Visbreaker

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A visbreaker is a chemical plant where thermal cracking in a furnace reactor (at high temperature) is used to transform heavy hydrocarbons (e.g. vacuum distillation residue) into lighter hydrocarbons (LPG, gasoline, etc). Heavy hydrocarbons are generally used as fuel oil in chemical plants. The product of the visbreaker has a lower viscosity. In ecomomic terms this means that less diluents have to be added to use the vacuum residue as fuel oil. The name visbreaker literally means "breaks the viscosity". Thermal cracking such as visbreaking is in general less efficient than catalytic cracking, and has therefore been largely superseded by catalytic cracking in modern oil refineries.

In visbreaking, residual from the distillation tower is heated (900 degrees Fahrenheit / 482 degrees Celsius), cooled with gas oil and rapidly burned (flashed) in a distillation tower. This process reduces the viscosity of heavy weight oils and produces tar.