[Gasification] A small literature review re: syngas

Wed Dec 29 15:47:03 CST 2010

Helo Bear K
 very good relevant literature work

On Wed, Dec 29, 2010 at 7:13 PM, Bear Kaufmann <bear at allpowerlabs.org>wrote:

> I looked through some of the papers I have on hand, and extracted the
> interesting parts as they relate to the latest discussion, FWIW:
>
> "Fuel gas can be used directly as fuel in gas burners or internal
> combustion engines and gas turbines. Fuel gas, after purification and
> possibly water gas shift to adjust the H2/CO ratio, can be described as a
> syngas (a mixture of H2 and CO), which can be used to manufacture methanol,
> ammonia, Fischer Tropsch liquids, or hydrogen for use in fuel cells (4). The
> suitability for a particular usage, i.e. the fuel gas quality, is determined
> by the gas composition and the level of contamination by particulates,
> alkali compounds, nitrogen-containing components, sulphur and tars (5)."
> from Kalisz, S. et al. Energy Balance of High Temperature Air/Steam
> Gasification of Biomass in Up-Draft, Fixed-Bed Type Gasifier. Int. Conf. on
> Incineration and Thermal Treatment Technologies, Phoenix, Arizona (2004).at
> <http://gasunie.eldoc.ub.rug.nl/FILES/root/2004/3265200/3265200.pdf>
>
> "Fast pyrolyzers rapidly (∼1 s) heat dry biomass (10% H2O) to ∼500°C and
> thereby thermally transform biomass into bio-oil (∼60% of mass), syngas
> (∼20% of mass), and charcoal (∼20% of mass). The energy required to operate
> a fast pyrolyzer is ∼15% of the total energy that can be derived from the
> dry biomass. Modern systems are designed to use the syngas generated by the
> pyro- lyzer to provide all the energy needs of the pyrolyzer."
> from Laird, D.A. The Charcoal Vision: A Win Win Win Scenario for
> Simultaneously Producing Bioenergy, Permanently Sequestering Carbon, while
> Improving Soil and Water Quality. Agron J 100, 178-181(2008).
>
> "To improve the thermal efficiency and predict the composition of syngas,
> several numeric models have been developed for biomass conversion systems."
> from Rogel, A. & Aguillón, J. The 2D Eulerian Approach of Entrained Flow
> and Temperature in a Biomass Stratified Downdraft Gasifier. American Journal
> of Applied Sciences 3, 2068-2075(2006).
> Comments: Shows a stratified downdraft model with inputs of air and
> biomass, outputs of syngas and ashes
>
> "The term ‘pyrolysis’ is typically used either for ...[analytical
> purposes]... or for bioenergy systems that capture the off-gases emitted
> during charring and used to produce hydrogen, syngas, bio-oils, heat or
> electricity (Bridgwater et al, 1999)."
> from Lehmann, J. & Joseph, S. Biochar for environmental management: science
> and technology. (Earthscan/James & James: 2009).
>
> "High purity syngas (i.e. low quantities of inerts such as N2) is extremely
> beneficial for fuels and chemicals synthesis since it substantially reduces
> the size and cost of downstream equipment. However, the guidelines provided
> in Table 5 should not be interpreted as stringent requirements. "
> "There is more latitude with regard to syngas composition for engine
> combustion than for turbine combustion."
> "To be considered interchangeable with conventional fossil fuels (natural
> gas or distillate oils) and to ensure maximum flexibility for industrial or
> utility applications, syngas heating value needs to be above 11 MJ/m3"
> "At temperatures greater than 1200-1300oC, little or no methane, higher
> hydrocarbons or tar is formed, and H2 and CO production is maximized without
> requiring a further conversion step."
> "Biomass gasification is the conversion of an organic...carbonaceous
> feedstock by partial oxidation into a gaseous product, synthesis gas or
> “syngas,” consisting primarily of [H2 and CO] with lesser amounts of [CO2,
> CH4], higher hydrocarbons (C2+), and nitrogen (N2). The reactions are
> carried out at elevated temperatures, 500-1400oC, and atmospheric or
> elevated pressures up to 33 bar (480 psia). The oxidant used can be air,
> pure oxygen, steam or a mixture of these gases. Air-based gasifiers
> typically produce a product gas containing a relatively high concentration
> of nitrogen with a low heating value between 4 and 6 MJ/m3 (107-161
> Btu/ft3). Oxygen and steam-based gasifiers produce a product gas containing
> a relatively high concentration of hydrogen and CO with a heating value
> between 10 and 20 MJ/m3 (268-537 Btu/ft3)."
> "Table 8. Compositions of Biomass-Derived Syngas" - includes N2 from 0-56%,
> H2 from 5-43.3%, CO from 9-67%, CO2 from 4-40%
> ...
> from Ciferno, J.P. & Marano, J.J. Benchmarking biomass gasification
> technologies for fuels, chemicals and hydrogen production. US Dep of Energy
> NETL (2002).at <
> http://seca.doe.gov/technologies/coalpower/gasification/pubs/pdf/BMassGasFinal.pdf
> >
>
> "The resulting fuel is a producer gas (a synthesis gas or syngas) that
> consists primarily of varying ratios of hydrogen and carbon monoxide (CO)."
> from Mukhtar, S. Manure to Energy: Understanding Processes, Principles and
> Jargon. (2006).at <
> http://repository.tamu.edu/bitstream/handle/1969.1/87462/pdf_2425.pdf?sequence=1
> >
>
> In short, the usage from the above doesn't appear entirely clear.
> But in general, syngas is often suggested to have been upgraded, or of a
> higher CO/H2/energy content. Syngas is often used to refer to gas intended
> to be used for synthesis of products. Syngas does also seem to be used as
> general term in some cases.
>
> My preferred usage has been to call the gas the air-blown GEK makes
> "producer gas". Wood gas notes that the carbon source was biomass, though I
> don't prefer the term. "Syngas" being made with O2 or steam.
> The problem with the above is it doesn't leave a general catch-all term.
>
> Cheers,
> Bear Kaufmann
> All Power Labs
>
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