Gas-Phase Reactor Production-Rate Control via Cooling-Medium Heat Balance
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Solution Overview
Problem
Existing methods struggle to accurately control and calculate the production rate of propylene homo- or copolymers in gas phase reactors, particularly when multiple reactors are involved, due to challenges in measuring gas flow between reactors and managing heat transfer and condensation, which complicates the determination of production rates and condensing degrees.
Innovation Solution
A process that calculates the production rate of propylene homo- or copolymers in a gas phase reactor by utilizing parameters from the cooling medium system, including specific heat capacity and mass flow of the cooling medium, allowing for precise control and adjustment of production rates and condensing degrees.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If gas flow is increased to remove heat from the gas phase reactor, then heat removal efficiency is improved, but gas circulation requirements increase and system complexity increases
Solution Approach 1:
The patent introduces a heat transfer agent as an intermediary substance that facilitates heat removal from the gas phase reactor. This agent absorbs heat from the reactor and transfers it to a heat exchanger, where the heat is dissipated to the environment. This intermediary approach allows effective heat removal without requiring excessive gas circulation, thereby reducing system complexity while maintaining temperature control.
2Productivity
If operating temperature is increased to maximize polymer production rate, then productivity is improved, but polymer quality deteriorates due to stickiness and low melting point
Solution Approach 1:
The patent employs parameter changes by dynamically adjusting the operating temperature within an optimized range (65-75°C) based on the specific polymer grade being produced. For propylene ethylene copolymers with 3-6 wt.% ethylene content, the temperature is maintained at the lower end of this range to prevent stickiness and maintain polymer quality. This parameter optimization allows achieving high productivity while preserving manufacturing precision.
Solution Approach 2:
The patent implements dynamic temperature control where the operating temperature can be adjusted in real-time based on reactor conditions, polymer grade requirements, and production targets. This dynamic approach enables the system to maximize productivity when producing stable polymer grades while switching to lower temperatures for sensitive copolymers, thereby resolving the contradiction between production rate and polymer quality.
3Adaptability or versatility
If comonomers with higher molecular weight than propylene are used to produce copolymers, then product versatility is improved, but dew point of circulation gas increases and temperature control range is reduced
Solution Approach 1:
The patent addresses this contradiction by optimizing the circulation gas temperature and pressure parameters to maintain operation below the elevated dew point when high molecular weight comonomers like 1-butene or 1-hexene are used. By carefully controlling these parameters, the system can produce versatile copolymer products while maintaining adequate temperature control range for efficient polymerization.
4Productivity
If multiple reactors are operated in a multistage system to increase production capacity, then productivity is improved, but measurement and control complexity increases due to unmeasured gas flow between reactors
Solution Approach 1:
The patent implements a feedback-based material balance approach where the production rate in each gas phase reactor is calculated using measurable parameters such as cooling medium flow rates, temperature differences across heat exchangers, and known feed compositions. This feedback mechanism allows accurate determination of polymer production rates in each reactor stage without requiring direct measurement of gas flows between reactors, thereby enabling multistage operation with enhanced productivity while avoiding excessive measurement and control complexity.
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
Enables cost-effective and efficient determination and control of production rates in gas phase reactors, facilitating accurate calculation of split flows between reactors and optimizing operating conditions.
Implementation Method 1
the circulation gas is cooled by indirect heat exchange with the cooling medium (cm) in the cooling circuit of the circulation gas cooler
Implementation Method 2
an exothermic polymerization reaction
Data Source
Figure 1
Figure 2
AI summary
The invention concerns a Process for controlling the production rate of a propylene homo- or copolymer in a selected gas phase reactor of a multistage reactor system, the multistage reactor system comprising a first reactor and one or more gas phase reactor(s) downstream of the first reactor, wherein each gas phase reactor is equipped with a gas circulation line, a circulation gas compressor and a circulation gas cooler, wherein the circulation gas cooler comprises a cooling medium inlet, a cooling medium outlet and a cooling circuit, the process comprising the steps of a) polymerizing propylene and optional comonomer in the first reactor and the one or more gas phase reactor(s), wherein in each gas phase reactor a polypropylene homo- or copolymer is produced by feeding a circulation gas via the gas circulation line into the gas phase reactor and at the same time feeding cooling medium (cm) through the cooling circuit of the circulation gas cooler, wherein the cooling medium (cm) has a temperature Tin at the cooling medium inlet of the circulation gas cooler and a temperature Tout at the cooling medium outlet of the circulation gas cooler, wherein the circulation gas comprises propylene and optional comonomer and wherein the circulation gas is cooled by indirect heat exchange with the cooling medium (cm) in the cooling circuit of the circulation gas cooler, b) selecting one gas phase reactor from the one or more gas phase reactor(s) of the multistage reactor system as the selected gas phase reactor, c) calculating the production rate Z - X (kg/h) of the propylene homo- or copolymer produced in the selected gas phase reactor by formula (1), and d) controlling the production rate Z - X (kg/h) of the propylene homo- or copolymer produced in the selected gas phase reactor.