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BOILER TECHNOLOGY OFFERS PATH TO LNG PROPULSION

Tuesday, October 22, 2019 

Alfa Laval says it is playing a key role in the move towards LNG propulsion, particularly in area of boilers for dealing with boil-off gas (BOG), which the company says is a critical step in making the shift to LNG.

Alfa Laval’s dual-fuel boilers, Gas Combustion Unit (GCU) and services form a complete portfolio of solutions for BOG safety.

“Customers are attracted to LNG propulsion for a variety of reasons, and it’s being considered for many vessel types besides LNG carriers,” said Markus Tauriainen, Manager Exhaust & Combustion System Sales, Alfa Laval.

In order to use LNG as fuel, vessels must be able to manage boil-off gas (BOG), the evaporated gas that can increase tank pressure. The pressure created by BOG in an LNG fuel tank must be kept at a level that avoids ventilation to atmosphere via the safety valve. Reliquefaction of the gas is possible, but doing this on board adds too much complexity and cost for most vessels. Likewise, burning the gas in auxiliary engines or gensets requires pressurisation, which demands a redundant expensive compression train.

“On some vessels you can use a Type C tank to allow pressure to accumulate,” said Tauriainen. “But what most vessels need is a safe solution for burning off the gas at low pressure. That can be a GCU on LNG carriers, but the best and most economical solution for vessels using LNG as fuel is usually a dual-fuel boiler.”

As boilers are needed onboard anyway, an Aalborg dual-fuel boiler that can be fired with LNG can take on the additional safety function of BOG management. Aalborg boilers, like the GCU, have another advantage - when a vessel enters dry dock for inspection, the tank environment must be made non-hazardous by replacing the LNG with inert gas. During this process, Aalborg dual-fuel boilers are capable of burning the mixture of inert gas and LNG.

“Our Aalborg dual-fuel solutions are designed with boil-off gas in mind and are influenced by our experience with the GCU,” said Tauriainen. “The boiler uses LNG efficiently for heating, but by managing the boil-off gas and making LNG propulsion possible, it also enables far greater savings. GCU or boiler, steam or thermal fluid – we have a solution to make LNG propulsion happen, on any size or type of vessel.”

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