Problem
Poor mixing in an existing low density polyethylene reactor gave:

• Excess decomp product formation
• Poor thermal stability
• High initiator requirements

Objective
Assess current reactor operation and optimize mixing based on chemical requirements.

Approach
The following main design parameters were investigated:

• Reaction rate and timescales
• Micromixing Initiator utilization
• Feed positions
• Turbulent energy required
• Impeller types
• Baffling

Results
Very good mixing is required in LDPE reactors to blend in intiator rapidly, ensure that mixing produces a homogeneous distribution and remove the heat of reaction to ensure decomp products are minimized and initiator usage maximized. Even local hot-spots can lead to runaway reactions.

Modifications suitable for the production process were recommended based upon the effect of modifying impeller types, feed positions and baffle arrangements on mixing and reaction.

Benefits
Retrofits were shown to give improvements to thermal stability of the reactor and product quality.

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