Continuous Pyrolysis Reactor for Waste Plastic Hydrocarbon Fuel
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Solution Overview
Problem
Current methods for converting waste plastic into high-quality hydrocarbon fuel are inefficient due to coke formation, high capital and operating costs, and reduced heat conductivity, leading to lower hydrocarbon yields and increased energy consumption.
Innovation Solution
A continuous pyrolysis process using an indirectly heated screw reactor with a metallic heat transfer medium and catalytic treatment to decompose waste plastics, reducing coke formation and enhancing heat transfer, while also treating chloride and sulfur components to produce high-quality hydrocarbon oil.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If thermal cracking is performed at high temperature with catalysts, then hydrocarbon production is enhanced, but coke formation increases and heat conductivity decreases
Solution Approach 1:
The patent introduces a liquid heat transfer medium as an intermediary substance between the heating source and the waste plastic feedstock. This medium facilitates heat transfer while preventing direct contact between the heating surface and plastic, thereby reducing coke formation on reactor walls. The liquid medium acts as a protective barrier that maintains heat conductivity without compromising hydrocarbon production efficiency.
Solution Approach 2:
The patent modifies the thermal parameters by controlling the temperature profile and residence time in the pyrolysis reactor. By optimizing the heating rate and maintaining specific temperature ranges, the process maximizes hydrocarbon yield while minimizing coke formation. The liquid heat transfer medium also enables more precise temperature control, preventing localized overheating that leads to coke deposition.
2Object-generated harmful factors
If liquid heat transfer medium is used to improve heat conductivity, then coke formation is reduced, but medium consumption increases during high pyrolysis temperature
Solution Approach 1:
The patent implements a system to recover and recycle the liquid heat transfer medium. The medium that contacts the pyrolysis vapors is condensed and separated from the reaction products, then returned to the reactor for continued use. This recovery system minimizes medium consumption and reduces operational costs associated with continuous make-up requirements.
3Productivity
If hydrocarbon vapors are subjected to extended high temperature exposure, then decomposition is enhanced, but residence time increases and fuel quality decreases
Solution Approach 1:
The patent divides the pyrolysis process into distinct zones with different temperature profiles and residence times. The first zone provides rapid heating and initial decomposition, while subsequent zones maintain optimal temperatures for hydrocarbon formation without excessive cracking. This segmented approach ensures efficient decomposition while preserving fuel quality by limiting the time vapors are exposed to high temperatures.
Solution Approach 2:
The patent employs rapid heating rates and quick vapor removal to minimize the time hydrocarbon vapors spend in the high-temperature zone. By rapidly transporting the vapors through the reactor and into the condensation system, the process captures the decomposition products before they can undergo excessive cracking or reforming reactions that would degrade fuel quality.
4Productivity
If two-step cracking process is used, then hydrocarbon yield is improved, but capital investment and operating cost increase
Solution Approach 1:
The patent combines multiple functions into a single pyrolysis reactor design. The reactor simultaneously performs heating, pyrolysis, vapor separation, and initial condensation functions that would otherwise require separate units. The liquid heat transfer medium serves dual purposes: heat transfer and coke prevention. This multi-functional approach achieves high hydrocarbon yields without requiring the complex two-step process infrastructure.
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
The process achieves increased hydrocarbon yields, reduces operational costs, and efficiently converts waste plastics into high-quality hydrocarbon fuel with improved heat transfer and reduced coke formation, allowing for flexible adjustment of process parameters based on plastic composition.
Implementation Method 1
enhancing heat transfer
Implementation Method 2
thermally decomposing residential and industrial waste plastics... decomposing the liquid plastic material by heating the liquid waste plastic to about 450° C. to 500° C. to produce a hydrocarbon vapor
Implementation Method 3
condensing the hydrocarbon vapor in a plurality of condensers
Data Source
AI summary
A process and apparatus for producing hydrocarbon oil from the thermal decomposition of waste plastics in a continuous process which comprises melting of a waste plastic feedstock into an auger assisted melt reactor to remove chlorine and organics contained in the waste plastic, and transferring the melted waste plastic into an heated screw pyrolysis reactor which includes a transitional metal heat transfer medium. The hydrocarbon gas from the pyrolysis reactor is fed into a vessel containing metal trays for a second decomposition which is connected with an alkali treatment 2-step process gas reactor to remove acidic gases, and any inorganic solids. The hydrocarbon gases are separated by three separate condensers. The hydrocarbon fraction of the first condenser is recycled back into the pyrolysis reaction for further thermal treatment, and the hydrocarbon fractions are collected in the remaining condensers.