CN218917187U

CN218917187U - Device for determining nitrogen oxides in air of workplace

Info

Publication number: CN218917187U
Application number: CN202222514490.XU
Authority: CN
Inventors: 冯琴琴; 张南南; 董一帆; 钱倩; 俞孝丰
Original assignee: Huzhou Standard Spectrum Environmental Testing Technology Co ltd
Current assignee: Huzhou Standard Spectrum Environmental Testing Technology Co ltd
Priority date: 2022-09-22
Filing date: 2022-09-22
Publication date: 2023-04-25
Anticipated expiration: 2032-09-22

Abstract

The utility model discloses a device for measuring nitrogen oxides in air of workplaces, which is characterized in that: the porous glass plate absorbing bottle comprises a first porous glass plate absorbing bottle (1), wherein the first porous glass plate absorbing bottle (1) is connected with a second porous glass plate absorbing bottle (3) through an oxidation bottle (2), the second porous glass plate absorbing bottle (3) is connected with a water stop clamp (6) through a drying bottle (4), the water stop clamp (6) is connected with a gas production pump (7) through a flowmeter (5), and absorbing liquid is filled in the first porous glass plate absorbing bottle (1) and the second porous glass plate absorbing bottle (3); and the oxidizing bottle (2) is filled with an acidic potassium permanganate solution. The utility model has the advantages of simpler operation, lower measurement cost and wider application range.

Description

Device for determining nitrogen oxides in air of workplace

Technical Field

The utility model belongs to the field of nitrogen oxide detection equipment, and particularly relates to a device for measuring nitrogen oxides in air in a workplace.

Background

Nitrogen oxides in the air of a workplace, including nitrogen monoxide and nitrogen dioxide, are toxic, and therefore, in the air mass measurement of a workplace, particularly a workplace where nitrogen oxides are easily generated, the concentration of nitrogen oxides needs to be measured. The toxicity of nitric oxide and nitrogen dioxide is different, so that the respective concentrations of nitric oxide and nitrogen dioxide can be accurately measured, which is beneficial to making more accurate judgment on the air quality.

The method for measuring the nitrogen oxides in the air of the workplace is carried out according to GBZ/T160.29-2004 (3), and two sets of devices are needed for measuring, including a nitrogen dioxide measuring device and a nitrogen monoxide measuring device. The nitrogen dioxide measuring device comprises a first porous glass plate absorption bottle, 5mL of absorption liquid is poured into the first porous glass plate absorption bottle, collected air is input from an inlet of the first porous glass plate absorption bottle, nitrogen dioxide in the air is dissolved in the absorption liquid to generate nitrous acid, the nitrous acid and aminobenzenesulfonic acid in the absorption liquid carry out a lifting nitridation reaction, then the nitrous acid and naphthalene ethylenediamine hydrochloride in the absorption liquid are coupled to form rose azo dye, and the concentration of nitrogen dioxide can be known by measuring absorbance at a wavelength of 540 nm. The nitrogen oxide measuring device comprises a second porous glass plate absorption bottle, 5mL of absorption liquid is poured into the second porous glass plate absorption bottle, a chromium trioxide-quartz sand oxidation tube is arranged at the inlet of the second porous glass plate absorption bottle, air is input from the oxidation tube, nitrogen oxide in the air is oxidized into nitrogen dioxide, the nitrogen dioxide enters the second porous glass plate absorption bottle, the absorption liquid turns into rose red, absorbance is measured at the wavelength of 540nm, the concentration of the nitrogen dioxide entering the second porous glass plate absorption bottle can be known, and the concentration of the nitrogen dioxide measured by the nitrogen dioxide measuring device is subtracted, and the difference value is the concentration of the nitrogen oxide.

At present, two sets of devices are needed for measuring the nitrogen oxides, two times of air are input, the flow rates of the two times of air input are equal, and the continuous input time is equal according to requirements, so that the accuracy of measuring results is improved, but the actual operation is difficult. Therefore, the conventional nitrogen oxide measuring device has a defect that the operation is difficult.

Disclosure of Invention

The utility model aims to provide a device for measuring nitrogen oxides in air of a workplace. The utility model has the advantages of simpler operation, lower measurement cost and wider application range.

The technical scheme of the utility model is as follows: a device for determining nitrogen oxide in workplace air, including first porous glass board absorption bottle, first porous glass board absorption bottle passes through the oxidation bottle and connects the porous glass board absorption bottle of second, and the porous glass board absorption bottle of second passes through the dry bottle and connects the stagnant water clamp, and the stagnant water clamp passes through the flowmeter and connects the gas production pump, has all been poured into the absorption liquid in first porous glass board absorption bottle and the porous glass board absorption bottle of second.

In the device for measuring the nitrogen oxides in the air of the workplace, the oxidizing bottle is filled with the acidic potassium permanganate solution.

Compared with the prior art, the utility model connects the first porous glass plate absorption bottle, the oxidation bottle and the second porous glass plate absorption bottle in series, nitrogen dioxide in the air is firstly absorbed by the first porous glass plate absorption bottle, so that the absorption liquid in the first porous glass plate absorption bottle changes color to measure the nitrogen dioxide concentration in the air, then nitric oxide in the air is oxidized into nitrogen dioxide by the oxidation bottle and then enters the second porous glass plate absorption bottle, so that the absorption liquid in the second porous glass plate absorption bottle changes color to measure the nitric oxide concentration in the air, and the sum of the measured nitrogen dioxide concentration and the measured nitric oxide concentration is the concentration of nitric oxide in the air. Because the same air is adopted when the nitrogen dioxide concentration is measured and the nitric oxide concentration is measured, the flow rates of the air passing through the two porous glass plate absorption bottles are necessarily equal, the time is also necessarily equal, and the manual control is not needed, so that the operation is simpler, and the data are more relevant. The method has the advantages that the nitric oxide is oxidized by using the acidic potassium permanganate solution in the oxidation bottle, so that the measurement cost can be reduced, the measurement error can be further reduced, the sensitivity to the environmental humidity is low, the requirement on the use environment is lower, and the application range of the method is wider.

Therefore, the utility model has the advantages of simpler operation, lower measurement cost and wider application range.

Drawings

Fig. 1 is a schematic structural view of the present utility model.

Fig. 2 is a schematic view showing a state in which nitrogen oxides pass through the first porous glass plate absorption bottle, the oxidation bottle and the second porous glass plate absorption bottle in sequence.

FIG. 3 is a schematic diagram of nitrogen dioxide measurement under the GBZ/T160.29-2004 (3) standard.

FIG. 4 is a schematic diagram of nitric oxide measurement under the GBZ/T160.29-2004 (3) standard.

The marks in the drawings are: 1-a first porous glass plate absorption bottle, 2-an oxidation bottle, 3-a second porous glass plate absorption bottle, 4-a drying bottle, 5-a flowmeter, 6-a water stop clamp and 7-a gas production pump.

Detailed Description

The utility model is further illustrated by the following figures and examples, which are not intended to be limiting.

Examples. The device for measuring nitrogen oxides in the air of workplaces comprises a first porous glass plate absorption bottle 1, wherein the first porous glass plate absorption bottle 1 is connected with a second porous glass plate absorption bottle 3 through an oxidation bottle 2, the second porous glass plate absorption bottle 3 is connected with a water stop clamp 6 through a drying bottle 4, the water stop clamp 6 is connected with a gas production pump 7 through a flowmeter 5, and absorption liquid is filled in the first porous glass plate absorption bottle 1 and the second porous glass plate absorption bottle 3. 10mL of acidic potassium permanganate solution is poured into the oxidation bottle 2. The drying bottle 4 takes silica gel as a drying agent.

Concentration of acidic potassium permanganate solution: c (KMnO 4) =25 g/L. The configuration method comprises the following steps: 25g of potassium permanganate is weighed into a 1000ml beaker, 500ml of water is added, the mixture is heated slightly to dissolve the potassium permanganate completely, then 500ml of sulfuric acid solution with the concentration of 1mol/L is added, the mixture is stirred uniformly, and the mixture is stored in a brown reagent bottle.

The configuration of the absorption liquid comprises the following steps: mixing the color development liquid (4.6) and water according to the proportion of 4:1 (volume part), namely the absorption liquid. The absorbance of the absorption liquid should be 0.005 or less.

Preparing a color development liquid: 5.0g of sulfanilic acid [ NH2C6H4SO3H ] was weighed and dissolved in about 200ml of hot water at 40-50 ℃, the solution was cooled to room temperature, transferred to a 1000ml volumetric flask, 50ml of N- (1-naphthyl) ethylenediamine hydrochloride stock solution (4.5) and 50ml of glacial acetic acid were added, and diluted with water to the scale. The solution is stored in a sealed brown bottle and can be stored in dark place below 25 ℃ for three months. If the solution is pale red, the solution should be reconstituted.

Preparation of N- (1-naphthyl) ethylenediamine hydrochloride stock solution: (C10H 7NH (CH 2) 2nh2.2hcl) =1.00 g/L: 0.50g of N- (1-naphthyl) ethylenediamine hydrochloride is weighed into a 500ml volumetric flask and diluted to a scale with water. The solution is stored in a sealed brown bottle, and is refrigerated in a refrigerator for three months.

Working principle: the air collecting pump 7 collects air of a workplace, the flow speed of the air collecting pump 7 is 0.3L/min, the collected air enters the first porous glass plate absorption bottle 1, nitrogen dioxide in the air completely reacts with absorption liquid, the absorption liquid becomes rose red, the absorbance is measured at the wavelength of 540nm, the quantity of the nitrogen dioxide entering the first porous glass plate absorption bottle 1 can be known, and the concentration of the nitrogen dioxide can be known by carrying out first calculation by combining the passing air quantity from the flowmeter 5. The air enters the oxidation bottle 2, nitric oxide in the air is completely oxidized into nitrogen dioxide by the acidic potassium permanganate solution, the nitrogen dioxide enters the second porous glass plate absorption bottle 3, the absorption liquid in the second porous glass plate absorption bottle 3 is changed into rose red, the absorbance is measured at the wavelength of 540nm, the quantity of the nitrogen dioxide entering the second porous glass plate absorption bottle 3 is known, namely the quantity of the nitric oxide in the air entering the oxidation bottle 2, and the concentration of the nitric oxide is known by carrying out second calculation by combining the quantity of the air passing through the flowmeter 5. And adding the nitrogen dioxide concentration obtained by the first calculation and the nitric oxide concentration obtained by the second calculation to obtain the concentration of the nitrogen oxides in the air of the workplace. After the air is sampled, the air sampling pump 7 is closed, and meanwhile, the water stop clamp 6 is closed, so that the solution is prevented from being sucked backwards. Both absorbance measurements should be performed after air sampling is completed.

Compared with two sets of devices used in the existing nitrogen oxide determination method:

first, the utility model is equivalent to connecting two sets of devices in series, and is provided with a drying bottle 4, a flowmeter 5, a water stop clamp 6 and a gas production pump 7. The advantage is, has guaranteed that the air flow through first porous glass board absorption bottle 1 and second porous glass board absorption bottle 3 is the same, easy operation, can also guarantee that detection error is little.

Secondly, replacing the chromium oxide-quartz sand oxidation tube with an oxidation bottle filled with an acidic potassium permanganate solution. The preparation of the original chromium trioxide-quartz sand oxidation tube: screening quartz sand with 20-40 meshes, soaking the quartz sand in hydrochloric acid solution for one night, washing the quartz sand with water to be neutral, and drying the quartz sand. Mixing chromium trioxide and quartz sand according to the mass ratio of (1+20), adding a small amount of water, uniformly mixing, drying at 105 ℃, and stirring for several times in the drying process. The prepared chromium trioxide-quartz sand should be loose, and if the chromium trioxide-quartz sand is stained together, the chromium trioxide proportion is too large, and some quartz sand can be properly added for re-preparation. The prepared chromium trioxide-quartz sand is put into a double-ball glass tube, the two ends are well filled with a small amount of finger-removing cotton, the two ends are sealed by a small cap made of a latex tube filled with glass beads, and the oxidation tube and the absorption bottle are connected by a small section of silicon rubber tube during use. 1) The preparation of the chromium trioxide-quartz sand oxidation tube is complicated, the contained chromium trioxide is dark red or purple crystals, and when nitric oxide is oxidized, the decomposition products are dark green crystals or green powder of chromium trioxide, so that the oxidation tube becomes invalid after becoming green, the chromium trioxide-quartz sand oxidation tube needs to be prepared again, the preparation process is complicated, and the cost is high. In contrast, the preparation of the potassium permanganate solution is simpler and the cost is lower. 2) In the process of measuring the nitrogen oxides, chromium trioxide-quartz sand oxide easily enters a corresponding porous glass plate absorption bottle along with air flow, so that absorption liquid in the bottle is yellow-brown, absorbance is changed, and an experiment result is inaccurate. The acidic potassium permanganate solution can not enter the porous glass plate absorption bottle along with the air flow, and the inaccurate experimental result can not be caused. 3) The environment relative humidity range suitable for the chromium trioxide-quartz sand oxidation tube is 30% -70% RH, when the air humidity is greater than 70% RH, the oxidation tube needs to be replaced frequently, when the air humidity is less than 30% RH, the wet air which needs to pass through the water surface is used for balancing for 1h through the oxidation tube before the use, and in the use process, whether the oxidation effect is weakened or invalid due to hardening or greening caused by moisture absorption or not needs to be noticed at any time, and the use condition is harsh. The oxidation bottle of the acidic potassium permanganate solution can overcome the influence of air or water vapor in the absorption bottle, and the applicable condition is wider. 4) The contact area of the oxidation bottle and nitric oxide is larger, and the continuous oxidation effect is better than that of a chromium oxide-quartz sand oxidation tube.

Claims

1. Device for determining nitrogen oxides in workplace air, characterized in that: including first porous glass board absorption bottle (1), first porous glass board absorption bottle (1) is through oxidation bottle (2) connection second porous glass board absorption bottle (3), and second porous glass board absorption bottle (3) are through dry bottle (4) connection stagnant water clamp (6), and stagnant water clamp (6) are through flowmeter (5) connection gas production pump (7), all are poured with the absorption liquid in first porous glass board absorption bottle (1) and the second porous glass board absorption bottle (3).

2. The apparatus for determining nitrogen oxides in workplace air of claim 1, wherein: and the oxidizing bottle (2) is filled with an acidic potassium permanganate solution.