MXPA98009936A

MXPA98009936A - System hybrid, solar and burning combustible, to generate electricity

Info

Publication number: MXPA98009936A
Application number: MXPA/A/1998/009936A
Authority: MX
Inventors: Arthur Cohn
Original assignee: Electric Power Research Institute
Priority date: 1996-05-31
Filing date: 1998-11-27
Publication date: 1999-04-27

Abstract

A system, which generates electric power, combines a gas turbine generator (11) with a solar power plant (15), and uses the gas turbine exhaust gas (14) to superheat the steam and heat Feed water only. The solar heater is only used for the boiling or evaporation of the steam feed water, this feed water has been previously heated by a portion downstream of the exhaust gas of the turbine, in order to balance the disparity between the specific loads of water and steam, in order to maintain the system, the steam is superheated (16) by a portion upstream of the turbine exhaust to first drive a turbine (21) of high pressure steam and then reheat by the same exhaust, in the same temperature range, to drive a steam turbine at low pressure

Description

HYBRID SYSTEM. SOLAR AND THAT BURNS COMBUSTIBLE- TO GENERATE ELECTRICITY.

The present invention is directed to a hybrid, solar and fuel burning system, to generate electricity and, more specifically, to that where the fuel portion of the power plant is a gas turbine, where, in addition to generating electricity, the Hot exhaust gas from the turbine is used to produce steam _ of water in combination with the solar unit, to drive the generators of the steam turbine.

BACKGROUND OF THE INVENTION Combined cycle electricity generation systems using solar and gas turbine units are probably known, as illustrated in the patent of E. U. A., No. 5,444,972. In addition, it is believed that the Bechtel Corporation, of San Francisco, California, has models that have been added to a standard gas turbine plant by General Electric (which also uses high pressure water vapor and low pressure steam turbines), a solar evaporator. However, in both of the above facilities, there has not been a specific effort to optimize the overall system. Rather, the solar energy portion of the system was merely added to the combined cycle, which uses the original water vapor generation equipment of the gas turbine and the cycle was arranged as originally designed to burn fuel.

Object and Compendium of the Invention It is a general object of the present invention to provide a hybrid, improved, solar and fuel burning system for generating electricity. According to the above object, an electric power generation system is provided, which has a substantially closed, water / water vapor feed path, to supply a common mass flow comprising a gas turbine generator , "which has a hot exhaust gas stream." A first element of the heat exchanger, placed in the downstream portion of the hot exhaust gas, heats the charging water to substantially its evaporation temperature. connected to the first heat exchanger, evaporates the charge water, a high pressure steam turbine generator, and a low pressure steam turbine generator, which have a low pressure exhaust, are connected to a condenser, which thus supplies the charging water A second heat exchanger element, placed, at least partially, in a rising current portion of the hot exhaust gas of the turbine receives the evaporated charge water from the boiler solar element and also the low pressure exhaust of the low pressure steam turbine and overheats this a predetermined temperature, to drive the steam turbines both high pressure as low pressure. The absolute thermal energy per degree of temperature rise, supplied by the second heat exchanger element for the superheat, is substantially equal to the thermal energy per degree of temperature rise provided by the first heat exchanger element, to heat the water of charge at the evaporation temperature.

Brief Description of the Drawings Figure 1 is a schematic representation of the total system. Figure 2 is a graph that helps explain the concept of the invention. Figure 3 is a characteristic curve that illustrates the real operation of the invention. Figures 4 and 5 are curves similar to Figure 3, which illustrate the undesired theoretical modes of operation. Figure 6 is a diagram of entropy temperature, illustrating the present invention. Figure 7 is a schematic representation, which is an alternative to Figure 1.

"Figure 8 is the diagram of Figure 6 modified to illustrate Figure 7.

Description of the Preferred Modality Figure 2 illustrates the electric power generation system of the present invention, which has as its key components, a turbine of gas of fuel power, which drives a generator 12, and a boiler "solar 13. As it will become evident, the solar heat used in conjunction with the heat of the exhaust gas of the gas turbines, the gas stream is shown by line 14 of dashes, it will produce much more water vapor energy than can be obtained by using each one separately, or in a combined or hybrid system, as discussed above, which is not optimal In general, the present invention takes into account that, since the exhaust heat of the gas turbine has the characteristic of supplying a percentage of its heat with a drop of a percentage of its temperature, from its given reference, it should not be used "for boiling, which occurs at a constant temperature, but only to heat the charge water to the evaporation temperature and also to superheat the water vapor. On the other hand, since solar heating occurs at almost a constant temperature, it is best used primarily for boiling or carrying the water to load. its evaporation temperature. Thus, as illustrated in Figure 1, the solar boiler can also be a nuclear boiler, since it has the same type of feature; that is, a constant temperature, even if the heat is removed from the system, in contrast to the exhaust gas from the gas turbine. Referring now to the hardware of the system of Figure 1, the exhaust gas 14 of the gas turbine 11 is first guided to a high pressure superheater 16 and a low pressure reheater. As indicated, they are actually interleaved heaters 18, in the form of tube sheets. The high pressure superheater 16 overheats the high pressure steam generated by the solar boiler 13. Thus, the temperature of the solar boiler is close to the evaporation temperature and the superheater 16 heats the resulting water vapor to the maximum approach temperature used to drive the generator 21 of the high pressure steam water turbine. After the expansion in the high pressure steam turbine 21, the outlet line 22 is still superheated to the original output temperature of the solar boiler 13. The low pressure reheating 17, again overheats the water vapor at the maximum approach temperature and drives the low pressure water turbine generator 23. The superheated steam is then expanded through the low pressure steam steam turbine to the condenser unit 24 and then, after condensing the water is pumped by the pump 26 to the charge water heater (or heat exchanger 27), this is located in the downstream portion 28 of the gas turbine exhaust 14. With the use of this The water is again heated to near its boiling point and fed to the solar boiler 13, to complete the closed water / steam route, since it is a closed route, of course, there is a flow common mass through the system. The superheater and reheater 16, 17, are located in the upstream or hottest portion of the hot exhaust gas stream 14. Theoretically, when the exhaust gas heat from the gas turbine is used only to heat the water and Overheating, it is convenient for the best thermodynamics to be close to a constant temperature difference between the fJ Turbine gas flow, as it cools, and the countercurrent water and water vapor flow as they heat, taking heat from the flow Of gas. However, Figure 2, which is a characteristic temperature-entropy (H) curve, indicates an inherent problem. The exhaust gas has a specific heat (Cp) of around 0.25. On the other hand, the steam has a specific heat of around 0.5 and water of 1.00. This leads to n imbalance since the water has a specific heat of about twice the specific heat of the water vapor. Thus, the amount of the degree of heat capture of the water flow, which could coincide with the degree of heat capture of the gas flow, is only around the. half of the amount of water vapor flow, whose heat uptake per degree would correspond to the heat of the gas flow supplied per degree. As noted above, the optimal thermodynamic situation is when there is a constant temperature in the heat exchange, between the flow of turbine gas and steam and water. This is illustrated in Figure 3, where the steam, water and gas curves are shown, with the horizontal axis representing the heat exchange in BTU per hour (0.253 Calories per hour) and the vertical axis is the temperature in ° F. Specific temperature values are indicated for an example that will be discussed below. The ideal characteristics of Figure 3 can be realized as will be discussed in detail below, heating each pound (kilogram) of steam twice over the same temperature range. However, if this is not done, the curves in Figures 4 or 5 show the undesirable theoretical results, which are only conceptual and simplified.; thus, they do not correspond to a real situation. Thus, in Figure 4, the counterflows of the. water and gas coincide, and leave a mismatch with the steam; In Figure 5, the steam matches, leaving a mismatch with the water. The temperature-entropy characteristic of Figure 6 briefly illustrates the technique of the present invention, which achieves the ideal characteristics of Figure 3. The main curve 31 of Figure 6 is a standard temperature-entropy curve, where the interior of the curve, bell-shaped, is the wet region, on the left is liquid and on the right is the dry region or the superheated region and vapor. Now relating the system of Figure 1 to the graph of Figure 6, the charge water heater 27 is illustrated by the curve 32, which heats this charge water to its boiling point, which is indicated at 33 and, for the example of the present invention it is about 296.6 ° C at a pressure of 83.3 kg / cm2 absolute. The crosslinked portion A, under the curve that rises to 33 and goes down to the absolute zero temperature, is the thermal energy supplied by that stage. Then the horizontal line 35 is the last evaporation heat that occurs in the solar boiler 13, to change the water phase from liquid to vapor, which occurs at 36. On the other side of the bell curve 31, the line of dashes, shown at 37, is an isopression line at 0.35, 7 and 70 kg / cm2 absolute. Substantially along the 70 kg / cm2 line, solid line 38 shows the operation of superheater 16, which superheats the vapor to the indicated temperature of 565.5 ° C at a pressure substantially similar to the original pressure of 79.5 kg / cm2 absolute. Then on line 22, it falls through typical valve elements in the high-pressure steam turbine and the movement of the turbine, by itself, at the low pressure of 10.5 kg / cm2 and 296.6 ° C, the temperature of original evaporation. The low pressure steam is again reheated by the low pressure reheater 17, as shown by the solid line 39, again at 566 ° C and substantially a pressure of 10.5 kg / cm2. And then the action of the low pressure turbine, in conjunction with the condenser 24 (see line 41) causes the exhaust gas to drop to substantially 0.07 kg / cm2 absolute and a pressure of 38 ° C. It is critical that this line 41, which indicates the escape of the low pressure turbine 23, collides with the curve 31 in the indian location, so that the combination of temperature and pressure supplies an exhaust which is not completely dry and not too much. damp. Referring to the crosslinked portions, the heat added by the high pressure superheater 16 is shown by the area A2 and the heat added by the low pressure reheater 17, by the area A3. As shown by the equation, it is convenient for the optimum efficiency that the area] divided by the temperature rise, T2 - T_ be equal to the sum of A2 and A3, divided by the temperature rise, T3 - T2 '. When this is done, it will effectively compensate the difference between the specific charges of water and steam, as discussed above, in order to supply the idealized characteristic curves of Figure 3. To explain the above "by equations, the following three apply: ( 1) M * Cpw = M * Cpg (2)? M * Crg = M * Cpg (3)? M * Cpg = M * Cpw where M = mass flow, Cp = average specific heat, Equation (1) shows the correspondence of the product of the mass flow and the specific heat of the water with the gas flow, and the equation (2) the correspondence of the superheat of the vapor to the gas. (3) is the necessary condn for maintaining equations 1 and 2. Since the specific charges of gas and water are not equal (one is double the other), the steam is superheated twice, first at high pressure "and then at low pressure, equation (3) is effectively satisfied.Thus, in general, the following are design criteria: 1) the steam is reheated twice as compared to water; (2) the same range of temperature for both the high pressure superheater 16 and the low pressure reheater 17, 3) the temperature of the solar boiler, given in the example of 296 ° C, is chosen to supply a cheap solar heater of the channel type ( also the pressure of 83.3 kg / cm2 absolute is chosen for the good compatibility with the output of the solar boiler, 4) the low pressure turbine falls to the condenser in a neither dry nor too humid state, 5) the inlet pressure to the high pressure turbine 21, for example, 79.1 kg / cm2 a bsolutos is not too high for a commercial turbine; 6) The pressures of the heaters 16 and 17 are chosen to provide the desired equality with the heating of the charge water. A theoretical system has been designed and the attached Table 1 illustrates the operation parameters. As illustrated, for example, in Table 1, the embodiment of Figure 1 with the appropriate temperatures and pressures, provides the optimum efficiency. For example, in some installation a pressure of 150.5 kg / cm2 absolute could provide higher efficiencies. However, Figure 7 illustrates an alternative, which is a modification of Figure 1, which uses an addnal low pressure solar heater, 41, with a modified charge water arrangement. This includes the existence of the charge water heater, which is now divided into sections of low temperature / high pressure and high temperature / low pressure, 40 and 42, and a section 43 of low temperature / low pressure. The sections 40 and 43 are fed by means of the high pressure pump 44 and the low pressure pump 46, respectively, which receive the charging water from the condenser 2. The high temperature section 42 again heats the charging water to its evaporation temperature and then allows the high pressure solar heater 13 to change it to steam. Then the output of the boiler 13 goes to the superheater 16 of high pressure, as before. However, according to this modification, the low temperature / low pressure section 43 now feeds the new low pressure solar boiler 41, which heats the charge water to its evaporation point and then an addnal new section 47 of the superheater of low temperature / low pressure, superheats the steam "and couples it by the line 48 to the inlet line 22 of the low pressure reheater 17. The units, 42 and 40, of the charge water heating, are in sequence in the portion of low temperature of the exhaust stream 14 of the gas turbine 11, as is the superheater 47 and the low temperature heater 43. Thus, in effect, two new sources of heat supply have been provided, as appropriately illustrated by the temperature-entropy diagram of Figure 8. Here, the thermal energy supplied to the area A4 elevates the charging water to its evaporation temperature, which is supplied by the low pressure heater 43 / low temperature and then the low pressure solar boiler 41 supplies the latent heat of evaporation, which is then fed to the superheater 47 and, as illustrated by line 48, it merges with the isopression line 39, which is actually the input 22 to the low pressure heater 17, as illustrated in Figure 7. The elevation of the temperature degree supplied by the superheater 47 is A '^. Referring to the equation in Figure 6, this would be added respectively to the left of the equation, with an adjustment for the mass flow. In this mode, the equilibrium of the equation occurs at the boiling point of high pressure, also known as the "compression" temperature. Referring to Figure 6, this is about 297 ° C. Although it is believed that the technique of Figures 7 and 8 may be less efficient, it is illustrative how the concept of the invention in the equilibrium of the temperature rise per unit He charge water heating, with overheating, can be achieved in many different ways. Thus, a system has been supplied to generate electricity, hybrid, solar and that burns fuel.

Table 1

Claims

CLAIMS 1. An electric power generation system, which has a substantially closed route of feedwater / water vapor, to supply a common mass flow, this system comprises: a gas turbine generator, which has a current of hot exhaust gas; a heat exchanger, of low temperature, located in the current portion, below the hot exhaust gas, to heat the feed water to substantially its evaporation temperature; a solar boiler, connected to the heat exchanger, of low temperature, to evaporate the feed water; • "a high pressure water vapor turbine generator, and a low pressure steam steam turbine generator; a first and second heat exchanger, high temperature, located in a portion upstream of the gas lift of turbine exhaust, - the first heat exchanger, high temperature, which receives the feed water evaporated from the solar boiler and overheats it to a predetermined temperature, to drive the steam turbine, high pressure, So this water vapor turbine, high pressure, which has a low pressure exhaust, at a temperature close to the evaporation temperature, and a second heat exchanger, high temperature, which receives the exhaust from the turbine of high pressure, and reheats it to substantially the same predetermined temperature, to drive the low pressure steam water turbine, the low pressure steam turbine exhaust, is connected to a condenser, where the water vapor is charged to the water, and then, by a charging water pump, at high pressure, to the heat exchanger, low temperature; The absolute thermal energy per degree of temperature rise, is supplied by the first and second heat exchangers at high temperature and used by the steam turbines, high pressure and low pressure, is substantially equal to the thermal energy supplied by the heat exchanger of the feed water, to heat the feed water to the evaporation temperature.
2- A system, according to claim 1, wherein the escape of the steam turbine, of low temperature, is substantially at or below the ambient air pressure, but at a temperature so that the exhaust does not dry out totally nor too wet.
3. A system, according to claim 1, wherein the first and second heat exchangers, of high temperature, are selected to supply the equality of thermal energy input per degree of elevation of the temperature.
4. A system, according to claim 1, wherein the solar boiler supplies substantially all the heat necessary to change the state of the feed water, from a liquid to a vapor.
5. An electric power generation system, having a substantially closed route of the feed water / steam, to supply a common mass flow, comprising: a gas turbine generator, having a hot gas stream escape; a first heat exchanger element, placed, at least partially, in a low current portion of the hot exhaust gas, to heat the feed water to substantially its evaporation temperature, - a solar boiler element, connected to the first heat exchanger element of heat, to evaporate the feed water; a steam turbine generator, high pressure; a steam generator, "" of low pressure, connected to a condenser, which thus supplies the feed water; a second heat exchanger element, placed in an upstream portion of the hot exhaust gas of the turbine, to receive the feed water evaporated from the solar boiler element and also the low pressure exhaust from the steam turbine of high pressure and superheat it to a predetermined temperature, to drive the steam turbines of both high pressure and low pressure; The absolute thermal energy per degree of temperature rise, supplied by the second heat exchanger element, for the superheat above the boiling point of high pressure is substantially equal to the thermal energy per degree of temperature rise, provided by the first element heat exchanger, to "heat" the feed water to the evaporation temperature and below the high-boiling point.
6. A system according to claim 5, wherein the escape of the steam turbine, of low temperature, is substantially at or below the ambient air pressure, but at a temperature, so that the exhaust is not completely dry Not too wet.
7. A system according to claim 5, wherein the solar boiler element supplies substantially all the heat necessary to change the state of the feed water from a liquid to a vapor.
8. A system according to claim 5, wherein the first heat exchanger element includes a feed water heater, at low temperature, placed in a downstream portion of the hot exhaust gas and a feedwater heater, at a high temperature, placed in the upstream portion of the hot exhaust gas.
9. A system according to claim 8, wherein the solar boiler element includes a high pressure solar boiler and a low pressure solar boiler, respectively connected to the high and low temperature feedwater heaters.
10. A system according to claim 5, wherein the second heat exchanger element includes high pressure and low pressure overcalenators, which receive the. Feeding water evaporated from the solar boiler element and a low pressure reheater, which receives the low pressure exhaust gas from the steam turbine generator, high pressure, this low pressure superheater and the low reheater pressure, which drive the low pressure water vapor turbine and the superheated ^ high pressure, to drive the high pressure steam water turbine.