Venturi reactor

Figure 50. Furnace black reactors A) Restrictor ring reactor B) Venturi reactor [4.15] C) Reactor with high-speed combustion chamber [4.16]...

Figure 2. Circulating loop venturi reactor (a) reactor setup (b) scheme of ejector (1 = ejector, 2 =main holding vessel, 3 =gas recycle (adapted from Ref. 8).

In bubble columns, agitation of the liquid phase, and hence suspension of the catalyst is effected by the gas flow. The gas is often recycled to cause more turbulence and thus better mixing. Circulation of the liquid is often required to obtain a more uniform suspension. This can either be induced by the gas flow (airlift loop reactor) or by use of an external pump. In the latter instance it is possible to return the slurry to the reactor at a high flow rate through an ejector (Venturi tube). The local under-pressure causes the gas to be drawn into the passing stream, thus affording very efficient mixing. This type of reactor is called a Jet-loop or Venturi reactor. 

L. L. van Dierendonck, J. Zaharadmlc and V. Linek, Loop Venturi reactor-a feasible alternative to stirred tank reactors , Ind. Eng. Chem. Res. 37 (1998) 734-738. 

Table 14.1-1 also mentions some less common types, used for very specific tasks. Venturi reactors are used, for instance, in antipollution devices to wash out small amounts of remaining SO2 by means of caustic. Their advantage resides in their low pressure drop, since the Venturi exhausts the gas into the liquid. 

C. M. van Dierendonck, L. L., Hydrodynamics and mass-transfer characteristics of a loop-venturi reactor with a downflow liquid jet ejector. Chem. Eng. Sci. 1992, 47 (13/14), 3557-3564. 

Cramers PHMR, van Dierendonck LL, Beenackers AACM. (1992a) Influence of the gas density on the gas entrainment rate and gas hold up in loop-venturi reactors. Chem. Eng. Sci., 47 2251-2256. 

Gourich B, El Azher N, Vial Ch, Belhaj Soulami M, Ziyad M, Zoulalian A. (2007) Influence of operating conditions and design parameters on hydrodynamics and mass transfer in an emulsion loop-venturi reactor. Chem. Eng. and Process., 46 139-149. 

Stefoglo EE, Zhukova OP, Kuchin IV, Albrecht SN, Nagirnjak AT, Dierendonck LL. (1999) Reaction engineering of catalytic gas-liquid processes in loop-venturi reactors in comparison with stirred vessels operation. Chem. Eng. Sci., 54 5279-5284. 

A novel venturi reactor has also been patented by Chemithon Corporation. The organic reactant is sulfonated by injection into a stream of gas containing sulfur trioxide at a venturi. The reaction mixture is quenched and recycled downstream until sulfonation is complete. This reactor design is utilized primarily for highly viscous, high molecular... 

Figure 13.5 shows a flowsheet for the manufacture of phthalic anhydride by the oxidation of o-xylene. Air and o-xylene are heated and mixed in a Venturi, where the o-xylene vaporizes. The reaction mixture enters a tubular catalytic reactor. The heat of reaction is removed from the reactor by recirculation of molten salt. The temperature control in the reactor would be diflficult to maintain by methods other than molten salt. 

The hydrocarbon gas feedstock and Hquid sulfur are separately preheated in an externally fired tubular heater. When the gas reaches 480—650°C, it joins the vaporized sulfur. A special venturi nozzle can be used for mixing the two streams (81). The mixed stream flows through a radiantly-heated pipe cod, where some reaction takes place, before entering an adiabatic catalytic reactor. In the adiabatic reactor, the reaction goes to over 90% completion at a temperature of 580—635°C and a pressure of approximately 250—500 kPa (2.5—5.0 atm). Heater tubes are constmcted from high alloy stainless steel and reportedly must be replaced every 2—3 years (79,82—84). Furnaces are generally fired with natural gas or refinery gas, and heat transfer to the tube coil occurs primarily by radiation with no direct contact of the flames on the tubes. Design of the furnace is critical to achieve uniform heat around the tubes to avoid rapid corrosion at "hot spots."... 

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. 

Conoco operated a stirred tank Pfaudler glass-lined reactor for the batch S03 sulfonation of detergent alkylate. The plant utilized over-the-fence S03 converter gas (8% S03 in dry air) having 6-8 h batch cycles (264). Allied Chemical Company provided details for batch S03 sulfonation (265,266) and Conoco also published their procedure for S03 batch sulfonation (267). Andrew Jergens Company patented a cyclic batch sulfonation and sulfation process introducing nondiluted S03 vapors into a venturi contacter that emitted reaction product into a stirred reservoir tank where it was recycled from the reservoir vessel through a heat exchanger and back to the venturi in the cyclic loop. The unit operated in a vacuum (268). Derived color quality was unspecified. 

The most frequently used contactors in full-scale waste water ozonation systems are bubble column reactors equipped with diffusers or venturi injectors, mostly operated in a reactor-in-series counter-current continuous mode. Many full-scale ozone reactors are operated at elevated pressure (2-6 barabs) in order to achieve a high ozone mass transfer rate, which in turn increases the process efficiency. 

Figure 17.11. Types of contactors for reacting gases with liquids many of these also are suitable for reacting immiscible liquids. Tanks (a) with a gas entraining impeller (b) with baffled impellers (c) with a draft tube (d) with gas input through a rotating hollow shaft, (e) Venturi mixer for rapid reactions, (f) Self-priming turbine pump as a mixer-reactor, (g) Multispray chamber. Towers (h) parallel flow falling film (i) spray tower with gas as continuous phase (j) parallel flow packed tower (k) counter flow tray tower. (1) A doublepipe heat exchanger used as a tubular reactor.

BCR STR JLR rise from bottom, Inflate and coalesce bubble size depends on stirrer design and reactor geometry tiny bubbles dragged downflow from Venturi neck to reaction zone 600 to 1000 1000 to 2000 2000 to 3000... 

Two-Fluid (Pneumatic) Atomizers This general category includes such diverse applications as venturi atomizers and reactor-effluent quench systems in addition to two-fluid spray nozzles. Depending on the manner in which the two fluids meet, several of the breakup mechanisms may be applicable, but the final one is high-level turbulent rupture. 

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