Reactor Shut-Down Sequence to Minimize Foam in Glycol Conversion
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Solution Overview
Problem
Existing methods for shutting down carbohydrate conversion processes in stirred reactors result in substantial foam formation, leading to fouling and safety issues due to the presence of undesired products and catalyst particles in off-gas treatment equipment, and do not effectively minimize the formation of degradation products like humins.
Innovation Solution
A method involving sequential steps of terminating liquid flows, cooling the reactor content to below 100°C, replacing part of the liquid with water, and depressurizing while maintaining stirring and hydrogen feed during the process, followed by replacing hydrogen with an inert gas before depressurization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the reactor is cooled down and depressurized during shut-down, then the process is terminated, but substantial foam formation occurs leading to fouling and safety issues
Solution Approach 1:
The patent applies preliminary action by replacing a portion of the reaction medium with water before cooling and depressurization. This pre-treatment step modifies the liquid composition to reduce surface tension and eliminate the conditions that lead to foam formation during subsequent temperature and pressure changes, preventing the harmful effect before it occurs.
2Loss of energy
If stirring is stopped during shut-down, then energy consumption is reduced, but catalyst particles settle and cause deposition on surfaces
Solution Approach 1:
The patent uses water as an intermediary substance that replaces part of the reaction medium. This water-catalyst mixture has different flow and suspension characteristics that prevent catalyst deposition even when stirring is reduced or stopped, allowing energy reduction without causing the harmful deposition effect.
3Device complexity
If the reactor is depressurized without replacing liquid with water, then the shut-down is simpler, but undesired products and catalyst particles contaminate off-gas treatment equipment
Solution Approach 1:
The patent applies preliminary action by performing liquid replacement with water before depressurization. This pre-treatment modifies the reactor contents to reduce foam formation and minimize the carryover of catalyst particles and undesired products into the off-gas treatment equipment during subsequent pressure reduction, preventing contamination before it occurs.
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
Reduces foam formation and minimizes the presence of undesired products, preventing reactor fouling and ensuring safe shut-down by maintaining catalyst suspension and reducing volatile components.
Implementation Method 1
cooling the reactor content to below 100°C
Implementation Method 2
during steps a. and b. hydrogen is fed to the reactor
Implementation Method 3
depressurizing the reactor to atmospheric pressure
Implementation Method 4
during all of steps a. to c. the reactor content is stirred
Data Source
AI summary
A method for shutting-down a process wherein a carbohydrate source is converted into one or more alkylene glycols. In particular the invention relates to a method for shutting-down such a process for the conversion of a saccharide into ethylene glycol. The procedure according to the invention aims to minimize foam formation occurring otherwise.