Use of biomass in domestic cookstoves leads to the release of oxides of nitrogen (NO<sub>x</sub>), nitric oxide (NO), nitrogen dioxide (NO<sub>2</sub>), carbon monoxide (CO) and hydrocarbons C&...Use of biomass in domestic cookstoves leads to the release of oxides of nitrogen (NO<sub>x</sub>), nitric oxide (NO), nitrogen dioxide (NO<sub>2</sub>), carbon monoxide (CO) and hydrocarbons C<sub>x</sub>H<sub>x</sub> that can be detrimental to health of the public and the environment. Attainment of complete combustion is the best strategy for mitigating the release of these emissions. This study sought to experimentally determine the effects of secondary air injection on the emission profiles of NO<sub>x</sub> (NO & NO<sub>2</sub>), CO and C<sub>x</sub>H<sub>x</sub> in a charcoal operated cookstove. Charcoal from Eucalyptus glandis was bought from Kakuzi PLC. Composites from three batches were analyzed for chemical composition and the stoichiometric air equivalent. Proximate analysis data show that the charcoal composed 58.72% ± 3.3% C, 15.95% ± 1.2% Volatile Matter, 4.69% ± 0.55% Moisture, 20.7% ± 0.8% Ash, High heat value (HHV) of 30.5 ± 1.1 and 29.3 ± 1.3 Low heat value (LHV) (MJ/kg) with a chemical formula of C<sub>18</sub>H<sub>2</sub>O and a stoichiometric air requirement of 5.28 ± 0.6 with a fuel flow rate of 1 kg fuel/hr. Emission profiles for CO and C<sub>x</sub>H<sub>x</sub> reduced significantly by 70% and 80% respectively with secondary air injection whereas those of NO<sub>x</sub> increased by between 15% and 20% for NO<sub>2</sub> and NO. The study reveals that secondary air injection has potential to mitigate on emission release, however other measures are required to mitigate NO<sub>x</sub> emissions.展开更多
Water hyacinth, E. crassipes, an invasive water weed thrives in fresh water bodies causing serious environmental problems. In Kenya the weed has invaded Lake Victoria and poses great socioeconomic and environmental ch...Water hyacinth, E. crassipes, an invasive water weed thrives in fresh water bodies causing serious environmental problems. In Kenya the weed has invaded Lake Victoria and poses great socioeconomic and environmental challenges. Currently the weed is harvested from the Lake and left in the open to rot and decay leading to loss of aesthetics, land and air pollution. There is therefore need for development of value addition and economic exploitation strategies. The aim of the study is to assess the potential for utilization of the weed as a renewable energy resource for biogas production. Samples were collected from Lake Victoria, pulped and blend with cow dung at a ratio of 3:1 as inoculum. The resultant mixture was mixed with water at a ratio of 1:1 and fed into a 6 m3 tubular digester. The digester was recharged with 20 kg after every three days. The temperature, pH variations, gas compositions, upgrading and gas yields were studied. The temperature ranged between 22.8°C - 36.6°C and pH 7.4 - 8.5. Biogas was found to contain 49% - 53% methane (CH4 ), 30% - 33% carbon dioxide (CO2 ), 5% - 6% nitrogen (N2 ) and traces of hydrogen sulphide (H2S). The biogas was upgraded using solid adsorbents and wet scrubbers increasing the methane content by up to 70% - 76%. The upgraded gas was used to power internal combustion engines coupled with an electricity generator and direct heat applications. The study concludes that E. crassipes is a potential feedstock for biogas production especially in areas where it is abundant.展开更多
Thermal gasification of biomass provides a potential renewable energy resource in rural areas in Kenya. Rice husks are a key byproduct of rice production that are not considered of economic value to millers. Rice husk...Thermal gasification of biomass provides a potential renewable energy resource in rural areas in Kenya. Rice husks are a key byproduct of rice production that are not considered of economic value to millers. Rice husks obtained from Mwea, Embu County, Kenya were converted into syngas using a locally assembled modified updraft gasifier. The syngas production was produced at temperatures between 450°C and 750°C with injection of limited supply of air and purified using series of gas cleaning and cooling devices. Proximate analysis shows that rice husks have a mean content of 21.9% ± 0.3% ash, 9.5% ± 3.3% moisture, 78.8% ± 0.3% volatiles and 91.8% ± 1.3% total solids. Carbonized rice husks have mean contents of 37.8% ± 1.2% ash, 3.1% ± 0.4% moisture, 62.3% ± 1.2% volatiles and 96.5% ± 0.4% total solids. The study shows that feedstock is consumed at a rate of 25 - 32 Kg/Hr with gas generation rate of 7.76 - 7.78 m3/hr;this translates to a gas yield of 0.31 - 0.35 m3/Kg. Process water was re-circulated at a rate of 2.2 m3/hr within the plant. The total electricity consumption per hour was 1.1 - 1.3 kWh. Carbon monoxide (CO) and temperature were monitored in the working area to assess the safety of the workers and were found to be in the range of 35 - 50 ppm and 24°C - 29.5°C respectively. The two were found to be within safe limits;however, the CO concentrations increased when leakages occurred. Syngas was found to be composed of 16.5% - 17.55% CO, 14.5% - 16.1% CO2, 4.1% - 4.5% H2, 6.8% - 7.2% CH4 and 17.9% - 45.7% N2 among others. The gas was used for direct heating applications and to run modified petrol engines. Carbonized husks were used to make energy briquettes and partly applied to the rice growing pads to improve soil properties. The technology provides energy solutions and aids in the abatement of climate change mitigation and abatement since it provides a permanent carbon sink. The technology provides a value addition chain for rice growers.展开更多
文摘Use of biomass in domestic cookstoves leads to the release of oxides of nitrogen (NO<sub>x</sub>), nitric oxide (NO), nitrogen dioxide (NO<sub>2</sub>), carbon monoxide (CO) and hydrocarbons C<sub>x</sub>H<sub>x</sub> that can be detrimental to health of the public and the environment. Attainment of complete combustion is the best strategy for mitigating the release of these emissions. This study sought to experimentally determine the effects of secondary air injection on the emission profiles of NO<sub>x</sub> (NO & NO<sub>2</sub>), CO and C<sub>x</sub>H<sub>x</sub> in a charcoal operated cookstove. Charcoal from Eucalyptus glandis was bought from Kakuzi PLC. Composites from three batches were analyzed for chemical composition and the stoichiometric air equivalent. Proximate analysis data show that the charcoal composed 58.72% ± 3.3% C, 15.95% ± 1.2% Volatile Matter, 4.69% ± 0.55% Moisture, 20.7% ± 0.8% Ash, High heat value (HHV) of 30.5 ± 1.1 and 29.3 ± 1.3 Low heat value (LHV) (MJ/kg) with a chemical formula of C<sub>18</sub>H<sub>2</sub>O and a stoichiometric air requirement of 5.28 ± 0.6 with a fuel flow rate of 1 kg fuel/hr. Emission profiles for CO and C<sub>x</sub>H<sub>x</sub> reduced significantly by 70% and 80% respectively with secondary air injection whereas those of NO<sub>x</sub> increased by between 15% and 20% for NO<sub>2</sub> and NO. The study reveals that secondary air injection has potential to mitigate on emission release, however other measures are required to mitigate NO<sub>x</sub> emissions.
文摘Water hyacinth, E. crassipes, an invasive water weed thrives in fresh water bodies causing serious environmental problems. In Kenya the weed has invaded Lake Victoria and poses great socioeconomic and environmental challenges. Currently the weed is harvested from the Lake and left in the open to rot and decay leading to loss of aesthetics, land and air pollution. There is therefore need for development of value addition and economic exploitation strategies. The aim of the study is to assess the potential for utilization of the weed as a renewable energy resource for biogas production. Samples were collected from Lake Victoria, pulped and blend with cow dung at a ratio of 3:1 as inoculum. The resultant mixture was mixed with water at a ratio of 1:1 and fed into a 6 m3 tubular digester. The digester was recharged with 20 kg after every three days. The temperature, pH variations, gas compositions, upgrading and gas yields were studied. The temperature ranged between 22.8°C - 36.6°C and pH 7.4 - 8.5. Biogas was found to contain 49% - 53% methane (CH4 ), 30% - 33% carbon dioxide (CO2 ), 5% - 6% nitrogen (N2 ) and traces of hydrogen sulphide (H2S). The biogas was upgraded using solid adsorbents and wet scrubbers increasing the methane content by up to 70% - 76%. The upgraded gas was used to power internal combustion engines coupled with an electricity generator and direct heat applications. The study concludes that E. crassipes is a potential feedstock for biogas production especially in areas where it is abundant.
文摘Thermal gasification of biomass provides a potential renewable energy resource in rural areas in Kenya. Rice husks are a key byproduct of rice production that are not considered of economic value to millers. Rice husks obtained from Mwea, Embu County, Kenya were converted into syngas using a locally assembled modified updraft gasifier. The syngas production was produced at temperatures between 450°C and 750°C with injection of limited supply of air and purified using series of gas cleaning and cooling devices. Proximate analysis shows that rice husks have a mean content of 21.9% ± 0.3% ash, 9.5% ± 3.3% moisture, 78.8% ± 0.3% volatiles and 91.8% ± 1.3% total solids. Carbonized rice husks have mean contents of 37.8% ± 1.2% ash, 3.1% ± 0.4% moisture, 62.3% ± 1.2% volatiles and 96.5% ± 0.4% total solids. The study shows that feedstock is consumed at a rate of 25 - 32 Kg/Hr with gas generation rate of 7.76 - 7.78 m3/hr;this translates to a gas yield of 0.31 - 0.35 m3/Kg. Process water was re-circulated at a rate of 2.2 m3/hr within the plant. The total electricity consumption per hour was 1.1 - 1.3 kWh. Carbon monoxide (CO) and temperature were monitored in the working area to assess the safety of the workers and were found to be in the range of 35 - 50 ppm and 24°C - 29.5°C respectively. The two were found to be within safe limits;however, the CO concentrations increased when leakages occurred. Syngas was found to be composed of 16.5% - 17.55% CO, 14.5% - 16.1% CO2, 4.1% - 4.5% H2, 6.8% - 7.2% CH4 and 17.9% - 45.7% N2 among others. The gas was used for direct heating applications and to run modified petrol engines. Carbonized husks were used to make energy briquettes and partly applied to the rice growing pads to improve soil properties. The technology provides energy solutions and aids in the abatement of climate change mitigation and abatement since it provides a permanent carbon sink. The technology provides a value addition chain for rice growers.
