Portable thermal cracker for plastic identification, analysis device and analysis method

Abstract

The invention discloses a portable thermal cracker for plastic identification, an analysis device and an analysis method.The portable thermal cracker comprises a reaction container part and a thermal cracking sample introduction part, the reaction container part is provided with an insertion opening end matched with the thermal cracking sample introduction part, and the thermal cracking sample introduction part is inserted into the reaction container part through the insertion opening end; and one end of the thermal cracking sample introduction part is provided with a plugging piece matched with the socket end. According to the invention, thermal cracking of common plastic products can be rapidly completed under low power, complete cracking of most plastics can be satisfied, and overall thermal cracking and analysis of a single sample can be completed within 3 minutes. The device has the advantages of small size, low power consumption, low cost, simplicity in operation, high safety and the like, can be used for daily screening and sorting in a plastic recovery process, and effectively solves the technical problems of easiness in plastic color interference, high energy consumption, high cost, large size and the like in the existing plastic raw material polymer type identification process.

Description

Technical Field

[0001] The invention belongs to the technical field of plastic detection and analysis, and in particular relates to a portable thermal cracker, an analysis device and an analysis method for plastic identification. Background Art

[0002] The mass production and use of plastic products has caused considerable environmental problems. Plastic recycling is an effective way to reduce plastic waste and provides a feasible solution to the environmental problems caused by it. In the entire plastic recycling process, classification and screening according to the type of plastic raw material polymer is the first and necessary step, which is related to the quality of the final product.

[0003] At present, the methods reported for identifying the type of plastic raw polymers include spectroscopy (such as Fourier transform infrared spectroscopy, Raman spectroscopy, laser induced breakdown spectroscopy, X-ray fluorescence spectroscopy), mass spectrometry (pyrolysis-gas chromatography-mass spectrometry) and manual sorting. Among them, spectroscopy is challenging in identifying dark samples and is easily interfered by the color of plastics; mass spectrometry has problems such as expensive instruments, large size and long time consumption, which limits its daily screening and on-site identification in the plastic recycling process. Summary of the invention

[0004] The purpose of the present invention is to provide a portable thermal cracker, an analysis device and an analysis method for plastic identification, so as to solve the above problems existing in the prior art.

[0005] In order to achieve the above-mentioned purpose, in a first aspect, the present invention adopts the following technical scheme: a portable thermal cracker for plastic identification, comprising a reaction vessel component and a thermal cracking injection component, the reaction vessel component is provided with a socket end adapted to the thermal cracking injection component, the thermal cracking injection component is inserted into the interior of the reaction vessel component through the socket end, and one end of the thermal cracking injection component is provided with a sealing member adapted to the socket end.

[0006] As an optional implementation of the above technical solution, the thermal cracking sampling component includes a sample cup, the sample cup is equipped with a heating device and a temperature detection device, and the sample cup is fixed on the sealing member.

[0007] As an optional implementation of the above technical solution, the heating device includes a ceramic heating rod, and both ends of the ceramic heating rod are respectively provided with a fixing part and a heating part, the fixing part is connected to the sealing member, and the heating part extends into the sample cup.

[0008] As an optional implementation of the above technical solution, a connecting tube is provided between the ceramic heating rod and the sample cup.

[0009] As an optional implementation of the above technical solution, the sample cup and the connecting tube are both made of copper.

[0010] As an optional implementation of the above technical solution, the temperature detection device includes a thermocouple, and the two ends of the thermocouple are respectively provided with a temperature measuring end and a fixed end, the fixed end is connected to the sealing member, and the temperature measuring end extends into the bottom of the sample cup.

[0011] As an optional implementation of the above technical solution, the reaction container component includes a reaction tube, one end of the reaction tube is provided with the socket end, and the reaction tube is connected to an air inlet pipe and an exhaust pipe.

[0012] As an optional implementation of the above technical solution, it also includes an annular fixing seat, the reaction tube is arranged on the inner side of the annular fixing seat, the socket end of the reaction tube passes through the annular fixing seat and extends to the outside of the annular fixing seat, and the end of the reaction tube away from the socket end is connected to the annular fixing seat; the air inlet pipe and the exhaust pipe both pass through the annular fixing seat and extend to the outside of the annular fixing seat.

[0013] As an optional implementation of the above technical solution, a heat dissipation fan is provided on the annular fixing seat, and the heat dissipation fan is used to dissipate heat and cool the reaction tube.

[0014] As an optional implementation of the above technical solution, the blocking member includes a blocking cap, and the blocking cap is threadedly connected to the socket end of the reaction container component.

[0015] As an optional implementation of the above technical solution, the blocking cap is made of polytetrafluoroethylene.

[0016] In a second aspect, the present invention adopts the following technical solution: an analytical device for plastic identification, comprising the above-mentioned thermal cracker, and also comprising a filtering device, a microplasma excitation device and a detection device, wherein the thermal cracker, the filtering device, the microplasma excitation device and the detection device are connected in sequence.

[0017] As an optional implementation of the above technical solution, the filtering device uses a polytetrafluoroethylene filter membrane, and the polytetrafluoroethylene filter membrane is arranged between the thermal cracker and the micro plasma excitation device.

[0018] In a third aspect, the present invention adopts the following technical solution: an analysis method for plastic identification, applied to the above-mentioned analysis device, the analysis method comprises the following steps:

[0019] Step A, loading the sample into a sample cup;

[0020] Step B, heating the sample in the sample cup by a heating device to crack it;

[0021] Step C, using a carrier gas to transport the cracking products to a micro plasma excitation device, the micro plasma excitation device generates a stable micro plasma region through a high voltage alternating current, so that the cracking products are dissociated in the micro plasma region and excite atomic / molecular emission spectra;

[0022] Step D, collecting atomic / molecular emission spectra through a detection device, and using machine learning methods to process and model the emission spectra to achieve detection and identification of plastic samples.

[0023] The beneficial effects of the present invention are:

[0024] The portable thermal cracker of the present invention can quickly complete the thermal cracking of common plastic products at low power. Except for a few special plastics (such as polytetrafluoroethylene and polyetheretherketone resin) that require higher thermal cracking temperatures, the thermal cracking temperatures of most polymers are between 500-600 degrees Celsius. Therefore, the thermal cracker can meet the complete cracking of most plastics, and the overall thermal cracking of a single sample can be completed in a short time. It has the advantages of small size, low power consumption, low cost, simple operation and high safety. It can be used for daily screening and sorting in the process of plastic recycling, and effectively solves the technical problems of being easily disturbed by plastic color, high energy consumption and cost, and large size in the existing identification process of plastic raw material polymer types. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a schematic structural diagram of a thermal cracking injection component in one embodiment of the present invention;

[0026] Figure 2 is a schematic structural diagram of a reaction vessel component in one embodiment of the present invention;

[0027] Figure 3 is a schematic diagram of the structure of an analysis device in one embodiment of the present invention;

[0028] Figure 4 is a heating temperature rise curve diagram of a thermal cracker in one embodiment of the present invention;

[0029] Figure 5 It is an emission spectrum diagram of a blank sample and five plastic samples in one embodiment of the present invention;

[0030] Figure 6 It is a linear discriminant analysis score diagram based on the emission spectra of five raw polymers and corresponding commercial plastic products in one embodiment of the present invention.

[0031] In the figure: 1-sample cup; 2-ceramic heating rod; 3-connecting tube; 4-thermocouple; 5-reaction tube; 6-intake pipe; 7-exhaust pipe; 8-annular fixing seat; 9-cooling fan; 10-sealing cap; 11-filtering device; 12-micro plasma excitation device; 13-detection device. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0033] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0034] First, as Figure 1 and Figure 2 As shown, this embodiment provides a portable pyrolysis device for plastic identification, including a reaction container component and a pyrolysis injection component, the pyrolysis injection component can store plastic samples and perform pyrolysis on them. The reaction container component is provided with a socket end adapted to the pyrolysis injection component, the pyrolysis injection component is inserted into the reaction container component through the socket end, and one end of the pyrolysis injection component is provided with a plugging piece adapted to the socket end.

[0035] The portable thermal cracker of this embodiment can quickly complete the thermal cracking of common plastic products at low power. Except for a few special plastics (such as polytetrafluoroethylene and polyetheretherketone resin) that require higher thermal cracking temperatures, the thermal cracking temperatures of most polymers are between 500-600 degrees Celsius. Therefore, the thermal cracker can meet the complete cracking of most plastics, and the overall thermal cracking of a single sample can be completed in a short time. It has the advantages of small size, low power consumption, low cost, simple operation and high safety. It can be used for daily screening and sorting in the process of plastic recycling, and effectively solves the technical problems of being easily disturbed by plastic color, high energy consumption and cost, and large size in the existing identification process of plastic raw material polymer types.

[0036] like Figure 3As shown, the portable thermal cracker is usually used in conjunction with a microplasma excitation device 12 and a detection device 13, and can be used to identify and screen the types of plastic raw material polymers. It is not affected by the color of the plastic and has a 100% recognition rate for five common plastic raw material polymers (polyethylene PE, polypropylene PP, polyethylene terephthalate PET, polystyrene PS and polyvinyl chloride PVC), and a recognition rate of ≥97.8% for commercial plastic products.

[0037] like Figure 1 As shown, in some specific embodiments, the thermal cracking sampling component includes a sample cup 1, the sample cup 1 is equipped with a heating device and a temperature detection device, and the sample cup 1 is fixed on the blocking member. The sample cup 1 is made of copper, the sample cup 1 is used to hold the plastic sample, and the heating device heats the plastic sample in the sample cup 1 to crack it.

[0038] In some specific embodiments, the heating device includes a ceramic heating rod 2, and the two ends of the ceramic heating rod 2 are respectively provided with a fixing part and a heating part, the fixing part adopts a hard wire, the fixing part is connected to the blocking member, and the heating part extends into the sample cup 1. The temperature detection device includes a thermocouple 4, and the two ends of the thermocouple 4 are respectively provided with a temperature measuring end and a fixing end, the fixing end is connected to the blocking member, and the temperature measuring end extends into the bottom of the sample cup 1.

[0039] In some specific embodiments, a connecting tube 3 is provided between the ceramic heating rod 2 and the sample cup 1. The connecting tube 3 is made of copper, and the connecting tube 3 connects the ceramic heating rod 2 and the sample cup 1 to ensure the stability of the sample cup 1.

[0040] like Figure 2 As shown, in some specific embodiments, the reaction container component includes a reaction tube 5, one end of the reaction tube 5 is provided with the socket end, and the reaction tube 5 is connected with an inlet pipe 6 and an exhaust pipe 7. The carrier gas enters the reaction tube 5 from the inlet pipe 6, and then the cracking product is transported to the micro plasma excitation device 12 through the exhaust pipe 7. The reaction tube 5, the inlet pipe 6 and the exhaust pipe 7 are all made of quartz tubes, and the inner diameter of the reaction tube 5 is 8 mm, the outer diameter is 10 mm, and the length is 92 mm. The inlet pipe 6 and the exhaust pipe 7 have the same size, with an inner diameter of 4 mm, an outer diameter of 6 mm, and a length of 35 mm.

[0041] In some specific embodiments, the portable thermal cracker also includes an annular fixing seat 8, which is rectangular, and its length, width and height are 80 mm, 63 mm and 13 mm respectively. The reaction tube 5 is arranged on the inner side of the annular fixing seat 8, and the socket end of the reaction tube 5 passes through the annular fixing seat 8 and extends to the outside of the annular fixing seat 8, and the end of the reaction tube 5 away from the socket end is connected to the annular fixing seat 8; the air inlet pipe 6 and the exhaust pipe 7 both pass through the annular fixing seat 8 and extend to the outside of the annular fixing seat 8. The air inlet pipe 6 is used to introduce the carrier gas, and the exhaust pipe 7 is used to discharge the carrier gas, so that the cracking product enters the micro plasma excitation device 12 with the carrier gas to be dissociated and excited and generate a carbon atom emission spectrum.

[0042] like Figure 3 As shown, in some specific embodiments, a cooling fan 9 is provided on the annular fixing seat 8, and the cooling fan 9 is used to dissipate heat and cool the reaction tube 5. The length, width and height of the cooling fan 9 are 60 mm, 60 mm and 25 mm respectively. After the plastic thermal cracking is completed, the cooling fan 9 can be used to quickly cool the sample cup 1.

[0043] In some specific embodiments, the plugging member includes a plugging cap 10, and the plugging cap 10 is threadedly connected to the socket end of the reaction container component. Preferably, the plugging cap 10 is made of polytetrafluoroethylene. The plugging cap 10 is provided with an internal thread, and the socket end of the reaction tube 5 is provided with an external thread. The sample cup 1 extends into the reaction tube 5, and the plugging cap 10 is threadedly connected to the socket end of the reaction tube 5 to seal the socket end. The fixed part of the ceramic heating rod 2 and the fixed end of the thermocouple 4 are both fixed on the plugging cap 10, which is conducive to the fixation of the sample cup 1. When in use, the operator can hold the plugging cap 10, insert the sample cup 1 into the reaction tube 5, and then tighten the plugging cap 10. It has a simple structure and is easy to operate.

[0044] like Figure 3 As shown, in the second aspect, this embodiment provides an analytical device for plastic identification, including the thermal cracker described in the first aspect, and also including a filtering device 11, a microplasma excitation device 12 and a detection device 13, wherein the thermal cracker, the filtering device 11, the microplasma excitation device 12 and the detection device 13 are connected in sequence. Among them, the filtering device 11 adopts a polytetrafluoroethylene filter membrane, and the polytetrafluoroethylene filter membrane is arranged between the thermal cracker and the microplasma excitation device 12. The pore size of the polytetrafluoroethylene filter membrane is 1μm, which is used to purify the thermal cracking gas to avoid contaminating the microplasma excitation device 12. The microplasma excitation device 12 serves as an excitation source, which can make the cracking product excite the carbon atom and carbon-related molecular emission spectrum, and the detection device 13 adopts a commercial charge-coupled device to collect the carbon atom emission spectrum of the cracking product.

[0045] The analytical device is compact and can greatly shorten the plastic identification time. The time reduction is specifically reflected in two aspects: (1) the above-mentioned thermal cracker can reach 600 degrees within 1 minute and heat the sample to crack it, and the cracking process is fast; (2) the cracking products after cracking are carried to the excitation source by the carrier gas and are immediately detected by the detection device 13, without the need for chromatographic separation, thus shortening the detection time.

[0046] In a third aspect, this embodiment provides an analysis method for plastic identification, which is applied to the analysis device of the second aspect, and includes the following steps:

[0047] Step A, loading the sample into the sample cup 1 , specifically comprising: firstly, ultrasonically cleaning the plastic sample at room temperature for 20 minutes, then rinsing with deionized water and drying, then cutting the dried plastic sample into a size of 1 mm×1 mm, and finally loading it into the sample cup 1 .

[0048] Step B, heating the sample in the sample cup 1 by a heating device to crack it, specifically includes: energizing the ceramic heating rod 2 so that the ceramic heating rod 2 quickly heats the plastic sample in the sample cup 1 to crack the plastic sample and produce cracking products.

[0049] Step C, using a carrier gas to transport the cracking products to the micro plasma excitation device 12, the micro plasma excitation device 12 generates a stable micro plasma region through high voltage alternating current, so that the cracking products are dissociated in the micro plasma region and excite carbon atoms and carbon-related molecular emission spectra.

[0050] Step D, collecting the atomic / molecular emission spectrum through the detection device 13, and using machine learning methods to process and model the emission spectrum to achieve detection and identification of unknown plastic samples.

[0051] Test Example 1

[0052] In order to ensure that all target plastics are quickly and completely pyrolyzed, the operating parameters of the portable pyrolyzer provided in the embodiment are characterized and optimized. Figure 4 As shown, when the ceramic heating rod 2 uses a working current of 0.93A and a working voltage of 24V, the maximum temperature of the sample cup 1 can reach and stabilize at 608°C, with an accuracy of ±1°C. The average heating rate is calculated to be 202°C / min. Among commonly used plastic products, except for a few special plastics (such as polytetrafluoroethylene and polyetheretherketone resin) that require a higher thermal cracking temperature, the thermal cracking temperature of most polymers is between 500-600°C. Therefore, the thermal cracker can meet the complete cracking of most plastics, and complete cracking and analysis can be completed within 3 minutes.

[0053] Test Example 2

[0054] like Figure 5 and Figure 6 As shown, the raw polymers (RP) and corresponding commercial products (CP) of five commonly used plastics (polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polystyrene (PS) and polyvinyl chloride (PVC)) were analyzed using the analysis device provided in the embodiment.

[0055] The results show that when the present invention screens the types of plastic raw material polymers, it can be unaffected by the color of the plastics and exhibits good discrimination ability for 5 kinds of plastic raw materials and commercial products. Through machine learning methods such as factor analysis (FA), EM clustering-assisted linear discriminant analysis (LDA) and support vector machine (SVM), it is found that the identification accuracy of the 5 kinds of polymer raw materials is 100%, and the recognition rates of FA-LDA (factor analysis-linear discriminant analysis) and FA-SVM (factor analysis-support vector machine) for the 5 kinds of commercial plastics are 97.8% and 99% respectively.

[0056] In the description of the present invention, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, and may be fixedly connected, detachably connected, or integrated; may be mechanically connected or electrically connected; may be directly connected or indirectly connected through an intermediate medium, may be the internal connection of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood. In addition, the specific features, structures, etc. described in the embodiments are included in at least one embodiment. Under the condition that there is no contradiction, those skilled in the art may combine the features of different embodiments. The protection scope of the present invention is not limited to the above-mentioned specific embodiments. According to the basic technical concept of the present invention, the embodiments that can be associated with by ordinary technicians in this field without creative work all belong to the protection scope of the present invention.

Claims

1. A portable thermal cracker for plastic identification, characterized in that: The invention comprises a reaction container component and a pyrolysis injection component. The reaction container component is provided with a socket end adapted to the pyrolysis injection component. The pyrolysis injection component is inserted into the reaction container component through the socket end. One end of the pyrolysis injection component is provided with a plugging piece adapted to the socket end.

2. The thermal cracker according to claim 1, characterized in that The pyrolysis sampling component comprises a sample cup (1), the sample cup (1) is equipped with a heating device and a temperature detection device, and the sample cup (1) is fixed on the sealing member.

3. The thermal cracker according to claim 2, characterized in that The heating device comprises a ceramic heating rod (2), wherein two ends of the ceramic heating rod (2) are respectively provided with a fixing portion and a heating portion, the fixing portion is connected to a sealing member, and the heating portion extends into a sample cup (1); a connecting pipe (3) is provided between the ceramic heating rod (2) and the sample cup (1); and the sample cup (1) and the connecting pipe (3) are both made of copper.

4. The thermal cracker according to claim 2, characterized in that The temperature detection device comprises a thermocouple (4), wherein two ends of the thermocouple (4) are respectively provided with a temperature measuring end and a fixed end, the fixed end is connected to the sealing member, and the temperature measuring end extends into the bottom of the sample cup (1).

5. The thermal cracker according to claim 1, characterized in that The reaction container component comprises a reaction tube (5), one end of the reaction tube (5) is provided with the socket end, and the reaction tube (5) is connected with an air inlet pipe (6) and an air exhaust pipe (7).

6. The thermal cracker according to claim 5, characterized in that It also comprises an annular fixing seat (8), the reaction tube (5) being arranged on the inner side of the annular fixing seat (8), the socket end of the reaction tube (5) passing through the annular fixing seat (8) and extending to the outer side of the annular fixing seat (8), and the end of the reaction tube (5) away from the socket end being connected to the annular fixing seat (8); the air inlet pipe (6) and the air outlet pipe (7) both passing through the annular fixing seat (8) and extending to the outer side of the annular fixing seat (8).

7. The thermal cracker according to claim 6, characterized in that A heat dissipation fan (9) is provided on the annular fixing seat (8), and the heat dissipation fan (9) is used to dissipate heat and cool the reaction tube (5).

8. The thermal cracker according to claim 1, characterized in that The blocking member comprises a blocking cap (10), and the blocking cap (10) is threadedly connected to the socket end of the reaction container component; the blocking cap (10) is made of polytetrafluoroethylene.

9. An analytical device for plastic identification, characterized in that: The invention comprises the thermal cracker according to any one of claims 1 to 8, and further comprises a filtering device (11), a microplasma excitation device (12) and a detection device (13), wherein the thermal cracker, the filtering device (11), the microplasma excitation device (12) and the detection device (13) are connected in sequence; the filtering device (11) adopts a polytetrafluoroethylene filter membrane, and the polytetrafluoroethylene filter membrane is arranged between the thermal cracker and the microplasma excitation device (12).

10. An analytical method for plastic identification, characterized in that: Applied to the analysis device according to claim 9, the analysis method comprises the following steps: Step A, loading a sample into a sample cup (1); Step B, heating the sample in the sample cup (1) by a heating device to cause cracking; Step C, using a carrier gas to transport the cracked product to a micro plasma excitation device (12), wherein the micro plasma excitation device (12) generates a stable micro plasma region through a high voltage alternating current, so that the cracked product is dissociated in the micro plasma region and excites an atomic / molecular emission spectrum; Step D, collecting the generated atomic / molecular emission spectrum through the detection device (13), using a machine learning method to process and model the emission spectrum, and realizing detection and identification of the plastic sample.

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