Vida Sharifi | The University of Sheffield (original) (raw)

Papers by Vida Sharifi

Proceedings of the ICE - Waste and Resource Management, 2009

Applied Thermal Engineering, 2013

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.

ABSTRACT This paper examines the use of low grade heat from process industries for thermal desali... more ABSTRACT This paper examines the use of low grade heat from process industries for thermal desalination processes as this is relevant not only to current energy conservation schemes but also may play a role in increasing the capacity to satisfy future water demands. The study focuses on low grade heat sources from a paper mill located on a British coastal area which presents a large quantity of recoverable waste heat at low temperature (<100 °C). Two scenarios are considered: (i) low grade heat is used directly to feed the desalination process, (ii) low grade heat is upgraded using a heat pump coupled with a desalination system.In the first scenario, a Humidification Dehumidification process was identified as a suitable technology due to its low operating temperature. In the second scenario, the low grade heat temperature was upgraded using a hybrid absorption heat pump and subsequently used to feed a Multiple Effect Distillation desalination system. These two cases were compared in terms of performances and economics. For both cases, a payback period of less than 10 years could be obtained for water price equal to £2 per tonnes of water. This is comparable to the price of home water supply. Environmental aspects were also discussed from the results of a full Lifecycle assessment. Low grade heat utilisation in both cases reduced the Global Warming Potential in comparison with fossil fuel powered systems, but toxicological impacts appeared higher in comparison to a system using natural gas.

Progress in Computational Fluid Dynamics, 2006

Sheffield University Waste Incineration Centre (SUWIC), Department of Chemical and Process Engine... more Sheffield University Waste Incineration Centre (SUWIC), Department of Chemical and Process Engineering, Sheffield University, Mappin Street, Sheffield, S1 3JD, UK Fax: 0044-114-2227501 E-mail: ybyang@shef.ac.uk E-mail: j.goodfellow@shef.ac.uk E-mail: vnsharifi@shef.ac.uk ...

Journal of Analytical Atomic Spectrometry, 2005

ABSTRACT A mobile continuous emissions monitoring laboratory, based on ICP-OES technology, was us... more ABSTRACT A mobile continuous emissions monitoring laboratory, based on ICP-OES technology, was used to study temporal variations in metal concentrations in the flue gas of a waste-to-energy plant. The concentrations of over 30 elements were monitored prior to flue gas clean-up. Despite harsh analytical conditions, with high particulate loading, variable gas matrix and high concentrations of numerous elements, semi-quantitative measurements were made. Realistic detection limits in the range 0.007–0.06 mg m−3 were achieved. For many volatile metals, significant variations (4–18 mg m−3 for Na, 0–0.18 mg m−3 for Cd) were observed, and were linked to properties of the metal in question, to incinerator operating conditions, and to variations in the waste feed charge. The concentrations of some metals were attributable to specific sources in the waste. It was concluded that better waste segregation could significantly reduce the concentration of toxic metals in the incinerator residues, and where concentration spikes were detected, accurate real-time metal concentration measurements had the potential to provide feedback to clean-up systems, thereby minimising the overall environmental effect.

Energy & Fuels, 2010

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.

International Journal of Environmental Analytical Chemistry, 2002

The potential of using tree bark as a passive sampling medium for detection of Polychlorinated di... more The potential of using tree bark as a passive sampling medium for detection of Polychlorinated dibenzo- p -dioxins and furans (PCDD/F) in an urban environment has been investigated. Bark samples (∼ 30 g) were extracted with toluene using accelerated solvent extraction. Extracts were then cleaned up via a multi-bed silica column and a Florisil column followed by GC-MS/MS analysis. It

Building Services Engineering Research & Technology, 2011

This paper presents a new decision-support framework and software platform for an integrated asse... more This paper presents a new decision-support framework and software platform for an integrated assessment of options for sustainable management of urban pollution. The framework involves three steps: (1) mapping the flow of pollutants associated with human activities in the urban environment; (2) modelling the fate and transport of pollutants; and (3) quantifying the environmental, health and socio-economic impacts of urban

Waste Management, 2007

Waste incineration is a politically sensitive issue in the UK. The major current technology is ba... more Waste incineration is a politically sensitive issue in the UK. The major current technology is based on direct combustion of wastes in a moving-grate furnace. However, general public opinion prefers non-direct burning technologies. Waste gasification is one of those nearest technologies available. By reducing the primary air-flow rate through the grate of a packed-bed system, operation of the existing solid-waste incineration equipment can be easily converted from combustion mode to gasification mode without major modification of the hardware. The potential advantages of this are lower dust carry-over in the flue gases, lower bed temperature (and therefore lower NO x formation in the bed), simplified gas-treatment procedures and lower running cost, among other benefits. The major disadvantages are, however, reduced throughput of the wastes and possibly higher carbon in the ash at exit. In this study, numerical simulation of both combustion and gasification of municipal solid wastes in a full-scale moving grate furnace is carried out employing advanced mathematical models. Burning characteristics, including burning rate, gas composition, temperature and burning efficiency as a function of operating parameters are investigated. Detailed comparisons between the combustion mode and gasification mode are made. The study helps to explore new incineration technology and optimise furnace operating conditions.

Waste Management, 2007

Recent developments in national recycling and re-use programmes for municipal waste have led to s... more Recent developments in national recycling and re-use programmes for municipal waste have led to segregation of an increasing proportion of waste to enhance material recovery. Several of the segregated streams contain materials that can not viably be re-used or recycled but can be used for energy recovery. In this study, the combustion of cardboard and waste wood was investigated in a small-scale packed bed reactor in order to provide fundamental data for the design/operation of moving bed furnaces. Key parameters of combustion including the ignition and burning rates were evaluated for various air flowrates and compared to the modelling results.

Waste Management, 2008

Fluidised bed combustor (FBC) is one of the key technologies for sewage sludge incineration. In t... more Fluidised bed combustor (FBC) is one of the key technologies for sewage sludge incineration. In this paper, a mathematical model is developed for the simulation of a large-scale sewage sludge incineration plant. The model assumes the bed consisting of a fast-gas phase, an emulsion phase and a fuel particle phase with specific consideration for thermally-thick fuel particles. The model further improves over previous works by taking into account throughflow inside the bubbles as well as the floating and random movement of the fuel particles inside the bed. Validation against both previous lab-scale experiments and operational data of a large-scale industrial plant was made. Calculation results indicate that combustion split between the bed and the freeboard can range from 60/40 to 90/10 depending on the fuel particle distribution across the bed height under the specific conditions. The bed performance is heavily affected by the variation in sludge moisture level. The response time to variation in feeding rate is different for different parameters, from 6 min for outlet H 2 O, 10 min for O 2 , to 34 min for bed temperature.

Progress in Computational Fluid Dynamics, An International Journal, 2007

Department of Chemical and Process Engineering, Sheffield University Waste Incineration Centre (S... more Department of Chemical and Process Engineering, Sheffield University Waste Incineration Centre (SUWIC), Sheffield University, Mappin Street, Sheffield, S1 3JD, UK Fax: 0044 -114-2227501 E-mail: ybyang@shef.ac.uk E-mail: vnyang@shef.ac.uk E-mail: j.swithenbank@shef.ac.uk ...

Progress in Computational Fluid Dynamics, An International Journal, 2007

... In order to be used for the reactor design, chemical reaction kinetics and transport phenomen... more ... In order to be used for the reactor design, chemical reaction kinetics and transport phenomena has been coupled to model conventional gasifiers (Groeneveld and van Swaaij, 1980; Manurung and Beenackers, 1994; Reed and Markson, 1985), but these works were still based ...

Progress in Computational Fluid Dynamics, An International Journal, 2007

Department of Chemical and Process Engineering, Sheffield University Waste Incineration Centre (S... more Department of Chemical and Process Engineering, Sheffield University Waste Incineration Centre (SUWIC), Sheffield University, Mappin Street, Sheffield, S1 3JD, UK Fax: 0044 -114-2227501 E-mail: ybyang@Sheffield.ac.uk E-mail: vnsharifi@shef.ac.uk E-mail: ...

Process Safety and Environmental Protection, 2013

This paper presents a new decision-support methodology and software tool for sustainable manageme... more This paper presents a new decision-support methodology and software tool for sustainable management of urban pollution. A number of different methods and tools are integrated within the same platform, including GIS, LCA, fate and transport modelling, health impact assessment and multi-criteria decision analysis. The application of the framework is illustrated on a case study which investigates the environmental and health impacts of pollution arising from different industrial, domestic and transport sources in a city. The example city chosen for the study is Sheffield, UK, and the main pollutants considered are NO x , SO 2 and PM10. The results suggest that the absence of the current large industrial sources in the city would lead to a 90% reduction of the SO 2 and 70% of the NO 2 ground concentrations, consequently preventing 27 deaths and 18 respiratory hospital admissions per annum for a population of 500,000.

Process Safety and Environmental Protection, 2005

B iomass fuels are being increasingly used for domestic heating and power generation to cut down ... more B iomass fuels are being increasingly used for domestic heating and power generation to cut down the net CO 2 emission to the atmosphere. In most cases, those fuels are thermally-thick under packed-bed combustion conditions. In this paper, a doublemesh numerical scheme is proposed and implemented to simulate the detailed combustion processes for a biomass fuel with sizes ranging from 5 mm to 50 mm. Bench-top experiments were also carried out to validate the theoretical simulation. Under the specific conditions of investigation, it is found that a bed packed with particles over 35 mm can develop a temperature gradient over 4008C inside the particles at the flame front, and significant overlapping of moisture evaporation, devolatilization and char burn-out is observed in the bed-height direction; CH 4 emission over the bed top is more focused on the central part of the combustion period for larger particles; CO level in the flue gases increases with decreasing particle sizes and the opposite is true for H 2 emission. The overall air to fuel stoichiometric ratio for the whole combustion period increases significantly with increasing particle sizes, from 0.57 (fuel-rich) at 5 mm to 1.2 (fuel-lean) at 35 mm, but for the constant stage during combustion, the range of ratio narrows to 0.32 -0.35.

Process Safety and Environmental Protection, 2004

T he disposal of waste that cannot be minimized, recycled or reused is a huge international probl... more T he disposal of waste that cannot be minimized, recycled or reused is a huge international problem. In the UK, we currently landfill about 30 million tonnes of waste per year. This is environmentally unfriendly due to greenhouse gas emissions, etc., and squanders energy equivalent to about 25% of our current coal consumption. The incineration of material in energy-from-waste plants has received relatively little attention from combustion scientists and engineers in the past and this work is directed at rectifying this situation. Incinerators generally burn waste on a moving grate that transports and mixes it during combustion. The combustion process involves drying, devolatilization, gasification and char burn-out. Thus gasifiers and pyrolysers are subsets of this combustion problem. Mathematically modelling combustion on the grate requires the solution of the flow field in a reacting packed bed, including radiant heat transfer. Since the burning in the channels is mixing-limited, reactions also occur in the gas phase above the bed. The conditions evaluated at the surface of the bed are the boundary conditions for conventional computational fluid dynamic modelling of the mixing and reactions in the secondary combustion zone in the freeboard above the bed. This permits the evaluation and minimization of emissions such as dioxins to the point that dioxins from incinerators now only contribute 3% of the total UK dioxin emissions. The validation of our reacting bed modelling code (FLIC) has been achieved by measurements in a pot burner using various wastes. Furthermore, a small 'ball instrument' that has been specially developed to contain instruments has complemented these measurements by withstanding temperatures up to 1000 C for well over an hour. This novel device passes through industrial incinerator furnaces with the waste and records parameters such as oxygen, vibration and several temperatures onto a computer memory chip. The ball is recovered from the incinerator ash pit and the information is downloaded onto an Excel spreadsheet for detailed analysis. Incinerator combustion is obviously one of the most complex combustion physics=chemistry processes known. At the present time it is also industrially important, however it is now yielding its secrets to scientific study.

Proceedings of the ICE - Engineering Sustainability, 2007

ABSTRACT Waste disposal, energy production and pollution minimisation are key problems that must ... more ABSTRACT Waste disposal, energy production and pollution minimisation are key problems that must be addressed for sustainable cities of the future. In a world with finite resources witnessing a population explosion, much effort is being made to change the way in which developed societies consume energy and materials and dispose of waste. This paper reviews the current UK practices of segregation and treatment of municipal solid waste (MSW) with focus on advanced thermal treatment technologies. MSW is segregated either at source or at dedicated facilities across the country. The residues of waste segregation can be thermally treated for energy recovery. Direct incineration of unsorted waste is currently the main route practiced by the energy from waste (EfW) industry. Typical MSW incinerators can burn wastes with a wide range of calorific values without any waste pre-processing. However, these incineration systems have low energy efficiency and suffer from unfavourable public opinion. Consequently, gas clean-up technologies associated with waste incinerators have been developed further, especially for dioxin removal and fly ash treatment. The two main alternatives to incineration are gasification of pre-processed waste and production of solid recovered fuel (SRF) from mechanical and biological treatment (MBT). Both processes have potentially higher energy efficiencies than incineration and more flexibility in the use of primary products. Further technology developments with regulatory drivers are required to compete with incineration. Another route available for EfW is pyrolysis, producing cheap and storable fuel products. Pyrolysis is suitable only for specific types of waste material. Pyrolysis of waste wood can produce a good-quality char that can be readily burned in coal-fired power plants or other higher energy efficiency thermal systems.

Journal of Analytical and Applied Pyrolysis, 2008

The role of pyrolysis is important in the thermal processing of municipal solid wastes, since it ... more The role of pyrolysis is important in the thermal processing of municipal solid wastes, since it decomposes wastes into three types of intermediate products to be collected as fuel feedstock or to be gasified/combusted. In this study, the main products from slow pyrolysis of key segregated waste materials were characterised for mass yield, energy content, elemental composition and chemical compounds. About 200 g of waste wood, cardboard or textile residues were pyrolysed in a small packed bed reactor at a final temperature ranging from 350 to 700 8C with a slow heating rate. The char contained about 38-55% of the energy content in the raw material. The difference in the properties of char between the materials was mainly due to the incombustible fraction that remained in the solid product. The pyrolysis liquids had a gross calorific value of about 10-12 MJ/kg, representing about 20-30% of the energy content in the raw material. The liquids consisted mainly of water and oxygenated compounds such as furans, derivative carboxylic acids and anhydrosugars. Over two thirds of the gases produced were CO and CO 2 with increased proportions of CH 4 and H 2 at high temperatures above 500 8C. #

Proceedings of the ICE - Waste and Resource Management, 2009

Applied Thermal Engineering, 2013

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.

ABSTRACT This paper examines the use of low grade heat from process industries for thermal desali... more ABSTRACT This paper examines the use of low grade heat from process industries for thermal desalination processes as this is relevant not only to current energy conservation schemes but also may play a role in increasing the capacity to satisfy future water demands. The study focuses on low grade heat sources from a paper mill located on a British coastal area which presents a large quantity of recoverable waste heat at low temperature (<100 °C). Two scenarios are considered: (i) low grade heat is used directly to feed the desalination process, (ii) low grade heat is upgraded using a heat pump coupled with a desalination system.In the first scenario, a Humidification Dehumidification process was identified as a suitable technology due to its low operating temperature. In the second scenario, the low grade heat temperature was upgraded using a hybrid absorption heat pump and subsequently used to feed a Multiple Effect Distillation desalination system. These two cases were compared in terms of performances and economics. For both cases, a payback period of less than 10 years could be obtained for water price equal to £2 per tonnes of water. This is comparable to the price of home water supply. Environmental aspects were also discussed from the results of a full Lifecycle assessment. Low grade heat utilisation in both cases reduced the Global Warming Potential in comparison with fossil fuel powered systems, but toxicological impacts appeared higher in comparison to a system using natural gas.

Progress in Computational Fluid Dynamics, 2006

Sheffield University Waste Incineration Centre (SUWIC), Department of Chemical and Process Engine... more Sheffield University Waste Incineration Centre (SUWIC), Department of Chemical and Process Engineering, Sheffield University, Mappin Street, Sheffield, S1 3JD, UK Fax: 0044-114-2227501 E-mail: ybyang@shef.ac.uk E-mail: j.goodfellow@shef.ac.uk E-mail: vnsharifi@shef.ac.uk ...

Journal of Analytical Atomic Spectrometry, 2005

ABSTRACT A mobile continuous emissions monitoring laboratory, based on ICP-OES technology, was us... more ABSTRACT A mobile continuous emissions monitoring laboratory, based on ICP-OES technology, was used to study temporal variations in metal concentrations in the flue gas of a waste-to-energy plant. The concentrations of over 30 elements were monitored prior to flue gas clean-up. Despite harsh analytical conditions, with high particulate loading, variable gas matrix and high concentrations of numerous elements, semi-quantitative measurements were made. Realistic detection limits in the range 0.007–0.06 mg m−3 were achieved. For many volatile metals, significant variations (4–18 mg m−3 for Na, 0–0.18 mg m−3 for Cd) were observed, and were linked to properties of the metal in question, to incinerator operating conditions, and to variations in the waste feed charge. The concentrations of some metals were attributable to specific sources in the waste. It was concluded that better waste segregation could significantly reduce the concentration of toxic metals in the incinerator residues, and where concentration spikes were detected, accurate real-time metal concentration measurements had the potential to provide feedback to clean-up systems, thereby minimising the overall environmental effect.

Energy & Fuels, 2010

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.

International Journal of Environmental Analytical Chemistry, 2002

The potential of using tree bark as a passive sampling medium for detection of Polychlorinated di... more The potential of using tree bark as a passive sampling medium for detection of Polychlorinated dibenzo- p -dioxins and furans (PCDD/F) in an urban environment has been investigated. Bark samples (∼ 30 g) were extracted with toluene using accelerated solvent extraction. Extracts were then cleaned up via a multi-bed silica column and a Florisil column followed by GC-MS/MS analysis. It

Building Services Engineering Research & Technology, 2011

This paper presents a new decision-support framework and software platform for an integrated asse... more This paper presents a new decision-support framework and software platform for an integrated assessment of options for sustainable management of urban pollution. The framework involves three steps: (1) mapping the flow of pollutants associated with human activities in the urban environment; (2) modelling the fate and transport of pollutants; and (3) quantifying the environmental, health and socio-economic impacts of urban

Waste Management, 2007

Waste incineration is a politically sensitive issue in the UK. The major current technology is ba... more Waste incineration is a politically sensitive issue in the UK. The major current technology is based on direct combustion of wastes in a moving-grate furnace. However, general public opinion prefers non-direct burning technologies. Waste gasification is one of those nearest technologies available. By reducing the primary air-flow rate through the grate of a packed-bed system, operation of the existing solid-waste incineration equipment can be easily converted from combustion mode to gasification mode without major modification of the hardware. The potential advantages of this are lower dust carry-over in the flue gases, lower bed temperature (and therefore lower NO x formation in the bed), simplified gas-treatment procedures and lower running cost, among other benefits. The major disadvantages are, however, reduced throughput of the wastes and possibly higher carbon in the ash at exit. In this study, numerical simulation of both combustion and gasification of municipal solid wastes in a full-scale moving grate furnace is carried out employing advanced mathematical models. Burning characteristics, including burning rate, gas composition, temperature and burning efficiency as a function of operating parameters are investigated. Detailed comparisons between the combustion mode and gasification mode are made. The study helps to explore new incineration technology and optimise furnace operating conditions.

Waste Management, 2007

Recent developments in national recycling and re-use programmes for municipal waste have led to s... more Recent developments in national recycling and re-use programmes for municipal waste have led to segregation of an increasing proportion of waste to enhance material recovery. Several of the segregated streams contain materials that can not viably be re-used or recycled but can be used for energy recovery. In this study, the combustion of cardboard and waste wood was investigated in a small-scale packed bed reactor in order to provide fundamental data for the design/operation of moving bed furnaces. Key parameters of combustion including the ignition and burning rates were evaluated for various air flowrates and compared to the modelling results.

Waste Management, 2008

Fluidised bed combustor (FBC) is one of the key technologies for sewage sludge incineration. In t... more Fluidised bed combustor (FBC) is one of the key technologies for sewage sludge incineration. In this paper, a mathematical model is developed for the simulation of a large-scale sewage sludge incineration plant. The model assumes the bed consisting of a fast-gas phase, an emulsion phase and a fuel particle phase with specific consideration for thermally-thick fuel particles. The model further improves over previous works by taking into account throughflow inside the bubbles as well as the floating and random movement of the fuel particles inside the bed. Validation against both previous lab-scale experiments and operational data of a large-scale industrial plant was made. Calculation results indicate that combustion split between the bed and the freeboard can range from 60/40 to 90/10 depending on the fuel particle distribution across the bed height under the specific conditions. The bed performance is heavily affected by the variation in sludge moisture level. The response time to variation in feeding rate is different for different parameters, from 6 min for outlet H 2 O, 10 min for O 2 , to 34 min for bed temperature.

Progress in Computational Fluid Dynamics, An International Journal, 2007

Department of Chemical and Process Engineering, Sheffield University Waste Incineration Centre (S... more Department of Chemical and Process Engineering, Sheffield University Waste Incineration Centre (SUWIC), Sheffield University, Mappin Street, Sheffield, S1 3JD, UK Fax: 0044 -114-2227501 E-mail: ybyang@shef.ac.uk E-mail: vnyang@shef.ac.uk E-mail: j.swithenbank@shef.ac.uk ...

Progress in Computational Fluid Dynamics, An International Journal, 2007

... In order to be used for the reactor design, chemical reaction kinetics and transport phenomen... more ... In order to be used for the reactor design, chemical reaction kinetics and transport phenomena has been coupled to model conventional gasifiers (Groeneveld and van Swaaij, 1980; Manurung and Beenackers, 1994; Reed and Markson, 1985), but these works were still based ...

Progress in Computational Fluid Dynamics, An International Journal, 2007

Department of Chemical and Process Engineering, Sheffield University Waste Incineration Centre (S... more Department of Chemical and Process Engineering, Sheffield University Waste Incineration Centre (SUWIC), Sheffield University, Mappin Street, Sheffield, S1 3JD, UK Fax: 0044 -114-2227501 E-mail: ybyang@Sheffield.ac.uk E-mail: vnsharifi@shef.ac.uk E-mail: ...

Process Safety and Environmental Protection, 2013

This paper presents a new decision-support methodology and software tool for sustainable manageme... more This paper presents a new decision-support methodology and software tool for sustainable management of urban pollution. A number of different methods and tools are integrated within the same platform, including GIS, LCA, fate and transport modelling, health impact assessment and multi-criteria decision analysis. The application of the framework is illustrated on a case study which investigates the environmental and health impacts of pollution arising from different industrial, domestic and transport sources in a city. The example city chosen for the study is Sheffield, UK, and the main pollutants considered are NO x , SO 2 and PM10. The results suggest that the absence of the current large industrial sources in the city would lead to a 90% reduction of the SO 2 and 70% of the NO 2 ground concentrations, consequently preventing 27 deaths and 18 respiratory hospital admissions per annum for a population of 500,000.

Process Safety and Environmental Protection, 2005

B iomass fuels are being increasingly used for domestic heating and power generation to cut down ... more B iomass fuels are being increasingly used for domestic heating and power generation to cut down the net CO 2 emission to the atmosphere. In most cases, those fuels are thermally-thick under packed-bed combustion conditions. In this paper, a doublemesh numerical scheme is proposed and implemented to simulate the detailed combustion processes for a biomass fuel with sizes ranging from 5 mm to 50 mm. Bench-top experiments were also carried out to validate the theoretical simulation. Under the specific conditions of investigation, it is found that a bed packed with particles over 35 mm can develop a temperature gradient over 4008C inside the particles at the flame front, and significant overlapping of moisture evaporation, devolatilization and char burn-out is observed in the bed-height direction; CH 4 emission over the bed top is more focused on the central part of the combustion period for larger particles; CO level in the flue gases increases with decreasing particle sizes and the opposite is true for H 2 emission. The overall air to fuel stoichiometric ratio for the whole combustion period increases significantly with increasing particle sizes, from 0.57 (fuel-rich) at 5 mm to 1.2 (fuel-lean) at 35 mm, but for the constant stage during combustion, the range of ratio narrows to 0.32 -0.35.

Process Safety and Environmental Protection, 2004

T he disposal of waste that cannot be minimized, recycled or reused is a huge international probl... more T he disposal of waste that cannot be minimized, recycled or reused is a huge international problem. In the UK, we currently landfill about 30 million tonnes of waste per year. This is environmentally unfriendly due to greenhouse gas emissions, etc., and squanders energy equivalent to about 25% of our current coal consumption. The incineration of material in energy-from-waste plants has received relatively little attention from combustion scientists and engineers in the past and this work is directed at rectifying this situation. Incinerators generally burn waste on a moving grate that transports and mixes it during combustion. The combustion process involves drying, devolatilization, gasification and char burn-out. Thus gasifiers and pyrolysers are subsets of this combustion problem. Mathematically modelling combustion on the grate requires the solution of the flow field in a reacting packed bed, including radiant heat transfer. Since the burning in the channels is mixing-limited, reactions also occur in the gas phase above the bed. The conditions evaluated at the surface of the bed are the boundary conditions for conventional computational fluid dynamic modelling of the mixing and reactions in the secondary combustion zone in the freeboard above the bed. This permits the evaluation and minimization of emissions such as dioxins to the point that dioxins from incinerators now only contribute 3% of the total UK dioxin emissions. The validation of our reacting bed modelling code (FLIC) has been achieved by measurements in a pot burner using various wastes. Furthermore, a small 'ball instrument' that has been specially developed to contain instruments has complemented these measurements by withstanding temperatures up to 1000 C for well over an hour. This novel device passes through industrial incinerator furnaces with the waste and records parameters such as oxygen, vibration and several temperatures onto a computer memory chip. The ball is recovered from the incinerator ash pit and the information is downloaded onto an Excel spreadsheet for detailed analysis. Incinerator combustion is obviously one of the most complex combustion physics=chemistry processes known. At the present time it is also industrially important, however it is now yielding its secrets to scientific study.

Proceedings of the ICE - Engineering Sustainability, 2007

ABSTRACT Waste disposal, energy production and pollution minimisation are key problems that must ... more ABSTRACT Waste disposal, energy production and pollution minimisation are key problems that must be addressed for sustainable cities of the future. In a world with finite resources witnessing a population explosion, much effort is being made to change the way in which developed societies consume energy and materials and dispose of waste. This paper reviews the current UK practices of segregation and treatment of municipal solid waste (MSW) with focus on advanced thermal treatment technologies. MSW is segregated either at source or at dedicated facilities across the country. The residues of waste segregation can be thermally treated for energy recovery. Direct incineration of unsorted waste is currently the main route practiced by the energy from waste (EfW) industry. Typical MSW incinerators can burn wastes with a wide range of calorific values without any waste pre-processing. However, these incineration systems have low energy efficiency and suffer from unfavourable public opinion. Consequently, gas clean-up technologies associated with waste incinerators have been developed further, especially for dioxin removal and fly ash treatment. The two main alternatives to incineration are gasification of pre-processed waste and production of solid recovered fuel (SRF) from mechanical and biological treatment (MBT). Both processes have potentially higher energy efficiencies than incineration and more flexibility in the use of primary products. Further technology developments with regulatory drivers are required to compete with incineration. Another route available for EfW is pyrolysis, producing cheap and storable fuel products. Pyrolysis is suitable only for specific types of waste material. Pyrolysis of waste wood can produce a good-quality char that can be readily burned in coal-fired power plants or other higher energy efficiency thermal systems.

Journal of Analytical and Applied Pyrolysis, 2008

The role of pyrolysis is important in the thermal processing of municipal solid wastes, since it ... more The role of pyrolysis is important in the thermal processing of municipal solid wastes, since it decomposes wastes into three types of intermediate products to be collected as fuel feedstock or to be gasified/combusted. In this study, the main products from slow pyrolysis of key segregated waste materials were characterised for mass yield, energy content, elemental composition and chemical compounds. About 200 g of waste wood, cardboard or textile residues were pyrolysed in a small packed bed reactor at a final temperature ranging from 350 to 700 8C with a slow heating rate. The char contained about 38-55% of the energy content in the raw material. The difference in the properties of char between the materials was mainly due to the incombustible fraction that remained in the solid product. The pyrolysis liquids had a gross calorific value of about 10-12 MJ/kg, representing about 20-30% of the energy content in the raw material. The liquids consisted mainly of water and oxygenated compounds such as furans, derivative carboxylic acids and anhydrosugars. Over two thirds of the gases produced were CO and CO 2 with increased proportions of CH 4 and H 2 at high temperatures above 500 8C. #