Thompson’s of Prudhoe lift and separate
In common with many waste recycling companies, Thompson’s of Prudhoe had become increasingly concerned that the high cost of dumping large tonnages of taxable waste in landfill sites was having a detrimental effect on their profitability. With this in mind, operations manager Aubrey Telfer and Craig Bateson, site manager of the company’s Springwell Quarry, embarked upon a project that would eventually result in a reduction of between 80% to 90%, by weight, in the amount of material going to landfill.
The recycling plant at Springwell Quarry handles skip and C&D waste. For a number of years the incoming material had been initially split over a 40mm trommel screen, with the –40mm product being acceptable for use as landfill cover material. However, with the tightening of legislation such material could no longer be used for this purpose since it contained paper, plastic, cardboard and polystyrene and therefore became subject to landfill tax.
Having established that there was a throughput of some 25 tonnes/h of this type of material, it was considered viable to re-screen the ‘fines’. A split which took out material at around 12–15mm would be ideal, as this soil-like material, with acceptably low levels of contaminants, could be used for cover material with no tax penalty.
However, the choice of screening method was critical, not only for accuracy, but also because the screening module would be required to operate with constantly changing materials and widely variable moisture conditions. The obvious choice was a star screen and after considering a number of different makes a Pearson star screen was included in the redesigned plant.
The Pearson screen module consists of 18 rows of rotating stars within a 5m long chassis. Each shaft is 1,560mm wide and driven by an independent electric motor, the speed of which can be controlled by an inverter, if required. The shafts run in sealed bearings, so little maintenance is required, other than a periodic cleaning of the star shafts. The stars are moulded from robust polyurethane for long service life, while retaining a flexibility, which helps to break down wet and matted materials, to allow more ‘fines’ to be screened.
The combination of variable apertures and variable shaft speeds on the star screen meant that the plant would be capable of infinite adjustment, with a special mechanism allowing the operator to adjust the size of ‘fines’ to be removed between 10mm and 50mm with the machine still in operation.
With the –15mm material removed, a –40mm +15mm material containing bricks, concrete, stones, wood, paper, plastics, cardboard, and polystyrene remained. The removal of the fines had already reduced the weight of the material going to landfill by 40–45% but there was still a considerable amount of valuable product remaining? The next stage was to separate the light material from the heavy material to leave a useful inert fill material.
A density separator was chosen to achieve this – a simple process whereby the remaining material that comes over the star screen is fed on to a vibrating feed table and over a defusing plate. High-velocity air is blown up through the waste stream, raising the light material to the top of the stream. The material is then fed over an air-knife which blows the light material out, while the heavy fraction drops on to a stockpiling conveyor. Airflow to both the defuser plate and the air-knife is infinitely variable and it is possible to change the settings while the machine is in operation, making it possible to determine the exact quality of the product extracted.
Having decided on the exact layout of the new waste-handling line, Master Magnets Ltd were enlisted to help design a framework to link the whole system together in a robust structure that would protect the machinery and ensure that the material was transferred from one section to another with the minimum of spillage, while at the same time providing easy and safe access for maintenance, cleaning and adjustment.
Master Magnets are best known as a leading supplier of magnetic separators and metal detectors, exporting their products to all parts of the world. However, with acquisition of Integrated Recycling Systems Ltd, the company can also design and manufacture complete plants for recycling and other metal-separation processes. At Springwell Quarry, Master Magnets designed and manufactured the support structure, access stairways, walkways, safety guarding and two belt conveyors.
Compared with the previous method of working, Thompson’s have seen a reduction of some 80–90%, by weight, in the amount of material going to landfill, and with the landfill tax in excess of £20 per tonne, it is estimated that the plant will recoup the capital expenditure in less than six months.
Pearson Separation Machinery Ltd, 90 Main Road, Hundleby, Spilsby, Lincs PE23 5LZ; tel: (0845) 458 5372; fax: (01790) 752080; email: perasonscreens@aol.com; website: www.pearsonseparation.co.uk
Master Magnets Ltd, Burnt Meadow Road, North Moons Moat, Redditch, Worcs B98 9PA; tel: (01527) 65858; fax: (01527) 65868; email: info@mastermagnets.co.uk; website: www.mastermagnets.co.uk
The recycling plant at Springwell Quarry handles skip and C&D waste. For a number of years the incoming material had been initially split over a 40mm trommel screen, with the –40mm product being acceptable for use as landfill cover material. However, with the tightening of legislation such material could no longer be used for this purpose since it contained paper, plastic, cardboard and polystyrene and therefore became subject to landfill tax.
Having established that there was a throughput of some 25 tonnes/h of this type of material, it was considered viable to re-screen the ‘fines’. A split which took out material at around 12–15mm would be ideal, as this soil-like material, with acceptably low levels of contaminants, could be used for cover material with no tax penalty.
However, the choice of screening method was critical, not only for accuracy, but also because the screening module would be required to operate with constantly changing materials and widely variable moisture conditions. The obvious choice was a star screen and after considering a number of different makes a Pearson star screen was included in the redesigned plant.
The Pearson screen module consists of 18 rows of rotating stars within a 5m long chassis. Each shaft is 1,560mm wide and driven by an independent electric motor, the speed of which can be controlled by an inverter, if required. The shafts run in sealed bearings, so little maintenance is required, other than a periodic cleaning of the star shafts. The stars are moulded from robust polyurethane for long service life, while retaining a flexibility, which helps to break down wet and matted materials, to allow more ‘fines’ to be screened.
The combination of variable apertures and variable shaft speeds on the star screen meant that the plant would be capable of infinite adjustment, with a special mechanism allowing the operator to adjust the size of ‘fines’ to be removed between 10mm and 50mm with the machine still in operation.
With the –15mm material removed, a –40mm +15mm material containing bricks, concrete, stones, wood, paper, plastics, cardboard, and polystyrene remained. The removal of the fines had already reduced the weight of the material going to landfill by 40–45% but there was still a considerable amount of valuable product remaining? The next stage was to separate the light material from the heavy material to leave a useful inert fill material.
A density separator was chosen to achieve this – a simple process whereby the remaining material that comes over the star screen is fed on to a vibrating feed table and over a defusing plate. High-velocity air is blown up through the waste stream, raising the light material to the top of the stream. The material is then fed over an air-knife which blows the light material out, while the heavy fraction drops on to a stockpiling conveyor. Airflow to both the defuser plate and the air-knife is infinitely variable and it is possible to change the settings while the machine is in operation, making it possible to determine the exact quality of the product extracted.
Having decided on the exact layout of the new waste-handling line, Master Magnets Ltd were enlisted to help design a framework to link the whole system together in a robust structure that would protect the machinery and ensure that the material was transferred from one section to another with the minimum of spillage, while at the same time providing easy and safe access for maintenance, cleaning and adjustment.
Master Magnets are best known as a leading supplier of magnetic separators and metal detectors, exporting their products to all parts of the world. However, with acquisition of Integrated Recycling Systems Ltd, the company can also design and manufacture complete plants for recycling and other metal-separation processes. At Springwell Quarry, Master Magnets designed and manufactured the support structure, access stairways, walkways, safety guarding and two belt conveyors.
Compared with the previous method of working, Thompson’s have seen a reduction of some 80–90%, by weight, in the amount of material going to landfill, and with the landfill tax in excess of £20 per tonne, it is estimated that the plant will recoup the capital expenditure in less than six months.
Pearson Separation Machinery Ltd, 90 Main Road, Hundleby, Spilsby, Lincs PE23 5LZ; tel: (0845) 458 5372; fax: (01790) 752080; email: perasonscreens@aol.com; website: www.pearsonseparation.co.uk
Master Magnets Ltd, Burnt Meadow Road, North Moons Moat, Redditch, Worcs B98 9PA; tel: (01527) 65858; fax: (01527) 65868; email: info@mastermagnets.co.uk; website: www.mastermagnets.co.uk
