A Breath of Fresh Air: Dresser-Rand contributes to green efforts with its compressor technology employing supersonic ejectors

As Dresser-Rand recently stated in one of its marketing newsletters, “The future is not canceled and the global economy will recover.” The company continues to be actively involved in a broad range of current and developing technologies that are contributing to “green” efforts across the industry. During the past 18 months, despite the difficult global economy, Dresser-Rand has invested in three particularly important technologies each consistent with its business strategies of enhancing core capabilities, focusing on the environment, adding new products, services and technologies, and providing access to new markets.

One of those advancements is a new compressor technology employing supersonic ejectors. By reclaiming gases ordinarily vented into the atmosphere, the ejectors offer environmental benefits and enable facilities to operate more efficiently. Ejectors are available as new equipment options and product upgrades for centrifugal compressors that compress hydrocarbon gases. They also work with any low-pressure, low-flow-rate vent streams, and high-pressure stream applications.

The tandem, or two-stage ejector system captures gas leakage from a drygas seal at low pressure and recompresses it to a pressure equivalent to the fuel gas pressure. Reclaiming these gases by injecting them into gas turbine fuel systems reduces hydrocarbon emissions to the atmosphere. The recovery and recycling process captures greenhouse gas emissions during normal operations, and recovers natural gas vented from the primary gas seal. A typical dry-gas seal is a noncontact end face seal comprising two seats. The first, known as the rotating seat, has grooves etched into the seal face and rotates with the shaft. The second, known as the stationary seat, has a smooth face and only moves along the axis of the shaft. Using this pair provides the sealing effect.

Because the ejectors have no moving parts, seals, shafts or packing, they are practically maintenance free compared to mechanical compressors and vacuum pumps. “With growing concern for the environment, this ejector system presents an excellent way to reduce harmful carbon emissions while increasing energy efficiency in a variety of applications,” said H. Allan Kidd, director of emerging technologies at Dresser-Rand. “Because the system pays for itself in a short time, it provides a cost-effective way to reduce the carbon footprint in gas transmission operations.”

Dresser-Rand signed a memorandum of understanding with TransCanada in 2008 to manufacture, use and market the supersonic ejectors, incorporating technology developed with NOVA Research and Technology Corp. Following successful field testing in 2007 and 2008, TransCanada installed a prototype system on a 24 MW gas turbine unit in one of its compressor stations in Alberta, Canada. The system has saved more than 99 kW of energy equivalence and reduced 1600 metric tons of CO2-E greenhouse gases a year.

The final design, which was the result of a collaboration between Dresser-Rand and TransCanada, is undergoing field evaluation in another compressor station in Alberta. The product launch strategy is to offer this energy-efficient device first in midstream applications, followed by upstream and downstream. Dresser-Rand is one of the largest suppliers of rotating equipment to the global oil, gas, petrochemical and process industries. They operate manufacturing facilities in the United States, France, Germany, Norway, United Kingdom, China and India. They maintain a network of 34 service and support centers covering more than 140 countries.

The ejectors have no moving parts, seals, shafts or packing. Compared to mechanical compressors and vacuum pumps, they are nearly maintenance free
The ejectors have no moving parts, seals, shafts or packing. Compared to mechanical compressors and vacuum pumps, they are nearly maintenance free

TransCanada Corp.’s core business focuses on the development and operation of North American energy infrastructure. The company was founded in 1951, employs more than 4000 throughout North America and is headquartered in Calgary, Alberta, Canada


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