Intermediate feed location

For systems involving recycle streams or intermediate feed locations, the method of successive substitution can be used [Mohan and Govind, 1988a]. Moreover, multiple reactions including side reactions and series, parallel or series-parallel reactions result in strongly coupled differential equations. They have been solved numerically using an implicit Euler method [Bernstein and Lund, 1993]. 

Figure 11.13. Schematic of a membrane reactor with an intermediate feed location and recycle (Mohan and Govind, 1988a]...

Continuous reactors comprised of a CSTR train are often operated with a single feed location in the first reactor. The use of intermediate feed locations can be advantageous for several reasons. First, if the conversion in the first reactor is low or... 

A second reason for intermediate monomer feed locations is to control copolymer composition and particle morphology. Unlike the batch reactor in which the more reactive monomer reacts first, the copolymer produced in a CSTR should have uniform composition. If all monomers are fed to the first reactor, however, the polymer formed in the downstream reactors will contain less of the most reactive monomer. Thus, the use of intermediate feed locations in a CSTR system is analogous to the programmed addition of reactive monomers in semibatch reactors. The location and rates of the various monomer streeims will influence copolymer composition and particle morphology. 

Intermediate feed locatioiis. Another way of improving the conversion of a simple membrane reactor is to introduce the feed stream at one or multiple intermediate locations along the reactor length. In the following type of reactions involving one reactant and two products... 

When reaction is instantaneous relative to mixing, the intermediate R does not survive but is fully converted to S. Thus A, = 1. Between these two limits of slow and instantaneous reaction, the reaction is said to be fast and A, takes an intermediate value. In the fast regime physical factors such as viscosity of the solution, feed location, stirrer speed, concentration level at constant stoichiometric ratio influence A,. 

E3. A distillation column with at total condenser and a total reboiler is separating ethanol from water. Reflux is returned as a saturated liquid, and boilup is returned as a saturated vapor. CMO can be assumed. Assume that the stages are equilibrium stages. Column pressure is 1 atm. A saturated liquid feed that is 32 mol% ethanol is fed to the column at 1000 kmol/h. The feed is to be input on the optimum feed stage. We desire a distillate conposition of 80 mol% ethanol and a bottoms conposition that is 2 mol% ethanol. A liquid side stream is removed on the eighth stage from the top of the column at a flow rate of S = 457.3 kmol/h. This liquid is sent to an intermediate reboiler and vaporized to a saturated vapor, which is returned to the column at its optimum feed location. The external reflux ratio is Lq/D = 1.86. Find the optimum feed locations of the feed and... 

D4. We wish to wash an alumina solids to remove NaOH from the entrained liquid. The underflow from the settler tank is 20 vol % solid and 80 vol % liquid. The two solid feeds to the system are also 20 vol % solids. In one of these feeds, NaOH concentration in the liquid is 5 wt %. This feed s solid flow rate (on a dry basis) is 1000 k hr. The second feed has a NaOH concentration in the liquid of 2 wt %, and its solids flow rate (on a dry basis) is 2000 k h. We desire the final NaOH concentration in the underflow liquid to be 0.6 wt % (0.006 wt frac) NaOH. A countercurrent operation is used. The inlet washing water is pure and flows at 4000 k h. Find the optimum feed location for the intermediate feed and the number of equilibrium stages required. 

In matter of fact, the feedstream may be prorated into any of the cells, at will, but would involve stage-to-stage or cell-to-cell calculations. However, in distillation, the rule of thumb is that multifeed locations are used only if there are several feedstreams with different compositions. Each feedstream is introduced at the point or location that most likely approximates its own composition. This is a facet of so-called optimum feed location, where the overall separation is made more efficient. The same sort of remarks can be made for intermediate permeate or reject withdrawal, if a stream product of a particular composition is desired.)... 

Columns with several inputs of feed have one or several intermediate sections, located between these inputs of feed. To calculate minimum reflux mode... 

The Great Lakes have suffered the invasion of numerous exotic species of which the smelt, alewife and sea lamprey are probably the best known. More recently, two more species have entered the lakes probably via ballast water from foreign ships. The ruffe (Gymnocephalus cemuus) a small percid, feeds on the eggs and larvae of other percids and whitefish. The ruffe is currently considered to be a threat to Lake Superior s 5- 10 million whitefish fishery. The zebra mussel (Dreissena polymorpha) was discovered in Lake St. Clair in 1985 (31). It has subsequently been discovered at locations throughout the Great Lakes and is of major concern not only environmentally but economically. It has already colonized numerous industrial and domestic water intakes in sufficient numbers to entirely block water flow and is also an intermediate host to parasites which eventually invade fish. 

Influence of the downstream plants. Up to now, we have regarded the coal gasification reactor with the waste heat recovery system as an isolated unit. In the event that the gas generated is intended to be used as fuel gas, for example in a combined power station, this approach is justified. If, however, the gas is to be used as synthesis gas, the effect of the downstream units must be taken into consideration. In such cases it is necessary to feed the gas to a CO shift conversion unit in order to obtain the C0/H2 ratio required for the synthesis process. Apart from gasification at atmospheric pressure, which requires an intermediate compression step, it has proved advisable to locate the CO shift conversion directly downstream of the gasification section. A stage in which dust particles are removed from the gas is situated between these two units. It is assumed that exergy losses do not occur in this unit. 

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