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Flexible operation of combined cycle gas turbine power plants with supplementary firing

Encabo Cáceres I., Montañés R. M., Nord L. O.

Journal of Power Technologies

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2018

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Vol. 98, nr 2

188--197

EN

This article covers the use of supplementary firing in a gas-combined cycle power plant when high flexibility is required depending on the penetration of variable renewable energies and under different gas turbine loads. Process models were simulated under different operating conditions with the software EBSILON® Professional. Five main conditions were studied for the designed combined cycle: gas turbine part-load without supplementary firing, gas turbine full load with supplementary firing, the use of supplementary firing to overcome the effect of changing ambient conditions, part-load gas turbine performance with supplementary firing technology and the use of supplementary firing in case of gas turbine shutdown.

2

Combined heat and power plant on offshore oil and gas installations

Følgesvold E., Skjefstad H. S., Riboldi L., Nord L. O.

Journal of Power Technologies

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2017

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Vol. 97, nr 2

117--126

EN

Implementation of energy efficient technologies is an issue of growing importance for the offshore oil and gas industry. Rising awareness of increasing levels of CO2in the atmosphere is a major driver in this move, with a main aim being to reduce the amount of released CO2 per unit of oil or natural gas produced. Subsequently, the addition of steam bottoming cycles to exploit exhaust heat from gas turbines offshore has become an attractive alternative. This paper will investigate two different combined cycle configurations, namely the extraction steam turbine- and the backpressure steam turbine-cycle. Both cycles were modelled using the process simulation software Ebsilon Professional with a single GE LM2500+G4 gas turbine as a topping cycle, and a once-through heat recovery steam generator to exploit GT exhaust heat. At design, the steam turbines produced 8.2 MW and 6.0 MW respectively, achieving net thermal efficiency of 45.5%/42.1%. This was a 12.3 pp/8.9 pp increase compared to the simple cycle GE LM2500+G4 configuration. The findings suggest that a backpressure steam turbine could be an attractive option for oil producing facilities with high demand for process heat, while an extraction steam turbine configuration is more suited to gas producing facilities with lower heat requirements and a higher demand for power and flexibility. Additionally, both cycles displayed a substantial reduction in emitted CO2 per MWh produced, with reductions 26% and 21% compared to the simple cycle configuration achieved for the extraction and backpressure cycle respectively.

3

Process simulation and plant layout of a combined cycle gas turbine for offshore oil and gas installations

Bimüller J. D., Nord L. O.

Journal of Power Technologies

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2015

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Vol. 95, nr 1

40--47

EN

Since the development of the first oil fields on the Norwegian Continental Shelf, the petroleum industry in Norway has been making continuous progress in oil production engineering. With greater environmental awareness and increasing taxation of NOx and CO2 emissions, the economic pressure has been rising in recent decades. The energy demand for o shore oil and gas production is high. With a view to improving power generation on offshore oil and gas installations, four models of dierent power cycles were investigated: a simple cycle gas turbine (currently the default option), a compact combined cycle with enhanced fuel utilization, a steam injection gas turbine cycle as an innovative solution, and a state of the art combined cycle for onshore applications as a reference cycle. Special requirements for o shore installations are discussed and sizing was identified as the major criterion. The power demand of an oil platform and its change during dierent states in field life were analyzed. To complete the simulations, the models were set to off-design conditions and the part-load behavior was investigated. The plant layouts were laid out and visualized with 3D CAD models.

4

Steam bottoming cycles offshore - challenges and possibilities

Nord L. O., Bolland O.

Journal of Power Technologies

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2012

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Vol. 92, nr 3

201--207

EN

This paper addresses the challenges and possibilities related to offshore steam bottoming cycles with a special focus on once-through heat recovery steam generators (HRSGs). The main focus of the paper is to investigate the compromise between weight and efficiency of the HRSG by process simulation. The cost per installed kg of equipment is high offshore. Therefore, any bottoming cycle, applied to the back-end of the gas turbine, needs to be compact, yet sufficiently efficient. Important parameters to make the HRSG compact were the number of steam pressure levels, the HRSG technology, the flue gas pressure drop in the HRSG, and the pinch-point temperature difference. While selecting the parameters as a compromise between weight and efficiency, the combined cycle net plant efficiency was found to be approximately 50% with a power output of 43 MW. The steam turbine gross power output was 11 MW or about 25% of the total combined cycle plant gross power output. These results were compared to an onshore reference plant model which utilized the same type of aeroderivative gas turbine. The weight of the offshore once-through HRSG was about one third of the onshore HRSG. The net plant efficiency was 3%-points lower for the offshore system.