BASIC PROPERTIES OF PETROLEUM Oil consists of a closely related r elated series of complex hydrocarbon compounds that range from gasoline to heavy solids. The various mixtures that constitute crude oil can be separated by distillation under increasing temperatures into such components as (from light to heavy) gasoline, kerosene, gas oil, lubricating oil, residual fuel oil, bitumen, and paraffin. BASIC PHYSICS
STATES OF MATTER : 3 PHYSICAL STATES – SOLID / LIQUID / GAS MELTING: PROCESS OF CHANGE CHANGE OF STATE FM SOLID TO LIQUID LIQUID TO GAS EVAPORATION: CHANGE OF STATE FROM LIQUID
SUBLIMATION: SOME SOLIDS DO NOT MELT WHEN HEATED. THEY CHANGE DIRECTLY FROM FROM SOLID TO GASEOUS GASEOUS STATE. MELTING OCCURS. MELTING POINT: TEMP AT WHICH MELTING BOIL WHEN ITS VAPOUR BOILING POINT: A LIQUID STARTS TO BOIL PRESSURE BECOMES EQUAL TO THE ATMOSPHERIC PRESSURE. HENCE THE BOILING POINT OF A LIQUID IS THE TEMP AT WHICH THE VAPOUR PRESSURE OF THE LIQUID IS EQUAL TO THE ATMOSPHERIC PRESSURE.
LIQUIDS
PHENOMENON BY VIRTUE VIRTUE OF WHICH WHICH THE SURFACE TENSION : THE PHENOMENON FREE SURFACE OF A LIQUID BEHAVES LIKE AN ELASTIC MEMBRANE UNDER TRENSION TO CONTRACT SO AS TO HAVE MINIMUM SURFACE AREA KNOWN AS SURFACE TENSION.
COHESION: IT IS THE FORCE WITH WHICH LIKE MOLECULES ATTRACT EACH OTHER. WITHIN A SOLID,THE FORCES OF COHESION ARE VERY LARGE SINCE THE MOLECULES ARE CLOSE TOGETHER. COHESION FORCES ARE LESS FOR LIQUIDS AND LEAST FOR GASES. MOLECULES. AT ADHESION: IT IS THE CONTRACTION OF UNLIKE MOLECULES. THE COMMON SURFACE OF 2 DIFFERENT SUBSTANCES UNLIKE MOLECULES ATTRACT EACH OTHER.
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VISCOSITY: IT IS THE INTERNAL RESISTANCE OF A LIQUID TO FLOW. IT DECREASES WITH RISE IN TEMPERATURE.
SATURATED VAPOUR PRESSURE (SVP): •
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WHEN A GAS FREE CONTAINER IS PARTLY FILLED WITH A VOLATILE LIQUID THEN BECAUSE OF EVAPORATION GAS IS LIBERATED INTO THE SPACE ABOVE THE LIQUID. SIMULTANEOUSLY THE GAS SO LIBERATED HAS A TENDENCY TO REDISSOLVE INTO THE LIQUID. AT A CERTAIN STAGE THE NUMBER OF MOLECULES LEAVING THE LIQUID WILL BE EQUAL TO THE NUMBER OF MOLECULES RECOMBINING WITH THE LIQUID. THIS STAGE OF EQUILIBRIUM IS CALLED S V P OF THAT LIQUID AT THAT TEMP. SVP CHANGE S WITH TEMP.
GASES •
GASES MIX THEY DIFUSE THROUGH THROUGH EACH DIFUSION: WHEN 2 GASES
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OTHER AND IS CAUSED DUE TO THE MOTION OF INDIVIDUAL MOLECULES OF GAS MOVING AT HIGH SPEEDS IN ALL DIRECTIONS. THE AVG VEL OF THE GAS MOLECULES DEPENDS UPON ON THEIR MASS (DENSITY). THE MAX TEMP AT WHICH CRITICAL TEMPERATURE : THIS IS THE A GAS CAN BE LIQUEFIED. AT ANY TEMP ABOVE THIS VALUE GAS CANNOT BE LIQUEFIED. CRITICAL PRESSURE : THIS IS THE PRESSURE AT THE CRITICAL TEMP TO CAUSE LIQUEFACTION OF GAS.
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THE PHYSICAL AND CHEMICAL PROPERTIES WHICH HAVE THE GREATEST BEARING ON THE HAZARDS ARISING FROM PETROLEUM LIQUIDS ARE VAPOUR PRESSURE • FLAMMABILITY OF GASES • DENSITY OF GASES. •
VAPOUR PRESSURE
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VAPOUR PRESSURE: PRESSURE: THE VAPOUR PRESSURE OF A PURE COMPOUND DEPENDS ONLY UPON ITS TEMP. THE VAPOUR PRESSURE OF A MIXTURE DEPENDS UPON BOTH ITS TEMP AND THE VOL OF GAS SPACE INTO WHICH VAPORIZATION OCCURS. AS THE TEMP OF PETROLEUM MIXTURE RISES ITS TRUE VAPOUR PRESSURE (TVP) INCREASES AND IF IT EXCEEDS ATMOSPHERIC PRESSURE, THE LIQUID BEGINS TO BOIL.
FLASH POINT IT IS THE LOWEST LIQUID TEMP AT WHICH A SMALL FLAME INITIATES A FLASH OF FLAME ACROSS THE SURFACE OF THE LIQUID THEREBY INDICATING THE PRESENCE OF A FLAMMABLE GAS / AIR MIXTURE ABOVE THE LIQUID. HEAVY GAS OILS AND DIESEL OILS HAVE A FLASH POINT OF 60 DEG C AND > WHEREAS AVIATION FUEL, KEROSENE HAS A FLASH POINT OF 60 DEG C AND <.
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IN THE PROCESS OF BURNING HYDROCARBON HYDROCARBON GASES REACT WITH OXYGEN IN THE AIR TO PRODUCE CO2 AND WATER . THE REACTION GIVES ENOUGH HEAT TO FORM A VISIBLE VISI BLE FLAME WHICH TRAVELS THROUGH THE MIXTURE OF HYDROCARBON GAS AND AIR. WHEN THE GAS ABOVE LIQUID HYDROCARBON IS IGNITED THE HEAT IS ENOUGH TO EVAPORATE SUFFICIENT FRESH GAS TO MAINTAIN THE FLAME, AND THE LIQUID IS SAID TO BURN. A MIXTURE OF HC GAS AND AIR CANNOT BE IGNITED AND BURN UNLESS ITS COMPOSITION LIES WITHIN A RANGE OF GAS IN AIR CONCENTRATIONS KNOWN AS “FLAMMABLE RANGE” HAVING A LOWER / UPPER FLAMMABILITY LIMITS (LFL / UFL).
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POLLUTION VIS-À-VIS PHYSICAL PROPERTIES OF PETROLEUM BASED OIL Petroleum-based oils have a broad range of natural hydrocarbon-based substances and refined petroleum products, each having a different chemical composition. As a result, each type of crude oil and refined ref ined product has distinct physical properties, that affect 1. The way it spreads and breaks down 2. The hazards it it may pose pose to marine and human life 3. The likelihood that it will will pose a threat to natural and man-made resources. Light refined products, such as gasoline and kerosene, spread on water • surfaces and penetrate porous soils quickly. Fire and toxic hazards are high, but the products evaporate quickly and leaves little residue. Heavier refined oil products may pose a lesser fire and toxic hazard and do • not spread on water as readily. Heavier oils are more persistent, however, and may present a greater remediation challenge. The rate at which an oil spill spreads will determine its effect on the environment. Most oils tend to spread horizontally into a smooth and slippery surface, called a slick , on top of the water. Factors which affect the ability of an oil spill to spread include Surface tension Specific gravity Viscosity. •
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Surface Tension is the measure of attraction between the surface molecules of a liquid. The higher the oil's surface tension, the more m ore likely a spill will remain in place. If the surface tension of the oil is low, the oil will spread even without help from wind and water currents. Because increased temperatures can reduce a liquid's surface tension, oil is more likely to spread in warmer waters than in very cold waters. Specific Gravity is the density of a substance compared to the density of water. Since most oils are lighter than water, they lie flat on top of it. However, the specific gravity of an oil spill can increase if the lighter substances within the oil evaporate.
