Runaway incident

The control of chemical reactions (e.g., esterification, sulfonation, nitration, alkylation, polymerization, oxidation, reduction, halogenation) and associated hazards are an essential aspect of chemical manufacture in the CPI. The industries manufacture nearly all their products, such as inorganic, organic, agricultural, polymers, and pharmaceuticals, through the control of reactive chemicals. The reactions that occur are generally without incident. Barton and Nolan [1] examined exothermic runaway incidents and found that the principal causes were ... 

Maddison, N., and R. L. Rogers (1994). "Chemical Runaways Incidents and Their Causes." Chemical Technology Europe, (November/December), 28-31. 

It should be noted that "rules of thumb" giving a ratio of the volume of the containment/ disposal system to the volume of the reactor may result in vast undersizing and could lead to overpressurisation of the reactor and relief system during a runaway incident. 

In order to control the reaction course and so avoid a runaway incident, it is essential to understand how heating-cooling systems of reactors work and what their performance is. These topics are reviewed in this chapter, where different heating and cooling systems are reviewed from the particular implications on process safety. In the first section, the different heating and cooling techniques... 

Nolan, P.F. and Barton, J.A. (1987) Some lessons from thermal runaway incidents. Journal of Hazardous Materials, 14, 233-9. 

Maddison, N. and Rogers, R.L. (1994) Chemical runaways, incidents and their causes. Chemical Technology Europe, (11-12) 28-31. 

The results of the runaway incidents ranged from a simple foam-over of the reaction mass, to large increases in temperature and pressure leading to violent loss of containment. In some instances this caused the release to the environment of quantities of flammable or toxic materials up to several tonnes. In a few cases where flammable materials were released, a fire or a secondary explosion followed. Thermal runaways caused four fatalities and 82 injuries (as defined in relevant health and safety legislation ) in the period 1962-1987. 

Manufacturing industries in which batch reactor runaway incidents have been reported during the period 1962-1987... 

Studies of industrial incidents have shown that certain types of reactions have resulted in runaway incidents and we can learn from their experience. Incidents involving the following processes (listed in decreasing order of incidents) have resulted in runaway reactions ... 

Fig. n.i. Number of runaway incidents, classified by reaction type. 

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. 

Accidental release, spillage Transport incidents Overfilling of containers Equipment failure Unexpected reactions Runaway reactions... 

Anonymous, How to Prevent Runaway Reactions, EPA 550-F99-004, U.S. Environmental Protection Agency Office of Solid Waste and Emergency Response, August 1999. In addition to the accidents mentioned in the reference, a significant number occurred prior to the 1989 time frame. Serious incidents arc recorded as early as 1957. Accident recording before 1957 was incomplete. 

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

This chapter is not concerned with accidents on the road. Rather, it describes some of the many incidents that have occurred while tank trucks and cars (known in Europe as road and rail tankers) were being filled or emptied. Section 18.8 shows how hazard and operability studies have been used to spot potential hazards in filling systems, and Section 22.3 describes some runaway reactions in tank trucks and cars.. 

Liquid nitrogen should always be analyzed before it is off-loaded. The same applies in other cases where delivery of the wrong material could have serious unwanted results, such as a fire or runaway reaction, as in the two incidents that follow. If analysis causes too much delay, the new load should be put in a holding tank. 

Many accidents, particularly on batch plants, have been due to runaway reactions, that is, reactions that get out of control. The reaction becomes so rapid that the cooling system cannot prevent a rapid rise in temperature, and/or the relief valve or rupture disc cannot prevent a rapid rise in pressure, and the reactor ruptures. Examples are described in the chapter on human error (Sections 3.2.1 e and 3.2.8), although the incidents were really due to poor design, which left traps into which someone ultimately fell. 

For the third edition, I added sections or chapters on heat exchangers, furnaces, inherently safer design, and runaway reactions, and extended many other chapters. Although I have read many accident reports since the first edition appeared, most have merely reinforced the messages of the book, and I added only those incidents that tell us something new. 

Fig. 5.4-66 outlines the probability and consequences of a thermal runaway in case of a plant incident. For the solvent process, failure results in a temperature rise from 27 °C to 119 °C. This is far from the onset temperature of secondary processes, which only start at 150 °C or higher. Consequently, the solvent process can be considered safe. A failure of the water process can cause a temperature rise from 50 to 95 C, i.e. higher than the onset temperature (90 °C) of the secondary decomposition of the di-nitro compound. The decomposition would start before the reaction mixture started boiling. Hence, the water process cannot be considered inherently safe. 

The great majority of incidents described in the text may be attributed to this primary cause of thermal runaway reactions. The scale of the damage produced is related directly to the size, and more particularly to the rate, of energy release. See RUNAWAY REACTIONS... 

See Other POLYMERISATION INCIDENTS, RUNAWAY REACTIONS, VIOLENT POLYMERISATION... 

See Other INDUCTION PERIOD INCIDENTS, RUNAWAY REACTIONS 10840. Thiirane (Ethylene sulfide)... 

Alcoholysis of the chloride on the plant scale was effected at 40°C (with brine cooling) by adding portions to the alcohol alternately with finely crystalline disodium phosphate to neutralise the hydrogen chloride produced. On one occasion, use of coarsely crystalline sodium phosphate (of low surface area) reduced the rate of neutralisation, the mixture became acid, and a runaway exotherm to 170°C developed leading to eruption of vessel contents. On another occasion, accidental addition of sodium sulfate instead of phosphate led to a similar situation beginning to develop, but an automatic pH alarm allowed remedial measures to be instituted successfully. See other neutralisation incidents... 

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... 

A publication summarises all the then available technical evidence related to the Seveso accident, and recommends operational criteria to ensure safety in commercial processes to produce trichlorophenol [4], All the plant scale incidents were characterised [ 1 ] by the subsequent occurrence of chloracne arising from the extremely toxic and dermatitic compound 2,3,7,8-tetrachlorodibenzodioxin (structure IX, p. S-3), formed dining the thermal runaway reaction and dispersed in the ensuing explosion. It is also extremely resistant to normal chemical decontamination procedures, and after the 1968 explosion, further cases occurred after transient contact with plant... 

See other GAS EVOLUTION INCIDENTS, runaway reactions See other HALOARYL COMPOUNDS... 

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