JP4499734B2 - Fuel combustion method and apparatus - Google Patents

Description

  The present invention relates to a fuel combustion method and a combustion apparatus in a combustor.

The classic way to convert fuel energy to heat is to oxidize or burn liquid or gaseous fuel with an oxidant such as, for example, air oxygen. In the case of a high-load combustion apparatus, there is generally a problem that generation of harmful substances, particularly NO _x , must be extremely reduced today. The combustor must be capable of stable and complete combustion over the entire operating range and can be operated inexpensively with a relatively low degree of maintenance. In order to solve this problem, three groups of combustion devices are known.

So-called standard low NO _x combustion apparatus performs premixing of fuel and combustion air prior inflow to the combustor. Subsequently, the generated flame is stabilized inside the combustor, thereby controlling the oxidation reaction. Occurs locally high temperatures to unmixed remaining inside the combustor, the high temperature causes a large amount generate unwanted NO _x. Therefore a standard low NO _x combustion devices are usually first flame aerodynamically stabilized and has been hot combustion gases sufficiently react with the gas mixture consisting of fuel and combustion air in which the gas flows into the combustor Cycle to do. Aerodynamic stability is supported by the use of a hot support flame (so-called pilot system), which results in a more non-uniform temperature distribution within the combustor. Such non-uniform temperature distribution is an additional cause of nitrogen oxide generation. Therefore usually the standard low NO _x combustor, is initially generated NO _x is reduced by the catalytic exhaust gas purifier.

  The range of use of this catalytic combustion apparatus is currently limited, and it cannot be used for a high-temperature combustion apparatus such as a stationary gas turbine having the latest structure. Catalytic combustion devices are only used in small stationary gas turbines.

  For industrial combustion devices, the so-called flameless oxidation burners described, for example, in EP-A-0463218 are known. In the case of the combustion device, the combustion air is preheated by the exhaust gas and is supplied to the radially peripheral region of the combustor with a large impulse. Gaseous fuel is separately injected into the center of the combustor. The preheated combustion air is mixed with the circulating exhaust gas stream in the peripheral region of the combustor and with the gaseous fuel supplied separately inside.

An object of the present invention is to provide a fuel combustion method and apparatus, particularly in a gas turbine combustor, capable of achieving stable complete combustion and a significant reduction in NO _x generation.

  According to the present invention, a fuel and combustion air is mixed with fuel and combustion air in a state where self-ignition is avoided before flowing into the combustor, and the first portion of the mixture is This part is placed in the combustor so that it circulates in the combustor, and additional fuel is supplied into the circulation of the first part of the mixture until it can be ensured that it is heated to ignition conditions. The problem is solved by mixing the two parts with the hot combustion gas that flows out of the circulation stream, raising the temperature and burning it to the combustor outlet. Further, according to the present invention, there is provided a mixing apparatus for mixing fuel and combustion air in a state avoiding self-ignition before flowing into the combustor, and a first of the mixture. Heating to ignition conditions is ensured in the first mixture injection device for entering the part into the combustor such that the first part circulates in the combustor and in the circulating flow of the first part of the mixture. A fuel supply system for supplying additional fuel until at least one second part of the mixture is mixed with the hot combustion gas, the second part flowing out of the circulating stream, heated and to the combustor outlet This is solved by providing at least one second gas mixture injection device for entering the combustor for combustion.

In accordance with the present invention, a first quantity of fuel (e.g., gaseous fuel 1) is premixed with combustion air, avoiding self-ignition before flowing into the combustor. When a portion of the mixture reacts later, there is a low temperature level that is below the average temperature level of the comparable combustion reaction. Therefore, this partial air-fuel mixture generates very little NO _x during combustion. In accordance with the present invention, an air-fuel mixture comprising fuel and combustion air is a hot exhaust gas in which a first portion of the air-fuel mixture circulates in a circulating vortex and at least one second portion of the air-fuel mixture flows out of the circulating vortex Or it puts into a combustor so that it may mix with combustion gas. The second part of the air-fuel mixture is heated to a sufficient state as it is mixed with the hot exhaust gas and burns up to the combustor outlet. On the other hand, the conventional normal separate pilot system is avoided according to the present invention, and the aerodynamic stabilization procedure by the swirl flow generator is also omitted.

In accordance with the present invention, in one or more separate stages, additional fuel (eg, gaseous fuel 2) is added in the circulating flow to ensure heating of the entire air / fuel mixture to ignition conditions or ignition. Provide sufficient energy until the condition exists. The additional fuel is mixed in accordance with the present invention so that uniform mixing into the combustion gas occurs at low temperature levels. Thus, based on the present invention, temperature peaks within the combustor can be prevented. As a result, NO _x generation from this range of reactive combustion gases is particularly small.

In an advantageous embodiment of the method of the invention, the fuel and combustion air are mixed before entering the combustor such that the ratio of combustion air to fuel is higher than the average air-fuel ratio of combustion in the combustor. The high air-fuel ratio by the present invention, ensures a relatively low temperature level, can be reduced NO _x generation have.

  The device according to the invention comprises a body in which a first and / or second part (and / or a further part in the case of multistage fuel addition) of a mixture of fuel and combustion air are arranged in the center of the combustor It is particularly suitable to flow through. The generation of the circulation flow of the first part of the air-fuel mixture targeted by the present invention and the injection of the second part of the air-fuel mixture into the flowing hot combustion gas can be realized very easily in terms of flow technology.

  The central inlet body for the first part and / or the second part of the mixture of fuel and combustion air makes it possible to further integrate a device for supplying liquid fuel to the combustor. The air-fuel injection device arranged in the center is further cooled by an air-fuel mixture consisting of fuel and combustion air flowing through it, so that the air-fuel mixture is heated to a minimum. As a result, the temperature level inside the circulating flow according to the present invention can be made more uniform.

  According to the invention, the circulating flow itself is formed in the peripheral region of the combustor, ie in the radially outer region of the combustion chamber. The circulation vortex so formed has the advantage of allowing as much as possible the incorporation of additional fuel into the combustor.

  According to the present invention, the combustor may be cylindrical, and the first portion of the air-fuel mixture composed of fuel and combustion air may be placed in the combustor in the radial direction. With the radial injection of the first part of the gas mixture, the circulating flow sought by the present invention can be excited and maintained. Alternatively, an annular combustor having a corresponding fuel supply path can be used.

  Unlike the radial injection of the first portion of the mixture of fuel and combustion air, the additional fuel may be placed axially into the combustor. The addition of residual fuel (gaseous fuel 2) to such circulating vortices provides the energy necessary to ensure the desired heating to the ignition conditions of the entire air / fuel mixture. Another advantage of the axial supply of additional fuel is that the supplied additional fuel simultaneously contributes to the cooling of the combustor end walls, so that the additional fuel is only slightly heated.

  In order to simplify the apparatus of the present invention and the method implemented therewith, the first and second portions of the mixture of fuel and combustion air may be divided into the combustor as a common flow and divided within the combustor.

  When injecting one or two parts of the mixture consisting of fuel and combustion air, a particularly adapted nozzle is used in order to accurately distribute each part of the mixture to reach the circulation flow. About 5 to 25% of the total fuel / combustion air mass (total gas mass) supplied per unit time, in particular about 10 to 10 in order to stably maintain the circulation flow according to the present invention and the combustion generated therewith. It is preferable to circulate 20% in the circulating flow every unit time.

  Hereinafter, embodiments of the method and apparatus of the present invention for burning fuel in a combustor will be described in detail with reference to the drawings.

  FIG. 1 shows a fuel combustion apparatus 10 of a combustor having a burner shape of a stationary gas turbine. The apparatus 10 has a combustor 12 as a main component, which is formed in a cylindrical shape along an axis 14. The combustor 12 includes a first end face wall 16 shown in the upper part of FIG. 1, an outer wall 18 extending downward from the wall 16, and a second end face wall 20 located in the lower part of FIG.

  A main body 22 disposed in the center of the first end face wall 16 passes therethrough. The body 22 is cylindrical and extends along the axis 14. The main body 22 includes an outer tube 24 and an inner tube 26 disposed concentrically therein. A plurality of nozzles 28 facing radially outward pass through the outer tube 24, and the nozzles 28 are located at the lower end of the outer tube 24 in FIG. 1. The lower end of the outer tube 24 is closed.

  An air supply path 30 (not shown in detail) is provided at the upper end of the outer pipe 24 in FIG. 1, and a gaseous fuel supply path 32 (not shown in detail) is provided inside the outer pipe 24. From the air supply path 30 through the gaseous fuel supply path 32, air and the first gaseous fuel are supplied to the outer pipe 24, and then in the middle of flowing toward the nozzle 28 in the outer pipe 24 from the gaseous fuel and the combustion air. An air-fuel mixture 34 is produced. A first partial flow 36 of the air-fuel mixture 34 flows from the nozzle 28 to the periphery of the outer tube 24, and thus into the combustor 24. The second partial flow 38 of the mixture 34 flows out through the nozzle 28 described above for the first partial flow 36 and another nozzle 28 'located in the outer tube 24 below in FIG.

  The outer tube 24 is surrounded by a circulation chamber 40, and a continuous combustion chamber 42 continues to the circulation chamber 40 inside the combustor 12. Between the circulation chamber 40 and the continuous combustion chamber 42, a flow guide surface 44 is disposed on the inner surface of the outer wall 18. Along with the injection of the surface 44 and the first partial flow 36 (and the second partial flow 38), which will be described later, a circulation flow 46 is generated inside the circulation chamber 40 and is stabilized. The circulating flow 46 exits the nozzle 28 first radially outward, then in the direction of the first end wall 16, radially inward along the first end wall 16, and finally the first end wall 16. To the nozzle 28 again.

  On the first end face wall 16 there is another gaseous fuel supply channel 48, not shown in detail, through which additional gaseous fuel is injected into the circulating flow 46.

  The combustion gas 50 finally flows out from the circulating flow 46 in the range in front of the nozzle 28 ′, reaches the outlet 52 formed as a central opening in the end face wall 20 through the continuous combustion chamber 42. In an embodiment (not shown) in which the combustor is formed as an annular combustor, the opening is annular.

  During operation of the combustion apparatus 10, an air-fuel mixture 34 composed of gaseous fuel and combustion air is supplied to the nozzle 28 and the nozzle 28 ′ via the outer tube 24, the air supply path 30 and the gaseous fuel supply path 32. The ratio of air to gaseous fuel is set to be higher than the average air-fuel ratio of combustion in the later combustor 12. Thus, self-ignition of the air-fuel mixture 34 can be avoided.

  The air-fuel mixture 34 enters the combustor 12 in the radial direction as a first partial flow 36 and a second partial flow 38. At that time, the nozzle 28 is arranged and formed so that the first partial flow 36 mainly reaches the circulation flow 46 and excites a circulation vortex inside the circulation chamber. By supplying additional gaseous fuel in the axial direction via another gaseous fuel supply path 48, additional energy is provided to support the circulating vortex additionally and in principle to ensure that the total mixture is heated to the ignition condition. it can.

Mixing is performed as homogeneously as possible in the circulation vortex, and an amount of gaseous fuel capable of avoiding a temperature peak is mixed in the second gaseous fuel supply path 48 every unit time. The mixing is performed at a relatively low temperature, so that the reaction between the gaseous fuel and the combustion air can be maintained, and the generation of NO _x accompanying the reaction can be kept extremely low. Further, the gaseous fuel supply path 48 contributes to cooling of the first end face wall 16 of the combustor 12.

  About 10 to 20% of the total combustion air / gaseous fuel mass supplied every unit time flows through the stable circulation flow 46 every unit time. The total gas mass is preheated in the circulating vortex. The combustion or reaction of the air-fuel mixture 34 achieved at that time proceeds in a relatively low temperature level state avoiding a particularly uniform gas mixture state and temperature peak. Therefore, the conventional aerodynamic stabilization procedure for the combustor 12 using a separate pilot device or a swirl flow generator can be omitted. Another major advantage of the two-stage supply of gaseous fuel to the combustor 12 and the circulation chamber 40 formed therein is that no catalyst is required.

  The second partial flow 38 of the mixture 34 and possibly further partial flows enter the effluent combustion gas 50 directly, for example via a nozzle 28 ', which may be formed as a small tube, or in whole or in part in an embodiment not shown. Cycle as well. Since the effluent combustion gas 50 is relatively hot, the second partial stream 38 is heated to a sufficient state and reacts completely to the outlet 52 as well.

  The main body 22 disposed in the center and the inner pipe 26 formed therein allow the liquid fuel nozzle to be integrated, and as a result, the combustion apparatus 10 can be used as a two-component fuel combustion apparatus as a whole. That is, in this combustion apparatus 10, liquid fuel can be oxidized with relatively little harmful substance generation, which is impossible with a conventional combustion apparatus equipped with a conventional catalyst.

1 is a longitudinal sectional view of an embodiment of an apparatus according to the present invention.

Explanation of symbols

12 Combustor, 22 Main body, 34 Mixture, 36, 38 Mixture part, 40 Peripheral area, 46 Circulating flow, 50 Combustion gas

Claims (21)

In the method for combusting fuel in the combustor (12),
Mix fuel and combustion air in a state avoiding self-ignition before entering the combustor (12),
A first portion (36) of the mixture (34) is placed in the combustor (12) such that the first portion (36) circulates in the combustor (12);
Supplying additional fuel into the circulation (46) of the first part (36) of the mixture (34) until heating to ignition conditions is ensured;
At least one second portion (38) of the gas mixture (34) flows perpendicularly to the outflow direction of the hot combustion gas (50) from which the second portion (38) flows out of the circulation flow (46). Mixing with the combustion gas (50) , raising the temperature and putting it into the combustor (12) to burn up to the outlet of the combustor (12).   2. The fuel and the combustion air are mixed before entering the combustor (12) so that the ratio of combustion air to fuel is higher than the average air-fuel ratio of combustion in the combustor (12). The method described.   Introducing a first part (36) and / or at least one second part (38) of an air-fuel mixture (34) comprising fuel and combustion air through a body (22) located in the center of the combustor (12). 3. A method according to claim 1 or 2, characterized in that   4. A method as claimed in claim 3, characterized in that gaseous fuel is supplied as fuel and additionally liquid fuel is supplied through a centrally arranged body (22).   5. A circulating flow (46) of a first part (36) of an air-fuel mixture (34) comprising fuel and combustion air is formed in the peripheral region (40) of the combustor (12). The method according to one of the above.   The combustor (12) is formed in a cylindrical or annular shape, and a first part (36) of a mixture (34) comprising fuel and combustion air is introduced into the combustor (12) in a radial direction. The method according to one of 1 to 5.   7. The method according to claim 1, wherein the combustor (12) is cylindrically or annularly formed and the additional fuel (38) is axially introduced into the combustor (12).   The combustor (12) is formed in a cylindrical shape or an annular shape, and at least one second portion (38) of the air-fuel mixture (34) composed of fuel and combustion air is introduced into the combustor (12) in the radial direction. A method according to one of claims 1 to 7.   A first part (36) and at least one second part (38) of an air-fuel mixture (34) consisting of fuel and combustion air are placed in a combustor (12) as a common flow and divided inside the combustor (12). A method according to one of claims 1 to 8, characterized in that:   A first part (36) and at least one second part (38) of a mixture (34) of fuel and combustion air are passed through at least one nozzle (28, 28 ') and into the circulating flow (46) and the combustor. 10. A method according to one of claims 1 to 9, characterized in that it is put in (12).   The circulating flow (46) is formed such that 5 to 25% of the total gas mass supplied per unit time circulates in the circulating flow (46) per unit time. The method according to one. Combustion device (10) for fuel in a combustor (12) for carrying out the method according to one of claims 1 to 11;
A mixing device (22) for mixing fuel and combustion air in a state avoiding self-ignition before flowing into the combustor (12);
A first portion (36) of the mixture (34) is placed into the combustor (12) so that the first portion (36) of the mixture (34) circulates in the combustor (12). 1 mixture injection device;
A fuel supply device (48) for supplying additional fuel into the circulation (46) of the first portion (36) of the mixture (34) until an ignition condition occurs;
At least one second portion of the mixture (34) to (38), the outflow of hot combustion gases at least one second portion of said mixture (34) (38) flows out of the circulation flow (46) (50) At least one second for entering the combustor (12) to flow perpendicularly to the direction, mix with the hot combustion gas (50) , rise in temperature and burn to the outlet of the combustor (12). A fuel combustion apparatus comprising an air-fuel mixture injection apparatus.   Device according to claim 12, characterized in that the first gas mixture injection device and / or the at least one second gas mixture injection device are formed as a body (22) arranged in the center of the combustor (12). .   A first mixture injection device and / or at least one second mixture injection device is configured to supply gaseous fuel and additionally to a centrally disposed body (22) at least for supplying liquid fuel 14. The device according to claim 13, wherein one device is provided.   The first mixture injection device and the combustor (so that the circulating flow (46) of the first portion (36) of the mixture (34) of fuel and combustion air occurs in the peripheral region (40) of the combustor (12) ( Device according to one of claims 12 to 14, characterized in that 12) is formed.   The combustor (12) is formed in a cylindrical or annular shape, and a first air-fuel mixture injection device radially feeds a first portion (36) of the air-fuel mixture (34) comprising fuel and combustion air into the combustor (12). Device according to one of the claims 12 to 15, characterized in that it is formed to fit in.   13. The combustor (12) is formed in a cylindrical or annular shape, and the fuel supply device (48) is formed so as to insert additional fuel into the combustor (12) in the axial direction. The apparatus according to one of 16. The combustor (12) is formed in a cylindrical shape or an annular shape , and at least one second air-fuel mixture injection device inserts the second portion (38) of the air-fuel mixture (34) composed of fuel and combustion air into the combustor (12). 18. Device according to one of claims 12 to 17, characterized in that it is adapted to be inserted radially into the device.   The first gas mixture injection device and / or the at least one second gas mixture injection device share a first portion (36) and at least one second portion (38) of the mixture (34) of fuel and combustion air. 19. Device according to one of claims 12 to 18, characterized in that it is configured to enter the combustor (12) as a stream. The first mixture injection device and / or at least one second mixture injection device, a first portion of the mixture consisting of fuel and combustion air (34) (36) and at least one second portion (38) 20. Device according to one of the claims 12 to 19, characterized in that it has at least one nozzle (28, 28 ') suitable for introducing a recirculation stream (46) into the combustor (12). . The combustor (12), the first gas mixture injection device, and the at least one second gas mixture injection device are configured so that 5 to 25% of the total gas mass supplied per unit time is in the circulating flow (46) every unit time. Device according to one of claims 12 to 20, characterized in that it is configured to circulate in the air.

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