Multi-Stage Acrylic Acid Crystallization for High-Purity Separation
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Solution Overview
Problem
Existing methods for preparing acrylic acid face challenges in achieving high purity and yield due to the need for high energy consumption in separation processes and the difficulty in obtaining desired purity levels, particularly when acetic acid is present, as it has a similar melting point to acrylic acid.
Innovation Solution
A multi-stage crystallization process using two or more crystallization units connected in series, each with a crystallizer and solid-liquid separator, where acrylic acid is crystallized and separated into a concentrated solution and mother liquor, with controlled temperatures and stream circulation to optimize purity and yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single-stage crystallization process is used, then the process complexity is low, but the purity of acrylic acid cannot be obtained at the desired level when large amounts of acetic acid are present
Solution Approach 1:
The crystallization process is divided into multiple stages with different crystallization temperatures. The first stage operates at -10 to 0°C to crystallize acrylic acid while minimizing acetic acid crystallization, and the second stage operates at -20 to -10°C to further purify the product. This segmentation allows each stage to target specific purification goals, achieving high purity acrylic acid while managing process complexity through systematic division of the crystallization process.
2Manufacturing precision
If high-temperature distillation is used to separate by-products, then the separation efficiency is improved, but polymerization of acrylic acid occurs and periodic washing is required
Solution Approach 1:
The process changes the temperature parameter from high-temperature distillation to low-temperature crystallization (first stage: -10 to 0°C, second stage: -20 to -10°C). This parameter change exploits the different melting points of acrylic acid and acetic acid to achieve separation through crystallization rather than distillation, avoiding polymerization while maintaining effective separation of by-products.
3Manufacturing precision
If distillation processes are used to separate by-products from acrylic acid solution, then the separation capability is improved, but energy usage becomes significantly high due to the specific heat of the absorption solvent
Solution Approach 1:
The process utilizes phase transition (crystallization) instead of phase change (distillation). By controlling temperature to induce crystallization of acrylic acid from the aqueous solution, the process avoids the high energy requirements of distillation. The crystallization occurs at -10 to 0°C in the first stage and -20 to -10°C in the second stage, efficiently separating acrylic acid from water and acetic acid with minimal energy input compared to distillation methods.
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
The method enhances the final yield and purity of acrylic acid by reducing the amount of mother liquor treated, minimizing energy usage, and improving the overall efficiency of the crystallization process.
Implementation Method 1
in the crystallizer of each stage, acrylic acid contained in an acrylic acid solution introduced into the crystallizer of each stage is crystallized to obtain a suspension containing acrylic acid crystals
Implementation Method 2
in the solid-liquid separator of each stage, the suspension is separated into a solid and a liquid to obtain a concentrated acrylic acid solution and a mother liquor
Data Source
Figure 1~2
Figure 3~4
AI summary
The present invention provides a method for preparing acrylic acid, the method including a multi-stage crystallization process performed by two or more crystallization units that are connected in series and each includes a crystallizer and a solid-liquid separator, wherein a first stage crystallization unit among the two or more crystallization units includes a crystallizer having a crystallization temperature of -20 to -10°C.