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What exactly are the efficiencies?

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The article mentions how gasification is an efficient process multiple times. Can someone put some numbers on how efficient it is for particular feedstocks and products?!

90% conversion of tars and oils to CO and H2 with controlled oxygen injection - per Thomas G. Kreutz et. al, as prepared for the 25th Annual International Pittsburgh Coal Conference, 29 Sept. - 8 Oct. 2008 ...JR@Large.... 02:08, 28 July 2010 (UTC) —Preceding unsigned comment added by Jerasmussen (talk • contribs)

If you read carefully, the article says that the efficiency is potentially more efficient that the usual steam cycles, and explains why: it is not limited by the theoretical carnot efficiency. It does evaluate the relative efficiencies between different gasification concepts. Also, it correctly states that the produced gas can be more efficiently converted to electricity that the solid fuel [when not counting losses during the conversion in the gasifier]. Documented net efficiencies of real gasification plants are almost impossible to find in the open. In many cases it is without doubt because it is low or even negative, but also because most (or all) of them are still development projects with the exception of coal gasification. --Claus Hindsgaul (talk) 06:04, 28 July 2010 (UTC)[reply]

Flow and fixed bed questions

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What is the air / steam flow co- and counter-current with, the motion of the fuel? If the fuel moves, why is it called "fixed-bed"? Thanks.

--- The final resting area of char, that is currently undergoing the gasification processes, resides at a fixed bed depth (downdraft) N/cm from the original (raw unburnt feedstock (before heat and air where applied)), this final resting area is where the said char is completely reformed to (A)gas (producer, or syn gas) and (B)mineral ash (ash). At this point, the spent ash simply falls through the final bed retainment, and is replaced by more char that will undergo the same reforming process. The consumption or reforming process retains this level N/cm from the raw fuel area, by means of mecanical or gravity retention. Therefore the fuel is constantly moving to the said fixed bed. 

Side note: some "slipped char" also moves past the final bed area and is known as "spent char".

A31ford 12:12, 30 April 2006 (UTC)[reply]

---


The optimal flow of the gasification agent (air/oxygen/steam) in a fixed bed gasifier depends on the reactivity of the fuel (how fast it reacts chemically with the gasification agent at the given temperature) and by the energy effect you need from the gasifier. A faster flow results in a faster conversion, but also in a thinner gas, eventually approaching the exhaust from pure combustion. The gas flow is much faster (several m/s) than the movement of the char (several cm/hour).

The fuel particles in the "fixed bed" is nearly fixed in space. It is a correct observation that it does move as the fuel is consumed. But as indicated above, this movement is very slow.

UK gas works elaboration

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My visits to the UK left me wondering why there are so many abandoned gas works there. Why were they built (what was the advantage over using the fuels involved to generate electricity), why are so many of them still around, and what did they usually run on? The article explains how the process works very well, but since gasworks redirects here, it'd be nice to elaborate on the actual gas works themselves. Bz2

The reason that there would be old gas plants is that when natural gas was discovered in UK waters, old fashioned 'town gas' (from coal as I understand it) became uneconomical and so the gas works closed. Having said that, I haven't noticed many abandoned gasworks but then I live in Scotland so I can't vouch for the whole of the UK. Neither am I confident that I would know what a gasworks looked like!Ewan carmichael 13:06, 15 October 2007 (UTC)[reply]

I think you will also find that the old gas works were pretty horrendously polluting. There were town gas facilities for municipal production but also dedicated facilities for factories. Many of the old gas works sites are highly polluted. In Stockport for instance the old gas works was demolished a number of years ago and a carpark built over the top with a shopping centre to seal in the pollutants. I think you will find most of them have suffered the same fate. Natural gas is much cleaner, safer and economical. You used to be able to commit suicide by poisoning yourself putting your head in the oven and turning the gas on.--Alex 13:27, 15 October 2007 (UTC)[reply]
Town gas had many environmental problems, but the reason you could commit suicide by inhaling it was due to its content of carbon monoxide, which is otherwise not really an environmental concern. The town gas process produced loads of problematic carcinogenic tar (mainly PAHs), which can indeed kill you, but it generally takes decades die from cancer. Just to explain that the instant lethality of town gas is not directly related to it being less clean.

--Claus Hindsgaul 07:22, 16 October 2007 (UTC)[reply]

We need the equation for this process written in the article

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A chemical reaction equation for this process needs to be presented in the article so that people know exactly what the inputs are, what the intermediate reactions are, and what the outputs of the process are. Could someone do that? AppleJuggler 04:47, 6 June 2007 (UTC)[reply]

Not really. The reason being every feedstock is different, especially considering the inclusions that go along with the process. For example, lower ranked coal is going to have a different reaction than, say, traditional west virginia bituminous coal. polymers are going to have an alotgether different reaction than heavy oil. Xilften 18:21, 10 August 2007 (UTC)[reply]

Yes, but the basic reactions are always the same; see biomass gasification. I'm going to add them here. --Jonathan Stray 10:03, 13 August 2007 (UTC)[reply]

Regasification

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We need a section in the article about regasification. (Could have a new article, but either article would not be very large.) WikiDon (talk) 00:55, 21 May 2008 (UTC)[reply]

As far as I can google, regasification is just the process of evaporating liquefied natural gas before unloading from a transport unit to a gas pipeline. It has no connection to the gasification process. Regasification is already explained at the Liquefied natural gas page. You may put up a new page to explain the process in detail, but I dont think that even a pointer from the top of the gasification page would be in place. --Claus Hindsgaul (talk) 05:23, 21 May 2008 (UTC)[reply]


Section: Potential for renewable energy

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TeH nOmInAtOr recently put a POV tag on the Potential for renewable energy section. I agree and found several factual errors and propaganda like misleading claims in it. I have tried to improve the section and ask if the POV tag can now be removed. Also, should we remove the mention of one of many gasification demonstration organisations? Güssing is indeed a very interesting case (I visited it myself in 2004), but should it be mentioned (alone) here? --Claus Hindsgaul (talk) 10:03, 10 March 2009 (UTC)[reply]

There's still a lot of work to be done. I'm starting to browse (crawl) all the energy articles to check for POV violations. You can help by looking at every single article in energy category and energy templates and reading. TeH nOmInAtOr (talk) 00:25, 12 March 2009 (UTC)[reply]
Indeed there is a lot of work to be done on Wikipedia, but can I remove your POV tag here?

--Claus Hindsgaul (talk) 07:07, 12 March 2009 (UTC)[reply]



I also noticed a couple of facts that might be wrong in this section. First, it says that gasification emits the same amount of CO2 as combustion of the original fuel; I thought one of the main benefits of gasification was that it could be used as a carbon capture method.

yes, but excluding CCS (which is an additional process that in principle can be applied to every combustion technology, with different removal efficiencies) this is true. we need to stick to the principle of mass conservation: the amount of carbon in the char is negligible, therefore since Cin=Cout the same quantity of carbon as there is in the input fuel is emitted. I suggest to remove "dubious" tag. Robyturco (talk) 09:56, 2 July 2012 (UTC)[reply]

Second, it says that production and combustion of biofuels is carbon neutral because they remove the same amount of CO2 from the air that they emit; however, I think plants draw carbon from the soil; so unless there is some process that puts carbon back into the soil, it is still carbon positive (in relation to the atmosphere), but less so than fossil fuels.
I added "dubious" tags to those two statements.
Qbert203 (talk) 19:47, 18 December 2011 (UTC)[reply]
From my brief research (wikipedia) it appears that plants fix carbon into the soil rather than draw carbon from it. It appears that the process is to some degree carbon negative.

the carbon cycle of a plant is based on the withdraw of CO2 from the air, therefore combustion of biomass and biofuel is carbon neutral. I suggest to remove "dubious" tag. Robyturco (talk) 09:56, 2 July 2012 (UTC)[reply]

Cleanup tag

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Hi, Somebody left at cleanup tag in the article with no explanation. Does anyone know the reason for this tag? If not, I suggest we simply delete it, as it serves no purpose without an explanation. --Claus Hindsgaul (talk) 09:11, 24 July 2009 (UTC)[reply]

Waste disposal

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Is it considered that gasification of waste is a specialised form of incinerator?

If that is so, the phrase: "Several gasification processes for thermal treatment of waste are under development as an alternative to incineration." could be changed to "...more basic forms of incineration".

("More basic" means "cruder" but that sounds a bit judgemental.) —Preceding unsigned comment added by 94.194.151.102 (talk) 12:13, 16 October 2009 (UTC)[reply]

Incineration is the complete oxidation of biomass to inert compounds, while gasification is partial oxidation to produce a synthesis gas that retains potential energy:

Biomass + unlimited O2 ---Incineration---> CO2 + H2O + Energy

Biomass + limited O2 ---gasification---> CO + H2 + Energy ... ... CO + H2 + O2 ---Combustion---> CO2 + H2O + Energy

Just as refining crude oil to gasoline is not the same thing as burning it, so gasification is not the same thing as incineration. ...JR@Large.... 01:37, 28 July 2010 (UTC) —Preceding unsigned comment added by Jerasmussen (talk • contribs)

I agree with Jerasmussen, however in some processes which portray themselves as gasification - they gasify waste, the syngas is imediately burnt to generate heat for the production of electricity in the same way as an incinerator. In this instance the first comment with respect to 'a more complex form of incineration' may be appropriate.--Alex Marshall (talk) 15:18, 20 May 2011 (UTC)[reply]

Gasifier types

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I suggest that:

  1. Plasma gasifiers be added as a separate type of gasifier under Gasification processes
  2. Fluidized bed reactor be subdivided into Bubbling fluidized bed (BFB, Circultaing fluidized bed (CFB) and Dual fluidized bed (Dual FB)

Sadly I don't know enough about these gasifiers to attempt to make the changes myself ... --Andersneld (talk) 14:23, 22 June 2011 (UTC)[reply]

Grammar

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"Waste gasification has several principal advantages over incineration:"

Can someone fix this? By definition, a thing can only have one "principal" anything.

net/gross efficiency

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A major challenge for waste gasification technologies is to reach an acceptable (positive) gross electric efficiency.

Really important is the net efficiency that takes into account the consumption of the process including fuel preparation and gas cleaning. — Preceding unsigned comment added by 212.203.109.254 (talk) 07:54, 24 August 2012 (UTC)[reply]

I believe the language in the efficiency section should be edited to include terms such as "May be" or "Has the potential for" when referring to its carbon neutrality. E.G.; "Gasification has the potential to be carbon neutral depending on processes used. If only biomass/renewable energy is used in the gasification process, carbon neutrality would be maintained. If nonrenewable or fossil fuel derived energy is used in the process, there would be a net carbon gain without carbon sequestration techniques." 65.130.17.55 (talk) 19:03, 16 October 2013 (UTC)[reply]

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With partial combustion!

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"This is achieved by reacting the feedstock material at high temperatures (typically >700 °C), without combustion, via controlling the amount of oxygen and/or steam present" I suggest change to "without complete combustuion" e.g. the reaction 2C+O2=> 2 CO is clearly a combustion albeit not complete. 150.227.15.253 (talk) 14:14, 22 April 2022 (UTC)[reply]

Totally agree Claus Hindsgaul (talk) 21:16, 24 April 2022 (UTC)[reply]
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