Analysis of an accident at a solvent recovery plant

An accident in a plant for solvent recovery from solvent-contaminated waste s was examined, An experimental investigation of the accident was carried o ut using calorimetric and thermogravimetric techniques, The immediate cause of the accident was an unforeseen exothermic decomposition reaction. The m ain underlying cause of the accident was the absence of safety culture in t he plant management, that resulted in the lack of a testing procedure to ev aluate the thermal stability of the process feed, A simplified screening pr ocedure based on differential scanning calorimetry was used in order to tes t the thermal stability of the nonvolatile fraction of the solvent-contamin ated wastes present on the plant in order to be processed, More than 75% of the samples examined showed exothermal decomposition phenomena starting at temperatures higher than 100 degrees C, These phenomena were common to sol vent wastes that originated from a number of different industrial activitie s. Thus, the thermal instability of the process feed is one of the main pro blems in solvent recovery operations. Our analysis of the accident suggeste d that the safe operation of waste solvent recovery processes requires an a ccurate characterization of the thermal stability of the process feed, Proc ess safety is also increased by an adequate emergency vent and an accurate control of operating temperature, that may be reduced operating under vacuu m, Safety devices may also include a water supply for emergency quench. (C) 1999 Elsevier Science B.V. All rights reserved.