Polyolefin Granule Volatile Removal via Low-Velocity Inert Gas
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Solution Overview
Problem
Current methods for removing volatile components from plastic materials, such as polypropylene and polyethylene, are inefficient, leading to residual emissions, high energy consumption, and operational risks, particularly in applications like drinking water and automobile parts, due to insufficient removal of monomers and potential explosive mixtures.
Innovation Solution
A process involving contacting polyolefin granules with a solvent in vapor form at a temperature slightly above its boiling point and a superficial vapor velocity of less than 0.2 m/s, allowing for effective accumulation and removal of volatile components with reduced energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If air purging is used to remove volatile components, then the volatile content is reduced, but the risk of explosive mixtures increases and high amounts of air are required
Solution Approach 1:
The patent replaces air purging with inert gas (nitrogen or carbon dioxide) to create an inert atmosphere in the treatment silo. This eliminates the risk of explosive mixtures between volatile hydrocarbons and oxygen while effectively removing volatile components through the inert gas stream, thereby resolving the contradiction between volatile removal efficiency and safety.
2Loss of substance
If steam treatment is used at high temperatures, then volatile components are removed, but operational problems occur due to condensation and pellet agglomeration
Solution Approach 1:
The patent changes the temperature parameter from high-temperature steam treatment to low-temperature inert gas treatment. By using inert gas at temperatures below the dew point of water vapor, the process avoids condensation issues and pellet agglomeration while still achieving effective volatile removal, thus resolving the contradiction between volatile removal and operational stability.
3Loss of substance
If liquid treatment at boiling point is used, then volatile components are removed, but extensive cleaning units are required
Solution Approach 1:
The patent extracts the volatile components directly into the inert gas phase through vaporization and carries them away in the gas stream. This eliminates the need for extensive liquid cleaning and separation units required in liquid-based treatment methods, as the volatiles are removed with the inert gas flow, thereby resolving the contradiction between volatile removal efficiency and device complexity.
4Loss of substance
If high steam consumption is used, then volatile components are removed effectively, but operational costs increase significantly
Solution Approach 1:
The patent replaces expensive steam with cheaper inert gas (nitrogen or carbon dioxide) as the treatment medium. The inert gas is used in moderate amounts and can be vented or recycled without the high energy costs associated with steam generation and condensation, thereby resolving the contradiction between effective volatile removal and operational cost.
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 efficiently removes volatile components, reducing emissions and energy usage, while minimizing the risk of explosive mixtures and operational hazards, and does not require extensive cleaning units or high steam consumption.
Implementation Method 1
contacting polyolefin granules in liquid with a solvent in vapour form... the first stream of vapour produces an upwards rising vapour stream in said treatment vessel
Implementation Method 2
accumulating the volatiles in the vapour and the liquid... first stream of liquid from said treatment vessel, wherein said first stream of liquid contains hydrocarboneous compounds
Data Source
AI summary
The present invention relates to a process for treating polyolefin granules in a treatment vessel comprising the steps of: —Providing a bed of granules in liquid in said treatment vessel —Withdrawing a first stream of liquid from said treatment vessel, wherein said first stream of liquid contains hydrocarboneous compounds —introducing a first stream of vapor into said treatment vessel —Withdrawing a second stream of vapor from said treatment vessel wherein said second stream of vapor contains volatile hydrocarboneous compounds —Recovering the granules from said treatment vessel wherein said first stream of vapor has a temperature from Tb to Tb+10° C., wherein Tb is the boiling point of the liquid at the applied pressure, and said first stream of vapor produces an upwards rising vapor stream in said treatment vessel, the superficial vapor velocity of which is no more than 0.2 m/s, and a plant suitable for conducting said process.