Heat Recovery in Oil & Gas Applications

Exergy is an Italy-based specialist in Organic Rankine Cycle (ORC) applications and recently started working on ORC unit for waste heat recovery from gas turbines in LNG regassification plants.

Luca Xodo, Exergy’s head of Sales, explained the technology behind Exergy’s ORC as well as specific details about how the system can be applied to LNG plants. “ORC is basically a steam cycle with vapor from organic fluid instead of water. This is a more efficient cycle for smaller size installations (smaller than conventional steam turbines) and lower temperatures. Turbines around 5 MW power output can produce in combination with ORC up to 7 or 8 MW power.”

He added that Exergy utilizes for the ORC its own Radial Outflow Turbines in versions that are essentially the same from a mechanical point of view but almost always customized to the needs of the customer and characteristics of the installation.

Exergy’s turbine portfolio is divided into two main families: one for geothermal applications, usually characterized by lower temperatures and high power (for ORC cycles), with two frames: 10 and 25 MW; and one for heat recovery applications, with three frames: 2.5, 5 and 10 MW.

The company has currently about 440 MW of power installed with its ORCs, out of which 350 MW are in operation with proprietary Radial Outflow Turbines.

Typically, for an Organic Rankine cycle application Exergy will deliver not just the turbine but a whole system composed of heat exchangers, pumps, valves, a condenser system, and the organic fluid of choice. “We utilize a palette of up to 10 different organic fluids, including all hydrocarbons (butanes, pentanes), refrigerants, siloxanes and perflourinated compounds,” said Xodo.

“A new product will be available in the course of 2019, that is capable of a direct exchange thermal cycle using a non-flammable fluid (which sometimes is a specific request in the projects for the oil & gas market). The product is currently being developed with some important partners and will be optimized using a limited number of components, thus aiming at being more price competitive.” Exergy is planning for an official launch later in the year.

The application of ORC to LNG plants actually opens two new markets for Exergy: one is pure power generation in combination with gas turbines or internal combustion engines; the other one is in the oil & gas industry, where Exergy’s ORC can be used both downstream internal combustion engines or turbines when used for driving compressors in pipeline compressing stations. “In both markets the absence of water consumption and the automatic operation of the plants is seen as a great advantage and less risk for the operator. It also makes this application very suitable for remote plants as well,” explained Xodo.

“Our technology is very flexible and easy to scale up, as the history of Exergy shows. Our first ORC was installed in 2011 with an output of 1 MW; in 2014 installations reached 4 MW output, while 12 MW were touched in 2015. In 2016 the threshold was set at 25 MW. The very quick upscaling of our technology let us believe that there is still a great potential for increases.”

Xodo concluded that “The application of our technology in the midstream and downstream sectors of the oil & gas industry will be a primary focus of our strategy in the near future, as we have seen outstanding growth of the demand in this sector in the recent years and forecasts set a promising target of US$14.90 billion by 2023.”