Category: Alfa Laval

Waste heat recovery economizers for marine engines

The Alfa Laval Aalborg XS-2V and XS-7V are robust smoke-tube

economizers. Easy to install, operate and maintain, they reduce

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. The Aalborg XS-2V

is equipped with its own steam space, which makes it a

complete exhaust gas boiler. The Aalborg XS-7V shares a steam

space with the fired boiler. The proven design of both

economizers includes a dual-inlet option, which creates high

installation flexibility.

Design

Built for simplicity and reliability, the Aalborg XS-2V and

XS-7V have a vertical, all-welded design with straight smoke

tubes. The option of dual inlets allows one economizer to

serve two engines, with half the tubes dedicated to one

engine and half dedicated to the other. This can reduce

installation costs and complexity.

The smoke-tube design is easy to clean and maintain,

especially as the high gas velocity through the economizer

minimizes fouling. If needed, individual smoke tubes can also

be repaired or replaced.

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.

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

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.

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.

Technical data

Gas Turbines fired with different fuels such as:

• Natural gas

• Diesel oill

Heating media:

• Hot water

• water-steam

• Superheated steam

• Thermal oil

• TEG or equal

Design options:

• Dry run or non-dry run

• With or without integral bypass and diverter damper

• External and Internal insulation

• Fixed or removable tube bundle

Materials:

• Tubes in carbon steel, alloy steel or stainless steel

• Casing and ducts in carbon or corten steel

Alfa Laval’s Waste Heat Recovery Unit (WHRU)

optimized for recovering waste heat after gas turbines.

Application

The waste heat recovery unit recovers thermal energy in

the waste heat from the gas turbine exhaust gas,

enabling generation of hot water, water-steam or

superheated steam. The WHRU is also capable of heating

up thermal oil and TEG, and can be designed to fit

individual customer needs and optimum performance.

Customer benefits

• Customized design

• Global service network

• Large installed base

• Large manufacturing capabilities

• WHRU incl. extended scope

Applications

• FPSO

• Process industry

• District heating

• Power generation

Standard scope of supply

• WHR-unit

• Insulation & cladding

• Ducts

• Stack

• Silencer

• Expansion joints

• Diverter

• Control system

• Instrumentation

• Deaerator/feed water tank

• Feed water treatment system (incl. chemical dosing unit)

• Bypass – external or internal byppass

• Documentation  (relevant manuals, certificates etc.)

Exhaust gas economizers capture waste heat energy from engines,

gas turbines and more, enabling its reuse for steam production or

other processes.This saves fuel, which provides rapid payback and

helps reduce CO2 and other emissions. It also reduces the running

hours of the fired boiler/heater, which lowers maintenance costs.

Our Alfa Laval Aalborg portfolio includes a wide range of economizers

for industrial and marine use, as well as standalone exhaust gas

boilers with integrated steam drums.

We have effective waste heat recovery solutions to match a wide

variety of needs. Our Alfa Laval Aalborg exhaust gas economizers

and exhaust gas boilers combine exceptional thermal efficiency

with proven reliability.

Benefits of Alfa Laval Aalborg exhaust gas economizers

• Significantly reduced emissions of CO2 and other greenhouse

gases

• Short payback time through fuel savings due to reduced reliance

on combustion

• Compact design ensured by optimized heating surfaces with high

thermal efficiency

• Innovative options for easy installation and integration – even in

retrofit situations

• Specific engineering to match each engine’s data and operating

conditions

Design

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

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

fuel: LNG, methanol or ammonia.* Additionally, it can produce

steam through waste heat recovery. It is delivered with a preas

sembled Aalborg burner built on Alfa Laval’s innovative Multi

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

and produced in-house to ensure the highest reliability.

• Aalborg OC-TCi boiler:

The Aalborg OC-TCi is a side-fired composite boiler with

a fired section comprised of helix tubes. This tube design

provides more heat transfer area than competing solutions,

which results in fuel-saving efficiency. For waste heat recovery,

the boiler has 1–3 exhaust gas sections with smoke tubes,

allowing it utilize exhaust gas heat from up to three engines.

Combustion heat from the burner – or exhaust gas heat

from waste heat recovery – is distributed uniformly through

the boiler’s convection 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 OC-TCi is a flexible marine boiler that can support

vessel operations in multiple ways:

• Steam generation:

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

– Tank cleaning– HVAC

– Engine room consumers

• Waste heat recovery:

Besides generating steam with waste heat on its own,

the Aalborg OC-TCi can support one or more exhaust

gas economizers by serving as a shared steam drum.

• LNG safety:

On vessels using LNG as fuel, the Aalborg OC-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

The Alfa Laval Aalborg OC-TCi is a marine composite boiler

for producing steam through combustion and/or waste heat

recovery. With its high efficiency and its ability to reclaim thermal

energy, it can help reduce environmental impact.

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

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

figured 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

• Reduced carbon footprint through waste heat recovery

• Energy efficiency maintained through self-cleaning TCi

(Turbo Clean, intelligent) technology

• Trouble-free uptime, secured through robust design

and user-friendly control