Teaching safety in the chem lab

Chem­ical engi­neering pro­fessor Ron Willey may tell you he’s a stoic, but it’s clear he is pas­sionate about at least one thing: the well being of his fellow chem­ical engi­neers. “My interest is in get­ting safety into chem­ical engi­neering edu­ca­tion and cre­ating mate­rial to com­mu­ni­cate about acci­dents so we can learn from them,” he said in an inter­view this afternoon.

Last year Willey’s article ana­lyzing the chem­ical reac­tion that led to the tragic explo­sion at T2 Lab­o­ra­to­ries in 2007 earned him the Bill Doyle Award for best paper pre­sented at the 2011 Amer­ican Insti­tute of Chem­ical Engi­neers Loss Pre­ven­tion Sym­po­sium, the second highest award in the spe­cial­ized area of process safety.

T2 was a small start-​​up com­pany man­u­fac­turing a gaso­line addi­tive. The process involved a large scale exothermic reac­tion — meaning it cre­ated lots of heat. The reac­tion took place in a 2450 gallon reactor vessel sur­rounded by cooling water. The heat from the reac­tion would transfer into the water, which would boil and release the heat with its steam while more cool water enveloped the reactor.

One day — December 19, 2007 — the cooling water mech­a­nism failed. The reac­tion began to heat up. The heating up caused the reac­tion to go faster. Which caused it to heat up even more. Even­tu­ally, the tem­per­a­ture rose so high that the sol­vent in which the reac­tion was taking place began to decom­pose — another more vio­lent exothermic reac­tion, which heated the system even more. And sped it up even more. As this process con­tinued (a run­away reac­tion), gas built up in the reactor. When the pres­sure reached 400 pounds, the relief valve opened releasing the pres­sure. But it was already too late. The reactor exploded with the force equiv­a­lent to 1400 lbs of TNT, according to the Chem­ical Safety Board, which com­pleted a report on the inci­dent in 2009.

Willey and his col­leagues H. Scott Fogler and Michael B. Cutlip used the data from the CSB report to ana­lyze the acci­dent to math­e­mat­i­cally model the chem­ical reac­tion involved in the accident.

The graph to the left shows some of the results from the team’s efforts. They offer three sce­narios: Diglyme decom­po­si­tion under normal con­di­tions, when cooling is func­tioning prop­erly, diglyme decom­po­si­tion under the con­di­tions present during the acci­dent, when the relief valve was set to 400 pounds, and diglyme decom­po­si­tion under an inter­me­diate set of con­di­tions, where the relief valve was set to 75 pounds. “If the relief valve had opened at a lower pres­sure, this second reac­tion would not have had the ini­ti­ating con­di­tions to bring it into a run­away,” said Willey.

The lesson to the reader is the phys­ical demon­stra­tion that the relief device should be set to open at slightly over working pres­sures instead of closer to the pres­sure rating of the reac­tion vessel.” This seems like common sense, Willey admitted. The problem is that it’s not.

The two owners of T2 had under­grad­uate degrees in chem­ical engi­neering and chem­istry, respec­tively. Nei­ther of them had any training chem­ical engi­neering hazard avoid­ance. They both died — one from the explo­sion, one from a heart attack after the explo­sion, according to Willey.

Willey’s paper now appears as a module in the Safety and Chem­ical Engi­neering Edu­ca­tion Pro­gram, an online resource for ChemE edu­ca­tors. “There are slides for pro­fes­sors to use, we show the devel­op­ment of the equa­tions used in the mod­eling,” he said. Fur­ther, the example is used in Fogler’s text­book on chem­ical reactor design, which is used by an esti­mated 75% of all chem­ical engi­neering pro­grams in the country.

When I asked Willey if this was the main area of his research he responded with the words “Run­away reac­tions. You know, as in Bhopal.” I’d told him ear­lier that I had a back­ground in chem­istry and when I didn’t rec­og­nize the words, I thought I was for­get­ting some essen­tial lesson from inor­ganic. “Type Bhopal reac­tion into Google and see what comes up,” he said. Bhopal reac­tion dis­aster came up.

Willey received the Bill Doyle Award once before, for his paper “The Acci­dent in Bhopal: 20 Years Later.” In that case it wasn’t four people who died, it was sev­eral thou­sand. It hap­pened in 1984 (2 years after I was born, my weak excuse for not knowing about it) as a result of cost cut­ting mea­sures which jeop­ar­dized the safety checks. Forty-​​one metric tons of methyl iso­cyanate were released into the atmos­phere. Since the chem­ical is heavier than air, it sank to the ground after being blown out the vapor stacks and infil­trated the sur­rounding land and the slums that were built on it. In addi­tion to the deaths, hun­dreds of thou­sands were exposed to the chem­ical resulting in serious illness.

I asked Willey how many people died in Cher­nobyl. That number is harder to pin­point, as people con­tinue to suffer from expo­sure related ill­ness after that 1986 tragedy. But he put Bhopal at second worst non-​​war related man-​​made dis­aster in his­tory. And I’d never heard of it. He picked up his cell phone and called his friend, “Dennis,” he said, “I’m sit­ting in front of a chemist who’s never heard of Bhopal.” I was kind of hor­ri­fied. When he hung up after a few min­utes of small talk I asked if I was unique.

No, you’re not unique,” Willey said. “That’s the problem.”

If you’re reading this, please com­ment: did you know about Bhopal before? Were you taught in a chem­istry or chemE class?

Photo: Aerial view of T2 Lab­o­ra­to­ries, Inc., fol­lowing explo­sion and fire, via Wikipedia