JPH10239268A - Gas sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve the zero gas of an NOx measuring instrument with atmosphere as a feed gas. SOLUTION: An NO oxidation absorption agent 8 is filled into an air introduction side within a container 2 and an NO2 absorption agent 10 is filled into a zero gas exhaust side. Polypropyrene cotton 6b of a spacer is included between the NO oxidation absorption agent 8 and the NO2 absorption agent 10 to prevent both from being mixed. NO out of nitrogen oxide in air being introduced from the air introduction port 5 is partially absorbed by the NO oxidation absorption agent 8 and the rest is oxidized and becomes NO2 . Nitrogen oxide in air through the part of the NO oxidation absorption agent 8 is entirely NO2 , the NO2 gas is absorbed by the NO2 absorption agent, and a gas delivered from an exhaust port becomes a zero gas where the nitrogen oxide is eliminated and is supplied to an NOx measuring instrument 12 by a suction pump 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a potentiostatic electrolytic NOx
The present invention relates to a gas sensor such as a gas sensor that measures the concentration of NOx in a sample gas.

[0002]

2. Description of the Related Art A gas sensor is an element mainly for detecting and quantifying a specific gas component in the atmosphere, and is used not only for general analysis but also for controlling various industrial equipment and industrial process systems. When using a measuring device equipped with such a sensor, an operation called calibration is performed before actual measurement is performed. In calibration, measurement is performed at two points when a zero gas containing no measurement target gas and a span gas containing a known concentration of the measurement target gas are flown, and a calibration curve is created using these values. Generally, a gas supplied from a dedicated gas cylinder is used as a gas for calibration.

[0003]

Considering portable measuring instruments for on-site measurement among such measuring instruments, in order to perform on-site calibration, respective gas cylinders for zero gas and span gas are also carried to the site. However, such a gas supply device for calibration has disadvantages in size and weight. Therefore, an object of the present invention is to create a zero gas using air as a raw material without using a gas cylinder for zero gas which is one of the calibration gases, and to supply it to a NOx measuring device at the time of calibration.

[0004]

According to the present invention, a zero gas supply apparatus is used which uses the air as a raw material and removes NOx in the air using an absorbent to obtain zero gas. Such a zero gas supply device has a cylindrical container having an air inlet at one end and a zero gas outlet at the other end, a gas introduction side filled with a NO oxidation absorbent, and a NO ₂ absorbent at the zero gas discharge side. And a pump provided upstream or downstream of the gas purifier to form a gas flow from the gas purifier to the NOx measuring device.

[0005] Of the nitrogen oxides in the air introduced into the container from the air inlet, NO is partially absorbed by the NO oxidation absorbent provided on the air introduction side, and the rest is oxidized to NO ₂ become. All nitrogen oxides in the air that have passed through the NO oxidation absorbent portion are NO ₂ . The NO ₂ gas is absorbed by the NO ₂ absorbent on the zero gas discharge side, and the gas discharged from the outlet is a zero gas from which nitrogen oxides have been removed. The gas is supplied to a NOx measuring device and subjected to zero gas calibration.

[0006]

FIG. 1 shows an embodiment. Reference numeral 1 denotes a purifier that uses air as a raw material and removes nitrogen oxides in the air to produce zero gas. The container 2 is a polyvinyl chloride cylinder, one end of which is closed by a lid 4. At the center of the lid 4, a hole for an air inlet 5 is formed.
The other end of the container 2 is a zero gas discharge port 3 protruding from the center.

The inside of the container 2 has NO on its air introduction side.
The oxidation absorbent 8 is filled, and the NO ₂ absorbent 10 is filled on the zero gas discharge side. NO oxidation absorbent 8 and NO ₂
0.2 g of polypropylene cotton 6b is interposed between the absorbents 10 as a spacer in order to prevent mixing of the two. Air inlet side of NO oxidation absorbent 8 and NO ₂ absorbent 1
0 zero gas discharge side also each polypropylene cotton 6
a, 6c are filled respectively, and the NO oxidation absorbent 8 and NO
_{(2) It} prevents the absorbent 10 from spilling out of the container 2 to the outside.

As the NO oxidation absorbent 8, Purafil (Purafil Co., Ltd.) obtained by coating a porous ceramic with KMnO ₄ can be used. As the NO ₂ absorbent 10, silica gel as a special grade reagent can be used. Reference numeral 12 denotes NO from a potentiostatic electrolytic gas sensor or the like.
It is an x-measurement device, the zero gas outlet 3 of the purifier 1 and NOx
A suction pump 14 is arranged in a flow path connecting the measuring device 12. During calibration, zero gas is supplied from the purifier 1 using the suction pump 14.

FIG. 2 (A) shows an example in which NO ₂ is diluted with air as a gas to be supplied to the purifier 1 in the embodiment of FIG.
This is a result of continuously flowing a standard gas with an O ₂ concentration of 100 ppm, and indicates the NO ₂ removing ability. No change was observed in the indication of the meter even when the standard gas was continuously flowed for more than 40 hours.

FIG. 2 (B) shows the result of continuously flowing a standard gas having a NO concentration of 100 ppm by diluting NO with nitrogen as the gas to be supplied to the purifier 1 in the embodiment of FIG. It shows the NO removal ability. In a state of flowing for about 1 hour, 100 ppb, which is 1/1000 of the supply gas concentration, was maintained, and after about 4 hours and 30 minutes, it reached 1 ppm, which was 1/100 of the supply gas concentration.

[0011]

According to the present invention, the zero gas can be supplied from the atmosphere at the time of the zero gas calibration of the NOx measuring instrument. Therefore, it is not necessary to carry a cylinder for the zero gas, which is advantageous in realizing a portable gas sensor. Becomes

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment.

FIG. 2 is a diagram of measurement results showing characteristics of the example,
(A) shows the NO ₂ removal capacity is, (B) is a view showing an NO removal capability.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Refiner 2 Container 3 Zero gas outlet 5 Air inlet 6a, 6b, 6c Polypropylene cotton 8 NO oxidation absorbent 10 NO ₂ absorbent

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Osamu Tahara, Inventor: 1 Nishinokyo Kuwaharacho, Nakagyo-ku, Kyoto-shi, Kyoto, Japan

Claims (1)

[Claims] 1. NO for measuring NOx concentration in a sample gas
a gas sensor comprising an x-measuring device and a zero gas supply device for supplying a zero gas to the measuring device at the time of zero gas calibration, wherein the gas supply device is provided in a cylindrical container having an air inlet at one end and a zero gas outlet at the other end. A gas purifier filled with a NO oxidation absorbent on its gas introduction side and a NO ₂ absorbent on its zero gas discharge side, and a gas purifier provided upstream or downstream of the gas purifier A gas flow from the device to the NOx measuring device.