Managing Fouling of Heat Exchangers
In 2014, the COSIA Water Environmental Priority Area was in search of non-fouling or cleanable in situ heat exchanger technology as a way to improve environmental performance of the oil sands. Through sharing their combined knowledge and best practices, procedures and new technologies, COSIA members have significantly advanced improvements to address the issue of fouling.
Water Director Update
Director, Water EPA
In 2014, the Water Environmental Priority Area (EPA) identified fouling-resistant heat exchangers at oil sands in situ facilities as one of six COSIA Water Challenges, which are focused descriptions of specific oil sands issues that COSIA uses to engage with experts and innovators around the globe who may be working on possible solutions. In situ facilities use steam assisted gravity drainage (SAGD) to produce bitumen from an oil sands reservoir. The water used needs to be heated to generate the steam to inject into the oil sands reservoir and then cooled in order to separate the bitumen and treat the water for reuse. The process, which uses heat exchangers, causes mineral and other contaminants to build up inside the equipment. The Water EPA set out to find ways for the exchangers to withstand this fouling.
“The exchangers required servicing as often as every two weeks,” explains Wayne Hillier, director of the Water EPA. “The damage to the equipment increased greenhouse gas emissions and water usage. It also increased maintenance costs.”
Water EPA members with in situ facilities have examined and addressed the issue from many angles. The companies—BP, Canadian Natural, Cenovus, ConocoPhillips Canada, Devon, Imperial Oil, Nexen, Shell Canada, Statoil and Suncor Energy—collaborated as part of the In Situ Water Best Practices Working Group and shared the best practices they used in their own facilities, as well as new procedures and technologies, to come up with a number of solutions for treating fouling.
One solution, in particular, uses a coating on the interior tubing of the heat exchanger to deflect scale from building up. By applying this product, maintenance has been extended by as much as three years, and puts the heat exchangers on the same schedule as regular plant maintenance. Other operators employ the “brush and basket” technique, which cleans the heat exchanger system while it is still online, eliminating the need for it to be shutdown. A similar technology uses balls pushed through the tubing to clean it. As a result of sharing knowledge and technologies, the EPA was able to find solutions to its heat-resistant fouling Water Challenge, inside its own network.
“While fouling of heat exchangers has not been solved completely, we have recognized substantial improvements” says Wayne. “It’s a success story for these member companies that have worked together, sharing technologies and best practices to manage the issue to such great results. Electing to withdraw the Challenge means that we can focus on other issues with external experts, including one for high temperature membranes, which could eliminate the need for these sorts of heat exchangers completely.”
The Water EPA is already investigating the potential for high temperature membranes through a number of projects, including a Natural Sciences and Engineering Research Council of Canada (NSERC) Collaborative Research & Development Chair at the University of Alberta. Stay tuned for more on these efforts in a future edition of Collaborator. For further reading see the Water EPA’s Challenge for High Temperature Membranes.