Central and Hanson show a lotta bottle

• 
• 25th January 2008
• Recycling
 

A track-mounted mobile impact crusher supplied by Lokotrack Central is helping pioneer the use of glass as a constituent ingredient in a range of tarmac products.

A Lokotrack LT1213 track-mounted impact crusher on hire from Lancashire Crushing is being used to turn recycled glass into a tarmac ingredient for roads in the Angelsey area of Wales.   The machine, which was supplied by England and Wales Lokotrack dealer Lokotrack Central, is crushing bottles, jars and other glass products into a sand substitute at Hanson Aggregates' Caer Glaw Quarry at Gwalchmai, Anglesey.

Cross Head
The 44 hectare Caer Glaw quarry had previously been a key supplier of pre-Cambrian granite but quarry operations were halted and the site mothballed with only the site's tarmac plant remaining operational.   This did, however, leave Hanson Aggregates with a problem.   "As a company, we have a policy of conserving mineral stocks anyway, but we face a constant challenge from Northampton northwards in that there is very little natural sand that can be used in aggregate or tarmac products," says quarry manager Gary Kitson.   "We have, therefore, been running experiments in which the sand was replaced with recycled glass."

As Kitson explains, glass is traditionally made from very high quality sand and, therefore, makes an ideal substitute if it is recycled correctly.   "We quickly realised that there was an opportunity to cure one environmental problem whilst simultaneously supplying the needs of an industry hungry for raw materials," he says.   "We knew that, if successful, it was a real win-win."

PRN Time Penalty
Kitson reports that the recycling of glass into a tarmac product is fuelled by Hanson's acquisition of Packaging (Waste) Recovery Notes (PRN), a certificate issued by an accredited reprocessor when waste has been recycled or recovered within the UK.    "PRNs are evidence that waste has been recovered or recycled and they're big business," says Kitson.   "Businesses are keen to sell the PRNs because that absolves them of responsibility for the waste materials and we are keen to acquire them as it affords us access to potentially valuable raw materials."

PRNs do, however, carry with them a time limit during which waste materials have to be processed, reused or recycled.   "We currently have a stockpile of around 3,500 tonnes of glass waste and glass is continuing to arrive at a rate of around 1,500 tonnes per month," Kitson asserts.   "We therefore needed a fast, effective and reliable way in which to process this material before we were hit with a PRN time penalty."

Long Shards
Kitson reports that the waste glass had been processed by its predecessor using cone crusher.   "The cone had a habit of producing long shards that contaminated the recycled product," Kitson explains.   "Longer and larger pieces of glass retain heat that prevents the tarmac from solidifying.   The replacement machine needed to be capable of consistently producing a >4 mm product."

The solution came in the shape of the LT1213 from Lancashire Crushing.   The machine, which until recently had been tackling more traditional crushing duties processing sandstone for concrete applications, has to contend not just with glass but a whole host of contaminants.   "Although the waste is pre-screened, the feed material often still contains plastics and metal jar lids," Kitson says.   "Thankfully, the Metso Minerals LT 1213 just crushes everything in its path.   The jar lids are removed by an overband magnet on the conveyor while plastics and paper waste is segregated by an additional screening unit."   The company says that around 60 percent of the waste glass is processed in the first pass but, to ensure optimum quality and size reduction, any oversized materials are reprocessed."

Economical & Environmental Sense
The system clearly works.   The LT 1213 is currently processing glass waste at a rate of around 180 tonnes per hour, approximately 100 tonnes of which is suitable for use in tarmac base products.   For Gary Kitson, it is the culmination of many years trial and error.   "Hanson has spent years testing the process and the end product, and we now know it will work.   Using this method is the best of both worlds.   It helps conserve resources and increases recycling.   But it is important to get this right.   Not only do we need to provide a recycled product which solves a raw materials shortfall, but it has to be of an equal if not better quality than the original product.   And this is," Kitson concludes.   "'The material produced by the Metso Minerals impactor is of a very high quality, much better than dredged sand and much closer to home than our natural reserves. I cannot source even coarse sand closer than Northampton. This product makes economical and environmental sense to use."

Lokotrack Central (Central Crushing & Screening Services Ltd)
Pipe Yard Lane Works
Worthington Lane
Newbold
Leics
LE67 8PJ
UK

T: 01530 225820
F: 01530 224011

Associated Links

• Hub-4 Profile of Lokotrack Central (Central Crushing & Screening Systems Ltd)
• Lokotrack Central (Central Crushing & Screening Systems Ltd) Company Website