Falling Film Cell

The largest falling film cell is 0.25 m wide and 1 m tall and has been tested as an electrolyzer. Since 1990, GDEs have been successfully used in falling film cells. 

This example demonstrates that the careful design of the stack for a specific application leads to significant improvements of AFCs and all other fuel-cell technologies. 

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The modification of hydrodynamic aspects is exploited in the falling-film cell [12], where the electrolyte flows as a thin fllm in the channel between an inclined plane plate and a sheet of expanded metal which work as electrodes. Other proposal is to include turbulence promoters in the interelectrode gap in conventional parallel plate electrochemical reactors [13-16], or the use of expanded metal electrodes immersed in a fluidized bed of small glass beads, called Qiemelec cell [17]. Likewise, the Metelec cell [18] incorporates a cylindrical foil cathode concentric arranged around an inner anode, with a helical turbulent electrolyte flow between the electrodes. The electrochemical hydrocyclone cell [19] makes use of the good mass-transfer conditions due to the helical downward accelerated flow in a modified conventional hydrocyclone. 

Coeuret F, Legrand J (1985) Mass transfer at the electrodes of the falling-film cell . J Appl Electrochem 15 181-190... 

A Corynebacterium propinquum microbial cell catalyst was employed to convert acrylonitrile to ammonium acrylate, where the final concentration of product was 10-20% and the concentration of unconverted acrylonitrile was <30 ppm [81], The ammonium acrylate solution was concentrated to 40-60% by falling film evaporation, the resulting solution acidified, and the acrylic acid extracted with diethyl ether at 0-10 °C to obtain high-purity acrylic acid. 

KU holds the patent for a new electrolyser technology, the falling film electrolyser [10] (FFE see Fig. 16.12), with an expected lowering of the cell voltage of... 

Since membrane-cell evaporators do not produce solids, forced-circulation evaporators are used less frequently. Rising-film and falling-film types appear in a number of plants. The rising-film evaporator depends on natural circulation of caustic from the bottom to the top of the tubes. Falling-film evaporators, as shown in Section 9.3.S.2, depend on pumps to lift caustic to the distribution system at the top. These units generally have better heat-transfer coefficients and less tendency to foul. Recirculated units in particular allow good control of flow to maintain a proper film on the tubes. This also permits the designer to provide more turndown capability. Liquid velocities are lower... 

In this case, under the condition of falling-film thickness 0.13 mm, liquid rate 2.76 X 10 m s and the countercurrent CO2 rate, respectively, 0.08, 0.1, 0.16, and 0.3 m s the interface structure is shown in Fig. 8.9a-d. At low gas rate, cellular structure appeared locally while at higher gas rate, the roU structure involving cells was developed with tendency to becoming aU roU structure. 

To remove chlorate and other salts, the 50 percent diaphragm cell caustic may be extracted with liquid ammonia in a pressurized system. The ammonia fraction then is processed through a stripper to remove and recycle the ammonia. The alkaline stripper bottoms are useful in neutralizing acidic waste streams. The purified caustic is evaporated further, and then fed to an anhydrous concentrator, typically an Inconel falling film evaporator, heated with molten salt. The anhydrous caustic, containing at least 97.5 percent NaOH, is marketed as one solid mass in drums, as flake caustic, or more desirably as beads or prills. The last are marketed in bulk or bags. 

Table 2 demonstrates that the concentration and diffusion coefficient of dioxygen in the recast film are quite different than those in the bulk ionomer, both parameters showing values which fall between aqueous solution and bulk ionomer levels. Table 2 shows why measurements of ORR kinetics should preferably be performed at model Pt/recast ionomer interfaces in order to evaluate the ORR process in fuel cell cathodes which employ recast films of the ionomer. Gottesfeld et al. interpreted the ORR results shown in Table 1 in light of the parameters shown in Table 2, suggesting... 

In commercial terms, the main advantage that DSSCs have over silicon p-n junction cells is that their cost per watt could be four to five times lower, because of their lower-cost materials and construction techniques. Moreover, the efficiency of DSSCs falls off less in low-intensity light or with increasing temperature than that of Si cells, and they have lower embodied energy i. e. less energy is required to make them). DSSCs can also be fabricated as translucent panels or laid down as flexible films on non-planar surfaces. 

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