GEA Process Engineering

The economic solution for 

Flue Gas Desulphurisation

GEA Niro Spray Drying Absorption

engineering for a better world
SDA: economical, efficient, ecological

Balancing interests

Climate change – and in particular, air pollution – has never been higher on the 

global agenda. An inherently international issue, policed by multilateral 

agreements, legislation is constantly tightening.

For power plant operators this is nothing new – it has long made good political 

sense to curtail harmful emissions. What is new, however, is the expanding role 

environmental technologies can play in enhancing plant performance. With a 

considerable portion of a modern plant’s costs linked to emission control, the 

right technologies not only cushion environmental impact, but fertilise 

competitive advantages.

When it comes to flue gas desulphurisation (FGD), GEA Niro’s spray drying 

absorption (SDA) process can give you an edge. By enhancing efficiency and 

limiting costs, SDA lets you comfortably balance regulatory and financial 

ambitions.

Empowering the power producers

First conceived by GEA Niro in the 1970s, SDA has been quickly adopted by 

fossil fuel based power plants around the world because of its numerous 

demonstrable benefits.

SDA removes acid gases and particulates from flue gases – at rates well above 

legislative targets – and converts them into a light, free-flowing powder. 

However, it’s in the sheer simplicity of SDA that its true merits lie. Using a 

minimum of equipment and raw materials, SDA requires far less capital 

expenditure upfront and lower running costs than many rival technologies. 

(Compared to wet scrubbers, SDA offers huge savings on energy, water 

consumption, and operating and maintenance costs.) The process’ 

uncomplicated basis also makes it remarkably robust (the first SDA systems, 

installed in 1980, are still running today) and easy to operate. The system can 

handle a broad fuel range, and simply adjusts itself to follow changes in boiler 

load and flue gas composition.

All of this means you can meet your commitment to regulators without 

neglecting your obligation to shareholders. Dependable, economical, verifiable 

– SDA literally puts the power back in your hands.

Absorber penthouse 

with absorbent supply 

arrangement and spare 

rotary atomizer.

2
GEA Niro can generate 

basic designs for new 

or retrofit SDA projects. 

Key Benifits

- SO22removal efficiencies well above 98%

- Superior SO3 capture rate 

- Superior micro-pollutant capture rates 

- Patented process for mercury removal

- Low capital expenditure 

- Low water consumption 

- Low auxiliary power consumption 

- Low operating and maintenance costs 

- High availability

- Highly flexible: easily adjusts to variations in boiler fuel and load

- No need to reheat flue gas 

- Absorbers made of mild steel – no high alloy materials

- Can use low quality water, incl. waste water or sea water

- No lining required 

- No waste water generated

- No sludge treatment equipment

- Fly-ash pre-collection optional

Large SDA’s clean the flue 

gas from a 550 MWe coal 

fired power plant in the USA.

Two parallel absorber 

modules treat the flue gas 

from 8 lignite fired boilers 

installed in the Czech Rep.

530 MWe

lignite fired 

power plant in 

the Czech Rep.

•	 Mixing tank with agitator, heating jacket and lid with gas dampers

•	 Feed tank with heating jacket and lid with gas dampers

•	 Multi-pipe with heat tracing

•	 Valve arrangements

•	 Two-fluid nozzle (patented) with mounting flanges

•	 Compressed air system

•	 Hot water system

•	 Main frame console with easy access to top of tanks

•	 Control panel (stand alone) with signals to main control

Main system components:

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A simple, precise process

SDA is based on a simple concept, honed over the years into a precise, effective 

system. Hot, untreated flue gas is fed into a spray drying absorption chamber 

and comes immediately into contact with a fine spray of alkaline slurry (usually 

slaked lime). Virtually all acidic components in the flue gas are absorbed into 

the alkaline droplets, while water is evaporated simultaneously. Precise control 

of the gas distribution, slurry flow rate and droplet size ensures that all droplets 

are converted into a fine powder. Some fly ash and reaction products drop to 

the bottom of the absorber and are discharged. The treated flue gas continues 

on to a dust collector, where any remaining suspended solids are removed. The 

cleaned outlet gases are then expelled through the stack. Meanwhile the dry 

powder from the bottom of the absorber and dust collector is conveyed to a silo. 

The SDA process can optionally include a partial recycling of the reaction 

products to the feed slurry to improve absorption and drying performance. 

Effective and adaptable

GEA Niro’s unique SDA process offers many advantages. SO22removal rates are 

freely adjustable up to 98% or more. In addition, micro-pollutants, such as SO3, 

Hg, HCl and HF, are also effectively removed during the process. A highly 

tolerant system, SDA is self-adapting to changes in flue gas flow rate, temperature 

and composition. On a practical level, SDA is suitable for power plants of all 

sizes, requiring only a single absorber and a single rotary atomizer per 500 

MWe. And absorption chambers are made entirely of mild steel and often 

produced locally. Furthermore, the process can utilise low-grade water like 

wet scrubber efficient and other waste water streams, and generates no 

waste water.

Typical Spray Dryer Absorber De

Roof gas 

disperser

Rotary

atomizer

Central

gas disperser

Inlet flue gas

(lower)

SDA product discharge

A rotary 

atomizer 

disperses the 

absorbent 

slurry into 

billions of 

tiny droplets.

Rotary atomizer

Spray dryer 

absorber

To end 

product

silo

Recycle

product

Recycle slurry

OPTIONAL PRODUCT RECYCLE

Lime slurry

Burned

lime

Stack Dust collector Dust collector

Fly ash

Inlet 

ue gas

Water Water

Head tank

OPTIONAL FLY ASH 

PRE-COLLECTION

THE SDA PROCESS: SO22+ Ca(OH)2 CaSO3 / CaSO4 + H2O

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The rotary atomizer and spray dryer absorber

Central to GEA Niro’s SDA process is the concept of 

using a spray dryer as both an absorber and dryer 

simultaneously. Achieving this hinges on two 

crucial pieces of equipment – the GEA Niro rotary 

atomizer and gas disperser. The former atomises 

feed slurry into billions of droplets, while the latter 

ensures the correct gas dispersion to optimise 

drying and reaction conditions. 

Years of development and refinement have resulted 

in a rotary atomizer that is extremely reliable, 

able to operate continuously for more than 4,000 

hours and requires little maintenance. Other key 

advantages of the GEA Niro rotary atomizer and 

spray dryer absorber includes:

Rotary atomizer:

•	 High capacity – one rotary atomizer per 500 MWe

•	 Low maintenance

•	 Patented wear-resistant design (WEARSERTTM)

•	 High availability

•	 Durable – lifespan over 30 years

•	 Broad turn down range

•	 Proprietary feed distributor design (VOLUTETM)

Spray dryer absorber:

•	 One absorber for 500 MWe boiler

•	 Optional flat bottom design (patent pending)

•	 Wear resistant gas disperser design

(patent pending)

•	 Broad turn down range

esign

Inlet flue

gas (upper)

Outlet 

flue gas

The abrasion-resistant atomizer wheel and 

insert design ensures reliable continuous 

operation, with a minimum of maintenance.

A single rotary atomizer 

can treat the flue gas from 

a 500 MWe unit.

Flat bottom 

absorber in 

China.

Operation of an SDA plant is 

typically handled from the 

central power plant control 

room, without extra staffing.

The dry free-flowing product from 

the SDA process can easily be handled 

in a pneumatic transport system.

GEA Niro patented rotary 

atomizer wheel insert.

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A pioneer of SDA 

In the mid-1970s, GEA Niro began testing the idea of using spray dryers to 

absorb acid compounds in combustion gases, with considerable success. 

By 1980 the process was patented and made commercially available. The 

SDA’s operational and economical advantages meant it was eagerly adopted 

by coal-fired power stations in Europe, North & South America and Asia.

Bringing expertise to bear

GEA Niro remains the world authority on SDA applications for flue gas 

cleaning, offering an unprecedented range of experience, process know-how 

and equipment. To date we have fitted over 500 rotary atomizers at more 

than 175 different SDA installations around the world. More importantly, 

we ensure this knowledge translates into tangible benefits for our customers. 

A familiarity with power plants of all sizes and legislative demands enables 

GEA Niro to quickly and professionally generate basic engineering designs 

for new SDA installations. And, whenever possible, we personally oversee 

the implementation and start-up phase of all projects to satisfy customers 

(and ourselves) that the process and equipment perform as expected.

A lasting commitment

Investing in an SDA system is really just the first step in a relationship that we 

hope is as durable and enduring as our technology itself.

GEA Niro is a world leader in industrial drying applications and has operations 

in more than 50 countries. Our global After Sales Division is dedicated solely to 

serving customers with routine maintenance checks, original GEA Niro spare 

parts and emergency technical support. Of course, our SDA-specialist engineers 

are also at hand for more complex repairs or process inquiries. Finally, our After 

Sales Division can provide training on both operation and maintenance issues, 

helping customers help themselves. 

With GEA Niro you can be confident that you are never far away from local 

support of a world-class standard. That’s because when you invest in a GEA 

Niro SDA system, you also gain the commitment of 4,500 employees, devoted 

to keeping your business performing optimally at all times.

Adjacent SDA’s at 

two parallel coal fired 

units in the USA.

A coal fired power 

plant in Denmark, 

2 x 350 MWe.

Flat bottom absorber 

design for large size 

SDA applications

6
GEA Niro SDA-specialists 

are at hand for process 

enquiries.

Large SDA module at 

a lignite coal fired power 

plant in the Czech Rep.

Left: Erection of an 

SDA plant in 

Denmark.

Bottom of SDA with 

flue gas inlet and 

outlet duct and 

product discharge.

Above: Upper deck 

of fabric filter 

downstream of SDA.

Right: A coal fired 

power plant in 

Denmark, 350 MWe.

Most SDA units have a 

spare atomizer, which can 

be brought into service 

within 30 minutes.

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Excellence	 Passion	 Integrity	 Responsibility	 GEA-versity

GEA Group is a global mechanical engineering company with multi-billion euro sales and operations

in more than 50 countries. Founded in 1881, the company is one of the largest providers of

innovative equipment and process technology. GEA Group is listed in the STOXX Europe 600 Index.

BNA 870/GB 0412 CBC

© GEA Niro. All rights reserved. Subject to modifications. Printed in Denmark.

GEA Process Engineering

GEA Niro

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Tel +45 39 54 54 54 Fax +45 39 54 58 00

E-mail: chemical@niro.dk Website: www.niro.com