O&M

Cleaning air heaters in power plants or recovery boilers has traditionally involved using high-pressure water, chemicals, or steam. These techniques, though effective on moderate airside fouling of heat exchange surfaces, are usually ineffective on the more tenacious deposits that can develop in coal-fired plants. If these deposits are not removed by periodic cleaning, heat transfer in the heaters is reduced, which in turn reduces boiler efficiency and increases a unit’s heat rate. Severe fouling on air preheaters (APHs) can even reduce a unit’s power output.

The air preheater is a critical, yet often overlooked, component of the boiler combustion air system. Evaluating and optimizing a heater’s performance is difficult given how entwined it is with the entire combustion system and the lack of standardized calculation tools. Reducing leakage by using modern seal technology will improve combustion efficiency, maintain fan performance, and keep your downstream air quality control equipment operating within spec.

In Part I of this two-part report we examined the various chemical forces at work in condenser tube leaks, the steam plant components placed at risk, and the suite of instrumentation most capable of providing early warning of a leak. Assuming you were able to repair the leak and quickly resume operation, the next step is to identify the damage mechanisms that caused the problem so you can minimize future leaks.

As a boiler fuel, biomass has shown great promise while suffering from a slow development history. One factor limiting its use has been the combustion system. For the most part, conventional grate-fired boilers have been the only option. Today, the most efficient approach to burning biomass to produce electricity and steam is fluidized bed combustion (FBC). Whether you choose FBC or grate, biomass presents unique challenges to control system designers.

We first reported on combined-cycle plant reliability concerns due to erosive wear and flow accelerated corrosion (FAC) in heat-recovery steam generator (HRSG) pressure parts at the 1999 EPRI Maintenance Conference. More than 10 years later, these damage mechanisms remain significant contributors to forced outages, pressure part repairs, and major component replacement.

Summer peaks are still with us, and every unit on your system must be prepared to operate at a moment’s notice. Spot power prices are so high that you expect phone calls asking for a few more megawatts from your units. Then your plant chemistry lab calls to report a condenser tube leak. Your options are few: Shut down immediately and get charged with a forced outage, ignore the leak and keeping running until fall, or schedule a maintenance outage next weekend and hope the leak can be found and fixed. In Part I, we examine what you need to know in order to make an informed decision. In Part II, we’ll explore the actual damage mechanisms.

Every power engineer must have a firm grasp of the rudiments of how fuel is processed to produce electricity in a power generation facility. With this article, we conclude our three-part series on the essentials of recovering heat from flue gas to dry and process coal, with the goal of improving overall plant operating efficiency.

Progress Energy has incorporated online combustion optimization/tuning to eliminate furnace reducing atmospheres at its Asheville Plant. The optimization project utilized individual burner airflow measurement and continuous burner coal flow measurement to adjust burner air/fuel ratios. The result: significantly improved boiler combustion.

Many claim that wind generation is beneficial because it reduces pollution emissions and does not emit carbon dioxide. This isn’t necessarily the case. When wind is introduced into a generation system that uses carbon technologies to back up the wind, it actually reduces the energy efficiency of the carbon technologies.

The amount of air leaking into the boiler envelope is difficult to estimate. Traditional methods of measuring oxygen at the furnace exit and economizer exit do not account for all types of air leakage. By using molar calculations and total airflow measurement, a good approximation of the total air in-leakage rates of a boiler can be quickly determined using station instruments.

The competitive push for more efficient power generation prompted the management of East Kentucky Power Cooperative’s Spurlock Station to provide training and to implement standardized work processes in order to achieve higher productivity. To that end, Spurlock’s management collaborated with salaried and hourly personnel to design and implement work process optimization. Two years later, their proactive, operations-driven culture is promoting continuous improvement at this facility.

American Electric Power’s (AEP’s) Cardinal Power Plant Unit 3 cooling tower in Brilliant, Ohio, was coated and lined in the spring of 2008 by a team of coatings professionals that included the plant’s project and coatings engineering staff, Sherwin-Williams (coatings supplier), Cannon Sline Industrial (contractor), and OTB Technologies (third-party inspector). The team completed the project in just 11 weeks through damp springtime conditions in the Ohio River Valley.

In April, Solvay Chemicals Inc. commissioned a new facility that uses an innovative process to recover and transform sodium carbonate waste streams into a market-grade sodium bicarbonate used in air emissions control.

Fogging systems have been successfully used in the material-handling industry for more than 30 years to control explosive dust at transfer points. Today, fogging systems are an EPA Best Demonstrated Technology for subbituminous coal preparation plants.

A recent trend in nuclear power plant upgrades has been the replacement of the motor-generator (MG) sets that drive the reactor circulating pumps with variable-frequency drives (VFD). Siemens’ first application of VFDs in this industry began in 2000 with an installation of six VFDs at the Browns Ferry Nuclear Plant. The use of the VFD continues to expand, and upgrades were recently completed at several U.S. plants, including the Hatch Nuclear Plant in Georgia.

One of the primary challenges of reliably burning coal is managing the corrosion experienced by the furnace heat transfer surfaces. Fireside corrosion remains a leading cause of failure in superheater and reheater tubes. In Part I, we examined three case studies of different failure modes experienced by tubes located throughout the furnace. In Part II, we conclude with two additional boiler tube failure case studies.

Austin Energy replaced the selective catalytic reduction (SCR) catalyst twice over five years for its four peaker turbines. The duct modifications and injection grid redesign, combined with new catalyst, are producing high NOx reduction and low ammonia slip, and the catalyst is now expected to last at least five years.

Every power engineer must have a firm grasp of the rudiments of how fuel is processed to produce electricity in a power generation facility. With this article, we continue our three-part series on the essentials of recovering heat from flue gas to dry and process coal, with the goal of improving overall plant operating efficiency.

Gas turbines require clean gas to operate efficiently. Particulate contamination fouls fuel nozzles, causes increases in flue stack emissions, and occasionally causes unplanned plant outages. Now a new real-time natural gas cleanliness monitoring and web-based alarm system is providing valuable protection for natural gas–fired power plants. The adaptation of laser light–scattering technology for the purpose of contaminant measurement in high-pressure gaseous pipelines provides a method of monitoring liquid and solid contamination levels.

This third and final installment addresses three more areas where an investment in good maintenance practices pays operating availability dividends.

At least 10 workers have died from natural gas piping explosions in the past 12 months. The most recent disaster, which occurred during gas system purging at the Kleen Energy Systems plant, claimed five lives and injured 27 workers. It’s time the industry understood the unique design and safety requirements for working with and purging natural gas piping.

Much like the crime scene investigators on the CSI TV shows, power plant investigation teams are increasingly employing forensic engineering methods to gather evidence and determine the causes of malfunctions of equipment, materials, or products that result in personal injuries or property damage. Case studies show how different investigation teams used their forensic engineering expertise to examine a dust collector explosion, a coal terminal fire, and the failure of a forced draft fan.

If not properly controlled, coal and coal dust can cause fires, explosions, and implosions at power plants. Strategies for promoting safer management of these combustibles include actions such as training personnel exposed to the hazards of coal and coal dust about safe handling methods.

Laser shaping technology has evolved from a two-step process into a single process that drills and shapes holes through a TBC, bond coat, and airfoil base metal to create a finished product.

Nearly every combined-cycle operator recognizes that cycling reduces the life expectancy of hot-gas-path components in combustion turbines. Often overlooked, however, is that the same phenomenon affects the heat-recovery steam generator (HRSG).

The power industry needs a straightforward definition of "fleet optimization" and a game plan to achieve the promised economic gains of optimizing. This need has become more urgent because integrating nondispatchable renewable resources requires more complex optimization strategies. The bottom-up approach presented here applies well-understood optimization principles and techniques that will help power producers minimize their fleetwide cost of production, independent of the technologies used to generate electricity.

Enhanced condenser tube designs can significantly improve the heat rate and performance of fossil and nuclear plants. Using the optimum number of tubes and replacement tube sheets will cost more than simply replacing plain tubes. However, the investment’s simple payback is measured in only weeks, which builds a strong case for using an enhanced tube design as part of your next condenser overhaul.

The "combined" portion of a combined-cycle plant is the heat-recovery steam generator (HRSG) that generates high-pressure and high-temperature steam and the steam turbine generator that expands the steam to produce electricity. Integrating the HRSG and steam turbine with the combustion turbine is a key challenge for plant designers, as each system has differing operating profiles, operational constraints, and design requirements.

One of the primary challenges of reliably burning coal is managing the corrosion experienced by the furnace heat transfer surfaces. Fireside corrosion remains a leading cause of failure in superheater and reheater tubes. Three case studies examine the different failure modes experienced by tubes located throughout the furnace.

Every power engineer must have a firm grasp of the rudiments of how fuel is processed to produce electricity in a power generation facility. With this article, we begin a series of Power 101 tutorials that present these fundamentals in a clear and concise way. First up are the essentials of recovering heat from flue gas.