Explosion and Fire in Phily Refinery

There was a massive explosion and fire in an Alkylation unit in a oil refinery in South Philadelphia. I hope that this unit uses sulfuric acid and not hydrofluoric acid.

Note: The article was updated after I posted. It was an HF acid Alky. If no HF was released, they are very fortunate. Nasty stuff.

The difference in acids being?


Comparatively HF is much more volatile and deadly. The toxicity and nature of HF is something to be feared, whereas sulfuric acid is relatively manageable. Note the differences in the hazard sections on their wikis:

The article mentions the unit involved did use HF as the catalyst, but no word on whether any HF was released or involved. Air quality reports have not indicated anything overly alarming yet, but full reports are due later.

Thanks very much… H2SO4 has a high boiling point as I recall and I’ve used it as a desiccant in my younger days… I didn’t realise that HF was that dangerous.


Yeah sulfuric is pretty much only dangerous if you:
a. spill it on yourself
b. expose yourself to it as an aerosol
c. get it into your body by mouth, nose, eyes, etc.

You can work with it using fairly minimal protection and stay safe though as long as you remain conscious that it can be dangerous if mishandled and respect the danger it does pose.

I usually like dangerous and interesting chemicals. Hydroflouric though, no thanks. I’ll happily keep my distance. The penetration into the bloodstream from skin contact, formation of calcium flouride, and the subsequent heart attack is enough for me to lose my curiosity for the stuff. I’ll gladly watch other people mess with it in videos.

I used sulphuric acid for desiccating a combination of Nitric acid and glycerine back in grade 7, 50 years back, when I was young and foolish… Worked like a charm.


I vaguely remember being curious what might happen if a little sulfuric acid was dropped into a jar with a little salt in it (Dad had a quart or so of the stuff, possibly for automotive battery use). Stopped being curious about mixing H2SO4 with most other things rather quickly. That would have been about 60 years ago, some lessons stick the first time.

As to the Sunoco explosion, I live about 20 miles away and happened to be awake at the time (4 AM-ish), heard the explosion and felt the house shake.


You can use that for generating Cl gas.

When you mix the chemicals in proper proportion at the right temperature, water molecules are ‘bonded’ to the resulting… and the concentrated H2SO4 is used to remove them.


My gut reaction to the butane tank explosion was “why didn’t the relief valves prevent this?”, but more than likely enough went wrong that the sizing case(s) that the valves were designed to just didn’t cut it. I’ll be interested to see if there’s any information from the CSB about the relief valve scenarios considered.

I’m amazed that so far all I’ve read is that there were 4 on site minor injuries - that area is fortunate that more people weren’t hurt. I wonder if there were any siting/zoning considerations that went into decreasing the chance of OSBL injuries?

@jari001 Sometimes during a fire, especially one this big and complex, there could be a concentration of heat (jet fire) impinging on a part of a pressure vessel where there is no liquid. The local hot spot weakens the vessel wall and it fails. This is a major cause on BLEVEs. In this case a better fire protection measure may have been a water spray system, but that can be taken out by explosions during the event. Also, during explosions, pipes and equipment can be rearranged such that the design basis for risk mitigation is no longer the actual situation. We can’t blame the relief valves solely. Fire protection and risk mitigation is a holistic approach. With only 4 minor injuries on something this big, the PES refinery must have done something right on risk mitigation ISBL. I suspect they applied it to OSBL too. I am interested to read the CSB’s final report too.

So a contact of a contact was an alky unit engineer for PES (unfortunately let go while on vacation when this happened). He shared some of the specifics that he came to learn. A propane leak developed on an elbow to a pump that became a jet fire that was oriented towards a horizontal storage tank of butane that was the source of the much larger fire ball that videos show.
Pretty much falls into your scenario @Latexman.