Dampening reactors

Prospects in the United States for deploying breeders on a large scale were bright when it was beHeved that rich uranium ore would be quickly exhausted as use of nuclear power expanded. The expected demand for uranium was not realized, however. Moreover, the utiliza tion of breeders requires reprocessing (39). In 1979 a ban was placed on reprocessing in the United States. A dampening effect on development of that part of the fuel cycle for breeder reactors resulted. The CRFBP was canceled and France and Japan became leaders in breeder development. 

When a capacitor circuit is compensated through a series reaetor. either to suppress the system harmonics or to limit the switching inrush currents (Section 23.11) or both, it will require suitable adjustment in its voltage and capacitive ratings, fhe series reactor will dampen the switching currents but consume an inductively reactive power and offset an equivalent amount of capacitive kVAr. and require compensation. The following example w ill elucidate this. 

The objective was to broaden the MWD by forcing initiator concentrations to change with periods long enough to allow marked changes in the reaction environment and short enough to use the reactor as its own blender to dampen the oscillations. 

Inputs from WWTP effluents can also affect the hydrologic and nutrient concentration regimes of recipient streams at different temporal scales. Daily variations of these parameters may be exacerbated in streams below the WWTP input by the diel patterns of the effluent discharge associated with plant operation [46]. In contrast, at the annual scale, seasonal variations of physical and chemical parameters upstream of the WWTP may be dampened by the constant input of additional water and nutrients from the WWTP. At its extreme, naturally intermittent or ephemeral streams may turn into permanent streams downstream of WWTPs [28, 30]. In these effluent-dominated streams, the relative contribution of WWTP inputs may vary widely on an annual basis, as shown by the 3-100% range measured in a Mediterranean stream [47]. Finally, WWTP inputs also cause shifts in the relative availability of N and P as well as in the relative importance of reduced and oxidized forms of N in the stream [30, 47]. The magnitude of these shifts depends on the level of wastewater treatment (i.e., primary, secondary, or tertiary treatment), the type of WWTP infrastructure (e.g., activated sludge reactor. 

Dynamic analysis of piston flow reactors is fairly straightforward and rather unexciting for incompressible fluids. Piston flow causes the d5mamic response of the system to be especially simple. The form of response is a hmiting case of that found in real systems. We have seen that piston flow is usually a desirable regime from the viewpoint of reaction yields and selectivities. It turns out to be somewhat undesirable from a control viewpoint since there is no natural dampening of disturbances. 

For chemiluminescence measurements, a postcolumn reactor with a pulse-dampening filter was added to the HPLC apparatus. A 3-cm piece of narrow-bore tubing joined the pulse dampener to a Valeo l-/tl T chemiluminescent reagent with the chromatographic eluent. A C8 ECONOSPHERE (250 X 4.6-mm ID) column was used. Modifications were made with the... 

Reactant feeds are generated by vaporizing liquid flows from HPLC pumps with manometric pulse dampeners or high-pressure syringe pumps and mixing this vapor with gas components metered through mass flow controllers. This reaction feed is then divided between the 48 channels equally by using flow restrictors such as silica capillaries or micromachined channels (Fig. 3.12). The capillaries feed into the inlet stand-offs of the reactor modules. 

Another method used to dampen the catalyst activity in the fluidized-bed process is to deliberately add poisons to the reactor, such as 02 in small amounts. It was discovered that these poisons sometimes cause a broadening or narrowing of the MW distribution of the polymer, because they also affect the active site distribution on the catalyst. 02, for example, tends to increase polymer MI and broaden the MW distribution, which makes the polymer more shear-thinning. Consequently, poisons are sometimes intentionally added to manipulate polymer properties in this process. 

Figure 18.14. This results in a reduction of mass-transfer at that end of the bed close to the bulk solution, which in turn dampens the local mass-transfer coefficient. As this process continues, there builds up a point across the profile of the reactor, where the flux is maximum. Toward the current collector, more and more of the product is produced and as a result, the flux values are lower. Toward the bulk, the mass transfer is sluggish and thus on either side of the point of maximum, the flux values are lower. This point of maximum reaction front moves toward the current collector surface with increase in the residence time (t) and toward the end of the residence...

A storage tank is being used in a chemical plant to dampen fluctuations in the flow to a downstream chemical reactor. The exit flow from this tank will be kept constant at 1.5 kg/s if the instantaneous flow into the tank exceeds this, the level in the tank will rise, while if the instantaneous flow is less, the level in the tank will drop. If the instantaneous flow into the storage tank is 1.2 kg/s, what is the rate of change of mass in the tank ... 

There is absolutely no reported study on k a in stirred tank reactors containing internal coils. The work of Nikhade (2006) indicates that the gas holdup in such stirred tank reactors increases due to the presence of the coils. This observation implies that the effective gas-liquid interfacial area is also correspondingly higher. However, because of the dampening of the turbulence caused by the coil, the true... 

Today some 432 operable reactors with combined capacity of 372 GWe require 65,0001 of uranium from mines (or the equivalent from stockpiles or secondary sources) each year. The capacity is growing slowly, and at the same time the reactors are being run more productively, with higher capacity factors and reactor power levels. However, these factors increasing fuel demand are offset by a trend for increased efficiencies, so demand is dampened over the 20 years from 1970 there was a 25% reduction in uranium demand per kWh output in Europe due to such improvements, which continue today. Each GWe of increased capacity will require about 200 tU/year of extra mine production routinely and about 2.5-times this for the first fuel load. 

The process sensitivity function for the modified reactor-separator problem is shown in Fig. 6. As seen from the figure, the recycle feedback increases the disturbance sensitivity by a factor 4,2 at low frequencies, while it in fact serves to slightly dampen the disturbance sensitivity, i.e., Sp < 1, at high frequencies. 

Figure G.2 Use of a surge tank to dampen the propagation of flow disturbances between a reactor and a separator.

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