Abstract: In a comparative study of the process schemes of atmospheric and vacuum distillation unit in a refinery, the effects of two processes, i.e. pumping a portion of the atmospheric residue to downstream unit and pumping the atmospheric residue to vacuum distillation column, on the energy consumption of unit are investigated. The results show that, without considering the effect of diesel fraction entrained by atmospheric residue on the energy consumption of VRDS unit, the process of pumping a portion of atmospheric residue to downstream unit significantly reduces the processing load of vacuum furnace and vacuum distillation column. The heat load of furnace and the consumption of pump are reduced by 3.68 MW and 258.9 kW respectively, and the steam consumption is increased by 3850.1kg/h. The overall energy consumption of the atmospheric and vacuum distillation unit is reduced by 180.5kg/h standard fuel, but the energy consumption of the downstream VRDS unit is increased by 195.2kg/h standard fuel. Therefore, this process is favorable for the energy saving and consumption reduction of atmospheric and vacuum distillation unit. Considering the effect of diesel fraction on the energy consumption of VRDS unit, the energy consumption of the two processes is basically the same in terms of refinery-wide energy consumption

Key words: atmospheric and vacuum distillation, energy consumption, pumping a portion of atmospheric residue to downstream unit, pumping atmospheric residue to vacuum distillation column