EP3798413B1 - Control valve for a steam engine, steam engine comprising said control valve, and combined heat and power plant comprising the steam engine - Google Patents

Description

technical field

The present disclosure relates to a control valve for a steam engine, for example a steam engine that performs mechanical work using steam as its working fluid. More specifically, the present disclosure relates to a control valve for a reciprocating steam engine, preferably having application in electric power generation. Furthermore, the present disclosure relates to a steam engine having the aforementioned control valve and a combined heat and power plant having the steam engine.

background

Decentralized combined heat and power plants (CHP plants) have long been established as an advantageous alternative to the conventional combination of local heating and central power plant. CHP plants are used to generate electrical energy and to generate useful heat, in particular CHP plants are preferably operated on site or in the vicinity of the useful heat sink. Combustion engines such as diesel or Otto engines, Stirling engines, steam engines, internal combustion turbines or steam engines can be used, for example, to drive the power generator.

With regard to CHP systems, the use of steam engines in particular has recently gained interest. This is primarily due to the achievable high overall efficiency with low pollutant emissions and the almost free choice of liquid or solid fuel, such as wood, pellets, biogas or biomass. The high level of efficiency can be achieved with steam pressures of 40 bar to 150 bar and steam temperatures of approx. 300 to 600 °C. Due to the advantages mentioned, steam engines are also used in smaller plants for biomass power generation, waste heat power generation plants, waste incineration plants and thermal post-combustion plants.

Well-known steam engines, such as the in WO 2016/146159 A1 described, which are used in particular for power generation, however, have the disadvantage that, for example, a relatively high level of leakage occurs during a cold start. This is due in particular to the fact that the steam injected into the steam engine (superheated steam or live steam) at a pressure of 40 bar to 150 bar is injected into the piston chamber in a relatively short time and acts there for a long time, which places high demands on the piston ring seal, which separates the water vapor from the lubricating oil in the crankshaft space or in the oil pan.

In order to be able to efficiently operate the steam engine, in particular the piston of the steam engine, with a sufficient amount of steam, which is under a correspondingly high pressure, it is necessary to deliver the pressurized steam/live steam to a working space of the steam engine in a very short time and with precise timing To supply the steam engine in order to be able to operate the working cycle of the piston without disturbances (with concentricity). A control valve is necessary for this in order to be able to optimally control or regulate the fluid flow of the live steam to the working chamber of the steam engine.

Such valves for controlling and/or regulating a fluid flow generally include a valve seat and a valve member that is mounted so that it can move axially. The valve member typically includes a valve stem and a valve body at one end thereof. To actuate the valve, i.e. to move the valve member, in particular the valve body, axially, a valve drive is also provided, which is directly or indirectly connected to the valve stem in a force-transmitting manner. As a result, the valve body can be lifted off the valve seat to open the valve and flow through the pipeline or the valve can be made possible. To place the valve in a closed position, the valve body is brought back into contact with the valve seat, thus blocking fluid flow through the tubing.

Due to the high temperatures described above when operating a steam engine, thermal changes, in particular material expansion, occur, which can lead to a change in the operating point of the valve. As a result, it can happen that the valve member, in particular the valve body, is pressed into the valve seat with too great a force. However, repeated actuation of the valve results in high wear of the valve body and/or the valve seat, which can lead to leakage of the valve in the closed state. In addition, he can Wear bypass flows in the valve and malfunctions in the overall system in which the valve is used to control and / or regulate a fluid flow result. Furthermore, it can also happen that conventional valves do not close completely due to material expansion and consequently a leak occurs.

Valves for controlling or regulating a fluid flow are known in the prior art, which are intended to enable simplified interaction of the valve body and the valve seat by means of a conical valve seat. In particular, this guides the valve body into the valve seat, which should lead to reliable and low-wear closing even with high forces. Nevertheless, even these valves do not provide a satisfactory result at high temperatures and pressures.

Other related techniques are in the U.S. 4,050,357A which is directed to a high-velocity steam inlet poppet valve structure for a steam engine, in which JP S 59-99016 A , which describes a steam engine with a pulse valve that is opened by a projection of the piston just before reaching top dead center, and in which U.S.A. 4,766,924 , which is directed to a relief valve with a stationary valve seat and poppet element.

subject of the invention

The object of the invention is to provide a control valve for controlling and/or regulating a steam flow in a steam engine, which is capable of reliably and permanently closing or shutting off the steam engine, despite the high temperatures and pressures present in the working cycle of a steam engine to ensure the valve while realizing ease of manufacture and easy maintenance.

This object is achieved by a control valve according to claim 1, a steam engine having the control valve according to claim 10 and a combined heat and power plant having the steam engine according to claim 14. Preferred developments of the invention are given in the dependent claims, the subject matter of the control valve relevant claims can be used in the context of the steam engine and vice versa.

One of the basic ideas of the present disclosure is to create a defined contact surface, in particular an annular contact surface between the valve body and the valve seat, with which a reliable and permanent closing or shutting off of the valve is ensured despite the high temperatures and pressures present in the working cycle of a steam engine can be performed while realizing ease of manufacture and maintenance.

When high temperatures are mentioned in the present application, this applies in particular to a stream of steam, ie temperatures above 100.degree. In addition, operating parameters with a fluid pressure (steam pressure) of 40 to 150 bar, as already mentioned above, and fluid temperatures (steam temperatures) of over 500° C. are not unusual for the efficient operation of a steam engine. With such operating parameters, a high thermal stress on all components, in particular high thermal stresses, is to be expected. Furthermore, a secure seal is more difficult to achieve in steam engines due to the smaller molecular size (H ₂ O) of the water vapor compared to the combustion gases (CO ₂ ) in the internal combustion engine.

In order to still enable a tight closure of the control valve, it is necessary to realize extremely high closing forces of the control valve, which can only be achieved by a correspondingly small contact surface between the valve body and the valve seat and a correspondingly high surface pressure. However, this leads to high demands on the quality of the contact surfaces of the two closing elements and to high wear.

In order to meet the needs outlined above, the present disclosure provides a control valve in which an easily definable and manufacturable annular surface is realized between a conical component and a flat component.

According to one aspect of the disclosure, a control valve for controlling and/or regulating a steam flow in a steam engine has: a valve seat, a valve body, which is guided in translation along a central axis CA of the control valve and is preferably subjected to a force against the valve seat by means of an elastic element , with a the valve seat axial end of the valve body facing toward the central axis of the valve body has a surface tapered toward the center axis of the valve body, thereby forming an annular contact surface with the valve seat, or an axial end of the valve seat facing the valve body has a surface tapered toward the central axis of the valve seat, thereby forming an annular contact surface with the Valve body is formed.

The term "axial" can be understood here as along the main axis of the valve member or the valve train or along the central axis of the control valve itself and corresponds to the longitudinal direction of said elements.

According to another aspect of the present disclosure, a slanted surface of the valve seat or that of the valve body is slanted inward toward the central axis, whereby the annular contact surface is formed in the region of the outer circumference of the slanted surface, the central axis of the valve seat and/or the central axis of the valve body runs parallel to the central axis CA, in particular approximately aligned with it. The term "inwards" can be understood in such a way that the surface is beveled in the direction of the material of the respective element, e.g. the valve body, which forms a depression in the middle of the valve body. In other words, the surface of the valve body, the facing the valve seat, funnel-shaped, ie has a conical shape.

Furthermore, it is advantageous if an angle of inclination α of the slanted surface of the valve seat or of the valve body to a plane that is defined by the contact surface between the valve body and the valve seat and runs perpendicular to the central axis is between 0.5° and 1.5° 1°, is.

In this way, seen in the radial direction, a very thin annular contact surface is formed between the valve seat and the valve body, which is also easy to manufacture.

Furthermore, the conical surface produced in this way and the contact surface connected thereto can easily be brought back to size after an optional heat treatment, in particular hardening, which can be achieved, for example, by grinding. The contact surface created in this way can also be easily repaired by grinding after a long period of use and the associated wear and tear.

Furthermore, it is preferred that the valve seat is formed by a valve seat disk, which has a flat surface, at least in the region of the contact surface with the valve body, which is preferably aligned perpendicularly to the central axis CA.

The formation of the valve seat from a valve seat disc also brings with it the advantage that it is easy to produce and to repair. Furthermore, the valve seat can be easily replaced in this way.

Furthermore, it is advantageous that the valve body has a projection on the axial end facing the valve seat, which is set up to interact with a valve drive in a force-transmitting manner in order to lift the valve body from the valve seat and thereby open the control valve, the valve drive and the Valve body are preferably formed decoupled.

A decoupling is to be understood here as meaning that the valve train and the valve body can move relative to one another and independently of one another.

It is also preferred that the valve body is made of a tough material, for example HSS steel (high-speed steel or high-alloy tool steel), which preferably has an elongation at break of at least 5%, more preferably at least 10%. It is also advantageous if at least one of the contact surfaces is plated. The contact surfaces are the upper surface of the valve body which comes into contact with the elastic element, the lower surface of the valve body which comes into contact with the valve train, and the contact surface with the valve seat.

It is advantageous here if the plating is carried out using a build-up welding process such as, for example, plasma powder build-up welding, also known as the PTA process. For example, nickel martensite, tungsten carbide or stellite or a cobalt-chromium hard alloy can be used as the coating material. After plating, the contact surfaces, which are thus provided with an anti-wear coating, are preferably ground.

Alternatively, there is also the possibility of shrinking a wear ring made of nickel martensite, tungsten carbide, stellite or a cobalt-chromium hard alloy or a composite of ceramic and metal onto a base body of the valve body made of HSS steel, for example. The shrunk-on ring can then be provided with the beveled surface described above to form the annular contact surface between valve seat and valve body.

The valve seat or valve seat disc is preferably made of a very hard, wear-resistant material that is impact-resistant. There is no need for a tough core, as there is no bending stress (fracture stress). The valve seat or the valve seat disc can also be made from a composite of ceramic and metal.

Furthermore, it is preferred if the valve seat disc has an inner diameter that is at least large enough for the projection of the valve body and/or the valve drive to extend/protrude at least partially into the inner bore of the valve seat disc in the axial direction, i.e. in the direction of the central axis CA. preferably reach/stand through them, can/can.

According to a further aspect of the present disclosure, the valve body is biased against the valve seat by steam pressure and the elastic member functions only as a damper. Here, the spring force of the elastic element, which presses the valve body against the valve seat, is adjusted so that the valve only opens when a certain force is applied by the valve drive, which means that the valve can be prevented from opening too early. A targeted opening of the valve can thus be achieved.

By subjecting the valve body to steam pressure, in particular to the pressure of the working fluid, the supplied live steam, a sufficiently high force application of the valve body against the valve seat can be ensured. Furthermore, the closing force of the control valve regulates itself in this way independently or automatically. In other words, if the steam engine is operated under increasing pressures (steam pressures) and thus higher power, the necessary closing forces of the control valve, which can be used to ensure adequate tightness/sealing of the control valve, increase. However, since the vapor pressure of the working fluid is used directly to provide the necessary closing force of the control valve, the available closing force also increases with higher working pressure.

The term "live steam" is to be understood in the present disclosure as steam/superheated steam which for example, from a steam generator to a steam engine for operating the steam engine. The live steam usually has pressures in the range from 40 to 140 bar and temperatures above 500°C.

Furthermore, it is preferred if at least the contact surface of the valve seat and/or the valve body is hardened, and preferably the hardness of the valve body is greater than the hardness of the valve seat. In this way, a sufficiently high hardness/strength of the contact surface can be ensured, which is necessary to be able to withstand the high surface pressure.

According to a further aspect of the present disclosure, the annular contact surface between the valve body and the valve seat has an annular width of 0.2 mm to 3 mm, preferably 0.5 mm to 2 mm, more preferably 1 mm.

Furthermore, the present disclosure relates to a steam engine, in particular a piston steam engine, which is preferably used for generating electric power, having: at least one cylinder which encloses a working space, one in the working space between a top dead center OT and a bottom dead center UT along a central axis CA of the cylinder reciprocating piston, and the control valve described above, wherein the control valve serves to control and/or regulate a fluid flow, in particular a steam flow, which acts as the working fluid (flow) of the steam engine.

Furthermore, it is preferred that the valve drive of the control valve is designed as a projection of the piston, which is arranged on an upper end of the piston that faces the control valve, the projection lifting the valve body from the valve seat when the piston moves in the area / near the top dead center to open the control valve.

This makes it possible to dispense with an additional valve drive, such as a piezo element or a piezo drive. In addition, short opening and closing times can be achieved in this way without having to accept extremely high stress on the valve train components. This is due in particular to the fact that the opening and closing forces of the control valve are made available on the one hand by the fluid flow and on the other hand are introduced by the piston, in particular the projection of the piston. Accordingly, the opening forces are absorbed by the connecting rod and its bearing, which are very robust due to the high torque of the steam engine.

It is also advantageous here if the projection has a conical shape, which has a flat contact surface, in particular aligned perpendicularly to the central axis CA, in particular on the side facing the valve body. In this way it is possible to form a circular contact surface between the valve body and the valve train and thus to reduce the surface pressure that occurs and the associated wear.

Furthermore, it is advantageous if the contact surface of the valve train is plated, in particular using a build-up welding process such as plasma powder build-up welding, also known as the PTA process. In this case, the piston is provided with a concave recess on its upper side, into which the coating material is introduced by means of build-up welding and is then ground to form a flat contact surface. For example, nickel martensite, tungsten carbide or stellite or a cobalt-chromium hard alloy can be used as the coating material.

Furthermore, it is advantageous if the steam engine has an antechamber that can be supplied with fresh steam from the outside, wherein the antechamber has an opening for introducing the live steam into the working space, and the opening can be opened and closed by the control valve.

According to a further aspect, the valve body is designed in the form of a cylindrical plunger, which can be moved in translation by an axial guide along the central axis CA of the control valve, which is preferably approximately aligned with a central axis CA of the cylinder 10, and preferably by pressure of the live steam that is applied to a side of the valve body facing away from the valve seat, a force is applied against the valve seat.

Furthermore, the present disclosure relates to a combined heat and power plant that has a steam generator and the steam engine described above, wherein the steam engine is coupled to a generator for generating electrical power.

Brief description of the figures

• 1 shows a schematic diagram of a combined heat and power plant,
• 2 Figure 12 shows a schematic sectional view of a vapor engine according to an embodiment of the present invention, with the control valve in the closed position and the piston at bottom dead center, and
• 3 shows an enlarged partial view of the schematic sectional view of FIG 2 , to clarify the design of the control valve.

Detailed Description of Preferred Embodiments

Preferred embodiments of the present invention are described in detail below with reference to the attached figures. Others mentioned in this context Modifications of specific features can each be individually combined with one another to form further embodiments.

The same or corresponding elements are denoted by the same or similar reference symbols in the various figures.

1 shows a schematic diagram of a combined heat and power (CHP) plant. The CHP system 100 shown consists of a steam generator 110, which is connected via a valve 180 to an inlet of a steam engine 1, 120, which drives a generator 130 to generate electricity. As already explained above, for fine sealing of the steam engine 1, 120 it is necessary to supply it with oil, which, however, mixes with the expanded water vapor during the operation of the steam engine 1, 120 and is discharged with it. For this reason, the expanded steam discharged from the steam engine 1, 120 has a relatively large amount of oil.

The steam engine 1, 120 is followed by a condenser 150 for condensing the expanded steam, which has a pressure of approximately 0.15 bar and a temperature of approximately 55° C. when it leaves the steam engine 120.

The condensed water vapor, which also contains a large proportion of oil, is fed to a condensate suction pump (or circulation pump) 170, in particular a piston pump, via a water column 190, which increases the pressure of the condensed water vapor to approx. 0.25 bar .sucked in by this one. The condensate suction pump increases the pressure of the condensed water vapor or the oil-water mixture that is now present to approximately 1.50 bar and conveys the oil-water mixture to a device 140 for separating oil and water.

Again 1 can also be removed, the separated or separated oil is routed back to a crankshaft chamber of the steam engine or injected into the steam engine for fine sealing and the cleaned water is routed to a feed water tank 160, which feeds the treated or cleaned water to the steam generator 110 again for steam generation Provides, so the cycle is closed.

figure 2 1 shows a schematic sectional view of a steam engine 1 equipped with a control valve 50 according to an embodiment of the present invention. The steam engine 1 shown has a cylinder 10 which has an upper end 11 and a lower end 12 . The cylinder 10 is connected to a crankcase 20 at the lower end 12 . A plurality of outlet openings 13 are provided in the circumferential direction in the cylinder wall/working space wall 14 of the cylinder 10 . The outlet openings 13 connect a cylinder chamber or a working space 15 with an annular chamber 16 in order to discharge or discharge used steam from the working space 15 . The outlet openings 13 are arranged close to a bottom dead center UT of a piston 30, which is located at bottom dead center UT in the view shown.

The piston 30 is translationally movable along a central axis CA of the cylinder 10 between the bottom dead center UT and a top dead center OT. The piston 30 is connected to a crankshaft (not shown) housed in the crankcase 20 via a piston connecting rod or piston control rod (not shown). The piston 30 has a sealing ring 31 at its lower end 32 and a plurality of sealing rings 31 at its upper end 33 .

The engine further includes a cylinder head unit 40 . The cylinder head unit 40 has a first case body 41 and a second case body 42 . Furthermore, in the first housing body 41 is provided with an antechamber (vapor chamber) 44 which communicates with the working space 15 via an opening 43 . The opening can be opened and closed by means of the control valve 50, which has a valve seat 51 and a valve body 52, with which the inflow of live steam (superheated steam that is under high pressure) into the working chamber can be controlled. In figure 2 the control valve 50 is in the closed state, ie the valve body 52 is pressed against the valve seat 51 in order to prevent the flow of live steam into the working chamber 15 .

The valve body 52 is guided in translation along the central axis CA by means of an axial guide 55 and is subjected to a force or pressed against the valve seat 51 by an elastic element 54, which is implemented by a compression spring in the illustrated embodiment. Furthermore, the second housing body 42 contains fluid channels, not shown, with which the valve body 52 can be acted upon on its side facing away from the valve seat 51 with the working fluid, i.e. the superheated steam, in order to increase the closing force between the valve seat 51 and the valve body 52 and thus a tight Complete the opening 43 to ensure.

Again figure 2 can further be seen, valve body 52 has, on an end facing valve seat 51, a surface 52A that is beveled inward toward a central axis of valve seat 51 or toward central axis CA, as a result of which the surface of valve body 52 facing valve seat 51 is funnel-shaped. In this way it is possible to realize a defined annular contact surface between the valve seat 51 and the valve body 52 .

figure 3 shows an enlarged partial view of the schematic sectional view of FIG figure 2 , to the training of Control valve, in particular the valve seat 51 and the valve body 52 further to clarify. Again figure 3 As can be seen, the valve seat 51 is formed of a simple valve seat disk which is inserted into the first housing body 41. This makes it possible to easily replace the valve seat 41 after a long period of use and the associated wear. In this case, the valve seat 51 can be repaired for reuse by simply grinding it again.

Like in the figure 3 As further shown, the inwardly tapered surface 52A forms with the plane defined by the contact area between valve body 52 and valve seat 51 and in which figure 3 is oriented horizontally, an inclination angle α, which is actually extremely flat, in a range of 0.5 ° to 1.5 °. However, to better illustrate the invention, the angle is shown much larger. Again figure 3 Also, as can be seen, the valve body 52 has a projection 52B which is provided on the slanted surface 52A facing the valve seat 51 and projects into the opening 43. As shown in FIG. The projection 52B makes it possible for the piston 30 to move the valve body 52 against the applied steam pressure and against the applied spring force of the Valve seat 52 is lifted and thus the opening 43 is released, whereby live steam can flow from the antechamber 44 into the working chamber 15 and thus the piston 30 can cause a downward movement from top dead center OT to bottom dead center UT. In order to prevent the valve body 52 from tilting in the axial guide 55 when the projection (valve drive 53) comes into contact with the valve body 52, the projection (valve drive 53) of the piston 30 has a spherical or curved surface/shape, whereby between the projection 52B of the valve body 52 and the projection of the Piston 30 a point contact point is realized and thus only forces in the axial direction, ie along the central axis CA, can be transmitted from the piston 30 to the valve body 52, but no transverse forces can be introduced into the valve body 52.

From the foregoing description, those skilled in the art will recognize that various modifications and variations can be made in the apparatus and method of the invention without departing from the scope of the invention. Furthermore, the invention has been described with reference to specific embodiments, which are intended only for a better understanding of the invention and are not intended to limit it. Those skilled in the art will also readily recognize that many different combinations of elements can be used to practice the present invention.

Claims (14)

1. Control valve (50) for controlling and/or regulating a steam flow in a steam engine (1), comprising:

   a valve seat (51),

   a valve body (52) which is guided in a translational manner along a central axis (CA) of the control valve (50) and is force-loaded against the valve seat (51) by means of an elastic element (54),

   characterised in that

   an axial end of the valve body (52) facing the valve seat (51) has a surface (52A) bevelled towards the middle axis of the valve body (52) which forms an annular contact surface with the valve seat (51), or

   an axial end of the valve seat (51) facing the valve body (52) has a surface (51A) bevelled towards the middle axis of the valve seat (51) which forms an annular contact surface with the valve body (52).
2. Control valve (50) according to claim 1, wherein a bevelled surface (51A, 52A) of the valve seat (51) or of the valve body (52) is bevelled inwards towards the middle axis, as a result of which the annular contact surface is formed in the region of the outer circumference of the bevelled surface (51A, 52A), wherein the middle axis of the valve seat (51) and/or the middle axis of the valve body (52) runs parallel to the central axis (CA), in particular being roughly aligned with this.
3. Control valve (50) according to claim 1 or 2, wherein an angle of inclination α of the bevelled surface (51A, 52A) of the valve seat (51) or of the valve body (52) relative to a plane defined by the contact surface between valve body (52) and valve seat (51) and perpendicular to the central axis (CA) is between 0.5° and 1.5°, preferably 1°.
4. Control valve (50) according to one of the preceding claims, wherein the valve seat (51) is formed by a valve seat washer, preferably having a flat surface, at least in the region of the contact surface with the valve body (52), which is preferably oriented perpendicular to the central axis (CA).
5. Control valve (50) according to one of the preceding claims, wherein the valve body (52) has a projection (52B) on the axial end facing the valve seat (51) which is configured to interact in a force-transmitting manner with a valve drive (53) in order to lift the valve body (52) from the valve seat (51) and thereby open the control valve (50), wherein the valve drive (53) and the valve body (22) are preferably decoupled.
6. Control valve (50) according to claim 5, which is dependent on claim 4, wherein the valve seat washer has an inner diameter (D1) which is at least so large that the projection (52B) of the valve body (52) and/or the valve drive (53) can reach/extend in the axial direction at least partially into the inner bore of the valve seat, preferably reach/extend through this.
7. Control valve (50) according to one of the preceding claims, wherein the valve body (52) is force-loaded against the valve seat (51) by vapour pressure, and the elastic element (54) functions as a damper.
8. Control valve (50) according to one of the preceding claims, wherein at least the contact surface of the valve seat (51) and/or the valve body (52) is hardened, and preferably the hardness of the valve body (52) is greater than the hardness of the valve seat (51).
9. Control valve (50) according to one of the preceding claims, wherein the annular contact surface has a ring width of 0.2 mm to 3 mm, preferably 0.5 mm to 2 mm, more preferably 1 mm.
10. Steam engine (1), in particular a piston steam engine, which is preferably used for the generation of electric current, comprising:

    at least one cylinder (10) which encloses a working chamber (15),

    a piston (30) which can move back and forth in the working chamber (15) along a central axis (CA) of the cylinder (10) between an upper dead centre (OT) and a lower dead centre (UT), and

    a control valve (50) according to one of the preceding claims 1 to 9, wherein the control valve (50) serves to control and/or regulate a steam flow that functions as the working fluid of the steam engine.
11. Steam engine (1) according to claim 10, wherein the valve drive (53) of the control valve (50) is formed as a projection of the piston (30) which is arranged on an upper end (33) of the piston facing the control valve (50), wherein the projection lifts the valve body (52) from the valve seat (51) when the piston (30) is located in the region of or near the upper dead centre (OT) in order to open the control valve (50).
12. Steam engine (1) according to one of the claims 10 or 11, further comprising:
    a prechamber (44) which can be supplied with fresh steam from the outside, wherein the prechamber (44) has an opening (43) for introducing the fresh steam into the working chamber (15), wherein the opening (43) can be opened and closed by the control valve (50).
13. Steam engine (1) according to one of the claims 10 to 12, wherein the valve body (52) is designed in the form of a cylindrical plunger which is, via an axial guide (55), moveable in a translational manner along the central axis (CA) of the control valve, which preferably aligns roughly with a central axis (CA) of the cylinder (10), and is preferably force-loaded against the valve seat (51) through the pressure of the fresh steam applied to a side of the valve body (52) facing away from the valve seat (51) .
14. Combined heat and power plant comprising:

    a steam generator (110), and

    a steam engine (1, 120) according to one of the preceding claims 10 to 13, wherein the steam engine is coupled with a generator (130) in order to generate electric current.

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