Decontamination of a Vacuum Distillation Unit: Mechanical versus Chemical Cleaning; A Case Study

摘要

Vacuum Distillation is a key aspect of the petroleum refining process, with over 80% of US refineries and nearly all Canadian refineries and upgraders capitalizing on the operational benefits of this unit. A secondary processing unit, the vacuum distillation unit (VDU) receives the heavy bottoms from the atmospheric distillation unit (ADU) and further separates them with the benefit of vacuum pressure to prevent the cracking, or break down, of the oil. The VDU is composed of an outer shell, distillation columns and a fired heat exchanger. When fouled with heavy residuum, the efficiency of the heat exchange process declines, reducing throughput and flow rate, and can introduce hot spots in the system leading to coking of the oil in the VDU. Maintenance of these units is imperative to the refining process; however, potential contamination by the heavy residuum poses significant environmental and health issues when the exchanger unit is pulled from the column. Here, the benefits and limitations of mechanical steam out and high-pressure water blasting (HPWB) versus vapour phase chemical cleaning of these units is discussed.