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Air Water Land: June 2011
Retrofitting compressor engines to reduce emissions

Cenovus Energy receives new funding from the Climate Change and Emissions Management Corporation

By Melanie Collison

One of the most significant players in the oilsands industry is also among Canada’s largest natural gas producers—and enhancing efficiency and reducing greenhouse gas (GHG) emissions is an investment for both plays.

While it continues a number of projects at its oilsands sites, Cenovus Energy Inc. is in the midst of pulling together a project team, finalizing the engineering details and scripting a schedule to begin a $10.7-million project to slash GHG emissions from its natural gas operations.

The result of the project—a retrofit of the aging natural gas–fired engines that power the compressors that fill its natural gas sales pipelines—will be equipment with the efficiency rating of a new fuel-injected engine. Cenovus is also going to install piping to capture fugitive emissions to use as fuel.

Taking some of the sting out of the expenditure, the company has garnered $3.6 million in funding—approximately one-third of the gross cost of the project—from the Climate Change and Emissions Management Corporation (CCEMC) in its second round of allocating funds generated by levies on industrial carbon emitters.

The engines and compressor emissions control project will upgrade natural gas compression facilities at 37 sites Cenovus operates in Alberta.

In approving the Cenovus application, CCEMC pegged the anticipated CO2-equivalent emissions reductions at about 19,980 tonnes per year, but Cenovus is actually forecasting reductions closer to 50,000 tonnes per year. That equates to a total of about half a million tonnes in reduced emissions, says Dave Hassan, the company’s team lead for environmental technology investments.

There are two parts to the retrofit, the systems for both of which are manufactured by REM Technology Inc., a subsidiary of Spartan Controls Inc.

REM stands for reciprocating equipment management. The company specializes in developing technology to optimize the fuel usage and reliability of reciprocating compressor engines used in upstream oil and gas.

The first piece of equipment for the Cenovus project is a computerized air/fuel ratio controller. This is bolted onto a natural gas–fired reciprocating engine that powers the compressors, which boost a low-pressure natural gas stream from the incoming 10-50 pounds per square inch to the 1,100 pounds per square inch required in a sales pipeline.

“A lot of these big industrial engines will run almost forever,” Hassan says. “They require continued maintenance and overhauls at some point, and you may need to replace the pistons and re-machine the heads and cylinders, but you rebuild them and put them back in service.”

Replacing an engine could cost around $700,000. An air/fuel ratio controller would come in at approximately $150,000 and is expected to make even aging engines function with as high a degree of energy efficiency as today’s fuel-injection engines.

“The air/fuel ratio controller lets the engine that drives the compressor run a little bit smarter,” Hassan says. “A lot of these machines are decades old. Compare it to a car engine, an old carburetor [model] versus a new fuel injector with a built-in computer. The [add-on] manages the fuel/air mixture to optimize the ratio according to the horsepower the compressor needs to put out. Depending on the age of the engine, you might see fuel savings of up to 10 per cent or more.”

The newer the engine, the less dramatic the improvement, so Hassan expects the average energy efficiency gain to be around five or six per cent.

The second technology Cenovus will employ is a system to capture fugitive natural gas that inevitably leaks out around the rings in a reciprocating engine.

“[The] vent gas capture equipment captures that escaping gas and redirects it back to be fuel for the engine,” Hassan says.

Cenovus expects to reduce fuel gas use by 10-25 per cent on a primary engine by combining the air/fuel ratio controllers and vent gas capture.

When they’re used together, the technologies provide the same level of engine speed control regardless of the volume and composition of the fugitive emissions available. These emissions can vary widely in composition and can include toxic benzene, toluene, ethylbenzene and xylene compounds that are normally vented.

Given that a typical 1,200 horsepower engine burns about $500,000 worth of fuel a year, payback time from capturing and burning the fugitive emissions can be very short.

To execute the project, Cenovus is drawing on funds Encana Corporation decided to begin setting aside for energy efficiency projects a couple of years before it split Cenovus off into a separate entity in 2009. CCEMC also gave Encana funding in this round—$2.4 million—for vent gas capture for engine fuel use.

Cenovus is happy with the performance of the REM air/fuel ratio controllers it has installed over the years, Hassan says, and is using technical reports from CETAC-WEST and Petroleum Technology Alliance Canada (PTAC) to inform its vent gas capture project, along with in-house technical expertise.

CETAC-WEST was established in 1994 by Environment Canada as a private sector not-for-profit organization with the purpose of helping small and medium-sized enterprises commercialize environmental technologies.

Along the way it has made an industry-changing specialty of fuel gas management, with the twofold purpose of saving fuel gas and reducing greenhouse gas emissions.

In developing a suite of best management practices to conserve fuel gas, CETAC-WEST determined that the industry’s fuel gas consumption currently equals 12 per cent of annual gas sales. CETAC-WEST was instrumental in generating industry interest in REM’s technology by sponsoring field demonstrations through its Unleashing Innovation program.

PTAC has participated in studies evaluating REM technology efficacy for nearly a decade. PTAC is a not-for-profit organization that facilitates collaborative research and technology development in the carbon energy industry.

Both of the REM technologies that Cenovus will use were designed for retrofitting compressor equipment in the field. It was a design priority to ensure the least possible downtime during installation to minimize clients’ production losses.

The vent gas capture piping, for example, can be installed while the engine is still in service, Hassan says. Still, even though a lot of the work can be done ahead of time, each engine is expected to be out of commission for two to five days.

“We’re trying to figure out how to plan our installations while we’re doing scheduled maintenance to minimize downtime and minimize production loss,” Hassan says. “That’s one of the big challenges, trying to schedule everything around our planned maintenance schedule. It will likely add a couple of days onto the planned maintenance because they can’t do everything in parallel.”

Hassan’s team will do the project planning and approvals, then pass the project to an implementation team.

“They will draw on project teams in the actual areas where the compressor is operating. We’ll also use external contractors and engineering houses.”

CCEMC has scheduled the announcement of its next round of funding recipients for June. It is now supporting 22 projects at all stages of innovation with a total planned investment of more than $98.2 million.

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