Halogen Gas Scrubbing with Warm Water
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Solution Overview
Problem
Current methods for scrubbing halogen-containing exhaust gases, particularly fluorine, in the semiconductor industry are inefficient and generate toxic by-products, failing to meet stringent disposal regulations due to slow reaction rates and high emission rates.
Innovation Solution
A method involving the use of warm water at temperatures above 30°C to enhance the reaction of fluorine with water, forming hydrogen fluoride, and a two-stage scrubbing process with a hot and cold wash chamber to effectively remove halogens and prevent toxic by-product formation, along with air dilution to manage pyrophoric gases like silane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fluorine is scrubbed with ambient temperature water, then the reaction forms hydrogen fluoride, but the reaction rate is slow and emission rate from the wet scrubber is high
Solution Approach 1:
The patent applies parameter changes by heating the water to temperatures between 30-100°C to increase the reaction rate between fluorine and water. This thermal energy input accelerates the chemical reaction F2 + H2O → 2HF + 1/2O2, thereby improving fluorine removal efficiency while reducing emission rates from the scrubber.
2Productivity
If sodium hydroxide or potassium hydroxide is dosed to improve scrubbing efficiency, then fluorine abatement increases, but conversion to toxic oxygen difluoride by-product increases
Solution Approach 1:
The patent converts the potentially harmful effect of base dosing (which causes toxic OF2 formation) into a beneficial approach by using heated water instead. The thermal energy enables direct reaction of fluorine with water to form safe hydrogen fluoride, eliminating the need for base additives and their associated toxic by-products while maintaining effective fluorine abatement.
3Productivity
If ammonia is used as additive to reduce fluorine content, then fluorine removal improves, but ammonium fluoride fine fume emission increases
Solution Approach 1:
The patent eliminates the harmful effect of ammonium fluoride fine fume emission by replacing ammonia-based scrubbing with heated water scrubbing. The thermal energy enables direct fluorine reaction with water to form soluble hydrogen fluoride, avoiding the formation of particulate ammonium fluoride while maintaining effective fluorine removal.
4Productivity
If water temperature is increased to improve reaction rate, then fluorine removal efficiency improves, but vapour pressure of fluorine increases reducing dissolution rate
Solution Approach 1:
The patent resolves this contradiction by changing the reaction mechanism through parameter changes. Instead of relying on physical dissolution (which is suppressed at high temperatures), the heated water enables direct chemical reaction F2 + H2O → 2HF + 1/2O2. This chemical pathway becomes dominant at temperatures above 30°C, overcoming the reduced dissolution rate and improving overall fluorine removal efficiency.
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 significantly improves fluorine removal efficiency, reduces toxic by-product formation, and ensures safe oxidation of silane, meeting stringent disposal regulations while maintaining scrubber capacity.
Implementation Method 1
reaction of the F2 with water according to the equation: F2+H2O→2HF+1⁄2O2 occurs readily
Implementation Method 2
at the temperatures of above 30° C. used in accordance with the invention, reaction of the F2 with water according to the equation: F2+H2O→2HF+1⁄2O2 occurs readily
Data Source
AI summary
A method for scrubbing a halogen-containing gas, comprises contacting the halogen-containing gas with water at a temperature of at least 30° C., the gas optionally subsequently being subjected to a further treatment step comprising contacting it with water at a temperature of less than 30° C. and/or a gas dilution step. An apparatus for carrying out the method comprises a hot wash chamber (6) and optionally a cold wash chamber (7) and/or a gas dilution device (13).