usage, the client asked for a study evaluating the benefit of upgrading the HP turbine on both units. This new HP turbine will allow the unit gross generation to be increased from the present 680 MW (nominal) to 720 MW (nominal) without any significant boiler modifi cations.

To maximize the HP turbine upgrade, the utility requested a balance-of-plant technical study be performed to identify what equipment will require replacement or upgrading. The most significant results of this analysis included:

• The HP feedwater heater, which was scheduled for replacement because of performance problems, would be replaced with one using stainless steel tubes per HEI recommendations and designed for the upgraded flow, pressure and temperature of the feedwater and extraction steam systems. The tube side velocity of the feedwater flowing through another HP feedwater heater (with the higher feedwater flow due to the HP turbine upgrade) was calculated to be 35. 6 percent higher than the HEI standards for closed feedwater heaters. A proposed solution recommended that stainless steel tubes be considered for the HP feedwater heater.

•The plant experienced elevated condenser shell pressures during summer months, preventing maximum load from being achieved on hot days. Since the condenser’s heat removal duty was expected to increase with the upgrade, the problem was thought to be worse after the upgrade. A detailed condenser cooling water optimization study was ordered to determine the necessary steps to achieve the desired condenser pressure and to obtain maximum generation under the worst summer ambient temperature conditions.

• It is suspected that the performance of the fresh-water, closed-cooling-water-system cooling towers was affected by fouling of the cooling tower fills caused by ash deposited

from a nearby fly ash silo. A detailed study was ordered to develop solutions.

•Three condensate pumps were found to need modification to operate at a higher head and desired condensate flow. In the alternative, consideration should be given to replacing the pumps with the revised design conditions required by the upgrade.

• Additional equipment was identified as presenting a potential bottleneck: main boiler feed pumps, induced draft fans, circulating water pumps, pulverizers and primary air fan motors.

These examples illustrate the need for the implementation of a balance-of-plant assessment methodology when upgrades to boilers and/or turbines are being considered.

Analytical techniques, with field testing confirmation, can be used to perform comparative studies on determining what upgrades will provide a cost-effective solution.

Combined with the modeling, knowledge of modern construction techniques and the latest offerings from equipment vendors allows developing an integrated plant upgrade solution with a desirable payback.

 

Authors: Anthony Munisteri is asset optimization director for Sigma Energy Solutions Inc., a unit of Alstom Power. He is a registered professional engineer with over 20 years of experience in the power industry and holds a BChE Degree from The Cooper Union and an MBA from Adelphi University. Peter Kelly is the chief electrical and I&C engineer for Sigma Energy Solutions. He is a registered professional engineer in four states with over 28 years of experience in the power industry and holds a BME Degree from Manhattan College and an MSME Degree from Columbia University. George Kotynek is a senior consulting engineer at Sigma Energy Solutions with over 40 years of power engineering experience. He is a professional engineer in Illinois and holds a BS in Mechanical Engineering from the Illinois Institute of Technology.

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Changes in your operating
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So, regardless of who originally
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