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The facility manufactures dimethyl terephthalate (DMT), terephthalic acid (TPA), and polyester polyols. Methanol and p-xylene are the two main raw materials and constitute the largest portion of the HAP air emissions. The numerous fuel combustion sources (boilers, heaters, flare) include the firing of No. 6 oil. The facility includes four production lines (A, B, C, & D) that can be separated into three steps: oxidation, esterification, and purification. Oxidate is produced in the oxidizers from p-xylene and methanol. The oxidate is then sent to esterification (methanol and heat added). The product is then sent to purification. Lines A & B have three small oxidizers each. Lines C & D are the newer, main production lines and have one large oxidizer each. The oxidizer emissions are controlled by dual regenerative carbon adsorbers. The emissions from the regeneration of an off-line carbon unit are sent via the MeOH header (which serves all process lines) to be incinerated by the No. 4 heater or flare. There are many condenser and scrubber systems used in the production process.
On May 31, 2001, the facility (owned by Kosa at that time) personal discovered that the manual bypass valve for the D Line carbon adsorbers had been left open for the past 34 days. The following quantities were released over the period:
benzene: 483 lbs. (14 lbs./day)
methanol: 25,386 lbs. (747 lbs./day)
p-xylene: 129,010 lbs. (3,794 lbs./day)
toluene: 7,172 lbs. (211 lbs./day)
The air emissions from the release exceeded the reportable quantity limits for benzene (10 lbs./24 hr period) and p-xylene (100 lbs./24 hr period). During start-up of the oxidizer, the manual by-pass valve is opened. This sends the off-gas directly to the stack and atmosphere. This is done to reduce the risk of fire in the carbon adsorbers potentially caused by high oxygen concentrations that occur during start-up. Normally, after start-up, the by-pass valve is closed and all the oxidizer off-gas vents to the carbon adsorbers before exiting the stack. This time it was not. The facility was issued an NOV/NRE on July 5, 2001 for improper operation (B6). The facility responded to the notice and described steps to prevent future releases of this nature. The facility owner at that time (Kosa) was assessed a civil penalty of $17,408.00 on 12/11/01.
On May 10, 2002, a severe thunderstorm caused every VOC blower to shutdown. The blowers for the flare and C & D Lines were restarted 25 minutes later. The blower on B Line (which also serves A Line) did not restart due to a failed relay. The instrumentation repair people had the problem fixed on the morning of May 11. Approximately 65.5 lbs of p-xylene was released. The release was reported because the amount was first believed to be over the reportable quantity threshold of 100 lbs.
On September 14, 2002, the safety relief valve on the D Line esterifier failed to close. It opened at 6:05 am in response to over pressurization of the esterifier. The valve was stuck open for approximately 20 minutes, resulting in 4,100 lbs. of methanol being released. The valve was replace. Shutdown procedures were followed. The safety valves are checked daily for blockages. This valve had been installed on July, 2001. The release was reported because the amount was first believed to be over the reportable quantity threshold of 5,000 lbs.