This interactive tool combines two key analyses: the determination of a substance's intrinsic stability via the **adiabatic TD24** calculation and the criticality classification of a chemical process using the **Stoessel method**.
The intrinsic thermal stability of a reactive substance is its tendency to decompose exothermically in the absence of external heat sources. Under adiabatic conditions (no heat exchange with the environment), the heat generated by the decomposition increases the substance's temperature, further accelerating the reaction and leading to a phenomenon known as "thermal runaway".
The **TD24** parameter (Temperature of Decomposition in 24 hours) is the initial temperature at which a substance, under adiabatic conditions, takes 24 hours to reach its maximum rate of decomposition. It is calculated using the Semenov model for the "Time to Maximum Rate" ($TMR_{ad}$):
Where: $C_p$ is the specific heat, $R$ is the gas constant, $T_0$ is the initial temperature, $E_a$ is the activation energy, $\Delta H_r$ is the reaction enthalpy, and $A$ is the pre-exponential factor.
The F. Stoessel method classifies the severity of a chemical reaction based on the consequences of a cooling system failure. The analysis relies on comparing key temperatures: the process temperature ($T_P$), the boiling point of the medium ($BP$), the decomposition onset temperature ($T_D$), and the "Maximum Temperature of the Synthesis Reaction" ($MTSR$).
The $MTSR$ represents the maximum temperature the system would reach if the entire mass of accumulated reactants were to react instantly under adiabatic conditions. It is calculated from the adiabatic temperature rise ($\Delta T_{ad}$):
The criticality class is assigned by comparing the $MTSR$ with $T_D$ and $BP$ to determine if a cooling failure could trigger decomposition and whether the boiling of the solvent can act as a thermal barrier.