Storage Bin

Improving Flow from a 60000 Tonne Storage Bin

26.08.2010 | Author / Deskman: D. Goodwill, B. Pittenger / Marcel Dröttboom

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Glensanda, one of the largest and most technologically advanced aggregate quarrying and shipping operations in the world.

At the Glensanda quarry, a massive bin was cut out from the hillside to store crushed stone ready for ship loading at 6000 tonnes per hour. To ensure that requirements are met and ROI is maximised, bulk solids handling specialists were continuously involved in the project to provide research data and engineering input.

Glensanda, one of the largest and most technologically advanced aggregate quarrying and shipping operations in the world, is located on the banks of Loch Linnhe in the Western Highlands of Scotland. The quarry, formerly owned by Foster Yeoman Ltd, is now part of Aggregate Industries Limited, a member of the Holcim Group following Foster’s acquisition in 2006. It has reserves in excess of 800 million tonnes and ships high quality crushed granite to markets in the UK, Europe and the Americas.

Glensanda Site Overview

Granite is quarried at the 500 meter level and loaded to a large primary crusher that feeds a 300 meter deep, 4 meter diameter shaft, known as the ‘Glory Hole’. Reciprocating plate feeders at the base of the glory hole feed the –200 mm crushed granite to a 1.8 kilometer horizontal tunnel belt conveyor that delivers the rock to a 500 000 tonne stockpile. Next, material is conveyed to secondary and tertiary crushing and screening operations, and from there to massive, 60 000 tonne capacity storage bins cut out from the hillside.

The glory hole provides a long-term solution to both economic and environmental aspects of the extraction of the deposit. The quarry is a crater, with only the uppermost benches visible from a distance. The primary crushing station level and glory hole collar are progressively lowered as the deposit is mined. The tunnel is a permanent installation for the life of the project. The stone is crushed and screened into sizes demanded by the market and stored in the hillside bins ready for ship loading. The granite is exported using bulk vessels such as the Yeoman Bridge, which, at the time of it completion in 2000, was the world’s largest self-unloading vessel, with a capacity of 97 000 tonnes. The reclaim, blending and shiploading facilities are rated at 6000 tonnes per hour, which means a typical 75 000 tonne cargo can be loaded at the harbour in under 24 hours.

Mr. David Yeoman invited Jenike and Johanson engineers to visit the quarry shortly after start up in January 1989 to solve flow problems in a wet sand storage bin. Since that time, engineers from the bulk solids handling, processing and storage specialist have visited the quarry frequently and have provided flow property testing and functional design recommendations for plant expansions and modifications involving bins and feeders.

On-Site Assessment

The most recent of these projects began in 2004 with a call from Mr. Neil Hyde of Hyde Engineering Projects Ltd. Foster Yeoman Ltd had just retained Hyde Engineering Projects to provide necessary consulting engineering and design services to bring existing hillside bin number four into service. Sixty thousand tonnes of live storage capacity were required for moist granite dust, and this must be available on demand to load ships at 6000 tonnes per hour.

Hyde Engineering Projects retained Jenike and Johanson Ltd to test granite dust samples and to recommend a tunnel reclaim system that would provide flow rate linearity with respect to reclaim belt speed. The flat bottom floor of bin number four is about 5 meter wide. It was recommended that the reinforced concrete reclaim tunnel should have a single line of ten, wedge-shaped mass flow hoppers set in the roof, feeding a 2 meter wide variable speed belt conveyor. Directly beneath each hopper is an emergency shut off gate, below which is a proprietary ‘swing-type’ flow control gate.

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