Isocyanate Quench Temperature Control to Prevent Nozzle Blockages
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing processes for preparing isocyanates by reacting amines with phosgene in the gas phase face issues with condensation or desublimation of reaction gases at the quench medium addition points, leading to reduced selectivity and nozzle blockages due to premature condensation or desublimation, which requires frequent cleaning of the quench apparatus.
Innovation Solution
The process involves maintaining the quench medium temperature above the condensation or desublimation temperature of the reaction gas to prevent condensation or desublimation, ensuring the quench medium is added at a temperature that prevents reaction gas from precipitating at the addition points and on the quench space walls, thereby preventing blockages and extending cleaning intervals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the quench medium is added at a temperature below the condensation point of the reaction gas, then the cooling efficiency is improved, but condensation or desublimation occurs at the addition points causing nozzle blockages and reduced selectivity
Solution Approach 1:
The patent changes the temperature parameter of the quench medium from below to above the condensation point of the reaction gas. This parameter change prevents condensation and desublimation at the addition points, eliminating nozzle blockages and maintaining process selectivity while still achieving effective cooling through the quenching process
2Reliability
If the quench medium temperature is increased above the condensation temperature of the reaction gas, then condensation and nozzle blockages are prevented, but the cooling efficiency is reduced
Solution Approach 1:
The patent utilizes the phase transition of the quench medium (from liquid to vapor) as it contacts the hot reaction gas. The quench medium evaporates upon contact, absorbing large amounts of latent heat and providing efficient cooling even at temperatures above the reaction gas condensation point, thus resolving the contradiction between cooling efficiency and preventing condensation
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 prevents premature condensation or desublimation, maintaining process selectivity and reducing the frequency of cleaning the quench apparatus by ensuring the quench medium is added at a temperature that prevents reaction gas from precipitating, thus maintaining process efficiency and reducing maintenance needs.
Implementation Method 1
The quench medium which is used for cooling has a temperature which is in the range from 50 to 200° C. The liquid stream sprayed in cools the reaction gas rapidly to temperatures generally between 100 and 200° C.
Implementation Method 2
the walls of the quench apparatus, especially close to the supply of the quench medium, have temperatures below the condensation or desublimation point of the reaction gas. For this reason, parts of the reaction gas may condense out or desublime as early as at these points.
Data Source
AI summary
The invention relates to a process for preparing isocyanates by reacting the corresponding amines with phosgene in the gas phase, if appropriate in the presence of an inert medium, in which the amine and the phosgene are first mixed and converted to the isocyanate in a reactor, and in which a reaction gas which comprises isocyanate and hydrogen chloride and leaves the reactor is cooled in a quench space of a quench by adding a quench medium. The quench medium on addition to the quench space has a temperature above the condensation temperature or the desublimation temperature of the reaction gas.