Objectives The new 1.0 Mt/a ethylene cracking unit and 0.8 Mt/a p-xylene unit in a 15.0 Mt/a refining-chemical integration project in China was designed to be matched with the original 12.0 Mt/a refining project and the new 3.0 Mt/a refining reconstruction and expansion project. After the project was implemented, the diesel to gasoline ratio was relatively high, and the total amount of refined oil was too much; the ethylene cracking feedstock were insufficient, and the overall properties were heavy; the competitiveness of p-xylene unit technology route was weak. Therefore, above problems need to be solved.
Method The route was determined that the refining processing project added "2.2 Mt/a diesel hydrocracking+2.6 Mt/a continuous reforming" to optimize the refinery processing schemes, increasing the feedstock of ethylene cracking and p-xylene.
Results Compared with before optimization, the diesel to gasoline ratio decreased from 1.74 to 1.00, and the total refined oil reduced by 1 876.8 kt/a; the total ethylene cracking unit feedstock reduced by about 17.4 kt/a but the ethylene production increased by 56.1 kt/a, the ethylene cracking feedstock were further lightened; p-xylene unit feedstock increased from 1 270.3 kt/a to 2 916.9 kt/a, which could meet the demand of 2 000 kt/a of p-xylene unit feedstock.
Conclusion Using the 2017 version of the crude oil price system of 50 US dollars/bbl (1 bbl=159 L), the incremental investment rate of return (after tax) of the project is 27.62%, which has good economic benefits.
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