4 replies to this topic

[alameehs]

Good day
I started with my colleagues to do push test by increasing C5 feed to steam cracker by 10 t/hr. These craker normally take a feed from three source ethane,propane and C5 to produce ethylene and propylene. Now the test is completed and I want to calculate the amount of propane and ethane which is equivalent to C5 addition to tje furnace to a achieved the same production of ethylene and propylene

Shall I ues the ethylene yeild calculation which is the ethylene product\total feed (C2,C3 and C5)

Thanks for help

[Pilesar]

The yield curves for your furnace depends on feed composition in addition to other parameters. Ethane does not make much propylene when it cracks. C5 produces a higher amount of heavier olefins. In other words, the change in ethylene yield will not be the same as the change in the propylene yield. The ethylene yield calculation you suggest can be applied to that single feedstock composition. Predicting yields for different feedstocks is tricky. I recommend your own set of historical yield curves to use in interpolation between feedstocks, but you can use commercial cracking prediction software. Much depends on the questions you are faced with and how you plan to use the answers.

[PingPong]

Ethane, propane and C5 each have their own optimal cracking conditions such as COT and dilation steam ratio. Mixing them as a combined furnace feed is not a good idea when you have multiple cracking furnaces available. Better send each feed to a separate furnace.

 

If, for whatever reason, you feed the furnace(s) with a mixture then the effect of adding extra C5 depends on what you do with the COT and amount of dilution steam: leave the same or change up or down, or .....

In any case adding extra C5 will affect the coil residence time of all feed components.

[alameehs]

Thanks gentlemen

We have in our plant dedicated furnaces for each feed stock. We just finish push test for C5.like and we plan to do other push test for ethane. I would like to calculate how much ethane need to be added to furnace to achieve same production of ethylene when we increase C5. Is there any help to do that.

Thanks

[PingPong]

I have never seen yields for steam cracking of C5 and I don't see the advantage of buying such feed compared to buying saturated C4's. Economics for C5 feed will likely be lower than for saturated C4's.

 

Anyway,

My best guess is that about 4.0 to 4.5 t/h C2 feed will yield the same amount of ethylene product as 10 t/h C5.

C2 feed produces very little propylene so it would take huge amount of C2 feed to produce the same amount of propylene product as 10 t/h C5.

 

I guess that about 7.5 to 8.5 t/h C3 feed will yield the same amount of ethylene product as 10 t/h C5.

And I guess that roughly 12 to 16 t/h C3 feed will yield the same amount of propylene product as 10 t/h C5.

 

Exact quantities depend very much on furnace licensor and design, operating severity, et cetera.

 

 

Your experienced coworkers should however know from operating experience how much products each feedstock yields in the given plant. How else have they optimized the operation and economics of the ethylene plant all those years?

Edited by PingPong, 16 February 2017 - 07:45 AM.