JPH0241706B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for measuring ultratrace amounts of ammonia nitrogen and total nitrogen. BACKGROUND ART In recent years, the amount and components of nitrogen in environmental water such as rivers, lakes, sea areas, and wastewater such as industrial wastewater, process wastewater, and sanitary wastewater, which are said to cause water eutrophication, have become a major problem. The form of nitrogen contained in water can be divided into four types: ammonia, nitrite, nitrate, and organic, but it is important to understand the total nitrogen content and ammonia nitrogen content in order to prevent pollution such as wastewater. is important.

Conventionally, devices for measuring ultratrace amounts of ammonia nitrogen use helium as a carrier gas to reduce the ammonia nitrogen in the sample water with a bromide ion-containing reaction solution in a reaction tube to nitrogen gas, completely removing the entrained moisture. A device has been proposed that uses gas chromatography to quantify the amount of oxidation. However, with this device, dissolved nitrogen gas in the reaction solution and sample water must be completely removed, and entrained moisture must also be completely removed after reduction to nitrogen gas, so pretreatment requires time. The disadvantage is that it requires a lot of time and is complicated to operate.

In addition, as a total nitrogen measurement device, a sample is introduced into a reaction tube filled with a reduction catalyst through which hydrogen gas is flowing, the nitrogen in the sample is reduced to ammonia, and acidic gas is extracted from the resulting reaction gas. There are commercially available devices that quantify the amount by coulometric titration after removal.
However, with this device, all of the water in the sample water is introduced into the coulometric titration tank in the form of water vapor, which is accompanied by a carrier gas. The amount of sample water to be injected was limited to about 0.5 ml because the liquid would be diluted and the temperature would rise, making accurate titration impossible. For this reason, the lower limit for measuring total nitrogen content is at most about 0.2 PPm, and there has been a desire to develop an apparatus that can measure even trace amounts of total nitrogen.

The present invention provides an apparatus for measuring ultratrace ammonia nitrogen and total nitrogen without such drawbacks, and the gist thereof is as follows: Instrument for measuring trace ammonia nitrogen and total nitrogen.

(a) Measuring section A reaction section consisting of a cylindrical reaction tube having a sample inlet and a hydrogen gas inlet at one end and a gas outlet at the other end filled with a reduction catalyst, a gas inlet and a gas outlet. an acidic gas removal section filled with a solid alkaline substance inside a container, a heating section for heating the reaction section and the acidic gas removal section, a gas introduction pipe, a gas outlet, an electrolytic electrode, an end point detection electrode, and an electrolytic cell. The coulometric titration section consists of a reaction section and an acidic gas removal section each housed in a heating section, a gas outlet of the reaction section is connected to a gas inlet of the acidic gas removal section, and a gas outlet of the acidic gas removal section is connected to a gas inlet of the acidic gas removal section. The gas introduction pipe of the coulometric titration unit is connected to a gas introduction pipe of a distillation tank, which will be described later, and is opened near the bottom of the electrolytic cell.

(b) Distillation section A distillation tank that has a sample inlet, a gas inlet pipe, and a gas outlet, and is made of alkali-resistant material.It consists of a reflux condenser, and the gas inlet pipe opens near the bottom of the distillation tank, and the reflux The lower end of the condenser is connected to the gas outlet of the distillation tank, and the upper end is connected to the gas inlet pipe of the coulometric titration section.

exists in

The present invention will be explained below with reference to the drawings. FIG. 1 is an explanatory diagram of an example of a device according to the present invention. 1 in the diagram
2 is a measuring section, 2 is a distillation section, 3 is a control section, 12 is a distillation tank, 18 is a coulometric titration section, 21 and 24 are heating sections, 2
2 is an acidic gas removal section, and 25 is a reaction section.

The measurement unit 1 includes a reaction unit 25 for reducing nitrogen compounds in a sample and converting them into ammonia, an acid gas removal unit 22 for removing acid gas from the converted gas, and a coulometric unit for quantifying ammonia. It is composed of a titration section 18.

The reaction section 25 has a cylindrical reaction tube having a sample inlet 4 and a hydrogen gas inlet tube 26 at one end and a gas outlet at the other end. It is filled with a metal catalyst made by coating the surface of inert particles such as alumina with these metals. Although the size of the catalyst particles depends on the size of the reaction tube, catalyst particles of about 0.5 to 15 mm are usually used. The catalyst is preferably filled with a heat-resistant inert material such as quartz, asbestos, alumina, etc. mixed with catalyst particles. The reaction section 25 is housed in a heating section 24 such as an electric furnace having a built-in heating wire, and
It is maintained at a high temperature of ~600℃.

The acid gas removal section 22 is for removing acid gases such as hydrogen sulfide contained in the gas discharged from the reaction section. It is filled with an alkali absorbent in which one or a mixture of two or more metal oxides or hydroxides is made into particles of about 1 to 7 mm. Specific examples of alkaline absorbents include a mixture of sodium hydroxide and calcium oxide (soda lime), a mixture of calcium hydroxide and calcium oxide, and a mixture of sodium hydroxide and α-
Examples include a mixture with alumina, a mixture of sodium hydroxide, potassium carbonate, and asbestos.
The acid gas removal section 22 is housed in the heating section 21 similar to the heating section 24, and is maintained at a temperature of about room temperature (20°C) to 300°C.

The coulometric adjustment unit 18 is for quantifying ammonia in the gas discharged from the distillation unit, which will be described later, and includes an electrolytic tank 19 with a sliding lid, an electrolytic electrode 16 installed in the nuclear tank, a detection electrode 17, and a gas. It is composed of an inlet pipe 15 and a gas outlet pipe 14. Each electrode 16, 17 and gas introduction pipe 15 are installed at a position where the lower end is submerged in the electrolyte.

The distillation section 2 is for removing ammonia nitrogen in the sample as ammonia gas and for absorbing and removing moisture in the gas derived from the acidic gas removal section 22. It is composed of a distillation tank 12 having an inlet pipe 10 and a gas outlet, a reflux condenser 6, and a heater 13. One end of the gas introduction pipe 10 is connected to the gas discharge pipe 20 of the acidic gas removal section 22, and the other end is opened near the bottom of the distillation tank 12, but it is preferable to attach a perforated plate to the open end. . The distillation tank 12 contains 20 to 50 wt%, preferably 20 to 40 wt%, of a strong alkali such as sodium hydroxide or potassium hydroxide.
% aqueous solution, it is preferable to use an alkali-resistant material such as high nickel alloy steel or ceramic. The reflux condenser 6 is preferably one with an obstruction in the gas flow path so as to avoid volatilization of the mist, and a coiled pipe is usually used, but if it is a straight pipe, it may be filled with a filler. The bottom opening of the reflux condenser 6 is the distillation tank 1.
The upper end opening is connected to the gas introduction pipe 15 of the coulometric titration section 18 through a conduit 5. The distillation tank 12 is heated by the heating unit 13 to 70° C. to the boiling temperature of the liquid, preferably 100° C. to the boiling temperature of the liquid.

The control unit 3 usually includes a coulometric titration control device 7, a temperature control device 8, and a gas flow rate control device 9. In the coulometric titration control device 7, the detection electrode 1
The electric signal corresponding to the hydrogen ion concentration obtained from step 7 is amplified, converted into a current output proportional to the deviation from the end point PH value, and an electrolytic current is supplied to the electrolytic electrode 16. On the other hand, if necessary, this electrolytic current is calculated as a current after subtracting the blank current, and is integrated after performing correction calculations such as analysis value unit conversion and sampling amount coefficient to indicate the ratio to the collected sample.
It is displayed as a direct reading of analysis that corresponds to the amount of electricity.

The temperature control device 8 is for adjusting the temperatures of the heating sections 21 and 24 and the heater 13 to a predetermined temperature.

The gas flow rate control device 9 is for adjusting the flow rate of hydrogen gas introduced from the hydrogen gas introduction pipe 26 to a predetermined amount. The flow rate of these gases is typically 200
~700ml/min, preferably 400-500ml/min.

Next, a case will be described in which water containing an ultratrace amount of nitrogen compounds is analyzed using the apparatus of the present invention configured as described above. First, to measure the total nitrogen amount,
A predetermined amount of sample water is injected through the sample inlet 4 of the measuring section 1. The injected sample water is passed through the hydrogen gas introduction pipe 26.
The reaction part 25 is entrained by the hydrogen gas introduced from
All nitrogen compounds are reduced to ammonia.
The generated ammonia gas is sent to conduit 2 along with hydrogen gas.
3 into the acid gas removal section 22, where the coexisting acid gas is removed. Then conduits 20 and 10
It is introduced into the distillation tank 12 through the. A portion of the water in the gas is removed by being absorbed by the alkaline liquid in the distillation tank 12, and most of the remaining water is removed in the reflux condenser 6, after which it is introduced into the electrolytic tank 19 via conduits 5 and 15. The sample is absorbed into an electrolytic solution, such as a 1% aqueous sodium sulfate solution, which has been placed in advance in the electrolytic cell 19, and coulometric titration is performed.
The titration results are displayed on the coulometric titration control device 7. The amount of sample water to be injected varies depending on the amount of nitrogen compounds contained, but is usually about 5 μ to 5 ml. One measurement is completed in about 4 to 8 minutes.

Next, ammonia nitrogen is measured as follows. A predetermined amount of sample water is injected from the sample inlet 11 of the distillation section 2. The ammonia nitrogen in the injected sample water becomes ammonia gas, which is entrained by the hydrogen gas introduced from the gas introduction pipe 10, and after most of the entrained water is removed by the reflux condenser 6, it is passed through the conduits 5 and 15. It is introduced into the electrolytic cell 19 of the coulometric titration section 18 and subjected to coulometric titration according to the method described above. The amount of sample water to be injected varies depending on the amount of nitrogen compounds contained, but is usually about 5 μ to 5 ml. One measurement is completed in about 6 to 8 minutes.

As described in detail above, since the device of the present invention is configured by combining the distillation section 2, which is not affected by water, with the measurement section 1, by changing the amount of sample collected,
It is possible to measure total nitrogen and ammonia nitrogen in ultra-trace amounts of around 0.005PPm with high precision and in a short time, making it ideal for total nitrogen analysis and ammonia analysis in environmental water, wastewater, agriculture, food, and pharmaceuticals. It is extremely useful for nitrogen analysis.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an example of a device according to the present invention. 1: Measuring section, 2: Distillation tank, 3: Control section, 12:
Distillation tank, 18: coulometric titration section, 21, 24: heating section, 22: acidic gas removal section, 25: reaction section.

Claims (1)

[Scope of Claims] 1. An apparatus for measuring ultratrace ammonia nitrogen and total nitrogen, characterized by having the following measurement section and distillation section. (a) Measuring section A reaction section consisting of a cylindrical reaction tube having a sample inlet and a hydrogen gas inlet at one end and a gas outlet at the other end filled with a reduction catalyst, a gas inlet and a gas outlet. an acidic gas removal section filled with a solid alkaline substance inside a container, a heating section for heating the reaction section and the acidic gas removal section, a gas introduction pipe, a gas outlet, an electrolytic electrode, an end point detection electrode, and an electrolytic cell. The coulometric titration section consists of a reaction section and an acidic gas removal section each housed in a heating section, a gas outlet of the reaction section is connected to a gas inlet of the acidic gas removal section, and a gas outlet of the acidic gas removal section is connected to a gas inlet of the acidic gas removal section. The gas introduction pipe of the coulometric titration unit is connected to a gas introduction pipe of a distillation tank, which will be described later, and is opened near the bottom of the electrolytic cell. (b) Distillation section A distillation tank that has a sample inlet, a gas inlet pipe, and a gas outlet, and is made of alkali-resistant material.It consists of a reflux condenser, and the gas inlet pipe opens near the bottom of the distillation tank, and the reflux The lower end of the condenser is connected to the gas outlet of the distillation tank, and the upper end is connected to the gas inlet pipe of the coulometric titration section.