Archive for July, 2013

Time Saving Detail in a Coking Cycles

{0 Comments}

Time Saving Detail in a Coking Cycles

Figure 2-5 shows the valves used during the coking cycle. Prior to switching out of a coke drum, the process operators must be sure that the empty coke drum is truly empty. Trying to speed up the cycle by cutting hot feed (900°F) into a coke drum that is incompletely drained will cause a foamover. …

Read More…

Human Factor in a Long Coking Cycles

{0 Comments}

Turning around a coke drum is a cooperative effort between the process operators and the decoking crew. It is labor intensive and normally accom­plished without the intervention of supervisors. The work itself is best charac­terized as dirty, difficult, and if not done with care, dangerous. To get a 12-hour cycle, every facet of the complex …

Read More…

Fighting Long Coking Cycles

{0 Comments}

How long should it take to turn a coke drum around? The elapsed time from when one switches out of a full drum until it is empty and ready to receive resid again is called the cycle time. Most delayed coking units are designed for a 24-hour cycle time. Shorter cycles can be used in …

Read More…

Increasing the recycle ratio is supposed to stop shot coke formation. However, in some cases, increased recycle ratio has no effect. Why?

{0 Comments}

Whether or not increased recycle ratio reduces shot coke forma­tion is dependent on the composition of the incremental recycle. Recycling 950°F-1,000°F coker gas oil will increase the formation of needle coke. Recycling 600°F-700°F coker gas oil will reduce the formation of needle coke by raising the coke drum outlet vapor temperature. Heavy recycle is necessary …

Read More…

Why is it important to reduce the sulfur content of needle coke, and how can it be controlled?

{0 Comments}

Sulfur causes puffing of the calcined needle coke. Increasing the delayed coker recycle ratio by cutting the heavy coker gas oil end point will make more needle coke and reduce the sulfur content of it. Other ways to improve needle coke quality include minimizing steam in the heater passes, reducing the gravitity of the recycle …

Read More…

Is there any shot coke in needle coke?

{0 Comments}

Needle-grade coke contains no shot coke. Commercial needle coke is typically produced by charging FCCU slurry oil to the delayed coker. All of the components in the slurry oil coker charge are produced as a vapor from the FCCU reactor fresh feed. Even if vacuum tower bottoms are charged to the FCCU, none of the …

Read More…