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FALLOUT FROM THE U.S. EPA’S CLEAN POWER PLAN, THE RISE OF COMBINED HEAT AND POWER, MERGER REPERCUSSIONS, EPC TRENDS AND COPING WITH THE RENEWABLE ONSLAUGHT
PowerGen 2015 brought more than 20,000 people to Las Vegas, Nevada, to attend almost 80 sessions and exhibits from 1,400 companies. At this year’s event, much was said about the rise of combined heat and power (CHP), merger repercussions, EPC trends, combustion optimization, fuel treatment and inlet air chilling.
Technologies to address these trends included those from Solar Turbines, NeuCo, Power Systems Manufacturing (PSM), CB&I, Stellar Energy, Rentech, Black and Veatch, Sargent & Lundy and Lambda Technologies.
Ascendant themes were the repercussions of the U.S. EPA’s Clean Power Plan (CPP) and coping with the renewable onslaught. These and other topics pervaded opening keynotes from Joe Mastrangelo, President and CEO of GE Power, Steve Berberich, CEO of the California Independent System Organization (CAISO), Stu Hemphill, Senior Vice President of Power Supply and Operational Services at Southern California Edison, and Steven Edwards, Chairman and CEO of Black and Veatch.
Mastrangelo kicked things off with his perspective on how quickly things can change. Ten years ago, he said, everyone was talking about $200 per barrel oil. This encouraged developers to push onward into challenging environments to recover unconventional sources. Yet today we are sitting below $40 per barrel.
The good news is that analysts predict that $5 trillion will be spent globally on new power plants in next 10 years to bring an additional 3 million MW of electricity online. That is 3% per year growth over the next 10 years. To meet rising demand, the speed of development has to ramp up.
“It used to take us six years to release the first .02 upgrade to a turbine, yet 18 months after the unveiling of our HA turbine, an upgrade is now available,” said Mastrangelo.
Gas, 35% cheaper now than it was five years ago, will account for the bulk of power plant additions over the next ten years, growing by 50% in that period. In terms of installed gas, he cited the cost to be $700 per kW, compared to $1,500 for solar, $1,600 for wind, $2,500 for coal and $5,000 for nuclear. Gas also offers the flexibility to be the ideal companion for a renewable-heavy grid.
Mastrangelo believes that gas is best equipped for rapid deployment. According to his figures, a simple cycle gas plant can be online within one month, while solar and wind take six months. A combined cycle plant means a 24-month wait, but that compares well to coal (48 months) and nuclear (72 months). The power density of gas at 80 MW per acre also compares well to 30 MW per acre for nuclear, 2 MW per acre for coal and 1 MW per acre for solar and wind.
With the Alstom acquisition still top of mind, many in the audience wondered how this deal might change GE’s focus. The company’s strength has traditionally been in the gas turbine side while Alstom has been strong in steam turbines and Heat Recovery Steam Generators (HRSGs).
Mastrangelo pointed out that GE will be able to expand its offerings to service Alstom steam and generator assets in the field, as well as its portfolio of transmission and distribution products and services. Alstom also adds 30 repair shops in 14 new countries. “It would have taken us two decades to build the installed base we now have from Alstom”.
He was followed by CAISO’s Steve Berberich, who surprised the audience by showing the degree to which renewables have infiltrated California’s grid. As much as 15,000 MW of renewables can be available and have made up 40% of overall load at some points.
The amount is only going to grow, he said. Almost 8,000 MW of solar is being installed on California roofs every month. The result is the California Duck Curve (Figure).
With increasing dependency on solar, the challenge is a huge late-afternoon drop-off in solar generation at the same time demand spikes. In November 2015, for example, 10,000 MW had to be added between 5 PM and 9 PM by bringing other power assets online rapidly. “Capability is more important than capacity, these days,” said Berberich. “Plants need to be able to start, stop and ramp up rapidly.”
Oversupply, though, is a problem for CAISO due to so many renewables on the grid. One solution is to provide cheap power to neighboring states which are more reliant on coal. This enables these states to move closer to compliance with the U.S. Clean Power Plan (CPP).
Black and Veatch started in the business with the company’s first power plant in Atwood, Kansas in 1915. Today it deals with everything from supercritical coal plants in Africa to combined cycle facilities in the U.S, to rooftop solar and microgrids.
Steven Edwards, Chairman and CEO, said that today five trillion cubic meters of water is consumed around the world. Some 10% to 15% of it is in the power sector (enough to supply North America’s drinking water). “With 50% more GWh forecast to come online by 2050, we will see increased pressure to reduce water use for power,” said Edwards.
As for the CPP, Black and Veatch expects coal to maintain a small but significant portion of overall U.S. power production. That opens the door to plenty of possibilities for maximizing asset value and reducing emissions.
Some $15 billion to $20 billion per year has to be spent on renewables to meet the CPP. This has expanded project development. In the past, utilities managed 80% of development projects. Today they share the load equally with independent developers.
Edwards also sees greater preference for the EPC execution model due to fewer internal resources, price certainty, and clear, delineated lines of responsibility. However, a widening diversity of project sizes prevails. This ranges from massive new facilities focused on first-of-a-kind technologies and a host of smaller plants, as well as exploration of plant betterment opportunities.
“As utilities evaluate their options under the CPP, there is plenty of interest in finding all possible viable improvements to existing assets,” said Edwards. Jeff Holmstead, attorney at Bracewell & Giuliani, covered the CPP in detail. As currently laid out, emission-rate targets for coalfired plants go from the current average rate of 2,200 lbs of CO2 per MWhr to 1,305 lbs/MWhr. For combined cycle plants, emissions are to be cut from 1,100 lbs/MWhr to 771 lbs/MWhr.
Holmstead cited recent U.S. Supreme Court decisions that call into question the EPA’s use of a long-extant statute to give them power to regulate a significant portion of the U.S. economy. He expects several legal battles over the next year to determine if the CPP survives in its current form.
CHP was a popular topic at PowerGen, as industry looks to improve efficiency by capturing heat that is normally wasted, while reducing CO2 and other pollutants. Mark Cutshaw, Director of System Planning and Engineering at Florida Public Utilities, discussed a project being built on Amelia Island, Florida, that would reduce overall power costs and improve reliability.
Known as Eight Flags Energy, it will supply power to local residents as well as a cellulose manufacturing plant for Rayonier. A 20 MW Solar Titan 250 GT and a Rentech HRSG make it possible to operate as a combined cycle power plant, or as a CHP plant to serve steam and hot water to Rayonier. Eight Flags Energy is scheduled to come online later this year.
Two existing biomass boilers at Rayonier are fueled by bark, wood chips and other materials. While this supplies current steam and power requirements, it operates at close to its steam limits.
With expansion planned, the new power plant not only offers more steam, it also enables Rayonier to take a boiler down for maintenance and switch the steam from a turbine to the factory.
The Rentech HRSG can recover 70,000 lbs of steam per hour. However, it can be increased as needed by turning on duct burners. This boosts production to 125,000 lbs per hour of process steam. De-mineralized water is also channeled through a hot water economizer in the HRSG to increase temperature by 70°F. This hot water is returned to Rayonier for production processes.
“By combining the Solar Titan 250 gas turbine with a Rentech HRSG, the CHP facility will produce electricity at a much lower cost than the current wholesale power cost,” said Cutshaw, who cautioned attendees that there is no one-size-fits-all approach to CHP.
In the case of Eight Flags Energy, a combined cycle gas-fired plant proved more viable than a simple-cycle configuration. But he also said a reciprocating engine may work better for some CHP applications.
“A gas turbine has lower efficiency but higher electrical and thermal output than a reciprocating engine,” said Cutshaw. “You have to analyze the electrical and thermal load and match it with the appropriate CHP technology.”
Jason Grimm, Boiler Manager for Xcel Energy, discussed the overhaul of the Sherco plant in Minnesota. Unit 2, commissioned in the late 1970s, has an output of 730 MW. Its low NOx control system was installed in 1994 and shared a common stack with Unit 1 that had a more modern low NOx system.
The problem came when Unit 1 needed an overhaul in 2015, which meant Unit 2 would have to perform in solo operation and the plant would have to maintain the average of emissions from Unit 1 and 2, which meant NOx staying below 0.15 lb/MMBtu and CO emissions being kept below 400 parts per million (ppm). To achieve the NOx goal required a variety of technologies.
This included CombustionOpt software from NeuCo for baseline characterization testing and assessment, combustion tuning and raising of coal boiler efficiency. The software optimizes fuel and air mixing by manipulating fuel and air injection points to reduce NOx and other emissions.
CombustionOpt adjusts the Distributed Control System (DCS) or other control system to match settings to conditions. It integrates into the DCS through a PI data historian. NeuCo can remote in and make changes as needed.
A dynamic classifier by Loesche Energy Systems was also retrofit to improve fuel fineness and distribution. This raised coal fineness by 15%.
For Sherco Unit 2, this reduced NOx by 10%. NOx, therefore, went from being out of compliance to being in compliance every day for one month even at higher loads.
Power Systems Manufacturing (PSM) also provides an automated combustion tuning and power optimization system for Fclass Dry Low NOx (DLN) GTs. “DLN combustors are difficult to tune,” said Peter Stuttaford, PSM’s Director of R&D. “As you drive emissions down, the challenge is to keep combustion dynamics down.”
Vibration, for example, may vary over time due to ambiences or engine degradation. Automated tuning increases reliability compared to having someone in the plant try to manipulate the fuel splits according to ambient conditions. The system sits adjacent to the control system. “Even GTs that are the same model and produced back-to-back can have different tuning needs,” said Stuttaford.
Power plant fuel treatment technology was the subject of a presentation by Chris Wedig, Senior Air Quality Compliance Solutions Specialist at CB&I. Treatment of fuel is done before you burn it. This can be accomplished at the exploration stage, during production and processing, during transport or just before it is combusted.
Proper treatment of fuels can improve purity, make the heating value higher, remove corrosive components, ensure safe handling, improve combustion heat efficiency, reduce maintenance and decrease flue gas emissions.
Treatment can accomplish hydrocarbon separation, removal of H2S, CO2 and other impurities. Biomass, for example, requires lots of work to make it compatible with coal units, such as sizing, shaping, pelleting, drying, gasification, pyrolysis and fermentation.
To maintain natural gas at the right quality for pipelines, it takes an understanding of the gas composition so you can eliminate unnecessary components. While methane is the primary ingredient in natural gas, its amount can vary from 80% to 95%.
Ethane content might vary from trace amounts to as high as 7%. Similarly, hydrogen, other hydrocarbons, CO, CO2, nitrogen and oxygen can be present in various amounts.
Natural gas must be free of particular solids and liquid water to prevent erosion, corrosion and other forms of damage to the pipeline, said Wedig. Water vapor must also be eliminated to prevent the formation of methane hydrates within the gas processing plant or transmission pipeline.
PowerGen delves into the many facets of the power industry. Among the varied sessions were briefings on inlet air chilling and alternative ways to address foreign object damage (FOD) in turbomachinery.
The Qurayyah IPP project in Saudi Arabia has six 2-on-1 combined cycle blocks consisting of 12 Siemens SGT6-PAC 5000F GTs, 12 HRSGs, six Siemens SST6- 4000 STs and six seawater cooled condensers. Each of the GTs is equipped with inlet air-chilled water coils supplied from two chilling plants consists of a 10 million gallon thermal energy storage tank, eight 5,760-ton refrigeration chiller modules, and ten secondary chilled water pumps.
Despite the intense heat, the chillers lower the turbine inlet air temperature to 59°F. Chilled water is also used for cooling the generators. The turbine inlet air coil condensate is collected and reused as chiller cooling tower make up water.
“The inlet chilling system is functioning as expected, and at the design ambient conditions the plant is producing about 619 MW more than it would if a chilling system were not provided,” said Doug Edgar, Senior Management Consultant at Sargent & Lundy (the design engineer on the project). Stellar Energy provided the chilling technology. The plant came online in 2015.
Dr. N. Jayaraman, Director of Materials Research at Lambda Technologies, showcased an alternate approach to repair. He talked about improving damage tolerance in turbines using low plasticity burnishing (LPB).
The current repair practice for the 7th stage compressor blade of the 501F turbine requires blending or removal if foreign object damage is observed along the leading edge. LPB can improve reliability and damage tolerance to extend the useful life of compressor blades. It is applied via conventional machine tools, robots or specialized delivery platforms.