Viscosity-Based Wobbe Index Determination for Hydrocarbon Gas Mixtures
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Solution Overview
Problem
Current methods for determining the energy content of hydrocarbon gas mixtures, such as natural gas and biogas, are complex and unreliable, particularly in measuring thermal conductivity, heat capacity, and viscosity, which are necessary for accurately calculating the Wobbe index and calorific value.
Innovation Solution
A method and apparatus that measure pressure- and temperature-dependent viscosity, temperature, and pressure values to calculate the Wobbe index or calorific value using correlation calculations, with optional inclusion of density and velocity of sound measurements, employing MEMS sensors and ultrasonic transducers to provide a simple, robust, and reliable determination of gas mixture properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thermal conductivity, heat capacity, and viscosity measurements are used to determine energy content, then measurement accuracy can be improved, but device complexity and measurement difficulty increase significantly
Solution Approach 1:
The patent extracts and focuses on measuring only the essential parameters (viscosity, temperature, pressure) that have the most significant impact on energy content determination. By eliminating the need to measure thermal conductivity and heat capacity, the device complexity is reduced while maintaining adequate measurement accuracy for practical applications.
Solution Approach 2:
The patent changes the measurement approach by using viscosity measurements at different temperatures to indirectly determine energy content, rather than directly measuring thermal conductivity and heat capacity. This parameter substitution simplifies the measuring arrangement while providing reliable energy content determination through correlation calculations.
2Reliability
If multiple measurement parameters (thermal conductivity, heat capacity, viscosity, density) are used to calculate Wobbe index and calorific value, then measurement reliability can be improved, but ease of operation and measurement speed decrease
Solution Approach 1:
The patent extracts and measures only the critical parameters (viscosity and temperature) that dominate the energy content determination. By removing the requirement to measure thermal conductivity, heat capacity, and density, the measurement process becomes simpler and faster while maintaining sufficient reliability for combustion control applications.
Solution Approach 2:
The patent applies partial action by measuring viscosity at multiple temperatures to obtain sufficient data for reliable energy content determination without measuring all possible parameters. This partial measurement approach achieves adequate reliability with reduced operational complexity.
3Measurement precision
If complex measurement methods involving thermal conductivity and heat capacity are employed, then measurement precision can be maintained, but loss of time and productivity decrease
Solution Approach 1:
The patent removes the time-consuming measurements of thermal conductivity and heat capacity, retaining only viscosity and temperature measurements. This extraction of essential parameters significantly reduces measurement time while maintaining adequate precision for combustion control through correlation-based energy content determination.
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
This approach allows for accurate and efficient characterization of hydrocarbon gas mixtures, enabling precise control of fuel gas supply and energy consumption with an error margin of less than 3% for Wobbe index and 1.5% for inert gas fraction, improving burner control and energy management.
Implementation Method 1
determining a pressure- and temperature dependent viscosity measured value, an associated measured value of temperature and an associated pressure measured value of the flowing gas mixture
Implementation Method 2
optional inclusion of density and velocity of sound measurements, employing MEMS sensors and ultrasonic transducers
Data Source
AI summary
A method for determining properties of a hydrocarbon containing gas mixture, especially natural gas or biogas, comprising: allowing the gas mixture to flow through a measuring arrangement; determining a pressure- and temperature dependent viscosity measured value, an associated measured value of temperature and an associated pressure measured value of the flowing gas mixture; ascertaining a first value of a first variable, which characterizes the energy content of the flowing gas mixture, based on viscosity measured value, the associated measured value of temperature, and the associated pressure measured value, wherein the first variable characterizing the energy content is the Wobbe index or the calorific value of the flowing gas mixture, wherein the Wobbe index is preferable.