Polypropylene Polymerization Flow for Low-Steam Oligomer Removal
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Solution Overview
Problem
The bulk-vapor phase combined process for producing polypropylene faces issues such as high steam consumption, oligomer vaporization difficulties, and contamination of final products with heavy components, leading to increased costs and operational challenges.
Innovation Solution
A device and method involving a polymerization unit with pre-polymerization, multiple reactors, and a steaming and drying unit to enhance product cleanliness and reduce costs, utilizing solvent-free catalyst introduction and flashing propylene for heat removal, with a compact modular design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mechanical stirrer is equipped in vapor phase reactors, then hot spots are reduced and polymer distribution is improved, but device complexity and maintenance costs increase due to mechanical seal requirements
Solution Approach 1:
The patent replaces the mechanical stirrer system with a fluidization-based mixing system. Gas-phase propylene and inert gas flow through the reactor to fluidize the polymer particles, achieving uniform distribution and heat removal without mechanical moving parts. This eliminates the mechanical seal requirement while maintaining effective mixing and hot spot prevention.
Solution Approach 2:
The invention uses gas flow (pneumatic system) to fluidize and mix the polymer particles in the reactor. Inert gas and propylene gas are circulated through the reactor bed to provide both mixing action and heat removal, replacing the need for mechanical agitation systems.
2Reliability
If bulk-vapor phase combined process is used, then operational reliability is improved, but steam consumption increases and oligomers cannot be vaporized
Solution Approach 1:
The patent utilizes phase transition of propylene (liquid to gas) to provide both reaction medium and heating/steam function. Propylene is vaporized in the reactor to provide the gas-phase reaction environment and simultaneously serves as the heat transfer medium, eliminating the need for separate steam systems and reducing energy consumption.
Solution Approach 2:
The propylene serves multiple functions simultaneously: it acts as the monomer for polymerization, the liquid phase reaction medium, the gas-phase heat transfer medium (after vaporization), and the cleaning agent for oligomer removal. This multi-functionality eliminates the need for separate steam systems used in bulk-vapor phase combined processes.
3Quantity of substance
If washing of high-pressure propylene washing tower is performed, then propylene purification is achieved, but heavy components and oligomers contaminate the final product
Solution Approach 1:
The patent uses temperature-controlled phase transition to separate oligomers from the final product. The reactor operates at temperatures where oligomers remain in liquid or semi-liquid state while the final polymer product is in solid particle form. This natural phase separation allows easy removal of oligomers without contamination of the final product.
Solution Approach 2:
The invention creates different local conditions in the reactor system. The polymerization zone maintains conditions for solid particle formation, while the oligomer-rich liquid phase is separated in a dedicated zone. This spatial separation of phases and properties prevents oligomer contamination of the final solid polymer product.
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 method achieves high-quality polypropylene production with flexible grade options, reduced energy consumption, and lower investment costs, while avoiding reactor fouling and block formation, ensuring safety and operability.
Implementation Method 1
a polymerization unit, a steaming unit and a drying unit; the polymerization unit includes a pre-polymerization kettle, a first reactor
Implementation Method 2
oligomers cannot be vaporized from slurry polymerization at 70° C.; there is a high steam consumption
Implementation Method 3
drying moist materials after steaming to obtain polypropylene
Data Source
AI summary
A device and method for preparing polypropylene. The device includes: a polymerization unit, a steaming unit and a drying unit, wherein the polymerization unit includes a pre-polymerization kettle, a first reactor, a first reaction condenser, a first propylene condensate tank and a second reactor; the first reactor is in communication with the pre-polymerization kettle; the first reaction condenser is in communication with a top of the first reactor; a top of the first propylene condensate tank is in communication with the first reaction condenser and the first reactor, respectively, and a bottom of the first propylene condensate tank is in communication with the first reactor; and a top of the second reactor is in communication with a bottom of the first reactor.