9 replies to this topic

[Ali_gholamalian]

Hello 

 

I wish to design a unit by HYSYS and I need some help. I want one or more distillation column to extract etylen from dry gas of FCCU but feed stream contain noncondenceable gases ( 1.13% H2, 5.51% CO2 and 11.88% N2 ) and so I want remove these gases first.

 

Is there any kind of absorber for this mean? Or is there any specific type of tower?

 

P.S. the feed stream components are as below: (numbers are wt%)

 

H2       1.13

CO2    5.51

N2     11.88

C1     25.59

C2     18.53

C2=    22.9

C3        0.68

C3=      5.48

IC4       0.54

NC4      0.18

C4=      7.47

IC5        0.11

[PKS]

You can try the following:

1. First you have to remove CO2 with some Amine absorption system, then Put a demethaniser, in this column methane, H2 and N2 will be removed from top, now u have check as per your facilities where to take them.

2. the Demethaniser bottom to a Deethaniser, from where C3+ goes from bottom and C2+ from top.

3. The top of Deethanizer can be sent for C2 and C2= distillation. 

 

This is very preliminary and superficial as we don't know about the refrigeration facilities etc available. Anyways, hope its helps.

 

PKS

[Ali_gholamalian]

You can try the following:

1. First you have to remove CO2 with some Amine absorption system, then Put a demethaniser, in this column methane, H2 and N2 will be removed from top, now u have check as per your facilities where to take them.

2. the Demethaniser bottom to a Deethaniser, from where C3+ goes from bottom and C2+ from top.

3. The top of Deethanizer can be sent for C2 and C2= distillation. 

 

This is very preliminary and superficial as we don't know about the refrigeration facilities etc available. Anyways, hope its helps.

 

PKS

Thanks for your attention & answer.

Upstream unit is an amine unit, but the amine is MDEA and as we know, MDEA can not remove CO2 and a mixture by DEA may help, but reboiler duty is not sufficient, so this CO2 must remove with a simpler method, I will not suggest another amine unit!! right now I looking for specific type of absorber to remove CO2 from feed. second I must find a way to remove N2 maybe partial condenser helps.

There is a long way to go I guess.

 

Sincerely

[PKS]

It is dangerous to suggest with partial knowledge of the system, like wild guesses!! 

 

You can check with caustic scrubbing.

[RockDock]

caustic will remove the co2, but cannot be regenerated. removing the CO2 upstream is best.

[Padmakar Katre]

Hello 

 

I wish to design a unit by HYSYS and I need some help. I want one or more distillation column to extract etylen from dry gas of FCCU but feed stream contain noncondenceable gases ( 1.13% H2, 5.51% CO2 and 11.88% N2 ) and so I want remove these gases first.

 

Is there any kind of absorber for this mean? Or is there any specific type of tower?

 

P.S. the feed stream components are as below: (numbers are wt%)

 

H2       1.13

CO2    5.51

N2     11.88

C1     25.59

C2     18.53

C2=    22.9

C3        0.68

C3=      5.48

IC4       0.54

NC4      0.18

C4=      7.47

IC5        0.11

Please tell us the background of this assignment and scope. Looking at the composition it should be simply blended to unit fuel gas system unless the economics of C2= extraction is lucrative.

[Ali_gholamalian]

first thank you guys for your attentions.
well the goal is more benefit from dry gas. price of ethylene is equal to total dry gas, so this is so important to remove it and sell in markets.

I find something good today, and this is what I did; a dryer by absorbant bed for inlet stream to remove water, then a coloumn with partial condenser to remove N2 and H2 and C1 as gas and line up to off gas so c3 n c4 (lpg) will captured as bottom product. Overhead product will be remain c1, c2 n c2= so another tower need to separate c1 from c2s and at the end a tower to separate c2 from c2=

all of these must be super fractionator ( OVH T about -100 centigrade and P about 25 barg )

what's your idea?

[PingPong]

Ethylene is normally produced in an olefins plant by cracking of ethane, or heavier hydrocarbons. The gas mixture from the cracking heaters is cooled, compressed to some 35 bar, H2S, CO2 and H2O removed, and then cooled in a chilling train, to condense light hydrocarbons, which are then separated in several distillation columns to produce ethylene and byproducts. Refrigerant systems are required too.

 

It makes no sense to me to try to do all that just to recover some ethylene from a relatively small amount of FCCU gas, and I don't think anybody in the world is doing it.

The only option that would make sense is to sell your FCCU gas to a nearby olefins plant so that they can mix it with their cracked gas and process it in their downstream equipment.

If there is no nearby olefins plant then the FCCU gas is only good for fuel gas. I guess this is not what you want to hear but it is reality.

[Ali_gholamalian]

Ethylene is normally produced in an olefins plant by cracking of ethane, or heavier hydrocarbons. The gas mixture from the cracking heaters is cooled, compressed to some 35 bar, H2S, CO2 and H2O removed, and then cooled in a chilling train, to condense light hydrocarbons, which are then separated in several distillation columns to produce ethylene and byproducts. Refrigerant systems are required too.
 
It makes no sense to me to try to do all that just to recover some ethylene from a relatively small amount of FCCU gas, and I don't think anybody in the world is doing it.
The only option that would make sense is to sell your FCCU gas to a nearby olefins plant so that they can mix it with their cracked gas and process it in their downstream equipment.
If there is no nearby olefins plant then the FCCU gas is only good for fuel gas. I guess this is not what you want to hear but it is reality.

I know what's your mean, I have two plants one need dry gas for OL plant and one need the ethylene. OL plant offered lower price than usual because of ethylene in gas.

[Ali_gholamalian]

at the end I did it. 3 columns, a refrigerant system, a dryer for water removal. outlet streams are offgas , LPG n high purity gases , 99% C1 n 99% C2 n 99% C2=