Patent Application
20130269347
The subject matter disclosed herein relates to combined power and water production systems.
Combined power and water production systems generate steam and use the steam to drive steam turbines to produce power. The steam is also used to produce water after expansion in a turbine. For example, the steam may be used in a desalination plant to heat saltwater to extract waste and produce potable water.
Combined power and water production systems generate ratios of power to water at differing levels, depending upon the design requirements of the system. To produce the varying ratios of water and power, a heat recovery steam generator (HRSG) having multiple steam drums is used. The multiple steam drums provide output steam at varying temperatures and pressures. The HRSG receives high temperature gas from a gas turbine exhaust and is sometimes augmented by supplementary firing to produce additional steam for water and/or power production. For increasing levels of supplementary firing in the HRSG, the steam production capability of intermediate and lower pressure drums decreases and overall efficiency of the HRSG and water or power plant decreases. Specifically, the subject matter disclosed herein relates to a system for extracting a portion of steam from steam turbine to heat water entering a power generator to improve system efficiency when varying levels of supplementary firing is adopted to achieve power to water ratios.
According to one aspect of the invention, a combined power and water production system includes a steam generator to generate steam; a power generating assembly to receive the steam from the steam generator, to generate power using the steam, and to output exhaust; a water producing facility to receive the exhaust from the power generating assembly and to use the exhaust to produce first liquid water; and a heater to heat second liquid water and to provide the second liquid water heated by the heater to the steam generator to generate the steam.
According to another aspect of the invention, a method of providing water and power in a combined water and power production system includes generating steam at a steam generator, providing the steam to a power generation assembly to generate power, providing the steam to a water production facility to produce first liquid water, and heating second liquid water used by the steam generator prior to supplying the second liquid water to the steam generator.
According to yet another aspect of the invention a combined power and water generation system includes a steam generator to generate steam; a power generation assembly to generate power with the steam; a water production facility to receive non-potable water and to use the steam to produce potable water; and a heater to heat water before the water is provided to the steam generator.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
The HRSG 10 receives a gas stream 9 and receives water 2 from the heater 40. In one embodiment, the gas stream 9 is introduced to the HRSG 10 as a heated gas stream, and the HRSG 10 converts the water to steam at one or more predetermined pressures and temperatures using the heated gas stream 9 and outputs the steam 3 to the power generation assembly 20 to drive the power generation assembly 20. The power generation assembly 20 uses the steam 3 to generate power. Steam 4 from the power generation assembly 20 is supplied to each of the water producing facility 30 and the heater 40.
The water producing facility 30 uses exhaust steam 4a to convert input liquid water 7 into output liquid water 8. According to one embodiment, the water producing facility 30 is a desalination facility, the input liquid water 7 is saltwater, and the output liquid water 8 is potable water. The desalination facility heats the saltwater 7 with the exhaust steam 4a to extract waste from the saltwater to produce the potable water 8.
The heater 40 receives steam 4b from the power generation assembly 20 and liquid water 2 from the water producing facility 30 and heats the liquid water 2 prior to providing the liquid water 2 to the HRSG 10. Since the liquid water 2 is heated prior to being provided to the HRSG 10, less energy is required by the HRSG 10 to convert the liquid water 2 to steam 3, making the HRSG 10 more efficient. In one embodiment, the steam 4b is extracted from the low pressure steam turbine 24 upstream from the exhaust, so that the steam 4b provided to the heater 40 has a higher energy level than the steam 4a provided to the water producing facility 30.
In the embodiment illustrated in
Although
The HRSG 10 includes an economizer 11 to heat the liquid water 2, an evaporator 12 including a steam drum 13 to evaporate the water from the economizer 11 to generate steam, and a superheater 14 to heat the steam 3 and output the steam to the power generation assembly 20. According to alternative embodiments, the HRSG 10 includes multiple evaporators to generate steam at different pressure levels.
According to another embodiment, illustrated in
While
Referring to
In one embodiment, after heating the liquid water 2 in the heater 40, the steam 4c is combined with the residual water 5 and condensed into the liquid water 2, which is then used by the HRSG 10 to generate steam 3, as discussed above. Consequently, the steam 4c and residual water 5 are recovered and re-used to generate power at the power generation assembly 20 and to produce potable liquid water 8 at the water producing facility 30.
It is understood by the present disclosure that the liquid water 2, 7, and 8, the steam 4, the residual water 5, and the steam 3 and 6 represent flows of molecules rather than specific molecules at one location at one point in time. For example, in some embodiments disclosed in the specification and recited in the claims, the steam 4b is described as heating the second liquid water 2, then being condensed and becoming a part of the second liquid water 2 that is heated by the steam 4b. This disclosure does not mean that molecules in the steam 4b having a gaseous form heat themselves in a liquid form. Instead, molecules that make up a gaseous flow of steam 4c are condensed into liquid form to become part of the second liquid water 2. Then, the molecules that now make up the second liquid water 2 are heated by subsequent molecules that make up the flow of steam 4b.
In operation 64, residual water from the water producing facility is condensed into liquid water. In operation 65, the liquid water is heated by a heater. In one embodiment, the heater is a feedwater heater that uses heated exhaust from the power generation assembly to heat the liquid water in the heater.
In operation 66, the heated liquid water is provided to the steam generator to generate steam, and the cycle begins again at operation 61. Since the liquid water is heated prior to being supplied to the steam generator, the steam generator is able to operate with increased efficiency.
According to the above embodiments since liquid water is heated prior to being provided to a steam generator, less energy is required to convert the liquid water to steam, and the steam generator is able to operate with increased efficiency. In particular, for varying levels of power to water ratio, increasing the temperature of the liquid water prior to providing the liquid water to the steam generator allows the power generator to be operated at higher levels of efficiency. In addition, exhaust from a power generating unit such as a steam turbine is used to produce potable water, heat water provided to an HRSG, and is then converted into the water to be provided to the HRSG to generate steam for the steam turbine. Thus, the water and steam is recycled within the HRSG/power generation/water generation system to operate with increased efficiency.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
