4 replies to this topic

[Rudra]

Hi ,

I am working on dehydration of natural gas using TEG.
I wanted to know why inlet scrubber is required prior to absorption.
I read in one article that if inlet scrubber is not provided, glycol loss will be more.
Can someone explain me why this happens?
Is it necessary to provide inlet scrubber? what may be the impacts of not providing the inlet scrubber?

[Art Montemayor]

Rudra:

It is considered foolhardy by everyone who has operated a TEG natural gas dehydration unit to operate without the efficient use of an inlet separator (or “scrubber”). No major engineering designer-fabricator of TEG units will design or install a dehydration unit without the employment of an efficient inlet separator. No major oil company – Shell, Exxon-Mobile, Total, etc., etc. – will operate a TEG unit without the use of an inlet separator. Some designer/fabricators use the bottom section of the TEG absorber (“contactor”) to incorporate an integral, compact type of separator prior to allowing the humid gas to enter the bottom section of the absorber. This is a low-cost method of incorporating a separator. Others, like some of the major oil companies, insist upon and specify a “filter-separator” – which is a very efficient type of separator in order to ensure that all liquid and vapor contaminants are removed from the natural gas prior to entering the TEG absorber.

The principal reason for using an inlet separator immediately prior to the absorber is to ensure that any liquids – whether water, salty water, oil, or other contaminants – do not enter into contact with the Rich TEG. The results of not using an inlet separator are usually foaming, contamination, fouling of TEG packing and exchangers - especially the reboiler tube bundle or fire tube, and off-specification product gas.

I have never seen or heard of TEG losses increasing due to a lack of a separator. Who wrote the article you cite and where was it published? A separator does not reduce TEG losses; it reduces TEG contamination.

[JoeWong]

...The results of not using an inlet separator are usually foaming, ...
...A separator does not reduce TEG losses...

Thanks to Mr. Montemayor detail explanation.

I guess...Without inlet separator potential lead to HC in TEG system and foaming may occur. Foaming potentially lead to TEG losses...

Having said that it is subject to how lean is the gas and the potential of HC knock out in the TEG system. A separator does not necessary reduce TEG losses.

[Geet]

Rudra,

As per my understanding TEG is used for absorbing moisture present in the Natural gas. An inlet scrubber is used to remove the free moisture content present in the gas, i.e. water droplets that can be removed by settling is removed in it, which in turn reduces the load on TEG contactor. and only bound moisture goes as a load to TEG contactor, thats why the glycol loss get reduced.

[amdady]

It is something related to the gas phase envelope; as you recall the major parameters effect the gas phase envelope are: temperature; pressure and compositions.

The main purpose of the inet seperators are to remove the liquid from the gas. If you remove the liquid the shape of the line will gonna change and based on it the hydration temperature will change also.
Many people in gas industry are taking care of the hydration temperature. You have to play with these parameters to avoid hydration.. You may refer to thermodynamic for more information