Only a few refiners in Baku make the fractional distillation test, and the ash determination is made only by Nobel Brothers. The Government exercises control over all petroleum leaving Baku, but only the flashing point and specific gravity are ascertained. As already mentioned, the crude oil is subjected at the refinery of Nobel Brothers to a process of continuous distillation in a series of 14 or 16 stills (Fig. 122). The form of the still is that of a Cornish boiler without flue, and the dimensions about 8 feet diameter by 24 feet long. The upper curved part of the still is made of -inch plates, the lower of -inch plates. Each still is supported by two walls in brickwork, leaving a free space under the bottom. The two walls are connected with an arch of firebrick, and from the top of the arch to the bottom of the still, there is an open space of about 18 inches. The arch is perforated, and is intended to prevent the fire from playing too fiercely on the still bottom. The fuel used is petroleum residuum, or astatki as it is called in Russia. A part of the hot astatki from the stills is conveyed to the fireplace through a -inch pipe, terminating in a flattened end at a distance of 18 inches from the top of the firebrick arch. Another -inch pipe supplies steam from an ordinary steam boiler, and is fastened by wire to the end of the astatki pipe in such a position that the steam jet meets the outflowing astatki and atomises it, a fierce flame, extending the whole length of the arch, being thus produced. More complicated atomisers1 (or forsunkas in Russian) have been constructed, but the general principle is the same in all, and the simple apparatus described is found to give very satisfactory results. When once the oil and steam supplies are adjusted in suitable proportions, the fire burns without attention for a long time, neither flame nor smoke being visible at the top of the chimney. Inside the still, and close to the bottom, are placed one or two pierced steam pipes, similar to an antiprimer in a steam boiler, and through these, superheated steam is passed to facilitate the distillation. The oil enters and flows out through two 4-inch pipes, arranged as shown in the figure. Both these pipes communicate on the outside of the still with the main 6-inch oil pipe, and the flow of oil is regulated by valves. When these valves have been properly adjusted, the oil flows into the still, becomes heated, gives off its vapours, and flows out into the next still, where the same process is gone through, the temperature being gradually increased. The oil passes by gravitation from one still to another, the series of stills being built on a slight incline. The temperatures in the stills are carefully watched, but when once the crude-oil valves and the fires are adjusted, one man can properly attend to the whole series of sixteen stills. Nobel Brothers have three such series in full work all the year round. When a still has to undergo repair, it can be disconnected from the series, for the time being, without interfering with the use of the others. The average distilling capacity of each still is 1,314 poods in twenty-four hours, making 16 x 1,314 21,024 poods for the series, but this can easily be increased to 25,000 poods in twenty-four hours. 1 Described in the section on the uses of petroleum. = From the still, the vapours pass through a dephlegmator (see p. 316), or an air condenser, to the water condensers. In many of the refineries, an air condenser, consisting of a pipe bent upwards and downwards, is employed, the condensed liquid being drawn from the lower bends. The dephlegmator adopted by Nobel Brothers consists of two cylinders, one inside the other, about 3 feet and 2 feet in diameter respectively. The air passes through the inner cylinder, and the vapours pass between the cylinders. The product condensed in this way is led from the bottom of the air condenser to the tailhouse, and is redistilled. As this distillate has a somewhat dark colour it is called black kerosene. The uncondensed vapours now pass to water condensers contained in square wooden tanks, into which sea water is constantly pumped. The simplest form of condenser consists of a castiron coil, and this is generally used in the smaller refineries. Nobel Brothers obtain a more perfect condensation by conducting the vapours into a square iron tank submerged in the wooden tank, and provided with a system of vertical 2-inch wrought-iron pipes, through which the water passes, this arrangement giving a condensing surface of 1,400 square feet. The inflowing water has the temperature of the sea, and it passes out at a temperature of 40° C. The condensers are provided with safety-valves. The distillate is conveyed from the condensers through 3-inch pipes submerged in water, and reaches the tailhouse at a temperature of 14° to 39° C. The highest temperature occurs in summer time, when the sea water has a temperature of 20° C., or more. The system of continuous distillation was adopted by Nobel Brothers in the manufacture of kerosene in 1883, and is now also employed by them in the production of lubricating oils, the hot residues from the kerosene stills passing through pipes which traverse the crude petroleum heating tanks, into the heavy-oil stills. In some cases the crude oil, instead of being fully heated before it reaches the stills, enters at a lower temperature, and then the first stills in the series are employed simply as heating vessels. 1 Table XL. gives the results of four distillations conducted in a series of stills, comprising four in which the crude petroleum is subjected to a preliminary heating, and fourteen in which the distillation takes place. The temperatures recorded are those of the contents of the different stills, and the specific gravities are those of the various kerosene distillates. Recently, the continuous-distilling apparatus patented by Schuchow, Intschik and Bary has been used in several Russian refineries. It consists (as described by Dr. Veith) of a metallic vessel fixed above an ordinary still, and divided by a number of flat pans into a series of compartments in which constant temperatures are maintained. The oil to be distilled traverses a chamber containing a coil through which the residues from the still are discharged. Having thus been heated, it passes through pipes into the vaporising apparatus, where it flows from pan to pan through a series of pipes. Beneath these pans for 1 Veith, Das Erdöl, 1892, TABLE XL.-RESULTS OBTAINED IN THE CONTINUOUS DISTILLATION OF CRUde Petroleum. STILLS FOR FRACTIONATING STILLS. 131 153 175 194 195 211 227 234 248 250 256 0.784 0.7920-801 0·809 0.8140.822 0.827 0.832 ... ... 280 285 288 297 307 129 159 177 200 206 221 230 238 257 259 ... ཡུ:སྐྱ: 133 157 175 ... 0.835 0.842 0.846 0.8490-855 126 150 179 192 195 219 228 233 243 247 256 ... 0.837 0.835 0.840 0.845 0.850 0.855 the crude oil, are arranged other similar pans which receive the distillates condensed in the several compartments. The vapour from the still enters the bottom compartment, and comes into contact with the surface of the lowest pan, warming the oil it contains, and becoming partially condensed. The uncondensed vapour passes through a seal formed by the oil, and is thus further condensed. The residual vapour, mixed with that which is evolved from the oil in the lowest pan, passes through an opening into the second compartment, where the process is repeated at a lower temperature. The vapour thus passe s from compartment to compartment, depositing liquid in each, and the uncondensed portion is finally conducted to a condenser. In this way, the ascending vapours warm the descending oil, and, as the lighter constituents are volatilised, it is only the heavy oil which reaches the still. The distillates which collect in the pans flow into their respective tanks through pipes passing through the vessel in which the crude oil is heated prior to distillation. The inventors claim that this apparatus occupies only a small space and requires but little fuel. The still employed holds 400 poods, and with the apparatus, from 8,000 to 10,000 poods of crude oil can be distilled in twenty-four hours. The specific gravity of the distillate from the first pan is 0.872, and that of the residue is 0.920. About 57 per cent. of the crude oil is obtained as distillate. The difference in temperature between any two adjacent pans is about 30° C., the total increase being 210° C. This apparatus, with considerable modification, has been used in the Schibaieff Works at Baku. It is said to work satisfactorily in the manufacture of kerosene, but has not yet been employed in the distillation of lubricating oils. Experiments have recently been made in a few refineries with Alexeieff's apparatus for continuous distillation, in which the superheated steam ordinarily employed, is replaced by light hydrocarbons, the more volatile products obtained in the distillation of the crude petroleum being separately collected and pumped back into the still. This principle is stated to be applicable to either intermittent or continuous distillation. Fig. 123 illustrates Alexeieff's plant for continuous distillation. A is the still whence the products of distillation are conducted through a pipe, a, into a series of condensers, B, C, D, E. From the fourth condenser, the more volatile hydrocarbons pass in the form of vapour through a pipe into a condensing coil, F, at the lower end of which is fitted a three-way cock, g. From this descends a pipe dipping 50 to 80 mm. into liquid in the vessel, R. Connected with the pipe i is a pump, V, by means of which the light hydrocarbons are forced back into the still, where they are discharged through a perforated pipe, k, extending along the bottom. condensers, B, C, D, and E, are placed in chambers, G, H, I, and K, maintained at temperatures corresponding to the character of distillate required. In the first, B, which is at a temperature of 360° to 400° C., vaseline is condensed. In the second, C, at 300° to 400°, machine oil is collected; in the third, D, at 200° to 300°, heavy oil is produced, 1 Memoirs of the Imperial Russian Technical Society, May, 1889. The |