JPH0442620B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a device for measuring the concentration of sulfur dioxide gas in the atmosphere or exhaust gas, and particularly to a measuring device that enables accurate measurement by removing ammonia gas coexisting in a sample gas. In order to prevent pollution, the sulfur dioxide gas contained in exhaust gas in the atmosphere is measured by the solution conductivity method specified in Japanese Industrial Standard B7952. This measurement method measures the concentration of sulfur dioxide gas contained in the sample gas from the change in conductivity of the absorption liquid when the sample gas is passed through the absorption liquid. When gas is included, the conductivity changes due to ammonia gas, causing an error and causing the inconvenience that accurate measurement values cannot be obtained. Therefore, it is necessary to remove such ammonia gas before measurement. The conventional method for removing ammonia gas has been to attach a trap filled with a solid acid such as oxalic acid to a stage upstream of a sulfur dioxide gas measuring device to collect the trap. It has also been known for a long time to adsorb ammonia gas using an exchanger. However, these methods still have some practical problems. For example, in a method using oxalic acid, if the sample gas is in a dry state, some of the solid acid may sublimate and mix into the sample gas, causing an error in the sample gas. It has become necessary to take secondary measures such as cooling and humidifying the air. In addition, as a method using an ion exchanger,
A method using a strongly acidic cation exchange resin was published in JP-A-Sho.
It is described in Publication No. 58-44344. In this method, acidic components volatilize from the strongly acidic cation exchange resin, which affects the measurement, so it is actually necessary to select the material of the resin, and it is necessary to aging for a long time before measurement. Involves complicated pre-processing. Furthermore, Nafion (trade name of DuPont) described in the above publication is expensive and has a small exchange capacity per unit area, so if it were used to construct an ammonia gas removal device, it would be large-scale.
Moreover, the price of the entire device will inevitably rise. As described above, in order to remove ammonia gas in a sulfur dioxide gas measuring device, it is essential not only to simply treat the ammonia gas, but also to meet the following conditions. (1) Allows 100% of sulfur dioxide at ppb level to pass through.(2) Adsorbs ammonia gas from ppb concentration level to ppm concentration at a gas flow rate of about 1/min.(3) Has a considerably long life. (4) The substance used for ammonia gas removal must not generate any chemical components that would affect the measurement. (5) The conditions (1) to (4) above must be met even in outdoor measurements. As a result of investigation from various viewpoints, it was discovered that a strongly acidic cation exchange resin made for non-polar, non-aqueous solutions is optimal for removing ammonia gas, and the present invention was thus completed. That is, the present invention is characterized in that a column filled with a strongly acidic cation exchange resin for non-aqueous solutions is disposed in a flow path for sample gas collection. Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the measuring device shown in FIG.
After passing through a flow meter 3, it is introduced into a measuring tube 4. This measuring tube 4 is filled with a predetermined amount of a sulfuric acid-based hydrogen peroxide solution from a tank 5 by a pump 6, and the sulfur dioxide in the sample gas is absorbed and oxidized when the solution is aerated. The solution becomes sulfuric acid, which increases the conductivity of the solution, and the conductivity is measured by electrodes 7, 7. After the sample gas absorbs sulfur dioxide gas in the measuring tube 4, it is exhausted into the atmosphere by an exhaust pump 8. In the figure, reference numeral 9 designates drain tanks 10 and 10 for the absorption liquid used in the measurement, respectively, which are electromagnetic valves. In such a measuring device, for example, a flowmeter 3
A column 20 for removing ammonia gas is disposed in a flow path 11 formed between the measuring tube 4 and the measuring tube 4 .
For example, as shown in FIG. 2, this column 20 has Teflon filters 22, 22 attached to both ends of a glass tube 21 with an inner diameter of 10 mm and a tube length of 80 mm, and has a strong acid positive polarizer for non-aqueous solutions inside. It is formed by being filled with ion exchange resin 23, and the joint portions at both ends are connected to the flow path 11 to adsorb and remove ammonia gas in the sample gas before it is vented into the measurement tube. ing. In this case, the strongly acidic cation exchange resin for non-aqueous solutions used is a strong acid cation exchange resin with wear resistance that is made for non-polar non-aqueous solvents with its surface area and porosity strictly specified. For example, a divinylbenzene resin in which a sulfone group is an acidic group is used. As such a strong acidic cation exchange resin for non-aqueous solutions, for example, Amberlyst 1
5 (manufactured by Rohm and Haas), and is easily available commercially. This strongly acidic cation exchange resin for non-aqueous solutions has the property of selectively adsorbing and removing ammonia gas without adsorbing any sulfur dioxide. Also, column 2
When the sample is filled into the sample, volatile acidic substances are removed by simple surface treatment such as washing with water, and no chemical components are generated that may cause problems during measurement. Therefore, sulfur dioxide gas can be measured accurately. Furthermore, the amount of strongly acidic cation exchange resin for non-aqueous solutions required to remove ammonia gas is as small as, for example, 2 g, and a smaller column can be used for packing, making it a major design change for measurement equipment. It can be incorporated without requiring any additional equipment, and there is no need to make the device large-scale. Moreover, since the amount of ammonia gas adsorbed is as large as 5 to 6 mmol/g, it can be used for a long period of time, the column needs to be replaced less frequently, and the operation is less complicated. Note that the column 20 filled with this strongly acidic cation exchange resin for non-aqueous solutions is not only disposed in the flow path 11 between the flow meter 3 and the measuring tube 4, but also in the flow path between the flow meter 3 and the filter 2. It may be arranged in path 12,
Further, it may be disposed in the suction channel 1 in front of the filter 2, and its location is not limited as long as it is in the channel before the sample gas is introduced into the measurement tube 4. or,
Not only one unit but two or more units may be provided, and the number is not limited. Next, the present invention will be explained with reference to examples. Example 1 Amberlyst 15 (manufactured by Rohm and Haas) was used as a strongly acidic cation exchange resin for non-aqueous solutions, and 2 g of Amberlyst 15 was packed into a column and placed in the suction channel 1. Next, a sample gas containing no sulfur dioxide was sent to the measuring device shown in FIG. 1 at a flow rate of 1/min, and the concentration was measured. As a comparative example, the same sample gas was sent under the same conditions using a measuring device without a column, and its concentration was measured. The results are shown in Table 1, where column A is the measured value with the column attached, and column B is the measured value without the column attached. From the same table, it can be seen that no chemical components that would interfere with measurement were generated from the column.

[Table] Example 2 A column packed with Amberlyst 15 was placed in the suction channel 1, and the concentration of sulfur dioxide was approximately 40 ppb.
The sample gas was measured under the same conditions as in Example 1. The results are shown in Table 2. In the same table, A and B are the same as in the example. From this table, it can be seen that no sulfur dioxide gas is adsorbed within the column.

[Table] Example 3 A mixed gas having a sulfur dioxide concentration of 45 ppb and an ammonia concentration of 100 ppb was used as a sample gas, and measurements were made under the same conditions as in Example 1. The results are shown in Table 3. From the same table, the measured values in column B when a column is installed are not affected by ammonia gas, compared to the measured values in column B when a column is not installed, and ammonia gas is a strong acid positive solution for non-aqueous solutions. It can be seen that it is completely adsorbed on the ion exchange resin.

[Table] Example 4 In order to investigate how strongly acidic cation exchange resin for non-aqueous solutions is affected by differences in ammonia gas concentration, sample gases containing ammonia gas with different concentrations were passed through a column. Measurement was carried out under the same conditions as in Example 1. The results are shown in Table 4, showing stable adsorption over a wide range of ammonia gas concentrations.
Accurate measurements are possible.

[Table] Example 5 Since the sample gas is humid when measured in the outdoor atmosphere, sample gases with different humidity were measured under the same conditions as in Example 1. Table 5 shows the measurement results when the humidity is 0% and the temperature is 20℃, and Table 6 shows the measurement results when the humidity is 70% and the temperature is 20℃. There are no signs of humidity in column A) either.

【table】

【table】

[Table] As explained above, in the present invention, a sample gas is passed through a column packed with a strongly acidic cation exchange resin for non-aqueous solutions, and ammonia gas is adsorbed by the resin, and the influence of ammonia gas is removed. This has the effect that the sulfur gas concentration can be measured accurately.

[Brief explanation of drawings]

Fig. 1 is an overall layout diagram of one embodiment of the present invention, Fig. 2
The figure is a cross-sectional view of the column. 1... Suction channel, 2... Filter, 3... Flow meter, 4... Measuring tube, 5... Tank, 6... Pump, 7... Electrode, 8... Pump, 9... Tank,
10... Solenoid valve, 11, 12... Channel, 20...
Column, 23... Strongly acidic cation exchange resin for non-aqueous solutions.

Claims (1)

[Claims] 1. A sulfur dioxide gas measuring device comprising a column filled with a strongly acidic cation exchange resin for non-aqueous solutions in a flow path for sample gas collection.