FI94895B - Arrangement in a combined cycle power plant - Google Patents

Description

! 94895 Arrangement in a combined cycle power plant

The invention relates to an arrangement for increasing the overall efficiency of waste heat in a combined cycle power plant, in which the first electric generator is powered by one or more supercharged reciprocating internal combustion engines. circulation.

10 The utilization of waste heat has long been known in connection with various power plants. In particular, low-temperature waste heat can be used for various heating purposes, regardless of the type of power plant. Such an arrangement is described, for example, in DIESEL & GAS TURBINE 15 WORDLWIDE, January-February 1993: "Prize-Winning CHP Plant Exploits Solvent Vapors", pp. 18-19 and "The Modigen Modular Power Plant Concept", pp. 30-31. These are not the actual so-called combined heat and power plants, which means power plants in which the primary circuit generates electrical energy through a generator and the waste heat is used in the secondary circuit to produce additional electrical energy. In this case, the problem specific to these combined heat and power plants arises from the fact that the thermal energy of the secondary circuit is at a relatively low temperature, whereby electricity is obtained from it only at a relatively low efficiency.

One way to improve the efficiency of the use of waste heat in the secondary circuit of a combined heat and power plant is to use additional heating, which raises the temperature of the exhaust gases from the primary circuit. In this case, more relatively hot steam is obtained from the secondary circuit in the steam boiler, whereby improved efficiency is obtained for the steam turbine and generator. In this case, however, the total amount of waste heat increases, which leads to a decrease in the overall efficiency of the entire power plant.

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There are also arrangements for increasing the overall efficiency in combined heat and power plants where the primary circuit consists of an internal combustion engine and an electric generator. When the internal combustion engine is a gas turbine with a relatively high exhaust gas temperature, about 500 ° C or well above, the waste heat 35 of the exhaust gases can be used relatively efficiently to generate steam and further electricity. Such arrangements are described, for example, in DIESEL & GAS TURBINE WORLDWIDE, January-February 1993: "Industrial CHP Plant Meet Flexible Steam Requirements", pp. 20-22, and JOURNAL OF ENGINEERING FOR GAS TURBI- 2 94895 NES AND POWER, October 1991, butter. 113, pp. 475-481: "Combined Cycle Plants With Frame 9F Gas Turbines". These publications describe several different circulation processes for generating steam for a steam turbine or turbines. Thus, these publications do not describe at all how the exhaust gas at a substantially lower temperature, about 300-350 ° C, of a reciprocating internal combustion engine, such as supercharged diesel engines used in power plants, can be effectively used to increase efficiency, and in particular power generation efficiency. With this exhaust gas at a lower temperature of the diesel engine and the steam generating circuits according to the above-mentioned references, it is not possible to operate steam turbines in their preferred operating range.

The use of waste heat contained in the exhaust gases of a diesel engine for the production of electricity is discussed in DIESEL ENGINEERING, Spring 1980: "MAN diesel based CHP schemes", pp. 5-11. Title arrangement presented a supercharged diesel engine 15 will at a temperature of approx. 500 ° C, the exhaust gases are first conducted to the compressor, which motor is supplied with compressed air from the inlet, through the drive side. The thermal energy of the exhaust gases is good enough for this. The exhaust gases are then passed to a steam boiler at a temperature of about 350 ° C, where steam is produced in a steam turbine using a steam generator and a superheater. The steam turbine is connected to a second electric generator, while the die-20 motor is connected to the first electric generator for electricity generation.

When using heavy fuel oil, the exhaust gases leaving the steam boiler must be at a temperature of approx. 160-180 ° C, so that condensation of sulfur compounds with harmful consequences does not occur. The temperature difference utilized by the steam boiler at about 170 ° C is thus small and still occurs at the above-mentioned low temperature, so the increase in electrical energy that can be achieved is relatively small. Even if the above-mentioned temperature limitation caused by the sulfur contained in heavy fuel oil »were not present, at lower temperatures the boiler plant would no longer receive essentially another form of energy, i.e. steam.

3 C DE publication 310 329 describes an exhaust gas circuit in which the exhaust gases are first led to a water preheater and only then to a supercharger turbine. In the arrangement of the reference publication, the exhaust gases do not use a superheater, but superheating takes place in all embodiments of the publication in a separate part of the plant, where the combustion of the second fuel is carried out independently of the diesel engine. Thus, in the ice arrangement of the reference publication, the increase in the power of the supercharger 25 is mainly taken from this additional energy, the primary aim being to lower the operating temperature of the internal combustion engine without increasing the overall efficiency of electricity production when the efficiency of additional fuel consumption is also taken into account.

3,94895 JP 58-143114 describes the boiler plant as a whole with its steam cylinders and superheater, but does not at all compensate for the reduction in power of the supercharger caused by the arrangement of the supercharger after the boiler. Thus, the efficiency of the power generation of this plant is no better than the efficiencies of the other arrangements described in the above-referenced publications FI-89969 describes an arrangement in which, in one embodiment, the supercharger is arranged between two sections of the boiler. This arrangement has a bypass tube with which the first part of the boiler can be bypassed, leaving the arrangement with a conventional arrangement in which the 10 superchargers are closest to the engine. The inventor has clearly not believed in the functionality of the supercharger. This publication, like the other publications mentioned above, also does not compensate for the power dissipation of the supercharger in any way, so the arrangement is as disadvantageous as other arrangements according to the prior art.

In addition, double long pipes between the supercharger and the boiler plant are expensive during the construction phase and cause additional losses, which alone make the construction of the publication impractical.

The object of the invention is thus to provide an ice arrangement in which an electric power plant operating primarily with a reciprocating internal combustion engine and in particular a supercharged diesel engine, 20 ns. a combined cycle power plant in which the the waste heat contained in the engine exhaust is utilized by steam power, typically a steam boiler and a steam turbine, to increase the efficiency of electricity generation. Another object of the invention is such an arrangement in which additional heating of the steam boiler is not necessary at all or only to a very limited extent, whereby the waste heat generated at a very low temperature, i.e. below about 160-180 ° C, is generated as little as possible. The aim is thus to obtain as much high-grade energy, i.e. electricity, as possible from the smallest possible total amount of fuel. Yet another object of the invention is an arrangement which also recovers a significant proportion of its heat content from the exhaust gas substantially below 160-180 ° C, increasing the efficiency of electricity generation, and this typically when low sulfur or sulfur-free fuel is used in the diesel engine, the exhaust gas temperature is corrosive. resulting lower limit.

The disadvantages described above can be eliminated and the objects defined above are achieved by the arrangement according to the invention, which is characterized by what is defined in the characterizing part of claim 1.

94895 4

The most essential advantage of the invention is that the arrangement according to it makes it possible to increase the temperature in the steam generating circuit compared to the arrangements according to the prior art, whereby the efficiency of the steam circuit in electricity production substantially increases. This advantage is maintained even in the overall efficiency, although it may be necessary to use 5 parts of the additional energy thus obtained for stowage. Another advantage of the invention, especially in a situation where the temperature of the exhaust gases is not lower due to corrosion or other reasons, is that the heat of the exhaust gases is recovered close to ambient temperatures up to the corresponding temperatures to increase the efficiency and overall efficiency of electricity generation.

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In the following, the invention will be described in detail with reference to the accompanying drawings.

Figure 1 schematically shows one arrangement according to the invention for increasing the efficiency of electricity generation in a combined heat and power plant.

Figure 2 schematically shows another arrangement according to the invention for increasing the efficiency of electricity generation in a combined heat and power plant.

Figure 3 schematically shows a third arrangement according to the invention for increasing the efficiency of electricity generation in a combined heat and power plant.

Figure 4 schematically shows a fourth arrangement according to the invention for increasing the efficiency of electricity generation, illustrating only a part of the process.

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Figure 5 shows an arrangement according to the invention implemented in a combined cycle power plant comprising several diesel engines.

Figures 1-5 show several arrangements according to the invention in different details in a combined heat and power plant. Power plants consist of power plants that provide net power. of supercharged reciprocating internal combustion engines, such as diesel engines 3, which may be in the power plant one, as in Figures 1-4, or generally more, as in Figure 5. The diesel engine 3 drives a first electric generator 1 to generate electric energy. The diesel engine inlet air unit by means of the exhaust gas turbocharger 8 6 jon-35 fl driving side 7 which is generally a gas turbine, the exhaust gases are passed through. The supercharged and cooled air is fed as combustion air to the 8 'diesel engine. The second net power source of the combined cycle power plant is hot pressurized steam 15a, b, c, which is generated in the steam boiler 10 and fed to the steam turbine 4.

5 94895 The steam turbine 4 uses a second electric generator 2 to generate electricity. This hot steam 15a, b, c is again generated by the exhaust gases 5 of the diesel engine 3 by passing them through this steam boiler 10. The steam boiler 10 includes at least a steam generator 18a with its respective boiler piping 20 and a superheated 19a for high-pressure steam 15a, which is fed to the steam turbine 4.

According to the invention, the hot exhaust gases 5a of the diesel engine 3 are led directly from the engine first to the steam boiler 10 and only from there to the drive side 7 of the supply air supercharger 7. This arrangement typically utilizes n in the steam boiler 10.

10 260 ° C temperature difference between approx. 500-240 ° C. The use of such steam provides a fairly good efficiency in the production of electricity in the steam turbine and thus in the second electric generator. Depending on the design of the diesel engine, the temperature of its exhaust gases can be higher, approx. 550 ° C, or as development progresses even approx. 700 ° C, which further increases the efficiency of steam use.

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However, it follows from the arrangement according to the invention that the temperature of the exhaust gases before the supercharger gas turbine is considerably lower in the arrangement according to the invention than in the arrangement according to the prior art. Since the power of a gas turbine operating at a certain pressure ratio and gas mass flow is directly proportional to the absolute temperature, the power of the supercharger also decreases correspondingly. According to the invention, this situation can be solved either by a) taking the additional power required for the supercharger 6 from the steam turbine 4 by connection 13, b) dimensioning (selecting) the gas turbine 7 so that the gas pressure before the gas turbine is higher than the prior art, or c) raising the combustion gas temperature by burning vapors -25 mode 10 some extra fuel. Options a) and b) are more cost-effective than options c) because they do not increase the amount of waste heat.

According to the invention, the above-mentioned connection of the steam turbine 4 to the drive shaft 9 of the supercharger 6 can take place in several different ways. In the embodiment 30 shown in Fig. 1, the steam turbine 4 has a high pressure portion 14a and a low pressure portion 14c, of which the low pressure portion 14c is connected 13 from its drive shaft 12 to the supercharger shaft 9. This connection can be direct or via a gearbox 16 or the like. The high-pressure steam turbine section 14a is connected by a shaft 17 only to the second generator 2 and not to the supercharger at all. In the embodiment of Figure 2, the steam turbine 4 consisting of the high pressure section 14a and the low pressure section 14c is connected indirectly or alternatively directly to the drive shaft 9 of the supercharger 6 from its shaft 17 by means of a gearbox 17 or the like. the supercharger does not need 6 94895 (at partial engine power the supercharger needs a lot of extra power, at full power the supercharger does not need much extra power), is recovered with another electric generator. In the implementation of Figure 4, the medium pressure part 14b of the steam turbine 4 is connected 13 directly to the drive shaft 9 of the supercharger 6. Here, the high pressure and low pressure parts 14a and the corresponding 14c of the steam turbine 4 are again connected to the second generator 2 by their shaft 17.

As can already be seen from the above, in the arrangement according to the invention, in which relatively hot exhaust gases 5a can be used for steam generation, it is advantageous to use steam at several pressure / temperature levels. Thus, the steam circuit according to the invention comprises high-pressure steam 15a and medium-pressure steam 15b and / or low-pressure steam 15c. Of these, at least the high-pressure steam 15a can be used in its entirety on the high-pressure side 14a of the steam turbine 4 to generate electricity with the second generator 2, since the additional energy required by the supercharger 6 in the ice arrangement according to the invention is quite small.

Typically, the additional energy required by the supercharger 6 is taken from either the medium pressure steam 15b steam turbine portion 14b, if tracked to the turbine, or the low pressure steam 15c low pressure section 14c, or both, depending on the amount of additional energy required and the steam turbine design.

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Figure 3 illustrates the above-mentioned second type of arrangement according to the invention, with which additional energy is supplied to the supercharger 6. There, additional heat 21 is introduced into the steam boiler 10 by burning, for example with a burner (not shown) in the figure, a suitable fuel, such as the same fuel as that used in the main power source diesel-25. in the engine. In this case, firstly, the pressure and temperature of the steam can be slightly increased, because the temperature on the side of the furnace 22 rises. In addition, the temperature of the exhaust gases 5b leaving the side of the steam boiler furnace 22 can be arranged high enough, for example to about 300 ° C, whereby this temperature and amount of exhaust gases 5b is sufficient to operate the supercharger 6 with the required power. The amount of waste-30 remaining after the supercharger is slightly higher than that provided by the first type of solution according to the invention, but its significance depends on how much of this waste heat has been or is not used in each combined heat and power plant, for example for heating purposes, etc. similarly, it is to take steam from somewhere in the steam circuit and feed it with the exhaust gases 35 to the supercharger turbine.

All the arrangements according to the invention described above, i.e. in which the supercharged gas turbine is located behind the steam boiler, are characterized by the special feature that on the furnace 22 side or flue gas side of the steam boiler 10, i.e. on the side of the steam boiler piping 20 the application uses the term furnace or flue gas side, regardless of whether the boiler burns fuel or not), there is a substantially higher pressure P2 than the outdoor pressure pj. The furnace 22 side thus has an overpressure pj-p2 = Δρ relative to the outside air, which means that the furnace is pressurized. The excess pressure depends on the supercharger 6 Δρ driving side 7, ie. The compressor of the gas turbine 7, the flow resistance. This same pressure of the boiler furnace 22 as such is also applied to the exhaust gases 5a leaving the diesel engine as a back pressure of the engine. If the operating conditions of the diesel engine 3 are considered to be approximately normal, in which case the above-mentioned back pressure is not increased so that the operating principle of the engine substantially changes, this overpressure of the furnace 22 according to the invention is preferably in the range of about 1.0-3 bar. the power of the gas turbine substantially increases and the engine decreases. In its most common range, the diesel engine operates when this overpressure Δρ is in the order of magnitude of 15 bar 2 bar. This overpressure is obtained to the desired extent by designing and manufacturing the flow cross-section of the exhaust gas turbine 7 driving the supercharger 6 such that the flow resistance leads to the intended overpressure. Mainly, the flow cross-section of the exhaust gas turbine 7 can be dimensioned along the length of the turbine blades, but this will not be described in detail here, as it is a matter of its own field.

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In case the combined cycle power plant comprises several piston internal combustion engines, such as supercharged diesel engines 3a, 3b, 3c, and corresponding electric generators 1, as shown in Figure 5, it is generally advantageous to use only one steam boiler 10 to which the exhaust gases 5a from the engines 3a, 3b, 3c are fed together. . It is also generally advantageous to use one supercharger 6 common to these several engines, to the drive side 7 of which all the exhaust gases 5b coming from the steam boiler are led. In this way, the supply air 8 is led and distributed as compressed and cooled combustion air 8 'to all diesel engines. Of course, it is clear that each diesel engine may be equipped with its own steam boiler and supercharger, or the combined cycle power plant may comprise one steam boiler and several superchargers or numbers may be tracked in some other way.

· It is clear that in this case too the additional energy required by the supercharger 6 or supercharges is traced according to the invention either by connecting the shaft 17 of the steam turbine 4 using the second electric generator or the shaft 14a, b, c of the turbine to the supercharger shaft 9 or by introducing additional heat energy to the steam boiler 10 or some combination thereof. 35 by.

It is clear that the steam generating circuit according to the invention also comprises, as necessary and as designed, steam generators 18b and superheaters 19b for lower pressure 8 94895 steam circuits 15b and 15c and always corresponding boiler pipes 20 in the furnace 22. or other possible components. Because they are known in the art, they are not described in more detail in this application. Figures 4 and 5 illustrate all of these additional components in block 25, which may include any of the known components used in steam processes.

The following is a comparison of a combined cycle power plant according to the prior art with a combined cycle power plant according to the invention in terms of the electric powers obtained therefrom and thus the efficiency of electricity generation. The starting point is a prior art combined cycle power plant consisting of a diesel engine and an electric generator, in which the combined electrical power of the generators is 100 MW. In the power plant, the exhaust gas temperature immediately after the cylinders is 495 ° C and immediately after the next turbocharger 15 325 ° C. The minimum permissible flue gas temperature is considered to be 160 ° C.

The condenser pressure is 0.03 bar and the total efficiency of the generators = 0.95.

In addition to the power generated by the diesel engine, the power of the steam turbine must be calculated in a prior art plant. In the case of a two-pressure process, the pressures of the steam process after the supercharger are 20 bar and 6 bar and the respective superheat temperatures are 300 ° C and 200 ° C. Exhaust turbine isentropic efficiency η56 = 0.81. The feed water is preheated by means of a preheater using the engine cooling water, an Ekono mixer and a mixing preheater. The electrical power generated by a steam turbine at ^ gt = 0.95 is 9.4 MW (excluding self-propelled power).

25.

In addition to the power generated by the steam turbine in the plant according to the invention, it must be taken into account that the exhaust turbine placed downstream of the steam boiler generates less power in the supercharger than in the prior art plant, as described above, because the exhaust gases are already cooled. Here again, the steam process is a two-pressure process with pressures of 80 bar and 23.2 bar and corresponding heating temperatures of 470 ° C and 270 ° C. Turbine isentropic efficiency% e = 0.83. The feed water preheater consists of a diesel engine cooling water preheater and three regenerative preheaters, the middle of which is a mixing preheater.

In this case, the mechanical power generated by the steam turbine is 23.9 MW. The efficiencies of the exhaust gas turbines are assumed to be the pressure ratio, i.e. the back pressure of the exhaust turbine, which in the arrangement of the invention is at the same time boiler furnace overpressure Δ 35 9 94895 p, 1.9 bar and isentropic efficiency η se = 0.85, the following values: "= 24.1 MW and plant according to the invention = 15.3 MW with a difference of 8.8 MW. In this embodiment of the invention, this power is taken directly from the shaft of the steam turbine, whereby the net power from the steam turbine of the plant 5 of the invention is 15.1 MW.

Overall, the increase in net power provided by the ice arrangement according to the invention is thus 5.7 MW, i.e. about 6% compared to the arrangement according to the prior art presented at the outset.

Claims (7)

94895 1. Arrangements for the production of total genocytes in the combination of a spark plug and a combination of a kraft mask for the production of a generator or a generator (1) in the case of an engraver (10) under a tricket ()2) väsentligen högre än lufttrycket (pj) i det fria, vilken ängpanna bestar ätminstone av en ambcylinder (18a) samt en överhettare (19a), för att alstra änga (15a, 15b ...) under tryck, vilken änga leds via en ängturbin (4) kopplad med en andra elgenerator (2) och vidare account 25 circulating, och avgasema leds först efter (5b) engpannan account gasturbinen eller gas-turbinema (7) för inluftens (8) compressor ( 6), the gas expander of the air compressor is detached from the air compressor (6), the efficiency of the air compressor (9), for which the air compressor (9) is used. network production in the combined production sector-30 Ning. An arrangement for increasing the overall efficiency of waste heat in a combined heat and power plant, wherein the first electric generator or generators (1) are powered by one or more reciprocating internal combustion engines (3), the exhaust (5) of which is first (5a) externally pressurized at a higher pressure (p2) to a steam boiler (10) consisting of at least a steam cylinder (18a) and a superheater (19a) for producing pressurized steam (15a, 15b ...) which is passed through a steam turbine (4) connected to another electric generator (2) and the exhaust gases are led only after the steam boiler (5b) to the gas turbine (7) or turbines of the supply air supercharger (6), where they expand to the outside air pressure, characterized in that in this arrangement the power of the supercharger (6) is increased on its drive shaft (9). ) by the proportion of the power of said steam turbine (4) connected (13), the power generation efficiency p of this combined cycle power plant to enhance your. 2. An arrangement according to claim 1, which comprises the effect of an angular turbine (4) with a compressor (6) drive (9) utilized by an entrainment turbine (14c and 14b) and an entrainer 35 bin (14a) driver nämnda andra elgenerator (2). Arrangement according to Claim 1, characterized in that the part of the power of the steam turbine (4) connected to the drive shaft (9) of the supercharger (6) is taken from a low-pressure and / or medium-pressure steam turbine (14c and / or 14b) and at least a high-pressure steam turbine (14a) said second electric generator (2). 3. Arrangement according to claim 1 or 2, which comprises a high pressure turbine (14a) The shaft (17) is provided with an opener for the compressor (6) drive (9) 94895 12 or alternatively a coupling for a medium and a copy, a medium en växel (16) eller direkt. Arrangement according to Claim 1 or 2, characterized in that the shaft (17) of the high-pressure steam turbine (14a) is either completely unconnected to the drive shaft (9) of the supercharger (6) or alternatively connected to it by a switch, such as a gearbox (16). , or directly. 25; Arrangement according to Claim 1, characterized in that on the flue gas side (22) of the steam boiler (10) on which the engine exhaust gases (5) file, a pressure (p2) substantially higher than the ambient pressure (pj) prevails, which overpressure (Δρ) is approximately 1.0-6 bar that the drive side (7) of the supercharger comprises an exhaust turbine and that this overpressure (Δρ) is preselected for the overall system 30 of the combined cycle power plant by the size of the flow cross section of the exhaust turbine (7) using the supercharger (6) or the like. The arrangement according to claim 1, which comprises a ratchet (22) and a bracket (10), the motors avgaser (5), a star tricket (p2) or a tracer (pi) and a detonator, Δρ) is omitted in the range of 1,0 to 6 bar, with the compression set (7) in the case of high-pressure and high-pressure (Δ p) at the end of the driving range of the combined power supply system (7), ), tvärsnitt eller 10 genom head faces give setting. 5. A method according to claim 1, comprising a diesel engine (3) and a diesel engine or a double engine and a seat (10) which is an integral part of an air or a single cylinder (18b) or more (19b) or more. tryck (15b, 15c) velvet mooring system (20) and spoon channel (22) velvet armature (11). Arrangement according to claim 1, characterized in that the piston combustion engine (3) is a diesel engine or a dual fuel engine or a gas engine and that the steam boiler (10) further comprises one or more steam cylinders (18b) and superheaters (19b) for lower pressure steam circuits (15b). 15c) and the corresponding boiler piping (20) and flue gas ducts (22) as well as condensers (11). > «U i aiit. i> t u 11 94895 6. A method according to claim 1, which comprises the invention (5) according to the invention (10), the genome of the genome upstream of the genome (21), or, alternatively, the gastric (7) auxiliary heat circulating or alternating heat tricket (p2) and air pannans (10) crotch channel (22) genome dimensioning of the gasturbant (7) flow channel for the temperature of the extraneous matter and / or heat efficiency (6). 25: Arrangement according to Claim 1, characterized in that in addition to the flow of exhaust gases (5), additional heating, such as additional heat (21) obtained by reflectors, is used in the steam boiler (10) or alternatively steam or the like is fed to the gas turbine (7). (10) in the flue gas ducts (22) a pressure (p2) for raising the temperature of the steam produced by the dimensioning of the flow channels of the gas turbine (7) and / or for increasing the power of the supercharger (6). Arrangement according to claim 1 in a combined heat and power plant with 10 or more internal combustion engines (3a, 3b, ...) operating the first electric generators (1), characterized in that the plant has one common supercharger (6) with two or more engines (3a and 3b and / or 3c) so that the hot exhaust gases (5a) of the engines are first fed together to one steam boiler (10) and then cooled (5b) to the gas turbine (7) and the produced compressed combustion air (8 ') is distributed to said engines. claims 7. Arrangement according to claim 1 and a combination of a rotary piston engine (3a, 3b, ...) for driving a motor generator (1), a rotating device according to claim 3a for a compressor (6) for a motor (6) for a motor (6) and 3b and / or 3c), the motor of which is (30a) led to 30 mounts for the stall (10) and then to the stall (5b) to the gastronomic (7) and compressed to the runners (8). ') may be replaced by a motor vehicle account. : l i anti l i ite *: