Phenyl formaldehyde resins-disaster (case study) By SonaliChavan HarshavardhanChaudhari Saurabh Das RohitDeora
Phenyl formaldehyde resins • The reaction of phenol or substituted phenol with an aldehyde, in the presence of an acidic or basic catalyst is used to prepare phenolic resins. • Uses: Phenolic resins are used in adhesives, coatings, and molding compounds. • Heat of reaction: -180 cal/g • Two step process: • Methylolation • Salification
Process description • Reaction in stirred vessel with condensor. • Provision for heating and cooling. • T=60oC, 37% wt. aq. formaldehyde + caustic soda, Phenol in molten state. • Stoichiometric amount of Caustic soda (30% wt. solution) addition over 30 mins at 50oC. • Emergency relief on the reactor is usually provided by rupture disks.
Type of catalyst used, the ratio of reactants, and the reaction conditions determine the molecular structure and physical properties. • Highly exothermic and sensitive to a variety of physical and chemical conditions. • Heat generated by the reaction increases the reaction rate generating more heat. • Reaction rate is typically an exponential function of temperature • Pressure of the system will increase suddenly due to the vigorous evaporation of liquid. • Internal Pressure > Ultimate tensile strength • Thermal runaway !!!
Case study • On September 10, 1997 the Georgia- Pacific Resins plant in Columbus experienced a large explosion in a resin kettle (reactor). • 8,000-gallon batch reactor • The explosion resulted from a runaway reaction in Kettle No. 2. • The reactor’s safety systems failed to contain the rapidly expanding gases
What happened? • An operator charged raw materials and catalyst to the reactor and turned on steam to heat the contents. • A high temperature alarm sounded and the operator turned off the steam. • There was a large, highly energetic explosion. • Separation of the top of the reactor from the shell. • A nearby holding tank was destroyed and another reactor was partially damaged. • Operator killed, 4 injured, 3 firemen burned severely. • Occupational Safety and Health Administration slapped the company with $400000 fine. • Residents within a ¾ mile radius of the facility were evacuated. • People complaining of burning of skin, rashes, sore throat, headaches, breathing problems due to bronchitis, burning of throat, and nausea.
Cause • All the raw materials and catalyst were charged to the reactor at once followed by the addition of heat. • Heat generated exceeded the cooling capacity of the system • Excessive pressure generated by a runaway reaction. • Pressure generated could not be vented through the emergency relief system.
Runaway due to • Accumulation of Formaldehyde • Deviation from process • Poor agitation • Improper heating or cooling
Lessons learned • Thorough hazard assesment • Complete identification of reaction chemistry and thermochemistry • Administrative controls • Temperature control • Addition of raw materials • Emergency relief • Learning from accident history and near misses
Steps To Reduce Hazards • Modify processes to improve inherent safety. • Minimize the potential for human error. • Understand events that may lead to an overpressure and eventually to vessel rupture. • Use lessons learned. • Evaluate Standard Operating Practices. • Evaluate employee training and oversight. • Evaluate the effectiveness of the emergency relief system.
Social Impact Concerns regarding future accidents: • Fear that the GPRI plant will experience another serious accident • The railroad and other plants in the area could also have a chemical accident • Concern that residents wouldn’t even know if an accident takes place (no alarm) • Residents have no information on what to do in the event of an accident (evacuation?) • Concern that a warning will come too late • Concerns about children at school or children being caught in a vapor cloud • Concern for elderly and sick people who may not hear or respond to a warning • When we see fire trucks or hear a loud noise, we don’t know what is going on
Social Impact Concerns regarding air emissions and odors • Reports of chemical smells and/or burning eyes • Experiences with odors, burning eyes, and visual plumes from the plant • Concern about formaldehyde emissions from Georgia Pacific Plant • Awareness that formaldehyde is highly toxic • General concern that air in the area is not healthy • Awareness of other emission sources in area (including large numbers of trucks) • Concern that high rates of asthma and other illness that may be attributable to air emissions • Concern that Ohio EPA doesn’t do enough to reduce air pollution in the area