A unique cogeneration application in a large pulp mill electrical system

Canadian utilities have begun investigating the viability of independent power producers providing generation facilities to operate in parallel wit the utility systems. Cogeneration in industrial plants is often an excellent source of such generation. In the case described it was determined that two 48.7 MVA, 13.8.kV, 0.84 pf, 3600 RPM steam turbogenerator would be the most economical method of power supply for the 1500 Adt/d green field pulp mill. In this application, the local utility could not guarantee a 230 kV or 138 kV tie circuit to be in place at the projected start-up date of the mill, hence it was decided to use a 25 kV construction power line which was already in the vicinity of the mill and used for servicing rural customers. The maximum capacity of the 25 kV line was 7 MVA at 1.0 pf. Since this capacity could not fully support the mill during construction, black start or stand-by service when one generator is out of service, an additional process independent power source was required. A 14.2 MW (turbine limited), 22.0 MVA, 13.8 kV, 0.8 pf, 1200 RPM pre-owned gas turbine generator was selected to meet the mill construction schedule.