Steady-state behavior robustness

The analysis of steady-state behavior allows the designer to explore the effect of kinetics, gas/liquid mass transfer and hydrodynamics and the steady-states of the unit. On the other hand, dynamic simulations are carried out to check the robustness of the design, in terms of the ability of maintain product purities and conversion in desired range... 

If all roots are different and their real parts are nonzero, then the corresponding steady states are robust in a sense that dynamic behavior of the systems is not changed upon small variations in the right side of Eq. (9.80). When 4 > 0, 0, <7 — 44 > 0, the roots are... 

Linear control theory will be of limited use for operational transitions from one batch regime to the next and for the control of batch plants. Too many of the processes are unstable and exhibit nonlinear behavior, such as multiple steady states or limit cycles. Such problems often arise in the batch production of polymers. The feasibility of precisely controlling many batch processes will depend on the development of an appropriate nonlinear control theory with a high level of robustness. 

A MCFC stack interacts with other system components and causes an interdependency between them. To investigate transient behavior, the plant is assumed to be at steady state corresponding to rated power and subjected to a sudden variation in power demand. This chapter has developed the control system with an adaptive minimum variance controller and based on the simulation study, the resulting controller is robust enough to stabilize the system for different operating conditions. 

Cases II. Single steady state Case Ila. 5i > 0 and S2 < 0, but not both zero Case Ilb. 5i < 0 and S2 >0, but not both zero) There is some cross talk between a very reactive species and a refiactoiy species. The latter dominates the system s long-time behavior, which is robust in that = k22 and X2 = 1 in Case Ila, and = ku and Xj = 1 in Case lib. 

It should be emphasized that the aforementioned observations regarding material behavior are in stark contrast to steady-state catalytic microreactor results [17]. At steady state, FeCr alloy microreactors provided more robust combustion (extended stability limits) against imposed external heat losses when compared to ceramic ones. On the other hand, the present transient studies clearly show the advantage of ceramic materials in terms of start-up. However, in either steady or transient operation, cordierite microreactors lead to higher wall temperatures (see Fig. 8.9). Both facts must be considered when selecting appropriate reactor materials for specific applications. 

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