7 replies to this topic

[phalgun]

hi
im working with NGL recovery process in hysys. in this process i have to control the DEWPOINT of the product gas also. so which method i have to use for dehydration. TEG absorption method or refrigeration method. what are the limitations for each method. finally, can we use both methods in one process to obtain both dewpoint and required NGL recovery.

[Art Montemayor]

You don't state the type of process you are planning to employ to do the NGL (Natural Gas Liquids) separation. Without this basic information, you can't make a reasonable and accurate process judgment in picking the type of feed preparation process for removing water from the natural gas. I think you should pay more importance to the process logic and planning than to the simulation that follows. Without concrete and accurate process knowledge, the resulting simulation is useless. Garbage in equals garbage out.

For example, if you plan to use a state-of-the-art cryogenic separation process for the NGLs, then you have no alternative except to select Adsorption as the process for removing all the water from the natural gas feed stream - neither TEG or refrigeration are capable of preparing the natural gas to a the dehydrated level required by a cryogenic process.

[ashetty]

hi
im working with NGL recovery process in hysys. in this process i have to control the DEWPOINT of the product gas also. so which method i have to use for dehydration. TEG absorption method or refrigeration method. what are the limitations for each method. finally, can we use both methods in one process to obtain both dewpoint and required NGL recovery.

phalgun,

Selection of the method required depends on a few things.For example...Feed gas composition..operating conditions... sales gas specs etc. There are various methods for dehydrating natural gas, and hydrocarbon dew point control.Dehydration can be achieved by absorption,adsorption,gas stripping...refrigeration etc.Firstly based on the gas composition please check the hydrate formation conditions using hysys (Gas or liquid must be below its water dew point or saturation condition).In certain cases dehydration may not be neccesary or feasible and you might opt for hydrate inhibition methods i.e inject glycol or methanol into the stream to lower the hydrate formation temperature at a given pressure.In those situations where inhibition is not feasible or practical,dehydration must be used.TEG is a good choice for NG systems, but again information supplied by you is insuffient to make a call. For example at very high acid gas content and
high pressures glycols can also be soluble in the gas.
Regarding the HC dew point control, you can go in for mechanical refrigeration using propane.Again...what is the HC dew point spec of the sales gas are we talking about, what is the inlet compostion from the wells.If we have very lean gas (very high C1 content) and the composition is not expected to change over the life cycle of reservoir and pessures are sufficiently high you might opt for a JT valve if the sales gas HCDP spec is not very stringent (I`ve seen it as high as 15 deg C) also for recovery of substantial condensate from these lean gases you might have to chill it to very low temperatures.If the pressures are low then JT will not be a good option due to the pressure drop involved.

Anyhow, for your simulation you can try TEG dehydration, downstream of the process gas booster compressor and the dehydrated gas can then be passed through a chiller plant using propane as refrigerant.

Thx,

[Zauberberg]

Also, one more thing worth to mention: hydrate formation studies should not be performed using Hysys. It is better to use OLGA, if available.
Hysys does not give consistent results, and hydrate forming regions are (sometimes) contradictory within the same flowsheet.

Regards,

[JoeWong]

Also, one more thing worth to mention: hydrate formation studies should not be performed using Hysys. It is better to use OLGA, if available.
Hysys does not give consistent results, and hydrate forming regions are (sometimes) contradictory within the same flowsheet.

Regards,

Zauberberg,
Thanks for sharing...

Have this reported to ASPEN ? What's the incident no ?
Do you mind to share more information on this aspect ? Things like composition used, how the inconsistent results were found...

OLGA ? Do you mind to advise the website for further check ?

Thanks in advance.

JoeWong

[leley]

asheety and zauberberg,

in NG recovery, can flash separator replaced JT-valve for lowering the dew point ?

thanx 4 advance,

ledyf

[y_zj]

Well, I want to Dehydrate using DEG absorption. What is the right operating pressure in the process ?

[Art Montemayor]

Yang:

If you have a legitimate and worthy problem that needs help or resolution, why don't you start a new thread dedicated to it? Your interuption within this thread detracts any responses meant for the original poster.

This is not a teenage chatroom. It is a serious attempt to help student and professional engineers who are seeking other opinions or help in establishing a resolution to a specific problem. We can help - but you must supply the background, basic data, and scope of what you are trying to do.

Without the above needed basic information, there is no answer to your query.