Boiling-Point Solvent Separation for Plastic Waste Suspensions
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Solution Overview
Problem
Existing methods for recycling plastics, particularly in large-scale industrial applications, face challenges in achieving efficient and safe separation of plastics with different melting points and densities, often requiring high temperatures and solvents that are flammable, leading to safety risks and inefficiencies.
Innovation Solution
A method using a solvent with a dissolving temperature near its boiling point, formulated to dissolve plastics within a closed, gas-tight system, combined with a centrifuge for rapid separation, allowing for controlled pressure and inert gas use to enhance safety and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thermal recycling processes are used to separate plastics, then plastics can be separated by melting and filtering, but the process reaches limits when separating multilayer composite structures due to closely spaced melting points and difficulty in controlling local temperatures
Solution Approach 1:
The patent replaces thermal recycling processes with a solvent-based chemical system. Instead of relying on melting and filtering plastics based on temperature differences, the invention uses a solvent to selectively dissolve specific plastics at controlled temperatures, enabling separation of multilayer composite structures that are difficult to separate thermally due to closely spaced melting points.
Solution Approach 2:
The patent changes the separation parameter from temperature-based (thermal) to solvent concentration and temperature-based (chemical dissolution). By controlling the solvent type, concentration, and temperature, the process can selectively dissolve specific plastics in multilayer composites, achieving reliable separation where thermal methods fail due to closely spaced melting points.
2Reliability
If solvents are used to dissolve plastics, then selective separation can be achieved, but the solvents are often highly or extremely flammable, increasing safety risks in large-scale industrial applications
Solution Approach 1:
The patent implements an inert atmosphere system by introducing inert gas (such as nitrogen or carbon dioxide) into the closed processing system. This displaces oxygen and prevents combustion of flammable solvents, enabling safe large-scale industrial use of solvent-based separation processes while maintaining high separation selectivity.
Solution Approach 2:
The patent creates different atmospheric conditions in different zones of the processing system. The dissolution chamber operates with an inert atmosphere to prevent fire hazards, while other zones may have different atmospheric compositions optimized for their specific functions, allowing selective separation to proceed safely.
3Productivity
If solvents are heated to dissolve plastics rapidly, then dissolution speed increases, but the solvent may evaporate or decompose, requiring closed systems and increasing process complexity
Solution Approach 1:
The patent implements a continuous closed-loop system where the solvent is heated under pressure in a sealed autoclave to achieve rapid dissolution, then the pressure is released and the solvent is condensed and recycled. This continuous operation maintains high dissolution speeds while the closed system prevents solvent evaporation and decomposition, managing complexity through systematic design.
Solution Approach 2:
The patent utilizes phase transitions of the solvent (liquid to supercritical fluid to liquid) by heating under pressure and then releasing pressure. This allows rapid dissolution at high temperature and pressure, followed by automatic condensation when pressure is released, enabling fast processing without permanent loss of solvent and reducing the need for complex containment systems.
4Productivity
If high temperatures are used to accelerate plastic dissolution, then separation speed increases, but energy consumption increases and safety risks from flammable solvents increase
Solution Approach 1:
The patent uses an inert atmosphere to enable safer operation at elevated temperatures. By preventing combustion through oxygen displacement, the system can utilize higher temperatures to accelerate plastic dissolution and improve separation speed without proportionally increasing safety risks, optimizing the energy-productivity balance.
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
Enables rapid and complete separation of plastics with high yield, reducing operational risks and costs, while ensuring solvent recovery and safe handling, suitable for large-scale industrial use.
Implementation Method 1
a solvent (L), in particular a hydrocarbon solvent, is added to the solid (F), such that a suspension (S) is formed. The suspension (S) is heated to a dissolving temperature (T1), in particular to a temperature close to the boiling point of the solvent (L), such that the plastic (K) dissolves at least partially in the solvent (L)
Implementation Method 2
a centrifuge for separating the dissolved plastic from the mixture
Implementation Method 3
an inert gas is introduced into a closed system, in particular a waste separation plant, such that oxygen within the closed system is at least partially displaced
Data Source
Figure 1
AI summary
The invention relates to a solvent (L) for separating a plastic (K) present within and/or upon a solid (F) within a suspension (S), especially waste suspension. According to the invention, said solvent (L) is such that its separating effect is dependent on the attainment of a separation temperature (T1) of the solvent (L), wherein the separation temperature (T1) of the solvent (L) is within a temperature range around, especially above, the boiling temperature (T2) thereof. The invention further relates to a method of separating a plastic (K) present within and/or upon a solid (F) within a suspension (S), for instance waste suspension, with a solvent (L). According to the invention, this involves heating or superheating the suspension (S) within a gas-tight system to a separation temperature (T1) within a temperature range around the boiling temperature (T2) of the solvent (L).