NL2031564B1 - Test method for Sampling Efficiency of Volatile Organic Compounds in Air and Special Device - Google Patents
Test method for Sampling Efficiency of Volatile Organic Compounds in Air and Special Device Download PDFInfo
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- NL2031564B1 NL2031564B1 NL2031564A NL2031564A NL2031564B1 NL 2031564 B1 NL2031564 B1 NL 2031564B1 NL 2031564 A NL2031564 A NL 2031564A NL 2031564 A NL2031564 A NL 2031564A NL 2031564 B1 NL2031564 B1 NL 2031564B1
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- 238000005070 sampling Methods 0.000 title claims abstract description 113
- 239000012855 volatile organic compound Substances 0.000 title claims abstract description 38
- 238000010998 test method Methods 0.000 title claims abstract description 13
- 238000001179 sorption measurement Methods 0.000 claims abstract description 63
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 53
- 239000010959 steel Substances 0.000 claims abstract description 53
- 239000003463 adsorbent Substances 0.000 claims abstract description 48
- 238000012360 testing method Methods 0.000 claims abstract description 34
- 239000007788 liquid Substances 0.000 claims abstract description 14
- 239000003085 diluting agent Substances 0.000 claims abstract description 11
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 13
- 229910052802 copper Inorganic materials 0.000 claims description 13
- 239000010949 copper Substances 0.000 claims description 13
- 229910001220 stainless steel Inorganic materials 0.000 claims description 10
- 239000010935 stainless steel Substances 0.000 claims description 10
- 150000001875 compounds Chemical class 0.000 claims description 6
- 238000004817 gas chromatography Methods 0.000 claims description 6
- 230000007613 environmental effect Effects 0.000 abstract description 8
- 238000012544 monitoring process Methods 0.000 abstract description 7
- 239000007789 gas Substances 0.000 description 87
- UHOVQNZJYSORNB-UHFFFAOYSA-N Benzene Chemical compound C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 description 24
- 238000000034 method Methods 0.000 description 20
- 150000001555 benzenes Chemical class 0.000 description 19
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 18
- URLKBWYHVLBVBO-UHFFFAOYSA-N Para-Xylene Chemical group CC1=CC=C(C)C=C1 URLKBWYHVLBVBO-UHFFFAOYSA-N 0.000 description 14
- PPBRXRYQALVLMV-UHFFFAOYSA-N Styrene Chemical compound C=CC1=CC=CC=C1 PPBRXRYQALVLMV-UHFFFAOYSA-N 0.000 description 14
- IVSZLXZYQVIEFR-UHFFFAOYSA-N m-xylene Chemical group CC1=CC=CC(C)=C1 IVSZLXZYQVIEFR-UHFFFAOYSA-N 0.000 description 14
- CTQNGGLPUBDAKN-UHFFFAOYSA-N O-Xylene Chemical group CC1=CC=CC=C1C CTQNGGLPUBDAKN-UHFFFAOYSA-N 0.000 description 12
- 239000000463 material Substances 0.000 description 10
- YNQLUTRBYVCPMQ-UHFFFAOYSA-N Ethylbenzene Chemical compound CCC1=CC=CC=C1 YNQLUTRBYVCPMQ-UHFFFAOYSA-N 0.000 description 9
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 7
- 238000004458 analytical method Methods 0.000 description 7
- 239000003517 fume Substances 0.000 description 7
- 239000000126 substance Substances 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- 239000007787 solid Substances 0.000 description 5
- 230000001276 controlling effect Effects 0.000 description 4
- 238000000354 decomposition reaction Methods 0.000 description 4
- 238000001514 detection method Methods 0.000 description 4
- 230000007423 decrease Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 230000002452 interceptive effect Effects 0.000 description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 238000004140 cleaning Methods 0.000 description 2
- RWGFKTVRMDUZSP-UHFFFAOYSA-N cumene Chemical compound CC(C)C1=CC=CC=C1 RWGFKTVRMDUZSP-UHFFFAOYSA-N 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 239000000741 silica gel Substances 0.000 description 2
- 229910002027 silica gel Inorganic materials 0.000 description 2
- 238000010561 standard procedure Methods 0.000 description 2
- 208000032467 Aplastic anaemia Diseases 0.000 description 1
- 238000004378 air conditioning Methods 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 230000000711 cancerogenic effect Effects 0.000 description 1
- 231100000357 carcinogen Toxicity 0.000 description 1
- 239000003183 carcinogenic agent Substances 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000010812 external standard method Methods 0.000 description 1
- 230000009931 harmful effect Effects 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 208000032839 leukemia Diseases 0.000 description 1
- 239000011368 organic material Substances 0.000 description 1
- 230000008520 organization Effects 0.000 description 1
- 231100000614 poison Toxicity 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000002594 sorbent Substances 0.000 description 1
- 239000012086 standard solution Substances 0.000 description 1
- 230000009897 systematic effect Effects 0.000 description 1
- 238000012353 t test Methods 0.000 description 1
- 230000002277 temperature effect Effects 0.000 description 1
- 239000003440 toxic substance Substances 0.000 description 1
- 239000003053 toxin Substances 0.000 description 1
- 231100000765 toxin Toxicity 0.000 description 1
- 108700012359 toxins Proteins 0.000 description 1
Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/0004—Gaseous mixtures, e.g. polluted air
- G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
- G01N33/0027—General constructional details of gas analysers, e.g. portable test equipment concerning the detector
- G01N33/0036—General constructional details of gas analysers, e.g. portable test equipment concerning the detector specially adapted to detect a particular component
- G01N33/0047—Organic compounds
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/40—Concentrating samples
- G01N1/405—Concentrating samples by adsorption or absorption
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/0004—Gaseous mixtures, e.g. polluted air
- G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
- G01N33/0011—Sample conditioning
- G01N33/0016—Sample conditioning by regulating a physical variable, e.g. pressure or temperature
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/0004—Gaseous mixtures, e.g. polluted air
- G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
- G01N33/0011—Sample conditioning
- G01N33/0018—Sample conditioning by diluting a gas
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/0004—Gaseous mixtures, e.g. polluted air
- G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
- G01N33/0011—Sample conditioning
- G01N33/0019—Sample conditioning by preconcentration
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- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Health & Medical Sciences (AREA)
- Engineering & Computer Science (AREA)
- Biochemistry (AREA)
- Physics & Mathematics (AREA)
- Analytical Chemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Food Science & Technology (AREA)
- Medicinal Chemistry (AREA)
- Combustion & Propulsion (AREA)
- Sampling And Sample Adjustment (AREA)
Abstract
The invention belongs to the field of environment monitoring, particularly relates to a test method for sampling efficiency of volatile organic compounds in air, and further relates to a special device used in the test method; the test method comprises the following steps: preparing a to-be-tested gas; controlling the gas pressure in a steel cylinder I and steel cylinders 11; adjusting pressure distributing meters; enabling a diluent gas and a standard gas to flow to the furnace box of a temperature and humidity control device according to a proportion; adjusting the temperature and humidity in the furnace box; enabling the gas to flow out from the top of the furnace box to enter a dynamic uniform-mixing device for uniform mixing; enabling the uniformly-mixed gas to enter sampling adsorption devices to be adsorbed by an adsorbent or an adsorption liquid in the sampling adsorption devices; emptying the residual gas; calculating; according to the invention, the test method is provided for the field of environmental monitoring, and the test device matched with the test method is designed, so that scientific research on gas sampling and adsorbing in the field of environment monitoring and even in other industries is more accurate, rigorous and scientific.
Description
t Test method for Sampling Efficiency of Volatile Organic Compounds in Air and Special Device
TECHNICAL FIELD The present invention relates to the technical field of environmental monitoring, particularly a test method for sampling efficiency of volatile organic compounds in air, and further relates to a special device used in the test method.
BACKGROUND Currently, standard analytical methods have been introduced for the determination of volatile organic compounds in air and exhaust gases in the environmental protection industry. But the method itself mainly emphasizes the analytical method. For the standards, the sampling method is also of paramount importance, because the sampling error is much greater than the analysis error. These standards do not pay attention to sampling methods, not because they do not know the importance of sampling methods, but because they have no suitable devices for testing sampling efficiency to simulate the sampling efficiency when sampling in the field. Therefore, these standards evade the importance of sampling methods. It is also a major reason for the low and slow introduction of volatile organic compound standards for air and exhaust gases in environment-friendly industries. In environment-friendly industries, there is no environmental standard method for the determination of volatile organic compounds in air and exhaust gases. Most of the methods are based on the “Determination of toxic substances in workplace air—Part 59: Volatile organic compounds” (GBZ/T 300.59-2017) in the national occupational health standards issued by the Ministry of Health of the People's Republic of China. This standard is more comprehensive and systematic, but the method itself is relatively crude, not to mention the consideration of sampling efficiency. And as a reference for environmental standards, the standard itself is uncertain about its significance and role.
At present, China's existing national standard methods of analysis of organic toxins in the workplace air are increasingly dominated by sampling with activated carbon tubes. The common sampling of organic vapor and its compounds by the original adsorption liquid or syringe sampling is gradually replaced by solid adsorbents with high adsorption power, such as activated carbon and silica gel.
According to the data, there are hundreds of activated carbon adsorbent sampling methods for monitoring organic vapors in air issued by OSHA and NIOSH in the United States, accounting for more than 60% of the total monitoring methods.
It is sufficient to show that activated carbon has a broad potential for application as a solid adsorbent.
Currently, gas samples in the air are generally collected using active sampling technology, where an integrated atmospheric sampler (with a built-in engine as the source of power, plus a flow meter to control the sampling rate) and a sampling adsorbent are used to complete the sampling.
The adsorbents for sampling mainly include activated carbon, silica gel, resin and adsorption liquid.
These selected adsorbents are theoretically the best adsorbers and have been tested to have positive results.
However, the adsorption process is complicated, and the effectiveness of adsorption is determined by many factors, including gas temperature and humidity, sampling flow rate, sampling time, meteorological conditions in the sampling area, the capacity of adsorbents, sampling interference, and breakthrough volume.
At present, it is very difficult and expensive to simulate the actual sample collection (using a room as the gas source), and there 1s hardly any method that can achieve this.
The breakthrough volume (BTV) test is a characteristic indicator of activated carbon tube sampling.
The BTV data is very important in determining the exact application of the activated carbon tube to the sampling of various standard gases with different concentrations (e.g. high concentration, high humidity) in the field with different humidity and temperature effects.
Usually, BTV data depends on the adsorption capacity of an adsorbent itself and changes with the environmental conditions of the site.
The smaller the BTV, the more restricted by the sampling time, the less it can reflect the true concentration of the site, and the less representative the sample.
On the contrary, the greater the BTV, the less restricted by time for the site of medium and high concentrations, the more representative the sample test results, and the more faithfully it can reflect the distribution of different concentrations in the site.
This invention can fully simulate the various requirements of the BTV experiment, the concentration can be freely configured, the sampling time and sampling volume are sufficient, and the environmental conditions of the site, such as temperature and humidity, can meet the requirements by changing the settings of the gas in the buffered stainless steel cylinder.
At present, in environmental monitoring, large plastic bags or fume hoods equipped with atmospheric samplers are often used to simulate the collection of volatile organic compounds in the air for the sampling efficiency test. These sampling devices currently have substantial drawbacks as follows: (1) The operation time 1s long and the stability is poor under the temporarily built and assembled system; (2) The volume of sampling is fixed. The volume of a large plastic bag or fume hood is the sampling volume (10-20L for a large plastic bag and 100-200L for a fume hood in a laboratory), and the sampling volume cannot be altered depending on actual demand; (3) During sampling in large plastic bags or fume hoods, the negative pressure formed by gas reduction is not considered, resulting in an uneven sampling rate; (4) It is difficult to mix the gas uniformly when sampling in large plastic bags or fume hoods; (5) The temperature and humidity of large plastic bags or fume hoods are not easily controlled, making it difficult to simulate field sampling conditions. Therefore, it is necessary to improve the above-mentioned drawbacks and design an efficiency testing device that can better simulate the actual sampling work, so that the staff can have a more accurate understanding of the collected samples.
SUMMARY The purpose of the invention is to overcome the above technical problems. The present invention provides a convenient test method for sampling efficiency of volatile organic compounds in air with accurate results, and further provides a test device for sampling efficiency of volatile organic compounds in air with a simple structure and ease of use based on the above method; Traditional methods of sampling efficiency testing are usually solved in two ways. One is the sampling with large plastic bags or fume hoods. In this way, the volume of the gas collected cannot be simulated with the actual conditions, and the meteorological parameters cannot be matched, and they are not stable and not scientific. The other is the addition of liquid specimens to the adsorbent. In this way, it can not characterize the adsorbent's adsorption capacity under actual conditions, and it is not scientific. The device simulates the sampling efficiency of the adsorbent in real sampling situations. For example, the humidity of the collected gas is a very important parameter during sampling. By testing the efficiency of the adsorbent, it is assumed that the efficiency of the adsorbent decreases significantly at a humidity above 90%.
Then, in the actual sampling, sampling should be avoided under such high humidity conditions, and the sample gas must be treated to keep its temperature and humidity within a certain range, in order to improve the accuracy of the test results.
To achieve the above purpose, the present invention provides the following solutions: The present invention provides a test method for sampling efficiency of volatile organic compounds in air, which comprises the following steps: Preparing a to-be-tested gas, controlling the pressure of a diluent gas in steel cylinder I to be between 5 and 15 MPa, and turning on the pressure distributing meters on steel cylinder I to be between 0.2 and 1.0 MPa; Controlling the pressure of the standard gas in steel cylinder II between 5 and 15 MPa; opening the valves of steel cylinder I and steel cylinder II and adjusting the pressure distributing meters to the above pressure range; Enabling a diluent gas and a standard gas to flow to enter a dynamic uniform-mixing device for uniform mixing and then to the furnace box of a temperature and humidity control device according to a proportion; adjusting the temperature and humidity in the furnace box to a temperature of 25°C and humidity of 10%; enabling the gas with adjusted temperature and humidity to flow out from the top of the furnace box to enter sampling adsorption devices to be adsorbed by an adsorbent or an adsorption liquid in the sampling adsorption devices; emptying the residual gas; The amount of volatile organic compounds C(adsorbed) adsorbed on the adsorbent or adsorption liquid is determined by gas chromatography; The total amount of volatile organic compounds entering the adsorption device, C (total), is calculated from the flow rate V of the flow meter, the collection time S, the proportion of standard gas R and the molecular weight M of the compound, C (total) =VxSxRxM; The sampling efficiency y of volatile organic compounds in air is calculated as: y=C (adsorbed)/C (total).
The devices of the present invention comprise the steel cylinder I for storing the diluent gas, several steel cylinders H for storing the standard gas, the dynamic uniform-mixing device, the temperature and humidity control device and several sampling adsorption devices;
The steel cylinder I and steel cylinders H are connected in parallel with one end of the dynamic uniform-mixing device, and the other end of the dynamic uniform-mixing device is connected in series with the temperature and humidity control device; the 5S other end of the temperature and humidity control device is connected in parallel with several sampling adsorption devices;
The steel cylinder I, steel cylinders II, the dynamic uniform-mixing device, the temperature and humidity control device and the sampling adsorption device are connected with tubes;
The steel cylinder I and steel cylinders H are connected with seven-way proportional valves, and the steel cylinder I, steel cylinders H are connected with the dynamic uniform-mixing device;
Flow meters are equipped between the dynamic uniform-mixing device and the temperature and humidity control device and between the temperature and humidity control device and the sampling adsorption device;
The temperature and humidity control device comprises the furniture box, wherein the bottom of the furniture box is provided with a temperature controller, and the top of the furniture box is provided with a humidifier; the air nozzle of the humidifier is located inside the furnace box, and the outer wall of the furnace box is provided with a fan.
The temperature and humidity control device comprises the furniture box, wherein the bottom of the furniture box is provided with a temperature controller, and the top of the furniture box 1s provided with a humidifier; the air nozzle of the humidifier is located inside the furnace box, and the outer wall of the furnace box is provided with a fan; the humidifier uses an ultrasonic atomized humidifier, which produces water vapor with high efficiency and short time, and controls the amount of water vapor produced by adjusting the size of the water flow, with the humidity control range between 0 and 95%; the temperature controller is a small air conditioning system that can control the internal temperature to increase or decrease according to the changes of the external ambient temperature; the outer wall of the furnace box is equipped with a fan, which is mainly used to cool down the sample quickly when testing at lower temperatures.
The resistance wire in the furnace box is used to clean the entire system at higher temperatures, with a maximum of 150°C to keep the system clean.
The furnace box can be equipped with a resistance wire to heat it.
The main body of the dynamic uniform-mixing device is a stainless steel cylinder made of stainless steel, and its interior is electropolished and inerted to prevent adsorption and facilitate cleaning, as well as to prevent the decomposition of gases that are susceptible to decomposition when exposed to light; The dynamic uniform-mixing device is equipped with an internal mixer. The gas entering the dynamic uniform-mixing device is re-mixed by the mixer inside the device to ensure that the gas in the dynamic uniform-mixing device meets the desired requirements.
The tube is copper, the copper tube is high-purity copper, the inner wall has been silanized to ensure that the test gas does not react with the copper tube, and the test gas does not remain in the copper tube; the copper tube is soft and durable.
The dynamic uniform-mixing device is equipped with a fixed bracket for fixing the dynamic uniform-mixing device; the top and bottom of the bracket are in the cross shape, or in other shapes, such as the asterisk shape; the purpose is to fix the position of the stainless steel cylinder firmly. The purpose is to hold the stainless steel cylinder firmly in place.
The dynamic uniform-mixing device withstands pressures greater than 100psi. The temperature and humidity control device comprises a temperature sensor, a humidity sensor, a display screen and a microprocessor; the temperature sensor and the humidity sensor are located inside the furniture box respectively; the temperature sensor, the humidity sensor, the temperature controller, the humidifier, the display screen and the fan are connected with the microprocessor respectively. The temperature sensor and the humidity sensor report the temperature and humidity inside the temperature and humidity control device to the microprocessor, and display the temperature and humidity on the display screen. The temperature and humidity of the gas inside the temperature and humidity control device can be regulated by the microprocessor, and the temperature controller, the humidifier or the fan operates to adjust the temperature and humidity of the gas in the temperature and humidity control device.
The microprocessor is also connected to a flow meter to control the flow rate of each tube; A pressure relief valve is also connected in parallel to the other end of the dynamic uniform-mixing device via a pipe. The sampling adsorption device can be either an adsorption tube or an adsorption bottle, and the sampling adsorption device has either a solid adsorbent or a liquid adsorbent inside.
The main purpose of the invention is to determine the meteorological conditions of the tested gases, and to select the best adsorbent material to achieve the best collection effect in the shortest time. The invention can also simulate the situation of five interfering gases, and the five simulated interfering gases of the adsorbent at this time can be selected from 1-5 of them, and the concentration range can be adjusted freely.
The gas from the multi-component flow distribution system has a total control valve to control the total pressure of the standard gas obtained, because too much or too little pressure can affect the effectiveness of the calibration test system.
The special device in the present invention discloses the following technical effects: (1) The use of the test device for sampling efficiency of volatile organic compounds in air: its structure is simple and no air pump is required, (2) The use of the temperature and humidity control device: it controls the temperature and humidity of the gas within a certain range or at a specific temperature or humidity, simulating the temperature and humidity conditions of the actual sampling environment for various field sampling scenarios. Moreover, the best adsorption material 1s used to locate the best temperature and humidity environment for sampling, so that the results of detection and analysis are more accurate.
(3) Wide range of application: The sampling effect of gases can be tested in various sampling methods, such as sampling tubes or adsorbent tubes with different kinds of adsorbent materials, and the adsorbent materials can be solid adsorbent or liquid adsorbent; (4) Accurate calculation of the adsorption efficiency of an adsorbent; (5) Selection of the best adsorbent material for the method; (6) Configuration of different concentrations of standard gases; (7) Simulation of the adsorption efficiency of adsorbent materials at different concentrations of interfering gases; (8) Determination of the optimum conditions of use of the optimal sorbent material (temperature and humidity range for atmospheric sampling), (9) Determination of the breakthrough volume of the optimal adsorbent material;
(10) Design of a method for the selection of optimal adsorbent materials for gases; (11) Development of a standard process for the selection of optimal adsorption materials for gases.
BRIEF DESCRIPTION OF THE FIGURES Figure 1 is a schematic diagram of the structure of the test device for sampling efficiency of volatile organic compounds in air of the present invention, Figure 2 is a side view of the temperature and humidity control device of the present invention; Figure 3 is the electrical schematic diagram of the present invention; Figure 4 is the structure diagram of the dynamic uniform-mixing device and bracket of the present invention; Figure 5 is the chromatogram of the seven benzenes; In the figures, 1-steel cylinder I, 2-steel cylinders II, 3-humidifier, 4-temperature and humidity control device, 5-temperature controller, 6-dynamic uniform-mixing device, 7-mixer, 8-sampling adsorption device, 9-temperature sensor, 10-humidity sensor, 11- fan, 12-microprocessor, 13-display screen, 14-pressure relief valve, 15-flow meters, 16-bracket, 17-seven-way proportional valve.
DESCRIPTION OF THE INVENTION Various exemplary embodiments of the present invention will now be described in detail, which should not be regarded as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics and embodiments of the present invention.
Embodiment 1 The most common and most analyzed volatile organic compounds in the air are benzenes. Benzenes is a collective term for benzene, methylbenzene, ethyl benzene, para-xylene, meta-xylene, ortho-xylene, isopropyl benzene, and styrene. It is the most common compound in the atmosphere and many pollution sources, and has certain harmful effects on human health. Among them, benzene was recognized as a strong carcinogen by the World Health Organization (WHO) in 1993, and is recognized by the medical community as a cause of leukemia and aplastic anemia. Therefore, they are critical pollutants for the environment. The sampling efficiency of benzenes in air is tested by the sampling efficiency testing device of the present invention.
Embodiment 1 of the present invention comprises the test method for sampling efficiency of volatile organic compounds in air, which include the following steps: Preparing a to-be-tested gas, controlling the pressure of a diluent gas in steel cylinder I to be between 5 and 15 MPa, and turning on the pressure distributing meters on steel cylinder I to be between 0.2 and 1.0 MPa; Controlling the pressure of the standard gas in steel cylinders II between 5-15 MPa; Opening the valves of steel cylinders I and steel cylinders H, and adjusting the pressure distributing meters to the above pressure range; Enabling a diluent gas and a standard gas to flow to enter a dynamic uniform-mixing device for uniform mixing and then to the furnace box of a temperature and humidity control device according to a proportion; adjusting the temperature and humidity in the furnace box to a temperature of 25°C and humidity of 10%; enabling the gas with adjusted temperature and humidity to flow out from the top of the furnace box to enter sampling adsorption devices to be adsorbed by an adsorbent or an adsorption liquid in the sampling adsorption devices; emptying the residual gas; The amount of volatile organic compounds C (adsorbed) adsorbed on the adsorbent or adsorption liquid is determined by gas chromatography; The total amount of volatile organic compounds entering the adsorption device, C (total), is calculated from the flow rate V of the flow meter, the collection time S, the proportion of standard gas R and the molecular weight M of the compound, C (total) =V>xSxRxM; The sampling efficiency y of volatile organic compounds in air is calculated as: y=C (adsorbed)/C (total).
The special devices for the test method for sampling efficiency of volatile organic compounds in air in the present invention comprise a steel cylinder I1 for storing the diluent gas, six steel cylinders H 2 for storing the standard gas, the dynamic uniform- mixing device 6, the temperature and humidity control device 4 and six sampling adsorption devices 8; The steel cylinder I 1 and steel cylinders II 2 are connected in parallel with one end of the dynamic uniform-mixing device 6, and the other end of the dynamic uniform- mixing device 6 is connected in series with the temperature and humidity control device 4; the other end of the temperature and humidity control device 4 is connected in parallel with six sampling adsorption devices 8; The steel cylinder I 1, steel cylinders II 2, the dynamic uniform-mixing device 6, the temperature and humidity control device 4, and the dynamic uniform-mixing device 6 and the sampling adsorption device 8 are connected with tubes; The steel cylinder I 1 and steel cylinders II 2 are connected with seven-way proportional valves 17, and the steel cylinder I 1, steel cylinders II 2 are connected with the dynamic uniform-mixing device 6; Flow meters 15 are equipped between the dynamic uniform-mixing device 6 and the temperature and humidity control device 4 and between the temperature and humidity control device 4 and the sampling adsorption device 8; The temperature and humidity control device 4 comprises the furniture box, wherein the bottom of the furniture box is provided with a temperature controller 5, and the top of the furniture box is provided with a humidifier 3; the air nozzle of the humidifier 3 is located inside the furnace box, and the outer wall of the furnace box is provided with a fan 11; the humidifier 3 uses an ultrasonic atomized humidifier 3, which produces water vapor with high efficiency and short time, and controls the amount of water vapor produced by adjusting the size of the water flow, with the humidity control range between 0 and 95%; The main body of the dynamic uniform-mixing device is a stainless steel cylinder made of stainless steel, and its interior is electropolished and inerted to prevent adsorption and facilitate cleaning, as well as to prevent the decomposition of gases that are susceptible to decomposition when exposed to light; The dynamic uniform-mixing device 6 is equipped with an internal mixer 7. The gas entering the dynamic uniform-mixing device 6 is re-mixed by the mixer 7 inside the device to ensure that the gas in the dynamic uniform-mixing device meets the desired requirements.
The tube is copper, the copper tube is high-purity copper, the inner wall has been silanized to ensure that the test gas does not react with the copper tube, and the test gas does not remain in the copper tube; the copper tube is soft and durable.
The dynamic uniform-mixing device 6 is equipped with a fixed bracket 16 for fixing the dynamic uniform-mixing device; the top and bottom of the bracket 16 are in the cross shape, or in other shapes, such as the asterisk shape; the purpose is to fix the position of the stainless steel cylinder firmly. The purpose is to hold the stainless steel it cylinder firmly in place.
The dynamic uniform-mixing device 6 withstands pressures greater than 100psi.
The temperature and humidity control device 4 comprises a temperature sensor 9, a humidity sensor 10, a display screen 13 and a microprocessor 12; the temperature sensor 9 and the humidity sensor 10 are located inside the furniture box respectively; the temperature sensor 9, the humidity sensor 10, the temperature controller 5, the humidifier 3, the display screen 13 and the fan 11 are connected with the microprocessor 12 respectively. The temperature sensor 9 and the humidity sensor 10 report the temperature and humidity inside the temperature and humidity control device 4 to the microprocessor 12, and display the temperature and humidity on the display screen 13. The temperature and humidity of the gas inside the temperature and humidity control device 4 can be regulated by the microprocessor 12, and the temperature controller 5, the humidifier 3 or the fan 11 operates to adjust the temperature and humidity of the gas in the temperature and humidity control device 4; the furnace box can be equipped with a resistance wire to heat it.
The microprocessor 12 is also connected to a flow meter 15 to control the flow rate of each tube; A pressure relief valve 14 is also connected in parallel to the other end of the dynamic uniform-mixing device 6 via a pipe.
The sampling adsorption device 8 can be either an adsorption tube or an adsorption bottle, and the sampling adsorption device 8 has either a solid adsorbent or a liquid adsorbent inside.
In the process of collecting benzenes, it consists of the following steps: Preparing standard benzenes gas with a concentration of 50.0 mg/m’ using the concentration of the gas to calculate the absolute content of the organic material adsorbed by the adsorbent; enabling the pressure of a diluent gas in steel cylinders H to be greater than 5 MPa and be controlled between 5 and 15 MPa; turning on the pressure distributing meters to be between 0.2 and 1.0 MPa, and enabling the pressure of the standard gas in steel cylinders H 2 to be more than 5 MPa and be controlled between 5 and 15 MPa; adjusting the actual flow rate by the mass flow meter 15 according to the breakthrough volume of the adsorption material; enabling the gas to enter a dynamic uniform-mixing device 6 for uniform mixing; enabling the standard gas to flow to the bottom of the furnace box of the temperature and humidity control device 4; adjusting the temperature and humidity in the furnace box to a temperature of 25°C and a humidity of 10%; enabling the gas to flow out from the top of the furnace box; enabling the uniformly-mixed gas to enter sampling adsorption devices 8 to be adsorbed by the activated carbon in the adsorption devices; outputting the gas.
S The range of the flow meter 15 in front of the sampling adsorption device 8 is the flow rate range of the atmospheric sampler in the usual field sampling between 10 and 1,000 ml/min. The flow meter 15 is designed for a flow rate of 500 mL/min and a collection period of 60 minutes. The standard gas flows through the adsorption device with activated carbon at a rate of 500 mL/min. The volume of gas collected is calculated from the sampling time and the sampling flow rate. The absolute amount of benzenes collected by the actual adsorbent is measured by gas chromatography and quantified by the external standard method, and then compared with the theoretical absolute amount of benzenes calculated from the concentration of the standard gas to determine the sampling efficiency. The gas in steel cylinders 11 and II is a compressed gas to ensure that there is enough gas volume for the test. And the gas pressure inside the steel cylinder I1 and HI is also the power source of the gas. Therefore, the volume of gas can be guaranteed and no negative pressure will be formed.
Embodiment 2 The difference from Embodiment 1 is that in Embodiment 2, the flow meter 15 is designed for a flow rate of 3,000 ml/min and a collection period of 10 minutes. Embodiment 3 The difference from Embodiment 1 is that in Embodiment 3, the flow meter 15 is designed for a flow rate of 500 ml/min and a collection period of 200 minutes. Embodiment 4 The difference from Embodiment 1 is that in Embodiment 4, the temperature is room temperature, the humidity is 80%, and the flow rate and collection period of the flow meter 15 are designed for the same.
Measured substance: Benzene, methylbenzene, ethyl benzene, para-xylene, meta- xylene, ortho-xylene and styrene.
Conditions for gas chromatography: Chromatographic columns: AT-WAX 30m*320pum™*0.5um Temperature of injection port: 180°C Detector (FID) Temperature: 300°C Column temperature: 65°C Column flow rate: 2.0ml/min;
Standard curve and instrument detection limit Standard solutions of benzenes are prepared at concentrations of 2.0 mg/L, 5.0 mg/L,
10.0 mg/L, 20.0 mg/L, 50 mg/L and 100 mg/L (this is the reference concentration sequence).
The correlation coefficients of the eight components in the concentration range are all greater than 0.999. The instrument detection limits of the substances are calculated using the signal-to-noise ratio, and the results are shown in the table below.
[0040] Linear equations for 7 benzenes substances Compound ~~ Linearequation Correlation coefficient Detection limit(mg/L) Benzene ~~ Y=0758X-0.02 ~~ r=0999%9 02 Methylbenzene Y=1.90X+0.11 =0.9999 0.1 Ethyl benzene Y=1.93X+ 0.07 =0.9999 0.1 Para-xylene Y=1.98X+0.07 =0.9999 0.1 Meta-xylene Y=1.98X+0.10 1=0.9999 0.1 Ortho-xylene Y=1.98X+0.12 1=0.9999 0.1 Styrene Y=2.44X-0.10 1=0.9992 0.05 The concentration of the standard gas is 50.0 mg/m” in all four embodiments, and the number of tests in each embodiment is 6. The standard gas collected in each embodiment is analyzed by gas chromatography after solvent analysis by standard analytical methods, and the data obtained are as follows: Embodiment 1 First Third Fourth Fifth Sixth Relative No.Component time Second time time time time Mean standard (mg) time (mg) (mg) (mg) (mg) (mg) (mg) deviation ] Benzene 1.37 140 1.38 1.41 1.38 140 130 113 2 Methylbenzene 46 1.43 L41 137 137 138 140 2.60 3 Ethylbenzene 140 1.37 137 143 144 140 140 219 4 Paraxylene 14] 1.40 144 138 138 137 140 1.92 5 Metaxylene | 43 141 1.34 1.41 143 146 141 2.85
6 Ortho-xvlene 1.38 1.37 1.31 1.40 1.43 1.41 1.38 3.07 7 Styrene 140 1.34 1.31 1.35 1.35 1.38 1.35 2.37 Embodiment 2 First Third Fourth Fifth Sixth Relative Second | | | Mean No.Component time _ time time time time standard time (mg) (mg) (mg) (mg) (mg) (mg) (mg) deviation 1 Benzene 0.80 0.86 0.78 0.75 0.78 0.81 0.80 4.46 2 Methylbenzeneg 86 0.83 077 0.78 080 086 081 473 3 Ethylbenzene 080 080 077 080 081 078 0.79 196 4 Para-xylene 0.81 0.75 0.78 0.84 0.83 0.78 080 419 Meta-xylene 0.83 0.71 0.77 0.77 0.77 081 077 5.46 6 Orthoxylene 078 0.90 081 080 081 081 082 516 7 Styrene 0.80 0.74 0.78 0.80 0.78 0.80 078 2.98 Embodiment 3 First Third Fourth Fifth Sixth Relative Second | | | Mean No.Component time _ time time time time standard time (mg) (mg) CL (mg) (mg) (mg) (mg) (mg) deviation 1 Benzene 299 2.99 2.84 3.08 3.05 293 298 2.90 2 Methylbenzene3 05 3.09 2.94 3.02 3.06 299 3.02 1.80 3 Ethyl benzene 309 3.11 287 3.05 3.02 3.02 3.02 284 4 Para-xylene 3.12 3.05 2.88 3.06 3.02 3.05 3.03 2.65 5 Meta-xylene 3.02 29] 2.84 3.03 3.08 3.06 299 3.17 6 Ortho-xylene 3.05 2.94 281 3.11 302 294 298 3.52 7 Styrene 297 2.84 2.85 3.02 3.02 2.99 2.95 2.76
Embodiment 4 First Second Third Fourth Fifth Sixth M Relative can No.
Component time time time time time time (ng) standard mg ne (mg) (mg) (mg) (mg) (mg) (mg) deviation | Benzene 0.35 0.35 0.33 0.36 0.33 0.57 0.38 24.67 2 Methylbenzeneg 41 0350 036 036 0.53 044 0.43 16.01 3 Ethylbenzene (035 032 057 036 044 054 043 2408 4 Paraxylene (036 0.35 0.62 0.32 0.56 0.50 0.45 27.84 Metaxylene (38 0.21 0.36 0.36 0.39 0.53 0.37 27.09 6 Orthoxylene (33 0,32 036 039 044 041 037 1232 7 Styrene 0.35 0.44 0.36 0.41 0.38 0.47 0.40 11.63 The data results show that: The relative standard deviations of the seven benzenes substances of Embodiment 1 for six acquisitions range from 1.13% to 3.07%. The relative standard deviations of 5 the seven benzenes substances in Embodiment 2 range from 1.96% to 5.46%. The relative standard deviations of the seven benzenes substances in Embodiment 3 range from 1.80% to 3.52%. They all meet or outperform other devices.
In the comparison between Embodiment 1 and Embodiment 2, the volume of gas collected is 30L.
Theoretically, the absolute amount of benzenes collected by both methods is the same.
However, because the gas flow rate of Embodiment 2 reaches 3 L/min, and the adsorbent cannot adsorb the gas effectively and quickly, Embodiment 2 has a lower adsorption efficiency than Embodiment 1. Both embodiments show that this device can test the optimal adsorption rate of the adsorbent.
In the comparison between Embodiment 1 and Embodiment 3, the volume of gas collected by Embodiment 1 is 30 L and the volume of gas collected by Embodiment 3 is 100 L.
Theoretically, the absolute amount of benzenes collected by Embodiment 3 is 3.3 times higher than that of Embodiment 1, but the absolute amount of benzenes collected by Embodiment 3 is about 2 times higher than that of Embodiment 1. In this case, the adsorbent of Embodiment 3 becomes saturated when a certain amount of benzenes is collected, and the adsorbent has no more adsorption efficiency at this point.
Both embodiments show that the device can test the optimal adsorption capacity of the adsorbent. In the comparison between Embodiment 1 and Embodiment 4, the room temperature is the same, the volume of gas collected is 30 L, the adsorbent for sampling is not saturated, and the gas sampling rate is the same. However, the relative standard deviations of the six collections of the seven benzenes substances of Embodiment 4 range from 11.63% to 27.84%, with a large deviation because an essential factor affecting the adsorption efficiency of the adsorbent is the humidity of the gas. When the humidity of the gas is high, the adsorption efficiency of the adsorbent decreases significantly.
Both embodiments show that the device of the present invention can test the optimal adsorption conditions of the adsorbent. The test device for sampling efficiency of volatile organic compounds in air of the present invention is not only applicable to the above-listed benzenes in air, but also applicable to other volatile organic compounds.
Claims (10)
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