Ethylene Copolymer Reactor Cascade With Flash Hydrogen Recycling
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Solution Overview
Problem
There is a need for a low energy consumption process to prepare multimodal ethylene copolymers, as existing methods are inefficient in terms of energy usage and component recycling.
Innovation Solution
A process involving a reactor cascade with a first and second polymerization reactor, utilizing a solid-liquid separator followed by a flash vessel to recycle diluent and hydrogen back to the first reactor without purification, and using neopentane as the diluent to minimize energy consumption and prevent cross-contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the recovered suspension medium is purified in a purification section before recycling, then the purity of recycled components is improved, but the energy consumption increases
Solution Approach 1:
The invention extracts only the essential separation step (solid-liquid separation) from the complete purification train, eliminating energy-intensive purification steps while maintaining sufficient purity for recycling. The diluent is separated from polymer particles through solid-liquid separation and recycled without further purification, resolving the contradiction between purity and energy consumption.
Solution Approach 2:
The invention applies different quality requirements to different streams: the diluent stream requires only solid-liquid separation for recycling, while the polymer product stream receives complete purification. This localized quality approach ensures sufficient purity where needed while minimizing energy consumption in the diluent recycling loop.
2Reliability
If comonomer separation is implemented in the diluent recycling process, then the purity of recycled diluent is improved, but the device complexity and energy consumption increase
Solution Approach 1:
The invention removes the comonomer separation step from the diluent recycling process. By extracting only the necessary solid-liquid separation and eliminating comonomer removal, the system achieves sufficient diluent purity without complex purification equipment, resolving the contradiction between purity and device complexity.
Solution Approach 2:
The first polymerization reactor operates with hydrogen as the only chain transfer agent, producing homopolymer that naturally separates from the diluent phase. This self-separation mechanism eliminates the need for active comonomer removal systems, reducing device complexity while maintaining recycling efficiency.
3Reliability
If hydrogen is removed in a flash section before recycling, then the purity of recycled hydrogen stream is improved, but the energy consumption increases
Solution Approach 1:
The invention uses pressure reduction (flash flashing) to separate hydrogen from the diluent stream. By changing the pressure parameter, hydrogen naturally flashes off and can be recycled, achieving sufficient purity without energy-intensive separation processes. The pressure change enables efficient hydrogen recovery while minimizing energy input.
4Productivity
If a reactor cascade with multiple polymerization reactors is used, then the productivity and multimodal product distribution are improved, but the device complexity increases
Solution Approach 1:
The invention divides the polymerization process into two sequential reactors: the first reactor produces homopolymer fraction and the second reactor produces copolymer fraction. This segmentation enables multimodal product distribution with controlled molecular weight characteristics, improving productivity and product performance while maintaining manageable system complexity through modular design.
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
The process significantly reduces energy consumption by eliminating the need for comonomer separation and using neopentane, resulting in efficient production of multimodal ethylene copolymers with controlled molecular weight distribution.
Implementation Method 1
feeding the first particles stream to a flash section comprising a first flash vessel and an optional second flash vessel to obtain a vapor stream rich in hydrogen and a hydrogen-depleted stream
Implementation Method 2
feeding at least part of the first suspension to a first solid-liquid separator to obtain a first diluent stream rich in the first diluent and a first particles stream rich in the solid particles
Data Source
AI summary
A process for the preparation of a multimodal ethylene copolymer in a reactor cascade, the process comprising:a) feeding ethylene, hydrogen and catalyst components and a first diluent to a first polymerization reactor to prepare a first suspension of solid particles of an ethylene homopolymer in a first suspension medium,b) feeding at least part of the first suspension to a first solid-liquid separator to obtain a first diluent stream rich in the first diluent and a first particles stream-rich in the solid particles,c) feeding the first particles stream to a flash section comprising a first flash vessel and an optional second flash vessel to obtain a vapor stream rich in hydrogen and a hydrogen-depleted stream, andd) feeding the hydrogen-depleted stream, ethylene and a comonomer and a second diluent to a second polymerization reactor to prepare a second suspension of solid particles of the multimodal ethylene copolymer in a second suspension medium.