Split-feed operation

Fig. 31 Schematic diagram of split-feed operation in continuous emulsion polymerization...

When a monomer split-feed operation based on the experimental result shown in Fig. 32 was applied, for example, to a continuous tubular pre-reactor with some backmixing, the number of polymer particles increased by about 30% at Mpi=0.02 g/cm -water, compared to the number produced in a batch reactor, as shown in Fig. 33. 

The monomer split-feed operation was also shown to work in a continuous stirred-tank pre-reactor. When certain conditions are fulfilled, the split-feeds... 

Newton, MA). Microfluidization based on patented technology in which a split feed stream flows into an interaction chamber at ultrahigh velocities and pressures (up to 1500 ft and 16,000 psi respectively). The two streams collide head-on and exit the chamber at a right angle to the collision. The force of the collision creates cavitation and shear forces to decrease the particle size. The feed stream was prepared in a manner similar to the coarse emulsion in which the orange oil was blended into the carrier solution with a whisk. The Microfluidizer was operated at a pressure of 11,000 psi and the sample was collected after one pass through the interaction chamber. 

Reactor configurations involved in continuous emulsion polymerization include stirred tank reactors, tubular reactors, pulsed packed reactors, Couett-Taylor vortex flow reactors, and a variety of combinations of these reactors. Some important operational techniques developed for continuous emulsion polymerization are the prereactor concept, start-up strategy, split feed method, and so on. The fundamental principles behind the continuous emulsion polymerizations carried out in the basic stirred tank reactor and tubular reactor, which serve as the building blocks for the reaction systems of commercial importance, are the major focus of this chapter. 

Figure 5-25. Effect of partial pressure of CO2 in feed gas on regeneration efficiency (split-stream operation). Data of Benson etal. (1956)...

The most frequent application of phase-equilibrium calculations in chemical process design and analysis is probably in treatment of equilibrium separations. In these operations, often called flash processes, a feed stream (or several feed streams) enters a separation stage where it is split into two streams of different composition that are in equilibrium with each other. 

All refining operations may be classed as either conversion processes or separation processes. In the former, the feed undergoes a chemical reaction such as cracking, polymerization, or desulfurization. Separation processes take advantage of differences in physical properties to split the feed into two or more different products. Distillation, the most common of all refinery separation processes, uses differences in boiling points to separate hydrocarbon mixtures. 

The fat oil is fed to a splitter or stripping tower, where the absorbed tight constituents are separated from the oil by distillation. Usually the lean oil is the same material as the heavier part of the absorber feed, so that the bottoms from the stripper are split into lean oil, which is recycled to the absorber, and a stabilized gasoline product, which is passed on to subsequent processing operations. 

Note This is not too accurate due to switched operating line equations before the feed compositions were reached, yet, one more calculation on the stripping line would have placed us below the feed plate composition. Hence a change in reflux ratio is necessary in order to split right at the feed composition. 

The automatic controls, which split the feed and recycle to the two reactors so that the temperature reached in each stage does not exceed 482°C, were operated for a considerable portion of the total on-stream time of the methanation section. They performed quite satisfactorily. 

A recycle PFR, operating at steady-state for the reaction A +. . - products, is shown schematically in Figure 15.6, together with associated streams and terminology. At the split point S, the exit stream is divided into the recycle stream (flow rate RqJ and the product stream (flow rate q,), both at the exit concentration cA1. At the mixing point M, the recycle stream joins the fresh feed stream (flow rate q0, concentration cAo) to form the stream actually entering the reactor (flow rate (1 + R)q0, concentration ca o)-The inlet concentration c Ao may be related to cAo, cA1, and R by a material balance for A around M ... 

Consider two CSTRs of unequal sizes, Vx and V2, operating in parallel, as shown in Figure 17.2. The liquid-phase reaction, A - products, is first-order and both tanks operate at the same T. How should the total feed rate, q0, be split (at S) so as to maximize the rate of production in the combined exit streams (at M) ... 

Two modes of operation are to be studied (a) All of the feed goes to the inlet, (b) Half of the feed goes to the inlet and the other half to the middle of the reactor. The reactor is of sufficient size to give 50% conversion when all of the material is charged at the inlet. What conversion is obtained by the split flow arrangement x = fraction of A that is converted nt = nl+na+nb+nd = 1 5naO+na = na0(2.5-x)... 

I well remember one pentane-hexane splitter in Toronto. The tower simply could not make a decent split, regardless of the feed or reflux rate selected. The tower-top pressure was swinging between 12 and 20 psig. The flooded condenser pressure control valve, shown in Fig. 3.1, was operating between 5 and 15 percent open, and hence it was responding in a nonlinear fashion (most control valves work properly only at 20 to 75 percent open). The problem may be explained as follows. 

The prior discussion assumes that the feed rate, feed composition, and heat content (enthalpy) are fixed. My purpose in presenting this review of the phase rule is to encourage the routine manipulation of tower operating pressures, in the same sense, and with the same objectives, as adjusting reflux rates. Operators who arbitrarily runs a column, at a fixed tower pressure, discards one-third of the flexibility available to them, to operate the column in the most efficient fashion. And this is true, regardless of whether the objective is to save energy or improve the product split. 

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