Polyolefin Reactor Control via Induced Condensing Agent Partial Pressure
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Solution Overview
Problem
Current polyolefin polymerization processes face challenges in controlling stickiness and agglomeration in gas-phase fluidized bed reactors, leading to reduced production rates and potential reactor discontinuity, as existing methods struggle to predict and prevent the onset of stickiness effectively.
Innovation Solution
A method is developed to model and control the stickiness temperature of resin by measuring its behavior at various concentrations of induced condensing agents (ICAs) and calculating an equivalent partial pressure, allowing the reactor to operate within a non-sticking regime defined by upper and lower temperature limits, thereby preventing agglomeration and maximizing production rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the recycle stream temperature is lowered below the dew point to increase cooling capacity and polymer production, then production rate increases, but polymer agglomeration and reactor plugging occur
Solution Approach 1:
The invention implements a feedback control system that continuously monitors reactor conditions (temperature, pressure, gas composition) and adjusts the recycle stream temperature accordingly. The controller compares actual conditions with target conditions and dynamically modifies cooling intensity to maintain operation within the non-sticking regime, preventing agglomeration while maximizing production.
Solution Approach 2:
The invention identifies and exploits a previously unrecognized operating window by changing the temperature parameter of the recycle stream. By lowering the temperature below the dew point without causing condensation issues, the system increases cooling capacity and polymer production while avoiding the harmful effects that were previously thought to be inevitable.
2Loss of energy
If induced condensing agents (ICAs) are added to increase cooling capacity, then heat removal efficiency improves, but resin stickiness and agglomeration increase
Solution Approach 1:
The invention changes the approach from adding chemical agents (ICAs) to achieve cooling to using physical parameter control (temperature and pressure of recycle stream). By adjusting the temperature and pressure parameters, the system achieves enhanced cooling capacity through increased condensation of existing gases without introducing additional condensable materials that would increase resin stickiness.
Solution Approach 2:
The invention extracts and eliminates the need for induced condensing agents from the system. Instead of adding ICAs to increase cooling capacity, the method utilizes the existing gas composition and controls its temperature and pressure to achieve the desired cooling effect, thereby removing the source of increased resin stickiness.
3Productivity
If the reactor operates at higher temperatures to increase production rate, then polymer production increases, but resin stickiness and agglomeration occur
Solution Approach 1:
The invention changes the operational parameters by introducing a new dimension of control through recycle stream temperature. This allows the system to operate at higher reactor temperatures for increased production while using the cold recycle stream to prevent resin stickiness, effectively decoupling the relationship between production temperature and resin stability.
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 enables the identification of a stable operating condition for gas fluidized bed polymerization, allowing for higher production rates with reduced risk of reactor discontinuity by maintaining the reactor within a non-sticking regime, thus optimizing process conditions and preventing resin stickiness.
Implementation Method 1
Cooling of the recycle stream to a temperature below the gas dew point temperature produces a two-phase gas/liquid mixture
Implementation Method 2
Vaporization of the liquid occurs only when heat is added or pressure is reduced. For example, as described in U.S. Patent Nos. 4,543,399 and 4,588,790, vaporization can occur when the two-phase mixture enters the fluidized bed, with the resin providing the required heat of vaporization.
Implementation Method 3
since the polymerization reaction is exothermic, the amount of polymer produced in a fluidized bed polymerization process is related to the amount of heat that can be withdrawn from the reaction zone
Data Source
AI summary
Methods and systems for controlling a polymerization reaction in a non-sticking regime are disclosed. An exemplary method includes measuring parameters for the polymerization reaction including a reactor temperature and a concentration of an induced condensing agent (ICA) in a polymerization reactor. An equivalent partial pressure ((PICA )equiv) of the ICA is calculated. The polymerization reaction is located in a two dimension space defined by a reactor temperature dimension and a ((PICA )equiv) dimension. The location in the two dimensional space is compared to an non-sticking regime, defined as the space between an upper temperature limit (UTL) curve and a lower temperature limit (LTL) curve. The parameters of the polymerization reaction are adjusted to keep the polymerization reaction within the non-sticking regime.