Abstract: . . .  r p assou t 129.7 T /h r p assou t 136 T /h r p assou t Total RB 152.6 Tt/hr t/hr 42.5 t/hr 42.7 t/hr 6.7 t/hr 231.2 t/hr 0 t/hr 8.0 t/hr 146.2 t/hr 18.7 MW 0.0 t/hr 0.0 MW 24.1 t/hr 85.0 t/hr 0.0 t/hr 110.8 t/hr 24.5 t/hr 148.1 t/hr 19.3 t/hr 136.5 t/hr 95.0 t/hr 246.0 t/hr 4.6 MW Figure 1. 45 barg Header 10.2 barg Header Raw Geothermal 7 barg 3.4 barg Header #2 Recovery Boiler (RB2) #2 Power Boiler (PB2) #3 Power Boiler (PB2) Turbo-Alternator 2 (TA 2) Heat Exchangers Turbo-Alternator 1 (TA 1) Geothermal Turbine (TA3) Pressure Reducing Valve #1 Recovery Boiler (RB1) Pressure Reducing Valve Total Load Total Load Figure 2: Operating Range of turbo-alternator 2. Range for TA1 is similar. 3445  . . .
. . .  Associate Professor Andrew Philpott, in particular, for his help and advice. Further assistance was provided by Tim Sharp, Andrew MacFarlane, Craig Wadsworth and other colleagues. 3443 Page 6 APPENDIX - USER INTERFACE A number of menus have been developed using Visual Basic for Applications in Microsoft Excel 5.0. These allow users of the model to update parameters with current real time values in PI, or override any of these parameters. This interface is shown below. Main Menu A customised menu titled Energy Use has been added to the standard Excel menus. These menus and their functions are: • Run Automatically Calls the linear program solver, solves the problem and displays the Report based on current actual values. • Solve Solves the problem with manual inputs as is. • Enter Costs Allows changes to costs of fuel, steam and fixed operating costs • Enter Demands Downloads current real time values from the PI system for steam demands, electricity price, and plant status or manual inputs for what . . .
. . .  stability when there is a change in demand in either process steam main. The final process steam temperature is controlled by adding water through de-superheating stations at selected points in the steam mains. This process also adds to the total mass of steam produced. Approximately 270 tonnes/hour of geothermal steam is imported from the Kawerau borefield through two pipelines. The steam is utilised in five heat exchangers, which produce 3.4 barg process steam, direct in the process (Recovery Boiler area) and boiler feedwater heaters. The remaining steam is passed through a turbine which has a number of functions: 1. Electrical power generation (8 MW max.) 2. The exhaust is utilised in a liquor pre-evaporator, water heater and foul condensate stripper. 3. The turbine has control systems which stabilise the pressure of the incoming geothermal steam to the mill. The two power boilers are primarily fired with waste wood (hog) as fuel. Provision to fire fuel oil is provided for boiler start-ups, . . .
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