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CALORIMETRIC STUDY OF THE INHIBITION OF THE RUNAWAY REACTION DURING POLYMERIZATION PROCESSES
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Sicurezza industriale di processo: reazioni fuggitive, alcuni esempi nei processi di polimerizzazione
No full textPost Investigation of an Incident due to the Self-Polymerisation of a Commercial Monomer
No full textIn the last decade, the importance of risk analysis in the transport of dangerous goods has been evidenced by several studies showing that in some cases the risk associated with the transport of hazardous substances can be compared to those in chemical plants (processing units and storage).
In this work the analysis of an accident in transport of dangerous goods is described. The objective of this study is to contribute to the determination of the causes that brought about the self-polymerization of commercial divinylbenzene (DVB 63%) contained in an isothermal-container, in order to prevent future occurrence of this type of accidents.
Residence time and conditions during transport and storage of monomers, in particular the storage temperature, are very important factors that affect their self-polymerization aptitude. Concerning the cause of accidents it has been supposed that the quantity of oxygen in the tanker probably was insufficient to activate properly the inhibition mechanism to prevent the self-polymerization. According to this consideration the self-polymerization of DVB and the inhibition mechanism of 4-tert-Butylcatechol (TBC) have been studied as a function of temperature and monomer exposure to air with Differential Scanning Calorimetry and Adiabatic Calorimetry
SENSITIVITY ANALYSIS FOR THE THERMAL STABILITY CRITERIA FOR HYDROGEN PEROXIDE
No full textChemical reactors carrying on exothermic processes may undergo to runaway reactions. To prevent from this hazard, Early Warning Detection Systems (EWDSs) can be used in industry, because they allow the on-line detection at an early stage of the runaway.
The stability criterion of Hub and Jones is frequently implemented in EWDSs. Despite its simplicity during the detection step (the criterion is based just on measurements of the temperatures inside the reactor and jacket), the effectiveness in distinguishing between dangerous and non-dangerous occurrence is strongly affected by the presence of noise in the monitored signals. Furthermore, the numerical methodology for the calculation of the derivative of the measured signals may be of great importance for the definition of alarm conditions.
In this paper, the sensitivity analysis of the performances of Hub and Jones criterion with respect to the Savitzky and Golay smoothing filter degree is discussed. The analysis is applied to experimental data on the decomposition of hydrogen peroxide 35%wt carried out in a Thermal Screening Unit.
The sensitivity analysis of the performances of Hub and Jones criterion with respect to the Savitzky and Golay smoothing filter degree has been discussed. The analysis is applied to experimental data on the decomposition of hydrogen peroxide 35%wt carried out in a Thermal Screening Unit.
The use of a pseudo adiabatic unit permits to analyze the performances of the thermal runaway criteria of an reacting system in conditions very close to a real runaway.
The SG 21 points for either smoothing, as low-pass data filtering or for first or second derivative is a useful methodology. The obtained results can be easily applied to other higher-order methodology for the on-line control of divergent reactions
AN INTEGRATED APPROACH FOR THE EARLY DETECTION OF RUNAWAY REACTIONS BY USING UV-VISIBLE AND TEMPERATURE SENSORS
No full textWe report here on a novel approach for the early runaway detection in chemical reactors, based on the integration of two kinds of sensors: i) a set of three Pt thermo-resistances for measuring the temperatures both within the reactor and in the cooling jacket and ii) an UV-visible probe for the indirect evaluation of the conversion through measurements of light absorbance. The measured variables (temperature and conversion) were used as input to our model based on the divergence calculation. The early warning detection system (EWDS) was tested for the sulphuric acid catalyzed esterification of acetic anhydride and methanol, a very simple reaction but releasing ~70 kJ per mole of anhydride consumed. The responses given by EWDS were examined during the simulation of runaway reactions in a lab-scale reactor working under batch isoperibolic conditions. Different chemical heat flows were generated by varying the concentration of the sulphuric acid and adding at once the acetic anhydride into the reactor. The behaviour of the detection criterion was evaluated comparing the EWDS signals using both temperature and conversion as input variables, with the responses obtained from only temperature measurements. A detailed kinetic model was also developed to solve the differential energy and mass balance equations and define the runaway boundaries. Results showed the importance of an input variable indirectly related to conversion in such kinds of processes where other enthalpy variations (i.e. due to an endothermic mixing of the reagents) may hide a runaway reaction occurring
Effect of amine compounds on the self-polymerisation of methyl methacrylate
No full textThis work is the result of the experimental analysis of the effect of different alkyl anilines (accelerators) on
the self-polymerisation of methyl methacrylate. The state of the art before this study suggested that there
should have been no significant increase in the rate of polymerisation reaction until the initiator (typically a
peroxide) is added to the stabilised mixture of monomer and accelerator. All the experimental results found
during this investigation indicated instead that the accelerators can affect the rate of polymerisation even if
no peroxide is present in the system. Different kinds of alkyl anilines in methyl methacrylate have been
tested by differential scanning calorimetry and adiabatic calorimetry. The experimental data allowed us to
define safety ranges for the polymerisation reaction
REACTION CALORIMETRY AND UV-VIS SPECTROPHOTOMETRY INTEGRATION AIMED AT RUNAWAY REACTIONS EARLY DETECTION
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