Date: February 18, 2013

To: Andrew Bouchard and Br enda Shine, EPA/OAQPS/SPPD

From: Jeff Coburn

Subject: Meeting Minutes for February 13, 2013, Meeting Between the U.S. EPA and Representatives from John Zink Hamworthy Combustion

On February 13, 2013, representatives of th e U.S. Environmental Protection Agency (EPA) and their contractor (RTI International) participated in a teleconference meeting with flaring experts from John Zink Hamworthy Combustion (John Zink) . The meeting was requested by the EPA to discuss minimum steam requirement s for flares. Prior to the meeting, the EPA provided representatives of John Zi nk a list of questions to aid the discussion. These questions are provided below as the outline for the discussi on topics. Prior to the meeting, John Zink representatives suggested that th e diagrams from the Marathon consent decree be reviewed as these figures would be useful as references dur ing the discussion. The Marathon consent decree figures are provided as Attachment 1 to this memorandum.

Attendees

John Zink Hamworthy Combustion Jim Franklin Zach Kodesh

U.S. EPA Representatives Andrew Bouchard Brenda Shine

RTI International (EPA contractor) Jeff Coburn

Discussion Topics

Q1. What determines the minimum steam usage rate s for a flare? That is, for steam assisted flares that are generally on sta ndby (no waste gas flow; purge gas flow only), why can’t the steam be turned way down or off?

A1. Minimum amounts of steam are needed to prol ong flare tip life. Ther e are potentially three types of steam used, depending on the flare tip design: upper steam, center steam, and lower2 steam (see Attachment 1). The simplest flare desi gn is Type I (see Attachment 1) and uses only upper steam.

Upper steam helps to keep flame off of pilot tubing and to shape the flame. You want a curtain of steam around the nozzles (150 pounds of steam at about 350 degrees Fahrenheit) for tip protection. You need at least a minimum of “warming” steam to keep water from condensing in line (water in line would get blown out when st eam rate increased and can knock out the pilot flame). “Cooling steam” is what usually is used for normal operation to keep from burning-up the flare tip or pilot nozzles. The amount of coo ling steam needed is dependent on a number of factors including wind speed (which can push to fl ame towards pilot nozzles) and flare gas flow rate (to keep from smoking). Typi cally, the flare operator will just fix the upper steam flow rate at a certain level to ensure cooling, and may increase at times of high flaring rates when needed to maintain smokeless operation.

For larger diameter flares, a Type II design that includes center and lower steam additions is often used (see Attachment 1). At low flow velocities (1-2 feet per second (ft/s)), center steam is used to make sure there is no oxygen ingress, so any fl ame does not start within the flare tip itself. Oxygen that comes in a few feet of the top of the flare can cause burning with in the flare, which is very hard on flares and shortens tip life. Molecu lar seals, which utilize an “S-trap” in flare gas riser lines, act to use the buoyanc y of methane to prevent air i ngress. Flares equipped with molecular sieves and can get down to very low flow rates (approximately 0.01 ft/s purge gas) without needing center steam to prevent oxygen ingr ess. Molecular seals look like a large bulge around the top of the flare. The a dditional size/weight of a molecula r seal flare tip often limits the number of flares that can be retrofitted to use mo lecular seals due to struct ural limitations of the existing flare stack. Velocity seals can be us ed reduce the minimum velocity at which center steam must be used down to 0.03-0.0 5 ft/s purge gas; velocity seal s are smaller and are therefore easier ( i.e. , more widely appli cable) for retrofits.

“Lower steam” or “Steam/Air tube s (S/A tubes)” are used for certain applications when the flare is servicing gases that cracks so fast that it is hard to keep the flare from smoking. Lower steam is added so that the steam flow will educt air into tu bes within the flare tip. This allows air to get into the middle of the flare to limit cracking/smoke formation. The internal tubes are also angled to spin and mix the flare gas with the air/steam to limit cracking. Larger flare tips are more likely to need lower steam (S/A tubes) to mix the flar e gas and ensure some oxygen gets into the center portion of the flame. Larger flares are also mo re likely to have oxygen ingress. Having S/A tubes in the flare tip makes it more important keep th e flame from burning within the flare tip (more internals that can burn-up/degrade), so it become s more important to have and use more center steam for large flares with S/A tubes.

Q2. Are there some flare tip designs that can operat e with lower or no steam flow as compared to other flare tip designs? If so, how long have these been available? What number (or percentage) of existing refinery flares ha ve the lower steam design?

A2. Molecular or velocity seals, discussed in A1 above, can limit the need for center steam. In general, the bigger the flare tip, the more steam needed for general and standby operation. To3 limit steam use and flare inefficiencies, it is generally preferable to use a staged flare system (two or three flares in series where flow only goes to the second flare when the first flare begins to reach capacity) rather than one large flare that ca n handle the full capacity at all times. In addition to improved efficiency and less steam use, sma ller flare tips generally last longer than lager diameter flare tips. Type I small flares may last 10 to 12 years. Larger flares must be replaced every 4 to 6 years.

Marathon is testing a new air-entra ined-in-steam system to see if they can reduce the amount of supplemental natural gas that must be added in order to meet the combustion zone heat value requirements. The entrained air does less to quen ch combustion than steam so this should allow use of less natural gas to supplement flare gas when flare gas flow is low. This technique is just being tested and it is unclear how well this system will work to improve combustion efficiencies at low gas flow rates.

Type III flare tip (see Attachment 1) has only “low er steam” (S/A tubes). This flare type design makes it easier to control steam usage rates because only one steam source/line is used. Based on the design and mixing afforded by this system , it typically uses 30 percent less steam (for smokeless rate) than Type I or II flares. Also, this flare design has better “premix” so it is expected to have higher combusti on efficiencies (or a wider range of operating conditions for high efficiency) than other flare tip designs, but this ha s not necessarily been veri fied in field tests.

Q3. Assuming there is a lower steam flare tip desi gn, what would be the typi cal costs to retrofit an existing flare tip to a low mi nimum steam usage flare design?

A3. Flare types are routinely replaced. Modifyi ng the flare type design can reduce steam use.

Molecular seals or velocity seals plus no leaks to flare ( i.e. , flare gas recovery system) could reduce minimum velocity and steam rates. Costs would be highly site-specific and the ability to retrofit would be dependent on the structural characteristics of the existing flare stack.

One can generally retrofit the flare tips to Type I II design. Type I flare tips are light, so the flare stack may not be able to structurally handle a Type III retrofit (since Type III would be a heavier). Most Type II flares (which are already heavy) woul d be able to retrofit to Type III. Type III flare tips have smaller restrictions at the outlet, which increases the back pressure of the flare slightly; this increased system back pre ssure must be considered on a re finery-specific basis and may limit the use of the Type III flare tip in a few applic ations. In general, a Type I tip replacement averages about $100,000; a Type II tip replacement is 2 to 3 times the cost of a Type I tip and a Type III tip is about 1.5 times the costs of a Type II tip.

Q4. If retrofits cannot be made, how much would a typical flare replacement cost?

A4. Replacing a large flare with a staged system would be an example of a flare replacement (versus a flare tip retrofit). Flare repl acement costs are highly site-specific.4 Q5. When installing a new flare, is there any significant capital cost difference for a low minimum steam flare versus a trad itional steam-assisted flare?

A5. See cost differences in flare tip costs in A3.

A cascade flare system would generally cost more than a single flare system but due to improved operation, less steam use, and longer tip life, cascade systems are often selected in preference to a single large flare.

There are some flare designs (like ground flares with staged flare bur ners) that can operate with no gas flow to the burners that ar e shut-off. You would still have to use a minimum of “warming steam” to prevent condensation in the steam pipes, but you would not need purge gas flow to the burners that were shut-off , so you would have less steam and purge gas use.

Q6. Are there any other issues associated with low minimum steam usage flares? E.g. , do they need better flow monitoring and au tomated steam controls to adjust steam levels quickly if there is a sudden, large flaring event?

A6. At low flow rates, the flame is closer to th e tip so you are more likely to burn-up a tip at low flow rates than high flow rates. Therefore, controlling steam addition at these low flow conditions is important. However, most operators do not really monitor flow rates and do not have valves/controls needed to accurately adjust steam usage at low flow conditions. As such, most refineries will likely need to add a small parallel steam line to better control steam at low rates.

Q7. Are there similar minimum air flow issues associ ated with air assisted flares? If so, why and are there different tip designs for minimizing air assist rates during “idle” conditions?

A7. Instances have been observed where too much assist gas can blow out the flare flame. Air assist systems designed with multiple blowers oper ate over a larger range of flows than a one blower system. Typically, a one blower syst em can operate with a minimum turndown of approximately 5 to 1. Assist air is typically added around the outside of a flare only (no “center air). Steam is generally more “energy” efficient th an air so facilities genera lly only use air-assist when steam is not available.

Unassisted flares generally do not have the combus tion efficiency issues as air or steam assisted flares and would not need combustion zone analysis. Most refinery flares are assisted to prevent smoking. Enclosed flares can ofte n operate with no assist steam or air and not smoke, so these flares can be unassisted. Enclosed flares can be ground flares or la rge diameter stack flares. The enclosed stack flares, even though they may have a large diameter stack (as much as 40 feet in diameter), take less space than other flares since they do not ha ve the radiant heat, although it is important to make sure the heat plume from the fl are stack does not cross a nother stack or elevated structure that someone might climb.ATTACHMENT 1

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