Olefin Polymerization Reactor Cooling via Phase Separation
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Solution Overview
Problem
Current gas fluidized bed reactors for olefin polymerization face limitations in heat removal, leading to degradation of catalysts and polymers, agglomeration, and reduced production rates due to insufficient cooling capacity.
Innovation Solution
A process involving the withdrawal of fluids from a reactor, cooling, separation into liquid and gas phases, and reintroduction of the gas/liquid phase into the reactor below a distribution plate, with liquid from a settling tank being reintroduced upstream of the cooling unit to enhance cooling capacity and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the cooling capacity is increased by introducing more liquid into the reactor, then the heat removal efficiency improves, but the fluidized bed becomes destabilized
Solution Approach 1:
The reactor is divided into multiple zones with different functions: a first zone for polymerization and a second zone for cooling and condensation. This segmentation allows liquid to be introduced in the second zone without directly destabilizing the fluidized bed in the first zone, while still achieving effective heat removal through the liquid's evaporation in the cooling zone.
Solution Approach 2:
The patent introduces an intermediary cooling zone between the polymerization zone and the reactor outlet. This intermediary zone acts as a buffer that absorbs excess heat through liquid evaporation without directly affecting the fluidized bed stability in the polymerization zone, thus mediating between heat removal requirements and bed stability.
2Productivity
If the production rate is increased, then the polymer output improves, but the heat removal capacity becomes insufficient
Solution Approach 1:
The patent utilizes the phase transition of liquid to vapor in the second zone to enhance heat removal. As liquid is introduced and evaporates, it absorbs the heat of vaporization, providing a powerful cooling mechanism that can handle the increased heat load from higher production rates without requiring proportionally larger cooling systems.
Solution Approach 2:
The patent changes the operating parameters by introducing liquid at specific locations and controlling its evaporation. By adjusting the amount and location of liquid introduction, the system can dynamically adapt to different production rates while maintaining effective heat removal through controlled phase change.
3Temperature
If conventional cooling methods are used, then the system complexity remains low, but the cooling capacity is limited
Solution Approach 1:
The system utilizes the heat of polymerization itself to drive the cooling process. The heat generated in the first zone naturally drives the evaporation of liquid in the second zone, creating a self-sustaining cooling mechanism that doesn't require external cooling utilities, thereby increasing cooling capacity without proportionally increasing system complexity.
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 improves the cooling capacity and production rate by efficiently utilizing the higher heat capacity of liquids, allowing operation in a broader range of conditions without the need for extended cooling units, thus preventing degradation and increasing the space-time-yield of polymer production.
Implementation Method 1
cooling the withdrawn fluids to a temperature below the dew point using a cooling unit
Implementation Method 2
The thus formed bottom recycle stream is then introduced into the fluidized bed polymerization reactor, where the liquid portion will vaporize upon exposure to the heat of the reactor, which vaporization will remove heat from the reactor
Data Source
AI summary
The invention relates to a process and system for the continuous polymerization of one or more α-olefin monomers comprising the steps of: (a) withdrawing fluids from a reactor (b) cooling fluids comprising the withdrawn fluids with a cooling unit (c) introducing the cooled fluids to a separator to separate at least part of the liquid from these fluids to form a liquid phase and a gas/liquid phase (d) introducing the gas/liquid phase below to the reactor below a distribution plate (e) introducing the liquid phase to a settling tank to separate liquid from fines that settle down in the settling tank (f) introducing liquid from the settling tank up stream of the cooling unit.