For more than 200 years, slurry pipelines that use water as a slurry agent have been employed to transport pulverised coal and ore in conventional mining operations. And, for over 30 years, they have been used to transport the sand left over from bitumen extraction at oil sands sites. Now, slurry pipelines have been given a new twist. In November 2008, Enbridge launched its CO2 Slurry Pipeline Project to construct a slurry pipeline that uses CO2 to transport several types of pulverised solids.

The project will compress captured CO2 from industrial emitters into a liquid, then pump it through a pipeline to efficiently transport sulphur, petroleum coke and limestone from the Fort McMurray area to local and international markets. Sulphur markets are mostly concentrated in Asia Pacific countries; petroleum coke markets are mostly concentrated around the US Gulf Coast; and, limestone markets are concentrated in western Canada.

After having served its purpose as a slurry agent, the CO2 would then be used in enhanced oil recovery operations, after which it would be stored underground in a manner similar to carbon capture and storage projects.

Enbridge Vice President of Alternative and Emerging Technology Chuck Szmurlo says “By providing additional useful work for CO2, companies – such as oil sands producers– can offset some of the costs associated with capturing and storing it. They can also create new markets for products – such as sulphur, petroleum coke and limestone – that are in demand throughout the world, but that have been stranded from their markets due to a lack of suitable transportation infrastructure.”

Transported slurry via CO2

Slurry pipelines use flowing liquid – traditionally water – to carry entrained solids through the pipeline. CO2 at pressure in a pipeline flows as a liquid.

Pipelines using water are mostly used for transporting mineral ores, however, many water slurry pipelines have been discontinued due to the large amounts of water they require, and to the costs of cleaning and recycling the water.

According to Mr Szmurlo, CO2 is a more efficient carrier fluid than water because it is less abrasive than water, and lengthens the lifespan of a pipeline. CO2 can also carry a greater volume of material than water, and it is cheaper to ‘de-slurry’ the contents of the pipeline because the solids are delivered dry rather than wet.

Project development

The CO2 Slurry Pipeline Project will be completed in three phases. Enbridge has commenced Phase 1 of the project, called the CO2 Slurry Pipeline Research Initiative. This phase will involve demonstrating proof of the concept, as well as demonstrating the technical viability of a long distance CO2 slurry pipeline for transporting petroleum coke, sulphur and limestone. Phase 2 will involve actually building the pipeline, and Phase 3 will involve running the pipeline as a commercial operation.

Jointly funded by the Government of Alberta and the CO2 Slurry Pipeline Project team, the $US2 million Phase 1 of the project is expected to be completed in the first quarter of 2011. This phase will determine the specifics of the pipeline, including length, diameter and steel grade.

“At this point we are assuming that the pipeline will be constructed of similar materials to other pipelines, such as carbon steel,” says Mr Szmurlo.

He says that engineering challenges will involve determining the best size of the pellets of the material to be transported for optimal flow through the pipeline. Project members must also determine how best to combine the materials to be transported, and must gain a thorough understanding of the slurrying and de-slurry process.

During Phase 1, the project partners also hope to understand:

  • The method and equipment needed to create a CO2 slurry for pipeline;
  • The method and equipment needed to de-slurry solids to contain and maintain CO2 pressure; and,
  • How to deliver CO2 and solid products that meet customers’ specifications.

Phase 1 will also determine the specifics of construction and commissioning of the pipeline. Enbridge plans to employ fail-safe valves and system control, and data acquisition technology. Assuming that the results of Phase 1 find the project feasible and that funding can be secured, Enbridge expects that construction of a pilot facility could begin as early as 2011. Full commercial operations could commence by 2015.