Measuring and testing – Liquid analysis or analysis of the suspension of solids in a... – Content or effect of a constituent of a liquid mixture
Reexamination Certificate
2001-10-17
2003-06-24
Williams, Hezron (Department: 2856)
Measuring and testing
Liquid analysis or analysis of the suspension of solids in a...
Content or effect of a constituent of a liquid mixture
C374S027000, C700S270000
Reexamination Certificate
active
06581443
ABSTRACT:
The present invention relates to a process for determining the distillation characteristics of liquid petroleum products by express mini-distillation.
The volatility or more precisely the ranges of boiling temperatures of the different constitutive fractions of the petroleum products correspond to essential characteristic permitting characterisation of these products; these depend directly on the molecular weights of these fractions.
Currently the volatility of petroleum products is generally determined by physical tests under empirical conditions defined by standards, in particular the ASTM standards which are universally recognized by specialists.
By way of example, the standard ASTM D 86 permits determination of the volatility of light petroleum products having a boiling point lower than 400° C., while the standards ASTM D 1160 and ASTM D 2892 also permit determination of the volatility of heavy petroleum products having a higher boiling point. In this last case, it is sometimes necessary to have recourse to distillation under vacuum to lower the boiling temperatures of the products analysed and thus avoid their decomposition.
Analysis apparatus suitable for these standards have been known for many years. These function schematically in accordance with the following principle:
The sample to be analysed is introduced into a distillation flask provided with an outlet tube and this flask is closed by a bung provided with a thermometer.
This outlet tube is connected to a condenser tube co-operating with a cooling system and the outlet orifice of which is situated over a graduated reception test-tube. The flask is heated under predetermined conditions in order to bring the sample to boiling and the vapours formed are collected in the reception test-tube after condensation.
The temperature of the vapours present in the distillation flask is noted for predetermined volumes of condensate collected in the reception test-tube.
The curve is plotted giving the percentage of the volume of sample collected as a function of temperature and from this curve, which characterises the sample, it is verified whether this is in accordance with the required specifications.
It is to be noted that the temperature indicated by apparatus functioning in accordance with these standards do not always correspond to the true boiling temperatures but may correspond to empirical temperatures, taking into account the test conditions, in particular the thermometers used.
These apparatus which are currently used by all specialists to characterise liquid petroleum products allow reliable results with good reproducibility to be obtained, which are therefore representative of the sample analysed, but they do however have many disadvantages: they are in fact particularly heavy and bulky; moreover, the volume of sample required to perform a volatility test is relatively large (of the order of 100 ml) and the duration of each test is not less than 45 minutes.
To correct these disadvantages, in accordance with Byelorussian publication 198 0 801, researchers at the State University of Polotsk have already proposed a process and an apparatus permitting determination of the distillation characteristics of liquid petroleum products by physical tests each only lasting approximately 10 mn and each only requiring a much reduced volume of sample (of the order of 5 to 15 ml).
Another advantage of this process and this apparatus is linked to the fact that the characteristics of the product analysed are determined directly from temperature and pressure measurements and therefore they require no measurement of the volume of condensate collected in a reception test-tube.
The apparatus in accordance with this prior publication includes schematically a distillation flask co-operating with heating organs and which is provided with a capillary tube at the level of its outlet tube and is closed by a bung provided with a temperature sensor which is immersed in the boiling liquid and a differential sensor allowing measurement of the pressure in the vicinity of the capillary tube inlet.
The process employed upon use of this apparatus is based on a particular algorithm which permits calculation of the temperature of the vapour of the sample from its temperature of the vapour of the sample from its temperature in the liquid state in the distillation flask and from the rise in pressure within the latter consequent upon the presence of the capillary tube.
This method of determination of the distillation characteristics of the petroleum products has certain advantages.
However, the curves thus obtained have insufficient reliability taking into account the fact that the barometric pressure variations together with the residues in the distillation flask and the losses of sample in the vapour phase are not taken into consideration.
Moreover, the heating organs interfere with the measurement values of the temperature of the sample in the liquid phase.
Moreover, this method is only suited to the determination of the distillation characteristics of light liquid petroleum products having boiling temperatures lower than 400° C., and cannot be used for the determination of the distillation characteristics of heavy liquid petroleum products, since, operating at atmospheric pressure, they would cause thermal decomposition of these products.
The essential disadvantage of this method is however linked to the fact that the tests performed by it are not in correlation with the standards and in particular with the ASTM standards, which constitutes a major fault as these standards are currently universally recognised by specialists in the field of analysis of petroleum products.
The present invention has the object of correcting these disadvantages by proposing a process permitting determination of the distillation characteristics both of light liquid petroleum products and of heavy liquid petroleum products and their mixtures by express mini distillation so as to provide reliable and reproducible results in correlation with those from tests in accordance with the standards and in particular with the ASTM standards universally recognised by specialists.
In accordance with the invention, it has been possible to attain this end by means of a process including the following steps:
1. a volume of the order of 5 to 15 ml of the sample to be analysed is introduced into a distillation flask co-operating with a heavy element at its lower part and provided with a pressure detector and two inertialess temperature sensors permitting measurement on the one hand of the true value of the temperature of the sample in the liquid phase and on the other the true value of the temperature of the sample in the vapour phase at a level situated a little below the inlet of the outlet tube with which the distillation flask is equipped,
2. the distillation flask is heated with a constant heating intensity depending on the nature of the sample to be analysed so as to progressively boil it,
3. the vapour pressure in the distillation flask is constantly measured at the level of the inlet of the outlet tube, as are the true values of the temperatures of the sample in the liquid phase T
L
and the vapour phase T
S
and the curves are plotted representing the variations in the pressure and these temperatures as a function of time &tgr;
1
,
4. the primary and secondary derivatives are established of the curve representing the variations of the temperature of the sample in the liquid phase and in the vapour phase:
ⅆ
T
S
ⅆ
τ
1
;
ⅆ
T
L
ⅆ
τ
1
;
ⅆ
2
T
S
ⅆ
τ
1
2
;
ⅆ
2
T
S
ⅆ
τ
1
2
and the temperature is deduced of initial boiling in the liquid phase T
L
IBP
which corresponds to the point for which
ⅆ
2
T
L
ⅆ
τ
1
2
=
0
,
5. the temperature of initial boiling in the vapour phase T
S
IBP
is determined which corresponds to the time for which a commencement of increase of pressure is observed,
6. the temperature T
L
END
is determined for which the value indicated by the temperature sensor which meas
Abaev Guenrikh
Andreeva Raissa
Kalesnik Victor
Spirydonau Aliaksandr
Urvantsau Viachaslau
Cygan Michael
Instrumentation Scientifique de Laboratoire I.S.L. SA
Kilpatrick & Stockton LLP
Williams Hezron
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