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Humid Air Injection Boosts CT Output

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Additional megawatt-hours (MWH) can be obtained at low cost during peak demand periods from gas turbines and combined cycle power plants by injecting externally compressed, humidified, and heated air into a combustion turbine (CT) up-stream of combustors. This novel approach is denoted as CT-HAI, (HAI is an acronym for Humidified Air Injection) for simple cycles and CC-HAI for combined cycles. It results in a significant power augmentation over the whole range of ambient temperatures, but it is the most effective at high ambient temperature conditions when reduction in power output is most severe.

The simplified explanation for reduced power production by CT and CC plants is that lower inlet air density, a result of the high ambient temperature, reduces mass flow through a CT with a corresponding reduction in power.

With HAI, power output can be maintained essentially constant over the range of 0 F to 95 F at about 20 % above the nominal 59 F rating. The overall heat rate for the total output of the power augmented CT also drops by about 8%-12% over that temperature range, saving fuel as the temperature rises. The heat rate for the incremental power is approximately 6000-6400 Btu/kWh, i.e. in the range of CC plants. Engineering and mechanical aspects of the air injection for CT-HAI concept are similar to the steam injection for the power augmentation, which has accumulated significant commercial operating experience.

This system can be operated to produce additional MW for sale whenever market conditions are attractive. The value to individual utilities will vary according to the number of hours that the additional megawatts can be sold at attractive prices. Specific capital costs of additional kWs (i.e. for installing HAI) are less than $200/kW. With lower net heat rates, the cost of electricity obtained with this technology can provide power at lower production costs in peak power markets.

The process is an interesting coming together of two separate ideas for getting more out of CTs: (1) adding humidity, and (2) (externally) compressing the air:

Just Add Water —
The output of a CT can be increased by adding water in various ways, like evaporative cooling, wet compression, and inlet chilling. Unfortunately, these technologies that may have low initial capital costs introduce the water into compression process and can create significant operational problems. For example, GE has told users to cease inlet fogging and evaporative cooler operation until compressor blade erosion inspections can be performed. Technologies that introduce condensation or carryover of water into the compressor section can cause blade erosion and ductwork corrosion, pitting and thermal stress.

While steam injection technology also bypasses the compressor, with HAI, humidity is introduced in the form of humidified air that, as compared with the steam injection, provides for a safer and more stable combustion process, and allows for higher injection rates with associated greater power augmentation. Steam injection flow is limited by a number of combustion related and other considerations.

Compressed Air —
The other development behind HAI is compressed air energy storage (CAES), a diurnal peak shifting method where air is compressed off-peak and stored in underground formations or piping systems. On-peak, the compressed air is fed to the CT, relieving it of the need to do its own compression and thus increasing output. From there it was a short step to realizing that an external compressor could be beneficial under certain operating conditions. Adding humidity to this external air supply enhances the performance even more.

Dr. Michael Nakhamkin, President, Energy Storage and Power Consultants (ESPC), has fourteen patents; including five on CAES technology and another five on the power augmentation technologies with humid and dry air injection into CT.
908-658-4815, mnakham@optonline.net, http://www.espcinc.com/

– Combustion Turbine with Humid Air Injection (CTHAI) -pat. 6038849
– Combustion Turbine with [Dry]Air Injection (CTDAI) -pat. pending
http://www.espcinc.com/poweraug.htm

Both methods can increase power output by 15%-25% or more; use proven equipment; and are simple to implement and operate. The humid version also reduces NOx by 15%. Developers have also come up with a clever means to avoid entraining impurities in the water, simplifying water treatment. A once-through boiler with partial steam generation requires only demineralized water.

Several HAI/DAI concepts as applied to simple-cycle (CT) and combined-cycle (CC) plants are available for commercial implementation. Successful validations have been done at Calpine on GE 7241 FA. HAI can be practical for any CT 5 MW and larger.

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Hill Energy System, a subsidiary of Hill International, is a licensee of the HAI technology, and is actively marketing systems. The website has contact information and a number of helpful documents.
http://www.hillenergysystems.com
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Also see a full discussion in the July 2003 issue of Power Engineering Magazine:
“Humid Air Injection Turns to Out-Of-Shelf Equipment to Enhance Viability for Combustion Turbine Power Augmentation”
http://pepei.pennnet.com/Articles/Article_Display.cfm?Section=CURRI&ARTICLE_ID=181509&VERSION_NUM=2&p=6

“Air Injected Power Augmentation Validated by Fr7FA Peaker Tests”, Gas Turbine World, March/April 2002.

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Ron Wolk, prominent power technology expert, has been involved in this program for years, and can provide additional insights. Contact him at:
408-996-7811 RonWolk@aol.com

Fwd: McIlvaine Co. offer

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McIlvaine Company
ANSWERS TO IMPORTANT POWER PLANT QUESTIONS OF THE MONTH

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POWER PLANT QUESTIONS OF THE MONTH

WILL POWER PLANTS HAVE PROBLEMS MEETING THE 2003 NOx REDUCTION REQUIREMENTS?
The answer is maybe. The bigger utilities with a number of affected plants are faced with only a few outages over the next three years. AEP and TVA have lined up partners in order to nail down the availability of engineering and equipment. But some of the mechanical contractors are already reporting full shops and a heavy workload. The secret is going to be maximum effort now to finalize plans and line up contractors. Those utilities who wait until 2001 are going to be out of luck.

WHAT KIND OF OPERATIONAL PROBLEMS COULD I HAVE WITH NOx CONTROLS?
Combustion modifications can result in accelerated tube wastage and unburned carbon in the fly ash. SCR problems include arsenic poisoning of the catalyst and ammonia slip. In fact, California and Massachusetts are toying with regulations to require zero ammonia emissions. But even absent regulations ammonia can cause problems. It can plug up your air heater and it can contaminate your fly ash. Buyers will definitely react negatively to ammonia contaminated fly ash? Some of the vendors say their methods of ammonia distribution and control eliminate this problem. Others say the answer is a staged system.

We are not going to devote too much attention to NOx issues in this Overview because we have a NOx Chat Room with detailed discussions of all these issues. It is free and easily accessible on our web site.

To go to the NOx Chat Room click here: http://www.mcilvainecompany.com/discuss.

IS THE AVERAGE UTILITY OVER REPORTING NOx AND SOx?
Many utilities are actually emitting less NOx and SOx than they are reporting. Flows are actually 5% lower than instruments are indicating. This could be worth $ millions per year to the medium size utility.

DO I HAVE TO CHANGE CEMS DUE TO PART 75 AMENDMENT?
EPA has amended sections of Part 75 to provide more accurate measurement of NOx mass emissions. The question is whether to upgrade from an emission rate monitoring system to a mass monitoring system or whether it is better to replace the system and start over. Newer analyzers do not confuse NO with total NOx . Keep in mind that the value of accuracy goes up substantially with the trading of NOx at $3,000/ton.

CAN YOU MEASURE MERCURY CONTINUOUSLY AND ACCURATELY ?
It appears that continuous emission monitors for mercury will be able to duplicate the wet chemistry methods within 20%. Don’t be surprised if within a few years both continuous mercury and mass particulate monitors are required for each power plant stack. Tests of mass particulate monitors on incinerators have been positive. A number of power plants in Europe are already using mass particulate monitors of the tape sampler type.

ARE PRECIPITATOR PARTICLE EMISSIONS PRECURSORS OF PM2.5?
One of the problems in quantifying PM2.5 emissions is going to be semantics. How is a large agglomerate of small particles which is emitted when rapping the precipitator classified? If it quickly disintegrates when it loses its electrical charge, isn’t it all small particles?

INFORMATION TECHNOLOGY
How important advances in IT instrumentation, controls, automation, monitoring and process optimization are changing the very nature of electric power generation. Jason Makansi advises that the individual information technology functions must be integrated into a cohesive system that communicates seamlessly with IT networks external to the plant. The ultimate goal is economic optimization.

IT changes and is integrated into the personnel organization and cultures-minimizing people, making work safer, focusing on results, moving towards predictive maintenance, pushing the envelope on operations and performance, breaking down barriers between departments (i.e. maintenance and operations). It will create “virtual plant staffs, crews and teams” responsible for multiple plants and will facilitate third-party service contracts. A 1400 MW coal-fired plant in Australia is supervised by two people on site during the second and third shifts. This will become commonplace in the future.

SHOULD YOU REPLACE PRECIPITATOR INTERNALS WITH BAGS?
The replacement of precipitator internals with bags at the State Line plant is a significant event. While other bidders were following the specs with bids on precipitator internals, Wheelabrator bid a conversion to a baghouse. The flexibility to burn a greater variety of fuels led Southern to select the baghouse conversion. This decision was followed by the Sheldon station award to ABB to replace the existing precipitators with fabric filters.

DO YOU HAVE TO WORRY ABOUT TITLE V AND THE TOTAL PARTICULATE EMMISSIONS?
The problem is that your present opacity monitor doesn’t tell you how much particulate is emitted during excursions. So it is going to be difficult to verify total mass emissions. Unfortunately your Title V permit probably limits you to a specific tons per year of particulate. But there are some simple steps to take to protect yourself. One is to do some stack testing during upset or start up and shut down conditions. If the emissions are only slightly higher than normal then you have some supporting evidence.

IS THERE A ROLE FOR WASTE BURNING IN MY PLANT?

While coal gasification is still a questionable option from a cost standpoint, the gasification of waste can be quite attractive. In parts of Europe power plants are forced to burn 10% biomass in each coal-fired boiler. Gasifying waste and using it as a reburn fuel provides both the economic benefits plus the reduction of NOx. But just simple fuel blending is in vogue. Connectiv is fueling one plant with chicken manure. Illinois Power will burn all the plastic pellets it can find.

WHEN IF EVER IS COFIRING GAS ATTRACTIVE?
The answer is that there are many situations that favor cofiring. In the ozone season it is a way to reduce NOx. During low load conditions the use of gas may be more economic than running the pulverizers and burning the lower cost coal. Most importantly you have a back up if your air pollution control or coal handling equipment fails at a time of high demand. Mississippi Power found that they could burn a combination of petroleum coke and natural gas more inexpensively than coal.

WHAT’S NEW IN GAS TURBINE COMBINED CYCLE SYSTEM COMPONENTS?
There is probably more new and useful technology being developed to improve the complete combined cycle system than there is in the turbines themselves. This is a pretty expansive claim since the new series of turbines has substantially higher output and efficiency. But a substantial part of the output and cost is found in the other components. New ways to cool and purify the intake air can substantially improve output and lower life cycle costs. As they say the devil is in the details. The disc centrifuge manufacturers have MADE improvements in fuel purification. The cooling tower people have more efficient packings.

There is even a better access door you should consider rather than let each component supplier furnish a hard-to-open home grown design.

For more information on the Power Plant Knowledge System click here: http://www.mcilvainecompany.com/PPKS.htm

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