In today's economic environment, a company's attempt to fast-track production from scaled down test models or to increase production without completely accounting for potential hazards can lead to costly, sometimes deadly results.
A report issued by the U.S. Chemical Safety and Hazard Investigation Board (CSB) on the December 2007 explosion and fire at T2 Laboratories, Inc., cites four similar runaway reaction incidents investigated by the CSB since 1998 resulting in 10 deaths and more than 200 injuries.
Paterson, NJ - April 8, 1998
An explosion and fire at a chemical plant in Paterson, NJ, occurred during the production of a dye used to tint petroleum fuel products. The explosion and fire were the consequence of a runaway reaction, which over-pressurized a 2,000-gallon chemical vessel and released flammable material that ignited. Nine employees were injured. The incident caused the hospitalization of two employees, the release of chemicals into the community and damage to the plant.
The investigation team determined that the product reaction accelerated beyond the heat-removal capability of the reactor. The resulting high temperature led to a secondary runaway decomposition reaction causing an explosion, which blew the hatch off the reactor and allowed the release of the reactor contents. The initial runaway reaction was most likely caused by excessive reactor heating and delayed use of the cooling water system. The reactor's cooling system could not control the exothermic reaction and had no emergency shutdown or quenching function.
The CSB investigation found that the company had not adequately evaluated or controlled the hazards of the dye production process. Neither a preliminary assessment conducted in 1990 nor a subsequent hazard analysis five years later considered the possibility of a runaway chemical reaction--one of the most common reactive hazards. As a result, the reactor was not provided with sufficient cooling capacity or adequate emergency shutdown or venting systems. The company's analyses never considered possible scenarios--such as excessive heat input or inadequate cooling--that could trigger a runaway reaction.
Allentown, PA - February 19, 1999
A process vessel containing several hundred pounds of hydroxylamine exploded at a production facility near Allentown, PA. Employees were producing the facility's first full-sized batch of hydroxyla-mine (HA). After the distillation process of an HA and potassium sulfate solution was stopped, the HA in the process tank and associated piping explosively decomposed, most likely due to high concentration and temperature. The explosion killed four employees and a manager of an adjacent business. Two employees survived the blast with moderate-to-serious injuries. Four people in nearby buildings were injured. The explosion also caused significant damage to other buildings in the light industrial use business complex where the facility was located and shattered windows in several nearby homes.
The company developed the HA production process through laboratory-scale experimentation in 1997, then constructed a 10-gallon pilot plant. In July 1998, the company set up a full production facility in a multi-tenant building. The production parameters that the company designed for the reaction involved a high concentration of HA, which could result in exothermic decomposition forming explosive crystals. Despite available MSDS, information regarding the fire and explosion hazards of such high concentrations was not consulted.
The CSB found that the company had not systematically evaluated the reactive hazards of the process during production development phases, determined the magnitude of the hazard, nor identified control measures. An adequate reactive chemical hazard evaluation and process hazard analysis (PHA) would have helped the company quantify, evaluate, and mitigate the hazards of HA production. Such analyses might have even caused management to question whether its planned process presented substantial or unacceptable risks to employees and to the community.
Dalton, GA - April 12, 2004
A runaway reaction over-pressurized a chemical reactor at a chemical manufacturing plant, releasing toxic allyl alcohol vapor into the community. The resulting toxic cloud sent 154 people to a local hospital, forced the evacuation of nearby residents, and killed vegetation and aquatic life near the plant.
The plant was producing its first batch of triallyl cyanurate (TAC) in a batch reactor as part of a tolling arrangement with a third-party company. The CSB investigation found that the company had not thoroughly researched the reactive hazards of the process before scaling up from laboratory tests to full production.
Although literature on the hazards of TAC manufacturing was readily available, the company's literature search focused on patent restrictions rather than the reactive chemistry hazards of the process. Although the company had tested the reaction at the bench scale, these tests were designed to maximize yield and minimize production cost and did not indicate that the process included an additional highly exo-thermic decomposition reaction which would require additional cool-ing. The company test-ed three batches in a 30-gallon reactor but then used a different batch recipe in the full production batch. A comprehensive process design and hazard review of the scale-up was not performed, and the company did not appreciate the significant difference in heat removal capacity of the 4,000-gallon reactor compared to the 30-gallon reactor.
The CSB concluded that this incident could have been avoided had the company thoroughly investigated the hazards of the process and properly designed the emergency vent system to contain a potential release of the toxic vapor.
Morganton, NC - January 31, 2006
A runaway chemical reaction and subsequent vapor cloud explosion and fires killed one worker, injured 14 (two seriously), damaged structures in the nearby community, and destroyed an industrial facility in Morganton, NC. This facility manufactured a variety of powder coating and paint additives by polymerizing acrylic monomers in a 1,500- gallon reactor.
The company had received an order for slightly more of an additive than the normal size recipe would produce. Plant managers scaled up the recipe to produce the required larger amount of polymer and added all of the additional monomer needed into the initial charge to the reactor. This more than doubled the rate of energy release in the reactor, exceeding the cooling capacity of the reactor condenser and causing a runaway reaction. The reactor pressure increased rapidly. Solvent vapors vented from the reactor's manway, forming a flammable cloud inside the building. The vapors found an ignition source and exploded.
The CSB investigation found that although the company combined monomers and reaction initiators in the presence of flammable solvent to produce polymer products, it failed to identify the hazards associated with this type of chemistry. Additionally, process safety information was poorly documented, product recipes were changed without systematic review and automatic safeguards to prevent or mitigate the effects of runaway reaction were not in place.
When performing reactive chemistry, companies must be aware of the hazards involved and take action to minimize potential consequences of all identified hazards. These examples illustrate the terrible dangers when this is not done.