| Title | NTGAL Clean Steam Supply To SCA Kawerau |
|---|---|
| Authors | Greg Moore |
| Year | 2011 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | Kawerau, clean steam |
| Abstract | Ngati Tuwharetoa Geothermal Assets Limited (NTGAL) is the owner of the Kawerau geothermal steam field. They currently supply about 300 tonnes/hour of raw geothermal steam to the adjacent timber processing mills. A majority of this is used in direct heat applications in either paper making or timber drying. In August 2009 NTGAL were contracted to supply clean, high-pressure steam to SCA Hygiene Australia Ltd for use in their tissue manufacturing plant. SCA required a high quality steam supply at up to 26 tonnes/hr and 16 barg. The option of converting to geothermally generated clean steam was appealing to SCA as it allowed the decommissioning of their two natural gas boilers and reinforces their commitment to minimising global CO2 production. This transfer to geothermal generated steam will eliminate up to 17,300 tonnes/year of CO2 emissions. NTGAL needed to supply high quality steam from a plant capable of maintaining a high level of reliability to ensure SCA could always continue production. For this reason run and standby plants were fabricated. The plant consists of a pair of separators and brine vessels which provide steam to two steam generating heat exchangers. The condensate is then sub-cooled in a feedwater heater before being flashed and stripped of dissolved gases to allow it to be used as feed water. This further improves the efficiency of the plant as the clean steam condensate can ultimately be used in the paper machine process as it is not required for further steam generation. The high pressure brine from the separators is also flashed again in low pressure plant that supplies 6 barg steam to Norske Skog. Dobbie Engineers were commissioned to design and manage the construction and commissioning of the plant. Despite a number of Challenges the plant has now successfully supplied SCA with steam for twelve months. |