Wednesday, November 19, 2014

Process Wednesday: the most horrifying plant story you will hear today

Thanks to a Derek Lowe post, longtime chemblogosphere commenter Thomas McEntee tells a story of his past: 
Complacency...can be a killer. In December 1974, I was called by the plant supervisor to come out to where the day shift was running another 2000-gal oxidation of tetrachlorocatechol using a process I'd developed for the production of high-purity o-chloranil. We had run this 15 or 20 times before without problems. The process involved use of considerably less than a stoichiometric quantity of nitric acid in hydrochloric acid under about 15 psig oxygen in the headspace. When the oxidation was complete, we centrifuged pure o-chloranil and washed the cakes with hexane..(uh oh). The problem I was presented with was that the reaction was not taking up oxygen. We checked the oxygen cylinders (OK), the dual manifold system (OK), and scratched our hard hats. 10 minutes later, the reactor exploded. Flames erupted from where the sight glass had been. 
Long story short, 3 of us nearly died and it was a week before I got out of the hospital.
The graveyard shift had the job of cleaning the GL reactor, finishing the cleaning with water washes and a final spark test for explosivity. 
After months of denials, the truth came out that the reactor cleaning had not been done at all and that about 100 gallons of hexane were in the reactor when the day shift loaded it for the new run. The batch sheet had been filled in as if all the cleaning and spark testing had been done. Under the agitation conditions we used and in the presence of pure oxygen, the hexane auto-ignited. 
Critics will say 'well, that should teach you..." but we had been able to bypass messy recrystallizations from carbon tet using this process. We had the forms and the boxes to check but the plant workers, all good guys but a tad lazy in those eerie hours after midnight, tried cutting some corners. As Derek wrote, it all gets back to people thinking about what they're doing.
This is pretty horrifying to me, for a variety of reasons. It's pretty clear that pencilwhipping the batch record was seen as an okay thing to do, which is an obvious problem (and not one that the chemist should be responsible for, said a chemist).

I wonder if the operators knew how deadly leaving hexane in the reactor was in this case. Also, I presume that a lot of development work had gone into avoiding the use of nitric acid. Yikes -- what a mess and I am glad no one died. 

7 comments:

  1. Knowing what o-chloranil was used for, there are only a few places that I would expect to have needed it by the ton like that. I lived near one of them in 1974. Forty years later, this still feels entirely too close to home. There are times that I am so glad that I run all my reactions in silico. --MG

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  2. What are your issues with nitric acid? Certainly must handle with appropriate care but compared to many hazards that might be encountered with other oxidizers employing aqua regia would not be too difficult to deal with.

    I would not characterize the above story as example of "complacency", expect possibly of the day shift personnel expectation in believing the night shift would fully and correctly perform and document duties. Even if the operators were not adequately training in the hazards and consequences, which would spread event mistakes more broadly, could you ever trust them again especially after months of denials? No one died but do wonder if the operators involved should have been introduced to the LA prosecutor.

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  3. Issues with nitric acid? Haha. My issues with nitric acid would be:
    1. The explosions it's caused in my department due to people not knowing how to use it and generally being unwise with safety,
    2. CJ's above post where three people nearly died.

    I don't worry too much when using it myself, but I still always think of the people in Point 1. It's a good reminder.

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  4. Thanks for posting this, CJ. Love the safety posts. Fascinating. I'm a dumb biochemist, probably for the best that I didnt go into organic.

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  5. Disappointed but not surprised. In my own brief industry experience, I've seen pilot plant operators do the same sort of thing. The protocol calls for 100*C for 5 hours but the reactor took an excursion to 120*C. The operator makes the unilateral decision to run at 120*C for 4 hours, record on the batch production log that he ran for 100*C for 5 hours, and not tell anyone. The analytical team spends a week investigating why the product is purple when it should be brown until finally, the truth comes out in an interview with the operator. To be fair, everyone makes mistakes. It just becomes frustrating when the same sort of mistake gets repeated and precious time is wasted scaling up a product. Customers lose patience, we lose business.

    -DDTea

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    Replies
    1. Mistakes are OK, conscious willingness to ignore one's lack of knowledge (why didn't you ask?) and to lie about one's actions afterwards is not.

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  6. Nitric acid and organics in an enclosed system. That always works out well.

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