Polyamide 6 Extraction Using Recycled Granulation Water
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Solution Overview
Problem
Current processes for extracting monomeric caprolactam and oligomers from polyamide-6 polymerization waste are energy-intensive and inefficient, requiring multiple stages of water evaporation and disposal of oligomers, leading to high raw material and energy costs.
Innovation Solution
The process involves using extract water from the granulation step, enriched with caprolactam and oligomers, as process water until it reaches a concentration of 4-6%, then recycling it back into the extraction column, eliminating the need for fresh water and reducing energy consumption by minimizing water evaporation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If extract water is evaporated in a multi-stage distillation plant to recover caprolactam, then caprolactam can be reused in polymerization, but energy consumption increases significantly
Solution Approach 1:
The invention combines the granulation cooling function and the caprolactam extraction function into a single integrated process. The extract water from the extraction column is directly used as process water in the granulator, eliminating the need for separate evaporation and recovery steps. This merging of functions reduces energy consumption while maintaining caprolactam recovery through the continuous circulation and concentration of extract water in the granulation system.
Solution Approach 2:
The extract water serves multiple functions: it acts as cooling liquid in the granulator, as extraction medium in the extraction column, and as a carrier for caprolactam and oligomers. By making the process water universal and reusable across different process stages, the invention eliminates waste streams and reduces the need for energy-intensive evaporation and fresh water input.
2Ease of operation
If fresh water is continuously added to granulator circulating water, then granulation can proceed effectively, but water consumption and subsequent evaporation costs increase
Solution Approach 1:
Instead of discarding the water from the granulator system or treating it as waste, the invention recovers and reuses this water in the extraction column. The extract water that would otherwise require evaporation is now directly fed back into the granulation process, creating a closed-loop water system that minimizes both water consumption and energy requirements.
3Device complexity
If oligomers in extract water are disposed of rather than processed, then processing complexity is reduced, but raw material loss increases
Solution Approach 1:
The granulation system itself serves the dual purpose of cooling the polymer and concentrating the extract water containing caprolactam and oligomers. The continuous circulation and evaporation in the granulator naturally concentrate the extract, and this concentrated extract water is then directly reused in the extraction column, allowing the system to self-process the oligomers without additional complex treatment steps.
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 reduces energy and raw material costs by eliminating the need for fresh water in granulation systems and optimizing the reuse of extract water, while maintaining effective recovery of caprolactam and oligomers for polymerization.
Implementation Method 1
the extract water has to be worked up, in some cases in several stages, before the entire extract or extract components, in particular ε-caprolactam, can be used for renewed polymerization
Implementation Method 2
the general goal is to keep this amount of water as low as possible, because evaporating water costs energy
Data Source
AI summary
A continuous process for the extraction of monomeric caprolactam and oligomers derived therefrom from the polymer crude product obtained during polymerization to polyamide-6 is described, in which process water or previously used extract water is used for granulation instead of fresh water.