9 replies to this topic

I am a student in last year of college, and i am doing a project about hydrogen production from natural gas reforming, with production of steam at 45 kg/cm2_g.
I need information about how to size and design a deaerator, and i also need information about designing a condensate stripper that makes a first separation of water recovered from the process passing saturated steam in counterflow.
I hope that my english has been clear, and thanks in advance for any info you can provide.

[smalawi]

Hi,

As for the deaerator its a simple vessel with two parts. the first is to strip the O2 from the boiler water and this is typically modeled as a flash vessel in a simulater, you have the boiler water O2 content and you strip it with stream up to your new O2 limit.

The mechanical design is more like a column with tray sections or packing. You can use say 1 - 1.5 meters of packing (CMR) and dia of the packing section is 70 % flood. In Hysys - Pro II you can use one stage column and do tray rating for quick estimate.

the second part of the deaerator is another vessel, horizontal or vertical. This is a surge vessel for the pump, typically sized for say 5 min Nmormal velvel to Low level / high level surge capacity for the high pressure pump. You might design for higher surge capacity if the supply boiler water fluctuates.

As for the condensate stripper its not a simple design. It depends on whats in the water that have to be stripped. If its just trace O2, then the deaerator is ok. However, if its NH3, CO2 or worse organic acids / bounded carbonates, then you need a special design.

Asuming you only have traces of CO2, you simply design a stripper column with live steam. The number of trays can be estimated from Hysys / Pro II simulation with simple stripper column. THe number of trays is subject to your CO2 concetration in the product. You can use ~30 % efficency for converting the theoritical trays to actual trays. The column can be trayed here and Hysys or Pro II tray rating can be used to check the column diameter.

You might consider using a reboiler rather than live stripping steam if the steam quanitiy is too high, by this way you reduce the amount of steam you loose and reduce the diameter of the column.


I asume you are a student, so keep things simple and dont complicate things. You will probably ask what limits should I traget for O2 and CO2, these can be found from the boiler water specs.

cheers,

sm

Hi,

Many thanks for your help. However, there is something i didn´t understood; when you said that in Hysys - Pro II i can use one stage column and do tray rating for quick estimate, you mean for a tray section or a packing section?, and the use of one stage is only to use it in Hysys - Pro II, right?

Thanks, and happy new year!!

[smalawi]

Hi,

that is for the packing section to check the diameter you need for the top section. You use one stage as it was a single vessel. If you cant meet your O2 limit you might need more, the sizing tool will give you the needed hight from HTEP calcs.

Hysys or Pro II they its the same approch,

cheers,

sm

[astro]

One person's condensate stripper is another's feed gas saturator:

Natural Gas Saturator

A saturator / condensate stripper is a gas / liquid contactor. Nothing special really. What are you after specifically?

[JoeWong]

A saturator / condensate stripper is a gas / liquid contactor. Nothing special really. What are you after specifically?

bryanb is a STUDENT and i guess he/she is looking for coaching and guidance in "...sizing and designing a deaerator...information about designing a condensate stripper...".

[astro]

A saturator / condensate stripper is a gas / liquid contactor. Nothing special really. What are you after specifically?

bryanb is a STUDENT and i guess he/she is looking for coaching and guidance in "...sizing and designing a deaerator...information about designing a condensate stripper...".

A statement of the design problem would be a start along with quantitative info such as flows, pressures, temperatures and any other process constraints.

For general guidance I recently put this up:
http://www.cheresour...x...ost&p=25008

Never hurts to open a text book or search the depths of the internet first. That way the request for help can be focused rather than leaving a respondent trying to guess what's needed.

I don´t think that a Natural Gas Saturator has much to do with the condensate stripper I mentioned; I thought it was clear that this one was to separate gases from a water stream using steam in counterflow. The first answer I got was helpfull, who gave it didn´t complain about the info I gave, and he understood well.

And I did a search on internet and books but I didn´t find anithing complete or clear enough about it.

[smalawi]

the missing keyword is "steam" condensate, but if you ever worked in a hydrogen plant you will likely know.

Deaerator design is not well documented as far as I know, if you know some referances please let me know

I only know by experaince.

Condensate could be many things; it could be steam, heavy gas hydrocarbons, crudes, or many other things.

cheers,

sm

[astro]

smalawi, thanks for helping out there.

For bryanb's benefit, the excess steam from the steam reforming and water gas shift reactions in an H2 plant front end is removed from the process stream by condensation. Side reactions from the shift catalyst beds can produce methanol and tertiary amines that are a waste disposal nuisance. One method of treatment that is applied in industry is to saturate the incoming feed gas with that process condensate (energy efficient and reduces treatment chemical usage too). The MeOH &c. are cracked in the reforming process and go forward with the reformed gas. I've seen that unit operation referred to as a feed gas saturator or a condensate stripper.

At first pass, your post appeared to relate to 2 design questions not 1, as it turns out.