Multizone Circulating Reactor Startup Without Seed Bed Storage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
There is a need to start a gas-phase olefin polymerization reaction in a multizone circulating reactor without carrying over fine particles into the gas recycle system and to avoid the formation of chunks, which is challenging when initiating polymerization in an empty reactor.
Innovation Solution
The process involves filling the reactor with a gas at specific pressure and temperature, controlling gas flow to prevent particle entrainment, and gradually introducing particulate material and olefins to establish a settled bed, with adjustments to maintain the balance of gas and particle flow to prevent chunk formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If gas-phase polymerization is started with an empty reactor, then no facilities for storing seed bed polymers are needed, but fine catalyst particles may be entrained with recycle gas and chunks may form due to temperature rise
Solution Approach 1:
The patent applies preliminary action by introducing a small amount of inert particulate material (such as sand or glass beads) into the reactor before starting polymerization. This pre-prepared bed of particles serves as a foundation that prevents catalyst particle entrainment and provides a heat sink to prevent chunk formation, while still allowing the reactor to start empty of polymer particles
Solution Approach 2:
The patent uses an intermediary substance (inert particulate material) that mediates between the gas phase and catalyst particles. This intermediary material acts as a buffer that prevents direct interaction between recycle gas and fine catalyst particles, and also serves as a heat transfer medium to prevent localized temperature rises that cause chunk formation
2Object-affected harmful factors
If polymerization is started with a pre-prepared seed bed, then particle entrainment is prevented, but facilities for storing and preparing seed bed polymers are required
Solution Approach 1:
The patent replaces the need for storing and preparing expensive seed bed polymers with a simple, inexpensive, and easily obtainable inert particulate material such as sand or glass beads. This disposable-like approach eliminates the need for complex seed bed preparation and storage facilities while achieving the same protective function
Solution Approach 2:
The patent changes the physical state and composition parameters by using inert particulate material instead of polymer seed beds. This parameter change maintains the functional benefits of having a particle bed (preventing entrainment and controlling heat) while eliminating the need for complex seed bed management infrastructure
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 method effectively initiates polymerization in a multizone circulating reactor without particle carry-over and chunk formation, ensuring efficient and controlled polymerization processes.
Implementation Method 1
a gas recycle line, which is equipped with a compressor and a heat exchanger for removing the heat of polymerization
Implementation Method 2
controlling the gas flow in the second reactor zone so that the upwards gas velocity in the bottom part of the second reaction zone is lower than the terminal free-fall velocity of the particulate material
Implementation Method 3
a gas recycle line, which is equipped with a compressor and a heat exchanger
Data Source
Figure 1
Figure 2
AI summary
A process for starting a multizone circulating reactor containing no polyolefin particles, comprising the steps of conveying gas through the reactor and the gas recycle line, feeding a particulate material comprising a polymerization catalyst and optionally polyolefin into the reactor, controlling the gas flow in a vertical reactor zone equipped with a throttling valve at the bottom so that the upwards gas velocity in the bottom part of this reaction zone is lower than the terminal free-fall velocity of the particulate material fed into the reactor, and, after the weight of the particulate polyolefin in this reactor zone is higher than the drag force of the upward moving gas, controlling the circulation rate of the polymer particles within the multizone circulating reactor by adjusting the opening of the throttling valve and adjusting the flow rate of a dosing gas.