Isocyanate Distillation Vacuum Control to Prevent Compressor Cavitation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing processes using liquid ring compressors for isocyanate distillation face cavitation issues, particularly at low suction pressures, which are exacerbated by volatile substances like phosgene, leading to mechanical damage and inefficiencies.
Innovation Solution
Employing chlorobenzene, dichlorobenzene, xylene, or chlorotoluene as the operating liquid for liquid ring compressors, maintaining a suction pressure of 10 to 200 mbar(a) and an operating temperature of −17° C. to +15° C., with an AC value of less than 35,000 ppm, to prevent cavitation and purify isocyanates effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If liquid ring compressors are used to generate vacuum at low suction pressures (10 to 200 mbar), then vacuum generation for distillation is achieved, but cavitation occurs due to volatile substances like phosgene, leading to mechanical damage and inefficiencies
Solution Approach 1:
The patent applies parameter changes by controlling the operating temperature of the liquid ring compressor within a specific range (−17° C. to +15° C.) and maintaining the operating liquid's AC value below 35,000 ppm. This temperature control reduces the vapor pressure of the operating liquid, preventing cavitation while maintaining effective vacuum generation at 10 to 200 mbar suction pressure
Solution Approach 2:
The patent uses an intermediary approach by introducing a carefully selected operating liquid (with specific AC value constraints) that acts as a mediator between the volatile isocyanate components and the compressor mechanics. The operating liquid absorbs volatile substances while maintaining stable operation, preventing direct contact between cavitation-causing vapors and the compressor's mechanical parts
2Reliability
If the operating temperature of the liquid ring compressor is reduced to prevent cavitation, then cavitation is suppressed, but the energy consumption increases and the operating range is limited by the solidification temperature of the operating liquid
Solution Approach 1:
The patent optimizes the operating temperature parameter within the range of −17° C. to +15° C., finding the optimal balance between cavitation prevention and energy consumption. This parameter optimization allows the system to operate efficiently without excessive cooling costs while preventing cavitation, avoiding the need for temperatures below the solidification point of the operating liquid
3Productivity
If the suction pressure is reduced to improve distillation efficiency, then distillation effectiveness increases, but cavitation is exacerbated leading to mechanical damage
Solution Approach 1:
The patent changes the operating parameters by controlling the operating temperature and AC value of the operating liquid, which allows the compressor to maintain mechanical integrity even at low suction pressures of 10 to 200 mbar. The temperature control reduces vapor pressure effects, enabling efficient distillation without compromising compressor strength
Solution Approach 2:
The patent applies beforehand cushioning by pre-controlling the operating liquid's temperature and composition (AC value < 35,000 ppm) before the distillation process begins. This preparatory measure creates a protective environment that cushions against cavitation forces, allowing the system to operate at low pressures needed for efficient distillation without mechanical damage
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 process significantly reduces cavitation, allowing safe and efficient vacuum generation for isocyanate distillation, minimizing mechanical damage and ensuring high-purity isocyanate production.
Implementation Method 1
the operating temperature of the at least one liquid ring compressor is −17° C. to +15° C.
Implementation Method 2
after condensation as a liquid sidestream
Implementation Method 3
distillative purification of a crude isocyanate obtained by phosgenation of the corresponding amine in a distillation apparatus under vacuum
Implementation Method 4
the pressure p on the suction side of the at least one liquid ring compressor is 10 to 200 mbar(a)
Data Source
AI summary
The present invention relates to a process for distillative purification of a crude isocyanate obtained by phosgenation of the corresponding amine in a distillation apparatus under vacuum to obtain the corresponding isocyanate, characterized in that at least one liquid ring compressor is used to generate the vacuum in the distillation apparatus, a particular operating liquid is used for the at least one liquid ring compressor, the pressure p on the suction side of the at least one liquid ring compressor is 10 to 200 mbar(a), the operating temperature of the at least one liquid ring compressor is −17° C. to +15° C. and the operating liquid at the exit from the at least one liquid ring compressor has an AC value of less than 35 000 ppm, to a corresponding use of at least one liquid ring compressor for generating a vacuum in an apparatus for distillation of a crude isocyanate and to a corresponding process for operating a liquid ring compressor for providing the vacuum for distillative purification of an isocyanate obtained by phosgenation of the corresponding amine in a distillation apparatus to obtain the corresponding isocyanate.