Measuring and testing – Liquid analysis or analysis of the suspension of solids in a... – Gelling or coagulation
Patent
1992-02-07
1993-09-28
Williams, Hezron E.
Measuring and testing
Liquid analysis or analysis of the suspension of solids in a...
Gelling or coagulation
G01N 3326
Patent
active
052478289
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The Patent Abstract of Japan, Vol. 6, No. 116 (P-125) (994), Jun. 29, 1982, 8 JP-A-57 44 852, Mar. 13, 1982 discloses a method and an apparatus for revealing the solid state of an intentionally-congealed fluid in the pipe of a nuclear reactor. This process is not adapted for measurement of petroleum products.
The present invention concerns a procedure and device for measurement of the gelling of paraffinic petroleum products, especially crude products.
It is known that paraffinic crudes can form gels at temperatures approaching, or less than, 40.degree. C. This gelling phenomenon, when it occurs during production or transport, may lead to problems involving the restart-up of facilities. It is thus critically important to have available a method making it possible to determine what crudes are capable of gelling within a given temperature range and, as needed, to determine the minimum quantities of gelling-inhibitor or doping product needed to prevent the formation of gel.
Current conventional practice can measure the pour point of crudes (see Standard ASTM D-97 or AFNOR T60-103), this method consisting in cooling crude under determinate conditions in a special test tube equipped with a thermometer, and in looking to see whether, at each three-degree interval, the surface has or has not congealed. The temperature at which the surface of the crude congeals is the pour point.
It is also known how to measure, by differential caloric analysis, the incipient crystallization temperature of the crude, this latter corresponding, in fact, to a detectable exothermic phenomenon.
It is further known how to measure the rheological behavior of crudes, the flow properties of these latter ceasing newtonian behavior below a certain temperature, when paraffin crystals form within them.
However, none of these data, i.e., the measurement of the pour point, measurement of the incipient crystallization temperature, and the temperature at which rheological behavior changes, make it possible to know with certainty that operating difficulties will not occur in the event the crude is cooled below that temperature.
SUMMARY OF THE INVENTION
The present application attempts to meet this need for more reliable knowledge concerning gelling of paraffinic crudes during use and proposes a procedure for measurement of gelling of paraffinic crudes which is characterized mainly by the fact that, to determine if a crude is about to form a gel capable of hindering its use at a given temperature, this procedure comprises the following steps: of propagation and the amplitude of an ultrasonic wave in the crude analyzed, change in the thermal variation of the reciprocal of the propagation speed is observed; rate of propagation obtained between the linear portions of the thermal variation of this latter around said break point corresponding to T.sub.t, below and above, respectively, the determined temperature T.sub.t, and signal between said temperature T.sub.t and a lower reference temperature equal, for example, to T.sub.t -5.degree. C., a significant break of slope (p>1) at said temperature T and a high value of the difference A (A>0.3 dB/cm at T.sub.t -5.degree. C.) signifying that gelling of the crude will very probably occur at temperatures below T.sub.t, but that, to the contrary, gelling is not very likely for a slight variation of one of these parameters.
Applicant has found that knowledge of p and .DELTA.A characterizes the physical state of crude paraffinic products. The gelling state of a crude implies, for the temperature below T.sub.t previously specified, the change of said thermal slope as well as a significant attenuation of the wave transmitted. Inversely, for crudes exhibiting no risks of gelling, at least one of these parameters remains more or less unchanged when the temperature T.sub.t is reached.
The invention also concerns a device for measurement of the rate of propagation and the amplitude of the ultrasonic wave. Any conventional device is suitable within the scope of the invention. The r
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Candau Sauveur P.
Lemarechal Pierre
Pesneau Bernard
Schranz Claude
Thiriet Yves
Roskos Joseph W.
Total Compagnie Francaise des Petroles
Williams Hezron E.
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