Flash Drum Hydrogen Removal in Multimodal Polyolefin Polymerization
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Solution Overview
Problem
Current suspension polymerization processes require larger work-up sections and higher costs due to the need to handle increased volumes of hydrogen-depleted material when transferring polymers from one reactor to another, as existing methods generate significant off-gas that must be laboriously processed.
Innovation Solution
A process involving a flash drum to reduce hydrogen concentration by vaporizing part of the suspension medium, condensing gas in a heat exchanger, and recycling the liquid back into the polymerization process, thereby reducing the material needing treatment in the work-up section.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If hydrogen removal is performed by expanding the reaction mixture to vent hydrogen, then hydrogen concentration is reduced, but the volume of material requiring work-up section treatment increases
Solution Approach 1:
The patent extracts hydrogen from the reaction mixture by expanding it into a flash drum where hydrogen and light components vaporize and separate from the polymer suspension. This allows hydrogen removal without requiring the entire expanded mixture to pass through the work-up section, as the liquid phase can be directly reused.
Solution Approach 2:
The patent recovers the liquid phase from the flash drum expansion and returns it to the polymerization process. This recovery eliminates the need to treat this material through the work-up section, converting what would be waste into a useful process stream while maintaining hydrogen removal effectiveness.
2Quantity of substance
If larger work-up sections are used to handle increased volumes of hydrogen-depleted material, then hydrogen removal effectiveness is improved, but equipment size and operational costs increase
Solution Approach 1:
The liquid phase recovered from the flash drum is returned to the polymerization process rather than being sent to the work-up section. This recovery strategy reduces the volume requiring work-up treatment, allowing for smaller, more economical work-up section design while maintaining effective hydrogen removal.
Solution Approach 2:
The flash drum expansion process itself serves the dual function of hydrogen removal and liquid phase preparation for reuse. The system essentially serves itself by generating a recoverable liquid stream from the expansion process, eliminating the need for additional large-scale work-up equipment.
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 effectively decreases the hydrogen concentration in the polymer suspension transferred between reactors, minimizing the load on the work-up section, reducing operational costs and energy consumption, and allowing for a smaller, more economical work-up section design.
Implementation Method 1
vaporizing part of the suspension medium
Implementation Method 2
feeding the suspension to a flash drum of a lower pressure than that of the first polymerization reactor
Implementation Method 3
condensing a part of the gas withdrawn from the flash drum
Implementation Method 4
condensing a part of the gas withdrawn from the flash drum
Data Source
Figure 1
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AI summary
Process for the preparation of a multimodal polyolefin polymer at temperatures of from 40 to 150°C and pressures of from 0.1 to 20 MPa in the presence of a polymerization catalyst in a first and a second polymerization reactor connected in series, wherein further polymerization reactors can be connected to said reactors upstream or downstream of said reactors, in which in the first polymerization reactor a first polyolefin polymer is prepared in suspension in the presence of hydrogen and in the second polymerization reactor a second polyolefin polymer is prepared in the presence of a lower concentration of hydrogen than in the first polymerization reactor, comprising a) withdrawing from the first polymerization reactor a suspension of solid polyolefin particles in a suspension medium comprising hydrogen; b) feeding the suspension to a flash drum of a lower pressure than that of the first polymerization reactor; c) vaporizing a part of the suspension medium; d) withdrawing a hydrogen-depleted suspension from the flash drum and feeding it to the second polymerization reactor; e) withdrawing gas from the gas-phase of the flash drum and feeding it to a heat exchanger; f) condensing a part of the gas withdrawn from the flash drum; and g) returning the liquid obtained in the heat exchanger to the polymerization process at a point where suspension is present, and apparatus for preparing a multimodal polyolefin polymer according to the process.