Holcim New Zealand, as part of its work on its cement supply options, is investigating the energy requirements for a possible new cement plant at Westport.
Holcim has one medium-term and two long-term options to meet the projected growth in demand for cement in New Zealand. The medium-term option is to continue the existing Westport plant, with an appropriate maintenance and capital works programme, in combination with supporting imports on a bulk basis. The two long-term options are either a new plant at Westport or a new plant at Weston, near Oamaru.
"We are working on narrowing the three options to two, which will be put forward to our parent company, Holcim Ltd, to decide," says Paul Commons, General Manager of Strategy and Development for Holcim New Zealand.
"At Westport, one of the key components for a new plant is forecasting the cost of both thermal (coal) energy and electricity for the projected life of a plant."
A cement kiln requires significant energy inputs to provide the heat (up to 1450°C) required for the chemical reactions that produce cement. Holcim New Zealand uses coal, supplemented by used oil, which is mixed with other materials and fed into the kiln.
Electricity requirements for a new plant are also being looked at. Electricity would be required to rotate the kiln, for the grinding mills, for lighting, fans, pumps and other electrical equipment as well as for employee and office facilities. Total electrical demand for a modern dry-process cement plant - of the size being proposed by Holcim - would be around 15 MW.
Security of supply is also essential and required for the life of a plant. Short, medium and long-term options are being assessed, as well as investigations looking at contingencies should an unexpected event interrupt normal energy supply. A new cement plant would have emergency power generators and coal stockpiles.
The suitability of the coal available for a new Westport plant is being analysed as part of these investigations. This involves trials of the coal's physical properties (looking at moisture, heat value, ash and grindability) as well as chemistry.
"Coal sulphur content is not typically a problem in cement production as almost all of the sulphur in coal is incorporated within the cement during the high-temperature chemical processes that occur in the kiln," concludes Paul Commons.
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