Olefin Polymerization Reactor Cooling via Liquid Phase Vaporization
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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 limited cooling capacity.
Innovation Solution
A process involving the introduction of cooled fluids from a loop reactor to a separator, forming a liquid and gas phase, which is then reintroduced into the reactor, along with a slurry of solid polymer particles from a settling tank, to enhance cooling efficiency and increase production rates by utilizing the higher heat capacity of liquids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If gas fluidized bed reactor is used for olefin polymerization, then capital investment and energy requirements are reduced, but heat removal capacity is limited causing catalyst and polymer degradation
Solution Approach 1:
The patent introduces a liquid phase recycle stream that undergoes phase transition from liquid to vapor within the fluidized bed reactor. The liquid recycle stream, cooled below its dew point, is introduced into the reactor where it vaporizes, absorbing heat and providing efficient cooling. This phase transition mechanism enables superior heat removal compared to conventional gas-phase fluidized bed reactors while maintaining the process simplicity and low capital investment advantages.
2Device complexity
If conventional cooling systems are used, then system complexity is minimized, but cooling capacity is insufficient leading to polymer degradation
Solution Approach 1:
The patent employs a self-cooling mechanism where the polymerization reaction heat is utilized to vaporize the liquid recycle stream. The endothermic vaporization process occurs within the reactor itself, using the reaction heat to cool the system. This self-service cooling approach eliminates the need for complex external cooling systems while ensuring reliable polymer stability by preventing degradation through effective heat removal.
3Temperature
If more liquid is introduced to increase cooling capacity, then heat removal improves, but fluidized bed destabilization occurs
Solution Approach 1:
The patent optimizes the parameters of the liquid recycle stream, specifically controlling its temperature to be below the dew point and regulating its flow rate to be between 1-50 wt% of the total recycle stream. By carefully adjusting these parameters, the system achieves enhanced cooling capacity through liquid vaporization while maintaining fluidized bed stability. The controlled introduction of liquid phase allows sufficient heat removal without causing bed destabilization.
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 cooling capacity and production rates by efficiently cooling a liquid and gas mixture, allowing for broader operating conditions without the need for extensive cooling systems, thus reducing polymer degradation and increasing space-time-yield.
Implementation Method 1
cooling the withdrawn fluids to a temperature below the dew point with a cooling unit, thereby separating a liquid phase and a gas/liquid phase
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) introducing catalyst and/or polymer from at least one loop reactor to at least one second reactor b) withdrawing fluids from the at least one second reactor c) cooling fluids comprising the withdrawn fluids with a cooling unit d) 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 e) introducing the gas/liquid phase below to the reactor below a distribution plate f) introducing the liquid phase to a settling tank to separate liquid from fines that settle down in the settling tank g) introducing liquid from the settling tank upstream of the cooling unit, h) introducing the slurry comprising solid polymer particles from the settling tank to the at least one loop reactor.