Continuous controller modes illustration

The use of IR pulse technique was reported for the first time around the year 2000 in order to study a catalytic reaction by transient mode [126-131], A little amount of reactant can be quickly added on the continuous flow using an injection loop and then introduce a transient perturbation to the system. Figure 4.10 illustrates the experimental system used for transient pulse reaction. It generally consists in (1) the gas flow system with mass flow controllers, (2) the six-ports valve with the injection loop, (3) the in situ IR reactor cell with self-supporting catalyst wafer, (4) the analysis section with a FTIR spectrometer for recording spectra of adsorbed species and (5) a quadruple MS for the gas analysis of reactants and products. 

Figure 14.4 is the three-dimensional view of the process. The figure illustrates the relative water head at different stages. Because of flexible design, Ultrox UV/oxidation treatment systems have a number of advantages (1) very few moving parts (2) operation at low pressure (3) minimum maintenance (4) full-time or intermittent operation in either a continuous or batch treatment mode (5) use of efficient, low-temperature, and long-life UV lamps and (6) use of a microprocessor to control and automate the treatment process (Zeff and Barich, 1992). 

The mechanism for ultrasonic emulsification is primarily that of cavitation. A typical sonicator for emulsification consists of a velocity transformer coupled to a transducer, capable of oscillating in a longitudinal mode, where the velocity transformer is immersed in the liquid. Figure 4 illustrates the basic parts of a sonicator with a continuous flow attachment, like the one used in this work. In this case, the flow cell is secured to the velocity transformer by a flange and a Teflon 0-ring. The intensity of cavitation depends on the power delivered to the velocity transformer, which is relayed to the transducer from a variable transformer or some other control device not shown in Fig. 4. 

The rationale behind the definitions of iow demand mode and high demand or continuous mode in lEC 61508 is based on the failure behaviour of a safety-related system due to random hardware faults. Underlying much of the reasoning is the distinction between safety-functions that only operate on demand and those that operate continuously . A safety function that operates on demand has no influence until a demand arises, at which time the safety function acts to transfer the associated equipment into a safe state. A simple example of such a safety function is a high level trip on a liquid storage tank. The level of liquid in the tank is controlled in normal operation by a separate control system, but is monitored by the safety-related system. If a fault develops in the level control system that causes the level to exceed a pre-determined value, then the safety-related system closes the feed valve. With such a safety function, a hazardous event (in this case, overspill) will only occur if the safety function is in a failed state at the time a demand (resulting from a failure of the associated equipment or equipment control system) occurs. A failure of the safety function will not, of itself, lead to a hazardous event. This model is illustrated in Figure 4. 

Gentilcore (2002) has illustrated how the loss of the replacement solvent in the distillate can he considerably reduced hy continuously adding the replacement solvent under the condition of a constant-level control of the liquid in the pot (instead of a conventional hatch distillation). This case Illustrates how the mode of feed Introduction influences the separation achieved, even though the basic separation mechanism and the force vs. flow pattern remain unchanged. For a general and hroad introduction to hatch distillation in all forms, consult Diwekar (1996) and Seader and Henley (1998, chap. 13). Section 8.1.3 will focus on other flow vs. force configurations in hatch distillation. 

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