Science
Monday, Aug 17, 2009
Substitute Natural Gas

Substitute natural gas can be produced from fossil fuels such as coal same as synthesis gas . As Methane is the main fraction of the gas, The heat value of substitute natural gas in comparison with synthesis gas is much more higher .

Synthesis Gas 

Synthesis gas is odorless , colorless and poisonous that it burns flameless at temperature of  574 ° C . The specific weight of synthesis gas depends on the percentages of Hydrogen and Carbon Monoxide .
The synthesis gas would be used as a fuel and also as a Hydrogen resource for producing Ammoniac , Methanol and Hydrogenous refining process. synthesis gas produced from natural gas , heavy materials , petroleum and coal . Typically to produce a tone of synthesis gas , with the mole ratio of H2/CO=1 , 55.0 tone methane is essential. Where as for the ratio of 3.49 Tones of Methane is required . Synthesis gas can be produced from hydrocarbon resources as follow :

1- Synthesis gas production from coal .
In process of synthesis gas production from coal , vapour and oxygen combine with coal , at temperature of 870° C and pressure of 27 atm . The product  contains Hydrogen (22.9%) , Carbon Monoxide(46.2%) , Carbon Dioxide(7.8%) , H2O (22.5%),Methane ,Carbon and Nitrogen(0.6%) . After separation of carbon dioxide the product will be delivered by pipelines for sale .

2- Synthesis gas production from heavy petroleum .
Combination of heavy petroleum with Oxygen at temperature of 1370° C and pressure of 102 atm produces synthesis gas.

Substitute Natural Gas

Substitute natural gas can be produced from fossil fuels such as coal same as synthesis gas . As Methane is the main fraction of the gas ,The heat value of substitute natural gas in comparison with synthesis gas is much more higher.

Synthesis Gas 

Synthesis gas is  odorless , colorless and poisonous that it burns flameless at temperature of  574 ° C . The specific weight of synthesis gas depends on the percentages of Hydrogen and Carbon Monoxide .
The synthesis gas would be used as a fuel and also as a Hydrogen resource for producing Ammoniac , Methanol and Hydrogenous refining process. synthesis gas produced from natural gas , heavy materials , petroleum and coal . Typically to produce a tone of synthesis gas , with the mole ratio of H2/CO=1 , 55.0 tone methane is essential. Where as for the ratio of 3 , 49 Tone of Methane is required . Synthesis gas can be produced from hydrocarbon resources as follow :

1- Synthesis gas production from coal .
In process of synthesis gas production from coal , vapour and oxygen combine with coal , at temperature of 870° C and pressure of 27 atm . The product  contains Hydrogen (22.9%) , Carbon Monoxide(46.2%) , Carbon Dioxide(7.8%) , H2O (22.5%), Methane , Carbon and Nitrogen(0.6%) . After separation of carbon dioxide the product will be delivered by pipelines for sale .

2- Synthesis gas production from heavy petroleum .
Combination of heavy petroleum with Oxygen at temperature of 1370° C and pressure of 102 atm produces synthesis gas .

3- Synthesis gas production from naphta.
Naphta combines with vapor in the presence of nickel catalyst and produces synthesis gas at temperature of 885°C and pressure of 25 atm.

4- Synthesis gas production from natural gas
This method which is more common in the world will carry out in two phase of cracking and purification.
In this method Cobalt , Molybdenum and Zink Oxide are used as catalyst.
The final product contains 83.8% hydrogen ,14.8% Carbon Monoxide , 0.1% Carbon Dioxide and a few Methane , Nitrogen and vapour.

Town gas

Colloquially town gas is a kind of gas that is delivered to consumers by pipeline from gas production complex. Town gas is produced from coal or petroleum and is used in the regions where the natural gas isn’t available  or coal is abundant . Town gas consists of 50% Hydrogen , 20% Methane , 30% Carbon Monoxide , 17% Carbon Dioxide , 3% Nitrogen and 8 % Hydrocarbon.
Other impurities such as vapour , ammoniac , sulphur , syanidric acid are also exists in town gas.
Town gas is called synthesis gas or coal gas too.
In Iran ,the composition of natural gas which is delivered to consumers by pipeline is not different from town gas.

Sweet gas    

Sweet gas is a kind of gas without hydrogen Sulfide and Carbon Dioxide.

Natural gas

Natural gas consists of Hydrocarbons with Carbondioxide , Nitrogen and sometimes Hydrogen Solfied . Methane is the main part of hydrocarbons and the others are such as , Ethane , Propane , Butane , Pentane and heavy Hydrocarbons . Impurities such as H2O , Carbon Dioxide , Hydrogen Sulfied and Nitrogen exist in natural gas too . Dissolved gas in crude oil is called solution gas where as associated gas is a gas which is found in association with crude oil or as a cap of free gas above the oil .
Non – associated gas exploite from those kind of resources that product commercial gas.

Compressed  natural gas
  

Natural gas made out of methane mainly and it exists in most parts of the world . Natural gas can be transfer with tanker by pipelines or LNG . CNG can be used in automobiles as a fuel . Nowadays CNG is used in one million means of transportation . In Italy CNG is used more than the other countries and compressed natural gas is used in Zelandenu and Latin America .
The components of natural gas is different and depends on the gas field . heavy Hydrocarbons , Nitrogen , Nioxide , Oxygen and Hydrogen Solfied are impurities in automobile . compressed natural gas stores in heavy reservoir and 220 atm .The heat value and the amount storage of CNG (8.8000 J ) is less in comparison with petrol (32000 J ) also because CNG is are limited they should be designed in away that contains petrol too.
The advantages of CNG are as follow :
1. Engine starts in cold weather easily .
2. it burns neatly .
3. The cost of engine repair is less .
4. CNG has the highest octan .
5. A few pollutions exude from exhaust (pipe ) .
1- It has lower volume performance cause it enters in engine as a gas form .
2- In comparison with the gasoline veichles if uses in a shorten distance weather we use gas and also gasoline in engine .
The CNG engines power is 15% less than petroleum vehicles .
3- In comparison with gasoline vehicles the risk of conflagration is more .
Using natural gas is vehicles as a fuel is one of the major plan of NIGC . Some CNG stations with installation and side facilities and a factory for changing the system of fuel from petrol to gasoline is erected and is putting in to operation and the others are under construction.

Liquified natural gas LNG

Natural gas liquids composed of methane and if it freezes up to -161 atm , it changes to liquid and the volume decrease to 116000th of primary volume so it can be transferred to consumption centers by  especial marine .
In order to liquidize methane , it must be freeze up to -5/2° C under pressure of 45 atm , this method is economical but on the other hand the transfer of gas with high pressure needs heavy tanks with thick wall that is impossible .
So in the process of producing LNG , the pressure decrease about 1atm in order to transfer it easily .
The first LNG cargo transfered from Britain to Algeria commercially in 1964 . Storing , loading and constructing esp marins for transferring LNG involved much expenses in the period of time .
As the price of selling LNG is reduced , so the sellers and costumer must sign a longterm contract about 15 to 20 years and concure on the gas price .
There are four stages in producing LNG .
1- Separation of impurities that composed of carbondioxide and sulfur compounds .
2- Separation of H2O , if it exists in system it changes to ice and causes pipe choke . 
3- All of the heavy hydrocarbons are separated just Methane and Ethan remains .
4- The rest of gas freezes up to -160° C and change to LNG  atmospheric pressure . LNG is kept in resualted specific reservoirs and then is transferred to countries by cryogenic tankers to countries . In shipment process usually some parts of vapoured gas is utilized as a fuel of tanker engine . In process of changing to LNG gas a huge frigidity released and it can be used for freezing foodstuffs.

Natural gas liquids    
 

Natural gas liquids are usually generate by the time of producing natural gas.
Natural gas liquid is not the same as LNG , the components of natural gas liquids are ethan , liquid gas (propan and butan) natural gasoline and condensate that the percentage of each components depends on the type of gas and exploitation facilities .
In 1996 the whole production of natural gas liquids was 5.7 million barrels per day and OPEC production was 2.6 million barrels per day.

Non associated gas 

Non associated gas is extracted from the fields that  has economical gas production.

Gas cap

The volume of reserroir layer in depth of the earth is called gap gas or (gas dome ) . In this state gas stay above oil and it is included the highest point of reservoir.

Gas cap gas    
  
Gas cap gas is a kind of gas which is entrapped  In gas cap.

LPG  

LPG made out of propan  and botan and it is kept in cylinder and utilizes at home . LPG can be produced from three recourses.
1- Non associated natural gas
2- Associated natural gas
3- Crude oil
After segregation and refining associated natural gas and crude oil , propan and botan remains in crude oil , also in molecular cracking process and octane number increasing process , propan and botan produced as side products . The percentage of propane and botan is important in liquid gas combination , in summer as the weather is hot the percentage of botan become variable between 10 to 50 more than five million barred of LNG is consumed per day the consumption amount of LNG is different in countries . The average consumption percentage in different sections in the world in 1999s is as follow :
Consumers 60% , chemical industries 15% , industries 15% , petroleum production 5%.
  
 


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