Antistatic Agent Feeding in Densified Gas-Phase Polymerization
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Solution Overview
Problem
Gas-phase polymerization processes face issues with polymer agglomerate formation due to electrostatic charges, leading to reactor shutdowns and operational inefficiencies, particularly in densified polymer beds where heat transfer is limited and agglomerates can plug discharge equipment.
Innovation Solution
A modified feeding method for an antistatic agent is introduced, where it is metered through a feed line positioned above a restriction in the densified bed, extending from the bed top, and a dosing gas is fed into the lower part of the bed to enhance neutralization of electrostatic charges and prevent agglomerate formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If polymer particles flow downward in densified form to improve heat transfer, then heat removal efficiency is improved, but electrostatic charge accumulation increases leading to agglomerate formation
Solution Approach 1:
An antistatic agent is introduced as an intermediary substance to neutralize electrostatic charges on polymer particles. The agent is fed into the densified bed through a feed line positioned above a restriction zone, allowing it to interact with charged particles and prevent agglomerate formation while maintaining the densified flow regime for efficient heat transfer
Solution Approach 2:
The electrical charge parameter of polymer particles is modified by introducing the antistatic agent. This changes the electrostatic properties of the particles, reducing charge accumulation and preventing the harmful effects of agglomeration while maintaining the beneficial densified flow conditions
2Reliability
If antistatic agent is fed into the densified bed to neutralize electrostatic charges, then agglomerate formation is reduced, but feeding complexity increases
Solution Approach 1:
The feeding system is segmented into distinct functional zones: a restriction zone at the bottom of the densified bed and a feed line positioned above the restriction. This segmentation allows the antistatic agent to be introduced at a specific location where it can effectively neutralize charges without complicating the overall feeding mechanism
Solution Approach 2:
The feed line acts as an intermediary structure that simplifies the introduction of the antistatic agent into the densified bed. By positioning the feed line above the restriction zone, the system provides a straightforward pathway for agent delivery without requiring complex feeding mechanisms
3Productivity
If fine catalyst particles are introduced to improve polymerization activity, then production rate increases, but fine polymer particle formation increases leading to wall deposition
Solution Approach 1:
The antistatic agent serves as a mediator that prevents fine polymer particles (originating from catalyst breakage) from depositing on reactor walls. The agent neutralizes electrostatic charges on these fine particles, eliminating the electrostatic adhesion that causes wall deposition and allowing continued use of active fine catalyst particles
Solution Approach 2:
The fine polymer particles, which would normally be harmful due to their tendency to deposit on walls, are converted into beneficial suspended particles through charge neutralization. The antistatic agent transforms the harmful electrostatic property into a neutral state, allowing fine particles to remain suspended and not cause deposition problems
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 approach effectively reduces polymer sheeting and agglomerate formation along the downcomer, maintains controlled skin temperatures, and ensures stable reactor operation by maximizing the anti-static effect, preventing reactor shutdowns and maintaining efficient polymer discharge.
Implementation Method 1
an antistatic agent is introduced into the polymerization reactor in order to neutralize the electrostatic charges present in the polymer particles
Implementation Method 2
a dosing gas is fed into the lower part of the bed to enhance neutralization of electrostatic charges
Implementation Method 3
metering an antistatic agent through a feed line connected to the densified bed at a feed point being located in a feed zone extending from the top of the restriction
Data Source
Figure 1
AI summary
A process and apparatus for producing olefin polymers are disclosed, comprising: a. polymerizing one or more olefins in the gas phase, in the presence of an olefin polymerization catalyst, whereby growing polymer particles flow along a cylindrically- shaped downward path in densified form under the action of gravity so as to form a densified bed of downward-flowing polymer particles b. allowing said polymer particles to flow through a restriction of the densified bed, such restriction being positioned in a restriction zone extending from the bed upward to a distance of 15% of the total height of the densified bed; and c. metering an antistatic agent through a feed line connected to the densified bed at a feed point being located in a feed zone extending from the top of the restriction upward, to a distance five times the diameter of the section of the densified bed above the restriction.