Feed-Temperature Hysteresis

At this point, the situation changes Any farther increase in the feed temperature, however small, causes the conversion to increase substantially, e.g., to point I and then to point J. The corresponding feed temperatures are Tqj and Tqj. 

The sudden increase in conversion when the feed temperature is being increased from a low initial value is known as Ught off, and the feed temperature at which this rapid jump is observed, 7b,EH in this example, is called the light-off temperature. The sudden decrease 

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The existence of multiple steady states for a CSTR gives rise to several interesting and important phenomena, two of which are known as blowout and feed-temperature hysteresis. 

CSTRs and combinations of an adiabatic reactor and a feed/ product heat exchanger can exhibit multiple steady states and associated phenomena, such as feed-temperature hysteresis and blowout ... 

Hysteresis loops of reactor temperature versus air feed temperature (Effect of gas oil flow rate)... 

Hysteresis of steady reactor temperature Tupon variation of feed temperature Tq. 

Figure 8-11 shows hysteresis. Over a certain region of feed temperature, the conversion is not the same when the feed temperature is being increased as it is when the feed temperature is being decreased, even though the actual feed temperature is the same in both cases. 

We should note that hysteresis effects could be observed in situations such as those depicted in Figure 10.5. Suppose that the temperature of the feed stream is such that the temperature intercept moves from slightly below T to slightly above T". Assuming that all other independent variables are held constant, the temperature of the reactor contents will rise slowly, because the conversion... 

As shown in Scheme 2.27, POEVE and PNIPAM have similar structures with both hydrophilic and hydrophobic parts in each monomer unit. Quite recently, our group examined another possibility for thermosensitive phase separation random copolymers of hydrophilic and hydrophobic monomers.Although random copolymers have been investigated previously, the achieved phase separation was broad, with hysteresis and low turbidity. By living cationic polymerization in the presence of added bases, our group successfully prepared random copolymers of IBVE and HOVE, both of which are typical hydrophobic and hydrophilic monomers, and which are not thermosensitive themselves. At low temperature, the polymers were soluble in water, but when the temperature was increased to a critical point, the transparent solution became opaque. The phase separation was quite sensitive (Scheme 2.27(a)) and the temperature of phase separation was governed by the monomer feed ratio. 

Increasing the adiabatic temperature rise B (from B = 0.1 (reference case) to B = 1.0) leads to the relocation of the hysteresis variety to lower values of Da and higher values of q. This situation results in a larger area of state multiplicity. However, the MSS region does not vanish when the heat of reaction is reduced to zero. Figure 7.8 depicts the feasibility boundaries at large heat of reaction and different feed condition 9q. ... 

For these two applications, the command is repetitive therefore, the drift and hysteresis can be anticipated through a feed-forward correction, which remains dependant on the temperature and the voltage. A typical command including a pre-shaper sent to the piezo actuator is shown in Fig. 6.24. The command anticipates the drift effect during the plateau. The command amplitude is a function of the temperature. This approach is simple (it does not need any position sensor) but requires a calibration effort. 

In figure 8 conversion plots are displayed for the oxidation of methane over A-Amox-2. It is noted that upon exposing the (completely reduced) catalyst to the reaction feed, which contains excess oxygen, the nickel is almost immediately converted to nickel oxide, the active phase in the oxidation of methane. The hysteresis between the curves at increasing and decreasing temperature indicates severe... 

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