CRUDE OIL DISTILLATION

foreign [Music] [Applause] this is petroleum or crude oil as it comes from the Earth like many other liquids it is made up of different substances petroleum is composed almost entirely of carbon and hydrogen joined together in various ways there are many forms of carbon but the best known to most of us is lamp black or soot hydrogen is an invisible gas it's lighter than air and is frequently used to fill balloons now let us suppose that this is the smallest particle of carbon and this the smallest particle of hydrogen chemists call these tiny particles of substance atoms actually they are so small that if we enlarged all the atoms in this drop of oil to the point where we could see them the oceans of the world would not be big enough to hold them atoms have the power to combine with each other and atoms of different substances have different powers of combination the carbon atom can be best Illustrated as having four arms and the hydrogen atom one arm now one atom of carbon can combine with four atoms of hydrogen carbon atoms can also join up with other carbon atoms and whole chains of carbon atoms can be created the arms that are free can link up with hydrogen atoms and branched chains in all directions are possible the number of different Arrangements is practically endless the chains may be bent into rings and Rings may be joined up with chains each arrangement of atoms is called a molecule and represents a definite substance with its own definite properties there are thousands of different molecules called hydrocarbons each with its own properties all mixed together in petroleum the problem is how can they be separated we know that if we heat water in a kettle its temperature will rise but after a certain point no matter how long we go on heating it the water will not get any hotter this point is called the boiling point when this temperature has been reached all the heat is used up in changing the water into steam well different liquids have different boiling points for example each hydrocarbon in crude oil has its own individual boiling point generally the more atoms there are in a hydrocarbon molecule the higher is its boiling point this light quick flowing oil is made up of fairly simple molecules and boils at a relatively low temperature this heavy slow moving oil is made up of larger and more complicated molecules and will not boil until it has been heated to a relatively high temperature let us combine two liquids a clear one having a low boiling point and a dark one having a high boiling point let us dissolve some crystals in the solution can the three substances the light boiling material the heavy boiling material and the crystals be separated again when we heat the mixture the clear liquid boils at a lower temperature than the dark one and comes off as Vapor before the dark one is hot enough to boil The Vapor passes into a tube that is cooled by a stream of cold water and is turned back into liquid or condensed the dark liquid remains in the flask when all the clear liquid has been collected we remove it now it is the dark liquids turn to boil away its vapor is condensed and collected like the first after all the liquid has been boiled away the crystals solidify again and are left behind so we can separate or distill a mixture of liquids and solids when the liquids have different boiling points and it is this principle of distillation that we use in separating the hydrocarbons in petroleum there are so many hydrocarbons in petroleum there are boiling points lie very close together the range of hydrocarbons is very much like the range of carbs in a pack from 1 to 52 but all shuffled up now instead of isolating each hydrocarbon for our main product we separate the hydrocarbons by groups having boiling points that are arranged together these groups are called fractions let us suppose the first fraction is represented by the ace to the King of Spades another fraction all boiling at temperatures above the first may be represented by the ace to King of Hearts and so on by means of this rather old-fashioned bench still we can see how petroleum can be split up into fractions through distillation six tanks or Stills are arranged so that the petroleum flows from the first down to the last each still is heated by a furnace to a point where a particular fraction of the petroleum will boil off the temperature increases from one still to the next and as the petroleum flows through the system each fraction is boiled off in turn each fraction comes off as a vapor and is Led away from the top of the still to be condensed by cold water this early method for distilling petroleum was both crude and inefficient improvements have been made through the years until now there are several methods used in modern refineries but in this picture we are concerned only with the general principles in distillation as we know it today instead of separating the fractions by boiling off each in turn all of them are converted into vapor and they're separated by individual Cooling this process is carried out in what is called a fractionating tower the petroleum is heated until most of the hydrocarbons are changed to Vapor and we have a forming mixture of vapor and heavy residue this mixture passes into the tower the heavy residue falls to the bottom where it can be drawn off the vapors rise in the tower and as they rise they gradually cool when they have cooled they are condensed trays are arranged to catch the various fractions as they turn into liquid the trays overflow and some of the liquid runs down and is redistilled the top of the tower is cool to such a temperature that only the lightest fraction of all remains as vapor this fraction is drawn off and condensed separately the correct temperature for the process is maintained by pumping back some of the cold condensed top fraction the trays help to separate the fractions by their Construction caps called Bubble caps Force the rising Vapors to Bubble through the liquid in the trays let's go back to the playing cards to see what happens any light hydrocarbon that doesn't belong there represented by this five of diamonds is carried off by the hot Vapors passing through the tray at the same time a heavy hydrocarbon in the vapors represented by this six of Spades is condensed and held by the cooler liquid in the tray the fractions now in liquid form are drawn off from their respective trays the first step in refining petroleum is now completed but only the first step we have seen the general principles involved in breaking down crude oil into fractions but now it must be remembered that each fraction is the source of a multitude of products that can result only from further refining methods some of these products we all know gasoline for instance for cars and airplanes kerosene for light and heat fuel oil for homes and diesel oil for heavy Vehicles such as trucks tractors trains and ships lubricating oils and greases for the smooth running of all machinery and from the residue asphalt for roads and building materials but before any of these specific product is created the fractions must go beyond the first simple step which we have just seen in the fractionating tower through further and even more complicated processes in vast and complex refineries [Applause] ultimately a thousand and more products will emerge from this pool of bubbling crude oil to bring comfort and convenience to mankind thank you