New Trends in Fabric Filter Technologies

R I C H M I L L E R

S R . C O N S U LTA N T A N D P R I N C I PA L

M I L L E R E N E R G Y & E N V I R O N M E N TA L S E R V I C E S , L L C

E T S FA B R I C F I LT E R S E M I N A R

M AY 4 T H A N D 5 T H , 2 0 1 6

Objectives

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Objectives of this presentation

• Fabric and filter bags design options available for power generation pulse jet fabric filters

• Discussion on use and benefits of expanded surface area filter bag designs for enhancing existing fabric filter operation

• Benefits of fabric filter optimization as a means of reducing ACI and other dry sorbents injection rates and cost while still maintaining current Utility and Boiler MACT limits

Past Pulse Jet FabricsIn the past, a limited number of fabrics were utilized on pulse jet fabric filters. Some were carry overs from reverse gas FF type collectors. These included some of the following:

• Woven fiberglass fabrics • Both light weight and heavy weight fabrics

• Various weaves and coatings

• PTFE membrane coated fiberglass (Still utilized)

• Heavy Weight PPS (Ryton) Fabrics with large (7-denier) fibers on PTFE Scrim (most currently utilize finer denier fibers – 2.2 to 2.7 denier standard with some utilizing even finer fibers or combination)

• In some cases, Aramids (Nomex) fabrics were used on CFB boiler designs

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SO WHAT CHANGES IS INDUSTRY DEVELOPING TO FURTHER THE DEVELOPMENT OF FABRICS TO MEET TODAY AND TOMORROW’S NEEDS

AND REGULATIONS?

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Newer Developments in Fabric Filtration

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Current developments in fabrics and fibers based on worldwide coal-fired boiler operating experience included some of the following ideas

Emerging Trends Product Approach

High efficiency filtration with stratified fabrics of multi-lobal fibres

PPS inner web with multi-lobal P84 fiber in the face (top cap) to lower emissions and reduce pressure drop, lowering operating costs and lengthening bag life

Fabrics for aggressive acid and non-agglomerating ash and high velocity dusts

Use of PTFE fiber blended with PPS to resist acid degradation and minimise impact of poor dust cake formation

Extended surface area bags to lower emissions with lower differential pressure and increased flows

Extended surface area bags achieve reduced emissions from reduced pulse frequency (Solaft’s StarBag)

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Use of Expanded Surface Area Bags (StarBagsTM) in Power Generation

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• The expanded surface area bags provides clients with a unique solution replacing standard filter bags without any expansion or change to the design of existing bag houses other than a change to the supporting cages

• Some of these benefits may include:• Reduced particulate, Hg and Acid Gas emissions• Reduced DSI sorbents and activated carbon usage • Increased full-load generation where high pressure drops may be limiting full-load operation• Compliance with MATS and Plant Operating licenses • Elimination of abrasion and early bag failures due to high velocities and filtration rates

• The expanded surface area bag alternative deliver these benefits by significantly increasing filtration area (lower A/C Ratios), thus enabling an increase in particulate loadings, greater residence time across the filter cake, while at the same time reducing differential pressure

With StarBagsTM, power plants can achieve lower filtration rates (A/C Ratios), lower pressure drops, reduced particulate emissions and lower their usage of activated carbon and other DSI sorbents

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Expanded Surface Area “StarBag” Solutions

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Benefits of fabric filter optimization as a means of reducing activated carbon and DSI

injection rates and cost while still maintaining current mercury MATS limits

When considering ways to optimize both the ACI injection and fabric filter particulate control operating systems designed to meet Hg MATS compliance requirements for EGU coal-fired boilers, one must consider the following:

◦ The impact of operating temperatures and fabric filter cleaning frequencies on both mercury capture and sorbent feed rates, as well as operating pressure drops

◦ Types of carbons being utilized (Treated or non treated, particle size, etc.)

◦ Benefits of combining Hg CEMS monitoring output data as part of an integrated feed forward/feedback, ACI system control logic technology

◦ Economic choices when looking at DSI injection rates to reduce SO3 levels at ACI injection points vs. Activated Carbon Injection rates when achieving required emission limits.

◦ Lower SO3 relates to reduce demand on Activated Carbon to achieve Hg emission levels

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225 235 245 255 265 275 285 295 305 315

Tota

l Hg

(µg/

m3)

Baghouse Temp (F)

Impact of Operating Temperatures

(FF on PRB-fired Boiler with PAC Injection)

• Hg observed to increase at higher BH temperatures, suggesting Hg release as maximum “capacity” decreases

Case Study – Mid-West Utility (PRB Coal)

• Baghouse was installed downstream of ESP (TOXECON) & originally sized for future CDS Scrubber

• Operation included very low air-to-cloth ratios and long dwell times between cleaning of the bags due to low filter cake pressure drops

• Activated carbon sat on the bags for extended time periods and was highly saturated with Hg

• When loads caused flue gas temperatures to increase above 370F, Hg was released from carbon, requiring higher PAC feed rates to maintain required Hg levels

Solution• Isolated FF compartments to force A/C ratio higher and cleaning cycles to increase, resulting

in a thinner filter cake with fresh PAC present.

• As a result, FF was able to maintain required mercury emissions with significantly lower PAC injection rates

Summary• Fabrics of all types have evolved over the years designed to serve both reverse gas and pulse

jet fabric filters

• A new generation of fabrics and filter bag types (StarBags) are now being offered, to enable pulse jet fabric filters to meet today’s and tomorrows regulations while operating under a wide range of operating conditions and coal types

• There are many benefits of optimizing both the fabric filter and ACI/DSI injection system operation to meet MATS compliance as a marriage between control technologies

• Higher operating temperatures may require more aggressive FF cleaning frequencies and intensities to produce a thinner, more carbon rich filter cake to achieve higher Hg reduction levels

• Implementation of feed forward/feed back controls tied to Hg CEMS for trim control in fabric filters has been demonstrated as a means to reduce PAC demands while achieving required Hg control levels over a wide range of operating conditions and loads

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Thank youAny Questions?