The future supply of fossil fuels is gradually becoming more dependent on sources outside of the ... more The future supply of fossil fuels is gradually becoming more dependent on sources outside of the United Kingdom. Not only does this pose a threat to the stability of supply, but it also undermines any cost predictability that may have otherwise existed. This situation, however, points to certain opportunities that may be usefully exploited. The continued use of fossil fuel is, in any case, not sustainable-other sources of fuel supply need to be found that are environmentally friendly, readily available and price stable. It is believed that Biomass Energy in the form of wood fuel fulfils all these criteria.
Biomass combustion is mainly used for heat production in a wide range of units. Few research stud... more Biomass combustion is mainly used for heat production in a wide range of units. Few research studies have been carried out to investigate the overall performance of small-scale residential heating systems when replacing coal with biomass in these units. Sheffield University (SUWIC) has carried out an extensive series of experimental tests at a small-scale residential heating plant. Various tests were conducted on two units: a wood pellet fired boiler and a coal fired boiler. In addition, mathematical modeling work using FLIC and FLUENT codes was carried out in order to simulate the overall performance of the small-scale biomass and coal-fired heating systems. The main objective of this study was to investigate the changes to the overall performance of the plant (e.g., combustion characteristics and emissions) when replacing coal with wood pellets. The concentrations of CO, NO x , particulate matter, and SO 2 in the flue gases were measured. Emission factors for both boilers were also compared. FLIC code integrated with FLUENT was employed to model the combustion process of wood pellets and coal in both boilers. The measured emission data were used in the development and validation of the modeling work. The modeling work helped to demonstrate the relationship between the fuel combustion behavior and pollutants formation in the residential boilers. Results showed that pollutant emissions from both boilers were within relative emission limits whereas pollutant emission factors for the wood pellet-fired boilers were lower than for the coal-fired boiler. The modeling analysis showed that the high CO emissions from the coal-fired boiler were attributed to the less mixing intensity and low residential time of flue gas in the furnace. For small-scale residential boilers, biomass with a high volatile fraction could be an ideal solid fuel to get higher combustion efficiency and low pollutant emissions. This study has provided valuable information that can be used to help improve future furnace design and retrofit existing small-scale heating systems to reduce overall emissions.
Biomass combustion is mainly used for heat production in a wide range of units. Few research stud... more Biomass combustion is mainly used for heat production in a wide range of units. Few research studies have been carried out to investigate the overall performance of small-scale residential heating systems when replacing coal with biomass in these units. Sheffield University (SUWIC) has carried out an extensive series of experimental tests at a small-scale residential heating plant. Various tests were conducted on two units: a wood pellet fired boiler and a coal fired boiler. In addition, mathematical modeling work using FLIC and FLUENT codes was carried out in order to simulate the overall performance of the small-scale biomass and coal-fired heating systems. The main objective of this study was to investigate the changes to the overall performance of the plant (e.g., combustion characteristics and emissions) when replacing coal with wood pellets. The concentrations of CO, NO x , particulate matter, and SO 2 in the flue gases were measured. Emission factors for both boilers were also compared. FLIC code integrated with FLUENT was employed to model the combustion process of wood pellets and coal in both boilers. The measured emission data were used in the development and validation of the modeling work. The modeling work helped to demonstrate the relationship between the fuel combustion behavior and pollutants formation in the residential boilers. Results showed that pollutant emissions from both boilers were within relative emission limits whereas pollutant emission factors for the wood pellet-fired boilers were lower than for the coal-fired boiler. The modeling analysis showed that the high CO emissions from the coal-fired boiler were attributed to the less mixing intensity and low residential time of flue gas in the furnace. For small-scale residential boilers, biomass with a high volatile fraction could be an ideal solid fuel to get higher combustion efficiency and low pollutant emissions. This study has provided valuable information that can be used to help improve future furnace design and retrofit existing small-scale heating systems to reduce overall emissions.
Decentralised energy in the UK is rare. Cities in the north of England however lead the UK in ter... more Decentralised energy in the UK is rare. Cities in the north of England however lead the UK in terms of sustainable, low-carbon, local/district heating, through the implementation of combined-heat-andpower (CHP) facilities; substantial schemes are installed in several cities, including Barnsley and Sheffield. This paper presents the results from extensive experimental and theoretical feasibility studies, in which the merits of these were explored. Barnsley has a number of biomass-fuelled community energy generators, where pollutant monitoring and mathematical modelling were conducted to assess combustion characteristics and overall system performance. Measured pollutant levels were within the relative emission limits, though emission concentrations (CO, CO 2 , NO and particles) in the flue gas from the coal boiler were higher than the wood pellet boiler. Sheffield already has a citywide district energy network, centred around a sustainably-sourced waste-to-energy facility; an expansion of this scheme was investigated here. This focuses mainly on the link to a 30 MW wood-fired CHP plant, which could be a significant provider of additional thermal capacity (low-grade heat) to an expanded network. Through identifying heat sources and sinks e potential suppliers and end-users e key areas were identified where a connection to the heat network would be feasible.
Killing by beta-lactams is well known to be reduced against a dense bacterial population, commonl... more Killing by beta-lactams is well known to be reduced against a dense bacterial population, commonly known as the inoculum effect. However, the underlying mechanism of this phenomenon is not well understood. We proposed a semimechanistic mathematical model to account for the reduced in vitro killing observed. Time-kill studies were performed with 4 baseline inocula (ranging from approximately 1 ؋ 10 5 to 1 ؋ 10 8 CFU/ml) of Escherichia coli ATCC 25922 (MIC, 2 mg/liter). Constant but escalating piperacillin concentrations used ranged from 0.25؋ to 256؋ MIC. Serial samples were taken over 24 h to quantify viable bacterial burden, and all the killing profiles were mathematically modeled. The inoculum effect was attributed to a reduction of effective drug concentration available for bacterial killing, which was expressed as a function of the baseline inoculum. Biomasses associated with different inocula were examined using a colorimetric method. Despite identical drug-pathogen combinations, the baseline inoculum had a significant impact on bacterial killing. Our proposed mathematical model was unbiased and reasonable in capturing all 28 killing profiles collectively (r 2 ؍ 0.88). Biomass was found to be significantly more after 24 h with a baseline inoculum of 1 ؋ 10 8 CFU/ml, compared to one where the initial inoculum was 1 ؋ 10 5 CFU/ml (P ؍ 0.002). Our results corroborated previous observations that in vitro killing by piperacillin was significantly reduced against a dense bacterial inoculum. This phenomenon can be reasonably captured by our proposed mathematical model, and it may improve prediction of bacterial response to various drug exposures in future investigations.
The future supply of fossil fuels is gradually becoming more dependent on sources outside of the ... more The future supply of fossil fuels is gradually becoming more dependent on sources outside of the United Kingdom. Not only does this pose a threat to the stability of supply, but it also undermines any cost predictability that may have otherwise existed. This situation, however, points to certain opportunities that may be usefully exploited. The continued use of fossil fuel is, in any case, not sustainable-other sources of fuel supply need to be found that are environmentally friendly, readily available and price stable. It is believed that Biomass Energy in the form of wood fuel fulfils all these criteria.
Biomass combustion is mainly used for heat production in a wide range of units. Few research stud... more Biomass combustion is mainly used for heat production in a wide range of units. Few research studies have been carried out to investigate the overall performance of small-scale residential heating systems when replacing coal with biomass in these units. Sheffield University (SUWIC) has carried out an extensive series of experimental tests at a small-scale residential heating plant. Various tests were conducted on two units: a wood pellet fired boiler and a coal fired boiler. In addition, mathematical modeling work using FLIC and FLUENT codes was carried out in order to simulate the overall performance of the small-scale biomass and coal-fired heating systems. The main objective of this study was to investigate the changes to the overall performance of the plant (e.g., combustion characteristics and emissions) when replacing coal with wood pellets. The concentrations of CO, NO x , particulate matter, and SO 2 in the flue gases were measured. Emission factors for both boilers were also compared. FLIC code integrated with FLUENT was employed to model the combustion process of wood pellets and coal in both boilers. The measured emission data were used in the development and validation of the modeling work. The modeling work helped to demonstrate the relationship between the fuel combustion behavior and pollutants formation in the residential boilers. Results showed that pollutant emissions from both boilers were within relative emission limits whereas pollutant emission factors for the wood pellet-fired boilers were lower than for the coal-fired boiler. The modeling analysis showed that the high CO emissions from the coal-fired boiler were attributed to the less mixing intensity and low residential time of flue gas in the furnace. For small-scale residential boilers, biomass with a high volatile fraction could be an ideal solid fuel to get higher combustion efficiency and low pollutant emissions. This study has provided valuable information that can be used to help improve future furnace design and retrofit existing small-scale heating systems to reduce overall emissions.
Biomass combustion is mainly used for heat production in a wide range of units. Few research stud... more Biomass combustion is mainly used for heat production in a wide range of units. Few research studies have been carried out to investigate the overall performance of small-scale residential heating systems when replacing coal with biomass in these units. Sheffield University (SUWIC) has carried out an extensive series of experimental tests at a small-scale residential heating plant. Various tests were conducted on two units: a wood pellet fired boiler and a coal fired boiler. In addition, mathematical modeling work using FLIC and FLUENT codes was carried out in order to simulate the overall performance of the small-scale biomass and coal-fired heating systems. The main objective of this study was to investigate the changes to the overall performance of the plant (e.g., combustion characteristics and emissions) when replacing coal with wood pellets. The concentrations of CO, NO x , particulate matter, and SO 2 in the flue gases were measured. Emission factors for both boilers were also compared. FLIC code integrated with FLUENT was employed to model the combustion process of wood pellets and coal in both boilers. The measured emission data were used in the development and validation of the modeling work. The modeling work helped to demonstrate the relationship between the fuel combustion behavior and pollutants formation in the residential boilers. Results showed that pollutant emissions from both boilers were within relative emission limits whereas pollutant emission factors for the wood pellet-fired boilers were lower than for the coal-fired boiler. The modeling analysis showed that the high CO emissions from the coal-fired boiler were attributed to the less mixing intensity and low residential time of flue gas in the furnace. For small-scale residential boilers, biomass with a high volatile fraction could be an ideal solid fuel to get higher combustion efficiency and low pollutant emissions. This study has provided valuable information that can be used to help improve future furnace design and retrofit existing small-scale heating systems to reduce overall emissions.
Decentralised energy in the UK is rare. Cities in the north of England however lead the UK in ter... more Decentralised energy in the UK is rare. Cities in the north of England however lead the UK in terms of sustainable, low-carbon, local/district heating, through the implementation of combined-heat-andpower (CHP) facilities; substantial schemes are installed in several cities, including Barnsley and Sheffield. This paper presents the results from extensive experimental and theoretical feasibility studies, in which the merits of these were explored. Barnsley has a number of biomass-fuelled community energy generators, where pollutant monitoring and mathematical modelling were conducted to assess combustion characteristics and overall system performance. Measured pollutant levels were within the relative emission limits, though emission concentrations (CO, CO 2 , NO and particles) in the flue gas from the coal boiler were higher than the wood pellet boiler. Sheffield already has a citywide district energy network, centred around a sustainably-sourced waste-to-energy facility; an expansion of this scheme was investigated here. This focuses mainly on the link to a 30 MW wood-fired CHP plant, which could be a significant provider of additional thermal capacity (low-grade heat) to an expanded network. Through identifying heat sources and sinks e potential suppliers and end-users e key areas were identified where a connection to the heat network would be feasible.
Killing by beta-lactams is well known to be reduced against a dense bacterial population, commonl... more Killing by beta-lactams is well known to be reduced against a dense bacterial population, commonly known as the inoculum effect. However, the underlying mechanism of this phenomenon is not well understood. We proposed a semimechanistic mathematical model to account for the reduced in vitro killing observed. Time-kill studies were performed with 4 baseline inocula (ranging from approximately 1 ؋ 10 5 to 1 ؋ 10 8 CFU/ml) of Escherichia coli ATCC 25922 (MIC, 2 mg/liter). Constant but escalating piperacillin concentrations used ranged from 0.25؋ to 256؋ MIC. Serial samples were taken over 24 h to quantify viable bacterial burden, and all the killing profiles were mathematically modeled. The inoculum effect was attributed to a reduction of effective drug concentration available for bacterial killing, which was expressed as a function of the baseline inoculum. Biomasses associated with different inocula were examined using a colorimetric method. Despite identical drug-pathogen combinations, the baseline inoculum had a significant impact on bacterial killing. Our proposed mathematical model was unbiased and reasonable in capturing all 28 killing profiles collectively (r 2 ؍ 0.88). Biomass was found to be significantly more after 24 h with a baseline inoculum of 1 ؋ 10 8 CFU/ml, compared to one where the initial inoculum was 1 ؋ 10 5 CFU/ml (P ؍ 0.002). Our results corroborated previous observations that in vitro killing by piperacillin was significantly reduced against a dense bacterial inoculum. This phenomenon can be reasonably captured by our proposed mathematical model, and it may improve prediction of bacterial response to various drug exposures in future investigations.
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Papers by Richard Bradford