Patent Application
20100095648
The subject matter disclosed herein relates to a combined cycle power plant and, more particularly, to a heat recovery system for improved output and efficiency.
A combined cycle power plant utilizes a gas turbine and a steam turbine, in combination, to produce electricity. The power plant is arranged such that the gas turbine is thermally connected to the steam turbine through a heat recovery system such as a heat recovery steam generator (“HRSG”). The HRSG is a heat exchanger that allows feed water for the steam generation process to be heated by hot gas turbine exhaust gas. The HRSG is essentially a large duct with water filled tube bundles disposed therein. Feed water is circulated through the tube bundles such that the water is heated to steam as the exhaust gas passes through the duct and over the tube bundles. A primary efficiency of the combined cycle arrangement is the utilization of the otherwise “wasted” gas turbine exhaust gas heat. The efficiency of the HRSG is directly related to the efficiency of heat transfer between the hot turbine exhaust gas (hot side) and the feed water and steam in the tube bundles (cold side). It is known to utilize flow fins to assist in the rate of heat transfer from the hot turbine exhaust gas to the feed water in the tube bundles, however overall heat transfer is limited by the cold-side surface area, and the condition of that surface area, within the tubes.
It is therefore desired to provide a combined cycle power plant having increased efficiency through the improvement of heat transfer in the HRSG.
In one embodiment of the invention a combined cycle power plant includes a heat recovery system for recovering heat from a hot exhaust flow. The heat recovery system includes heat pipes interposed therein. The heat pipes transfer heat from within the heat recovery system to a heating system associated therewith, in which feed water is circulated about the exterior of the heat pipes such that the water is heated to steam.
The invention, in accordance with preferred and exemplary embodiments, together with further objects and advantages thereof, is more particularly described in the following detailed description taken in conjunction with the accompanying drawings in which:
Referring now to the drawings, in which like numerals indicate like elements throughout the views,
The gas turbine system 12 and the steam turbine system 18 are associated with a heat recovery steam generator (“HRSG”) 24. The HRSG 24 is a heat exchanger having an exhaust flow duct 28 defined by walls 26. A heating system 34 is associated with the HRSG and is the mechanism through which feed water 36 flows for heating to steam as described in further detail below. A series of heat pipes 30 have first ends 29 that are partially disposed within the HRSG exhaust flow duct 28 and second ends 31 which extend into the reheat system 34. As high temperature exhaust gas 32, from the turbine 16, passes through the HRSG, the heat pipes 30 transfer heat from the high temperature exhaust gas 32 to the heating system 34, resulting in the transfer of heat from the high temperature exhaust gas to feed water 36, flowing therethrough. The feed water 36 flows, with the aide of feed water pump 46, from the condenser 42, where it is collected from the steam turbine system 18, to the HRSG 24 via conduit 44. The feed water passes through the heating system 34 where it is heated to steam using heat from high temperature exhaust gas 32, and is subsequently delivered to the steam turbine system 18 via return conduit 48.
The heat pipes 30 may be of a convective or a conductive, solid-state construction. Conductive, solid-state heat pipes comprise a vacuum tight carrier such as a tube or conduit containing a solid or semisolid superconducting heat transfer medium placed within the cavity of the conduit. The medium is applied to the conduit walls in layers resulting in highly efficient conduction of heat. A convective heat pipe includes a vacuum tight tube or conduit in which is disposed a wick structure and a working fluid. The convective heat pipe operates by transferring heat through mass transfer of the working fluid and the phase change of the carrier from a liquid state to a vapor state within the tube.
In an exemplary embodiment of the present invention shown schematically in
While the heat pipes 30, shown in
The written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.
