Materials Handling - engineeringinfo.co.za Handling.pdf · scraper reclaimer These reclaimers are ... Material moves in a solid placid column along with the conveying chain equipped

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Materials HandlingIn the process stages of size reduction, size control, enrichment and upgrading the values of the minerals or rock are brought to their optimum.

We will now look closer into what forms these process stages into a continuous operation.

With materials handling we understand the technologies for moving the process forward with a minimum of disturbances in capacity and flow.

These technologies are:

• Loading and Unloading• Storing• Feeding• Transportation

For practical reasons we are using the term Materials Handling for dry processes only.

Of course, the technologies for moving a wet process forward are equally important.

loading and Unloading

In this section we will only cover loading and unloading conditions related to rail cars and sea vessels (high capacity conditions)

railcar dumpers

Rail is the most common inland way of hauling large quantities of raw ore, upgraded minerals and coal etc, and unit trains up to 200 rail cars have to be unloaded during shortest possible time observing safety and environmentalrequirements.

Railcar Dumper – rotary type

• Reliable and proven design• Capacities up to 100 cars/h• Single, tandem or triple car dumper configurations• Dust sealed operation• Integrated dust containment system

Railcar Dumper – “Crescent” design

• Low in energy (rotation axis close to gravity centre of loaded cars).

• Hopper position close to rail track• Hydraulic car clamping system (closed loop)• Rate of unloading 60 cars/h and line

Rail car Dumper - Rotaside® type

• Hopper position at the side of rail track gives simplified installation.

• Proven and simple design• Low in maintenance• Rate of unloading 12 cars/h

train Positioners

A Train Positioner has to have a high utilisation capability to enable it to precisely position blocks of 1-10 railcars up to heavy train in excess of 200 railcars using a preset velocity pattern. In duties ranging from 5 to 90 cars unloading per hour there are a number of options for Positioners.

System

Side Arm System (rack and pinion drive), (see picture).

Reversible Hydraulic Indexer.

Wire Rope Car Pullers.

Vertical Capstan System.

Double side Arm System (Gemini®).

Unloading Duty

Heavy 100 car, or more, trains at high capacity.

25 ton pull, 5-15 cars/hour.

From 2-12 ton pull at variablespeeds.

Manual operation - limited pull and distances.

For very high unloading rates.

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grab Unloader

Grab Unloading is a classical way of unloading ships and barges. This concept is still valid but has undergone a massive development.

Today’s high speed grab unloaders feature short duty cycles and large capacity buckets for greater unloading volume and efficiency.

• Reliable equipment• Low operating costs• ABC system (Automatic Bucket Control) with grab control on

closing, filling, loading and positioning• Integrated dust containment system

Unloading capacities (typical)

• Grab capacity coal 6 to 25 tonnes• Grab capacity iron ore 6 to 40 tonnes• Duty cycle: 36 to 45 sec• Free digging rate coal 500 to 2000 tonnes/h• Free digging rate iron ore 500 to 3400 tonnes/h

Continuous unloading

For high capacity unloading applications (for faster ship or barge turnarounds) continuous unloading is an option.

CBU (Continuous Barge Unloaders) and CSU (Continuous Ship Unloaders) can be manual, semi automatic or fully automatic “Self-Unloading” systems of type.

• Inclined Bucket Elevator• Loop Belt System• Vertical Conveying System (FLEXOWELL) • Capacities up to 6000 tonnes per hour• Operator friendly, less polluting operation (dust & noise)• Long service life• Flexible in sizes and capacities

CsU- bucket wheel type

• Optimal for unloading sea dredged sand or other suitable bulk material.

• Varying number of buckets to suit vessel size (1400-4500m³)• Discharge rate to shore 1200 m³/h• Bucket wheel protected in “sea position”

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storage in oPeration

The main purpose of storage is to smooth out:

• Different production rates (cont.-cyclic).• Shift variations.• Interruptions for repair.• Size variations.• Flow variations.• Variations in mineral value (metal content etc.).

storage Buffering

Buffer storage is some time called “the key to processing”, meaning that without a proper storage throughout a continuous rock or mineral process, production up-time will be gone.

Storage of rock (1)

A matter of material flow (retention time).

Storage of ore and minerals (2)

A matter of material flow (retention time) and blending.

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stacker reclaimer

Large storages with high capacities for feeding mineral processing plants, combustion plants (coal),ships etc. cannot use loader and truck technology. Here effective Stacker Reclaimers are the only option.

Trenching type Stacker Reclaimers are used for low-volume, high active storage capacities between 30 000 and 60 000 tons. Reclaiming operations are accomplished by longitudinal pass through the pile. Stacking and reclaiming rate usually vary from 2000 - 4500 tons per hour.

Slewing type Stacker Reclaimers are typically used where large quantities of material must be readily available, where blending of material grades is required and where yard length is limited. Stacking and reclaim rate up to 6000 tons/h for coal and 8000-10000 tons/h for iron ore.

scraper reclaimer

These reclaimers are designed to handle materials as (typical) phosphate, coal, sulphur, fertilizers and woodchips servicing parallel storage piles from booms mounted on either or both sides of the machine.

They incorporate the cost advantage of “back stacking” (the ability to reverse boom flight direction up the storage pile).

• Capacities up to 4000 tons /h.• Single, twin and double- boom options.

Barrel reclaimer for “Full Cross section recovery”

The optimal machine reclaiming from a blending pile is the Barrel reclaimer. The heart of the machine is a rotating barrel fitted with a large number of buckets. Material collected in the buckets is discharged into an internal conveyor feeding a downstore conveyor running alongside the pile.

• Very robust a reliable design for high capacities · Variable speed for differing reclaim rates

• Automatic operation (optional)

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Feeding

Feeders are necessary whenever we want to deliver a uniform flow of dry or moist fractions of rock or minerals.

Generally they are categorised by the size of material to be fed, see below.

Primary Feeders

Feeding vs Feed Sizes

“In circuit” feeders

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Wobbler feeders

Feeding and scalping - when things get sticky!

Openings between eliptic bars remain constant

Fines, mud or dirt drop through the openings

Oversize moves forward

Size range

• See apron and table feeders.

Applications

Wet and sticky for: metallic, industrial and construction minerals.

Pitch (scalping)

• Fixed and adjustable.

Capacity range

• Up to 3 500 t/h (5 sizes).

Conveying

In this section we will focus on mineral mass flow by conveying, by far the dominating method when transporting dry material in a mineral processing operation.

Conveyor – general

Conveyors are selected from 4 key parameters:

• Tonnage.• Size of material.• Inclination.• Distance.

We also must consider wear in operation and the environment (dust, heat, oil or chemicals etc).

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Conveyor belts

Although the conveyor structure is important, most of the conveying work falls back on the conveyor belt, exposed to the material.

Flat belts are dominating, conveying up to a lifting or lowering angle of approx. 18°. Depending on duty the belts are reinforced with different materials (Polyester/Polyamide, Aramid fibres or mesh net Steel Cords) in 2-5 plies, protected by a top cover of 2-6mm thickness.

The polymer material in the belt (mainly rubber) is selected according to appearance of heavy wear, heat, flames, oil etc.

Profile belts must be used when lifting angle is exceeding 18°. With a limitation of approx. 30° different profiles of the top cover must be selected to prevent bulk material or unit loads from sliding backward. Otherwise reinforcement and material selection criteria are similar as for flat belts above.

Conveying systems

Flexowell® Conveyor System “when space is critical”

The Flexowell system normally is the only option when lifting angle is exceeding 30°. The system is very flexible and gives a number of transportation solutions when space and lifting angles are critical.

Cable Belt® Conveyor System “when distance is critical”

Conveying with high capacities over long distances means that conventional conveying systems are out. An alternative to truck hauling is Cable Belt® conveyors which become competitive from, say, 500 m and upwards taking on capacities from 500 up to 5000t/h.

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En-Masse Conveying System “when dust and emissions are critical”

Transportation of free-flowing bulk material with or without gas emissions or high temperatures places special demands on the conveyor system. En-Masse conveying system is aiming at gentle handling and a closed material flow system for transportation in all directions. Material moves in a solid placid column along with the conveying chain equipped with different types of conveying flights depending on duty.

Conveyor Capacities

In order to estimate the capacity and max. recommended inclination of a conventional conveyor the figures below can be of use.

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Volume Weight and angle of inclination

The capacity and the inclination of the conveyors depend on the character of the material to be conveyed.

Conveyor – More than a rubber belt

The conveyors are the working horses of every dry processing plant in mineral processing, of key importance to keep the process flow stable. Pictures below indicate the vital parts of the conveyor and the critical service points to be checked regularily for reliable operation.

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Conveyor – service points

Feeder – apron

*Approx, weight of an Apron feeder, length 3 m (10ft) excl. load, skirts, chutes etc. For each additional feet (or 0.3 m) add 7

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Materials Handling - engineeringinfo.co.za Handling.pdf · scraper reclaimer These reclaimers are ... Material moves in a solid placid column along with the conveying chain equipped