Shortages. Until recently, there was too little of just about anything. As we all know, the construction industry was plagued with a lack of essential materials such as cement, rebar steel and manpower.
The fleet or plant manager, meanwhile, was more concerned with the lack of the round black rubber so essential to keeping their big machines rolling. It seemed everywhere was short of them, and nobody knew where to find the elusive products, short of joining a waiting list, which in some cases was longer than the life of the tyre.
Actually, there was one place where tyres were in abundance, an inexhaustible supply in fact. However, you might not want many of the units in stock on your vehicle – most of them are distinctly past their best. The place? The Sharjah Municipal tyre dump.
In this vast expanse of the out-of-town desert a seemingly endless pile of tyres stretches in to the distance. Conservative estimates put the number of casings in the pile at around seven million, though as more tyres are thought to have been buried in the sand years ago, the real figure quite frankly is anybody’s guess.
Besides spoiling the wild beauty of the UAE, the tyres cause an enviro-hazard in a number of ways. Firstly, tyres in the ground can ‘leachate’ into the ground water table,but more seriously if the stack was ever to catch fire it would be extremely hard if not impossible to put it out.
Fortunately, the emirate of Sharjah has taken its responsibilities seriously and has actually put its money where its mouth is.
Among the various recycling projects masterminded by Bee’ah, which is a public/private waste management partnership, the flagship has surely got to be the US $50m plant for turning the discarded rubber in to a new material which can be used for making a number of products, the most significant of which is used in a new kind of asphalt for resurfacing roads.
EXCLUSIVEÂ VIDEO:Â Click here to see the Bee’ah plant in action
RUBBISH
Anyone who has ever seen a recycling plant of any type in action will know that they all follow a broadly similar pattern. First of all, while the material that is to be recycled is by definition rubbish, if the feedstock is unsuitable then the end product will also be no good.
To this end Bee’ah has started on the seemingly endless task of sorting the tyre mountain into more organized stacks, with the waste piled in rough size order.
Additionally, every ten metres or so, a large sand berm acts as a fire break, so any freak conflagration won’t be totally unmanageable.
To build this, the environmental group has laid its hands on a number of large wheel loaders. We spotted a number of examples of Caterpillar 950H, as well as some newer Volvo L50F models, though there seemed to be a mix and match of equipment brands generally at the site.
Of course, there is no ‘used tyre sorting’ attachment as far as we are aware, so this task falls to a number of guys with pitchforks. With up to 7,000 tyres coming into the dump each day, it is safe to assume that they will not be out of work anytime soon.
From this vast wall of tyres, feedstock is moved up to the ‘in’ gate of the brand-new plant factory. From here a worker physically rolls a tyre into the plant room, where another worker catches it and either puts it on a ‘debeader’ which is a machine similar in appearance to a tyre mounting machine. However, the debeader’s sole purpose is to rip out the largest steel bands in larger tyres.
CONVEYOR
All other tyres are fed on to an elevating conveyor, which dumps them into a funnel-shaped shredder, which as the name implies rips the rubber to pieces. From here the destroyed tyres fall onto a vibrating screener where large pieces that need to go through the shredder again are sorted from the more useable bits.
At this point, the product is just torn up bits of tyre. It still contains nylon cord, rayon and bits of the steel belts. Fortunately, the next part will loose most of the unwanted material – cryogenic freezing.
When most people think of cryogenics, an image of 1960’s industrialists and Walt Disney come to mind (For the record, Disney was never actually frozen, as he died a year before the method had been invented.)
Here, however, it is mangled pieces of tyre going up another elevated conveyor, and receiving a blast of liquid nitrogen. This process is understandably shielded inside the innards of the machine, and from there, presumably some kind of pulveriser smasheds the frozen shreds to crumbs.
The machine is made by a Canadian firm called RTI Cryogenics which claims to have developed the most efficient cryogenic freezing system to date.
EXCLUSIVEÂ VIDEO:Â Click here to see the Bee’ah plant in action
VIOLENCE
Following this violent end to the product looking anything like a tyre, the next stage is a spell under a powerful electro magnet. This draws out the bits of steel present in the mix, which are then deposited in a separate container for recycling.
Screeners meanwhile shake out bits of cord into a tray, so the product should be simply rubber granules. The final stage is to put the granules through a mill to grind them to one of a number of uniform sizes for use in various different products.
That essentially is it. The company has a machine for re-dying the rubber crumb to be any colour required, and there is an autoclave (a sort of large, pressurised, drum-shaped oven) for baking the crumb into the various finished products.
On our visit, the machine was busy churning out hexagonal tiles for gym floors. Interestingly, if a tile doesn’t meet the standard for whatever reason, it can simply be chucked back to square one and reprocessed again.
The milled rubber can be used to make soft loose flooring for paddocks as well as an almost springy surface for children’s playgrounds and the like.
However, the main use for the crumb is set to be a new kind of road surface, which Bee’ah claim will be quieter to drive on, longer lasting and very cheap to produce.
Obviously, such a new ingredient in road surfacing needs to be tested first, so the intention is to lay some road actually in the recycling yard itself.
From there, the Sharjah authorities can conduct tests on it to see if it really is suitable for blacktop, and if so, what types of mix are needed and so on.
A key test will be making sure that the reprocessed rubber doesn’t add to the pollution levels in groundwater, something that the plant owners and makers assure us is perfectly safe.
If the pilot is successful, more plants could be set up around the region. Both Dubai and Abu Dhabi have expressed interest int the project. With no end of tyres, and lots of highways it looks like the rubber could meet the road for a long time to come.
What are the concerns?
So, if tyre recycling is so great, why are the authorities demanding rigorous tests before it can be used as a road surface? Essentially, the product has to pass two tests, practical and environmental.
On a practical side, city bosses need to be sure that the new material can deal with the extreme temperatures found on the emirate’s roads. Also, they want to be sure that the surface is reasonably hard wearing and allows for water run off and reacts well to heavy braking and so on.
However, there are also concerns from an environmental point of view. Tyre ‘rubber’ is actually a complex substance which varies between manufactures, but often has heavy metals such as zinc used in it’s compound.
One concern cited in various studies the world over is that that by grinding tyres up and spreading them over the roads, the toxic metals might ‘leachate’, or sink into the ground water table causing a larger problem than merely storing tyres in landfill.
It should be stressed though, that no study has found this to be the case and that the manufacturers of tyre shredding equipment say that the problem has been eliminated.
EXCLUSIVEÂ VIDEO:Â Click here to see the Bee’ah plant in action
However, some countries have stopped using crumb rubber as playground surfaces while further tests are carried out.
RTI Cryogenics tyre recycling plant specs
- Operational uptime: 22 hours per day, 7 days a week
- Maintenance time: 2 hours for each 24-hour shift, on average
- Capacity: 6,000 – 10,000 pounds (2,700 – 4,500 kgs) per hour input
- Crumb size: 4 ‘mesh’ (6mm) to less than 100 minus mesh (less than 0.150 mm) Technology: fully controlled by a touch screen PLC, and includes a complete dust collection and fire detection system
- Manpower: as few as one operator and one bagger, in addition to 2 shredder operators
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