Nitrous Oxide Gas Treatment via UV Photodissociation
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Solution Overview
Problem
Current methods for treating nitrous oxide (N2O) gases in semiconductor fabs are costly and inefficient, as they often require high-energy processes that can lead to secondary pollution and are ineffective due to the stability of N2O, which does not undergo complete cracking without specialized treatment, and existing patents fail to consider the absorption of ultraviolet by N2O and the timing of ozone reactions.
Innovation Solution
A gas treatment device with multiple chambers uses specific ultraviolet sources and energy supply systems to produce excited-state ionized gases and reactants, which react efficiently in a turbulence system to convert N2O into nitrogen dioxide (NO2), utilizing ultraviolet wavelengths of 160-210 nm and 230-280 nm to crack N2O and ozone, respectively, and a scrubbing system with water to dissolve NO2, enhancing reaction efficiency and cost-effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If combustion, plasma cracking, or electrothermy is used to treat N2O, then N2O can be eliminated, but high costs in fuel, electricity, and electrode dissipation are incurred
Solution Approach 1:
The treatment process is divided into separate stages: N2O cracking in a first chamber followed by ozone treatment in a second chamber. This segmentation allows each stage to be optimized independently, using UV irradiation at specific wavelengths (160-210 nm for N2O cracking, 230-280 nm for ozone generation) rather than high-energy combustion or plasma methods, thereby reducing energy and cost requirements while maintaining treatment effectiveness.
Solution Approach 2:
The invention changes the parameter of UV wavelength to specifically target N2O absorption (160-210 nm range) rather than using broad-spectrum UV or high-temperature methods. This parameter optimization enables selective and efficient N2O cracking at lower energy input, avoiding the high fuel and electricity costs associated with combustion and plasma cracking.
2Reliability
If combustion, plasma cracking, or electrothermy is carried out at high temperature, then N2O can be cracked, but N2 is cracked into NOx again, causing secondary pollution
Solution Approach 1:
The invention replaces high-temperature thermal cracking with UV photochemical cracking. By using UV irradiation at 160-210 nm, N2O is cracked into N and O atoms through photochemical reactions rather than thermal decomposition. This substitution eliminates the high temperatures that would otherwise crack N2 into NOx, thereby preventing secondary pollution while achieving complete N2O conversion.
Solution Approach 2:
The invention performs preliminary cracking of N2O into N atoms before introducing ozone. The N atoms generated from UV cracking of N2O then react with subsequently introduced ozone to form NO, which is further oxidized to NO2. This preliminary action ensures complete N2O decomposition at low temperatures, preventing any reverse reaction that would form NOx from N2.
3Reliability
If ozone of high concentration (1.5 moles) is used for oxidation, then N2O and NOx can be treated, but cost-effectiveness deteriorates
Solution Approach 1:
The invention changes the parameter of ozone concentration from high (1.5 moles) to low (0.01-0.1 moles) by optimizing the UV wavelength (230-280 nm) for efficient ozone generation. The lower ozone concentration is sufficient because the UV irradiation conditions are precisely controlled to maximize reaction efficiency, thereby reducing costs while maintaining effective oxidation of N2O and NOx.
Solution Approach 2:
The invention uses UV irradiation at specific wavelengths to generate the necessary reactive species (ozone and excited oxygen atoms) in-situ within the reaction chamber, rather than introducing pre-formed high-concentration ozone. This 'copying' of the oxidation function through photochemical generation achieves the same oxidation effectiveness at much lower material cost.
4Productivity
If full-band ultraviolet lamps are used to decompose smelly gases, then gases can be treated, but the lamps cannot endure strong draft or high concentration of smelly gas
Solution Approach 1:
The invention applies local quality by using UV lamps with specific wavelength ranges (160-210 nm for N2O cracking, 230-280 nm for ozone generation) rather than full-band UV. These targeted wavelengths are optimally absorbed by N2O and ozone molecules, enabling efficient decomposition at lower intensities that do not overwhelm the lamps, thus improving both productivity and lamp durability under high gas concentration conditions.
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 a destruction and removal efficiency (DRE) of 6%-8% for N2O, improving upon prior art by ensuring complete conversion and reducing environmental pollution, while being cost-effective and addressing the stability and reactivity challenges of N2O.
Implementation Method 1
a first ultraviolet source (111) with a wavelength of 160-210 nm is provided such that the ultraviolet at this wavelength cracks nitrous oxide (N2O) of the gas into NO and N
Implementation Method 2
the second ultraviolet source (212) has a wavelength of 230-280 nm so as to crack the ozone
Implementation Method 3
the excited-state ionized gas and the excited-state oxygen atom are then delivered to the third chamber (30) to undergo a reaction so that the resultant gas in the third chamber (30) comprises nitrogen dioxide (NO2)
Data Source
AI summary
Method of treating gas and gas treatment device, the gas treatment device comprising: a first chamber, comprising a first inlet, a first outlet and a first energy supply system, allowing the gas to enter the first chamber through the first inlet; a second chamber comprising a second outlet and a second energy supply system; a third chamber comprising a third inlet in communication with the first outlet and the second outlet; and a fourth chamber comprising a fourth inlet and a scrubbing system containing a solvent comprising water molecules (H2O), wherein the third outlet of the third chamber is in communication with the fourth inlet of the fourth chamber.