FCC Gasoline: Gas Oil Cracked over Fluidised Silica-Alumina at 975 °F, 71.5 % Conversion (Gulf, US 3,071,535)

In a fluid catalytic cracker, gas oil vapour streams up through a bed of fine silica-alumina powder kept floating by the gas, and breaks into gasoline and lighter products. Gulf ran theirs hotter than usual, at 975 °F, to make more butylenes for alkylation. Result (Gulf's example, barrels per day): from 44,840 of gas oil, 15,052 of gasoline boiling to 400 °F plus 4,393 of pentane fraction, with 7,547 of C4-C5, 4,230 of C3, 10,555 of light gas oil and fuel gas. Conversion 71.5 %. Source: Condrasky & Glazier, US 3,071,535 (Gulf, filed 1959). The heavy gas oil and coker gas oil come from Gulf's own crude unit and coker. Not given: catalyst regeneration, space velocity, how the gasoline is sweetened. Hot oil vapour: fire risk. Picture drawn by Youblob.

خبير

1 day

التعليمات

Charge the gas oils

The fresh charge is heavy straight-run gas oil boiling from 620 to 1,050 °F, 36,950 barrels per day in Gulf's example, plus 7,890 of coker gas oil boiling above 400 °F.

المواد لهذه الخطوة:

زيت الغاز الثقيل36950 parts by volume

زيت غاز التفحيم7890 parts by volume

الأدوات المطلوبة:

خزان نفط

مضخة نقل

Crack over a suspended bed of silica-alumina powder

Vaporise the charge and pass it upward through a suspended bed of powdered silica-alumina catalyst, as in a conventional fluid catalytic cracker.

الأدوات المطلوبة:

مفاعل الطبقة المميّعة

حفاز هلام السيليكا والألومينا

Run at 975 °F or hotter, to 70 % conversion or more

Hold the cracking temperature at 975 °F or more, preferably 975 to 1,050 °F, and set the space velocity to convert at least 70 % by volume of the fresh charge. Gulf's example: 975 °F, 71.5 %.

الأدوات المطلوبة:

مفاعل الطبقة المميّعة

مقياس الحرارة العالية

Fractionate the products

Split the cracked products: fuel gas, a C3 fraction (4,230), a C4-C5 fraction (7,547), a C5 fraction (4,393), gasoline boiling from C6 to 400 °F (15,052), light gas oil (10,555) and heavy oils. The C3 fraction and the light gas oil are kept for polymerisation and hydrotreating. Gulf does not describe the fractionator. Ours: a fractionating still.

الأدوات المطلوبة:

قَرْعة تقطير تجزيئي

Sweeten the C5 fraction and the gasoline

The C5 fraction and the gasoline are preferably sweetened in a conventional unit that turns mercaptans into less objectionable sulphur compounds. Gulf does not give the method. This is the FCC gasoline; its part boiling up to 200 °F is the light FCC of the premium blend.

الأدوات المطلوبة:

خزان نفط