Polyolefin Particle Transfer Between Gas-Phase Reactors
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Solution Overview
Problem
Existing multistage polymerization processes for olefins face challenges in continuously transferring polyolefin particles from one gas-phase reactor to another without introducing reaction gases from the first reactor into the second, leading to suboptimal polymerization conditions and residual gas components.
Innovation Solution
A process involving a separation chamber at lower pressure to separate polyolefin particles from reaction gas, followed by transfer to lock hoppers that are intermittently pressurized with reaction gas from the second reactor, ensuring minimal carryover of reaction gases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If polyolefin particles are directly discharged from the first reactor to the second reactor, then the transfer process is simple and continuous, but reaction gases from the first reactor are carried over into the second reactor, compromising polymerization conditions
Solution Approach 1:
The patent introduces an intermediary device (transfer hopper or lock hopper) between the first and second reactors. This intermediary acts as a buffer that receives polymer particles from the first reactor, allows reaction gases to be vented or separated, and then transfers the purified polymer particles to the second reactor. This mediator eliminates the direct connection that causes gas carryover while maintaining continuous transfer capability.
Solution Approach 2:
The transfer process is segmented into distinct stages: (1) discharge from first reactor to transfer device, (2) gas separation/venting in transfer device, (3) transfer to second reactor. This segmentation allows the system to achieve both continuous operation and gas separation by dividing the transfer function into multiple sequential operations.
2Object-affected harmful factors
If degassing and compression stages are added to remove reaction gases, then gas carryover is reduced, but the process becomes discontinuous and operates periodically
Solution Approach 1:
The patent designs the transfer system to operate continuously rather than periodically. The transfer hopper or lock hopper maintains a continuous supply of polymer particles while simultaneously and continuously venting reaction gases. This is achieved through continuous agitation, controlled discharge rates, and ongoing gas venting ports that operate throughout the entire transfer process, eliminating the need for periodic batch operations.
3Productivity
If lock hoppers working intermittently in parallel are used, then continuous transfer is achieved, but device complexity increases
Solution Approach 1:
The patent combines multiple functions into a single integrated transfer hopper device: polymer reception, gas venting, particle agitation, and controlled discharge all occur in one unit. This merging of functions achieves continuous transfer capability without requiring multiple separate lock hoppers operating in parallel, thereby reducing overall system complexity while maintaining productivity.
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 enables a continuous and efficient transfer of polyolefin particles with nearly no reaction gas from the first reactor entering the second, allowing for maintained distinct polymerization conditions and improved polymer properties.
Implementation Method 1
a separation chamber in which the polyolefin particles are separated from concomitantly discharged reaction gas, the separation chamber being at a lower pressure than the pressure in the first gas-phase polymerization reactor
Implementation Method 2
into which a fluid is introduced in an amount that an upward stream of the fluid in the bed of polyolefin particles above the fluid introduction point is induced
Implementation Method 3
simultaneously pressurizing another of the at least two lock hoppers working intermittently in parallel by means of a gas comprising reaction gas coming from the second gas-phase polymerization reactor
Data Source
AI summary
A process for polymerizing olefins at temperatures of from 30°C to 140°C and pressures of from 1.0 MPa to 10 MPa in the presence of a polymerization catalyst in a multistage polymerization of olefins in at least two serially connected gas-phase polymerization reactors, the process for transferring polyolefin particles from a first gas-phase polymerization reactor to a second gas-phase polymerization reactor comprising the steps of a) discharging polyolefin particles from the first gas-phase polymerization reactor into a separation chamber in which the polyolefin particles are separated from concomitantly discharged reaction gas, the separation chamber being at a lower pressure than the pressure in the first gas-phase polymerization reactor; b) transferring the polyolefin particles within the separation chamber into a lower part of the separation chamber which contains a bed of polyolefin particles which moves from top to bottom of this part of the separation chamber and into which a fluid is introduced in an amount that an upward stream of the fluid in the bed of polyolefin particles above the fluid introduction point is induced, c) withdrawing polyolefin particles from the lower end of said lower part and transferring them to one of at least two lock hoppers working intermittently in parallel; and d) simultaneously pressurizing another of the at least two lock hoppers working intermittently by means of a gas comprising reaction gas coming from the second gas-phase polymerization reactor, and apparatus for the multistage polymerization of olefins, comprising at least two serially connected gas-phase polymerization reactors and a device for transferring polyolefin particles from an up-stream gas-phase polymerization reactor to a downstream gas-phase polymerization reactor, the transferring device comprising - a gas/solid separation chamber placed downstream of the upstream gas-phase polymerization which gas/solid separation chamber is equipped at a lower part with an inlet for introducing a fluid, and - connected to the gas/solid separation chamber at least two lock hoppers, placed in a parallel arrangement, each connected to the downstream gas-phase polymerization reactor.