In order to be a member of a flock of sheep, one must above all be a sheep oneself. -- Albert Einstein

MOST OF THE COMPOUNDS THAT MAKE UP FOSSIL FUELS ARE HYDROCARBONS - THAT IS, THEY CONTAIN MOSTLY CARBON AND HYDROGEN. CARBON IS A UNIQUE ATOM IN THAT IT CAN BOND TO ITSELF TO FORM MILLIONS OF COMPOUNDS. THE COMPOUNDS THAT MAKE UP FOSSIL FUELS WOULD BE OF THE TYPE:

PETROLEUM WAS FORMED WHEN LARGE QUANTITIES OF PLANKTON AND ALGAE WERE BURIED BENEATH SEDIMENT AND EVENTUALLY SUBJECTED TO ENOUGH HEAT AND PRESSURE TO BE CONVERTED TO PETROLEUM. THERE IS A MINIMUM AND A MAXIMUM TEMPERATURE FOR THIS PROCESS. IF THE TEMPERATURE IS TOO LOW, THE MATERIAL REMAINS AS KEROGEN (WAXY LIKE MATERIAL). IF THE TEMPERATURE IS TOO HIGH, THE PETROLEUM IS CRACKED TO NATURAL GAS.

CRUDE OIL TYPES PARAFFIN BASE CRUDE - WAX IS PRIMARY RESIDUE ASPHALT BASE CRUDE - ASPHALT IS PRIMARY RESIDUE MIXED BASE CRUDE - SOME OF BOTH

A REFINERY AT NIGHT

THE MAIN REFINERY PROCESS IS DISTILLATION, WHICH SEPARATES THE FRACTIONS BY BOILING POINT. ATMOSPHERIC DISTILLATION CAN SEPARATE MATERIALS THAT HAVE BOILING POINTS UP TO ABOUT 800 o F. IF MATERIALS HAVE HIGHER BOILING POINTS, VACUUM DISTILLATION WOULD HAVE TO BE USED.

AN ATMOSPHERIC DISTILLATION COLUMN WOULD SEPARATE MATERIALS THAT BOILED UP TO ABOUT 800 O F. ABOVE THAT TEMPERATURE, MOLECULES WOULD START TO DECOMPOSE (CRACK). ANY MATERIAL LEFT THAT DID NOT DISTILL (ATMOSPHERIC RESID) WOULD BE TAKEN TO A VACUUM STILL FOR FURTHER DISTILLATION. THE MATERIAL THAT WOULD DISTILL HERE WOULD BE THE LUBRICANT BASE OIL STOCKS.

STAR REFINERY, THAILAND

THERE ARE A NUMBER OF PROCESSES IN A REFINERY THAT ARE USED TO CONVERT HEAVIER MOLECULES TO GASOLINE RANGE MATERIAL. THERE ARE ALSO PROCESSES TO CONVERT STRAIGHT CHAIN HYDROCARBONS TO BRANCHED CHAIN HYDROCARBONS. THIS INCREASES THE OCTANE RATING OF THE GASOLINE.

OCTANE RATING IS IMPORTANT FOR ELEMINATING ENGINE KNOCK.

MOST CARS HAVE AROUND AN 8.5 TO 1 COMPRESSION RATIO. THE COMPRESSION RATIO IS THE VOLUME OF THE CYLINDER WITH THE PISTON DOWN TO THE VOLUME WITH THE PISTON UP. THE OCTANE RATING NEEDED DEPENDS ON THE COMPRESSION RATIO OF THE ENGINE.

N-HEPTANE IS GIVEN AN OCTANE RATING OF 0.

ISOOCTANE IS GIVEN AN OCTANE RATING OF 100.

A DIESEL ENGINE DOES NOT USE A SPARK PLUG, BUT DEPENDS ON COMPRESSION TO IGNITE THE FUEL. DIESEL FUEL IS HEAVIER AND CONTAINS ABOUT 20% TO 30% MORE ENERGY THAN GASOLINE. DIESEL FUEL IS RATED ON A CETANE SCALE. CETANE IS USED FOR 100. MOST DIESEL ENGINES WILL RUN IF THE CN IS 45 OR ABOVE. BIODIESEL IS USUALLY 56 TO 60.

DIESEL ENGINES HAVE COMPRESSION RATIOS OF FROM 14:1 TO 25:1. MOST AUTOMOBILE ENGINES HAVE COMPRESSION RATIONS OF AROUND 8.5:1.