Dry Bulk Cargo Intake, Processing and Distribution.
Andreas Markiewicz, 1. March 2018
Storage, Reclaim and Blending at Bulk Terminals, Process and Power Plant
Automated storage and reclaim are now a fundamental part of all new bulk terminals, process and power plant; generally divided into two categories to maximise the flexibility of the raw material and fuel intake and distribution. At large bulk terminals strategic storage must provide the capacity to discharge the largest vessels with a margin of flexibility. Similarly for central prep plants and transhipment terminals very high reclaim rates from strategic stockpile are essential for rapid train loading and onward distribution. Often at process and power plant strategic stockpiles will be combined with blending beds to homogenise the materials to ensure a consistent grade for burning, or processing or export.
The AUMUND Group including particularly SCHADE are heavily involved in this market with a range of Stacker and Reclaimer designs from around 100 to 6,500 tons per hour handling materials as diverse as Solid Fuels, Sulphur Prills, Fertilisers, Iron Ore, Concentrates, Ores, Limestone and many other specialist products.
To satisfy modern environmental demands the vast majority of new storage and blending facilities are fully enclosed based either on circular or longitudinal stockpile configurations depending upon the site topography and the management demands of the storage system plus the range of segregated materials to be stored.
Circular storages are popular for handling a single material type, such as Limestone in a cement plant, and when combined with a Bridge style Reclaimer offers a compact solution delivering a homogenised output. The radial and luffing stacker builds a layered stockpile on the chevron principle ensuring materials of varying specification are deposited in discrete vertical layers. When this material is recovered using the Bridge Reclaimer incorporating a reciprocating Harrow the resultant output represents a part of each layer and is thus blended creating a homogenised discharge. Both the Radial/Luffing stacker boom and the discharge of the Bridge Reclaimer are supported on slew bearings mounted to the central supporting column which is extended above the inlet chute of the stacker to support the head of the incoming belt conveyor. This arrangement eliminates any machinery loading applied to the enclosing dome structure thereby reducing the structural weight and relative cost. Material is discharged from the horizontal Reclaimer to the centre via a conical transfer chute to the feed boot of a belt conveyor mounted within a tunnel below the storage dome.
Clearly the effective control of the stacking and reclaiming system is critical to avoid material engulfing the Bridge Reclaimer boom, SCHADE offer a control package that may be integrated to the plant control system and sequenced to the incoming conveyor system. The control system and associated field instrumentation ensures the relative motion of the Stacker and Reclaimer are controlled such that the Stacker follows the Reclaimer and in addition the layering of the incoming material is generated to ensure effective blending.
All SCHADE Reclaimers are based on the scraper chain principle with shovels that convey the material either to the side of the building for longitudinal storages or to the centre for circular designs; whether Bridge Scrapers or Portal/Semi-Portal designs the fundamental principle is the same for all.
SCHADE have developed a unique range of heavy duty conveyor chains with shovels in excess of 3 metres wide able to convey vast volumes of material efficiently and reliably.
Longitudinal storages come in various formats based primarily on the full portal design or the semi portal arrangement; typically half a full portal. Full portal Reclaimers have a symmetrical frame supported to rails either side of the storage building, or allocated storage area for open stockpiles. The concept is primarily reliable offering high performance with minimum degradation and complete control of the discharge rate by controlling the speed of travel along the stockpile. This is a flexible design able to handle a range of materials in segregated storage bays, with rail span of over 75 metres possible and handling rates over 6,000 tph using a twin boom design with two Reclaimer booms mounted to a common portal frame.
The Portal Reclaimer is often combined with a travelling, luffing and slewing Stacker used to generate the stockpile which may be also offer a degree of blending using the Strata stacking profile where layers are built up by continuously travelling the Stacker along the designated working zone. When recovered by the Portal Reclaimer elements of layers are combined and the output will be a relative blend of the differing grades loaded to the stockpile. As with circular storage SCHADE offer automated control options allowing the Stacker and Reclaimer to operate as an integrated system linked to the main plant control equipment.
For installation within an enclosed storage building the full portal design is generally combined with a two part boom Reclaimer design such that the total height is reduced to minimise the building size.
In addition to the Full Portal design SCHADE also offer the Semi-Portal concept as mentioned above using half of the portal with the upper part supported on the stored material retaining wall. This design can also be arranged with multiple units mounted back to back with a common central retaining wall giving maximum stored volume for a given building footprint. Differing materials including raw materials and fuels may be stored together using concrete dividing wall for segregation, the Reclaimer Boom may be raised up sufficiently to travel over the bay walls to move to another section. The operating concept is similar to the full portal design but offers greater flexibility particularly where multiple material type must be handled.
These examples of differing storage techniques are a representative sample of the core designs offered by SCHADE with the knowledge gained over many decades’ in this market specifically and nearly 140 years in the materials handling business. Now part of the world wide AUMUND Group SCHADE is able to offer a wealth of experience and support in any location and any application.
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