影响催化裂化汽油加氢脱硫装置压力降增大的原因及对策

Cause of increased pressure drop of FCC naphtha HDS unit and countermeasures

催化裂化(FCC)汽油加氢脱硫装置工业结果表明加工原料在长期贮存、储运过程中与空气长期接触会氧化,并可能受到粉尘等污染;FCC装置掺炼重芳烃后,主反应器入口原料终馏点从224℃剧增到348℃,胶质质量浓度由10.2 mg/(100 mL)剧增到6 080.0 mg/(100 mL)。工业试验表明原料氧化与污染;催化裂化原料掺炼重芳烃;二烯烃等结焦前身物以脱臭单元带入的镍、钴、铁为晶核,在加热炉、换热器等局部过热部位聚合结焦是造成反应器上部压力降上升过快的主要原因。非新鲜汽油原料先进FCC装置分馏塔切割分离是解决汽油加氢脱硫装置压力降的实用办法。FCC汽油加氢脱硫装置设轻重汽油分馏塔,重汽油热料直接进加氢脱硫单元,利用无碱脱臭、柴油吸收、切割处理FCC轻汽油,既能降低轻汽油的硫含量,又能够避免脱臭单元对反应器造成的不利影响。

The commercial operation results of FCC naphtha hydrodesulfurization （HDS） units showed that the feed was oxidized by air and polluted by dust in long-term storage. After mixing heavy aromatics into FCU feed, the end point of feed of HDS unit was raised from 224℃ to 348 ℃ and gum was increased from 10, 2 rag/（ 100 mL） to 6 080.0 mg/（ 100 mL）. It was shown that the major cause of pressure drop on top of reactor of FCC naphtha HDS unit was the coking by superheating in heater and heat exchangers as resuhed from long-term feed storage, mixed heavy aromatics, sodium and cobalt ions carry-over into reactor in sweete- ning unit in which coke precursors like diolefins, etc formed coke upon iron, sodium and cobalt ions in over- heated area in furnace and heat exchanger. The effective way to solve the problem of pressure drop of FCC naphtha hydrodesulfurization （HDS） unit is to pre-treat non-fresh FCC naphtha in FCC unit fractionator. HDS unit is provided with light/heavy splitter. Heavy catalytic naphtha goes directly to HDS reactor and light cata- lytic naphtha is treated by sweetening, diesel absorption and fractionation. All these can reduce sulfurs in light catalytic naphtha and avoid the negative impact on sweetening section of HDS units.