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Thursday
Mar182010

Oleum

     Regardless of the size of a tank, some accumulated depth spills or fires can be handled differently depending on the characteristics of the Hazardous Material. Oleum is one such example. Many chemical hazards such as Titanium Chloride, and the Chlorosilanes, as well as most water reactive chemicals, behave like this example, and if they are in your response area, you should know how to handle them. A tiny leak from the head of a 55-gallon drum creates a large plume of contaminant. The resulting toxic gas will travel downwind for thousands of feet. Imagine the vaporization potential of a drum of this material near your downtowns center.

     “Oleum”, is an industrial corrosive of sulfur trioxide in sulfuric acid. When released, the acidic mists that rises in the atmosphere is a concentrated asphyxiate that will burn lung tissue, irritate eyes, and generally inhibit respiration. Anyone with respiratory illnesses or without respiratory protection can easily become a fatality when exposed to this gas. When released into the atmosphere, the acid mist is generated from both constituents. The liquid to gas expansion ratio is roughly 200 times, so there is ample supply to saturate a large portion of the local atmosphere for an extended time period. Toxic gasses from a flammable tank farm also behave in this manner, insofar as vaporization and atmospheric expansion is concerned. The “key” to both these events is control of the “reaction zone” between the suppressant and product. Since firefighting Foam is a superior vapor suppressant, we will focus our attention towards using this tactical option.

     The residue film that forms between the newer “Green” Foams, and this compound behaves much like the aqueous film formed with AFFF {Aqueous Film Forming Foam} on a polarized hazard tank fire. The “AFFF” film lowers surface tension allowing the Foam blanket to flow quickly across the fuels surface, creating a fast vapor/fire knockdown. This of course, quickly eliminates vapors, fire, heat and all the associated hazards. With the introduction of firefighting “Green” Foams, to the surface of “Oleum” a barrier is created that operates as an exchange point or “reaction zone”, much like coffee filters in a drip dispenser. As long as the filter remains intact, the unwanted “grounds” stay in the basket. When the filter becomes over saturated or physically exhausted, we end up with grounds in the pot. As spent “filters” are replaced, and Foam “blankets” are replenished, the grounds remain in the basket just as the acid vapors stay in their container. By applying and maintaining a properly finished Foam blanket, the Foam acts as our “filter” keeping the unwanted “grounds” from vaporizing. This concept, saves lives, extinguishes fire, and eliminates toxic vaporization from affecting the civilian population.

     A second benefit using this tactic is the reduction of sulfur trioxide. Once the finished Foam blanket is applied to the oleum surface, the “reaction zone” interstitial space begins to interact with the Foam blanket. As the “¼ drain time” reaches its endpoint, the Foam bubble breaks and “reverts” back into Foam solution becoming a heavier liquid solution. This liquid then sinks in the oleum solution and chemically transforms the trioxide. As this reaction continues, the trioxide component in the “oleum” slowly transforms the entire container into liquid sulfuric acid. Over time and constant finished Foam blanket application, the entire container will transform into sulfuric acid. The result is a vapor suppressed, drum of acid with low vaporization capabilities, and lower toxicity threat to the area. The length of time for this reaction to run to completion depends on the volume of oleum, and the area of spread covered in the spill. Generally, the greater the area covered the quicker the reaction time however, also the greater vaporization. With a leaking container, you have low surface area and high depth, so expect this project to be prolonged.

     Once this reaction has “gone to completion”, the resulting sulfuric acid is relatively easy to clean up. The Hazardous Materials Technician can comfortably transfer the resulting acid into an appropriate corrosive container. Once properly labeled and sealed, shipment to the appropriate TSD {Treatment, Storage, and Disposal Facility} is all that remains. If your organization uses older Foam that was originally sold as “HazMat” type, this is a separate issue.  This older designate, “HazMatFoam” contained a rubberized component that would “physically” seal the surface of a contaminant. These are no longer sold or recommended, due to the fact that the resulting “rubberized” blanket is hazardous waste, very difficult to remediate, and will not operate this reaction. Today, the next generation of this Foam is “Green” in structure as it breaks down into constituents that are not harmful to the environment. So much the better for our earth.

                                                      Haz Mat Mike

                                                              

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