| Abstract |
The Tasman Pulp & Paper Company Ltd's mill at Kawerau has been utilisingthe geothermal resource available in the area surrounding the mill for more than 30 years. This resource was just one of the many factors considered for the final siting of the mill although it wasn't till much later that the potentialof the geothermal field was fully appreciated. The original concept was to deliver "steam only" to the mill with the water separation as close as practicalto the well heads. Over the years the resource has been developed to give a very reliable supply of steam to meet the requirementsof the The mill produces per annum approximately 200,000 tonnes of kraft pulp and 400,000 tonnes of newsprint. Geothermal resources make up approximately30% of the process steam and 5% of the load required by the mill and without this resource other forms of energy such as oil, gas or coal would be required. "Clean" processsteam is producedin Heat Exchangersbecause of the non-condensiblegases associated with geothermal steam it has not been practical to use it direct in the pulp and paper drying process. However it is used direct in heating combustion air and shatter sprays in the Chemical Recovery Boilers, black liquor boiler feedwater heatingand timber drying kilns used by an associated company. Electricalenergy is produced in a 8MW Turbo Alternator exhausting to atmospherevia a water evaporationplant in the liquor cycle of the pulp milland a water heater that supplies hot process water at to both the pulp and paper mills. All the condensate produced from the use of geothermal steam in the mill is collected and processed to provide high quality make up use in the Heat Exchangers, Power and Recovery Boilers in place of high cost demineralisedwater. Separated water at the borefieldinstead of being dischargeddirectly to the local river as in the early days has been further utilisedfor electrical generation (three Ormat type units), a pilot plant to recover silica to be used as a newsprint additive and reinjection in selectedwells. Only then is the remainingwater discarded. |