Pictures right showing various views of bulk unloading of soda ash from ship into the hopper feeding the 350 tph bucket elevator
places, although mostly now they are covered in tarmac. The quay itself is 320 metres long and 10.5 metres deep, allowing it to accommodate some very big vessels of up to 65,000 tonnes deadweight. The site is leased on a long-term basis from the Port Authority by BPT, which owns and operates all the infrastructure they have installed upon it, at a cost in excess of £8 million.
Giant Silos Those vertigo-inducing giant silos each hold 8000 tonnes, usually of soda ash, which is a raw material used mostly by the glass industry although it has some limited application for feed. The silos are constructed from a special steel, specified to be less liable to corrosion by soda ash than normal metal, with benefits both for the longevity of the silos and the quality of the materials they store. The groundworks required for such huge silos took a long time to complete and cost a great deal of money, requiring 180 concrete piles for each one, sunk 18 metres into the bedrock below. As Andrew commented: “They’re not going anywhere.” Being so large, they also had to be manufactured on-site. Using the so-called ‘lip method’, the roof of each one started on the floor and then rolls of steel were unwound beneath it to create the walls, progressively raising the roof higher and higher, day by day, until the silo was fully formed, then welded internally to make it waterproof. The silos are loaded by a 350 tonne per hour bucket elevator, itself
fed by a giant quayside crane which unloads bulk materials from the ships. Sitting alongside the crane is another, even more impressive piece of equipment called a Vigan, which is essentially a giant vacuum cleaner. Although still being refined by its manufacturer to make it capable of handling soda ash without damaging the product, once it is up and running the Vigan will be capable of emptying the hold of the vessels at an incredible rate of up to 600 tonnes per hour. It will probably never need to operate at such a rate because, like a lot of the equipment used here, it is over-specified to ensure it can run at well below capacity and therefore minimise mechanical stress. Besides helping to look after the equipment which is installed, the policy also leaves a good deal of scope for expanding the throughput of the facility if and when required.
Holding Bins The soda ash is extracted from these silos by a tapered screw which ensures bridging of the product is avoided. It is transferred to two 200 tonne capacity holding bins at a steady rate of 100 tonnes per hour; once again, the conveyor is capable of much faster speeds but the system is over-specified and run well below its maximum for gentler handling of the product and lower stress on the equipment. From the holding bins, it takes about six minutes to discharge a full 28-30 tonnes tanker load, plus another four minutes to close all the pots; so it is very fast – in fact, the fastest in the whole of Europe according to Andrew.
FEED COMPOUNDER SEPTEMBER/OCTOBER 2019 PAGE 35
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