What factors impact the calorific value of petrol from coal liquefaction?

[ruzfactor]

Hi

I am bit confused regarding the heating/calorific value of petrol (used for vehicle) extracted from crude oil and from liquefaction of coal. Should they be same? or Petrol extracted from crude oil will have different calorific value compared to the petrol from liquefaction (direct/indirect) of coal? Could anyone please give any reference?

Thanks in advance.

 

[Simon Bridge]

They are different substances (mixtures) after all.
Different petrols will have different calorific values even if they are all made from oil.
http://www.engineeringtoolbox.com/fuels-higher-calorific-values-d_169.html#.UpKFmzztkjA

But the properties of individual hydrocarbons won't depend on how you got them.

 

[ruzfactor]

Thanks for the reply. The link you referred gives heating value of many fuels. Is there any source where I can get heating values of petrol extracted from crude oil and, from liquefaction of coal. Are they really different?

 

[Simon Bridge]

Yeah - the idea was to show you that heat output varies a lot between petrochemicals - you can easily see that different mixtures will produce different values.

Modern direct-liquifaction plants can manage 60-70% of input coal calories to the resulting fuel.[1]
Anthracite coal is very shiny, repels moisture, calorific value 7,800 – 8,000 kcal/kg.[2]
... so you can do the math.

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[1] http://www.netl.doe.gov/technologies/coalpower/gasification/gasifipedia/pdfs/technology-status-coal-liquefaction.pdf
[2] http://www.coalmarketinginfo.com/coal-basics/

 

[AlephZero]

It depends what you meant by "petrol". The petrol you put in your car is manufactured to meet a set of standards for its properties, so it won't wreck your engine. Whatever you make it from, the end product will have the same properties.

But if you take a "random" sample of coal and liquefy it in an uncontrolled way, the end result could be almost anything, from methane gas to heavy oil sludge. The same applies to cracking crude oil.

 

[Simon Bridge]

The liquified-coal "petrol" can be as close to regular petrol as you like of course.
However, it is likely to differ if only a little bit... probably different impurities.
How tight is the domestic petrol standard in different countries anyway?

I suspect that there is a specific goal behind the question... perhaps someone has been making claims about synthetic fuel and ruzfactor wants a reality check? If so - it would be best just to state the claims.

 

[ruzfactor]

Actually I wanted to know if a country ,for example, chooses to extract petrol from liquefaction of coal over cracking of crudeoil, will the petrol be the same as (in terms of energy content) from crude oil.

 

[etudiant]

Coal liquefaction is a very flexible process, so the end products can be tailored to a desired specification.
Caloric content is a very basic measure, the process engineers would want to tune the composition much more exactly. Issues such as freezing point, viscosity and vapor pressure become important when the end use is in engines.
If you would like a bit more detail, a nice primer is provided by SASOL, currently the world leader in coal liquefaction, here:
http://m.everythingscience.co.za/grade-12/05-the-chemical-industry/05-the-chemical-industry-02.cnxmlplus