CRACKING PROCESS

Oil is an oily liquid with a characteristic spicy smell and different, depending on the place of production, color. According to its chemical structure, it is an extremely complex mixture of different chemical compounds, especially organic substances - hydrocarbons. Hydrocarbons are called so because they represent a simple chemical compounds of elements: carbon and hydrogen. On top of that oil is composed of sulfur, nitrogen, oxygen and other impurities (including water and sand). Despite the fact that hydrocarbons include only two elements, the number of them is enormous. This is because the carbon and hydrogen may be joined together in many different combinations and proportions. Therefore, the properties of hydrocarbons is very different, and their study is a large section of chemistry - chemistry of organic substances.

Hydrocarbons may be liquid, gaseous and solid. Some are easier to water and boil at lower temperatures, the other is heavier - and boil at a higher. Very different in their specific gravity or density (recall that the weights are called the number that shows how many times the amount of a substance harder or easier for the same volume of water collected at 4 degrees). The most important property of petroleum and its products, which is based on the primary distillation of petroleum, is their ability to evaporate. The composition of crude oil includes hydrocarbons, which are beginning to evaporate, even at ordinary temperatures. If the oil is left to stand in an open vessel without heating more or less extended period of time, then part of it evaporates, and the remainder become denser and denser.

Due to the fact that the oil consists of various hydrocarbons with different boiling point, oil is not a constant boiling point, such as water. If we are going to heat the water in the vessel, then notice the following phenomena: the thermometer, immersed in water at first will show the constant increase in temperature, but once the temperature reaches 100 degrees, raising stops. And further, how would we heated vessel, the temperature will not rise until all the water evaporates. This is due to homogeneity of the water, that is the fact that water is composed of identical molecules.

Quite a different picture, we will observe when heated in a vessel of oil. In this case, how would we let a warm, rising temperatures will not stop. And at the beginning of the heating will evaporate very light on specific weight hydrocarbons, which is produced from a mixture of gasoline, then more heavy - forming kerosene, diesel and lubricating oil. This principle was established primary distillation of petroleum. Before the invention of cracking in large kerosene distillation plants were in large distilling cubes, which constantly let large quantities of superheated water vapor and at the same time to warm up the oil from the firebox under the boiler, burning coal or fuel gas. Passing through the oil vapor carry a light most of the oil compounds with low boiling point and low specific gravity.

Photo — «Cracking Process»

This mixture of kerosene and gasoline with water, then went into the refrigerator and protected. As the distillation of the products were much easier to water, they can be easily separated from it. Then, place the plums. First, drain the upper layer with a specific gravity of up to 0, 77 - gasoline, which is sent to a separate tank. Then poured kerosene, which is heavier hydrocarbons with a density of up to 0, 86. Thus obtained crude kerosene burned badly. Require cleaning. To do this it first treated with a strong (66%) sulfuric acid solution, then the solution edkogo sodium. The result is a refined kerosene - a colorless, not having a sharp odor and burnt flat flame, no fire and soot.

The composition of crude oil includes such heavy hydrocarbons, which, before reaching its boiling point, begin to decompose, and the more heat the oil, the more intense will be expansion. The essence of this phenomenon is that of a single large molecules of heavy hydrocarbons formed by several smaller molecules with different boiling point, and different weights. This expansion is called cracking (from English to crack - burst, split). Thus, the cracking, it was understood decomposition under the influence of high temperature (and not only the temperature, decomposition can occur, for example, from high blood pressure and some other reasons) and large particles of complex hydrocarbons into simpler and smaller. A significant difference cracking process from the primary distillation is that cracking occurs in the chemical modification of a number of hydrocarbons, while the primary distillation of a simple separation of the individual parts, or, as they say, fractions of oil, depending on their boiling points.

The phenomenon of expansion of oil was observed long ago, but with such a simple distillation of crude oil degradation was undesirable, and therefore used superheated steam, which has contributed to oil evaporation without decomposition. Refining industry was in its development through several stages. At first (from 60-ies. XIX century. And until the beginning of XX century. ) Oil was pronounced paraffin, then there is a major petroleum product was kerosene, which remained for half a main source of light. At the Russian oil refineries, for example, formed during the distillation of lighter fractions were considered as waste: they were burned in pits or dumped into water bodies.

However, intensive development of road transport ра��тавило other accents. If the United States in 1913 there were 1 million 250 thousand cars in 1917 - about 5 million, 1918 - 6, 25 million, and in 1922 - already 12 million petrol, which in the XIX century, very little use, and was almost unnecessary waste, gradually became the main objective of distillation. From 1900 to 1912 world consumption of gasoline increased by 115 times. However, when even a rich distillation of light fractions of petroleum for gasoline accounted for only about 1 / 5 of total output.

Photo — «Cracking Process»

Then the idea of subjecting heavy fractions released after the primary distillation, cracking and get out of them thus more light gasoline fractions. Soon it was found that the starting raw material for cracking can serve not only the heavy fraction (Diesel or fuel oil) and crude oil. It appears also that the cracking on the quality of gasoline exceeds the one obtained by conventional distillation, as has in its structure such hydrocarbons that burn smoothly in the engine cylinders, without explosion (detonation). The engine that runs on a gasoline, and is no longer knocks.

When liquid cracking the key points defining the essence of the whole process are: temperature and time during which the product is under the influence of the temperature. Oil starts to decompose already at 200 degrees. Further, the higher is the temperature, the intensity is expansion. Similarly, - longer than the cracking, the greater the yield of light fractions. However, too high temperature and long duration cracking process is not as you want - the molecule is not split into equal parts, and split so that one side is too light fractions, and on the other - too heavy. Or is it even comes complete decomposition of hydrocarbons into hydrogen and carbon (coke), which, of course, very desirable.

Optimal conditions for the cracking, yielding the largest output of light gasoline fractions, were found at the beginning of XX century, the English chemist Barton. Back in 1890, Barton was in England by distillation under pressure of Russian heavy oils (fuel oil) to get them out of kerosene, and in 1913 he took an American patent for the first time in history the way you get gasoline from heavy oil fractions. For the first time cracking process according to the way of Burton in the industrial environment was implemented in 1916, and by 1920 in manufacturing were more than 800 of its facilities.

The most favorable temperature for cracking - 425-475 degrees. However, if you just heat the crude to such high temperatures, much of it evaporates. Cracking products in the vapor was associated with some difficulties, so the aim was not to give Burton the oil to evaporate. But how to achieve such a state that, when heating oil is not to boil? This is possible if the entire process under high pressure. We know that under great pressure, any liquid to boil at a higher than under normal conditions, temperature, and that the higher the temperature, the greater the pressure.

Installing the device was as follows. Working under the pressure of the boiler (1) is over the fireplace (1a), bearing dymogarnoy pipe (4). Boiler made of durable iron with a good wall thickness of about 2 cm and was carefully proklepan. Rises up the pipe (5) leads to the water refrigerator (6), where the pipeline (7) went to the gathering the barrel (8). Once the product is passed through a cracking counting apparatus for liquids (10) are at the bottom of the reservoir tube (9) bifurcate into two side tubes (10A and 10B).

Photo — «Cracking Process»

Each side tube supplied with a control valve, one of which led to the pipe 11 and the other to the pipe 12.

At the beginning of cracking boiler (1) filling the fuel oil. Due to heat the furnace (1a), the contents of the boiler is slowly heated to about 130 degrees. At the same time of the oil evaporated residues contained in the water. Sguschayas in the refrigerator (6), then drain the water in the reservoir (8), which through a pipe (21) came in a ditch (22). At the same time from the fuel oil out air and other gases. They also came through the fridge in the reservoir (8) and the pipe (14a) is in the pipeline (16).

Once the oil to get rid of water, dissolved in the air and gases, he was ready for cracking. Furnace increased, and the temperature in the pot is slowly increased to 345 degrees. Thus began the evaporation of light hydrocarbons, which, even in the refrigerator to remain in a gaseous state. They fall into the reservoir (8), and then through the tube 14a (the output valve which was closed) in the pipeline (17), trumpet (14) and back to the reservoir (8). Because these light gaseous fraction is not found out, the pressure inside the installation began to rise. When it reached 5 atm, light hydrocarbons are no longer able to evaporate from the main boiler. These compressed gases maintain the same pressure in the boiler (1), refrigerators (6) and the reservoir (8). Meanwhile, under the influence of high temperature process of decomposition of heavy hydrocarbons, which become lighter, which is in gasoline. At temperatures around 250 degrees it evaporates, falling into the refrigerator and there condense. From the refrigerator and into the fuel tank (8) and the pipe 9 and then 11 or 12 came in a special sealed boilers. Here at reduced pressure of the gasoline evaporated dissolved in the light gaseous hydrocarbons. These gases are gradually removed from the boiler, and the resulting crude petrol merged into special bins.

As the evaporation of light fractions with increasing temperature the contents of the boiler (1) became more persistent relative to the heat. Work stopped as soon as more than half of its contents, turned into gasoline and passes through the condenser. (This number was easy to calculate due to meter fluid (10). ) Then connect to the pipeline (17) suspension, and tap the pipeline (14a), connected to the compressor, open, and the gas slowly evaporate in the low-pressure compressor (both closed conduit ( 9), interrupting communications with the installation received gasoline). Gasili furnace, and when the contents of the boiler (1) cool down, it poured. Then the boiler purified from coke flying and to prepare for the next launch.

Cracking method, developed by Barton, who has started a new phase in the oil industry. It managed to increase in the number of times output value of petroleum products such as gasoline and aromatic hydrocarbons.