Estimation of Time to Maximum Rate under Adiabatic Conditions (TMRad) Using Kinetic Parameters Derived from DSC - Investigation of Thermal Behavior of 3-methyl-4-nitrophenol

摘要

Kinetic parameters of the decomposition of hazardous chemicals can be applied for theestimation of their thermal behavior under any temperature profile. Presented paper describes theapplication of the advanced kinetic approach for the determination of the thermal behavior also underadiabatic conditions occurring e.g. in batch reactors in case of cooling failure.The kinetics of the decomposition of different samples (different manufacturers and batches) of 3-methyl-4-nitrophenol were investigated by conventional DSC in non-isothermal (few heating ratesvarying from 0.25 to 8.0 K/min) and isothermal (range of 200-260°C) modes. The kinetic parametersobtained with AKTS-Thermokinetics Software were applied for calculating reaction rate and progressunder different heating rates and temperatures and verified by comparing simulated and experimentalsignals. After application of the heat balance to compare the amount of heat generated during reactionand its removal from the system, the knowledge of reaction rate at any temperature profiles allowed thedetermination of the temperature increase due to the self-heating in adiabatic and pseudo-adiabaticconditions.Applied advanced kinetic approach allowed simulation the course of the Heat-Wait-Search (HWS) modeof operation of adiabatic calorimeters. The thermal safety diagram depicting dependence of Time toMaximum Rate (TMR) on the initial temperature was calculated and compared with the results of HWSexperiments carried out in the system with F-factor amounting to 3.2. The influence of the F-factor andreaction progress reached at the end of the HWS monitoring on the TMR is discussed. Presentedcalculations clearly indicate that even very minor reaction progress reduces the TMRad of 24 hrscharacteristic for a sample with initial reaction progress amounting to zero.Described estimation method can be verified by just one HWS-ARC, or by one correctly chosen ISOARCrun of reasonable duration by knowing in advance the dependence of the TMR on the initialtemperature for any F-factor. Proposed procedure results in significant shortening of the measuring timecompared to a safety hazard approach based on series of ARC experiments carried out at the beginningof a process safety evaluation.