Definition of "visbreaker" [visbreaker]

• A processing unit in oil refinery that reduces the quantity of residual oil produced in the distillation of crude oil to increase the yield of more valuable middle distillates (heating oil and diesel) by thermally cracking large hydrocarbon molecules in the oil. (noun)

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• "Work is being carried out on a crude unit, a vacuum plant and a visbreaker, two people familiar with the situation said."