Polymer Polyol CSTR Recirculation to Limit Heat Exchanger Fouling
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Solution Overview
Problem
Heat exchanger fouling in continuous stirred tank reactors used for producing polymer polyols reduces production efficiency, necessitating frequent cleaning and interrupting production campaigns.
Innovation Solution
A continuous process involving a continuous stirred tank reactor with an external recirculation loop and specific residence time ratios for reactor and recirculation loop times to minimize heat exchanger fouling, allowing for longer production campaigns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If continuous polymer polyol production is carried out using a heat exchanger in a recirculation loop, then heat removal efficiency is improved, but heat exchanger fouling increases over time requiring frequent cleaning
Solution Approach 1:
The patent applies parameter changes by optimizing the residence time ratio between the reactor system and recirculation loop to a specific range (10:1 to 93:1). This parameter optimization reduces the frequency and severity of fouling while maintaining effective heat removal, thereby resolving the contradiction between temperature control efficiency and heat exchanger reliability.
2Productivity
If production campaigns are extended to increase production capacity, then productivity is improved, but heat exchanger fouling accumulates requiring production interruption
Solution Approach 1:
By changing and optimizing the residence time parameters of the system, the patent enables extended production campaigns. The specific ratio range (10:1 to 93:1) allows the system to maintain heat exchanger functionality for longer periods, directly supporting increased productivity without frequent interruptions for cleaning.
3Temperature
If frequent cleaning is performed to maintain heat exchanger efficiency, then heat removal capability is preserved, but production time is lost and capacity is reduced
Solution Approach 1:
The optimized residence time ratio parameter changes enable the system to maintain heat removal efficiency for extended periods. By operating within the specified ratio range, the frequency of cleaning operations is significantly reduced, preserving production capacity while maintaining thermal performance.
4Temperature
If recirculation flow rate is increased to improve heat removal, then temperature control is enhanced, but fouling rate in the heat exchanger increases
Solution Approach 1:
Rather than simply increasing recirculation flow rate, the patent optimizes the residence time ratio parameter. This approach achieves effective temperature control while managing fouling rates by balancing the time spent in the reactor versus the recirculation loop, preventing excessive fouling accumulation that would occur with higher flow rates alone.
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
Significantly extends the duration between cleaning intervals, enhancing production capacity by maintaining heat exchanger efficiency.
Implementation Method 1
a heat exchanger, often a shell and tube heat exchanger, to remove the heat of reaction by passing reactor contents through the tube side of the heat exchanger
Implementation Method 2
passing reactor contents through the tube side of the heat exchanger and passing a coolant liquid, such as cooling water, through the shell side of the heat exchanger
Implementation Method 3
an external recirculation loop comprising a pump and a heat exchanger arranged in series with respect to each other
Data Source
Figure 1
AI summary
Processes for continuously producing a polymer polyol ("PMPO"). The process includes free-radically polymerizing an ethylenically unsaturated monomer composition in the presence of a base polyol, in which the polymerizing occurs in a continuous stirred tank reactor ("CSTR") that has an external recirculation loop comprising a pump and a heat exchanger arranged in series with respect to each other. A stream of the reactor contents is (i) continuously removed from the reactor, (ii) then continuously flows through the pump and the heat exchanger, and (iv) then continuously returns to the CSTR. A ratio of reactor system residence time to recirculation loop residence time is 10 to 93.