Upgrade of Wet FGD Systems

A low-cost approach to upgrade your older wet FGD system to 

meet today’s performance requirements

	 • Above 98% SO2 removal 

	 • Above 90% oxidized Hg removal

	 • 70% particulate removal

	 • Uninterrupted operation between scheduled outages

	 • Dry byproduct for sale or landfill

	 • Zero liquid discharge operation

Power

Process 

Technologies
Industry Challenges

The power industry faces the challenge of increasingly stringent 

environmental regulations. As a result, existing FGD systems 

must operate at peak efficiency and reliability, and must provide 

maximum and sustainable performance to meet current and 

future emissions requirements. A large portion of the existing 

U.S. fleet of FGD systems were not designed to meet the 

emission standards currently being adopted or considered. In 

addition, these older systems often suffer from poor reliability 

and high O&M costs due to their age or design. 

In today’s competitive environment, performance, operating 

costs, maintenance requirements, and reliability all have a 

significant impact on the bottom line, or worse, the viability of 

an aging asset. Through a cost-effective upgrade project, the 

performance and reliability of an older FGD system can be 

improved to levels matching or exceeding new FGD systems, 

regardless of age and design. In addition, new dewatering, 

wastewater treatment and reagent preparation systems can be 

installed to lower operating costs and/or meet future regulatory 

requirements.

URS FGD Experience

URS has been an FGD industry leader for the past 35 years 

working with utilities to improve the operation and performance 

of their FGD systems. URS has worked with every FGD process 

and design, and worked at most of the FGD systems installed in 

North America. URS can and has applied our technology and 

know-how to all OEM’s designs and processes, having more 

than 52,000 MW of FGD upgrade experience. URS understands 

how to upgrade an older system and improve performance and 

reliability, in spite of the design and operating limitations 

inherent with the system. URS understands the capabilities and 

limitations of all FGD processes and designs.

FGD 

Solutions

URS is recognized as 

an FGD industry leader 

•	35+ years of experience

•	More than 52,000 MW 

of upgrade experience

•	More than 14 GW 

of new and retrofit 

experience

•	Installed more than 

100 trays at 25 plants

Benefits To Your FGD System

•	Increase performance and reliability

•	Provide even and uniform gas distribution

– No recirculation zones

– Improved performance through spray zone and mist 

eliminator

•	Create vigorous gas-liquid contact

– Increased removal performance

– Reduce or eliminate performance additives

•	Provide stable and controlled chemistry

– Increase reagent use

– Improve byproduct quality

– Eliminate scaling

•	Improve mist elimination 

•	Improve dewatering, reagent preparation, and 

wastewater treatment operation

Benefits To Your Bottom Line

•	Increase SO2 removal efficiency

•	Improve removal of other regulated pollutants

•	Improve reliability and availability of scrubber

•	Implement innovative and low-cost solutions

•	Reduce or eliminate performance additives

•	Allow switch to lower-cost, higher sulfur fuels

•	Extend life of existing equipment

•	Reduce operating and maintenance costs

•	Improve byproduct quality and properties
The reasons why a utility may want to upgrade an existing FGD 

system generally fall into one of three categories: improved 

performance, improved reliability and operation, and rehabilitation and life extension of existing equipment. URS has the 

know-how to successfully meet all of your project objectives—

with innovative and low-cost solutions.

FGD Upgrade Projects

Below are examples of the types of projects URS has 

successfully completed.

•	Increased SO2 removal performance to meet a lower 

emission limit, reduced scrubber operating costs by 

eliminating a costly performance additive, and reduced plant 

operating costs by firing a lower cost, higher sulfur fuel.

•	Upgraded scrubbers to improve the removal of other 

pollutants such as fine particulate and oxidized mercury.

•	Improved scrubber controls and scrubber chemistry to 

improve system reliability and performance and resolve 

process problems.

•	Improved the performance of mist eliminators and mist 

eliminator wash systems.

•	Improved the performance of reagent preparation and 

dewatering systems.

•	Converted a system to forced oxidation to produce a saleable 

gypsum byproduct.

•	Designed and installed dewatering systems to eliminate liquid 

disposal ponds. 

•	Designed and installed systems to treat FGD wastewater. 

CFD Gas Flow Modeling: 

Bottom figure shows improved 

distribution resulting from design 

upgrades. 

Technologies to Improve Your 

System

•	Liquid Distribution Rings

– Improve gas-liquid contact

– Reduce “gas sneakage” along 

absorber walls and corners

– Protect absorber walls from spray 

impingement

•	Side-by-side Double Hollow Cone

Spray Nozzles

– Improved droplet interactions 

(secondary atomization)

– Enhanced removal performance

•	Dual-flow Sieve Trays

– Improved gas-liquid contact

– Improved gas distribution 

– Reduced pump requirements

•	CFD Modeling

– Improved gas distribution

– Improved mist eliminator 

performance

– Improved oxidation air sparger 

design

•	Spray Coverage Design Tools

•	Mist Eliminator Design Guidelines

•	Material Selection Guidelines

SCOPE RESULT

FGD performance upgrade 

and conversion to F.O. 

New dewatering system

SO2 removal increased from high 80%

range to 97%. High quality saleable

gypsum produced.

Single hollow cone spray 

nozzles replaced with 

double hollow cone spray 

nozzles

SO2 removal efficiency increased from 

91% to over 98% allowing plant to

eliminate additive and use higher S fuel.

Absorber upgrade, new mist 

eliminators, and conversion 

to F.O.

SO2 removal efficiency increased from 

89% to over 98%. High quality gypsum

byproduct produced. Improved system 

reliability and operation

Absorber upgrade with new 

headers, trays, LDR, recycle 

pumps and mist eliminators

SO2 removal increased from high 80%

range to 99%.

Absorber upgrade with new 

headers, trays, and mist 

eliminators. Conversion to 

F.O. New dewatering, 

reagent preparation, and 

wastewater treatment 

system installed.

SO2 removal efficiency increased to over 

98%. High quality gypsum byproduct

produced. Improved system reliability 

and operation. New systems performed 

as expected.

Project Success
URS Corporation is a leading provider of engineering, construction and technical 

services for public agencies and private sector companies worldwide. We offer a full 

range of program management; planning, design and engineering; systems engineering 

and technical assistance; information technology; construction and construction 

management; operations and maintenance; and decommissioning and closure services 

for federal, oil and gas, infrastructure, power and industrial projects.

URS CORPORATION

600 Montgomery Street

26th Floor

San Francisco, CA 94111

www.urs.com

2.7.13

Federal OI L & G A S i n f r a s tructure P o wer I NDU S TR I AL

For More Information Contact:

Gordon Maller

Tel: 512.419.5045

gordon.maller@urs.com

Jonas Klingspor

Tel: 512.419.5439

jonas.klingspor@urs.com

P.O. Box 201088

Austin, TX 78720

For 35 years, URS has been recognized as a world leader in air 

pollution and FGD control technology—installing new units, upgrading 

existing units, and helping utilities effectively and efficiently operate 

their FGD systems. Since the days when the FGD industry began, URS 

has been at the forefront, performing laboratory, pilot-scale, and fullscale studies aimed at obtaining a deeper understanding of FGD 

processes and systems. URS offers an experienced team of FGD 

engineers and technologists to support our utility and industry clients in 

developing, evaluating, and implementing proven technology and 

solutions for their FGD systems. As a result of our broad experience 

and know-how, URS offers designs and approaches that are more 

innovative and cost-effective than our competitors. 

© 2013 URS Corporation