Why 1,597 lbs of sulfur dioxide was emitted the other day at the oil refinery in Sweeny, Texas

"When operations switched from the overhead fractionator (29-D-2) to the blowdown settling drum (29-D-9), the pressure spiked causing the Flare No. 29 water seal to blow. As soon as the water seal blew, the pressure dropped to 1 psig. The make-up fuel gas line, which regulates the system pressure at 6 psig, came fully open. The valve remained open for approximately 1.5 hours, attempting to regulate the system pressure. After 1.5 hours, process controls completed the re-filling of the water seal thereby ending the flaring event."

Then what?

"Once the water seal blew, process controls automatically actuated the re-filling of the water seal, ending the flaring event. As a result of this event, operating procedures are being re-written to allow the "manual" override of the automatic re-filling of the water seal. The manual re-filling of the water seal will be accomplished more rapidly than the automated process, resulting in lowering of flare emissions in the future."

How do you know the amount of emissions that were released?

"Engineering calculations. Presuming that the check valve between 29-D-2 and 29-D-9 did not fully close, the high concentration of H2S likely came from both the blowdown system and the main fractionator."

Oh.

OK.