Hatch completed a 54-MVA capacity steam turbine alternator plant for Samancor in Meyerton, South Africa. The plant uses waste gas from the furnaces to generate steam from gas-fired boilers.

Scope of Services
Hatch completed the conceptual investigations and process definition through to detail engineering, construction and commissioning for the Elgin project.

The following services were also completed by Hatch:

• Gas Measurement and Analysis
  • Gas measurement and analysis were conducted to determine the volume of gas available from the furnaces for use in an energy recovery plant as well as the gas quality and the calorific value of the gas. Because of the specialized nature of the work, the CSIR (Council for Scientific and Industrial Research) was engaged to do the gas flow measurement and calorific value analysis
• Feasibility Studies
  • Feasibility studies were done to evaluate energy recovery technologies to identify the most cost-effective process for converting the furnace waste gas into electrical energy. Typical processes evaluated were:
    • Gas turbine coupled to an alternator
    • Combined-cycle plant comprising a gas turbine and alternator, waste heat boiler and steam turbine driven alternator
    • Gas-fired boiler and steam-driven alternator
  • The gas-fired boiler option was selected because of the dust content of the furnace off-gas and the variability of the gas supply which is dependent on the furnace operations
• Plant Engineering
  • Plant engineering included process definition, plant, equipment and services design and specification for all disciplines including civil, mechanical, structural, piping, electrical, instrument and control engineering. Typical major items of equipment and systems included:
    • Low pressure gas cleaning and storage systems
    • Boilers and boiler-feed water systems. Because of the variability of the gas supply, the boiler was specified and designed with a large turn-down ratio such that the boiler could operate over a range between 30% to 100% of the design rating
    • Turbine, turbo-alternator, condenser and de-aerator plant. Air-cooled condensers were used at this installation because of scarcity of water
    • HT and LT electrical distribution. The alternator generated at 11kV. This was stepped up to 33 kV via a threephase transformer for synchronizing and interconnection to the Samancor Metalloys Meyerton distribution system
    • Water treatment plant
    • Plant instrumentation and control systems
    • Fire protection systems
• Construction
  • The cogeneration plant was completed and handed over for operation in 1996