Difference between revisions of "Gasifier Stoves"
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= Introduction – the Gasifier Principle<br/> = | = Introduction – the Gasifier Principle<br/> = | ||
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In a conventional fire the heat is controlled by regulating the fuel supply: the more fuel we add, the more heat we generate, provided sufficient air is available for the combustion. In contrast to this, gasifiers control and optimize both processes separately to achieve efficient and clean utilization of the fuel: | In a conventional fire the heat is controlled by regulating the fuel supply: the more fuel we add, the more heat we generate, provided sufficient air is available for the combustion. In contrast to this, gasifiers control and optimize both processes separately to achieve efficient and clean utilization of the fuel: | ||
| − | regulating the heat that is reaching the solid biomass to optimize the drying and pyrolysis process | + | *regulating the heat that is reaching the solid biomass to optimize the drying and pyrolysis process |
| + | *controlling the supply of air and regulating the availability of oxygen for optimizing the subsequent steps of wood gas combustion and char gasification. More air to the ‘gas-generator’ produces more gas that can be combusted in the ‘gas-burner’. The regulation, however, is a bit tricky and one of the challenges is to find a better solution to this.<br/> | ||
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| − | Gasifier stoves are currently the cleanest burning option to burn solid biomass in a cook stove. The “gas burner” provides the convenience and efficiency similar to cooking on fossil gas with very little soot and other emissions. | + | Gasifier stoves are currently the cleanest burning option to burn solid biomass in a cook stove. The “gas burner” provides the convenience and efficiency similar to cooking on fossil gas with very little soot and other emissions.<ref name="Roth, C. et al. / GIZ Sector Programme “Basic Energy Services” (HERA) (2014): Micro-gasification: Cooking with gas from dry biomass">Roth, C. et al. / GIZ Sector Programme “Basic Energy Services” (HERA) (2014): Micro-gasification: Cooking with gas from dry biomass</ref> |
| − | For more information on the process of wood gas generation see also [[ | + | For more information on the process of wood gas generation see also [[Cooking with Woodgas|Cooking with Woodgas]].<br/> |
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| + | = Advantages of Gasifier Stoves = | ||
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| + | Compared to solid biomass burning improved cookstoves, gasifiers have certain advantages:<ref name="Roth, C. et al. / GIZ Sector Programme “Basic Energy Services” (HERA) (2014): Micro-gasification: Cooking with gas from dry biomass">Roth, C. et al. / GIZ Sector Programme “Basic Energy Services” (HERA) (2014): Micro-gasification: Cooking with gas from dry biomass</ref> | ||
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| + | *Cleaner burning of solid biomass (considerable reduction of soot, black carbon and indoor/outdoor air pollution). | ||
| + | *More efficient due to more complete combustion (less total biomass consumption). | ||
| + | *Uses a wide variety of small-size biomass residues (no need for wood pieces or charcoal). | ||
| + | *Easy lighting allows for cooking to commence within minutes, much faster compared to lighting charcoal. | ||
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| + | There are also advantages compared to stoves operated on alternative fuels like liquid fuels or solar:<ref name="Roth, C. et al. / GIZ Sector Programme “Basic Energy Services” (HERA) (2014): Micro-gasification: Cooking with gas from dry biomass">Roth, C. et al. / GIZ Sector Programme “Basic Energy Services” (HERA) (2014): Micro-gasification: Cooking with gas from dry biomass</ref> | ||
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| + | Solid biomass fuels are often available locally (affordable access at own convenience), easy to transport and easy to store after gathering.<br/>Creation of gas from dry biomass can be achieved with very simple inexpensive technology directly in the burner unit, which is portable and does not require piping or special burner-heads (in most cases).<br/>Performance similar to biogas (but not dependent on water and bio-digester) and approaching the convenience of fossil gases. | ||
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| + | Furthermore, pyrolytic micro-gasifiers can create charcoal, which may be used in a charcoal stove, further processed into charcoal briquettes or used to improve soil productivity as biochar.<ref name="Roth, C. et al. / GIZ Sector Programme “Basic Energy Services” (HERA) (2014): Micro-gasification: Cooking with gas from dry biomass">Roth, C. et al. / GIZ Sector Programme “Basic Energy Services” (HERA) (2014): Micro-gasification: Cooking with gas from dry biomass</ref> | ||
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| + | = Disadvantages and Challenges of Gasifier Stoves = | ||
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| + | Users may encounter some challenges when using gasifier cookstoves:<ref name="Roth, C. et al. / GIZ Sector Programme “Basic Energy Services” (HERA) (2014): Micro-gasification: Cooking with gas from dry biomass">Roth, C. et al. / GIZ Sector Programme “Basic Energy Services” (HERA) (2014): Micro-gasification: Cooking with gas from dry biomass</ref> | ||
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| + | *Micro-gasifiers need small-sized fuel. They are only useful if fuel is available in the right size. Firewood in the form of large logs or sticks is not suited and needs other types of improved stoves. | ||
| + | *Most micro-gasifiers are batch-loaded and cannot be refueled during use. Thus, cooking times are pre-determined by the size of the fuel container. | ||
| + | *The heat output of most micro-gasifiers is not easy to regulate unless the stove is operated with a fan for forced convection. In this case the power of the fan can be regulated. | ||
| + | *Micro-gasifiers burn the biomass in two stages: first the gas-generator produces the wood gas, which is a thick whitish ‘smoke’ or fume. This “smoke” is burnt by the gas-burner, which is thus basically a ‘smoke-burner’. If the gas-burner operates well then there is no problem. However, should the flame of the gas-burner extinguish (e.g. blown out by gusty wind), the gas-generator will continue producing wood gas, which will not be burnt and then escape as thick white smoke from the stove. | ||
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Revision as of 10:40, 19 December 2016
Introduction – the Gasifier Principle
Micro-gasifiers cookstoves are small gasifier devices that create their own gas from solid biomass and are small enough to fit directly under a cook-pot. Gasifiers can separate gas generation from gas combustion in space and time. In a reactor (gas generator) that is optimized for heat-dependent drying and pyrolysis, solid biomass is first converted into gases and vapors. These are guided into a combustion zone (gas burner) where they are burnt with a surplus of oxygen from a secondary air inlet. The following infographic shows this principle.
In a conventional fire the heat is controlled by regulating the fuel supply: the more fuel we add, the more heat we generate, provided sufficient air is available for the combustion. In contrast to this, gasifiers control and optimize both processes separately to achieve efficient and clean utilization of the fuel:
- regulating the heat that is reaching the solid biomass to optimize the drying and pyrolysis process
- controlling the supply of air and regulating the availability of oxygen for optimizing the subsequent steps of wood gas combustion and char gasification. More air to the ‘gas-generator’ produces more gas that can be combusted in the ‘gas-burner’. The regulation, however, is a bit tricky and one of the challenges is to find a better solution to this.
Gasifier stoves are currently the cleanest burning option to burn solid biomass in a cook stove. The “gas burner” provides the convenience and efficiency similar to cooking on fossil gas with very little soot and other emissions.[1]
For more information on the process of wood gas generation see also Cooking with Woodgas.
Advantages of Gasifier Stoves
Compared to solid biomass burning improved cookstoves, gasifiers have certain advantages:[1]
- Cleaner burning of solid biomass (considerable reduction of soot, black carbon and indoor/outdoor air pollution).
- More efficient due to more complete combustion (less total biomass consumption).
- Uses a wide variety of small-size biomass residues (no need for wood pieces or charcoal).
- Easy lighting allows for cooking to commence within minutes, much faster compared to lighting charcoal.
There are also advantages compared to stoves operated on alternative fuels like liquid fuels or solar:[1]
Solid biomass fuels are often available locally (affordable access at own convenience), easy to transport and easy to store after gathering.
Creation of gas from dry biomass can be achieved with very simple inexpensive technology directly in the burner unit, which is portable and does not require piping or special burner-heads (in most cases).
Performance similar to biogas (but not dependent on water and bio-digester) and approaching the convenience of fossil gases.
Furthermore, pyrolytic micro-gasifiers can create charcoal, which may be used in a charcoal stove, further processed into charcoal briquettes or used to improve soil productivity as biochar.[1]
Disadvantages and Challenges of Gasifier Stoves
Users may encounter some challenges when using gasifier cookstoves:[1]
- Micro-gasifiers need small-sized fuel. They are only useful if fuel is available in the right size. Firewood in the form of large logs or sticks is not suited and needs other types of improved stoves.
- Most micro-gasifiers are batch-loaded and cannot be refueled during use. Thus, cooking times are pre-determined by the size of the fuel container.
- The heat output of most micro-gasifiers is not easy to regulate unless the stove is operated with a fan for forced convection. In this case the power of the fan can be regulated.
- Micro-gasifiers burn the biomass in two stages: first the gas-generator produces the wood gas, which is a thick whitish ‘smoke’ or fume. This “smoke” is burnt by the gas-burner, which is thus basically a ‘smoke-burner’. If the gas-burner operates well then there is no problem. However, should the flame of the gas-burner extinguish (e.g. blown out by gusty wind), the gas-generator will continue producing wood gas, which will not be burnt and then escape as thick white smoke from the stove.
