Halkyn Quarry Replant Completed Major Redevelopment Scheme Safeguards Limestone Production at North Wales Site for the Next 30 Years
Total Page：16
File Type：pdf, Size：1020Kb
The new processing plant at Halkyn Quarry with part of the old plant still visible (top left) prior to dismantling Halkyn Quarry Replant Completed Major redevelopment scheme safeguards limestone production at North Wales site for the next 30 years EMEX have recently completed the location of the former processing plant, largest single investment project in thereby safeguarding production continuity at their UK aggregates business with the the site for the next 30 years. replacement of the original processing The quarry itself is situated on the northern Cplant and quarry infrastructure at Pant-y-Pwll flank of Halkyn mountain in Flintshire, North Dwr Quarry (aka Halkyn Quarry), installed in Wales, a wild grazing landscape steeped in the 1950s, with a new state-of-the-art industrial history that lies between the processing facility. As well as delivering modern Clwydian mountain range and the Dee estuary, standards of production efficiency and close to the village of Pentre Halkyn and some environmental control, the scheme has also 15 miles west-north-west of Chester. The site successfully achieved its overriding aim of covers a total area of 51ha, with some 32ha releasing 32 million tonnes of reserves that currently active. had previously been made inaccessible by the Halkyn mountain and its natural resources ® QM October 2006 www.quarrymanagement.com 11 The new Kleemann + Reiner long Milwr Tunnel from sea level at Bagillt in SHH15 primary impactor the north to Loggerheads in the south. Started in 1897 and completed in the mid-1900s, this tunnel effectively drained 60 miles of mine passages, some up to 800ft below ground level, and even today is believed to influence the level of the water table around Halkyn mountain. During their heyday between 1845 and 1938, the Halkyn mines produced nearly 500,000 tons of lead, representing nearly 10% of the UK’s total production at that time. Early quarrying in the area was carried out on a small scale by locals digging limestone for buildings and walls, or for grinding into a powder to use as fertilizer. Gradually, as demand for building stone and agricultural lime increased throughout the 1900s, larger quarries developed and eventually supplanted the once booming mining operations, which finally came to an end in 1987. Today there are three active commercial quarrying operations on Halkyn mountain, supplying materials to construction sites across north-west England and North Wales. have been exploited by man for many Halkyn replant centuries. Over the years this corner of North Initial planning for the replant at Halkyn Wales has given up vast quantities of lead, Quarry began in the mid-1980s when chert and limestone. Evidence of lead mining permission for an extension to the site was dates as far back as Roman times, but it was granted, although it was some 10 years later not until the early 1600s that mining in this before the project finally began in earnest. area really began to flourish. As the mines Between 1996 and 2001 the design of the new grew in both depth and extent, flooding of the plant was re-engineered several times, with tunnels and shafts was a constant danger to projected costs ranging from £10 million to the miners, a problem that was partly solved £20 million. The scheme eventually selected by the advent of steam-powered Cornish represented a total investment of £13.5 million. Primary crushed material is pumping engines at the turn of the 18th Approval to start the replant was granted in conveyed from the base of the century. 2002 although this was subsequently deferred quarry to a 900-tonne The ultimate solution to this problem, for a year. Following extensive best-value capacity surge bin however, was the construction of the 10-mile design exercises, the main contracts were awarded to a restricted number of suppliers during March and April 2004, with Whitwick Engineering (Coalville) Ltd appointed as main contractors for the mechanical engineering and materials handling aspects, and RMB Contractors Ltd and Glenace Electrical Ltd looking after the civil works and electrics respectively. A project-management team led by CEMEX Central Engineering Services’ head of engineering, Andrew Boam, was established to ensure tight cost control and smooth delivery of the various phases of construction. Work on site commenced in August 2004 with the project being conducted in accordance with current CDM and health and safety regulations. One of the first tasks was the creation of a new access road to increase site safety and efficiency and to allow work to commence on the civil engineering works for the new infrastructure. The physical and logistical demands of the redevelopment were considerable. The new primary crusher had to be situated on the floor of quarry void some 600m from the position of old primary plant, which itself was located at an elevation 100m ® 12 www.quarrymanagement.com QM October 2006 The 900-tonne surge bin with continuity, the old processing plant remained overflow and re-feed in operation until the new facility was fully conveyors commissioned, during which time employees underwent intensive training on the new plant’s computerized systems and processes. Unlike its predecessor, the replacement plant is fully automated for maximum production flexibility and features comprehensive diagnostic capabilities. Decommissioning and dismantling of the old plant commenced at the end of July this year. Processing operations The Carboniferous Limestone worked at Halkyn Quarry lies predominantly within the Loggerheads Limestone Formation and extends to a depth of at least 22m AOD, which is some 232m below the level of the main plant. The deposit itself comprises a very clean, largely clay-free material with a crushing value of 22, an LA abrasion test value of 21 and a particle flakiness index of 6. Despite the bulk of the reserves lying at considerable higher on the quarry rim. The scheme also depth, the quarry suffers from very little called for a new 1km long trestle-mounted groundwater infiltration, as the area is thought conveyor incorporating a 43m long high-level to be drained by the Milwr Tunnel, which is gantry section to deliver material to the new located 550m east of the quarry at a depth of secondary crusher at the top of the quarry. In 10m AOD. Nevertheless, some water-filled total, almost 3,000 tonnes of steel were used in fissures or pockets are anticipated during the new structures. development of the site, which may have some As a testament to the skill and bearing on future extraction plans. professionalism of the teams working on site, During each 10h loading shift, blasted no lost-time incidents were recorded limestone is loaded into three 40-tonne Cat throughout the 15-month construction period, 771D rigid dumptrucks by a Cat 988G wheel and according to Andrew Boam, the various loader for the current 400m haul from the face contractors’ approach to CDM and health and to the new primary crusher installation, a safety issues was ‘exemplary’. Formal complete load-and-haul cycle taking around commissioning of the new plant began in 9min. At the primary station the material is December 2005 and continued through to dumped into a 150-tonne feed hopper February 2006. To ensure production equipped with a Kleemann+Reiner 1,250mm ® Part of the 1km long trestle- mounted conveyor system showing the 43m long gantry section 14 www.quarrymanagement.com QM October 2006 View from the secondary plant looking back towards the surge bin and primary crushing station beyond x 6,000mm reciprocating tray feeder, which in stockpile conveyor and equipped with two turn discharges on to a Kleemann+Reiner Skako feeders at its base, this vessel on its twin-deck grizzly screen with bars set at own is designed to provide around 1.5h of 150mm. All +150mm material is fed directly production capacity in the event of a primary into a Kleemann+Reiner SHH15 primary section breakdown or planned shutdown. In impact crusher, which has a throughput addition, a re-feed hopper situated adjacent to capacity of 525 tonnes/h. Any oversize boulders the surge bin allows the overflow stockpile are handled by a PRF Engineering rock breaker material to be shovel-fed back on to the feed mounted adjacent to the crusher. conveyor to the secondary plant selector Scalpings rejoin the –150mm crusher screen when necessary. product for delivery to a 900-tonne capacity On arrival at the top of the secondary plant, surge bin located at an intermediate elevation situated on the quarry rim, the primary within the quarry. Featuring an overflow crushed material is a discharged into a twin- ® View from the main screen house showing the secondary plant and covered storage bays 16 www.quarrymanagement.com QM October 2006 Photo showing the clean, virtually dust-free environment within the main screen house deck Don Valley selector screen, which is used The 450 tonnes/h Kleemann+Reiner SNH20 to split the material into +75mm, –75mm secondary impactor discharges its –40mm +40mm and –40mm fractions. The two coarser product on to the main screen house sizes are discharged into two 230-tonne conveyor. Final screening is carried out by capacity selector bins equipped with 450 three dust-encapsulated Don Valley screens — tonnes/h Skako vibratory tray feeders, which in a 3,430mm x 7,000mm triple-deck unit, a turn feed a 180-tonne surge bin mounted 3,000mm x 7,000mm double-deck unit, and a above the secondary crusher. The –40mm 2,400mm x 5,000mm single-deck unit — all fraction is discharged into a third selector bin equipped with Tema Isenmann modular panels. from where it can be fed directly on to the A highly effective dust-extraction system, main screen house feed conveyor or, supplied by Enviroflo Engineering Ltd, ensures alternatively, to a lorry load-out conveyor rated that the main screen house remains virtually at 850 tonnes/h or to a 2,000-tonne ground dust-free at all times.