow was simulated [94]. 

Figure 5.6 Flow pattern map for a gas/liquid flow regime in micro channels. Annular flow wavy annular flow (WA) wavy annular-dry flow (WAD) slug flow bubbly flow annular-dry flow (AD). Transition lines for nitrogen/acetonitrile flows in a triangular channel (224 pm) (solid line). Transition lines for air/water flows in triangular channels (1.097 mm) (dashed lines). Region 2 presents flow conditions in the dual-channel reactor ( ), with the acetonitrile/nitrogen system between the limits of channeling (I) and partially dried walls (III). Flow conditions in rectangular channels for a 32-channel reactor (150 pm) (T) and singlechannel reactor (500 pm) (A) [13].

Benchmarking of the micro reactors themselves - slug flow vs. falling film... 

GL 18] [R 6b] [P 18] Using a stoichiometric amount of hydrogen and operating in the slug-flow mode, it was shown that the yield of a micro reactor exceeds that of a mini fixed-bed reactor (LHSV = 60 h ) [61]. A maximum yield of 30% was obtained for the micro reactor for the range of pressure investigated (10-35 bar). 

In advance, comparative fixed-bed measurements were undertaken. It was ensured that the performance of a plug-flow operation with both flows having the same direction is superior to trickle-bed operation, using counter-flow instead. The plug flow was assumed to model the slug-flow behavior in the micro reactor. 

Fig. 10. Top images Improved flow distribution of the liquid-liquid slug flow at 80°C and 5 bar at the reactor inlet (left) and the reactor center (right). Less regular flow distribution of the liquid-liquid slug flow at 20°C and 1 bar at the reactor inlet (left) and the reactor centre (right)...

Hovmand, S. and Davidson, J. F. (1971). Pilot Plant and Laboratory Scale Fluidized Reactors at High Gas Velocities The Relevance of Slug Flow. In Fluidization. Ed. Davidson and Harrison. London Academic Press. 

The influence of interphase mass transfer between liquid-liquid slugs was investigated for nitration of aromatic compounds in a capillary-flow reactor (see Figure 5.2) [22]. This was achieved by changing flow velocity via volume flow setting, while residence time was kept constant by increasing the capillary length. 

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