Radiant energy – Invisible radiant energy responsive electric signalling – Infrared responsive
Patent
1986-01-27
1987-11-17
Fields, Carolyn E.
Radiant energy
Invisible radiant energy responsive electric signalling
Infrared responsive
250301, 250343, G01N 2135
Patent
active
047076038
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention concerns a procedure for measuring contents of hydrocarbons in liquids containing such, in which liquids the main component is water and which may in addition to hydrocarbons contain salts (seawater) or other dissolved chemicals (industrial emission waters). In the procedure, the liquid to be measured is conducted into a transparent measuring cuvette which is irradiated with IR radiation from a radiation source, and the contact of the hydrocarbon present in the liquid is determined on the basis of the attenuation caused by the hydrocarbon in the 3.4 to 3.5 .mu.m wavelength range.
The IR absorption method is commonly used, for instance, in laboratory determinations of the oil content of waters. An advantage of the procedure is its universal applicability based on the fact that the absorptions of different oil types at 3.4 .mu.m wavelength are very close to one another. Because of the strong absorption of water, it is however necessary, in laboratory measurements, to concentrate the sample before it is measured, this being accomplished by extracting the oil in carbon tetrachloride and separating from the water the extract thus obtained. As a consequence, the procedure is slow and introduces a risk of toxic emissions.
In a procedure known in the prior art, the absorption of water is compensated for by forming, from the sample proper, a reference sample from which the oil has been removed. When these two are pumped through the cuvette in alternation, the attenuation due to the oil can be measured. In order to achieve sufficient measuring accuracy, the differential temperature between the samples is equalized prior to the cuvette with the aid of a heat exchanger, and for eliminating the differential pressure, they are always stopped in the cuvette for the duration of measurement. To produce the reference sample, an ultrafilter is employed, which removes, on the side of the oil, any solid particles which may occur therein. The attenuation caused by these is compensated by using, in addition to the measuring wavelength, another wavelength at which the oil effects no absorption. The procedure combines the accuracy and reliability of the laboratory method and the advantage of high measuring speed. Its hydraulics part is, however, still complicated, comprising an ultrafilter, a pipe line for the reference sample, pumping means for the reference liquid and a heat exchanger.
SUMMARY OF THE INVENTION
The object of the invention is to provide an improvement in the measuring methods known in the art. A more detailed aim of the invention is to provide a procedure in which the sample processing involved in the measuring procedure known in the art can be substantially simplified. The other aims of the invention, and the advantages to be gained therewith, are readable in the disclosure of the invention.
The aims of the invention are achieved by means of a procedure which is mainly characterized in that the infra-red absorption spectrum of the liquid containing hydrocarbons is measured in a preselected wavelength range of relatively great width, the width of this wavelength range exceeding that of the range in which the absorption of the hydrocarbon under investigation has an effect, and that the proper absorption of the liquid, in the hydrocarbon absorption range, is determined by calculation with the aid of the spectral part outside said range, whereby the absorption of the hydrocarbon in the liquid is obtained on the basis of the difference between said absorptions.
By the procedure of the invention, numerous remarkable advantages are gained. The procedure of the invention allows the hydraulics component required in the measurement to be substantially simplified. Hereby, it is possible to omit, for instance, the ultrafilter inserted in the liquid flow line, the reference liquid pipe line going to the measuring cuvette, the reference liquid pumping means required in said pipe line, and the heat exchanger.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is described in
REFERENCES:
patent: 3732017 (1973-05-01), Welber
patent: 3783284 (1974-01-01), McCormack
patent: 3795810 (1974-03-01), Conley et al.
patent: 4045671 (1977-08-01), Dille et al.
patent: 4103162 (1978-07-01), Iwamoto et al.
patent: 4587427 (1986-05-01), Talbot et al.
Jaatinen Jarl
Miemela Pentti
Fields Carolyn E.
Sahkoliikkeiden Oy
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