Alfa Laval Aalborg Micro Waste heat recovery economizer for marine auxiliary engines

The Alfa Laval Aalborg Micro is a uniquely compact

water-tube economizer. Easy to install, operate and

maintain, it reduces the use of the fired boiler by

recovering heat energy that otherwise would be

lost through the engine exhaust gas. This ensures

a rapid return on investment.

Despite its minimal footprint, height and weight,

the Aalborg Micro has an extended heating surface

created by coiled fin tubes. Even more efficient than

smoke-tube economizers, it provides an ideal retro

fit solution where no other economizer will fit.

Application

Only a portion of the fuel energy released by marine engines

actually goes to propulsion. A large amount of it escapes

as heat, and it makes sense to reclaim as much of this en

ergy as possible. This is true for auxiliary engines as well as

main engines.

Steam produced with the Aalborg Micro can support or fulfil

steam needs in port, but it can also serve other functions.

For vessels whose long-stroke main engines produce

cooler exhaust, it can provide a needed steam boost during

a voyage. If there is no steam shortage while sailing, the

additional steam produced with the Aalborg Micro can

be used to generate electricity, for example by means of

Organic Rankine Cycle (ORC) technology.

Benefits

• Extremely compact, plug-and-play design for easy retrofit

• Easy improvement of Carbon Intensity Indicator (CII)

• Short payback time (typically 1–2 years) through up to

25% fuel savings on the oil-fired boiler

• Reduced wear and maintenance on the fired boiler

• Internal damper for dynamic management of

pressure drop

Working principle

The Aalborg Micro is installed after a vessel’s auxiliary engine

(or small main engine). It has a short start-up time of just

two minutes. When the exhaust gas passes over its heating

surface, the waste heat energy in the gas is absorbed for the

production of hot water or steam. An internal damper, which

allows up to 80% of the exhaust gas to bypass the heating

surface, keeps back pressure within safe limits.

The Aalborg Micro is not designed with its own steam space.

It is used in connection with one or more fired boilers, which

act as the steam/water space. Forced-circulation pumps pro

vide the Aalborg Micro with water at saturation temperature

from the fired boiler(s).

In the Aalborg Micro, heat from the engine exhaust gas is

transferred to the water side by convection. The generated

steam/water mixture is then discharged into the steam space

of the fired boiler(s), where the heavier water particles sepa

rate from the steam.

Design

Built for lasting performance, the Aalborg Micro has a durable

construction where the coaxial tubes of the heating surface

are arranged within a vertical cylindrical shell plate. The

heating surface is designed for easy maintenance, with an

integrated soot blower that supports the daily cleaning of

the coiled fin tubes.

In operation, a control damper forces the exhaust gas flow

from the engine to pass between the tube coils. This damper

also acts as an internal bypass, allowing back pressure to be

regulated without the need for an external bypass.