To satisfy the insatiable energy demands of the emerging economies in China and India, the coal logistics chain

is having to up its game. From the mine to the power plant, the supply chain is striving to deliver the vast volumes of coal required at the right quality and in the right quantity, but most importantly at the right price, to remain competitive in a fast-moving global market.

Schade Lagertechnik of Germany (part of the Aumund Group since 2001), has over 60 years of experience

in the chain-scraper reclaimer business. The company responds to the demands of the market by continually refining its products and expanding the storage volume and reclaim rates to match its client’s needs. Schade has had several industry firsts, including the first twin boom scraper reclaimer, the largest (at that time) bridge reclaimers and the first and the largest circular storages. With its huge circular and longitudinal blending beds, the company has reinforced its position at the top of the market, working under the most arduous conditions for mining

operations and power utilities where continuous availability is paramount.

The fundamentals of opencast coal mining remain the same today as they did a century ago: overburden is removed and the coal is extracted and hauled to a central plant for crushing, screening and washing. The finished coal product is transported to consumers, sometimes on a different continent, by any combination of rail and ship. Over the years, unit labour and fuel costs have driven the development of ever-larger excavators and haul trucks, and thus intake and

Barry Woodbine, Schade Lagertechnik – Aumund Group, Germany, considers supply chain logistics from the mine

to the power plant.

A STURDY CHAIN

Pylon-design travelling boom stacker at

Dartbrook Coal in Australia, designed to create longitudinal strategic

stockpiles with a stacking rate of 2750 tph.

October 2012 | Reprinted from World Coal

storage facilities to maximise truck fleet utilisation. In parallel, driven by economies of scale, ship sizes have expanded with ore carriers now reaching up to 400,000 DWT capacity and coal shipments normally carried in capesize vessels of 120,000 – 180,000 DWT capacity or more. All of these factors put pressure on the coal preparation plant to receive and process large volumes of material, as well as on the logistics infrastructure, to deliver coal at high capacity to the export terminal and similarly from the ocean-going vessel (OGV) to the coal-fired power plant.

If the power plant is located inland, there are additional links in the logistic chain to tranship via barge or rail. These extra stages necessitate extra equipment into the total logistics package. In this situation, the coal would be discharged from the OGV

and transferred to longitudinal stockpiles where segregation of shipments may be achieved for subsequent blending. This is an ideal application for the new generation of high performance Schade portal scraper reclaimers.

Servicing the Chinese and Indian markets, both Australia and South Africa have seen considerable expansion in coal exports in recent years. This is driving demand for high-capacity centralised coal preparation plants able to deliver the quantities required at the export terminal to maintain existing and service new supply contracts. Schade is active in both markets and, in both cases, a similar approach was adopted by combining the output of several mines operating in close proximity to a central high performance preparation plant.

Performance at the minesite preparation plantThe Blackwater mine complex in Australia includes a single high performance centralised coal preparation plant supporting six major opencast mining operations. The plant uses a combination of heavy haul trucks, belly dumpers and eight triple side dumper rigs to bring the ROM coal from the mine to the preparation plant. The operation is owned by BHP Billiton Mitsubishi Alliance (BMA).

A range of coal qualities, including metallurgical coal and thermal coal for power plants, is exported from the mine to Japan, Asia, South America, Europe and the Middle East. Proven reserves are greater than 800 million t and the new preparation plant is designed to produce some 14 million tpa finished coal product.

Coal is delivered to one of three 600 t capacity intake hoppers, then fed from the hoppers using apron feeders through three stages of crushing. Here, it is reduced from a maximum of 1200 mm down to a typical size of <50 mm. The coal may be directed to a 60,000 t capacity blending stockpile, from which the coal is transferred to the washery and then to product stockpiles. Alternatively, using bifurcated chutes, the washery may be bypassed and the coal directed straight to the product stockpiles for stacking out, ready for reclaim to the batch weigh rapid train load-out facility, which is capable of loading 7000 t trains in 1.4 hours.

This new preparation plant replaces three older-style plants with a reduced operating cost/t handled and improved overall availability. Furthermore, a single high capacity preparation plant requires only one rail line, representing a significant reduction in both capital and operating cost requiring less rolling stock and locomotives.

With the cost of a 320 t Komatsu 930 haul truck now around US$ 5 million – with an operating cost to match – maximum truck utilisation is critical and therefore the intake and blending rate of the coal preparation plant must be sufficient to guarantee tip-and-run discharge at the intake hoppers with no delay and no queuing to tip. By tripling up the feeders and crushers, there are no bottlenecks at this point and therefore

A 60,000 t circular blending bed at Blackwater mine, Australia, provides a homogeneous output of coals delivered from six satellite mining operations.

Travelling, slewing and luffing boom stacker for creating layered “chevron”-style stockpiles for longitudinal blending bed at Anglo American’s Dawson coal mine in Australia.

Reprinted from World Coal | October 2012

the following conveyors – and particularly the stacker-reclaimer – is the critical point in the intake line.

Schade circular storages with radial and luffing stacker and bridge-style reclaimers provide the necessary blending of varying grades of coal received from different parts of the mine complex. In this case, the radial stacker has a design handling capacity of 2700 tph and the reclaimer operates at 2200 tph to feed the dual module washery. Operating with multiple

minesites with varying coal qualities, the ability to effectively blend the material at high capacity is critical to the operation of these larger centralised coal preparation plants. Using the radial and luffing boom stacker, a layered stockpile is generated automatically such that at any point along the stockpile a cross section would yield samples of coal from every source. Using the circular concept the output may be maintained without interruption, as the blending bed is continuously generated and recovered as the stacker and reclaimer work together around the central column.

Whether circular or longitudinal, the blending bed system operates principally in the same manner based on a radial or travelling boom stacker. The luffing facility allows the stockpile to be generated in layers from a low level, often by declining the stacker, up to the maximum height set by the peak inclined angle of the stacker boom and the width of the stockpile base combined with the material repose angle. By continually travelling and incrementally increasing the discharge height, the incoming grades of coal are spread along the stacking range. This enables maximum effective homogenisation when reclaimed using a bridge reclaimer with reciprocating harrows.

This is a different concept to the strategic longitudinal stockpile, in which the coal is stacked out in discrete sections to be recovered by a portal reclaimer working along the pile between selected fixed points. In a larger preparation plant that handles varying coal types, including metallurgical and thermal coals, the longitudinal stockpile allows segregation of these varying coal specifications. In this situation, the Schade twin boom portal reclaimer is able to recover some 4000 tph per unit, which is more than sufficient to feed the rapid train load-out.

Centralised high performance coal preparation is also a feature of Anglo American’s Lake Lindsay Capcoal complex in Australia, where the coal is brought to the preparation plant from three existing mining sources, as well as from the Lake Lindsay lease, by a combination of truck and conveyor haulage. The new preparation plant,

along with the existing facilities, brings the total capacity of the complex to 9 million tpa of coal product. Using conveyor haulage implies crushing and screening at the minesite, combining the flexibility of truck haulage to the in-pit crusher and the operational economies of conveyor haulage to the central preparation plant and rapid train load-out station.

For the Lake Lindsay project, Schade supplied longitudinal blending beds using a travelling luffing boom stacker and bridge type reclaimers with dual harrows that enable reclaim from both travel directions with a rated handling capacity of 1000 tph. The project included two portal reclaimers for the finished product coal, each rated at 3300 tph, to feed the rapid train load-out station in the same manner as at the BMA facility.

The Douglas-Middelburg Optimisation (DMO) project in South Africa provides for the economic exploitation of reserves across the Douglas and Middelburg Mine Services (MMS) coal mines and development of new mining, with ROM coal being fed into a new 14 million tpa coal processing plant similar to the centralised preparation plants in Australia. This new project incorporates a Schade circular storage system to receive and blend the various coals at a handling rate of 2300 tph. After washing and removal of general impurities, the coal product is stacked out using a travelling, radial and luffing boom stacker. In this operation, a large twin boom style portal reclaimer will be employed with a continuous handling rate of 3000 tph to recover the coal to a rapid train loading station in the same manner as previously described.

Performance at the power plant and import terminalOnce the coal is afloat the miner may have fulfilled their contract but Schade remains involved, as the same factors that drive the minesites to ever higher levels of plant performance also drive the importer and utility operator to achieve maximum ship discharge rates to minimise the vessel time in port. Where the vessels are discharged by continuous ship unloader (CSU) or grab cranes, free digging unloading rates of around

Bridge reclaimer with twin reciprocating harrows recover and blend the coal from the chevron stockpile producing a homogeneous output from multiple mines.

Circular storage at Hulai power plant in China with radial stacking boom and cantilevered reclaim boom mounted to a common column able to stack at 4000 tph and reclaim at 2000 tph. The fabricated dome structure encloses the storage machine and stockpile, eliminating air pollution.

Rotary wagon tippler provides fast automated discharge of flat bottom open top rail wagons using either random wagons as illustrated or unit trains.

October 2012 | Reprinted from World Coal

4000 tph are mandatory if the vessel is to be released within the contractual free discharge period and thus avoiding penal demurrage charges. With capesize vessels typically around 120,000 t, the on-port storage capacity must comfortably exceed this with a good margin of safety to provide some flexibility in vessel timing.

Since 1982, Schade has delivered 67 chain scraper reclaimers to Chinese coal handling operations, including 50 circular storage designs linked to power plants. These storages are typically 120 m dia. with an active volume up to 230,000 m3, including a radial stacking boom rated at 4000 tph plus a single reclaimer boom rated at 2000 tph. Using the company's automated stockpile control system, coal may be loaded to the storage and at the same time discharged to the mill bunkers. These circular storages are often linked directly to a deep-water berth with conveyor transfer from the CSU or grab crane, making the performance of the stacker critical to the ship discharge time.

Material is conveyed directly from the reclaimer boom to the coal mill bunkers. Typically, for a standard 600 MW power plant, a single storage of 180,000 t is sufficient, providing around 45 days running at 4000 tpd, depending upon load factor and coal quality, or 30 days operation between vessel deliveries (assuming a ship size of 120,000 DWT).

Circular storages offer the highest capacity per square metre of plant footprint and, using a fabricated or geodesic dome, are easy to enclose, eliminating the risk of windblown dust or contaminated rain water runoff pollution.

Such circular storages are considered strategic and offer no practical blending function, since the coal is blended at the preparation plant. The characteristics are known to the buyer and generally specified in the contractual arrangements between miner and consumer.

New developmentsSince the 1920s, Aumund has been involved in the design of automated

wagon discharging equipment based either on hydraulic tippers or rotary tipplers. Schade has extended these designs significantly and is introducing to the market a range of rotary wagon tipplers able to handle random wagons, tipped individually, or gondola-style unit train wagons that may be rotated singularly or in pairs in the tippler while still joined together as a train.

Schade is expanding its range of circular storages to 150 m dia. with a storage capacity of 400,000 t, enabling a single storage dome to service a pair of 600 MW generators, receiving at 5000 tph from larger capesize vessels.

Dual boom portal reclaimers for longitudinal storages are to be expanded to achieve a reclaim rate of 5000 tph. This will enable two portal reclaimers to challenge the performance of the largest bucket wheel reclaimers with the benefit of reduced project cost and greater flexibility, plus fully-automated operation. This eliminates the need for dozer clean-up, leaving the stockpile neat and with the live capacity 100% recovered.

Reprinted from World Coal | October 2012