Composition of Producer Gas

If there is no smoke, the concentration of those will be negligible. Why the interest?

PWS,

We are producing "Producer Gas" for reheating furnace for rolling of steel. I am not getting your comment properly.

OK. Trying again: why is the concentration of these gases in the exhaust stack of any interest, other than their presence indicating insufficient air?

At combustion:

• CO + ¹/₂O₂ → CO₂
• H₂ + ¹/₂O₂ →H₂O
• CH₄ + 2O₂ → CO₂ + 2H₂O
• C₂H₆ + 3¹/₂O₂ → 2CO₂ + 3H₂O

So the percentage of the original gases in the combustion products should be zero. If it isn't, then something is wrong.

Producer Gas in UK terminolgy is carbon monoxide and nitrogen and was used as a low grade fuel. It is also a "reducing fuel" preventing the oxidation of molten steel. Can't do better than quote Wikipedia:

"In the UK, producer gas, also called suction gas, specifically means a fuel gas made from coke, anthracite or other carbonaceous material. Air is passed over the red-hot carbonaceous fuel and carbon monoxide is produced. The reaction is exothermic and proceeds as follows:

2C + O₂ + 3.73 N₂ → 2CO+ 3.73 N₂

The nitrogen in the air remains unchanged and dilutes the gas, giving it a very low calorific value. The concentration of carbon monoxide in the "ideal" producer gas was considered to be 34.7 carbon monoxide (carbonic oxide) and 65.3% nitrogen. After "scrubbing", to remove tar, the gas may be used to power gas turbines (which are well-suited to fuels of low calorific value), spark ignited engines (where 100% petrol fuel replacement is possible) or diesel internal combustion engines (where 40% - 15% of the original diesel fuel is still used to ignite the gas). During World War II in Britain plants were built in the form of trailers for towing behind commercial vehicles, especially buses, to supply gas as a replacement for petrol (gasoline) fuel. A range of about 80 miles for every charge of anthracite was achieved."

I assume that any methane and ethane come from the coal. Hydrogen? Perhaps by pyrolysis of some organics in the coal.

If any of you has visited the Lane Automobile Museum in Nashville, TN, you may have noticed a WW2 Citroen Big 15, with a producer gas system installed in the two front fenders. One contained coal solid fuel and the other, the reactor for making the producer gas, which was fed to the IC engine in its normal place, driving the front wheels. The Lane write-up states that the fuel is methane, but I think he has got it wrong - it's carbon monoxide. Desperate times called for desperate measures. The smell during operation must have been pretty bad.

Picture of another version: coal to gas converter at the rear. Sacks of coal on the roof.

Perhaps we may revisit this when oil runs out?

I know about the production of the "Producer Gas", we are into it. However, I am not able to predict( without resorting to analysis) to a reasonable extent the percentage of all the constituent gases by analyzing the sample of the coal to be burnt. I think I have made it clear.

Mr. Govind Rao, Earlier also you started a thread "Analysis of Producer Gas from Bituminous Coal" which has the same intention, I believe.

Earlier some one asked- why you need this information, you didn't reply. You are using this gas for furnace for re-rolling. You should be only interested in calorific value of gas produced per tonne of coal (it is a combination of two parameters- Nm3 of gas produced per tonne of coal & calorific value of gas per Nm3).

"I am not able to predict( without resorting to analysis) to a reasonable extent the percentage of all the constituent gases by analyzing the sample of the coal to be burnt." You should have given a sample analysis.

You will not be able to predict it correctly because it will depend on some other factors too, like quantity of air used per tonne of coal for making producer gas (and whether it is nearly constant) and the speed of the combustion process. Anyway, instead of predicting it it is better to analyse the gas for its constituents, if you you really need.

Pritam,

If you read my query in the heading as mentioned by you. It is how to analyse the constituent of the producer gas....... Whereas, now I am asking how to predict the producer gas constituents by analysing the coal. The reason is to by analysing the coal is to "predict"( if possible) the quality of gas much before it is burnt. Since the Calorific value is not a constant quantity but changes from coal to coal.The gas can be used in various ways not only for Reheating Furnace

since this producer is made by starved oxidation of coal with air, with the inert nitrogen carried through there may well be components distilled off the coal. It seems to me that there is an optimization carried out en situ to minimize the CO2, maximize the CO and also reduce the methane/ethane/hydrogen as close to zero as is practical.

So a feedback process to maintain the temperature gradient through the coal to distil off and partially burn the volatiles and slowly advance the coal towards hotter zones as it loses volatiles and turns into coke which also partially burns. A witches brew will come off this, and gas analyzers may get fouled, requiring frequent sampling and analysis of the output.

I would expect a system like this to be constantly fiddled with to get the maximum calorie fuel output

Just to point out (after a bit more research) that the fuel used in making producer gas is not ordinary coal, but coke or anthracite, which is very low in volatiles. (I should have realised this.) Anthracite occurs naturally (and approaches graphite in composition), whilst coke is "man-made" by heating coal to 1,000+ C. Again from Wiki:

"Anthracite is the most metamorphosed type of coal (but still represents low-grade metamorphism), in which the carbon content is between 92.1% and 98%. The term is applied to those varieties of coal which do not give off tarry or other hydrocarbon vapours when heated below their point of ignition. Anthracite ignites with difficulty and burns with a short, blue, and smokeless flame." (Sorry, can't get rid of those pesky links.)

Will Govind Rao please confirm (or otherwise) that he is not using ordinary coal?

The coal in question is bituminous coal, where the volatile material would be as high as 23%. We are producing the gas by coal gasifier and feeding into to the reheating furnace for rolling of steel and can be used in variety of furnaces after cleaning it. Now the problem is that, we would like to accept or reject the coal consignment on basis of the coal analysis. But sometimes we no choices. Therefore, if we know the quality of the gas which a coal can produce, we can adjust the working accordingly.

Assuming that you are trying to make "Producer Gas" of the carbon monoxide + N2 variety (the UK definition), then could you not test the coal for volatile content (fairly simple, I think) and reject any batch of coal below a chosen figure?

Since coal contains 1,001 different components, mainly organic, a full analysis is going to be a rather complicated procedure and would probably need a gas chromatograph, with multiple columns, linked to an FT-IR analyser. Exactly what you would do with the results, I don't know.

It's beginning to look like there is some confusion on exactly what you are doing - certainly from my point of view - and we have not been told enough information. Don't think I should add any more.

http://www.allpowerlabs.org/gasification/index.html

Thanks a lot, Ron, for the site!