Choosing the Right BWTS for an LNG Carrier

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A ballast water treatment system needs to be able to consistently match the loading rate of an LNG carrier. Although, LNG operators have many options when it comes to ballast water treatment systems, but priority is the engineering requirements of fitment and maintenance, says an article published in LNG World Shipping.

LNG Carrier Owners’ Advantage

The owners and operators of large LNG carriers (LNGC) have certain advantages over other shipping sectors when it comes to the fitment of ballast water treatment systems (BWTS).

Smaller vessels have limited room among their machinery spaces and thus may need to use a modular BWTS; this is not necessarily a negative, but it does demand more planning. And while BWTS have various power requirements, some LNGCs have a source of relatively cheap energy from the boil-off gas.

Training the crew?

Another important consideration for non LNGCs is the training and safety culture required for the crew. It is a step change for a bulk carrier crew to go from the culture required to operate a large but relatively benign vessel to the more complex chemical analysis required with some BWTS.

On a sophisticated ship like a chemical carrier or LNGC, the training and operation demands required of a crew are already of a higher level, and the operation of a BWTS is less daunting.

Refits Unlikely?

LNG carriers also tend to be younger and are less likely to have undergone refits and alterations in their short lives. The vessel will be closer to the original spec, but even series-built sister ships will have significant differences in the machinery spaces, which is where the planning of the BWTS requires careful thought.

Issues Can Be Dealt?

Marine engineering firm 21 Knots has undertaken the planning, engineering and retrofit of several types of BWTS and founder and chief executive Nitesh Ranvah notes that the same issues occur.

“In some LNG vessel designs there are constraints on available space for the integration of piping and treatment units, but with proper planning and selection of the right BWMS, these issues can be overcome”

Engineering Combined With Power Requirements

“What we are seeing is a bottleneck…the supply of engineering support is becoming tight and there is a shortage of experienced personnel in the yards,” he says. “The crucial point is that engineering has to come first and has to be combined with power requirements.”

What LNG operators should do?

Nitesh Ranvah (21 Knots): Operators need to consider the engineering first before the make of ballast water treatment system

Mr Ranvah notes that owners tend to spend months visiting trade shows, talking to manufacturers and negotiating price. In his opinion, deciding the make and model should be a low priority compared to scanning the available space and sourcing the engineering. Otherwise millions of dollars of income could be lost through time wasted fitting a compromised system.

USCG approval the key?

A key concern for any choice of BWTS on a large LNGC is the potential to trade into US waters. Few predicted the rate at which US LNG exports would grow; at an output of 8.9Bn ft3 by the end of 2019, up from a predicted 4.9Bn ft3 in 2018 (according to the US Energy Information Administration), the export capacity of the US will soon be the third-largest in the world, behind only Australia and Qatar.

As a consequence, four additional export terminals have received all necessary approvals from the Federal Regulatory Commission and the Department of Energy, amounting to a combined additional LNG export capacity of 7.6Bn ft3.

Deballast in US Waters Requirement

Under current and future US LNG export scenarios, being able to de-ballast in US waters is a requirement, which means choosing a US Coast Guard (USCG) type-approved system.

Similarly, the de-ballasting must be able to take place in a manner that does not interfere with the cargo loading procedure.

How Ecochlor helped in DeBallasting?

US company, Ecochlor was one of the first companies to receive USCG type-approval for its filtration and treatment with the ClO2 BWTS.

Ecochlor’s newly appointed vice president of business development Andrew Marshall outlines the specific demands of the LNGCs when it came to ballast water treatment.

LNGCs Challenges

“The challenges facing LNGCs are similar to those of any vessel with a high ballast pumping rate. Specifically, finding a ballast water management systems (BWMS) that has the ability to reliably meet those high rates over an extended ballasting period,” he says.

“In some LNG vessel designs there are constraints on available space for the integration of piping and treatment units, but with proper planning and selection of the right BWMS, these issues can be overcome.”

Designing Space for BWTS

The design of a newbuilding would naturally take into consideration the space required for modern compliance equipment, from BWTS to exhaust gas scrubbers, but space can be a premium when retrofitting a BWTS.

Mr Marshall notes that a modular system could have a smaller footprint. “A compact, modular system with minimal footprint provides several options for placement on the vessel,” he says.

Ecochlor Designing 

The Ecochlor system starts with precursor tanks that have a footprint of 12.7 m2 and treatment systems with a footprint from 0.3 m2 upward.

The pumping rate is another factor when assessing a BWTS for a large LNGC: “The maximum flow rate capacity of an Ecochlor BWMS is up to 16,200 m3 per hour with an option for up to three ClO2 injection points,” says Mr Marshall. For a 150,000 m3 LNGC, Mr Marshall says only one BWMS system is needed for the entire vessel.

LNG type approved BWTS Fit

Elsewhere, Erma First of Greece secured a fleet-wide agreement from Norway’s Golar LNG in December 2017 to supply its USCG type-approved BWTS Fit system. Erma First uses filtration, electrolysis and electro-chlorination as its treatment method and the company said in a statement that its equipment would be installed “on up to 16 LNG vessels”, which potentially covers the whole Golar fleet.

Alfa Laval’s USCG type-approved UV-based BWTS was specified by Nakilat, the Qatari shipping and maritime company with the world’s largest LNG fleet. Two of Alfa Laval’s PureBallast 3.1 systems of 2,000 m3/h will be retrofitted. PureBallast 3.1 was selected, stated Alfa Laval head of PureBallast Anders Lindmark, for its small footprint, simple installation and ease of use.

Innovative solutions

Large vessels with high cargo loading rates, and therefore large volumes of ballast water being taken on-board, have another option: not to treat the ballast water as it enters the tanks. This is the approach offered by Coldharbour Marine and Environcleanse, among others. Environcleanse’s inTank model is an electrolysis and chemical injection BWTS.

The Environcleanse treatment methodology is relatively simple: all port-based ballasting and de-ballasting activities are completed as normal. There is no filtration, no increase in power demand and no concern of ballast water quality.

How does it operate during voyage?

During the voyage, an electro-chlorination cell uses clean seawater to create sodium hypochlorite. At the same time, ballast water is circulated and the newly-created disinfectant is injected into the circulation loop. The mixture is then returned to the ballast tank through the in-tank mixing nozzles which diffuse the biocide in the tank. The levels of biocide are monitored and confirm the lack of new growth during the voyage.

USCG Type Approval Required?

It is not a requirement for BWTS to have USCG type-approval for global operation, but it has become a de facto standard by which many systems are judged. LNG World Shipping’s sister publication Ballast Water Treatment Technology maintains a database which contains 112 announced and/or fully developed BWTS. Of these, 17 have been type-approved by the USCG and a further 12 are under review pending type-approval. In some cases, BWTS have already been approved in original form, but variations, such as the fitment of a different filter system or a request to change the power setting of UV lamps, triggers another review.

Alternative BWTS

“Large vessels with high cargo loading rates, and therefore large volumes of ballast water being taken on-board, have another option: not to treat the ballast water as it enters the tanks”

There are several alternative BWTS available to LNGC owners. The LNG bunker supply vessel Kairos is owned by Babcock Schulte Energy (BSE), a joint venture between Babcock International Group and Bernhard Schulte Shipmanagement, and was developed using Babcock’s Fuel Gas Supply Vessel Zero technology, which eliminates the release of boil-off and flash gas to the atmosphere during normal operations.

Some Bold Designs

Nauticor, a provider of LNG for maritime customers, is chartering Kairos to serve marine clients in the North Sea & Baltic Sea, the Klaipėda LNG fuelling station in Lithuania and the Linde LNG terminal in Nynäshamn.

The designers have taken the bold step of not incorporating a BWTS by moving the accommodation forward to overcome LNG bunker vessel design constraints relating to line-of-sight from the wheelhouse. That also had the benefit of longitudinally balancing the ship, reducing the need to transfer ballast.

Coupled with the low-density LNG cargo, this design removed the need for sea water ballast and associated treatment systems. Only a limited volume of permanent fresh water ballast is used for trim purposes.

As the number of vessels using LNG as a marine fuel increases, this design could become the template for a new generation of bunker vessels. LNG PRO Bunkers’ chief executive, Alexander Prokopakis told LNG World Shipping that the company is examining its options, with 20 designs on the table, of which three are ballast-free.

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Source: LNG World Shipping

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