Advanced Combined Cycle Alternatives With the Latest Gas Turbines

Abstract

The last decade has seen remarkable improvements in industrial gas turbine size and performances. There is no doubt that the coming years are holding the promise of even more progress in these fields. As a consequence, the fuel utilization achieved by combined cycle power plants has been steadily increased. This is, however, also because of the developments in the heat recovery technology. Advances on the gas turbine side justify the development of new combined cycle schemes, with more advanced heat recovery capabilities. Hence, the system performance is spiraling upward. In this paper, we look at some of the heat recovery possibilities with the newly available gas turbine engines, characterized by a high exhaust temperature, a high specific work, and the integration of some gas turbine cooling with the boiler. The schemes range from classical dual pressure systems, to triple pressure systems with reheat in supercritical steam conditions. For each system, an optimum set of variables (steam pressures, etc.) is proposed. The effect of some changes on the steam cycle parameters, like increasing the steam temperatures above 570°C are also considered. Emphasis is also put on the influence of some special features or arrangements of the heat recovery steam generators, not only from a thermodynamic point of view.

Advanced Combined Cycle Alternatives With the Latest Gas Turbines

“…It must be mentioned that a beneficial effect of supplemental firing on efficiency had already been established in repowering configurations, for single pressure level plants with reheat and high pressures (> 100 bar) (Dechamps et al, 1993). It is not the case here, because of the intrinsically high exhaust temperature of the gas turbine.…”

Experimental and Theoretical Investigations of New Power Cycles and Advanced Falling Film Heat Exchangers

“…A typical power plant working on a simple Rankine or Brayton cycle has efficiencies on order of 35 percent, much lower than the efficiency of a combined cycle that couples a Brayton gas topping cycle with a bottoming Rankine cycle (Harlock, 1995, Kehlhofer, 1997and Khartchenko, 1998. The combined power cycles achieve efficiencies well above 50 percent and are approaching an efficiency of 60 percent (Briesch, et al, 1995, Dechamps, 1998, Razani and Kim, 2000. In this study a gas ammonia (Brayton/Rankine) combined cycle is proposed in which an ammonia compression refrigeration cycle is added to the bottoming cycle.…”

Conceptual Recovery of Exhaust Heat From a Conventional Gas Turbine by an Inter-Cooled Inverted Brayton Cycle

“…Hot gas with atmospheric pressure Exhaust gas 4 H x Cooling medium the market. These new machines hold the promise of even higher combined cycle efficiencies, for two reasons: when the gas turbine TIT is increased, both the gas turbine efficiency and the gas turbine exhaust temperature are increased for the optimum pressure ratio under combined cycle operation (Brandt, 1992;Jury et al, 1994;Dechamps, 1998). The Rankine cycle efficiency is highly dependent on the superheated steam temperature.…”