Plant study in Colombia pinpoints potential repowering problems

Thoroughly assessing the utility`s existing units led to recommended actions which will ensure the repowered plant can achieve its operational goals

Thomas C. Coleman and Jaime G. Miranda

Parsons Power Group Inc.

In early 1994, Termobarranquilla S.A. Empresa de Servicios Publicos (TEBSA) commissioned Parsons Power Group to carry out a plant assessment study for the Termo Barranquilla Plant, Units 1 to 4 in Colombia. TEBSA is a mixed-economy stock company formed as part of an agreement between the consortium selected to repower the plant and Corporacion Electrica de la Costa Atlantica (CORELCA), a state-owned industrial and commercial company operating under the auspices of the Colombian Ministry of Mines and Energy. CORELCA currently owns the plant which is to undergo repowering by installing a 900 MW combined-cycle plant next to the existing gas-/oil-fired station. The consortium is composed of ABB, Energy Initiatives and Distral, a Colombian manufacturing and contracting company.

The existing steam power plant has an installed capacity of 274 MW. Units 1 and 2, at 66 MW each, have been operating for 20 years; Units 3 and 4, at 71 MW each, have been operating for 13 years. All units are in reasonably good condition and their operation in terms of start-up cycles has been conservative relative to units of this vintage. Past station practices have focused primarily on corrective actions while preventive maintenance has been limited because of budget constraints.

The assessment plan

Parsons` charge was to evaluate the units` present condition as it relates to the risk of not achieving the operational goals established by TEBSA. By quantifying costs of recommended actions, the study allows TEBSA to mitigate the aforementioned risk by performing repairs or upgrades to existing equipment during project construction and by monitoring CORELCA`s operation of the existing plant until TEBSA accepts it.

Parsons found all four units to be viable for continued operation in a study which addressed several areas. By studying the physical condition of the equipment, Parsons identified known plant deficiencies and estimated the cost for renovation to ensure the plant meets its goals for operational life. It also listed those renovations necessary to assure the 75 percent plant availability required after asset transfer to TEBSA. The study recommended cost-effective upgrades which might improve plant availability and heat rate during the operating transition period when both old and new equipment is being used. In addition, Parsons` study recommended a typical spare-parts list based on plant design and operating intent.

Study findings

The study used operational and physical condition data observed during site visits and maintenance data from plant outage reports to determine recommendations for operating the plants in the following modes:

– operate Units 1 to 4 until 1997,

– operate Units 1 and 2 on standby until 2017 or

– operate Units 3 and 4 on standby until 2017.

In general, the generating units were found to be well run and well maintained and are candidates for continued operation. The heat rate had degraded more than expected for units such as these, even taking into account individual equipment performance deficiencies. Suspected reasons for this degradation include fuel gas flow measurements and severely leaking turbine bypass valves. The report listed action items required for continued operation and provided corresponding cost estimates. The sidebar (page 44) lists Parsons` recommendations for the various plant components.

Authors:

Thomas Coleman is a senior mechanical engineer with Parsons Power Group Inc. He has been associated with the design and construction of power generation facilities, both foreign and domestic, for more than 25 years.

Jaime G. Miranda is a principal project manager with Parsons Power Group Inc. in Boston, Mass., USA. His duties include supervision and responsibility for power plant design and construction both domestically and abroad.