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conversion required for kg/hr to mmscfd

conversion required for kg/hr to mmscfd

conversion required for kg/hr to mmscfd

(OP)
hello, i am in need of a conversion factor from kg/hr to mmscfd - have no eng. textsbooks on the plant to look up, i need this to see how much our flash gas compressors are putting through our dew point plant - none of our meters are working yet - plant has just been commisioned. Thanks for your help - lowly tech here, nt an engineer !

RE: conversion required for kg/hr to mmscfd

opstech:

scf/day = (kg/hr)(2.204 lb/kg)(lb-mol/lb)(379.48 scf/lb-mol)(24 hr/day)

Since lb-mol/lb = 1/MW :

scf/day = (kg/hr)(2.204 lb/kg)(1/MW)(379.48 scf/lb-mol)

where:
MW = molecular weight of the gas
scf = standard cubic feet at 60 degrees F and 1 atmosphere

Divide scf/day by 1,000,000 to get mmscfd

Milton Beychok
(Contact me at www.air-dispersion.com)
.

RE: conversion required for kg/hr to mmscfd

Converting kg/hr to mmscfd requires a density of the gas.  Using air density as 0.00256 slugs/ft^3, you would multiply Kg/Hr by 642 to get Ft^3 per day.  Using 1.25x10^-3 gm/cm^3 yields a multiplier of 657.

RE: conversion required for kg/hr to mmscfd

opstech:

The second equation in my response omitted the 24 hr/d term and it should read:

scf/d = (kg/hr)(2.204 lb/kg)(1/MW)(379.48 scf/lb-mol)(24 hr/d)

Please excuse my typographical error.

Milton Beychok
(Contact me at www.air-dispersion.com)
.

RE: conversion required for kg/hr to mmscfd

IFRs:

Don't forget that opstech asked for mmscfd (i.e., millions of scfd) ... your multipliers still have to be divided by 1,000,000. You should also tell him the reference temperature and pressure applicable for your density look-ups.

Milton Beychok
(Contact me at www.air-dispersion.com)
.

RE: conversion required for kg/hr to mmscfd

(OP)
Thanks guys - it took me a half hour of puzzling in front of a calculator, but we are getting around 20mmsfd from the MP/LP seps as flash gas. Cheers once again.

... i may need to glue a calculator to the panel now though ... ;D

RE: conversion required for kg/hr to mmscfd

>>
... i may need to glue a calculator to the panel now though ... <<

If it's really a consideration, consolidate all your constants and lay out a really simple equation, or even better: tape an excel spreadsheet to the wall.

RE: conversion required for kg/hr to mmscfd

If you are looking for a calculator to do this, there is one built into my freeware units conversion program, Uconeer. Unfortunately it does not include mmscfd, but it will take the conversion as far as scfm and you will have to apply a factor (0.00144) to convert the output from scfm to mmscfd.

You can download this free program from
www.katmarsoftware.com

I deliberately delayed posting this link because I believe it is important that you first understand how the calculation is done, and thanks to Milton Beychok you now know how to do it

RE: conversion required for kg/hr to mmscfd

You don't need a density to convert from kg/hr to MMscfd.

convert kg/hr to lb/hr

Convert lb/hr to lbmole/hr using the MW

1 lbmole occupies 379.6 scf

RE: conversion required for kg/hr to mmscfd

This has already being treated in past threads.
It all depends on what "standard" P,T conditions selected for the ideal gas:

System                           T                P               V

SI                         273.15K   101.325 kPa  22.415 m3/kgmol  
Universal scientific    0oC       760 mm Hg   22.415 L/g mol
Nat. gas industry      60oC     14.696 psia   379.4 ft3/lb mol
American engineering 32oF    1 atm        359.05 ft3/lb mol

RE: conversion required for kg/hr to mmscfd


A typing error: it should be 60oF not 60oC

RE: conversion required for kg/hr to mmscfd

25362,
From 15 years in natural gas measurement, that industry uses 14.73 psia as "standard" for the Natural Gas Industry (see API 14.3).  I don't know where it came from, but that is the number they use.  As long as everyone in a given transaction uses the same value it doesn't much matter.

TD2K,
Your technique implicitly determines density at "STP".  I recently worked through a mass balance on a compressor station using density (at actual conditions) and got exactly the same numbers as another engineer who did the job last time using MW, moles, and actual pressures/temperatures.  Neither calculation was particularly more difficult than the other, but each of us was more comfortable with our technique.  

David

RE: conversion required for kg/hr to mmscfd


To zdas04,

I believe this strange pressure (762 mm Hg = 14.734 psia) used by AGA, stems from selecting a standard "round" value of 30 inches of mercury, instead of the more common 29.92, as used, for example, in air conditioning.

RE: conversion required for kg/hr to mmscfd

25362,
Thanks, that makes more sense than any of the other explainations that I've heard over the years.

Now, maybe you can tell me why New Mexico (average elevation in the north around 5,500 ft, call atmospheric pressure 12.01 psia) uses 15.025 psia as the "standard" pressure for calculating volumes reported to the state?

David

RE: conversion required for kg/hr to mmscfd


I"ll try.

The standard average atmospheric pressure is taken at 14.4 psia (at about 100 ft elevation).
Then you add 10 oz/in2 to correct for sea level.

10 oz/in2 = 0.625 psi

14.4 + 0.625 = 15.025 psi

QED.

RE: conversion required for kg/hr to mmscfd

ADD???????????????  Must be a government thing.  Thanks for the chuckle.

David

RE: conversion required for kg/hr to mmscfd


Considering the pressure changes with elevation, I should have said 500-600 ft, not 100 ft. Nevertheless, the explanation stands.

RE: conversion required for kg/hr to mmscfd

Zdas, good point.  

I should have remembered there's been more than a coupleof threads here which have shown if you want to start a debate, ask a group of engineers to define 'standard' conditions

RE: conversion required for kg/hr to mmscfd

Ignoring 25362's little typo in the above post (you might want to subtract mate ;) ) I can't believe you calculate things like that in imperial units ... so much easier to do in SI and convert back to imperial if you must (mind you I wish imeprial would vanish from the face of the planet!)

Read the Eng-Tips Site Policies at FAQ731-376  

RE: conversion required for kg/hr to mmscfd


To ColourfulFigsnDiags and Zdas, no error: as you go down (ie, lower elevation as at sea level) atmospheric pressure increases.

Thus, add 10 oz/in2 to the average 14.4 psia at an average elevation above sea level, not substract.

RE: conversion required for kg/hr to mmscfd

Sorry, the real answer is that a not-too-bright (but very cunning) beaurecrat in the state thought that he could get more revenue for the state by slightly overstating the atmospheric pressure.  The difference ends up paying the state 2% more severance tax on every chunk of gas extracted so they can have "lower" incremental tax rates than the surrounding states.  

An atmospheric pressure of 15.025 (103.539 kPa) would happen at 500 ft (152 m) below sea level.  Atmospheric pressure in the Death Valley isn't that high.

TDK2,
A "micro" definition of standard conditions is really easy, every gas-sales contract has one that both parties have agreed to (it may not be the same as the next contract, but who cares?).  The problem is that when you try to define a global standard, people keep bringing their own personal axes to grind.  It is never technical, simply political.

David

RE: conversion required for kg/hr to mmscfd


To zdas04, if 1 psi ~ 2.3 ft of water (less for seawater), then an atmospheric pressure difference of 15.025-14.696 = 0.33 psia, can hardly be 1 ft of water, let alone 500 ft. Am I right ?

RE: conversion required for kg/hr to mmscfd

23562:

David (aka zdas04) did not mean submerged 500 feet below the surface of the sea ... he meant land that is 500 feet below sea level.  

He was trying to tell you that atmospheric pressure decreases with increasing elevation ... i.e., the atmospheric pressure atop a mountain is lower than the atmospheric pressure on the beach at sea level. I am sure that you know that ... so why keep chewing on this discussion thread which I think we have already gnawed down to the bone.

Milton Beychok
(Contact me at www.air-dispersion.com)
.

RE: conversion required for kg/hr to mmscfd


Zdas04, sorry for the misinterpretation. Mbeychock, you are right: more than enough is too much.

RE: conversion required for kg/hr to mmscfd

Let me give this a shot, hope you guys don't mind me reviving this thread:


Converting from kg/hr to mmscfd            
                                            
What does MMSCFD stand for?  Millions of Standard Cubic Feet per Day (measure of gas produced in a reservoir)    

From the Ideal Gas Law                    
PV    =    nRT                        =    m/MRT                                    
i.e.                                            
m/V    =    PM/RT
                
i.e. the density of the gas                                            
rho    =    PM/RT                

At standard conditions (T=15.556ºC  and P=1 atm  from Milton's post) (Note: I would have used T=0ºC)
                            
rho    =    101325 M / [8314 x(15.556+273.15)]        
    =    0.04221 M                
where:

M    = molecular weight of the substance in kg/k-mol    

Thus to convert from a value of n kg/hr to mmscfd:    

Vol flowrate    =    Mass flowrate /    Density            =    n kg/hr    x  1hr/3600s  x  1/0.04221 M            =    n / 151.956 M    (in m3/s)            =    n / 151.956 M x (3.2808)^3 ft3    x  86400/day    =    20078.68 n/M    (in ft3/day)            =    0.02007868 n/M    mmscfd    (divide by 1million)                        

Example:  For 1000kg/hr O2                    
    M    =    32.0     for O2                        
then                                            
Vol flowrate    =    0.02007868 n/M                                    
    =    0.02007868 x 1000/32            

    =    0.6275    mmscfd
                

---engineering your life---

RE: conversion required for kg/hr to mmscfd

Sorry, the editing has gone bonkers. Let me try again:

Converting from kg/hr to mmscfd            
                                            
What does MMSCFD stand for?  Millions of Standard Cubic Feet per Day (measure of gas produced in a reservoir)    

From the Ideal Gas Law                    
PV    =    nRT    =    m/MRT                                    
i.e.                                            
m/V    =    PM/RT
                
i.e. the density of the gas
rho    =    PM/RT                

At standard conditions (T=15.556ºC  and P=1 atm  from Milton's post) (Note: I would have used T=0ºC)
                            
rho    =    101325 M / [8314 x(15.556+273.15)]        
    =    0.04221 M                
where:

M    = molecular weight of the substance in kg/k-mol    

Thus to convert from a value of n kg/hr to mmscfd:    

Vol flowrate    =    Mass flowrate /    Density        
=    n kg/hr    x  1hr/3600s  x  1/0.04221 M            
=    n / 151.956 M    (in m3/s)            
=    n / 151.956 M x (3.2808)^3 ft3    x  86400/day    
=    20078.68 n/M    (in ft3/day)            
=    0.02007868 n/M    mmscfd    (divide by 1million)                        

Example:  For 1000kg/hr O2                    
    M    =    32.0     for O2                        
then                                            
Vol flowrate    =    0.02007868 n/M                                    
    =    0.02007868 x 1000/32            

    =    0.6275    mmscfd
                

---engineering your life---

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