Safe operating region

Calvert found that reentrainment from the baffles was affected by the gas velocity, the liquid-to-gas ratio, and the orientation of the baffles. Horizontal gas flow past vertical baffles provided the best drainage and lowest reentrainment. Safe operating regions with vertical baffles are shown in Fig. 14-112. Horizontal baffles gave the poorest drainage... 

FIG. 14-112 Safe operating region to prevent reentrainment from vertical zigzag baffles with horizontal gas flow. (Calveii, Yung, and Leung, NTIS Puhl. PB-24S050, 1975.)... 

Liquid-liquid reactions safe operation regions given in co-ordinates Steensma and Westerterp (1988, 1990)... 

The defense against this type of accident is to prevent the accident in the first place. Inherent safety, described in chapter 1, is the first line of defense. The second line of defense is better process control. A major effort is always directed toward controlling the process within safe operating regions. Dangerous high-pressure excursions must be prevented or minimized. 

Chemical analysis of reactor contents and of the surrounding environment is an important way to understand the status of a plant and to identify problems at the incipient state of development. When problems are identified at an early stage, action can be taken to return the system to safe operating regions with no adverse consequences. 

Figure 5.23 IsSpice results of safe operation region circuitry.

FIG. 14-124 Effect of gas and liquid rates on onset of mesh reentrainment and safe operating regions. To convert meters per second to feet per second,... 

MPT curve safe operating region is to the right of the curve. 

The dependence of the risk parameters on process variables such as the concentrations of monomer, polymer, initiator or catalyst, solvent, water and particle size (in emulsion) and MWD are of paramount importance to establish the safe operation regions of polymerization reactors, and furthermore to develop optimal control strategies imder safe conditions. The maximum pressure, Pmax> and maximum temperature, Tmax achieved during the runaway depends on the process conditions (e.g., the higher the amount of monomer in the reactor and the process temperature, the higher Pmax and Tmax)- Also important is the rate at which the runaway reaches the maximum pressures and temperatures. This rate will provide an indication of the time that the operator/control system of the plant has to react in order to keep the polymerization imder safe conditions. 

When operation parameters exceed normal operational limits the protection system actuates automatically and tries to return to normal operational conditions. If it fails it might give an alarm signal for possible corrective operator actions. However, if departure from a safe operational region occurs, protection system initiates die safety function. Examples of protection systems are the systems measuring temperature, pressure, neutron flux etc. 

Choice of Safe Operating Regions (Initial Conditions and Phase Diagram)... 

Yu et al.f made a proposal to prescribe an operating region for co-crystal production. The safe starting point is situated in the domain common to domain 4d at the initial and final temperatures. Depending on the evolution of the phase diagram with the temperature, this safe operating region may be only a part of domain 4d. 

The presence of co-crystals may act as a nucleation substrate for another solid phase by a heterogeneous nucleation mechanism. Nevertheless starting the crystallization by seeding in the safe operating region prevents the occurrence of such undesired heterogeneous nucleation. 

If the feed flow is within the safe operating region, then the signal from the multiplier will pass through the high selector, since it is higher than the low limit. It will also pass... 

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