Looking Back: An Early Trial of Marine Scrubbers

Back in 2009, the 2015 Emission Control Areas established in IMO Annex VI seemed a long way off to many in the marine and emission control industry. Belco Technologies Corporation (BELCO), a DuPont company, anticipated the marine industry’s imminent need for reliable emission control solutions to meet the upcoming regulations. BELCO re-engineered its proven, land-based refinery wet scrubber technology for marine service. The company had over 40 years of experience removing sulfur oxides and particulates from various industrial processes.

In bringing its technology to the seas, the DuPont group needed a ship operator to test its prototype Exhaust Gas Cleaning System (EGCS). At the same time, Maersk, one of the largest shipping companies in the world, was also thinking ahead and looking to assess alternatives to expensive low sulfur fuels in order to meet the IMO requirements. In 2010, the two companies decided to partner to pilot the new DuPont EGCS technology. This article sets out what the two companies learned over the years of their collaboration and looks at how far marine scrubbers have come.

The objective of the pilot

IMO Annex VI allows shippers the option to consume low sulfur fuel or to use an abatement technology that allows for an equivalent amount of SOx emissions as a low-sulfur fuel. Seven years ago, the idea of an abatement device sounded dubious to many in the marine industry. Putting a shower over an engine seemed risky to operators for a number of reasons. What if the engine got flooded? How would the device fit? What about back pressure issues? How would the system affect the ship’s stability and weight limits? Would it be easy to operate or require additional crew? Questions like these needed to be answered, but many shipping companies did not have the resources or interest to investigate. One major exception was Maersk.

Maersk operates an innovative and efficient fleet that is large, diverse, and reaches every corner of the world. The company’s commitment to innovation meant it was open to piloting different technological solutions while most shipping operators preferred the simpler yet pricier option of operating on low sulfur fuels. With a drastic cap on SOx emissions looming for 2015, and a large fleet to fuel, Maersk wanted to evaluate the feasibility of retrofitting an exhaust gas cleaning system (EGCS) aboard one of its vessels to see if this would prove to be a sound commercial and operational solution.

It was important for Maersk to understand the complexity and challenge of installing, commissioning and running an EGCS on board one of its vessels. A ship moves between different climates and oceans at different speeds, so ‘marinizing’ a land-based stationary system that uses ambient seawater as its scrubber liquor presented design challenges. It was also important to expose Maersk crews to the EGCS to familiarize them with operating the system. When BELCO offered to design and test one of its marine scrubbers on a Maersk vessel, Maersk agreed to the pilot. In 2013, Maersk retro-fitted a hybrid scrubber in Qingdao, China to a 3.2 megawatt auxiliary engine aboard the Maersk Tukang, a 8,200 TEU container ship. The exhaust gas cleaning system replaced the auxiliary engine silencer.

Lessons learned from the pilot

The pilot taught both parties a good deal about marine scrubbers. Maersk realized that EGCS retrofits require aggressive installation strategies, excellent project management, and close collaboration with the classification society – in this case, ABS. Considerable modifications have to be made to an existing vessel in a relatively short dry dock period. Business cases are not always easy to validate. However, what started as an innovation project for Maersk in 2010 demonstrated a viable technology to bring down SOx emissions to meet the IMO requirements that entered into force in January 2015.

DuPont was always confident of its ability to meet sulfur emission targets on the exhaust gas side. However, for marine service, wash-water discharge quality was just as important in order to meet the IMO limits of PAH, pH, and turbidity. The pilot allowed the company to test wash-water samples and improve its wash-water treatment strategy and overall design. Many of these learnings have been applied to DuPont Marine Scrubbers currently in service in USA and European waters. DuPont now has two different wash-water treatment technologies available for closed loop operations, and the ability to offer open loop wash-water treatment if required. Working on the Maersk ship taught the group a lot about how to customize systems based on the needs of the owner/operator.

The Maersk pilot also helped DuPont to optimize the wash-water spray nozzles in the scrubber tower. This resulted in two important design improvements: energy savings and lower back-pressure on the engine. By testing different types of nozzles DuPont was able to reduce the amount of water required for effective sulfur removal and thus cut pumping power. Additionally, an optimized spray pattern lowered the pressure drop through the tower to less than 100 mmwc. The pilot with Maersk further proved the “Run Dry” concept pioneered by BELCO. For some of the pilot period, the Tukang sailed outside of an emission control area where the system was not run. This actually allowed DuPont to validate that prolonged exposure to hot, sooty exhaust did not affect the DuPont™ Marine Scrubber tower structure nor the system’s ability to perform when it was brought back in service, proving that the scrubber did not require a bypass.

Which solution, or combination of solutions Maersk will go for to meet the SOx emissions caps is yet to be determined, but the conclusion the shipping company came to was that scrubbers seem to be a workable and functional solution for certain vessels. Both companies consider the pilot a success.

The industry as a whole has come a long way in its attitude toward scrubbers since 2009. With over 300 contracted on ships, marine scrubbers are now an accepted, proven, safe, and ecologically sound abatement option. Given the IMO ruling that a global fuel sulfur content cap of 0.5 percent will take effect in 2020, it is expected that many shipping company’s will elect to install scrubbers, and will greatly benefit from the pioneering work performed by Maersk and DuPont.

Tim Reeve is a senior project manager with Maersk Maritime Technology. Melanie Davidson is the sales director for DuPont Marine Scrubbers, DuPont Clean Technologies.

The DuPont Clean Technologies division applies real-world experience, history of innovation, problem-solving success, and strong brands to help organizations operate safely and with the highest level of performance, reliability, energy efficiency and environmental integrity. Learn more at www.cleantechnologies.dupont.com.