Reactor parameters, manipulating

One advantage of the second method is that the design need not be limited to the same type of reactor. Data taken in a stirred reactor and manipulated to get intrinsic kinetic parameters could be used to estimate the performance of a tubular reactor, a packed bed, or perhaps a new type of contactor for the same reaction. Fundamental kinetic parameters obtained from a small fixed-bed reactor might lead to consideration of a fluidized-bed reactor for the large unit. Of course, pilot-plant tests of the alternate reactor type would be advised. 

Basic process control system (BPCS) loops are needed to control operating parameters like reactor temperature and pressure. This involves monitoring and manipulation of process variables. The batch process, however, is discontinuous. This adds a new dimension to batch control because of frequent start-ups and shutdowns. During these transient states, control-tuning parameters such as controller gain may have to be adjusted for optimum dynamic response. 

It is well known that a nonlinear system with an external periodic disturbance can reach chaotic dynamics. In a CSTR, it has been shown that the variation of the coolant temperature, from a basic self-oscillation state makes the reactor to change from periodic behavior to chaotic one [17]. On the other hand, in [22], it has been shown that it is possible to reach chaotic behavior from an external sine wave disturbance of the coolant flow rate. Note that a periodic disturbance can appear, for instance, when the parameters of the PID controller which manipulates the coolant flow rate are being tuned by using the Ziegler-Nichols rules. The chaotic behavior is difficult to obtain from normal... 

The non-linear dynamics of the reactor with two PI controllers that manipulates the outlet stream flow rate and the coolant flow rate are also presented. The more interesting result, from the non-linear d mamic point of view, is the possibility to obtain chaotic behavior without any external periodic forcing. The results for the CSTR show that the non-linearities and the control valve saturation, which manipulates the coolant flow rate, are the cause of this abnormal behavior. By simulation, a homoclinic of Shilnikov t3rpe has been found at the equilibrium point. In this case, chaotic behavior appears at and around the parameter values from which the previously cited orbit is generated. 

Exploitation of liquid-liquid microreactor in organic synthesis offers attractive advantages, including the reduction of diffusion path lengths to maximize the rate of mass transfer and reaction rates. Despite the advantages, interest in liquid-liquid micro reactors did not take off until recently, perhaps because of the complication of flow pattern manipulation combined with the limited numbers of liquid-liquid reactions. Initial interest focused on the control of parameters responsible for variation in flow patterns to engineer microemulsions or droplets. However, it was soon realized that liquid-liquid microdevices are more than just a tool for controlling flow patterns and further interest developed. 

Two types of disturbances are used to test the response of the system a step change in toluene recycle flowrate and a step change in the setpoint of the reactor inlet temperature controller. These two variables are the primary manipulators for production rate. In the results presented below we will explore which of the two is better. In addition we will see how several design parameters (FEHE area and heat-exchanger bypassing) impact the load response of the process. 

Through this systematic study, Exelus was able to identify an optimal window of design parameter values that were then used to develop the catalyst. By judicious manipulation of the active material composition, researchers at Exelus developed a unique solid-acid catalytic system that has roughly 400% more active sites than a typical solid-acid catalyst. The catalyst activity was found to be higher than a typical liquid acid catalyst, which means that smaller amounts of catalyst are required, allowing one to design alkylation reactors with significantly lower volumes. 

Mapping of the behaviour of the system undo- this premise shows that, undo- all conditions permitted by the above restrictions, the operation should be carried out at the highest temperature allowed. The oxidation of CO is a highly exothermic reaction and allowing the temperature to increase to this maximum from some lowo inlet temperature will not increase productivity over that available under isothermal operation at the maximum allowed temperature. In practice this type of operation causes problems since maintaining isothermality in highly exothermic reactions is difficult, but we will ignore this issue. The free parameters one can manipulate are then the feed ratio and the reactor total pressure. 

Properties of the reactive fluid within the inner tube are identified by the subscript Rx, and represents the kinetic rate law that converts reactant A to products. Only one independent variable is required to simulate reactor performance because axial coordinate z and average residence time for the reactive fluid trx are related by the average velocity of the reactive fluid j)rx. In comparison with the single-pipe reactor discussed earlier, the double-pipe reactor contains two additional design parameters that can be manipulated to control thermal runaway radius ratio k and average velocity ratio x/f, defined as follows ... 

The important dimensionless parameter that determines the significance of external mass transfer resistance for nth-order irreversible chemical kinetics in packed catalytic tubular reactors was introduced in equation (30-63) as a = iS(CA.iniet)" Simple algebraic manipulation allows one to relate a to the interpellet Damkohler number, the effectiveness factor, the mass transfer Peclet number, and a few other dimensionless parameters. For example, let the coefficient of the chemical reaction term in the dimensionless mass transfer equation be defined as follows ... 

A multi-purpose mast manipulator, based on the CEGB Oldbury Mk III design modified to accommodate the Calder/Chapelcross space restrictions, has been built by Taylor-Hitec. The manipulator is pneumatically powered and comprises a two-section mast (because of reactor building space limitations), an arm and a knuckle sections, with the basic design parameters being shown schematically in Figure 9. The movements are controlled from a central console which has TEACH-AND-REPEAT and RE-TRACE facilities. There are two independent... 

The above example illustrates that changing falling-film reactor design (diameter, length) has consequences in terms of required volumetric flow and gas concentration, assuming a max allowable organic feed per mm circumference per hour. This latter parameter can not be manipulated upwards due to heat transfer limitations. 

The states c, cb are the concentrations of A and B respectively, T is the reactor temperature and Tc is the coolant temperature. The heat flow Q that influences the temperature of the coolant is assumed to be constant. The variable to be regulated is the product concentration cp in the outflow and the manipulated variable is the inlet flow rate q. A schematic of the process is depicted in Fig. 2. For further details on the process and parameter values we refer to Ref. 19. 

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