KR100787378B1 - Method for sampling flue gas for analysis containing gas component having high susceptibility to adsorption - Google Patents

Abstract

In order to adjust the density | concentration of the ammonia gas added in the denitrification apparatus of exhaust gas, it aims at the accurate analysis of the ammonia gas contained in trace amount in exhaust gas. The target ammonia gas is a highly adsorptive gas, and the phenomenon that component gas is adsorbed to the collecting pipe of the exhaust gas during the collection of the exhaust gas is remarkable, so that the adsorption loss occurs during the collection of the conventional gas collecting tube. There was a problem in obtaining a highly accurate measurement value. Therefore, as a more precise gas collection method instead of the conventional heating method, the ammonia gas attached to the inner wall of the exhaust gas collection conduit 2, which is the target, is completely washed by using the absorbent liquid as a cleaning liquid to wash it from the inside of the conduit wall. Recover gas components. And a precise analysis result is obtained by analyzing this washing | cleaning liquid.

Denitrification, Exhaust Gas, Extraction, Precision, Ammonia, Conduit Walls, Recovery, Analysis, Adsorption, Concentration, Adjustment.

Description

Analytical exhaust gas collection method containing highly adsorptive gas components {METHOD FOR SAMPLING FLUE GAS FOR ANALYSIS CONTAINING GAS COMPONENT HAVING HIGH SUSCEPTIBILITY TO ADSORPTION}

The present invention collects an analysis exhaust gas containing highly adsorbable gas components for the purpose of precisely analyzing ammonia gas contained in a small amount in the exhaust gas for adjusting the ammonia gas concentration added in the exhaust gas denitrification apparatus. It is about a method.

Conventionally, the measurement of the gas component in exhaust gas has been generally performed by sampling in the field, performing a wet analysis, or measuring with a gas monitor. In this exhaust gas measurement, gas components such as nitrogen oxide, sulfur oxide, and the like do not have any problem regarding the harvesting technique in this gas collection step, and can be measured with a target accuracy relatively easily.

Here, the target ammonia gas is a highly adsorptive gas, and the phenomenon that component gas is adsorbed to the collecting pipe of the exhaust gas during the exhaust gas collection is remarkable. There was an obstacle in getting the value.

As a countermeasure, conventionally, the method of aiming at the adsorption | suction reduction by heating a gas collection tube is common. In addition, in the JIS standard, a method for analyzing ammonia in exhaust gas is specified in JIS K0099, and countermeasures against adsorption have been proposed, such as the need for heating of an introduction pipe for introducing exhaust gas. This JIS K0099 is a standard method performed by manual analysis at a normal scale exhaust gas collection site.

We have an exhaust gas collection tube with a large scale heating mechanism for automatic continuous measurement for monitoring at a relatively large power plant boiler, such as the year of the boiler, and a large amount of exhaust gas is used to automatically The method of connecting to an analysis device is adopted. This method is the method of Patent 3229088 and Patent 3322420.

However, it is not sufficient for the measurement of the trace analysis range near the concentration range of 100 to 1 ppm, which requires higher precision, and it causes a loss of adsorption due to the lack of heating of the exhaust gas collecting tube or the occurrence of partial heating insufficiency. there was.
In installations such as boilers using coal as fuel, the exhaust gases produced therefrom contain large amounts of dust. The problem arises that such dust blocks the branched section of the selector valve or harvesting tube, which interferes with the exhaust gas analysis.

That is, in the step of sucking the exhaust gas, passing it through an absorbing liquid that absorbs the ammonia gas component in the gas, analyzing the ammonia trapped in the absorbing liquid, and measuring the concentration in the exhaust gas. This is a phenomenon in which only this gas component is trapped in the absorbent bottle because part of is attached.
In the case of collecting exhaust gas containing a large amount of dust, the narrow portion of the exhaust gas selector valve or the bent branched portion of the collecting pipe is clogged with dust, which causes a problem of obstructing suction of the exhaust gas, thereby Can't analyze The phenomenon occurs.

Therefore, the analysis value is lower than the expected value. The present invention relates to an improvement of the exhaust gas collecting tube portion of Patent Nos. 3229088 and 3332420.

Since ammonia gas is a component that is easily soluble in water and is easily adsorbed by the exhaust gas collecting tube, gas collection is usually performed by heating the collecting tube to reduce condensation of moisture and adsorption of ammonia itself. In this case, the entire gas collecting tube needs to be sufficiently heated, and at least part of the gas collecting tube must not be sufficiently heated. Therefore, know-how and skill are required to obtain a particularly sufficient heating effect at the connection part of the collecting tube.

In the case of collecting exhaust gas containing a large amount of dust, the narrow portion of the exhaust gas selector valve or the bent branched portion of the collecting pipe is clogged with dust, which causes a problem of obstructing suction of the exhaust gas, thereby Can't analyze
In order to analyze trace components in the exhaust gas, such a conventional method is insufficient, and in order to find a more reliable method, it is one problem to improve the analysis accuracy by recovering the gas component attached to the exhaust gas collecting tube.
In the case of extracting exhaust gas containing a large amount of dust, the conventional method mentioned above is insufficient. Therefore, another object of the present invention is to prevent clogging with dust. On the other hand, in the measurement of ammonia for the treatment performance of the NOx denitrification apparatus, the level of unreacted ammonia passed through the catalyst must be measured accurately. Since dust with certain properties adsorbs ammonia, the ammonia so adsorbed must also be measured. Therefore, another goal includes washing the dust recovered from the collection tube with the cleaning liquid and transferring the cleaning liquid into the absorption bottle for recovering the NH ₃ adsorbed to the dust, so that the total amount of NH ₃ can be measured.

The present invention provides a gas collection method that prevents clogging with dust and prevents a decrease in analytical accuracy due to adhesion gas during the collection of the exhaust gas collection tube. According to this method, no selector valve is provided at the end of the collecting pipe, whereby dust clogging is prevented. In addition, by washing the inner surface of the collection pipe with washing water, and also including the washing water as the sample water to be analyzed, the entire gas composition including the sampling gas and the adherent gas is analyzed. The precision can be improved.

In order to clean the inside of the pipe automatically in the installation state such as the exhaust gas pipe when collecting the exhaust gas, it is necessary to have a high convenience as a device in the structure of the collecting pipe. A structure in which the washing water flows in the middle of the appearance, forming pores for injecting the washing water in the middle of the collecting pipe, recovering the absorbing bottle by sucking with an exhaust gas suction pump, and washing water collecting the exhaust gas It is made possible by the structure which pushes in a pipe with a pump. Therefore, the present invention also makes it possible to extract the position of the pore portion for pouring the washing water by designing conditions such as the amount of water and the washing time.

1 is a conceptual diagram of an exhaust gas collection method according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a portion of the exhaust gas collecting tube in FIG. 1 according to an embodiment of the present invention. FIG.

3 is a diagram showing experimental results of various exhaust gas collection methods in the case of high concentration of NH ₃ gas according to an embodiment of the present invention.

4 is a diagram showing experimental results of various exhaust gas collection methods in the case of low concentration of NH ₃ gas according to an embodiment of the present invention.

5 is NH ₃ according to an embodiment of the present invention. It is the frequency chart which shows the comparative experiment result of various exhaust gas collection methods in the case of high gas concentration.

6 is NH ₃ according to an embodiment of the present invention. It is a frequency diagram which shows the comparative experiment result of various exhaust gas collection methods in the case of low gas concentration.

For reference, description of the code | symbol used in the drawing is enumerated below. These codes are used additionally in the following sentences.

1: Year 2: Collection pipe

3: exhaust gas 4: inner tube

5: appearance 6: handwork

7: flange 8: seal

9 cleaning liquid injection port 10 gas suction port

11: washing liquid pump 12: gas absorption bottle

13: washing liquid 14: suction pump

15 gas meter

Hereinafter, the present invention will be described in detail with reference to the embodiments posted in the drawings, FIG. 1 is a conceptual diagram of an automatic measuring device according to the present invention. 2 is an enlarged view of a gas collection tube part. The tip of the gas collecting tube 2 is in contact with the exhaust gas 3 in the flue 1, and this portion is a short tube. The gas collecting tube is usually made of stainless steel which can withstand the temperature of the exhaust gas. In addition, the diameter of the collecting tube is about 5 mm.

In the vicinity of the attachment of the flange 7 of the flue, the collection pipe has a double structure 4 and 5 toward the outside of the flue. The gas collecting tube 2 is connected to the absorption bottle 12 of the exhaust gas, and further connected to the suction pump 14 and the gas meter 15. Thereafter, although omitted here, the number of samples absorbing the exhaust gas components is automatically collected and connected to the automatic analyzer.

In addition, the inside of the double pipe | tube structure part 4 and 5, ie, the structure in which the washing | cleaning liquid is inject | poured in the middle of an inner pipe | tube and an outer pipe | tube. The cleaning liquid is a structure in which the cleaning liquid is injected by the cleaning liquid pump 11 from the cleaning liquid injection port 9 at the end of the double pipe structure portions 4 and 5.

The gas collection method is demonstrated. First, the exhaust gas suction pump 14 is operated. Accordingly, the suction of the exhaust gas of the flue 1 starts, and the exhaust gas passes through the collecting pipe, and after the reaction of absorbing the component to be analyzed in the gas absorption bottle 12, namely ammonia gas in this case, the exhaust gas again. Aspirated and discarded via the gas meter 15.

Immediately before completing a certain amount of exhaust gas collection, the exhaust gas suction pump 14 operates the cleaning liquid pump 11 while operating, and injects the cleaning liquid 13 into the dual structure portion of the collection pipe.
However, depending on the state of the exhaust gas passage pipe (for example, condensation of water during the process of gas collection), the cleaning liquid pump 11 can be operated during the process of exhaust gas collection of a certain amount, so that the condensed water It can be released with the cleaning liquid. In this case, the exhaust gas suction pump 14 continues to operate.

The cleaning liquid passes through the dual structure portions 4 and 5 between the inner tube and the outer tube, and the cleaning liquid is injected into the inner tube, that is, the exhaust gas collecting tube 2, from the pores 6 at the tip end thereof.
Thereafter, the cleaning liquid flows downstream from the exhaust gas passage pipe over about 10,000 mm and is recovered with the absorbing liquid.

Since the suction pump 14 is operated, the cleaning liquid injected into the exhaust gas collecting tube flows in the suction direction toward the gas absorbing bottle 12, and thus the inner surface of the collecting tube is cleaned to clean the ammonia component attached to the inner surface. It is transported and collected in the gas absorption bottle 12, where the ammonia component is combined with an absorption liquid which has already absorbed ammonia from the exhaust gas. Therefore, ammonia can be efficiently and reliably recovered by the method of washing the inner surface of this collection pipe.

The phenomenon occurring in the double structure part of the exhaust gas collecting tube is further explained. In the initial stage when the cleaning liquid is injected at a temperature of 200 to 300 ° C. and the cleaning liquid is injected since the gas is in contact with the exhaust gas near the tip of the flue side, the cleaning liquid (in this case, pure water) ) Is boiled in this part, and the boiled water vapor is sucked from the pores 6 in the exhaust gas suction direction, cooled during passage and becomes a liquid and recovered into the absorption bottle.

Furthermore, if the cleaning liquid is continuously injected, the entire double pipe is cooled, and this time, the cleaning liquid is injected from the pores 6 in the liquid state. This washing liquid is similarly recovered in the absorption bottle and ammonia (hereinafter referred to as NH ₃ ) is collected.

The analysis accuracy of the NH ₃ gas in the exhaust gas analysis obtained in this example will be described below. The experiment was carried out in a case where the exhaust gas collecting hole formed in the flue of the power generation boiler of the thermal power plant equipped with the denitrification apparatus was provided with a large scale of collecting tubes of three different methods on the same flange. The length of the collection pipe within the year was consistently equal to 1150 mm, and the conditions such as the collection time and interval were unified. The exhaust gas collection method to be compared is a continuous measurement method and a JIS method (JIS K0099) as a manual analysis method for reference as well as the method of the present invention and the heating method (meaning the conventional method according to the methods of Patent Nos. 3229088 and 3322420). By three methods). All were measured simultaneously with one type of continuous measuring method and the JIS method.

In addition, the heating method made the heating degree two levels. Each exhaust gas collection condition is shown in Table 1. The result of experiment which adjusted these measurement conditions is shown in Table 2, FIG. 3 and 5 Table 3, FIG. Table 2 and FIG. 3 show comparative experiments at a level of about 130 ppm of relatively high NH ₃ concentration range, and the continuous test No. is a sequence of experiments conducted in order to avoid unevenness of the experiment as much as possible. In addition, the continuous measurement method and the manual analysis JIS method are simultaneous measurements. Table 3, Figure 4 shows the relatively low NH ₃ It is a comparative experiment at the level of the concentration range of about 15 ppm.

The characteristics of each data can be roughly seen in FIGS. 3 and 4, but in order to make it easier to understand, the difference in measured values from the JIS method based on the continuous measuring method is plotted as a histogram. 6. According to FIG. 5, in the high concentration range, the heating method 1 exhibits a low value with respect to the JIS method, and somewhat NH _3. It was estimated that the gas could not be captured completely, but the continuous measurement method yielded stable results.

The heating method 2 shows almost the same value with respect to the JIS method, and it is considered that the effect of the heat up came out compared with the heating method 1. In addition, the method of the present invention shows a considerably higher value for the JIS method, and NH ₃ It is estimated that the gas has been sufficiently captured. Similarly, when looking at the low concentration range in FIG. 6, the heating method 1 clearly shows a low value. In addition, the method of the present invention shows high values as well as the high concentration range. In other words, the process according to the invention is NH ₃ It can be seen that the gas concentration is a very good method from the high range to the low range.

As described above in detail, according to the exhaust gas collection method according to the present invention, the concentration of the ammonia gas component of the exhaust gas can be analyzed very precisely. Comparing the method according to the present invention with that of the conventional method, it is a very excellent method as shown in Figs. 3, 4, 5, and 6, and this method is introduced into an automatic analysis device for continuous measurement. It becomes an analysis device.

Claims (1)

As an automatic exhaust gas measuring device, in the exhaust gas collection process for analysis in the year, In order to collect and collect the gas components attached to the exhaust gas collecting tube, the collecting tube is doubled between the inner tube and the outer tube, and the inner tube flows the collecting gas, and the inner exhaust gas is collected in the gap between the outer tube and the inner tube. During the condensation of the exhaust gas component attached to the pipe and another moisture gas component attached to the surface of the exhaust gas passage pipe during the condensation of moisture, a cleaning liquid is injected, and the cleaning liquid is introduced to the inner side facing the outer tube through which the exhaust gas passes. A method for collecting exhaust gas for analysis comprising a highly adsorbable gas component, which flows out from pores bored in the middle of the tube and recovers the cleaning liquid into an exhaust gas absorption bottle disposed at a downstream end of the exhaust gas passage tube.

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