JPH03152445A - Method and apparatus for chemical emission quantification of ammonia - Google Patents

Abstract

PURPOSE:To enable intermittent quantification of ammonia or ammonium ions in a successive manner or at a short-time interval by bringing the ammonia or the ammonium ions into contact with hypohalogenous acid ions or a halogen gas. CONSTITUTION:When vapor-phase ammonia is quantified, a sample gas I is introduced in a prescribed quantity into a reaction cell C through a flowmeter J, while a sodium hypochrolite water solution G and a hydrochloric acid water solution H are mixed in a mixer E and then introduced into the reaction cell C at a certain speed. In the case when ammonium ions in a liquid phase are quantified, a sample solution G and a sodium hydroxide water solution H are mixed E and then introduced into the cell C, while a chlorine gas I is introduced into the cell C through the flowmeter J. A liquid introduced from the lower part N of the reaction cell is not disturbed since the bottom of the cell is shaped in a funnel, and it is supplied sequentially to a vapor- liquid interface and reacts thereon with the gas, causing emission of light. The liquid and the gas are discharged from a discharge port at a prescribed speed, and therefore a distance between the surface of the liquid and a photomultiplier tube D is maintained to be fixed. A generated chemical emission is sensed by the tube D, amplified L and recorded M.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a quantitative method that utilizes a luminescence phenomenon based on a chemical reaction of ammonia or ammonium ions. This is particularly useful when measuring intermittently at intervals.

[Prior Art] As air pollution caused by nitrogen oxides becomes a problem, interest in so-called flue gas denitrification, which removes nitrogen oxides from flue gas, is rapidly increasing.

When performing denitrification by catalytic reduction as a denitrification method, ammonia is mainly used as the reducing gas, but in addition to the problem of bad odor when unreacted ammonia is discharged, 803 and 803 in the exhaust gas are also used. It is necessary to reduce the amount of unreacted ammonia as much as possible because ammonium sulfite and the like react and accumulate in the smoke pipe, causing problems in maintenance and management, and also causing acid rain. Therefore, it is desirable to constantly monitor whether unreacted ammonia is generated.

Currently, the commonly used method for quantifying trace amounts of ammonia is to dissolve ammonia gas in a solvent and quantify it as ammonium ions using the indophenol method. It is not possible to control the ammonia supply amount by continuously measuring and applying feedback control. On the other hand, continuous analysis methods include the solution conductivity method and infrared gas analysis method, which examine changes in conductive dust by bringing the sample gas and absorption liquid into contact, but these methods have the disadvantage of being easily influenced by other coexisting gases. ing.

[Problems to be Solved by the Invention] The present invention has been made in view of the above circumstances, and provides a method for quantifying ammonia or ammonium ions continuously or intermittently at short intervals. This is what we are trying to provide.

[Means for Solving the Problems] The quantitative method of the present invention brings ammonia or ammonium ions into contact with hypohalite ions or halogen gas, and generates a reaction between ammonia or ammonium ions and hypohalite ions or halogen gas. The key point is to measure the intensity of the chemiluminescence generated. In addition, the measurement of the present invention is an apparatus for measuring light emission (chemiluminescence) based on a chemical reaction occurring at the interface between a liquid phase and a gas phase, and the bottom of the reaction cell is funnel-shaped. A liquid inlet, a gas-liquid outlet on the side, and a gas inlet located higher than the outlet and facing the gas-liquid outlet, facing the liquid surface when the liquid is introduced. The method can be carried out using an apparatus having a reaction cell equipped with a photomultiplier tube.

[Operations and Examples] As a result of examining various methods for continuously measuring ammonia, the present inventors found that ammonium ions dissolved in gaseous ammonia or liquid phase react with halogen or hypohalogen ions to produce chemiluminescence. It was found that this occurs. These are completely new types of chemiluminescence that were previously unknown, and although the details of the luminescence mechanism are unknown, the 550nm and 75nm
Maximum light emission was shown at 0r+m. Chemiluminescence also occurs through the reaction of ammonium ions and hypohalogen ions in gaseous ammonia to halogen gases or liquid phases, but in order to easily measure weak chemiluminescence, the site of the reaction can be identified at the gas-liquid interface. gaseous ammonia and hypohalite ions,
The combination of ammonium ions and halogen gas was suitable. Conditions for quantifying ammonia and ammonium ions using the chemiluminescence were investigated by the following method. The case where hypochlorite ion or chlorine ion is used will be described below as a representative example.

Figure 1 shows a schematic diagram of the quantitative device used in the experiment. When quantifying ammonia in the gas phase, the sample gas I is
Sodium hypochlorite aqueous solution G and hydrochloric acid aqueous solution H are mixed in mixer E and then introduced into reaction cell C at a constant rate. When quantifying ammonium ions in the liquid phase, the sample solution G and the sodium hydroxide aqueous solution H are mixed in the mixer E and then introduced into the reaction cell, and the chlorine gas I passes through the flowmeter J and enters the reaction cell C. will be introduced in In either case, the air inside the reaction cell
A chemical reaction occurs at the liquid interface, producing light emission. In order to accurately measure the weak light generated at the gas-liquid interface, (1) new liquid surface is constantly supplied, (2) the liquid surface area is kept constant, and (3) the distance between the liquid surface and the photomultiplier tube is required. It is necessary to keep it constant. Figure 2 shows an example of a schematic cross-sectional view of a gas-liquid contact type reaction cell.The liquid introduced at a constant rate from the bottom N of the reaction cell is sequentially supplied to the gas-liquid interface without disturbance because the bottom surface is funnel-shaped. and reacts with gas to produce luminescence. Since the liquid and gas are discharged from the discharge port at a constant speed, the distance between the liquid surface and the photomultiplier tube is kept constant.

The generated chemiluminescence passes through a quartz glass filter, is received by a photomultiplier tube, is amplified, and is sent to a recorder M.
recorded in

Note that in the above method, a solution mixer is incorporated for the purpose of setting conditions, but in the case of actual measurement, reagents that have been mixed in advance may be used. The position of the pump can also be changed. The chlorine gas used in the experiment was packed in a cylinder manufactured by Tetsutsu Kagaku Co., and the ammonia gas was diluted with air purified through a glass tube filled with activated carbon, silica gel, and molecular sieve 5A.

◎Quantification of ammonia in the gas phase In order to find the optimal conditions for quantifying ammonia in the gas phase, we investigated the effects of hydrochloric acid concentration, sodium hypochlorite aqueous solution concentration, gas flow rate, and liquid flow rate on chemiluminescence.

(Effect of Hydrochloric Acid Concentration) Figure 3 shows the relationship between the pH of hydrochloric acid mixed with a 0.17N sodium hypochlorite aqueous solution and the luminescence intensity. Note that the mixing ratio was 5:3.

As shown in the figure, the maximum luminescence intensity was exhibited when the pH of hydrochloric acid was 0.8. At this time, the pH of the solution before the chemical reaction was 8.
It was 1 to 8.2. The acid used is not limited to hydrochloric acid; similar results were obtained with sulfuric acid, nitric acid, and iaI solution. In short, anything that promotes the absorption of ammonia may be used, and in some cases, it is possible to achieve sufficient results without using acids.

(Influence of concentration of sodium hypochlorite aqueous solution) Figure 4 shows the relationship between concentration of sodium hypochlorite aqueous solution and luminescence intensity when the pH of the hydrochloric acid aqueous solution is 0.8. The luminescence intensity became strong up to a concentration of 0.5M, but did not increase much above that. Considering the stability of the solution, the concentration of sodium hypochlorite aqueous solution is 0.
．． 1 to 0.5N is appropriate. Note that when measuring high concentrations of ammonium ions, it was necessary to increase the concentration of the sodium hypochlorite aqueous solution.

(Influence of gas flow rate and liquid flow rate) As the gas flow rate and liquid flow rate increased, the emission intensity increased. Considering the stability of the gas-liquid interface, the time required for measurement, etc., the gas flow rate was set to 0.5 to 11/win, and the liquid flow rate was set to 0.5 to 8 mIL/win, but these may be changed as appropriate depending on the sample concentration, etc. is possible.

Based on the above results, using a 1=1 mixture of 0.51N sodium hypochlorite aqueous solution and pH 0.8 hydrochloric acid aqueous solution, the gas flow rate was 117 mIn, and the liquid flow rate was 0.5 mj2/a+.
Fig. 5 shows the luminescence signal when ammonium ions were measured in the in vitro test, and Fig. 6 shows the calibration curve. As shown in the figure, there was an approximately first-order linear relationship for gaseous ammonia in the range of 0.1 to 200 ppm. Liquid flow rate is 1mj! /
The calibration curve became a nearly quadratic straight line when the temperature was set to be higher than win, but this is thought to be because the process of dissolving ammonia in the liquid phase has a linear relationship with the ammonia concentration. Note that clean air was flowed between the samples.

◎Quantification of ammonium ions in the liquid phase In order to find the optimal conditions for quantifying ammonium ions in the liquid phase, we investigated the effects of the sodium hydroxide aqueous solution concentration and chlorine gas concentration on the luminescence intensity. In addition, according to the quantitative determination of ammonia in the gas phase, the gas flow rate is 0.5 to 1 sb/ll.
1 inch, and the liquid flow rate was 0.5 to 8 mu/win.

(Influence of sodium hydroxide aqueous solution concentration) 188 in Figure 7
The relationship between the concentration of sodium hydroxide aqueous solution and the luminescence intensity when using ppm chlorine gas is shown. The luminescence intensity increased until the sodium hydroxide concentration reached ION, and remained constant even if the concentration was increased further. This is thought to be because the rate at which chlorine gas dissolves becomes faster as the sodium hydroxide concentration increases. However, when the NaOH concentration becomes high, ammonium ions escape as ammonia gas and the liquid level becomes unstable, so it was not preferable to increase the NaOH concentration to 18 or more. It was also possible to use potassium hydroxide instead of sodium hydroxide. In some cases, sufficient results can be obtained by absorbing chlorine gas without using an alkali.

(Influence of chlorine gas concentration) Figure 8 shows the relationship between chlorine gas concentration and luminescence intensity when IN NaOH is used. Chlorine gas concentration is 188pp
The luminescence intensity increased up to m. It is thought that it would increase further if the concentration was increased, but it could not be measured due to the cylinder used this time. However, the release of excess chlorine gas has a negative effect on the human body and causes pollution, so 188 ppm
is considered to be sufficient.

From the above results, the sodium hydroxide aqueous solution concentration IN, the chlorine gas concentration tsappm, and the gas flow rate 1fL/lll1n
The ammonium ions in the liquid were determined at a liquid flow rate of 3 mf/ff1 inch. The resulting luminescent signal is shown in Figure 9, and the calibration curve is shown in Figure 10. there were. Note that pure water was flowed between the samples.

As described above, this method, which has been shown to be capable of quantifying ammonia in the gas phase and ammonium ions in the liquid phase using chemiluminescence, has excellent reproducibility by keeping the conditions constant. There is no need to draw a calibration curve each time a measurement is made, and because it uses a unique reaction called chemiluminescence, there is no interference from hydrocarbons, carbon monoxide, nitrogen dioxide, amines, hydrogen sulfide, etc. .

[Effects of the Invention] The present invention is configured as described above, and by utilizing chemiluminescence of ammonia or ammonium ions,
It has become possible to provide a new method for measuring trace amounts of ammonia or ammonium ions either continuously or over a single period of time.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of the entire measuring device, Figure 2 is a schematic cross-sectional view of the vicinity of the reaction cell, and Figures 3 to 6 are diagrams showing the relationship between the pH of hydrochloric acid and the luminescence intensity in the determination of gaseous ammonia. Figure 3), Diagram showing the relationship between sodium hypochlorite concentration and luminescence intensity (Figure 4), Luminescence signal (Figure 5), Calibration FA
(Figure 6), and Figures 7 to 10 are diagrams showing the relationship between the concentration of sodium hydroxide aqueous solution and luminescence intensity in the determination of liquid ammonia (Figure 7), and the relationship between chlorine gas concentration and luminescence intensity. The diagram shown (Figure 8), the luminescence signal (Figure 9),
This is a calibration curve (Figure 10). A... Pump B... Waste liquid reservoir C... Reaction cell D... Photomultiplier tube E... Mixer
F... Peristaltic pump G... Sodium hypochlorite aqueous solution or sample solution H... Hydrochloric acid aqueous solution or sodium hydroxide aqueous solution ■... Sample gas or chlorine gas J... Flow meter K... Cleaning Air L...Amplifier M...Recorder N...Mixed solution
O... Drainage and exhaust Figure 1

Claims (2)

[Claims] (1) Ammonia characterized by contacting ammonia or ammonium ions with hypohalite ions or halogen gas and measuring the intensity of chemiluminescence produced by the reaction between ammonia or ammonium ions and hypohalite ions or halogen gas. chemiluminescence assay. (2) This is a device that measures luminescence based on a chemical reaction occurring at the interface between a liquid phase and a gas phase, and the bottom of the reaction cell is funnel-shaped. A liquid outlet, a gas inlet at a higher position than the outlet and facing the gas/liquid outlet, and a photomultiplier tube facing the liquid level when the liquid is introduced. 1. An ammonia chemiluminescence quantitative device characterized by having a reaction cell.