[Stoves] How to make smokeless coal?

[Crispin Pemberton-Pigott]

Dear Darpan

>Emission factor for PM for residential stove is approximately 10 times to that of a power plant with electrostatic precipitator (USEPA, 2007).

That depends on the type of stove and its operating sequence. It is not ‘generally true’ it is true for certain stoves. The emission factor for improved domestic stoves in Ulaanbaatar is far below those of traditional stoves. This alone shows that the ‘rating’ has to be accompanied by the context in which the number is generated.

>The order of magnitude difference of Emission Factor (EF) of coal cook stoves compared to LPG varies between 10-100 times (Venkatramanet al., 2010; Zhang et al., 1999) for carbon monoxide and particulate matter emissions.

That again depends on the type of stove. It is probably true for some stoves and is certainly not true for stove supported by the World Bank pilot programmes in Hebei province (800,000 units), Tajikistan, Kyrgyzstan and the on-going UB-CAP in Mongolia. I do not see the point in reporting what some stove produced instead of what the best available technology produces.

A well-made LPG stove has very low emissions of those pollutants. A well made coal stove has comparable emissions. In many cases the emissions of PM for both cases are below the detection limit.

>It is unfair to compare emissions of raw coal and semicoke as mentioned above. Were the conditions same?

It is entirely fair as the test conditions were the same.

>What about size of the samples? We do not how much of heat and mass transfer is happening across the fixed bed for the two conditions.

The stove was the same and the heat requirement was the same.

>Did they compare the EC-OC content of the final emissions.

They did not. Most of the emissions in both cases, in the first 45 minutes, were from the wood needed to ignite the fuel. Many test procedures ignore the ignition emissions, even though, in the case of Ulaanbaatar, that is the primary source.

>I assume if they have measure that, they would have got a higher value of the EC content in the semi-coke as the toxic components of the OC were already removed during carbonization.

I think you have assumed that coal content and emissions are ‘toxic’. Semi-coking does not remove ‘toxic content’. It removes volatiles that are in virtually all cases a set of combustible volatiles.  Toxicity can be measured in the emissions from any fire by seeing what has been produced by the stove. If the stove burns everything completely there are no ‘toxic’ emissions from incomplete combustion.

Regards
Crispin

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