Adsorbed and Free VOCs Detection Device and Working Method

Abstract

The present invention provides a detection device and working method for adsorbed and free VOCs, including an analyzer; the second port of the first multi-way valve selectively communicates with the first port and the fourth port, and the third port selectively communicates with the first port and the fourth port; the first port and the fifth port are connected through a pipeline; one end of the particulate matter trap is adapted to communicate with the analyte to be measured, and the other end communicates with the second port; the fifth port of the second multi-way valve selectively communicates with the sixth port and the seventh port, and the eighth port selectively communicates with the ninth port and the eleventh port; the analyzer communicates with the tenth port of the second multi-way valve, and the tenth port selectively communicates with the seventh port; both ends of the adsorbed VOCs trap are respectively connected to the seventh port and the eighth port of the second multi-way valve; the heating module is used to heat the particulate matter trap and the adsorbed VOCs trap; the pump is connected to the fourth port of the first multi-way valve and the ninth port of the second multi-way valve. The present invention has the advantages of multiple detection methods, accuracy, etc.

Description

Technical Field

[0001] The present invention relates to gas detection, and particularly to a detection device for adsorbed and free VOCs. Background Art

[0002] Current technical means for VOCs detection can be classified into canister sampling, trap sampling, solvent absorption, and on-line sampling from the perspective of sampling, and adsorption thermal desorption and optical detection from the perspective of analysis. Currently, instrument companies are all developing various technologies to analyze free VOCs in the air (referring to VOCs that move freely in the air and are not adsorbed), ignoring the fact that there is a part of adsorbed VOCs in the atmosphere (referring to VOCs adsorbed by particulate matter in the air).

[0003] The content of particulate matter in the air is high and the specific surface area is large, which can adsorb a large amount of VOCs. For example, Mustafa Odabasi collected adsorbed and free VOCs respectively and found that the higher the boiling point of the substance, the higher the proportion of the adsorbed state. The proportion of isopropyltoluene in the adsorbed state accounts for nearly 2% of the total amount, and the proportion of adsorbed SVOCs will be even higher. When the environmental temperature rises or the air pressure drops, the VOCs adsorbed by particulate matter will volatilize into the free state, while when the environmental temperature drops, the air pressure rises or the dust in the air increases, the free VOCs in the air will be adsorbed and converted into adsorbed VOCs. Therefore, only monitoring the concentration of free VOCs not only fails to reflect the true VOCs concentration, but the detected value is often on the low side, and the VOCs value also fluctuates with the gas phase conditions. With the continuous improvement of the accuracy of air monitoring in the industry, it is inevitable to measure the total amount of VOCs as a development trend.

[0004] From the literature reports, there are few relevant reports, and the methods for measuring adsorbed VOCs are relatively single. It mainly involves pump sampling, filtering particulate matter with a glass fiber membrane, and then putting the collected sample into a quartz tube and heating and desorbing for analysis. Measuring adsorbed VOCs is carried out by sampling with an adsorption tube or a Summa canister and then analyzing. The main problems existing in the current technical solutions are as follows:

[0005] 1. Lack of attention to adsorbed VOCs, few detection means, and simple devices;

[0006] 2. It is only possible to measure adsorbed and free VOCs separately through two sets of instruments, and the system is complex;

[0007] 3. Too much manual operation, introducing a lot of errors. Summary of the Invention

[0008] To solve the deficiencies in the above-mentioned existing technical solutions, the present invention provides a detection device for adsorbed and free VOCs with high accuracy and diverse detection modes.

[0009] The object of the present invention is achieved through the following technical solutions:

[0010] An apparatus for detecting adsorbed and free VOCs, the detection apparatus comprising an analyzer; the apparatus for detecting adsorbed and free VOCs further comprising:

[0011] A first multi-way valve having a plurality of ports, a second port selectively communicating with a first port and a fourth port, and a third port selectively communicating with the first port and the fourth port; the first port of the first multi-way valve is connected to the fifth port of a second multi-way valve through a pipeline;

[0012] A particulate matter trap, one end of the particulate matter trap being adapted to communicate with a test substance, and the other end communicating with the second port of the first multi-way valve;

[0013] A second multi-way valve having a plurality of ports, a fifth port selectively communicating with a sixth port and a seventh port, and an eighth port selectively communicating with a ninth port and an eleventh port; the analyzer is connected to a tenth port of the second multi-way valve, and the tenth port selectively communicates with the seventh port;

[0014] An adsorbed VOCs trap, both ends of the adsorbed VOCs trap being respectively connected to the seventh port and the eighth port of the second multi-way valve;

[0015] A heating module for heating the particulate matter trap and the adsorbed VOCs trap;

[0016] A pump, the pump being connected to the fourth port of the first multi-way valve and the ninth port of the second multi-way valve.

[0017] The present invention also aims to provide a working method of the apparatus for detecting adsorbed and free VOCs according to the above, and this invention aim is achieved through the following technical solutions:

[0018] According to the working method of the apparatus for detecting adsorbed and free VOCs according to the above, the working method is as follows:

[0019] Detecting free VOCs alone:

[0020] During sampling, the first multi-way valve and the second multi-way valve are switched so that the flow direction of the test gas is: the second air pipeline - the first multi-way valve - the second multi-way valve - the adsorbed VOCs trap - the second multi-way valve - the second flow control module - the pump;

[0021] During desorption, the adsorbed VOCs trap is heated, the second multi-way valve is switched, and the VOCs are transferred to the analyzer by using a carrier gas, and the flow direction of the carrier gas is: the carrier gas pipeline - the fourth flow control module - the second multi-way valve - the adsorbed VOCs trap - the second multi-way valve - the analyzer;

[0022] Separate detection of adsorbed VOCs:

[0023] During sampling, switch the first multi-way valve so that the gas to be measured flows: the first air pipeline - particulate trap - first multi-way valve - third flow control module - pump;

[0024] During transfer, the particulate trap is heated, and the first multi-way valve and the second multi-way valve are switched so that the purge gas flows: particulate trap - first multi-way valve - second multi-way valve - adsorbed VOCs trap - second multi-way valve - second flow control module - pump;

[0025] During desorption, the adsorbed VOCs trap is heated, and the first multi-way valve and the second multi-way valve are switched so that the carrier gas flows: carrier gas pipeline - fourth flow control module - second multi-way valve - adsorbed VOCs trap - second multi-way valve - analyzer.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] 1. Accurate detection;

[0028] Implement a device to perform combined or separate detection of free and adsorbed VOCs, reduce operation and maintenance costs, reduce human participation, and improve the accuracy of analysis results;

[0029] 2. Multiple working modes, suitable for different application scenarios, such as:

[0030] (1) Optionally detect free VOCs alone; (2) Optionally detect adsorbed VOCs alone; (3) Optionally detect the total amount of adsorbed and free VOCs; (4) Combine the two methods, that is, detect free VOCs in time period A and adsorbed VOCs or the total amount in time period B. It is especially suitable for research institutions that need to frequently change the determination of different forms of VOCs. Description of the Drawings

[0031] Referring to the accompanying drawings, the disclosure of the present invention will become more understandable. It is easy for those skilled in the art to understand that these drawings are only used to illustrate the technical solutions of the present invention and are not intended to limit the protection scope of the present invention. In the figures:

[0032] Figure 1 is a structural schematic diagram of a device for detecting adsorbed and free VOCs according to an embodiment of the present invention;

[0033] Figure 2 is a desorption state diagram of a device for detecting adsorbed and free VOCs according to an embodiment of the present invention;

[0034] Figure 3 is a sampling state diagram of a device for detecting adsorbed and free VOCs according to an embodiment of the present invention;

[0035] Figure 4 is the transfer state diagram of the adsorbed and free VOCs detection device according to an embodiment of the present invention;

[0036] Figure 5 is the desorption state diagram of the adsorbed and free VOCs detection device according to an embodiment of the present invention;

[0037] Figure 6 is the sampling state diagram of the adsorbed and free VOCs detection device according to an embodiment of the present invention. Detailed implementation manners

[0038] Figure 1-6 The following description and the following explanations describe alternative embodiments of the present invention to teach those skilled in the art how to implement and reproduce the present invention. To teach the technical solution of the present invention, some conventional aspects have been simplified or omitted. Those skilled in the art should understand that variations or substitutions derived from these embodiments will fall within the scope of the present invention. Those skilled in the art should understand that the following features can be combined in various ways to form multiple variations of the present invention. Thus, the present invention is not limited to the following alternative embodiments, but is only defined by the claims and their equivalents.

[0039] Embodiment 1.

[0040] Figure 1 Schematically shows a structural diagram of the adsorbed and free VOCs detection device according to an embodiment of the present invention, as Figure 1 shown, the adsorbed and free VOCs detection device includes:

[0041] An analyzer 51, the analyzer 51 is used to detect the VOCs content;

[0042] A first multi-way valve 11, the first multi-way valve 11 has a plurality of ports, the second port selectively communicates with the first port and the fourth port, and the third port selectively communicates with the first port and the fourth port; the first port of the first multi-way valve is connected to the fifth port of the second multi-way valve 12 through a pipeline;

[0043] A particulate matter trap 41, one end of the particulate matter trap 41 is adapted to communicate with the analyte to be measured, and the other end communicates with the second port of the first multi-way valve 11;

[0044] A second multi-way valve 12, the second multi-way valve 12 has a plurality of ports, the fifth port selectively communicates with the sixth port and the seventh port, and the eighth port selectively communicates with the ninth port and the eleventh port; the analyzer 51 is connected to the tenth port of the second multi-way valve 12, and the tenth port selectively communicates with the seventh port;

[0045] The adsorbed VOCs trap 42, with both ends of the adsorbed VOCs trap 42 communicating with the seventh port and the eighth port of the second multi-way valve 12 respectively;

[0046] A heating module for heating the particulate matter trap and the adsorbed VOCs trap;

[0047] A pump 61, with the pump 61 communicating with the fourth port of the first multi-way valve 11 and the ninth port of the second multi-way valve 12.

[0048] In order to control the flow rates of the sample gas, carrier gas, and purge gas, further, the adsorbed and free VOCs detection device further includes:

[0049] Flow control modules 31-34, which are arranged on the pipeline between the fourth port and the pump, or on the pipeline between the ninth port and the pump, or upstream of the eleventh port, or upstream of one end of the particulate matter trap.

[0050] In order to reduce the structural complexity, further, the third port is adapted to communicate with the analyte, the eleventh port is adapted to communicate with the carrier gas, and the sixth port is adapted to communicate with the purge gas.

[0051] Embodiment 2.

[0052] An application example of the adsorbed and free VOCs detection device according to Embodiment 1 of the present invention in atmospheric VOCs.

[0053] In this application example, as Figure 1 shown, the first multi-way valve 11 is a four-way valve, the first flow control module (MFC1) 31 and the first air sampling pipeline 21 communicate with one end of the particulate matter trap 41, and the second air sampling pipeline 22 communicates with the third port; the fourth port sequentially communicates with the third flow control module (MFC3) 33 and the pump 61;

[0054] The particulate matter trap 41 includes a flow-through tube and a metal mesh, and the metal mesh is arranged inside the flow-through tube to trap particulate matter in the flowing air, and air and VOCs pass through;

[0055] The second multi-way valve 12 is an eight-way valve, the purge gas pipeline communicates with the sixth port, the fourth flow control module (MFC4) 34 communicates with the eleventh port, and the ninth port sequentially communicates with the second flow control module (MFC2) 32 and the pump;

[0056] The analyzer 51 includes a chromatographic column and a detector connected in series; the heating module uses an electric heater.

[0057] The working method of the adsorbed and free VOCs detection device in this embodiment includes 4 modes, which are respectively:

[0058] 1. Measuring free VOCs alone

[0059] As Figure 1 shown, during sampling, the first multi-way valve 11 and the second multi-way valve 12 are switched so that the air flow direction is: the second air pipe 22 - the first multi-way valve 11 - the second multi-way valve 12 - the adsorbed VOCs trap 42 - the second multi-way valve 12 - the second flow control module 32 - the pump 61.

[0060] As Figure 2 shown, during desorption, the adsorbed VOCs trap 42 is heated to 300 °C, and the second multi-way valve 12 is switched to transfer the VOCs to the analyzer 51 using the carrier gas. The carrier gas flow direction is: the carrier gas pipe - the fourth flow control module 34 - the second multi-way valve 12 - the adsorbed VOCs trap 42 - the second multi-way valve 12 - the analyzer 51.

[0061] 2. Measuring adsorbed VOCs alone

[0062] As Figure 3 shown, during sampling, the first multi-way valve 11 is switched so that the air flow direction is: the first air pipe 21 - the particulate matter trap 41 - the first multi-way valve 11 - the third flow control module 33 - the pump 61.

[0063] As Figure 4 shown, during transfer, the particulate matter trap 41 is heated to 300 °C, and the first multi-way valve 11 and the second multi-way valve 12 are switched so that the purge air flow direction is: the particulate matter trap 41 - the first multi-way valve 11 - the second multi-way valve 12 - the adsorbed VOCs trap 42 - the second multi-way valve 12 - the second flow control module 32 - the pump 61.

[0064] As Figure 5 shown, during desorption, the adsorbed VOCs trap 42 is heated to 300 °C, and the first multi-way valve 11 and the second multi-way valve 12 are switched so that:

[0065] The carrier gas flow direction is: the carrier gas pipe - the fourth flow control module 34 - the second multi-way valve 12 - the adsorbed VOCs trap 42 - the second multi-way valve 12 - the analyzer 51;

[0066] At the same time, the purge air flow direction is: the second multi-way valve 12 - the first multi-way valve 11 - the particulate matter trap 41 - the first air pipe 21 to purge the particulate matter trap 41 clean.

[0067] 3. Measuring the total amount of adsorbed and free VOCs

[0068] As Figure 6 shown, during sampling, the first multi-way valve 11 and the second multi-way valve 12 are switched so that:

[0069] Air flow direction: Second air duct 22 - First multi-way valve 11 - Second multi-way valve 12 - Adsorbed VOCs trap 42 - Second multi-way valve 12 - Second flow control module 32 - Pump 61; Meanwhile, air flow direction: First air duct 21 - Particulate matter trap 41 - First multi-way valve 11 - Third flow control module 33 - Pump 61.

[0070] As Figure 4 shown, during the transfer, the particulate matter trap is heated to 300 °C, and the first multi-way valve 11 and the second multi-way valve 12 are switched, so that the purge air flow direction is: Particulate matter trap 41 - First multi-way valve 11 - Second multi-way valve 12 - Adsorbed VOCs trap 42 - Second multi-way valve 12 - Second flow control module 32 - Pump 61.

[0071] As Figure 5 shown, during the desorption, the adsorbed VOCs trap is heated to 300 °C, and the first multi-way valve 11 and the second multi-way valve 12 are switched, so that:

[0072] The carrier gas flow direction is: Carrier gas pipeline - Fourth flow control module 34 - Second multi-way valve 12 - Adsorbed VOCs trap 42 - Second multi-way valve 12 - Analyzer 51;

[0073] Meanwhile, the purge air flow direction is: Second multi-way valve 12 - First multi-way valve 11 - Particulate matter trap 41 - First air duct 21, purging the particulate matter trap clean.

[0074] 4. Combination of two methods

[0075] Since the particulate matter sampling sample is relatively large and at least 4 hours of sampling is required, while only 1 L of free VOCs sampling can be analyzed, and the entire sampling and analysis can be completed in only 1 hour. Therefore, during the particulate matter sampling, the free VOCs can be analyzed cyclically 3 times. After the particulate matter sampling is completed, the particulate matter in the particulate matter trap is then transferred to the adsorbed VOCs trap, and the adsorbed VOCs trap is then desorbed and analyzed. Then, in this operation mode, there are 3 groups of free VOCs data and 1 group of total VOCs data for each set.

Claims

1. An adsorption-state and free-state VOCs detection device, the detection device comprising an analyzer; characterized in that: The detection device for adsorbed and free VOCs further includes: A first multi-way valve having a plurality of ports. The second port selectively communicates with the first port and the fourth port, and the third port selectively communicates with the first port and the fourth port. The first port of the first multi-way valve is connected to the fifth port of the second multi-way valve through a pipeline, and the third port is adapted to communicate with the analyte. A particulate matter trap, one end of which is adapted to communicate with the analyte and the other end is connected to the second port of the first multi-way valve. A second multi-way valve having a plurality of ports. The fifth port selectively communicates with the sixth port and the seventh port, and the eighth port selectively communicates with the ninth port and the eleventh port. The analyzer is connected to the tenth port of the second multi-way valve, and the tenth port selectively communicates with the seventh port. The sixth port is adapted to communicate with the purge gas, and the eleventh port is adapted to communicate with the carrier gas. An adsorbed VOCs trap, both ends of which are respectively connected to the seventh port and the eighth port of the second multi-way valve. A heating module for heating the particulate matter trap and the adsorbed VOCs trap. A pump connected to the fourth port of the first multi-way valve and the ninth port of the second multi-way valve.

2. The adsorption-state and free-state VOCs detection device according to claim 1, characterized in that: The first multi-way valve is a four-way valve, and the second multi-way valve is an eight-way valve.

3. The adsorption-state and free-state VOCs detection device according to claim 1, characterized in that: The detection device for adsorbed and free VOCs further includes: A flow control module disposed on the pipeline between the fourth port and the pump, or on the pipeline between the ninth port and the pump, or upstream of the eleventh port, or upstream of one end of the particulate matter trap.

4. The adsorption-state and free-state VOCs detection device according to claim 1, characterized in that: The particulate matter trap includes: A flow-through pipe and a metal screen disposed inside the flow-through pipe.

5. The adsorption-state and free-state VOCs detection device according to claim 1, characterized in that: The analyzer includes a chromatographic column and a detector connected in series.

6. A working method of the adsorption-state and free-state VOCs detection device according to any one of claims 1-5, the working method being: Measuring free-state VOCs alone: During sampling, the first multi-way valve and the second multi-way valve are switched so that the gas to be measured flows: the second air pipeline - the first multi-way valve - the second multi-way valve - the adsorption-state VOCs trap - the second multi-way valve - the second flow control module - the pump; During desorption, the adsorption-state VOCs trap is heated, the second multi-way valve is switched, and the VOCs are transferred to the analyzer by using a carrier gas. The carrier gas flow direction is: the carrier gas pipeline - the fourth flow control module - the second multi-way valve - the adsorption-state VOCs trap - the second multi-way valve - the analyzer; Measuring adsorption-state VOCs alone: During sampling, the first multi-way valve is switched so that the gas to be measured flows: the first air pipeline - the particulate matter trap - the first multi-way valve - the third flow control module - the pump; During transfer, the particulate matter trap is heated, the first multi-way valve and the second multi-way valve are switched so that the purge gas flows: the particulate matter trap - the first multi-way valve - the second multi-way valve - the adsorption-state VOCs trap - the second multi-way valve - the second flow control module - the pump; During desorption, the adsorption trap for VOCs in the adsorbed state is heated, and the first multi-way valve and the second multi-way valve are switched so that the carrier gas flow direction is: carrier gas pipeline - fourth flow control module - second multi-way valve - adsorption trap for VOCs in the adsorbed state - second multi-way valve - analyzer.

7. The working method of the detection device for adsorbed and free VOCs according to claim 6, characterized in that: Measuring the total amount of adsorbed and free states: During sampling, the first multi-way valve and the second multi-way valve are switched so that the flow direction of the analyte gas is: the second air pipeline - the first multi-way valve - the second multi-way valve - the adsorbed VOCs trap - the second multi-way valve - the second flow control module - the pump; meanwhile, the air flow direction is: the first air pipeline - the particulate matter trap - the first multi-way valve - the third flow control module - the pump. During transfer, the particulate matter trap is heated, and the first multi-way valve and the second multi-way valve are switched so that the purge gas flow direction is: the particulate matter trap - the first multi-way valve - the second multi-way valve - the adsorbed VOCs trap - the second multi-way valve - the second flow control module - the pump. During desorption, the adsorbed VOCs trap is heated, and the first multi-way valve and the second multi-way valve are switched so that the carrier gas flow direction is: the carrier gas pipeline - the fourth flow control module - the second multi-way valve - the adsorbed VOCs trap - the second multi-way valve - the analyzer.

8. The working method of the detection device for adsorbed and free VOCs according to claim 6, characterized in that: During the measurement of adsorbed VOCs, during desorption, the purge gas flow direction is: the second multi-way valve - the first multi-way valve - the particulate matter trap - the first air pipeline to purge the particulate matter trap.

Images