Off-Design and Part-Load Behaviour of PFBC Combined Cycle Power Plant

Author(s):  
K. K. Pillai ◽  
A. G. Roberts

Combined cycle power plant utilising pressurised fluidised bed coal combustors (PFBCs) have, of necessity, to be designed to suit the particular gas turbine chosen. The gas turbine characteristics set not only the design point but also the turndown available. The interactions between the gas cycle, the combustor and the steam cycle are different to those normally associated with combined cycle plant. This paper describes the methods available when designing for plant operation at off-design conditions. It is shown how available techniques are capable of meeting commercial plant requirements for start-up, rates of load change and turndown.

Author(s):  
Edgar Vicente Torres González ◽  
Raúl Lugo Leyte ◽  
Martín Salazar Pereyra ◽  
Helen Denise Lugo Méndez ◽  
Miguel Toledo Velázquez ◽  
...  

In this paper is carried out a comparison between a gas turbine power plant and a combined cycle power plant through exergetic and environmental indices in order to determine performance and sustainability aspects of a gas turbine and combined cycle plant. First of all, an exergetic analysis of the gas turbine and the combined is carried out then the exergetic and environmental indices are calculated for the gas turbine (case A) and the combined cycle (case B). The exergetic indices are exergetic efficiency, waste exergy ratio, exergy destruction factor, recoverable exergy ratio, environmental effect factor and exergetic sustainability. Besides, the environmental indices are global warming, smog formation and acid rain indices. In the case A, the two gas turbines generate 278.4 MW; whereas 415.19 MW of electricity power is generated by the combined cycle (case B). The results show that exergetic sustainability index for cases A and B are 0.02888 and 0.1058 respectively. The steam turbine cycle improves the overall efficiency, as well as, the reviewed exergetic indexes. Besides, the environmental indices of the gas turbines (case A) are lower than the combined cycle environmental indices (case B), since the combustion gases are only generated in the combustion chamber.


Author(s):  
Feliciano Pava´n ◽  
Marco Romo ◽  
Juan Prince

The present paper is a thermodynamics analysis, i.e. both energy and exergy analyses for a natural gas based combined cycle power plant. The analysis was performed for an existing 240 MW plant, where the steam cycle reduces the irreversibilities during heat transfer from gas to water/steam. The effect of operating variables such as pressure ratio, gas turbine inlet temperature on the performance of combined cycle power plant has been investigated. The pressure ratio and maximum temperature (gas turbine inlet temperature) are identified as the dominant parameters having impact on the combined cycle plant performance. The work output of the topping cycle is found to increase with pressure ratio, while for the bottoming cycle it decreases. However, for the same gas turbine inlet temperature the overall work output of the combined cycle plant increases up to a certain pressure ratio, and thereafter not much increase is observed. The exergy losses of the individual components in the plant are evaluated based on second law of thermodynamics. The present results form a basis on which further work can be conducted to improve the performance of these units.


Author(s):  
Wancai Liu ◽  
Hui Zhang

Gas turbine is widely applied in power-generation field, especially combined gas-steam cycle. In this paper, the new scheme of steam turbine driving compressor is investigated aiming at the gas-steam combined cycle power plant. Under calculating the thermodynamic process, the new scheme is compared with the scheme of conventional gas-steam combined cycle, pointing its main merits and shortcomings. At the same time, two improved schemes of steam turbine driving compressor are discussed.


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