Monday, April 26, 2010

How is crude oil refined?

Can you please include all major processes.





Thanks


:)How is crude oil refined?
Most of it is done by franctional distillation, in which is uses the various boiling points of the compounds in crude oil to separate them.





Wiki will help you explain fractional distillation





http://en.wikipedia.org/wiki/Fractional_…





Specially the industrial distillation part.





http://en.wikipedia.org/wiki/Fractional_…How is crude oil refined?
Crude oil is a heterogenous mixture of saturated hydrocarbons ranging mainly from C1 to C30 in their carbon chain.





To isolate certain species of hydrocarbon from others, the companies use a process of distillation. They put the oil in a vat at the bottom of a sort of pipe/tank which contains no oxygen, nitrogen or any other reactants. They then heat it up to a certain temprature so that it evaporates, but it doesn't react with anything.





As it travels up the pipe, they are separated from the heat source and they start to condense. The larger hydrocarbons condense first. At the first stage of distilation, you'll get hydrocarbons ranging from C25-C30-ish. The smaller hydrocarbons will condense last, and they appear toward the top of the distillation/pipe/thing. Here you'll get stuff like methane, ethane and small traces of propane. All of the smaller hydrocarbons ranging from C1 to C30-ish will be isolated somewhere in between the top and the bottom of the pipe.





C20 and onwards are hydrocarbons that are usually used to make things like candlewax and tar for roads. It's the C1-C10 stuff that's used as fuel.





Once they've isolated what they wanted, the oil companies refine their product further until they've completely isolated what they want. Most fuel uses a lot of octane, so to get enough of it, they usually have to use catalytic cracking one the larger hydrocarbons like the C15 ones to make them a lot smaller, and then refine the products into stuff like octane.





Once they've got what they want, they react the hydrocarbons with water to get stuff like 2-ethanol, 3-octanol or whatever. Once they've got the exact proportions of what they need, they mix it all together to make fuel.





I think the new E10 fuel has about ten percent ethanol, but I think that's made by fermenting corn or something. I don't know much about that, to be honest.
From Crude Oil


The problem with crude oil is that it contains hundreds of different types of hydrocarbons all mixed together. You have to separate the different types of hydrocarbons to have anything useful. Fortunately there is an easy way to separate things, and this is what oil refining is all about.











The oil refining process starts with a fractional distillation column.





Different hydrocarbon chain lengths all have progressively higher boiling points, so they can all be separated by distillation. This is what happens in an oil refinery - in one part of the process, crude oil is heated and the different chains are pulled out by their vaporization temperatures. Each different chain length has a different property that makes it useful in a different way.





Quiz Corner





Test your knowledge of oil and oil production with our ­Oil Shale Quiz.


­To understand the diversity contained in crude oil, and to understand why refining crude oil is so important in our society, look through the following list of products that come from crude oil:





Petroleum gas - used for heating, cooking, making plastics


small alkanes (1 to 4 carbon atoms)


commonly known by the names methane, ethane, propane, butane


boiling range = less than 104 degrees Fahrenheit / 40 degrees Celsius


often liquified under pressure to create LPG (liquified petroleum gas)


Naphtha or Ligroin - intermediate that will be further processed to make gasoline


mix of 5 to 9 carbon atom alkanes


boiling range = 140 to 212 degrees Fahrenheit / 60 to 100 degrees Celsius


Gasoline - motor fuel


liquid


mix of alkanes and cycloalkanes (5 to 12 carbon atoms)


boiling range = 104 to 401 degrees Fahrenheit / 40 to 205 degrees Celsius


Kerosene - fuel for jet engines and tractors; starting material for making other products


liquid


mix of alkanes (10 to 18 carbons) and aromatics


boiling range = 350 to 617 degrees Fahrenheit / 175 to 325 degrees Celsius


Gas oil or Diesel distillate - used for diesel fuel and heating oil; starting material for making other products


liquid


alkanes containing 12 or more carbon atoms


boiling range = 482 to 662 degrees Fahrenheit / 250 to 350 degrees Celsius


Lubricating oil - used for motor oil, grease, other lubricants


liquid


long chain (20 to 50 carbon atoms) alkanes, cycloalkanes, aromatics


boiling range = 572 to 700 degrees Fahrenheit / 300 to 370 degrees Celsius


Heavy gas or Fuel oil - used for industrial fuel; starting material for making other products


liquid


long chain (20 to 70 carbon atoms) alkanes, cycloalkanes, aromatics


boiling range = 700 to 1112 degrees Fahrenheit / 370 to 600 degrees Celsius


Residuals - coke, asphalt, tar, waxes; starting material for making other products


solid


multiple-ringed compounds with 70 or more carbon atoms


boiling range = greater than 1112 degrees Fahrenheit / 600 degrees Celsius


You may have noticed that all of these products have different sizes and boiling ranges. Chemists take advantage of these properties when refining oil. Look at the next section to find out the details of this fascinating process.





The Refining Process


As mentioned previously, a barrel of crude oil has a mixture of all sorts of hydrocarbons in it. Oil refining separates everything into useful substances. Chemists use the following steps:


The oldest and most common way to separate things into various components (called fractions), is to do it using the differences in boiling temperature. This process is called fractional distillation. You basically heat crude oil up, let it vaporize and then condense the vapor.


Newer techniques use Chemical processing on some of the fractions to make others, in a process called conversion. Chemical processing, for example, can break longer chains into shorter ones. This allows a refinery to turn diesel fuel into gasoline depending on the demand for gasoline.


Refineries must treat the fractions to remove impurities.


Refineries combine the various fractions (processed, unprocessed) into mixtures to make desired products. For example, different mixtures of chains can create gasolines with different octane ratings.




















The products are stored on-site until they can be delivered to various markets such as gas stations, airports and chemical plants. In addition to making the oil-based products, refineries must also treat the wastes involved in the processes to minimize air and water pollution.

No comments:

Post a Comment