Systems and procedures for controlling emissions

Abstract

Method for influencing combustion emission parameters associated with a combustion chamber (104) of a gas turbine (106), wherein the method comprises: Providing a probe (204) comprising a light source (114) and an optical detector (122) in a common housing (202), wherein the light source (114) comprises at least one laser, and wherein the probe (204) also comprises a reflector mirror (206) arranged at an end of the probe (204) opposite the housing (202), such that the probe (204) provides an optical path through an exhaust duct (110) of the gas turbine (106); Propagation of light along the optical path, wherein incident light (208) generated by the light source (114) propagates towards the end of the probe (204), is reflected there at the reflector mirror (206), and reflected light (210) returns to the housing (202) where it strikes the optical detector (122); Measuring the absorption of light inside the exhaust duct (110) caused by species of an exhaust gas (108); and Influence at least one of the combustion parameters at least partially on the basis of the measured absorption by species of the exhaust gas (108).

Description

AREA OF INVENTION

[0001] The invention relates generally to turbine emission control and in particular to systems and methods for controlling emissions. BACKGROUND TO THE INVENTION

[0002] Industrial gas turbines often require complex control systems to efficiently convert energy while minimizing pollutant emissions. Pollutants such as nitrogen oxides can be reduced by lowering the maximum gas temperature, which can be achieved by maintaining a lean fuel / air ratio in the combustion chamber. However, if the fuel / air mixture is too lean, incomplete combustion can produce excess carbon monoxide and unburned hydrocarbons. Operating with lean combustion also leads to other problems, such as unstable load transitions and combustion instabilities. Consequently, it is necessary to control the fuel / air mixture and the temperature in the reaction zone to support complete combustion.

[0003] Systems have been proposed for controlling the fuel / air mixture that measure a variety of combustion parameters and use these measurements as input signals for regulating / controlling the fuel system. For example, a conventional system includes a control system that uses fuel flow rates, pressure levels, and exhaust gas temperature distributions as input signals to actuate fuel limiting control valves.

[0004] Other techniques for controlling combustion dynamics involve measuring light emission from the combustion chamber flame and using the measured signal to control certain combustion parameters. For example, a conventional system uses a closed-loop control system that employs a silicon carbide photodiode to detect the combustion flame temperature by measuring UV radiation intensity. The UV radiation reading is used to control the fuel / air ratio of the fuel mixture to keep the flame temperature below a predetermined level, which corresponds to a desired low level of nitrogen oxides.

[0005] Other conventional systems can use optical fibers. Still other conventional systems can use a video camera to capture images of the flame, primarily for monitoring its presence or absence.

[0006] It has been proposed to use mass flow measurement techniques in turbines. For example, laser-based Doppler displacement measurement systems can be used to determine airflow in a turbine's air intake duct, and similar systems have been proposed to determine static temperature by comparing the absorption properties of two light generators (lasers) operating at different frequencies. There is still a need for improved systems and methods for controlling emissions.

[0007] DE 199 44 006 A1 describes a method for analyzing and monitoring exhaust gas parameters in an aircraft engine. Spectrometers can be used for this purpose. Laser light is directed through the engine's exhaust duct downstream of the turbine and received by a detector on the side of the exhaust duct opposite the laser emitter. A spectral analysis of the laser light can then be performed. However, this requires very precise alignment of the laser emitter and the detector along a common optical axis.

[0008] US Patent 7,414,726 B1 discloses a system and a method for determining oxygen concentrations in exhaust gases from stationary installations. Here, too, a laser beam is emitted by an emitter and received by a unit aligned along the optical axis, which is also configured to analyze the received light. For example, the CO content in the exhaust gas can be determined between the laser emitter and the detector.

[0009] An exhaust gas control system for a gas turbine is described in US 2004 / 0255595A1. The aim is to minimize the proportion of nitrogen oxides (NOx) in the exhaust gas. To improve NOx reduction, the exhaust gas is controlled to a target temperature depending on external parameters, including relative humidity, compressor inlet pressure drop, and turbine exhaust back pressure.

[0010] From WO 2011 / 018 115 A1, a gas turbine is known in which gas components of a gas stream in an exhaust duct are determined by means of an optical measuring device, and the gas turbine is controlled based on this determination. The measuring device has a light source and a light receiver, which can be arranged in a common housing of a probe. In one embodiment, the probe can have a reflector that is arranged opposite the light source and the light receiver on the opposite side of the exhaust duct.

[0011] A method and apparatus for monitoring a combustion process are described in WO 2008 / 015 292 A1. For this purpose, a measuring device is provided in which a light beam is emitted along an optical path and received again at the end of the optical path. In one embodiment, a laser light source can emit laser light, which is reflected by a reflector and the reflected light is then received by a photodetector. BRIEF SUMMARY OF THE INVENTION

[0012] Some or all of the aforementioned needs can be addressed by specific embodiments of the invention. Specific embodiments of the invention may include systems and methods for controlling emissions.

[0013] According to one embodiment of the invention, a method for regulating / controlling combustion emission parameters associated with a combustion chamber of a gas turbine is provided. The method can include the steps of: providing an optical path through an exhaust duct; propagating light along the optical path; measuring the absorption of light caused by exhaust gas species inside the exhaust duct; and influencing at least one of the combustion parameters, at least partially, based on the measured absorption.

[0014] According to a further embodiment, a system for influencing combustion emission parameters associated with a combustion chamber of a gas turbine is provided. The system can include: one or more optical detectors connected to an optical path leading through the exhaust duct; one or more light sources that can be actuated to propagate light along the optical path to the one or more optical detectors; and a control device that can be actuated to control at least one of the combustion emission parameters, at least partially, based on one or more signals.

[0015] According to a further embodiment, a gas turbine is provided. The gas turbine can have: a combustion chamber; an exhaust duct; an optical path leading through the exhaust duct; one or more optical detectors connected to the optical path; and one or more light sources configured to propagate light along the optical path to the one or more optical detectors.

[0016] Further embodiments and aspects of the invention are explained in detail herein and are considered to be part of the present invention. These further embodiments and aspects will become clear with reference to the following detailed description, the accompanying drawings, and the accompanying claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The attached tables and drawings, which are not necessarily drawn to scale, will now be discussed:

[0018] Table 1 lists exemplary detectable exhaust gas species and light absorption wavelengths according to embodiments of the invention. Fig. Figure 1 shows a diagram of an optical scanning system for illustrative purposes, which is connected to the exhaust duct, according to an embodiment of the invention. Fig. Figure 2 shows a diagram of an optical probe used for illustration purposes according to an embodiment of the invention. Fig. Figure 3 shows a flowchart for an exemplary process according to an embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] Exemplary embodiments of the invention are described in more detail below with reference to the accompanying drawings, which illustrate exemplary embodiments of the invention. However, the invention can be implemented in numerous ways and should not be considered limited to the exemplary embodiments presented here; rather, these exemplary embodiments are presented to make this description thorough and complete, and to fully explain the scope of protection of the invention to those skilled in the art. Recurring reference numerals denote identical elements throughout.

[0020] Specific embodiments of the invention enable the measurement of combustion emission parameters in the exhaust duct of a combustion chamber by testing or scanning the exhaust duct with light to detect the temporal and / or spectral attenuation of the light after it has passed through the regions of interest. According to these embodiments, the measured combustion parameters can then be used to control various combustion chamber parameters, including, but not limited to, fuel feed rates, fuel / air ratios, combustion chamber equilibrium, and fuel feed distributions, in order to optimize operating parameters such as, but not limited to, nitrogen oxide emissions, dynamic pressure fluctuations, and fuel utilization rates.

[0021] According to certain embodiments of the invention, specific emission species in the exhaust duct or exhaust shaft of the combustion chamber can be monitored by utilizing the principle of light absorption. In one embodiment, light directed through an exhaust duct can be measured to determine the presence and concentration of exhaust species by means of the spectral and / or temporal attenuation of the light. According to embodiments of the invention, the light used to measure the exhaust species can have mean IR (infrared) wavelengths in the range of 3.5 to 24 µm. According to further embodiments of the invention, the light used to measure the exhaust species can have additional wavelengths in the range of 1.0 to 3.5 µm and 24 to 500 µm.According to exemplary embodiments, spectrally resolved light absorption can be used to identify chemical substances, for example, but not limited to, NO, NO2, CO, CO2, SO2, and H2O. The measured signals can be correlated with the fuel / air ratio, fuel flow distribution, airflow velocity, water injection rate, heat release rate, combustion chamber equilibrium, temperature, etc.

[0022] Furthermore, the absorption signals can be used as feedback in a combustion control system. Table 1 below lists some of the exemplary detectable exhaust gas species and their corresponding absorption wavelengths at ambient temperature. Table 1. Detectable exhaust gas species Wavelength (microns) Wave number (cm) -1 ) CO2 4,42 2262 CO2, N2O 4,48 2232 CO2, CO 4,86 2058 CO2, CO 4,87 2053 NO, H2O 5,25 1905 NO 5,45 1835 NO2 6,13 1631 NO2, NH3 6,29 1590 SO2, H2S, CH4 7,43 1346 N2O, CH4, H2S 7,62 1312 H2O, CH4, N2O, C2H2, H2S 7,85 1274 H2O, CH4, N2O, C2H2, H2S 7,87 1271 NH3 10,09 991

[0023] Various options and designs of sensors for applications for regulating / controlling combustion according to exemplary embodiments of the invention are now described with reference to the attached figures.

[0024] Fig.Figure 1 illustrates an exemplary emission control system 100 according to embodiments of the invention, which serves to detect and control emission parameters associated with the various components of a gas turbine 102, 104, 106. According to certain embodiments of the invention, a combustion chamber 104 can take in air 128 via a compressor 102. The combustion chamber 104 can also take in fuel 126 and can combine and ignite the air 128 and the fuel 126 in the combustion chamber 104 to produce flames and a high-pressure area that can be used to rotate a gas turbine 106. Emissions or exhaust gases 108 leaving the gas turbine 106 can be branched via an exhaust duct 110 to an exhaust stack 112.

[0025] According to exemplary embodiments of the invention, one or more light sources 114 and one or more components of detectors 122 can be arranged or mounted near the exhaust duct 110. In one exemplary embodiment, light originating from the light source 114 can pass through an optically transparent input channel 116 and interact with the exhaust gas 108 in the exhaust duct 110. The light 118 interacting with the exhaust gas can exit the exhaust duct 110 via an optically transparent output channel 120. The portion of the light 118 that interacts with the exhaust gas 108 can undergo spectral attenuation due to wavelength-specific absorption of the light 118 by emission species present in the exhaust gas 108.The light exiting the exhaust duct 110 can be directed onto an optical detector 122, and the resulting detector signal 123 can be used by a control device 124 to regulate / control fuel 126, air 128, combustion chamber equilibrium and / or any number of variables associated with the gas turbine 106.

[0026] Fig. Figure 1 illustrates two exemplary arrangements and embodiments of the optical sensing system, which includes the light source 114, the input channel 116, the output channel 120, and the optical detector 122. One embodiment illustrates the sensing system arranged in the region of the exhaust duct 110, and another embodiment illustrates the sensing system arranged in the region of the exhaust shaft 112. According to specific embodiments of the invention, one or more such systems can be arranged at any suitable location in the combustion chamber exhaust system.

[0027] According to one embodiment of the invention, a light source 114 can generate light to monitor the outlet. The generated light can pass through an inner region of the exhaust duct 110 via a number of associated optical components. According to one embodiment, the light generated by the light source 114 can be coupled into a waveguide, for example, an optical fiber, to facilitate branching to a suitable inlet area on the exhaust duct 110. According to one embodiment, the light exiting the waveguide or optical fiber can be scattered and produce a diverging optical beam, which can be collimated by a lens or a concave mirror to generate a collimated optical beam.According to a further embodiment, the light generated by the light source (especially if it has already been collimated by the light source) can propagate through free space and reach the inlet channel 116 directly or via reflector mirrors or intermediate optical elements. The inlet channel 116 and an outlet channel 120 can be formed within the body of the exhaust duct 110 to allow the optical energy to traverse at least a portion of the exhaust duct 110 and interact with the exhaust gas 108. The inlet channel 116 and the outlet channel 120 can be made of an optically transparent material resistant to high temperatures, for example, quartz, sapphire, or other suitable materials that cause low loss and have a suitable transmission bandwidth for the wavelengths of interest.

[0028] According to embodiments of the invention, two or more optical channels 116, 120 can be positioned at various locations on the exhaust duct 110 or exhaust shaft 112 in order to detect emission species at different points along the exhaust path. According to embodiments, the portion of the light 118 propagating in the exhaust duct 110 can interact with emission species and, due to the interaction with the species averaged over the path, can undergo a wavelength-specific spectral attenuation that can correlate with the concentration of the specific emission species present in the exhaust gas 108.

[0029] According to one embodiment of the invention, the spectrally attenuated light exiting the exhaust duct 110 through the outlet duct 120 can pass through a lens or a concave mirror to produce a converging optical beam for detection by one or more detectors 122. According to embodiments of the invention, the optical detector(s) 122 can be selected with a view to a response within certain wavelength spectral windows of interest. For example, a silicon (Si) photodetector can be used to monitor the emission from chemical substances in the spectral range from about 0.4 µm to about 1.0 µm. According to another embodiment, indium gallium arsenide (InGaAs) photodiodes can be selected with a view to measuring infrared wavelengths in the spectral range from about 1.0 µm to about 1.7 µm.Detector systems using indium gallium arsenide / aluminium indium arsenide (InGaAs / AlInAs) or gallium arsenide / aluminium gallium arsenide (GaAs / AlGaAs) materials can be used to detect wavelengths in the spectral range of approximately 3.5 to 24 µm. The optical signals detected by the detectors 122 can be converted by the detectors 122 into electronic detector signals 123, which can be further processed (filtered, amplified, etc.) by the control unit 124. The detector signals 123 can be used by the control unit 124 to dynamically adjust combustion chamber parameters (air / fuel ratios, fuel distribution, mass flow rate, acoustic impedance of fuel nozzles, airflow distribution, etc.) in order to optimize the combustion and emission parameters associated with the combustion chamber 104.

[0030] According to certain embodiments, the light source 114 can contain one or more QC (quantum cascade) lasers. The QC lasers can be wavelength-invariant or tunable. For absorption measurements of the exhaust gas 108 over a specific wavelength spectrum, the QC lasers can produce an output with tunable or chirped wavelengths. According to further embodiments, the light source 114 can contain one or more vertical resonator lasers. The vertical resonator lasers can be wavelength-invariant or tunable and can monitor specific wavelengths, or they can have an output with tunable wavelengths for absorption measurements over a wavelength spectrum.According to yet another embodiment, the light source(s) 114 can contain one or more interband cascade lasers, which may be fixed or tunable with respect to their wavelength. In another embodiment, the light source 114 can contain multiple lasers or lasers having multiple spectral lines. In yet another embodiment, the light source 114 can contain a tunable laser diode. According to a further embodiment, the light source 114 can contain a broadband light source, for example, an amplified stimulated emission (ASE) source, a supercontinuum source, or a superluminescent light-emitting diode (SLED).

[0031] The details of the design of the measuring system for querying the emission species of the exhaust gas 108 can depend on the chemical substances of interest and can range in complexity from a light source 114 as a single-line laser light source having a single detector 122, to a tunable laser or an ASE source. Additional optical components can be used to enable resolution and measurement of spectral ranges. According to certain embodiments, and as mentioned above, a (narrowband) laser with a single wavelength or a laser diode can be used as the light source 114. The narrowband emission emitted by the laser can be matched with an absorption band of a chemical emission species of interest.For example, the emitted laser wavelength can be matched to specific emission species and detectable absorption wavelengths, examples of which are shown in Table 1. By matching the wavelength of the light source 114 to one or more of these absorption wavelengths and by selecting a suitable optical detector 122, the ratio of input to output optical energy can be measured and correlated with the relative concentration of the emission species of interest. According to a further embodiment of the invention, the light source 114 can produce an output with a tunable or chirped wavelength and can enable the measurement of exhaust gas absorption curves over a spectrum of wavelengths.

[0032] According to one embodiment, several laser light sources, e.g. 114, and several corresponding detectors, e.g. 122, can be used to measure several combustion species simultaneously or to detect a single combustion species. In one embodiment, one or more light sources, e.g. 114, can be coupled into one or more input channels 116, can use colinear (or approximately parallel) but spatially separated optical paths, can exit a common output channel 120, and can be detected by corresponding optical detectors 122 thanks to the optical path separation or coupling angle. In another embodiment, the multiple light sources can follow individual paths and can use specified optics (lenses, mirrors, input and output channels, detectors, etc.).

[0033] The resulting detected detector signals 123 can represent an absorption spectrum of emission species in the exhaust duct 110. The measured absorption spectra can then be related to the relative concentrations of the emission species of interest and can be used to regulate / control the parameters of the combustion chamber 104, e.g., the mixtures of fuel 126 and air 128 and / or flow rates. According to a further embodiment, filtering the light (performed before it reaches the detector) can simplify the arrangement of the detector 122 and can serve to eliminate crosstalk (due to scattering, etc.) from multiple light sources 114. Arranging a filter above the detector 122 can also reduce unwanted scattered or ambient light. According to further embodiments of the invention, many combinations and variations of the above-mentioned embodiments can be used.

[0034] Fig. Figure 1 shows a block representing the control unit 124, which may contain the detector electronics and the combustion control system. According to one embodiment, the detector electronics arranged in the control unit 124 can condition, amplify, filter, and process the detector signals 123 originating from the optical detector(s) 122. The resulting signals can be used via the control unit 124 as a control signal for the combustion control system. For example, the measured concentration of NO₂ or the measured ratio of NOₓ can be used. xAccording to one embodiment of the invention, the H2O can be used as feedback in the control unit 124 and can provide control to regulate the fuel / air ratio or the flow rate. According to one embodiment of the invention, the control unit 124 can utilize an adaptive algorithm and an associated model that can be tuned by the detector signals 123 generated by the optical detector(s) 122. The adaptive algorithm can use detector signals 123 to control emission control parameters in order to adjust the model calculations on a semi-continuous basis.

[0035] Fig.Figure 2 illustrates an exemplary optical probe 204 according to an embodiment of the invention. In this embodiment, the inlet channel 116 and the outlet channel 120 can be the same physical channel and can be based on a single opening in the side wall of the exhaust duct 110 to allow insertion of the probe into the exhaust duct 110 to measure the flow of the exhaust gas 108. According to a certain embodiment, the light source 114 and the detector 122 can be mounted on the same side as the duct, or, as in Fig.As shown in Figure 2, the optical system is housed in a common casing 202. The incident light 208 generated by the light source 114 can travel towards the end of the probe 204 and can be reflected by a reflector mirror 206. The reflected light 210 can then return to the casing 202, where it can strike a detector 122. In this embodiment, the probe 204 can have an opening to allow the exhaust gas 108 to interact with the incident light 208 and the reflected light 210. This embodiment can minimize, in whole or in part, the need for a separate detector 122 on the opposite side of the exhaust duct 110, and it can also minimize, in whole or in part, the need for alignment, since the optical system, comprising the light source 114, the mirror 206, and the detector 122, can be pre-adjusted before installation in the probe 204.In another specific embodiment, a detector 122 can be mounted near the end of the probe 204 instead of the mirror 206. Incident light 208 generated by the light source 114 can move towards the end of the probe 204 while interacting with the exhaust gas 108, and can then strike the detector 122 at the end of the probe.

[0036] An exemplary method 300 for measuring exhaust emission species and for regulating / controlling a combustion characteristic based on the measured values ​​is now described with reference to the flowchart of Fig.3 described. The method begins in block 302. In block 304, and according to an embodiment of the invention, a light source 114 can be provided. At least one optical path can be formed in the body of the exhaust duct 110 or the exhaust shaft 112 adjacent to an area of ​​interest in order to allow light 118 emanating from the light source 114 to pass through and interact with the exhaust gas 108 in order to monitor the emission species present in the exhaust gas 108 by means of optical absorption.

[0037] In the optional block 306, and according to one embodiment, a collimator may be provided adjacent to the input channel 116, if necessary, to correct any beam scattering of the light originating from the light source 114 and to collimate the beam 118. Adjacent to the output channel 120 (which may physically coincide with the input channel 116), a focusing device may be provided to concentrate the modified light after its interaction with exhaust gas 108 in the exhaust duct 110 or exhaust shaft 112. According to embodiments, the focusing device may be a lens or a concave mirror. Block 308 may include a termination photodetector 122, which is arranged adjacent to the output channel 120 and may be capable of receiving the modified light after its interaction with exhaust gas 108 in the exhaust duct 110 or exhaust shaft 112.

[0038] In block 310, and according to one embodiment, an absorption signal can be obtained by directing light through the optical path in the exhaust duct 110 or exhaust shaft 112 and by measuring the absorption signal, which varies depending on the wavelength and / or time, at one or more optical detectors 122 designed as end-of-line photodetectors. In block 312, the measurement signal, and specifically the absorption signal, can be used to extract data dependent on the absorption spectrum and / or time-varying from the measured exhaust gas 108. In block 314, the extracted measurement data dependent on the absorption spectrum and / or time-varying can be used to regulate / control and optimize the combustion characteristics of the combustion chamber 104 by means of the control unit 124.The extracted emission parameters can be used in a feedback control loop to adjust the fuel / air ratio, flow rates, fuel distribution to the burners, etc. Procedure 300 ends in Block 316.

[0039] Many modifications and further embodiments of the invention will occur to a person skilled in the art after the advantages of the teaching have been explained in the preceding descriptions and with reference to the accompanying drawings. Accordingly, it is self-evident that the invention is not intended to be limited to the specific embodiments described, and that modifications and further embodiments are intended to be covered by the scope of protection of the appended claims. Although specific terms are used herein, they are used only in a general and descriptive sense and not for the purpose of limitation.

[0040] Specific embodiments of the invention may include systems and methods for controlling combustion emission parameters associated with a combustion chamber 104 of a gas turbine. The method may include the steps of: providing an optical path leading through an exhaust gas duct 110 of a gas turbine 106; propagating light along the optical path; measuring the absorption of the light by species of an exhaust gas 108 inside the exhaust gas duct 110 of the gas turbine 106; and controlling at least one of the combustion parameters, at least partially, based on the measured absorption by species of the exhaust gas 108. REFERENCE MARK LIST 100 Emission control system 102 compressors 104 Combustion chamber 106 Gas turbine 108 Exhaust gas 110 Exhaust duct 112 Exhaust shaft 114 light source(s) 116 Input channel 118 Part of the light that interacts with the exhaust gas 120 output channels 122 optical detector(s) 123 Detector signal 124 Control unit 126 Fuel 128 air 202 cases 204 Optical probe 206 mirrors 208 Incident light 210 Reflected light

Claims

[1] Method for influencing combustion emission parameters associated with a combustion chamber (104) of a gas turbine (106), the method comprising: Providing a probe (204) comprising a light source (114) and an optical detector (122) in a common housing (202), wherein the light source (114) comprises at least one laser, and wherein the probe (204) also comprises a reflector mirror (206) arranged at an end of the probe (204) opposite the housing (202), such that the probe (204) provides an optical path through an exhaust duct (110) of the gas turbine (106); Propagation of light along the optical path, wherein incident light (208) generated by the light source (114) propagates towards the end of the probe (204), is reflected there at the reflector mirror (206), and reflected light (210) returns to the housing (202) where it strikes the optical detector (122); Measuring the absorption of light inside the exhaust duct (110) caused by species of an exhaust gas (108); and Influence at least one of the combustion parameters at least partially on the basis of the measured absorption by species of the exhaust gas (108). [2] Method according to claim 1, wherein the at least one laser of the light source (114) is a quantum cascade laser. [3] Method according to claim 2, wherein the step of propagating light along the optical path includes providing one or more quantum cascade lasers for each measured species of the exhaust gas (108). [4] Method according to claim 1, wherein the step of propagating light along the optical path includes propagating narrowband optical radiation to measure absorption by species of the exhaust gas (108). [5] Method according to claim 1, wherein the step of propagating light along the optical path includes propagating light (118) in a wavelength range between about 3.5 µm and about 24 µm to measure absorption in the mid-infrared range of the exhaust gas species (108). [6] Method according to claim 1, wherein the combustion parameters include at least one of the following parameters: fuel feed rate, fuel feed distribution, air flow velocity, water injection rate, combustion chamber equilibrium, or air / fuel ratio. [7] System for influencing combustion emission parameters associated with a combustion chamber (104) of a gas turbine (106), wherein the system comprises: a probe (204) comprising a light source (114) and an optical detector (122) in a common housing (202), wherein the light source (114) comprises at least one laser, and wherein the probe (204) further comprises a reflector mirror (206) arranged at an end of the probe (204) opposite the housing (202), such that the probe (204) provides an optical path through the exhaust duct (110), such that incident light (208) generated by the light source (114) propagates towards the end of the probe (204), is reflected at the reflector mirror (206), and reflected light (210) returns to the housing (202) where it is incident on the optical detector (122); and a control device (124) which serves to control at least one of the combustion emission parameters at least partially on the basis of one or more detector signals (123) from the one or more optical detectors (122). [8] System according to claim 7, wherein the one or more light sources (114) are based on a narrowband optical radiation source to measure the absorption by species of the exhaust gas (108). [9] System according to claim 7, wherein the at least one laser of the light source (114) is a quantum cascade laser, a vertical resonator laser, an interband cascade laser and / or a tunable diode laser. [10] System according to claim 7, wherein at least one light source (114) is provided for each measured species of exhaust gas (108). [11] System according to claim 7, wherein the one or more light sources (114) produce light in a wavelength range between about 3.5 µm and about 24 µm in order to measure absorption of the exhaust gas species (108) in the mid-infrared range. [12] System according to claim 7, wherein the one or more detector signals (123) from the one or more optical detectors (122) include at least one absorption signal of a species of the exhaust gas (108). [13] Gas turbine (106), which includes: a combustion chamber (104); an exhaust duct (110); a probe (204) comprising a light source (114) and an optical detector (122) in a common housing (202), wherein the light source (114) comprises at least one laser, and wherein the probe (204) also comprises a reflector mirror (206) arranged at an end of the probe (204) opposite the housing (202), such that the probe (204) provides an optical path through the exhaust duct (110), such that incident light (208) generated by the light source (114) propagates towards the end of the probe (204), is reflected at the reflector mirror (206), and reflected light (210) returns to the housing (202) where it is incident on the optical detector (122). [14] Gas turbine (106) according to claim 13, which further comprises at least one control device (124) which serves to control one or more combustion emission parameters at least partially on the basis of one or more detector signals (123) from the one or more optical detectors (122). [15] Gas turbine (106) according to claim 14, wherein the one or more detector signals (123) from the one or more optical detectors (122) include at least one absorption signal of a species of the exhaust gas (108). [16] Gas turbine (106) according to claim 13, wherein the at least one laser of the light source (114) is a quantum cascade laser, a vertical resonator laser, an interband cascade laser or a tunable diode laser. [17] Gas turbine (106) according to claim 13, wherein at least one light source (114) is provided for each measured species of exhaust gas (108). [18] Gas turbine (106) according to claim 13, wherein the one or more light sources (114) are configured to produce light in a wavelength range of about 3.5 µm to about 24 µm in order to measure absorption in the mid-infrared range of the species of the exhaust gas (108).

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