[Stoves] Coal stoves in Mongolia

[Crispin Pemberton-Pigott]

Dear Ron

 

A BLDD stove with good cooking performance (two pot) has been patented in RSA a couple of months ago. It is of course a little radical and will be made in prototype shortly (not counting the existing prototype).

 

All coal stoves that are refuelled from time to time make coke. From what we have measured, after the coal is fully coked ( about 40% into the burn time) there are virtually no particulates (PM2.5) produced at all unless the fire is kept quite cold with large excess air volumes passing through. Even really bad stoves can reach 20 micrograms/m^3 (O2 factored to zero). Good stoves reach zero, sometimes for hours. That means they are cleaning the air entering the stove because (as we demonstrate to visitors) the lab air runs from 80 to 600 micrograms/m^3.

 

The BLDD stoves made so far in Mongolia tend to be on the large end of the domestic spectrum (11 kW). They are extremely clean but we did not yet fiddle consistently with them – too much else on the agenda. This winter…

 

The dry, devolatilised coal (coke) contains about 70% of the energy in the initial energy in the coal. The cost of coal is $0.85 per 8 kg bag which is $0.0136 per MJ. This is less expensive than the Witbank D bituminous coal burned in Johannesburg but people earn less. The available improved stoves pay for themselves in about 4 months with higher efficiency.

 

Regards

Crispin

 

 

 

Crispin  (cc list)

1.  Changed thread name to reflect the dialog.

  2.  I had great hopes (based on your writings) for a simple Mongolian BLDD.  Where does that fit into the general scheme for Mongolia?  The BLDD doesn't seem appropriate for most cooking chores - but seemed pretty perfect for heating.  (Not thinking about making coke - but there should be that possibility also    Ron

  _____  





Dear Roger

 

P.S. any idea's how I can get a sample of the coal being used in Mongolia? I understand they use 4 metric tones a year by 1,300,000 yurts per year. I think I could cut this down to less than one ton, but need a sample of this stuff.

Saving coal is not as straight forward as burning less. The need for heat is absolute, meaning that you have to deliver an average of 4kW minimum into the home. If the system is 80% efficient it means having a 5kW fire going constantly.

The number of yurts (gers, as they are called) is about 100,000 with the number declining slowly as people build more permanent housing. Coal is not used outside Ulaanbaatar domestically, and in fact viewed historically is only a recently used fuel.

I am interested in know what you think of as ‘clean’ with your coal burner. We are expressing the emissions in terms of heat delivered into the home so that the figure incorporates the thermal efficiency into the number. For stoves receiving a subsidy to the homeowner, the CO limit is 7 g/MJ delivered and PM2.5 is 70 mg/MJ. Some stoves are below 1 mg/MJ which is extremely clean. One is a crossdraft and the other is a TLUD that can be refuelled under certain circumstances. They are very different to look at.

The coal consumption per urban domestic home is 4,500 kg per year on average, burning about 1 kg per hour in winter. The coal is from the Nalaikh Mine, mostly, and the analysis is 25% moisture, 50% volatiles after drying and 8-12% ash. The sulphur is very low at <0.4%.

It lights easily and has enormous volumes of smoke if placed on a burning fire (which is the main air quality problem in UB). If a TLUD is refuelled hot, it is a nightmare. It is essential that the stove be refuelled for continuous operation. That has led to hopper stoves having the most promise. 

The qualifying stoves range from $80 to $160 and one imported TLUD made of cast iron with a ceramic liner is $275 or so. The cleanest, cheap stove is a crossdraft burner with a flame tube for the smoke and CO to burn inside the heat exchanger. This layout has been successful in several very different products.

Regards

Crispin

 

 

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