text: Apart from information given here, sources shown will give more information.  Even refer books are from the wiki source.\nOil refineries are typically large sprawling industrial complexes with extensive piping running throughout. The refining process releases numerous different chemicals into the atmosphere; consequently, there are substantial air pollution emissions and a notable odor normally accompanies the presence of a refinery. Aside from air pollution impacts there are also wastewater concerns, upset risks of fire and explosion, and both occupational noise and environmental noise health effects.\n\nCommon process units found in a refinery\nDesalter Unit (washes out salt from the crude oil before it goes into the atmospheric distillation unit) \nAtmospheric Distillation Unit (distills crude oil into fractions) \nVacuum Distillation Unit (further distills residual bottoms after atmospheric distillation) \nNaphtha Hydrotreater Unit (desulfurizes naphtha from atmospheric distillation. Must hydrotreat the naphtha before sending to a Catalytic Reformer Unit.) \nCatalytic Reformer Unit (contains catalyst used to convert the naphtha-boiling range molecules into higher octane reformate (reformer product). The reformate has higher content of aromatics, olefins, and cyclic hydrocarbons). An important byproduct of a reformer is hydrogen released during the catalyst reaction. The hydrogen is used either in the hydrotreaters and hydrocracker.) \nDistillate Hydrotreater Unit (desulfurizes distillate (diesel) after atmospheric distillation) \nFluid Catalytic Cracking (FCC) Unit (upgrades heavier fractions into lighter, more valuable products) \nHydrocracker Unit (upgrades heavier fractions into lighter, more valuable products) \nCoking unit (processes asphalt into gasoline and diesel fuel, leaving coke as a residual product) \nAlkylation unit (produces high octane component for gasoline blending) \nDimerization Unit \nIsomerization Unit (converts linear molecules to higher octane branched molecules for blending into gasoline or feed to alkylation units) \nSteam reforming Unit (produces hydrogen for the hydrotreaters or hydrocracker) \nLiquified gas storage units for propane and similar gaseous fuels at pressure sufficient to maintain in liquid form - these are usually spherical or bullets (horizontal cylinder with rounded ends). \nStorage tanks for crude oil and finished products, usually cylindrical, with some sort of vapor enclosure and surrounded by an earth berm to contain spills \nUtility units such as cooling towers for circulating cooling water, boiler plants for steam generation, and wastewater collection and treating systems to make such water suitable for reuse or for disposal. \n\nVR