Client: Solid Energy New Zealand
Scope: Turnkey Delivery of a Greenfiled Coal Handling & Processing Plant
Timeframe: 18 months from design to construction completion
Overview
Solid Energy New Zealand operates an open-cast coal mine on the Stockton Plateau, 35km north of Westport, on the West Coast of the South Island. The Stockton mine produces high-quality coal for export to the steelmaking industry.
As of 2008 the Stockton mine had accumulated stockpiles of up to 15 million tonnes of contaminated coal due to operating in areas of historic underground mining. A prefeasibility study conducted by Brightwater and Downer Engineering identified that a Coal Handling and Preparation Plant (CHPP) would produce 10 million tonnes of saleable high value product from this stockpile.
Solution
Solid Energy engaged Brightwater as the principal contractor to design (in conjunction with Downer Engineering), procure, and manage the fabrication and construction of the NZ$124 million green-fields Coal Handling and Processing Plant project, all within a fast-track schedule.
The coal handling and processing plant was designed to separate large volumes of high-value coal from rock, old underground mine propping timbers and other waste material, and washing and grading it. The Coal Processing Plant (CPP) was designed to handle between 600,000 tonnes and 1 million tonnes of coal a year. The two key processing steps in the CPP are a dense-medium cyclone for the separation of coarse coal (-60mm(ww) +1.4mm), along with three parallel circuits of hydraulic classifiers for the separation of fine coal (separation (-1.4mm (ww) + 0.045mm).
A key design challenge was the high wind speeds at the Stockton site which would result in high loadings on conveyor truss sections of rectangular profile. Brightwater designed totally enclosed circular cross-section conveyors, with a resultant drag force coefficient 40% lower than those of the rectangular type.
The site layout also called for long conveyor spans; traditionally square gallery style conveyors would be specified but the required size and leg spacing proved costly. Brightwater’s innovation was the introduction of tubular gallery sections for the CPP feed conveyors, which offered significant cost savings to the client.
