Method for determining rate of formation of nitrogen oxides during combustion of ammonia-hydrogen mixture in bunsen burner

Abstract

FIELD: fuel industry.SUBSTANCE: invention relates to the field of experimental studies of combustion processes of gaseous fuels and can be used to determine the kinetic characteristics of the formation of nitrogen oxides during the combustion of ammonia-hydrogen mixtures, including in the development and verification of mathematical models of chemical combustion kinetics, as well as in the energy and chemical industries. The invention presents a method for determining the rate of formation of nitrogen oxides during combustion of an ammonia-hydrogen mixture, including the formation of a combustible mixture of ammonia, hydrogen and air, feeding said mixture into a burner device with the formation of a stabilized flame, sampling combustion products and measuring the concentration of nitrogen oxides, in which the formation of a flame is carried out in a quartz tube with a laminar flow regime, the combustion products are sampled spatially locally along the axis and along the radius of the flame, the concentration of nitrogen oxides is measured by a gas analyser, the measuring element of which is insensitive to the presence of ammonia, and the rate of formation of nitrogen oxides is determined by the change in the concentration of nitrogen oxides along the length of the flame at a given flow rate of the ammonia-hydrogen mixture.EFFECT: ability to determine the rate of formation of nitrogen oxides by the length and radius of the flame of an ammonia-hydrogen mixture under controlled combustion conditions.4 cl, 1 dwg

Description

[0001] The invention relates to the field of experimental studies of combustion processes of gaseous fuels and can be used to determine the kinetic characteristics of the formation of nitrogen oxides during the combustion of ammonia-hydrogen mixtures, including in the development and verification of mathematical models of chemical combustion kinetics, as well as in the energy and chemical industries.

[0002] Methods for studying combustion processes of gaseous fuels are known, including the formation of a combustible mixture, its supply to a burner device, flame stabilization and measurement of the concentration of combustion products.

[0003] For example, patent RU 2680534 C1 describes a method for stabilizing hydrogen diffusion combustion in a microburner, which involves the formation of a stable flame and the study of hydrogen combustion characteristics. However, this method does not include the study of ammonia-hydrogen mixtures and is not aimed at determining the rate of nitrogen oxide formation.

[0004] Patent RU 2727259 C1 discloses a method for diffusion combustion of a hydrogen microjet in an inert environment, including supplying gaseous fuel, flame stabilization, and regulating combustion intensity. This method focuses on combustion stability and does not include spatially localized sampling of combustion products or determination of the rate of nitrogen compound formation.

[0005] Methods for burning ammonia-hydrogen mixtures aimed at improving flame stability and reducing nitrogen oxide emissions are also known (US 9,506,400 B2; US 8,691,182 B2), however, these methods are intended for power plants and do not provide for experimental determination of the rate of formation of nitrogen oxides in the flame zone.

[0006] The closest in technical essence to the claimed invention is a method for studying the combustion of gaseous fuels in a Bunsen burner, including the formation of a combustible mixture, stabilization of a laminar flame and measurement of the concentration of combustion products (see, for example, RU 2428628 C2).

[0007] The disadvantage of the prototype is that it does not provide for spatial-local measurement of the concentration of nitrogen oxides along the flame and, accordingly, does not allow determining the rate of their formation during combustion of an ammonia-hydrogen mixture.

[0008] The technical objective of the invention is to create a method for determining the rate of formation of nitrogen oxides during combustion of an ammonia-hydrogen mixture, ensuring the receipt of spatially resolved data on the concentration of nitrogen oxides in the flame-stabilized zone.

[0009] The technical result of the invention is the possibility of determining the rate of formation of nitrogen oxides by the length and radius of the flame of an ammonia-hydrogen mixture under controlled combustion conditions.

[0010] The stated technical problem is solved in that the method for determining the rate of formation of nitrogen oxides during combustion of an ammonia-hydrogen mixture involves forming a combustible mixture of ammonia, hydrogen and air, feeding said mixture into a burner device with the formation of a stabilized flame, sampling combustion products and measuring the concentration of nitrogen oxides, wherein the sampling of combustion products is carried out spatially locally along the axis and along the radius of the flame, and the rate of formation of nitrogen oxides is determined by the change in their concentration along the length of the flame at a given flow rate of the combustible mixture.

[0011] Fig. 1 shows a burner device for implementing a method for determining the rate of formation of nitrogen oxides during combustion of an ammonia-hydrogen mixture in a Bunsen burner.

[0012] Designations: 1 - hydrogen cylinder, 2 - ammonia cylinder, 3 - compressor for air supply, 4 - filters for cleaning the supplied air from compressor oil, 5 - flow regulator of ammonia-hydrogen mixture, 6 - flow regulator of air supplied to the mixing chamber, 7 - mixing chamber, 8 - air flow regulator for forming a cocurrent flow, 9 - sampler with a thermocouple and a coordinate device, 10 - gas analyzer, 11 - computer, 12 - quartz tube, 13 - external quartz tube.

[0013] Implementation of the invention.

[0014] When performing measurements, the condition l / D>0.06Re was met, at an average mixture speed = 0.466 m / s, Reynolds number Re=370, and accordingly 0.06Re=22.2.

[0015] The fuel-air composition was regulated using a UFPGS-2 ammonia-hydrogen mixture flow regulator and a Bronkhorst MassView air flow regulator. Atmospheric air from the compressor at a pressure of 3.5 bar was supplied through a line to a system of three filters (AME 350C–F04, AME 350C–F04, AME 350C–F04–T), which prevented compressor oil vapor from entering the test object. The air was then fed to the Bronkhorst MassView flow regulator to form a coflow and to the MassFlow flow meter, which subsequently formed a combustible mixture. The fuel mixture composition and flow parameters were selected to ensure a stationary flame front position. The volumetric content of H2 and O2 at the test point of the flame was determined by electrochemical sensors of the Test-1 gas analyzer. The NO content is determined using a continuous gas analyzer SIEMENS Ultramat, the infrared measuring element of which is insensitive to the presence of ammonia in the measured sample.The gas to be analyzed is sampled using a 1.2 mm diameter quartz sampler, whose radial and vertical position is adjusted using a coordinate device. The pre-measured sample passes through a gas dryer, where water vapor is condensed in a Peltier cooler. A computer is used to control the precision gas flow controller and process the data.

[0016] The proposed method allows:

[0017] • obtain data on the kinetics of nitrogen oxide formation during combustion of ammonia-hydrogen mixtures;

[0018] • use the obtained data to model the chemical kinetics of combustion processes;

[0019] • apply the method regardless of the specific design of the burner device.

Claims

1. A method for determining the rate of formation of nitrogen oxides during combustion of an ammonia-hydrogen mixture, which includes the formation of a combustible mixture of ammonia, hydrogen and air, feeding said mixture into a burner device with the formation of a stabilized flame, sampling combustion products and measuring the concentration of nitrogen oxides, characterized in that the formation of the flame is carried out in a quartz tube with a laminar flow regime, the sampling of combustion products is carried out spatially locally along the axis and along the radius of the flame, the concentration of nitrogen oxides is measured by a gas analyzer, the measuring element of which is insensitive to the presence of ammonia, and the rate of formation of nitrogen oxides is determined by the change in the concentration of nitrogen oxides along the length of the flame at a given flow rate of the ammonia-hydrogen mixture.

2. The method according to paragraph 1, characterized in that flame stabilization is carried out by preventing flame breakthrough using a metal mesh placed in a quartz tube.

3. The method according to paragraph 1, characterized in that a cocurrent air flow is formed at the outlet of the quartz tube.

4. The method according to paragraph 1, characterized in that the measurement of the concentration of nitrogen oxides is carried out after preliminary drying of the collected gas sample.

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