Nanoparticle Counting with Catalytic Gas Treatment
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Solution Overview
Problem
Current nanoparticle counting technologies, such as Condensation Particle Counters, face challenges in distinguishing between solid particles and volatile or nucleating species in exhaust gas streams from internal combustion engines, leading to inaccurate counting due to interference from hydrocarbons and sulphur compounds.
Innovation Solution
A gas treatment stage comprising an oxidation catalyst and an absorber, supported on a high-open-area metal flow-through monolith, is used to preprocess the exhaust gas before nanoparticle counting, effectively oxidizing hydrocarbons and absorbing gaseous sulphur compounds and nitrogen oxides to prevent nucleation and improve counting accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If a Condensation Particle Counter is used to count nanoparticles in exhaust gas, then nanoparticle detection capability is improved, but measurement precision deteriorates due to interference from hydrocarbons and sulphur compounds that act as pseudo-nuclei
Solution Approach 1:
The patent applies preliminary action by treating the exhaust gas stream with a catalytic stripper before particle counting. The catalytic stripper pre-oxidizes hydrocarbons and converts sulphur compounds to sulphate aerosols, removing interfering species before they can act as pseudo-nuclei in the condensation particle counter. This pre-treatment ensures that only true solid particles remain to be counted, resolving the measurement precision issue while maintaining nanoparticle detection capability.
Solution Approach 2:
The patent introduces a catalytic stripper as an intermediary component between the exhaust source and the particle counter. This intermediary device performs chemical transformations on the gas stream, converting interfering hydrocarbons and sulphur compounds into forms that do not interfere with particle counting. The catalytic stripper acts as a mediator that protects the measurement system from harmful chemical interferences while allowing genuine particles to pass through unchanged.
2Measurement precision
If a catalytic stripper is used to remove interfering species, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent merges the catalytic stripper function with the particle counting system by integrating it into the existing exhaust analysis apparatus. The catalytic stripper is positioned in series with the dilution system and particle counter, creating a unified flow path. This integration approach minimizes additional complexity while achieving the desired measurement precision improvement.
3Quantity of substance
If high dilution is used in the counting technique, then particle concentration is reduced for accurate measurement, but interference from volatile species is exacerbated
Solution Approach 1:
The patent applies preliminary action by performing catalytic treatment of the gas stream before dilution and particle counting. The catalytic stripper removes interfering volatile species through oxidation and conversion to sulphate aerosols prior to the dilution step. This ensures that when high dilution is applied to reduce particle concentration for accurate measurement, the interfering volatile species have already been eliminated and cannot cause false positive readings.
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 solution significantly enhances the reliability of nanoparticle counting by reducing interference from volatile species, allowing for accurate differentiation of solid particles and achieving high penetration rates for 10 nm particles, even at high dilutions, and maintaining effectiveness over prolonged use without substantial particle diffusion losses.
Implementation Method 1
A gas treatment stage comprising an oxidation catalyst and an absorber effective to absorb gaseous sulphur compounds
Implementation Method 2
an absorber effective to absorb gaseous sulphur compounds, desirably nitrogen oxides and other acid vapour species that when cooled could nucleate to form particles
Implementation Method 3
supported on a metal flow-through monolith of no more than 400 cells/sq in and having an open area of not less than 80%
Implementation Method 4
Instruments known as Condensation Particle Counters (CPC) are commercially available, which pass the particle-containing gas through a supersaturated vapour
Implementation Method 5
so that the particles act as nuclei for vapour condensation. Accordingly, under suitable conditions, nanoparticles can grow to sizes of up to 10-12 um
Data Source
AI summary
An improved instrument for counting nanoparticles suspended in a gas, particularly in a combustion gas, incorporates a counter device such as a Condensation Particle Counter, incorporates a pre-treatment stage to remove substances which can cause nucleation and false results, comprising a flow through monolith carrying an oxidation catalyst and an absorber, wherein the monolith has a call density of no more than 400 cells per square inch and an open area of at least 80%.