Segmented thermal cracking method for mixed plastic

Abstract

The invention discloses a sectional thermal cracking method for mixed plastic, and belongs to the technical field of plastic thermal cracking. The technical problems that multiple components in the mixed plastic cannot be subjected to thermal cracking at the same time, and industrial application cannot be achieved due to insufficient thermal cracking are solved. By setting a plurality of temperature sections of 280-300 DEG C, 350-360 DEG C, 420 DEG C, 580 DEG C and 580-600 DEG C, various plastic components can be subjected to thermal cracking in one-time thermal cracking process of the mixed plastic, so that various components in the mixed plastic can be subjected to thermal cracking to the maximum extent, a large amount of cracking gas can be prevented from being accumulated in the thermal cracking process, and meanwhile, the thermal cracking state can be observed in real time, so that the thermal cracking efficiency is improved. And after the plastic components are subjected to maximum thermal cracking in each stage, the next stage is started, the cracking of each component can be more sufficient, and the sectional thermal cracking method for the mixed plastic, provided by the invention, is simple to operate, high in cracking product yield, high in efficiency, free of a catalyst, energy-saving and capable of being industrially applied.

Description

Technical Field

[0001] The invention relates to the technical field of plastic thermal cracking, and in particular to a mixed plastic segmented thermal cracking method. Background Art

[0002] With the rapid development of the economy, plastic products have brought great convenience to human production and life. However, the non-degradability of plastics has also caused serious environmental pollution, especially plastic bags, ground films, plastic bottles, food packaging, etc., which seriously pollute water bodies, soil and ecosystems, and ultimately damage human health. The comprehensive recycling of plastics is an important way to recycle resources and avoid secondary pollution. Thermal cracking technology is an important technology to solve the problem of waste plastic treatment and resource recycling. This technology heats plastics to high temperatures to decompose them into some small molecular compounds, such as fuel oil, natural gas, solvent oil, synthesis gas, petroleum coke and other products. Plastic products are mainly divided into several categories such as polyvinyl chloride, polyethylene, polypropylene and polystyrene according to their components. The value of their thermal cracking products is not the same, but plastic waste is mostly in the form of mixed plastics when recycled. Sorting by type and then recycling will greatly increase the cost of plastic recycling and reduce the recycling efficiency. This leads to the inability to sort mixed plastics by type or to produce a certain substance for a specific need. Therefore, it is necessary to develop a mixed plastic thermal cracking method that can thermally crack different plastic components in one thermal cracking process. However, the recycling of mixed plastics is a large-scale industrial application, but its thermal cracking research is mostly carried out in the laboratory. The difference in volume between the two makes it very difficult to put the technical research in the laboratory into actual production and use. This is because the mixed plastics will not be fully thermally cracked during the thermal cracking process due to the large processing volume, which may lead to explosion accidents.

[0003] In summary, it is necessary to develop a mixed plastic pyrolysis method that can simultaneously pyrolyze multiple components in the mixed plastic and fully carry out the pyrolysis to meet industrial applications. Summary of the invention

[0004] In order to solve the technical problem that multiple components in mixed plastics cannot be thermally cracked simultaneously and cannot be industrially applied due to insufficient thermal cracking, the present invention provides a mixed plastic segmented thermal cracking method.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] The purpose of the present invention is to provide a mixed plastic segmented thermal cracking method, the method comprising: loading the mixed plastic into a pyrolysis furnace, heating and thermal cracking in stages, the first stage is heated to 90-100°C, after the first stage water vapor is released, the second stage is entered, the second stage is heated to 280-300°C, after the second stage thermal cracking is completed, the third stage is entered, the third stage is heated to 350-360°C, after the third stage thermal cracking is completed, the fourth stage is heated to 420°C, after the fourth stage thermal cracking is completed, the fifth stage is entered, the fifth stage is heated to 580°C, after the fifth stage thermal cracking is completed, the sixth stage is entered, the sixth stage is maintained at the pyrolysis furnace temperature between 580-600°C for a period of time to complete the thermal cracking.

[0007] It is further defined that the criteria for judging the completion of the first stage of water vapor release are: no white gas is discharged, the pressure gauge pointer rotates and the pressure indication number drops below 0.02MPa.

[0008] It is further defined that the criteria for judging the completion of thermal cracking in the second stage, the third stage, the fourth stage and the fifth stage are: the pressure gauge pointer rotates and the pressure indication number drops below 0.02MPa.

[0009] It is further defined that the holding time of the sixth stage is 30 minutes.

[0010] It is further specified that the heating time for the first stage and the second stage is 2h.

[0011] It is further specified that the heating time of the third stage, the fourth stage and the fifth stage is 1 hour.

[0012] The beneficial effects of the present invention are as follows:

[0013] The invention can thermally crack different components in a cracking process of a mixed plastic by thermal cracking at multiple different temperature stages. Between 280°C and 300°C, PP, PE, PU, ​​ABS, POM, PBT, PS, PMMA and other components in the mixed plastic are thermally cracked. Between 350°C and 360°C, PVF, PA6, PA66, PP, PC, PE and other components in the mixed plastic are thermally cracked. At 420°C, PVF, PP, PE, HDPE and other components in the mixed plastic are thermally cracked. At 580°C, PVF, HDPE, PI, PEEK and other components in the mixed plastic are thermally cracked. This process enables various components in the mixed plastic to be thermally cracked to the maximum extent. When staying in each thermal cracking temperature section, the generated cracking gas enters the cooling system through the collecting gas bag and is condensed into a cracking liquid, thereby preventing excessive cracking gas from accumulating due to the large volume of the mixed plastic. The accumulation of plastic waste in the pyrolysis furnace will cause safety hazards. At the same time, by observing the thermal cracking state of each stage, the components in the mixed plastic will enter the next stage after reaching the maximum degree of thermal cracking in each stage, which also makes the cracking of each component in the mixed plastic more complete, improves the cracking product yield, and reduces the accumulation of cracking gas. In addition, the thermal cracking temperature of the second and third stages is a temperature range and is not fixed at a certain temperature. This is because in the recycling process of waste plastics, the components of mixed plastics from different sources are different and the density is different, which makes their thermal cracking temperatures slightly different each time in actual industry. Setting the thermal cracking start temperature to a fixed temperature will cause insufficient thermal cracking of some components. Therefore, setting the temperature to a temperature range at the beginning of thermal cracking can maximize the thermal cracking of mixed plastics from a wide range of sources. The segmented thermal cracking method of the present invention is simple to operate, efficient, does not require a catalyst, saves energy, and can be applied industrially. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a photo of the plastic pyrolysis liquid obtained in Example 1. DETAILED DESCRIPTION

[0015] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0016] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0017] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0018] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained through commercial channels by those skilled in the art.

[0019] Example 1

[0020] The plastic products in the mixed plastics of this embodiment come from a wide range of sources, including scraps and end-of-use waste generated during the production and processing of plastic consumer products, including plastic packaging precipitated during the pulping process of waste paper recycled by paper mills; protective nets, dust-proof tarpaulins, and cement woven bags used in the construction industry; plastic bags in domestic garbage; agricultural films, plastic greenhouses, drip irrigation tapes, and seedling trays in agricultural production; scraps and post-use waste from electronics, luggage, shoemaking, and wind turbine blade manufacturing companies, etc.

[0021] 10t of mixed plastics were loaded into the pyrolysis furnace and pyrolysis was started in stages. The first stage: the temperature in the furnace was raised to between 90℃ and 100℃ within 2h. The water in the mixed plastics in this temperature range was released in the form of water vapor (white). Whether the water was completely evaporated was judged by observing the pressure gauge of the pyrolysis furnace and the color of the exhaust gas: as the temperature increased and the water evaporation process proceeded, the pressure reading gradually increased. When the pointer turned back, that is, the pointer deflected in the opposite direction and the pressure reading dropped below 0.02MPa, the first stage was completed, and there was no white water vapor at this time;

[0022] The second stage: After the water evaporates, the pyrolysis furnace is heated to a temperature between 280°C and 300°C for 2 hours. In this stage, the PP, PE, PU, ​​ABS, POM, PBT, PS, PMMA and other components in the mixed plastics are thermally cracked. The generated plastic pyrolysis gas (cracking gas) enters the condensation system through the collection gas bag and condenses into plastic pyrolysis liquid (pyrolysis liquid) and pyrolysis gas. The pressure gauge of the pyrolysis furnace is observed. As the temperature rises and pyrolysis gas is generated, the pressure gauge pointer increases. When the pointer rotates, that is, the pointer deflects in the opposite direction and the pressure indication falls below 0.02MPa, it means that no pyrolysis gas is generated, which also means that the second stage is completed.

[0023] The third stage: the pyrolysis furnace is heated to a temperature between 350℃ and 360℃ for 1h. In this stage, the PVF, PA6, PA66, PP, PC, PE and other components in the mixed plastics are thermally cracked. The generated pyrolysis gas enters the condensation system through the collection gas bag and condenses into pyrolysis liquid and pyrolysis gas as in the second stage. The pressure gauge of the pyrolysis furnace is observed. As the temperature rises and the pyrolysis gas is generated, the pressure indication increases. When the pointer rotates, that is, the pointer deflects in the opposite direction and the pressure indication falls below 0.02MPa, it means that no pyrolysis gas is generated, which also means that the third stage is completed.

[0024] The fourth stage: continue to heat the pyrolysis furnace to 420℃ for 1h. In this stage, the PVF, PP, PE, HDPE and other components in the mixed plastics are thermally cracked. The pyrolysis gas enters the condensation system through the collection gas bag and condenses into pyrolysis liquid and pyrolysis gas. Observe the pressure gauge of the pyrolysis furnace. The pressure indication number increases. When the pointer rotates, that is, the pointer deflects in the opposite direction and the pressure indication number falls back to below 0.02MPa, it means that no pyrolysis gas is produced, which also means that the fourth stage is completed.

[0025] The fifth stage: continue to heat the pyrolysis furnace to a furnace temperature of 580°C for 1 hour. In this stage, the PVF, HDPE, PI, PEEK and other components in the mixed plastics are thermally cracked. The pyrolysis gas enters the condensation system through the collection gas bag and condenses into cracking liquid and pyrolysis gas. Observe the pressure gauge of the pyrolysis furnace. As the temperature rises and pyrolysis gas is generated, the pressure indication increases. When the pointer rotates, that is, the pointer deflects in the opposite direction and the pressure indication falls below 0.02MPa, it means that no pyrolysis gas is generated, which also means that the fifth stage is completed.

[0026] Stage 6: Continue to maintain the temperature in the pyrolysis furnace between 580 and 600°C for 30 minutes to ensure that all the mixed plastics are thermally cracked, then stop heating and the thermal cracking process ends.

[0027] The plastic pyrolysis liquid (naphtha), plastic pyrolysis gas, and pyrolysis residue obtained by the staged pyrolysis process in this embodiment have a kinematic viscosity of 1.220 mm at 100° C. 2 / s.

[0028] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A mixed plastics staged thermal cracking method, characterized in that: The method comprises: loading mixed plastics into a pyrolysis furnace, heating and thermal cracking in stages, heating to 90-100°C in the first stage, entering the second stage after the release of water vapor in the first stage is completed, heating to 280-300°C in the second stage, entering the third stage after the thermal cracking of the second stage is completed, heating to 350-360°C in the third stage, entering the fourth stage after the thermal cracking of the third stage is completed, heating to 420°C in the fourth stage, entering the fifth stage after the thermal cracking of the fourth stage is completed, heating to 580°C in the fifth stage, entering the sixth stage after the thermal cracking of the fifth stage is completed, and maintaining the temperature of the pyrolysis furnace between 580-600°C for a period of time in the sixth stage to complete the thermal cracking.

2. The method according to claim 1, characterized in that The judgment criteria for the completion of the first stage of water vapor release are: no white gas is discharged, the pressure gauge pointer rotates and the pressure indication number drops below 0.02MPa.

3. The method according to claim 1, characterized in that The judgment criteria for the completion of thermal cracking in the second, third, fourth and fifth stages are: the pressure gauge pointer turns back and the pressure indication drops below 0.02MPa.

4. The method according to claim 1, characterized in that: The holding time of the sixth stage is 30 minutes.

5. The method according to claim 1, characterized in that The heating time for the first and second stages is 2h.

6. The method according to claim 1, characterized in that The heating time of the third stage, the fourth stage and the fifth stage is 1h.

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