Volvo Owners Club Forum - View Single Post - Is it a myth or do CNG V70 Volvo really exist?!

volvobaggen · Sep 8th, 2012, 01:38

Well, its not that simple.

Natural gas found in oil fields is a mixture of light weight hydrocarbons often found a reservoir with heavier hydrocarbons when you drill for it out in the north sea.

Natural gas isn´t just methane, but methane is the lightest of the hydrocarbons and the most plentiful and dominating of the light weight hydrocarbons(somewhere in the range of 70-90% volume of gas)

This is very simplified:

Natural gas is a blend of:

Methane is CH4, one carbon atom and four hydrogen atoms. (70-90%)
Ethane is C2H6, has two carbon atoms and therefore heavier than methane.
Propane is C3H8, has three carbon atoms etc
Butane is C4H10
Pentane C5H12
Hexane C6H14
Benzene C6H6
Not all molecules are listed.

These are liquid in the high pressure pockets underground, but gaseous at atmospheric pressure. The higher the carbon number, the more their boiling point goes up.

For instance, this is why you guys in England and we here in Norway only get propane as autogas year around that boils at -42C. If we blend in butane which boils -0,5 C, the boiling point goes up and there would be problems with the vaporizer on a really cold winters day.

Petrol is a blend of:

Butane C4H10
Pentane C5H12
Hexane C6H14
Heptane C7H16
Octane C8H18
Nonane C9H20

Diesel-fuel is a blend of alkenes (these same hydrocarbons) with carbon numbers from 10-22 carbon atoms.

My point is that when we drill for hydrocarbons, depending on the nature on the reservoir, we always get a blend of the different hydrocarbons. Often you find find oil and natural gases together. Sometimes you find natural gas without oil etc.

AT the drill head and at the refineries you separate the hydrocarbons. Methane is separated, ethane is separated, propane separated, and it goes on and on.

If you compress natural gas you get CNG. If you compress and freeze natural gas you get LNG. Both CNG and LNG are not pure methane, you will find some ethane and propane in there. LPG will become liquified only by relatively low preassure alone.

LPG can be "polluted" by so called "bad gas" in which longer chains of hydrocarbons from about 20 carbonatoms (C20) is suspended in the LPG. From this carbon range, hydrocarbons form solids like paraffin wax that dont evaporate in the vaporizer.

My point is therefore that the production of methane is linked to the production of propane, petrol and diesel oil etc. LPG as we use it today is not a biproduct from the refinery, it is a biproduct of drilling and is separated at the refinery, just as methane is separated. Before these petroleum gases had no market and were burned off.

Also, by cracking longer chains of hydrocarbons, propane/buthane can easily be produced at the refinery if needed in the same ways cracking is used to produce petrol and diesel fuel.

Landfill and and methane production from bacteria is another story.

Sep 8th, 2012, 01:38	#25
volvobaggen Member Last Online: Jan 18th, 2015 21:13 Join Date: Jun 2011 Location: Haugesund	Well, its not that simple. Natural gas found in oil fields is a mixture of light weight hydrocarbons often found a reservoir with heavier hydrocarbons when you drill for it out in the north sea. Natural gas isn´t just methane, but methane is the lightest of the hydrocarbons and the most plentiful and dominating of the light weight hydrocarbons(somewhere in the range of 70-90% volume of gas) This is very simplified: Natural gas is a blend of: Methane is CH4, one carbon atom and four hydrogen atoms. (70-90%) Ethane is C2H6, has two carbon atoms and therefore heavier than methane. Propane is C3H8, has three carbon atoms etc Butane is C4H10 Pentane C5H12 Hexane C6H14 Benzene C6H6 Not all molecules are listed. These are liquid in the high pressure pockets underground, but gaseous at atmospheric pressure. The higher the carbon number, the more their boiling point goes up. For instance, this is why you guys in England and we here in Norway only get propane as autogas year around that boils at -42C. If we blend in butane which boils -0,5 C, the boiling point goes up and there would be problems with the vaporizer on a really cold winters day. Petrol is a blend of: Butane C4H10 Pentane C5H12 Hexane C6H14 Heptane C7H16 Octane C8H18 Nonane C9H20 Diesel-fuel is a blend of alkenes (these same hydrocarbons) with carbon numbers from 10-22 carbon atoms. My point is that when we drill for hydrocarbons, depending on the nature on the reservoir, we always get a blend of the different hydrocarbons. Often you find find oil and natural gases together. Sometimes you find natural gas without oil etc. AT the drill head and at the refineries you separate the hydrocarbons. Methane is separated, ethane is separated, propane separated, and it goes on and on. If you compress natural gas you get CNG. If you compress and freeze natural gas you get LNG. Both CNG and LNG are not pure methane, you will find some ethane and propane in there. LPG will become liquified only by relatively low preassure alone. LPG can be "polluted" by so called "bad gas" in which longer chains of hydrocarbons from about 20 carbonatoms (C20) is suspended in the LPG. From this carbon range, hydrocarbons form solids like paraffin wax that dont evaporate in the vaporizer. My point is therefore that the production of methane is linked to the production of propane, petrol and diesel oil etc. LPG as we use it today is not a biproduct from the refinery, it is a biproduct of drilling and is separated at the refinery, just as methane is separated. Before these petroleum gases had no market and were burned off. Also, by cracking longer chains of hydrocarbons, propane/buthane can easily be produced at the refinery if needed in the same ways cracking is used to produce petrol and diesel fuel. Landfill and and methane production from bacteria is another story. Last edited by volvobaggen; Sep 8th, 2012 at 02:05.