Two-Zone Condensing Process for Low-Loss Propylene Recovery
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Solution Overview
Problem
Existing methods for recovering propylene from a gaseous stream containing light-boiling compounds in the HPPO process are energetically inefficient and result in substantial propylene loss or require significant energy consumption, while also failing to effectively remove water from the stream.
Innovation Solution
A process involving a condensing unit with separate but thermally conductive zones, where a liquid cooling medium is cooled in multiple steps and used to recover propylene, with the gaseous stream being expanded adiabatically to reduce light-boiling compounds, and incorporating a drying step to manage water content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If distillation is used to remove light-boiling compounds from recovered propylene, then purification is achieved, but substantial propylene loss and high energy consumption occur
Solution Approach 1:
The patent uses phase transition (condensation) of propylene at low temperature to separate it from light-boiling compounds. The gaseous stream is cooled to condense propylene while light-boiling compounds remain gaseous, achieving purification without the substantial losses associated with distillation
Solution Approach 2:
The patent changes the temperature parameter to a low temperature range (-40°C to -100°C) to enable selective condensation of propylene. This parameter change allows separation based on condensation temperature differences rather than boiling point differences, reducing propylene loss
2Manufacturing precision
If distillation is used to remove light-boiling compounds from recovered propylene, then purification is achieved, but high energy consumption occurs
Solution Approach 1:
The patent replaces energy-intensive distillation with low-temperature condensation, utilizing the phase transition of propylene from gas to liquid. This approach consumes significantly less energy as it operates at lower temperatures without requiring the large heat input needed for distillation
Solution Approach 2:
The patent changes the operating temperature parameter to sub-ambient ranges, enabling separation through condensation rather than vaporization. This parameter change dramatically reduces energy consumption compared to conventional distillation operations
3Temperature
If conventional cooling methods are used, then cooling is achieved, but water freezing occurs in the stream
Solution Approach 1:
The patent extracts water from the gaseous stream before the cooling step by passing it through a drying agent or dryer. This removal of water prevents freezing during subsequent low-temperature cooling while still enabling effective condensation of propylene
Solution Approach 2:
The patent performs water removal as a preliminary action before cooling. By drying the stream first, the system prepares the gas for low-temperature processing without the harmful effect of water freezing, ensuring smooth operation throughout the cooling and condensation process
4Device complexity
If single-zone condensing unit is used, then device complexity is low, but separation efficiency is insufficient
Solution Approach 1:
The patent divides the condensing unit into two separate zones: a first zone for initial condensation and a second zone for final condensation and drying. This segmentation improves separation efficiency by providing staged cooling and separation, while the zones remain thermally conductively coupled to maintain system integration
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 high-purity propylene recovery with reduced light-boiling compounds and minimal energy consumption, allowing for efficient recycling and integration into the epoxidation process.
Implementation Method 1
cooling the liquid cooling medium stream in two or more cooling steps to a temperature T4, which is lower than the temperature T1
Implementation Method 2
expanding the liquid cooling medium stream, preferably adiabatically, within the second zone
Implementation Method 3
first and second zone are spatially separated from each other but are thermally conductive coupled to each other
Implementation Method 4
obtaining from the first zone an at least partially liquid stream comprising propylene
Data Source
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AI summary
The present invention relates to a process for recovering propylene from a gaseous stream comprising propylene and a light-boiling compound, the light-boiling compound having a boiling point at 1013 mbar(abs.) below - 50 °C, in a condensing unit, wherein the condensing unit has a first zone, preferably being a condensing zone, and a second zone, preferably being an evaporation zone, wherein first and second zone are spatially separated from each other but are thermally conductive coupled to each other, the process comprising (i) providing a gaseous stream comprising propylene and a light-boiling compound; (ii) providing a liquid cooling medium stream having a temperature T1; (iii) cooling the liquid cooling medium stream in two or more cooling steps to a temperature T4, which is lower than the temperature T1, thereby obtaining a liquid cooling medium stream having temperature T4; (iv) feeding the gaseous stream comprising propylene and a light-boiling compound from (i) into the first zone of the condensing unit and feeding the liquid cooling medium stream having the temperature T4 obtained from (iii) to the second zone of the condensing unit; (v) expanding the liquid cooling medium stream, preferably adiabatically, within the second zone, thereby obtaining from the first zone an at least partially liquid stream comprising propylene, which is depleted in light-boiling compounds compared to the stream provided in (i).