## How to convert MMSCFD of natural gas to lb/hr

## How to convert MMSCFD of natural gas to lb/hr

(OP)

**Hello,**

I am struggling big time converting MMSCFD of natural gas to lb/hr. I would greatly appreciate any help.

I am struggling big time converting MMSCFD of natural gas to lb/hr. I would greatly appreciate any help.

## RE: How to convert MMSCFD of natural gas to lb/hr

Dan - Owner

http://www.Hi-TecDesigns.com

## RE: How to convert MMSCFD of natural gas to lb/hr

Give it a try and let us see your calculation.

BA

## RE: How to convert MMSCFD of natural gas to lb/hr

BA

## RE: How to convert MMSCFD of natural gas to lb/hr

Bill

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Ohm's lawNot just a good idea;

It's the LAW!## RE: How to convert MMSCFD of natural gas to lb/hr

BA

## RE: How to convert MMSCFD of natural gas to lb/hr

Bill

--------------------

Ohm's lawNot just a good idea;

It's the LAW!## RE: How to convert MMSCFD of natural gas to lb/hr

## RE: How to convert MMSCFD of natural gas to lb/hr

I don't know what there is to "figure". The definition of a standard cubic foot follows:

A standard cubic foot defines an amount of gas contained in a volume of one cubic foot at standard temperature and pressure. This standard unit of molecular quantity for gases can be used with the ideal gas law to compute the quantity per unit of volume for other pressures and temperatures. In spite of the label "standard", there is a variety of definitions, mainly depending on the type of gas. Since, for a given volume, the quantity is proportional to the pressure and temperature, each definition fixes base values for pressure and temperature.

The conversion from MMSCFD to pounds/hour is not an approximation. It is precise. The approximation has more to do with whether or not compressed natural gas was stored under standard temperature and pressure.

EDIT: Based on the information provided below, the conversion from volume to weight depends on the chemical composition of natural gas, which is not consistent.

BA

## RE: How to convert MMSCFD of natural gas to lb/hr

Why? Because there is not a standard definition of the composition of natural gas and therefore it does not have a "standard" molecular weight, nor specific density.

Additionally it must be calculated at "standard" conditions, which are not always "standard".

You can calculate the weight of a cubic foot of a specific natgas, if you know its composition, or if you know its laboratory measured specific density and you can set the "standard" conditions of pressure and temperature.

Any calculation you do concerning natural gas should reference the standard conditions that you used. In the USA, it is

usually14.696 psia and 68°F. A ref temp of 0°C is often used in Europe and sometimes other countries or organizations use 15°C.Sometimes one just assumes natgas is 100% CH4, methane, but that can at times be a poor approximation. Typical specific densities of Natgas vary between 0.6 and 0.7 referenced to air, again at "standard conditions".

Do you know the composition, molecular weight, or the specific density of your gas stream?

Do you know the temperature and pressure of your gas stream?

Do you know what standard reference conditions are being used?

## RE: How to convert MMSCFD of natural gas to lb/hr

## RE: How to convert MMSCFD of natural gas to lb/hr

Is 3.43 actually the value for Propane C3?

I will assume it is C3

Comp quantity MW MWmix(i)

C1 0.8044 16.042 12.90

C2 0.0492 30.068 1.48

C3 0.0344 44.09 1.52

IC4 0.0055 58.12 0.32

NC4 0.0092 58.12 0.53

IC5 0.0028 72.14 0.20

NC5 0.0019 72.14 0.14

C6+ 0.0038 100.198 0.38

N2 0.0018 28.016 0.05

CO2 0.0871 44.01 3.83

H2O 0 18.016 0.00

H2S 0 34.076 0.00

MWmix 21.36

MW(air) 28.964

SG(relative to air) 0.737

Compressibility Factor Z = 0.809 (Benedict-Webb_Rubin)

GasDensity_pcf = P_psia * SG_rel2air * 28.964 / (z * 10.73 * T_degR)

GasDensity_pcf = 4.619 lbs/ft3 at 80F & 1015 psia

You should check that. Its a new spreadsheet.

## RE: How to convert MMSCFD of natural gas to lb/hr

Replying to 1503-44 (Petroleum). That means for that gas composition 1 MMCFD will give an equivalent density of 3.55 lbs/ft3? . How do i relate that to the mass flow in lb/hr?## RE: How to convert MMSCFD of natural gas to lb/hr

1 MMCFD. What is the reference temp & pressure? 14.696 psia and 68 F?

4.691 lbs/ft3 at 1015 psia and 80F, z = 0.809

convert that to 14.696 psia and 68 F

Ohhh. *%&^$^%#^ I have to run out for an hour. I'll be back soon.

## RE: How to convert MMSCFD of natural gas to lb/hr

## RE: How to convert MMSCFD of natural gas to lb/hr

1 MMCFD. What is the reference temp & pressure? 14.696 psia and 68 F?

We found previously that mass of 1ft3 at pipe flow conditions was

4.691 lbs/ft3 at 1015 psia and 80F, z = 0.809

convert that to 14.696 psia and 68 F

GasDen1 = 4.691 lbs/ft3

Vol1 = 1ft3

Z1 = 0.80767

P1 = 1015 psia

T1 = 80F = 539.67R

A = P1 * V1 / T1 / Z1 = 2.329

Z2 at 14.696psia and 68F = 1.000

P2 = 14.696 psia

T2 = 68F = 527.67R

B = P2 * T2 / Z2 = 35.9057

Vol2 = A x B = 2.329 x 35.9057 = 83.61 ft3

GasDen2 = 4.691 lbs / 83.61 ft3 = 0.05544 lbs/ft3

Air at 14.696psia and 68F weighs 0.0765 lbs/ft3

SG

_{gas}= 0.05544 / 0.0765 = 0.725================== Calculate weight directly from quantity of gas at STP ==============================

1 Million

StandardCubic Feet (MMSCF) gas at 14.696psia and 68F (Our Standard Conditions) with aSpecific Gravity of 0.737 relative to air, from our Composition Calculation above, which was close to what I calculated using BWR compressibility. But here we don't have to worry about compressibility factors, because 1MMCFD is at normal pressure and temps where Z=1.

Gas weighs SG * Weight of Air

0.737 x Weight of Air at 14.696psia & 68F

Weight of 1ft3 of air at 14.696psia & 68F = 0.0765 lbs/ft3

Therefore 1 ft3 Gas at 14.696psia and 68F weighs

0.737 * 0.0765 lbs/ft3 =

0.564 lbs/ft3x 1,000,0001MM SCF is 564,000 lbs of 0.737 SG natural gas

If that MM SCF of gas passes by in 1 Day, that's 24h

564,000 lbs/24h

Mass flow rate is 2349 lbs/h

Mass flow rate is constant at all pressures and temperatures inside any diameter pipe.

## RE: How to convert MMSCFD of natural gas to lb/hr

Thanks alot for your time and your help. I appreciate from the bottom of my heart. Have a blessed day and stay safe.