Falling film generator

Mixed titania/alumina collodiai spheres were prepared in an apparatus consisting of two falling film generators in series upstream of the manifold. In the first generator, Ti(OEt)4 was vaporized at temperatures ranging between 78 and l0l°C, and the droplets, obtained by condensing this vapor, were then introduced into the... 

The size of the particles is determined by the particular material selected and the vapor concentration used. In practice, limited variation in particle size can be achieved for a particular aerosol material because conditions for stable aerosol formation require a particular set of thermal and vapor concentration conditions. The monodispersity of the aerosol can be improved by revaporization and recondensation. In systems in which the condensation occurs in a container with a high ratio of volume to surface areas, relatively monodisperse particles can be obtained (frg 1.1). Otherwise, the particle size varies with the proximity to the wall. In cylindrical or tubular systems, such as in the condensation aerosol generator developed by Liu et al. [10] or the falling-film generator, the particle size that is produced varies radially (see Ref. [3]). A more monodisperse aerosol can be produced by extracting the central portion of the flow, which is less subject to wall effects. Liu et al. [10] found that the monodispersity improved from a ug value of 1.35 to 1.15 by using only the central 5% of the aerosol flow. A commercial version of a modified Sinclair-LaMer generator is available with particle size control suited for inhalation studies [11]. 

P 12] A falling film micro reactor was applied for generating thin liquid films [6]. A reaction plate with 32 micro channels of channel width, depth and length of 600 pm, 300 pm and 66 mm, respectively, was used. Reaction plates made of pure nickel and iron were employed. The micro device was equipped with a quartz window transparent for the wavelength desired. A 1000 W xenon lamp was located in front of the window. The spectrum provided ranges from 190 to 2500 nm the maximum intensity of the lamp is given at about 800 nm. 

The hydroformylation reaction is highly exothermic, which makes temperature control and the use of the reaction heat potentially productive and profitable (e.g, steam generation). The standard installation of Ruhrchemie/Rhone-Poulenc s aqueous-phase processes is heat recovery by heat exchangers done in a way that the reboiler of the distillation column for work-up of the oxo products is a falling film evaporator... 

Another generator that was successfully used in the formation of polymer colloids, particles of mixed composition, and coated particles is shown in Figure 1.5.3f, in which the falling film tube is replaced by a boiler (38). The complete apparatus described in Figure 1.5.3 makes it possible to produce cores and shells in a continuous process (39). 

Fig. 1.5.1 Schematic diagram of the falling film aerosol generator. (A) Constant-temperature oil bath (B) and (C) reservoirs containing the reactant liquid (D) and (J) glass joints controlling the flow of the moving film (E) and (F) tubes to the variable-speed pump (G) exit tube (I) boiler lube (K) carrier gas (laden with nuclei) entrance. (From Ref. 31.)...

Falling-film reactors have a liquid reactant flowing down the walls of a tube with a gaseous reactant flowing up or down (usually countercurrent). This reactor is particularly advantageous when the heat of reaction is high. The reaction surface area is minimal, and the total reaction heat generated can be controlled. 

The heat of reaction generates 1) process steam in the reactor and 2) 5.5 bar pure steam. The process steam is used to preheat boiler feed water and nitric acid as well as operate the falling film evaporator. The pure steam is fed to the plant steam header295. 

Figure 4.28 Principle to generate a falling film on a structured plate with channels (left). Falling-film microreactor, laboratory version up to 1 l/h (by courtesy of IMM).

The photooxygenation of cyclopentadiene with Rose Bengal as photosensitizer was performed using a falling-film microreactor in methanol [317]. The endoperoxide is first generated and then reduced to 2-cyclopenten-l,4-diol, which is used as an intermediate in pharmaceutical drug synthesis. This route is not easily possible by batch processing because the explosive endoperoxide intermediate is formed in substantial amounts. 

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