JP3973412B2 - Waste heat recovery system by gas turbine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust heat recovery system using a gas turbine using ammonia vapor as a working fluid.
[0002]
[Prior art]
There has been proposed an exhaust heat recovery system that uses a gas turbine (also referred to as an ammonia steam turbine) that uses ammonia vapor (ammonia gas) as a working fluid to recover the thermal energy of the exhaust gas as power.
[0003]
This exhaust heat recovery system uses an ammonia absorption cycle. As shown in FIG. 3, an aqueous ammonia solution [eg, 70% concentration (ammonia concentration, hereinafter the same)] and exhaust gas (eg, 500 ° C.) are introduced. An exhaust gas heat exchanger (equivalent to an evaporator) (EG) 51 that evaporates an aqueous ammonia solution by the heat of exhaust gas, and ammonia vapor generated in the exhaust gas heat exchanger 51 (for example, a temperature of 300 ° C. and a pressure of 3. 0 MPa) through the ammonia vapor transfer pipe 61, for example, a gas turbine (T) 71 for rotating a generator (not shown), and low-pressure ammonia vapor discharged from the gas turbine 71 through the ammonia vapor transfer pipe 62. An absorber (vapor pressure is, for example, 0.49 MPa) (A) 52 which is guided through and absorbed in an aqueous ammonia solution which is an absorbing solution, A regenerator (steam pressure of, for example, 1.52 MPa) that guides and heats a concentrated aqueous ammonia solution (for example, 54.4%) that has been concentrated by absorbing ammonia vapor in the collector 52 through the concentrated ammonia water transfer pipe 63. ) (R) 53, a condenser (C) 54 for guiding and condensing ammonia vapor (for example, 97.8%) generated by heating in the regenerator 53 through the ammonia vapor transfer pipe 64, and the condenser Ammonia liquid transfer pipe 65 for transferring the ammonia liquid condensed in 54 to the exhaust gas heat exchanger 51, and a dilute aqueous ammonia solution (for example, 45.6) whose concentration has been reduced by separation of ammonia vapor in the regenerator 53. %) In the ammonia liquid transfer pipe 65 in order to adjust the concentration of the aqueous ammonia solution in the absorber 52. Ammonia liquid transfer pipe 67 for supplying a part of the ammonia liquid to the absorber 52, and concentrated ammonia water transfer for adjusting the concentration of the ammonia liquid led to the exhaust gas heat exchanger 51 (for example, 70%). It is composed of an adjusting ammonia water transfer pipe 68 for supplying the concentrated ammonia aqueous solution in the pipe 63 into the ammonia liquid transfer pipe 65, and the ammonia vapor transfer pipe 62 and the concentrated ammonia water transfer pipe 63 are connected to each other. And between the diluted ammonia water transfer pipe 66 and the concentrated ammonia water transfer pipe 63 are respectively provided heat exchangers (HV) (HL) 81, 82, and further, the concentrated ammonia water transfer pipe 63 and the ammonia liquid transfer. The pipes 65 are provided with pumps 83 and 84, respectively.
[0004]
In FIG. 3, 91 is an exhaust gas supply pipe for supplying exhaust gas to the exhaust gas heat exchanger 51, 92 is a heated water supply pipe for supplying heated water (for example, 90 ° C.) as a heat source for the regenerator 53, 93. Is a cooling water supply pipe for supplying cooling water (for example, 30 ° C.) to the absorber 52 and the condenser 53.
[0005]
In the above configuration, high temperature exhaust gas of about 500 ° C. and high concentration aqueous ammonia solution of about 70% are supplied to the exhaust gas heat exchanger 51, and the ammonia vapor having a temperature of 300 ° C. and a pressure of 3.0 MPa is generated by the heat of the exhaust gas. Is generated.
[0006]
The ammonia vapor generated in the exhaust gas heat exchanger 51 is supplied to the gas turbine 71 as a working fluid, and electric power is taken out by rotating the generator, and the thermal energy of the exhaust gas is recovered.
[0007]
The low-pressure ammonia vapor after driving the gas turbine 71 is guided to the absorber 52 and absorbed by the aqueous ammonia solution, then becomes an ammonia liquid through the regenerator 53 and the condenser 54, and further the ammonia from the absorber 52. The aqueous solution is mixed and adjusted to a 70% high-concentration aqueous ammonia solution and supplied to the exhaust gas heat exchanger 51, and the absorption cycle is repeated.
[0008]
By the way, the energy that can be extracted from the gas turbine 71, that is, the work amount, depends on the differential pressure between the inlet pressure and the outlet pressure in the gas turbine 71, and more specifically, in the absorber 52 that is the back pressure. Depends on the pressure.
[0009]
That is, as can be seen from the dueling diagram in the absorption cycle shown in FIG. 4, the outlet pressure of the exhaust gas heat exchanger (EG) 51 is 3.0 MPa, and the pressure in the absorber (A) 52 is 0.49 MPa. Therefore, the work amount in the gas turbine (T) 71 corresponds to a differential pressure component of 2.51 MPa.
[0010]
[Problems to be solved by the invention]
According to the configuration of the exhaust heat recovery system, the amount of work that can be taken out by the gas turbine 71 depends on the difference between the inlet pressure and the outlet pressure of the gas turbine, that is, the steam pressure in the absorber 52. Although it depends, further improvement in work efficiency in the gas turbine 71 is desired.
[0011]
Then, an object of this invention is to provide the exhaust-heat recovery system by the gas turbine which can aim at the further improvement of work efficiency.
[0012]
[Means for Solving the Problems]
In order to solve the above problems, an exhaust heat recovery system using a gas turbine according to the present invention includes an exhaust gas heat exchanger that introduces an aqueous ammonia solution and exhaust gas, heats the aqueous ammonia solution with the heat of the exhaust gas, and generates ammonia vapor. A gas turbine that guides the ammonia vapor generated in the exhaust gas heat exchanger to obtain power, a low-pressure absorber that introduces the low-pressure ammonia vapor discharged from the gas turbine into the aqueous ammonia solution, and ammonia vapor that is absorbed by the low-pressure absorber Regenerator that absorbs concentrated ammonia aqueous solution that has been absorbed and becomes concentrated by heating and separates the ammonia vapor, and ammonia vapor separated by this regenerator and the concentrated ammonia aqueous solution in the low-pressure absorber are led to the concentrated ammonia A high-pressure absorber that further absorbs ammonia vapor into the aqueous solution, and A high-concentration aqueous ammonia solution whose concentration has been increased by the high-pressure absorber is transferred to the exhaust gas heat exchanger, and a dilute aqueous ammonia solution whose concentration has been reduced by separation of the ammonia vapor by the regenerator is transferred to the low-pressure absorber. Further, a part of the ammonia vapor led from the regenerator to the high pressure absorber is supplied to the intermediate stage of the gas turbine .
[0013]
According to the above configuration, instead of the condenser in the absorption cycle, a high-concentration aqueous ammonia solution to be supplied to the exhaust gas heat exchanger corresponding to the evaporator is obtained using a high-pressure absorber, so that the vapor pressure in the regenerator Therefore, a dilute aqueous ammonia solution having a low concentration can be obtained, so that the vapor pressure in the low-pressure absorber can be lowered. That is, the back pressure of the gas turbine is reduced, and the amount of work in the gas turbine can be increased.
[0014]
Furthermore, since a part of the ammonia vapor generated in the regenerator is supplied to the intermediate stage of the gas turbine to work, for example, compared with the case where all of it is condensed in the condenser, the energy recovery Efficiency can be improved.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the exhaust heat recovery system by the gas turbine which concerns on embodiment of this invention is demonstrated based on FIG. 1 and FIG.
[0016]
This exhaust heat recovery system generates ammonia vapor (ammonia gas) from exhaust gas from a diesel engine, for example, using an ammonia absorption cycle (based on a carina power generation cycle), and a gas turbine (ammonia) with this ammonia vapor. The heat energy of exhaust heat is recovered by driving a steam turbine) to obtain power.
[0017]
That is, as shown in FIG. 1, this exhaust heat recovery system leads to a highly concentrated aqueous ammonia solution (for example, about 50% (ammonia concentration, hereinafter the same)) and a high temperature (for example, about 500 ° C.) exhaust gas. An exhaust gas heat exchanger (equivalent to an evaporator in a carina power generation cycle) (EG) 1 that evaporates an aqueous ammonia solution with the heat of exhaust gas, and ammonia vapor generated in the exhaust gas heat exchanger 1 (for example, 300 ° C., 3 Gas turbine (T) 21 for rotating a power recovery device such as a power generator (not shown) and low-pressure ammonia vapor discharged from the gas turbine 21. A low-pressure absorber (vapor pressure is 0, for example, which is guided through the low-pressure ammonia vapor transfer pipe 12 and absorbed by the ammonia aqueous solution as the absorbing liquid. (About 12 MPa) (LA) 2 and a concentrated ammonia aqueous solution (for example, about 27.7%) whose concentration has been increased by absorbing ammonia vapor by the low-pressure absorber 2, and a first concentrated solution having a solution pump 31 in the middle. A regenerator (steam pressure is, for example, about 0.44 MPa) (R) 3 that is guided through the ammonia water transfer pipe 13 and is heated with high-temperature (for example, about 90 ° C.) heated water to generate ammonia vapor, Ammonia vapor (for example, about 87.4%) generated in the regenerator 3 is guided through the ammonia vapor transfer pipe 14, and the concentrated aqueous ammonia solution in the low-pressure absorber 2, that is, the first concentrated ammonia water transfer pipe 13. The high concentration absorber (H) which guides the concentrated aqueous ammonia solution through the second concentrated aqueous ammonia transfer pipe 15 and further absorbs the ammonia vapor in the concentrated aqueous ammonia solution. 4) and a high-concentration aqueous ammonia transfer pipe 16 for transferring a high-concentration aqueous ammonia solution (for example, about 50%) further concentrated in the high-pressure absorber 4 to the exhaust gas heat exchanger 1 and having a solution pump 32 in the middle. A dilute aqueous ammonia transfer pipe 17 for supplying a dilute aqueous ammonia solution (e.g., about 21.5%) whose ammonia vapor is separated in the regenerator 3 and having a reduced concentration, to the low pressure absorber 2; The ammonia vapor generated in the regenerator 3, that is, the ammonia vapor in the ammonia vapor transfer pipe 14, is composed of an ammonia vapor supply pipe 18 for supplying the intermediate stage of the gas turbine 21, and low-pressure ammonia Between the steam transfer pipe 12 and the first concentrated ammonia water transfer pipe 13 and between the diluted ammonia water transfer pipe 17 and the first concentrated ammonia water transfer pipe 13, A first heat exchanger (HV) 33 and a second heat exchanger (HL) 34 are provided for heat recovery.
[0018]
In FIG. 1, 41 is an exhaust gas supply pipe for supplying exhaust gas to the exhaust gas heat exchanger 1, 42 is a heated water supply pipe for supplying high-temperature heated water as a heat source for the regenerator 3, and 43 is a low-pressure absorber 2. And a cooling water supply pipe for supplying cooling water (for example, about 30 ° C.) to the high-pressure absorber 4.
[0019]
Next, the operation of the exhaust heat recovery system will be described.
Exhaust gas having a high temperature of about 500 ° C. and a highly concentrated aqueous ammonia solution having a high ammonia concentration of 50% are supplied to the exhaust gas heat exchanger 1, where the temperature of the exhaust gas is about 300 ° C. and the pressure is 3. A high-pressure ammonia vapor of about 0 MPa is generated.
[0020]
The ammonia vapor generated in the exhaust gas heat exchanger 1 is supplied as a working fluid to the gas turbine 21 via the ammonia vapor transfer pipe 11, and the generator is rotated to extract electric power. That is, the heat energy of the exhaust gas is recovered.
[0021]
The low-pressure ammonia vapor after driving the gas turbine 21 is guided to the low-pressure absorber 2 having a vapor pressure of about 0.12 MPa through the low-pressure ammonia vapor transfer pipe 12 and is absorbed therein by the aqueous ammonia solution. .
[0022]
The concentrated ammonia aqueous solution having the ammonia vapor absorbed by the low-pressure absorber 2 and having a concentration of about 27.7% is supplied to the regenerator 3 through the first concentrated ammonia water transfer pipe 13, where 90% When heated with heated water at 0 ° C., ammonia vapor having a concentration of about 87.4% is generated. Note that the vapor pressure in the regenerator 3 is about 0.44 MPa.
[0023]
A part of the ammonia vapor generated in the regenerator 3 is supplied to the middle of the gas turbine 21, that is, to the intermediate stage via the ammonia vapor transfer pipe 14 and the ammonia vapor supply pipe 18 to drive the gas turbine 21. Provided.
[0024]
On the other hand, the remainder of the ammonia vapor from the regenerator 3 is supplied to the high-pressure absorber 4 via the ammonia vapor transfer pipe 14, where it is absorbed by the solution pump 31 via the second concentrated ammonia water transfer pipe 15. The concentrated ammonia aqueous solution having a concentration of about 27.7% supplied from the vessel 2 is absorbed into a high concentration ammonia aqueous solution having a higher concentration of about 50%, and this high concentration ammonia aqueous solution passes through the high concentration ammonia water transfer pipe 16. To the exhaust gas heat exchanger 1 and an absorption cycle using ammonia vapor is performed.
[0025]
The dilute aqueous ammonia solution having a concentration of about 21.5% from which the ammonia vapor is separated in the regenerator 3 is transferred to the low-pressure absorber 2.
Here, FIG. 2 shows a Duhring diagram in the absorption cycle. As can be seen from FIG. 2, the outlet pressure of the exhaust gas heat exchanger (EG) 1 is 3.0 MPa, and the steam pressure in the low-pressure absorber (LA) 2 is 0.12 MPa, and therefore the gas turbine (T) 21. The differential pressure corresponding to the amount of work at 2.88 MPa is 2.88 MPa, which is a considerable increase compared to the conventional 2.51 MPa.
[0026]
As described above, instead of the condenser in the absorption cycle, a high-concentration aqueous ammonia solution to be supplied to the exhaust gas heat exchanger (equivalent to an evaporator) is obtained using a high-pressure absorber. Therefore, even with heated water at the same temperature (90 ° C.) as before, a dilute aqueous ammonia solution with a lower concentration can be obtained. That is, as shown in the dueling diagram of FIG. 2, the steam pressure in the low-pressure absorber 2 can be considerably lowered from 0.49 MPa to 0.12 MPa. The amount of work in the turbine 21 increases.
[0027]
Furthermore, since a part of the ammonia vapor generated in the regenerator 3 is supplied to the intermediate stage of the gas turbine 21 to perform work, for example, when all of the ammonia vapor is transferred to the condenser and condensed as in the conventional case. Compared to the above, in other words, the entire amount is condensed and the part that has been returned to the absorber for concentration adjustment is taken out as work in the gas turbine, so that the energy recovery efficiency can be improved. .
[0028]
For example, when the specifications of the heat exchanger and the like (specifically, the heat transfer area) are the same, the exhaust heat recovery system according to the above configuration and the exhaust heat recovery system according to the conventional example are compared with each other by about 1.6 times. Can be obtained.
[0029]
By the way, in the said embodiment, although demonstrated as what heat-recovers the exhaust gas from a diesel engine, it is not limited to this, It is using exhaust gas discharged | emitted from various facilities. it can.
[0030]
In addition, the waste heat source of the second type [when waste heat is used as a heat source for the exhaust gas heat exchanger (evaporator) and the regenerator to obtain a higher-temperature output fluid with an absorber] It can be applied in some cases.
[0031]
【The invention's effect】
As described above, according to the configuration of the exhaust heat recovery system of the present invention, a high-concentration aqueous ammonia solution to be supplied to an exhaust gas heat exchanger corresponding to an evaporator is obtained using a high-pressure absorber instead of a condenser in an absorption cycle. As a result, the vapor pressure in the regenerator can be lowered, and thus a dilute aqueous ammonia solution having a low concentration can be obtained. Therefore, the vapor pressure in the low-pressure absorber can be lowered as compared with the conventional case. That is, since the back pressure of the gas turbine can be reduced, work efficiency in the gas turbine can be improved.
[0032]
Furthermore, since a part of the ammonia vapor generated in the regenerator is supplied to the intermediate stage of the gas turbine to perform work, for example, when all of the ammonia vapor is transferred to the condenser and condensed as in the past. In comparison, the energy recovery efficiency can be improved.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of an exhaust heat recovery system according to an embodiment of the present invention.
FIG. 2 shows a dueling diagram of a working fluid in the exhaust heat recovery system.
FIG. 3 is a diagram showing a schematic configuration of an exhaust heat recovery system according to a conventional example.
FIG. 4 shows a dueling diagram of a working fluid in a conventional exhaust heat recovery system.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Exhaust gas heat exchanger 2 Low pressure absorber 3 Regenerator 4 High pressure absorber 11 Ammonia vapor transfer pipe 12 Low pressure ammonia vapor transfer pipe 13 First concentrated ammonia water transfer pipe 14 Ammonia vapor transfer pipe 15 Second concentrated ammonia water transfer pipe 16 High Concentration ammonia water transfer pipe 17 Rare ammonia water transfer pipe 18 Ammonia vapor supply pipe 21 Gas turbine

Claims (1)

An exhaust gas heat exchanger that introduces an aqueous ammonia solution and exhaust gas and heats the aqueous ammonia solution with the heat of the exhaust gas to generate ammonia vapor, a gas turbine that derives the ammonia vapor generated in the exhaust gas heat exchanger and obtains power, and A low-pressure absorber that guides the low-pressure ammonia vapor discharged from the gas turbine and absorbs it into the aqueous ammonia solution, and a high-concentration aqueous ammonia solution that absorbs the ammonia vapor in this low-pressure absorber and concentrates it to heat and separate the ammonia vapor. And a high-pressure absorber that introduces the ammonia vapor separated in the regenerator and the concentrated aqueous ammonia solution in the low-pressure absorber and further absorbs the ammonia vapor in the concentrated aqueous ammonia solution,
In addition, the high-concentration ammonia aqueous solution whose concentration is increased by the high-pressure absorber is transferred to the exhaust gas heat exchanger, and the low-pressure absorption is performed for the dilute ammonia aqueous solution whose concentration is reduced by separation of ammonia vapor in the regenerator. Not to be transferred to the vessel ,
Furthermore, a waste heat recovery system using a gas turbine, characterized in that a part of the ammonia vapor led from the regenerator to the high pressure absorber is supplied to an intermediate stage of the gas turbine.

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