JP2000088718A - Pretreatment of sample gas for gas analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continuously remove contaminants contained in a sample gas introduced into a gas analyzer without stopping the gas analyzer, and to read the indicated value of the gas analyzer over a long period of time. To provide a method for pre-treating a gas sample for a gas analyzer for extremely stabilizing a gas sample. A method for pre-treating a sample gas by introducing a sample gas to be introduced into a gas analyzer into a filtration unit and then introducing the sample gas into a washing unit, wherein the filtration unit comprises a gas flow having a filter element. A gas passage having a plurality of passages arranged in parallel and introducing a sample gas, wherein when the filter element is contaminated, the gas passage is switched to a gas passage having a non-contaminated filter element. Pretreatment method for measurement sample gas. The method for pretreating a sample gas for a gas analyzer described above, wherein the filtration means is kept at a temperature of 50 to 85 ° C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for pretreating a sample gas for a gas analyzer, and more particularly to a method for removing impurities contained in a sample gas introduced into the gas analyzer without stopping the gas analyzer. The present invention relates to a method for pretreating a sample gas for a gas analyzer for continuously removing and stabilizing an indicated value of the gas analyzer for a long period of time.

[0002]

2. Description of the Related Art Conventionally, gas analyzers have been widely used for controlling the operation of various apparatuses and managing the processes of chemical apparatuses. For example, an oxygen meter controls the optimal operation of combustion equipment and heating furnaces by measuring the oxygen concentration in the flue gas, and controls the NOx emissions and the engine to reduce fuel consumption by measuring the oxygen concentration in the exhaust gas from automobiles. It is actively used for optimal operation control. Oxygen meters and hydrogen meters are widely used for process control of chemical devices such as petroleum refining and chemical synthesis.

As such a gas analyzer, various analyzers such as a magnetic oxygen meter, an electrochemical oxygen meter, a thin film diffusion hydrogen meter, an electrochemical hydrogen meter, and a hydrogen meter using a hydrogen storage alloy have been developed. I have. Regarding a method for analyzing a gas containing moisture, for example, Japanese Patent Application Laid-Open No. 59-9559 discloses a method of analyzing a sample gas having a high temperature and a high humidity by measuring the gas concentration measured by dehumidification. A gas analyzer equipped with a memory and an arithmetic means for automatically correcting a time delay until the drain amount is measured for the purpose of quickly correcting the moisture to the previous gas concentration is described. Japanese Patent Laid-Open No. 63-292058 discloses a method for analyzing gas in which oxygen gas and moisture coexist, by continuously measuring oxygen and moisture in the gas from the oxygen concentration measured without dehumidification and the oxygen concentration measured after dehumidification. Describes the method of measurement.

[0004] In these gas analyzers, in order to perform gas analysis continuously for a long time without any trouble, the sample gas introduced into the gas analyzer is not the sample gas itself collected from the gas stream to be analyzed, but the sample gas itself. It is required that the sample gas is a clean sample gas from which impurities have been removed by performing the treatment. Usually, the pretreatment method of a sample gas is performed by bubbling a sample gas collected from a gas stream to be analyzed with a cleaning liquid to wash impurities and then separating accompanying liquid droplets by a drain separator.

However, in such a sample gas pretreatment method, although most of the contaminants are removed, when the gas analyzer is operated for a long period of time, a trace amount of the residual gas remains in the sample gas. Impurities gradually accumulate and adhere in the gas flow path leading to the detection section of the analyzer, causing the sample gas flow rate to fluctuate irregularly, and the accumulated impurities being separated and mixed into the detection section. Therefore, there is a problem that the indicated value of the gas analyzer is largely disturbed and unstable. In other words, it is not possible to accurately measure the concentration of the gas component to be analyzed, so that the optimal operation control of the apparatus cannot be performed. In the case of gas, there is an extremely dangerous problem in safe operation of the apparatus.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to remove contaminants in a sample gas introduced into a gas analyzer continuously without stopping the gas analyzer, and to remove the gas for a long period of time. It is an object of the present invention to provide a method for pretreating a gas sample for a gas analyzer for making the indicated value of the analyzer extremely stable.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies on the relationship between the pretreatment method of a sample gas and the stability of the indicated value of the gas analyzer in the gas analyzer. The collected sample gas is introduced into one gas flow path of a filtration means comprising a plurality of gas flow paths having a filter element to remove most of the impurities in the sample gas, and then further introduced into the cleaning means. By removing a trace amount of contaminants remaining as well as by introducing a sample gas, by switching the gas flow path of the filtration means to a gas flow path having a non-contaminated filter element when the filter element is contaminated, Impurities in the sample gas can be continuously removed without stopping the gas analyzer, and even when the gas analyzer is operated for a long period of time, It found that 示値 is extremely stable, and have completed the present invention.

That is, the present invention is a method for pre-treating a sample gas by introducing a sample gas to be introduced into a gas analyzer into a filtering means, and then introducing the sample gas into a washing means. A plurality of gas flow paths having elements are arranged in parallel, and the gas flow path into which the sample gas is introduced is switched to a gas flow path having a non-contaminated filter element when the filter element is contaminated. An object of the present invention is to provide a method for pretreating a sample gas for a gas analyzer. The present invention also provides the method for pretreating a sample gas for a gas analyzer as described above, wherein the filtration means is kept at a temperature of 50 to 85 ° C.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The method for pretreating a sample gas for a gas analyzer according to the present invention is characterized in that a sample gas collected from a gas stream to be analyzed is introduced into a filtering means comprising a plurality of gas passages having filter elements arranged in parallel, and then further washed. Introduced into the means.

(Filtration Means) The filtration means used in the present invention comprises:
A plurality of gas passages provided with a filter element in the middle of the gas passage are arranged in parallel, and when a sample gas is introduced into one of the gas passages and the filter element is contaminated, contamination occurs. This is to switch to a gas flow path having a filter element that is not provided. Examples of the filter material of the filter element include a sintered body of metal powder or synthetic resin powder, a nonwoven fabric of synthetic resin, and filter paper. Usually, the average pore size of the filter element is from 5 to 50 μm, preferably from 5 to 10 μm. If it is less than 5 μm, clogging of the filter element is likely to occur, and if it is more than 50 μm, there is a problem that fine impurities pass through the filter element.

(Cleaning means) The cleaning means used in the present invention comprises:
There is no particular limitation, and known ones can be used. For example, a cleaning tank filled with a cleaning liquid (hereinafter, referred to as a cleaning tank)
Also called bubbler. ) May be used singly or in combination, and may be further combined with a drain separator. The cleaning liquid may be simply clean water or a gas absorbing liquid having a gas absorbing function for a specific gas component. For example, a gas absorbing solution such as an acidic aqueous solution for ammonia gas, an alkaline aqueous solution for hydrogen chloride gas, and an ammoniacal cadmium chloride aqueous solution for hydrogen sulfide can be used.

In the method for pretreating a sample gas for a gas analyzer according to the present invention, the sample gas is first introduced into the above-mentioned filtration means. Here, most impurities can be removed. Further, when the filter element is contaminated, the gas flow path into which the sample gas is introduced is switched to a gas flow path having a non-contaminated filter element so that the gas flow path can be continuously operated for a long time without stopping the filtration means. To operate the gas analyzer. After the gas flow path has been switched, the contaminated filter element can be used again as a non-contaminated filter element by replacing it with a new filter element or cleaning it in any way. The degree of contamination of the filter element can be detected by any method, for example, by measuring the internal pressure of the gas flow path downstream of the filter element and detecting the degree of decrease in the internal pressure. If the filter element is contaminated and clogged, the flow rate of the sample gas decreases, the reading of the gas analyzer fluctuates, and it becomes impossible to obtain a correct reading of the concentration of the measurement gas component.

When the sample gas is a gas containing a large amount of volatile components such as moisture and organic solvents, when the gas analyzer is operated for a long period of time, these moisture and volatile components are filtered. The filter element becomes clogged because it gradually condenses into the filter medium of the element and wets it, thereby substantially reducing the pore diameter. Therefore, when the sample gas contains a large amount of moisture and volatile components, the filter means is kept at 50 to 85 ° C. and the filter element is kept in a dry state so that the pore diameter does not decrease. Is desirable. If the temperature is lower than 50 ° C., the water does not evaporate, so that clogging is likely to occur. If the temperature is higher than 85 ° C., the performance of the filter element deteriorates.

The sample gas that has passed through the filtering means is subsequently introduced into the above-mentioned washing means. Although the sample gas from the filtration means has most of the impurities removed, a trace amount of the impurities remains in the sample gas. In the case where the cleaning means has the above configuration, the sample gas is bubbled (bubble aerated) into the cleaning liquid in one or a plurality of bubblers to completely remove the remaining trace impurities, and to further remove the known drain. Droplets accompanying the liquid are removed by passing through the separator. When a gas absorbing liquid is used as the cleaning liquid, gas components unnecessary for gas analysis can be removed.

The sample gas that has passed through the cleaning means can be directly introduced into the detection section of the gas analyzer. However, if desired, it can be introduced into the gas analyzer after passing through a second filtration means, a drain separation means and a cooling means, or a combination thereof. In this case, the content of impurities and moisture in the sample gas can be further reduced. In particular, it is effective when the sensitivity of the gas analyzer is greatly affected by a very small amount of impurities or moisture.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described based on embodiments. In addition,
The present invention is not limited at all by the following Examples.

FIG. 1 is a view for explaining the main configuration of a method for pretreating a sample gas for an analyzer according to the present invention. In FIG. 1, a sample gas collected from a gas flow
The flow rate was adjusted to the amount of gas required for gas analysis by the valve 5, and the gas was first introduced into the filtration means 1. In the filtration means 1,
The sample gas was introduced into one of the gas channels having the filter element 4 via the gas channel switching valve 3. Impurities were removed by passing the sample gas through the filter element 4. After adjusting the flow rate of the sample gas from the filtration means 1 with the valve 5, the sample gas was introduced into the cleaning means 2. Here, the sample gas was bubble-aerated through a bubbler 6 filled with the cleaning liquid 7 to remove impurities remaining in the sample gas. The sample gas after washing was introduced into the drain separator 8, and the accompanying droplets were separated. During the gas analysis, the internal pressure of the gas flow path was measured with a pressure gauge (not shown) provided between the filter element 4 of the filtering means and the downstream gas flow path switching valve 3, and the internal pressure reached 7.6 mmHg / cm ² . When lowered, the gas flow path switching valve 3 was used to switch to another gas flow path having a non-contaminated filter element 4. The sample gas from the cleaning means was introduced into the detection part of the gas analyzer, and gas analysis was performed for three consecutive days. FIG.
2 shows a part of the result of continuously measuring the oxygen concentration in the tank A in the cotton-leaving step of the hydroxyethylcellulose production apparatus.

[0018]

Comparative Example FIG. 2 is a drawing for explaining the main configuration of a conventional sample gas pretreatment method for an analyzer. It is the same as FIG. 1 except that the filtering means 1 shown in FIG. 1 is not used. In the same manner as in the example, a sample gas collected from a gas flow to be measured (not shown) was directly introduced into the cleaning means, subsequently introduced into the gas analyzer, and gas analysis was performed continuously for three days. FIG. 4 shows the results (part) of the oxygen gas concentration in the tank A measured in the same manner as in the example.

As is clear from FIGS. 3 and 4, in the case of the embodiment employing the pretreatment method of the sample gas for an analyzer of the present invention (FIG. 3), the indicated value of the oxygen concentration in the A tank is During the measurement, the value was extremely stable, and the oxygen concentration could be accurately measured. On the other hand, in the case of the comparative example measured by the conventional sample gas pretreatment method for the analyzer (FIG. 4), the indicated value of the oxygen concentration in the tank A repeatedly moved up and down frequently during the measurement. It was unstable and the oxygen concentration could not be measured accurately.

[0020]

As described above in detail and specifically, according to the method for treating a sample gas for a gas analyzer of the present invention, the sample gas introduced into the gas analyzer is introduced into the filtering means, and then the cleaning means is further added. A method for pretreating a sample gas by introducing the sample gas into the filter, wherein the filtering means comprises a plurality of gas flow paths having filter elements arranged in parallel, and the gas flow path into which the sample gas is introduced is provided in the filter. When the element is contaminated, it is switched to a gas flow path having a non-contaminated filter element. In the present invention, the above-mentioned filtration means is kept at a temperature of 50 to 85 ° C. By making the present invention such a configuration,
Impurities in the sample gas introduced into the gas analyzer can be continuously removed without stopping the gas analyzer, and when the gas analyzer is operated for a long period of time, There is an effect that the indicated value is extremely stable and the concentration of the gas component can be accurately measured. Also,
By keeping such a filter at a temperature of 50 to 85 ° C., the frequency of switching the gas passage of the filter can be significantly reduced. Therefore, the method for pretreating a sample gas for a gas analyzer of the present invention is a method for controlling the process of a chemical apparatus such as an exhaust gas analyzer for optimal operation control of a combustion equipment such as a heating furnace and a boiler, petroleum refining, and chemical synthesis. Of the sample gas in the gas analyzer. In particular, when the gas component to be analyzed is a dangerous gas such as oxygen or hydrogen, this is a pretreatment method for a sample gas for an analyzer which is extremely effective for safe operation of the apparatus.

[Brief description of the drawings]

FIG. 1 shows an example of a main configuration of a method for pretreating a sample gas for an analyzer according to the present invention.

FIG. 2 shows an example of a main configuration of a conventional sample gas pretreatment method for an analyzer.

FIG. 3 shows an example (part) of an analysis result obtained by an example.
Is shown.

FIG. 4 is an example (part) of an analysis result obtained by a comparative example.
Is shown.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Filtration means 2 Cleaning means 3 Gas flow switching valve 4 Filter element 5 Valve 6 Bubbler 7 Cleaning liquid 8 Drain separator

Claims (2)

[Claims] 1. A method for pre-treating a sample gas by introducing a sample gas to be introduced into a gas analyzer into a filtration unit and then introducing the sample gas into a washing unit, wherein the filtration unit comprises a gas having a filter element. A gas comprising a plurality of flow paths arranged in parallel, and wherein the gas flow path in which the sample gas is introduced is switched to a gas flow path having a non-contaminated filter element when the filter element is contaminated. Pretreatment method for sample gas for analyzer. 2. The method for pretreating a sample gas for a gas analyzer according to claim 1, wherein said filtration means is kept at a temperature of 50 to 85 ° C.