TCEQ Study Suggests that Flare Emissions Could be Larger Than Reported

EDITOR’S NOTE: The final draft report was released May 24. Download the PDF here.

A soon-to-be released key flare emissions report could help answer the question of why Texas air toxics concentrations are higher than those reported through industrial emission inventories.


Footage of flare emissions captured by advanced monitoring technology at facility in Texas. The video was presented by TCEQ at the Hot Air Topics Conference on Jan 13, 2011 in Houston, TX. Flare is described as being oversteamed, resulting in reduced destruction efficiency and increased emissions.

Across the state, there are 1,500 flares registered with the Texas Commission on Environmental Quality. The “flaring” or burning of excess gases using these flares has been accepted industrial practice for combusting routine waste gases as well as for combusting large volumes of gases that may result from plant emergencies, such as those that could lead to a facility explosion. Air quality experts have long held that an increase in flare pollution has been a significant contributing factor in escalating smog levels and toxic “hot spots,” particularly in fenceline communities.

To address these issues, TCEQ, along with the University of Texas at Austin, conducted a $2.2 million study to evaluate the accuracy of flare emissions estimates and provide data as the basis for potential improvements to flare operation or monitoring requirements. Initial findings from the Texas Commission on Environmental Quality 2010 Flare Study Draft Report were posted today on the TCEQ website, with the final study draft report to be posted soon for public comment.

Flare Study Findings Summary
In conjunction with the study, TCEQ formed an open-participation Flare Task Force Stakeholder group, seeking input on flare performance, operation and regulations. Many members from both the industrial and environmental community participated in the stakeholder group. Results as presented in the initial findings indicate that this study will be a real game changer for how flares are managed and operated.

Here are my impressions on a few of the key findings:

  • Operation of the flare is critical in combusting the waste gases. The heating value of the waste stream is essential to the process – and it makes sense. If the components of a chemical reaction are not optimized, then the reaction may not be efficient.
  • Oversteaming of the flare appears to result in dramatic reductions of combustion efficiency.
  • Results reported in this study mimic findings from two previous studies, including one from the Environmental Protection Agency back in 1983. This is especially beneficial in that it provides further evidence that operational changes can be made to impact destruction efficiencies – the amount of pollution burned in a flare – in some cases by more than 50%.
  • It is not possible to determine by sight alone whether a flare is operating efficiently. Therefore, if a flare is smoking, it doesn’t necessarily mean that it has a low destruction efficiency. (Note: this was generally assumed to be true until now.)
  • TCEQ plans to use the new information to help with future air modeling initiatives. The problem here is that there is more pollution measured in the air than is reported through emission inventories. However, that’s precisely why this report helps us understand why concentrations of air toxics are higher than reported.

In light of the report conclusions, my hope is that industry acts immediately to assess the current state of its flare operations and takes steps accordingly to implement improvements. Public comments on this flare study are greatly encouraged. Once the final study draft report is posted, comments may be submitted to TCEQ as follows:

  • Attend a stakeholder group open to the public and all interested persons.  The meeting will be June 1, 2011, 2:00 – 4:00 p.m., Houston-Galveston Area Council, 3555 Timmons Lane, Suite 120, Conference Room A, Houston, Texas 77027 Directions | Agenda
  • Staff will be accepting informal written comments on the information discussed at this stakeholder meeting until June 6, 2011.
  • Written comments may be submitted at the stakeholder meeting or submitted to Russ Nettles, MC-164, TCEQ Air Quality Division, P.O. Box 13087, Austin, Texas 78711-3087, or faxed to 512/239-1515. Electronic comments are preferable and may be submitted via e-mail to All electronic comments should reference the “Flare Task Force Stakeholder Group” in the subject line.
  • For more information on the scheduled meeting or questions regarding the informal comments, please contact Lindley Anderson of the Air Quality Planning Section at 512/239-0003.

Technical Findings Summary
This study looked at dual-service flares, meaning flares characterized as low-flow (used for routine emissions most of the time), but also used for emergency flaring. Of the 1,500 total flares across the state of Texas, 45% are dual-service and of the type tested in this study.

In the study, two different flare tips were used:

  1. 36-in steam assisted flare with upper and center steam (typically, steam is added from the upper portion of the flare to prevent smoking of the flare. Steam added from the center portion of the flare is used to push the combustion out of the flare tip and prolong the life of the flare).
  2. 24-in air assisted flare (a fan on the flare is capable of fine-tuning the amount of air added to the flare).

Three types of data collection were taken in the study:

  1. Extractive (emissions from flares was measured continuously using a specially developed tool designed to capture emissions coming from the tip of the flare; it looked like one of the tools that you’d use to snuff out a candle);
  2. Remote sensing techniques (including a portable radiometric spectrometer) were used to measure the type and quantity of specific hydrocarbons coming from the flare plume (flare plume could measure as much as 30 feet long); and
  3. FLIR (forward looking infrared) – imaging technology that detects heat.

Operational changes in the way in which a flare is operated can change the destruction efficiency of the flare. For instance, the heating value of the waste gas stream is critical in terms of the destruction efficiency (i.e., if the reaction is not hot enough, then the waste gas will not combust as efficiently as it should).

This chart is an example from the report of how the amount of steam added to a flare can alter the destruction efficiency:

Vent gas sent to flareBtu/scf (the heating value of the waste stream)*Upper steam assistCenter steam assistDestruction efficiency**
937 lb/hr350 Btu540 lb/hr430 lb/hr46.6%
937 lb/hr350 Btu0099.9%
*the heating value of the waste stream depends on the type of waste that is being burned
** destruction efficiency is the % of hydrocarbons, or waste, that is destroyed by the flare
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