New Tricks Old Dog Power Engineering

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March 2012 www.power-eng.com

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New Tricks for the Old Dog:Coal Conveyingfor the 21stCenturyBy Greg Bierie, Engineered Projects Group, Martin Engineering

At the Superior Midwest Coal Terminal in Superior, Wis., an engineered-flow chute guides the coal downa nearly 26-foot (7.9 meter) drop onto the receiving belt. All photos courtesy of Martin Engineering.


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Using this hood and spoon design, these chutes lay thecargo onto the receiving belt at the proper speed and directionof travel. This reduces impact and abrasive wear on the receivingbelt and minimizes the positive pressure that creates and drives offairborne dust. The use of these engineered-flow chutes stabilizesthe material flow rate, reduces cleanup and maintenance expenses,and controls the risk of explosion and fire in coal handling.

To develop the chute for a given transfer point, the design forthe chute relies on the information generated by material testing.

Testing of samples of the actual material to be conveyed providesimportant data. Information drawn from this testing includes ma-terial composition and physical properties, moisture content, lumpsize range, and fines size. After the various conveyor and materialparameters are spelled out, the material discharge trajectory canbe determined. This detailed information is used in developing acomputer-generated 3D model of flow through the chute.

The Benefits Of Engineered- Flow ChutesEngineered-flow chutes offer a number of benefits, including: Passive dust control to reduce dust escape while minimizing

baghouse collection. Increased flow rate to eliminate chutes as a production

bottleneck. Reduced material buildups and blockages to reduce chute

plugging. Reduced loading impact to extend belt life by reducing

damage and abrasion. Reduced degradation of material to minimize dust genera-

tion. Controlled load placement to prevent mistracking, spillage,

and belt-edge damage. Reduced wear on liners to extend service life and cut re-

placement cost and time.

A New Conveyor ArchirectureA second new trick for coal conveying one that can be com-

bined with the first trick of engineered chutesis a modern con-veyor architecture. Part of this new architecture label stems fromthe systems back to the drawing board approach, where manylong-standing conventions of conveyor design are reexamined.Users of the new system are not afraid to ask why components aredesigned the way they have been. Safety and maintenance-friendly

Editors Note: This article is based on a paper given at COAL-GEN 2011 in Columbus, Ohio.

T

he efficient handling of coal on belt con-veyors is essential to coal-fired powerplants. The conveying of coal is prone toproblems including the escape of spillageand airborne dust. These are typical prob-lems, common problems, problems oflong-standing, problems that continue to

make the handling of coal a dirty, inefficient, unpleasant, highmaintenance, low reward joba dog of a job.

A key to improving coal conveying is the implementation ofadvanced systems to improve performance and prevent fugi-tive material. These new technologies present the opportu-nity to teach the old dog that is coal handling some newtricks. When I say tricks, I do not mean magic trick,--that is something not repeatable by the average individual.I am using another definition of trick, as pulled out of onmy computers thesaurusas in knack, technique, or habit.

The new technologies that this ar ticle will examine includeengineered chutes that channel the material stream to reducethe entrainment of air into the material flow, and so minimizethe release of dust. The art icle will also feature a modern ar-chitecture with improved belt support and sealing systemsthat reduce maintenance requirements and allow mainte-nance work to be performed from safely outside enclosuresand away from moving parts.

Engineered-Flow Transfer ChutesThe loading and discharge of the conveyor belts is the area

where many, i f not most, of the environmental problems incoal conveying occur. Fortunately, a new technology provideschutes that can accomplish conveyor loading and discharge

without blockages, and while minimizing the dust generated.This innovation is engineered-flow chutes. With a design basedon testing and computer-based flow studies of the specific

material to be handled, these transfer chute systems pro-vide better material control, continuous flow at highercapacities, and dramatic reductions in material spillageand the release of airborne dust.

Engineered-flow chutes typically include a hooddischarge chute and a spoon receiving chute. Insideeach conveyor transfer point, the hood controlsthe flow of material from the discharging conveyor,maintaining a coherent material stream, and min-imizing induced air. At the bottom, a smooth-line transfer loading chute or spoon directsthe stream of material onto the receiv-ing belt at the proper speed and angle,

without impact, to minimize materialdegradation, belt abrasion, and theexpulsion of airborne dust.


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ponents improve the shiploaders ser-viceabil ity, because they are engineeredto be accessible from outside the struc-ture. This allows terminal personnelto inspect the components while thesystem is in operation. Then, if mainte-nance is required, this work can be donequickly, cleanly, and safely, from outside

the conveyor and chute.When terminal management realized

they could increase through-put, improvesafety, and reduce environmental impactall at once with this new conveyor archi-tecture, they were all for it, said TerminalGeneral Foreman Vic Stoltz.

With the new architecture conveyorcomponents in place, the Port of Sewardhas increased the loading rate to 850mtph, an increase of more than 15 percent.Shiploading time has been reduced by an

average of 21 hours, resulting in a sig-nificant reduction in demurrage charges.

With the improved control of the materialstream, there is less dust. Now, operation

officials report, cleanup is minimal and theshiploader has been cleaned in less thanfour hours.

Weve reduced the cleanup time on theshiploader and dock by over 40 man-hoursper ship, Stoltz said.

Wyoming Power PlantA power generation facility in Wyo-

ming has also taken advantage of thenew conveyor architecture. The plantsfuel is fr iable PRB coal that creates sig-nificant amounts of coal dust, and the

skirtboards and stilling zones, will help tomanage airflow and control dust. Skirt-board covers with a peaked roof form asettling zone to prevent escape of airbornedust from the conveyor loading zone,

while improving safety by keeping work-ers away from moving cargo and rollingcomponents.

Applications of AdvancedConveyor Technologies

These advanced conveyor technologieshave already achieved improvements in op-

erations and maintenance in coal-handlingoperations in terminals and power plants.

Port of Seward Coal TerminalTo allow the expansion of its cross-Pa-

cific coal exports, Aurora Energy Services(AES) needed to increase the flow of coalthrough the shiploader at its coal terminalin the Port of Seward, Alaska. But transferchutes on the shiploader choked at ratesabove 750 mtph, which limited loadingspeed and slowed turnaround. And worse,the escape of coal dust during loading led

to concerns from a nearby cruise ship dockand marina, as well as environmental inter-est groups. AES officials looked for ways toupgrade the terminals material handlingsystem, and selected the modern con-

veyor architecture as developed by Mar-tin Engineering. The new architecturesexternal wear liner and self-adjusting,double-life skirtboard sealing systemprovided effective containment to pre-

vent dust and spillage escaping from thesides of the conveyor belt.

The components of the system com-

features are the dominant characteristics ofthis design standard. Some of the designinnovations included in this new conveyorarchitecture include:

Slide-In/Out Components

To simplify maintenance in the newconveyor architecture, belt support sys-tems such as impact cradles, support cra-dles, and idlers incorporate track-mountedsub-assemblies that slide out on one side ofthe conveyor for maintenance. This servicesystem will minimize conveyor downtimeand enhance employee safety, as workers

will no longer need to crawl into the struc-ture to remove and replace components.

External Wear LinerFor years, wear liners have been installed

on the inside of the transfer points skirt-board, to help preserve the steel structureand protect the skirtboard sealing system.But this internal liner proved too difficultinstall and inspect, and even harder to re-place. Now, the modern conveyor architec-ture has developed an external wear liner;that is, a liner that is mounted on the out-side of the skirtboard. External liner allows

for safer installation and maintenance. Theexternal wear liners effectively protect theskirtboards and the sealing system, yetare easily inspected and maintained or re-placed without requiring confined spaceprocedures.

Modular Chute Walls and Covered

SkirtboardPreventing the escape of fugitive mate-

rial is another important aspect of mod-ern conveyor architecture. Pre-engineeredmodular chute wall, which simplifies thedesign and construction of transfer point

The engineered-flow chutes in this Wyomingcoal-fired power plant improve the loading of itsair-supported conveyor system.

Components of the new conveyor architecture are incorporated in the loading zoneof the shiploader conveyor at the coal terminal at Port of Seward, Alaska.


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Attached on unique mounting blocksoutside the chute, the wear liner is read-ily adjustable through a specially-de-signed bolt-on alignment system. Rath-er than scheduling a full plant outage,the installation was completed during

singleshift downtime. The techniciansprefabricated additional support struc-ture to be installed below the idlers, de-signed so it could be moved into placethrough very confined spaces. When allsections were in place or repaired, theycut out the existing skirtboard and re-

installed it two inches inboard on bothsides, to provide additional room for ef-fective sealing.

Finally, the technicians installed theexternal wear liner and a skirtboardsealing system that can be flipped overto double the service life. The design ofthe wear liner allows it to be mountedoutside of the transfer point skir tboard,keeping the coal away from the sealingsystem to extend the seals life.

All work was performed outside thechutes, eliminating the need for a long

system outage to install the upgrades.The upgrades have eliminated the dustand coal piles adjacent to the coal han-dling components, improving safetyand reducing material waste.

points coming out of the belt feeders.Included in the reconstruction were new

head chutes at the belt feeder discharge,new spoons at the loading zone wherethe cargo is placed on the receiving belt,and new impact cradles and belt supportcradles to stabilize the belts line oftravel though the transfer point. In

addition, the project called for in-stallation of modular chutewall andskirtboard to provide a stilling zone

where dust will settle out of the air,external wear liners to provide ef-fective protection for the skirtboardseal and are easy to install, inspect,and replace, and a self-adjustingsealing system that provides a dou-ble service life simply by invertingthe elastomer strip.

Following project completion,plant officials have agreed tothe reconstruction of additionaltransfer points.

Indiana Power PlantOne of Indianas largest power

generators has announced a signifi-cant upgrade to its conveyor feedsystem, virtually eliminating fugitive ma-terial and the problems that it causes. Byupdating the facilitys longest conveyor,company officials anticipate that reduced

waste will contribute to greater produc-tivity, plant safety, and environmental re-sponsibility.

For years, the plant struggled to achieveconsistent and reliable operation of theconveyor system feeding its largest coal-fired generator. The surge of material asrailcars unloaded combined with the highhead pressure from the hoppers, causedextensive spillage in the plant that wastedmaterial and created housekeeping andsafety concerns. Worn-out chutes com-pounded the issue.

The plant decided to install a retro-fit wear liner on the four feeders belowthe rail car dump, as well as on the two

feeders from the reclaim system. Theinstallation of this external wear linersaves labor by eliminating the need forconfined space entry, without requiringextensive tear-out of the exist ing chutes.

problems this dust can create. Companymanagement emphasizes cleanliness in-side all of their facilities, and they areconscious of maintaining environmen-tally-friendly coal-handling systems.To improve their coal handling sys-tems and maintain their environmen-tally conscious operation, management

elected to replace a number of transferchutes and belt conveyors that were not

working to their design specifications.The coal handling system upgrades at

this plant were completed in three stag-es. First, a new engineered-flow loadchute was installed on an existing air-supported conveyor. Then an airsup-ported conveyor was commissioned forthe bunker room along with new loadchutes for one of the pant leg chutesbelow the primary crusher. Finally, asecond load chute beneath the primarycrusher was upgraded with the installa-tion of an engineered-flow chute.

This power generation facility has ben-efited from the installation of these leadingedge conveyor technologies with the fol-lowing results:

Reduced risk of fire and explosionsfrom the handling of PRB Coal.

Reduced risk of employee health is-sues due to exposure to dust.

Improved cleanliness in the coal han-dling system with minimal mainte-nance requirements.

Increased safety associated with thereduction in maintenance efforts.

Center loading of the air-supportedconveyor, reducing mistracking, spill-age, and other problems.

Kansas Power PlantIn northern Kansas, a power plant

fired with PRB coal has begun a pro-gram to improve its material handlingsystem. The plant was experiencingexcessive airborne dust and spillage attransfer points. Worn out skirtboard in

the loading zones increased the prob-lems and the plant was willing to try anew solution. The plant determined touse components of the new conveyorarchitecture, starting with the loading

The enlarged settling zone on this transfer point at the Kansaspower plant allows dust to settle out of the air.

Martin Engineering USA

One Martin Place Neponset, IL 61345-9766 USA

Toll Free: 800.544.2947 or Ph: 309.852.2384Fx: 800.814.1553 [email protected] www.martin-eng.com

Reprinted with revisions to format, from the March 2012 edition of Power EngineeringCopyright 2012 by PennWell Corporation

New Tricks Old Dog Power Engineering

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