Hydraulic Model Studies for Modifications of the Cooling Water Intake for Unit No. 4 - Clay Boswell Plant of the Minnesota Power and Light Company

Abstract

The Minnesota Power and Light Company (MP&L), an investor owned public utility, has an existing steam-electric generating plant located on Black- water Lake in Itasca County near the City of Cohasset in Northcentral Minnesota. The plant has an intake and pumping station drawing water from the lake. The intake supplies cooling and other water for existing plant Units #1 and #2, each of which is rated at 70 MW. These units employ an open circulating cooling water system and return the heated water to Black- water Lake. The station also includes service pumps which supply makeup water for plant Unit #3. Unit #3 is rated at 350 MW and employs a closed circulating water system with mechanical draft wet cooling tower. Unit #4 will employ a closed circulating water system with a cooling tower. The existing intake pumping station, comprised of two intake sumps, is to be modified to provide water for all four steam units. The modifications will necessitate the replacement of some existing pumps with larger pumps and a rearrangement of the service water pumps. The four existing main circulating water pumps and the traveling screens for intake Units 1 and 2 are not to be replaced. The proposed design modifications of the intake were prepared by Ebasco Services, Inc., Atlanta, Georgia. This report is a brief resume of hydraulic model studies which were carried out at the St. Anthony Falls Hydraulic Laboratory (SAFHL) to clarify and validate the hydraulic performance of the proposed modifications.