Polyolefin Catalyst Deactivation via Segmented Purge and Steam Treatment
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Solution Overview
Problem
In gas fluidized bed polymerization processes, it is challenging to ensure complete deactivation of residual catalyst in polyolefin products without overloading the product purge bin with steam, which can lead to catalyst deactivation in the reactor, resulting in suboptimal polymer quality and process inefficiencies.
Innovation Solution
A process involving a reactor with a fluidized bed, a product purge bin, and a granular feed bin, where the product purge bin removes dissolved hydrocarbons and partially deactivates catalysts with an inert gas purge, and the granular feed bin completes catalyst deactivation with a controlled steam stream, ensuring the recycled stream is steam-free and the polymer is substantially free of active catalysts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If steam is fed to the product purge bin to deactivate residual catalyst, then catalyst deactivation is improved, but the product purge bin may be overloaded with steam leading to catalyst deactivation in the reactor
Solution Approach 1:
The catalyst deactivation process is segmented into two distinct stages: first, inert gas purging in the product purge bin to remove dissolved hydrocarbons and partially deactivate catalyst; second, steam treatment in the granular feed bin to complete catalyst deactivation. This segmentation allows controlled steam application away from the reactor, preventing harmful steam carryover while ensuring complete catalyst deactivation.
Solution Approach 2:
The granular feed bin serves as an intermediary device between the product purge bin and the reactor. It receives polymer powder from the product purge bin, applies steam for catalyst deactivation, and then feeds the treated polymer to the reactor. This intermediary structure enables steam treatment without direct steam introduction into the reactor, solving the contradiction between complete deactivation and reactor protection.
2Object-affected harmful factors
If the product purge bin capacity for steam handling is limited, then reactor catalyst protection is improved, but incomplete catalyst deactivation in the polymer occurs
Solution Approach 1:
The deactivation function is segmented between two units: the product purge bin handles inert gas purging and initial deactivation with limited steam capacity, while the granular feed bin handles final steam deactivation. This segmentation allows the product purge bin to operate within its steam handling limits while the granular feed bin provides additional deactivation capacity using steam that does not need to be recovered.
Solution Approach 2:
The solution adds a spatial dimension to the deactivation process by introducing a second treatment location (granular feed bin) downstream of the product purge bin. This dimensional expansion allows the system to achieve complete deactivation without increasing the steam handling capacity of the original product purge bin, as steam is applied in a separate location where recovery is not required.
3Reliability
If more steam is used to ensure complete catalyst deactivation, then polymer quality is improved, but excess steam enters the reactor causing catalyst deactivation
Solution Approach 1:
The steam treatment step is extracted from the reactor vicinity and relocated to the granular feed bin. This extraction allows aggressive steam application for complete catalyst deactivation without the risk of steam entering the reactor and deactivating the active catalyst, thereby maintaining both polymer quality and reactor productivity.
Solution Approach 2:
The granular feed bin acts as an intermediary that decouples the steam treatment process from the reactor operation. It enables the use of sufficient steam for complete catalyst deactivation while preventing steam from reaching the reactor, thus resolving the contradiction between polymer quality improvement and reactor productivity maintenance.
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 allows for the production of polyolefin with reduced yellowness and minimal active catalysts, enabling the recycling of streams back to the reactor without catalyst deactivation, thus enhancing the catalyst deactivation capacity and maintaining polymer quality.
Implementation Method 1
the circulating fluids are cooled using a heat exchanger, resulting in a cooled recycle stream comprising liquid
Implementation Method 2
the liquid portion will vaporize upon exposure to the heat of the reactor, which vaporization will remove more heat from the reactor
Implementation Method 3
contacting a deactivating stream comprising steam with the purged polyolefin in the granular feed bin to obtain a polyolefin that is substantially free of active polymerization catalyst
Implementation Method 4
a continuous gas fluidized bed polymerization process for the production of polymer from monomer
Implementation Method 5
a cycling gas stream is heated in the reactor by the heat of polymerization
Data Source
AI summary
Process for the preparation of a polyolefin in a reaction system comprising a reactor comprising a fluidized bed and a distribution plate, product purge bin, and granular feed bin, wherein the process comprises feeding a polymerization catalyst to the fluidized bed, feeding α-olefin monomer(s) to the reactor, circulating fluids from the top of the reactor to the bottom of the reactor, withdrawing a stream comprising the polyolefin and fluids from the reactor and passing said stream into the product purge bin, purging the product purge bin with a purge stream comprising an inert gas to obtain a stream comprising a purged polyolefin and a stream comprising fluids, introducing part of the stream comprising fluids back into the reactor, introducing the stream comprising the purged polyolefin into the granular feed bin, and contacting a deactivating stream with purged polyolefin in granular feed bin to obtain the polyolefin free of polymerization catalyst.