Metso Minerals crushing plant boosts production
Tarmac Middle East’s Al Dhahira Quarry in Oman is set to benefit from crushing restrictions in other Gulf States
With Sharjah becoming the latest Gulf State to ban crushing operations on environmental grounds and others restricting wadi or riverbed gravel operations, one quarry in Oman is set to almost double its designed production capacity to meet the resulting increased demand for highway and construction projects in Abu Dhabi.
Tarmac Middle East’s Al Dhahira quarry in Oman saw production increase by more than 35% to 4.8 million tonnes at the end of its first 12 months and, according to general manager Julian James, this will increase to 7 million tonnes by the end of 2004.
At the heart of the operation is a crushing and screening installation from Metso Minerals comprising a primary Nordberg C100 jaw crusher, three NP1110 impactors, a Nordberg HP200 cone crusher, five 12m2 screens and over 40 conveyors.
In a turnkey project, Metso Minerals designed, built and installed the plant for a production output of 650 tonnes/h, but by the end of its first year of operation the installation was producing almost 800 tonnes/h; achieved, according to Mr James, by producing the best mix of aggregate for the plant configuration, and improved efficiency resulting from experience of operating the Metso units.
The quarry started production in May 2002 and is Tarmac’s largest wadi gravel deposit, occupying a site of almost 40km2 close to the Oman–UAE border. Owing to environmental concerns, the Gulf States of Kuwait, Bahrain and Qatar, and the Emirate of Sharjah, have closed down crushing and screening operations. Consequently, quarries such as Al Dhahira are poised not only to supply Oman and the UAE, but the entire Gulf region.
At present, however, the increased production is predominantly geared towards highways construction projects in Abu Dhabi and Al Ain.
The quarry, with a recent 40-million-tonne-plus extension, has the potential for at least 16 years of operation at the increased level of production. The rock extracted is a very hard gabbro with a density of up to 3 tonnes/m3 and a crushing value of 13.1 tonnes. It is also highly abrasive and has a 44–50% silica content.
‘This gabbro product represents at least 60% of our production for asphalt plants in Abu Dhabi,’ said Mr James. ‘It provides us with the highest investment return. The remaining 40% is used for concrete production throughout the region.’
Metso installation
The Metso Minerals plant comprises primary, secondary and tertiary crushing and screening equipment. The primary circuit comprises a single Nordberg C100 single-toggle jaw crusher with a feed opening of 760mm x 1,000mm. Material is fed to the crusher via a push feeder and twin-deck primary screen, with undersized material passing through one of the site’s five Nordberg CVB2060 2.0m x 6.0m triple-deck screens.
Crushed material is then fed to the three Nordberg NP1110 horizontal impactors which deliver three discrete product streams for asphalt, ready-mixed concrete and sand.
Each of the impactors feeds on to a dedicated CVB2060 triple-deck screen for product sizing and classification. The processing plant also includes a single HP200 cone crusher for sand production.
To meet stringent pollution regulations, the plant incorporates a dust-suppression system that includes infrared-triggered spray systems at the feed points. The processing area is close to nearby water-bottling plants supplying Oman and the UAE, so any pollution or dust from the site has to be strictly controlled.
‘To meet recent tightened environmental controls we will shortly be completely enclosing the sand conveyors to further restrict dust,’ said Julian James, who confirmed that the installation meets the strictest Omani regulations.
The Al Dhahira operation produces a wide range of aggregates to standard sizes including 40/25mm, 20/10mm, 10/5mm, 5/3mm and 0/3mm. Three sizes of natural sand are also produced: 20/10mm, 10/5mm and 0/5mm.
In order to meet the continuing increases in production, Tarmac are transferring a 700 tonnes/h crusher to Al Dhahira from a nearby quarry which is closing down. The company have also placed an order with Metso Minerals for two four-deck CVB2060 IV screens for the relocated plant.
‘We opted for Metso screens to give a synergy with spare parts,’ commented Mr James. Delivery of the screens is expected to take place in mid-2004, via the Muscat office of local Metso distributors Arabian Car Marketing Co., who also provide regular back-up and spare-parts support for the Al Dhahira operation.
