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July 04, 2006

Comments

JN2

The Fischer-Tropsch process converts the feed gas into liquid organic compounds, carbon dioxide and water...

Great. FT produces CO2 and burning the liquid fuel produces CO2. Let's fry the planet some more!

al fin

Coal is plentiful and will be utilised for fuel unless a more economical alternative is devised.

People who believe that Peak Energy is a certainty, and a respite from AGW, will be dismayed at more efficient conversions of coal to usable liquid fuels. Peak Energy will be put off by at least a century, and accelerated CO2 output will force a real-world test of climatological models.

mcr

The availability of new FT catalysts is interesting since the major problem with most GTL technologies seems to be energy efficencies. Way to low! (At a maximum of 60% of traditional oil-derived peterochems from memory?).
However, I am only happy to see coal utilized for fuel as A BYPRODUCT of new commodity synthesis (olefin synthesis & metathesis) - NOT purely for energy fuel production. This is just replacing OIL with another carbon fuel source - and sequestration technologies for CO2 are far too primitive I feel! We're going to create problems for ourselves further down the CHEMICAL LIFECYCLE (from a primitive-LCA analysis by mere inspection).
My personal opinion is that we should see DIVERSIFICATION of energy and NOT throw all our eggs into a COAL-mine... It's time we went for CARBON NEUTRAL FUELS it should be the very least of our objectives since anything lower would be a failure with regard to CO2 emissions.
In my opinion ANY new technology in this area relating to this is good - providing it is used wisely and NOT USED ACROSS THE BOARD. This can be a steping stone to buy more time ... until the fully INTEGRATED-BIOREFINERY is finally rolled out or evolves.
FT-SYNTHESIS (which IS ACTUALLY economical! Yet to be seen...) is one more important tool in the "CLEAN TECHNOLOGY TOOLKIT".
I suggested to an academic friend of mine today to obtain figures for these new FT-catalysts used with BIOMASS-GASIFICATION derived (Synth Gas streams) in olefin synthesis. Then compare these to the coal versions. He's being doing this for prior Fisher-Tropsch technologies as I know - but this may change the data set somewhat if the energy useage is lower? You incidentally would have to compare the product distribution and thermodynamic calculations of products with that of solid biomass - pyrrolytic products also!

At this point I may have to go sit in a dark room and lay down!

Anyway - in my view (havn't yet read the SCIENCE article) - but this may be interesting, we will have to see if the catalysts live up to scrutiney.

barry hanson

I have a question:
My understanding is that, using FT to convert coal to diesel, 45 pounds of CO2 is produced per gallon of diesel. There should be no CO2 coming from the gasification of the coal...should there? The gasification process itself is essentially a closed process, right? thank you for an explanation here.

matt mcmahon

Does anyone have a current estimate of the differential cost of producing diesel fuel from coal vs natural gas using FT technology in combination with gasification?

Jim Baerg

"There should be no CO2 coming from the gasification of the coal...should there? The gasification process itself is essentially a closed process, right? thank you for an explanation here"

It depends- The main reaction in coal gassification is 1) C + H2O -> CO + H2, but there is also 2) CO + H2O -> CO2 + H2.

You need to have reaction 2) going since the FT reaction needs more than 1 H2 for each CO to run.

Now I have a question: The article stated that the mediun length hydrocarbons are unwanted, but this puzzles me since in oil refineries all the various lenght hydrocarbons are salable products, & medium length = gasoline, or shorter lenght are propane or butane.

What are these undesired medium 'weight' hydrocarbons.

mcr

I assume it's to do with two things:

The octane number being poor (?) if used in fuels manufacture of medium-Mw fractions... requires large amounts of lead substitutes (MBTE for example) to enable efficient combustion.

No viable C-C bond formation catalysts exist for large scale commodities inter-conversion! So you have to do it at source to limit the mass (AND ENERGY) intensity of the process (MINIMISE WASTE). This is the limitation of the FT process and anything similar! Remember we’re dealing on VERY LARGE SCALES HERE PEOPLE (1000’s tonnes per day!).

In (organic chemistry) the synthesis of pharmaceuticals for example, Pd group metal catalysts (EXPENSIVE-RARE METAL) are used for variations of the HECK REACTION, Suzuki, Sonogashira, Stille and coupling reactions to do this sort of thing in more complex examples of C-C bond formation. They require specialist conditions etc that really are only really usable for SPECIALITY chemicals (smaller reaction scales 1-10’s tonnes per day maximum!!! – that’s why they have higher value added status).

FOR A PROCESS TO BE GREEN/ECONOMIC THE RULE OF THUMB IS – IT NEEDS TO BE SIMPLE!!! LOW/NO SOLVENT USE, BENIGN CONDITIONS, SMALL NUMBER OF STEPS TO MAXIMISE “ATOM ECONOMY” AND SO ON. THIS IS THE IDEAL…

Also inspection of the article text indicates the answer I believe:

I think the MEDIUM LENGTH HYDROCARBONS THAT ARE UNWANTED ARE AROMATICS…

SEE BELOW.

“Catalytic Alkane Metathesis by Tandem Alkane Dehydrogenation-Olefin Metathesis”
Alan S. Goldman, Amy H. Roy, Zheng Huang, Ritu Ahuja, William Schinski, and Maurice Brookhart, Science, 14 April 2006: 257-261.

…Unfortunately, neither natural sources nor Fischer-Tropsch production yield alkane mixtures with a tightly controlled molecular weight (MW) distribution, which is important for varied applications. For example, n-alkanes in the range of C9 to C20 constitute the ideal fuel for a diesel engine (which runs E30% more efficiently than a gasoline engine); the absence of aromatic impurities results in cleaner burning than that of conventional diesel fuel or even gasoline (2, 3). n-Alkanes lower than C9, however, suffer from high volatility and lower ignition quality (cetane number) (4). In addition to F-T product mixtures, low–carbon number, low-MW alkanes are also major constituents of a variety of refinery and petrochemical streams. In general, there is currently no practical method for the interconversion of alkanes to give products of higher MW; this challenge provides extremely large-scale potential applications of alkane metathesis (Eq. 1). Additionally, Eq. 1 might be applied to the formation of low-MW products from high-MW reactants (e.g., by reaction with ethane). Although hydrocracking is already a well-established process for this purpose, Eq. 1 might offer an advantage, for some applications, of higher selectivity and/or less severe conditions.

Robert

The medium-weight hydrocarbons (I assume we're talking about C4-C7 compounds here) are all salable, but probably not salable in the quantities they would be produced in if billions of liters of fuel were being produced. In a co-product process, the size of the market for the least salable coproduct limits capacity for the entire process.

mcr

Robert - you put it far more elegantly than myself.

Thats what I meant by "waste minimisation". Waste = UNDESIRABLE BYPRODUCTS ...

If we're generating stoichiometric byproducts on 1000's tonnes per day scale
THATS 1000's tonnes per day WASTE that needs disposal of/selling!

I remember one previous comment on this blog stating "one definition of hazardous waste is chemicals you can't sell"

... that gave us a good laugh in our laboratory!

Not the sort of thing the EU has in mind with it's REACH legislation either...

Paul Dietz

Unsaleable hydrocarbons wouldn't be disposed of as waste, they'd be returned to the gasifier or combusted in a turbine. What this does is reduce the overall efficiency of the process vs. a process that could produce a more desirable range of molecular weight hydrocarbons.

mcr

yes Paul...

Putting that in perspective.

In these sorts of scales even if its 10% (just a random number) thats going to be for every 10 tonnes of C9 we make 1 tonne lower Mw hydrocarbons that have to go back to the gasifier etc... a significant drain on the energy efficiency. Not to mention intensive use of catalysts will eventually deactivate them due to some inevitable "coke-ing" of the active sites & leaching of the catalyst... I'd imagine to happen.

Even at 1% for every 100 tonnes usable product we get 1 tonne that needs re-gasification... AT THESE SCALES 1% EVEN IS SIGNIFICANT! Especially on an industry (Petrochems) that operates at such high efficiencies - to be economical!

I compare with the biorefinery concept - which I've been banging on about.
If that sort of thing were transfered to the biorefinery (AQUEOUS-PHASE CHEMISTRY rather than GAS-PHASE) ... imagine all the potential waste (the waste stream that would need treatment...?) and associated energy costs along with separating that.

e.g. chemical separation IS A BIG ISSUE in the chemical industry!

This is not to say that the biorefinery is far from a good idea - it's technically very feasible & beneficial with some of the new technologies. Also the energy costs with actually running the reactions are lower etc.... and the good thing about aqueous solvent --- IT NATURALLY SEPARATES FROM ORGANICS! ... making things very easier as one moves from polyhydroxylated biomolecules to the synthetic fuels we are interested in here, generally that are monofunctional in the main...

Also remember the use of aqueous-phase chemistry DOES HAVE POTENTIAL BENEFITS ALSO...

It's just the principles of GREEN CHEMISTRY need to be strictly applied in TECHNOLOGY SELECTION...

This is all in my humble opinion anyway.

Paul Dietz

mcr: if the FT process is being used as a topping cycle on a thermal powerplant, then sending the low value hydrocarbons (and unreacted syngas) to the turbine doesn't affect the efficiency much at all, compared to the efficiency of an IGCC plant without FT.

Having this once-through approach also lets you use air-blown gasification; this would prevent recycling of off-gas back to the gasifier, since the nitrogen would build up. Condensible hydrocarbons could be recycled, though.

About waste from the catalyst: this will be a much lower volume than the waste hydrocarbons (not thousands of tons a day, certainly). If the FT catalyst is cobalt based it would very likely be sent for cobalt recovery (cobalt is currently around $15/lb., I think.)

The dominant waste streams (aside from CO2) are going to be mine tailings and slag from the gasifier, if the system is using coal or coal waste.

mcr

I refer to the undesired hydrocarbons not the catalyst-residues as the "large scale waste", on tonnes per day scale. Yes you're right about the Cobalt catalyst - all the large mutlinationals use Cobalt barring one whom use an Iron catalyst for FT-synthetic processing. I also understand that these catalysts are robust enough go through hundreds of cycles and only generate waste on a Kg scale... sorry if I misled anyone unintentionally.

When I refer to the inefficiency - I mean in "chemical equivalents" or "CO2 equivalents" ... i.e. the amount of energy required to maintain this reaction. Why put materials through the reactor mutliple times - ONE REALLY WANTS CATALYSTS / REACTIONS with sufficiently high selectivity (95%+) not require this.

In clean technology terms this is the level one must go to when doing "CO2 book keeping". Remember CO2 trading (Koyto) is going to have an effect (large or small) on the economics also of all the processes in chemicals manufacture. It could make or break large scale processes...

I'm no expert in this area of chemistry (my research is in another area)... I take the point of having INTEGRATED-POWER GENERATION ... ie the lower Mw are sent to the generator for combustion to actually power the gasification reactor / FT-reactor ???

I'll have to go look up IGCC and some related chemical engineering literature ... thanks for the info though Paul.

If you think theres anything I should read post it on here, that would be great.

Rima

i need some favor here... i need more detail information bout indirect coal liquefaction.FT process and other process!!! i need it to make a papper, which is my home work..please!!

im waitin for your favorably reply soon,,,
thank you,

Rima

sorry forget to say merry Xmas...
happy holiday!!!
in indonesia its already december 26th

Dump Truck

wow cleaner burning fuels, i wonder if this can be applied to already existing vehicles

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