Multistage Absorption Tower for Isocyanate Solvent Refining
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current solvent refining methods for isocyanates produced by the phosgene method are inefficient in simultaneously removing water content, iron, phosgene, hydrogen chloride, and colored substances, leading to high costs, resource waste, and poor product quality due to high impurity levels.
Innovation Solution
A multistage absorption tower with a specific design and composition of desiccants and adsorbents, including alkaline desiccants and macroporous resin or activated carbon, is used to effectively remove water, iron, phosgene, and hydrogen chloride from solvents, reducing the color number and enhancing solvent reuse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional solvent refining methods are used, then the solvent can be processed, but the removal of multiple impurities (water, iron, phosgene, hydrogen chloride, colored substances) is inefficient and costly
Solution Approach 1:
The refining process is segmented into multiple sequential stages, each targeting specific impurities: first stage removes water and phosgene using molecular sieves and alkaline substances, second stage removes iron and colored substances using activated carbon, third stage removes hydrogen chloride using basic substances. This segmentation allows each stage to focus on specific contaminants, improving overall purification efficiency while maintaining manageable process complexity.
Solution Approach 2:
The patent recovers and reuses the refined solvent after impurity removal, transforming what would be waste solvent into a reusable resource. The process discards only the removed impurities (water, iron, phosgene, hydrogen chloride, colored substances) while recovering the purified solvent for continued use in isocyanate production, reducing waste and operational costs.
2Manufacturing precision
If solvent is not refined, then production cost is lower, but product quality deteriorates due to high impurity levels affecting isocyanate quality
Solution Approach 1:
The patent implements a solvent recovery system where impurities are removed and the purified solvent is reused in production. This eliminates the need to constantly discard and replace solvent, reducing both waste generation and the costs associated with purchasing fresh solvent, while ensuring product quality through consistent purification.
Solution Approach 2:
The patent changes the chemical and physical parameters of the solvent by removing specific impurities (water content, iron content, phosgene content, hydrogen chloride content, color number) to transform low-quality solvent into high-quality reusable solvent, thereby improving product quality without proportionally increasing costs.
3Manufacturing precision
If multiple separate refining steps are used to remove each impurity, then purification is thorough, but processing time and cost increase
Solution Approach 1:
The patent merges multiple refining functions into an integrated sequential process where molecular sieves, activated carbon, and basic substances work in coordinated stages. This combining of multiple impurity removal functions into a unified process flow achieves thorough purification while maintaining efficient processing speed, avoiding the delays of multiple separate operations.
Solution Approach 2:
The patent performs preliminary removal of certain impurities (water and phosgene) in the first stage using molecular sieves and alkaline substances before proceeding to subsequent stages. This preliminary action prepares the solvent for more effective treatment in later stages, improving overall processing efficiency and reducing the time required for complete purification.
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 achieves rapid and efficient removal of impurities, reducing solvent loss, lowering production costs, and improving product quality by achieving low ppm levels of water, iron, and phosgene, and significantly reducing the Pt—Co color number, thus enabling the recycling of refined solvents.
Implementation Method 1
the content of water is lower than 100 ppm, the content of iron is lower than 5 ppm, the content of phosgene and hydrogen chloride is lower than 50 ppm
Implementation Method 2
the content of phosgene and hydrogen chloride is lower than 50 ppm
Implementation Method 3
the color number of Pt—Co is lower than 30
Data Source
AI summary
A solvent refining method for isocyanate prepared by the phosgene method and multistage absorbing towers used in same. Solvent to be refined which contains water, iron, and/or phosgene, hydrogen chloride and other materials with color is dealt by the present method and multistage absorbing towers, which can effectively prevent a drying agent from absorbing water and hardening, partial overheating in the tower and generating channeling. Meanwhile, the pressure drop is effectively lowered. In addition, the content of water is ≦50 ppm, the content of iron is ≦5 ppm, the content of phosgene and hydrogen chloride is ≦20 ppm, Pt—Co chroma is ≦20 in the refined solvent. Therefore, the refined solvent can be used as the solvent for preparing isocyanate in the phosgene method and remarkably improve an L color of isocyanate.