Arborion Global | Process Safety & Engineering Consultancy

Technical overview

Reactive Chemistry &
Thermal Hazard Engineering

Reactive chemistry incidents — T2 Laboratories (2007, four fatalities, MCMT runaway), MFG Chemical (2004), Concept Sciences hydroxylamine (1999), and the Dixie Crystals / Imperial Sugar precursor events — have repeatedly demonstrated that thermal-hazard engineering must precede scale-up, not follow it. The Stoessel six-class framework (Industrial Chemistry, 1993, codified in CCPS Guidelines for Reactive Chemical Evaluation in Equipment) provides the dominant decision logic: classify the reaction by relationship between process temperature (Tp), MTSR (Maximum Temperature of Synthesis Reaction), Tmax of technical equipment, and decomposition onset (Td or TD24). Calorimetric methods cluster by sensitivity: DSC for screening (mg-scale), ARC for adiabatic worst-case characterisation, RC1 for isothermal kinetic resolution, VSP/Phi-Tec for two-phase vent-sizing data per DIERS. The hardest decisions are calorimetric-condition selection (basket vs cell, adiabatic vs near-adiabatic), criticality scoring under cooling failure and loss-of-stirring, and translating Class 4–6 findings into ISD process redesign rather than reliance on instrumented protection.

Engineering process

Reactive Chemistry & Thermal Hazard Engineering workflow

Chemistry Review & Calorimetry Plan

Review reaction chemistry, safety data, and literature to assess thermal hazard potential; plan calorimetric testing programme (DSC screening, ARC, RC1 kinetics, VSP / Phi-Tec).

Calorimetric Testing & Interpretation

Execute DSC, ARC adiabatic characterisation, and RC1 isothermal calorimetry; extract Tonset, ΔHrxn, MTSR, Tmax, adiabatic dT/dt, and dP/dt for scale-up evaluation.

Stoessel Class Assignment

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.

Cooling Failure & TMR Analysis

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.

Vent Sizing 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.

Scale-Up Safety Basis

Develop safe operating envelope (Tp, dose rate, accumulation limit, cooling capacity); issue scale-up safety basis document with calorimetric traceability and ISD redesign recommendations.

Reactive Chemistry & Thermal Hazard Engineering — Scope

Scope of work

Every deliverable — from basis to handover

Complete Reactive Chemistry & Thermal Hazard Engineering scope — every calculation, drawing, specification, and construction support activity.

DSC screening (mg-scale) — onset temperature, heat of reaction, decomposition energy

ARC (Accelerating Rate Calorimetry) — Phi-corrected adiabatic worst-case (Tonset, Tmax, dT/dt, dP/dt)

RC1 isothermal calorimetry — kinetic resolution, dose-control time, heat-flux profiles

VSP2 / Phi-Tec adiabatic two-phase calorimetry for DIERS vent-sizing input

MTSR derivation from Δadiabatic, accumulation factor, and feed-control rate

TMR24 (Time to Maximum Rate at 24-hour adiabatic) for storage and transport stability

SADT (Self-Accelerating Decomposition Temperature) per UN MTC Test H — storage and transport classification

Stoessel Class I–VI assignment with cooling-failure and loss-of-stirring scenario logic

DIERS two-phase vent-sizing — Omega method, vapour / gassy / hybrid system classification

ISD-first redesign — solvent substitution, semi-batch dosing, continuous flow conversion

Engineering outcomes

Outcomes of Reactive Chemistry & Thermal Hazard Engineering

Runaway Reaction & Decomposition Prevention

Prevents the T2 Labs / MFG-class runaway-decomposition events that drive reactive-chemistry fatalities
Establishes MTSR / TMR24 / SADT bounds with calorimetric evidence
Identifies Stoessel Class 4–6 reactions requiring ISD redesign before scale-up
Drives realistic relief / quench / emergency-cooling design

CEFIC / AIChE DIERS Thermal Defence

Satisfies OSHA PSM 1910.119(d) PSI on reactive chemicals
Withstands EU Seveso III reactive-hazard demonstration
Provides UN MTC SADT data for transport classification
Aligns with ICH Q9 / Q11 quality-risk-management for pharma reactive processes

Reactor Control & Emergency Cooling Quality

Defines safe operating envelope (Tp, dose rate, cooling capacity, accumulation factor)
Anchors DCS / SIS trip and alarm setpoints in calorimetric reality
Drives scale-up decisions with engineering-grade thermal margin
Supports realistic emergency-response procedure for thermal upset

Thermal Incident & Reactive Loss Prevention

Avoids the catastrophic batch / reactor / facility loss of a runaway event
Sequences ISD investment ahead of expensive instrumented protection
Reduces R&D cycle time through earlier go / no-go gating
Cuts insurance loadings for reactive-chemistry facilities

Reactive Chemistry & Thermal Hazard Engineering

Reactive Chemistry &Thermal Hazard Engineering

Reactive Chemistry & Thermal Hazard Engineering workflow

Every deliverable — from basis to handover

Outcomes of Reactive Chemistry & Thermal Hazard Engineering

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Reactive Chemistry &
Thermal Hazard Engineering