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Working principle

During fired operation, heat from fuel combustion is transferred

to the furnace shell, mainly through radiation. Flue gases leaving

the furnace enter vertical uptakes where the heat is transferred

to helix tubes, mainly through convection.  If the boiler is config

ured as a hybrid, the electric heater provides an alternative

heat source.

Heat transferred through the furnace shell or the helix tube walls

evaporates the adjacent saturated water on the boiler’s water

side. This causes steam bubbles to form. Because the steam

bubbles have a much lower specific density than the water, they

rise rapidly into the steam space, where the water and steam

are separated.

Maintenance

The Aalborg OS-TCi is effectively self-cleaning thanks to its

TCi (Turbo Clean, intelligent) technology, which keeps the boiler

running efficiently and prolongs its service life. The TCI cleaning

process is fully automatic.

Electric hybrid capability (option)

Besides serving as a fired boiler, the Aalborg OS-TCi can be

configured as a hybrid boiler, allowing it to operate on electrici

ty. This lets it utilize shore power or surplus electricity on board,

producing steam or hot water without direct emissions. It also

enhances the boiler’s turn-down ratio, which improves startup

time and reduces maintenance by enabling continuous

operation at lower loads.

The optional electric heater comprises one or two heating

elements, each 600 kW in capacity. To incorporate it, the

boiler interior must be modified. This has no impact on the

boiler’s high efficiency, but it may require small adjustments

in height or diameter.

Design

Compact and easy to install, the Aalborg OS-TCi operates

on oils and biofuels and can also be configured for one alternative

fuel: LNG, methanol or ammonia.* It is delivered with a preassem

bled Aalborg burner built on Alfa Laval’s innovative MultiFlame

(MF) concept. The boiler and burner are both engineered and

produced in-house to ensure the highest reliability.

• Aalborg OS-TCi boiler:

The Aalborg OS-TCi is a side-fired, two-drum boiler with a

combustion section comprised of helix tubes. This tube design

provides more heat transfer area than competing solutions,

which results in fuel-saving efficiency. A baffle plate in the

steam space forces the steam to pass through the tube

bundle twice, ensuring that the steam is absolutely dry.

Combustion heat from the burner is distributed uniformly

through the boiler’s combustion section. This ensures

optimal heat transfer and reduces damaging thermal

stress inside the boiler.

• Aalborg MF PA burner:

The Aalborg MF PA is a side-fired, pressure-atomizing

burner that supports conventional fuels and gas fuels like

LNG. By pre-mixing air and gas, it reduces the production

of CO2. NOx and other emissions.

• Aalborg MF SAS burner:

The Aalborg MF SAS is a side-fired, steam/air-atomizing

burner that supports conventional fuels and methanol.

Application

The Aalborg OS-TCi is a flexible marine boiler that can support

vessel operations in multiple ways:

• Steam generation:

The Aalborg OS-TCi is primarily used to provide steam for:

– Tank cleaning– HVAC– Engine room consumers

• Shared steam drum:

The Aalborg OS-TCi can support one or more exhaust gas

economizers, serving as a shared steam drum for waste

heat recovery.

• LNG safety:

On vessels using LNG as fuel, the Aalborg OS-TCi can:

– Support boil-off gas (BOG) management by safely

combusting BOG that cannot be consumed by an

auxiliary engine or genset– Combust a free flow from the LNG

tank if the vessel’s compression train should fail

– Combust the mix of inert gas and methane that arises

before and after tank inspection, eliminating detours for gas disposal

Aalborg OS-TCi

Self-cleaning fired boiler with multi-fuel and hybrid options

Intended for auxiliary use, the Alfa Laval Aalborg OS-TCi

is a fired marine boiler for producing steam. Designed with

helix tubes that provide a larger heat transfer area than

conventional solutions, it offers fuel-saving efficiency.

Ready for the fuel transition, the OS-TCi can use oils, biofuels

and one alternative fuel of your choice. Additionally, it can

be configured as an electric hybrid. These options can be

implemented directly, or the boiler can be prepared for their

installation later.

Benefits

• Configuration for your choice of alternative fuels

– implemented now or later

• Hybrid and hybrid-ready options for electric operation

• Energy efficiency maintained through self-cleaning TCi

(Turbo Clean, intelligent) technology

• Trouble-free uptime, secured through robust design

and user-friendly control

High efficiency, reduced fuel consumption and

less emissions

The upgraded thermal design with optimized flue gas

oxygen content ensures a total efficiency of 89–92%

depending on boiler load conditions, which is in aver

age 6% above the typical boilers in this capacity range.

This means less fuel consumption and lower CO2

and NOx emission levels. On a 16.000 kg/h boiler operating

5.000 hours at 75% load every year, this means USD

170.000*) saved on fuel cost annually.

*) at the fuel price of 650 USD/ton

Features & benefits

• High thermal efficiency range 89 – 92% with low fuel

consumption as a standard concept

• Thermal efficiency can be further improved up to 93 –

96 % (LHV) by adding external economizer

• The standard boiler can be fired with gas and various

fuels, like methanol and biofuels.

• Option for electrical steam generation with shore-pow

er and clean electricity

• Proven design, ready to install and easy to operate

and clean

System solutions

Alfa Laval offers total solutions. All marine accessories

for heat recovery and auxiliary boiler systems can be

supplied by Alfa Laval. Aalborg OM-TCi can operate as a

steam drum for the exhaust gas economizers onboard.

Design data

• Thermal output: up to 14 MW

• Steam capacity: 8.000 – 20.000 kg/h

• Design pressure: 10 bar(g)

Burner & Control system

The boiler will be delivered with a multi fuel-burner,

which is designed to automatically modulate according

to the system’s heat demand. The burner is designed

for a high turndown ratio with complete combustion

at low oxygen levels. To ensure optimal combustion,

pressurized air or steam is used as an atomizing media.

The burner adjusts automatically, but the operator can

switch to manual control if needed. The burner system

allows the use of various alternative fuels, as well as the

combustion of boil-off gas from gaseous fuels (GCU

functionality, gas combustion unit).

The burner and the boiler are controlled by a

specifically designed and standardized control system,

which is included in the delivery. This system consists

of all the required components for the heat recovery

system according to Alfa Laval standards, including

the main control with HMI-panel located in each

engine room. The control system enables connectivity

and intelligent data collection, and it has the capacity

for remote support. In systems with two engine

rooms, each has its own control system, but they

communicate and work seamlessly together, enabling

flexible operating modes.

Steam boiler for gas and various fuels, including

methanol and biofuels

Aalborg OM-TCi sets the new standard for fuel economy

in marine boilers. High efficiency means less fuel

consumption, thereby lower operating cost for the ship

owner and reduced emissions to our environment.

Aalborg OM-TCi is a vertical boiler with a large furnace

and an enhanced convection part. The standard boiler

can be fired with gas and various fuels, including

biofuels, methanol, and other alternative fuels.

The capacity range of Aalborg OM-TCi is 8.000–20.000

kg/h. It has been developed based on our well-proven

technology and long experience

Furnace

Aalborg OM-TCi consists of a large furnace with gas

tight membrane walls. A sufficient number of down

comers ensures safe natural circulation, and adequate

furnace dimensioning guarantees good combustion

and low emission, moderate loading and low material

stresses.

Convection part

A cylindrical shell surrounds the smoke tubes and the

water/steam space. These smoke tubes have enhanced

heat transfer features guaranteeing low exhaust gas

temperature and thus high efficiency.

A pioneering project to support decarbonization

The Alfa Laval Aalborg methanol-fired boiler was developed to

support fuel transition with a future-proof design. Unlike typical

newbuild projects, integrating the first methanol boiler required

navigating new class regulations, ensuring seamless integration

with the ship’s design, and managing tight timelines. Alfa Laval’s

experience in alternative fuel systems, particularly its pioneering

work with steam boilers for LNG, was instrumental in ensuring a

smooth and successful commissioning process.

Driving project success through collaboration and planning

This first-of-its-kind initiative required a high level of planning,

technical expertise, and collaboration among stakeholders to

ensure seamless integration of equipment and functionality. The

close cooperation between the shipyard, Alfa Laval service and

R&D team created valuable learning opportunities throughout

the process.

Given the shipyard’s demanding timeline, the commissioning

process required systematic execution and alignment with the

shipyard’s progress. Alfa Laval ensured on-time delivery of

engineering and equipment, completing the final inspection

ahead of the deadline.

“Alfa Laval’s strong coordination within the internal project team

and with the shipyard was key to the project’s timely completion.

Pre-installation preparations, including training, laid the foun

dation for a smooth installation process. During commissioning,

the collaboration between Alfa Laval’s R&D, system engineers,

software engineers, and commissioning experts allowed for

real-time problem-solving, while the commissioning team’s

cooperation with the shipyard ensured that any technical

challenges were swiftly addressed,” says Jeppe.