Foam reactor

Packing height of composite foam reactor Recycle liquid volume (1) Gas-liquid flow Gas flow rate, liBRT ... 

CDP1-Aa Calculate the time to consume 80% of species A in a constant-volume batch reactor for a first- and a second-order reaction. (Includes Solution] CDPl-B Derive the differential mole balance equation for a foam reactor. [2nd Ed. P1-10b]... 

Heterog. catalyzed solid foam reactors Reactive L L L... 

The comparion of pressure drop in three different types of microstructured reactors, foam reactor, square channels and packed bed, is shown in Example 6.2. 

Example 6.2 Comparison of pressure drop in microstructured packed bed reactor, microchannel reactor and foam reactor... 

Now we can estimate the pressure drop in all devices with the presented relations Equations 6.5 and 6.7 for the foam Equations 6.9 and 6.10 for the microchannel reactor and Equation 6.4 for the packed bed with spherical particles. For the microchannel reactor we suppose that 60% of the cross section of the reactor is occupied by the channel walls and catalytic layer (see Figure 6.7). Therefore, the channel volume available for the fluid corresponds to the void volume in the packed bed i.e. =0.4 = e. For a given superficial fluid velocity u, the velocity in the void volume is given by = u/e. From Figure 6.10 it becomes evident that the pressure drop in packed bed reactors are several times higher than in foam reactors. The difference can be explained by the high porosity in the foam (efoam = .9) compared to the packed bed = 0.4). The lowest pressure and, therefore, the lowest energy dissipation is found for the multichannel microreactor. 

The results are plotted as the function of the interstitial velocity in Figure 6.13. Whereas the multichannel and the foam reactor reaches transfer effectiveness of 035> t] >0.1, the values for micro packed beds is found to be between 0.006 >t > 0.002. The highest effectiveness can be obtained with microchannel... 

In addition to the commercial reactors, the Germans tested at the lab or pilot scale many types of reactors. These reactors are included in the reviews mentioned later in the text and will not be described, except for work with the slurry bubble column reactor and the foam reactor. 

Phtha/k anhydride is the most important type of dibasic acid derivative ki alkyd preparation because of its low cost and the excellent overall properties it imparts to the reski. The anhydride stmcture allows a fast esterification to form half-esters at relatively low reaction temperatures without hberatkig water, thereby avoiding the danger of excessive foaming ki the reactor. However, skice the two carboxyl groups of phthaUc anhydride are ki the ortho position to each other on the benzene ring, cycHc stmctures may and do occur ki the reski molecules. 

At higher total flow rates, particularly when the Hquid is prone to foaming, the reactor is a pulsed column. This designation arises from the observation that the pressure drop within the catalyst bed cycles at a constant frequency as a result of Hquid temporarily blocking gas or vapor pathways. The pulsed column is not to be confused with the pulse reactor used to obtain kinetic data ia which a pulse of reactant is introduced into a tube containing a small amount of catalyst. 

Foam Production This is important in froth-flotation separations in the manufac ture of cellular elastomers, plastics, and glass and in certain special apphcations (e.g., food products, fire extinguishers). Unwanted foam can occur in process columns, in agitated vessels, and in reactors in which a gaseous product is formed it must be avoided, destroyed, or controlled. Berkman and Egloff (Emulsions and Foams, Reinhold, New York, 1941, pp. 112-152) have mentioned that foam is produced only in systems possessing the proper combination of interfacial tension, viscosity, volatihty, and concentration of solute or suspended solids. From the standpoint of gas comminution, foam production requires the creation of small biibbles in a hquid capable of sustaining foam. 

Ironically, the reactor was used to produce Antiblaze 19, a flame retardant used in textiles and polyurethane foam. Antiblaze 19 is a cyclic phosphorate ester produced from a mixture of trimethyl phosphite, dimethyl methylphosphonate (DMMP), and trimethyl phosphate (TMOP). The final product is not considered flammable, but trimethyl phosphite is moisture sensitive and flammable, with a flash point of about 27 C. 

Reactor weight Foam level Off gas composition Biomass concentration... 

The Ford hydroglycolysis process is an example of a combined approach for die depolymerization of PURs. In a reactor, polyurethane foam is reacted with a mixture of water, diethylene glycol, and alkali metal hydroxides at high temperature to form polyols. When sodium hydroxide is added as a catalyst, a cleaner polyol is formed because all of the carbamates and ureas in the product are converted into amines and alcohols by hydrolysis.33... 

After 8 h of reaction, the reactor was allowed to cool. A two-layer liquid formed. The top layer was found to contain mostly polypropylene ether triols with about 20% by weight diethylene glycol and 5% by weight toluene diamines. The top layer was purified by vacuum distillation at 2 mm Hg and 200° C to produce 320 g of a light brown liquid residue. This residue (polyols) was used as a replacement for 5% by weight of the Pluracol 535 polyol in the formulation of a flexible polyurethane foam. A flexible foam which had good resiliency and a density of 2.2 Ib/ft3 was obtained. At higher replacement levels, lesser quality foams were obtained. 

The application of a selective pyrolysis process to the recovery of chemicals from waste PU foam is described. The reaction conditions are controlled so that target products can be collected directly from the waste stream in high yields. Molecular beam mass spectrometry is used in small-scale experiments to analyse the reaction products in real time, enabling the effects of process parameters such as temperature, catalysts and co-reagents to be quickly screened. Fixed bed and fluidised bed reactors are used to provide products for conventional chemical analysis to determine material balances and to test the concept under larger scale conditions. Results are presented for the recycling of PU foams from vehicle seats and refrigerators. 12 refs. 

Meanwhile, many investigations have paved the ground for the use of micro reactors with functional chemicals. Among these is work on emulsification [322-326], foaming [327, 328], creaming [329], and particle formation [17,136, 330-332]. 

GP 8[ [R 7[ Syngas generation with commercial Pt-Rh gauzes, metal-coated foam monoliths and extruded monoliths has been reported. For similar process pressure, process temperature, and reaction mixture composition, methane conversions are considerably lower in the conventional reactors (CH4/O2 2.0 22 vol.-% methane, 11 vol.-% oxygen, 66 vol.-% inert species 0.14—0.155 MPa 1100 °C) [3]. They amount to about 60%, whereas 90% was reached with the rhodium micro reactor. A much higher H2 selectivity is reached in the micro reactor the CO selectivity was comparable. The micro channels outlet temperatures dropped on increasing the amount of inert gas. 

Another major drawback stems from the disperse nature of the system itself involving a size distribution of the bubbles in the continuous liquid, which can be broad. The interface is not as defined as for two-phase continuous reactors, as described in Section 5.1.1. However, in the case of making foams, regular micro flow structures, such as hexagon flow, were described [22]. 

GL 19] [R 9] [P 20] The range of solvents to be used for a micro-reactor test tmit is limited as a stable foam has to be established. In turn, this range is large for a mini batch reactor [70]. 

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