(44o) The Hidden Risks of Deposits, by-Products, and Residues On Exhaust and Waste Streams

Barrera, C. A., Exponent

The safety risks associated with reactive compounds are usually captured and addressed during the conceptual design and pre-construction process safety reviews as, and for well-established chemistries these risks are well understood for the main processes and reactions.  Lest time, if any, is devoted to the analysis of the reactive nature of the compounds present waste streams or exhaust lines. These lines are often overlooked during HAZOPs because of their secondary nature, or because they go to a scrubber or flare, which erroneously is considered a “catch-all” device that will “take care of everything.”  Waste streams and exhaust lines from certain physicochemical processes contain highly reactive compounds in the form of residues or by-products that in the right conditions can accumulate and form dangerous deposits. Some examples of such deposits are pyrophoric, shock-sensitive, and corrosive compounds. The purpose of this paper is to create awareness in the process safety community about the importance of a complete understanding of the chemistry of the reactive species present in these streams and the possible physical mechanisms than can lead to the formation of dangerous deposits, as well as the importance of including these streams in the process hazard analysis.  Examples drawn from multiple processes will be presented.