Image: Stockton: High quality coal production despite harsh conditions

Minerals & Metals1 min read

Stockton: High quality coal production despite harsh conditions

Stockton Plateau, New Zealand
Solid Energy
2008 - 2010

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.

A Front-End Engineering Design (FEED) Study was conducted by Ausenco QCC prior to the project moving into execution phase.

Design and engineering were conducted on the 275 t/h CPP. Ausenco QCC also provided overall project management and CHPP commissioning management responsibilities.

Client requirements

  • Prefeasibility study
  • Feasibility study
  • CHPP design
  • EPCM project design

Project solutions and approach

Stockton traditionally bypassed raw coal and the plant needed to process poorer quality, contaminated and diluted coal feeds. Quite wide design envelopes for yield/ ash and size were incorporated in design. The nature of the coal and the handling of the raw coal meant that the coal was quite fine.

The site experiences high rainfall (typically 600 mm per month), so flexible construction scheduling was required.

Some critical design parameters included:

  • Low temperatures (-5°C during winter nights) - structural steel specification ensured risk of brittle fracture was eliminated.
  • Earthquakes - plant designed for a 1 in 500-year event.
  • Wind loads - structures designed for wind speeds >230 km/h.
  • Low pH water (< pH 4) - design of hydrated lime dosing plant included and subsequent dosing in-plant with pH monitoring and control.

Outcomes and achievements

  • No lost time injuries were recorded over a total of 241,000 man-hours worked across 466 days at site LTI stats
  • Design and engineering of a 275 t/h CPP incorporating a dense medium cyclone, three stages of fine coal processing (TBS/RC) and tailings thickener.
  • Completed 2010, below budget and on schedule.