Surfaces types

Allyl Bromide. Introduce into a 1-litre three-necked flask 250 g. (169 ml.) of 48 per cent, hydrobromic acid and then 75 g. (40-5 ml.) of concentrated sulphuric acid in portions, with shaking Anally add 58 g. (68 ml.) of pure allyl alcohol (Section 111,140). Fit the flask with a separatory funnel, a mechanical stirrer and an efficient condenser (preferably of the double surface type) set for downward distillation connect the flask to the condenser by a wide (6-8 mm.) bent tube. Place 75 g. (40 5 ml.) of concentrated sulphuric acid in the separatory funnel, set the stirrer in motion, and allow the acid to flow slowly into the warm solution. The allyl bromide will distil over (< 30 minutes). Wash the distillate with 5 per cent, sodium carbonate solution, followed by water, dry over anhydrous calcium chloride, and distil from a Claisen flask with a fractionating side arm or through a short column. The yield of allyl bromide, b.p. 69-72°, is 112 g. There is a small high-boiling fraction containing propylene dibromide. 

In a 500 ml. round-bottomed flask place 65 ml. of rectified spirit, 50 g. (47 5 ml.) of pure benzaldehyde (1) and a solution of 5 g. of sodium cyanide (96-98 per cent.) CAUTION) in 50 ml, of water. Attach a reflux condenser (preferably of the double surface type) and boil the mixture gently for half an hour (2). Cool the contents of the flask (preferably in an ice bath). Filter the crude benzoin, wash it with cold water, drain well (3) and dry. The yield of crude benzoin, which is white or pale yellow in colour, is 45 g. 

Fig. 10. Plate-—coil heat exchangers. Plate—coil is a very efficient and versatile prime surface-type heat exchanger.

Two other deposition mechanisms, in addition to the six listed, may be in operation under particular circumstances. Some dust particles may be collected on filters by sieving when the pore diameter is less than the particle diameter. Except in small membrane filters, the sieving mechanism is probably limited to surface-type filters, in which a layer of collected dust is itself the principal filter medium. 

Colloid mills which are employed for dispersion or for emulsification fall into four main groups the hammer or turbine, the smooth-surface disk, the rough-surface type, and valve or orifice devices. 

Surface Condensers Surface condensers (indirect-contact condensers) are used extensively in the chemical-process industiy. They are employed in the air-poUution-equipment industry for recoveiy, control, and/or removal of trace impurities or contaminants. In the surface type, coolant does not contact the vapor condensate. There are various types of surface condensers including the shell-and-tube, fin-fan, finned-hairpin, finned-tube-section, ana tubular. The use of surface condensers has several advantages. Salable condensate can be recovered. If water is used for coolant, it can be reused, or the condenser may be air-cooled when water is not available. Also, surface condensers require less water and produce 10 to 20 times less condensate. Their disadvantage is that they are usually more expensive and require more maintenance than the contac t type. 

Condensers may be of one or two general types depending on the specific application. Contact condensers operate with the coolant, vapors, and condensate intimately mixed. In surface condensers, the coolant does not come in contact with either the vapors or the condensate. The usual shell-and-tube condenser is of the surface type. Figure 29-14 illustrates a contact condenser which might be used to clean or preclean a hot corrosive gas. 

The production of aluminum begins with the mining and beneficiation of bauxite. At the mine (usually of the surface type), bauxite ore is removed to a crusher. The crushed ore is then screened and stockpiled, ready for delivery to an alumina plant. In some cases, ore is upgraded by beneficiation (washing, size classification, and separation of liquids and solids) to remove unwanted materials such as clay and silica. 

There are many filter media from which to choose from however, the optimum type depends on the properties of the suspension and specific process conditions. Filter media may be classified into several groups, however the two most common classes are the surface-type and depth-media-type. 

Surface-type filter media are distinguished by the fact that the solid particles of suspension on separation are mostly retained on the medium s surface. That is, particles do not penetrate into the pores. Common examples of this type of media are filter paper, filter cloths, and wire mesh. 

Diesel Trap Concepts [subscriber access]. .. in the surface-type filters. That layer is commonly referred to as "filtration cake" and the process is called "cake filtration", http // www.dieselnet.com/tech/dpf concept.html. 

The Polarizable Continuum Model (PCM) employs a van der Waals surface type cavity, a detailed description of the electrostatic potential, and parameterizes the cavity/ dispersion contributions based on the surface area. The COnductor-like Screening... 

Condenser tail pipes, used tvith any condenser, are sealed with a 34-foot leg into a sump, or with a condensate pump operating under vacuum on suction. With surface-type condensers, the level may be sealed in a receiver with a float or other type of level control. 

Figure 6-6. Two-stage ejector employing surface type inter-and-after-condenser. By permission, Eiiiott Co.

Palen and Taborek modified the Gilmour equation to better accommodate the effect of surface types and the effect of pressure, with the results agreeing with all the data + 50% and —30%, which is better than other proposed correlations. 

The best dollar value considering amount of basic surface, type of fans, etc. 

Steam condensate can be recovered in surface type units. 

The dimensions of Figure 11-4 for barometric-type units and Figure 11-5 for surface-type units are a general guide as to space requirements. 

Figure 11-5. Surface-type condenser, steam jets with three boosters. (Used by permission Ingersoll-Rand Company.) tBased on required N.P.S.H. of pump. May be reduced by pump pit or by pump requiring less N.P.S.H.

When the steam leaves a condensing turbine, it passes to a surface-type condenser for recovery of the condensate. Vacuum equipment (jets or pumps) are necessary to achieve high vacuums on the condenser. 

Figures 6-5 and 6-6 illustrate two-stage ejector installations with barometric and surface type inter-after condensers respectively. The discharge of the steam non-condensables from the second stage jet of Figure 6-5 is exhausted to the atmosphere, while in Figure 6-6 the steam is condensed in the aftercondenser and, essentially, only non-condensables leave the vent of the aflercon-denser. Figure 6-7A indicates a diagram of a three-stage barometric type installation.

B—Barometric Counter-Flow Condenser, Intercon-denser and Aftercondenser S—Surface Type Condenser, Intercondenser and Aftercondenser... 

Corrosion has been encountered infrequently to date and has been a surface type, as opposed to pitting corrosion that can result in perforations. Entrapped air in the beverage or in the cans headspace increases the corrosive action of the product according to Koehler et at (21). As with beer and other canned foods, aluminum ends provide electrochemical protection when combined with tinplate or tin-free-steel can bodies. The level of iron pickup is reduced while the amount of aluminum dissolved in soft drinks increases without detrimental effect. Aluminum containers with vinyl epoxy and vinyl organosol coatings are compatible with carbonated soft drinks. 

Place 25 g. of methyl methacrylate polymer (G.B. Diakon (powder). Perspex (sheet) U.S.A. Lucite, Plexiglass) in a 100 ml. Claisen flask, attach an efficient condenser e.g., of the double surface type) and distil with a small luminous flame move the flame to and fro around the sides of the flask. At about 300° the polymer softens and undergoes rapid depolymerisation to the monomer, methyl methacrylate, which distils over into the receiver. Continue the distillation until only a small black residue (3-4 g.) remains. Redistil the hquid it passes over at 100-110°, mainly at 100-102°. The yield of methyl methacrylate (monomer) is 20 g. If the monomer is to be kept for any period, add 0 -1 g. of hydro-quinone to act as a stabiliser or inhibitor of polymerisation. 

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