TRAA Science Advisory Panel member Dr. George Harpoles’ seminal article on the equivalent behavior of HF and MHF in a catastrophic accidental release concludes with the paragraph:
“Dangerous concentrations of HF could persist miles away from the refinery. The typical layers-of-protection approach (barriers, water sprays, pumps to spare vessels, etc.) may save lives for certain smaller leaks. However, a more catastrophic rupture, simultaneous with failure or bypass of the protection systems, is easy to imagine – in large earthquakes, accidental or deliberate explosions, or fire. Moreover, the delivery trucks traveling to the refinery carry MHF in similar quantities, and are even more vulnerable. They have no spare vessel or water-spray system. They are exposed to the public and subject to crashes. There is clear danger to the community in the use of MHF at refineries in urban settings.”
Some Thoughts on the South Coast AQMD Rule 1410 Refinery Committee Meeting by the TRAA Science Advisory Panel
Several members of the TRAA Science Advisory Panel attended the AQMD Refinery Committee Meeting in Wilmington CA on September 22, 2018. This was a particularly important meeting because two of the world’s leading experts on the dangers of hydrogen-fluoride use in refineries gave presentations: Dr. Ronald Koopman on the large-scale HF release experiments — The Goldfish Tests — he conducted in the Nevada desert in 1987, and John Cornwell of Quest Consultants, conductor of the only field-scale MHF release tests in Quest’s Oklahoma facility in 1993.
The high point of the meeting was when these two experts answered the $64,000 Question: “Would 6-wt-% MHF act the same as pure HF?
Dr. Koopman expressed his profound skepticism that the additive would do much good — “I would guess that would be a very small effect.” (Watch:https://youtu.be/qwo08BtEQuM?t=7460)
John Cornwell emphasized the small amount of additive is unlikely to have much of an effect, and there’s no data to show that it does. He pointed that physical chemists use mole percent (molecule count), and states, “If MHF is 6% by weight and 1% by mole, and you are going to modify the vapor pressure or modify the characteristics of the fluid, you’ve got to have some data to show that’s true” (Watch:https://youtu.be/qwo08BtEQuM?t=8874).
This publicly-stated testimony by the world’s two leading experts expressed a high degree of skepticism of the refineries’ safety assertions for MHF. They are in line with the TRAA Science Advisory Panel and the SCAQMD Staff. MHF and HF behave the same and both form ground-hugging toxic clouds.
Torrance Refining Company’s (ToRC) MHF website postings deliberately spread misinformation that is not only misleading, but also dangerous in that it conveys a false sense of safety with MHF.
In one of ToRC’s March 30, 2017 “Setting the Record Straight” videos (scroll down to find them), Tim Shepperd, lobbyist with HF Alkylation Consultants, presents “Why MHF Works.” He features a false analogy between water (a compound) and MHF (a mixture). Fifth-grade science standards in California include: a) that properties of a chemical compound are entirely different from those of its constituents, while b) properties of a mixture retain the properties of its constituents. Water, which is a safe compoundof oxygen and hydrogen, is in no way analogous to MHF, which is an unsafe, highly toxic, volatile mixtureof sulfolane and hydrofluoric acid. Continue reading ““ToRC Misinformation in Postings about MHF” by George Harpole, Ph.D.”
“A major trucking spill of MHF onto hot highway pavement could vaporize thousands of pounds of hydrofluoric acid — more than twice the largest release of the 1986 Goldfish test.”
Boil-off is one of several paths that highly toxic Hydrogen Fluoride (HF) can go airborne into the community. In the past, the primary focus has been on the release of superheated HF and Modified Hydrofluoric Acid (MHF) from oil refineries’ settler tanks, because flash atomization causes 100% to form a visible, ground-hugging, highly toxic cloud (see: Flash Atomization of HF and MHF).
Mobil’s original intent to suppress flash atomization was to add sufficient additive that the MHF was subcooled, that is, the boiling point is above the operating temperature. (As we now know, an additive level sufficient for subcooling is incompatible with the alkylation process.) However, even subcooled MHF spraying under high pressure from a rupture of a tank will break up into small droplets. While not nearly as fine as droplets from flash atomization, they nevertheless evaporate. Evaluation of how much was the objective of the large-scale MHF release tests conducted by Quest Consultants in 1993 (see: Superheated MHF Excluded from the Only Large-Scale Test Series).
Another significant path for MHF to go airborne is boil-off. This occurs, for example, if the rupture is in the top section of a settler tank. At the release of pressure, the superheated hydrocarbons (typically isobutane with a boiling point of 11F) and MHF (boiling point of 71F at 6-wt% sulfolane) are highly out of thermodynamic equilibrium at the tank process temperature of 106F. The tank’s contents will boil violently and much will be expelled from the tank before plunging in temperature to the low boiling point of the remaining liquid. The volatile hydrocarbons and MHF will then boil off at a rate governed by the transfer of heat from the environment through the tank walls to the cold liquid.
Consider a massive spill from a truck transporting 33,000 lbs of 15 wt% MHF (boiling point 76F) onto a sun-baked highway pavement at 140F. The MHF immediately cools the surface of the pavement to its boiling point of 76F. The temperature response of the pavement with typical parameters is shown in Figure 1.
On the heels of the 1986 “Goldfish” Release Test of hydrofluoric acid (HF), Mobil engineers sought some method to prevent the HF from forming a ground-hugging toxic cloud. In his illuminating presentation at the September 22, 2018 AQMD Refinery Committee Meeting (Watch:https://youtu.be/qwo08BtEQuM?t=5108), Goldfish Test Principal Investigator Dr. Ronald Koopman stated that the affect of the HF release “was much larger than we had expected and the downwind distance was further than we had expected” and “we found that the HF that was released all flashed into an aerosol and a vapor and so there was nothing that ended up on the collection pan or in that tank — nothing was captured — and that was a great surprise to us.”
In their attempt to do something to prevent the formation of a toxic cloud, in the early 1990s, Mobil engineers settled on the additive sulfolane to suppress the vapor pressure and move HF fluid properties into the subcooled regime, where flash atomization will not occur. But, as seen in the graph above, at least 45% sulfolane by weight (45 wt%) is needed to achieve subcooled HF at a typical settler-tank temperature of 105F. Although they did not know it at the time, this level of sulfolane is far higher than the alkylation process can tolerate and still function. In refineries that use MHF, the sulfolane level is as low as 6 wt%. That’s 1 mole% or one molecule of sulfolane for every 100 molecules of HF. Continue reading ““Superheated MHF Excluded from the Only Large-Scale Test Series” by Jim Eninger, Ph.D.”