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7. The method of manufacturing the barrel or drum and the materials used must be well adapted to producing a uniform product. Leaks in a new barrel or drum must not be stopped by soldering, but must be repaired by the method used in constructing the barrel or drum.
BLENDING GASOLINE WITH NAPHTHA.
In the foregoing pages the word "gasoline" has been loosely applied by the authors to mean the liquid obtained from natural gas subjected to treatment. The term has been retained because it has become a trade name. The term "condensate" would be more suitable, because the liquid first obtained is usually so volatile that it comes quite outside the meaning that is usually applied to the term gasoline. The refinery gasoline as prepared for the trade is not a definite compound, nor is the natural-gas condensate, as it is collected in storage tanks before it is prepared for market. After this preparation, if properly done, natural-gas condensate comes under the same category as refinery gasoline.
At present practically all natural-gas condensate is mixed with lower grade refinery naphthas. This process constitutes the socalled blending. In the early days of the industry the handling of the natural-gas condensate involved its weathering or the evaporation of its light constituents until a product was obtained that could be used as refinery gasoline is ordinarily used and could be safely transported under rules promulgated by the Bureau for the Safe Transportation of Explosives. By the process of "weathering" a loss of material as much as 60 or 70 per cent of the total quantity frequently occurred. Sometimes the loss was even greater. By the process of blending a product is obtained that has a slower rate of evaporation than the natural-gas condensate used in making the blend.
COMMERCIAL NAMES OF DISTILLATION PRODUCTS FROM CRUDE OIL.
Below is presented a table showing the commercial names of different grades of naphthas, gasolines, kerosenes, etc., their gravities, boiling points, and the chemical names of the constituents that comprise them:
Data regarding distillation products of crude oil.
DISCUSSION OF THE PRODUCTS.
According to this table, any condensate having a gravity of 94° to 108° B. will contain a large proportion of pentane and butane. Probably most of the condensate having a gravity of 108° B. will be butane and most of that having a gravity of 94° B. will be pentane, although a certain proportion of each will consist of the heavier constituents, among which will be those of ordinary gasoline. Butane and pentane have boiling points of 0° C. (32° F.) and 36° C. (97° F.), respectively. These temperatures (especially that of butane) are below ordinary atmospheric temperature; hence a rapid loss of these constituents in a natural-gas condensate will occur when the con-, densate is exposed to the air.
Rhigolene, it will be noticed, consists chiefly of butane and pentane. The boiling point of rhigolene is given as 18° C. (64° F.). This boiling temperature is midway between that of butane and pentane. Most natural-gas condensates have a gravity of 80° to 94° B. Such a mixture is classified as petroleum ether in the above scale. This scale has reference to refinery products. Such mixtures are of a more uniform composition than natural-gas condensates that are freshly drawn from accumulator tanks, whereas petroleum ether may be a mixture that contains chiefly pentane and hexane and will not boil when freshly prepared, yet natural-gas condensates, especially those of the higher gravity, may boil violently. The ebullition is probably due chiefly to the escape of butane and some propane. In the natural-gas condensate there will be more of these constituents and less of the pentane and hexane. There will also be some of the still higher liquid paraffins and some of the dissolved gases methane and ethane. The above table, as far as the intermediate members are concerned, can scarcely be applied to naturalgas condensates, because the latter are of a more complex composition. It is inserted here only because its use brings out several instructive points. Probably the above classification is little used in the trade. Different trade names for practically the same distillates from petroleum are used by different refiners.
EVAPORATION LOSSES IN BLENDING.
The following tables (Tables 6 to 9) show the results of some blending tests made by the authors. The condensate as it was drawn from the storage tank was allowed to stand in graduated vessels, and the loss sustained by evaporation over different periods of time was noted. The containers were graduated glass cylinders having a capacity of 1,000 c. c. Their inside diameter was 2 inches and they were 13 inches high. Some of the same condensate, as it was drawn from the storage tanks, was also mixed with naphtha and allowed to stand and the loss noted.
TABLE 6.-Evaporation losses of natural-gas condensate from plant A when allowed to stand exposed to the air.
Test ity of gasoline.
perature of outside
F. C. F. C. P. ct. 206.7 60 16 4.5 8-13
G -18 60 16
End of 1 hour.
in mixture. gravity of
81 50 10 8.5
F. C. P. ct.
Specific gravity of gasoline.
• B. 69
54 12 10.0
Specific gravity of
• Computed from original volume of condensate.
TABLE 7.-Evaporation losses of natural-gas condensate from plants B and C when allowed to stand exposed to the air.
End of 2
1 33.0 91.0
87.5 13.0 87.0 22.0 89.5 26.0 88.5 40.0 88.0
• B. P.ct.
Temperature of mix
End of 3
• B. 75.5
TABLE 8.-Evaporation losses of natural-gas condensate from plant A mixed with refinery
° C. P.ct. • B
End of 18
End of 5 End of 18
B. P. ct.
End of 24 hours.
End of 10 hours.
53.0 84.5 50.0 84.0
End of 24
• B. 73.5
TABLE 9.-Evaporation losses of different mixtures of natural-gas condensates and refinery
a In conducting this test the mixture was exposed to the atmosphere to a greater extent than in tests 1 and 2. It was poured from one vessel to another eight times, thus exposing more liquid surface to the atmosphere and causing more rapid evaporation than would have occurred if it had been allowed to remain in the same vessel all the time without disturbance.
REMARKS ON TABULATED DATA.
As regards the results shown in Table 6, the condensate was exposed to the air in the graduated glass cylinders already mentioned.
The pressure exerted on the natural gas in making the condensate varied between 140 and 200 pounds per square inch. The storage tank was so arranged that after each test the entire volume of condensate could not be removed in order to provide an empty tank for a succeeding test. Hence, the condensate from one test was always mixed with some condensate from a preceding test. For this reason the exact pressure that was exerted on the gas for any particular test is not recorded here. A gas meter was not connected to the "plant," so that the quantity of gas used in making the condensate could not be measured.
It will be observed that as the gravity of the condensates increased the losses by evaporation also increased, ranging from 4.5 per cent to 24 per cent at the end of one hour, from 8.5 to 33 per cent at the end of two hours, from 9.5 to 40 per cent at the end of three hours, and as much as 53 and 54 per cent at the end of 24 hours and 18 hours.
The condensate used in test 1 started to boil slightly when first drawn from the storage tank and continued to do so for two hours.
This boiling was probably due mainly to the liquid butane present in the mixture changing to the gaseous condition. Butane boils at 1° C. (34° F.), and when exposed to the temperature of this particular condensate, which was 20° F. (-7° C.), the liquid of course changed to the gaseous condition. A small part of the gaseous butane remained dissolved in the condensate, but the proportion that could not be held in solution escaped.
The condensate used in test 3 lost 8 per cent by evaporation during the first hour and 13 per cent at the end of three hours; at the end of 18 hours 25 per cent of the original mixture had evaporated. The original condensate must have contained considerable quantities of butane and pentane to account for such a loss. Most of the butane was probably eliminated during the first two hours, and then a much slower evaporation of the other constituents, principally pentane, followed.
The condensate used in test 7 was a very volatile product, being nearly the lightest gasoline obtained in the plant operation.
The results mentioned above are presented to show actual losses sustained at the particular plants where the tests were conducted under certain conditions that is, exposure of the condensates to atmospheric pressure and temperatures in certain forms of containers.
The total loss through evaporation was not exactly determined. This total loss includes the losses shown in the above tables plus that sustained when the condensate was removed from the storage tank. As soon as the valve on the storage tank was opened and the condensate came in contact with the outside air in flowing to the graduated vessel provided to catch it, the evaporation commenced; hence some loss of liquid occurred before the condensate could be measured in the vessel provided to receive it. The storage tank was provided with a glass gage which showed the height of the liquid therein. As the liquid was drawn from the tank its level, of course, fell in the gage. By noting this level before and after some of the liquid from the tank had been drawn into the graduated glass vessel, the loss of liquid occurring could be approximately determined. The loss amounted to about 10 per cent, and was of course due principally to the volatilization of the liquid gases. This loss is to be added to the losses shown in the preceding table in order to get the total loss.
In Tables 7 and 8 are shown the evaporation losses that resulted when freshly drawn condensate from plants B and C were allowed to stand exposed to the atmosphere for 10 and 24 hours. The losses shown are much smaller than those from plant A. This result is to be expected, because more of the heavier paraffin hydrocarbons were contained in the condensates. The temperatures of the freshly drawn condensates were also higher than the temperature of the condensate obtained at plant A. Hence the constituents present in the condensate had higher boiling points and evaporated more slowly.