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Daniel Ward's picture
Marketing Coordinator ElectraTherm

As a recent graduate from the University of Georgia, I'm very eager to help advance the clean energy movement. In my current position with ElectraTherm, a waste heat recovery specialist using the...

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The Potential of ORC Flare Elimination

image credit: Gas Flaring, ElectraTherm

The Reality of Flaring

The flaring of methane is commonplace at many landfills, biogas and wastewater treatment plants (WWTP), and well sites across the globe. Industries routinely flare this gas to prevent pressure build up or to separate the gas as part of an industrial process. Not only are these flares an unsightly reminder of our impact on the planet but have grown to be a topic of concern as the world strives for a carbon-neutral future. Flares are currently responsible for 2% of the world’s total greenhouse gas emissions – which means if flaring were to be represented as a country, that country would be the 5th largest gas consumer in the world after the US, Russia, China, and Iran.

By visiting SkyTruth, one can observe global natural gas flaring via satellite. However, this satellite will only pick up the larger concentrations of gas flaring, indicating there are many more smaller sites also flaring. With that in perspective, the burning of this gas is not only a significant contributor to GHGs, but an immense waste of a valuable resource as well. Globally, the emissions from flared gas equate to an estimated 280 million metric tons of CO2 a year. To put things further into perspective, the value of gas flared in New Mexico alone in 2019 was $10 million.

With the data revealing the scale of the issue, it is easy to understand why this practice has come under increasing scrutiny with regulatory agencies seeking to eliminate or reduce flaring through the imposing of fines and stricter air quality standards. Some US states such as Alaska, Colorado, and New Mexico have already banned the practice of routine flaring. States such as Pennsylvania and Texas are close in pursuit, eager to appease industry regulators and environmental lobbyist. In the oil and gas industry, being ahead of the curve will be the key to longevity.

Take BP for example. Facing increasing pressure from regulators, investors, and buyers of natural gas to reduce their carbon footprint, BP pledged to spend $1.3 billion to build a network of pipes and other infrastructure to capture natural gas in their Texas and New Mexico oil fields that will effectively eliminate natural gas flaring at those locations by 2025. While this news is excellent, it is a drop in the bucket and not feasible for many locations currently flaring natural gas. Since numerous industries flare – such as landfills, wastewater treatment plants, oil and gas wells, and even biogas plants – a solution needs to be both practical and profitable to see widespread integration.

There are two main approaches to flare elimination. The first approach is to burn the excess gas in an engine to generate power. This route requires the installation of biogas cleanup and storage along with an engine genset. The cost of this equipment can easily be in excess of $1 million USD and engines running off biogas routinely face issues with siloxane buildup. Siloxane buildup requires expensive maintenance leading to increased downtime (lost revenue and more flaring) or even a complete engine replacement.

Another approach is to burn the excess gas in a boiler. Not only is this approach far less extensive and expensive, but modern biogas boilers are designed to be less susceptible to siloxane buildup and damage. Since biogas and wastewater treatment plants already have boilers installed, this method is simple and more cost-effective than the one mentioned above. In other instances, such as well site applications where a boiler will need to be installed, the capital costs are still far less than the alternative. The only dilemma with this approach is that those who cannot make use of the thermal energy provided by the biogas boiler are simply wasting energy, which leads us to a simple solution…

ORC Flare Elimination

An easily adaptable solution is an Organic Rankine Cycle (ORC) waste heat recovery system integrated with a biogas boiler. All we need to know about an ORC is that it exploits the temperature difference between hot and cold water to generate electricity. This means converting heat into power, using hot water as fuel. No fuel consumption or emissions. The process for ORC flare elimination is simple.

// Excess gas is routed to a boiler which heats water for the ORC.

// The water is then routed through the ORC, which is a closed-loop system, and generates electricity.

// By using excess gas to fuel a boiler, the flare is eliminated.

// By routing more gas to the boiler, water production can be increased and ORC output maximized.

An appropriate ORC flare elimination system must be able to handle fluctuations due to the inconsistent supply of thermal energy. With turbine systems incapable of reliably operating under those conditions, the only ORC technology that makes sense are those utilizing screw expanders. This is due to their comparatively better turndown ratios and transient operation capabilities. In collaboration with the Department of EnergyGulf Coast Green Energy, and HESS, an ORC system was installed at a North Dakota oil well. The application saw carbon monoxide emissions decrease by 98%, nitrogen oxide by 48%, and VOCs by 93% - all while generating emission-free electricity.

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Mark Silverstone's picture
Mark Silverstone on Apr 30, 2021

Yes, the prevalence of flaring, not to mention venting,  and the resultant GHG emissions is a significant portion of total GHG emissions and is scandalous.

Offshore installations and onshore petrochemicals plants usually keep a pilot flare going 24/7 in order to be able to flare when plant conditions make it necessary to divert gas safely. More and more installations, mostly in the North Sea, manage to operate pilotless flares and ignite gas from the flare boom only when necessary.  Yes, it is more expensive, but, as you say, it avoids the "immense waste of a valuable resource."

As you describe, with land oil and gas production, flaring from wellheads is, unfortunately, strictly a matter of convenience and cost.  At least it´s better than simply venting. I am glad to hear that some states ban the practice. I will be happier when the ban is enforced.

The Biden administration has recently managed to reinstate the Obama era controls on methane emissions.  I hope this leads to far less flaring and venting.  I believe that satellite surveillance will be useful in this effort.

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