(86f) The Evaluation of Risks of Ethoxylation Processes

Alkoxylation (ethoxylation and/or propoxylation) is commonly performed in industry for the production of surfactants and polyglycols. To this aim, the most current type of reactor consists of a simple liquid-stirred reactor equipped sometimes with an external circulation loop to increase the reactor heat exchange capacity. More advanced chemical processes are now performed in semi-batch Venturi Loop reactors or in Spray Tower Loop Reactors. In particular, in the last two cases, the liquid phase is dispersed into the gaseous one by means of recirculation loop. The set of these three different reactor types used in the manufacture of ethoxylated products has been recently compared in terms of efficiency. However, few indications for risk assessment have been given in terms of accident consequences, whose evaluation is mandatory when sound risk analyses of chemical processes are due. In this paper, the added risk due to the presence of recirculation loop has been assessed, aiming at evaluating the differences of cited reactor and processes by varying the operating conditions, either in terms of temperature or partial pressure of alkoxide. More specifically, the analysis of consequences of the ethoxylation of dodecanol at different partial pressure of EO and process temperature among those typically used has been considered. Results have shown that dramatic accidental scenarios should be considered only if large leakages (section >> 1?) occur on recycling loop/pipelines added to semi-batch reactor for the VLR and STLR reactors. Indeed, in this case flash fires and toxic effects can hit lethally any operator even at large distances, in particular for very low wind velocity (i.e. for heavy gas behaviour). On the other hand, when leakages with release section smaller than 1? occur, the hazard is only for the safety of operators in the close vicinity of the reactor for pool fire, flash fire and toxic effects. The effect of the increase of total mass of product (the polyethoxylated dodecanol) in the reactor and, more important, to the risk assessment of the entire process, hence considering the risk deriving of EO/N2 mixture from feeding line or from the reactor gas space will also assessed.