[pervez]

Dear Respected Engineers,

Is there any calculation method to find out flow rate & density of the liquid of a Natural Gas Filter Separator? I have the following information / specification,

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Filter Separator:
The Filter Separator Should be fabricated steel/ vessels to ASME VIII Div. 1, Vertical type for separator of solid and liquid particles from Natural Gas having specific Gravity 0.6 Dimension and drilling in accordance with ANSI B 16.5 carbon steel. The unit should be 100% capacity.

a) Connection Size    : 6” x 6” dia ANSI Class 300 RF Flanged.

b) Maximum Operating Pressure   : 500 psig.

c) Normal Operating Pressure   : 350 psig.

d) Minimum Operating Pressure    : 250 psig.

e) Capacity    : 15 MMCFD at Pressure differential 1 psig (Max).

f) Filtration type   : Two stage- first stage filter cartridge type and second
             stage vane mist eliminator type. Cartridge made of fibre
             glass vane mist eliminator type. Cartridge made of fibre
              glass and vane mist extractor made of S.S.

g) Filtration Efficiency    :  i) Solid up to 3 micron and above 100%
               ii) Liquid droplets 10 micron and above 100%

h) Application       : Natural Gas Spec. Gr 0.6, Vertical cylinder type.

i) Closure    :  Quick easy opening & Closure system.

j) Design Code      :  ASME VIII Div-1.

k) Operation Temperature    :  Upto 50 Degree C

l) Corrosion Allowance       :  3mm for all pressure parts.

m) Flange Material   :  ASTM A 105

n) Body Material       :  ASTM  A 106 Gr. B

o) Cap Material    :  ASTM  A 234 Gr. WPB.
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CAN ANYBODY PLEASE ASSIST ME TO FIND OUT THE FLOW RATE & DENSITY OF THE LIQUID FROM THE ABOVE INFORMATION OF A NATURAL GAS FILTER SEPARATOR???

Regards,

R Islam
Dhaka, Bangladesh
email: info (at) kingfisher-woodpecker.com
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[eugenedakin]

Hello pervez,

I hope that I am interpreting your question correctly (please correct me if I am wrong). 

Taking a step back and looking at this question, it appears that you have a known production rate of natural gas (SG = 0.6 kg/L).  I am also assuming that you have the correct diameter, height, retention time, gas velocity, and height/diameter ratio determined for your seperator.  Also, excessive particles can plug filters (so these are clean filters).

All of these steps could be incorporated into a mathematical spreadsheet (such as Excel) that could be used to improve your mathematical model until you are satisfied with the results.

An accurate way which immediately comes to mind would be to actually have an accurate sample taken before the filter and analyzed by gas chromatograph (this is assuming the pipeline is producing, or is built).  The gas chromatograph (Flame Ionization Detector) could provide you with an approximate carbon distribution based on boiling point.

I have seen people follow an incorrect assumption that this distribution follows a bell-curve. 

This distribution (derived at atmospheric pressure) could then be mathematically modified to estimate those hydrocarbons which would change phases from a gas to a liquid under your operating pressure (250 psig - 500 psig) and temperature (not defined).  More liquid hydrocarbons will be present at the higher pressure. There are some good calculators which use derivation of the Clausius-Clapeyron. A calculator that seems to provide acceptable results for some of the projects I have been working on is at http://www.trimen.pl/witek/calculators/wrzenie.html appears to provide consistant results as long as you have correct data to begin with.

From this information you are now able to calculate the liquid fraction of your production and are able to determine the specific gravity (based on G.C. data and increased pressure) and the flow rate (based on 15 MMCFD).

I hope this helps, and feel free to correct me if I misinterpreted something.

Sincerely,

Eugene