Runaway sensitive

The most reliable method of detecting a runaway is online analysis of a product formed in the runaway reaction. For example, CO2 can be monitored in the offgas during the runaway-sensitive synthesis of ethylene oxide. If its concentration increases above a specified limit, the reactor must be shut down, purged with nitrogen, and for a certain period cooled to a lower temperature before operation is recommenced. 

The variations were mainly due to operating conditions very close to the parametrically sensitive region, i.e., to the incipient temperature runaway. Small errors in the estimation of temperature effects caused runaways and, consequently, large differences. 

Heat exchanger-like, multi-tube reactors are used for both exothermic and endothermic reactions. Some have as much as 10,000 tubes in a shell installed between tube sheets on both ends. The tubes are filled with catalyst. The larger reactors are sensitive to transient thermal stresses that can develop during startup, thermal runaways and emergency shut downs. 

As can be seen most of the tubes were still in a non-sensitive state while about ten were in runaway conditions. This wiU give an operational feel for how uniform the catalyst charge should be and how closely the system may approach incipient runaway, for a single tube in a multi-tube production unit. 

The absolute and spectral sensitivities can often vary by up to 100% within a few millimeters on the surface of the photocathode [49]. Figure 19 illustrates this effect for a sideways and vertical adjustment of a photomultiplier, in addition slight maladjustment of the light entrance can lead to zero hne runaway as a result of thermal effects. 

During the development of these criteria the Semenov analysis was extended to systems with heat-exchanger reservoir temperatures different from feed temperatures (Tr < Tq) and with delayed runaway (larger value of e), which resulted In significant concentration drift prior to runaway. Since values of e for chain-addition polymerizations are not nearly as small as those for the gaseous explosions Investigated by Semenov, R-A Is not as sensitive nor Is It as early In terms of extent of reaction. 

Reactive hazards, 44, 228 explosive, 235 mixtures, 231, 468 pyrophoric, 17, 214 thermal runaway, 252 unstable, 228 water-sensitive, 228... 

Castleford, England (Ref. 13) 5 (3 in buildings) Heat-sensitive and unstable nitrotoluene residue was overheated during the preparation for maintenance. A runaway reaction caused a jet flame that destroyed a wooden control room. 

The monomer is sensitive to light, and even when inhibited (with aqueous ammonia) it will polymerise exothermally at above 200° C [1]. It must never be stored uninhibited, or adjacent to acids or bases [2], Polymerisation of the monomer in a sealed tube in an oil bath at 110° C led to a violent explosion. It was calculated that the critical condition for runaway thermal explosion was exceeded by a factor of 15 [3]. Runaway polymerisation in a distillation column led to an explosion and fire [4], See other polymerisation incidents... 

Several commercial calorimeters are available to characterize runaway reactions. These include the accelerating rate calorimeter (ARC), the reactive system screening tool (RSST), the automatic pressure-tracking adiabatic calorimeter (APTAC), and the vent sizing package (VSP). Each calorimeter has a different sample size, container design, data acquisition hardware, and data sensitivity. 

Explanation of Principal Application Codes 1 = screening 6 = reaction due to oxidation 2 = thermal stability 7 = runaway behavior (initial phase) 3 = sensitive thermal stability 8 = complete runaway behavior and 4 = very sensitive thermal stability simultaneous pressure measurements 5 = study autocatalysis, contaminations, 9 = time to maximum rate of reaction inhibitor depletion ... 

The discussions in Sections 3.1 and 3.2 show that the interaction among enthalpies of reaction, reaction kinetics, and surrounding conditions is of paramount importance relative to the existence of potential thermal hazards such as runaways. Whereas valuable information on parameter sensitivity can be estimated by a theoretical approach, it remains of vital importance to evaluate hazards by appropriate and adequate laboratory tests to obtain information on the rates of heat and gas generation, and the maximum quantities of heat and gas involved. Materials which are real to the process should be used in tests to assure that the effects of any contaminants are recognized. 

Intentional heating of a vessel containing thermally sensitive material, due to lack of recognition of the runaway hazard or other reason... 

Chemical reactivity has many different names, such as reactive materials, runaway reaction hazards, instability, thermal sensitivity, and incompatibility. Flammability, toxicity, and corrosion are also forms of reactivity. Since these topics are addressed elsewhere, our focus here will be on those reactions that fall outside the normal definitions of flammable or toxic and that generally occur far more rapidly than corrosion. 

Several types of hazardous chemical reactivity, with 36 percent attributed to chemical incompatibility, 35 percent to runaway reactions, and 10 percent to impact-sensitive or thermally sensitive materials. 

Loss prevention of polyethylene plants is outlined in Chapter 7.2. The major hazard that can occur is the runaway of the high-pressure reactor and decomposition of ethylene besides fire and disintegration of high-pressure separators, pipes, and compressors. The critical conditions for runaway and ethylene decomposition during homo- and copolymerization are revealed together with the influence of decomposition sensitizers. Relief devices and venting systems are described. 

Shortly after interruption of vacuum distillation from an oil-bath at 115°C to change a thermometer, the ester exploded violently and this was attributed to overheating [1]. A commercial sample of undetermined age exploded violently just after vacuum distillation had begun [2]. In an examination of thermal explosion behaviour, the title compound was used as a model compound in autoclave experiments at low, high or constant pressure. Three stages in the overall process were identified thermal runaway, initiation, and then explosion, and these are studied and discussed in detail. In the high pressure experiments, maximum rates of pressure rise approaching 1000 kbar/s were observed [3]. It is shock sensitive [4]. 

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