WO2010046450A1

WO2010046450A1 - Combined heat and power generation subsystem, combined heat and power generation system, and method for the operation of a combined heat and power generation system

Info

Publication number: WO2010046450A1
Application number: PCT/EP2009/063923
Authority: WO
Inventors: Heinrich Baas
Original assignee: Mwm Gmbh
Priority date: 2008-10-22
Filing date: 2009-10-22
Publication date: 2010-04-29
Also published as: DE102008052640A1; EP2342442A1

Abstract

The invention relates to a combined heat and power generation (sub)system (1) comprising an exhaust gas system (2) for an internal combustion engine (V), a cooling circuit (3) for an internal combustion engine (V), and a heating circuit (4) for utilizing heat. An exhaust gas heat exchanger (2.5) is provided in the exhaust gas system (2), while a cooling heat exchanger (3.4), via which the heating circuit (4) is coupled to the cooling circuit (3) of the internal combustion engine (V), is provided in the heating circuit (4). An exhaust gas cooling circuit (5) and a heating heat exchanger (5.4) are also provided. The exhaust gas cooling circuit (5) is coupled to the exhaust gas system (2) via the exhaust gas heat exchanger (2.5) while being coupled to the heating circuit (4) via the heating heat exchanger (5.4). The invention further relates to a method for operating a combined heat and power generation system (10) in which the waste heat from the exhaust gas of the internal combustion engine (V) is transferred to a coolant of a separate exhaust gas cooling circuit (5) via the exhaust gas heat exchanger (2.5) and to the heating circuit (4) via the exhaust gas cooling circuit (5).

Description

Combined heat and power plant, cogeneration plant and method for operating a combined heat and power plant

The invention relates to a cogeneration power plant with an exhaust system for an internal combustion engine, with a cooling circuit for an internal combustion engine and with a heating or low pressure heating circuit for heat utilization, wherein an exhaust gas heat exchanger is provided in the exhaust line and in the heating circuit, a cooling heat exchanger is provided via the heating circuit is coupled to the cooling circuit of the internal combustion engine, wherein an exhaust gas cooling circuit and a heating heat exchanger are provided and the exhaust gas cooling circuit is coupled via the exhaust gas heat exchanger to the exhaust system and via the heating heat exchanger to the heating circuit. The invention also relates to a combined heat and power plant and a method for operating a combined heat and power plant, in which the direct waste heat of the internal combustion engine via a cooling circuit and the waste heat of the exhaust gas of the internal combustion engine are removed by means of an exhaust gas heat exchanger to a heating or low pressure heating circuit, and at the waste heat of the exhaust gas of the internal combustion engine is discharged via the exhaust gas heat exchanger to a coolant of a separate exhaust gas cooling circuit and the exhaust gas cooling circuit to the heating circuit.

There are already known from the prior art cogeneration plants according to Figures Ia and Ib. These have an internal combustion engine with an exhaust line and a cooling circuit, as well as a heating circuit for the use of heat. The heating circuit and the cooling circuit are coupled via a cooling heat exchanger. In addition, an exhaust gas heat exchanger is provided, via which the exhaust gas line is coupled either directly to the heating circuit or else to the cooling circuit. Thus, the cooling water waste heat and the exhaust heat of the internal combustion engine are transferred into the heating circuit.

DE 10 2007 057 164 A1 describes an organic Rankine cycle with a system having at least one first circuit for cooling the internal combustion engine, with at least one exhaust gas heat exchanger and with at least one organic Rankine cycle for an expansion machine, the organic Rankine cycle in addition to a preheating stage, a second heat exchanger stage for vaporizing and / or overheating of the medium, wherein the second heat exchanger stage is coupled only to the exhaust gas heat exchanger.

The media used in the Organic Rankine cycle generally have a boiling temperature well below 100 ⁰ C, so that the desired and required in Organic Rankine cycle temperature levels are as small as possible. This has the advantage that heat sources with a relatively low temperature can be used. The Organic Rankine cycle must be designed as a high-pressure circuit at least between the compressor and the expansion machine.

According to TA-Luft, the formaldehyde emissions of stationary gas engines must not exceed a limit of 60 mg / mN. In natural gas operation, the threshold value is exceeded by installing a corresponding oxidation catalytic converter. In biogas plants, for example, the use of this oxidation catalyst is not possible because sulfur in the biogas attacks the catalyst. In addition, SO _{2 is} also oxidized to SO ₃ in this oxidation catalyst. Thereby the dew point temperature rises above the operating temperature of the exhaust gas heat exchanger wall, causing acidic condensate to precipitate. This leads to corrosion damage to the exhaust gas heat exchanger. This could be remedied by a fuel gas desulphurisation plant with corresponding costs.

The object of the invention is to design and arrange a cogeneration unit in such a way that corrosion damage to the flue gas heat exchanger can be prevented in a simple manner.

The object is achieved by a cogeneration power plant according to claim 1, a cogeneration plant according to claim 5 and a method according to claim 8.

According to the exhaust gas cooling circuit with the exhaust gas heat exchanger and the heating heat exchanger as Zwertentempe- raturkreis formed such that in operation an inlet temperature T in the exhaust gas heat exchanger of at least 100 ⁰ C, HO ⁰ C, 12O ⁰ C, 13O ⁰ C or 14O ⁰ C. The heating or low pressure heating circuit and the exhaust gas cooling circuit are separated from each other here. This ensures that by means of the exhaust gas cooling circuit, a further temperature level can be provided on the exhaust side of the exhaust gas heat exchanger on the exhaust side, in which a condensation of acidic condensate is prevented in the exhaust system. The cooling circuit forms an intermediate circuit which has the desired temperature level on the heating circuit side and, above all, ensures a sufficiently high temperature level on the exhaust gas side, ie at the exhaust gas side of the exhaust gas heat exchanger. With such a high inlet temperature T of the cooling medium is a condensation of acidic condensate in the exhaust gas heat exchanger or at the Flue gas-carrying inner wall prevents, since the dew point of acidic components is not reached. Even if the inlet temperature T decreases at a refrigerant pipe leading the tube wall of the exhaust gas heat exchanger below the dew point, this can be harmless as long as the flue gas-carrying inner wall of the exhaust gas heat exchanger has a temperature above the dew point.

In this way, a biogas plant can also be operated without an expensive desulphurization plant while maintaining the formaldehyde limit. Due to the increased coolant temperature, the pipe wall temperature in the exhaust gas heat exchanger is raised above the dew point temperature of the sulfur in the exhaust gas, so that no condensate is produced during operation.

The combined heat and power plant can be supplemented according to the invention with the use of an internal combustion engine to a cogeneration plant, which offers the same advantages of the invention.

Characterized in that the inlet temperature T of the coolant is selected to be at least so high that a flue gas-carrying inner wall of the exhaust gas heat exchanger does not fall below the dew point of one or more acidic components of the exhaust gas, the advantages of the invention are also achieved. The exhaust gas heat exchanger is coupled according to the invention via the exhaust gas cooling circuit and a heating heat exchanger with the heating circuit, so that a condensation of these components is excluded on the inner wall.

The prior art, the DE 10 2007 057 164 Al does not address the problem solved according to the invention concerning the protection of the exhaust gas heat exchanger from condensation products, in particular in a cogeneration plant for the purpose of supply of a low-pressure heating circuit, ie without an expansion machine for generating electrical energy. Furthermore, it may be advantageous if a liquid cooling medium with water and / or oil is provided for the exhaust gas cooling circuit. For temperatures up to about 14O ⁰ C can be used with appropriate additives as a cooling medium using an elevated pressure level. When using a higher temperature level, the use of oil as a cooling medium is necessary. For both cases, a corresponding design of the exhaust gas cooling circuit or the exhaust gas heat exchanger and the heating heat exchanger is necessary.

In this regard, it may be advantageous if the exhaust gas cooling circuit with the exhaust gas heat exchanger and the heating heat exchanger as an intermediate temperature circuit and / or the heating circuit is designed such that overheating or evaporation of the cooling medium in the exhaust gas cooling circuit and / or in the heating circuit is prevented. All the exhaust gas cooling circuit and the heating circuit forming components, in particular the exhaust gas heat exchanger and / or the heating heat exchanger, can thus be designed for normal pressure or at least slight overpressure up to 1.5 bar. Thus, in addition to cost and the safety requirements for such a system lower.

It can be advantageous here if the oxidation catalytic converter provided in the exhaust gas line is designed to be resistant to sulfur. The use of a desulfurization is inventively not necessary. However, the oxidation catalyst in this case must be resistant to sulfur in order to ensure the longevity of the plant.

Accordingly, it may be advantageously possible to form the exhaust gas heat exchanger from a material that does not is sulfur resistant. The exhaust gas heat exchanger is formed resistant to sulfur at least on its exhaust side and thus significantly cheaper.

The muffler may be arranged with respect to the flow direction of the exhaust gas in principle after the exhaust gas heat exchanger.

Advantageously, it can be provided that during operation with an internal combustion engine, the inlet temperature of the exhaust gas cooling circuit or the cooling medium in the exhaust gas heat exchanger at least 100 ⁰ C, HO ⁰ C, 12O ⁰ C, 13O ⁰ C or 14O ⁰ C. The temperature of the flue gas-carrying inner wall of the exhaust gas heat exchanger thus does not reach the dew point temperature, so that a defective condensation of acidic condensate in the exhaust gas heat exchanger is prevented. Since the dew point temperature depends on the sulfur content of the exhaust gas, at low sulfur content, an inlet temperature T of the coolant of 100 ^° C. may already be sufficient.

Of particular importance may be for the present invention, when the inlet temperature of the exhaust gas cooling circuit is variable in the exhaust gas heat exchanger in dependence of the sulfur content of the exhaust gas. With the sulfur content in the exhaust gas, the dew point temperature of the various acids, especially sulfuric acid, sulfurous acid and nitric acid, varies. At low sulfur levels, the inlet temperature can be very low without causing harmful condensation. With increasing sulfur content, a higher inlet temperature is necessary to prevent harmful condensation. With the inlet temperature also varies the required operating pressure of the exhaust gas cooling circuit and thus the required derliche pressure stage of the exhaust gas and the heating heat exchanger. A corresponding adjustment or selection is necessary.

It may be sufficient if the inlet temperature T is selected to be at least as high as the dew point temperature of one or more components of the exhaust gas. The coolant is heated with the entry into the heat exchanger, so that a condensation of acidic condensate is excluded.

If an inlet temperature T of at least 100 ⁰ C, HO ⁰ C, 12O ⁰ C, 13O ⁰ C or 14O ⁰ C is selected, a condensation of acid condensate in the exhaust gas heat exchanger can also be excluded, since the dew point temperature is usually a value of 100 ⁰ C does not fall below. The dew point temperature depends on the sulfur content of the exhaust gas. At low sulfur content, an inlet temperature T of 100 ^° C. may already be sufficient.

Finally, it is advantageous that a biogas can be used as fuel for the internal combustion engine without the exhaust gas of the internal combustion engine being desulphurized before it enters the exhaust gas heat exchanger. The cost of a desulfurization be saved.

Further advantages and details of the invention are explained in the patent claims and in the description and illustrated in the figures. It shows:

Figure Ia, Ib each a schematic diagram of the structure of a

Combined heat and power plant according to the prior art; Figure 2 is a schematic diagram of a structure of a combined heat and power plant with separate exhaust gas cooling circuit.

The previously known in the art Kraftwärmekopplungs- systems 10, according to Figure Ia and Ib, have an internal combustion engine V with an exhaust line 2 for discharging the hot exhaust gases and a cooling circuit 3 for deriving the engine heat. Within the exhaust line 2, an exhaust gas heat exchanger 2.5 is arranged for the purpose of emitting the exhaust gas heat, while a cooling heat exchanger 3.4 is arranged in the cooling circuit 3 for the purpose of delivery of the heat dissipated therewith.

The combined heat and power plant 10 comprises a cogeneration unit 1, which is supplemented by the addition of the combustion system V to the combined heat and power plant 10.

Furthermore, the combined heat and power plant 10 has a heating circuit 4, via which the dissipated engine and exhaust heat is fed into a consumer circuit not shown in detail or a low-pressure heating circuit or hot water circuit.

In the exhaust line 2, in addition to a muffler 2.1, and a control valve 2.3 with a bypass 2 ^" provided over which the exhaust gas can be passed to the exhaust gas heat exchanger 2.5.

According to embodiment Ia, both the cooling heat exchanger 3.4 and the exhaust gas heat exchanger 2.5 are coupled to the heating circuit 4. The cooling heat exchanger 3.4 is arranged in relation to the flow direction of the heating circuit 4 in front of the exhaust gas heat exchanger 2.5. The heating circuit Laufmedium occurs with about 7O ⁰ C in the cooling heat exchanger 3.4 and with about 9O ⁰ C from the exhaust gas heat exchanger 2.5 from.

Both in the cooling circuit 3 and in the heating circuit 4, a circulation pump 3.2, 4.2 is provided in each case.

According to embodiment 1b, the exhaust gas heat exchanger 2.5 can also be coupled to the cooling circuit 3, so that both the heat obtained from the cooling of the internal combustion engine V, as well as the heat recovered from the exhaust line 2 is discharged together via the cooling heat exchanger 3.4 to the heating circuit 4. Here, the cooling medium enters the combustion engine V with about 8O ⁰ C, with about 92 ⁰ C in the exhaust gas heat exchanger 2.5 and at about 104 ⁰ C in the cooling heat exchanger 3.4 a.

In the exemplary embodiment according to FIG. 1 a, the inlet temperature T of the heating circuit medium in the exhaust gas heat exchanger 2.5 is approximately 85 ^° C.

In the exemplary embodiment, according to FIG Ib, the inlet temperature T of the cooling water in the exhaust gas heat exchanger 2.5 is about 92 ⁰ C.

In the embodiment according to the invention shown in FIG 2, the internal combustion engine V is coupled via the cooling circuit 3 and the cooling heat exchanger 3.4 with the heating circuit 4 according to embodiment of FIG Ia.

About the heating circuit 4, the exhaust gas heat dissipated is fed into a not shown consumer circuit or a low-pressure heating circuit or process water circuit. However, an exhaust gas cooling circuit 5 with a heating heat exchanger 5.4 is additionally provided between the exhaust gas heat exchanger 2.5 and the heating circuit 4. The exhaust gas heat exchanger 2.5 is coupled via the exhaust gas cooling circuit 5 and the heating heat exchanger 5.4 with the heating circuit 4. The exhaust gas cooling circuit 5 also comprises a pump 5.2 and a mixing valve 5.1 with a bypass 2 ^". The inlet temperature T on the exhaust gas heat exchanger 2.5 is, depending on sulfur content of the exhaust gas at least between 100 ⁰ C and 14O ⁰ C.

Reference sign list

1 combined heat and power plant

2 Exhaust Line 2 'Bypass

2.1 silencer

2.2 Oxidation catalyst

2.3 butterfly valve

2.5 Exhaust gas heat exchanger

3 cooling circuit

3.2 pump

3.4 Cooling heat exchanger

4 heating circuit

4.2 pump

5 Exhaust gas cooling circuit 5.1 Mixing valve

5.2 pump

5.4 Heating heat exchanger

10 combined heat and power plant

V internal combustion engine

T inlet temperature

Claims

claims

1. cogeneration power plant (1) with an exhaust line (2) for an internal combustion engine (V), with a cooling circuit (3) for an internal combustion engine (V) and with a heating circuit (4) for heat utilization, wherein in the exhaust line (2) an exhaust gas heat exchanger (2.5) is provided and in the heating circuit (4) a cooling heat exchanger (3.4) is provided, via which the heating circuit (4) with the cooling circuit (3) of the internal combustion engine (V) is coupled, wherein an exhaust gas cooling circuit (5) and a heating heat exchanger ( 5.4) are provided and the exhaust gas cooling circuit (5) via the exhaust gas heat exchanger (2.5) with the exhaust line (2) and via the heating heat exchanger (5.4) with the heating circuit (4) is coupled, characterized in that the exhaust gas cooling circuit (5) with the exhaust gas heat exchanger ( 2.5) and the heating heat exchanger (5.4) is formed as an intermediate temperature circuit such that in operation an inlet temperature T in the exhaust gas heat exchanger (2.5) of at least ens 100 ⁰ C, HO ⁰ C, 12O ⁰ C, 13O ⁰ C or 14O ⁰ C is reached.

Second power twärmekopplungsteilanlage (1) according to claim 1, characterized in that for the exhaust gas cooling circuit (5) a liquid cooling medium with water and / or oil is provided.

3. cogeneration power plant (1) according to one of claims 1 to 2, characterized in that the exhaust gas cooling circuit (5) with the exhaust gas heat exchanger (2.5) and the heating heat exchanger (5.4) as intermediate temperature circuit and / or the heating circuit (4) is designed such that overheating or evaporation of the medium in the exhaust gas cooling circuit (5) and / or in the heating circuit (4) is prevented.

4. Kraftwärmekopplungsteilanlage (1) according to one of claims 1 to 3, d a d u r c h e g e c e n e c e in that the exhaust gas heat exchanger (2.5) at least on the exhaust side is not formed sulfur resistant.

5. Combined heat and power plant (1) according to one of claims 1 to 4, a d u c h e c e n e c e s in that in the exhaust line (2) an oxidation catalyst (2.2) is provided, wherein the oxidation catalyst (2.2) is formed sulfur resistant.

6. Combined heat and power plant (10) with a combined heat and power plant (1) according to one of the preceding claims, characterized in that an internal combustion engine (V) is provided, which is coupled to the exhaust line (2) and with the cooling circuit (3).

7. Kraf twärmekopplungsanlage (10) according to claim 6, characterized in that in operation the inlet temperature (T) of the exhaust gas cooling circuit (5) in the exhaust gas heat exchanger (2.5) at least 100 ⁰ C, HO ⁰ C, 12O ⁰ C, 13O ⁰ C or 14O ⁰ C.

8. A fuel cogeneration installation (10) according to claim 6 or 7, characterized in that the inlet temperature (T) of the exhaust gas cooling circuit (5) in the exhaust gas heat exchanger (2.5) is variable as a function of the sulfur content of the exhaust gas.

9. A method for operating a combined heat and power plant (10), wherein the direct waste heat of the internal combustion engine (V) via a cooling circuit (3) and the waste heat of the exhaust gas of the internal combustion engine (V) by means of an exhaust gas heat exchanger (2.5) to a heating circuit (4) dissipated be discharged, and in which the waste heat of the exhaust gas of the internal combustion engine (V) via the exhaust gas heat exchanger (2.5) to a coolant of a separate exhaust gas cooling circuit (5) and the exhaust gas cooling circuit (5) to the heating circuit (4), characterized in that the inlet temperature T of the coolant is selected to be at least so high that at a flue gas-carrying inner wall of the exhaust gas heat exchanger, the dew point temperature of one or more acidic components of the exhaust gas is not exceeded.

10. The method according to claim 9, characterized in that the inlet temperature T is selected to be at least as high as the dew point temperature of one or more components of the exhaust gas.

11. The method according to claim 9, characterized in that an inlet temperature T of at least 100 ⁰ C,

HO ⁰ C, 12O ⁰ C, 13O ⁰ C or 14O ⁰ C is selected.

12. The method according to claim 9, 10 or 11, in that a biogas is used as fuel for the internal combustion engine (V) and the exhaust gas of the internal combustion engine (V) is not desulphurized before it enters the exhaust gas heat exchanger (2.5).