Segmented stream reactor

B. Postcolumn Derivatization Three types of reactors for postcolumn derivatization are used, depending on reaction kinetics. Straight, coiled, and knitted open-tubular reactors are used for fast reactions, whereas packed-bed reactors are used for intermediate kinetics. Segmented-stream reactors are used for slow reactions. The simplest reactors are the open-tubular reactors a T connector is the most common. Pickering44 has described the performance requirements for instrumental components of HPLC postcolumn systems. 

Fig. 2.4p shows three types of post-column reactor. In the open tubular reactor, after the solutes have been separated on the column, reagent is pumped into the column effluent via a suitable mixing tee. The reactor, which may be a coil of stainless steel or ptfe tube, provides the desired holdup time for the reaction. Finally, the combined streams are passed through the detector. This type of reactor is commonly used in cases where the derivatisation reaction is fairly fast. For slower reactions, segmented stream tubular reactors can be used. With this type, gas bubbles are introduced into the stream at fixed time intervals. The object of this is to reduce axial diffusion of solute zones, and thus to reduce extra-column dispersion. For intermediate reactions, packed bed reactors have been used, in which the reactor may be a column packed with small glass beads. 

The reactor is represented by the cross-flow discretization shown in Fig. 11. Here, we choose seven reactor segments (NE=7), with uniform segment lengths, Aa,. Since the reaction is exothermic, this corresponds to 14 hot streams and 7 cold streams. Thus, the streams in the reactor may be enumerated as hot streams HI-HI 3 (2NE - 1, since the entry point is fixed to be a preheater), and cold streams C1-C7. The streams H15-H16, and C8-C9 correspond to the condensers and reboilers of the distillation column. As described in (PIO), the specific heats are assumed to be linear with the inlet temperatures. The objective function here as the total profit for the plant and is given in simplified form by... 

FIGURE 2.4 Flow diagram of a single-channel segmented flow analyser and the associated recorder tracing. S/C — sample/carrier wash stream Air = air R = reagent R( = coiled reactor DB — de-bubbler D = detector arrows = sites where pumping is applied. 

FIGURE 8.11 A segmented flow system exploiting LLE designed with the classical manifold architecture. C/S = carrier/sample stream Air = air Org — lower density organic solvent Ec = extraction reactor PS — phase separating device D — detector. 

The main characteristic of the classical manifold architecture for in-line LLE (Fig. 8.11) is that analyte extraction occurs mostly via the thin liquid film established on the inner wall of the tube, which is continuously renewed. Phase separation however is often a limiting factor in determining system performance. Nonetheless, the flow system can be designed to permit segmentation of the sample zone by the confluent organic stream, analyte extraction in the downstream reactor and... 

Pinch Point Analysis starts with the input of data. The first step is the extraction of stream data from a flowsheet simulation, which describes typically the material balance envelope (Reactors and Separators). Proper selection and treatment of streams by segmentation is a key factor for efficient heat integration. The next step is the selection of utilities. Additional information regards the partial heat transfer coefficients of the different streams and segments of streams, and of utilities, as well as the cost of utilities and the cost laws for heat exchangers. 

In a totally segmented CPFR of the stratified agitated tower design, the feed stream is considered to enter the reactor as macro-molecular capsules which maintain their integrity throughout their life-time inside the reactor. The capsules each act as though they were batch reactors and theoretically should produce a monodisperse polystyrene having a Poisson distribution. 

EVA copolymers represent the largest-volume segment of ethylene copolymer market and are the products of low-density polyethylene (LDPE) technology. Commercial preparation of EVA copolymer is based on the same process as LDPE with the addition of controlled comonomer stream into the reactor. EVA copolymers are thermoplastic materials consisting of an ethylene chain incorporating 5-20 mol% vinyl acetate (VA), in general. The VA produces a copolymer with lower crystallinity than conventional ethylene homopolymer. 

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