How To Calculate The Flowrate of Motive Fluid in An Ejector PDF
How To Calculate The Flowrate of Motive Fluid in An Ejector PDF
How To Calculate The Flowrate of Motive Fluid in An Ejector PDF
Dear Friends,
In one of my ongoing projects, there is a requirement of ejectors which
uses fuel gas as motive fluid. Process fluid has the pressure of 0.02 Saeid Rahimi Mofrad
barg and this is to be pressurized upto 0.2 barg using the motive fluid in Senior Specialty Process Engineer at Fluor
the ejector. Could anyone share your experiences on how to calculate
the motive fluid flowrate for this application? See all members
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Saeid Rahimi Mofrad
Senior Specialty Process Engineer at Fluor
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I had the same question couple of month age. See below link: Saeid, get the latest on Jaguar Land Rover Jobs,
http://www.linkedin.com/groups/Using-fuel-gas-as-motive-3822450.S.58700098?qid=1c7e2578- News & more!
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I searched a lot but found almost nothing, especially, when it comes to gas ejectors! There are
lots of theoretical discussions about how ejectors work but not what a process engineer in EPC
business is interested to see, practical and simple!
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I tried to correlate the data I received from the gas ejector vendor with available steam ejector Mohammad Dadkhah, AMIChemE
calculation charts but I failed. I guess you have to finally hang on vendors. joined a group:
Delete November 15, 2012 Chemwork
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Amir Mofidi
48m ago
Sr. Process Engineer at Wintershall
I have developed a spreadsheet which calculates the motive fluid by iteration. I can search in my Lakshmi Shanmugam commented on
a discussion in Chemwork.
Amir files and sent it to you
Sridhar Pokala Shanmugam
Like Reply privately Delete November 15, 2012 Scrubber liquid outlet line
design conditions We have a
compressor discharge scrubber
ARIJIT SEN vessel with the operating conditions as
Proposal Engineer at Process Group International 76 barg and 45degC. Design
conditions are: 95 barg and 93degC.
Dear Sampath, The vessel is 600# CS with 316L lining
Below link can be useful for your problem. and the gas outlet... more
ARIJIT 3h ago
http://www.1877eductors.com/pdf/Pumping_Liquids_V2010.pdf
Like (1) Reply privately Delete December 16, 2012
Nooshin Harandi likes this
Regards
Arijit
Unlike Reply privately Delete December 17, 2012
Nooshin Harandi, Saeid Rahimi Mofrad and 1 other like this
Hooman Tabaraei
Specialist Process Engineer (MIChemE, CEng)
Dear Sampath,
Hooman
Currently I was involved in a similar assignment for ejector sizing, and we did it by UNISIM,
however we need to get confrmation from relevant vendor, CALTEC, for nozzles size. You can
build it easily in HYSYS or UNISIM, to estimate HP (motive fluid) flow rate. Hope it helps you, pls,
feel free to contact me if you need more information.
Like Reply privately Delete December 20, 2012
Sampath Kumar R
Upstream Process Engineer at Technip
Dear Friends,
Sampath Thanks for your information.
Kind Attn: Mr.Hooman:- I checked the motive fluid requirement in HYSYS and it gives very high
flowrate for the following conditions:
Process fluid inlet pressure = 0.02 barg
Process fluid outlet pressure = 0.2 barg
Process fluid flowrate = 1600 kg/hr
Motive fluid pressure = 15 barg
The flowrate of motive fluid is calculated (by HYSYS) is 31000 kg/hr which seems to be very high.
Anyway, as you told, we need to rely on vendor only. No other go...
Kind Regards
Sampath Kumar R
Like Reply privately Delete December 21, 2012
Sampath
I guess you have used the gas ejector option in Hysys along with the default sizes for suction,
motive and discharge nozzles (which are quite large) for your calculations.
The ejectors are strange equipment items. They are designed almost for a single point duty ( one
discharge pressure , one motive fluid pressure and suction condition) with a very narrow operating
range. The compression is achieved through creating a very high velocity at the motive gas nozzle
exit to reduce the pressure inside the ejector body low enough to suck the suction gas in. The
motive gas nozzle (and in general ejector internals) is customized for the specified duty.
This means that if you dont correctly design/select the optimum size/model in your sizing
calculation, you will end up with wrong results (basically high or low motive gas flow rate). In your
case, you have used very large ejector for your application, that is why you need a high flow rate
of motive gas in order to establish the required velocity at the nozzle.
In other words, for the case that you have specified above partially (as the motive ad suction gas
molecular weights a temperature also affect the motive gas flow calculation), you could compress
the same amount of gas to the same discharge pressure with much lesser motive gas if you
would have reduced the size of ejector in Hysys (especially the motive gas nozzle).
Hope it helps.
Saeid
Delete 1 month ago
Prashant Yadav
Asst. Manager, Process Design
in my case ejector was working and i had to calulate the how much steam is going in. but in my
case it was not able to get the value of Dn so i calculate the flow indirectly.
Please share your expereince.
Unlike Reply privately Delete 1 month ago
Saeid Rahimi Mofrad likes this
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