Runaway process

In Figure 9, we have also represented the variation of (Rp)max with the temperature at which this quantity was measured (curve b). At first sight, this nearly straight line seems to indicate that an increase of the temperature leads to a faster polymerization, a typical behavior observed in thermal runaway processes. Actually, the polymerization rate is growing here because the light intensity was increased, which leads in turn to a greater rise in temperature. 

The amazing thing about Example 2.5.2 is that the system has solutions that reach infinity in finite time. This phenomenon is called blow-up. As the name suggests, it is of physical relevance in models of combustion and other runaway processes. 

There are many kinds of system failures that can create emergencies. For example, intermption of operations may create hazardous conditions. Boiler overheating can cause dangerous conditions requiring quick action. Failure of temperarnre limit controls can lead to runaway processes. Failure of pressure limit controls can lead to rupmre of pipes, gaskets, vessels, and other equipment. Sudden releases of steam, gas, fuel, or hazardous chemicals can create dangers... 

I. Uchida, H. Ishikawa, M. Mohamedi, and M. Umeda [2003] AC-Impedance Measurements during Thermal Runaway Process in Several Lithium/Polymer Batteries, Journal of Power Sources 119-121, 821-825. 

R. D. Coffee, in H. H. Fawcett and W. S. Wood, Safety and Accident Prevention in Chemical Operations, 2nd ed., Wiley-Interscience, New York, 1982, p. 305 International Symposium on Runaway Reactions, Center for Chemical Process Safety, New York, 1989, pp. 140, 144,177, 234. 

Hazards from combustion and runaway reactions play a leading role in many chemical process accidents. Knowledge of these reactions is essential for control of process hazards. It is important that loss of containment be avoided. For example ... 

Opening a manual valve. Manual valves which are normally closed to isolate two or more pieces of equipment or process streams can be inadvertently opened, causing the release of a high-pressure stream or resulting in vacuum conditions. Other effects may include the development of critical flows, flashing of liquids, or the generation of a runaway chemical reaction. 

Runaway Reactions Runaway temperature and pressure in process vessels can occur as a resiilt of many fac tors, including loss of cooling, feed or quench failure, excessive feed rates or temperatures, contaminants, catalyst problems, and agitation failure. Of major concern is the high rate of energy release and/or formation of gaseous produc ts, whiai may cause a rapid pressure rise in the equipment. In order to properly assess these effec ts, the reaction kinetics must either be known or obtained experimentally. 

The second context is the process reac tor. There is a potential for a runaway if the net heat gain of the system exceeds its total heat loss capabihty. A self-heating rate of 3°C/day is not unusual for a monomer storage tank in the early stages of a runaway. This corresponds to 0.00208°C/min, 10 percent of the ARC s detection limit. ARC data for the stored chemical would not show an exotherm until the self-heating rate was 0.02°C/min. Therefore, onset temperature information from ARC testing must be used with considerable caution. 

Reactive System Screening Tool (RSST) The RSST is a calorimeter that quickly and safely determines reactive chemical hazards. It approaches the ease of use of the DSC with the accuracy of the VSP. The apparatus measures sample temperature and pressure within a sample containment vessel. Tne RSST determines the potential for runaway reactions and measures the rate of temperature and pressure rise (for gassy reactions) to allow determinations of the energy and gas release rates. This information can be combined with simplified methods to assess reac tor safety system relief vent reqiiire-ments. It is especially useful when there is a need to screen a large number of different chemicals and processes. 

Equipment Constraints These are the physical constraints for individual pieces of eqiiipment within a unit. Examples of these are flooding and weeping limits in distillation towers, specific pump curves, neat exchanger areas and configurations, and reactor volume limits. Equipment constraints may be imposed when the operation of two pieces of equipment within the unit work together to maintain safety, efficiency, or quahty. An example of this is the temperature constraint imposed on reactors beyond which heat removal is less than heat generation, leading to the potential of a runaway. While this temperature could be interpreted as a process constraint, it is due to the equipment limitations that the temperature is set. 

Runaway reaction Interlock manway with vessel pressure with manway, Design system for closed manual operation open—foam out (can be acid based), operator contacted by process materials. CCPS G-22 CCPS G-23 CCPS G-29 Fisher 1990 ISAS84.01... 

A polymerization process involving a monomer, an organic peroxide initiator and an organic solvent underwent an energetic runaway reaction. All the contents in the polymerization reactor were lost. The emergency relief system prevented major damage to the equipment. 

At shift change the operator verbally told the relief operator what process steps remained. The relief operator tested for, and detected unreacted monomer in the copolmerization process. In an attempt to complete the reaction, the relief operator added additional initiator to the reactor a runaway reaction promptly occurred. 

After the incident, an investigation team determined that the first operator had not added the initiator when required earlier in the process. When the relief operator added the initiator, the entire monomer mass was in the reactor and the reaction was too energetic for the cooling system to handle. Errors by both operators contributed to the runaway. Both operators were performing many tasks. The initiator should have been added much earlier in the process when much smaller quantities of monomer were present. There was also no procedure to require supervision review if residual monomers were detected. The lesson learned was that operators need thorough training and need to be made aware of significant hazardous scenarios that could develop. 

Tuma, L. and C. Bagner 1998. Assurance of Safe Pilot Plant Scale-Up of Chemical Processes, in (G. A. Melhem and H. G. Fisher, eds.). International Symposium on Runaway Reactions, Pressure Relief Design, and Effluent Handling, American Institute of Chemical Engineers, New York. 

Have formal process hazard analyses (PHAs) been completed for highly hazardous processes (for example, those processes involving toxic or volatile substances, highly toxic materials, severe lachrymators, flammables, explosive compounds or potential runaway reactions) If yes, please summarize status of each. 

A particularly striking recent application was by Deevi and Sikka (1997) they developed an industrial process for casting intermetallics, especially nickel alumi-nides, so designed (by modifying the furnace-loading sequence) that the runaway temperature rise which had made normal casting particularly dangerous was avoided. 

In certain processes, decomposition reactions or temperature runaways may... 

Barton, J. A. and Nolan, P. F. Incidents in the Chemical Industry due to Thermal-runaway Chemical Reactions, Hazards X Process... 

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