Steam and power generation expansion at Lautoka mill, Fiji

This paper describes the methodology used in selecting a new boiler and a new turbo-generator to overcome the shortages in steam and power at Lautoka Mill, Fiji, which had become serious due to increases in crushing rate and deteriorating condition of plant. The steam pressure in the corporation's mills was increased from 1030 kPa to 1720 kPa about 10 years ago. With the need for a new boiler and turbogenerator an opportunity presented itself to investigate higher pressures and to investigate the possibility of generating electrical power in excess of internal requirements. Steam balances were made for various conditions of pressure, crushing rates for the intermediate and future years and allowing for aged plant to be de-commissioned at the right time. The most cost effective combination of steam pressure and temperature was determined for the prevailing conditions, including the inexperience of staff in maintenance of relatively high pressure equipment. It was found that a steam pressure of 3310 kPag and a temperature of 360 DC would serve best. There was no difficulty in sizing the boiler and turbo-generator from the energy balances and other considerations. The capacities were 200 tonnes per hour for the boiler and 12 MW for the turbo-generator. This paper also describes the commissioning and operation of the new system. The level of exportable power has been very rewarding and the overall operation of the existing mill machinery has been enhanced through the ability to maximise the steam pressure at the user.