1) When was the first oil well drilled? When did the first refinery open?
A. The first Oil well was dug in 1859. The first refinery was opened in 1861.
2) How are the crude oil fractions separated?
A. Crude oil is physically separated by fractionation in atmospheric and vacuum distillation towers, into groups of hydrocarbon molecules with various boiling-point ranges, called fractions or cuts. Crude oil is heated and put into a distillation column. Different products can be recovered at different temperatures. The lighter products- LPG, naphtha, and straight run gasoline are recovered at the lowest temperatures. Middle distillates-jet fuel, kerosene and gas oil come next. The heavier fractions are separated under vacuum and may be reprocessed into lighter products.
3) What are the conversion processes which alter the hydrocarbon structure?
A. Conversion processes used to change the size and/or structure of hydrocarbon molecules include:
- decomposition (dividing) by hydro, thermal and catalytic cracking, coking and visbreaking
- unification (combining) through alkylation and polymerization
- alteration (rearranging) with isomerization and catalytic reforming
- treatment processes.
4) What is blending?
A. Blending is the process of mixing and combining hydrocarbon fractions to produce finished products with desired performance properties and required specifications.
5) What is cracking?
A. Cracking is a petroleum refining process in which heavy-molecular weight hydrocarbons are broken up into light hydrocarbon molecules by the application of heat and pressure, with or without the use of catalysts, to derive a variety of fuel products.
6) Types of cracking
A. Thermal cracking is a refining process in which heat (~800°C) and pressure (~700kPa) are used to break down, rearrange, or combine hydrocarbon molecules.
Steam cracking is a petrochemical process sometimes used in refineries to produce olefinic raw materials (e.g., ethylene) from various feedstock ranging from ethane to vacuum gas oil, for petrochemicals manufacture.
Visbreaking, a mild form of thermal cracking, significantly lowers the viscosity of heavy crude-oil residue without affecting the boiling point range.
Coking is a severe method of thermal cracking used to upgrade heavy residuals into lighter products or distillates. It produces straight-run gasoline (coker naphtha) and various middle-distillate fractions used as catalytic cracking feedstock.
Catalytic cracking breaks complex hydrocarbons into simpler molecules in order to increase the quality and quantity of lighter, more desirable products. It is similar to thermal cracking except that catalysts is employed instead of heat.
Fluid Catalytic Cracking uses intense heat (~ 1,000 oF), low pressure and a powdered catalyst in an elutriated reactor to convert most heavy fractions into smaller molecules.
Hydrocracking is a two-stage process combining catalytic cracking and hydrogenation, wherein heavier feedstocks are cracked in the presence of hydrogen at high temperature and pressure to produce more desirable products.
7) What is catalytic reforming? What are the reactions involved in it?
A. Catalytic reforming is an important process used to convert low-octane naphthas into high-octane gasoline blending components called reformates.
Reforming represents the total effect of numerous reactions such as cracking, polymerization, dehydrogenation, and isomerization taking place simultaneously.
8) What is Hydrotreating? What is its significance?
A. Catalytic hydrotreating is a hydrogenation process used to remove contaminants such as nitrogen, sulfur, oxygen, and metals from liquid petroleum fractions.
9) What is Hydro-desulphurization?
A. Hydrotreating for sulfur removal is called hydrodesulfurization. In a typical catalytic hydrodesulfurization unit, the feedstock is mixed with hydrogen, preheated in a fired heater (320°- 430°C) and then charged under pressure (up to 70 kg/cm 2) through a fixed-bed catalytic reactor. The operating conditions for Hydrotreating differ, depending upon the contaminants to be removed, the feedstock and the catalyst used.
10) What are by-products and co-products typically obtained in a refinery?
A. Coke, Sulphur, Chemicals and Petrochemical feed stocks, Wax, Hydrogen, Asphalt, Process Oils, Petroleum jelly.
11) How is Crude Oil pretreatment done?
A. Crude oil often contains water, inorganic salts, suspended solids, and water-soluble trace metals. Prior to distillation, to reduce corrosion, plugging, and fouling of equipment and to prevent poisoning the catalysts in processing units, these contaminants must be removed by desalting (dehydration). The two most typical methods of crude oil desalting—chemical and electrostatic separation—use hot water as the extraction agent.
12) How is hydrogen produced in a refinery?
A. High-purity hydrogen (95%-99%) principally recovered from catalytic reformer product gases often is not enough to meet the total refinery requirements.
Hydrogen is also produced from steam reforming of natural gas and mainly naphtha. After pretreatment to remove sulfur compounds, naphtha is mixed with steam and taken to the reforming furnace (650°-850°C), where hydrogen is produced.
13) How is sulphur produced?
A. Sulfur recovery converts hydrogen sulfide in sour gases and hydrocarbon streams to elemental sulfur. The most widely used recovery system is the Claus process, which uses both thermal and catalytic-conversion reactions. A typical process produces elemental sulfur by burning hydrogen sulfide under controlled conditions.
14) What are the important quality requirements for the main products?
A. The important qualities for motor spirit (gasoline) are octane number (antiknock), volatility (starting and vapor lock), vapor pressure (environmental control) and low contaminant (S, N etc.) concentration.
Distillate fuels such as diesel fuels have boiling ranges of about 200°-380°C. The desirable qualities include controlled sulfur, flash point and Cetane Number.
The important specifications for proper performance of Liquified petroleum gas (LPG) include vapor pressure and control of contaminants.
The critical quality for kerosene when used as a jet fuel (ATF) is freeze point.
The two most critical specifications of residual fuel oils are viscosity and low sulfur content for environmental control.