Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Chemical analysis
Reexamination Certificate
1999-09-24
2001-04-10
Shah, Kamini (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Chemical analysis
C137S101310, C700S282000, C073S861280
Reexamination Certificate
active
06216091
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to ultrasonic measurement systems, for example systems such as are used to determine properties of a fluid flowing within a conduit. These systems operate by creating an ultrasonic signal burst, and transmitting the burst into the fluid and receiving the signal after it has traveled along a path through the fluid. Two or more related paths may be used (for example upstream and downstream paths, orthogonal paths, or clockwise and counterclockwise paths) to develop signals indicative of sound speed, or of directional differences in sound speed that depend on flow components. Generally the property of the fluid is determined as a function of the transit times of these signals.
Often it is desired to obtain from the signals useful information such as the mass flow rate, or the caloric value of the material flowing in the conduit. In that case further information is necessary and this often requires the system to operate in controlled environments where the user enters extrinsic data via a keyboard to specify the known components of material in the flow so that the signal processor can perform its calculations with the corresponding values of physical parameters for those materials. However, such operation is only possible in a limited number of well controlled circumstances. In some plants, and especially in situations where flue gases are present, the composition of the gas stream will vary over time. It may also be subject to certain fast fluctuations, as occurs in flare gases or certain hydrocarbon processing environments. When the gases present under these measurement conditions are used in bulk processes involving hydrocarbons, the monetary value of material flowing in the conduit can be substantial, and it may be necessary to know its volume and composition with relatively high accuracy for processing, control or environmental reasons.
It would therefore be desirable to extend the useful operating conditions of ultrasonic measurement systems to include flows with varying but unknown composition of hydrocarbon components.
It would also be desirable to provide an ultrasonic measurement system which determines the molecular weight of a component of a fluid flow.
SUMMARY OF THE INVENTION
These and other useful ends are achieved in accordance with a basic embodiment of the invention wherein an ultrasonic transducer propagates a signal through a fluid and determines the average molecular weight of an unknown mixture of hydrocarbons present in the fluid. A processor receives sound speed, pressure and temperature information, and performs an iterative procedure to match a hypothetical composition or average molecular weight to the observed sound speed. In accordance with a preferred aspect of the present invention, the microprocessor stores a number of tables in which the critical pressure, compressibility, acentric factor and heat capacity of hydrocarbon gas have been tabulated as functions of molecular weight. The microprocessor executes a programmed set of calculations for determining the sound speed of a mixture of gases by using the virial equations, determining the virial coefficients from these four properties of the gas.
The processor includes a plurality of stored tables of critical constants of hydrocarbon mixtures as a function of the average molecular weight of the mixture, and is configured to iteratively set a hypothetical molecular weight, determine the corresponding critical properties, and compute a predicted sound speed. If the two speeds differ, a new weight is set and the procedure is repeated until the predicted sound speed matches the measured speed, indicating that the current estimate is the correct average molecular weight. Once the processor has determined the critical constants from its stored tables, it applies the virial equation of state and mixing rules to determine the predicted sound speed for each hypothetical molecular weight of an unknown mixture of hydrocarbons present, together with one or more known inorganic components, in the fluid material. The processor may be configured for user input of known quantities of one or more gases such as nitrogen, hydrogen, sulfur dioxide, carbon dioxide or other inorganic or non-hydrocarbon gases present in the conduit. Alternatively, all or some of this data may be provided in an automated manner from suitable signals, settings or measurements from upstream conduits, valves or measurement and control instrumentation. The hydrocarbon analysis may be used to detect leaky valves or upstream process occurrences, or to evaluate gases in feed loops or outflow conduits.
REFERENCES:
patent: 4856321 (1989-08-01), Smalling et al.
patent: WO9313414 (1993-07-01), None
Nutter & McClennen & Fish LLP
Panametrics, Inc.
Shah Kamini
LandOfFree
Ultrasonic measurement system with molecular weight... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Ultrasonic measurement system with molecular weight..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ultrasonic measurement system with molecular weight... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2474210