CN107305009B

CN107305009B - Method for combusting fuel and combustion device

Info

Publication number: CN107305009B
Application number: CN201610245936.XA
Authority: CN
Inventors: N.舍普夫; S.格泽
Original assignee: SAACKE GmbH
Current assignee: SAACKE GmbH
Priority date: 2016-04-20
Filing date: 2016-04-20
Publication date: 2020-03-03
Anticipated expiration: 2036-04-20
Also published as: CN107305009A

Abstract

The invention relates toA method for burning fuel in a combustion device and a combustion device for carrying out the method, in which method inert gas is mixed with combustion air with a mixing intensity of at least 0.5 while forming a combustion air mixture flow, the combustion air mixture flow is mixed with a fuel flow in a swirling manner, the combustion air mixture flow encloses an angle of 35 DEG to 90 DEG with the fuel flow, and a pulse flow of the combustion air mixture flow and a pulse flow of the fuel flow are in a range of 15: 1 to 2: 1, wherein in the adiabatic flame-holding and ignition zone the fuel stream is brought to combustion with a combustion air mixture stream with formation of an exhaust gas stream, the residence time of the fuel in the flame-holding and ignition zone is not less than 0.01 seconds, heat is extracted from the exhaust gas stream in a heat discharge zone locally separated from the flame-holding and ignition zone, and wherein less than 30mgNO in the exhaust gas stream is achieved with an oxygen content of 3% by volume in the exhaust gas_x/m³Nitrogen oxide content of (a).

Description

Method for combusting fuel and combustion device

Technical Field

The invention relates to a method for combusting fuel with combustion air in a combustion device, wherein in a first step an inert gas is mixed with the combustion air with a mixing intensity of at least 0.5 while forming a combustion air mixture flow, and in a second step the combustion air mixture flow is mixed with a fuel flow in a swirling manner, wherein the combustion air mixture flow encloses an angle of from 35 ° to 90 ° with the fuel flow, and wherein a pulse flow of the combustion air mixture flow is at 15% to a pulse flow of the fuel flow: 1 to 2: 1, wherein in a third step the fuel stream is brought to combustion with a combustion air mixed stream in an adiabatic or nearly adiabatic flame holding and ignition zone with formation of an exhaust gas stream, wherein the residence time of the fuel in the flame holding and ignition zone is not less than 0.01 seconds, wherein in a fourth step heat is extracted from the exhaust gas stream in a heat discharge zone locally separated from the flame holding and ignition zone, and wherein an oxygen content of less than 30mgNOx/m in the exhaust gas stream is achieved at a volume percentage of 3% in the exhaust gas³Nitrogen oxide content of (a).

Disclosure of Invention

The method results in a stable low partial pressure of gaseous, liquid or solid fuel in a boiler or combustion chamber with a slowed combustion reaction and a lower flame temperatureAnd (4) burning on a fixed basis. Since the reaction rate, reaction temperature and oxygen partial pressure are the main factors in the generation of nitrogen oxides, less than 30mgNO can be achieved during combustion by this method_x/m³(in exhaust gas O)₂At 3 volume percent) nitrogen oxide emissions.

The method is based on a combination of:

1. the partial pressure of oxygen in the combustion air is reduced by uniformly mixing (part of) the inert gas,

2. mixing air and fuel with high turbulence, an

3. The flame source (Flammenwurzel) is stabilized by locally separating the flame holding-and-ignition zone from the heat discharge zone.

The mixed intensity IM can be calculated as IM =1- √ IS, where IS the separation intensity:

variance σ²A measure of the dispersion width of the mass concentration around the mean value of the cross section under consideration is determined:

n represents the number of measuring planes in the cross section (measuring plane)

V_Zelle,gesRepresenting the total volume of the measured surface in cross section

V_Zelle,iRepresenting the volume of a single measuring plane in cross section

c_iIndicates the mass concentration of the substance in each unit

Means representing the mass concentration of the substance in the cross-section

The maximum achievable system variance is obtained as follows:

provision may be made for a portion of the exhaust gas stream to be used as inert gas.

Gaseous, liquid or solid fuels may be used.

In particular, it can be provided that the combustion air mixture flow is swirled before or in the second step. The turbulence can be so strong that an internal recirculation zone is formed in the region of the ignition and flame holding zone.

The invention further relates to a combustion device for carrying out the method according to the invention, comprising: a mixing chamber for mixing an inert gas with combustion air while forming a combustion air mixture flow, wherein a mixing device is associated with the mixing chamber, by means of which a mixing intensity of at least 0.5 of the inert gas and the combustion air can be achieved; with a precombustion chamber for mixing the combustion air mixture flow with the fuel flow in a swirling manner and for producing a flame holding and ignition zone, wherein the precombustion chamber is designed to produce an angle of from 35 ° to 90 ° between the combustion air mixture flow and the fuel flow and a flow of 15 ° between the combustion air mixture flow and the fuel flow when the exhaust gas flow is formed: 1 to 2: 1 pulse flow ratio; and with a heat discharge means for extracting a heat flow from the exhaust gas stream, wherein less than 30mgNO in the exhaust gas stream can be achieved with an oxygen content of 3 volume percent in the exhaust gas_x/m³Nitrogen oxide content of (a).

The pre-combustion chamber can be associated with a swirl generating device for swirling a combustion air mixture flow.

Drawings

List of reference numerals

2 mixing chamber

4 air for combustion

6 inert gas

10 precombustion chamber

12 fuel

14 ignition region

16 flame holding and ignition zone

18 heat discharging device

20 exhaust gas stream

22 heat flow.

Detailed Description

Fig. 1 shows a schematic view of a combustion device according to the invention, having: a mixing chamber 2 into which mixing chamber 2 combustion air 4 and inert gas 6 are introduced; a pre-combustion chamber 10 coupled to the mixing chamber 2, into which pre-combustion chamber 10 fuel 12 is introduced; an ignition region 14 in which a flame holding-and-ignition zone 16 is formed; and a heat discharge region 18, flowed through by an exhaust gas stream 20, that extracts a hot stream 22 from the exhaust gas stream 20.

The mixing chamber 2 is provided with a mixing device in which the combustion air 4 is mixed with the inert gas 6 with a mixing intensity of at least 0.5, wherein preferred values of the mixing intensity are at least 0.6, 0.7, 0.8 or 0.9. A combustion air mixture flow introduced into the combustion chamber 10 is generated in the mixing chamber 2. The combustion air mixture flow is mixed in the combustion chamber 10 with a high swirl with a fuel flow, wherein the directional vector of the fuel/combustion air mixture is at an angle of 35 ° to 90 °, in particular 45 ° to 75 °. The ratio of the fuel flow to the mixed combustion air flow is between 1: 2 and 1: 15 and preferably between 1: 4 and 1: 10, respectively.

In the ignition region 14, which is connected to the precombustion chamber 10, a flame holding and ignition zone 16 is formed, which is spatially separated from the hot discharge zone 18. The flame holding and ignition region 16 is substantially thermally insulated, i.e. no or virtually no outward heat conduction is achieved. This heat transfer is not achieved, preferably in combination, convectively and by radiation, until in the heat discharge zone 18, in which a certain heat flow 22 is extracted from the exhaust gas flow 20.

Claims

1. A method for combusting fuel (12) and combustion air (4) in a combustion device, wherein in a first step a mixing intensity of at least 0.5 is used in the formation of a combustion air mixture flowDegree (I)_M) Mixing an inert gas (6) with combustion air (4), in a second step, the combustion air mixture flow being mixed in a swirling manner with a fuel flow, wherein the combustion air mixture flow encloses an angle of from 35 ° to 90 ° with the fuel flow and the pulse flow of the combustion air mixture flow is at 15 ° with the pulse flow of the fuel flow: 1 to 2: 1, wherein in a third step the fuel stream is brought to combustion with the combustion air mixture stream with formation of an exhaust gas stream (20) in an adiabatic flame holding and ignition zone, wherein the residence time of the fuel in the flame holding and ignition zone (16) is not less than 0.01 seconds, wherein in a fourth step heat is extracted from the exhaust gas stream (20) in a heat discharge zone (18) locally separated from the flame holding and ignition zone (16), characterized in that an oxygen content of less than 30mgNO in the exhaust gas stream (20) is achieved with a volume percentage of 3% in the exhaust gas_x/m³Nitrogen oxide content of (a).

2. The method according to claim 1, characterized in that a part of the exhaust gas stream (20) is used as inert gas (6).

3. A method according to claim 1 or 2, characterized in that a gaseous, liquid or solid fuel is used.

4. Method according to any one of claims 1 to 2, characterized in that the combustion air mixture flow is swirled before or in the second step.

5. A combustion apparatus for performing the method according to any one of the preceding claims, the combustion apparatus having: mixing chamber (2) for mixing inert gas (6) with combustion air (4) while forming a mixed flow of combustion air, wherein a mixing device is associated with the mixing chamber (2) by means of which a mixing intensity of at least 0.5 of inert gas (6) and combustion air (4) can be achieved: (2)I_M) (ii) a A pre-combustion chamber (10) for swirling the combustion air mixture flow in combination with a fuel flow and for creating a flame holding and ignition zone (16), wherein the pre-combustion chamber (10) is set for creating an angle of 35 ° to 90 ° between the combustion air mixture flow and the fuel flow and for creating an angle of 15 ° between combustion air mixture flow and fuel flow: 1 to 2: 1 pulse flow ratio; and a heat discharge device for extracting a hot stream (22) from the exhaust gas stream (20), wherein less than 30mgNO in the exhaust gas stream (20) can be achieved with an oxygen content of 3 volume percent in the exhaust gas_x/m³Nitrogen oxide content of (a).

6. An arrangement according to claim 5, characterized in that a swirl-generating device for swirling the combustion air mixture flow is associated with the pre-combustion chamber (10).