14 replies to this topic

[dhrubabasu2013]

Dear Sir

 

 

Sorry some of the datas are corrected here.We have amine regenerator column whose bottom temperature is maintained by two reboilers. The LP steam of around 4 Kg/ cm²(g) and capacity of 25000 Kg/hr (each reboiler) is used for heating purpose. The one rebolier condensate level is almost steady but the other level is always hunting. The condensate level pot is controlled by condendate level controller.LT was suspected faulty and it was replaced but it is still hunting. LG was cleaned and fluctuation is still seen on glass gauge.The level control valve does not fluctuate when taken on auto mode. The steam taping for fluctuating one reboiler takes from extreme header end and other one is also taking from header (around 7 m from extreme taping).The condensates of both level pots goes to deareator whose pressure is around 1 Kg/ cm²(g). The stalling effect is neutralised as we kept fully open the steam valve for both reboilers. Please suggest some ways to improve the condition of level pot.The condensate pot is around 6 m below the exchanger. The P& ID will be attached shortly.The taping of steam line means here the connection from header.

Edited by dhrubabasu2013, 15 April 2016 - 08:21 PM.

[Bobby Strain]

Absorbers are not usually equipped with reboilers. Steam only 25 Kg/hr? Please give us a sketch or picture from P&ID. Otherwise we will be unable to help you.

 

Bobby

[Art Montemayor]

Bobby Strain is absolutely correct.  This thread needs a lot more basic data furnished as well as a detailed sketch of the piping and instrumentation installed from the takeoff on the steam supply headers to the steam condensate entering the condensate return line(s).  The written information given only raises more questions instead of furnishing basic data:

• As Bobby notes, the steam rate of less than 1.0 lb/min in a "reboiler" raises a lot of doubts and questions.
• What kind of amine unit is this that needs not one, but TWO miniature reboilers to heat up an absorber???  Why are vapors required in an absorber as in the amine stripper??  If heating the rich amine at the bottom of the absorber is really a necessity, then why not just rely on sensible heat transfer in a coil or external heat exchanger instead of latent heat transfer??
• But the real issue is the "trapping" of the produced steam condensate and its efficient transfer to the condensate return system.  Here, the word "taping" is, I presume a typo error or an erroneous conception of what happens when steam is condensed and returned as condensate.
• Are we to assume that BOTH "reboilers" are consuming approximately 1.0 lb/min of steam?  Or is that the steam rate for each "reboiler"?
• I find it very difficult to believe that anyone would use a level transmitter (LT) to detect the level of condensate being formed at the rate of 1.0 lb/hr.  That sounds ludicrous.  For that amount of steam condensate, any engineering contractor would normally recommend and use a simple float-activated steam trap with only a level gauge on the condensate drum - and that would be the most exotic design.  The design I would use would be a simple steam trap with a level gauge.
• At the condensate rate being controlled, the appropriate control valve being used to drain the product is probably in the order of ½" in size.  If anything larger than that is being used, that would explain the "hunting" being reported.

We need a detailed sketch and explanation of what is being done and why.

[Pilesar]

Do you have adequate steam traps in the steam supply to the exchanger? The condensate pot for the exchanger is probably not designed for the case where a large amount of condensate from the header surges into the exchanger. If your inlet steam is dry, then the source of instability may be in the reboiler itself. If this is a thermosiphon and you have a valve in the process inlet piping, you might try throttling that valve to see if operation becomes more stable.

[Bobby Strain]

Show elevations and locations for equipment, controls, valves, transmitters, and the tappings you refer to. Has this problem always existed?

 

Bobby

[rychurek]

Bobby, Art, question is about amine regenerator with LP steam flow rate 25000 kg/h each, so why your reply is about absorber with steam flow rate 25 kg/h?

[Art Montemayor]

rychurek:

 

The answer to your question is simple:  The O.P. (Original Poster) has revised what he/she first wrote.  Look again at the post and you will see that it was revised (edited) after Bobby and I noted the discrepancies.

 

The O.P. originally wrote the following:

"Dear Sir

We have amine absorber column whose bottom temperature is maintained by two reboilers. The LP steam of around 4 Kg/ cm2(g) and capacity of 25 Kg/hr (each reboiler) is used for heating purpose. The one rebolier condensate level is almost steady but the other level is always hunting. The condensate level pot is controlled by condendate level controller.LT was suspected faulty and it was replaced but it is still hunting. LG was cleaned and fluctuation is still seen on glass gauge.The level control valve does not fluctuate when taken on auto mode. The steam taping for fluctuating one reboiler takes from extreme header end and other one is also taking from header (around 7 m from extreme taping).The condensates of both level pots goes to deareator whose pressure is around 1 Kg/ cm2(g). The stalling effect is neutralised as we kept fully open the steam valve for both reboilers. Please suggest some ways to improve the condition of level pot."

 

I don't think the O.P. knows the workings of an Amine Unit since he/she hasn't responded to our questions and requests.

Edited by Art Montemayor, 20 April 2016 - 08:07 AM.
To include original O.P. post

[rychurek]

Read this topis on smartphone, I can't see any marks show that original post was revised, so edition should be blocked by admin or information about content changes should be added, becouse it's introduced confusion like this and unnecessary non engineering time consumption best regards

[dhrubabasu2013]

 51E102.xlsx   16.58KB   37 downloads

[dhrubabasu2013]

Please find the attached file for more details, if any more detail is required or to be corrected, reply.

[Bobby Strain]

Your sketch contains only one reboiler and pot. We need to see everything!

 

Bobby

[dhrubabasu2013]

 51E102.xlsx   26.23KB   36 downloads

[dhrubabasu2013]

Pls see the uploaded sketch

[Bobby Strain]

There is still not enough information. Is this a new problem?Maybe it is no problem at all.

Are there any steam flow meters?

 

Bobby

Edited by Bobby Strain, 24 April 2016 - 10:13 PM.

[dhrubabasu2013]

There always has been a hunting problem in control valve of condensate level...I ll update more sketch