9 replies to this topic

[P Thakur]

I was designing an absorber for flue gas application wherein CO2 from incoming flue gas will be absorbed by amine. The absorber operating pressure would be slightly above atmospheric pressure.

 

1) What should be design pressure of absorber? - Will it be 0.07 barg or 3.5 barg or some other value? Reference to any standard would be greatly appreciated.

 

2) Whether this absorber would be excluded from PED classification since it is operating close to atmospheric conditions or not. If not, then it should belong to which PED Category? Since it is having both gas Group 2 & liquid Group 1, what is to be mentioned as fluid phase & group classification?

 

[spchauhan12]

1) As per PDVSA (Company located in USA) : Max. Op. Pressure (MOP) < 247 psig , you may calculate : Min. Design pressure (Process) as : MOP +/- 25PSI , The max. operating pressure should be 5% higher than controlling case.

 

Hope in this way, you can fix process design pressure.

 

 

2) For PED - Query Refer below link to download this doucment. You may refer example section ( Steam flash drum - Example)

 

www.blackmonk.co.uk/downloads/PED_Guide.pdf

 

Hope this helps you.

 

Regards,

 

SPC

[Saml]

P Thakur:

 

1) Whatever you decide based on your engineering judgement. There is no standard regarding how to define the design pressure. What many mention as "standards" are company engineering guidelines like Exxon Desing Practices or Shell DEP. Please check the following thread that has very nice insights into what these standards are and where you should (not) use them

 

https://www.cheresou...rent-standards/

 

2) The PED scope is set by the Design Pressure, not the operating pressure. So a vessel operating at 0.05 barg with design pressure of 2 barg falls into PED while a vessel operating at 0.4 barg with a design pressure of 0.48 does not.

[P Thakur]

Thanks Saml for your response.

[Art Montemayor]

P Thakur:

 

What do you mean by the acronym “PED”?  Please do not use acronyms in our Forums without defining their meaning.

I believe you are referring to the “Directive” of the European Parliament and the Council on pressure equipment, which is one of the main product  "harmonization" Directives based on the European “New Approach” principles.  Am I correct?

 

I have designed and built numerous flue gas systems for the selective removal of CO₂ (as have many other U.S. engineers who have applied the famous Bottoms Amine Process patented in 1930 for the Girdler Corporation).  There must be thousands of such units operating in the world today based on that technology and the basis for designing the amine absorber has always been that the flue gas is first cooled, cleaned, stripped of any contaminants such as sulfides and soot at the flue gas available pressure - which is normally the pressure exiting the combustion chamber where the flue originates.  This pressure is usually measured in inches of water column - depending on the design of the combustion device (usually a boiler).  What kind or type of combustion chamber are you dealing with that has such a high operating pressure on the flue gas side?  Please furnish detailed basic data on this application.

 

I identify the acronym “PDVSA” as Petróleos de Venezuela, S.A., the Venezuelan state-owned oil and natural gas company.  This company may have an office in the USA, but I don’t believe it has engineering offices here.  Venezuela is certainly not a member of the European Union (EU), so I don’t see the relationship between both entities.  Please explain.

 

The document you refer to is a British document and Britain is now seeking to remove itself from the EU, as I understand it.  If this is true, then the document may not be acceptable to the EU.

 

If you are in India, why would you be applying a EU directive to a South American application?  Just my curiosity and interest in learning the details of your application.

[P Thakur]

Dear Art Sir,

 

I am referring PED as 2014/68/EU - Pressure Equipment Directive. I am in India  and working for Norwegian  Project wherein this directive compliance is to be followed. There are two sources of the flue gases. One in ammonia reformer flue gases (operating P& T are 1 bara & 200 C) & other source is incineration of waste (operating P & T as 1.01 bara & 80-100 C). Currently in both cases gases are emitted from stack to atmosphere. Therefore we are providing one fan for compensating for pressure drop across direct contact cooler column and absorber column. Their design pressure are considered as 1.3 bara & 1.4 bara since operating pressure would be very close to atmosphere.

 

I am curious about increase in cost of equipment (factor?) by PED compliance as compared to ASME or other relevant less stringent design standards? 

[Art Montemayor]

P Thakur:

 

Now, with further basic data, your inquiry starts to make sense - although you still do not furnish a flow diagram or sketch of the proposed process.  You still do no reveal a lot of important basic data (nor do you answer my direct questions!):

• Are you trying to recover the CO₂ in the flue gas?  If so, what “amine” are you employing?  There are a lot of different amines that can be used; simply state which one you are using.
• As I stated previously, you must first cool down and “scrub” the flue gas in a packed tower, using scrubbing water.  Next, you should submit the cooled flue gas to a soda ash scrubber for further removal of impurities.  You should show this in a sketch, with temperatures and pressures.
• Any direct-fired reformer is going to essentially have “atmospheric” pressure flue gas being generated.  You should show in your sketch how you intend to make the flue gas flow through the required water scrubber and soda ash towers.  HINT: use a centrifugal, induced blower after the soda ash tower and before the amine absorber.  Show this in the flow sketch.
• You say one flue gas source is at 1 bara & 200 ^oC while the other is at 1.01 bara & 80-100 ^oC.  I don’t believe this until you can prove otherwise.  No flue gas exiting a combustion chamber - even with a heat economizer - will have temperatures that low.  State how you expect to accomplish that.
• I don’t know if you are an engineer or not, but you show little if any practical knowledge of what is involved in this application - regardless of the PED.  Practical, common sense should tell you that the flue gas pressures involved do not merit a pressure vessel design for either the water scrubber, soda ash tower, or the absorber.  All these towers are essentially atmospheric pressure design-based and their wall thickness is given more for structural, seismic, wind, and external stress needs than for any internal pressure.  Why you want to apply the PED “directives” is beyond me.

You asked two questions in your initial post and I give answers to them:

1) What should be design pressure of absorber? - Will it be 0.07 barg or 3.5 barg or some other value?  Reference to any standard would be greatly appreciated.
The process pressure design of the absorber should logically be the maximum discharge pressure of the induced draft blower that has to overcome the absorber packing pressure drop.  This should be approximately less than 1/2 psi - depending on the size of the packed beds and their diameter.  However, as I have indicated, common sense dictates that you will wind up with more absorber shell steel required to sustain the required ladders, platforms, pipe supports, wind, seismic, corrosion allowance, and other external loads than you will need to contain the internal pressure.  That is why I believe you are wasting your time with PED, ASME, etc., etc.

 

2) Whether this absorber would be excluded from PED classification since it is operating close to atmospheric conditions or not.  If not, then it should belong to which PED Category?  Since it is having both gas Group 2 & liquid Group 1, what is to be mentioned as fluid phase & group classification?
I don’t know.  Why don’t you ask the Norwegian engineers who specify it.  I’m a USA engineer who has done this application many times and who believes the Euros are doing nothing more than building bureaucratic paperwork empires with their so-called directives.  Perhaps one of our European Forum members can help here.

 

 

[IGC]

PED applies to pressure vessels with a design pressure greater than 0.5 barG.  If your vessel is operating close to atmospheric pressure, then maybe you can get away with specifying a design pressure below this, however it is more down to the overall process in case there is an upset condition where the pressure could raise above this. You will need to speak with your client to find out what design pressure they want for the vessel.

 

The category is dependent on the;

 

Pressure

Volume

Fluid group

 

Fluids are defined via CLP Regulation (No 1272/2008, classification, labelling and packaging of substances and mixtures).  

 

With this, you would be able to determine the required table for the classification of press

 

All in all, you might ending up falling under SEP (sound engineering practice), which has its own rules under PED and is quite lax to be honest!

 

 

2) Whether this absorber would be excluded from PED classification since it is operating close to atmospheric conditions or not.  If not, then it should belong to which PED Category?  Since it is having both gas Group 2 & liquid Group 1, what is to be mentioned as fluid phase & group classification?

I don’t know.  Why don’t you ask the Norwegian engineers who specify it.  I’m a USA engineer who has done this application many times and who believes the Euros are doing nothing more than building bureaucratic paperwork empires with their so-called directives.  Perhaps one of our European Forum members can help here.

 

 

Regarding PED, you must remember that Europe is made up with many different countries each with their own pressure vessel design rules and standards.  CODAP, AD Merkblatt, BS5500, Stoomwezen, to name a few.  The New Approach method was developed to remove technical barriers to trade - and this was done by "ensuring that all equipment place on the market or put into service in the EU for the first time, meets minimum safety requirements."

 

You can still use ASME codes as well to meet the EU PED, it is just that the ASME codes do not have a presumption of conformity with the PED which means that you are required to do extra work.  If you were to follow the EN 13445 for instance, it should be easier (and cheaper), to meet the minimum requirements.  

 

Off topic:  In the 2017 edition of ASME VIII, Div 1 is pretty much getting sidelined now.  Div 2 being split into Class 1 and class 2 vessels.  Class 1 has allowable stresses based on UTS/3 while class 2 is UTS/2.4, which is more along the lines of European standards, so 

[P Thakur]

Art,

 

• I am using patented amine for CO2 capture from flue gases. I am using centrifugal fan followed by cooling in direct contact cooler and absorption & water wash in Absorber Column. Both are packed column.
• The outlet temperature is waste incineration is really 80-100 C since they want to extract heat for their district heating network.
• I am aware that wind load, structural, snow load & other factors would be deciding factor for thickness calculation rather than design pressure. 
• Thanks for help. 

IGC,

 

 

 however it is more down to the overall process in case there is an upset condition where the pressure could raise above this

Upstream of the column is fan with just enough pressure to compensate for the pressure drop across packing & flue gas duct.So, I think a design pressure of 1.3 bar would be more than sufficient.

 

Thanks everyone for response.

[Art Montemayor]

P Thacur:

 

What do you mean by "patented amine"?   If it is patented, then the design should be fixed and handled by the entity that owns the patent.  Are you referring to the a-MDEA as patented by BASF?  If so, then BASF has a voice in deciding how to apply the process and what to expect from it.  

 

No flue gas CO₂ removal system using an amine absorber that I've seen has a blower located directly downstream of the flue gas generator followed by the required water scrubber.  The blower is located downstream of the water scrubber in order to subject it to cool flue gas, not hot flue gas.  I have done this process analysis in the past and the most efficient and reliable operating location for the flue gas blower is downstream of the water scrubber.  I offer this personal field experience for your benefit and profit.

 

Another experience factor:  Be sure to ensure that your flue gas generator has careful and continuous excess oxygen content control on the flue gas generated - especially if comes from an incinerator.  If you don't ensure this, your water scrubber will be subjected to excessive corrosion and quick failure due to corrosion - necessitating that you furnish extra corrosion allowance on the water scrubber wall thickness.  Also, I would not proceed with the design described without a soda ash scrubber.  Experience has shown it is a necessary safeguard.