At Daw Mill, Britain’s biggest coal producer, the versatility of the Metso Minerals Trellex systems have been well proven with many screens using Trellex T-Step decks; including the country’s first banana screen to be fitted with T-Step modular panels; all ensuring extended life, ease of handling and replacement, plus noise reduction.
Daw Mill, located at Arley, near Coventry in the West Midlands of England, is Britain’s biggest coal producer, mining a 5 m thick section of the Warwickshire thick seam some 750 m below the Warwickshire countryside.
It is a very clean Run of Mine (ROM) coal, requiring only crushing and dry screening for its production of power station fuel (PSF). It also produces waste and tailings are produced from the mine.
Its complete product range includes: Large cobbles 100-150 mm; Trebles38-80 mm; Doubles 35-50 mm; Singles 16-35 mm; PSF 0-50 mm; and Industrial Smalls 0-19 mm.
Daw Mill’s operation is based on Dense Media Separation (DMS) using a mixture of water and magnetite (the dense media) to achieve the required DMS specific gravity (SG) separation of 1.4 and 1.7.
The SG of all minerals like coal is a unique property. SG is a relative measurement between the weight of a mineral and water. Some minerals are light and can float on water and other minerals are much heavier and sink in water. DMS is a process that takes advantage of the differences in SG between various minerals.
The No. 1 process plant uses the dense medium cleaning process. The ROM is separated into a product with an SG of 1.4, which is used for household coal and a second 1.7 SG fraction that is used for PSF.
The ROM coal undergoes its first screening at 150 mm through a primary screen, at a peak capacity of 1,000 t/h. This ROM primary screen features Metso Minerals Trellex T-Flex, a self-supporting screen media designed for coarse applications. This screen according to Tim Rawlings, Daw Mill’s Deputy Marketing and Quality Control Manager, “Suffers huge impact from raw coal over the full size range and a whole mess of materials from down the mine, including steel, wood and even steel girders.”
Trellex rubber with steel backed plates fitted to the screen are achieving a six-month life at the front end of the screen. At the discharge end, the wear life is even longer.
Oversize from the drift screen is sent to a crusher to provide a –150-mm product. It is then fed into a 600 t capacity bunker which is equipped with three separate outputs to feed three individual processing plant.
First banana screen
The 150 mm coal passes through the washing plant and is separated by a jigging screen, with the –40 mm coal fed to a secondary bunker for PSF production. The coal passes over a banana screen with slotted 16 mm by 14 mm aperture T-Step panels.
Daw Mill’s is the first banana screen in the UK to be fitted with T-Step modular panels in a coal application. Previously the screen had been equipped with hardwearing steel plates.
“These were difficult and heavy to replace,” says Tim Rawlings, continuing, “T-Step allows easy changes and extended life expectancy.”
With a throughput of 200-300 t/h, the high capacity banana screen has been designed to separate out fine sizes. It is fitted with 60 T-Step panels. The undersize from the banana screen feeds into PSF product.
Trellex T-Step
The Trellex modular T-Step system provides improved screening accuracy, maximum service life and a higher throughput. It features a cascade effect generated by the step design which continuously breaks up the layer of feed material so that smaller particles are screened out faster.
Stratification is maximised and fines are minimised from step to step. This results in faster screening which means that critical sizes are separated more effectively.
Oversize materials from the banana screen is fed to Wemco DMS separator which separates stones and other non-volatile, unwanted ‘gangue’ from the ROM coal at an SG of 1.7. The coal is passed over Allis Chalmers drain and rinse and classifying screens – once again both equipped with T-Step panels to produce a variety of coal sizes from 50 to 90 mm. The drain and rinse screen media is made of polyurethane and shaped to allow fast run-off of water.
Trellex Poly-Cer plates are also fitted at the impact edge of the screen offering additional protection against the high impact abrasive coal and according to Tim Rawlings are exceeding an average of nine months life per panel. Today, impact areas on a number of screens are fitted with Poly-Cer and Trellex 60 rubber pads with steel backing.
The classifying screen features rubber T-Step panels. These pass -100 mm coal but this is regularly changed to accommodate product demand, for instance to produce trebles and cobbles. The –100 mm undersize is graded for both industrial and domestic markets.
Second flow
The second product stream from the 600 t bunker to No. 2 plant is mainly smalls and singles for industrial use. The coal from the bunker is fed to two vibration screens, separating at –50 mm.
The undersize reports to a Trisomat ‘flip-flop’ screening machine fitted with Trellex panels to remove –6 mm fines. This stream is further screened to separate –35 mm coal as smalls and singles.
The oversize (+50 mm) from No. 2 plant is fed to a ripple flo screen fitted with T-Step panels and was only installed last year under a modernisation programme.
“Formally we were constantly changing screen decks almost daily to suit our product demands – but currently we have settled for 50 mm decks to suit most products,” says Tim Rawlings.
Third flow
The third plant is fed directly from the 600 t bunker via conveyor belts onto a Ripl-Flo screen where +50 mm is crushed to meet an underflow of the same top size.
“We try to balance the second and third flow systems to achieve 600 t/h over the screens,” says Tim Rawlings, adding, “Since its installation last year we have not yet changed any of the 50 mm T-Step panels.”
Trials
The T-Step story at Daw Mill goes back eight years to when they were first persuaded to trial T-Step panels on one of the drain and rinse screens. According to Tim Rawlings the mine was having problems with the metal decks of the original system.
“Changing them was very labour intensive and they were very noisy. Life expectancy also wasn’t too good,” he says.
“With T-Step, long life is a bonus but for me ease of fitting is the vital factor. Today panels can be changed quickly and easily by the operators.”
“The trials were very successful,” adds Ted Chomiuk, Northern Area Sales, Metso Minerals UK, “We were able to fit T-Step to the second drain and rinse screen. Today we have T-Step and other Trellex products fitted to 10 screens throughout the Daws Mill process plant.”
The trend at Daw Mill is away from domestic coal and to providing more products for PSF and industrial use. The annual saleable products these days include around 3 million tonnes for PSF products.
The present Daw Mill shafts, 558 and 553 metres deep, were sunk between 1956-59 and 1969-71. In 1983, a drift was completed, linking the underground workings with the surface, enabling Daw Mill to increase production capacity by removing the bottleneck of winding coal up the shafts.
Other UK Coal collieries using Trellex screen media includes Welbeck, Thoresby, Rossington and Harworth.
First Banana Screen Media
October 18, 2005
First banana screen media in UK for coal industry
At Daw Mill, Britain’s biggest coal producer, the versatility of the Metso Minerals Trellex systems have been well proven with many screens using Trellex T-Step decks; including the country’s first banana screen to be fitted with T-Step modular panels; all ensuring extended life, ease of handling and replacement, plus noise reduction.
Daw Mill, located at Arley, near Coventry in the West Midlands of England, is Britain’s biggest coal producer, mining a 5 m thick section of the Warwickshire thick seam some 750 m below the Warwickshire countryside.
It is a very clean Run of Mine (ROM) coal, requiring only crushing and dry screening for its production of power station fuel (PSF). It also produces waste and tailings are produced from the mine.
Its complete product range includes: Large cobbles 100-150 mm; Trebles38-80 mm; Doubles 35-50 mm; Singles 16-35 mm; PSF 0-50 mm; and Industrial Smalls 0-19 mm.
Daw Mill’s operation is based on Dense Media Separation (DMS) using a mixture of water and magnetite (the dense media) to achieve the required DMS specific gravity (SG) separation of 1.4 and 1.7.
The SG of all minerals like coal is a unique property. SG is a relative measurement between the weight of a mineral and water. Some minerals are light and can float on water and other minerals are much heavier and sink in water. DMS is a process that takes advantage of the differences in SG between various minerals.
The No. 1 process plant uses the dense medium cleaning process. The ROM is separated into a product with an SG of 1.4, which is used for household coal and a second 1.7 SG fraction that is used for PSF.
The ROM coal undergoes its first screening at 150 mm through a primary screen, at a peak capacity of 1,000 t/h. This ROM primary screen features Metso Minerals Trellex T-Flex, a self-supporting screen media designed for coarse applications. This screen according to Tim Rawlings, Daw Mill’s Deputy Marketing and Quality Control Manager, “Suffers huge impact from raw coal over the full size range and a whole mess of materials from down the mine, including steel, wood and even steel girders.”
Trellex rubber with steel backed plates fitted to the screen are achieving a six-month life at the front end of the screen. At the discharge end, the wear life is even longer.
Oversize from the drift screen is sent to a crusher to provide a –150-mm product. It is then fed into a 600 t capacity bunker which is equipped with three separate outputs to feed three individual processing plant.
First banana screen
The 150 mm coal passes through the washing plant and is separated by a jigging screen, with the –40 mm coal fed to a secondary bunker for PSF production. The coal passes over a banana screen with slotted 16 mm by 14 mm aperture T-Step panels.
Daw Mill’s is the first banana screen in the UK to be fitted with T-Step modular panels in a coal application. Previously the screen had been equipped with hardwearing steel plates.
“These were difficult and heavy to replace,” says Tim Rawlings, continuing, “T-Step allows easy changes and extended life expectancy.”
With a throughput of 200-300 t/h, the high capacity banana screen has been designed to separate out fine sizes. It is fitted with 60 T-Step panels. The undersize from the banana screen feeds into PSF product.
Trellex T-Step
The Trellex modular T-Step system provides improved screening accuracy, maximum service life and a higher throughput. It features a cascade effect generated by the step design which continuously breaks up the layer of feed material so that smaller particles are screened out faster.
Stratification is maximised and fines are minimised from step to step. This results in faster screening which means that critical sizes are separated more effectively.
Oversize materials from the banana screen is fed to Wemco DMS separator which separates stones and other non-volatile, unwanted ‘gangue’ from the ROM coal at an SG of 1.7. The coal is passed over Allis Chalmers drain and rinse and classifying screens – once again both equipped with T-Step panels to produce a variety of coal sizes from 50 to 90 mm. The drain and rinse screen media is made of polyurethane and shaped to allow fast run-off of water.
Trellex Poly-Cer plates are also fitted at the impact edge of the screen offering additional protection against the high impact abrasive coal and according to Tim Rawlings are exceeding an average of nine months life per panel. Today, impact areas on a number of screens are fitted with Poly-Cer and Trellex 60 rubber pads with steel backing.
The classifying screen features rubber T-Step panels. These pass -100 mm coal but this is regularly changed to accommodate product demand, for instance to produce trebles and cobbles. The –100 mm undersize is graded for both industrial and domestic markets.
Second flow
The second product stream from the 600 t bunker to No. 2 plant is mainly smalls and singles for industrial use. The coal from the bunker is fed to two vibration screens, separating at –50 mm.
The undersize reports to a Trisomat ‘flip-flop’ screening machine fitted with Trellex panels to remove –6 mm fines. This stream is further screened to separate –35 mm coal as smalls and singles.
The oversize (+50 mm) from No. 2 plant is fed to a ripple flo screen fitted with T-Step panels and was only installed last year under a modernisation programme.
“Formally we were constantly changing screen decks almost daily to suit our product demands – but currently we have settled for 50 mm decks to suit most products,” says Tim Rawlings.
Third flow
The third plant is fed directly from the 600 t bunker via conveyor belts onto a Ripl-Flo screen where +50 mm is crushed to meet an underflow of the same top size.
“We try to balance the second and third flow systems to achieve 600 t/h over the screens,” says Tim Rawlings, adding, “Since its installation last year we have not yet changed any of the 50 mm T-Step panels.”
Trials
The T-Step story at Daw Mill goes back eight years to when they were first persuaded to trial T-Step panels on one of the drain and rinse screens. According to Tim Rawlings the mine was having problems with the metal decks of the original system.
“Changing them was very labour intensive and they were very noisy. Life expectancy also wasn’t too good,” he says.
“With T-Step, long life is a bonus but for me ease of fitting is the vital factor. Today panels can be changed quickly and easily by the operators.”
“The trials were very successful,” adds Ted Chomiuk, Northern Area Sales, Metso Minerals UK, “We were able to fit T-Step to the second drain and rinse screen. Today we have T-Step and other Trellex products fitted to 10 screens throughout the Daws Mill process plant.”
The trend at Daw Mill is away from domestic coal and to providing more products for PSF and industrial use. The annual saleable products these days include around 3 million tonnes for PSF products.
The present Daw Mill shafts, 558 and 553 metres deep, were sunk between 1956-59 and 1969-71. In 1983, a drift was completed, linking the underground workings with the surface, enabling Daw Mill to increase production capacity by removing the bottleneck of winding coal up the shafts.
Other UK Coal collieries using Trellex screen media includes Welbeck, Thoresby, Rossington and Harworth.
For more information, please visit:
https://edir.bulk-online.com/profile...o-minerals.htm
Attachments
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