Positive Displacement Catalyst Dosing Device
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Solution Overview
Problem
The production of polyolefins, particularly polyethylene, is challenged by the need for precise control of catalyst dosing to avoid underdosing or overdosing, which can lead to inefficient processes, suboptimal reaction conditions, and extended downtime in polymerization reactors.
Innovation Solution
A method using a positive displacement device with a first and second chamber, each with a ball and an inlet and outlet, connected by a pump chamber, to accurately feed metallocene catalyst slurry into an olefin polymerization loop reactor, ensuring the difference between the ball and chamber diameters is between 5 to 200 times the average catalyst particle size, allowing precise dosing and reducing wear and blockages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional catalyst dosing systems are used, then catalyst can be supplied to the reactor, but precise control of catalyst dosing is difficult leading to underdosing or overdosing
Solution Approach 1:
The positive displacement device is divided into multiple chambers (first chamber, second chamber, pump chamber) that work in sequence. Each chamber handles a specific phase of the dosing cycle (intake, displacement, discharge), enabling precise control of catalyst slurry flow and eliminating the imprecision of conventional dosing systems.
Solution Approach 2:
The catalyst slurry is prepared in advance in the first chamber before being transferred to the reactor. The device pre-charges the pump chamber with catalyst slurry during the intake phase, ensuring the exact required amount is ready for controlled discharge, thereby achieving precise dosing control.
2Productivity
If catalyst dosing is not precisely controlled, then production costs increase and downtime extends, but implementing precise control requires complex dosing equipment
Solution Approach 1:
The positive displacement device operates in periodic cycles, with each cycle consisting of an intake phase (charging the pump chamber) and a discharge phase (delivering catalyst slurry to the reactor). This periodic operation ensures consistent, precise dosing with each cycle while maintaining simple mechanical construction through the use of basic components like balls and chambers.
Solution Approach 2:
The device uses the movement of balls within chambers to automatically control the dosing process. The balls move freely between chambers based on pressure differentials and gravity, self-regulating the intake and discharge of catalyst slurry without requiring complex control systems, thereby achieving precise dosing with simple equipment.
3Reliability
If catalyst slurry is fed using conventional methods, then catalyst is delivered to the reactor, but wear and blockages occur reducing system reliability
Solution Approach 1:
The positive displacement device acts as an intermediary between the catalyst storage system and the reactor. It receives catalyst slurry in the first chamber, processes it through the pump chamber, and delivers it to the reactor in controlled amounts. This intermediary function protects the system from wear and blockages by containing the abrasive slurry within the device's chambers and moving components during transfer.
Solution Approach 2:
The device creates a controlled environment within its chambers that replicates ideal dosing conditions. By using multiple chambers with balls that move catalyst slurry in a controlled manner, it copies the function of complex dosing mechanisms while using simpler, more wear-resistant components, thereby extending device operational lifespan.
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 results in lower production costs, better process control, reduced downtime, and the production of more optimal polyolefin products by ensuring precise and controlled dosing of metallocene catalyst slurry, particularly when supported on porous silica.
Implementation Method 1
charging the positive displacement device with catalyst slurry into the pump chamber by aspirating catalyst slurry between the ball and the wall of the first chamber
Implementation Method 2
discharging the catalyst slurry into the loop reactor by displacing catalyst slurry between the ball and the wall of the second chamber
Data Source
AI summary
The present invention relates to a method for feeding metallocene catalyst slurry to an olefin polymerization loop reactor (1) using a positive displacement device (5) positive displacement device comprising a first chamber and a second chamber, each chamber having an inlet and an outlet and each chamber comprising an ball arranged between the walls of said chamber, wherein said chambers are connected to each other by a pump chamber operably connected to a pump, wherein, the difference between the diameter of said ball and the diameter of said chamber is comprised between 5 to 200 times the average particle size (d50) of said catalyst.