Purge Bin Mid-Vent Control for Low-Loss Polymer Degassing
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Solution Overview
Problem
Existing gas phase olefin polymerization processes suffer from significant loss of unreacted monomers and hydrocarbons due to direct venting without separation, leading to economic loss and environmental emissions.
Innovation Solution
A degassing system utilizing a purge vessel with a mid-vent stream and membrane separators to separate and recover unreacted monomers and hydrocarbons, allowing controlled flaring of inert gas to minimize hydrocarbon loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If direct venting of purge gas is used to remove nitrogen, then nitrogen removal efficiency is improved, but hydrocarbon loss increases significantly
Solution Approach 1:
The vent stream is divided into multiple fractions through sequential membrane separators. The first membrane separator produces a hydrocarbon-rich permeate stream and a nitrogen-rich residue stream. The residue stream is further processed by a second membrane separator to recover additional hydrocarbons. This segmentation allows selective removal of nitrogen while recovering hydrocarbons in each stage, resolving the contradiction between nitrogen removal efficiency and hydrocarbon loss prevention.
2Loss of substance
If separation facilities are added to recover hydrocarbons from vent gas, then hydrocarbon loss is reduced, but device complexity increases
Solution Approach 1:
Traditional mechanical separation systems (distillation columns, compressors, condensers) are replaced with membrane separation technology. The membrane separators use selective permeability properties of membrane materials to separate hydrocarbons from nitrogen based on differences in permeation rates, eliminating the need for complex mechanical separation equipment while achieving effective hydrocarbon recovery.
3Loss of substance
If membrane separators are used to separate hydrocarbons, then hydrocarbon recovery efficiency is improved, but energy consumption increases
Solution Approach 1:
The membrane separation process utilizes the inherent permeability differences of membrane materials to hydrocarbons and nitrogen, allowing separation to occur without external energy input. The partial pressure gradients that drive permeation are naturally established by the pressure differential across the membrane, enabling the system to perform separation work autonomously without requiring additional energy-consuming equipment.
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
Significantly reduces hydrocarbon loss by up to 90% through controlled flaring of inert gas, achieving cost savings and environmental compliance.
Implementation Method 1
The gaseous effluent stream can be separated, within a first membrane separator, into a first permeate stream that is richer in hydrocarbons and a first residue stream that is leaner in hydrocarbons
Data Source
AI summary
Methods for recovering polymer product from gas phase polymerization. A polymer product can be introduced to a purge vessel and contacted with a purge gas to provide a stripped, polymer product. Hydrocarbons such as unreacted monomers can be removed and recycled to polymerization and the purge gas can be recovered and recycled to the purge vessel. Hydrocarbon loss can be eliminated or negligible by using a mid-vent stream from the purge vessel. The mid-vent stream can be selectively flared to control the purge gas concentration within the purge vessel.