Cascade example

This is a group of compounds having a ladder-like array of macrorings through which a cation or other species may cascade. Examples of such structures may be found in Ref. 2. 

Examples of cascading use have existed for many years in Italy and Japan (see Minohara Sekioka 1980 Lund 1987). Further cascading examples can be found in Dickson Fanelli (1990, 1995). 

A bioresource can be used multibranched—to produce one main product and one or more coproducts. Furthermore, after food consumption and after substantial utilization of a biobased product, some of the components of the original product may be used again. In this way bioresources can be used in cascades. Examples are shown in Ref. 30. However, utilization never can be repeated unlimited, since losses occur in each step.The final stage in the bioresource utilization chain is either energetic utilization or disposal. 

Designof enamine-enamine cascades Examples of enamine-enamine and enamine-enamine cyclization cascades... 

Design of enamine-iminium cascades Examples of [4-1-2] reactions with enamine-activated dienes Inverse-electron-demand [4-1-2] reactions with enamine-activated dienophiles Enamine-iminium-enamine cascades... 

Example 6.3 The problem table cascade for the process in Fig. 6.2 is given in Fig. 6.18. Using the grand composite curve ... 

Example 6.5 The stream data for a heat recovery problem are given in Table 6.7. A problem table analysis for AT , = 20°C results in the heat cascade given in Table 6.8. The process also has a requirement for 7 MW of power. Two alternative combined heat and power schemes are to be compared economically. 

Example 6.6 The problem table cascade for a process is given in Table 6.9 for — 10°C. It is proposed to provide process cooling by steam generation... 

Many misconceptions exist about cascade control loops and their purpose. For example, many engineers specify a level-flow cascade for every level control situation. However, if the level controller is tightly tuned, the out-flow bounces around as does the level, regardless of whether the level controller output goes direcdy to a valve or to the setpoint of a flow controller. The secondary controller does not, in itself, smooth the outflow. In fact, the flow controller may actually cause control difficulties because it adds another time constant to the primary control loop, makes the proper functioning of the primary control loop dependent on two process variables rather than one, and requites two properly tuned controllers rather than one to function properly. However, as pointed out previously, the flow controller compensates for the effect of the upstream and downstream pressure variations and, in that respect, improves the performance of the primary control loop. Therefore, such a level-flow cascade may often be justified, but not for the smoothing of out-flow. 

Application. In addition to providing a relatively simple means for estimating the production of separation cascades, the separative capacity is useful for solving some basic cascade design problems for example, the problem of determining the optimum size of the stripping section. 

Equations 27 and 28 can be used in conjunction, along with the corresponding equations for the stripping section, to produce an ideal plant profile such as is shown in Figure 4 where F is plotted against for the example of an ideal cascade to produce one mol of uranium per unit time enriched to 90... 

For the example considered above, the total cascade upflow is found to be 33 x 10 mols per unit time. 

The great utility of the separative capacity concept Hes in the fact that if the separative capacity of a single separation element can be deterrnined, perhaps from equations 7 or 10, then the total number of such identical elements required in an ideal cascade to perform a desired separation job is simply the ratio of the separative capacity of the cascade to that of the element. The concept of an ideal plant is useful because moderate departures from ideaUty do not appreciably affect the results. For example, if the upflow in a cascade is everywhere a factor of m times the ideal upflow, the actual total upflow... 

Continuous polymerization in a staged series of reactors is a variation of this process (82). In one example, a mixture of chloroprene, 2,3-dichloro-l,3-butadiene, dodecyl mercaptan, and phenothiazine (15 ppm) is fed to the first of a cascade of 7 reactors together with a water solution containing disproportionated potassium abietate, potassium hydroxide, and formamidine sulfinic acid catalyst. Residence time in each reactor is 25 min at 45°C for a total conversion of 66%. Potassium ion is used in place of sodium to minimize coagulum formation. In other examples, it was judged best to feed catalyst to each reactor in the cascade (83). 

Example. With the example cascaded system at an evaporator temperature of -100°F, the horsepower requirement is 6.2hp/ton refrigeration. A ton of refrigeration is equal to 12,000 BTU/hr. 

Our example system has a flow-controlled feed, and the reboiler heat is controlled by cascade from a stripping section tray temperature. Steam is the heating medium, with the condensate pumped to condensate recovery. Bottom product is pumped to storage on column level control overhead pressure is controlled by varying level in the overhead condenser the balancing line assures sufficient receiver pressure at all times overhead product is pumped to storage on receiver level control and reflux is on flow control. 

As an example of the use of AES to obtain chemical, as well as elemental, information, the depth profiling of a nitrided silicon dioxide layer on a silicon substrate is shown in Figure 6. Using the linearized secondary electron cascade background subtraction technique and peak fitting of chemical line shape standards, the chemistry in the depth profile of the nitrided silicon dioxide layer was determined and is shown in Figure 6. This profile includes information on the percentage of the Si atoms that are bound in each of the chemistries present as a function of the depth in the film. 

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