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The 2012 Turbo Symposium took place in Houston in September with attendance at a similar level to last year, according to Dr. Dara Childs, Director of TexasA&M’s Turbomachinery Laboratory, which organizes the event. Consisting of numerous technical sessions, a large exhibit hall and short courses, it attracts the main players in the oil & gas field each year.
Richard Dennis, Turbine Technology Manager for theU.S.Department of Energy’s National Energy Technology Lab (NETL) provided a keynote encompassing hydrogen turbines, supercritical CO2 (S-CO2), gas-fired generation opportunities and Integrated Gasification and Combined Cycle (IGCC).
NETL is working on a coal gasification approach which can capture 90% of the carbon. The Summit IGCC project in Texas is an ongoing test project for this technology. Combined cycle accounts for about 20% of the total cost of IGCC.
Current development work involves the transition to turbines operating at 2,640° F. If that goal can be attained, the efficiency leap could be as much as 14%.
A GE H2 turbine is another aspect of ongoing research. Combustion goals include 2 ppm NOx at 15% O2 by 2015, the ability to operate with syngas and carbon-free syngas, as well as natural gas startup and backup.
But plenty of challenges remain. Flashback, for example, is a significant issue to overcome.
Due to the dynamics and properties ofH2, the fuel is lowin density, and therefore difficult to inject.Thismeans a larger amount of piping to maintain the same speed, as well as broader flammability limits. The laminar flame speed of H2 is 10X faster than natural gas. It also diffuses 3X faster than natural gas in air.
GE’s small-scalemachine has been operating for 100 hourswith 90%H2 fuel, and 20 hours at 100% H2 fuel. During that time, it has successfully maintained NOX levels below 3 ppm.
According to the International Energy Agency (IEA) Carbon Capture and Storage (CCS) technology will contribute about 19% to the overall reduction in CO2 emissions by 2050.Renewableswill add 17%, nuclear 6%, power generation efficiency 5%, end-use fuel switching 15% and end-use efficiency 38%. That adds up to huge opportunities for reducing carbon emissions from both combinedcycle and simple-cycle plants as those areas are where most of the generation expansion will take place over the next 25 years.
S-CO2 continues to be in the spotlight (Sept/October12, p.22), with the potential of it adding 10 to 20 points to cycle efficiency. While Echogen utilizes a closed cycle for S-CO2, others such as Southwest Research Institute (SwRI) are working on a direct cycle where the working fluid receives the combustion fuel. S-CO2 technology’s high molecular weight means there is a small equipment footprint. It is also stable and inert with a low critical temperature and pressure. Further, it is agnostic as to heat source and has applications in fossil fuels, nuclear, marine and renewables.
The event progressed with several informative presentations.KlausBrun,Machinery Program Director at SWRI, briefed the gathering on solid particle surface impact behavior in turbomachines as way to assess blade erosion and fouling.
This is a complex area as the flow field is difficult to predict, and the particles can rotate and be of an uneven nature. Thus damage assessment must take into account multiple parameters and requires a detailed look.
“Solid particle admission is one of the big causes of failure,” said Brun. “We can use impact analysis to optimize flowpath design.”
He advocated the use of harder coatings in high-erosion areas, improved filtering techniques to target the particles which cause the most damage, and better maintenance strategies.
Petrobras presented on the subject of fixed speed compressors for operation in offshore production platforms. Turbomachinery Engineer Michel Stathakis Neto outlined several years of operational lessons learned in the usage of fixed and variable speed drivers. His company operates dozens of platforms using both gas turbine and electric motor-driven compressors
“Fixed speed direct drive should give lower capex and maintenance costs, as well as having slightly lower efficiency at partial load,” said Neto. “However, our experience revealed that they also had more trips, and suffered premature performance degradation due to internal corrosion.”
Due to problems with system overload, his company reviewed the design with the electric motor manufacturer. The result was the addition of a 5% to 10% power margin without compromising expected life. By doing so, Petrobras experienced far greater reliability.