Method and system for treating volatile organic compounds in solid polymers, method for granulating solid polymers

Abstract

The present application relates to the technical field of solid polymer treatment, and particularly relates to a treatment method and a treatment system for volatile organic compounds in solid polymers, and a method for granulating solid polymers, which comprises: blowing a mixed gas containing gaseous light hydrocarbons and nitrogen through solid polymers containing volatile organic compounds to perform degassing. The treatment method is safe and efficient, can effectively reduce the content of volatile organic compounds in the solid polymers, and improves the environmental protection of solid polymer production and the quality of the solid polymers.

Description

Technical Field

[0001] This invention relates to the field of solid polymer processing technology, specifically to a method and system for processing volatile organic compounds in solid polymers, and a method for granulation of solid polymers. Background Technology

[0002] Polymers are materials formed by the polymerization reaction of one or more monomers, including fibers, plastics, rubber, coatings, and adhesives. Plastics are solid polymers, and polyethylene, a solid polymer, accounts for nearly 40% of all plastics, widely used in agriculture, transportation, construction, light industry, heavy industry, defense, and daily life. Although my country has become a major polyethylene producer globally, it primarily produces low- to mid-range products, relying heavily on imports for high-end products such as medical and electronic products, and even mid-range food products. A significant reason for this is the strong odor produced during the processing of domestically produced polyethylene.

[0003] Gas-phase fluidized bed polyethylene (GaS) process is one of the main processes for polyethylene production. It uses gaseous ethylene and nitrogen as fluids to move solid polyethylene particles from bottom to top, allowing the particles to flow freely within the bed. This polymerization process features high heat transfer efficiency, easy particle flow, and convenient feeding and discharging. It uses chromium catalysts, Ziegler catalysts, titanium-modified chromium catalysts, and metallocene catalysts to catalyze ethylene polymerization. Hydrogen is used to adjust the molecular weight, and α-olefins such as butene and hexene are used as comonomers to adjust the density. It can produce polyethylene with a density ranging from 0.90 g / cm³. 3 -0.97g / cm 3 The range of polyethylene resins. The main site of the polymerization reaction in the gas-phase fluidized bed polyethylene process is a specially designed fluidized bed reactor, including a straight section, a lower distribution plate, and an upper spherical expansion section. Powdered or slurry-like catalyst is injected into the reactor and comes into contact with ethylene and comonomers from the bottom distribution plate to generate polyethylene solid particles.

[0004] Polymerization is an exothermic process. The heat released by the reaction is transferred to the unreacted gases. The unreacted gases are discharged from the top of the reactor, cooled and pressurized, and then enter the reactor from the bottom distribution plate along with the newly added ethylene and comonomers. The polyethylene particles discharged from the reactor are loose and porous. The polyethylene produced in the polymerization reactor is a loose and porous powdery solid particle. At the same time, the polymerization reaction produces a small amount of small-molecule polymers, also known as oligomers, mainly C8-C18 hydrocarbons. These small molecules, along with ethylene, comonomers, condensers (mostly isopentane or n-hexane), catalysts, and solvents, are adsorbed in the polyethylene powder. During transportation, granulation, and post-processing, they volatilize from the resin, becoming volatile organic compounds (VOCs), producing odors, smoke, and other problems. The degradation and carbonization of small molecules result in a high carbon content detection rate in the finished product. In addition, the small molecules remaining in the polyolefin resin particles affect the mechanical properties of the product, limiting the application scenarios and application levels of the resin product. For example, when used in pipe materials, it can only meet the PE80 grade requirements; it cannot meet the requirements for use in medical, electronic, or even food packaging fields.

[0005] The degassing chamber is a specially designed container. Solid polyethylene granules enter from the top, while low-pressure nitrogen enters from near the bottom. The nitrogen and polyethylene granules flow counter-currently within the chamber, ensuring thorough contact and removing adsorbed substances from the granules. Hydrocarbon-containing nitrogen is filtered under system pressure and discharged from the top of the chamber to the flare system. The contact time between the polyethylene granules and nitrogen in the degassing chamber is controlled by the feeding speed of the downstream rotary feeder, and is generally 2-6 hours (affected by production load) due to the continuous production and upstream / downstream material balance. After degassing, the polyethylene granules are discharged from the bottom of the chamber and sent to the mixing and granulation unit for high-temperature melt mixing and granulation. Thermogravimetric analysis shows that the volatile organic compound (VOC) content in the degassed polyethylene granules is approximately 0.2%-0.4%. Even when nitrogen is used to remove adsorbed substances from polyethylene granules, the removal effect is poor due to the limited degassing time in continuous production processes, resulting in poor removal of hexene, condensers, especially solvents, and low-polymerization-degree hydrocarbons. These substances remaining in the polyethylene granules continue to be released during subsequent storage, transportation, mixing, processing, and use, becoming volatile organic compounds (VOCs), causing strong odors and even smoke in the mixing and processing processes and the final products.

[0006] Currently, most methods for removing adsorbates from solid polymers involve washing with steam or high-temperature water followed by hot nitrogen dehydration. This process is effective for removing low-molecular-weight substances like methane, ethylene, and ethane, but less effective for removing hexene, condensers, solvents, and oligomeric hydrocarbons. Some technicians have proposed increasing the contact efficiency between the solid polymer and the degassing medium by adding agitators or rotating the degassing equipment, or redesigning the internal structure of the degassing chamber to extend the contact time. However, these methods require modifications to the main production process equipment. Modifying large pressure vessels is not only cumbersome but also time-consuming; directly replacing equipment is an even greater investment. Another technology uses multiple degassing devices in parallel, repeatedly washing and drying, combined with vacuuming to improve efficiency. This approach is not only extremely expensive but also impractical for many existing production facilities that lack the space to add multiple degassing facilities. Furthermore, this technology is cumbersome to operate, and the energy consumption for transporting materials between multiple degassing devices is enormous.

[0007] Not only polyethylene, but other domestically produced solid polymers such as polypropylene and polyvinyl chloride also have the same problem of strong odor. This has resulted in China's current reliance on imports for polymers used in medicine, electronics, and even food. Summary of the Invention

[0008] The purpose of this invention is to overcome the problem of high volatile organic compound (VOC) content in solid polymers in existing technologies, and to provide a method and system for treating VOCs in solid polymers. This treatment method can efficiently remove VOCs from solid polymers, improving the environmental friendliness of production and the quality of products.

[0009] The first aspect of the present invention provides a method for treating volatile organic compounds in a solid polymer, the method comprising: purging the solid polymer containing volatile organic compounds with a mixture of gaseous light hydrocarbons and nitrogen to degas the polymer.

[0010] A second aspect of the present invention provides a system for treating volatile organic compounds in a solid polymer, comprising a mixed gas supply unit for providing a mixture of gaseous light hydrocarbons and nitrogen, and a degassing chamber for purging the solid polymer containing volatile organic compounds with the mixed gas of gaseous light hydrocarbons and nitrogen to degas the polymer.

[0011] A third aspect of the present invention provides the application of the processing system described herein in the processing of volatile organic compounds in solid polymers.

[0012] A fourth aspect of the present invention provides a method for granulating a solid polymer, the method comprising: treating volatile organic compounds in a solid polymer according to the processing method of the present invention, and then mixing and granulating the treated solid polymer.

[0013] Compared with the prior art, the present invention has at least the following beneficial effects:

[0014] (1) The processing method of the present invention is safe and efficient, and can effectively reduce the content of volatile organic compounds in solid polymers, improve the environmental protection of solid polymer production and the quality of solid polymers, and avoid the occurrence of problems such as smoke, odor and impact on the mechanical properties of products during subsequent granulation or post-processing.

[0015] (2) The processing method of the present invention removes VOCs from solid polymers, thereby reducing the degradation and carbonization of small molecules during the compounding and granulation of solid polymers, reducing the amount of carbides in solid polymers; improving the mechanical properties and odor level of solid polymers, and expanding the application fields of solid polymers while improving product quality.

[0016] (3) The processing method of the present invention does not require adjustments to the main process for preparing solid polymers and the equipment on the main process, and the cost is low;

[0017] (4) The processing method of the present invention can avoid the use of steam and reduce the impact on product quality;

[0018] (5) The processing method of the present invention has been industrialized. After implementation, the carbonation detection rate of high-density polyethylene granules at Qilu Petrochemical Plastics Plant decreased from 20.37% in 2021 to 5.36% in the second half of 2022. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a process for treating volatile organic compounds in a solid polymer according to one embodiment of the present invention.

[0020] Explanation of reference numerals in the attached figures

[0021] 1. Nitrogen flow control valve for air 2. Gaseous light hydrocarbon flow control valve

[0022] 3. Mixer; 4. Online detection chromatograph for gaseous light hydrocarbon concentration.

[0023] 5. Mixed gas heater 6. Degassing chamber

[0024] A. Nitrogen B. Gaseous light hydrocarbons Detailed Implementation

[0025] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0026] The first aspect of the present invention provides a method for treating volatile organic compounds in a solid polymer, the method comprising: purging the solid polymer containing volatile organic compounds with a mixture of gaseous light hydrocarbons and nitrogen to degas the polymer.

[0027] In this invention, purging solid polymers containing volatile organic compounds with a mixture of gaseous light hydrocarbons and nitrogen can effectively remove volatile organic compounds from solid polymers, thereby improving the environmental friendliness of production and the quality of products.

[0028] According to some embodiments of the present invention, the gaseous light hydrocarbon is selected from C2-C4 hydrocarbons.

[0029] According to some preferred embodiments of the present invention, the gaseous light hydrocarbon is a C2-C4 olefin.

[0030] According to some preferred embodiments of the present invention, the gaseous light hydrocarbon is ethylene and / or propylene.

[0031] According to some preferred embodiments of the present invention, the gaseous light hydrocarbon is ethylene.

[0032] In this invention, the mixed gas has better compatibility with the volatile organic compounds in the solid polymer and can better remove the volatile organic compounds from the solid polymer.

[0033] According to the present invention, the content of gaseous light hydrocarbons in the mixed gas is not particularly limited as long as the purpose of the present invention can be achieved. In some embodiments, the molar concentration of gaseous light hydrocarbons in the mixed gas is 0.1-10%, for example, 0.1%, 0.3%, 0.5%, 1%, 2%, 3%, 5%, 8%, 10%, or any combination of two of the above values, preferably 0.5-5%. The processing method of this embodiment has higher operational safety and can also better remove volatile organic compounds from solid polymers.

[0034] According to the present invention, in some preferred embodiments, the temperature of the mixed gas is 30-105°C, for example, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, or any combination of two of the above values, preferably 60-100°C. This method of processing can better remove volatile organic compounds from the solid polymer and can avoid polymer melting caused by excessively high mixing temperatures, resulting in a product obtained by compounding and granulating the solid polymer after volatile organic compound removal with excellent mechanical properties.

[0035] According to some embodiments of the present invention, a mixture of gaseous light hydrocarbons and nitrogen is used to degas a solid polymer containing volatile organic compounds by blowing it from bottom to top. This embodiment can better remove volatile organic compounds from the solid polymer.

[0036] According to the present invention, the volume of the mixed gas is not particularly limited as long as the objective of the invention can be achieved. In some preferred embodiments, the volume of the mixed gas to the solid polymer is 1-5 L / h: 100g, for example, 1 L / h: 100g, 1.5 L / h: 100g, 1.8 L / h: 100g, 2 L / h: 100g, 3 L / h: 100g, 4 L / h: 100g, 5 L / h: 100g, or any range of two of the above ratios. This method can better remove volatile organic compounds from the solid polymer while reducing degassing costs.

[0037] According to the present invention, the degassing conditions are not particularly limited as long as the purpose of the invention can be achieved. In some embodiments, the degassing treatment conditions include a time of more than 2 hours, preferably 2-6 hours. The treatment method of this embodiment can better remove volatile organic compounds from solid polymers.

[0038] According to the present invention, in some embodiments, the processing method further includes: simultaneously degassing the solid polymer containing volatile organic compounds by purging it with a mixture of gaseous light hydrocarbons and nitrogen, and feeding a nitrogen stream from different locations to purge the solid polymer to remove residual gaseous light hydrocarbons, preferably, the amount of nitrogen stream is 5-10% of the amount of the mixed gas. This processing method can achieve nitrogen sealing and removal of residual ethylene, reducing safety risks to downstream facilities or minimizing the impact on product quality.

[0039] According to some preferred embodiments of the present invention, a nitrogen gas stream is used to purge the solid polymer from bottom to top.

[0040] According to the present invention, after the solid polymer removes volatile organic compounds, the removed volatile organic compounds and the mixed gas are discharged as the degassed gas. Preferably, the degassed gas is discharged after filtration, and can be discharged to a flare system or a recovery system. That is, the processing method of the present invention further includes: the degassed gas is discharged after filtration. The present invention has no particular limitations in this regard.

[0041] According to some embodiments of the present invention, the solid polymer includes olefin-based solid polymers.

[0042] In this invention, there are no special restrictions on the content of volatile organic compounds in the solid polymer, for example, it can be 0.09-0.4 wt%.

[0043] According to the present invention, in some embodiments, the volatile organic compounds include hydrocarbon compounds, including C8-C18 hydrocarbon compounds.

[0044] In this invention, the volatile organic compounds in the solid polymer generally include small molecule impurities generated during the synthesis of the corresponding solid polymer, such as hydrocarbons, as well as small molecule compounds used in the synthesis of the solid polymer, such as condensers, solvents, dispersants, etc.

[0045] In this invention, olefin solid polymers refer to polymers formed by polymerizing olefin compounds, such as polyethylene, polypropylene, polystyrene, and polyvinyl chloride. These polymers can be homopolymers or copolymers, and this invention does not have any particular limitation on them.

[0046] According to some preferred embodiments of the present invention, the solid polymer is a polyethylene-based solid polymer and / or a polypropylene-based solid polymer.

[0047] In this invention, the treatment method of this invention can effectively remove volatile organic compounds from polyethylene solid polymers and / or polypropylene solid polymers, thereby improving the environmental friendliness of production and the quality of products.

[0048] A second aspect of the present invention provides a system for treating volatile organic compounds in a solid polymer, the system comprising: a mixed gas supply unit for providing a mixture of gaseous light hydrocarbons and nitrogen; and a degassing chamber for purging the solid polymer containing volatile organic compounds with the mixed gas of gaseous light hydrocarbons and nitrogen to degas the polymer.

[0049] In this invention, the processing system of this invention degassing a mixture of gaseous light hydrocarbons and nitrogen with a solid polymer in a degassing chamber, which can effectively reduce the content of volatile organic compounds in the solid polymer, improve the environmental friendliness of the production process and the quality of the solid polymer products.

[0050] In this invention, the structure of the degassing chamber is not particularly limited. Its volume is sufficient to ensure stable flow and full contact between the mixed gas and the solid polymer, and that the gas after volatilization has enough time to escape. Its specific structure is the structure of a conventional degassing chamber in the art, and this invention will not elaborate on it further.

[0051] According to the present invention, in some embodiments, the mixed gas supply unit is connected to the bottom of the degassing chamber, and the mixed gas containing gaseous light hydrocarbons and nitrogen flows from bottom to top through the degassing chamber, purging the solid polymer in the degassing chamber for degassing. Using this embodiment, the mixed gas can fully contact the solid polymer in the degassing chamber, more effectively removing volatile organic compounds from the solid polymer.

[0052] According to some embodiments of the present invention, the mixed gas supply unit includes a mixer and a mixed gas heater along the direction of the mixed gas flow.

[0053] In this invention, the mixer can be used to mix gaseous light hydrocarbons or exhaust gas containing gaseous light hydrocarbons (including gaseous light hydrocarbons and nitrogen) with nitrogen to obtain a mixed gas containing gaseous light hydrocarbons and nitrogen. The mixed gas is then introduced into a mixed gas heater for heating. The heated mixed gas then enters a degassing chamber to fully contact the solid polymer in the degassing chamber.

[0054] According to some preferred embodiments of the present invention, the mixed gas heater is equipped with a high-temperature interlock to prevent the solid polymer from melting due to excessively high mixed gas temperature.

[0055] According to the present invention, in some embodiments, the bottom of the degassing chamber is provided with a nitrogen purging unit at a different location from the feed position of the mixed gas supply unit. While the mixed gas containing gaseous light hydrocarbons and nitrogen purges the solid polymer containing volatile organic compounds for degassing, a nitrogen stream is fed from a different location to purge the solid polymer and remove residual gaseous light hydrocarbons. This embodiment can achieve nitrogen sealing and removal of residual ethylene, reducing safety risks to downstream facilities or minimizing the impact on product quality.

[0056] According to the present invention, in some embodiments, the processing system of the present invention further includes: an online monitoring unit for gaseous light hydrocarbon concentration, used to detect the concentration of gaseous light hydrocarbons in the mixed gas.

[0057] In this invention, the online monitoring unit for gaseous light hydrocarbon concentration can be any instrument in the art capable of qualitatively and quantitatively identifying components in a gas, such as an online chromatograph, which is referred to in this invention as an online detection chromatograph for gaseous light hydrocarbon concentration.

[0058] In this invention, the online monitoring unit for gaseous light hydrocarbon concentration can be connected to various connecting pipelines, mixers, and mixed gas heaters in the system as needed to monitor the concentration of gaseous light hydrocarbons and use it as a basis for adjusting the amount of gaseous light hydrocarbons or exhaust gas containing gaseous light hydrocarbons (including nitrogen and gaseous light hydrocarbons) added, thereby controlling the molar concentration of gaseous light hydrocarbons in the mixed gas to the required molar concentration.

[0059] In the system described in this invention, the various units and devices can be connected by pipelines. Valves can be installed on each pipeline as needed. For example, a gaseous light hydrocarbon flow control valve can be installed on the pipeline that introduces gaseous light hydrocarbons or exhaust gas containing gaseous light hydrocarbons (including gaseous light hydrocarbons and nitrogen) into the mixer, a nitrogen flow control valve can be installed on the pipeline that introduces nitrogen into the mixer, and a valve can be installed on the pipeline that introduces mixed gas into the degassing chamber. Each pipeline can also be insulated as needed. For example, the pipeline between the mixed gas heater and the degassing chamber needs to be insulated. This invention has no special limitations on this, and will not elaborate further on it.

[0060] A third aspect of the present invention provides the application of the processing system described herein in the processing of volatile organic compounds in solid polymers.

[0061] A fourth aspect of the present invention provides a method for granulating a solid polymer, the method comprising: treating volatile organic compounds in a solid polymer according to the processing method of the present invention, and then mixing and granulating the treated solid polymer.

[0062] In this invention, mixing and granulation is a conventional operation in the polymer field. Those skilled in the art can select the appropriate mixing and granulation process according to the type of solid polymer. This invention will not elaborate further on this.

[0063] In this invention, the solid polymer obtained through the processing method of this invention exhibits reduced molecular degradation and carbonization during granulation, thereby lowering the amount of carbides in the solid polymer. For example, after implementing this technology, the carbonite detection rate of high-density polyethylene granules leaving Qilu Petrochemical Plastics Plant decreased from 20.37% in 2021 to 5.36% in the second half of 2022. Simultaneously, it can also improve the mechanical properties and odor levels of the solid polymer resin, expanding the application areas of solid polymer resin while improving product quality.

[0064] Figure 1 This is a schematic diagram of a process for treating volatile organic compounds in a solid polymer according to one embodiment of the present invention, as shown below. Figure 1 As shown, after nitrogen A and gaseous light hydrocarbon B are metered, nitrogen flow air valve 1 and gaseous light hydrocarbon flow control valve 2 are opened to introduce the metered nitrogen A and gaseous light hydrocarbon B into mixer 3 to mix and obtain a mixed gas. At the same time, the concentration of gaseous light hydrocarbon in mixer 3 is monitored by online gaseous light hydrocarbon concentration detection chromatograph 4, and used as the basis for adjusting the amount of gaseous light hydrocarbon added (the amount of gaseous light hydrocarbon added can be controlled by gaseous light hydrocarbon flow control valve 2). The above mixed gas is introduced into the mixed gas heater 5 through pipeline for heating. The mixed gas heater 5 is equipped with a high temperature interlock (not shown) to avoid the polymer melting due to excessively high mixing temperature.

[0065] The high-temperature mixed gas from the mixed gas heater 5 is introduced into the degassing chamber 6 through a pipeline (the pipeline between the mixed gas heater 5 and the degassing chamber 6 needs to be insulated). It is injected from the bottom of the degassing chamber 6 and flows through the degassing chamber 6 from bottom to top. It is mixed with the solid polymer in the degassing chamber 6 in a counter-current flow to fully contact and degas. At the same time as the degassing is performed, nitrogen gas is blown from the bottom of the degassing chamber 6 through the nitrogen purging unit (not shown) to purge the solid polymer from bottom to top to remove residual gaseous light hydrocarbons in the solid polymer.

[0066] After degassing, the gas in the degassing chamber is discharged from the filter (not shown) at the top of the degassing chamber 6;

[0067] After degassing, the solid polymer is sent from the bottom of degassing chamber 6 through a pipeline to the mixing and granulation unit for mixing and granulation.

[0068] The present invention will be described in detail below through embodiments.

[0069] Example 1

[0070] exist Figure 1 In the processing system, on May 5, 2022, the volatile organic compounds in 100g of powdered polyethylene were degassed in the laboratory of Qilu Petrochemical Research Institute: Nitrogen A and gaseous light hydrocarbon B (ethylene) were metered separately, and the nitrogen flow air valve 1 and the gaseous light hydrocarbon flow control valve 2 were opened to introduce the metered nitrogen A and ethylene into the mixer 3 to mix and obtain a mixed gas (the molar concentration of ethylene in the mixed gas was 10%). At the same time, the concentration of ethylene in the mixer 3 was monitored by the gaseous light hydrocarbon concentration online detection chromatograph 4, and used as the basis for adjusting the amount of ethylene added (the amount of ethylene added can be controlled by the gaseous light hydrocarbon flow control valve 2). The above mixed gas was introduced into the mixed gas heater 5 through the pipeline for heating (heated to 25°C). The mixed gas heater 5 was equipped with a high temperature interlock (not shown) to avoid the polymer melting caused by excessively high mixing temperature.

[0071] The high-temperature mixed gas (flow rate of 2 L / h) from the mixed gas heater 5 is introduced into the degassing chamber 6 through a pipeline (the pipeline between the mixed gas heater 5 and the degassing chamber 6 needs to be insulated). It is injected from the bottom of the degassing chamber 6 and flows from bottom to top through the degassing chamber 6, making full contact with the 100g of powdered polyethylene in the degassing chamber 6 in a counter-current flow to degas. At the same time as degassing, nitrogen gas (flow rate of 0.2 L / h) is purged from bottom to top from the nitrogen purging unit (not shown) at the bottom of the degassing chamber 6 to remove residual gaseous light hydrocarbons in the solid polymer. After 4 hours of degassing treatment, the gas in the degassing chamber is discharged from the filter (not shown) at the top of the degassing chamber 6.

[0072] The content of volatile organic compounds in powdered polyethylene was tested using a thermogravimetric analyzer at a constant temperature of 260℃ for 5 minutes, and the result was a decrease from 0.34 wt% to 0.12 wt%.

[0073] Example 2

[0074] On May 9, 2022, degassing treatment of volatile organic compounds in 100g of powdered polyethylene was carried out in the laboratory of Qilu Petrochemical Research Institute.

[0075] The process is carried out according to the method of Example 1, except that the mixture is heated in the gas heater 5 to 100°C.

[0076] The content of volatile organic compounds in powdered polyethylene was tested using a thermogravimetric analyzer at a constant temperature of 260℃ for 5 minutes, and the result was a decrease from 0.34 wt% to 0.02 wt%.

[0077] Example 3

[0078] On May 10, 2022, degassing treatment of volatile organic compounds in 100g of powdered polypropylene was carried out in the laboratory of Qilu Petrochemical Research Institute.

[0079] The process was carried out according to the method of Example 1, except that the mixed gas components were nitrogen A and gaseous light hydrocarbon B (ethylene), the molar concentration of ethylene was 10%, and the mixed gas was heated in heater 5 to 100°C.

[0080] The content of volatile organic compounds in powdered polypropylene was tested using a thermogravimetric analyzer at a constant temperature of 260℃ for 5 minutes, and the result was a decrease from 0.09 wt% to 0.04 wt%.

[0081] Example 4

[0082] On May 12, 2022, degassing treatment of volatile organic compounds in 100g of powdered polypropylene was carried out in the laboratory of Qilu Petrochemical Research Institute.

[0083] The process was carried out according to the method of Example 1, except that the mixed gas components were nitrogen A and gaseous light hydrocarbon B (propylene), the molar concentration of propylene was 10%, and the mixed gas was heated in heater 5 to 100°C.

[0084] The content of volatile organic compounds in powdered polypropylene was tested using a thermogravimetric analyzer at a constant temperature of 260℃ for 5 minutes, and the result was a decrease from 0.09 wt% to 0.02 wt%.

[0085] Example 5

[0086] On July 18, 2022, the high-density polyethylene polymerization line B at Qilu Petrochemical Plastics Plant underwent degassing treatment to remove volatile organic compounds from 38 tons of powdered polyethylene.

[0087] The processing was carried out according to the method of Example 1, except that: the molar concentration of ethylene in the mixed gas was 2%; the mixture was heated in the mixed gas heater 5 to 60°C; and the flow rate of the high-temperature mixed gas exiting the mixed gas heater 5 was 700 m³ / s. 3 / h; flow rate is 60m³ / h 3 A nitrogen stream of / h is purged from bottom to top through a nitrogen purging unit (not shown) at the bottom of degassing chamber 6 to remove residual gaseous light hydrocarbons from the solid polymer.

[0088] The content of volatile organic compounds in powdered polyethylene was tested using a thermogravimetric analyzer at a constant temperature of 260℃ for 5 minutes, and the result was a decrease from 0.24 wt% to 0.05 wt%.

[0089] Powdered polyethylene that has not undergone this degassing treatment technology is sent to a mixing and granulation unit for mixing and granulation (granulation conditions: mixing temperature 200℃, load 8.5t / h). The resulting granulated polyethylene has a tensile strength of 20.4MPa and a notched impact strength of 13.4kJ / m². 2 ;

[0090] The solid polymer treated using this degassing technology is piped from the bottom of degassing chamber 6 to the mixing and granulation unit for mixing and granulation (granulation conditions are the same as described above). The resulting polyethylene granules have a tensile strength of 21.2 MPa and a notched impact strength of 15.3 kJ / m². 2 .

[0091] Example 6

[0092] On July 4, 2022, at the Qilu Petrochemical Plastics Plant's high-density polyethylene polymerization line A, volatile organic compounds were degassed from 38 tons of powdered polyethylene.

[0093] The processing was carried out according to the method of Example 1, except that: the molar concentration of ethylene in the mixed gas was 5%; the mixture was heated in the mixed gas heater 5 to 80°C; and the flow rate of the high-temperature mixed gas exiting the mixed gas heater 5 was 600 m³ / s. 3 / h; flow rate is 60m³ / h 3 / h of nitrogen is purged from bottom to top by the nitrogen purging unit at the bottom of the degassing chamber 6 (not shown) to purge the solid polymer.

[0094] The content of volatile organic compounds in powdered polyethylene was tested using a thermogravimetric analyzer at a constant temperature of 260℃ for 5 minutes, and the result was a decrease from 0.32 wt% to 0.04 wt%.

[0095] Powdered polyethylene that has not undergone this degassing treatment technology is sent to a mixing and granulation unit for mixing and granulation (granulation conditions: mixing temperature 200℃, load 8.5t / h). The resulting granulated polyethylene has a tensile strength of 20.7MPa and a notched impact strength of 13.3kJ / m². 2 .

[0096] The solid polymer treated using this degassing technology is piped from the bottom of degassing chamber 6 to the mixing and granulation unit for mixing and granulation (granulation conditions are the same as described above). The resulting polyethylene granules have a tensile strength of 21.5 MPa and a notched impact strength of 15.8 kJ / m². 2 .

[0097] Comparative Example 1

[0098] The method according to Example 1 differs in that:

[0099] On May 17, 2022, degassing treatment of volatile organic compounds in 100g of powdered polyethylene was carried out in the laboratory of Qilu Petrochemical Research Institute.

[0100] The treatment was carried out according to the method of Example 1, except that the molar concentration of ethylene in the mixed gas was 0%, that is, nitrogen was used alone for degassing.

[0101] The content of volatile organic compounds in powdered polyethylene was tested using a thermogravimetric analyzer at a constant temperature of 260℃ for 5 minutes, and the result was a decrease from 0.34% to 0.21%.

[0102] The results of the examples show that the treatment method of the present invention can effectively reduce the content of volatile organic compounds in solid polymers, improve the environmental friendliness of solid polymer production and the quality of solid polymers, and avoid problems such as smoke, odor and impact on the mechanical properties of products during subsequent granulation or post-processing.

[0103] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for treating volatile organic compounds in a solid polymer, characterized by, The method comprises: purging the solid polymer containing volatile organic compounds with mixed gas containing gaseous light hydrocarbon and nitrogen to perform degassing, while feeding nitrogen stream from different position to purge the solid polymer with nitrogen stream to remove gaseous light hydrocarbon remaining in the solid polymer; The amount of gas of the nitrogen stream is 5-10% of the amount of gas of the mixed gas; The amount of gas of the mixed gas: solid polymer = 1-5 L / h: 100 g; The condition of the degassing treatment includes: time greater than 2 hours.

2. The treatment method according to claim 1, wherein, the gaseous light hydrocarbon is selected from C2-C4 hydrocarbon; and / or the molar concentration of the gaseous light hydrocarbon in the mixed gas is 0.1%-10%; and / or the temperature of the mixed gas is 30-105℃.

3. The treatment method according to claim 2, wherein, the gaseous light hydrocarbon is C2-C4 olefin; and / or the molar concentration of the gaseous light hydrocarbon in the mixed gas is 0.5%-5%; and / or the temperature of the mixed gas is 60-100℃.

4. The treatment method according to claim 2, wherein, the gaseous light hydrocarbon is ethylene and / or propylene.

5. The treatment method according to claim 2, wherein, the gaseous light hydrocarbon is ethylene.

6. The treatment method according to claim 1 or 2, wherein, the mixed gas containing gaseous light hydrocarbon and nitrogen purges the solid polymer containing volatile organic compounds from bottom to top to perform degassing; and / or the condition of the degassing treatment includes: time is 2-6 hours.

7. The treatment method according to claim 1 or 2, wherein, the nitrogen stream purges the solid polymer from bottom to top; and / or the treatment method further comprises: the gas after degassing is filtered and discharged.

8. The treatment method according to claim 1 or 2, wherein, the volatile organic compounds include hydrocarbon compounds; and / or the solid polymer includes olefin-based solid polymer.

9. The treatment method according to claim 8, wherein, the volatile organic compounds include C8-C18 hydrocarbon compounds; and / or the solid polymer includes polyethylene-based solid polymer and / or polypropylene-based solid polymer.

10. A system for the treatment of volatile organic compounds in a solid polymer, characterized in that The treatment system comprises: a mixed gas supply unit for providing mixed gas containing gaseous light hydrocarbon and nitrogen; a degassing bin for purging the solid polymer containing volatile organic compounds with mixed gas containing gaseous light hydrocarbon and nitrogen to perform degassing; the bottom of the degassing bin is provided with a nitrogen purging unit different from the feeding position of the mixed gas supply unit, while purging the solid polymer with mixed gas containing gaseous light hydrocarbon and nitrogen to perform degassing, nitrogen stream is fed from different position to purge the solid polymer with nitrogen stream to remove gaseous light hydrocarbon remaining in the solid polymer.

11. The treatment system according to claim 10, wherein, the mixed gas supply unit communicates with the bottom of the degassing bin, and the mixed gas containing gaseous light hydrocarbon and nitrogen flows through the degassing bin from bottom to top to purge the solid polymer in the degassing bin to perform degassing; and / or along the flow direction of the mixed gas, the mixed gas supply unit includes a mixer and a mixed gas heater.

12. The processing system of claim 11, wherein, The mixed gas heater is provided with high temperature interlocking.

13. The treatment system according to claim 10 or 11, wherein, The processing system further comprises a gaseous light hydrocarbon concentration on-line monitoring unit for detecting the concentration of gaseous light hydrocarbon in the mixed gas.

14. Use of the processing system according to any one of claims 10-13 for processing volatile organic compounds in solid polymers.

15. A method of solid polymer pelletization, characterized by, The method comprises: The solid polymers processed by the processing method according to any one of claims 1-9 are then subjected to mixing and granulation.

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