Radiant energy – Invisible radiant energy responsive electric signalling – Infrared responsive
Reexamination Certificate
2001-02-23
2003-04-29
Hannaher, Constantine (Department: 2878)
Radiant energy
Invisible radiant energy responsive electric signalling
Infrared responsive
C250S339020, C250S339070, C250S339120, C250S339130
Reexamination Certificate
active
06555820
ABSTRACT:
The invention relates to a photometric device for determining the gross calorific value of a test gas with a radiation source that generates a measuring beam and a spectral unit for dividing the measuring beam spectrally, with a test cell for the absorption of the test gas and a radiation receiver, which generates electric measuring signals in dependence on the measuring beam intensity and which is electrically connected with an evaluation unit that is equipped with at least one signal amplifier for amplification of the measuring signals, being arranged successively in the path of the measuring beam.
The invention furthermore relates to a method for the photometric determination of the gross calorific value of a test gas, in which a test cell that is filled with test gas is interspersed with the measuring beam, in which the measuring beam intensity that is permitted to penetrate by the test cell is measured with the help of a radiation receiver that generates measuring signals, in which the measuring signals are generated in relation to appropriate measuring signals without test gas in the test cell and spectral absorption values that are allocated to wave ranges are generated, and in which the allocated spectral absorption values are amplified with the help of at least one signal amplifier.
From U.S. Pat. No. 4,594,510 we know of a photometric device and a method for determining the gross calorific value of a test gas that is equipped both with a radiation source that generates a measuring beam and a spectral unit for dividing the measuring beam spectrally. A test cell for the intake of the test gas and a radiation receiver are arranged in the path of the measuring beam. With the radiation receiver, electric measuring signals can be generated in dependence on the measuring beam's intensity. The radiation receiver is electrically connected with an evaluation unit, which is equipped with at least one signal amplifier for the amplification of the measuring signals. In order to determine the gross calorific value of test gases whose material composition is not known, a calibration must first be performed during which the gross calorific values of calibrating gases, which contains at least as many material components as the test gas of unknown composition, are determined. Since the exact material composition of the test gas is inherently not known, in practice the calibration is generally performed with considerably more material components in the calibrating gases than would theoretically be required. For sufficient accuracy of the determination of the gross calorific value, it is furthermore necessary that when determining the proportionality factors for amplifying the measuring signals the spectral support areas are selected under the assumption of a certain, very likely accurate material composition of the test gas in order to record the material components adequately. In practice, it showed that sufficiently exact determinations of gross calorific values of test gases with different origins, and therefore with different material compositions, are very complex.
From DE-A-48 00 279 we know, with regard to the methods and devices for the determination of physical properties of samples in the short-range infrared spectral region, that a Fourier transform spectrometer is used.
In the report by H. M. Heise entitled “Infrarotspektrometrische Gasanalyse” (Infrared Spectrometric Gas Analysis) from the publication “Infrarotspektroskopie” (Infrared Spectroscopy), issued by H. Güunzler, Springer-Verlag, Heidelberg, Germany 1996, both dispersive and non-dispersive methods and spectrometers are revealed for performing these methods. While a dispersive device is equipped with a dispersive element such as a grating for the spatial splitting of infrared radiation in dependence on its wavelength, the revealed non-dispersive devices are, for example, equipped with a filter device for selecting a wavelength.
The gross calorific value of a gas creates a connection between the gas volume consumed during combustion and the amount of heat produced during the same and has achieved great importance for the control engineering of natural gas operated equipment, for example. Among gas mixtures such as natural gas, the gross calorific value is dependent upon the composition of the gas mixture. When purchasing natural gas, the gas volume is generally used as the basis for calculating the purchase price, with the gas gross calorific value affecting the purchase deal directly. Therefore, a volume-related purchase price assumes information about the gross calorific value of the gas intended to be purchased in order to justify a higher purchase price for gases with high gross calorific value over less expensive offers.
Due to the ongoing liberalization of the energy market, which is associated with the decline of regional energy monopolies, natural gases of various providers and composition will be fed through joint pipeline systems in the near future. The quality of the natural gas used by an end user from the pipeline system is therefore not known until it is consumed so that problems with regard to volume-related purchase price billing can occur. It would, therefore, be desirable to have a method and a device that would allow a determination process of the gross calorific value of a gas, for example when removing it from the pipeline system, that is quick and requires few metrology efforts. This way, calculating the cost on the amount of heat achieved with the gas is possible without the provider knowing the gas that is used or its exact composition.
Direct measurement of the gross calorific value of a gas is generally performed with calorimeters. For this, a specified volume of the test gas is burned, and the thermal energy released thereupon to a defined quantity of a coolant medium is measured by the temperature increase of the coolant medium. Suitable coolant media are for, example, air or water. While the high degree of inertia of the measurement proves disadvantageous for the quick recording of the gross calorific value of a natural gas, despite its high degree of accuracy when utilizing water, the disadvantages for utilizing air as a coolant medium lie especially in the complicated mechanics for setting a certain quantitative proportion of gas, combustion air and cooling air.
We furthermore know of cost-intensive calorimeters based on stoichiometric combustion, where a certain air requirement that is needed for the combustion of a defined quantity of the test gas is determined.
One method for determining the gross calorific value indirectly involves gas chromatography, in which the gas composition is determined quantitatively and the gross calorific value of the overall gas mixture is calculated based on knowledge of the gross calorific values of the individual components. The disadvantages of gas chromatography are the high procurement costs of the necessary devices as well as the personnel qualifications required for their operation.
Compared to gas chromatography, previously-known methods for determining the gross calorific value place fewer demands on the types of devices required to perform the method and have the benefit of a shorter measuring time, especially in comparison with the calorimetric method. For this method, an absorption spectrum of the natural gas is measured in the short-range or medium-range infrared spectral region, which is composed cumulatively of the sum of the individual spectra of the gas components present in the gas, and analyzed with the help of suitable spectral analysis methods. The percentage of absorbance of a component from the overall spectrum thus determined is equal to the concentration percentage of this component in the test gas. Thereafter, based on knowledge of the respective gross calorific value of the components, the gross calorific value of the entire gas mixture is calculated. The spectral analysis, however, is difficult due to heavy overlapping of the absorption bands of different gas components, often leads to inaccurate results and requires a
Kastner Joachim
Tacke Maurus
Flow Comp Systemtechnik GmbH
Stevens Davis Miller & Mosher LLP
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