Process for increasing ethylene and propylene yield from a propylene plant
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Solution Overview
Problem
On-purpose propylene plants experience significant losses of ethylene and propylene due to their conventional separation processes, resulting in substantial economic losses, as these hydrocarbons are diverted into lower-value fuel gas streams, with current methods failing to effectively recover these valuable components.
Innovation Solution
A process that involves cooling and partially condensing the de-ethanizer overhead and cracked gas vapor to achieve high condensation rates, followed by passing the condensate to a rectifier where it is contacted with a countercurrent stream rich in C2 components, producing a rectifier overhead stream with enhanced separation of C1, C2, and C3 components, allowing for improved recovery of ethylene and propylene.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If conventional separation apparatus (quench tower, de-ethanizer, C3 splitter, depropanizer) are used, then separation of hydrocarbon components is achieved, but significant losses of ethylene and propylene occur into fuel gas stream
Solution Approach 1:
The separation process is divided into multiple specialized columns: de-ethanizer for C2 components, C3 splitter for propylene/propane separation, and depropanizer for C3+ components. Each column is optimized for specific separation tasks, improving overall recovery efficiency and reducing losses to fuel gas stream.
Solution Approach 2:
The process utilizes temperature and pressure parameter optimization in each separation column to maximize component recovery. By carefully controlling operating conditions (temperature, pressure, reflux ratios), the process achieves high separation efficiency while minimizing ethylene and propylene losses to fuel gas.
2Manufacturing precision
If sequential unit operations with multiple columns are employed, then separation precision is improved, but device complexity increases
Solution Approach 1:
Each separation column is designed to perform multiple functions: separation, purification, and partial condensation. The de-ethanizer not only separates C2 components but also provides reflux for the C3 splitter. The C3 splitter simultaneously separates propylene and propane while providing reflux to the depropanizer, reducing the need for additional dedicated equipment.
Solution Approach 2:
The separation columns are arranged in a nested configuration where the output of one column serves as input to the next, and reflux streams are integrated between columns. The de-ethanizer overhead feeds the C3 splitter, which in turn feeds the depropanizer, creating a compact nested arrangement that reduces overall system complexity.
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 significantly reduces the loss of ethylene and propylene into fuel gas streams, achieving high recovery rates of these valuable hydrocarbons and minimizing economic losses by effectively separating and recovering C2 and C3 components from the on-purpose propylene plant.
Implementation Method 1
cooling and partially condensing the de-ethanizer overhead and cracked gas vapor to achieve high condensation rates
Implementation Method 2
passing the condensate to a rectifier where it is contacted with a countercurrent stream rich in C2 components, producing a rectifier overhead stream with enhanced separation of C1, C2, and C3 components
Data Source
AI summary
A process for recovery of C2 and C3 components in an on-purpose propylene production system includes utilizing a packed rectifier with a countercurrent stream to strip C2 and C3 components from a combined de-ethanizer overhead lights vapor and cracked gas vapor stream.