减压渣油换热器在线清洗技术的研究与应用

Research of on-line cleaning technology and its application in vacuum residue heat exchanger

中国石油天然气股份有限公司乌鲁木齐石化分公司1.2 Mt/a延迟焦化装置投产后出现了渣油换热器换热效率下降快的问题,检修时发现换热器壳程(渣油侧)结垢严重。分析认为,焦垢主要为渣油中高稠环胶质、沥青质氧化后在高温下析出的产物;用新鲜水、焦化柴油和重芳烃浸泡不同硬度的垢样,发现重芳烃对硬焦块有一定的溶解性,对软焦块及焦粉溶解性更好,当温度升至130℃时,重芳烃可以完全溶解软焦块及焦粉。对装置在线清洗流程进行了改造,将重芳烃物流并入换热器柴油冲洗流程,实现了渣油换热器的在线清洗。清洗后在相同操作条件下换热后温度由250℃上升至295℃左右,效果非常明显。且清洗后的污油由装置自己回炼,对环境没有影响。

The heat exchange efficiency of the residue heat exchangers fell down rapidly in a 1.2 MM TPY delayed coking unit after start-up in PetroChina Urumqi Petrochemical Company.The maintenance found that the shell side （residue oil） of the heat exchanger fouled seriously.The analysis concluded that the heavy fouling was mainly caused by the educts of high-molecule gum and asphaltene in residue after oxidation at high temperature.The submerging of fouling sample of different hardness in the clean water,coker diesel oil and heavy aromatics found that the heavy aromatic had a certain solubility on coke pieces and good solubility on soft coke piece and coke powder.When the temperature rose to 130 ℃,the heavy aromatics would completely dissolve soft coke pieces and coke powder.After revamping of existing on-line cleaning process and integration of the heavy aromatic process with diesel cleaning process for the heat exchanger,the on-line cleaning of residue oil heat exchanger was realized.After cleaning,the temperature was raised from 250 ℃ to 295 ℃ after heat exchange under the same operating conditions.The result is very obvious.The slurry oil after cleaning is recycled in the unit and there is no impact on the environment.