From: Freshairconsult@aol.com

To: Brenda Shine/RTP/USEPA/US@EPA
Cc: Chittim@api.org

Date: 11/24/2009 05:18 PM
Subject: Additional Detail on Flare Seal Drum Monitoring

Brenda:

Here is some additional detail on the flare drum seal monitoring approach, that API believes should be allowed as an option, to supplement the flare flow monitoring required under Subpart Ja. It represents my understanding from discussions with API and WSPA memb ers. Let me know if you have any questions.

Have a great Thanksgiving.

Norm

Norman Morrow, Ph.D. Fresh Air Consulting 18126 Spellbrook Drive Houston, TX 77084 (281) 813-8633 freshairconsult@aol.com

(See attached file: Flare Seal Drum Monitoring Supplement 11-24-09.docx)November 24, 2009 Flare Water Seal Monitoring Specifics

In order to identify if low flare ga s flow meter readings are real in flare systems with water seals, it has often proved valuable to mon itor the seal integrity as a check on the flare gas flow meter. As long as the flare water seal remains intact, ther e will be no gas flow to the flare and any flare gas flow meter reading is assumed to be incorrect or to reflect flow in the flare header associated with changing pressures as flare gas recovery sy stems operate. This approach has been accepted by both the South Coast Air Quality Manageme nt District and the Bay Area Air Quality Management District.

Typically, the water level in a fl are seal drum is maintained us ing an overflow weir inside the drum or in drums with only one internal compartment an overflow drain from the drum, though in some cases the level is maintained using a level controller. The am ount of seal is set by placing the downward pointing inlet flare line at the desired dist ance below the water level. Depending on the system design, make-up water is s upplied continuously or as needed or both to maintain the level. Flare water seal integr ity may be confirmed by continuously monitoring the water level along with either the flare gas header pressure or the pressu re drop across the seal drum. In some configurations, water level in the seal drum will vary as the flare header pressure, flare stack backpressure and wate r makeup varies. In monitoring for seal integrity, the primary purpose of the level instrument is to assure that the water level has not varied significantly from the design value, but in situa tions where the water level does vary significantly, the level instrument may be used to determine the drum ups tream pressure or pressure drop that indicates flow to the flare at any given time.

Water seal height depends on the size of th e drum, the size of the flare header, and the characteristics of the gas streams that are potentia lly routed to the flare. Thus, the backpressure the seal exerts on the flare header will vary from drum to drum. Typically, this backpressure is in the range of 0.1 to 1.0 psi, corresponding to rou ghly a 3” to 30” water seal. For systems where the flare stack exerts negligible and/or constant , known backpressure on th e seal drum, a pressure monitor in the flare header upstream of the wate r seal can be used to indicate if the design backpressure has or has not been exceeded. B ecause flare headers are typically large diameter and, for safety reasons, are designed without low points that could form liquid seals, the upstream pressure can be measured anywhere in th e flare header between the last gas entry point and the seal drum. For systems where the flare stack has a significant bac kpressure or a variable backpressure, the seal drum delta pressure may be monitored. Flare stack backpressure depends on the type of flare (i.e., elev ated or ground), specifics of the flare stack design and combustion assist system (i.e., air, steam), if any, presen ce and impact of purge gas on the flare stack pressure drop and other factors.

Typical process type pressure and level instrume nts are used for this monitoring and, as already done throughout the NSPS rules (including NSPS Ja) they are simply specified in the rules as continuous monitors. For instance, §60.105a of S ubpart Ja specifies parameter monitoring for FCCU controls using CPMS as follows:November 24, 2009 (b) Control device operating parameters . Each owner or operat or of a FCCU or FCU subject to the PM per coke burn-off emissi ons limit in §60.102a(b)(1) shall comply with the requirements in paragraphs (b)(1) through (3) of this section.

(1) The owner or operator sh all install, operate, and ma intain continuous parameter monitor systems (CPMS) to measure and r ecord operating parameters for each control device according to the requirements in paragr aph (b)(1)(i) thr ough (iii) of this section.

(i) For units controlled using an electrostatic precipitator, the owner or operator shall use CPMS to measure and record the hourly average total power input and secondary voltage to the entire system.

(ii) For units controlled using a wet scrubber, the owner or operator shall use CPMS to measure and record the hourly average pre ssure drop, liquid feed rate, and exhaust gas flow rate. As an alternative to a CPMS, th e owner or operator must comply with the requirements in either paragraph (b)( 1)(ii)(A) or (B) of this section.

(A) As an alterative to pre ssure drop, the owner or operato r of a jet ejector type wet scrubber or other type of wet scrubber equipped with atomizing spray nozzles must conduct a daily check of the air or water pre ssure to the spray nozzles and record the

results of each check.

(B) As an alternative to exha ust gas flow rate, the owner or operator shall comply with the approved alternative for monitoring exha ust gas flow rate in 40 CFR 63.1573(a) of

the National Emission Standards for Hazardous Air Pollutants for Petroleum Refineries: Catalytic Cracking Units, Catalytic Refo rming Units, and Sulfur Recovery Units.

(iii) The owner or operator shall install, operate, and maintain each CPMS according to the manufacturer's specifi cations and requirements.

Thus for flare water seal monitoring, the requ irement would be to use continuous parameter monitors for pressure (or delta pressu re) and water level, as applicable.

In addition to whether the upstream pressure or seal drum delta pressure are monitored and the location of the monitors, the pressu re and level values that indicat e the water seal has been lost are specific to every individual flare seal drum . Therefore, it is recommended that, where a source chooses to use this supplemental monitoring, they include the spec ifics of the monitoring and the process values that indicate seal lo ss in the flare management plan required by §60.103a(a).From: Brenda Shine/RTP/USEPA/US

To: Freshairconsult@aol.com

Date: 11/24/2009 10:41 AM
Subject: Re: NSPS Ja

Thanks Norm.

Yes, I 'm still concerned that we don't have the actual method well specified. My understanding is that its a continuous pressure measurement of the waste ga s and a comparison against the pressure exerted by the water seal (which is measured by height). If the pressure ever exceeds the pressure from the water

seal then a release has occurred.

The devil is in the details, however.

I need details to understand:

- where the pressure monitoring occurs for the waste gas, - what frequency (it would seem to have to be contin uous, but in our rules continuous is often every 15 minutes, which wouldn't seem adequate) - what accuracy/precision on the pressure monitor - how the pressure exerted by the water seal is measured - what frequency - what accuracy/precision on the water seal measurement

Also, possibly a qualitative description on what syst ems this can work on and what systems it can't.

Brenda Shine Environmental Engineer US Environmental Protection Agency Research Triangle Park, NC 27711 (919) 541-3608, Mail Drop E143-01

From: Freshairconsult@aol.com

To: Brenda Shine/RTP/USEPA/US@EPA

Date: 11/20/2009 04:06 PM
Subject: NSPS Ja

Brenda:

Here's electronic copies of yesterdays handouts. It was a good discussion. Thanks for your attention.

Doug Van Pelt tells me you could so me details on flare water seal monitoring. I will round those up and send that info to you as soon as I can, probably Monday or Tuesday.

Norm