JP4220931B2 - Exhaust gas recombustion device for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust gas reburning device for an internal combustion engine.

  Patent Document 1 below discloses a technology related to a cogeneration system that generates steam in a boiler using high-temperature exhaust gas generated in an internal combustion engine such as a gas turbine.

  In this technology, in order to improve the steam generation capacity of the cogeneration system, a recombustion device is provided in the exhaust passage of the internal combustion engine, and a mixed gas of exhaust gas and fuel is burned by a burner of the recombustion device. Increases the heat energy.

  On the other hand, the technology for reburning exhaust gas is used not only for cogeneration systems but also for diesel engines used as prime movers for marine engines and work machines.

  In this case, the engine performance can be improved by burning the exhaust gas by the recombustion device at the time of loading or accelerating, and increasing the energy given to the turbine of the supercharger driven by the exhaust gas. In addition, harmful substances such as graphite contained in the exhaust gas can be removed.

  By the way, in order to burn the exhaust gas by the recombustion device as described above, it is necessary that the exhaust gas is at a high temperature and oxygen with a certain concentration remains.

  However, the residual oxygen concentration of the exhaust gas in the internal combustion engine is as low as 10 to 16%. If the residual oxygen concentration is low, it is difficult to maintain the burner flame and stably maintain combustion. Further, when both the residual oxygen concentration and the exhaust gas temperature are low, it becomes difficult to sustain combustion more stably.

  As a technique for solving such a problem, in Patent Document 1, the exhaust gas of the internal combustion engine supplied to the burner is directly mixed with the fuel of the burner to form a primary flame, and the downstream side of the primary flame. The secondary exhaust gas is divided into the secondary exhaust gas, and the secondary exhaust gas is brought into contact with the primary flame and combusted to thereby ensure stable combustion.

  Also, when the conditions are particularly severe (when the exhaust temperature and residual oxygen concentration are both low), the primary flame is caused by the exhaust with the residual oxygen concentration increased by mixing the air supplied by the blower and the excess fuel. There is also a method of ensuring stable combustion by forming and contacting exhaust gas downstream of the primary flame.

  In addition, a shielding plate or the like is provided in the exhaust gas flow, and a part of the exhaust gas flow is cut off to generate a reverse flow region with a low flow velocity. A method of giving a swirl component to the gas and generating a circulation region to maintain the flame is also conventionally known as a method of ensuring stable combustion.

JP-A-9-72504

  Each of the conventional methods as described above is effective as such when the residual oxygen concentration of the exhaust gas is about 10 to 16%. However, for example, when the engine is loaded or accelerated in a prime mover such as a marine engine, the residual oxygen There is also a condition that the concentration is 10% or less, and under such a condition, it is difficult to stably maintain combustion over the entire operating range of the internal combustion engine.

  Further, in the conventional method in which the exhaust gas is brought into contact with the downstream of the primary flame formed by the exhaust gas and the excess fuel whose residual oxygen concentration is increased by mixing the air supplied by the blower, the residual oxygen concentration of the exhaust gas is low. As the amount of air required tends to increase, new problems such as an increase in blower fan power and a decrease in heat recovery efficiency occur.

  The present invention has been made in view of the above problems, and an object of the present invention is to perform exhaust recombustion of an internal combustion engine that can stably maintain combustion by a burner even when the residual oxygen concentration of the exhaust gas is low. To provide an apparatus.

According to the first aspect of the present invention, a recombustion chamber 8 is provided in the exhaust passage 4 of the internal combustion engine, and a mixed gas of the exhaust gas from the exhaust passage 4 and the fuel from the fuel supply pipe 15 is combusted in the recombustion chamber 8. In the exhaust gas reburning apparatus for an internal combustion engine including the main burner unit 9, the reburning chamber 8 includes a sub burner unit 10 independent of the main burner unit 9, and the sub burner unit 10 includes an air supply pipe 20. And a fuel supply pipe 15 separate from the fuel supply pipe 15 of the main burner section 9, and a sub-burner for burning a mixed gas of air from the air supply pipe 20 and fuel from the separate fuel supply pipe 21. The main burner portion 9 and the sub burner portion 10 are arranged so that the respective flames are in contact with each other.

According to a second aspect of the present invention, in the first aspect of the invention, the auxiliary burner portion 10 is arranged so that the front end opening of the fuel supply pipe 21 is retreated from the front end opening of the air supply pipe 20. In the air supply pipe 20 between the front end opening of the air supply 21 and the front end opening of the air supply pipe 20, there is a combustion space 23 in which air and fuel are not subject to the interference of exhaust gas from the main burner portion 9. It is characterized by that.

  According to the first aspect of the present invention, the air and fuel supplied to the sub-burner can be controlled independently of the main burner section, so that it is always optimal regardless of the state of the exhaust gas of the internal combustion engine. A combustion state can be obtained. Therefore, combustion can be stably maintained even when the residual oxygen concentration of the exhaust gas becomes 10% or less. The sub-burner unit only needs to supply a small amount of air and fuel because it is sufficient to maintain the combustion state in the re-combustion chamber. When the air is supplied by a blower or the like, the fan power increases and the heat recovery efficiency increases. The decrease can be suppressed.

  According to the invention of claim 2, since the sub-burner part has a combustion space in which the supplied air and fuel are not subject to the interference of the exhaust gas, it can hold the flame reliably in the entire operation range, A more stable combustion state can be obtained.

[First Embodiment]
FIG. 1 is a block diagram of a cogeneration system that employs an exhaust gas reburning apparatus according to a first embodiment of the present invention. Reference numeral 2 in FIG. 1 denotes an internal combustion engine such as a diesel engine, a gas engine, or a gas turbine. A generator 3 is connected to the internal combustion engine 2, and the generator 3 is driven by the output of the internal combustion engine 2. In the exhaust passage 4 of the internal combustion engine 2, a recombustion device 5 is disposed that burns a mixed gas of exhaust gas or air and fuel and heats the exhaust gas.

  A heat exchanger 6 made of an exhaust heat recovery boiler is disposed adjacent to the downstream side of the recombustion device 5, and the exhaust gas heated by the recombustion device 5 is supplied to the heat exchanger 6. The heat exchanger 6 generates steam by heating the water supplied through the water supply pipe 7 with exhaust gas, and the generated steam is a hot water supply device, a cooling / heating device, a steam turbine that drives a generator, or the like To the device 25.

  FIG. 2 is an enlarged block diagram showing the recombustion device 5. The recombustion device 5 includes a recombustion chamber 8 and burner portions 9 and 10 that form flames F1 and F2 in the recombustion chamber 8. I have. The burner unit includes a main burner unit 9 and a sub-burner unit 10, and the main burner unit 9 includes an exhaust supply unit 11 that supplies exhaust gas and a fuel supply unit 12 that supplies fuel.

  The exhaust supply unit 11 includes an exhaust supply pipe 13 that forms the exhaust passage 4, and an exhaust supply port 14 that is open to the wall of the recombustion chamber 8 at a connection portion of the exhaust supply pipe 13 to the recombustion chamber 8. The fuel supply unit 12 includes a fuel supply pipe 15 that has at least a distal end portion disposed in the exhaust supply pipe 13 and circulates fuel, and a burner nozzle 16 that is provided at the front end of the fuel supply pipe 15 and discharges the fuel. . The burner nozzle 16 is disposed in the center of the exhaust supply port 14.

  A large number of swirl vanes 17 are provided around the burner nozzle 16 of the exhaust supply port 14. 3 is a side view of the swirl vane 17 and FIG. 4 is a plan view of the swirl vane 17. The swirl vanes 17 are provided radially around the burner nozzle 16, and each swirl vane 17 is curved or inclined in the same direction. Has been. The exhaust gas flowing through the exhaust passage 4 is given a swirl component by passing through the swirl vanes 17 at the exhaust supply port 14 to form a circulation region. In addition, as shown in FIG. 2, a flow guide cylinder 24 is provided around the exhaust supply port 14 in the recombustion chamber 8 to prevent the exhaust gas flowing out from the exhaust supply port 14 from diffusing.

  The sub-burner unit 10 is provided independently of the main burner unit 9 and includes an air supply unit 18 that supplies air and a fuel supply unit 19 that supplies fuel. The air supply unit 18 includes an air supply pipe 20 through which air flows. The air supply pipe 20 passes through the wall of the recombustion chamber 8 and protrudes into the recombustion chamber 8, and the opening 20A at the tip thereof is recombusted. It is arranged in the chamber 8.

  The fuel supply unit 19 has a fuel supply pipe 21 in which at least a tip part is disposed in the air supply pipe 20 and circulates fuel, and a burner nozzle 22 that is provided at the tip of the fuel supply pipe 21 and discharges fuel. ing. The burner nozzle 22 is disposed at a position retracted from the front end opening 20A of the air supply pipe 20, and a space in the air supply pipe 20 between the burner nozzle 22 and the front end opening 20A of the air supply pipe 20 is air and fuel. A combustion space 23 for burning the mixed gas is used.

  The air supply pipe 20 and the fuel supply pipe 21 of the sub-burner unit 10 are formed narrower than the exhaust supply pipe 13 and the fuel supply pipe 15 of the main burner unit 9, and the sub-burner unit 10 has a small amount compared to the main burner unit 9. The flame F2 is formed with the mixed gas.

  The fuel supply units 12 and 19 of the main burner unit 9 and the sub burner unit 10 may supply the fuel for the internal combustion engine 2 via the fuel supply pipes 15 and 21, or separately prepared fuel. It may be supplied. The air supply unit 18 of the sub-burner unit 10 may supply air for supplying air to the internal combustion engine 2 through the air supply pipe 20, or may be provided by a blower (air supply device) such as a separately provided blower. It is good also as what supplies air.

  In the example shown in FIG. 2, the main burner portion 9 is provided with respect to one wall 8 </ b> A of the recombustion chamber 8 and is directed downward. On the other hand, the auxiliary burner portion 10 is provided on the wall 8A of the recombustion chamber 8 that is the same as the main burner portion 9 with a distance from the main burner portion 9. The sub-burner portion 10 is directed obliquely downward so that the tip side approaches the main burner portion 9, and by such arrangement, the sub-burner portion 10 is formed by the flame F <b> 1 formed by the main burner portion 9 and the sub-burner portion 10. The flame F2 can contact each other.

[Action]
The operation of the exhaust gas reburning apparatus 5 having the above configuration will be described. The main burner unit 9 of the recombustion device 5 remixes the mixed gas of the exhaust gas supplied from the exhaust supply unit 11 and the fuel supplied from the fuel supply unit 12 while the internal combustion engine 2 is driven. 8 burns to form a flame F1.

  On the other hand, the auxiliary burner unit 10 burns a mixed gas of the air supplied from the air supply unit 18 and the fuel supplied from the fuel supply unit 19 to form a flame F2. This flame F2 is formed in the combustion space 23 in the air supply pipe 20, protrudes from the tip opening 20A of the air supply pipe 20, and comes into contact with the flame F1 of the main burner portion 9. In the auxiliary burner unit 10, constant air and fuel are always supplied independently of the main burner unit 9, and stable combustion is maintained without being affected by the main burner unit 9.

  When the residual oxygen concentration of the exhaust gas supplied to the main burner unit 9 is low (for example, 10% or less) and the flame F1 formed by the main burner unit 9 becomes unstable, the flame F2 of the sub-burner unit 10 Is maintained stably and the flame F2 of the sub-burner unit 10 is in contact with the flame F1 of the main burner unit 9, so that the main burner is used by using the flame F2 of the sub-burner unit 10 as a so-called "seed fire". It is possible to maintain the flame F1 of the main burner portion 9 by burning the exhaust gas and fuel supplied to the portion 9.

  Since the auxiliary burner unit 10 has the combustion space 23 in the air supply pipe 20, the supplied air and fuel are interfered with the exhaust gas flowing into the recombustion chamber 8 from the exhaust supply port 13. And the formation of a stable flame F2 by the auxiliary burner 10 is ensured.

  Further, the exhaust gas supplied to the main burner portion 9 is given a swirl component by passing through the swirl vane 17, and thereby a circulation region is formed, so that the effect of holding the flame F1 is exhibited.

  The sub-burner unit 10 only needs to supply a small amount of air and fuel because it is sufficient to maintain the combustion state in the re-combustion chamber 8. Increase in fan power and heat recovery efficiency when air is supplied by a blower or the like. Can be suppressed.

[Second Embodiment]
FIG. 5 is a block diagram showing an exhaust reburning apparatus 5 according to the second embodiment of the present invention. In the present embodiment, the sub burner portion 10 is provided on the wall 8B orthogonal to the wall 8A of the recombustion chamber 8 where the main burner portion 9 is provided. The main burner portion 9 and the sub burner portion 10 are oriented in directions orthogonal to each other, and the respective flames F1, F2 are in contact with each other. Other configurations and operational effects are the same as those of the first embodiment.

  The present invention is not limited to the embodiments described above, and can be appropriately modified within the scope of the claims. For example, in the sub-burner unit 10, the flow rate of air or fuel supplied from the air supply unit 18 or the fuel supply unit 19 can be adjusted by a metering valve or the like. In this case, you may make it control a metering valve according to the state of the flame F1 of the main burner part 9. FIG. The number of the main burner portions 9 and the sub burner portions 10, the mounting positions with respect to the recombustion chamber 8, and the like can be appropriately changed. It is also possible to play a role of maintaining the flame by providing a shielding plate that partially shields the exhaust gas flow instead of the swirl vane 17. The present invention is particularly effective when the residual oxygen concentration is low and the conditions for reburning are severe, such as exhaust gas from a diesel engine.

  INDUSTRIAL APPLICABILITY The present invention can be used for an exhaust gas reburning device for an internal combustion engine used in a cogeneration system, an exhaust gas reburning device for an internal combustion engine used in a marine engine, a work machine, and the like.

1 is a block diagram of a cogeneration system that employs an exhaust gas reburning device for an internal combustion engine according to a first embodiment of the present invention. It is a block diagram of an exhaust gas reburning device. It is a top view of a turning blade. It is a side view of a turning blade. It is a block diagram of the exhaust gas recombustion apparatus which concerns on 2nd Embodiment.

Explanation of symbols

2 Internal combustion engine 4 Exhaust passage 5 Recombustion device 8 Recombustion chamber 9 Main burner portion 10 Sub burner portion 23 Combustion space

Claims (2)

A recombustion chamber (8) is provided in the exhaust passage (4) of the internal combustion engine, and a mixed gas of exhaust gas from the exhaust passage (4) and fuel from the fuel supply pipe (15) is supplied to the recombustion chamber (8). In an exhaust gas reburning device for an internal combustion engine comprising a main burner section (9) for combustion,
The recombustion chamber (8 ) is provided with a sub-burner part (10) independently of the main burner part (9) ,
The sub-burner part (10) includes a fuel supply pipe (21) separate from the air supply pipe (20) and the fuel supply pipe (15) of the main burner part (9), and the air supply pipe (20). A sub-burner section (10) for burning a mixed gas of air from the fuel and fuel from the another fuel supply pipe (21),
The exhaust gas reburning apparatus is characterized in that the main burner portion (9) and the auxiliary burner portion (10) are arranged so that the respective flames are in contact with each other. The auxiliary burner portion (10) is arranged such that the tip opening of the fuel supply pipe (21) is retreated from the tip opening of the air supply pipe (20), so that the air supply pipe extends from the tip opening of the fuel supply pipe (21). In the air supply pipe (20) up to the tip opening of (20), there is a combustion space (23) in which air and fuel are not subject to the interference of exhaust gas from the main burner part (9). The exhaust gas reburning apparatus for an internal combustion engine according to claim 1.

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