Pressure Swing Distillation for Methanol MMA Azeotrope Separation
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Solution Overview
Problem
Current methods for breaking methanol/methyl methacrylate (MMA) azeotropes are inefficient due to high energy consumption and limited ability to separate methanol from MMA without using large amounts of entrainers or azeotropic agents, which can lead to reduced MMA yield and increased equipment costs.
Innovation Solution
The process involves raising the pressure in a first distillation column to collect the azeotrope, then transferring it to a second column at higher pressure, where methanol is recovered, and using a heat pump to reduce energy consumption by transferring heat from the high-pressure column to the low-pressure column, potentially with or without an azeotropic agent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pressure is raised in the distillation column to break the methanol/MMA azeotrope, then separation between methanol and MMA is improved, but energy consumption increases prohibitively
Solution Approach 1:
The distillation process is divided into two separate columns operating at different pressures. The first column operates at lower pressure to produce overheads enriched in methanol, while the second column operates at higher pressure to break the azeotrope and recover pure methanol. This segmentation allows each column to operate more efficiently than a single high-pressure column would require.
Solution Approach 2:
The system employs periodic pressure swing operation where the second column periodically switches between high pressure (for separation) and low pressure (for product recovery). This periodic action allows the azeotrope to be broken during high-pressure operation while enabling energy-efficient product recovery during low-pressure operation.
2Manufacturing precision
If a large number of trays and high reflux ratio are used to approach the azeotropic composition, then separation precision is improved, but equipment size and complexity increase
Solution Approach 1:
Instead of increasing the number of trays or reflux ratio to improve separation, the invention changes the operating pressure parameter. By operating the second column at higher pressure, the azeotrope composition shifts, allowing efficient separation with a reasonable number of trays and reflux ratio.
Solution Approach 2:
The pressure difference between the two columns acts as an intermediary mechanism to achieve separation. The high-pressure operation in the second column modifies the vapor-liquid equilibrium to break the azeotrope, serving as a mediator that enables separation without requiring excessive trays or reflux.
3Manufacturing precision
If hexane entrainer is used to remove methanol from MMA, then methanol removal is improved, but the amount of entrainer required increases significantly, resulting in high energy usage and large equipment
Solution Approach 1:
The invention extracts and removes the need for large amounts of hexane entrainer by using pressure swing distillation. The high-pressure operation in the second column directly breaks the azeotrope and enables methanol recovery without requiring excessive entrainer, thus taking out the problematic substance (hexane) from the process.
Solution Approach 2:
Instead of using large amounts of hexane entrainer that requires continuous recycling and large equipment, the invention uses a simple pressure change approach that requires minimal additional substances. The pressure swing operation itself becomes the primary separation mechanism rather than relying on disposable entrainer materials.
4Manufacturing precision
If water is added to the overhead decanter to form organic and aqueous layers, then phase separation is improved, but the ability to dry the recycle stream is limited
Solution Approach 1:
The invention changes the pressure parameter to achieve both phase separation and effective drying. By operating the second column at high pressure to break the azeotrope and then allowing pressure reduction, the system achieves phase separation while the high-pressure operation inherently limits water content in the overheads, providing self-drying capability.
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 method effectively reduces energy consumption by 50% and achieves efficient separation of methanol from MMA, minimizing MMA in the recycle stream and reducing equipment costs, while allowing for the use of azeotropic agents if desired.
Implementation Method 1
Methanol and MMA form an azeotrope or a 'near azeotrope'
Implementation Method 2
separation of technical methanol-MMA mixtures by polymerization of the MMA... and the methanol is recovered by distillation
Implementation Method 3
raising the pressure within a first vessel, e.g., a distillation column, that contains a methanol/MMA azeotrope... raising the pressure sufficiently to allow for the recovery of the methanol
Data Source
AI summary
A methanol/MMA azeotrope is broken or avoided by a method comprising the steps of (1) raising the pressure within a first vessel, e.g., a distillation column, that contains a methanol/MMA azeotrope, (2) collecting the azeotrope as a liquid, and then in a second, separate vessel, e.g., another distillation column, (3) raising the pressure sufficiently to allow for the breaking of or avoidance of the azeotrope and the recovery of the methanol.