Release in a chlorine production plant

An explosion occurred in a diaphragm chlorine plant. A cloud of hydrochloric acid, sulphuric acid and chlorine was released.
The cause was a blockage in the outlet for condensed water vapour from the hydrogen system of the plant. Plastic anti-corrosion material from inside the pipes is believed to have caused the blockage. Hydrogen was then forced back into the electrolytic cell and through its diaphragm into the chlorine system.
The excess hydrogen reacted violently with the chlorine causing an explosion in the drier section of the plant where chlorine is washed with sulphuric acid to remove water vapour.

The precursor cause was the deterioration of an anticorrosion coating, causing the blocking of the water circuit. INITIATING CAUSE was the permeation of hydrogen through the diaphragm into the chlorine cell.

Although nothing is reported on root cause, inadequate inspection and/or maintenance could have plaid part.

venting sytsem, condensed water line, diaphragm, dryer

27 employees and 3 external people were slightly intoxicated due to the direction of wind carrying the aerosol of hydrogen chloride and sulphuric acid .
The damage was estimated at 30 Deutsche Mark (1996)