A method for measuring the concentration of volatile organic compounds

Abstract

The present invention provides a method for measuring the concentration of volatile organic compounds, comprising the following steps: S1. Place the material to be tested in a test chamber with a volume of V, and continuously introduce gas at a gas velocity Q starting from time t0. The sampling tube samples and enriches VOC gas at a gas velocity q; S2. Obtain C 实际 and M 实 , continuously introduce gas, and obtain the total mass M of the enriched VOC gas during the sampling time t sample ; S3. Measure the concentration C 测试 of the enriched VOC gas, and perform derivation and calculation on the gas concentration C 实际 according to the obtained total mass M of the enriched gas to obtain a calculation formula and obtain the true concentration of the VOC gas at the sampling time t0. The method for measuring the concentration of volatile organic compounds according to the present invention can solve the problem of how to obtain the true concentration of a certain volatile organic compound at the start of sampling, and is helpful to improve the reliability of using the volatile organic compound concentration value as a reference limit or evaluation basis in the test experiment.

Description

Technical Field

[0001] The present invention belongs to the technical field of VOC test and analysis, and in particular relates to a method for calculating the concentration of volatile organic compounds. Background Art

[0002] VOC (Volatile Organic Compounds) refers to volatile organic compounds. The World Health Organization (WHO) defines it as the general term for volatile organic compounds with a melting point lower than room temperature and a boiling point between 50°C and 260°C. VOCs in the sense of environmental protection are volatile organic compounds that will cause harm. Common ones include benzene, toluene, xylene, ethylbenzene, styrene, formaldehyde, acetaldehyde, ketones, TVOC (alkanes of C6 - C16), etc. VOCs have a great impact on human health, can damage people's livers, kidneys, and brains, cause adverse reactions such as loss of appetite and nausea, result in serious consequences such as memory loss, and may even cause cancer. Inhalation of a large amount of benzene in a short time will cause acute poisoning, mainly manifested as nervous system symptoms; usually, people are often exposed to VOCs indoors and in cars during activities. These VOC pollutions are mainly caused by various interior decoration materials, including synthetic thermal insulation boards, wallpapers, carpets, artificial boards and furniture, paints, adhesives, and sound-absorbing materials, etc.; the VOC pollution in cars is mainly caused by the release of harmful substances in automotive parts and interior materials, such as carpets, seats, door interior parts, roof linings, steering wheels, and various genuine leather, PVC materials, foaming materials, fiberboards, rubber materials, paint coatings, adhesives, etc.

[0003] At present, the main methods for analyzing the content of VOCs in materials are as follows: sampling bag method, chamber method, headspace method, thermal desorption method, and formaldehyde hanging bottle method. Because the VOC test chamber test is more in line with the actual emission situation of VOCs in materials in the environment and has the characteristics of convenient sampling, it is often used for testing the VOC content in materials. During the experiment of testing the VOC content in materials, the VOC concentration enriched by the sampling tube obtained through testing is not always equal to the VOC concentration corresponding to the material at the beginning of sampling. If the VOC test concentration is still regarded as equal to the VOC concentration corresponding to the material at the beginning of sampling in actual VOC gas detection, it will make people mistakenly think that the VOC concentration content in the material is not high, resulting in deviations when making judgments using relevant standards. However, the true concentration of VOCs may be nearly twice higher than the test result, thus affecting the judgment of whether the VOCs in the material exceed the standard. When people use materials with a relatively high VOC concentration without knowing it, it will cause harm to human health; if engaged in scientific research related to VOCs, without deriving and calculating the VOC concentration at the beginning of sampling during the test, it will cause deviations in the experimental results and affect the credibility and accuracy of the experiment; for this reason, this patent application involves a method for calculating the concentration of volatile organic compounds. Summary of the invention

[0004] In view of this, the present invention aims to propose a method for measuring the concentration of volatile organic compounds to solve the shortcomings of the above-mentioned problems. By inferring the actual concentration of a certain volatile organic compound at the start of sampling based on the VOC gas concentration measured by the sampling tube within a certain sampling time, it is helpful to improve the reliability of using the volatile organic compound concentration value as a reference limit or evaluation basis in the test experiment.

[0005] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0006] A method for measuring the concentration of volatile organic compounds comprises the following steps:

[0007] S1. Place the material to be tested in a VOC test chamber with a volume of V. From time t0, gas is continuously introduced at a gas velocity Q. At the same time, the sampling tube samples and enriches VOC gas at a gas velocity q.

[0008] S2. Obtain the VOC gas concentration C actually collected at sampling time t0 实际 and the enriched VOC gas mass M 实 , continue to introduce gas, obtain t sample The total mass M of VOC gas enriched in the collection tube during the collection time;

[0009] S3. The VOC gas concentration C enriched in the sampling tube is measured by the test instrument. 测试 , according to t obtained in step S2 sample Total mass M of enriched gas collected in the collection tube during the collection time versus gas concentration C 实际 Derived calculations were performed to derive the measurement formula and obtain the actual concentration of VOC gas at sampling time t0.

[0010] Furthermore, step S2 is specifically as follows:

[0011] S21. Define the change between two consecutive sampling times as Δt, and obtain the actual VOC gas concentration C collected at time t0. 实际 At this time, the VOC gas mass collected by the sampling tube is:

[0012] M 实 =C 实际 *q*Δt;

[0013] S22, continue to introduce gas, the gas concentration in the VOC test chamber is gradually diluted, and the VOC concentration in the VOC test chamber continues to decrease. At this time, the concentration balance is broken, and the material to be tested continues to emit VOC gas, causing the VOC gas concentration in the VOC test chamber to increase by σ. After t sampleGas collection at a certain time. During this period, the mass of the enriched gas collected by the sampling tube is M.

[0014] Furthermore, in step S22, since the VOC concentration σ emitted by the material in a short time is much smaller than C 实际 , σ can be ignored, and the formula for the mass M of the enriched gas can be expressed as:

[0015]

[0016] V is the volume of the VOC test chamber, in liters; t0 is the start time of collection, in minutes; Δt is the change between two consecutive sampling times, in minutes; t sample is the time for the VOC gas collected to be enriched, in minutes; Q is the ventilation rate in the VOC test chamber, in liters per minute; q is the sampling gas velocity of the sampling tube, in meters 3 / min; σ is the value of the increased VOC concentration emitted by the material after ventilation in the VOC test chamber, in micrograms per cubic meter 3 , C 实际 is the VOC concentration value corresponding to the start sampling time, in micrograms per cubic meter 3 , C 测试 is the measured VOC concentration value enriched in the sampling tube, in micrograms per cubic meter 3 .

[0017] Furthermore, the specific method of step S3 is as follows:

[0018] Measure the VOC concentration C enriched in the sampling tube through a test instrument 测试 , and at this time, the mass of the VOC enriched in the sampling tube is:

[0019] M 测 = C 测试 *q*t sample ;

[0020] Since M 测 = M, from it can be obtained that:

[0021]

[0022] Compared with the prior art, the method for calculating the concentration of volatile organic compounds described in the present invention has the following beneficial effects:

[0023] (1) The method for calculating the concentration of volatile organic compounds according to the present invention is to deduce the VOC concentration corresponding to the start sampling moment by measuring the VOC gas concentration in the sampling tube within a certain sampling time under the set test conditions and methods. It can solve the problem of how to obtain the true concentration of a certain volatile organic compound at the start of sampling, and is helpful to improve the reliability of using the volatile organic compound concentration value as a reference limit or evaluation basis in the test experiment;

[0024] (2) The method for calculating the concentration of volatile organic compounds according to the present invention can play a certain positive guiding role in people's material selection, and can avoid the health hazards and environmental pollution caused by the excessive actual concentration of volatile organic compounds during the use of materials or their processed products. At the same time, it can enable material production enterprises to pay more attention to improving the concentration problem of volatile organic compounds emitted from materials, and is helpful to promote the development of materials towards a more healthy and environmentally friendly direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0026] Figure 1 It is a schematic diagram of the collection and enrichment of a certain VOC gas according to an embodiment of the present invention;

[0027] Figure 2 It is a graph of the changes of various parameters during the VOC gas collection process according to an embodiment of the present invention;

[0028] Figure 3 It is a curve graph of the change of the VOC gas concentration during a certain sampling process according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0030] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise stated, the meaning of "a plurality" is two or more.

[0031] In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific situations.

[0032] The present invention will be described in detail below with reference to the drawings and in conjunction with embodiments.

[0033] When implementing this solution,

[0034] 1) Place the material in a VOC test chamber with a certain volume V (L);

[0035] 2) Starting from time t0, continuously introduce gas into the VOC test chamber at a gas velocity Q (L / min), and at the same time, connect a gas sampling pump to the sampling tube to sample the enriched gas at a gas velocity q (m 3 / min);

[0036] 3) During the sampling process, the change between two consecutive sampling times is Δt (min). We propose that when Δt is short enough, at the instant t0 when sampling starts, the volume of the gas in the VOC test chamber is the volume V (L) of the test chamber. At this time, the concentration of the VOC gas is C 实际 , then the mass of the VOC gas enriched into the sampling tube is M 实 = C 实际 * q * Δt (μg);

[0037] 4) As the gas is introduced, the gas concentration in the VOC test chamber is gradually diluted, which will cause the VOC concentration in the VOC test chamber to continuously decrease, breaking the concentration balance. The materials in the VOC test chamber continue to emit VOC gas, increasing the VOC gas concentration in the chamber by σ (μg / m 3 );

[0038] 5) In the time period from t0 to t0 + Δt (min), the total volume of the gas is V + Q * Δt (L), and the gas concentration is V / (V + Q * Δt) C 实际 + σ (μg / m 3 ). The mass of the gas enriched in the sampling tube is (V / (V + Q * Δt) C 实际 + σ) * q * Δt (μg); in the time period from t0 + Δt (min) to t0 + 2Δt (min), the mass of the gas enriched in the sampling tube is (V / (V + Q * 2Δt) C 实际 + 2σ) * q * 2Δt (μg). Generally, a certain VOC sampling needs to experience a sampling time of t sample . By analogy, the mass of the gas enriched in the sampling tube in each Δt can be obtained, as shown in Figure 1 ; in the time period from t0 to t0 + t sample (min), the change curve of the VOC concentration is as shown in Figure 3 ;

[0039] 6) By summing up the gas enrichment masses corresponding to all Δt, the mass of the VOC gas enriched on the sampling tube in t sample (min) can be obtained as follows:

[0040]

[0041] 7) During the sampling process, since the VOC concentration σ emitted by the material in a short time is much smaller than C 实际 , σ can be ignored. Then, the formula for the mass M of the VOC gas enriched on the sampling tube in t sample (min) can be expressed as:

[0042]

[0043] By measuring the concentration C 测试 of the VOC enriched on the sampling tube with a test instrument, at this time, the mass M 测 of the VOC enriched in the sampling tube is:

[0044] M 测 = C 测试 * q * t sample ;

[0045] Since M 测=M, by C 测试 The expression is:

[0046]

[0047] After sorting, we get C 实际 and C 测试 Relationship between:

[0048]

[0049] In order to further demonstrate the reliability of the measurement method proposed in the present invention, the following parameters commonly used in the VOC sampling process are selected to introduce the method into The results are as follows Figure 2 As shown, it can be seen from the following calculation results that C 实际 Greater than C 测试 , when t sample When Δt is small, C 实际 It is approximately equal to C 测试 ; Under the set test conditions and methods, by sampling time t sample The VOC concentration corresponding to the start sampling time t0 can be calculated from the VOC gas concentration measured by the sampling tube, which can solve the problem of how to obtain the true concentration of a certain volatile organic compound within the sampling time, and help improve the reliability of using the volatile organic compound concentration value as a reference limit or judgment basis in the test experiment.

[0050] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for measuring the concentration of volatile organic compounds, characterized in that, It includes the following steps: S1. Place the material to be tested in a VOC test chamber with a volume of V. Starting from time t0, continuously introduce gas at a gas velocity of Q. At the same time, sample and enrich VOC gas with a sampling tube at a gas velocity of q; S2. Obtain the VOC gas concentration C actually collected at the sampling moment t0 实际 and the mass M of the enriched VOC gas 实 , continuously introduce gas, and obtain t sample The total mass M of the VOC gas enriched in the sampling tube during the collection time; S3. Measure the concentration C of the VOC gas enriched in the sampling tube by a testing instrument 测试 , according to the t obtained in step S2 sample . For the total mass M of the VOC gas enriched in the sampling tube during the collection time, derive and calculate the gas concentration C 实际 to obtain a calculation formula and acquire the true concentration of the VOC gas at the sampling moment t0; Specifically, step S2 is as follows: S21. Define the change between two consecutive sampling moments as Δt, and obtain the concentration C of the VOC gas actually collected at time t0. 实际 , at this time, the mass of the VOC gas collected by the sampling tube is: M 实 = C 实际 *q*Δt; S22. Continuously introduce gas. The gas concentration in the VOC test chamber is gradually diluted, and the VOC concentration in the VOC test chamber continuously decreases. At this time, the concentration equilibrium is broken, and the material to be tested continues to emit VOC gas, causing the VOC gas concentration in the VOC test chamber to increase by σ. After gas collection for t sample time, during this period, the total mass of the enriched VOC gas collected by the sampling tube is M; In step S22, since the VOC concentration σ emitted by the material in a short time is much smaller than C 实际 , σ can be negligible, and the formula for the total mass M of the enriched VOC gas can be expressed as: V is the volume of the VOC test chamber, in liters (L), t0 is the start time of sampling, in minutes (min), Δt is the change between two consecutive sampling times, in minutes (min), t sample is the time for VOC gas enrichment collection, in minutes (min), Q is the ventilation rate in the VOC test chamber, in liters per minute (L / min), q is the sampling gas velocity of the sampling tube, in meters 3 per minute (m / min), σ is the value of the increased VOC concentration continuously emitted by the material after ventilation in the VOC test chamber, in micrograms per cubic meter (μg / m 3 , C 实际 is the VOC concentration value corresponding to the start time of sampling, in micrograms per cubic meter (μg / m 3 , C 测试 is the measured VOC concentration value enriched in the sampling tube, in micrograms per cubic meter (μg / m 3 ; The specific method of step S3 is as follows: The VOC concentration C enriched in the sampling tube is measured by a testing instrument 测试 , at this time, the mass of VOC enriched in the sampling tube is: M 测 = C 测试 * q * t sample ; Since M 测 = M, from it can be obtained that:

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