Melt Pump Plastic Feeding for Pyrolysis Reactors
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Solution Overview
Problem
Conventional methods for feeding plastic waste into thermochemical reactors, such as pyrolysis reactors, face challenges in maintaining a consistent feed rate due to variations in plastic form, cohesiveness, and size, leading to issues like bridging and ratholing, which negatively impact reactor performance.
Innovation Solution
A process involving conveying plastic waste into a feed hopper, supplying it to a melting tank via a control mechanism, melting the plastic at temperatures between 200 to 300°C using a melt pump and agitator, and then delivering the molten plastic to the reactor in a controlled, metered flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional feeding methods (screw conveyors, rotatory conveyors, star feeders, piston feeders, hoppers) are used to convey plastic waste to the reactor, then the system can handle various forms of plastic waste, but the feed rate becomes inconsistent due to bridging and ratholing issues
Solution Approach 1:
The patent changes the physical state parameter of the plastic material from solid to liquid by heating it above its melting point in the melting tank. This phase change eliminates the bridging and ratholing problems that occur with solid plastic feeding, while the melt pump maintains consistent feed rate control. The liquid state allows the material to flow smoothly without the mechanical issues encountered in solid conveying systems.
Solution Approach 2:
The patent replaces the mechanical conveying systems (screw conveyors, rotatory conveyors, star feeders, piston feeders) with a thermal processing system followed by a melt pump. Instead of using mechanical forces to push solid plastic through conveyors, the system uses heat to melt the plastic and then pumps the liquid melt, substituting thermal and fluid mechanical approaches for traditional mechanical conveying.
2Adaptability or versatility
If variable feed rates are allowed to accommodate different plastic forms, then the system can be more flexible, but reactor performance deteriorates due to liquid residence time variations
Solution Approach 1:
The patent changes the physical state of plastic to liquid form through heating, which fundamentally alters the flow characteristics. Liquid plastic melt can be pumped with consistent flow rates unlike solid plastic, thereby maintaining stable liquid residence time in the reactor while still accommodating different plastic types. The melt pump's positive displacement mechanism ensures precise metering regardless of the original plastic form.
Solution Approach 2:
The patent performs preliminary melting of the plastic material in the melting tank before it enters the reactor. By converting all plastic forms to liquid melt in advance, the system ensures that the reactor receives material in a uniform state ready for consistent processing. This preliminary phase change and homogenization step eliminates the need for variable feed rates during reactor operation.
3Device complexity
If conventional feeders are used, then the system structure remains simple, but gas backflow occurs due to inability to maintain discharge plug
Solution Approach 1:
The patent replaces mechanical plug-based isolation systems with a liquid seal created by the melt pump. The continuous stream of molten plastic exiting the pump creates a physical barrier that prevents gas backflow into the melting tank. This liquid seal mechanism is more reliable than mechanical plugs because it maintains consistent pressure and flow, automatically preventing gas ingress without requiring precise mechanical positioning.
Solution Approach 2:
The molten plastic acts as an intermediary medium between the reactor and the external environment. The continuous flow of liquid melt from the melt pump creates a seal that mediates the interface, preventing direct communication between the reactor interior and external gases. This liquid intermediary provides more reliable gas isolation than mechanical components.
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 process ensures a consistent and controlled feed of molten plastic to the reactor, independent of the plastic's melt properties or form, thereby maintaining reactor performance and preventing issues like backflow of gases.
Implementation Method 1
melting the plastic waste in the melting tank at a temperature from about 200 to about 300° C. using a melt pump and a melting tank agitator
Data Source
AI summary
Process for feeding plastic material, e.g. a plastic waste, to a processor such as a thermochemical reactor, e.g. a pyrolysis reactor. The process comprises an optional shredder or disintegrator (1), a conveying system (2), a feed hopper (3) with a lock hopper or rotary valve, a melting tank (6) with an agitator (5) followed by a melt pump (7) for the delivery of molten plastic to the processor. The advantage of the current process includes the ability to supply a consistent, metered flow to the processor, independent of the recycled plastic's melt properties, or the form or particle size and distribution of the plastic material.