Dear Nurhuda >Three years ago, I developed a formula for coal briquettes and pellet that are easy to light and provide good flame instead of radiant heat.
The stoves being requested are primarily needed for space heating with cooking as a secondary function. There are several stoves on the market which cannot cook but they are not selected by the project for subsidised roll-out as the subsidy is primarily aimed at low income people who will also have to cook with the same stove. The number of stoves involve is quite large. To date the subsidy programme has placed about 100,000 stoves at a cost of maybe $20m. Phase One is ending and Phase Two will start immediately with a different funding source. >The feedstock is low grade coal, which is abundant in Mongolia. I am not so sure what you mean by low grade coal. The coal available in town came from two sources, one of which has been forced to close by the government. Both have a high hydrogen content because of the high volatiles content (hydrocarbons). Both are easily lit and were available in the raw state or as semi-coked briquettes. The history of semi-coked briquette promotion is not very encouraging. They are hard to ignite. There has been a JICA team here for years working on various aspects of fuelling (and changing) the boilers in apartment buildings which were not designed for high hydrocarbon fuel. The result of a mismatch between the burner and the fuel is usually high emissions of unburned gases. This is pretty easy to demonstrate by putting the same fuel (say, raw coal from Nalaikh Mine) into four different stoves and seeing a 2000:1 difference in the PM 2.5 emissions. For many years people blamed the emissions on the fuel, not the burner, or rather, the fuel+burner combination. That old idea is no longer accepted. It is widely realised that testing a stove means testing it with a particular fuel and assisting the manufacturer to adapt the combustion conditions to the fuel. As you have shown in your video, this can be done for any particular blend. The pinkish flame is, from my experience, hydrogen, or very high temperature water vapour. The hydrogen is liberated from the fuel (if it is not fully coked) or from the decomposition of water lower in the fire (water gas shift reaction). The water vapour is from the fuel or from the combustion of the hydrogen lower down. In any of these cases the result is still a pinkish flame. The hydrogen content of the fuel, being higher than regular 'hard coal' makes it much easier ignite and hydrogen has 4 times the heat of carbon, per kg. In terms of desirable qualities from the perspective of both the home owner and the manufacturer, the most useful fuel is a briquetted raw coal pellet of about 10-20 g with a controlled moisture content - about 10-12%. As briquetting involves a certain amount of drying (the raw coal Is quite wet) there is some advantage to the briquettes over lump coal. Prof Lloyd has reported that South African producers managed to get raw coal to bind without any additives if it was high in volatiles. That makes the product really cheap. Here in Ulaanbaatar, briquettes have been typically lower in energy per kg, harder to light and three times the price. One attempt was made to produce a 1/3 clay 'holey briquette' about 160mm tall but it was reliant on waste Nalaikh 'duff coal' and there is only a limited quantity of that. In other words the coal was free and sitting at ground level. It was used to fuel a TLUD large briquette burner and it was pretty good, as a stove. It is no longer on the market. I think the main reasons were the power was too low and the extraction of heat was too high (leading to condensation and corrosion). The CO/CO2 ratio was about 3.8% which is not great but better than the baseline. It could easily have been improved with a better burner. Regards Crispin _______________________________________________ Stoves mailing list to Send a Message to the list, use the email address [email protected] to UNSUBSCRIBE or Change your List Settings use the web page http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org for more Biomass Cooking Stoves, News and Information see our web site: http://stoves.bioenergylists.org/
