Oil Refining Process

Oil Refining Process

The refining of heavy oil requires exacting and thorough chemical, engineering, and computing processes.  

Crude oil, also called petroleum, is a complex mixture of carbon and hydrogen (hydrocarbons), which exist as a liquid in the earth's crust. Crude oil has many compositions, some is black, thick and tar like, while other crude oils are lighter in color and thinner. The carbon and hydrogen in crude oil are thought to have originated from the remains of microscopic marine organisms that were deposited at the bottom of seas and oceans and was transformed at high temperature and pressure into crude oil and natural gas. This oil and gas migrates upward through the porous rock, as it is less dense than the water which fills the pores. The oil and gas is trapped by a layer of impermeable rock through which they can't flow. Several different types of oil and gas "traps" exist; a common dome formed by folded sedimentary rocks. Crude oil is obtained by drilling a hole into the reservoir rock (sandstone, limestone etc.) and pumping it out.

Petroleum refining is the process of separating the many compounds present in crude petroleum. This process is called fractional distillation where the crude oil is heated; the various of the compounds boil at different temperatures and change to gases; and are later recondensed back into liquids. Fossil Fuels The principle which is used is that the longer the carbon chain, the higher the temperature at which the compounds will boil. Boiling Points and Hydrocarbons The crude petroleum is heated and changed into a gas. The gases are passed through a distillation column which becomes cooler as the height increases. See the figure on the left. When a compound in the gaseous state cools below its boiling point, it condenses into a liquid. The liquids may be drawn off the distilling column at various heights.

Although all fractions of petroleum find uses, the greatest demand is for gasoline. One barrel of crude petroleum contains only 25-35% gasoline. Transportation demands require that over 50% of the crude oil be converted into gasoline. To meet this demand some petroleum fractions must be converted to gasoline. This may be done by "cracking" - breaking down large molecules of heavy heating oil; "reforming" - changing molecular structures of low quality gasoline molecules; or "polymerization" - forming longer molecules from smaller ones. Conversion Oil Refining

For example if decane is heated to about 500 C the covalent carbon-carbon bonds begin to break during the cracking process. Many kinds of compounds including alkenes are made during the cracking process. Alkenes are formed because there are not enough hydrogens to saturate all bonding positions after the carbon-carbon bonds are broken.

Nevertheless, it is hoped that this discussion has provided some basic insight into the complex and highly integrated refining process.

Once all these tasks have been completed, and the various fractions produced, usually according to market needs, the actual refining process is complete.

Refineries also produce pure chemicals, called feedstocks, from crude oil. These feedstocks are sold to the petrochemical industries, where a great variety of products are made.

Feedstock	Products
Methane (Natural Gas)	Fertilizers	Polyethylene
Ethylene	Plastics	Explosives
Propylene	Rayon	Synthetic Rubber
Butylene	Vinyl	Polystyrene
Naphthene	Nylon	Dyes
	Dacron	Drugs
	Teflon	Antifreeze

Some of the technical aspects of refining which are explained more fully at this website include those in the table below: (short explanatory articles on these topics would be welcome)

Aromatic complexes	Fractation
Alkylation and Polymerization	Gasification	Separation Processes
Catalytic Re-Forming	Hydro-treating	Sulfur Extraction
Cracking	Isomerization	Sweetening
Dehydrogenation		Visbreaking and Coking

 Blending

A final and critical step is the blending of our products. Gasoline, for example, is blended from treated components made in several processing units. Blending and Shipping Area operators precisely combine these to ensure that the blend has the right octane level, vapor pressure rating and other important specifications. All products are blended in a similar fashion.