the coal handbook: towards cleaner production || coal handling along the supply chain

© Woodhead Publishing Limited, 2013

654

20 Coal handling along the supply chain

E. BACH, FLSmidth, Australia

DOI : 10.1533/9780857097309.3.654

Abstract : This chapter discusses the possibilities of the use of materials handling machines for coal applications. It gives an overview on conveying, storing, loading/unloading and crushing for coal in today’s industry environment. It talks about different coal industries and would like to encourage a cross-industry and out-of-the-box style of thinking. The chapter will give a general approach to the selection of equipment for the different needs of coal applications. Details will not be discussed and can be further explored in separate literature.

Key words : material handling, belt conveying, stacking reclaiming, shiploading shipunloading, train loading, solution engineering.

20.1 Introduction

Although bulk materials handling technology has developed quite rap-

idly over the recent years, the fundamental design criteria and applications

remain more or less unchanged.

The main focuses today are on safety, effi ciency, quality, costs of design

and construction and, of course, higher capacities.

The growing globalization of markets demands more investigation of

transportability and constructability, which adds additional levels of com-

plexity to the execution of materials handling projects.

In some areas of the world, original equipment manufacturers (OEM)

and machine designers face issues with some business models applied,

which involve more and more engineering companies defi ning materials

handling machines and processes up to the last bolt and nut. One might

claim, on the one hand, this does not do any good for materials handling

development, invention or creativity but, on the other hand, it does allow

certain market segments to standardize and plan more effi ciently with the

existing designs.

However, the question remains how the industry can improve time-lines,

costs, and also the safety and quality of materials handling plants.


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Coal handling along the supply chain 657


20.1.1 Coal fl ow sheet

A typical coal (process) fl ow sheet involves a series of processing equip-

ment, materials handling equipment and auxiliary equipment, e.g. sampling

plants, dedusting units, utility systems, and others (Fig. 20.1). The materials handling equipment is used to link processes but also to

link different machinery and, as such, is an integral part of plant/process

planning (Fig. 20.2).

Whereas it is extremely important to design processing equipment cor-

rectly, it is just as important to consider an optimized materials handling

plant in order to avoid material segregation, deterioration of raw material

or fi nished product, double handling of materials, improvement on overall

amount of materials and structural steel used, etc.

In short, the right selection of stackers and reclaimers, together with belt

conveyors, loading and unloading machinery, and auxiliary equipment is

just as important, and defi nitely price- and quality-driving as the defi nition

of the right process choices and defi nitions.

The outline below will give some ideas and pre-selection criteria for

choosing the right approaches for coal handling plants in different market

segments.

20.2 Conveying

In general, conveying systems connect process or materials handling

machines, and are widely used in the industry. An intelligent connection

and combination of different technologies available in the market will allow

defi ning the best possible solution for the respective application.

A very good overview concerning belt conveying developments and

design features is given in Chapter 19. Different types of conveying equip-

ment with some typical applications are also mentioned in other chapters.

20.2.1 In-plant conveyors

In-plant conveyors are widely used in all coal applications, with belt widths

ranging from 400 up to 2500 mm (and wider) depending on application and

capacities.

Predominant calculation methods are included in CEMA and DIN

standards.

Typical applications can be found in mines, preparation plants, port facil-

ities, etc. with capacities starting from a few hundred tons per hour to high

export rates of ten to fi fteen thousand tons per hour.

658 The coal handbook


As for all industries and markets, the right application of norms, stan-

dards and regulations under actual side and site conditions is the key to

a successful design, especially in belt conveyor design, where perhaps,

much too often, a ‘cut-copy-paste design’ is adopted, and different tem-

perature levels, material fl ow characteristics, or changed process require-

ments are often overlooked. It is also much too often the case that the

industry has to refurbish plants, for which crucial aspects such as safety

assurance, accessibility, maintainability, etc. were neglected in the origi-

nal design.

With the existing expertise and experience in belt conveyor and transfer

chute design, designers are able to produce very good belt conveying sys-

tems; but these will still always have to be re-checked and re-validated, to

ensure that the right level of knowledge is applied.

20.2.2 Overland conveyors

In general, the requirements for overland conveyors and conveyor systems

grow with the expanding materials handling capacities, loading times and

connectivity when compared with those of road haulage using trucks.

New technology developments, such as intermediate drives, higher belt

qualities, low friction idler rollers, more effi cient electrical and control sys-

tem support, and combinations with curved belt/pipe conveyors, can also

make overland conveying systems more and more viable in comparison

with other means of transportation.

Examples of overland conveying systems of 100 km and more already

exist, and many have worked for several years.

One of the biggest challenges for designers is the integration of new tech-

nologies with safety and also environmental requirements. The biggest ques-

tion is how to merge industrial conveyor design with architectural design to

avoid further ‘pollution’ of our already stretched environment.

Overland conveyors are dealt with in further detail in Chapter 19.

20.2.3 Pipe conveyors

Pipe conveyors were developed in the late 1970s and have since been

further improved. Today, the pipe conveyor is a proven technology with

many applications all over the world. The main reason to think ‘outside

the box’ of conventional conveying is that green-fi eld and brown-fi eld

coal plants often require special applications in extreme fi eld conditions,

i.e., in congested existing industrial facilities, and always in alignment

with health, safety and environment (HSE) requirements and other

regulations.



The pipe conveyor technology comes into play when some of the follow-

ing questions are asked:

Can transfer towers be avoided?

Are there special requirements concerning environmental protection,

e.g. protected marshland with special fauna and fl ora?

Are steep inclines necessary to reach high/low points over the shortest

possible distances?

Are 3D curves necessary?

Is there a congested existing facility between the two machines/process

areas requiring connection?

Can material spillage from the lower strand be avoided and with it the

maintenance and cleaning activities along the conveying route?

Is there a serious space constraint?

The pipe conveyor principle:

The heart of the pipe conveyor is a fl exible rubber belt that forms a pipe/

tubular shape during transportation. In the material loading area, the con-

veying belt is still open. The material is charged in the same way as with

a conventional belt conveyor. Once the material is loaded, special devices

close the belt, securely enclosing the material within the formed pipe. For

the entire conveying line, the belt forms a sealed pipe. Thus, the content is

protected against external infl uences, while the environment is protected

against any potential material losses. At the end of the conveying line, and

before the discharge point, the belt opens on its own, forms a troughed belt

conveyor, and the material is discharged. The belt then closes again so that

on the way back, it is also rolled in a tubular shape with the ‘dirty’ side

inside, eliminating the risk of contaminating the conveyor line with spilled

material (Fig. 20.3).

Along the whole conveying line, the tubular belt is guided by idlers that

are arranged in a hexagonal shape, and is able to negotiate curves in any

direction. The curves can be horizontal, vertical, or a combination of both,

with a minimum radius of 300 or 500 times the tube diameter for fabric or

steel cord belts, respectively. (These minimum radii may vary depending on

the application, the belt material, the length of the conveyor, etc.)

This geometry allows a pipe conveyor to be installed with a multitude of

curves in place of a network of conventional conveyors and the associated

transfer points. The resulting elimination of transfer stations reduces the

need for additional pulleys, chutes, dust collection or dust suppression sys-

tems, electrical power supply equipment, and foundations. Fewer material

transfers also mean minimized material degradation. Further, the exclusion

of transfer stations translates into an elimination of the associated mainte-

nance requirements.



With lengths of 10 km and more without transfer stations, pipe conveyors

are easily able to handle not only long distances but also problematic topo-

graphical areas (Fig. 20.4).

Thus, pipe conveyors can transport bulk materials dust-free over roads,

tracks, waterways or open seas, through existing plants, over public streets,

in environmentally protected zones. A special design of the idlers minimizes

noise emissions so that pipe conveyors can be operated even in close prox-

imity to residential areas.

The pipe conveyor can also negotiate steep angles of inclination. The

enclosed round cross-section of the pipe increases the surface contact

between the material and the belt, allowing a 50% increase in the angle of

incline to about 30 ° . With these steeper incline angles, the elevated run of

the pipe conveyor may become shorter. A pipe conveyor having the same

Materialloading

Closedpipe

Return belt alsoforms closed pipe

Material discharge

20.3 Pipe conveyor principle.

20.4 Pipe conveyor in diffi cult terrain.



conveying capacity as a conventional belt conveyor occupies about only

65% of the space required by a conventional belt conveyor. This is espe-

cially interesting for areas with limited space, e.g. tunnel or mining appli-

cations, as well as for installations in existing plants where pipe conveyors

can wind easily around buildings, across roadways, other transportation

lines, etc.

As a result of customized designs, even the most complex applications can

be incorporated in a pipe conveyor system:

Multiple feed points can be integrated along the conveying line.

Reversible designs, a pipe conveyor can work as a two-way-system (see

Fig. 20.5).

On steep downhill grades, pipe conveyors may be equipped to make use

of the elevation drop to generate electrical power.

With a movable head station pulled by a crawler, the discharging station

can be designed to be fl exible within a certain radius.

Special arrangements of the pipe conveyor lines above or alongside each

other allow the installation of several pipe conveyors in a minimum

of space.

As there are no transfer stations along the conveying line, pipe convey-

ors allow simultaneous conveying on the feed and return belt even

over long distances. Equipped with a belt turning station at the dis-

charge point, an additional feed connection for conveying different

material on the return belt may be realized.

The pipe conveyor utilizes the same standard conveyor components as

a conventional belt conveyor. This means that no specially designed items

Return belt loading point Conventional discharge

Belt turning station

Closed pipe

Return belt discharge point

Feed belt loading point

Belt turning station

20.5 Simultaneous conveying in upper and lower strand.



are required. Standard idler rollers, pillow blocks, drives and other standard

components of conventional belt conveyors can be used.

And while pipe conveyor belting is different in its structure, there are a

number of manufacturers worldwide producing it.

The proven design, high handling capacities, and the availability of stan-

dard components familiar to customers promotes the pipe conveyor as an

acceptable alternative to, or a good combination with, conventional belt con-

veyors. Table 20.1 gives an overview on approximate handling capacities of

pipe conveyors.

20.2.4 Apron feeders and belt feeders

Apron and belt feeders are widely used in the industry and can be found for

a large variety of applications, e.g.:

Feed to and discharge from primary crushers;

Loading and unloading trucks and railcars;

Removing frozen materials from storage;

Feeding belt conveyors for metering weighing;

High-abrasion applications frequently found in reclaim circuits; and

Discharge/extraction of material from silos and stockpiles.

The design of belt and apron feeders is fairly standardized, and most of

the producing companies use pre-defi ned models and calculation methods

Table 20.1 Pipe conveyor capacities

Transport capacity of pipe conveyors

Coal Iron ore

Density (t/m 3 ) 0,8 2,4

Density (lb/ft 3 ) 50 150

Ø Pipe conveyor Velocity Capacity Capacity Capacity

in mm in inch in m/s in ft/min in m 3 /h in ft 3 /min in t/h in t/h

150 6 2,1 421 94 55 75 224

200 8 2,1 421 165 97 132 396

250 10 3,0 594 366 215 292 877

300 12 3,0 594 520 306 416 1248

350 14 3,0 594 716 421 573 1718

400 16 3,7 722 1131 665 904 2713

450 18 3,7 722 1430 841 1144 3432

500 20 3,7 722 1761 1036 1409 4227

550 22 4,5 890 2630 1547 2104 6312

600 24 4,5 890 3152 1854 2521 7564

650 26 4,5 890 3675 2162 2940 8820

700 28 5,4 1065 5103 3002 4083 12248



to get short delivery times with a low-cost approach. The main features of

the apron and belt feeders are:

Use of standard components (e.g. caterpillar chains/conveyor belts,

idlers, pulleys);

Very robust construction providing long life;

Variable or constant speed drives;

Reverse operation possible;

Handle wet sticky feed material; and

Have virtually no limitation to length.

Although the conveying devices are reasonably well defi ned and stan-

dardized, there is still room for improvement of the overall plant layout and

construction, e.g. crushing plant, silo discharge system, train unloading sys-

tem, etc. One of the most obvious ways to improve the overall design of such

systems is to develop a better understanding of the equipment itself. Today,

most OEMs want to be involved in the process of seeking the solution rather

than only the supply of the equipment. This will enable the market to make

use of the expertise of the equipment supplier and, at the same time, use

their knowledge base for developing a wider scope, including other aspects

such as silo design, hopper design, electrical and hydraulic issues, etc.

20.2.5 Drag chain conveyors

Drag chain conveyors are used for special transportation of smaller capaci-

ties. Drag chain conveyors work on the principle of a chain-and-fl ight com-

bination pulling a volume of material along. The chain is equipped with

different fl ights/paddles and drags the material from various charging points

to a number of discharging points.

The enclosed conveying device is used mainly for dusty, abrasive or hot

material and, as such, has only a very limited application in coal. However,

the power plant industry and other coal industry players ask for specialized

conveying systems, for which the very fl exible drag chain conveyor might be

a solution.

Horizontal, vertical or inclined solutions, with a possible explosion-proof

and dust-tight design, might be necessary for some special applications in

the coal industry.

20.2.6 Mobile and movable/shiftable conveyors (overburden, rejects)

Movable and/or mobile conveyors were mainly developed for transporting

overburden, reject, waste and tailings material.



These material handling components are specifi cally designed to enable

large heaps and piles of material to be developed with as much fl exibility

as possible, i.e. the equipment needs to be relocated frequently in order to

extend piles and storage areas (Fig. 20.6).

These material handling systems receive the material from process plants

and convey and distribute via the following options:

standard belt conveyors;

pipe conveyors;

skid-mounted conveyors;

extendable conveyors;

crawler-mounted conveyors;

stackers; and

spreaders.

For a long time movable conveyors were planned to be skid-mounted, and

the shifting of belts and drive stations had to be done with mobile equip-

ment and operational personnel.

Latest developments have promoted fully automated and crawler-

mounted stacking systems. For some areas, especially in tailings systems,

these systems can be combined with the appropriate fi ltration systems in

order to improve on the overall water usage for plants.

20.6 Tailings and overburden stacking system.



All over the world, reduced water requirements, tangible water-saving

issues, and environmental requirements lead to the requirement to develop

new materials handling systems for the tailings/waste management in mines

and processing plants.

The technology behind the mobile stacking conveyors and crawler-

mounted stackers is well proven, operating at up to more than 12 000 tph. It

is again a question of using technologies developed for other industries in

order to get a better outcome for the coal industry.

The combination of fi ltration technology and materials handling made a

so-called ‘dry stack tailings system’ an ideal choice for dry climate mining

operations. Along with reduced water requirements (achieved through pro-

cess water recycling and the virtual elimination of water losses through evap-

oration and/or seepage), other direct benefi ts include substantially smaller

tailings storage footprint and improved site rehabilitation potential. In this

application, some form of mechanical dewatering device will be needed to

reduce the retained moisture content of the tailings to around 15%, giving

the tailings a handleable consistency. The tailings material could then be

delivered to the designated storage area by conveyor and dispersed from

the mobile stacking conveyor. An area 2 km × 2 km (4 km 2 ) has been allo-

cated for tailings storage. By comparison, if the more traditional pond stor-

age system was to be utilized, an equivalent area of around 52 km 2 would be

required to store the tailings in this project. In many cases, especially when

the clay content of the tailings is low, this form of disposal is both feasible

and economical.

Constructed of space frame truss sections, the system is mounted on

crawler tracks that level and move individually to maintain the required

levelling and alignment as material is continuously stacked. These systems

are fully automatic and controlled by a global positioning system (GPS).

Various ‘sweeps’ and layers are gradually built up, sometimes up to 90 m in

height. Further reasons for selecting such a relatively new system are the

environmental possibilities for future reclamation and revegetation.

In short, the engineering expertise and knowledge from other industries

will enable the coal industry to create fully automated machines, which will

improve operational effi ciency, be environmentally friendlier, and involve

minimal manpower.

20.2.7 High-angle conveyors

The coal industry increasingly demands a wide variety of standard, mobile,

movable conveyors, crushing stations, and also special belt conveyors such

as high-angle conveyors. Engineers usually begin by comparing different

technical solutions, e.g. truck transportation vs belt conveying. Specialized



options, such as in-pit-crushing and conveying (IPCC) technology, seek ways

of optimizing the mining approach. One of the key questions, when chang-

ing the mining approach from predominantly shovel-truck operation to a

conveying operation, is how to get the material out of the pit in the shortest

possible path. One solution is to use a high-angle conveyor, which can be

designed to be much steeper than a conventional troughed belt conveyor.

Different technologies are still emerging and will soon add value to the

mine operations. Depending on the mine planning, available ramps, high-

wall angles and other conditions, a number of options are available, includ-

ing the sandwich belt, variants of the pipe conveyor (described earlier), or a

series of ‘grasshopper’ type conveyors, etc.

20.3 Coal storage

Some form of storage is usually needed for various reasons between two

connected processes. The key is to select the correct storage and the right

size for the application.

The tendency has often been to opt for a previous ‘design’ rather than

to design for the specifi ed needs. Since the different applications are never

exactly the same the tailored approach is recommended and some very

basic questions include the following:

Why do we need storage?

Disconnection of mine and process, or vice versa

Compensation of shut-down times

Buffer storage for material delivery (e.g. ship, truck, train)

Blending of coal

Improvement of material handling and control

Improvement of process times

What are the parameters for the right storage selection?

Environmental and climatic condition

Future up-grading requirements

Blending requirements

Blending method

Segregation method (Processing each raw material in separate stock-

piles)

Combined method (Mixing of two or more raw materials in the same

stockpile)

Raw material properties

Enlargement capability

Available space – area



Layout possibilities

Open/closed store

Stacking and reclaiming at the same time

What is the right size of storage?

Depending on the longest dead time of mine operation

Based on the target standard deviation of the raw material

Depending on usage of storage facility

Depending on how many different qualities/types of material need to be

stored separately

Some industries use a ‘rule of thumb’ approach, e.g., 15–30 days of coal

consumption in process

Depending on precedent and following processes.

All these questions are very basic, although still needing to be taken into

account. However, answering these questions and evaluating them properly

can often create the need for very complex evaluation models to defi ne the

right storage approach.

20.3.1 Introduction to stacking

Similar to the approach in the previous section, some very basic theory needs

to be considered for selecting the right stacking equipment. Stacking is only

one component of material storage. The correct combination between stack-

ing and reclaiming is needed to get the required results for the application.

Stacking for conical stockpile: Stacking from a high point to form a conical pile.

Stacker is fi xed and cannot move in any direction.

Reclaiming is carried out by mobile equipment; or via underground

extraction by means of vibrating feeder, belt feeder, coal valves, etc.

Stacking for kidney-shaped stockpile: Stacking from a high point of discharge.

Stacker is pivoting around a fi xed point to form the kidney-shaped pile.

Reclaiming is carried out by mobile equipment, or underground extrac-

tion via vibrating feeder, belt feeder, coal valves, etc.

Chevron stacking (Fig. 20.7): Stacking into roof like layers with a travelling stacker.

The stacker is a luffi ng type, (raised and lowered) to reduce the dust

generation.



Yard cross-section during stacking is non-homogeneous due to segrega-

tion effects.

During reclaiming, homogenization can be achieved only if machines

capable of reclaiming across the whole cross-section, such as bucket

wheel machine, bridge type scrapers, bridge type bucket wheel, and

drum-type reclaimers, are used.

Windrow stacking (Fig. 20.8): Stacking in cells built up with a Chevron approach.

20.7 Chevron stacking.

20.8 Windrow stacking.



Using the same stacker as with the strata method (see later), i.e., by

means of luffi ng and slewing – or telescopic.

Good homogeneity of the stockyard cross-section.

Face reclaiming by bridge type bucket wheel machines, bridge type

scrapers or bucket wheel reclaimers and drum reclaimers.

A longer boom is necessary to reach across the entire stockpile width.

Best material homogenization is achieved during stacking, avoiding

segregation.

Strata stacking (Fig. 20.9): Stacking in layers with a travelling stacker.

Stacker is a luffi ng, slewable or telescopic type.

Reclaiming is via side or portal scraper types.

Cone-shell stacking (Fig. 20.10): Stacking in shapes of cone shells with a travelling stacker.

Depending on requirements, a luffi ng, or slewable stacker is necessary.

Reclaiming is usually from the side or the front.

Chevron stacking (Fig. 20.11): Stacking with Chevron method is a combination of cone-shell and

Chevron, applied to a circular stockpile.

20.9 Strata stacking.



Stacking in sections, or governed by the angle of repose; after a cone has

been built, travelling back and forth moving in the direction of travel

(by a distance, corresponding to the fi rst cone).

Stacker must be capable of luffi ng and slewable.

At a continuous operation, a good homogeneous stockyard can be

achieved.

Reclaiming is usually done with bridge type scrapers and bridge type

bucket wheel reclaimers.

All these different stacking methods (and combinations of them)

result in various stockyards and also machine layouts and requirements

(Fig. 20.12).

20.10 Cone-shell stacking.

20.11 Chevron stacking.



The following stacking equipment is used in the coal market to form

these described stockyards. Depending on the type of stacking equip-

ment there are limitations when it comes to different stacking methods as

described above:

Mobile equipment (no further discussion in this chapter).

Belt conveyor (fi xed/slewing): The simplest stacking equipment, after

the usage of mobile equipment, is a belt conveyor which is fi xed and

forms a cone pile.

Overhead gantry belt conveyor with tripper cars: a longitudinal pile is

formed with a tripper car chute or a conveyor belt distributing the

stacked material to one or both sides of the stacking belt (Fig. 20.13).

fi xed (slewing) stackers;

travelling (slewing, luffi ng) stackers on rails; and

travelling (slewing, luffi ng) stackers on crawlers.

The choice of right stacking equipment requires detailed investigation

of capacity, norms, conditions, requirements, etc. Unfortunately, some sup-

pliers may opt for employing machine design parameters that are copied,

or re-used from earlier applications. This general development in machine

design will lead to non-optimal solutions and probably unnecessarily higher

operational costs in the long term. This issue needs to be critically reviewed,

especially under stretched and diffi cult economic situations (Fig. 20.14).

Triangular-parallel Triangular-in-line

Trapezoidal-parallel Trapezoidal-in-line

Circular

20.12 Stockyard arrangements.



20.3.2 Bucket wheel machines

Bucket wheel reclaimers, or combined bucket wheel stacker reclaimers, are

used for high capacity stacking and reclaiming in coal applications.

The main types of bucket wheel reclaimers can be defi ned as follows:

Boom type bucket wheel reclaimer (and combined stacker/reclaimer)

Pylon design

Pantograph design

C-frame design

Bridge type bucket wheel reclaimer

Single bucket wheel bridge type reclaimer

Double bucket wheel bridge type reclaimer

Bridge type barrel reclaimer

20.13 Stockyard with tripper car stacking.

20.14 Coal stackyard with stacker and reclaimer.



Depending on the application, the different machines have their pros and

cons. In coal applications the boom type machines are most common and

reclaim (and stacking) capacities range from a few hundred tons per hour

up to 10 000–15 000 tons per hour.

The boom type bucket wheel reclaimer consists of a vertically mounted

rotating bucket wheel mounted at the end of a slewing and luffi ng boom.

The reclaiming is done by a combination of slewing, travelling, and turning

of the bucket wheel. The reclaim capacity is defi ned by the speed of travel,

slewing, cutting speeds, cutting depth, and size of the buckets and bucket

wheel. Several benches are taken into account for the reclaiming function,

and the determination of the average reclaiming capacity must be properly

evaluated to determine the maximum reclaim rate requirement and with

that the necessary sizing of subsequent materials handling equipment.

The blending capability of the material is limited and, as previously stated,

will also depend on the stacking method.

Boom type bucket wheel reclaimers can achieve the highest reclaim rates,

can be used for two parallel piles, and can also be built as combined machines

with stacking and reclaiming mode combined in one machine (Fig. 20.15).

Similar to scraper reclaimers, the bucket wheel machines can be fully

automated, but the automation required is slightly more complicated due to

the more complex combination of machine movements.

A full discussion of the design of bucket wheel reclaimers is not possible

in the framework of this chapter; it must suffi ce to mention two of the main

and basic design decisions that must be made. Tables 20.2 and 20.3 show the

pros and cons of the choice of different pylon and bucket wheel designs.

20.15 Boom type bucket wheel reclaimer.



Bridge type bucket wheel reclaimers and barrel reclaimers represent

an alternative to a front-face reclaiming machine with scraper reclaimer.

In very simple terms, the reclaim capacity is reached by a combination of

rotating speed of the wheel or barrel, combined with the travel speed. For

the bridge type bucket wheel reclaimer the activation of the material over

the full face is done in a similar way as for the bridge type scraper reclaimer.

The barrel reclaimers reclaim at the full face of the pile and have by far the

best blending effect (Fig. 20.17).

20.3.3 Scraper reclaimer

The scraper reclaimer machines can in general be subdivided into front fac-

ing reclaimers and side scrapers.

Portal scraper reclaimers consist of a boom with scraper blades suspended

from an A-frame which travels on rails along a stockpile. The scraper boom

is equipped with sprockets pulling the reclaim chain around drive, bend and

tail sprocket. Scraper blades are attached to the chain and ‘scrape’ the coal

towards the reclaim conveyor. Most of the portal scrapers in the coal indus-

try will have a bent chain to transport the coal from the bottom of the pile

up to a discharge point above the reclaim belt conveyor. Other industries,

e.g. the cement industry, would use an expensive concrete table, over which

the material is dropped onto the belt conveyor. This eliminates the need for

the chain to be bent but, as stated earlier, it is a costly exercise when it comes

to the construction of necessary civil works.

The scraper boom is lowered after each traversing travel and, with that,

cuts into the pile as it reclaims the coal.

Table 20.2 Bucket wheel reclaimer design 1

Type of design Advantages Disadvantages

Pylon support

(Ballast moves

with BW boom)

Light weight design

No bending moments on

pylon

Low centre of gravity

No space for loop car, not

usable for combined

machines

C-Type (with

clearance for

Loop Car)

Free access for loop car

and bypass

Large shifting of centre of

gravity during luffi ng

More heavy due to bending

moments on pylon

Pantographic

design

Low shifting of centre of

gravity

Cost savings on ball

bearing, lower car and

travel drives

More expensive due to

additional pivot points

More sensitive against wind

and earthquake



Table 20.3 Bucket wheel reclaimer design 2

a) Cell-less bucket wheel

- Most common design

- Better discharge conditions

- Higher cutting speed

- Requires inner ring chute

b) Cell bucket wheel

- For special use only

- Less capacity

- Less maximum cutting speed

- Not for sticky material

c) Semi-cell bucket wheel

X

X

X

(a)

(b)

(c)

20.16 Bucket wheel reclaimer designs. (a) Cell-less bucket wheel,

(b) cell bucket wheel and (c) semi-cell bucket wheel.



The portal reclaimer will not have any blending effect if the stacking

method is cone-shell. With the strata method, a certain but very limited

blending effect for the coal can be achieved.

The portal scraper reclaimer gives a huge amount of fl exibility to the

operations since the machine can travel to any point of the pile and is ‘not

stuck’ or trapped in the centre of the pile. The portal scraper operation can

be fully automated and easily combined with a stockpile management sys-

tem (Fig. 20.18).

The semiportal reclaimer and side scraper operate on the same principle

as described previously: they reclaim the material from the side and can

travel along the pile to any point at any time. Semi-portals and side scrapers

are normally used for smaller capacities. They are usually lower in initial

investment for the machine itself, but additional costs might be created by

structural additions for buildings and supporting walls.

When considering a need for the greatest degree of homogenization

the best option is to look at front-face reclaimers. This group of machines

includes bridge type scraper reclaimers reclaiming material at the front face

and foot of the pile on the whole width of the pile. The material is either free

fl owing towards the base of the pile or is activated by means of rakes (full

face, half face, active rakes or small scrapers). The material is reclaimed onto

a reclaim conveyor.

The scraper chain with the attached scraper blades is pulled around

sprockets and is suspended underneath a lattice girder or box-type bridge.

Travel drives on the pendulum and the fi xed side move the machine dur-

ing reclaiming operation and relocation.

20.17 Double bucket wheel bridge type reclaimer.



Bridge reclaimers are used in longitudinal and circular stockyards.

Their main advantage is the mixing or blending of the material, whereas

the main disadvantage is that the machine is trapped in between two piles

(Fig. 20.19).

20.3.4 Special applications (silos, screw reclaimer)

Other alternative and innovative approaches need to be considered for

some applications within the coal industry, especially in some specifi c loca-

tions; for example, built-up areas and in certain areas of the world, e.g. very

cold climates.

One example is silo storage for coal.

The main criteria in deciding whether to use a silo form of storage are:

Space and capacity considerations. Particularly for restricted areas, the

volume-to-area storage factor is of major importance. Silos are the

most compact form compared to covered storage piles, whether circu-

lar or rectangular.

Environmental considerations, dust in particular.

Cold climates dust emission, waste water issues, etc., which have become

decisive factors in obtaining permits.

Safety and fi re considerations. Silo storage, by its confi guration, mini-

mizes the intrusion of oxygen in the stored coal mass; the tight

20.18 Portal scraper with two reclaim booms.



packing reduces the potential for possible fi res. In a situation where

self-heating is discovered by carbon monoxide or methane (CO/

CH 4 ) detection at an early stage, effective measures can be taken; if

necessary, it is even possible to make the silo fully inert by nitrogen

purging.

High degree of automation. Storage silos with a mechanical fi lling and

reclaim system can be remotely controlled. An online blending facility

can also be included through controlled reclaiming from two or more

silos simultaneously.

The silo system for coal storage consists of a concrete slip-formed silo

shell, ranging from 30 up to 50 m in diameter, with a storage height of 30–50

m. The silo is mounted on a concrete foundation that includes a concrete

reclaim tunnel, and is covered by a structural steel roof, which supports the

infeed conveyor that then discharges the coal into the silo. Unlike conven-

tional silo designs with a number of draw-off points with vibro- or other

types of feeders, the Euro-type silos have a stacker/reclaimer arrangement

inside the silo, which is further explained below (Fig. 20.20).

The silo receives the coal via a telescopic chute supported by the

upper structural ring bearing. The upper slewing bridge is supported by a

20.19 Bridge type scraper reclaimer.



silo-ridge-mounted circumferential crane track. The upper bridge also con-

tains the electrical equipment, the slip-ring assembly with its electrical and

air connection, the slewing drive wheel assemblies, and the winches that

support and operate the screw reclaimer frame.

The screw reclaimer frame is suspended from the upper bridge by steel

cables and contains the main twin screw system and the lower section of

the telescopic chute. The frame is accessed by a motorized cable-suspended

personnel cage.

The coal is discharged via the infeed conveyor into the telescopic chute

and reaches the screw reclaimer frame on the coal-pile surface. The two

main parallel screw conveyors, when operating in stacking mode, convey

and distribute the material over the entire area of the silo. The lower frame

is guided along the silo wall by horizontally and vertically mounted wheels.

After each complete rotation, the screw reclaimer frame is raised by the

winches to fi ll the silo, layer by layer, until the coal reaches its maximum

level or when reclaiming commences. The reclaiming capacity may vary up

to 1500 tons per hour.

Each silo has a redundant system of vibrating reclaimers. By withdrawing

the coal from the bottom of the silo, a core fl ow is established. The two screw

reclaimers located on the surface of the coal level start reverse rotation, thus

directing the fl ow of the coal towards the centre of the silo, continuously

feeding towards the middle outlet with vibrating feeders.

This technology is installed and has proven its worth in various places in

the world, including several coal installations.

20.20 Inside view of coal storage silo, EuroSilo.



20.4 Shiploading/unloading and trainloading/unloading

Loading and unloading activities are an important link between different

means of transportation of process areas. In the following paragraphs the

shiploading and – unloading as well as the train loading is looked at.

20.4.1 Shiploading

There is a huge variety of shiploading equipment available, and the follow-

ing list includes most of the more common.

A-frame shiploaders (travelling, luffi ng);

Slewing shiploader (travelling, slewing, luffi ng, telescopic);

Fixed type shiploaders (slewing, telescopic);

Gantry type shiploaders;

Quadrant and dual quadrant shiploaders; and

Mobile shiploaders.

The last three of these are not described further in this chapter, but

numerous other publications offer more details.

The A-frame type shiploader mainly consists of:

the tripper car;

the A-frame type portal/gantry;

the luffi ng loading boom with extendable belt conveyor;

the pendulum and fi xed side with travel drive;

the hoist system; and

all electrical and hydraulic equipment.

The shiploader is a travelling and luffi ng machine with a rail travel mecha-

nism and rope winch luffi ng. The coal is received via the jetty belt conveyor,

from which the connected tripper car transfers the coal onto the boom belt

conveyor of the shiploader. The shuttle extends the boom outreach to cover

the complete hatch width (Fig. 20.21).

Via an optional telescopic tubular discharge spout, the coal can be distrib-

uted into the area of the ship’s hold.

The slewing type shiploader mainly consists of

the tripper car;

the travel drive;

the boom with boom belt conveyor;

the luffi ng system;



the slewing system;

the discharge chute; and

the electrical equipment.

The coal is lifted up and discharged to the boom conveyor of the ship-

loader by a tripper car. From there it is conveyed towards the discharge

chute for loading the ship. Based on the loading level of the ship or the

tides (low, high), the boom height can be adjusted by the operator. With the

extendable boom design and the slewing and travel mechanism, the ship’s

hatches can be reached without moving the ship.

The fi xed, slewing type shiploader mainly consists of (Fig. 20.22)

the fi xed supporting pylon;

the boom with boom belt conveyor;

the slewing system;

the discharge chute; and

the electrical equipment.

The coal is discharged from a belt conveyor onto the boom belt and from

there is loaded into small ships or barges. A discharge chute can be attached

to extendable boom conveyors, to allow dust-free loading (Fig. 20.23).

General discussion concerning the right selection of shiploaders

The choice of the right shiploader for the respective coal application is mainly

determined by performance parameters (outreach, throughput rate, utiliza-

tion, design life, etc.), but also needs to take into account future expansion

20.21 A-frame type shiploader.



plans, new ship sizes, and any other changes in the business approach. The

right choice of shiploader always goes along with the specifi cation of the

largest ships to be loaded. In all cases, the coverage of ship hatches should

be an important factor in determining the type of shiploader. The choice of

shiploader type will also defi ne the approach to berth design, and can dra-

matically affect associated costs.

For example: compared to a long-travelling A-frame shiploader, the use

of radial loaders or linear loaders can lead to a reduction in berth length.

20.22 Shiploader (travelling, slewing, luffi ng, telescopic).

20.23 Fixed type barge shiploader.



Both linear and radial shiploaders pivot above a central point, the former

having a longitudinal runway beam adjacent to the berth, and the latter hav-

ing a quadrant beam on a radius.

A variation of the A-frame long-travelling shiploader is the long-travelling

slewing shiploader. This type of loader has the advantage that it requires a

shorter wharf rail length, as the shiploader can slew to cover the end bow

and stern hatches. Ships can also be loaded on both sides of the berth, allow-

ing for layout effi ciencies.

Bridge shiploaders may be long-travelling, radial or linear types. These

shiploaders tend to be large and relatively heavy compared to A-frame type

and portal slewing types.

In general, the right choice of shiploading activity is dependent on a series

of capital cost expenditure (CAPEX) and operating cost (OPEX) evalua-

tions, and the project optimization will necessitate an intensive comparison

of different possibilities.

20.4.2 Ship-unloading

Continuous unloading

Continuous ship-unloaders are now increasingly accepted for the following

reasons:

higher unloading effi ciency;

easier operation, due to their automatic control;

lower operation and maintenance costs; and

greater environmental protection, especially with high capacity ship-

unloaders.

Looking at continuous unloading systems, there are three main systems

to be evaluated:

Chain-and-bucket elevator type;

Screw type unloader;

Pneumatic unloader (not further looked at in the framework of this

chapter); and

Continuous bucket wheel type barge unloaders (special application).

The chain-and-bucket elevator system mainly consists of (Fig. 20.24):

Digging foot with suspension;

Elevator leg;



Drive system with discharge chute;

Platform for the large scale slew bearing; and

Slew gear with slew bearing, tooth rim and a hydraulic drive unit.

The horizontal and vertical sections of the bucket elevator form an inte-

gral unit. The scooped material is conveyed directly, without additional

transfer, in the vertical direction. The whole leg is slewable by 360 ° ; by this,

the areas under the hatch wings are reached to effectively recover the mate-

rial nearby the walls of the hold and the bulkheads.

The screw type system mainly consists of

Gantry with rail drives – longitudinal dock motions.

Horizontal arm with slewing and luffi ng motion.

Vertical arm with pendulum motion.

Electrical cubicles – insulated and air-conditioned container.

Insulated housings for the hydraulic pump unit and electric motor.

20.24 Continuous bucket elevator type ship-unloader.



The vertical arm of the ship-unloader is equipped with a screw conveyor

that can reach into the holds of the different ship designs. The feeding device

at the lower part of the vertical screw feeds the material into the vertical

screw and conveys the material to a horizontal screw conveyor on the hori-

zontal arm. The material is then further conveyed through the central turret

to a gantry screw conveyor positioned on the gantry. From this conveyor the

material can be conveyed to the jetty belt conveyor. The jetty belt conveyor

is fi tted with a cover belt, and the transfer point from gantry conveyor to

jetty belt is operated through a belt lifter.

All transfer points should be fi tted with suffi cient dust removal systems

to ensure that no dust escapes from the system. The method of dust removal

is usually by fi lter bag type dust collectors situated at the transfer point for

belt conveyor.

The screw type ship-unloader can travel continuously along the quay rails

during the unloading operation (Fig. 20.25).

The bucket wheel type barge unloader consists of (Fig. 20.26):

Bucket wheel;

Bucket wheel boom;

Lateral belt conveyor; and

Portal for bucket wheel boom and belt conveyor.

20.25 Continuous screw type unloader.



The principle involves a (double) bucket wheel, assembled on a lower-

able boom. The bucket-wheels unload the coal from the barge and feed it

onto a belt conveyor. The bucket wheel boom can cover the width of the

barge by horizontal movement. The barge is pulled by a towing system, so

that all areas of the barge can be reached by the bucket wheel. Unloading

capacity of up to 4000 t/h of coal can be achieved.

Discontinuous unloading

There is a large range of different types of grab unloaders. In the framework

of this chapter, we will look at only those most commonly used for coal

unloading:

Gantry type ship-unloaders with integrated hopper;

Double-lever luffi ng cranes with integrated hopper; and

Level luffi ng cranes.

Gantry type ship-unloaders

Gantry type ship-unloaders are common in international ports, as their

design is particularly suitable for unloading bulk materials.

20.26 Bucket wheel type barge unloader.



Gantry cranes have straight booms, they are non-slewable and the grab

moves straight from the hatch of the ship to the hopper. Gantry cranes of

up to 85 t for ships up to 400 000 DWT are available in the market. An auto-

matic control system is provided for the grab to ensure precise positioning

in the hatch and on top of the hopper (Fig. 20.27).

Double-lever luffi ng cranes

Double-lever luffi ng cranes with integrated hoppers are mainly used for

dry bulk handling. The crane can also handle general cargo. The cranes with

integrated hoppers operate in luffi ng mode. The grab movements are similar

to those of gantry cranes. An automatic control system can be provided for

grab luffi ng. The double-lever luffi ng crane can slew and, therefore, is more

fl exible than the gantry unloader; however, it performs at lower operation

speeds. Slightly reduced capacities are compensated by multi-purpose func-

tions (Fig. 20.28).

Level luffi ng cranes

Cranes in this category, also known as multi-purpose cranes, are designed

for handling all kinds of material. These cranes can handle, apart from coal

and other bulk materials, scrap, boxes of general cargo, and containers using

hook, magnet, spreader or grab.

Variations often used in small ports are mobile cranes. Mobile cranes

operate independently of any rail system. The operator can position the

20.27 Gantry type grab ship-unloader.



crane wherever necessary to load or unload cargo or lift something. Once

the mobile crane is correctly positioned, it will perform similarly to rail-

mounted slewing cranes because the design of what is on top of the turning

platform is similar.

The travelling mechanism, however, is different. Rail-mounted slewing

cranes are bound to the rail track whereas mobile cranes travel freely. On

the other hand, rail-mounted cranes can be repositioned more accurately

and faster than mobile cranes.

The above-mentioned cranes are also used for offshore unloading or trans-

shipment, which is a typical operation for stevedoring companies without

their own quaysides. Also ships, which are too big to reach the quayside, can

be pre-unloaded (please also refer to Section 20.6.1). These ships have to be

pre-unloaded offshore to reduce the draft of the ship. Offshore cranes, also

named ‘fl oating cranes’, are generally used for unloading seagoing vessels and

20.28 Double-lever luffi ng grab type ship-unloader.



the loading of barges, and examples can be seen in Kalimantan, Indonesia,

and in Colombia and Venezuela in South America.

For all the above-mentioned types of discontinuous ship-unloaders, the

average ship-unloading capacity is between 60% and 65% of the free dig-

ging capacity, whereas the free digging capacity is a theoretical capacity and

is the only one which determines the real performance of a grab unloader

and, therefore, is essential for designing any such machine.

A summary and comparison of discontinuous ship-unloaders follows:

The gantry type ship-unloader is a high performance unloader designed

for grab operation only.

The double-lever luffi ng crane with integrated hopper is slightly lower

in capacity, but is designed mostly for grab operation and occasional

cargo handling.

Both the level luffi ng crane and the double-lever luffi ng crane with sep-

arate hoppers are medium performance grab unloaders, very fl exible

in hand ling cargo.

Table 20.4 Comparison of different type of ship-unloaders

Criteria Type of bulk unloader

Discontinuous

operation

Continuous operation

Grab Pneumatic Screw Bucket

elevator

Multiple material

properties

Very good Very negative Negative Very good

Operator skills

required

Negative Good Good Negative

Usable for ships

above 65

000DWT

Neutral Negative Neutral Very good

Usable for high

capacities

(above 2500tph)

Neutral Very

negative

Negative Very good

OPEX Neutral Negative Negative Neutral

Environmental

conditions

(e.g. Dust)

Negative/

neutral

Good Good Neutral

Power

consumption

Negative Very

negative

Negative Very good

Total weight Negative Very good Very good Very

negative

CAPEX Neutral Good Good Very

negative

Civil costs for jetty Neutral Very good Good Negative



Table 20.4 summarizes the main pros and cons of ship-unloaders. However,

it provides only general guidelines, and project-specifi c requirements will

always need to be discussed in detail before a confi dent selection can be

made.

20.4.3 Trainloading

Train load-out stations are the fi nal discharge point at the mine onwards to

further process facilities, power plants or port facilities. Typically, two sys-

tems are utilized: gravimetric (batch weigh) and volumetric (fl ood system).

Depending on the application and on the market segment the choice of

the system is predetermined. The coal industry typically uses gravimetric

(batch) loading (although there are some examples of alternatives) and the

iron ore industry typically uses volumetric loading (Fig. 20.29).

20.29 Train loading station.

Table 20.5 Main components for train loading stations

Volumetric system (fl ood) Gravimetric system (batch weigh)

• Input conveyor

• Structure

• Surge bin

• Loading gate

• Telescopic chute

• Control room

• Hydraulic systems

• Control equipment

• Input conveyor

• Structure

• Surge bin

• Surge bin gates (radial, clam and sliding)

• Weigh bin

• Weighing system (load cells)

• Weigh bin gate (radial, clam and sliding)

• Telescopic chute

• Control room



Table 20.6 Comparison batch loading versus volumetric loading

Criteria Superior

system

Critical

to mine

Critical

to rail

Comment

Capital cost V Yes No Volumetric systems are

signifi cantly cheaper due

to the simplicity of the

system.

Control of

loading

= Yes Yes Systems can use the same

loading chute design.

Consistency

of loading

= Yes Yes Systems can use the same

loading chute design.

Speed of

loading

V Yes Yes Volumetric systems can

load faster as they do not

need the time to load and

empty the weigh bin/fl ask.

Accuracy of

loading

G Yes Yes Batch weighing will ensure

greater accuracy and

handle changes in density

of material.

Ease of use V Yes No Less complexity in the

volumetric system and

easier to use and operate.

Criteria Superior

system

Critical

to

mine

Critical

to

rail

Comment

Level of

automation

= Yes No Same level of automation.

System safety V Yes Yes More complexity in the

gravimetric systems adds

more safety hazards and

more things that could

go wrong leading to a

higher safety risk both

for the operator and rail

operations.

Adapt to

process

changes

= Yes Yes Limited difference between

systems.

Operational

cost

V Yes No Volumetric system is subject

to less wear and has fewer

components thus less spar

quicker repair times.

Reliability –

due to

complexity

V Yes Yes Volumetric system is a far

simpler system and is thus

less likely to maintenance

issues. This will lead to

higher availability.

Criteria Superior

system

Critical

to

mine

Critical

to

rail

Comment.



The two above-mentioned systems are further described and com-

pared below to give a better understanding of their differences and

applications:

The predominant technology used in the coal in industry is batch loading,

mainly due to the ‘easy-to-handle’ and very economical technical approach.

20.5 Crushing stations

The coal coming from the mine (ROM) needs to be crushed to allow further

handling. Most of the time, coal is delivered by truck and consists of variable

lumps up to 1 m and more in size. In underground mines, the crushing sta-

tions are already installed underground to get the material to a conveyable

size (approximately <250 mm).

Most of the subsequent coal preparation requires coal sizes of <60 mm

or even smaller, depending on the process. As such, additional sizing sta-

tions need to be installed. The use of roll crushers or sizers is very common,

whereas rotary breakers are also still used in some applications, usually

where the differential hardness of coal and waste encourages this selection.

While it is necessary to crush the coal to a smaller top size, for most of the

processes it is also necessary to minimize the amount of fi nes generated,

which are more costly and less effi cient to process. Different coal handling

options will result in different levels of coal degradation, and this topic is

adequately covered in Chapter 9.

Criteria Superior

system

Critical

to mine

Critical

to rail

Comment

Reliability –

due to

wear

V Yes No Gravimetric will see greater

wear in the weigh bin/

fl ask.

Reliability –

due to

cyclic

loading

V Yes Yes Signifi cant cyclic loading

in gravimetric system

which will lead to more

downtime and shorter life

of the system.

Ease of repair V Yes Yes Volumetric systems are

less complex thus fewer

items to repair and easier

to solve if problems are

encountered leading to

less downtime.

Ease of

inspection

V Yes No Less complexity leads

to simple and short

inspections.

Table 20.6 Continued



The correct allocation of the crushing stations with the right choice of

crushing equipment plays a big role nowadays and the discussion about

IPCC is becoming of growing interest to mining companies seeking to

increase production capacities but reduce equipment fl eet size.

The question of mobility of the plant will now be discussed in relation to

the fully mobile sizing stations, whereas other ideas around fi xed or semi-

mobile crushing stations are covered in a subsequent section.

20.5.1 Fully mobile sizing station

In the large-scale fully mobile crushing station world (Fig. 20.30), only a

handful of machines have ever been commissioned with capacities that range

from 8000 to 12 000 mtph. These are very large machines, with capital costs

between 30 and 40 million USD. Within this group of machines, operational

success rates have tended to be poor. One signifi cant factor behind this low

success rate has to do with the current trend in chassis design. Traditionally,

all the equipment manufacturers have elected to design each station with

a single fi xed car body (generally retrofi tted from large rope shovels), sus-

pending the entire machine from a single point on a central slew bearing.

Note that only one other manufacturer has developed a multi-track system,

to try to improve stability, but still basically utilizes the single point machine

pivot on the slew bearing.

These machines have masses in the 1000–1500 tons range and utilize a

cantilevered discharge boom of about 25 m. Conversely, a couple of hun-

dred tons of steel and equipment in the form of an apron feeder and hopper

are cantilevered opposite the discharge boom – all suspended over one cen-

tral point. This requires some extreme engineering, with some major risks

associated. This cantilevered design is obviously not ideal when used in con-

junction with the world’s largest rope shovels dumping 100 tons of material

into the hopper from a height of 12 m, not to mention a hopper that already

has 300 tons of material in it. This has led manufacturers to design machines

that have a luffi ng style of apron feeder to rest the tail on the ground while

in operation. When the machine needs to be relocated (this can be as fre-

quently as every few hours), the operator needs to completely evacuate the

machine of any material, raise the apron feeder and hopper with very large

hydraulic cylinders, and relocate the machine to match the rope shovel’s

new location. This takes signifi cant time out of production, besides requir-

ing massive expenditure in the form of capital costs and in extra steel and

mechanicals to make this cantilever system all work together cohesively.

Only a few new companies have entered the mobile crushing arena with

some interesting new designs, but these are limited in their mobility aspect

because of the confi guration of the undercarriage. Geometry always plays a



major role when designing these stations. Rope shovels can load only hop-

pers that have a maximum height of around 8 m, as with any height above

that there is simply not enough shovel swing clearance. Compounding this

is the fact that each hopper needs to accommodate approximately three

shovel dipper volumes for needed surge capacity (300 tons). To keep the

hopper at a maximum of 8 m high and hopper walls at 65 ° –70 ° , the apron

feeder almost needs to sit on the ground to accommodate all this volumetri-

cally. With the apron feeder so low to the ground, this leaves almost no room

to install a crawler type suspension underneath.

In the meantime, the market has completed a working concept that will

accommodate the afore-mentioned design parameters, with the added ben-

efi t of full range mobility while supporting a fully loaded hopper. Moreover,

the loading rope shovel can directly load into the hopper without the aid

of hydraulic luffi ng and can follow the shovel path in real time. The design

incorporates a unique car body undercarriage that fully supports the apron

feeder concentrically with shovel loading. This rear car body also incorpo-

rates a unique universal joint suspension to allow the machine to negotiate

undulating terrain in all directions up to a maximum of 5% grade. Further,

the car body has the freedom of skid steering a full 360 ° . When combined

with a second conventional head car body located directly below the sizer

unit, complete mobility is achieved, doing so under operational mode. This

20.30 Mobile sizing stations; different concepts from different

suppliers.



gives the machine complete freedom to crawl in all directions, and even

to turn on all virtual radiuses, including pivoting the entire machine 360 °

about the station’s own centre. Included in this high degree of mobility is

the fact that the machine is inherently stable. This dramatically reduces

operational risk when moving a 1500 tons station from one bench level to

the next.

For this new design, the overall height and mass were minimized by bor-

rowing crawler technologies from the heavy lifting crane and crawler trans-

porter industry. These robust track designs are extremely height compact,

and not only minimize the overall machine height but also allow for the

shortest possible apron feeder design. This is important to note, because the

apron feeder can generally be one of the single-most power intensive units

on the station. Keeping its overall length to a minimum, as well as minimiz-

ing its installed power, is a high design priority. The advent of a compact

track system is a key driver in achieving this.

20.6 Auxiliaries

Material handling plants and systems require the machines to work together

in one process fl ow. For that reason it is necessary to also evaluate best pos-

sible solutions for additional or auxiliary equipment to work in combination

with the above described machines. Some areas are further outlined in the

following paragraphs.

20.6.1 Trans-shipment

The coal industry, both importing and exporting, sometimes requires trans-

shipment of coal from large seagoing coal vessels to smaller barges or vice

versa. This trans-shipment is mainly required in areas where only barge

access is possible, for example shallow sea waters or where a river leads to/

from a processing plant.

There are several ways of meeting this requirement. One example is

the way in which coal is imported to a power plant in Iskenderun, Turkey

(Figs 20.31 and 20.32).

Because the bay of Iskenderun is very shallow in front of the power plant,

a different solution is required to unload the seagoing coal vessels (Panamax

or Capsize up to 200 000 tons).

A trans-shipper was designed consisting of:

one catamaran with three grab cranes on top (30 000 t/day);

two self-unloading barges, each 10 000 tons load capacity;

two tug boats;



20.31 Trans-shipment equipment.

20.32 Self-unloading barges.



one service boat; and

three single-point mooring (SPM) buoys to keep the trans-shipper and

barges safe during adverse weather conditions.

Similar requirements for other facilities are required all over the world,

connecting process plants with sea/river transportation of coal. Again, it is

a challenging requirement for materials handling companies to choose the

right machinery and the right combination to fi nd the best outcome for the

different applications and requirements.

20.6.2 Dedusting and dust suppression

Dedusting and dust suppression are very important parts of the planning

of a materials handling plant. Not only will strict environmental rules and

regulations defi ne limits of emissions, but the rapidly expanding industry is

demanding an increasing environmental awareness, especially in areas of

rapid growth such as China, India, etc. Hence, a key focus is to avoid dust

emission as much as possible.

Dedusting units, such as fi lters, are a solution to extract dust from air in

transfer chutes, silos, hoppers, and loading and unloading stations. Filters

tend to be space consuming and also major power consumers, so an empha-

sis on good design is essential. Water using dust suppression systems are

being mainly used for:

Haul road dust suppression;

Dust generated during above ground mining and blasting;

Stockpile dust suppression;

Dust generated during and transferring, discharging, crushing and

processing;

Dust generated during dumping;

Conveyor belt and product transfer points;

Open area dust control methods; and

Underground traffi c generated dust control.

All of the above-mentioned dust suppression and extraction activities are

important, but at the same time consume water, wetting agents and polymer

binders (chemicals), machinery, power, space and manpower.

Therefore, an integrated engineering approach, involving all specialized

engineers from the outset, will allow technical changes to improve overall

CAPEX and OPEX of the plants, e.g. chute design with dust settlement

zones, different design of discharge and loading areas, avoiding truck traffi c

by using different technologies (e.g. belt conveyors), fogging systems instead

of water sprinklers, and many other solutions can be found to improve the

design of coal handling plants.



20.6.3 Defrosting of railway wagons

In cold climates, such as in Russia, China, Mongolia, Canada, USA and oth-

ers, a defrosting plant for railway wagons may become necessary to be able

to defrost and then unload the coal (Table 20.7).

Four main alternatives can be considered for the defrosting of railway

wagons:

Chemical pre-treatment on loading using freeze reduction chemicals;

Use of steam directly blown onto the wagons;

Use of steam directed into ducting work: the surface of the ducts is

heated and this surface heat is used for defrosting; and

Use of steam directed through a heat exchanger to heat the air.

Some form of infrared system.

20.6.4 Electrical and automation

Electrical and plant control systems are an integral part of all materials

hand ling machines and systems. It is important to understand the machine

and equipment philosophies to achieve the optimal solution for electrical

and automation scope. When it comes to plants and systems, the standardi-

zation, and ability to exchange is just as important as in-depth understand-

ing of the equipment itself.

Important issues for the selection of suppliers for electrical and automa-

tion are:

Using same interface across the plant;

Built-in process and machine knowledge;

Built-in trending of all available values;

Customized solution built with standard blocks;

Being able to understand trends and changes;

Logging of events and operator actions;

Effi cient alarm handling;

Simple and advanced reports;

Built-in device simulation; and

Easy remote support.

It is important to take an integrated approach when planning the electri-

cal and automation of a machine or plant, i.e. much too often a disjointed

approach is taken for bigger plants and the mechanical/structural part of

the plant is not planned together with the electrical and automation part.


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By applying new and smarter technologies, overall project costs can be low-

ered. The mechanical and electrical/automation teams need to coordinate

efforts exchange early on; even better, companies should combine these lev-

els of expertise in-house, to be able to incorporate developments and better

solutions.

Looking at automated materials handling solutions today, the minimum

that should be asked for is a coordinated electrical and mechanical design,

an individual machine control, central plant supervision, process optimiza-

tion and, fi nally, business reporting. Integrated systems with the described

functionalities will eliminate the human factor more and more, allow remote

control of plants and process, and lower costs through fully automated

equipment and plants.

It is worthwhile mentioning examples of fully automated materials han-

dling machinery, which will undoubtedly become widely used in the coming

years and will tie in with automated management systems (e.g. stockyard

management, and inventory and maintenance management systems).

Operator-less and remotely controlled operations are the key words in that

respect.

Stacker/reclaimer automated/operator-less system

This system allows for fully automatic no-operator operation of a stacker/

reclaimer in all common modes. A real-time terrain model (Fig. 20.33) makes

sure that the system can be effectively used without requiring unproductive

scan runs, and ensures a constantly high conveying performance. The high

conveying performance is available almost independently of external infl u-

ences 24/7. In particular, for storage areas working non-stop, it provides a

signifi cant potential of rationalization. Furthermore, by precise compliance

with limits defi ned, it reduces wear and tear of the equipment as well as

20.33 Image of real-time terrain stockyard model.



signifi cantly decreasing the probability of damage, through an in-built colli-

sion management system.

The described automated system for stockyard machines has proven per-

formance; tests have shown that throughput can be achieved equal to or

better than for manual operation. The operation can take place remotely,

from a central control room, and up to eight machines can be operated by

a single operator.

Similar developments can help in shiploading and unloading activities,

and features such as 3D laser scanning, automated positioning, and hatch

management (Fig. 20.34) will safely help to lower costs, and improve opera-

tional performance, quality and accuracy.

20.6.5 Sampling

In order to guarantee the quality of incoming and outgoing or export and

import streams, it is important to know the quality of the product trans-

ported. In addition, the correct adaptations of processes need a precise

knowledge of raw materials being fed into the process to achieve customer

requirements of the fi nished product.

Sampling is the extraction of a representative volume of predetermined

size from the main stream of material at predetermined intervals. In most

developed countries there are standards for coal and coke sampling. These

1600

Breite SektorLänge luke

SoilMasse

::

:

5.00 m67.00 m

2000 to

Breite SektorLänge luke

SoilMasse

::

:

5.00 m67.00 m

2000 to

2200

775

10150

Frete

Frete

875

775

675

575

475

3600

9550

1250

1150

1200

2100

3100

4100

5100

6100

7100

8550

20.34 Pre-set barge loading pattern for automatic barge loading.



standards defi ne the minimum sample mass acceptable and the minimum

number of samples to be taken from a consignment, together with other

requirements depending on the material being sampled. However, standards

do not exist for all materials and differ from industry to industry. Materials

handling and sampling companies, and their respective clients, should dis-

cuss requirements, conditions and objectives of sampling to achieve the

best outcome for a tailor-made design of the sampling plant. This discussion

needs to take place at an early planning stage of the plant, and needs to

involve adjacent equipment, such as belt conveyors, train loading/shipload-

ing, stockyard equipment, etc., in order to defi ne the correct interfaces and

battery limits.

For coal the following standards and conditions apply and need to be

agreed upon:

ASTM, ISO, BS;

Consignment mass/lot size (t);

Sample Increment (kg/inc);

Number of samples (per lot);

Unknown factors;

Required precision – increment variance/prep and testing variance;

System design and process; and

Agreement between system supplier, customer and end user.

In general, three types of samples are taken: chemical, moisture and

physical samples. With regard to the chemical sample, the smallest sam-

ple may be as little as 200 g, with a particle size of minus 150 micron. This

size is normally achieved after a multi-stage sample processing plant.

A moisture sample is taken at a point prior to crushing and, consequently,

of varying size, depending upon the particle size. A physical sample, on the

other hand, may be required for any number of tests, such as sieve analysis,

tumble test or shatter test. More details of the sampling aspects are covered

in Chapter 5.

Sampling systems are available as fi xed open and enclosed stations, or

as mobile sampling stations. Most systems today are planned as integrated

turnkey systems with a direct link to the plant control system.

Depending on the application online analysers are available as well, which

can perform the above-described analytical requirements in series.

Today, in most of the plants, fully automatic sampling (or online analysis)

is applied, and even fully automated laboratories are used after the mechan-

ical sampling to get a precise and up-to-date view of the quality of products.

This prompt reporting of quality changes can reduce the amount of defec-

tive product and lost revenue. Low quality production can often mean extra

costs as a result of reworking out-of-specifi cation material.



This technology is being used extensively in various industries but, espe-

cially, also in the coal industry, for power generation, shiploading and

unloading as well as in the steel industries.

By continuously checking products at various stages of the process and

transport points, sampling systems enable plant operators to produce appro-

priate quality statements, backed by analytical evidence.

Again, proper planning, in line with the planning of the overall materials

handling (and processing) plant, is key to a successful design, integration

and installation of a sampling system. Today, there are companies in the

market that provide this integrated planning approach, instead of just look-

ing at a separate ‘black-box’.

20.7 Conclusion

One of the biggest challenges for materials handling companies is to choose

the right machinery, and the correct plant systems, to fi nd the best outcomes

for the different applications and requirements. Integrating the design and

operational parameters is just as important as making use of all available

knowledge, experience and development. It has been proven that cross-

referencing between industries is helping to overcome technical issues and

problems the industries are facing every day.

The equipment and associated design requirements described in the

above chapters should encourage the mining companies to invent, test and

accept new designs and approaches to further improve the effi ciencies and

the cost profi les of the coal industry.

20.8 Bibliography Anders Paulsen (2003), Continuous and effi cient ship unloading and loading, paper

for ‘Proceedings Bulk India’.

Arne O. Nilsen, Paul P. Jacobsen, Gelnn R. Hopper (2003), Continual improve-

ment in marine structures and seaboard bulk materials handling design at the

Dalrymple Bay Coal Terminal

B. Kuesel (2003), The strongest conveyor belts between 1970 to 2003, paper for

‘Proceedings Bulk India’.

B. Velan (2003), Bulk terminal operations, paper for ‘Proceedings Bulk India’.

Christopher Duffy, Choosing the right ship loader for handling bulk materials, Dry

Bulk and Specialist Cargo Handling.

Detlef Kaross (2011), Isam automation for stockyard machines.

Frigate, New offshore ship loading facility concept in lightweight construction.

J. Staribacher (2003), The state of the art Pipe Conveyor, paper for ‘Proceedings

Bulk India’.

Jaap P.J. Ruijgrok, Succesful silostorage (Eurosilo).

M. Vishwanthan (2003), Features of continuous ship unloaders (bucket elevator

type), paper for ‘Proceedings Bulk India’.



Qi Zaiqiang, A comparison of different designs of bridge grab ship-unloaders, Dry

Bulk and Specialist Cargo Handling.

Rainer Borgemann, Ruediger-Wolf Bentjen, Succesful completion of 1320 MW coal-

fi red power plant Iskenderun.

Richard Morgan (2011), Bulk Materials Handling Berths, Paper and Technical

Article.

W. Mueller (2011), Comparison of international design codes to AS4324.1.

Walter Kueng (2011), Semi-mobile crushing plants.

Wolfgang Knappe (2003), Port cranes for bulk handling, paper for ‘Proceedings Bulk

India’.

the coal handbook: towards cleaner production || coal handling along the supply chain

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