Engine & Turbine Technology
suffered a catastrophic failure, with the combustion pressure dropping from 125psia to 28psia and output from 66.26MW to 3.72MW in less than two seconds. Upon opening the unit, they found shredded blades and diaphragms, and a build-up of blade debris in compressor bleeding areas. To determine what caused the failure, the utility
requested that the Engineering Department of the local university conduct an inspection and root cause analysis. Te engineers determined that operating the fogging system with excess water caused a premature failure in the early stages of the compressor. Ten, when nozzle detached and damaged the blades, the repairs caused a change in the natural frequency of the blades, increasing vibration and eventually leading to a surge condition which damaged the high pressure section.
Te university also inspected Unit 5 and found
premature erosion and material removal from the compressor blades caused by entrained water droplets. Judging by the paths traced on the blades, it appeared that droplets were still impacting the blades up to Stage 8 before fully evaporating. Computational fluid dynamic modelling determined that the use of overspray, poor nozzle placement and a 90 degree angle in the inlet duct caused the fogging droplets to agglomerate into larger droplets that did not fully evaporate. Te droplets would collect on the spiral baffle at the turbine inlet and then get sucked into the turbine inlet. Combined with the SOx and NOx in the air, this water led to erosion, corrosion and crystallization on the blades. While this damage could have caused the utility to cease using fogging on all of its turbines, the benefits of
fogging are significant enough that the utility decided to give it a second shot. Tis time, however, it decided to switch to a Meefog system. Mee Industries has been building high-pressure fogging systems since the 1960s and has installed inlet cooling systems on more than 750 gas turbines ranging from 5 MW aeroderivatives to 250MW frame turbines and has the knowledge and experience to design a system to meet the exact needs of a particular plant. In this case, the utility kept the earlier water filtration system, but upgraded the nozzle array and pump skid with a Meefog system consisting of 890 impaction pin nozzles with a 127 micron orifice and operating at 207 bar (3000psig). Each nozzle produces a flow of 0.162l/min for an aggregate maximum water flow of 144.2l/min. Te system can produce an 11° C cooling +0.4
per cent overspray. Te system provides 13 cooling stages so the operators can precisely control the amount of water going into the air in order to obtain the maximum cooling available without excess water pooling in the inlet entering the turbine. With the new Meefog system, the utility achieves a 40MW power increase when fogging on all four turbines, with a maximum 50.4kW power usage when operating all 13 fogging stages. And it doesn’t have to worry about the fogging system causing another failure. ●
For more information ✔ at
www.engineerlive.com/ipe
Kelly Oeffinger is with Mee Industries, Irwindale, California, USA.
http://meefog.com/applications/gas-turbine-cooling
New electricity market rules, business models and technologies needed
T
he challenges inherent to integrating renewable energy into utility power grids were focus
at the Renewable Energy Integration & Energy Storage Conference in Amsterdam. “Over the past decade we have seen an explosive growth of renewable energy markets”, said Elly Kreijkes, producer for the Renewable Energy Integration & Energy Storage Conference. She continues: “Supportive government policies, rising costs of conventional energy and new technology improvements have contributed to the dramatic growth levels. But, with the increase of renewables comes huge logistical and technical challenges in adapting the existing infrastructure. European utilities in particular have to invest in the grids. And renewable integration is
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www.engineerlive.com
not just about hardware but also about how power markets function. There are many options available for utilities to balance variable renewables and each grid is unique so that solutions will be diverse.” Variability of RES (Renewable Energy
Systems) infeed is a real challenge for system stability, said Hubert Lemmens, Chief Innovation Officer, Elia Group, Belgium. He explained: “In order to cope with this challenge, RES have to participate in delivery of system services, consumers have to be incentivised to concentrate power consumption when it is available, storage has to go down the price curve and for the periods with low RES, biomass and gas fired plants have to fill the gap.” Catarina Naucler, Nordic Smart Grid
Development Lead at Fortum Distribution
in Sweden, said the main renewable energy integration challenge will be for the industry “to have a holistic view of the transformation of the energy system. Investments will be needed in the whole system and subsidies in one part of the system will drive even more investments in another part. It is a challenge to fund all needed investments and a holistic view among decision makers and industry is the key.” Energy storage already plays a major role
said Paul Giesbertz, Head of Infrastructure and Market Policies at Statkraft Markets BV in the Netherlands. Existing hydro reservoirs in the Nordic and Alp countries are the cheapest source of flexibility, he said. ●
For more information,
www.european-utility-week.com
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