Reduction reactions involving heterogeneous catalytic hydrogenations, complex metal hydrides, and to lesser degree hydrogen-transfer reactions, are regularly scaled-up in pilot plants. Unfortunately, thermal runaway incidents involving reduction reactions do occur, despite best efforts to prevent them through the application of a chemical reaction hazard assessment strategy. A review of the literature, plant incidents, thermochemical and calorimetric techniques, identified the requirements for a unique assessment strategy for reduction reactions. The preference was to safeguard the plant using preventive measures first which were supported by adequate protective measures. The basis of safety was defined by, the boiling point of the reaction mass, the process temperature and the adiabatic temperature rise for the desired and/or adverse reactions including other kinetic data, e. g., "time to maximum rate". A number of instrumental and thermochemical procedures were adopted for the hazard identification portion of the strategy. The DSC capillary and ampoule techniques were used for substrate thermal decomposition and air oxidation determinations including reaction solution thermal stability studies. An estimation technique (Yoshida) used DSC exothermic data to predict a substrate's susceptibility of being shock sensitive and/or explosion propagating. An evolved gas mass flow detector was coupled to a reaction calorimeter to determine the maximum off-gas rate. A modified stirred ARC for hydrogenations and a stirred-micro-calorimeter for the quantification of the adverse reaction were developed. Adiabatic determinations for quantification of the adverse reaction were variable. The heat losses were unacceptable for a controlled hydrogenation in a modified stirred ARC. Results for the stirred-micro-calorimeter were satisfactory. However, adverse reactions for hydride decompositions and "shot additions" yielded adequate calorimetric results. A series of controlled experiments by reaction calorimeter coupled with an insitu FTIR, characterised the thermochemistry, reaction kinetics, mass transfer coefficient and reaction mechanism for the desired and inhibited hydrogenations. A customised What-If? /Checklist process hazard analysis technique was developed for reduction reactions and two worked examples are presented. A hazard assessment strategy with appropriate hazard identification procedures was developed. Eight case studies (three hydrogenations, three hydride reductions and two hydrogen-transfer reactions) were used as examples to validate the reduction assessment strategy and hazard identification procedures.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:298377 |
| Date | January 2000 |
| Creators | Kwasny, Richard S. |
| Publisher | London South Bank University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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