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

Abstract

The invention relates to the technical field of solid polymer treatment, in particular to a treatment method and a treatment system for volatile organic compounds in a solid polymer and a solid polymer granulation method. The method comprises the step of purging the solid polymer containing the volatile organic compounds by mixed gas containing gaseous light hydrocarbon and nitrogen for degassing. The treatment method is safe and efficient, the content of volatile organic compounds in the solid polymer can be effectively reduced, and the environmental protection property of solid polymer production and the quality of the solid polymer are improved.

Description

Technical Field

[0001] The invention relates to the technical field of solid polymer processing, and in particular to a method and system for processing volatile organic compounds in solid polymers, and a method for granulating solid polymers. Background Art

[0002] Polymers are materials made from one or more monomers through polymerization reactions, including fibers, plastics, rubbers, coatings and adhesives. Plastics are solid polymers, and solid polymer polyethylene accounts for nearly 40% of plastics, which is widely used in agriculture, transportation, construction, light industry, heavy industry, national defense and various fields of life. Although my country has become a major polyethylene producer in the world, it generally produces low-end and mid-end products. High-end products such as medical and electronic products and even mid-end food products are basically dependent on imports. One of the important reasons is that the domestic polyethylene products have a strong odor during the processing process.

[0003] Gas phase fluidized bed polyethylene process is one of the main processes for polyethylene production. It is a polymerization process that uses gas phase ethylene and nitrogen as fluids to drive solid polyethylene particles from bottom to top, so that polyethylene particles can flow freely in the bed. It has the characteristics of high heat transfer efficiency, easy particle flow, convenient material loading and unloading, etc. Chromium catalysts, Ziegler catalysts, titanium modified chromium catalysts, metallocene catalysts, etc. are used to catalyze ethylene polymerization, hydrogen is used to adjust the molecular weight, and alpha olefins such as butene and hexene are used as comonomers to adjust the density. It can produce 0.90g / cm 3 -0.97g / cm 3 The main place for the polymerization reaction of gas phase fluidized bed polyethylene process is a specially designed fluidized bed reactor, including a straight cylinder section, a lower distribution plate and an upper spherical expansion section. The powdered or slurry catalyst is injected into the reactor and contacts with ethylene and comonomer from the bottom distribution plate of the reactor to generate polyethylene solid particles.

[0004] The polymerization reaction is an exothermic process. The heat released by the reaction is transferred to the gas that does not participate in the reaction. The unreacted gas is discharged from the top of the reactor. After cooling and pressurization, it enters the reactor from the distribution plate at the bottom of the reactor together with the newly added ethylene and comonomer. The polyethylene particles discharged from the reactor are loose and porous. The polyethylene generated in the polymerization reactor is a loose and porous powder-like solid small particle. At the same time, the polymerization reaction process will produce a small amount of small molecular polymers, also known as oligomers, mainly C8-C18 hydrocarbons. These small molecules, together with ethylene, comonomers, condensing agents (mostly isopentane or n-hexane), solvents from catalysts, etc., are adsorbed in the polyethylene powder. During the transportation, granulation and post-processing processes, they evaporate from the resin and become volatile organic compounds (VOCs), causing odor, smoke and other problems. Small molecules are degraded and carbonized, resulting in a high detection rate of carbonized products leaving the factory. In addition, the small molecules remaining in the polyolefin resin particles will affect the mechanical properties of the product, limiting the application scenarios and application levels of the resin products. For example, when used for pipe materials, it can only meet the use requirements of PE80 grade; it cannot meet the use requirements in the medical, electronic and even food packaging fields.

[0005] The degassing bin is a specially designed container. Solid polyethylene particles enter from the top of the degassing bin, and low-pressure nitrogen enters from the bottom of the degassing bin. Nitrogen and polyethylene particles are mixed in reverse flow in the degassing bin and fully contact each other, so as to remove the adsorbed substances in the polyethylene particles. Nitrogen containing hydrocarbons is filtered by the filter under the control of system pressure and discharged from the top of the degassing bin to the flare system. The contact time between polyethylene particles and nitrogen in the degassing bin is controlled by the feeding speed of the rotary feeder downstream of the degassing bin, which is affected by the balance of materials upstream and downstream of continuous production, and is generally 2-6 hours (affected by production load). The degassed polyethylene particles are discharged from the bottom of the degassing bin and sent to the mixing and granulating unit for high-temperature melting, mixing and granulation. According to the thermogravimetric method, the content of volatile organic compounds in the polyethylene particles degassed in the degassing bin is about 0.2%-0.4%. Even when nitrogen is used to remove adsorbed substances in polyethylene particles, the removal effect of hexene, condensing agent, especially solvent and low-polymerization hydrocarbons is very poor due to the limited degassing time in the continuous production process. These substances remaining in the polyethylene particles are continuously released during the subsequent storage, transportation, mixing, processing and use, becoming volatile organic compounds (VOCs), causing strong odors in the mixing and processing process and the final product, and even smoke.

[0006] At present, the methods for removing adsorbents in solid polymers mostly adopt the process of first washing with steam or high-temperature water and then dehydrating with hot nitrogen. The removal effect is good for methane, ethylene, ethane and other small molecular weights, but the removal effect is not ideal for hexene, condensing agents, solvents and oligomeric hydrocarbons. Some technicians proposed to increase the contact efficiency between solid polymers and degassing media by adding agitators or rolling the degassing equipment or redesigning the internal structure of the degassing chamber to increase the contact time between solid polymers and degassing media, but this requires the transformation of equipment in the main process of the production process. The transformation of large pressure vessels is not only cumbersome, but also time-consuming; directly replacing equipment is a huge investment. Another technology uses multiple degassing equipment in parallel, repeatedly washing and drying, and vacuuming to improve efficiency. Not only is the investment huge, but many existing production facilities do not have space to add multiple degassing facilities and cannot be applied; and the technology is cumbersome to operate, and the energy consumption of transporting materials between multiple degassing equipment is huge.

[0007] Not only polyethylene, but other domestic solid polymers such as polypropylene and polyvinyl chloride also have the same strong odor problem. This has resulted in the current domestic medical, electronic and even food polymers being basically dependent on imports. Summary of the invention

[0008] The purpose of the present invention is to overcome the problem of high volatile organic compound (VOC) content in solid polymers in the prior art, and to provide a method and system for treating volatile organic compounds in solid polymers. The treatment method can efficiently remove volatile organic compounds in solid polymers, improve the environmental protection of production and the quality of products.

[0009] A first aspect of the present invention provides a method for treating volatile organic compounds in a solid polymer. The method comprises: using a mixed gas containing gaseous light hydrocarbons and nitrogen to purge the solid polymer containing the volatile organic compounds for degassing.

[0010] The second aspect of the present invention provides a system for treating volatile organic compounds in solid polymers, which includes a mixed gas supply unit for providing a mixed gas containing gaseous light hydrocarbons and nitrogen; and a degassing chamber for degassing solid polymers containing volatile organic compounds by purging the mixed gas containing gaseous light hydrocarbons and nitrogen.

[0011] The third aspect of the present invention provides use of the treatment system of the present invention in treating 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 the solid polymer according to the treatment 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 treatment 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 friendliness of solid polymer production and the quality of solid polymers, and can avoid the occurrence of problems such as smoke and odor during subsequent granulation or post-processing, as well as the impact on the mechanical properties of the product;

[0015] (2) The treatment method of the present invention is used to remove VOCs from solid polymers, thereby reducing the degradation and carbonization of small molecules during solid polymer mixing and granulation, and reducing the amount of carbides in the solid polymers; improving the mechanical properties and odor level of the solid polymers, and expanding the application field of the solid polymers while improving the quality of the products;

[0016] (3) The processing method of the present invention does not require any adjustment to the main process for preparing solid polymers and the equipment in the main process, and thus has low cost;

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

[0018] (5) The treatment method of the present invention has been industrially applied. After implementation, the carbonization detection rate of high-density polyethylene granules produced by Qilu Petrochemical Plastic Factory in the second half of 2022 was reduced from 20.37% in 2021 to 5.36%. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0020] Description of Reference Numerals

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

[0022] 3. Mixer 4. Chromatography for online detection of gaseous light hydrocarbon concentration

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

[0024] A. Nitrogen B. Gaseous light hydrocarbons DETAILED DESCRIPTION

[0025] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0026] A first aspect of the present invention provides a method for treating volatile organic compounds in a solid polymer. The method comprises: using a mixed gas containing gaseous light hydrocarbons and nitrogen to purge the solid polymer containing the volatile organic compounds for degassing.

[0027] In the present invention, the solid polymer containing volatile organic compounds is purged by a mixed gas containing gaseous light hydrocarbons and nitrogen, so that the volatile organic compounds in the solid polymer can be removed well, thereby improving the environmental protection of the production and the quality of the product.

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

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

[0030] According to the present invention, in some preferred embodiments, the gaseous light hydrocarbons are ethylene and / or propylene.

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

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

[0033] According to the present invention, as long as the purpose of the present invention can be achieved, the content of gaseous light hydrocarbons in the mixed gas is not particularly limited. 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 a range consisting of any two of the above values, preferably 0.5-5%. The treatment method of this embodiment has higher operational safety and can better remove volatile organic matter 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 a range consisting of any two of the above values, preferably 60-100° C. The treatment method of this embodiment can better remove volatile organic matter from solid polymers, and can avoid polymer melting caused by excessively high mixed gas temperature, so that the product obtained by mixing and granulating the solid polymer from which volatile organic matter has been removed has excellent mechanical properties.

[0035] According to the present invention, in some embodiments, a mixed gas containing gaseous light hydrocarbons and nitrogen is blown from bottom to top through a solid polymer containing volatile organic compounds for degassing. This embodiment can better remove volatile organic compounds from the solid polymer.

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

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

[0038] According to the present invention, in some embodiments, the treatment method of the present invention further comprises: while the mixed gas containing gaseous light hydrocarbons and nitrogen is purged to degas the solid polymer containing volatile organic compounds, nitrogen streams are fed from different positions so that the nitrogen streams purge the solid polymers to remove the residual gaseous light hydrocarbons in the solid polymers, and preferably the gas volume of the nitrogen stream is 5-10% of the gas volume of the mixed gas. The treatment method of this embodiment can play the role of nitrogen sealing and removing residual ethylene, reducing the safety risk to the operation of downstream facilities or reducing the impact on product quality.

[0039] According to the present invention, in some preferred embodiments, a nitrogen 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 degassed gas, preferably the degassed gas is discharged after being filtered, and can be discharged to a flare system or a recovery system, that is, the treatment method of the present invention further includes: the degassed gas is discharged after being filtered. The present invention has no special limitation on this.

[0041] According to the present invention, in some embodiments, the solid polymer comprises an olefinic solid polymer.

[0042] The content of volatile organic compounds in the solid polymer of the present invention is not particularly limited, and may be, for example, 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 the present invention, the volatile organic compounds in the solid polymer generally include small molecular impurities generated when synthesizing the corresponding solid polymer, such as hydrocarbons, and small molecular compounds used when synthesizing the solid polymer, such as condensing agents, solvents, dispersants, etc.

[0045] In the present invention, olefin solid polymer refers to a polymer obtained by polymerization of olefin compounds, such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, etc. The polymer may be a homopolymer or a copolymer, and the present invention has no particular limitation on this.

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

[0047] In the present invention, using the treatment method of the present invention to treat polyethylene solid polymers and / or polypropylene solid polymers can better remove volatile organic compounds in polyethylene solid polymers and / or polypropylene solid polymers, thereby improving the environmental friendliness of production and the quality of products.

[0048] The second aspect of the present invention provides a system for treating volatile organic compounds in solid polymers, which comprises: a mixed gas supply unit for providing a mixed gas containing gaseous light hydrocarbons and nitrogen; and a degassing chamber for using the mixed gas containing gaseous light hydrocarbons and nitrogen to purge solid polymers containing volatile organic compounds for degassing.

[0049] In the present invention, the treatment system of the present invention is used to degas a mixed gas containing gaseous light hydrocarbons and nitrogen and a solid polymer in a degassing chamber, which can effectively reduce the content of volatile organic compounds in the solid polymer, improve the environmental protection of the production and the quality of the solid polymer product.

[0050] In the present invention, the structure of the degassing bin is not particularly limited, and its volume can ensure that the mixed gas and the solid polymer flow stably and fully contact, and the gas after devolatilization has enough time to escape. Its specific structure is the structure of a conventional degassing bin in the art, and the present invention will not go into details about it.

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

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

[0053] In the present invention, a 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 the present invention, in some preferred embodiments, the mixed gas heater is provided with a high-temperature interlock to prevent the mixed gas temperature from being too high and causing the solid polymer to melt.

[0055] According to the present invention, in some embodiments, a nitrogen purge unit is provided at the bottom of the degassing bin at a different feeding position from the mixed gas supply unit, and 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 position so that the nitrogen stream purges the solid polymer to remove the gaseous light hydrocarbons remaining in the solid polymer. This embodiment can achieve the effects of nitrogen sealing and removal of residual ethylene, thereby reducing the safety risk to the operation of downstream facilities or reducing the impact on product quality.

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

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

[0058] In the present invention, the gaseous light hydrocarbon concentration online monitoring unit 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 serve 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 to control the molar concentration of gaseous light hydrocarbons in the mixed gas to the required molar concentration.

[0059] In the system described in the present invention, various units and various equipment can be connected through pipelines, and valves can be set on various pipelines as needed. For example, a gaseous light hydrocarbon flow control valve is set on the pipeline for introducing gaseous light hydrocarbons or exhaust gas containing gaseous light hydrocarbons (including gaseous light hydrocarbons and nitrogen) into the mixer, a nitrogen flow control valve is set on the pipeline for introducing nitrogen into the mixer, and a valve is set on the pipeline for introducing the mixed gas into the degassing bin; each pipeline can also be insulated as needed, for example, the pipeline between the mixed gas heater and the degassing bin needs to be insulated. The present invention has no special limitation on this, and the present invention will not go into details on this.

[0060] The third aspect of the present invention provides use of the treatment system of the present invention in treating 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 the solid polymer according to the treatment method of the present invention, and then mixing and granulating the treated solid polymer.

[0062] In the present invention, mixing and granulating is a conventional operation method in the field of polymers. Those skilled in the art select corresponding mixing and granulating processes according to the types of solid polymers, and the present invention will not elaborate on this.

[0063] In the present invention, the solid polymer obtained by the treatment method of the present invention has reduced molecular degradation and carbonization during granulation, which can reduce the amount of carbides in the solid polymer. For example, after the implementation of this technology, the carbonization detection rate of high-density polyethylene granules produced by Qilu Petrochemical Plastics Factory in the second half of 2022 was reduced from 20.37% in 2021 to 5.36%; at the same time, it can also improve the mechanical properties and odor level of the solid polymer resin, which can expand the application field of the solid polymer resin while improving the quality of the product.

[0064] Figure 1 is a schematic diagram of a process for treating volatile organic compounds in solid polymers according to one embodiment of the present invention, such as Figure 1 As shown, after nitrogen A and gaseous light hydrocarbon B are respectively measured, the nitrogen flow air valve 1 and the gaseous light hydrocarbon flow control valve 2 are opened, and the measured nitrogen A and gaseous light hydrocarbon B are respectively introduced into the mixer 3 for mixing to obtain a mixed gas. At the same time, the gaseous light hydrocarbon concentration online detection chromatograph 4 is used to monitor the concentration of the gaseous light hydrocarbon in the mixer 3, and used as a basis for adjusting the amount of gaseous light hydrocarbon added (the amount of gaseous light hydrocarbon added can be controlled by the gaseous light hydrocarbon flow control valve 2). The above-mentioned mixed gas is introduced into the mixed gas heater 5 through a pipeline for heating. The mixed gas heater 5 is provided with a high-temperature interlock (not shown) to prevent the mixed gas temperature from being too high to cause polymer melting;

[0065] The high-temperature mixed gas from the mixed gas heater 5 is introduced into the degassing bin 6 through a pipeline (the pipeline between the mixed gas heater 5 and the degassing bin 6 needs to be insulated), injected from the bottom of the degassing bin 6, flows through the degassing bin 6 from bottom to top, and is fully contacted with the solid polymer in the degassing bin 6 in a countercurrent mixed flow to perform degassing treatment. While the degassing treatment is being performed, a nitrogen flow is purged from the nitrogen purge unit (not shown) at the bottom of the degassing bin 6 from bottom to top to purge the solid polymer to remove the residual gaseous light hydrocarbons in the solid polymer;

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

[0067] The solid polymer after degassing is sent from the bottom of the degassing bin 6 through a pipeline to the mixing and granulating unit for mixing and granulating.

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

[0069] Example 1

[0070] exist Figure 1 In the treatment system, on May 5, 2022, in the laboratory of Qilu Petrochemical Research Institute, volatile organic compounds in 100g of powdered polyethylene were degassed: nitrogen A and gaseous light hydrocarbon B (ethylene) were measured respectively, and the nitrogen flow air valve 1 and the gaseous light hydrocarbon flow control valve 2 were opened, and the measured nitrogen A and ethylene were respectively introduced into the mixer 3 to mix to obtain a mixed gas (the molar concentration of ethylene in the mixed gas was 10%), and the gaseous light hydrocarbon concentration online detection chromatogram 4 was used to monitor the ethylene concentration in the mixer 3, and used as a 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), and the above-mentioned mixed gas was introduced into the mixed gas heater 5 through a pipeline for heating (heating to 25°C), and the mixed gas heater 5 was provided with a high-temperature interlock (not shown) to avoid the mixed gas temperature being too high to cause polymer melting;

[0071] The high-temperature mixed gas (flow rate is 2 l / h) coming out of the mixed gas heater 5 is introduced into the degassing bin 6 through a pipeline (the pipeline between the mixed gas heater 5 and the degassing bin 6 needs to be insulated), injected from the bottom of the degassing bin 6, and flows through the degassing bin 6 from bottom to top, and is fully contacted with the powdered polyethylene 100g in the degassing bin 6 in a countercurrent mixed flow to be degassed. While degassing, a nitrogen flow (flow rate is 0.2 l / h) is purged from the nitrogen purge unit (not shown) at the bottom of the degassing bin 6 from bottom to top to purge the solid polymer to remove the residual gaseous light hydrocarbons in the solid polymer; after 4 hours of degassing treatment, the gas in the degassing bin is discharged from the filter (not shown) at the top of the degassing bin 6.

[0072] The volatile organic compound content in the powdered polyethylene was tested using a thermogravimetric analyzer at a constant temperature of 260° C. for 5 minutes and found to be reduced from 0.34 wt % to 0.12 wt %.

[0073] Example 2

[0074] On May 9, 2022, the volatile organic compounds in 100g of powdered polyethylene were degassed in the laboratory of Qilu Petrochemical Research Institute:

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

[0076] The volatile organic compound content in the powdered polyethylene was tested using a thermogravimetric analyzer at a constant temperature of 260° C. for 5 minutes and found to be reduced from 0.34 wt % to 0.02 wt %.

[0077] Example 3

[0078] On May 10, 2022, the volatile organic compounds in 100g of powdered polypropylene were degassed in the laboratory of Qilu Petrochemical Research Institute:

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

[0080] The volatile organic compound content in the powdered polypropylene was tested using a thermogravimetric analyzer at a constant temperature of 260° C. for 5 minutes and found to be reduced from 0.09 wt % to 0.04 wt %.

[0081] Example 4

[0082] On May 12, 2022, the volatile organic compounds in 100g of powdered polypropylene were degassed in the laboratory of Qilu Petrochemical Research Institute:

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

[0084] The volatile organic compound content in the powdered polypropylene was tested using a thermogravimetric analyzer at a constant temperature of 260° C. for 5 minutes and found to be reduced from 0.09 wt % to 0.02 wt %.

[0085] Example 5

[0086] On July 18, 2022, volatile organic compounds in 38 tons of powdered polyethylene were degassed at the high-density polyethylene polymerization line B of Qilu Petrochemical Plastics Plant:

[0087] The treatment method of Example 1 is used, except that the molar concentration of ethylene in the mixed gas is 2%; the mixed gas is heated in the mixed gas heater 5 to 60° C., and the flow rate of the high-temperature mixed gas coming out of the mixed gas heater 5 is 700 m 3 / h; flow rate is 60m 3 / h nitrogen flow is blown from the nitrogen blow unit (not shown) at the bottom of the degassing bin 6 from bottom to top to blow the solid polymer to remove the gaseous light hydrocarbons remaining in the solid polymer.

[0088] The volatile organic compound content in the powdered polyethylene was tested using a thermogravimetric analyzer at a constant temperature of 260° C. for 5 minutes and found to be reduced from 0.24 wt % to 0.05 wt %.

[0089] The powdered polyethylene without the degassing treatment technology was sent to the mixing and granulating unit for mixing and granulating (granulation conditions: mixing temperature 200°C, load 8.5t / h), and the tensile strength of the obtained granular polyethylene was 20.4MPa and the notched impact strength of the simply supported beam was 13.4kj / m 2 ;

[0090] The solid polymer after degassing treatment technology is sent from the bottom of the degassing bin 6 to the mixing and granulating unit through a pipeline for mixing and granulating (the granulation conditions are the same as above), and the tensile strength of the obtained polyethylene granules is 21.2MPa and the notched impact strength of the simply supported beam is 15.3kj / m 2 .

[0091] Example 6

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

[0093] The treatment method of Example 1 is used, except that the molar concentration of ethylene in the mixed gas is 5%; the mixed gas is heated in the mixed gas heater 5 to 80°C, and the flow rate of the high-temperature mixed gas coming out of the mixed gas heater 5 is 600m 3 / h; flow rate is 60m 3 / h nitrogen is purged from the nitrogen purge unit (not shown) at the bottom of the degassing bin 6 from bottom to top to purge the solid polymer.

[0094] The volatile organic compound content in the powdered polyethylene was tested using a thermogravimetric analyzer at a constant temperature of 260° C. for 5 minutes and found to be reduced from 0.32 wt % to 0.04 wt %.

[0095] The powdered polyethylene without the degassing treatment technology was sent to the mixing and granulating unit for mixing and granulating (granulation conditions: mixing temperature 200°C, load 8.5t / h), and the obtained granular polyethylene had a tensile strength of 20.7MPa and a simple supported beam notched impact strength of 13.3kj / m 2 .

[0096] The solid polymer after degassing treatment by this technology is sent from the bottom of the degassing bin 6 to the mixing and granulating unit through a pipeline for mixing and granulating (the granulation conditions are the same as above), and the obtained granular polyethylene has a tensile strength of 21.5MPa and a simple supported beam notched impact strength of 15.8kj / m 2 .

[0097] Comparative Example 1

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

[0099] On May 17, 2022, the volatile organic compounds in 100g of powdered polyethylene were degassed in the laboratory of Qilu Petrochemical Research Institute:

[0100] The treatment was carried out according to the treatment 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 volatile organic compound content in the powdered polyethylene was tested using a thermogravimetric analyzer at a constant temperature of 260° C. for 5 minutes and found to be reduced from 0.34% to 0.21%.

[0102] It can be seen from the results of the embodiments that the treatment method of the present invention can effectively reduce the content of volatile organic compounds in the solid polymer, improve the environmental protection of the solid polymer production and the quality of the solid polymer, and avoid the occurrence of problems such as smoke, odor and impact on the mechanical properties of the product during subsequent granulation or post-processing.

[0103] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for treating volatile organic compounds in solid polymers, characterized in that: The method comprises: using a mixed gas containing gaseous light hydrocarbons and nitrogen to purge solid polymer containing volatile organic compounds for degassing.

2. The processing method according to claim 1, wherein: The gaseous light hydrocarbons are selected from C2-C4 hydrocarbons, preferably C2-C4 olefins, more preferably ethylene and / or propylene, and even more preferably ethylene; and / or The molar concentration of gaseous light hydrocarbons in the mixed gas is 0.1%-10%, preferably 0.5%-5%; and / or The temperature of the mixed gas is 30-105°C, preferably 60-100°C.

3. The processing method according to claim 1 or 2, wherein: A mixture of gaseous light hydrocarbons and nitrogen is blown from bottom to top through the solid polymer containing volatile organic compounds for degassing; and / or Gas volume of mixed gas: solid polymer = 1-5L / h: 100g; and / or The conditions for the degassing treatment include: the time is greater than 2 hours, preferably 2-6 hours.

4. The processing method according to any one of claims 1 to 3, wherein: The treatment method further comprises: while the mixed gas containing gaseous light hydrocarbons and nitrogen is purged through the solid polymer containing volatile organic compounds for degassing, nitrogen streams are fed from different positions so that the nitrogen streams purge the solid polymers to remove residual gaseous light hydrocarbons in the solid polymers, preferably the gas volume of the nitrogen stream is 5-10% of the gas volume of the mixed gas, and preferably the nitrogen stream purges the solid polymers from bottom to top; and / or The treatment method also includes: the degassed gas is discharged after filtering.

5. The processing method according to any one of claims 1 to 4, wherein: The volatile organic compounds include hydrocarbon compounds, preferably C8-C18 hydrocarbon compounds; and / or The solid polymer includes an olefin solid polymer, preferably a polyethylene solid polymer and / or a polypropylene solid polymer.

6. A system for treating volatile organic compounds in solid polymers, characterized in that: The processing system includes: A mixed gas supply unit for providing a mixed gas containing gaseous light hydrocarbons and nitrogen; A degassing chamber used for degassing solid polymers containing volatile organic compounds by purging them with a mixed gas containing gaseous light hydrocarbons and nitrogen.

7. The processing system according to claim 6, wherein: The mixed gas supply unit is connected to the bottom of the degassing bin, and the mixed gas containing gaseous light hydrocarbons and nitrogen flows through the degassing bin from bottom to top to purge the solid polymer in the degassing bin for degassing; and / or Along the mixed gas flow direction, the mixed gas supply unit includes a mixer and a mixed gas heater, and preferably the mixed gas heater is provided with a high-temperature interlock.

8. The processing system according to claim 6 or 7, wherein: The bottom of the degassing bin is provided with a nitrogen purge unit at a different feeding position from 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 position so that the nitrogen stream purges the solid polymer to remove the residual gaseous light hydrocarbons in the solid polymer. and / or The processing system also includes: an online monitoring unit for gaseous light hydrocarbon concentration, which is used to detect the concentration of gaseous light hydrocarbons in the mixed gas.

9. Use of the treatment system according to any one of claims 6 to 8 for treating volatile organic compounds in solid polymers.

10. A method for granulating a solid polymer, characterized in that: The method includes: The volatile organic compounds in the solid polymer are treated according to the treatment method according to any one of claims 1 to 6, and then the solid polymer obtained by the treatment is kneaded and granulated.

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