Abstract:

Olefin has been traditionally used as an octane-boosting component in gasoline. However, its impact on the environment has led many countries to develop legislation to reduce its content in their gasoline pool. On the other hand, the light olefins, especially propylene market are quite energetic. The Flexible Dual-riser Fluid Catalytic Cracking (FDFCC) licensed by Luoyang Petrochemical Engineering Corporation offers an attractive solution to make the production of propylene congruent with the trends in future specifications and compositions of transportation fuels.

FDFCC utilizes a dual-riser reaction system to process residue oil and upgrade FCC gasoline in separate riser reactors under different operation conditions. The olefins in FCC gasoline were converted in gasoline riser reactor to iso-paraffins and aromatics by hydrogen transfer reaction at low temperature, or to light ends by cracking reaction at high temperature. The enthalpy of gasoline upgrading process including the evaporation of the feed was provided by the combustion heat of coke generated in the unit. FDFCC has recently been applied in several refineries and is performing as expected. It can reduce FCC gasoline olefin content to less than 20v% and decrease its sulfur content by 15% ~ 40%, with RON increase of 0.5 ~ 2 units.

INTRODUCTION

The future of China's refining is clearly linked to the adaptability of its refineries to new market structures. Over the past ten years, the major two challenges have been to produce clean fuels, particularly gasoline and diesel, and to enhance the capacities for the production of light olefins, especially propylene. Moreover the fluid catalytic cracking (FCC) unit is the main gasoline machine; over 80% of the product streams are from FCC units and contribute the vast majority of the pool olefins and sulphur.

Olefins in FCC gasoline have been paid more and more attention nowadays. The reason is that FCC units are urged to produce low olefin gasoline stream to be able to use for formulating commercial gasoline and they are also needed to yield the bulk of the additional propylene for higher profit margin. Catalysts and additives to some extent can of course reach the targets, abating the olefin content in FCC gasoline and raising the yield of propylene. But the evolution of process would be the most effective way.

Luoyang Petrochemical Engineering Corporation's Flexible Dual-riser Fluid Catalytic Cracking (FDFCC) technology is commercialised and available to meet the needs of refineries for production of low olefin gasoline and additional propylene. FDFCC process utilizes a dualriser reaction system to process residue oil and upgrade FCC gasoline in separate riser reactors under different operation conditions. It can economically reduce olefin content of FCC gasoline to less than 20v% and decrease its sulphur content by 15%~40%, with RON increase of 0.5~2 units. Also, It can enhance propylene yield remarkably.

FDFCC process is available for grassroots or revamp for FCC application and has successfully been used in several refineries.

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