Chemical Reaction Hazard Assessment
Stoessel criticality classification using the maximum synthesis temperature, the time to maximum rate and the cooling failure scenario for thermal process safety
Chemical Reaction
Hazard Assessment
Most thermal runaway incidents are not failures of chemistry but failures to assess it before scale up, because a reaction that is benign in a flask can turn destructive in a reactor once the capacity to remove heat falls behind the rate at which heat is generated. Chemical reaction hazard assessment, built on Francis Stoessel's framework in Thermal Safety of Chemical Processes and the CCPS reactive chemistry guidelines, evaluates that balance rigorously, and it is work our team does day in and day out. We characterise both the desired reaction and any secondary decomposition through calorimetry, using DSC screening, RC1 reaction calorimetry and adiabatic methods such as ARC, to establish the heat of reaction, the maximum temperature of the synthesis reaction, the adiabatic temperature rise and the time to maximum rate under adiabatic conditions. From the interplay of process temperature, the maximum synthesis temperature, the boiling point or maximum technical temperature and the decomposition onset, we place the process in one of Stoessel's criticality classes from one to five, and that class directly dictates the basis of safety, whether that is adequate cooling and control, a quench or dump, or an emergency relief system sized to the measured energetics. The output turns reactive hazard management from intuition into a defensible thermal basis of safety that holds from the laboratory through the pilot plant to full scale production.
How the study is executed
A structured, facilitated process that runs from scope definition through close out and produces defensible, actionable outputs.
Review reaction chemistry, safety data, and literature to assess thermal hazard potential, plan calorimetric testing programme (DSC screening, ARC, RC1 kinetics, VSP / Phi Tec).
Execute DSC, ARC adiabatic characterisation, and RC1 isothermal calorimetry, extract Tonset, ΔHrxn, MTSR, Tmax, adiabatic dT/dt, and dP/dt for scale up evaluation.
Classify reaction criticality (Class I, VI) from the relationship between Tp, MTSR, Tmax of technical equipment, and decomposition onset (Td / TD24), identify Class 4, 6 redesign requirements.
Model adiabatic temperature rise (ΔTad) under cooling failure and loss of stirring, calculate time to maximum rate (TMR24) and onset of heat accumulation for emergency response basis.
Develop DIERS / Omega vent sizing basis for two phase reactive relief, calculate required orifice area and scale up vent dimensions, provide data for DIERS VSP2 or Phi Tec confirmation.
Develop safe operating envelope (Tp, dose rate, accumulation limit, cooling capacity), issue scale up safety basis document with calorimetric traceability and ISD redesign recommendations.
What the study covers in full
Outcomes of Chemical Reaction Hazard Assessment
- We identify Class 4 and 5 runaway scenarios before you meet them at scale
- We quantify the cooling failure worst case rather than assuming benign behaviour
- We separate the desired reaction energy from the decomposition energy that drives a catastrophe
- We set the basis of safety on measured energetics rather than engineering judgement
- You satisfy the OSHA PSM and MSIHC reactive chemistry process safety information
- You hold a defensible thermal basis of safety for regulators and insurers
- Your work aligns with the CCPS reactive chemistry and Stoessel criticality methodology
- It supports management of change and pre startup review for new or modified chemistry
- We set a safe operating envelope covering dose rate, accumulation and cooling limits
- We de risk your scale up from the laboratory through the pilot plant to full production
- We inform your reactor, cooling, quench and relief design with calorimetric data
- We reduce the aborted or failed batches that come from poorly understood exotherms
- You avoid reactor loss, fire and business interruption from a thermal runaway
- You target cooling, quench and relief capital at the genuinely critical reactions
- You prevent costly late stage redesign by assessing hazards before commitment
- You protect product supply and your licence to operate reactive processes
Codes & standards we work to
Triggers that signal the need
Where Chemical Reaction Hazard Assessment applies
We assess nitration, oxidation, hydrogenation and exothermic batch reactions.
We cover exothermic synthesis, crystallisation and solvent processing.
We handle toxic and exothermic intermediates and formulation chemistry.
We address polymerisation exotherms, peroxides and runaway potential.
We assess electrode and precursor chemistry that carries thermal runaway risk.
We support new route scale up and process intensification.
Tangible deliverables
- A report with the Stoessel criticality class
- A calorimetric data pack covering the heat of reaction, the maximum synthesis temperature, the adiabatic temperature rise, the time to maximum rate and the decomposition onset
- A cooling failure scenario analysis with severity and probability
- A basis of safety document covering control, quench, dump and emergency relief
- A reactive chemical compatibility and incompatibility matrix
- A safe operating envelope covering dose rate, accumulation and temperature limits
- A DIERS two phase reactive relief sizing basis
- A scale up thermal safety dossier from laboratory to plant
Ready to start your project?
Speak with our team to scope an engagement tailored to your facility, regulatory context, and lifecycle stage.