WO2020144395A1

WO2020144395A1 - A method and a combined heat and power plant for producing heat energy and electricity

Info

Publication number: WO2020144395A1
Application number: PCT/FI2019/050021
Authority: WO
Inventors: Jani Kaaresto; Jarno Haapakoski; Iikka KORVA; Iikka Ylikoski
Original assignee: Volter Oy
Priority date: 2019-01-11
Filing date: 2019-01-11
Publication date: 2020-07-16

Abstract

In a method a combined heat and power plant produced gaseous medium, whether it be synthesis gas or internal combustion engine's exhaust gas, is used for electricity production or its contained heat energy is recovered to be used e.g. for house heating, comprises method steps of separating a first gas portion and a second gas portion from the gaseous medium. This enables to change the ratio of the produced heat and power in multiple ways. The combined heat and power plant in the method comprises a valve configured to separate the gaseous medium into a first gas portion and into a second gas portion.

Description

A METHOD AND A COMBINED HEAT AND POWER PLANT FOR PRODUCING HEAT ENERGY AND ELECTRICITY

Description

Technical Field

The invention relates to a method for producing heat energy and electricity in a combined heat and power plant. The method comprising method steps of producing gaseous medium comprising heat energy which gaseous medium comprises syn thesis gas and exhaust gas, conducting the synthesis gas into an internal combus tion engine, and burning the synthesis gas in the internal combustion engine to gen erate mechanical energy and thereby producing the exhaust gas. The method fur ther comprising method steps of converting mechanical energy generated by the internal combustion engine into electricity by using a first electric generator, con ducting gaseous medium either onto an external combustion engine or into a heat exchanger, and recovering heat energy from the gaseous medium into a liquid heat ing medium by using the heat exchanger. The method further comprising method steps of converting heat energy of the gaseous medium into mechanical energy by using the external combustion engine and converting mechanical energy generated by the external combustion engine into electricity by using an electric generator. The invention further relates to a combined heat and power plant used in the method.

Background Art

Unit-type heat-and-power station is described in DE19643109(A1). Therein heat and power generation has the following steps: (a) A hot fuel gas is generated by wood gasification, (b) this fuel gas is cooled, and (c) at least one internal combustion engine is run with the cooled fuel gas. The cooling of the fuel gas is done using a Stirling cycle, i.e. external combustion engine. The waste heat of the internal com bustion engine(s) is used for a second Stirling process. The energy recouped from the Stirling processes is used for electricity generation.

Summary

Combined heat and power plants in the state of the art are incapable or inflexible for adjusting the ratio of the produced heat and power. Although the need for heat and power varies greatly on the geographic location and time of the year; sometimes there is bigger need for heat energy, due to the heating season, and sometimes the need is almost only for electricity production, due to the high electricity consumption or high price peak when the produced electricity is supplied into grid.

An object of the invention is to provide a method and combined heat and power plant for producing heat energy and electricity so that deficiencies related to prior art can be reduced. The objects of the invention are obtained with a method and a combined heat and power plant, which are characterized in what is presented in the independent claims. Some advantageous embodiments of the technology are pre sented in the dependent claims.

The invention relates to a method for producing heat energy and electricity in a combined heat and power plant. The method comprising method steps of producing gaseous medium comprising heat energy which gaseous medium comprises syn thesis gas and exhaust gas, conducting the synthesis gas into an internal combus tion engine, and burning the synthesis gas in the internal combustion engine to gen erate mechanical energy and thereby producing the exhaust gas. The method fur ther comprising method steps of converting mechanical energy generated by the internal combustion engine into electricity by using a first electric generator, con ducting gaseous medium either onto an external combustion engine or into a heat exchanger, and recovering heat energy from the gaseous medium into a liquid heat ing medium by using the heat exchanger. The method further comprising method steps of converting heat energy of the gaseous medium into mechanical energy by using the external combustion engine and converting mechanical energy generated by the external combustion engine into electricity by using an electric generator.

The method further comprises method steps of separating a first gas portion from the gaseous medium and conducting the first gas portion into the heat exchanger to recover heat energy from the first gas portion into liquid heating medium, separating a second gas portion from the gaseous medium and conducting the second gas portion onto the external combustion engine to convert heat energy of the second gas portion into electricity, and adjusting the ratio of the first gas portion and the second gas portion of gaseous medium to change the ratio of the recovered heat energy and generated electricity. The first gas portion means in other words a first volume from the gaseous medium and the second gas portion a second volume from the gaseous medium, respectively.

It would be clear to a skilled person that the ratio of the first gas portion and the second gas portion could be a such that the gaseous medium is separated either into the first gas portion, into the second gas portion or between these two gas portions. This means that when the gaseous medium is separated only into the first gas portion there is no gaseous medium left to be separated into the second gas portion. Respectively, when the gaseous medium is separated only into the second gas portion there is no gaseous medium left to be separated into the first gas portion. When the gaseous medium is separated into between the first gas portion and sec ond gas portion there is gaseous medium in the both portions to be conducted fur ther.

In an embodiment of the method according to the invention the gaseous medium is exhaust gas which is conducted into a first heat exchanger, wherein heat energy from the exhaust gas is recovered into the liquid heating medium.

In an embodiment of the method according to the invention the gaseous medium is exhaust gas which is conducted onto a first external combustion engine, wherein heat energy of the exhaust gas is converted into mechanical energy, which mechan ical energy is further converted into electricity by using a second electric generator.

In an embodiment of the method according to the invention the gaseous medium is exhaust gas which is separated into a first exhaust gas portion, i.e. a first exhaust gas volume, conducted into the first heat exchanger to recover heat energy from the first exhaust gas portion into the liquid heating medium. The exhaust gas is sepa rated into a second exhaust gas portion, i.e. a second exhaust gas volume, con ducted onto the first external combustion engine to convert heat energy of the sec ond exhaust gas portion into mechanical energy, which mechanical energy is further converted into electricity by means of a second electric generator. The ratio of the recovered heat energy and generated electricity is changed by adjusting the ratio of the first exhaust gas portion and second exhaust gas portion.

In an embodiment of the method according to the invention air is introduced into the synthesis gas by using a mixer to create a mixture of air and synthesis gas, which mixture of air and synthesis gas is conducted into the internal combustion engine, wherein the temperature of the produced exhaust gas is raised by adjusting the ratio of air and synthesis gas, which adjusting is done in the mixer.

In an embodiment of the method according to the invention the gaseous medium is synthesis gas which is conducted into a second heat exchanger, wherein heat en ergy from the synthesis gas is recovered into the liquid heating medium.

In an embodiment of the method according to the invention the gaseous medium is synthesis gas which is conducted into a filtration unit, wherein the synthesis gas is cleaned, i.e. purified. This cleaning of the synthesis gas includes collection of con tamination, e.g. tar and soot, formed in the fuel gasification.

In an embodiment of the method according to the invention the gaseous medium is synthesis gas which is conducted after the cleaning of the synthesis gas into a third heat exchanger, wherein heat energy from the synthesis gas is recovered into the liquid heating medium.

In an embodiment of the method according to the invention the gaseous medium is synthesis gas which is conducted onto a second external combustion engine, wherein heat energy of the exhaust gas is converted into mechanical energy, which mechanical energy is further converted into electricity by means of a third electric generator.

In an embodiment of the method according to the invention the gaseous medium is synthesis gas which is separated into a first synthesis gas portion, conducted into the third heat exchanger to recover heat energy from the first synthesis gas portion into said liquid heating medium. Synthesis gas is separated into a second synthesis gas portion, conducted onto the second external combustion engine to convert heat energy of the second synthesis gas portion into mechanical energy, which mechan ical energy is further converted into electricity by the third electric generator. The ratio of the recovered heat energy and generated electricity is changed by adjusting the ratio of the first synthesis gas portion and the second synthesis gas portion.

In an embodiment of the method according to the invention heat energy recovered into the liquid heating medium is conducted into a closed liquid circulation system.

The combined heat and power plant according to the invention for producing heat energy and electricity comprises a gasifier configured to convert fuel into synthesis gas and an internal combustion engine configured to generate mechanical energy by burning the synthesis gas and thereby forming exhaust gas. The combined heat and power plant comprises a pipeline which comprises a plurality of pipes config ured to conduct gaseous medium comprising heat energy, which gaseous medium comprises synthesis gas and exhaust gas, a first electric generator configured to convert mechanical energy generated by the internal combustion engine into elec tricity, a heat exchanger configured to recover heat energy from gaseous medium into a liquid heating medium, an external combustion engine configured to convert heat energy of the gaseous medium into mechanical energy, and an electric generator configured to convert mechanical energy generated by the external com bustion engine into electricity.

The combined heat and power plant further comprises a valve configured to sepa rate the gaseous medium into a first gas portion, i.e. a first gas volume, and into a second gas portion, i.e. a second gas volume.

An external combustion engine, i.e. Stirling engine, is a heat engine where a work ing fluid, contained internally, is heated by an external source, in this case by gase ous medium, through the engine wall or a heat exchanger. The fluid then, by ex panding and acting on the mechanism of the engine, produces motion and usa ble work, i.e. converting heat energy into mechanical energy. In other words, heat energy for th© external combustion engine is applied from outside the engine. In the present invention external combustion engine is heated by applying gaseous me dium, i.e. synthesis gas or exhaust gas, into the vicinity of the engine wail or through the engine’s heat exchanger if if is used for heat energy transferring. The gaseous medium is then cooled.

An internal combustion engine is a heat engine where the combustion of a synthesis gas occurs with an oxidizer, usually air, in a combustion. This combustion produces high-temperature exhaust gas. In an internal combustion engine, the expansion of the high-temperature and high-pressure gases produced by combustion applies di rect force to some component of the engine. The force is applied typically to pistons, turbine blades, rotor or a nozzle. This force moves the component over a distance, converting chemical energy into mechanical energy.

In an embodiment of the combined heat and power plant according to the invention the pipeline is a synthesis gas pipeline which comprises a plurality of pipes config ured to conduct the synthesis gas from the gasifier into the internal combustion en gine.

In an embodiment of the combined heat and power plant according to the invention the synthesis gas pipeline further comprises a second heat exchanger configured to recover heat energy from the synthesis gas into the liquid heating medium.

In an embodiment of the combined heat and power plant according to the invention the synthesis gas pipeline further comprises a filtration unit configured to clean, i.e. purify, the synthesis gas. The filter of the filtration unit may be also a filter made some other material than cloth such as e.g. a filter made some suitable ceramic material. Therefore, the filter unit is possible configure to endure hot synthesis gas. Still another embodiment of the combined heat and power plant according to the invention the synthesis gas pipeline further comprises a third heat exchanger con figured to recover heat energy from the synthesis gas into the liquid heating medium.

Still another embodiment of the combined heat and power plant according to the invention the synthesis gas pipeline further comprises a second external combus tion engine configured to convert heat energy of the exhaust gas into mechanical energy, which second external combustion engine is connected to a third electric generator configured to convert this generated mechanical energy into electricity.

Still another embodiment of the combined heat and power plant according to the invention the synthesis gas pipeline further comprises a first synthesis gas valve configured to separate the synthesis gas into a first synthesis gas portion, to conduct the first synthesis gas portion into the third heat exchanger, and into a second syn thesis gas portion to conduct the second synthesis gas portion onto the second ex ternal combustion engine.

Still another embodiment of the combined heat and power plant according to the invention the synthesis gas pipeline further comprises a mixer configured to intro duce air into the synthesis gas and to adjust this ratio of air and the synthesis gas. This adjustment of air and synthesis gas can be accomplished with a controller which can be e.g. a user, computer, engine control unit (ECU) or programmable logic unit (PLC).

Still another embodiment of the combined heat and power plant according to the invention the pipeline is an exhaust gas pipeline which comprises a plurality of pipes configured to conduct the exhaust gas from the internal combustion engine to an exhaust gas outlet, which exhaust gas outlet is configured to conduct the exhaust gas outside from the combined heat and power plant.

Still another embodiment of the combined heat and power plant according to the invention the exhaust gas pipeline further comprises a first heat exchanger. This heat exchanger is configured to recover heat energy from the exhaust gas into the liquid heating medium.

Still another embodiment of the combined heat and power plant according to the invention the exhaust gas pipeline further comprises a first external combustion en gine configured to convert heat energy of the exhaust gas into mechanical energy, which first external combustion engine is connected to the second electric generator configured to convert this mechanical energy into electricity. Still another embodiment of the combined heat and power plant according to the invention the exhaust gas pipeline further comprises an exhaust gas valve config ured to separate the exhaust gas into a first exhaust gas portion, to conduct the first exhaust gas portion into the first heat exchanger, and into a second exhaust gas portion, to conduct the second exhaust gas portion onto the first external combustion engine.

Still another embodiment of the combined heat and power plant according to the invention the liquid heating medium comprises a closed liquid circulation system configured to conduct recovered heat energy outside from the combined heat and power plant, e.g. to be used for house heating. Individual heat exchangers can be connected into this water circulation system in either a series connection, a parallel connection or combinations of both series and parallel connections.

An advantage of the invention is that it enables flexibility for the use of heat and power plant. In more precise words, the technology makes possible to convert fuel into heat energy as much is currently needed, e.g. for house heating, and the rest produced heat energy is possible to convert into electricity. Produced electricity can be either stored or supplied into the grid. This functionality improves the overall ef ficiency of the heat and power plant.

An advantage of the invention is further that it enables to make maintenance work when the plant is running; e.g. when a heat exchanger is inoperative, gaseous me dium can be conducted by a valve completely into an external combustion engine, or vice versa.

Still another advantage of the invention is that it enables modular manufacturing of heat and power plants with different types of sets of heat exchangers and external combustion engines. This makes easier to manufacture optimally workable plants to different geographical locations which adapt their heat energy and electricity pro duction depending the time of the year. The technology according to the invention is also possible to install afterwards to heat and power plants. Brief Description of Drawings

In the following the invention will be described in detail, by way of examples, with reference to the accompanying drawings in which:

Fig. 1 shows a schematic view of a first, preferred embodiment of the combined heat and power plant according to the invention.

Fig. 2 shows a schematic view of a second, preferred embodiment of the com bined heat and power plant according to the invention. Fig. 3 shows a schematic view of a third, preferred embodiment of the combined heat and power plant according to the invention.

Fig. 4 shows a schematic view of still another, combined heat and power plant re lating to the invention.

Detailed Description

Fig. 1 shows a schematic view of the first preferred embodiment of the combined heat and power plant 101 according to the invention. This first preferred embodiment comprises a gasifier 1 configured to convert fuel via a gasification process into syn thesis gas 53. This synthesis gas 53 is conducted from the gasifier 1 into an internal combustion engine 19 by means of a first synthesis gas pipeline 11. It has a first end at the gasifier 1 and a second end at the internal combustion engine 19. Be tween the gasifier and the internal combustion engine 19 the first synthesis gas pipeline 11 , starting from the gasifier, comprises a second heat exchanger 3, a fil tration unit 5, a third heat exchanger 7, and a mixer 13. In the method the synthesis gas 53 originates from the gasifier 1 flows hence first into the second heat exchanger 3, wherein heat energy from the synthesis gas 53 is recovered into a heating me dium. After that the synthesis gas 53 is conducted into a filtration unit 5. In the filtra- tion unit 5 the synthesis gas 53 is cleaned from impurities formed during the gasifi cation. The cleaned synthesis gas 53 is then conducted into a third heat exchanger 7 to recover more heat energy from the synthesis gas 53 into the heating medium. Before the synthesis gas 53 enters the internal combustion engine 19 it is further conducted through a mixer 13. The mixer 13 is configured to introduce air into the synthesis gas and to adjust the ratio of the introduced air and synthesis gas 53.

The internal combustion engine 19, located at the end of the first synthesis gas pipeline 11 , produces mechanical energy by burning air and synthesis gas. This mechanical energy is further converted into electricity by means of a first electric generator 23, connected to the internal combustion engine 19. Furthermore, the ra tio of the introduced air and synthesis gas 53 can optimize by the mixer 13 in such way that increase the temperature of formed exhaust gas 57 and hence increase the internal combustion 19 produced heat energy, i.e. waste heat, which is further recovered or converted into electricity.

A first exhaust gas pipeline 47 is configured to conduct the exhaust gas 57 from the internal combustion engine 19 into the exhaust gas valve 43. Therein the method further comprises method steps of separating a first exhaust gas portion from the exhaust gas 57. To recover heat energy from the first exhaust gas portion into the liquid heating medium the first exhaust gas portion is conducted through a second exhaust gas pipeline 29 into a first heat exchanger 61 , located at the end of the second exhaust gas pipeline 29. Furthermore, in the exhaust gas valve 43 from the exhaust gas 57 is separated a second exhaust gas portion. This portion is con ducted through a third exhaust gas pipeline 41 onto a first external combustion en gine 37, located at the other end of the third exhaust gas pipeline 41 . By means of the external combustion engine 37 heat energy of the second exhaust gas portion is converted into mechanical energy. This energy is further converted into electricity by means of a second electric generator 59, connected to the first external combus tion engine 37.

The exhaust gas valve 43 is configured to adjust the ratio of the first exhaust gas portion and the second gas portion. This adjustment changes the ratio of the recov ered heat energy and generated electricity.

A fourth exhaust gas pipeline 79 is configured to conduct the exhaust gas 57 outside from the heat and power plant 101 . The fourth exhaust gas pipeline 79 has a first pipe starting at the first external combustion engine 37 and a second pipe starting at the first heat exchanger 61 , which first and second pipe are joined together before an exhaust gas outlet 79.

The internal combustion engine 19 comprises a fourth heat exchanger 17 configured to cool the engine. Furthermore, the external combustion engine may comprise a fifth heat exchanger 39 configured to cool the engine’s cool end. These two heat exchangers 17,39 as well as the other heat exchangers 3,17, 61 can be connected into the liquid heating medium which comprises a closed liquid circulation system 49. This is configured to conduct recovered heat energy outside from the combined heat and power plant to be used e.g. for house heating. Individual heat exchangers can be connected into this water circulation system 49 in either a series connection, a parallel connection or combinations of both series and parallel connections. In the first preferred embodiment depicted on Fig. 1 all five heat exchangers are connected in series into the closed liquid circulation system 49.

Fig. 2 shows a schematic view of a second preferred embodiment of the combined heat and power plant 102 according to the invention. This second preferred embod iment is similar as depicted on Fig. 1 and in narration of the first preferred embodi ment, including the reference signs, but the pipeline configured to conduct synthesis gas from the gasifier 1 into the internal combustion engine 19 is implemented differ ently. In a second preferred embodiment a first synthesis gas pipeline 1 1 has its first end at the gasifier 1 and the other end at a first synthesis gas valve 67 comprising a filtration unit 5 in between these two ends. From the first synthesis gas valve 67 start two pipelines to conduct in the synthesis gas valve 76 separated synthesis gas portions, which one pipeline is a second synthesis gas pipeline 73, comprising a third heat exchanger 7, and other pipeline is a third synthesis gas pipeline 71 , com prising a second external combustion engine 63. These two pipelines are joined to a second synthesis gas valve 69 configured to combine synthesis gas portions and to conduct it into a fourth synthesis gas pipeline 75. The fourth synthesis gas pipe line 75 starts from the second synthesis gas valve 69 and ends at the internal com bustion engine 19, comprising a mixer 13 before connected into the internal com bustion engine 19.

In the method of this second preferred embodiment the synthesis gas 53 is con ducted first from the gasifier 1 through the first synthesis gas pipeline 1 1 into the filtration unit 5 without preceding recovery of heat energy by means of heat ex changer. From the filtration unit 5 the synthesis gas 53 is conducted into the first synthesis gas valve 67. The method further comprises method steps of separating a first synthesis gas portion from the synthesis gas 53. This first synthesis gas por tion is conducted through a second synthesis gas pipeline 73 into a third heat ex changer 7 to recover heat energy from the first synthesis gas portion into liquid heat ing medium. Furthermore, in the first synthesis gas valve 67 from the synthesis gas 53 is separated a second synthesis gas portion which is conducted through a third synthesis gas pipeline 71 onto the second external combustion engine 63. Therein heat energy of the second synthesis gas portion is converted into mechanical en ergy, which mechanical energy is further converted into electricity by means of a third electric generator 65, connected to the second external combustion engine 63. The first synthesis gas valve 67 is configured to adjust the ratio of the first synthesis gas portion and the second synthesis gas portion. This adjustment changes the ratio of the recovered heat energy and generated electricity.

The method further comprises method steps of conducting the first synthesis gas portion from the third heat exchanger 7 through the second synthesis gas pipeline 73 and the second synthesis gas portion from the second external combustion en gine 63 through the third synthesis gas pipeline 71 into the second synthesis gas valve 69. In the second synthesis gas valve 69 the first synthesis gas portion and the second synthesis gas portion are combined which combined synthesis gas is conducted into the fourth synthesis gas pipeline 75. From there on the method com prises the same method steps as the first preferred embodiment described above.

The second external combustion engine 49 may comprise a sixth heat exchanger 83, as depicted on the Fig. 2. This exchanger is configured to recover heat energy from the engine’s cool end into the closed liquid circulating system 49.

Fig. 3 shows a schematic view of a third preferred combined heat and power plant 103 according to the invention. This third embodiment is similar as depicted on Fig. 1 and in narration of the first preferred heat and power plant 101 , including the ref erence signs, but the fourth exhaust gas pipeline comprises also a seventh heat exchanger 85 in the branch which starts from the first external combustion engine 37. The seventh heat exchanger 85 is configured to recover residual heat energy from the exhaust gas 57 into the heating medium.

In the method of the third preferred embodiment according to the invention the ex haust gas which is conducted from the first external combustion engine 37 into the seventh heat exchanger 85, wherein heat energy from the exhaust gas is recovered into the liquid heating medium. Apart from this the method of the third preferred embodiment is similar as the first preferred embodiment.

Fig. 4 shows a schematic view of still another preferred combined heat and power plant 104. This example is similar as depicted on Fig. 1 and on Fig. 3 and in narration of the first and third preferred embodiments of the heat and power plant 101 , 103, including the reference signs, but the exhaust gas pipelines are applied differently. In this example the fourth exhaust gas pipeline 87 is configured to conduct the ex haust gas 57 directly from the internal combustion engine 19 onto the first external combustion engine 37. Flence, all exhaust gas 57 from the internal combustion engine is conducted onto the first external combustion engine 37, no exhaust gas valve 43 is used in this example.

The fourth exhaust gas pipeline 87 comprises a pipe between the internal combus tion engine 19 and the first external combustion engine 37. From there the fourth exhaust gas pipeline 87 comprises a pipe containing, similarly as the third preferred embodiment, the seventh heat exchanger 85. After the seventh heat exchanger 85 the fourth exhaust gas pipeline comprises an exhaust gas outlet 79.

In the fourth example of the method relating to the invention the method is similar as in the first preferred embodiment but the exhaust gas is conducted directly from the internal combustion engine 19 onto the external combustion engine 37. Therein heat energy of the exhaust gas is converted into mechanical energy. This energy is further converted into electricity by means of a second electric generator 59, con nected to the first external combustion engine 37. From the external combustion engine 37 the exhaust gas 57 is conducted into the seventh heat exchanger 85 to recover residual heat energy from the exhaust gas 57 into liquid heating medium. After the seventh heat exchanger 85 the exhaust gas 57 is conducted outside from the heat and power plant 101 via the exhaust gas outlet 79.

The present invention is not restricted merely into the described embodiments but it can be applied in different ways within the scope of the claims. Reference Signs:

1 gasifier

3 second heat exchanger

5 filtration unit

7 third heat exchanger

1 1 first synthesis gas pipeline

13 mixer

17 fourth heat exchanger

19 internal combustion engine

23 first electric generator

29 second exhaust gas pipeline

31 fourth exhaust gas pipeline

37 first external combustion engine

39 fifth heat exchanger

41 third exhaust gas pipeline 43 exhaust gas valve

47 first exhaust gas pipeline

49 closed liquid circulation system

53 synthesis gas

57 exhaust gas

59 second electric generator

61 first heat exchanger

63 second external combustion engine 65 third electric generator

67 first synthesis gas valve

69 second synthesis gas valve

71 third synthesis gas pipeline

73 second synthesis gas pipeline

75 fourth synthesis gas pipeline 79 exhaust gas outlet

83 sixth heat exchanger

85 seventh heat exchanger

87 fourth exhaust gas pipeline

101 heat and power plant

Claims

Claims:

1. A method for producing heat energy and electricity in a heat and power plant, the method comprising method steps:

- producing gaseous medium comprising heat energy, which gaseous medium comprises synthesis gas (53) and exhaust gas (57),

- conducting the synthesis gas (53) into an internal combustion engine (19),

- burning the synthesis gas (53) in the internal combustion engine (19) to generate mechanical energy and thereby producing the exhaust gas (57),

- converting mechanical energy generated by the internal combustion engine (19) into electricity by using a first electric generator (23),

- conducting gaseous medium either onto an external combustion engine (37, 63) or into a heat exchanger (3, 7, 61 ),

- recovering heat energy from the gaseous medium into a liquid heating medium by using the heat exchanger (3, 7, 61 ), - converting heat energy of the gaseous medium into mechanical energy by using the external combustion engine (37,63),

- converting mechanical energy generated by the external combustion engine (37,63) into electricity by using an electric generator (59, 65), characterized in that the method further comprises method steps:

- separating a first gas portion from the gaseous medium and conducting the first gas portion into the heat exchanger (7, 61 ) to recover heat energy from the first gas portion into liquid heating medium;

- separating a second gas portion from the gaseous medium and conducting the second gas portion onto the external combustion engine (37, 63) to convert heat energy of the second gas portion into electricity; and

- adjusting the ratio of the first gas portion and the second gas portion of gaseous medium to change the ratio of the recovered heat energy and generated electricity.

2. A method according to claim 1 , characterized in that said gaseous medium is exhaust gas (57) which is conducted into a first heat exchanger (61 ), wherein heat energy from the exhaust gas (57) is recovered into said liquid heating medium.

3. A method according to claim 1 , characterized in that said gaseous medium is exhaust gas (57) which is conducted onto a first external combustion engine (37), wherein heat energy of the exhaust gas is converted into mechanical energy by using the first external combustion engine (37), which mechanical energy is further converted into electricity by using a second electric generator.

4. A method according to any of the claims 1 to 3, characterized in that said gaseous medium is exhaust gas (57) which:

- is separated into a first exhaust gas portion, conducted into the first heat ex changer (61 ) to recover heat energy from the first exhaust gas portion into said liquid heating medium;

- is separated into a second exhaust gas portion, conducted onto the first external combustion engine (37) to convert heat energy of the second exhaust gas portion into mechanical energy, which mechanical energy is further converted into electricity by the electric generator (59); and

- ratio of the recovered heat energy and generated electricity is changed by adjust ing the ratio of the first exhaust gas portion and second exhaust gas portion.

5. A method according to any of the claims 1 to 4, characterized in that air is introduced into the synthesis gas (53) by using a mixer (13) to create a mixture of air and synthesis gas (53), which mixture of air and synthesis gas (53) is conducted into the internal combustion engine (19), wherein the temperature of the produced exhaust gas (57) is raised by adjusting the ratio of air and synthesis gas (53), which adjusting is done in the mixer (13).

6. A method according of the claims 1 to 5, characterized in that said gaseous medium is synthesis gas (53) which is conducted into a second heat exchanger (3), wherein heat energy from the synthesis gas (53) is recovered into said liquid heating medium.

7. A method according to any of the claims 1 to 6, characterized in that said gaseous medium is synthesis gas (53) which is conducted into a filtration unit (5), wherein the synthesis gas (53) is cleaned.

8. A method according to claim 7, characterized in that said gaseous medium is synthesis gas (53) which is conducted after the cleaning of the synthesis gas (53) into a third heat exchanger (7), wherein heat energy from the synthesis gas (53) is recovered into said liquid heating medium.

9. A method according to any of the claims 1 to 8, characterized in that said gaseous medium is synthesis gas (53) which is conducted onto a second external combustion engine (63), wherein heat energy of the exhaust gas (53) is converted into mechanical energy, which mechanical energy is further converted into electricity by a third electric generator.

10. A method according to any of the claims 1 to 9, characterized in that said gaseous medium is synthesis gas (53) which

- is separated into a first synthesis gas portion, conducted into the third heat ex changer (7) to recover heat energy from the first synthesis gas portion into said liquid heating medium;

- is separated into a second synthesis gas portion, conducted onto the second ex ternal combustion engine (63) to convert heat energy of the second synthesis gas portion into mechanical energy, which mechanical energy is further converted into electricity by the third electric generator (65); and

- ratio of the recovered heat energy and generated electricity is changed by adjust ing the ratio of the first synthesis gas portion and the second synthesis gas portion.

1 1 . A method according to any of the claims 1 to 10, characterized in that heat energy recovered into said liquid heating medium is conducted into a closed liquid circulation system (49).

12. A combined heat and power plant for producing heat energy and electricity comprises:

- a gasifier (1 ) configured to convert fuel into synthesis gas (53),

- an internal combustion engine (19) configured to generate mechanical energy by burning the synthesis gas (53) and thereby forming exhaust gas (57),

- a pipeline which comprises a plurality of pipes configured to conduct gaseous me dium comprising heat energy, which gaseous medium comprises synthesis gas (53) and exhaust gas (57), - a first electric generator (23) configured to convert mechanical energy generated by the internal combustion engine (19) into electricity,

- a heat exchanger (3,7,61 ) configured to recover heat energy from gaseous me dium into a liquid heating medium,

- an external combustion engine (37,63) configured to convert heat energy of the gaseous medium into mechanical energy,

- an electric generator (59,65) configured to convert mechanical energy generated by the external combustion engine (37,63) into electricity, characterized in that the combined heat and power plant further comprises a valve (43,67) configured to separate the gaseous medium into a first gas portion and into a second gas portion.

13. A combined heat and power plant according to claim 12, characterized in that said pipeline is a synthesis gas pipeline which comprises a plurality of pipes config ured to conduct the synthesis gas (53) from the gasifier into the internal combustion engine (19).

14. A combined heat and power plant according to claim 12 or 13, characterized in that said synthesis gas pipeline further comprises a second heat exchanger (3) configured to recover heat energy from the synthesis gas (53) into said liquid heating medium.

15. A combined heat and power plant according to any of the claims 12 to 14, characterized in that said synthesis gas pipeline further comprises a filtration unit (5) configured to clean the synthesis gas (53).

16. A combined heat and power plant according to any of the claims 12 to 15, characterized in that said synthesis gas pipeline further comprises a third heat ex changer (7) configured to recover heat energy from the synthesis gas (53) into said liquid heating medium.

17. A combined heat and power plant according to any of the claims 12 to 16, characterized in that said synthesis gas pipeline further comprises a second exter nal combustion engine (63) configured to convert heat energy of the exhaust gas (57) into mechanical energy, which second external combustion engine is connected to a third electric generator (65) configured to convert this generated me chanical energy into electricity.

18. A combined heat and power plant according to any of the claims 12 to 17, characterized in that said synthesis gas pipeline further comprises a first synthesis gas valve (67) configured to separate the synthesis gas (53) into a first synthesis gas portion, to conduct the first synthesis gas portion into the third heat exchanger (7), and into a second synthesis gas portion to conduct the second synthesis gas portion onto the second external combustion engine (63).

19. A combined heat and power plant according to any of the claims 12 to 18, characterized in that said synthesis gas pipeline further comprises a mixer (13) configured to introduce air into the synthesis gas (53) and to adjust this ratio of air and the synthesis gas (53).

20. A combined heat and power plant according to claim 12, characterized in that said pipeline is an exhaust gas pipeline which comprises a plurality of pipes config ured to conduct the exhaust gas (57) from the internal combustion engine (19) to an exhaust gas outlet (79), which exhaust gas outlet (79) is configured to conduct the exhaust gas (57) outside from the combined heat and power plant (101 ).

21 . A combined heat and power plant according to claim 12 or 20, characterized in that said exhaust gas pipeline further comprises a first heat exchanger (61 ) con figured to recover heat energy from the exhaust gas (57) into said liquid heating medium.

22. A combined heat and power plant according to any of the claims 12, 20, or 21 , characterized in that said exhaust gas pipeline further comprises a first external combustion engine (37) configured to convert heat energy of the exhaust gas (57) into mechanical energy, which first external combustion engine is connected to the second electric generator (59) configured to convert this mechanical energy into electricity.

23. A combined heat and power plant according to any of the claims 12, 20, 21 or 22, characterized in the said exhaust gas pipeline further comprises an exhaust gas valve (43) configured to separate the exhaust gas (57) into a first exhaust gas portion, to conduct the first exhaust gas portion into the first heat exchanger (61 ), and into a second exhaust gas portion, to conduct the second exhaust gas portion onto the first external combustion engine (37).

24. A combined heat and power plant according to any of the claims 12 to 23, characterized in that said liquid heating medium comprises a closed liquid circula tion system (49) configured to conduct recovered heat energy outside from the com bined heat and power plant.