# US 2019/0317067 A1 · Gas Analyzer and Method for Measuring Nitrogen Oxides in an Exhaust Gas > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0317067 A1 - Document ID: US20190317067A1 - Status: Published application - Kind: A1 - Application number: 16/383,034 - Filed: 2019-04-12 - Published: 2019-10-17 - Earliest claimed: 2018-04-13 - Assignees: Siemens Aktiengesellschaft - Applicants: Siemens Aktiengesellschaft - Inventors: Camiel HEFFELS; Daniel ROßFELD - Web page: https://patentgrep.com/patent/US20190317067A1 ## CPC - G01N 21/33: using ultraviolet light (G01N21/39 takes precedence) - G01N 33/0037: {NOx} - F01N 11/00: Monitoring or diagnostic devices for exhaust-gas treatment apparatus - G01N 21/3151: {using two sources of radiation of different wavelengths (G01N21/33 - G01N21/39 take precedence)} - G01N 31/005: {investigating the presence of an element by oxidation (G01N31/12 takes precedence)} - G01N 33/0009: {General constructional details of gas analysers, e.g. portable test equipment (devices for withdrawing samples in the gaseous state G01N1/22)} - G01N 33/0013: {by a chemical reaction (a chemical reaction taking place or a gas being eliminated in one or more analysing channels G01N33/0024)} - B01D 53/30: Controlling by gas-analysis apparatus (regulating non electrical variables in general G05D) - B01D 53/56: Nitrogen oxides (B01D53/60 takes precedence) - B01D 2251/104: Ozone - F01N 2560/026: for measuring or detecting NOx - F01N 2560/12: Other sensor principles, e.g. using electro conductivity of substrate or radio frequency - G01N 2201/062: LED's - Y02A 50/20: Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters - Y02T 10/40: Engine management systems - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) - F01N: GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES (arrangements in connection with gas exhaust of propulsion units in vehicles B60K13/00; combustion-air intake silencers specially adapted for, or arranged on, internal-combustion engines F02M35/00; protecting against, or damping, noise in general G10K11/16) - B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28) - Y02A: TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE - Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION ## Abstract Gas analyzer and method for measuring nitrogen oxides in an exhaust gas, wherein to measure the nitrogen oxides, ozone is generated from oxygen, the exhaust gas is treated with the ozone generated to convert nitrogen monoxide within the exhaust gas into nitrogen dioxide, the nitrogen dioxide concentration in the treated exhaust gas is measured photometrically using a first light-emitting diode which emits with a central wavelength between 350 nm and 500 nm and output as the nitrogen oxide concentration in the exhaust gas, and the ozone concentration in the treated exhaust gas is measured photometrically using a second light-emitting diode which emits with a central wavelength between 250 nm and 265 nm, where generation of the ozone using the measured ozone concentration as an actual value is regulated to a prespecified setpoint value to enable reliable continuous measurement of nitrogen oxides in exhaust gases with a low outlay on equipment. ## Claims ### Claim 1 A gas analyzer for measuring nitrogen oxides in an exhaust gas comprising: an oxidation device comprising an ozone generator for generating ozone from oxygen and configured to treat the exhaust gas with the ozone to convert nitrogen monoxide within the exhaust gas into nitrogen dioxide; a first light-emitting diode which emits with a central wavelength of between 350 nm and 500 nm; a second light-emitting diode which emits with a central wavelength of between 250 nm and 265 nm; a measuring chamber through which the treated exhaust gas flows and light from the first light-emitting diode and light from the second light-emitting diode pass; a detector which detects the light from the first light-emitting diode and the light from the second light-emitting diode after said light passes through the measuring chamber and which generates a detector signal with a first signal component resulting from the light from the first light-emitting diode and a second signal component resulting from the light from the second light-emitting diode; an evaluation device which ascertains nitrogen dioxide concentration in the treated exhaust gas in the measuring chamber from the first signal component and outputs said concentration as the nitrogen oxide concentration in the exhaust gas and ascertains ozone concentration in the exhaust gas in the measuring chamber from the second signal component; and a regulating device which controls the ozone generator and obtains the ascertained ozone concentration as an actual value to regulate said concentration to a pre-specified setpoint value. ### Claim 2 (depends on 2) The gas analyzer as claimed in claim 2, further comprising: a beam splitter which diverts a part of the lights from the first and second light-emitting diodes to a reference detector; wherein that the reference detector generates a reference signal with first and second reference-signal components resulting from the light from the first and second light-emitting diode; and wherein the evaluation device references the signal components of the detector signal with the associated reference-signal components. ### Claim 3 (depends on 1) The gas analyzer as claimed in claim 1, wherein the ozone generator comprises an ultraviolet light source. ### Claim 4 (depends on 2) The gas analyzer as claimed in claim 2, wherein the ozone generator comprises an ultraviolet light source. ### Claim 5 (depends on 3) The gas analyzer as claimed in claim 3, wherein the ultraviolet light source comprises at least one xenon excimer emitter. ### Claim 6 (depends on 3) The gas analyzer as claimed in claim 3, wherein the ultraviolet light source is arranged in a closed reaction chamber through which the exhaust gas flows and which is configured to generate the ozone from a residual oxygen content of the exhaust gas. ### Claim 7 (depends on 5) The gas analyzer as claimed in claim 5, wherein the ultraviolet light source is arranged in a closed reaction chamber through which the exhaust gas flows and which is configured to generate the ozone from a residual oxygen content of the exhaust gas. ### Claim 8 (depends on 1) The gas analyzer as claimed in claim 1, further comprising: a third light-emitting diode which emits with a central wavelength of between 250 nm and 300 nm, light emitted by the third light-emitting diode also passing through the measuring chamber and subsequently being detected by the detector such that the detector signal contains a third signal component resulting from the light from the third light-emitting diode; and wherein the evaluation device ascertains a sulfur dioxide concentration in the exhaust gas in the measuring chamber from the third signal component. ### Claim 9 (depends on 8) The gas analyzer as claimed in claim 8, further comprising: a beam splitter which diverts a part of the lights from the first and second light-emitting diodes to a reference detector; wherein that the reference detector generates a reference signal with first and second reference-signal components resulting from the light from the first and second light-emitting diode; wherein the evaluation device references the signal components of the detector signal with the associated reference-signal components; and wherein the beam splitter diverts a part of the light from the third light-emitting diode to the reference detector such that the reference signal contains a third reference-signal component resulting from the light from the third light-emitting diode and such that the evaluation device references the third signal component of the detector signal with the third reference-signal component. ### Claim 10 (depends on 1) The gas analyzer as claimed in claim 1, further comprising: a third light-emitting diode which emits with a central wavelength of between 250 nm and 300 nm; a fourth light-emitting diode which emits with a central wavelength of between 350 nm and 500 nm with the same central wavelength as the first light-emitting diode; a further measuring chamber through which the untreated exhaust gas flows and the light from the third and fourth light-emitting diode passes; a further detector which detects the light from the third and fourth light-emitting diode after said light has passed through the further measuring chamber and which generates a further detector signal with a third signal component resulting from the light from the third light-emitting diode and a fourth signal component resulting from the light from the fourth light-emitting diode; a further evaluation device which ascertains a sulfur dioxide concentration in the untreated exhaust gas in the further measuring chamber from the third signal component and nitrogen dioxide concentration from the fourth signal component; and a device which outputs a difference between the nitrogen dioxide concentrations ascertained by the two evaluation devices as the nitrogen monoxide concentration in the exhaust gas. ### Claim 11 (depends on 10) The gas analyzer as claimed in claim 10, further comprising: a further beam splitter which diverts a part of the light from the third and fourth light-emitting diode to a further reference detector, wherein the further reference detector generates a further reference signal with third and fourth reference-signal components resulting from the light from the third and fourth light-emitting diode; and wherein the further evaluation device references the third and fourth signal components of the further detector signal with associated reference-signal components. ### Claim 12 (depends on 1) The gas analyzer as claimed in claim 1, further comprising: a third light-emitting diode which emits with a central wavelength of between 250 nm and 300 nm; a further measuring chamber through which the untreated exhaust gas flows and the light from the third light-emitting diode passes; a beam-splitter arrangement which conducts a part of the light from the first light-emitting diode through the further measuring chamber; a further detector which detects the light from the first and third light-emitting diodes after said light has passed through the further measuring chamber and which generates a further detector signal with a third signal component resulting from the light from the third light-emitting diode and a fourth signal component resulting from the light from the first light-emitting diode; wherein the evaluation device further ascertains a sulfur dioxide concentration in the untreated exhaust gas in the further measuring chamber from the third signal component and the nitrogen dioxide concentration from the fourth signal component and outputs a difference between the nitrogen dioxide concentrations ascertained from the first and fourth signal components as the nitrogen monoxide concentration in the exhaust gas. ### Claim 13 (depends on 12) The gas analyzer as claimed in claim 12, wherein the beam-splitter arrangement is configured to divert a part of the lights from the first, second and third light-emitting diodes to a reference detector which generates a reference signal with reference-signal components resulting from the light from the light-emitting diodes; and wherein the evaluation device references the signal components of the detector signals with the associated reference-signal components. ### Claim 14 A method for measuring nitrogen oxides in an exhaust gas, the method comprising: generating ozone is generated from oxygen; treating the exhaust gas with the generated ozone to convert nitrogen monoxide within the exhaust gas into nitrogen dioxide; measuring the nitrogen dioxide concentration in the treated exhaust gas photometrically via a first light-emitting diode which emits with a central wavelength of between 350 nm and 500 nm and outputting the measured concentration as the nitrogen oxide concentration in the exhaust gas; measuring the ozone concentration in the treated exhaust gas photometrically via a second light-emitting diode which emits with a central wavelength of between 250 nm and 265 nm; and regulating the generation of the ozone via the measured ozone concentration as an actual value to a prespecified setpoint value. ### Claim 15 (depends on 14) The method as claimed in claim 14, wherein a sulfur dioxide concentration in the treated or untreated exhaust gas is measured photometrically via a third light-emitting diode which emits with a central wavelength of between 250 nm and 300 nm. ### Claim 16 (depends on 14) The method as claimed in claim 14, wherein the nitrogen dioxide concentration in the untreated exhaust gas is measured photometrically via a fourth light-emitting diode which emits with a central wavelength of between 350 nm and 500 nm with the same central wavelength as the first light-emitting diode and the nitrogen monoxide concentration in the exhaust gas is ascertained from a difference between the nitrogen dioxide concentrations ascertained in the treated exhaust gas and in the untreated exhaust gas. ### Claim 17 (depends on 15) The method as claimed in claim 15, wherein the nitrogen dioxide concentration in the untreated exhaust gas is measured photometrically via a fourth light-emitting diode which emits with a central wavelength of between 350 nm and 500 nm with the same central wavelength as the first light-emitting diode and the nitrogen monoxide concentration in the exhaust gas is ascertained from a difference between the nitrogen dioxide concentrations ascertained in the treated exhaust gas and in the untreated exhaust gas.