JP5875253B2 - Combined power generation system - Google Patents

Description

  The present invention relates to a combined power generation system, and more particularly to a gas engine combined power generation system that generates power using exhaust heat of a gas engine.

  Conventionally, a combined power generation system in which power generation efficiency is improved by performing power generation using exhaust heat of internal combustion power generation has been widespread. For example, a Rankine cycle heating source including a gas turbine driven by combustion gas and a steam turbine driven by steam generated by collecting exhaust heat of the gas turbine, and using steam on the steam turbine side as a working fluid A combined power generation system that improves power generation efficiency by using gas turbine exhaust gas is known (see Patent Document 1).

JP 2005-207259 A

  By the way, in a combined power generation system using a gas engine, exhaust heat at two different temperature levels (for example, exhaust gas from 400 to 500 ° C. and exhaust heat from engine jacket cooling water at 85 ° C.) accounts for a large proportion of the total exhaust heat. Therefore, it is indispensable to use them effectively in order to improve power generation efficiency and reduce carbon dioxide emissions.

  However, when the prior art described in Patent Document 1 is applied to a gas engine combined power generation system, there has been a problem that the engine jacket cooling water heat having a relatively low temperature cannot be effectively used. In addition, since the working fluid is steam in the above-described conventional technology, it is not possible to use a cold heat source below the freezing point (for example, cold heat of LNG (Liquefied Natural Gas) or brine cold heat of a refrigerator) in the cooling process of the working fluid. There is also a problem that it is difficult to effectively use low-temperature exhaust heat.

  The present invention has been devised in view of such problems of the prior art, and provides a combined power generation system capable of improving power generation efficiency by effectively using exhaust heat of a gas engine. The main purpose is to do.

  In a first aspect of the present invention made to solve the above problems, a gas engine (2) using combustible gas as fuel, a first generator (4) driven by the gas engine, and a hydrocarbon system A refrigerant turbine (3) using the refrigerant as a working fluid, a second generator (5) driven by the refrigerant turbine, and a first heater that heats the refrigerant using a coolant that cools the gas engine as a heat source (31), a second heater (11) for further heating the refrigerant heated by the first heater using the exhaust gas of the gas engine as a heat source, and condensation for condensing the refrigerant discharged from the refrigerant turbine And a vessel (22).

  According to this, since the refrigerant turbine that uses a hydrocarbon-based refrigerant as the working fluid is configured to use the exhaust heat of the gas engine (heat of exhaust gas and coolant), the exhaust heat recovery rate of the gas engine increases, The power generation efficiency of the system can be improved.

  As a second aspect of the present invention, a gas engine (2) using combustible gas as a fuel, a first generator (4) driven by the gas engine, and a hydrocarbon-based refrigerant as a working fluid. A refrigerant turbine (3), a second generator (5) driven by the refrigerant turbine, a first heater (11A) for heating the coolant of the gas engine using the exhaust gas of the gas engine as a heat source, A second heater (31A) that heats the refrigerant using the coolant heated by the first heater as a heat source; and a condenser (22) that condenses the refrigerant discharged from the refrigerant turbine. Features.

  According to this, since the refrigerant turbine that uses a hydrocarbon-based refrigerant as the working fluid is configured to use the exhaust heat of the gas engine (heat of exhaust gas and coolant), the exhaust heat recovery rate of the gas engine increases, The power generation efficiency of the system can be improved. In addition, because the refrigerant is heated by using the coolant heated by the exhaust gas of the gas engine without directly exchanging heat between the combustible hydrocarbon refrigerant and the exhaust gas of the gas engine, the safety of the system is increased. There are also advantages.

  As a third aspect of the present invention, the condenser condenses the refrigerant using the liquefied natural gas.

  According to this, it becomes possible to effectively use the cold heat of LNG delivered from an LNG base or the like in the process of cooling the working fluid.

  As a fourth aspect of the present invention, the combustible gas is a boil-off gas of liquefied natural gas.

  According to this, the boil-off gas generated from the LNG base or the like can be effectively used without the need for adjusting the amount of heat by mixing LP gas or the like as in the case of using as city gas.

  As a fifth aspect of the present invention, the condenser condenses the refrigerant using the brine.

  According to this, it becomes possible to effectively use the exhaust heat of the factory or the like by cooling the brine using steam or the like of a relatively low pressure (for example, 0.2 to 0.7 MPaG) discharged from the factory or the like.

  As a sixth aspect of the present invention, the refrigerant is a mixed medium of methane and propane.

  According to this, by changing the mixing ratio of methane and propane, it becomes possible to easily and appropriately cope with the low and high temperature levels of the Rankine cycle of the working fluid in the refrigerant turbine.

  As described above, according to the present invention, it is possible to improve the power generation efficiency by effectively using the exhaust heat of the gas engine.

The block diagram which shows the outline of the gas engine combined power generation system 1 which concerns on 1st Embodiment. The block diagram which shows the outline of the gas engine combined power generation system 1 which concerns on 2nd Embodiment. The block diagram which shows the outline of the combined power generation system 100 which concerns on 3rd Embodiment. The block diagram which shows the outline of the combined power generation system 201 using the conventional gas turbine

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<First Embodiment>
FIG. 1 is a configuration diagram showing an outline of a gas engine combined power generation system 1 according to a first embodiment of the present invention. The combined power generation system 1 includes a gas engine 2 that is an internal combustion engine using a combustible gas as a fuel, and a refrigerant turbine 3 that uses a hydrocarbon-based refrigerant boiling at a low temperature (a temperature lower than water) as a working fluid. Power generation is performed by a first generator 4 and a second generator 5 driven by the engine 2 and the refrigerant turbine 3, respectively, and is arranged in parallel to the LNG base 6 that delivers LNG for city gas.

  Boil-off gas (hereinafter referred to as BOG) generated at the LNG base 6 is supplied to the gas engine 2 as fuel (at least a part thereof), and the gas engine exhaust gas at a relatively high temperature (here 410 ° C.) after combustion is supplied. It is discharged toward the heat exchanger 11 for exhaust heat recovery. The gas engine 2 is provided with a cooling engine jacket (not shown), and jacket cooling water at a relatively low temperature (88 ° C. in this case) is discharged from the engine jacket. The discharged jacket cooling water is circulated through the cooling water circulation line 13 provided with the cooling water pump 12 in the direction indicated by the arrow in FIG. The output of the gas engine 2 is converted into electric power by the first generator 4.

  In the refrigerant turbine 3, a mixed refrigerant of methane and propane (here, methane 50 to 55% by weight, propane 45 to 50% by weight) is used as a working fluid. This working fluid is heated by the gas engine exhaust gas in the heat exchanger 11 before being introduced into the refrigerant turbine 3. The heat exchanger 11 is provided with a plurality of heating units composed of heat transfer tube groups, so that efficient heat exchange between the gas engine exhaust gas and the working fluid is possible. As a result, a working fluid (gas) having a predetermined temperature and pressure (here, 103 ° C., 4.9 MPaG) is introduced into the refrigerant turbine 3, and turbine blades (not shown) are rotated by the kinetic energy of the working fluid. The output is converted into electric power by the second generator 5.

  The working fluid discharged from the refrigerant turbine 3 (here, gas having a temperature of −5 ° C. and a pressure of 0.4 MPaG) is sent to the condenser 22 through the refrigerant circulation line 21 in the direction indicated by the arrow in FIG. A discharge pipe 23 from the LNG base 6 is connected to the condenser 22, and the cold energy of the introduced LNG (here, temperature: −160 ° C., pressure: 7.0 MPaG, flow rate: 70 t / hr) is the working fluid. Used for cooling. On the other hand, the heat of the working fluid is used to vaporize LNG.

  The condensed working fluid is temporarily stored in a circulating refrigerant storage tank 25 provided in the refrigerant circulation line 21. Thereafter, the working fluid (here, −128 ° C., 5.0 MPaG, 99.4 t / hr) pressurized by the refrigerant pump 26 provided in the refrigerant circulation line 21 is sent to the refrigerant evaporator 27. The refrigerant evaporator 27 is connected to a seawater introduction pipe 28 for introducing seawater (here, 15 ° C.), and the working fluid is heated to a temperature at which the jacket cooling water does not freeze due to heat exchange with the seawater (here, 5 ℃).

  The working fluid from the refrigerant evaporator 27 is sent to the refrigerant heater 31 where it is heated by heat exchange with jacket cooling water (88 ° C., 270 t / hr here) (here, heated to 29 ° C.). ) On the other hand, the jacket cooling water is cooled to a temperature at which the gas engine 2 can be cooled in the refrigerant heater 31 (here, 50 to 80 ° C.). The working fluid from the refrigerant heater 31 is sent to the heat exchanger 11, and the heated working fluid (103 ° C., 4.9 MPaG) is supplied to the refrigerant turbine 3 again.

  The LNG from the LNG base 6 is discharged from the condenser 22 and then sent to the LNG heater 32 through the discharge pipe 23. The LNG heater 32 is connected to a seawater introduction pipe 33 for introducing seawater (here, 15 ° C.), and the working fluid is heated by heat exchange with seawater (here, a gas at 5 ° C. Sent to the city gas line for use as city gas.

  In the gas engine 2, the supply amount of BOG is 1.94 t / hr (fuel consumption is 29600 kw), and the exhaust amount of gas engine exhaust gas is 83.2 t / hr. The amount of power generated by the first generator 4 is 13500 kW, and the amount of power generated by the refrigerant turbine 3 is 4060 KW. In addition, the total power generation efficiency of the combined power generation system 1 is 59.3% (the effective power generation efficiency including auxiliary power consumption is 57.2%), and a higher power generation efficiency can be realized as compared with a combined power generation system using a conventional gas turbine.

  Here, as a comparative example, a conventional combined power generation system 201 using a gas turbine is shown in FIG. In this combined power generation system 201, BOG (supply amount: 2.02 t / hr, consumed fuel: 30706 kW, pressure: 0.02 MPaG) is compressed to 21 MPaG by the fuel gas compressor 202 and introduced into the gas turbine generator 203. The discharged gas turbine exhaust gas (temperature: 504 ° C., flow rate: 136.2 t / hr) is introduced into the exhaust gas boiler 204 for exhaust heat recovery.

  In the exhaust gas boiler 204, heat exchange is performed between the gas turbine exhaust gas and the steam, and the high-pressure steam (temperature: 482 ° C, pressure: 5.4MPaG, flow rate: 14.6t / hr) generated thereby is sent to the steam turbine generator 205. be introduced. Exhaust steam (temperature: 41 ° C., pressure: 0.093 MPaG) from the steam turbine generator 205 is cooled in the condenser 206, and again through the condenser pump 207, the deaerator 208, and the high-pressure feed water pump 209, the exhaust gas boiler. Cycled to 204. The cooling water introduced into the condenser 206 is circulated through the air cooling cooling tower 210.

  In the conventional combined power generation system 201 described above, the amount of power generated by the gas turbine generator is 9754 kW, and the amount of power generated by the steam turbine generator is 3656 kW. The total power generation efficiency of the combined power generation system 201 is 47.3% (the effective power generation efficiency including auxiliary power consumption is 41.1%).

  Thus, in the combined power generation system 1 according to the first embodiment, the gas turbine exhaust gas and the jacket cooling water are used as a high heat source by the refrigerant turbine 3 using a mixed refrigerant of methane and propane as a working fluid. Electricity is generated by the binary Rankine cycle method using the cold heat during gasification as a low heat source. Thereby, the exhaust heat recovery rate can be increased by effectively using the heat of the gas engine exhaust gas and the jacket cooling water, which occupy a large proportion of the exhaust heat of the gas engine 2, and thus the power generation efficiency of the combined power generation system 1 is improved. Can be made. In addition, you may use well-known coolant other than water instead of jacket cooling water. Moreover, since the mixed refrigerant is flammable, the heating temperature in the heat exchanger 11 is preferably relatively low (for example, 130 ° C. or less) from the viewpoint of system safety.

  Further, since the condenser 22 is configured to condense the working fluid using LNG, it is possible to effectively use the cold heat of the LNG discharged from the LNG base 6 or the like in the cooling process of the refrigerant. Furthermore, since BOG is used as the fuel gas (or part thereof) of the gas engine 2, it is generated from the LNG base 6 and the like without the need for adjusting the amount of heat by mixing LP gas or the like as in the case of use as city gas. BOG can be effectively used, and the cold heat of LNG can be effectively utilized in the cooling process of the working fluid.

Second Embodiment
FIG. 2 is a configuration diagram showing an outline of the gas engine combined power generation system 1 according to the second embodiment of the present invention. In FIG. 2, the same components as those in the first embodiment described above are denoted by the same reference numerals. In the second embodiment, the detailed description is omitted as in the case of the first embodiment, except for the matters specifically mentioned below.

  The second embodiment is different from the first embodiment in that the heat exhaust gas and the working fluid are indirectly heat-exchanged via jacket cooling water. As shown in FIG. 2, the jacket cooling water discharged from the gas engine 2 is sent to the heat exchanger 11A and heated by heat exchange with the gas engine exhaust gas. Thereafter, the jacket cooling water (here, pressurized hot water of 150 to 160 ° C.) is sent to the refrigerant heater 31A through the cooling water circulation line 13 and used for heating the working fluid. The jacket cooling water cooled by the refrigerant heater 31A is supplied again to the engine jacket by the cooling water pump 12. On the other hand, the working fluid (103 ° C., 4.9 MPaG) heated by the refrigerant heater 31 </ b> A is supplied to the refrigerant turbine 3.

  As described above, the combined power generation system 1 according to the second embodiment has an advantage that the safety of the system is improved because the gas engine exhaust gas and the combustible working fluid are not directly heat-exchanged.

<Third Embodiment>
FIG. 3 is a configuration diagram showing an outline of the combined power generation system 100 according to the third embodiment of the present invention. 3, the same code | symbol is attached | subjected about the component similar to the above-mentioned 1st Embodiment.

  The combined power generation system 100 mainly includes a refrigerant turbine 3 using a hydrocarbon-based refrigerant boiling at a low temperature as a working fluid, and a generator 4 driven by the refrigerant turbine 3, and serves as a discharge source of steam and hot water. It is installed in parallel with a factory that does not (for example, petrochemical factory).

  In the refrigerant turbine 3, propane alone or a refrigerant obtained by mixing propane with a small amount of ethane or butane is used as a working fluid. The working fluid is heated by exchanging heat with warm water (here, 100 ° C., 24.3 Gcal / hr) in the refrigerant heater 131 before being introduced into the refrigerant turbine 3. As this hot water, hot water (hot water) discharged from a factory or low-pressure steam can be used. As a result, a working fluid having a predetermined temperature and pressure (here, 90 ° C., 3 MPaG) is introduced into the refrigerant turbine 3, and turbine blades (not shown) are rotated by the kinetic energy of the working fluid, and the output thereof is a generator. 4 is converted into electric power.

  The working fluid (here, 20 ° C., 0.5 MPaG gas) discharged from the refrigerant turbine 3 is sent to the condenser 122 through the refrigerant circulation line 121 in the direction indicated by the arrow in FIG. A brine circulation line 42 from the vapor absorption refrigerator 41 is connected to the condenser 122, and the cold of the introduced brine (here, −8 ° C., 21.4 Gcal / hr ethylene glycol) is used as the working fluid. Used for cooling. In the vapor absorption refrigerator 41, low-pressure steam discharged from the factory (for example, saturated steam of 0.5 to 0.7 MPaG) is used as a heat source.

  The working fluid (2 ° C.) cooled in the condenser 122 is temporarily stored in the circulating refrigerant storage tank 25 on the refrigerant circulation line 21. Thereafter, the working fluid whose pressure has been increased by the refrigerant pump 26 is sent to the refrigerant heater 131, where the working fluid (90 ° C., 3 MPaG) heated again is supplied to the refrigerant turbine 3.

  In the combined power generation system 100 according to the third embodiment, hot water discharged from the factory is used as a high heat source, and brine cold using the low-pressure steam discharged from the factory is used as a low heat source to generate power. There is an advantage that no new fuel (such as LNG) is required as in the case of the first and second embodiments described above. In the condenser 122, chiller water of a factory can be used instead of brine.

  In the combined power generation system 100, the refrigerant discharged from the refrigerant turbine is condensed using brine, so that a highly efficient power generation amount can be realized. Here, for example, assuming that the hot water introduced into the refrigerant heater 131 and the working fluid introduced into the refrigerant turbine 3 have the same conditions as described above, the condenser 122 is supplied with cooling water (25 ° C., 22.6 Gcal / hr) (conventional technology). In this case, the working fluid discharged from the refrigerant turbine 3 has a temperature of 50 ° C. and a pressure of 1.2 MPaG, and is cooled by the cooling water in the condenser 122. The cooled working fluid (35 ° C.) is temporarily stored in the circulating refrigerant storage tank 125 on the refrigerant circulation line 21. And the electric power generation amount by the generator 4 becomes a low value (2500 kW) compared with the case where it condenses using the brine cold heat of this invention (4000 kW).

  Although the present invention has been described based on specific embodiments, these embodiments are merely examples, and the present invention is not limited to these embodiments. For example, in the first and second embodiments, an example in which LNG cold heat is used as a low heat source has been described. However, the present invention is not limited thereto, and brine cold heat or the like may be used in the same manner as in the third embodiment. Further, the working fluid of the refrigerant turbine is not limited to the above-described one, but a hydrocarbon-based refrigerant composed of a simple substance such as methane, ethane, propane, or butane having a relatively small molecular weight or a mixture of two or more thereof. Can be used. When the mixed refrigerant is used, the weight ratio of the hydrocarbon components can be set according to the temperature levels of the high heat source and the low heat source in the applied combined power generation system. It should be noted that all the components of the combined power generation system according to the present invention shown in the above embodiment are not necessarily essential, and can be appropriately selected as long as they do not depart from the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Combined power generation system 2 Gas engine 3 Refrigerant turbine 4 1st generator 5 2nd generator 6 LNG base 11 Heat exchanger (2nd heater)
11A heat exchanger (first heater)
22 Condenser 31 Refrigerant heater (first heater)
31A Refrigerant heater (second heater)
100 Combined power generation system 122 Condenser 131 Refrigerant heater

Claims (6)

A gas engine using combustible gas as fuel,
A first generator driven by the gas engine;
A refrigerant turbine using a hydrocarbon-based refrigerant as a working fluid;
A second generator driven by the refrigerant turbine;
A first heater that heats the refrigerant using a coolant that cools the gas engine as a heat source;
A second heater for further heating the refrigerant heated by the first heater using the exhaust gas of the gas engine as a heat source;
A condenser for condensing the refrigerant discharged from the refrigerant turbine using a cold source below freezing point ;
A combined power generation comprising: a preheating device that preheats the refrigerant circulating through the condenser to the first heater to a temperature at which the coolant in the first heater does not freeze. system. A gas engine using combustible gas as fuel,
A first generator driven by the gas engine;
A refrigerant turbine using a hydrocarbon-based refrigerant as a working fluid;
A second generator driven by the refrigerant turbine;
A first heater that heats the gas engine coolant using the exhaust gas of the gas engine as a heat source;
A second heater that heats the refrigerant using the coolant heated by the first heater as a heat source, and a condenser that condenses the refrigerant discharged from the refrigerant turbine using a cold source below freezing point ;
A combined power generation comprising: a preheating device that preheats the refrigerant circulating through the condenser to the second heater to a temperature at which the coolant in the second heater does not freeze. system. The condenser condenses the refrigerant using liquefied natural gas as a cold source below the freezing point ,
The cooling liquid is cooling water of the gas engine, and the preheating device passes the refrigerant circulating through the condenser to the first heater to a temperature at which the cooling liquid in the first heater does not freeze. combined cycle power generation system according to claim 1, characterized that you preheated by seawater.   The combined power generation system according to any one of claims 1 to 3, wherein the combustible gas is a boil-off gas of liquefied natural gas. The combined power generation system according to claim 1 or 2, wherein the condenser condenses the refrigerant by using brine as a cold heat source below the freezing point .   The combined power generation system according to any one of claims 1 to 5, wherein the refrigerant is a mixed medium of methane and propane.

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