Analysis of Gas Turbine Cooling Technologies for Higher Natural Gas Combined Cycle Efficiency

This study aims to propose the repowering of an existing Italian natural-gas fired combined cycle power plant through the integration of Molten Carbonate Fuel Cells (MCFC) downstream of the gas turbine for CO2 capture and to pursuit an exergetic analysis of the two schemes. The flue gases of the turbine are used to feed the cathode of the MCFC, where CO2 is captured and transported to the anode while generating electric power. The retrofitted plant produces 787.454 MW, in particular, 435.29 MW from the gas turbine, 248.9 MW from the steam cycle, and 135.283 MW from the MCFC. Around 42.4% of the exergy destruction has been obtained, the majority belonging to the combustion chamber and, in minor percentages, to the gas turbine and the MCFC. The overall net plant efficiency and net exergy efficiency are estimated to be around 55.34 and 53.34%, respectively. Finally, the specific CO2 emission is around 66.67 kg/MWh, with around 2 million tons of carbon dioxide sequestrated.

Download Full-text

Reheat Air-Brayton Combined Cycle Power Conversion Off-Nominal and Transient Performance

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4026612 ◽

2014 ◽

Vol 136 (7) ◽

Cited By ~ 5

Author(s):

Charalampos Andreades ◽

Lindsay Dempsey ◽

Per F. Peterson

Keyword(s):

Natural Gas ◽

Gas Turbine ◽

Nuclear Power ◽

Power Plants ◽

Power Conversion ◽

Companion Paper ◽

Combined Cycle ◽

Natural Gas Combined Cycle ◽

Reference Design ◽

Molten Fluoride

Because molten fluoride salts can deliver heat at temperatures above 600 °C, they can be used to couple nuclear and concentrating solar power heat sources to reheat air combined cycles (RACC). With the open-air configuration used in RACC power conversion, the ability to also inject natural gas or other fuel to boost power at times of high demand provides the electric grid with contingency and flexible capacity while also increasing revenues for the operator. This combination provides several distinct benefits over conventional stand-alone nuclear power plants and natural gas combined cycle and peaking plants. A companion paper discusses the necessary modifications and issues for coupling an external heat source to a conventional gas turbine and provides two baseline designs (derived from the GE 7FB and Alstom GT24). This paper discusses off-nominal operation, transient response, and start-up and shutdown using the GE 7FB gas turbine as the reference design.

Download Full-text

Optimizing Natural Gas Combined Cycle Part Load Operation

ASME 2019 Power Conference ◽

10.1115/power2019-1942 ◽

2019 ◽

Author(s):

Robert Flores ◽

Jack Brouwer

Keyword(s):

Natural Gas ◽

Gas Turbine ◽

Combined Cycle ◽

University Of California ◽

Inlet Guide Vane ◽

Outlet Temperature ◽

Part Load ◽

Carbon Neutrality ◽

Natural Gas Combined Cycle ◽

The University

Abstract The University of California, Irvine (UCI) uses a 19 MW natural gas combined cycle (NGCC) to provide nearly all campus energy requirements. Meanwhile, the University of California system has committed to achieving carbon neutrality at all facilities by 2025. This has resulted in an influx of new energy efficiency and onsite solar generation, increasing the duration of NGCC part load operation. In addition, the shift towards carbon neutrality has resulted in the pursuit of renewable natural gas via anaerobic digestion to replace conventional fossil fuels. The combination of other sources of renewable generation and the shift towards more expensive fuels has created the need to boost NGCC part load performance. This work focuses on the methods used at UCI to explore the NGCC operating space in order to optimize part-load performance. In this work, a physical gas turbine and heat recovery steam generator model are developed and used with an exhaustive search optimization method to predict maximum part load plant efficiency. NGCC control elements considered in this work include gas turbine inlet guide vane modulation and changing combustor outlet temperature. This optimization was also used to explore replacing the current engine with a two-shaft or smaller gas turbine. Results indicate that there are some possible benefits with increased modulation of inlet guide vanes, but the largest efficiency gains are achieved when allowing the compressor to operate at variable speed. Shifting towards a smaller engine could also enable more consistent full power operation, but must be paired with additional resources in order to meet the campus demand.

Download Full-text

Using Dynamic Simulation to Evaluate Attemperator Operation in a Natural Gas Combined Cycle With Duct Burners in the Heat Recovery Steam Generator

Volume 3: Coal, Biomass and Alternative Fuels; Cycle Innovations; Electric Power; Industrial and Cogeneration Applications; Organic Rankine Cycle Power Systems ◽

10.1115/gt2017-63301 ◽

2017 ◽

Author(s):

Eric Liese ◽

Stephen E. Zitney

Keyword(s):

Natural Gas ◽

Gas Turbine ◽

Saturation Temperature ◽

Control Valve ◽

Pressure Control ◽

Combined Cycle ◽

Training Simulator ◽

Natural Gas Combined Cycle ◽

Loading And Unloading ◽

Pressure Control Valve

A generic training simulator of a natural gas combined cycle was modified to match operations at a real plant. The objective was to use the simulator to analyze cycling operations of the plant. Initial operation of the simulator revealed the potential for saturation conditions in the final high pressure superheater as the attemperator tried to control temperature at the superheater outlet during gas turbine loading and unloading. Subsequent plant operational data confirmed simulation results. Multiple simulations were performed during loading and unloading of the gas turbine to determine operational strategies that prevented saturation and increased the approach to saturation temperature. The solutions included changes to the attemperator temperature control setpoints and strategic control of the steam turbine inlet pressure control valve.

Download Full-text

Using Dynamic Simulation to Evaluate Attemperator Operation in a Natural Gas Combined Cycle With Duct Burners in the Heat Recovery Steam Generator

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4037709 ◽

2017 ◽

Vol 140 (1) ◽

Cited By ~ 3

Author(s):

Eric Liese ◽

Stephen E. Zitney

Keyword(s):

Natural Gas ◽

Gas Turbine ◽

Saturation Temperature ◽

Control Valve ◽

Pressure Control ◽

Combined Cycle ◽

Training Simulator ◽

Natural Gas Combined Cycle ◽

Loading And Unloading ◽

Pressure Control Valve

A generic training simulator of a natural gas combined cycle (NGCC) was modified to match operations at a real plant. The objective was to use the simulator to analyze cycling operations of the plant. Initial operation of the simulator revealed the potential for saturation conditions in the final high pressure superheater (HPSH) as the attemperator tried to control temperature at the superheater outlet during gas turbine loading and unloading. Subsequent plant operational data confirmed simulation results. Multiple simulations were performed during loading and unloading of the gas turbine to determine operational strategies that prevented saturation and increased the approach to saturation temperature. The solutions included changes to the attemperator temperature control setpoints and strategic control of the steam turbine (ST) inlet pressure control valve.

Download Full-text