Flare Gas Analysis
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Flare Gas legal compliance
As the federal US Refinery Sector Rule (RSR) has come into effect, flare owners and operators are mandated to comply before January 30th, 2019. In order to comply, refinery flares have to be monitored to guarantee a minimum net heating value (NHV) of 270 BTU/SCF.
To meet the new regulation, calorimeters and compositional analysis using gas chromatographs (GCs) are permitted. The exact requirements are described in Article 63.670 and 63.671 of 40 CFR part 63, subpart CC. But whereas GCs require daily calibration, calorimeters only require a calibration interval as recommended by manufacturers. Our Hobré calorimeter – the WIM COMPASTM – only needs a monthly calibration check.
The Hobré WIM COMPASTM for flare gas analysis and recovery is the preferred technology at supermajor refineries because of its proven track record in challenging applications. The BTU analyzer can handle applications with high H2 fluctuations (0-100 mol%) and non-combustibles such as N2, CO2. 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 offers an unmatched combination of response time, availability, accuracy and robustness, which enables users to comply with industry regulations, and optimize natural gas blending against minimum installation and maintenance costs.
Flare gas recovery
Legislation around flaring is increasing, as flaring is both environmentally and economically undesireable. Recovery systems are used to recycle flare gas for use in plants’ fuel gas networks.
The composition, and therefore the energy content, of flare gas can fluctuate heavily. This fluctuation has a negative impact on the stability of the fuel gas network. When burning fuel gas in a furnace, control over the energy flow is vital to optimize the product quality, throughput and efficiency.
Still, many industrial furnaces are equipped with flowmeters, density meters and traditional stack analyzer-based feedback control only. These control loops are too slow and/or inaccurate to handle fast fuel gas fluctuations. As a result, these furnaces cannot be operated with maximum efficiency.
To overcome the slow response of the stack analyzers, the fast-responding WIM COMPASTM F is installed in the fuel gas line to allow feed-forward combustion control. By providing information on the energy flow (and/or air-fuel ratio), efficiency, product quality and throughput are increased, while emissions are reduced – even where high hydrogen fluctuations are expected.
Payback time on this application is typically measured in months.
Energy loss reduction
Continuously monitoring flare gas to ensure a proper combustion is a hot topic in refineries throughout the USA. In cases where the heating value drops below the prescribed minimum, natural gas is added to increase the heating value and enhance complete combustion. Adding natural gas to flare gas to optimize combustion is a waste of money, and should therefore be reduced to a minimum.
Taking the possible complex gas matrices of flare gas into account, compositional measurement methods like gas chromatography can take up to 8-15 minutes per cycle. In order to prevent non-compliance situations, users of GCs often add a surplus of natural gas to compensate for the slow response of the GC.
The Hobré WIM COMPASTM F has an update time of only 30 seconds. The fast response, in combination with its high availability and low maintenance requirements, allow flare operators to reduce natural gas cost by optimizing the blending process. In some cases, GC users can justify installing the WIM Compas for natural gas control only.
To optimize blending, a fast-responding measurement method is a must.