SU1408319A1 - Chemoluminescent gas analyzer for nitrogen oxides - Google Patents

Abstract

The invention relates to gas analysis and is intended to investigate nitrogen oxides in process lines. The goal is to reduce the cost of conducting periodic calibration of the gas analyzer under operating conditions while simultaneously maintaining a stable level of nitric oxide concentration in the test gas. To accomplish this goal in a bi-luminescent gas analyzer, two additional pipelines connecting the output and input of the ozone-air mixture generator to the valve inlet and outlet are connected The reaction chamber, at this time, the ozone-air generator is supplied with a thermostat. 1 dw., 3 tab. from 0

Description

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The invention relates to analytical instrumentation, in particular, to chemiluminescent gas analyzers of nitrogen oxides in process lines.

The aim of the invention is to reduce the cost of carrying out periodic calibration of a chemiluminescent gas analyzer under operating conditions while maintaining a stable level of nitrogen oxide concentration in the test gas,

The drawing shows a functional block diagram of the proposed gas analyzer.

The gas analyzer contains a reaction chamber 1 connected by pipelines 2 and 3 to the outputs of a thermo-catalytic converter 4 and an electric discharge generator 5 of the ozone-air mixture, the input of which through filter 6 is connected to the surrounding atmosphere. The ozone-air mixture generator is equipped with a thermostat 7. A two-valve valve 8 is installed at the input of thermal-catalytic converter 4; 11 with one with the output of the reaction chamber, to which, through the regulator 2 pressure the pump 13o is connected

The gas analyzer works as follows.

The pump 13 creates in the reaction chamber 1 a reduced pressure, the value of which is maintained automatically at a predetermined (constant) level by means of the pressure regulator 12.

In the measurement mode, valve H is included in position A - B and the analyzed gas, containing oxide and nitrogen dioxide, under the influence of the pressure differential flows from the process line to the thermocatalytic converter 4, in which nitrogen dioxide is converted to nitrogen oxide. Next, the analyzed gas through the pipeline 2 enters the reaction chamber 1. At the same time, through the pipeline 3, an ozone-air mixture enters the reaction chamber, produced by an electric discharge generator 5 from the atmospheric air previously cleaned and dried Wen filter 6,

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As a result of the chemical interaction of nitric oxide with ozone, optical radiation occurs in the reaction chamber, detected by a photodetector (not shown), the output signal of which is proportional to the sum of concentrations of nitrogen oxides (NOg –N0). In the mode of calibration of the gas analyzer, Valve 8 is switched to position B – Bj at the same time, part of the ozone-air mixture through an additional pipeline 10 from generator 5 enters the thermo-catalytic converter 4, in which ozone is reduced to the molecular temperature by exposure to (200-400 ° C) The resulting isloroda ,, together with ozone in the bottom of the electric generator 5 higher oxides of nitrogen (N0, etc.,) when entering termokata- lytic converter on the catalyst are reduced to nitric oxide which is fed through conduit 2 into the reaction chamber. Here, the ozone molecules emit light, the intensity of which is proportional to the content of nitrogen oxides in the ozone-air mixture.

The stability of the concentration of nitrogen oxides in the ozone-air mixture at the output of the generator 5, and therefore, the output signal of the gas analyzer in the verification mode is maintained by a constant oxygen and nitrogen content in the atmospheric air, temperature stability in the generator 5, which is maintained by the thermostat 7, by the PURE of the atmospheric air entering the generator 5, which is provided by the filter 6, the stability of the electrical voltage of the power supply of the generator 5, which is provided by the electric circuit of the generator, quantitative ( 1: 1) conversion of higher nitrogen oxides to nitric oxide, which is ensured by the choice of an appropriate catalyst and parameters (temperature, volume of the working chamber, etc.,) of the thermocatalytic converter, as well as by changing the atmospheric pressure by stabilizing the air flow through the ozone-air generator that is provided by an additional pipe 115 connecting the input of the generator 5 to the outlet of the reaction chamber 1, the pressure in which is maintained at

preset level by pressure regulator 2.

Example 1 o The proposed technical solution is implemented on a gas analyzing unit built on the basis of an industrial chemiluminescent gas measuring converter of nitrogen oxides, HIP N0, which is part of a multichannel exhaust gas monitoring system of automobile engines (ASGA-T system).

In the GUI Converter N0, an electric valve is additionally installed at the inlet of the standard thermo-catalytic converter and pipelines connecting the inlet and outlet of the standard electric discharge ozone-air mixture generator. Accordingly, one of the electrovalve inputs and the outlet of the reaction chamber. The ozone-air mixture generator is placed in a thermostat in which the temperature AOi is maintained at 1 ° C. The transformer is powered from a stabilized AC source of 220 + 1. The output signal is monitored by a recording potentiometer.

Table 1 shows the values of the HIP output signal N0 in the sensitivity test mode on the O range — 200 p, p.m (O — 1000 mV) depending on the operating time.

It follows from Table 1 that a change in the output signal of the HIP N0 during 75 hours of operating time in the sensitivity test mode does not exceed 17 mV, which is 2% of the average value of the output signal, ToV. satisfies the requirement for the stability of the calibration gas mixture

Example 2; Temperature control in the electric circuit of the thermostat is set to different temperatures in the thermostat.

LLOLO2 shows the results of studying the dependence of the output signal of the converter of the HIP N0, (in the sensitivity test mode) on the temperature in the thermostat, in which the ozone-air mixture generator is placed

Table 2

Table 1

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It follows from tabLo2 that a change in the temperature of the ozone-air mixture generator from 20 to 30 ° C significantly affects the nitrogen oxide yield. Hence the need for thermostating of the indicated generator,

Example Transducer HIP N0 is placed in a pressure chamber, which simulates a change in atmospheric pressure from 86 to 106 kPa.

B shows the output signal of the converter in the sensitivity test mode at various ambient air pressures for two cases: in the absence of an additional pipeline 11 connecting the inlet of the oxygen-air mixture to the outlet of the reaction chamber and in the presence of the specified pipeline.

Table3

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Claims (1)

Invention Formula From Table 3 it follows that the presence of an additional pipeline connecting the input of the ozone-air-HC1Y mixture to the outlet of the reaction chamber weakens the dependence of the output C1 of the GIL NOj converter, in the sensitivity test of the ambient air, which due to the stabilization of air pressure at the inlet to the ozone-air mixture generator five 0 50 A chemiluminescent gas analyzer of nitrogen oxides in production lines containing a reaction chamber, the inputs of which are connected by pipelines to the output of a thermal catalytic converter of nitrogen dioxide to nitrogen oxide and to a code of an electric discharge generator of an ozone-air mixture, which is inlet through a filter connected to the surrounding atmosphere installed at the entrance of the thermal-catalytic converter. two-input converter - valve, the first input of which is connected to the process line, and the second - to the source of test gas, the pump, connected through a pressure regulator to the outlet of the reaction chamber, characterized in that, in order to reduce the cost of conducting periodic calibration of the gas analyzer under operating conditions while maintaining a stable level of nitrogen oxide concentration in the test gas, the output and inlet of the ozone-air mixture generator are connected additional pipelines, respectively, with the second valve inlet and with the outlet of the reaction chamber, while the ozone-air generator is equipped with a thermostat