Also known as: VBU
The visbreaker is a mild bottoms conversion unit. It upgrades vacuum resid by cracking it so that viscosity is reduced and the amount of high-value cutter stock required to blend it into residual fuel oil is reduced. The conversion of vacuum resid into light products is very low in a visbreaker -- typically less than 15% by volume. However, the cost of a visbreaker is much lower than for other, more severe bottoms upgrading units, making it an attractive investment in markets where the demand for residual fuel oil is high.