Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Chemical analysis
Reexamination Certificate
2003-06-12
2004-06-22
Bui, Bryan (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Chemical analysis
C702S023000, C702S024000
Reexamination Certificate
active
06754592
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the field of measuring constituent components of gas mixtures, and more particularly, to measuring the concentration of nitrogen in a gas mixture.
DESCRIPTION OF THE RELATED ART
U.S. patent application Ser. No. 09/550,431, entitled “System and Method to Determine Thermophysical Properties of a Multi-Component Gas” and U.S. patent application Ser. No. 10/237,492 entitled “A System and Method to Determine Thermophysical Properties of a Multi-Component Gas at Arbitrary Temperature and Pressure” describe systems and methods for measuring heating value and energy flow rates of natural gas. An advantage of these methods is that they do not require a full composition assay. The methods correlate the speed of sound in the gas to the heating value of the gas, which depends on the gas composition, flow temperature, and pressure. The calculations for determining the heating value require known values for the diluent concentrations in the gas, such as carbon dioxide and nitrogen. However, there is no need for other constituent values to be known.
The concentration of nitrogen in a natural gas mixture is difficult to measure directly. Nitrogen has low infrared absorption characteristics, which makes infrared sensing methods difficult. Also, it is chemically inert, which makes electrochemical sensing methods difficult.
Yet, the amount of nitrogen in a gas mixture does affect heating value. Experimentation has indicated that a plus or minus shift of 0.075 mole % in nitrogen concentration will produce a plus or minus shift of 1.0 BTU/SCF in standard volumetric heating value. Thus, to make use of the above-described methods for relating speed of sound and diluent measurements to heating values, some means for measuring nitrogen content is important.
This is but one example of a need for measuring nitrogen content in a natural gas—there may be other applications in which measurement of nitrogen content may be useful. In the absence of satisfactory sensors for direct measurement, indirect measurement methods have been considered.
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U.S. Pending Continuation-in-Part patent application Ser. No. 10/401,206 entitled “Indirect Measurement of Nitrogen in a Multi-Component Gas by Measuring the Speed of Sound at Two States of the Gas”, filed by Thomas B. Morrow et al., filed Mar. 27, 2003.
U.S. Pending Continuation-in-Part patent application Ser. No. 10/237,492 entitled “A System and Method to Determine Thermophysical Properties of a Multi-Component Gas at Arbitrary Temperature and Pressure”, filed by Thomas B. Morrow et al., filed Sep. 9, 2002.
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Behring, II Kendricks A.
Morrow Thomas B.
Baker & Botts L.L.P.
Bui Bryan
Southwest Research Institute
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