Heating Value
measurement of
Flare Gas

Flares are used to eliminate waste gas and are an important part of a plant’s safety system. Legislation around flaring is increasingly intensified as flaring is an undesirable process both environmentally and economically. Users are forced to minimize their flaring activities and guarantee a minimum BTU value to ensure high destruction efficiency.

New legislation

January 30th, 2019

Starting January 30th 2019, the 40 CFR part 63.670 and 63.671 of Environmental Protection Agency’s (EPA) Clean Air Act will come into effect requiring Petroleum Refineries to reduce toxic air emissions caused by flaring. Control devices must be installed to ensure a minimum BTU value of 270 BTU/scf. Large refinery corporations are already preparing for these strict measures to prevent high penalties, that can go up to USD 37,500 a day.

How we can help

Flare Gas Measurement btu Analyzer

According to the Act, BTU may be measured with a continuous calorimeter. Hobré has developed a dedicated version of the WIM Compas™ flare gas measurement BTU analyzer to measure Net Heating Value (NHV) of flare gas. This is an fast-responding, injection-based version of the WIM Compas™ and offers an unmatched, robust solution with high availability for measuring the most challenging applications. The BTU analyzer can measure applications with high H2 fluctuations (0-100 mol%) and non-combustibles such as N2, CO2 with a proven track record in flaring applications. Optionally the WIM Compas™ can directly measure the H2 concentration of flare gas, in accordance with 40 CFR 63.670 section J. The integrated H2 measurement enables the operator to use the so called “H2 credit” to increase the BTU of the flare vent gas directly. This will improve compliance even more.

The WIM Compas™ F can be heated till 55°C (131°F)  as a standard. By using the High Temperature (HT) version the WIM Compas™ F can be kept above dew point of the gas (max. 150°C/300°F). This flare gas measurement BTU analyzer makes the WIM COMPAS™ F the ultimate tool to meet compliance and optimize natural gas blending. With our BTU analyzer you will be guaranteed of the legislation of the EPA refinery sector rule (RSR), CRF 63.670 and 63.671 of Environmental Protection Agency’s Clean Air Act.

Experience in the field

Over the last decades, Hobré has installed over a hundred analyzers dedicated to flare gas applications. We have collaborated with multiple industry supermajors to create the best fit-for-purpose solutions meeting their needs. Owners / operators of these solutions include refineries and chemical plants. Our continuing collaborations serve as testimonies for the provided level of quality..


Benefits of the technology include

  • Low operating pressure (-0,3-1.5 barG).
  • Suitable for percentage levels of corrosive elements.
  • Typical update time of 30 seconds.
  • Validation interval: monthly (manufacturers recommendation)
  • Low maintenance (the maintenance interval is typically six months to one year).
  • Unburned sample can be returned to the process.
  • High-temperature solution available, to allow sample temperatures up to 150˚C/300˚F.
  • No external sample system required. The heated sample bundle can be routed directly to the analyzer.
  • Suitable for outdoor installation (under a three-sided shelter). No need for an air-conditioned analyzer building.
flare gas measurement btu analyzer

Detailed info legislation

Gas Chromatographs and Calorimeters

Monitoring flares may be conducted by using a calorimeter (WIM COMPAS) or a gas chromatograph (GC).

Whereas capital expenditure of a WIM and GC are nearly equal, the OPEX of a WIM is considerably lower in terms of maintenance, validation gasses, carrier gasses and EPA’s validation requirements. Additionally, a calorimeter is a more adequate tool for natural gas blending.

A GC is a better tool to analyze H2, which has a positive effect on the destruction efficiency of a flare. Nonetheless, a calorimeter has proven to provide quicker response times. In accordance to Table 13 of the 40 CFR 60 Subpart CC, when using a GC, a daily mid-level calibration per specification 9 of 40 CFR 60 appendix B is required in combination with a quarterly triplicate analysis. The sampling line temperature must be maintained at a minimum temperature of 60C.

Minimum required accuracy: As specified in performance specification 9 of 40 CFR part 60 appendix B. Calorimeters can be calibrated per manufacturers recommendation (for the WIM this is once per month). The sampling system should be setup to ensure p[roper year-round operation. Minimum required accuracy +/- 2% of span.


Calorimeter requirements

For each flare, the owner or operators shall operate the flare to maintain the heating value of flare combustion zone gas (NHV cz) at or above 27O BTU/SCF determined on a 15 minute block period basis when regulated material is routed to the flare for at least 15 minutes.

Contact us directly

United States
Stephan Zuijdendrop
+1 (832) 679 3377

Michel Eskes
+31 (0) 299 420 871