Feeds alternative arrangements

In the Type II case, the copolymerization tends toward an alternating arrangement of monomer units. Curve II of Figure 1 shows an example of an alternating copolymer that has an azeotropic copolymer composition, ie, a copolymer composition equal to the monomer feed at a single monomer feed composition. This case is analogous to a constant Foiling mixture ia vapor—Hquid equihbria.T) III... 

Interdigital micro mixers comprise feed channel arrays which lead to an alternating arrangement of feed streams generating multi-lamellae flows [39 2]. If processes have to be carried out with extended residence times (> 1 s) and/or at a temperature level different from the mixing step, tubes have to be attached to the interdigital micro mixers. Their internals comprise millimeter dimensions or below, if necessary. 

Two to four distillation columns are usually required to separate the liquid hydrocarbon product stream that contains unreacted isobutane, alkylate mixture, n-butane, and propane. The major column is designated as the deisobutanizer (DIB) column. Often this column separates the isobutane as the overhead stream, the alkylate as the bottom stream, and a n-butane rich sidestream. In many plants, the feed isobutane is also fed to the DIB to remove most of the n-butane. A second column is generally needed to remove propane from the isobutane. Sometimes a third column is provided to purify further the n-butane sidestream and to recover more isobutane. In an alternate arrangement, the bottom stream of the DIB column is a mixture of alkylate and n-butane. This mixture is then separated in another column. 

Continuous Simple Distillation. Distillations that approximate this type are usually carried out on a continuous basis such that the liquid feed is added continuously to a well-mixed still in which a definite fraction is vaporized and removed and the excess unvaporized liquid is withdrawn from the still. An alternate arrangement is to preheat the feed and add it to a flash or disengaging section where vapor and liquid are separated and removed without additional heat requirements. In either case, assuming that the vapor and liquid leaving are in equilibrium with each other, the two fractions are related to each other by equilibrium constants and material balances. Thus for each component in a mixture the following material balance can be written ... 

When bottoms flow is the manipulated variable, as in the alternate arrangement mentioned earher, the dynamic response is different. Without dynamic compensation, an increase in feed rate will cause an immediate increase in bottoms flow. This, in turn, will start bottoms level falling, thereby reducing heat input through the action of the bottoms-level controller. If bottoms flow is but a small fraction of the feed, the effect will be reduced. But dynamic compensation which will prevent a change in heat input is desirable. This would ordinarily take the form of a multiple lag. 

Equation (12.19) may be implemented for control of product quality by manipulating either heat input or feed rate in relation to the other. The choice depends on the relative availability of each. If short-term reductions in steam availability are common, feed rate should be manipulated accordingly. But if feed is coming from another processing unit without intermediate surge capacity, the alternate arrangement is favored. 

A third alternative is to rate the transformer in-feeds for single supplies but to arrange for automatic switching of the bus section and two incomers in the event of loss of supply to one section. A rapid transfer switching to the remaining supply in the event of loss of single supply can prevent the total loss of motor loads. In such a situation, the effect of the current taken by motors to which the supply has been restored must be taken into account. 

Typically, chemical formulations were supplied as balls or briquets and dispensed through bypass feeders or hanging baskets. Alternatively, pulverized or powdered treatments were dissolved in water and pumped to FW tanks or added via drip-feed arrangements. 

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