What Happened in the Brine System

Another unit in the same chemical complex supplied the hydrochloric acid via pipeline. The acid was a by-product of a process that manufactured large quantities of flashing flammable liquids. Supervision directed the crew to promptly collect acid samples and deliver them to the Main Lab to analyze for flammables. Lab analysts did not detect the presence of flammable chemicals. 

When the operator pressed the start button on the agitator, the strong acid and finely-divided calcium carbonate solids instantaneously reacted, creating and liberating 400 cubic ft. (11.3 cubic meters) of carbon dioxide within a relatively small tank nearly filled with salt water. 

The investigating team recommended both hardware and procedural changes. They recommended that the vent stacks on each tank be increased from 6 inches (15 cm) in diameter 

Supervision instituted new procedures. When slurry feed supply is shut down, procedures require the operators to continue agitation and acid flow for at least 30 minutes. On startup, the agitators and acid feed will be restored before starting up the slurry pumps. Both of these steps were designed to eliminate the possibility of having an undetected layer of calcium carbonate. 

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