### Follow-ups on P&R1 Questions robert. j .morehouse to: Nick Parsons 02/25/2011 01:00 PM
Cc: Ken Hustvedt, Penny Lassiter
History: This message has been replied to and forwarded.

Nick:

As a follow-up to questions from last week's meeting I've included some additional information below:

Flare systems for Butyl Rubber Source Category :

Baytown Butyl Rubber: Control device for front-end Group 1 vents is FS-12, a dedicated flare with no flare gas recovery . [some safety devices would route, if a failure occurs, to the Chemical plant Flare Loop, which does have flare gas recovery ] Baton Rouge Halobutyl Rubber: Control device for front-end Group 1 vents is a primary flare (with a backup) that bypasses two interconnected loops with 4 flares so gases are not sent to the flare gas recovery system. (36" diameter on the main riser

Startup/Shutdown Considerations

Recommended Procedures for Handling Group 1 Front-end Process Vents During Startup and Shutdown

Background: At some point in the startup and shutdown of Butyl Rubber and Ethylene Propylene Rubber source category units the requirements to achieve 98% organic HAP removal and, additionally for halogenated vents 99% HCl removal, cannot be met because the vents have inadequate heat content or pressure. On shutdown, where the equipment is to be gas-freed, these instances occur after feed forward has stopped and thus the vent streams will contain only the organic HAP and halogen that is trapped in the process equipment being vented. On startup of equipment that has been gas-freed, flow-through of process gas must occur to displace the nitrogen in the equipment. It may take several equipment volumes of process gas to remove the nitrogen to the point where the Group 1 vent may be routed to the thermal oxidizer/scrubber.

Proposed shutdown procedure: Keep halogenated Group 1 front-end process vents aligned to the thermal oxidizer /scrubber until equipment to be shutdown is isolated (i.e., no additional hydrocarbon or halogen is entering the equipment) and depressured to the point where it can no longer safely be routed to the thermal oxidizer /scrubber. Then either route the vent to the flare or demonstrate by engineering analysis that the vent contains <50 ppmv organic HAP. Route to the flare halogenated Group 1 front-end process vents that have been diverted from the thermal oxidizer/scrubber and any Group 1 non-halogenated process vents that are normally routed to the flare until either 1) the vent pressure is too low to go to the flare, or 2) the vent contains <50 ppmv organic HAP as demonstrated by engineering analysis . Then, the vent may be routed to the atmosphere.Proposed startup procedure ( from point where equipment is under nitrogen

pressure): Align the Group 1 front-end process vent to the flare and begin displacing nitrogen to the flare with process gas . For Group 1 front-end process vents that are routed to the thermal oxidizer /scrubber for compliance, route the vent to the thermal oxidizer /scrubber when the vent composition is acceptable and 98% organic HAP destruction in the thermal oxidizer/scrubber, based on engineering assessment.

Surge Control Vessels

Baytown Butyl Rubber: 2 front-end surge control vessels both meet the Group 1 storage vessel criteria. Baton Rouge Halobutyl Rubber: 3 front-end surge control vessels meet the Group 1 storage vessel criteria.

Also, as I mentioned last week EPA's cost estimate has several fundamental errors that we highlighted. I'd be glad to arrange a meeting with our cost estimators to provide additional information if necessary .

Thanks, Bob

Bob Morehouse ExxonMobil Office: 281-870-6524; Cell: 281-384-5390 robert.j.morehouse@exxonmobil.com