JP2676602B2 - Method for measuring the concentration of combustion produced fine particles contained in exhaust gas - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention continuously measures the concentration of combustion produced fine particles such as soot contained in exhaust gas in combustion equipment such as diesel engines and boilers whose main combustion process is diffusion combustion. It is about the method.

[Conventional technology]

Currently, the filter weighing method is generally used to measure particulate matter emitted from diesel engines, but it takes a long time for measurement due to batch processing, and transient emission characteristics cannot be measured in real time. There are difficulties. Therefore, there is a strong demand for the development of a continuous measurement apparatus for diesel particulates having a good time response, and several continuous particulate measurement methods or apparatuses have been proposed so far.

[Problems to be solved by the invention]

There is a light transmittance densitometer in the old days, which measures the transmittance of aerosol by a light source and a photodetector, and the same principle is used for the Hartridge method and the US Health and Safety Administration (USPHS) Opacimeter. However, since the absorption coefficient differs depending on the particle size, the obtained value is not a function of only the mass concentration but has only a qualitative meaning. Also, by using infrared rays as a light source and measuring in the Rayleigh scattering range, the particle size dependency is eliminated,
PAS (photoacoust) measuring mass concentration by photoacoustic method
ic) method has also been developed, but it is difficult to sufficiently eliminate the difference in the complex refractive index of particles and the effects of coexisting gases such as hydrocarbons. In addition to this, the change in mass when fine particles are collected in the filter is detected as the change in the bending resonance frequency of the pipe.
A TEOM (tapered element ocillating microbalance) method has also been proposed. However, it is difficult to obtain high accuracy because it is necessary to convert the differential value of the frequency change into the mass concentration based on the measurement principle, and due to the influence of water condensation during sampling, the correlation with the filter method is also present. Not good.

The present invention has been made in view of such circumstances, and has a high correlation with the filter method, and an object thereof is to provide a concentration measurement method capable of highly accurate continuous measurement of combustion produced fine particles such as soot contained in exhaust gas. I am trying.

[Means for solving the problem]

The present invention has means for solving the above-mentioned problems as follows.

That is, it is characterized by detecting the difference in carbon dioxide concentration generated when the unburned components contained in each of the sample gas and the comparative sample gas obtained by removing the combustion-produced fine particles contained in the sample gas by the filter are oxidized and burned. I am trying.

[Action]

The difference in the concentration of carbon dioxide detected is the difference in the concentration of the combustion-produced fine particles contained in the sample gas and the comparative sample gas, which is proportional to the concentration of the combustion-produced fine particles collected in the filter. In addition to being able to obtain a measurement result having a high correlation with, it is not affected by the unburned hydrocarbons in the gas phase contained in the sample gas.

Also, with this method, it is possible to make the dead volume of all flow paths on the sample side and the comparative sample side almost the same as that of a general gas analyzer, and the consistency without time delay compared with the gas analysis result. It is possible to quickly obtain good continuous measurement results.

〔Example〕

FIG. 1 shows an example of a configuration in which an apparatus for carrying out the method for measuring the concentration of fine particles of combustion products such as soot contained in exhaust gas of the present invention is applied to a diesel engine exhaust. In FIG. 1, the sample gas (exhaust gas) introduced from the exhaust pipe enters the sample channel 1 and the comparative sample channel 2. In the comparative sample flow path 2, combustion-produced fine particles such as soot are collected by the filter 3 here. Next, both the sample flow path 1 and the comparative sample flow path 2 enter the reburner 4, where they are heated to oxidize the combustion-produced fine particles and general carbon oxides and unburned hydrocarbons to carbon dioxide and water vapor. After that, both flow paths enter the carbon dioxide concentration meter 9 through the pressure adjusting capillary tube 5, the backup filter 6, the pump 7, the flow meter 8, etc., and the carbon dioxide concentration of the sample flow path 1 and the comparative sample flow path 2 is measured. Detect the difference. In addition, since a diesel engine normally contains several percent of oxygen in exhaust gas even at maximum load, complete combustion can be achieved by giving a sufficiently high temperature. Therefore, in this embodiment, the recombustor 4 is wound in a coil shape. The stainless steel tube was directly energized.
In addition to this, various methods using a catalyst, microwave, or the like can be considered for the reburner. Further, the carbon dioxide concentration meter 9 is a fluid modulation type non-dispersion infrared analyzer and can accurately measure the concentration difference between the sample flow path and the comparative sample flow path.

As described above, in the present embodiment, the difference in carbon dioxide concentration that occurs when the unburned components contained in each of the comparative sample gas in which the combustion product fine particles in the sample gas are removed by the sample gas and the filter is continuously measured. By performing the selective detection, it is possible to obtain a measurement result having a high correlation with the filter method. Furthermore, by using a carbon dioxide concentration meter having a high detection sensitivity, it is possible to relatively easily improve the measurement accuracy of fine particles.

FIG. 2 shows an example of the measurement results, and shows the difference in the carbon dioxide concentration between the sample flow channel and the comparative sample flow channel corresponding to the torque, rotational speed, and particle concentration of the diesel engine. According to this, the output corresponding to the load fluctuation is obtained,
It can be seen that measurement with good time response is possible.

[Brief description of the drawings]

FIG. 1 is an example of an apparatus for carrying out the method for measuring the concentration of combustion-produced fine particles contained in exhaust gas according to the present invention, which is applied to continuous measurement of the fine particle concentration in diesel engine exhaust.
FIG. 2 is an example of the measurement results using the apparatus shown in the example, in which the carbon dioxide concentrations of the sample flow channel and the comparative sample flow channel corresponding to the engine torque, rotational speed, and particle concentration during engine transient operation are shown. Shows the difference. 1 ... Sample flow path, 2 ... Comparative sample flow path, 3 ... Filter, 4 ... Reburner, 5 ... Capillary tube, 6
…… Backup filter, 7 …… Pump, 8 …… Flow meter, 9 …… Carbon dioxide concentration meter.

Claims (1)

(57) [Claims] 1. A difference in carbon dioxide concentration generated when oxidatively burning unburned components contained in a sample gas and a comparative sample gas obtained by removing combustion produced fine particles contained in the sample gas by a filter is detected. A method for measuring the concentration of combustion produced fine particles contained in exhaust gas, comprising: