Methane Number Calculation Using Inert Gas Correction
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Solution Overview
Problem
Natural gas compositions vary, leading to uncertainties in heat generation by inert gas components like nitrogen and carbon dioxide, resulting in calculation errors in methane number due to unquantified concentration ratios, which existing methods fail to accurately account for.
Innovation Solution
A methane number calculation method that measures refractive index and sonic speed, calculates converted calorific values, and uses concentration measurements of nitrogen and carbon dioxide to correct for inert gases, employing a specific relational expression to determine the methane number based on basic calorific value, concentration of inert gases, and pre-established correlations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If gas composition measurement is performed to calculate methane number, then calculation accuracy is improved, but measurement complexity and time consumption increase
Solution Approach 1:
The invention changes the measurement parameters from direct gas composition analysis to physical property measurements (refractive index, sonic speed, thermal conductivity). These physical parameters correlate with methane number and can be measured more simply and quickly, resolving the contradiction between accuracy and complexity.
Solution Approach 2:
The invention replaces the mechanical/gas chromatographic composition analysis system with physical measurement systems that detect refractive index, sonic speed, and thermal conductivity. This substitution maintains measurement accuracy while significantly reducing device complexity and measurement time.
2Adaptability or versatility
If gas composition varies, then fuel properties change, but existing calculation methods produce errors due to unquantified inert gas components
Solution Approach 1:
The invention uses physical property measurements as feedback to continuously monitor and determine methane number despite gas composition variations. The measured physical parameters (refractive index, sonic speed, thermal conductivity) provide real-time feedback that accounts for changes in inert gas content, maintaining calculation reliability.
Solution Approach 2:
The invention establishes pre-correction relationships between physical properties and methane number that account for inert gas effects in advance. By incorporating correction factors for nitrogen and carbon dioxide content based on physical measurements, the system prepares for composition variations before they affect calculations, ensuring reliable results.
Data Source
Figure 1~2
AI summary
The present invention has as its object the provision of a methane number calculation method that allows for readily acquiring a methane number of a natural gas, which is a sample gas to be measured, with acceptable reliability irrespective of the gas composition, and as another object the provision of a methane number measurement device that is capable of monitoring the fuel property of a natural gas to be used as a fuel gas. The present invention includes: acquiring in advance a particular relational expression between the methane number and the basic calorific value of a plurality of types of reference gases, each formed of a natural gas and each having a different methane number value; measuring the basic calorific value of a natural gas, which is a sample gas, as well as the concentration of the nitrogen gas and the concentration of the carbon dioxide gas, both gases being contained in the sample gas; and calculating the methane number of the sample gas from the value of the basic calorific value of the sample gas, the value of the concentration of the nitrogen gas and the value of the concentration of the carbon dioxide gas, and the particular relational expression.