nyie watanzania mnafunzwa nini vyuoni...mimi nimepigwa na butwaa kuona mnapinga ata hili...dah! kweli education system yenu matata....there are oil classifications mainly according to sulphur levels and it affects the prices significantly...watu kama
Annael sijui kama shule umewahi kukanyaga hata kaski moja....hivi, mnafunzwa kemia? i have been meaning to ask, what are you guys actually taught down under??? ama ni kuboronga tu swahili na kuenda nyumbani
Sweet crude oil
From Wikipedia, the free encyclopedia
Sweet crude oil is a type of
petroleum. The
New York Mercantile Exchange designates petroleum with less than 0.42%
sulfur as
sweet.
[1] Petroleum containing higher levels of sulfur is called
sour crude oil.
Sweet crude oil contains small amounts of
hydrogen sulfide and
carbon dioxide. High-quality, low-sulfur crude oil is commonly used for processing into
gasoline and is in high demand, particularly in the industrialized nations.
Light sweet crude oil is the most sought-after version of crude oil as it contains a disproportionately large fraction that is directly processed (
fractionation) into
gasoline (
naphtha),
kerosene, and high-quality
diesel (
gas oil). The term
sweet originates from the fact that a low level of sulfur provides the oil with a mildly sweet taste and pleasant smell. Nineteenth-century prospectors would taste and smell small quantities of oil to determine its quality.
[2]
Light vs Heavy Crude Oil
Light Crude oil is liquid petroleum that has low density and that flows freely at room temperature. It has low viscosity, low specific gravity and high API gravity due to the presence of a high proportion of light hydrocarbon fractions. It generally has a low wax content as well. On the other hand, heavy crude oil or extra heavy crude oil is any type of crude oil which does not flow easily. It is referred to as “heavy” because its density or specific gravity is higher than that of light crude oil. Heavy crude oil has been defined as any liquid petroleum with an API gravity less than 20°. Extra heavy oil is defined with API gravity below 10.0 °API (API gravity, is a measure of how heavy or light a petroleum liquid is compared to water. If its API gravity is greater than 10, it is lighter and floats on water; if less than 10, it is heavier and sinks. )
Light crude oil receives a higher price than heavy crude oil on commodity markets because it produces a higher percentage of gasoline and diesel fuel when converted into products by an oil refinery. Heavy crude oil has more negative impact on the environment than its light counterpart since its refinement requires the use of more advanced techniques an the use of contaminants.
The sweet light crude oil Western Texas Intermediate (WTI) is used as a benchmark in oil pricing.
What Is “Sweet” Crude Oil?
Crude oil with low sulfur content is classified as “sweet;” crude oil with a higher sulfur content is classified as “sour.” Sulfur content is considered an undesirable characteristic with respect to both processing and end-product quality. Therefore, sweet crude is typically more desirable and valuable than sour crude.
What Makes a Crude Oil “Light?”
Crude can be classified as “light” or “heavy,” a characteristic which refers to the oil’s relative density based on the
American Petroleum Institute (API) Gravity. This measurement reflects how light or heavy a crude oil is compared to water. If an oil’s API Gravity is greater than 10, it is lighter than water and will float on it. If an oil’s API Gravity is less than 10, it is heavier than water and will sink.
Lighter crude is easier and less expensive to produce. It has a higher percentage of light hydrocarbons that can be recovered with simple distillation at a refinery.
Heavy crude can’t be produced, transported, and refined by conventional methods because it has high concentrations of sulfur and several metals, particularly nickel and vanadium. Heavy crude has density approaching or even exceeding that of water. Heavy crude oil is also known as “tar sands” because of its high bitumen content.
With simple distillation, dense, heavier crude oil produces a greater share of lower-valued products. Heavy crude requires extra refining to produce more valuable and in-demand products.
What Determines Crude Oil’s Relative Economic Value?
Generally, the less processing or refining a crude oil undergoes, the more valuable it is considered. Price differentials between crude oils typically reflect the ease of refining.
Crude oil can be refined to create products ranging from asphalt and gasoline to lighter fluids and
natural gas, along with a variety of essential elements such as sulfur and nitrogen. Petroleum products are also key components in the manufacturing of medicines, chemicals, and plastics.
How Distillation Impacts Price
Simple distillation -- first-level refinement -- of different crude oils produces different results. For example, the U.S. benchmark crude oil, West Texas Intermediate (WTI), has a relatively high natural yield of desirable end-products, including gasoline. But the process also yields about one third “residuum,” a residual by-product that must be reprocessed or sold at a discount. In contrast, simple distillation of Saudi Arabia's Arabian Light, the historical benchmark crude, yields almost half "residuum." This difference gives WTI a higher premium.
The lighter the oil, the more of the desirable, in-demand products it produces through distillation at a range of temperatures. At the lowest distillation temperatures, products produced include liquid petroleum gases (LPG), naphtha and so-called "straight run" gasoline. In the middle range of distillation temperatures, the refinery produces jet fuel, home heating oil and diesel fuel.
At the highest distillation temperatures -- over 1,000 degrees Fahrenheit – the heaviest products are produced, including residuum or residual fuel oil, which can be used for lubricants. To maximize output of more-desirable products, refineries commonly reprocess the heaviest products into lighter products.
Are Some Crude Oils More Toxic Than Others?
“Toxicity” refers to how harmful an oil might be to humans and other living organisms, as well as to land and water. Generally, the lighter the oil the more toxic it is considered. Because of the constant potential of spills, the Environmental Protection Agency has classified crude oil in four categories that reflect how the oil would behave in spills and its aftermath:
Class A: Because they are light and highly liquid, these clear and volatile oils can spread quickly on impervious surfaces and on water. Their odor is strong and they evaporate quickly, emitting volatiles. Usually flammable, these oils also penetrate porous surfaces, such as dirt and sand, and may remain in areas into which they seep. Humans, fish, and other plant and animal life face danger of toxicity to Class A oils.