Destructive distillation

“ Sometimes the stills are encased in wood or brick work to prevent loss of heat. Superheated steam is frequently introduced into the stills, especially during the distillation of the heavy oils. The very large stills recently constructed are used for carrying on the process known as “cracking.” After the removal of the gasolene and different grades of naphtha, the remainder is subjected to destructive distillation. Any method that will heat the vapors above the boiling point of the oil will decompose the heavy oil, with deposition of carbon and the production of lighter oils richer in hydrogen. ”

“ The term is restricted to the action of heat upon complex organic substances out of contact with the air. The products of destructive distillation are numerous and varied. On the manufacturing scale the process is conducted sometimes for the sake of one part of the products, sometimes for the sake of another. Coal, for example, may be distilled not solely for the gas, but also for ammoniacal water, benzene, anthracene, as well as for the sake of the fixed carbon or coke, the volatile portions being too often neglected and practically wasted. ”

“ That of another advertised nostrum is a mixture of mercury and chalk, with a little rhubarb and ipecacuanha.
DISTILLA′TION. The evaporation and subsequent condensation of the vapour of fluids, by means of a still and refrigerator, or other similar apparatus. Dry distillation is a term applied to the distillation of substances per se, or without the addition of water or other volatile fluid. Destructive distillation is the distillation of substances at temperatures sufficiently high to decompose them, by which their elements are separated, or evolved in new combinations. ”

“ The second liquid product of the destructive distillation of coal is the ammoniacal or gas liquor, which consists of water containing ammonia salts in solution, partly condensed from the hot gas, and partly added to wash the gas in the scrubbers. ”

“ All the varied and interesting products obtained by the destructive distillation of coal are combinations of two or more of these four or five elements. Illuminating gas is far from being the only product when coal is heated without access of air; for of the numerous substances volatized at the red heat of the gas-retort a great number are not only incapable of affording light, but liable to generate noxious compounds when burnt. Besides this there are numerous bodies which, though leaving the retort in the gaseous form, immediately assume the liquid or solid state at ordinary temperatures. ”

“ Marsh gases often occur in great quantities in faulted zones in the coal measures, though the bituminous substances found in coal are not true bitumens that dissolve in the usual solvents, while the tars derived from the destructive distillation of coal in no way resemble natural petroleums or the products of oil-shale distillation. ”

“ The bituminous part is melted out in the form of coal tar, there is disengaged at the same time a large quantity of an aqueous fluid, contaminated with a portion of oil, and various ammoniacal salts. A large quantity of carburetted hydrogen, carbonic oxide, carbonic acid, and sulphuretted hydrogen also makes their appearance, and the fixed base of the coal, alone remains behind in the distillatory apparatus, in the form of a carbonaceous substance called coke. An analysis of the coal is thus effected by the process of destructive distillation. ”

“ The hot producer-gas formed in V is passed round the retort E in the flues n2 n2, and ultimately goes away through K to the furnace where it is to be used. The retort E is charged with ordinary bituminous coal which is submitted to destructive distillation by the heat communicated through the flues n2 n2 and is thus converted into coke. The gases formed during this process pass into the upper portion of V and get mixed with the producer-gas formed in the lower portion. ”

“ Of artificial productions the most fruitful and important is provided by the destructive or dry distillation of many organic substances; familiar examples are the distillation of coal, which yields ordinary lighting gas, composed of gaseous hydrocarbons, and also coal tar, which, on subsequent fractional distillations, yields many liquid and solid hydrocarbons, all of high industrial value. ”

“ With regard to the chemical properties of petroleum, it is not necessary to say more in the present place than that the lighter and more volatile constituents, known commercially as naphtha and benzene, must be removed by distillation in order to leave a residue composed principally of hydrocarbons which, while containing the necessary carbon for combustion, shall be sufficiently free from volatile qualities to avoid premature ignition and consequent danger of explosion. ”

“ As may be imagined, the industry of petroleum refining has had to adapt itself to the altered conditions of to-day. For instance, prior to the advent of the internal combustion engine, which now is responsible for such a wide application of motor spirit, the demand for this, the lightest product of petroleum distillation, was non-existent. ”

“ Assuming the tar as the medium form, it is seen that when exposed to heat it gives over oil, and that pitch remains. Thus, petroleum yields naphtha and asphaltum; and thus too, asphaltum exhibits all the gradations which I have described in the pitch, in properties varying in a similar manner, according to its particular state. In the process of distillation the principal difference will be found to consist in the relative quantities of acetic acid and ammonia, which they severally yield ”

“ The first products of distillation are gases which, at ordinary temperatures, pass through the coil without being condensed, and escape. When the vapors begin to condense in the worm the oil trickles from the end of the coil into the pipe leading to the appropriate receiving tank.
The first oil obtained is known as gasoline, used in portable gas machines for making illuminating gas. Then, in turn, come naphthas of a greater or less gravity, benzine, high test water white burning oil, such as Pratt's Astral common burning oil or kerosene, and paraffine oils. ”

“ If we distill either of these more solid substances with a very gentle heat, we obtain naphtha, in which the proportion of the hydrogen to the carbon is increased to a maximum ratio. If the heat is greater, we obtain a substance of a darker colour, in which that ratio is less; and, for this reason, the distillation of asphaltum affords a darker oil than that of petroleum, because its composition cannot be dissolved but in a higher temperature. ”

“ Unless special chemical cleaners and purifiers are employed, thereby complicating the plant, the coal utilized should yield as little tar as possible during distillation; for the tendency of the tar to choke up the pipes and to clog the valves is one of the chief causes of defective operation of producer-gas engines. [203]
Tar changes the proper composition of the explosive mixture. When it catches fire in the cylinder it causes premature ignition, which is so dangerous in large engines. ”

“ Various arrangements have been proposed and patented for the continuous distillation of petroleum, in which crude oil is supplied to a range of stills a fast as the distillates pass off. The system is largely employed in Russia, and its use has been frequently attempted in the United States, but the results have not been satisfactory, on account, it is said, of the much greater quantity of dissolved gas contained in the American oil, the larger proportion of kerosene which such oil yields, and the less fluid character of the residue. ”

“ The vaporization of a substance below its normal boiling-point can also be effected by blowing in steam or some other vapour; this operation is termed “distillation with steam.” “Dry distillation” is the term used when solid substances which do not liquefy on heating are operated upon; “sublimation” is the term used when a solid distils without the intervention of a liquid phase. ”

“ In the refining of crude shale-oil, the greatest care is exercised to prevent dissociation of the paraffin, large volumes of superheated steam being passed into the still, through a perforated pipe, at a pressure of from 10 to 40 lb, to facilitate distillation at the lowest possible temperature. The original system of intermittent distillation is now employed only at the works of Young's Company. The stills have cast-iron bottoms and malleable-iron upper parts, their former capacity being 1200 to 1400 gallons, but those now made usually holding 2000 to 2500 gallons. ”

“ A thin limpid Oil will rise, accompanied with white vapours, and with a prodigious quantity of air, which will issue out with such impetuosity, that if you do not open the little hole in the receiver time enough to give it vent, it will burst the vessels with explosion. An acid liquor will rise at the same time. Continue the distillation, increasing the heat by insensible degrees, and frequently unstopping the little hole of the receiver, till the elastic vapours cease to issue, and the oil to distil. ”

“ As this takes place in each successive distillation, if we make use of large vessels and a considerable degree of heat, we at last decompose the whole of the oil, and it entirely into water and charcoal. When we employ a slow fire, and especially when we employ a slow fire, or degree of heat little above that of boiling water, the total decomposition of these oils, by repeated distillation, is greatly more tedious, and more difficulty accomplished. ”

“ This may be brought about by a distillation under pressure, or by allowing the condensed distillate to fall into the highly heated residue in the still. The result of this treatment is that the comparatively heavy oils undergo dissociation, as shown by the experiments of Thorpe and Young, into specifically lighter hydrocarbons of lower boiling points, and the yield of kerosene from ordinary crude petroleum may thus be greatly increased. ”

“ The crude petroleum, of course, is not fit for illuminating purposes, but it contains components which are satisfactory. The various components are sorted out by fractional distillation and the oil for burning in lamps is selected according to its volatility, viscosity, stability, etc. It must not be so volatile as to have a dangerously low flashing-point, nor so stable as to hinder its burning well. ”

“ An objectionable feature of the system of allowing the vapour to escape from the still to the condenser through a loaded valve, viz: the irregularity of the distillation, is thus removed, and the benefits of regular vaporization and condensation under high pressure are obtained. In the American petroleum refineries it is found that sufficient cracking can be produced by slow distillation in stills of which the upper part is sufficiently cool to allow of the condensation of the vapours of the less volatile hydrocarbons, the condensed liquid thus falling back into the heated body of oil. ”

“ The refuse in its descent through the high furnace is exposed to the drying action of the hot gases of distillation and the hot products of combustion, its temperature increasing in its descent the nearer it approaches the tuyeres, and becomes completely desiccated and combustible when it reaches the blast. The high heat in this way obtained by the combustion of the organic portion melts all of the inorganic portion, forming a vitreous slag or glass, which may be allowed to run continuously, or by closing the tap may be allowed to accumulate, and can be drawn off at intervals. ”

“ The substance of the evidence as to whether the shipments complained of were gasoline or unrefined naphtha is given in the opinion of the Circuit Court of Appeals, and need not be repeated here. The first distillation of crude oil takes off the elements more volatile than kerosene, and these taken together are known as the 'naphtha fraction.' After treatment with sulphuric acid, this fraction is divided by further distillation into three products-gasoline, the lightest, benzine, the intermediate, and naphtha, which is called 'painter's naphtha,' the heaviest. ”

“ As crude petroleum and the higher fractions first distilled from it affect the skin injuriously, wetting the skin should be avoided, and careful cleanliness on the part of the workers enjoined. Workers exposed to the influence of gases escaping from naphtha springs and wells should be equipped with breathing apparatus (smoke helmets) ; this applies to those who have to enter stills and other apparatus connected with the distillation of petroleum.
In the preparation of petroleum by sulphuric acid sulphur dioxide in great quantity is developed, constituting a distinct danger to the workers. ”

“ The general method of procedure which has yielded the best results, is to remove the adsorbed hydrocarbons by various processes of combined oxidation and distillation, whereby the hydrocarbons of high boiling points are broken down into more volatile substances and removed at lower temperatures, or under conditions less likely to result in subsequent deposition of inactive carbon. Thin layers of charcoal and rapid gas currents are used so that contact between the volatilized hydrocarbons and the hot active charcoal may be as brief as possible. ”

“ Each retort has an iron exit pipe affixed to it, through which the gases generated by the furnace are carried off. The exit pipes all empty themselves into what is known as the hydraulic main, a long horizontal cylinder, and in this the gas begins to deposit a portion of its impurities. The immediate products of distillation are, after steam and air, gas, tar, ammoniacal liquor, sulphur in various forms, and coke, the last being left behind in the retort. In the hydraulic main some of the tar and ammoniacal liquor already begin to be deposited. ”