Mr. Benjamin J. Crew describes a condenser in which water condensation is supplemented by an arrangement for aërial condensation. The apparatus is rigged immediately above the water tank and rests upon it. In the winter season it adds very materially to the condensing surface, besides affording an easy, rapid method of dividing the products of distillation at one operation into at least three distinct gravities of oil or benzine.

Fig. 108 will illustrate this form of aërial condensation :

Fig. 108.

A

E

B

F

M

A represents the large pipe leading direct from the still and connecting this with the condenser. B, the first air condenser, is an iron cylinder of three-sixteenth iron, 30 feet in length, 24 inches in diameter. C, is an elbow connection between B and the second condenser D, of same diameter as the first. E is an elbow connection between the second condenser D and the third condenser F. G is an elbow connection between the third air condenser F, and the usual condensing pipe H, which here enters the water in the tank I.

Any light benzine which admits of condensation by simple exposure to the air of the condenser B, passes through the pipe I into the appropriate tank. A heavier grade of benzine requiring a still greater degree of cold, is subjected to this in the second cylinder and runs off through the pipe T. A still heavier grade of the lighter products, which will not admit of condensation, passes into the third air condenser and passes off through the pipe K. Any product which requires a greater degree of cold than the air will supply passes into the regular condensing worm at H and is graded subsequently at the receiving house in the usual manner. In the working of the apparatus in the early part of the operation, three grades of benzine are running at the same time, and also during the "cracking" process, a portion of light product the result of the decomposition of the heavier oils may also be received through the medium of the air condensers.

Distillation of lubricating oil with the assistance of a vacuum is now much carried on, especially for the production of very heavy oils. The apparatuses used for the purpose vary in construction so that no general rules can be laid down.

Fig. 109 shows an apparatus with vacuum for the distillation of lubricating oil as used in Nobel's refineries. a b are pipes for introducing and discharging the residuum; the superheated steam enters at c. The distillates are conducted from the still Dinto the dephlegmators d, d,, d2, the diameter of the pipe d being 24 inches, that of d, 20 inches and that of d, 15 inches. At all lower points are discharge pipes leading to the condensing coils e, e,, e,, from which the oils run through the pipes f f, fa, into the tanks. The vacuum apparatus H serves to assist distillation, the necessary vacuum in the dephlegmators being produced by the exhaust pipe g. h is the water pipe for the vacuum apparatus, h, the outlet pipe from the vacuum still, while h2 forms the hydraulic seal for the vacuum still; the water pipe is provided with a sieve through which the cold water is injected into the apparatus. With this arrangement special condensers can be dispensed with, and on the other

of oil are greater and their quality better. The fire-place is separated from the still by the arch i,; i, is the smoke-flue leading to the chimney K. The still itself is 24 feet long, with a diameter of from 5 to 6 feet. In place of this vacuum apparatus of simple construction, pulsometers and directly acting exhaustors and ejectors are also used. With this separate condensation, a great difference between the first and second condensing pipes cannot be well determined, and they are generally taken together. The lightest oils condensing with steam are as a rule worked into illuminating oils (solar oils) of an inferior quality. In working Russian residuum, the specific gravity of the oil increases from 0.860 to 0.925, while the specific gravity of the black-brown residuum, which in the cold is viscous and almost solid, is 0.950 or more. There are, of course, variations according to the nature of the residuum and the manner of distillation and condensation.

The yield and specific gravity of the separate fractions are, according to experience gained in one of the largest factories, as follows:1

In another large refinery the results were as follows:

Hence the total yield of non-refined lubricating oil varies between 38 and 54 per cent. of the weight of residuum, and with a yield of 56 per cent. of residuum between 20 and 30 per cent. of the weight of crude naphtha. From the light Bibicybat

1 C. Engler. "Erdöl von Baku."

naphtha worked near Tagieff and Sarkisoff only 14 or 15 per cent. is obtained.

By further subdivisions in the aërial condensers the number of fractions can, of course, be increased, but, as a rule, not more than two or three fractions of lubricating oil are worked for. A considerable loss amounting to 2 or 3 per cent. is always incurred.

The subjoined table shows the gradual increase, counted from the commencement of distillation, in the specific gravity of the distillates obtained with separate condensation from Caucasian petroleum residuum.