13 replies to this topic

[ken0564]

Good day and thanks in advance for you assistance.

I need to convert a crude unit off-gas stream (not natural gas) to equivalent barrels of oil

Stream composition is as follows in mol%:

Carbon Dioxide  9.0

Ethane  9.7

Ethylene  0.1

Hexanes Plus  0.2

Hydrogen Sulfide  38.2

Iso-Butane  2.8

Iso-Pentane  0.3

Methane  6.0

N-Butane  6.4

N-Pentane  0.1

N-Propane  26.7

Nitrogen  0.3

Propylene  0.2

 

The MW of the stream is 38.64

The density of the stream is 0.824lb/ft3 at flow conditions

The visocisty of the stream is 0.011cp at flow conditions

Flow conditons are 100psig and 85degF

 

Can you assist or direct me on how I can get this converted?

Thanks again

 

[ankur2061]

ken0564,

 

What is so complicated about convesrion of volumes from one unit to another? Any unit conversion table will tell you that a volume of one cubic meter is equal to 6.2898 barrels (oil) (USC units: 1 ft³ = 0.178 barrel(oil)). Why all the molar compositions are needed as long as you have a volume available in some unit and which needs to be converted to another unit.

 

You should be aware that gas volumes and volumetric flow rates are generally defined at some base conditions such as 1 atm abs(101.325 kPa (abs)) and 0°C (273.15 K) which means the volume in cubic meter gets qualified as normal cubic meter (Nm³) or 1 atm abs (101.325 kPa(a)) and 15°C which means that the volume in cubic meter gets qualified as standard cubic meter (Sm³).

 

If you are looking to convert volume from one condition 1 to condition 2, you still need to provide the volume, temperature and pressure  at condition 1, which has not been provided in your query. By having the volume, temperature and pressure at condition1 simply convert the volume to condition 2 using the ideal gas law  P1V1 / T1 = P2V2 / T2, where V2 is the volume at condition 2 and T2 & P2 are temperature and pressure at condition 2 (545 R and 114.7 psia as provided by you). Once you have the volume at condition 2 then multiply by 6.2898 if you are using m³ for volume at condition 2 or multiply by 0.178 if using ft³ to get equivalent barrels of oil.

 

Hope this helps.

 

Regards,

Ankur.

[Haripriya]

If we change that from one form to other form will there be any change in efficiency or quality sir???

Edited by Haripriya, 17 February 2013 - 06:31 AM.

[ankur2061]

Haripriya,

 

Welcome to Cheresources.

 

Your question is not clear to me. What do you mean by change in efficiency or quality? We are talking of a straight forward application of the ideal gas law for volume conversion from one set of conditions (temperature & pressure) to another set of conditions using consistent units.

 

Regards,

Ankur.

[kkala]

Asked conversion to "equivalent barrels of oil" and given data indicate that you need to know the barrels of crude oil having the same total heating value (HHV or LHV?) as this for the off-gas stream. Can you please confirm?

For instance, 1000 actual ft3 of concerned gas (824 lb) would represent 824×Q/5.8E6 BOE (barrels of oil equivalent), according to US   Internal Revenue Service, having conventionally adopted 5.8E6 Btu/barrel as HHV of crude.  Q=HHV of the off-gas (Btu/lb). 

See more on BOE in <http://en.wikipedia...._oil_equivalent>. Using LHVs for both gas and crude would give a somehow different result, but official per said US service seems to be that based on HHV.

To estimate off-gas HHV, you can take 100 kgmol of gas (38640 kg) and estimate total combustion heat from its composition, e.g.

CO2:   9.0 kgmol×0 MJ/kgmol = 0 MJ

CH4:   6.0 kgmol×889 MJ/kgmol=5334 MJ  (see <http://en.wikipedia....t_of_combustion>)

C2H6: 9.7 kgmol×1560 MJ/kgmol=15132 MJ
...................................................................................

 Sum of all  (38640 kg)                 XXXXX MJ

Thus off-gas HHV  = XXXXX/38640 MJ/kg, or  Q=XXXXX/89.88 Btu/lb.

Edited by kkala, 17 February 2013 - 11:48 AM.

[Art Montemayor]

I believe Kkala has hit on the real intent of the query.

 

In the Oil & Gas industry (as well as in LNG)  we here in Houston, Texas have always equated hydrocarbon gas streams with crude oil quantities ony with regards to the Heating Value of the subject gas stream.  Usually, it is the (lower heating value) LHV.

 

Therefore, what ken0564 intends to ask is:  what is the equivalent quantity of crude oil heat energy in the given gas stream, expressed as barrels of crude.

 

However, not enough information is furnished.  The equivalent heating value of the crude has to be defined.  The heating value of the gas stream can be easily calculated from its composition.  The basis of the conversion should be stated in the result.

[kkala]

US Internal Revenue Service has conventionally defined value of crude HHV to be considered, see first link in post no 5 (by kkala).

Edited by kkala, 17 February 2013 - 12:30 PM.

[ankur2061]

Art,

 

I do not see any mention of LHV or HHV in the OPs post. It is not difficult to obtain the HHV and LHV of the off-spec gas given the correct gas composition. Notice that the OP has mentioned a mole percent of 0.2 for hexanes plus. When you say hexanes plus it could be hexane and higher i.e. heptane, octane, nonane, Decane or cyclic hydrocarbons. If you want to obtain LHV or HHV on a compositional basis you need to be precise in defining the composition of the gas mixture. Another way is to use a simulation software where you define the physical properties of the gas density such as density and viscosity at 2 or 3 reference temperatures which would then use a black oil model to generate the complete set of properties including HHV & LHV.

 

Unless the OP clarifies whether he is looking for HHV (which he has not mentioned) or simple conversion of volume from one unit to another post # 5 remains speculative.

 

Regards,

Ankur.

[kkala]

ankur2061, on 17 Feb 2013 - 20:14, said: ....Unless the OP clarifies whether he is looking for HHV (which he has not mentioned) or simple conversion of volume from one unit to another post # 5 remains speculative.  Regards, Ankur.

 

a. Reader is requested to look into post no 1 (I need to convert a crude unit off-gas stream (not natural gas) to equivalent barrels of oil) and into the first lines of responding post no 5.

b. Googling "speculative" returns following meaning, in big letter box:

1. Engaged in, expressing, or based on conjecture rather than knowledge

2.(of an investment) Involving a high risk of loss

c. A more impartial style would help distinguish the true query meaning.

 

 

 

 

 

[Bobby Strain]

Based on the gas composition, it looks like hazardous waste, not a natural resource. What is the need to convert to crude equivalent?

 

Bobby

[kkala]

Probably to know the barrels of oil equivalent (BOE) of this waste (evaluation), if the case is so.

The need in concern is expressed in the second sentence of post no 1.

Edited by kkala, 18 February 2013 - 02:44 AM.

[thorium90]

maybe OP wants to burn it so he needs the Equivalent Barrels Of Oil to find the heat released? Its odd, but maybe...

I thought the conversion was simple, just go to any website and it can do it for you...

 

http://www.unitjuggl...-to-GcftNG.html

 

http://www.conversio...atural_gas.html

[kkala]

Well, the websites consider a natural gas of (assumed) typical heating value. Concerned off-gas is "not natural gas".

Base is not identical in the two sites (difference about 7.7%).

[Propacket]

There is a spreadsheet available in Downloads section of Cheresources. It must have been checked by Art.

 

http://www.cheresour...eld-calculator/

Edited by Propacket, 19 February 2013 - 06:57 AM.