[Gasification] A small literature review re: syngas
Kevin
kchisholm at ca.inter.net
Wed Jan 26 12:59:36 CST 2011
Dear Gerald
What would you think of the following proposed definitions?
WOOD GAS:
Wood gas is a combustible gas produced by gasifying non-fossilized biomass with sufficient oxygen to leave little or no char. The biomass feed to a "Wood Gas Gasifier" could be woody biomass, agricultural wastes, or any other non-fossil biomass based material. The gas produced has a heating value in the range of about 125 to 150 BTU per Standard cubic foot. It may, or may not, contain significant quantities of tars. With adequately low tar content, it would be termed "Engine Grade Wood Gas", or if the tar content was too much for longer term use in an engine, it would be termed "Fuel Grade Wood Gas."
PYROLYSIS GAS:
Pyrolysis gas is the gas product produced when non-fossil biomass is either heated in a sealed retort, or, when it is "internally heated" through partial combustion of the pyrolysis gases. It has a high tar content, and a heating value in excess of 200 BTU per Standard Cubic foot.
SYNTHESIS GAS, and "SYNGAS"
Synthesis gas is any gas produced for the purpose of synthesizing a higher value product. Wood gas and Pyrolysis gas can be termed "Synthesis Gas" or "SYNGAS" if they are used to synthesize a higher value product. Any such gas that is burned as fuel to release its energy content as heat is not "Synthesis Gas" or "SYNGAS".
How do those proposed definitions sound to you?
Best wishes,
Kevin Chisholm
---------- Forwarded message ----------
From: Gerald Kutney <gkutney at shaw.ca>
Date: Tue, Jan 25, 2011 at 17:59
Subject: Re: [Gasification] A small literature review re: syngas
To: Discussion of biomass pyrolysis and gasification <gasification at lists.bioenergylists.org>, gasification at bioenergylists.org
I have followed the discussion on the definition of syngas (synthesis gas) with great interest. Although there are adamant views that syngas should be narrowly defined, I have yet to see early references that back up this claim. The term "synthesis gas" appears to have gained popularity during the '40's (possibly before) to describe the raw material for the FT process; however, it quickly became the popular term for manufactured gas. In the second edition of the iconic Kirk-Othmer, Encyclopedia of Chemical Technology, one is directed to the chapter on manufactured gas when looking for synthesis gas (see vol. 10, p. 355, 1966), where it is mentioned to produce synthetic chemicals from the water gas and water gas shift reactions. In Riegel's, Industrial Chemistry, 1962, a list of synthesis gas methods are listed that mimic manufactured gas and includes gasification with air. And on p. 892, synthesis gas is simply defined as the mixture of CO and H2.
I respect the opinion of the members of this list, but could you supply early references to back up your definitions. I believe that this is an important issue to be cleared up, as there is definite confusion on whether syngas should have a limited definition or a broad definition.
Gerald Kutney, Ph.D.
Managing Director
Sixth Element Sustainable Management
www.6esm.com
-----Original Message-----
From: gasification-bounces at lists.bioenergylists.org [mailto:gasification-bounces at lists.bioenergylists.org] On Behalf Of jim mason
Sent: Wednesday, December 29, 2010 2:40 PM
To: gasification at bioenergylists.org
Subject: Re: [Gasification] A small literature review re: syngas
On Wed, Dec 29, 2010 at 1:13 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:
>
> 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.
>
bear, in reading through your 6 examples here, i find 4 of them use
the term "syngas" in some flavor of a general term for the gas
produced through some form of biomass thermal conversion. its
relationship to synthesis processes and no/low nitrogen gas is also
there of course. but the prevalence of the "generic" usage is
surprising. i'm surprised to see even some major names in
pyrolysis/biochar are using it to name the gas from pyrolysis.
given this over majority leaning towards the generic use, why do you
summarize the state of affairs by affirming the more "traditional"
senses of the term? it seems the numbers are leaning in the other
direction. of course your sample is anecdotal, so putting numbers to
the resulting statistics is suspect. but still, the emphasis in your
conclusion i do not see in the sample. btw, how did you generate this
sample?
when we started this disucssion, my guess was that the generic usage
of the term was maybe a 10-20% phenomenon. examples are piling up
that it is actually much higher than this. it seems even higher in
the academic world than in our local online circle.
j
>
> "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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