NMHC Analysis Apparatus Using Molecular Sieve Separation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for detecting non-methane total hydrocarbons (NMHC) in the atmosphere face challenges such as interference from CO2 and water, errors due to direct subtraction when methane concentration approaches total hydrocarbons concentration, and require intricate control of oxidation and reduction rates, leading to inaccurate and unstable results.
Innovation Solution
A non-methane total hydrocarbons analysis apparatus and method utilizing a six-pass valve, multi-pass valve, molecular sieves, and a hydrogen flame ionization detector, where the gas under test is passed through molecular sieves to remove NMHC, and zero-grade compressed air is used to create a baseline, eliminating the need for oxidation and reduction processes and reducing errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If oxidation and reduction processes are used to convert NMHC to CH4 for detection, then the measurement can be performed with a CH4-oriented FID detector, but the measurement process is subject to interference from CO2 and water and requires intricate control of oxidation and reduction rates
Solution Approach 1:
The patent extracts and removes non-methane hydrocarbons from the gas sample using a molecular sieve column, separating them from methane before detection. This allows direct measurement of methane without requiring oxidation and reduction processes, thereby eliminating the need for intricate control of conversion rates and avoiding interference from CO2 and water in the conversion process
Solution Approach 2:
The patent introduces a molecular sieve column as an intermediary component between the sample inlet and the detector. This molecular sieve selectively adsorbs non-methane hydrocarbons while allowing methane to pass through, serving as a mediator that separates the two components before detection and eliminates the need for complex chemical conversion processes
2Productivity
If direct subtraction method is used when methane concentration approaches total hydrocarbons concentration, then the calculation can be performed, but errors increase significantly
Solution Approach 1:
The patent performs preliminary separation of non-methane hydrocarbons from methane using a molecular sieve column before detection. By removing non-methane hydrocarbons in advance, the system directly measures methane concentration without needing to perform subtraction calculations, thereby eliminating error accumulation while maintaining fast measurement speed
3Reliability
If high temperature conversion furnace is used to destroy non-methane total hydrocarbons, then only residual methane undergoes the test, but the test result depends greatly on the degree of conversion and destruction
Solution Approach 1:
The patent replaces the high-temperature mechanical conversion furnace with a molecular sieve column operating at lower temperatures. The molecular sieve uses selective adsorption properties to separate non-methane hydrocarbons from methane without requiring high-temperature conversion, thereby improving reliability by eliminating dependence on conversion degree while reducing the temperature requirement
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 apparatus achieves accurate and stable detection of NMHC with a measurement limit of less than 0.1 mg/m3, enhancing accuracy and reliability by avoiding interference from CO2 and water and eliminating the need for complex rate control, while extending the service life of molecular sieves through reverse decomposition.
Implementation Method 1
the gas under test is passed through molecular sieves to remove NMHC
Implementation Method 2
hydrogen flame ionization detector
Data Source
AI summary
A non-methane total hydrocarbons analysis apparatus and method are introduced. The analysis apparatus includes a six-pass valve, quantification ring, first stored gas pipe, second stored gas pipe, multi-pass valve, molecular sieve filling pipe, first air source, and detector. The six-pass valve and the multi-pass valve are configured to have a load status bit. A gas under test passes through the molecular sieve to remove non-methane total hydrocarbons such that the treated gas functions as a background gas for filling the first stored gas pipe and the second stored gas pipe. The six-pass valve and the multi-pass valve are configured to have an entered sample status bit such that zero-grade compressed air drives the gas inside the second stored gas pipe, quantification ring, and first stored gas pipe to enter the detector. The background gas inside the second stored gas pipe and the second stored gas pipe provides a baseline.