High-Pressure Pump Leakage Gap for Ethylene Copolymerization
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Solution Overview
Problem
The existing high-pressure processes for producing low-density polyethylene (LDPE) in tubular reactors face issues such as high ethylene gas leak rates, seal fouling, and polymerization problems due to excessive heat generation, leading to unsafe conditions and maintenance difficulties.
Innovation Solution
A process using a high-pressure pump with a positive leakage gap along the plunger to reduce friction and heat, coupled with cooling the (meth)acrylate before injection, prevents unwanted polymerization and seal failure, while injecting ethylene and (meth)acrylate at pressures between 100 MPa to 350 MPa into a tubular reactor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a high-pressure compressor is used to inject both ethylene and (meth)acrylate, then the polymerization reaction can proceed, but ethylene gas leaks and seal fouling occur due to excessive heat generation
Solution Approach 1:
The patent segments the injection system into two separate paths: ethylene is injected through a high-pressure compressor while (meth)acrylate is injected through a high-pressure pump with a positive leakage gap. This segmentation prevents the (meth)acrylate from experiencing excessive heat generation and polymerization in the compressor, eliminating seal fouling and gas leaks while maintaining polymer production
Solution Approach 2:
The positive leakage gap in the high-pressure pump acts as an intermediary cooling mechanism. The leakage gap allows a portion of the (meth)acrylate to bypass the compression zone, preventing excessive heat generation and unwanted polymerization, thereby protecting the seal from fouling while still enabling the main flow to be pressurized for reaction
2Temperature
If cooling water is flowed through the reactor jacket to remove heat, then the reaction temperature can be controlled, but the system complexity increases
Solution Approach 1:
The patent applies preliminary cooling action by cooling the (meth)acrylate before it enters the high-pressure pump and injection system. This pre-cooling prevents excessive heat generation during compression and injection, reducing the heat load on the reactor cooling system and simplifying overall temperature control while maintaining safe operation
3Reliability
If the plunger slides through the seal without a leakage gap, then sealing efficiency is high, but friction and heat generation cause seal fouling and failure
Solution Approach 1:
The patent converts the potentially harmful effect of leakage into a beneficial cooling mechanism. The positive leakage gap allows controlled leakage that prevents excessive heat generation and polymerization, transforming what would normally be a sealing defect into a protective feature that eliminates seal fouling and failure while maintaining adequate sealing performance
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 results in improved safety, easier maintenance, and the production of LDPE with enhanced web stability, neck-in, draw-down, adhesion, printability, and heat-sealing performance, along with reduced gel levels and higher coating speeds, ensuring consistent quality.
Implementation Method 1
a leakage gap is present along the plunger and is in communication with the pump suction chamber
Implementation Method 2
a tubular reactor provided on the outside with a jacket through which cooling water flows in order to remove the developed heat of reaction via the wall
Implementation Method 3
Metering an initiator such as for example organic peroxide, azodicarboxylic acid ester, azodicarboxylic acid dinitrile and hydrocarbons that decompose into radicals can start the polymerisation
Implementation Method 4
Owing to the exothermic nature of the reaction, the temperature increases as the reaction proceeds to a maximum peak temperature and considerable heat is evolved
Data Source
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AI summary
The invention relates to a process a system and a high pressure pump for the preparation of a copolymer of ethylene and a di- or higher functional (meth) acrylate in a tubular reactor, comprising the steps of: injecting ethylene at a pressure of 100 MPa to 350 MPa into the reactor from a high pressure compressor and injecting the (meth)acrylate at a pressure of 100 MPa to 350 MPa into the reactor from a high pressure pump, wherein the high pressure pump comprises - a pump suction chamber for receiving a medium to be compressed; - a cylinder for receiving the medium to be compressed from the pump suction chamber; - an outlet for discharging a compressed medium from the cylinder, - a seal fixed to the inner wall of the cylinder at an end of the cylinder distal to the outlet and - a plunger movable in the cylinder by sliding through the seal, wherein a leakage gap is present along the plunger and the leakage gap is fluidly connected to the pump suction chamber.