Feed Flow Rate Essay

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4.2.4 Effect of Feed flow rate (Fgr) on Product Distribution
An increase in the flow of gas oil means an increase in the velocity of the gas oil feed, also a decrease in the residence time of the gas oil in the riser; hence a rise in the conversion of gas oil and yields of the products is expected(Akpa et al. 2010).
When the flow rate of gas oil is increased, there is an increase in the heat inflow into the reactor, rate of cracking reactions are high, feed also spends less time in the reactor and hence less endothermic cracking reactions take place. This resulted in a slight increase of the conversion of gas oil from 73% - 74% (Fig 4.5).
It was observed that as the flow rate of gas oil to the riser increases from 34Kg/s to 63Kg/s the gasoline
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4.5: Effect of feed flow rate (Fgr) on yield. Gas oil – y1 (wt %), gasoline – y2 (wt %), light gases – y3 (wt %) and coke - y4 (wt %). Operating Conditions: Tf = 600K; Trg = 960K; Fgr = 33.9Kg/s: 5: 67.8Kg/s; Frc = 480Kg/s.
4.2.5 Effect of Catalyst flow rate (Frc) on product distribution
Increase in the catalyst flow rate means the catalyst spends less time in the riser, reduction in deactivation of catalyst, catalyst average activity in the riser will be higher and the cracking reactions will be more intensive. These will lead to an increase in the conversions of gas oil and subsequent increase in the yield of the products. There will also be an increase in the sensible heat accompanying the catalyst, hence there is an initial increase in the riser outlet temperature but as reaction proceeds, the increased cracking reaction causes an increase in the heat absorbed and results in a decrease in the outlet temperature until steady state is attained (Akpa et al.
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4.6: Effect of Regenerated Catalyst flow rate on the yield of y1 (Gas oil), y2 (Gasoline), y3 (light gases) and y4 (coke). Operating conditions: Tf = 790K; Trg = 960K; Fgr = 67.8Kg/s; Frc = 3*67.8Kg/s: 5: 14.7*67.8Kg/s;

4.2.6 Effect of Catalyst- to- Oil Ratio (COR)
The changing of values for the catalyst - to - oil ratio (COR) in the riser mainly affect yield of various products. Due to more catalyst flow rate, the number of active sites increases, causing more cracking, increasing conversion of gas oil and yield of fuel gases and coke. The activity of the catalyst decreases after some time due to deactivation of catalyst by deposition of coke and drop in gasoline yield occur as well (Prabha et al. 2012).
As observed from the Fig 4.7 there is high conversion of gas oil of about 76% between COR of 3 and 7.5. Also, the yield of gasoline increase up to a maximum point of 0.54 wt% beyond which increase in the COR led to a drop in the gasoline yield. This is as a consequent of the higher rate of reaction resulting from increasing the COR which produces more coke. Deactivation of the catalyst due to coke deposition could be said to reduce the catalyst activity, hence the drop in gasoline yield later on. This is consistent with the work of Alvarez – Castro et al.

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