POWER PRODUCING ORGANIC RANKINE CYCLE INTERMEDIATE LOOP USING INVERTED BRAYTON CYCLE
Publication Date: 2012-Sep-20
The IP.com Prior Art Database
This disclosure presents a method of improving the efficiency of power generation from waste heat in turbine applications. An organic Rankine cycle (ORC) typically uses an intermediate water or thermo-oil loop for cooling when the heat source is at a high temperature and the working fluid has a low decomposition temperature, which results in power consumption and a decrease in the efficiency of the power plant. The proposed embodiments may replace the state-of-the-art intermediate thermo-oil loop ORC with a potentially simpler system, such as an inverted Brayton cycle (IBC) system, boosting the total power generated from the waste heat. The embodiments also may be used to manage the risk of auto-ignition and decomposition of organic fluid, thereby resulting in a higher operational efficiency in a simpler system.
This disclosure relates to power production from exhaust gases produced by gas turbines, diesel engines, or any other heat source. Many power plants employ organic Rankine cycle (ORC) for geothermal, waste heat recovery, and combined heat and power applications. State-of-the-art ORC typically uses an intermediate water or thermo-oil loop when the heat source is at a high temperature (300°C - 550°C) and the working fluid is at a low decomposition temperature (up to 250°C for refrigerant and 300°C for hydrocarbons). This intermediate loop reduces the exposure of the organic fluid to a high exhaust temperature to prevent it from decomposition. However, the intermediate heat exchange loop results in the consumption of power and decreases the overall efficiency of the power plant. Currently, in the ORC system, the organic working fluid is either directly heated by the exhaust gas stream known as direct evaporation or the losses to the ancillary oil loop are compromised. One existing process of electric power production is by the utilization of waste heat from gas turbine with the application of Brayton humid cycle and Rankine-Clausius steam cycle. Another process uses a gas turbine-fuel cell hybrid cycle, where an inverted Brayton-Joule cycle is employed to reduce turbine power used by compressor. This disclosure proposes a combination of an inverted Brayton cycle (IBC) and an organic Rankine cycle (ORC) for the generation of power from waste heat to increase the plant efficiency.
BRIEF DESCRIPTION OF DRAWINGS
A method of improving the efficiency of power generation with a combined application of organic Rankine cycle (ORC) and inverted Brayton cycle (IBC) is disclosed, wherein:
Figure 1shows a non-recuperated, non-preheated ORC/IBC combination for power generation in a turbine.
Figure 2 presents an IBC with recuperated ORC scheme in a turbine.
Figure 3 shows a plant employing IBC with ORC preheater.
Figure 4 illustrates an IBC with two ORCs in a turbine.
The state-of-the-art intermediate thermo-oil loop of organic Rankine cycle (ORC) is replaced with an inverted Brayton cycle (IBC) for efficient power production. A waste stream of hot exhaust gas is first expanded to sub-atmospheric pressure to generate shaft power. It is then cooled down in a heat exchanger. On the cold side of the heat exchanger, organic fluid is preheated, and evaporated. After evaporation, the organic fluid is superheated, if the cycle considered is subcritical; supercritically heated, if the cycle considered is supercritical; or preheated if the cycle considered is a trilateral flash cycle. Finally at the hot outlet of the heat exchanger, the waste heat stream is recompressed to atmospheric pressure, and at the cold outlet of the heat exchanger, the organic fluid is led to an expander where it generates shaft power.
Exhaust gas from a gas turbine, a gas...