Chemistry Related Mishaps

    I recently came across an article published in Chemical Engineering Progress entitled Remember the 'Ch' in ChE" (February 1998, Marcel J.P. Bogart).  In this article, the author shares some of his experiences where oversights in chemistry gave rise to very dangerous and costly situations.  I'd like to share some of these situations with you and examine what went wrong.

A.  "Aluminum Isn't Always Great"
    Ethanol was being converted to n-butanol via an aldol condensation reaction.  The butanol was to be removed by two distillation columns.  The process stream proceeded through the first column where water was removed in the bottom and the other product out the top.  This separation proceeded without incident within the beautiful, new column constructed of nearly pure, rust-proof aluminum.  Then the stream entered the second column, also made of aluminum.  Unfortunately, the engineer failed to realize that when n-butanol is near its boiling point of 117 ⁰C, it reacts quickly with aluminum to form a salt.  The bottom dropped out of the second column!  Closer attention to the material of construction could have prevented this amazing incident.

B.  "The Instruments Were Right"
    A naphtha mixture was being converted to a mixture of hydrogen, carbon monoxide, and carbon dioxide.  This mixture was then being fed to a Fischer-Tropsch reactor where it was combined with steam to force the following reaction:
H₂ + CO + H₂O ---> 2H₂ + CO₂
This reaction was to help increase the hydrogen content and the hydrogen would be separated out for other uses.  When the Fischer-Tropsch reactor was designed to be an adiabatic reactor....it might as well have been buried then!   During normal operation, the steam flow meter suddenly dropped to zero.   Simultaneously, the thermocouples in the reactor began to show extremely high readings.  Operators were ordered to fix the flow meter and replace the thermocouples (there was no way that they could be reading correctly).  The problem was that neither were necessary because they were reading perfectly.  When the steam flow stopped, the previous reaction was replaced by a very exothermic reaction:
3H₂ + CO ---> CH₄ + H₂O
With no way to remove heat from the reactor, it got so hot that it had to be replaced!

C.  "Knowing What You're Absorbing"
    It's nice to be able to use water in your absorption unit.  But, it's also nice to know what the water is absorbing.  After a pyrolysis unit, water was being used to quench a gas stream.  No one realized that the gas stream contained significant amounts of benzene.  The benzene (being water soluble) was transferred to the water.  From there, the water was sent to a cooling tower where conditions were favorable for air stripping of the benzene from the water. Benzene then was released to the atmosphere.  Oops!  Eventually, the benzene rich air was blown into the plant's air in take and the problem was discovered.