Paper-plastic-aluminum composite packaging waste recovery method and system

Abstract

The invention discloses a paper-plastic-aluminum composite package waste recovery method and system, and the method comprises the following steps: crushing: crushing waste aluminum-plastic packages into particles; mixing: mixing the particles with a conducting medium; heating: performing pulse heating on the mixture; and collecting, namely collecting the obtained solid graphene after heating, extracting mixed gas of aluminum steam and hydrocarbon gas, condensing the aluminum steam to obtain solid aluminum, and collecting and storing the hydrocarbon gas. According to the paper-plastic-aluminum composite packaging waste recycling method, waste paper-plastic aluminum is converted into graphene, high-purity aluminum and hydrogen-rich gas through pulse heating, recycling and high-value utilization of the waste paper-plastic aluminum are achieved, and economic benefits are remarkable. And a multi-stage cyclic utilization system is established, so that waste heat and products are effectively utilized, the process energy consumption is reduced, and product circulation is realized. In addition, the production cost of the graphene is greatly reduced, and low-cost, continuous and stable preparation of the graphene is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of paper-plastic-aluminum recycling, and in particular to a method and system for recycling paper-plastic-aluminum composite packaging waste. Background Art

[0002] Paper-plastic-aluminum composite packaging is a packaging system based on food-grade cardboard. It's a composite of polyethylene, paper, and aluminum foil. Tetra Pak packaging, for example, has a six-layer composite structure consisting of paper cellulose (approximately 75%), polyethylene plastic (approximately 20%), and aluminum foil (approximately 5%), offering excellent barrier properties and freshness preservation. Currently, producing one ton of paper-plastic-aluminum composite packaging requires approximately 11 ten-year-old trees, 0.3 tons of oil, and 7.5 tons of aluminum ore. Over 100 billion Tetra Pak packaging are consumed annually, and over 80% of discarded paper-plastic-aluminum packaging is landfilled or incinerated, with a recycling rate of less than 20%. This severely harms the environment and results in a massive waste of resources and energy.

[0003] Because the polyethylene and aluminum foil in paper-plastic-aluminum composite packaging are chemically stable and form a tightly bonded, multi-layered structure with paper, all three materials are difficult to degrade. Traditional direct recycling methods, such as plastic-wood technology, suffer from poor product quality and low recovery rates. Separate recycling methods, such as hydraulic repulping, suffer from incomplete recovery and easily damaged raw materials. Chemical separation technologies are limited by the difficulty of separation and secondary pollution. Furthermore, all traditional recycling technologies for paper-plastic-aluminum composite packaging waste suffer from the common problem of low product value-added. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the present invention proposes a method and system for recycling paper-plastic-aluminum composite packaging waste, which has low recycling cost and can obtain high value-added products.

[0005] In order to achieve the above object, the present invention is implemented through the following technical solution: a method for recycling paper-plastic-aluminum composite packaging waste, comprising the following steps: Crushing: crushing the discarded aluminum-plastic packaging into particles; mixing, mixing the particles with a conductive medium; heating, pulse heating the mixture; The solid graphene obtained after heating is collected, and a mixed gas of aluminum vapor and hydrocarbon gas is extracted. The aluminum vapor is condensed to obtain solid aluminum, and then the hydrocarbon gas is collected and stored.

[0006] After the waste aluminum-plastic packaging is crushed, the raw material processing is completed. Due to the poor conductivity of paper-plastic-aluminum, a conductive medium is added, and then pulse heating is performed to achieve material conversion. The resulting products include high-purity graphene, high-purity aluminum, and hydrogen-rich gas.

[0007] Furthermore, the method further comprises the following steps: Cleaning: Use water to clean the crushed particles to remove impurities in the particles; Drying: Heat and dry the cleaned particles.

[0008] Washing and drying are used to remove impurities from the raw materials.

[0009] Furthermore, in the drying step: The extracted aluminum vapor and hydrocarbon gas are used to heat and dry the cleaned particles. During the hot air conveying process, the aluminum vapor releases latent heat and condenses when it cools down. It adheres to the surface of the particles and acts as a conductive medium, heating together with the particles to form a cycle. After completing the preset number of cycles, the aluminum vapor condenses and the solid aluminum is recovered.

[0010] The products obtained after pulse heating include high-temperature aluminum vapor and hydrogen-rich gas, which can be used as the main heat source for drying during the recovery process, effectively utilizing preheating and reducing process energy consumption. The condensed solid aluminum can also be used as a conductive medium for pulse heating of paper-plastic aluminum, forming a product cycle.

[0011] Furthermore, in the drying step: After hydrocarbon gas releases waste heat, it is stored after primary condensation and secondary condensation. The primary condensation removes residual aluminum in the gas, and the secondary condensation removes water vapor in the gas.

[0012] Two-stage condensation can recover residual aluminum and water vapor, and the condensed water can be recycled for the cleaning step.

[0013] Furthermore, in the mixing step: Assume that the conveying rate of the conductive medium is M1 kg / h, the conveying rate of the particles is M2 kg / h, M1:M2=K, and as the number of cycles increases, the K value is adjusted to decrease.

[0014] Since there is less metallic aluminum attached to the paper-plastic aluminum at the beginning of the cycle, the conveying rate of the conductive medium is relatively large at this time. As the number of cycles increases, the amount of aluminum increases accordingly. The conveying rate of the conductive medium relative to the particles can be relatively lowered by reducing the K value.

[0015] The beneficial effects of this paper-plastic-aluminum composite packaging waste recycling method include: through pulse heating, waste paper-plastic-aluminum is converted into graphene, high-purity aluminum, and hydrogen-rich gas, achieving resource-based and high-value utilization of waste paper-plastic-aluminum, with significant economic benefits. Furthermore, a multi-stage recycling system is established, effectively utilizing waste heat and products, reducing process energy consumption, and achieving product recycling. Furthermore, compared to traditional graphene production processes, which suffer from high costs, complex processes, and unstable quality, this method significantly reduces graphene production costs, enabling low-cost, continuous, and stable graphene production.

[0016] A paper-plastic-aluminum composite packaging waste recycling system is used for any of the above-mentioned paper-plastic-aluminum composite packaging waste recycling methods, comprising a crushing device, a cleaning device, a drying device, a vacuum feeding device, a process pipe, a Joule device and a collection tank connected in sequence.

[0017] The crushing device breaks the paper, plastic, and aluminum into particles, which are then removed by a cleaning device and dried by a drying device. A vacuum feeder mixes the particles with a conductive medium, separating the air from the mixture. The mixture is then fed through a process pipe into a Joule device, which heats the mixture through high-voltage and high-current pulse discharges, achieving millisecond-level temperature increases. The resulting mixture is graphene, aluminum vapor, and hydrocarbon gas, which is then collected and stored in a collection tank.

[0018] Furthermore, it also includes a purification device, which can purify the water after cleaning, and its water inlet and water outlet are respectively connected to the water outlet and water inlet of the cleaning device.

[0019] The purification device is used to purify the wastewater after cleaning the particles so that it can continue to be used for cleaning as clean recycled water, thereby achieving the effect of energy conservation and emission reduction.

[0020] Furthermore, it also includes an air extraction device and an air storage tank, the air extraction end of the air extraction device is connected to the Joule device, the air outlet end is connected to the drying device, and the air storage tank is connected to the drying device.

[0021] The exhaust device is used to extract the high-temperature gaseous products produced by pulse heating—aluminum vapor and hydrocarbon gases—from the reaction zone, generating high-velocity hot air that is transported to the drying unit for drying. During this hot air transport process, most of the aluminum vapor condenses and adheres to the surface of the paper-plastic aluminum particles, continuing to circulate as a conductive medium. The hydrocarbon gases are stored in a gas tank for subsequent use as high-value-added products.

[0022] Furthermore, it also includes a primary condensing device and a secondary condensing device, the primary condensing device is connected to the drying device, the secondary condensing device is connected to the primary condensing device, and the gas storage tank and the cleaning equipment are both connected to the secondary condensing device.

[0023] The first stage condensation is used to remove and recover trace aluminum remaining in hydrocarbon gas, and the second stage condensation is used to remove water vapor in the gas and recover it to the cleaning device for reuse, thereby obtaining dry and pure hydrocarbon gas.

[0024] Furthermore, the Joule device includes a reaction chamber and a conductive electrode, one side of the reaction chamber is connected to a process pipe, a compression piston is provided in the process pipe, two conductive electrodes are symmetrically arranged in the reaction chamber, the collection tank is connected to the other side of the reaction chamber, and an automatic door is provided at the connection; A weight sensor is provided in the process tube. When the weight signal reaches a threshold value, the weight sensor sends an instruction to the compression piston through the controller to push the mixture into the reaction chamber. A weight sensor is also provided at the bottom of the reaction chamber. When the mixture enters, the weight sensor transmits a signal through the controller to close the automatic door, and the conductive electrodes on both sides move toward each other to compress the mixture, so that the mixture is in a closed space.

[0025] After the mixture enters the process tube, the internal weight sensor sends a command to the compression piston, pushing the mixture into the reaction chamber. The weight sensor in the reaction chamber then transmits a signal to control the automatic door to close, and the conductive electrodes on both sides approach each other, compressing the mixture. The capacitor bank provides a high voltage and high current pulse discharge to heat the mixture.

[0026] The aforementioned paper-plastic-aluminum composite packaging waste recycling system has the following benefits: The pulsed current heats the waste to ultra-high temperatures in a very short time, eliminating the need for step-by-step reduction. This system is simple, efficient, and low-cost, and can produce high-value-added products such as graphene, aluminum vapor, and hydrocarbon gas. Furthermore, by recycling the gas, it achieves product recycling and energy conservation and emission reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the specific embodiments of the present invention, the following briefly introduces the drawings required for use in the specific embodiments. In all the drawings, each element or part is not necessarily drawn according to the actual scale.

[0028] Figure 1 A schematic flow chart of a method for recycling paper-plastic-aluminum composite packaging waste provided by one embodiment of the present invention; Figure 2 for Figure 1 Schematic diagram of a Joule device for recycling waste paper-plastic-aluminum composite packaging Figure 1 ; Figure 3 for Figure 1 Schematic diagram of a Joule device for recycling waste paper-plastic-aluminum composite packaging Figure 2 ; Figure numerals: 1-reaction chamber, 2-conductive electrode, 3-process tube, 31-compression piston, 4-collecting tank, 5-automatic door, 6-threaded sleeve, 61-screw, 62-spiral slide, 7-motor. DETAILED DESCRIPTION

[0029] The following embodiments of the technical solution of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention and are therefore only examples and are not intended to limit the scope of protection of the present invention.

[0030] See also Figure 1 The present invention provides a method and system for recycling paper-plastic-aluminum composite packaging waste, the method comprising the following steps: Crushing: crushing the discarded aluminum-plastic packaging into particles; Cleaning: Use water to clean the crushed particles to remove impurities in the particles; Drying: heating and drying the cleaned particles; mixing, mixing the particles with a conductive medium; heating, pulse heating the mixture; The solid graphene obtained after heating is collected, and a mixed gas of aluminum vapor and hydrocarbon gas is extracted. The aluminum vapor is condensed to obtain solid aluminum, and then the hydrocarbon gas is collected and stored.

[0031] This recycling process begins with raw material pretreatment. The waste aluminum-plastic packaging is crushed, cleaned to remove impurities, and then dried. Pulse heating is then applied. Because paper, plastic, and aluminum have poor electrical conductivity, a conductive medium is added to the mix, followed by pulse heating to achieve material conversion. The resulting products include high-purity graphene, high-purity aluminum, and hydrogen-rich gas.

[0032] Specifically, during the drying step, the cleaned particles are heated and dried using extracted aluminum vapor and hydrocarbon gas as the primary heat sources. The hydrocarbon gas releases excess heat, which is then stored in a gas tank. During the hot air transport, the aluminum vapor releases latent heat, condenses upon cooling, and adheres to the particle surface, acting as a conductive medium and mixing with the particles to heat them. This cycle continues until a predetermined number of cycles are completed, at which point the aluminum vapor condenses and the solid aluminum is recovered.

[0033] The products obtained after pulse heating include high-temperature aluminum vapor and hydrogen-rich gas. These can serve as the primary heat source for drying during the recovery process, effectively utilizing preheating and reducing process energy consumption. Furthermore, the condensed solid aluminum can be used as a conductive medium for further pulse heating of paper-plastic aluminum, forming a product cycle, ultimately yielding high-purity solid aluminum. The hydrogen-rich gas can also be stored as a high-value-added product for subsequent use.

[0034] Specifically, in the drying step, after the hydrocarbon gas releases waste heat, it is stored after primary condensation and secondary condensation. The primary condensation is used to remove residual aluminum in the gas, and the secondary condensation is used to remove water vapor in the gas. The two-stage condensation can recover the residual aluminum and water vapor, and the condensed water can be recovered for the cleaning step.

[0035] Specifically, in the mixing step, the conveying rate of the conductive medium is set to M1 kg / h, and the conveying rate of the particles is set to M2 kg / h, where M1:M2 = K. As the number of cycles increases, the K value is adjusted to decrease. Since less metallic aluminum adheres to the paper-plastic aluminum at the beginning of the cycle, the conveying rate of the conductive medium is relatively high. As the number of cycles increases, more aluminum is recovered from the paper-plastic aluminum. Therefore, by reducing the K value, the conveying rate of the conductive medium relative to the particles can be reduced.

[0036] The above-mentioned paper-plastic-aluminum composite packaging waste recycling method converts waste paper-plastic-aluminum into graphene, high-purity aluminum, and hydrogen-rich gas through pulse heating, achieving resource-based and high-value utilization of waste paper-plastic-aluminum, with significant economic benefits. Furthermore, a multi-stage recycling system has been established to effectively utilize waste heat and products, not only reducing process energy consumption but also achieving product recycling. Furthermore, compared to traditional graphene production processes, which suffer from high costs, complex processes, and unstable quality, this method significantly reduces graphene production costs, achieving low-cost, continuous, and stable production of graphene.

[0037] The recovery system used in the above method comprises a crushing device, a cleaning device, a drying device, a vacuum feeding device, a process pipe, a Joule device and a collecting tank which are connected in sequence.

[0038] The crushing unit features a common drive motor and crushing blade structure, suitable for crushing PE film and tough paper sheets, and is used to shred paper, plastic, and aluminum into pellets. A cleaning unit is used to clean and remove impurities from the pelletized raw materials. The drying unit uses high-temperature aluminum vapor and hydrocarbon gas as its primary heat source, with an auxiliary electric heating module as a temperature compensation unit. A built-in humidity sensor monitors the humidity of the pellets in real time, discharging solids when a set threshold is reached. The vacuum feeder is also connected to a discharger for adding a conductive medium. The pellets and conductive medium are mixed and transported by the vacuum feeder, which uses internal negative pressure to completely separate the air from the material. The mixture is then fed through a process pipe into a Joule device, which uses high-voltage and high-current pulsed discharges to raise the temperature to 3000°C in milliseconds. A vacuum pump maintains the reaction chamber under low vacuum, heating the mixture to produce graphene, aluminum vapor, and hydrocarbon gas. The graphene is then collected and stored in a collection tank.

[0039] Specifically, the system also includes a purification device capable of purifying the water after washing. The purification device has a water inlet and a water outlet connected to the water outlet and water inlet of the cleaning device, respectively. The purification device is used to purify the wastewater after washing the particles so that it can be used as clean recycled water for further washing, thereby achieving the effect of energy conservation and emission reduction.

[0040] The system also includes an exhaust device and a gas storage tank. The exhaust end of the exhaust device is connected to the Joule device, and the exhaust end is connected to the drying device. The gas storage tank is connected to the drying device. The exhaust device is used to extract the high-temperature gas products generated during the high-temperature pulse process, namely aluminum vapor and hydrocarbon gases, from the reaction zone and form high-velocity hot air, which is transported to the drying device for drying. During gas extraction, the gas first passes through a filter with adjustable porosity to intercept dust particles in the airflow and prevent pipeline clogging. The filtered high-temperature gas enters the high-temperature resistant pipeline and forms high-velocity hot air. During the hot air transportation, most of the aluminum vapor condenses and adheres to the surface of the paper-plastic aluminum particles, continuing to circulate as a conductive medium. The hydrocarbon gas is stored in the gas storage tank for further use as a high-value-added product. The exhaust device is also connected to a buffer tank. When the aluminum vapor circulates a preset number of times, the exhaust device switches the pipeline to the buffer tank, allowing the remaining aluminum vapor to enter the buffer tank. Upon contact with the cold pipe wall, it quickly condenses and deposits, thus achieving aluminum recovery.

[0041] The system also includes a primary condensing unit and a secondary condensing unit. The primary condensing unit is connected to the drying unit, which in turn is connected to the secondary condensing unit. The gas storage tank and cleaning equipment are also connected to the secondary condensing unit. The primary condensing unit is used to remove and recover trace aluminum remaining in the hydrocarbon gas. The secondary condensing unit removes water vapor from the gas and recycles the condensed water back into the cleaning unit for reuse, resulting in dry and pure hydrocarbon gas. The hydrocarbon gas is then stored in the gas storage tank as a high-value-added product for subsequent use.

[0042] The Joule device includes a reaction chamber and a conductive electrode. One side of the reaction chamber is connected to a process pipe. A compression piston is provided in the process pipe. Two conductive electrodes are symmetrically arranged in the reaction chamber. The collection tank is connected to the other side of the reaction chamber, and an automatic door is provided at the connection. like Figure 2As shown, the Joule device includes a reaction chamber 1 and a conductive electrode 2. One side of the reaction chamber 1 is connected to a process tube 3, which contains a compression piston 31. Two conductive electrodes 2 are symmetrically arranged within the reaction chamber 1. A collection tank 4 is connected to the other side of the reaction chamber 1, and an automatic door 5 is installed at the connection. A weight sensor is installed within the process tube 3. When the weight signal reaches a threshold, the weight sensor sends a command to the compression piston 31 via a controller, pushing the mixture into the reaction chamber 1. A weight sensor is also installed at the bottom of the reaction chamber. When the mixture enters, the weight sensor transmits a signal via the controller, causing the automatic door 5 to close. The conductive electrodes 2 on both sides move toward each other to compress the mixture, and together with the reaction chamber 1, the compression piston 31, and the automatic door 5, the mixture is enclosed.

[0043] After the mixture enters the process tube 3, the internal weight sensor sends a command to the compression piston 31 to push the mixture into the reaction chamber 1. The weight sensor in the reaction chamber then transmits a signal to control the automatic door 5 to close, and the conductive electrodes 2 on both sides approach each other and compress the mixture. The capacitor group provides high voltage and high current pulse discharge, and the temperature rises to 3000°C in milliseconds to heat the mixture. The pulse process uses infrared non-contact temperature detection, and real-time data acquisition and recording of voltage, current, temperature, and discharge time. The touch screen control integrates charge and discharge control, gas path switching, heat dissipation management and other functions, making it easy for operators to adjust parameters according to actual conditions. The reaction time is set according to the parameters. After the pulse ends, the automatic door 5 opens, and the compression piston 31 pushes the produced graphene into the collection tank 4 to complete the collection of all products. The compression piston 31 returns to its position and enters the next cycle.

[0044] like Figure 3 As shown, the Joule device also includes a threaded sleeve 6 and a screw 61, which are arranged outside the reaction chamber 1. The internal thread of the threaded sleeve 6 consists of two sections of threads in opposite directions, which are respectively threadedly connected to the two screws 61, and the two conductive electrodes 2 are respectively connected to the two screws 61. In addition, the surfaces of both ends of the threaded sleeve 6 are provided with spiral grooves 62. The automatic door 5 is a structure of two relatively movable baffles. The two baffles are inserted at the connection between the reaction chamber 1 and the collection tank 4, and the external ends of each baffle are provided with a slider that is slidably connected to the spiral grooves 62.

[0045] After the controller transmits the signal, the motor 7 drives the threaded sleeve 6 to rotate through the gear transmission structure, so that the two screws 61 can drive the conductive electrodes 2 to move relative to each other. At the same time, the spiral groove 62 on the surface also drives the baffle structure to move relative to each other, so that the automatic door 5 opens or closes.

[0046] The aforementioned paper-plastic-aluminum composite packaging waste recycling system uses pulsed current to heat the waste to ultra-high temperatures in a very short time, eliminating the need for step-by-step reduction. This simple, efficient, and low-cost process also yields high-value-added products such as graphene, aluminum vapor, and hydrocarbon gas. By recycling the gas as a heat source and conductive medium, it achieves product recycling and energy conservation and emission reduction.

[0047] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and description of the present invention.

Claims

1. A method for recycling paper-plastic-aluminum composite packaging waste, characterized in that: The following steps are involved: Crushing: crushing the discarded aluminum-plastic packaging into particles; mixing, mixing the particles with a conductive medium; heating, pulse heating the mixture; The solid graphene obtained after heating is collected, and a mixed gas of aluminum vapor and hydrocarbon gas is extracted. The aluminum vapor is condensed to obtain solid aluminum, and then the hydrocarbon gas is collected and stored.

2. The method for recycling paper-plastic-aluminum composite packaging waste according to claim 1, characterized in that: The following steps are also included: Cleaning: Use water to clean the crushed particles to remove impurities in the particles; Drying: Heat and dry the cleaned particles.

3. The method for recycling paper-plastic-aluminum composite packaging waste according to claim 2, characterized in that: During the drying step: The extracted aluminum vapor and hydrocarbon gas are used to heat and dry the cleaned particles. During the hot air conveying process, the aluminum vapor releases latent heat and condenses when it cools down. It adheres to the surface of the particles and acts as a conductive medium, heating together with the particles to form a cycle. After completing the preset number of cycles, the aluminum vapor condenses and the solid aluminum is recovered.

4. A method for recycling paper-plastic-aluminum composite packaging waste according to claim 3, characterized in that: During the drying step: After hydrocarbon gas releases waste heat, it is stored after primary condensation and secondary condensation. The primary condensation removes residual aluminum in the gas, and the secondary condensation removes water vapor in the gas.

5. The method for recycling paper-plastic-aluminum composite packaging waste according to claim 3, characterized in that: During the mixing step: Assume that the conveying rate of the conductive medium is M1 kg / h, the conveying rate of the particles is M2 kg / h, M1:M2=K, and as the number of cycles increases, the K value is adjusted to decrease.

6. A paper-plastic-aluminum composite packaging waste recycling system, used in the method according to any one of claims 1 to 5, characterized in that: The utility model comprises a crushing device, a cleaning device, a drying device, a vacuum feeding device, a process pipe, a Joule device and a collecting tank which are connected in sequence.

7. The paper-plastic-aluminum composite packaging waste recycling system according to claim 6, characterized in that: It also includes a purification device, which can purify the water after cleaning, and its water inlet and water outlet are respectively connected to the water outlet and water inlet of the cleaning device.

8. The paper-plastic-aluminum composite packaging waste recycling system according to claim 6, characterized in that: It also includes an air extraction device and an air storage tank. The air extraction end of the air extraction device is connected to the Joule device, and the air outlet end is connected to the drying device. The air storage tank is connected to the drying device.

9. The paper-plastic-aluminum composite packaging waste recycling system according to claim 8, characterized in that: It also includes a primary condensing device and a secondary condensing device. The primary condensing device is connected to the drying device, the secondary condensing device is connected to the primary condensing device, and the gas storage tank and the cleaning equipment are both connected to the secondary condensing device.

10. The paper-plastic-aluminum composite packaging waste recycling system according to claim 6, characterized in that: The Joule device includes a reaction chamber and a conductive electrode. One side of the reaction chamber is connected to a process pipe. A compression piston is provided in the process pipe. Two conductive electrodes are symmetrically arranged in the reaction chamber. The collection tank is connected to the other side of the reaction chamber, and an automatic door is provided at the connection. A weight sensor is provided in the process tube. When the weight signal reaches a threshold value, the weight sensor sends an instruction to the compression piston through the controller to push the mixture into the reaction chamber. A weight sensor is also provided at the bottom of the reaction chamber. When the mixture enters, the weight sensor transmits a signal through the controller to close the automatic door, and the conductive electrodes on both sides move toward each other to compress the mixture, so that the mixture is in a closed space.

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