Plastic Flotation Separation via Pulsating Liquid Medium
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Solution Overview
Problem
Current methods for separating plastics based on their chemical composition are inefficient, leading to impure recycling due to the similar density of different plastic types, which causes unsatisfactory separation results in flotation processes.
Innovation Solution
A flotation system with a perforated plate and pulsation device in a tank filled with water, where plastic particles settle based on specific gravity, using controlled vibration and sensors to ensure even sedimentation and separation, and a discharging mechanism that prevents re-floating, followed by quality checking to achieve pure plastic fractions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If air flotation is used to separate plastics by density, then the process is simple and inexpensive, but the separation precision is insufficient due to similar density of different plastics
Solution Approach 1:
The invention changes the flotation medium from air to liquid (water), fundamentally altering the separation parameter from air-density-based to liquid-density-based flotation. This parameter change enables better separation of plastics with similar densities because liquid provides a different buoyancy environment that enhances density differentiation between plastic types.
Solution Approach 2:
The invention replaces the mechanical air stream system with a liquid-based flotation system. Instead of using air flow to carry and separate particles, the system uses liquid medium where particles settle or float based on their density differences, substituting one mechanical separation mechanism with another that is more effective for closely-dense materials.
2Manufacturing precision
If liquid flotation medium is used with aeration to separate light and heavy particles, then separation of materials with different density is improved, but plastic particles re-float to the surface due to their slight density differences and large surface area
Solution Approach 1:
The invention extracts and removes the aeration step from the liquid flotation process. By eliminating air injection into the liquid medium, the system prevents the formation of air bubbles that would attach to plastic particles and cause them to re-float. This extraction of the problematic element (aeration) resolves the re-floating issue while maintaining the benefits of liquid flotation.
Solution Approach 2:
The invention converts the potential harm of liquid medium (which could allow re-floating) into a benefit by carefully controlling the liquid system without aeration. The liquid provides stable buoyancy forces that, when not disturbed by air injection, enable particles to maintain their settled positions. The slight density differences that initially caused re-floating problems now provide sufficient separation when the liquid environment is stable and non-aerated.
3Productivity
If paddle shafts are mounted close together to transport settled material efficiently, then productivity increases, but turbulences are generated that disturb settling of plastic material
Solution Approach 1:
The invention extracts and removes the rotating paddle shafts from the flotation tank entirely. Instead of using mechanical paddles to transport settled material, the system uses alternative transport mechanisms that do not introduce turbulence into the flotation medium. This extraction eliminates the source of turbulence while maintaining the ability to efficiently remove settled plastic particles from the separation zone.
Solution Approach 2:
The invention introduces an intermediary transport system that operates outside the flotation tank or in a separate chamber. Settled material is transferred from the flotation medium to the transport mechanism through a interface that minimizes disturbance. This intermediary approach allows efficient material removal without the transport mechanism directly interacting with and disturbing the settling particles in the flotation zone.
4Productivity
If vibration is applied to the flotation liquid to enhance separation, then separation speed increases, but already settled particles may be disturbed and re-suspended
Solution Approach 1:
The invention applies periodic or pulsed vibration rather than continuous vibration to the flotation liquid. Short, controlled vibration pulses are applied at specific stages to enhance separation of unsettled particles, while the duration and intensity are limited to prevent disturbance of already settled particles. This periodic action provides the benefits of enhanced separation speed while minimizing the risk of re-suspending settled material.
Solution Approach 2:
The invention uses dynamic, adjustable vibration parameters that can be adapted to different separation stages. The vibration frequency, amplitude, and duration are dynamically controlled based on the separation progress. This dynamic approach allows optimization of separation speed at each stage while automatically preventing excessive vibration that would disturb settled particles, providing adaptability to maintain both productivity and settling stability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method allows for clear separation of plastic materials by chemical composition, ensuring high purity and re-usability without pre-treatments, optimizing cost and time efficiency by maintaining a homogeneous particle size and controlled vibration to prevent re-floating.
Implementation Method 1
a pulsation device which effects by pulsating air, that the liquid in the flotation tank be put in vibration
Implementation Method 2
plastic particles settle based on specific gravity
Implementation Method 3
Heavier particles of the material to be separated sink, due to gravity, to the bottom of the flotation tank
Implementation Method 4
a delivery device for discharging of settled materials... settled particles are discharged... in a sealed manner
Data Source
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AI summary
The invention relates to a process and device for separating fragmented plastics depending on their chemical composition, and makes use of the different density of these plastics, since a different density is associated with each plastic, depending on its chemical composition. The resultant "pure" plastic fractions are thus prepared for appropriate recycling, depending on their type, thus taking into account that in the future thermal disposal will no longer be desirable. For this purpose, a flotation process was developed in which the flotation liquid is made to vibrate at a frequency which causes the desired particles to precipitate, depending on their density. This is achieved, for example, by a pneumatic or hydraulic pulsation system. Both the frequency and intensity of the vibrations should be controllable in order to assist the separation of lighter and heavier plastic fractions. The heavier plastics are deposited on a sieve bottom and discharged through a sluice into a discharge container filled to the same level with the same liquid as in the flotation basin, and conveyed from the discharge container into a quality control container by a conveyor. Lighter plastic particles float to the surface and are conveyed into other similar downstream separators for further separation.