What A Barrel Of Crude Oil Makes?

Crude oils are complex mixtures containing many different hydrocarbon compounds that vary in appearance and composition from one oil field to another. Crude oils range in consistency from water to tar-like solids, and in color from clear to black. An "average" crude oil contains about 84% carbon, 14% hydrogen, 1%-3% sulfur, and less than 1% each of nitrogen, oxygen, metals, and salts. Crude oils are generally classified as paraffinic, naphthenic, or aromatic, based on the predominant proportion of similar hydrocarbon molecules. Mixed-base crudes have varying amounts of each type of hydrocarbon. Refinery crude base stocks usually consist of mixtures of two or more different crude oils.

Relatively simple crude oil assays are used to classify crude oils as paraffinic(West Texas crude, ,Brent), naphthenic (Louisiana crude, Nigerian Light), aromatic (Maya Crude), or mixed(Assam crude). One assay method (United States Bureau of Mines) is based on distillation, and another method (UOP "K" factor) is based on gravity and boiling points. More comprehensive crude assays determine the value of the crude (i.e., its yield and quality of useful products) and processing parameters. Crude oils are usually grouped according to yield structure.

Crude oils are also defined in terms of API (American Petroleum Institute) gravity. The higher the API gravity, the lighter the crude. For example, light crude oils have high API gravities and low specific gravities. Crude oils with low carbon, high hydrogen, and high API gravity are usually rich in paraffin’s and tend to yield greater proportions of gasoline and light petroleum products; those with high carbon, low hydrogen, and low API gravities are usually rich in aromatics. The price of a crude oil is usually based on its API gravity, with high gravity oils commanding higher prices.

Crude oils that contain appreciable quantities of hydrogen sulfide or other reactive sulfur compounds are called "sour." Those with less sulfur are called "sweet." Some exceptions to this rule are West Texas crudes, which are always considered "sour" regardless of their H2S content, and Arabian high-sulfur crudes, which are not considered "sour" because their sulfur compounds are not highly reactive.

Tell me about Hydrocarbon Groups?

The main constituents of petroleum can be grouped into four categories:

Paraffin: A series of saturated straight chain or branched hydrocarbons, the lowest members of which are methane, ethane and propane.

Olefins: Double-bonded hydrocarbons that are not normally present in crude oil but are formed during refinery processing and vehicle combustion of fuel. Olefins help improve the octane rating, but their use may lead to gum formation or deposits in engine intake systems.

Aromatic: Unsaturated cyclic hydrocarbons are known as aromatics. Aromatics occur naturally in crude oil and can also be produced in some refining processes. Aromatics common in petrol include benzene, toluene and xylene. Controlling the level of aromatics directly limits evaporative losses and exhaust emissions.

Naphthenes: Naphthenes are a class of compounds that are saturated hydrocarbons typified by cyclic hydrocarbon molecular structure. The general formula for cyclic hydrocarbons is CnH2n.

If the evaporation temperature exceeds +2oc then there is a probability that heavier hydrocarbons are present in LPG and if the evaporation temperature is less then +2oc then there is a probability that lighter fractions are more.

Significance: This test is intended to find out the presence of heavier hydrocarbons in LPG, which may not readily evaporate.

This test is done specially for LPG.

This test serves as measure of corrosivity of fuel with copper, brass, or bronze parts of a fuel system.

The copper strip is polished smoothly and immersed in the sample and put into a bomb. This is placed into a water bath which is maintained at the specified temperature for the specified time. The strip is removed from the sample, washed with iso-octane or normal heptane, and examined for evidence of etching or discoloration. The colour of the strip is compared with ASTM copper strip standards colour code.

Significance: Copper corrosion limits provides assurance that difficulties will not be experienced in deterioration of the copper and copper alloy fittings and connections that are commonly used in many types of utilization, storage and transportation equipments.

This test is required mainly for LPG, Naphtha, SKO, HSD, ATF and MS.

Flash point (BIS) requirements for some petroleum products are:

S.K.O.- 35 C
U.L.S.H.S.D.- 35 C
H.S.D.- 35 C
F.O.- 66 C
A.T.F.- 39 C

Significance: High aniline point indicates that the fuel is highly paraffinic and hence has a high Diesel index and very good ignition quality. In case of aromatics the aniline point is low and the ignition quality is poor.

This test is useful for calculating Diesel Index.

Diesel Index = (Aniline Point in oF X oAPI)/ 100

Significance: High aniline point indicates that the fuel is highly paraffinic and hence a high Diesel Index and a very good ignition quality. In case of aromatics the aniline point is low and the ignition quality is poor.

Cetane Number =0.72* Diesel Index +10
Significance: Cetane number is the index of ignition quality of a fuel. High cetane number fuel will enhance easy starting of compression ignition engines and lessen engine roughness.

This test is required mainly for HSD.

In cold weather, a gasoline that is not volatile enough may cause hard starting and poor warm-up. In the winter months, for example, your vehicle's engine is extremely cold before startup, and the gasoline must have a high enough volatility to be able to vaporize easily in a cold engine.Vapour pressure can be measured by a variety of methods including Reid, dynamic, static, vapour pressure balance, and gas saturation.

The most commonly used method for crude oils has been the Reid vapour pressure , as determined by ASTM D323 (American Society for Testing of Materials) method (Reid Method). This test method determines vapour pressure at 37.8 'C (100 'F) of petroleum products and crude oils with initial boiling point above 0 'C (32 'F). It is measured by saturating a known volume of oil in an air chamber of known volume and measuring the equilibrium pressure, which is then corrected to one atmosphere (101.3 kPa).

Octane number is influenced by different factors like speed of engine, ambient weather conditions, altitude, combustion chamber deposits and coolant temperature. Knocking rating is tested by CFR engine for different purposes. Motor method gives the octane rating of high way driving (high speed), while research method gives for city driving (low speed) conditions and aviation method is for aviation gasoline.The rating can be done by either Research Method or Motor Method. If the fuel meets the minimum requirements in respect of Octane number it ensures trouble free operation. Apart from being a nuisance, the knocking in an engine may result in loss of energy and at times may cause severe damage to the engine.

Other factors also influence your car's knocking characteristics:
Temperature: Generally, the hotter the ambient air and engine coolant, the greater the octane requirement.
Altitude: The higher the altitude above sea level, the lower the octane requirement. Modern computer-controlled engines adjust spark timing and air-fuel ratio to compensate for changes in barometric pressure, and thus the effect of altitude on octane requirement is smaller in these vehicles.
Humidity: The drier the air, the greater the octane requirement. The recommendations that vehicle manufacturers give are for normal- to low-humidity levels.
spark timing: The octane requirement increases as the spark timing is advanced. Both the basic setting of the spark timing and the operation of the automatic spark advance mechanisms are important in controlling knock
Method of driving: Rapid acceleration and heavy loading, such as pulling a trailer or climbing a hill, may result in a greater octane requirement. Stop-and-go driving and excessive idling can increase octane requirements by causing the buildup of combustion chamber deposits.

Viscosity is an important characteristic of diesel. Fuels outside the required range may cause power loss or improper atomization of the fuel in a diesel engine. Lubrications assist in removing the frictional forces between two moving bodies. Absolute viscosity divided by fluid density equals kinematic viscosity. Absolute viscosity and kinematic viscosity are expressed in fundamental units. Commercial viscosity such as Saybolt viscosity is expressed in arbitrary units of time, usually seconds.

API gravity = (141.5/Specific Gravity at 60F) - 131.5

In gasoline, the distillation characteristics, along with vapor pressure, define and control starting, warm-up, acceleration, vapor lock, crankcase oil dilution, and, in part, fuel economy and carburetion icing. The tendency of a fuel to vaporize is also characterized by determining a series of temperatures at which various percentages of the fuel have evaporated (boiling temperatures), as described in ASTM D86, Test Method for Distillation of Petroleum Products. The temperatures at which 10%, 50%, and 90% evaporation occurs are often used to characterize the volatility of gasoline. The 10% evaporated temperature is directly affected by the seasonal blending of the gasoline. This temperature must be low enough to provide easy cold starting, but high enough to minimize the vapor lock and hot weather driveability problems. Most cool weather driveability problems occur from the use of summer season gasoline in the winter months. This is especially true in premium grades, which normally have a high 10% evaporated temperature.

The 50% evaporated temperature must be low enough to provide good warm-up and cool weather driveability without being so low as to contribute to hot driveability and vapor locking problems. This portion of the gasoline greatly affects fuel economy on short trips.

The 90% and end-point evaporation temperatures must be low enough to minimize crankcase and combustion chamber deposits, as well as spark plug fouling and the dilution of engine oil. If the end-point temperature exceeds the ASTM maximum requirement, it is usually because of the presence of a distillate fuel. This contamination can be directly attributable to the delivery of diesel prior to the delivery of the gasoline. This problem is avoided if care is taken in handling the product.

The catalyst is usually a mixture of aluminium oxide and silica. Most recently, the introduction of synthetic zeolite catalysts has allowed much shorter reaction times and improved yields and octane numbers of the cracked gasolines.

they create extra isobutane feed for alkylationthey improve the octane of straight run pentanes and hexanes and hence make them into better petrol blending components.

Isomerisation is achieved by mixing normal butane with a little hydrogen and chloride and allowed to react in the presence of a catalyst to form isobutane, plus a small amount of normal butane and some lighter gases. Products are separated in a fractionator. The lighter gases are used as refinery fuel and the butane recycled as feed.

Pentanes and hexanes are the lighter components of petrol. Isomerisation can be used to improve petrol quality by converting these hydrocarbons to higher octane isomers. The process is the same as for butane isomerisation.