Processing Light Hydrocarbons C1-C5 2

[DutchDeutschEng]

Hi Guys,

Looking into possible solutions to process a vapor mixture mainly containing short-chain hydrocarbons (C1 to C5).

In general this vapor is treated as a waste gas stream and needs some kind of reliable treatment whereas a flare as simple engineering solution comes to mind. (Energy "wasted")
1. But what chemical processing possibilities do I have to retrieve some kind of valuable product? (sell-able Product)
2. OR is there an easy solution to break down those chains to get methane for easier combustion in an engine? (Energy recovered)

The vapors result from several thermal cracking processes (Temperature around 752 F /400 C).
Mass flow is relatively low with 10 kg/h per production line. (Up to 12 lines are planned, so maybe merging those streams is possible)

Any improvement to a flare would be great.
Looking forward to your reactions ( First time post in this forum & at all in a forum )

 

[georgeverghese]

Use these as fuel gas in furnaces, provided there is no H2S or other corrosive components. Pressure boosting may be required. Otherwise, consider recycling these streams to the cracking furnace feed.

 

[DutchDeutschEng]

Hi georgeverghese,

Thank you for the quick answer.
The vapors are free of H2S (or other corrosive components) and therefore ideal as fuel gas for a furnace. I will look into options like this on the site. If I am not mistaken there is some kind of district heating system (boiler) available.

There is some kind of reactor available for cracking, but I need to look deeper into the operating conditions to formulate a better question for that. But as well I will look into that.

Do you know of a "low temperature" process to crack those kind of vapors? I am talking about 572-752 F (300-400 C). For example a catalytic conversion? Or am I bullshitting around with my small knowledge about this topic? ^^

 

[LittleInch]

DDE,

Whilst I admire your desire not to just stick this "waste gas" up the stack, you need to understand why its done and in the main it's $$$

This mix of gases is usually split into their respective gases and cryogenic liquids, methane, ethane, propane, butane, pentane by chilling and distilling. This takes a lot of energy and fairly expensive equipment. Hence you need a lot of gas for it to make commercial sense to do this and also no other "nasties" in it. 10kg/hr is nothing, even total of 100kg/hr is low so no one is going to spend $500,000 in plant to process this amount of gas.

I'm not aware of any easy system to reduce C5 say to C1, especially when it's a mix of C1 to C5.

Burning this stuff in anything other than a furnace (e.g gas turbine or IC engine) would be difficult as the MW changes so much and it become difficult to burn. Just add lots of air and fire it to produce steam or something else which needs heat. You might have it as a second burner in your main furnace which is optimised for one type of gas. Just adding it to a methane stream will increase heating and messes up the burners.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[DutchDeutschEng]

LittleInch,

Thanks for the insights. I already assumed so, but didn't have the expertise/experience/knowledge to proof it.
And in my blue-eyed-newbie optimism I thought that there might be a miraculous way to solve this in a more resource saving manner.
There probably isn't and the easiest solution at hand actually is the one to go with.

Again thanks for the input

 

[georgeverghese]

Even with a max of 120kg/hr with all 12 waste streams, flows are still too low to justify extraction of C4 / C5 as light naphtha in a new plant. Good there is no H2S in these waste streams. Also check for vanadium content; have seen reports stating potential for furnace process tube failure due to Va from contaminated fuel gas.
Suggested scheme for FG would be:
a)Cool to ambient and pressure boost these streams to say 5-10psig
b)Knock out liquids and route vapors to dedicated low pressure burners in some furnace.
c)Pump out liquid on flow control to the debutaniser feed. Else recycle to cracking furnace feed.

 

[poli60]

george,
it's the first time I read/hear of vanadium in fuel gas.
I know/use several process standards (exxon, shell, fw, eni, aramco, fluor, total....) but no one covers this topic (well known for heavy fuel oils).
regards

 

[DutchDeutschEng]

Hey Guys,

Thanks for the feedback. I am truly amazed about how lively this forum is.

@george The Va content is expected to be very low to non existent. But thank you for the tip, I will keep it in mind for further projects. The scheme is a good starting point for the design, great!

 

[poli60]

just to be clear: vanadium doe not exist in fuel gas!
but i'm ready to be denied, on the base of trusted documents...
vanadium could be present in flue gases generated by heavy (liquid or solid) fuels
kind regards

 

[georgeverghese]

The option suggested for routing condensed liquids to the plant deC4 assumes the incremental H2S or acetylene in this condensed liquid stream (if any), has little or no effect on overheads or bottoms product quality or present any HSE concerns since this liquid stream would be very small in comparison to the main feed to the deC4 column. Gas composition is not stated.
@poli60 - this detail on Va content in FG is from an oil major's inhouse operations / design document.

 

[poli60]

thank you, george. hoping to see it in the future