Polyolefin Depolymerization in Tower Flow Reactor with Heated Packing
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Solution Overview
Problem
Existing methods for depolymerizing polyolefin waste materials face challenges such as uneven heat distribution, high coke production, and a high content of unsaturated compounds in the depolymerization products, which hinder the efficient production of hydrocarbon fuels.
Innovation Solution
A method involving continuous depolymerization in a tower flow reactor with movable packing, where polyolefin waste materials are mixed with heated packing elements to form a uniform plastic layer, and then subjected to thermal depolymerization in a temperature gradient atmosphere of synthesis gas (CO:H2 ratio 0.25:1.5 to 0.5:3) followed by catalytic hydrogenation and isomerization to produce saturated hydrocarbon fuels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If thermal depolymerization is carried out at high temperature to break down polyolefin waste materials, then depolymerization efficiency is improved, but local overheating occurs leading to high coke production
Solution Approach 1:
The patent applies local quality by mixing polyolefin waste materials with heated inert packing material (such as ceramic balls or metal oxides) in a specific ratio (1:3 to 1:10 by weight). The packing material provides localized heat sources distributed throughout the reaction mass, creating uniform temperature distribution and preventing local overheating that leads to coke formation, while maintaining high depolymerization efficiency through sustained temperatures of 400-600°C.
2Speed
If temperature is increased to improve depolymerization rate, then reaction speed is improved, but coking of heating surfaces occurs requiring process interruption
Solution Approach 1:
The patent implements self-service by using the inert packing material as both a heating medium and a heat distribution system. The packing material absorbs heat from external sources and redistributes it uniformly throughout the reaction mass through its high surface area and thermal conductivity, enabling continuous operation at high temperatures without coking of heating surfaces. This eliminates the need for periodic decoking interruptions.
3Device complexity
If conventional thermal depolymerization is used, then process simplicity is maintained, but high content of unsaturated compounds is produced in the fuel
Solution Approach 1:
The patent applies parameter changes by modifying the thermal environment through the introduction of inert packing material with specific thermal properties (high heat capacity, high thermal conductivity). This changes the temperature distribution parameters within the reaction mass, promoting more controlled and uniform heating that reduces the formation of unsaturated compounds while maintaining process simplicity. The packing material acts as a heat buffer that prevents thermal runaway and promotes selective bond breaking.
4Loss of energy
If low thermal conductivity of plastics is considered, then heat distribution difficulty is identified, but uniform temperature distribution cannot be achieved in the plastic mass
Solution Approach 1:
The patent uses inert packing material (ceramic balls, metal oxides, or other thermally conductive inert materials) as an intermediary heat transfer medium. This packing material has high thermal conductivity and heat capacity, acting as a mediator that absorbs heat from external sources and distributes it uniformly throughout the polyolefin waste material. The packing material particles are mixed with the plastic waste in a ratio of 1:3 to 1:10 by weight, creating a composite reaction mass that achieves uniform temperature distribution and eliminates local overheating.
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 achieves efficient depolymerization with reduced unsaturated compounds, improved temperature distribution, and cost-effective production of high-purity hydrocarbon fuels, including a low-boiling fraction, benzine, and oil fractions, under atmospheric pressure, reducing the need for catalyst regeneration and environmental hazards.
Implementation Method 1
the collected products of the depolymerisation are subjected to catalytic hydrogenation and isomerisation in an atmosphere of synthesis gas
Implementation Method 2
catalytic hydrogenation and isomerisation in an atmosphere of synthesis gas (CO:H2 ratio 0.25:1.5 to 0.5:3) followed by catalytic hydrogenation
Implementation Method 3
subjected to thermal depolymerization in a temperature gradient atmosphere of synthesis gas
Implementation Method 4
continuous depolymerization in a tower flow reactor with movable packing, where polyolefin waste materials are mixed with heated packing elements to form a uniform plastic layer, and then subjected to thermal depolymerization in a temperature gradient atmosphere
Data Source
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Figure 2
AI summary
Method of producing hydrocarbon fuels from polyolefin waste materials, wherein: polyolefin waste materials are subjected to continuous depolymerisation in a tower flow reactor with a movable packing, which comprises a heating system for heating the lower half of the reaction chamber, where products of depolymerisation are collected in a gaseous state through an outlet in the upper half of the reaction chamber; and the obtained products of depolymerisation are subjected to catalytic hydrogenation and isomerisation in an atmosphere of synthesis gas, under atmospheric pressure, to obtain a mixture of hydrocarbon fuels; characterised in that: polyolefin waste materials are mixed with heated elements constituting the packing of the reactor until the surface of the packing elements is coated with a thin layer of plasticised material, wherein in the depolymerisation process the obtained mixture is fed as a stream into the reaction chamber from the top of the chamber, whereas a synthesis gas is fed in a counter current from the bottom, the gas comprising carbon monoxide (CO) and hydrogen (H2) with the molar ratio CO:H2 being from 0.25 to 1.5 : from 0.5 to 3.