Lessons learned from reactive chemical incidents

https://www.aiche.org/resources/publications/cep/2022/february/spotlight-on-safety-lessons-learned-reactive-chemical-incident

“Even a simple task can turn deadly if it is not performed properly,”

"The accident took place in July 2021 at the LyondellBasell Industries complex in La Porte, near Houston, in the acetic acid production unit. The facility is the third-largest acetic acid producer in the US. The CSB’s report found that the inadvertent removal of pressure-retaining components of a valve caused the release of nearly 75,000 kg of an acetic acid mixture. The incident killed two contract workers, severely injured a third, and sent some 29 others to hospital.


“Even a simple task can turn deadly if it is not performed properly,” CSB Chairperson Steve Owens says in a press release. The incident involved a common plug-valve system, and CSB found similar serious incidents in which these valves were taken apart when removing connected equipment."

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How to prevent runaway chemical reactions - EPA

" PROBLEM: Many industrial chemical processes involve exothermic (heat generating) reactions. Uncontrolled, or runaway, reactions can occur as a result of various situations, such as mischarged raw materials, failure of a reactor's cooling system or the presence of contaminants. If the heat generation exceeds the reactor's ability to remove it, the reaction can accelerate - or run away - and cause the temperature and pressure to increase. A sudden energy release from such an uncontrolled reaction has the potential to harm workers, the public, and the environment. The following Case Study aims to increase awareness of possible hazards connected with exothermic reactions."

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Runaway reactions

"A typical runaway scenario involves reactants being charged into a reactor at room temperature and heated with stirring until the reaction temperature is reached. Temperature is held constant to optimise cycle time and yield. On completion, the reactor is cooled and emptied. However, if no provision is made in the process to account for cooling failure at reaction temperature e.g. due to power failure or operator error (forgot to start the stirrer), etc. then unconverted material still present in the reactor may react at an uncontrollable rate proportional to the amount of unreacted material. This may lead to over-pressure in the vessel and subsequent rupture by virtue of the normal reaction exotherm. Alternatively, a secondary decomposition reaction may be initiated and the heat so produced may lead to yet a further increase in temperature and eventual runaway conditions1 . The prime causes of runaways are associated2,3 with – process chemistry – inadequate design – substandard operational procedures – lack of training – raw-material quality control – temperature control – agitation – mischarging of reactants – maintenance – human factors (which may impact all of the foregoing)".

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Accident due to agitator lubricating fluid entering reactor

 "This report investigated the causes of a chemical release accident caused by an abnormal reaction and recommended certain safety steps to prevent the reoccurrence of similar accidents. An abnormal reaction occurred during the input of raw materials (t-BuOH, KMnO4, and H2O), and some foreign impurities (4% MeOH, 13% glycerin) that may have influenced the reaction were identified. The MeOH may have entered the reactor during t-BuOH reuse or the cleaning of mechanical parts, and glycerin was released from the seal oil reservoir to enhance lubrication with the agitator in the reactor. The pilot test carried out to reproduce the abnormal reaction revealed a rapid reaction, with an increase in the mixture temperature when the KMnO4 and glycerin (13%, released from the broken seal oil reservoir) were added to the mixture that contained 96% t-BuOH and 4% MeOH (impurity). Furthermore, some deficiencies in the safety system and some human errors were discovered. The reactor was not equipped with either a safety instrumental system or an automated emergency shutdown system, and the workers did not wear PPE. These factors could have had a significant impact on the accident".

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