Technical: Scrubber Tests

The emission control technology selected=While Holland America Line continues to test its scrubber system, Royal Caribbean Cruises has also launched a test program. The emission control technology selected for testing on the Independence of the Seas is new, with Royal Caribbean partnering with Ecospec to install the CSNOx system.

The system uses patented Ultra Low Frequency Electrolysis System (ULFELS) to treat the seawater being used as scrubber washwater with an anti-fouling system to eliminate marine organisms to reduce fouling of piping and pumps.

The water used for Stage 1 SOx removal passes through the SO2  absorption enhancer unit and is then sprayed in the abator tower’s lower section as the engine exhaust gas rises upward. The scrubbing process removes the SO2.

In Stage 2 of the process for CO2 and NOx removal, the water is conditioned in the pH exciter system PHX that improves the water’s absorption capability and is sent to the ULFELS treatment tank where the physical structure of the water is modified and the pH is raised to between 9.2 and 9.5. The ULFELS treated water is then pumped through the mineral scale control unit followed by the CO2 – NOx reducer unit and the then directed into the abator tower’s upper section where water sprays remove the CO2 and the NOx from the rising exhaust gas. The washwater then passes into the treatment system controlling the water quality and returns it to a pH of at least 6.5 in the discharge mixing tank before the washwater is discharged into the sea. The treated clean emission gas is discharged into the air.

Holland America Update

Holland America Line’s in-service testing of the Hamworthy-Krystallon SOx seawater scrubber aboard the Zaandam is continuing after modifications. The test program has been based on “technology that uses the natural chemistry of seawater to neutralize the acidic emissions and capture the particulates emitted from large combustion engines” and if “it could be successfully designed, installed and operated within the tight confines of an existing Holland America cruise ship,” according to a company America report.

Since 2006, a Krystallon seawater scrubber has been connected to the exhaust system of one of the Zaandam’s five Sulzer Wartsila ZA 40S 12 diesel engines. According to Tina Stotz, with the cruise line’s sustainability and ISO management systems, there was “one verifiable test for SOx and PM while the scrubber was 66 percent operational, but we got about 75 percent of the SOx and 57 percent of the PM. Other tests, with all sections of the scrubber operational, proved removal over 98 per cent of the SOx.”

The Hamworthy-Krystallon system and other SOx control systems use various technologies, some of which are considered to be proprietary, either individually or in combinations. Andrew Scaplehorn, head of operations with Hamworthy Krystallon, explained that the company’s SOx removal technology requires that “engine exhaust streams be cooled down to about 60 degrees C and the seawater then must be mixed with the exhaust gas on a molecular level to achieve reduction of SOx from 500 ppm at the entry level to 20 ppm at discharge.”

The pH level of the discharged washwater is also strictly regulated and must be 6.5 ph within four meters of the ship. “We add clean seawater as necessary to the washwater just before discharge and the pH level recovery is very quick.” The total volume of washwater discharged after treating the single engine’s exhaust is about 800 cubic meters an hour.

During July 2010, a number of modifications were made to the Krystallon scrubber for the next series of tests that began in September. A new approved monitor was installed on the scrubber to provide continuous monitoring of SOx levels in the exhaust gas. “We will use that for our results in addition to independent testing,” said Scaplehorn.

As the next phase of testing and development is underway, Michael Inman, director system management and program development at Holland America stated, “This initiative is demonstrative that Holland America Line has been very committed to addressing the many vessel emission challenges.”

Excerpt from Cruise Industry News Quarterly Magazine: Fall 2010  

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