WO1989006306A1

WO1989006306A1 - Process and installation for performing mechanical work

Info

Publication number: WO1989006306A1
Application number: PCT/HU1988/000076
Authority: WO
Inventors: Károly PERÉDI
Original assignee: Peredi Karoly
Priority date: 1987-12-30
Filing date: 1988-12-07
Publication date: 1989-07-13
Also published as: HUT55084A

Abstract

In conventional processes, a fuel is burnt by direct combustion in compressed air, the air/gaseous fuel mixture so obtained is further heated to yield a calorific medium, hot water or steam, and superheated steam is produced from the latter. In the development according to the invention, the compressed air is preheated indirectly, possibly in a separate combustion device, prior to direct combustion with the fuel. In known systems for producing mechanical work, an internal combustion device, a compressor connected thereto, a furnace boiler fired at least partially by the air/gaseous fuel mixture and a device for producing mechanical power are used. In the development according to the invention, the internal combustion device is a gas turbine (5) connected to the compressor (4) which itself is connected to a furnace device (6) for heating the compressed air, which device in turn is connected to the gas turbine (5). This solution makes is possible to increase the output of the power station, which can also be used as a peak-load station, as well as to enhance the utilisation of low-grade fuels for the production of energy, while reducing pollution.

Description

METHOD AND DEVICE FOR PRODUCING MECHANICAL WORK

Subject of the invention

The invention relates to a method for generating mechanical work, wherein a fuel is burned by direct firing of the fuel in compressed air. The invention also relates to a device for the same purpose, which is provided with an internal combustion engine, a compressor connected to it, a firing boiler operated at least partially with the air / fuel gas mixture and at least one device providing mechanical work.

State of the art

Basically, two main methods are conventionally available for generating mechanical work in the manner specified above: firstly with the aid of gas turbines or internal combustion engines, whereby the work-performing ability of the correspondingly prepared gas is exploited; secondly with the help of steam turbines or steam machines that are powered by steam. Both options are associated with the combustion of fuels, with the aim of extracting as much heat as possible. In all related solutions, the goal is to increase the thermal and economic efficiency, as well as to reduce the investment costs of the heat-generating capacity and the expenditure of the increasingly expensive, high-quality fuels, which fall into one performance unit. By the way, economic efficiency is understood to mean the efficiency of the net heat equivalent of energy generation and useful heat generation. Another type of problem associated with these solutions can be summarized as harmful effects on the environment. The previously known solutions are characterized by the fact that they each favor one or more of the aspects mentioned above; know from where the others are not fulfilled. The firing technology currently used uses, for example, a combustion process that is concentrated in terms of time and space, whereby the increase in efficiency and the demands on service life, air purity, uniformity of the heat load and the composition of the combustion chamber atmosphere are in contrast to one another. Furthermore, today the fuel is burned in the heat supply or industrial firing devices so that the burning process is not part of the energy-generating cycle. In the conventional power plants, a cycle is implemented, but the heat-carrying medium is also used as the working medium of the cycle. As a result, the thermal and economic efficiency of energy generation can only be approx. 35% can be increased because the so-called latent or bound heat of water vapor must be conducted into the environment. When using internal combustion engines such. B. gas turbines or diesel engines, the cycle is carried out with air, but the optimal recovery of the resulting physical heat to reduce the amount of fuel could not be solved. At the high temperature and high pressure used there, the formation of NO _{x is} particularly high, which is extremely disadvantageous with regard to environmental pollution.

It is also well known that the thermal efficiency of a gas turbine with double heat supply is approx. Is 25% and that these gas turbines are operated with refined diesel oil. Because of these disadvantages, the operation of the existing power plants has become uneconomical, so that most of them have been shut down.

So-called combined power plants, in which gas and steam turbines are present at the same time, have been proposed for the purpose of increasing the efficiency. In these solutions A cycle is carried out on the side of the combustion air and the air / fuel gas mixture generated therefrom, in which the physical heat content of the air / fuel gas mixture leaving the gas turbine in a boiler of a steam power plant is used to the greatest possible extent. For this purpose, in the known solutions in the air-fuel gas mixture emerging from the gas turbine with a temperature of z. B. 400 ° C fuel of high quality (such as natural gas or diesel oil) fired in the amount that this causes the temperature of this mixture up to the value of z. B. 800 to 850 ° C is increased. With this air-fuel gas mixture, superheated steam can be generated in a convective steam boiler from the recirculated feed water and a steam turbine can thus be operated. With these measures, the total thermal efficiency of the gas and steam turbines on cca. 42% can be increased.

In practice, however, it has been found that this proposal also has some disadvantages. The compressed air after the compressor has a temperature of approx. 260 ° C, which indicates the entry temperature of e.g. B. 750 ºC of the gas turbine must be increased, the amount of heat required for this is introduced exclusively with direct firing into the gas turbine. For this purpose, extremely pure and very expensive liquid fuels or natural gas with a high calorific value are required. However, diesel oil or natural gas can be used to generate e.g. B. electrical energy is not provided in sufficient quantity. It has therefore also been proposed to use coal for these purposes, but this requires special high-pressure gasification with oxygen in order to produce a gas with a calorific value of approx. To be able to generate 16 500 kJ / Nm ³ . It goes without saying that this circumstance does not tolerably increase the production costs of the energy.

The method described above has other disadvantages. After the above-mentioned firing up to 850 ºC, a different one from the conventional power plant boilers is required special convective steam boilers can be used to generate the steam required for the steam turbine with the necessary pressure and the required hot steam temperature. Since the initial temperature is relatively low (e.g. 850 ° C), the mean temperature difference between the fuel gas and the steam becomes smaller than usual. As a result, larger heating surfaces are required for the same output compared to conventional power plant boilers. This solution cannot therefore be applied to the existing firing equipment, since the special steam boiler mentioned is not available in the already existing equipment and its installation requires additional investment costs.

It is also disadvantageous that when the compressed air is heated to 850 ° C., the total amount of air available in the fuel gas-air mixture cannot be used as combustion air, but only part of it. As a result, the excess air is not greater than 2.3 to 2.4, which prevents the optimal recovery of the total physical heat content exiting the turbine.

Essence of the invention

In addition to eliminating the disadvantages of the known solutions, the object of the invention is to create a solution for producing mechanical work, with which the efficiency of the processes is increased, but the facilities necessary for this can be made simpler and less expensive. An important object of the invention is to use the inferior fuels for energy production and to make the composition of the exhaust gases more environmentally friendly.

The further development of the method according to the invention now consists in that the compressed air is preheated in an indirect manner, possibly in a separate combustion device, before the fuel is directly fired. In the sense of the invention, it is advantageous if the superheated steam is produced in at least one combustion device which is independent of the combustion device producing the steam. It is furthermore advantageous if the flue gas producing the steam and / or the independent combustion devices is cooled and the amount of heat obtained thereby is used further,

The invention also proposes a procedure in which the air-fuel gas mixture created by the direct firing is cooled after the expansion and fed to the combustion devices as at least part of the combustion air and the amount of heat obtained by the cooling is further used. We can also proceed in such a way that the air / fuel gas mixture is fed in parallel to the combustion devices.

In a further advantageous implementation of the method according to the invention, the air / fuel gas mixture leaving the combustion device producing the steam or the heat-supplying agent is cooled below 170 ° C.

In the sense of the invention, it is also advantageous if in the separate combustion devices low-quality fuels are used, with which a combustion temperature of at least 900 ° C. is created. It can be advantageous if the compressed air is generated by a compressor driven by an internal combustion engine, with direct firing also taking place. According to the invention, the internal combustion engine can only be operated temporarily and the associated structural parts can be used as a peak power plant.

With regard to the operating parameters, it is advantageous if the combustion of the fuel takes place temporally and spatially.

In connection with the invention for the production of mechanical work, the further development according to the invention is that the internal combustion device as one gas turbine connected to the compressor is formed, wherein a combustion device that heats the compressed air and is connected to the gas turbine is connected to the compressor. In the sense of the invention, the embodiment is advantageous in which the firing boiler is designed as a steam boiler, to which at least one separate firing device which overheats the steam is connected and with which a superheated steam a high pressure steam turbine is operated. In a further embodiment which is advantageous according to the invention, at least one independent firing device which reheats the partially cooled steam and at which a small-pressure steam turbine is connected are connected to the high-pressure gas turbine. The firing devices can be connected to a supply of poor gases.

According to the invention, the embodiment is also advantageous in that it is provided with a steam collector, the water space of which is connected to the inputs of steam-generating heat exchangers of the boiler, the steam room of which is connected to a steam-side input of the overheating firing device and the steam distributor of which is connected to the steam-side outputs of the heat exchangers of the boiler.

Another embodiment which is advantageous according to the invention is characterized in that a heat exchanger, which preheats the feed water, is provided in the fuel pull-outs of the firing boiler or the firing devices, the input of which is assigned to the outlet of the small-pressure steam turbine and the outlet to the water space of the steam collector.

According to the invention, another embodiment is advantageous in which a condenser and then a feed water pump are arranged after the outlet of the small-pressure steam turbine, the amount of heat recovered by the condenser being used to preheat the feed water.

Finally, it is advantageous according to the invention if, after the gas turbine, a heat exchanger which cools the fuel gas / air mixture and preheats the feed water is connected is not.

Brief description of the drawing

Further details of the invention will be described in more detail using an exemplary embodiment with reference to the accompanying drawing.

In the single figure of the drawing, a circuit diagram of an advantageous embodiment of the device according to the invention is shown.

Detailed description of the execution examples

In the figure, the circuit diagram of an exemplary arrangement is shown, which was based on an existing power plant. The steam-producing devices of the power plant are symbolized here as a firing boiler 1. The power plant also has a high-pressure steam turbine 2 and a small-pressure steam turbine 3.

In the sense of the invention 4 compressed air is created with the aid of a compressor. The compressor 4 is driven by an internal combustion engine, in this example a gas turbine 5. The compressed air emerging from the compressor 4 is heated in a separate firing device 6, specifically in its irradiated heat exchanger 7 and in the convective heat exchanger 8 connected thereafter. The heat exchangers 7 and 8 are thus connected in series, and the heated compressed air is fed into the gas turbine 5 through a combustion chamber 9. The air / fuel gas mixture available after the combustion chamber 9 is expanded in the gas turbine 5 and mechanical work is thereby gained. The expanded mixture is returned from the outlet of the gas turbine 5 as at least part of the combustion air through a heat exchanger 10 cooling the mixture into the firing device 6

In the sense of the invention, the firing boiler 1 already present in the power plant is used only for the production of saturated steam. For this purpose you are radiated heat exchanger 11 and convective heat exchanger with regard to the feed water in parallel! switched and are both connected to a steam collector 13. The water space 15 of the steam collector 13 is connected to the inputs and a steam distributor 14 of the steam collector 13 is connected to the outputs of the heat exchangers 11 and 12.

The steam room 16 of the steam collector 13 is connected to a separate firing device 17, specifically to its radiated heat exchanger 18, whereby a convective heat exchanger 19 of the firing device 17 is connected in parallel as seen in the flow direction of the steam. The superheated steam created here is then fed to the inlet of the high-pressure steam turbine 2 and expanded there, which in turn produces mechanical work. The steam expanded in the steam turbine 2 is now led to a further firing device 20, namely to its irradiated heat exchanger 21, with which a convective heat exchanger 22 of the firing device 20 is also scraped in parallel. At the outlet of the heat exchanger 22 of the firing device 20 there is again superheater steam with the outlet temperature of the expansion available, which is led to the small-pressure steam turbine 3 and expanded there again. The expanded steam is then left in a condenser 23, from which the condensed water as feed water is returned to the system by a pump 24.

The feed water is preheated and the in the

Flue gas contained amount of heat used. In flue gas flues of the firing boiler 1 and the firing devices 6, 17 and 20 there are heat exchangers 25, 26, 27 and 28 which are connected to the pump 24 on the inlet side and to the water chamber 15 on the outlet side 15 of the steam collector 13. According to the invention, the temperature of the flue gas leaving the furnace 1 is to be cooled below 170 ° C. for which purpose a separate heat exchanger 29 is available at the fuel gas outlet of the firing boiler 1, which with regard to the flow of the feed water to the heat exchanger shear 25 is connected in parallel.

For the purposes of the invention, at least the firing devices 6, 17, 20 are operated with inferior gas. For this purpose, a gas generator 30 is present in the embodiment shown, which is connected to the firing devices 6, 17, 20. A remote-operated valve 31 is arranged in front of each firing device 6, 17, 20 in the gas line, with which the amount of gas introduced into the firing device 6, 17, 20 can be regulated. The air-fuel gas mixture expanded in the gas turbine 5 is also fed as at least part of the combustion air through the heat exchanger 10 to the further firing devices 17 and 20 and the firing boiler 1. In order to be able to ensure the sufficient amount of combustion air for each operating mode, a valve 32 is provided in the arrangement, which is connected to the firing boiler 1 and to the firing devices 6, 17, 20.

In this way, the firing boiler 1 and the firing devices 17, 20 and 6 are connected in parallel with respect to the combustion air.

In the illustrated embodiment, we started from an existing power plant. The firing boiler 1 already there is mostly operated with "conventional", ie relatively high-quality fuels, which are supplied through a line 33 as usual.

During the operation of the device shown in the figure, the air is compressed with the compressor 4. The compressed air has a temperature of z. B. 250 ° C, but it will be in the gas turbine 5 an operating temperature of z. B. 750 ° C. In order to reach this temperature, the compressed air in the firing device 6 operated with the inferior gases is brought up to approx. Heated to 600 ° C. Accordingly, the combustion chamber 9, which is operated with high-quality fuels, only has a temperature increase. 150 ºC required. The air / fuel gas mixture expanded in the gas turbine 5 is in the heat exchanger 10 recooled using the amount of heat recovered to heat the feed water. Because of the excess air, the fuel gas-air mixture - as mentioned earlier - can be used as combustion air, which means that the entire physical heat quantity contained can be used. Depending on the air content of the air / fuel gas mixture, the air still required for the firing can be supplied from the ventilator 32.

The expanded steam is condensed into the water in the condenser 23 after the small-pressure steam turbine 3 and is fed as feed water into the heat exchangers 25 to 29 for preheating the feed water. As a result, the feed water is heated to the prescribed pressure up to near the saturation temperature and then introduced into the steam collector 13. From the water space 15 of the steam collector 13, the feed water goes into the irradiated heat exchanger 11 or into the convective heat exchanger 12 of the boiler 1, which are dimensioned for the evaporation of the water with the power of the steam superheater used in the conventional application. The saturated steam is then blown through the steam distributor 14 into the feed water located in the steam collector 13. The steam then collects in the steam room 16.

As mentioned earlier, the firing boiler 1 is operated with the previous conventional fuel. In comparison to the previous application, however, the amount of saturated steam increases because the amount of heat previously used for overheating now also produces saturated steam.

The amount of steam increased in this way is now overheated in the separate firing device 17, which, however, is operated with the inferior gas derived from the gas generator 30. The desired final temperature is reached by the heat exchangers 13 and 19, and the superheated steam is now passed to the high-pressure steam turbine 2. It expands to an intermediate pressure. The partially cooled, overheated Damüf is in the irradiated Heat exchanger 21 and further into the convective heat exchanger 22 of the firing device 20, wherein the steam is reheated to the final temperature of the overheating. This steam is now let into the small-pressure steam turbine 3, in which it expands and reaches the condenser 23 at saturation temperature, in which it condenses again into the water. The firing device 20 is also operated with the inferior gas derived from the gas generator 30. The amount of heat required for overheating can be changed by adjusting the valves 31. The amount of heat input into the compressed air can also be set in the firing device 6 through the valve 31.

As can be seen from the previous ones, the gas turbine 5 with the heat exchangers 10, 7, 8 and the combustion chamber 9 connected to it can be operated independently of the other parts of the device. As a result, this part of the facility can be used as a so-called peak power plant, which is only put into operation during peak loads. Another advantage is that the gas generator 30 does not have to be switched off when the gas turbine 5 and the firing device 6 connected to it are switched off, since inferior gas is also required for the firing devices 17 and 20. If the solution according to the invention is compared with the conventional arrangements, it appears that not only is the amount of mechanical work produced higher, but only low-quality fuels are used for this. In this way, coal regains importance as an energy source. In the solution according to the invention, namely, the coal is not burned with a firing technique with a concerted combustion process, predominantly in the form of throat dust combustion, as before, but rather the low-quality gases mentioned with lower calorific values are produced from the lump coal in the gas generator 30. However, this method enables better extraction of the in the Coal contained amount of energy.

The use of coal mentioned above has another significant advantage. The generation of the generator gas is much more environmentally friendly than the concentrated combustion, whereby the fly ash and the NO _x gas have an intolerable proportion in the fuel gases. When generating the generator gas, the so-called rotary generator can be used, whereby the fly ash and the sulfur content can be brought into the slag in the solid state, the gas becomes practically sulfur-free. It is also important that the combustion of the generator gas takes place at a relatively low temperature, with practically no NO _{x being} generated.

The solution according to the invention further enables the use of a combustion process which is temporally and spatially extended and which likewise takes place at a lower temperature. As a result, the combustion temperature remains below 1300 ° C, which is the limit of the formation of the NO _x gas, which is particularly dangerous for the environment. For the same reason, it is advisable to replace the original burner of the boiler 1 with a so-called combustor burner. As a result, in addition to environmental pollution, the heat load can also be reduced, since the radiated amount of heat in the combustion chamber becomes larger.

The device according to the invention therefore leave neutral, non-toxic smoke gases.

Claims

Patent claims

1. A process for the production of mechanical work, wherein a fuel is burned by direct firing of the fuel into compressed air, the air / fuel gas mixture thus generated is further heated and thereby a heat-supplying agent, hot water or steam and steam from the latter are created , characterized in that the compressed air is preheated in an indirect manner, possibly in a separate combustion device, before the fuel is directly fired.

2. The method according to claim 1, characterized in that the superheated steam is usually produced in a combustion device which is independent of the combustion device producing the steam.

3. The method according to claim 1 or 2, characterized in that the steam-producing and / or independent combustion devices leaving flue gas cooled and the amount of heat thereby obtained is used further.

4. The method according to any one of claims 1 to 3, characterized in that the air-fuel gas mixture created by the direct combustion is cooled after the expansion and fed to the combustion devices as at least part of the combustion air and the amount of heat obtained by the cooling is further used.

5. The method according to any one of claims 2 to 4, characterized in that the air-fuel gas mixture is fed to the combustion devices in a parallel circuit.

6. The method according to any one of claims 1 to 5, characterized in that the air-fuel gas mixture leaving the combustion device producing the steam or the heat-supplying agent is cooled below 170 ° C.

7. Traverser. according to one of claims 1 to 6, characterized. that at least in the separate Vercren low-quality fuels are used with which a combustion temperature of at least 900 ° C is created.

8. The method according to any one of claims 1 to 7, characterized in that the compressed air is generated by a compressor driven by an internal combustion engine, the direct firing also taking place.

9. The method according to claim 8, characterized in that the internal combustion engine is operated only temporarily and the associated construction site are used as a peak power plant.

10. The method according to any one of claims 1 to 9, characterized in that the combustion of the fuel takes place temporally and spatially.

11. Device for generating mechanical work with an internal combustion device, a compressor connected thereto, a firing boiler operated at least partially with the air / fuel gas mixture of the internal combustion device and at least one mechanical work-providing device, characterized in that the internal combustion device as one with the compressor (4) is connected to the gas turbine (5), a combustion device (6) heating the compressed air and being connected to the gas turbine (5) being connected to the compressor (4).

12. The device according to claim 11, characterized in that the firing boiler (1) is designed as a steam boiler, to which at least one separate steam-overheating firing device (17) is connected and with the superheated steam a high-pressure steam turbine (2) is operated. 13. Device according to claim 11 or 12, characterized in that at least one independent firing device (20) reheating the partially cooled steam and at least one small pressure steam turbine (3) are connected to the high-pressure gas turbine (29. 14. Device according to claim 12 or 13, characterized thereby indicates that the firing devices (6, 17, 20) are connected to a supply of poor gases.

15. Device according to one of claims 11 to 14, characterized in that it is provided with a steam collector (13), and a water space (15) of the steam collector (13) with inputs of steam-generating heat exchangers (11, 12) of the furnace ( 1), its steam chamber (16) with a steam-side input of the overheating firing device (17) and its steam distributor (14) with steam-side outputs of the heat exchangers (11, 12) of the firing boiler (1).

15. Device according to one of claims 11 to 15, characterized in that in the fuel gas flues of the firing boiler (1), or the firing devices (6, 17, 20) in each case one of the feed water preheating heat exchanger (25 to 28) is provided, the input the outlet of the small pressure steam turbine (3) and the outlet are assigned to the water space (15) of the steam collector (13).

17. The device according to claim 16, characterized in that a further heat exchanger (29) in the direction of the fuel gas flow after the preheating the feed water heat exchanger (25) of the furnace (1) is connected in parallel.

13. Device according to one of claims 13 to 17, characterized in that after the exit of Klekle¬

Steam turbine (3), a condenser (23) and then a feed water pump (24) are arranged, the amount of heat recovered by the condenser (23) being used to preheat the feed water. 19. Device according to one of claims 11 to 18, characterized in that after the gas turbine (5) a cooling the fuel gas-air mixture, the feed water preheating heat exchanger (10) is arranged.