A Crude Distillation Unit (CDU), also referred to as an Atmospheric Distillation Unit (ADU) or topping plant, is the first step in the refining process. Products derived from an ADU include naphtha, kerosene, diesel and residuum. Naphtha can be further refined to produce motor gasoline. Kerosene can be used as a jet fuel if treated and blended with additives. Diesel fuel may require further processing to meet required sulfur specifications. Residuum may be used as a heavy fuel or further refined in a vacuum unit to produce marine diesel. Under certain circumstances, naphtha and residuum can be remixed and put back into a crude supply to be delivered as part of a crude stream.
Additional information on Chemex Modular's ADUs