| Boiling Point No. 28- August 1992 |
Coal Briquette Desulphurisation
by Somchai Osuwan, Kunchana Bunyakiat and Duangporn Theerapabpisit, The Department of Chemical Technology, Faculty of Science, Chulalongkorn University, Bangkok 10500, Thailand.
Summarized from SCNCER - No. 976 ASEAN
The combustion of coal briquettes causes corrosion and air pollution from sulfur in the coal. Coal briquette desulfurization by addition of lime was studied. Calcium oxide reacts with sulphur dioxide, evolved from combustion, according to the equation:
2CaO + 2SO2 + O2 ---> 2CaSO.
The resulting calcium sulphate remains in the ash after combustion.
Variables that affected sulphur oxides capture by lime during combustion of coal briquettes at true operating conditions in bucket-type cooking stoves were found to be: amount of lime added in teens of mole ratio of CaO/ S (from 0 to 4), percentage of clay used as binder (from 0 to 40) and types of coal fines used.
Lime was found to be highly effective in desulphurization as the percentage of calcium sulphate in coal ash increased sharply with increasing CaO/S mole ratio from 0-2 and levelled off at higher ratios. The maximum insitu sulphur capture was 90-95%, based on the total sulphur present initially, leaving only 5-10% emitted as sulphur oxides. Clay produced a similar (but less pronounced) effect to that of lime.
In conclusion, it is demonstrated that coal briquettes made from coal fines from various sources in Thailand can be well desulphurized by lime. The recommended value of CaO/S mole ratio is in the range of 2.0-2.5, together with a 20% addition of clay.
In this experiment, ovoid shape briquetting (3x5 cm, approx I 5 g/piece) was selected because these briquettes
were found to be suitable as a substitute for wood charcoal in Thai bucket-type domestic stoves. Clay was selected as the binder from the results of a previous investigation apart from the fact that it is suitably abundant and cheap.
Effect of time and clay on stove efficiency
With no lime and/or clay, stoves employing coal briquettes as fuel displayed low efficiencies. It was observed that such briquettes were more dense and burned more slowly and incompletely, leaving unburned carbon core inside the briquettes. With either lime or clay addition, the briquettes presumably became more porous providing better air diffusion into the centre. However, as more and more lime or clay was added, the briquettes became harder and more dense and their efficiencies again dropped.
In conclusion, for various coal samples from significant sources in Thailand the optimum addition of lime is 2.02.5 CaO/S mole ratio and of clay is 20% for the production of good coal briquettes.
Research into ITDG's Work with Women
Three ITDG programmes are working with women in different parts of Kenya: Stoves & Household Energy work with women potters in West Kenya, Shelter works with Masai women, and Agriculture and Fisheries work with women farmers in Turkana, Meru, Ukambani, and Samburu. None of these were designed as "women's projects" but the combination of ITDG technology and existing women's roles in particular settings has led to extensive project work with women. In each project, ITDG has different ways of working, and has learnt lessons about what does and does not lead to success, and what the problems and the particular benefits are of working with women. But the experience of the three programmes has never been drawn together or compared.
This research project will study the work of different projects to document the involvement of and impact on women and to draw out lessons for the future. The main output will be a brief report which, in the first instance, will provide recommendations for planning in Kenya. However, it may lead on to further proposals to look at the work of other agencies in Kenya, or at ITDG work with women in other countries, and it should ultimately contribute to the formulation of policies on working with women.
For more details contact Emma Crewe, SINE, ITDG, Myson House, Railway Terrace, Rugby, CV21 3HT.
Stoves as a Springboard
Some development agencies are successfully using improved stoves as part of broader household development programmes. In Kenya, Home Economists use stoves as a starting point for discussions on nutrition and kitchen hygiene. We should learn from them and other examples, to find out how stoves can be promoted in the context of household energy, rather than as a tool for reducing deforestation, or as an income-generating product.
ITDG's Stoves & Household Energy Programme is initiating a research project to explore how agencies in Kenya and Sri Lanka use stoves as a component of more integrated household development work. The aims are to document the value of stoves in connection with other household issues, such as nutrition, improved kitchens and women's domestic workload; and to identify potential projects for collaboration.
For more details please contact Caroline Ashley, SHE, ITDG, Myson House, Railway Terrace, Rugby, CV21 3HT.