Sweden: Alfa Laval Offers Economical Alternative for LNG Carriers
With rising fuel costs, environmental regulations and the continuing shortage of qualified seagoing engineers to operate marine steam turbines, diesel propulsion continues to gain ground as a sound economical alternative to traditional steam propulsion for liquefied natural gas (LNG) carriers.
Alfa Laval’s recent acquisition of gas combustion technology provides owners of LNG carriers using dual-fuel diesel electric (DFDE) engines or low-speed diesel (LSD) engines with a compact gas combustion unit (GCU) that has lower installation costs and operating expenditures than comparable units. Moreover, the Alfa Laval GCU comes backed by the company’s global sales and service network.
The growing global demand for LNG has increased the demand for new LNG carriers. While LNG carriers have recently been touted as the global shipping industry’s most profitable sector, LNG shipping companies continue to look for ways to lower costs as a measure to ensure long-term profitability. While steam propulsion has been the mainstay on LNG carriers for decades, rising fuel costs, environmental regulations and the continuing shortage of qualified seagoing engineers are forcing LNG ship owners to re-evaluate critical systems onboard.
As more countries look to LNG for power generation and production needs, LNG shipping companies must determine how best to build new LNG carriers or retrofit existing vessels to ensure long-term profitability. The selection of DFDE or LSD engines as economical green alternatives to the traditional steam propulsion systems onboard is one example of fuel-saving and environmental conservation efforts undertaken by LNG ship owners. This use of these engines provides additional means with which to regulate LNG cargo tank pressure. In some cases, this is accomplished by re-liquefaction but, in most cases, gas combustion units have been introduced to burn excess boil-off gas safely.
According to industry estimates, approximately 85% of all LNG carriers using either two- or four-stroke dual fuel engines today have some type of combustion chamber to regulate the pressure in the cargo tanks by burning excess boil-off gas from the cargo tanks under safe and controlled conditions. With its recent acquisition of gas combustion technology from Snecma, part of the Safran Group, Alfa Laval is well positioned to meet the future needs of LNG carriers. The Alfa Laval GCU offers LNG ship owners a smart way to lower total cost of ownership further.
“The Alfa Laval GCU is not, by any means, new technology,” admits René Fich Jespersen, Alfa Laval’s General Manager, New Boiler & Global Sales Support, Marine & Diesel Division. “The big news here is that LNG ship owners can rely on Alfa Laval as a well-known partner who is focusing on providing what is essential for the marine industry to succeed in this competitive business environment and who has the infrastructure in place to ensure the delivery of the service and support required.”
By extending the company’s portfolio of products and solutions for the marine industry with the Alfa Laval GCU, Alfa Laval now offers a comprehensive LNG carrier product range, which includes Aalborg marine boiler systems with dual-fuel burners, waste heat recovery systems, inert gas generators and heat exchangers.
Simple, streamlined design for 100% natural BOG disposal
Why consider the Alfa Laval GCU over comparable gas combustion units? Jespersen says that the unit has the simplest design overall with fewer parts than comparable systems, straightforward operation, compact design, no pilot fuel and the smallest footprint in the business, all of which translates into cost-effective installation and operation.
“Only the burner, combustion chamber and monitoring sensors are in the stack of the Alfa Laval GCU,” says Jespersen. “The design philosophy behind the Alfa Laval GCU essentially shares the same approach as that of our heat exchangers, separators and other equipment and solutions; in other words, we always put great effort into making designs simpler, more reliable, more economical and more efficient.”
Available in four standard sizes, Alfa Laval GCU handles capacities of 3, 4.5, 6 and 9 t/h methane using either single or dual combustion chambers. In addition, the Alfa GCU is approved by major classification societies, including American Bureau of Shipping, Bureau Veritas, Det Norske Veritas and Lloyd’s Register.
According to Jespersen, the Alfa Laval GCU provides the LNG industry with the lowest possible operating expenditures for gas combustion technology. When asked how this is possible, he points to these facts: No oil is needed for ignition of the flame; the reduced parts count and smaller footprint; and, no perforated dome, refractory lining or expansion joints required.
“The beauty of the Alfa Laval GCU is that it is by far a simpler and more reliable system than the other gas combustion units out there,” says Jespersen. “It is easier for shipyards to install, allowing great flexibility to arrange the unit in the vessel, and it’s easier for the crew to operate and maintain as well.”
Fewer parts translate into reduced installation and maintenance costs. Unlike other gas combustion units, the Alfa Laval gas combustion unit has low-noise fans that serve a dual purpose – both as combustion air fans as well as dilution air fans for exhaust gas. This effectively does away with the need for separate combustion air fans and dilution air fans along with the associated ductwork, cabling and silencers.
Operating costs are reduced because the Alfa Laval GCU uses an electrical ignition device that enables fast start-up. This eliminates the requirement for a marine diesel oil (MDO) or distillate marine fuel (DMA) system with the requisite tank, pilot and oil lines. The self-purging burner is another example of smart design that reduces maintenance costs because it has no rotating parts. It also promotes safety due to its ability to handle combustion under conditions with high excess air and/or high inert gas content.
Without the additional fans and oil system required for other GCUs, the overall space requirement of the all-stainless-steel combustion chamber for the Alfa Laval GCU is much smaller than that required for other GCUs.
All this good news begs the question: Why then aren’t all LNG ship owners with DFDE or LSD engines installing Alfa Laval GCUs onboard? Jespersen is candid in his assessment.
“We often see that new technology has a very slow adoption rate in our industry, which makes sense because safety is the number one concern. However, new technology should not be confused with ‘unsafe’,” Jespersen states. “Using electronic ignitors on gas burners is often questioned, but Alfa Laval has been using these on our traditional gas burners for years – and these have a proven safety record. We see the same holding true for combustion and the GCU.”
“Despite using a principle which differs from the traditional burners used on our boilers, for instance, the flame is maintained across variable loads,” he adds. “Ship owners sometimes forget that the objective of the combustion on a GCU differs from that of a boiler.”
“The Alfa Laval GCU is a beautiful product as it is,” remarks Jespersen. “It is high on reliability, simplicity and safety, yet low on installation, operation and maintenance costs,” he adds.
Alfa Laval, March 22, 2013