Thermal Processes

Highlights of SUWIC research in thermal processes

Microwave Pyrolysis-Torrefaction of Biomass

 

PhD Students: Noor Afiqah Mohd, Siti NA Abd Halim
Investigators: Professor V Sharifi, Professor J Swithenbank
Work funded by Malaysian Government and Industry

Key points in pyrolysis of biomass wood are to prevent undesired secondary reactions of the volatiles and to increase the yields of useful volatile products. It is also important to produce chars that have large specific surface areas. A slow heating process favours an increase in char yield. On the other hand, slow heating leads to decreasing the yield of volatiles. Microwave pyrolysis has the potential to satisfy both requirement. The main research tasks for this project include design and construction of a pilotscale microwave experimental system , experimental work and modelling. 

 

Hydrogen Separation from Syngas using membranes

 

PhD Student: Stephen McCord
Investigators: Professor V Sharifi, Professor J Swithenbank
Work funded by Engineering and Physical Science Research Council (EPSRC) studentship and Industry

The overall objective of this PhD project is to investigate the separation of hydrogen (to be used a fuel) from syngas produced in a bio-char gasification process. This will also includes the removal of sub-micron particles. Membranes will be used for separation process in this project instead of using pressure swing absorption or cryogenic separation. The main research tasks for this project include design and construction of a membrane separation system , experimental work and modelling. 

 

High Efficient Gasification Technology

 

PhD Student: Tom Lakey
Investigators: Professor V Sharifi, Professor J Swithenbank
Work funded by Engineering and Physical Science Research Council (EPSRC) studentship

The overall objective of this PhD project is to develop a novel high efficient biomass gasifier. The novel features of the ultra superheated steam flame will be investigated as part of this project. This will result in the production of tar free high levels of CO and Hydrogen (syngas) which can be sold to industry or used for production of power/electricity. The main research tasks for this project include construction of a pilotscale USS gasifier, experimental work and kinetic modelling. 

 

Innovative Three Stage Tar Cracking Gasifier

 

PhD Student: Peter Weston
Investigators: Professor V Sharifi, Professor J Swithenbank
Work funded by Engineering and Physical Science Research Council (EPSRC) studentship

The overall objective of this PhD project is to develop a novel three stage fixed bed biomass gasifier for domestic use (small scale) which employs blue flame coanda burner in order to generate a clean tar free synthetic gas product. The novel features of the blue flame burner configuration make it an ideal device to be considered to be fitted between the pyrolysis stage and char gasification stage of a complete gasifier. This will result in a production of a clean tar free synthetic gas which can be sold to industry or used for production of power/electricity for small scale operation. The main research tasks for this project include design and construction of a pilotscale gasifier, experimental work and FLUENT modelling. 

 

Efficient Harvesting, Processing and Conversion of Wetland Biomass

 

Project Partners: Sheffield University (SUWIC), Carbon Compost ltd, Crops for Energy ltd, Loglogic ltd,
Sheffield University Investigators: Professor V Sharifi, Professor J Swithenbank
Work funded by Department of Energy and Climate Change (DECC)

The recently published Bio-energy Strategy by DECC emphasised the need for sustainably supplied feed-stocks to underpin any future bioenergy system in the UK. The strategy considers a number of factors that can affect the overall value of bio-energy including: i) the impact that land use change as a result of bio-energy feedstock production can have either directly or indirectly on carbon emissions, ii) potential competition for land with other sectors such as food production and housing. The UK undertakes a considerable amount of land management activities on private and public land, forexample to maitain parkland or to conserve wildlife habitats. This land management results in the production of biomass arisings that in many cases are either burned or left to decompose. The main objectives of this research programme is to develop a cost effective and energy/carbon efficient bioenergy conversion process (gasification) capable of utilising the wetland biomass materials 9e.g. reeds, rushes, grasses and fen). 

 

Advanced Heat Storage Technologies

 

PhD Student: Rob Raine
Investigators: Professor V Sharifi, Professor J Swithenbank
Work funded by Engineering and Physical Science Research Council (EPSRC) DTC studentship, Sheffield City Council, Veolia Environmental Services

As dwellings account for some 70% of the UK's heat demand, compared to 1.7% for the sum of all other non-domestic and non-process heat demand, it is the domestic sector that merits closest attention for district heating. This project aims to evaluate a number of different short and longer term thermal storage technologies that are available or could be available in the UK in the future with the focus firmly on the domestic sector demand. Fluctuations in heat demand must be related to the increasing fluctuations in associated energy systems, caused for example by some renewable energy sources. The project will improve understanding of the important role thermal storage could play in the UK and give insights into the practicalities of achieving this by combining the perspectives of key stakeholders including industrialists, local authorities and the general public.

 

Development of a Novel Feeding System for Pressurised Combustion/Gasification Processes

 

PhD Student: James Craven
Researcher: Dr Nigel Russell
Investigators: Professor V Sharifi, Professor J Swithenbank
Work funded by Engineering and Physical Science Research Council (EPSRC) DTC studentship and BF2RA (Biomass and Fossil Fuel Research Alliance )

The overall objective of this PhD project is to develop a novel and reliable feeder for continuously feeding solid fuel (e.g. Biomass, coal or waste) into high pressure environments. This type of feeder will enhance the commercial viability of high pressure biomass/coal gasifiers and combustors. The project will explore feeding into environments at pressures up to 30 bar. In biomass energy conversion plants, the materials handling systems often are susceptible to malfunctions. Operating problems with the fuel feed and handling equipment are by far the most general reason for unforeseen shutdowns of gasification processes and reliable solids handling systems are essential to the development of pressurised processes. Pressure causes changes in the tension and compression strength of the feed material. These changes affect its flow characteristics and hence also its behaviour in the feed equipment. The flow characteristics of the material should be kept as uniform as possible while constant feed system pressure should be maintained. The feeder should also operate reliably over the pressure difference between the atmosphere and the reactor. The handling characteristics of biomass such as wood residues are affected by quality, moisture content, particle size and contaminants. Hence feeding these bulk materials into a pressure vessel may sometimes differ greatly from feeding into a low pressure process due to changes in the behaviour and properties of the material. Hence highly reliable operating fuel feed equipment is considered to be crucial to the successful operation of the pressurised combustion and gasification systems. Removal of ash and other residues from the pressurised vessels is also one of the key factors in the operation of pressurized plants. The main objective of this proposed PhD study is to develop a novel pressure feeder with the following properties:

  • high reliability,
  • low construction, maintenance and operational costs,
  • low power consumption,
  • and wide applicability.

Other technical requirements are smooth and continuous feed, suitability for handling a variety of bulk solid materials, accurate feed control, durability and availability. 

 

Particle Characterisation in Chemical Looping Combustion with Solid Fuels

 

PhD Student: Chern Yean Sim,
Investigators: Professor Vida Sharifi, Professor Jim Swithenbank
Funded by Engineering and Physical Science Research Council (EPSRC China NetworkConsortium)

The increasing threat posed by enhanced global warming as well as the requirement to secure energy supplies around the world have led to the development of several novel technologies to produce clean energy from fuels. Among these new technologies is chemical looping combustion (CLC) which uses a solid metal oxide (oxygen carrier) to react with fuels. This technology has the potential advantage to produce a pure stream of carbon dioxide (CO2) which can then be utilised or sequestrated. In a CLC process, the oxygen carrier is reduced by fuels in one reactor while being reoxidised by air in a separate reactor.  The typical operating conditions for a CLC system is 800–1200°C  under pressurised or atmospheric pressure.  The low temperature range used in a CLC system ensures that thermal NOx does not form as a side reaction in the system. Most recent research studies on CLC systems have focused on the development of various oxygen carriers for application with gaseous fuels. Very little work has been done on the use of solid fuels in CLC systems. The main objective of this research program is to investigate the morphological and compositional changes to the oxygen carriers (i.e. iron oxide and copper oxide supported on alumina) in a CLC system with solid fuel.

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Novel High Pressure Oxy-Fuel Power Generation with Carbon Capture and Sequestration using Biomass or Other Fuels

 

PhD Student: Dr Qun Chen
Investigators: Professor V Sharifi, Professor J Swithenbank
Work funded by EPSRC and Industry

The main objective of this project is to develop the underpinning technology needed to contribute to the mitigation of greenhouse gas emissions by exploiting new concepts and extending the applications of high pressure oxyfuel power generation in conjunction with exhaust gas clean up and carbon capture and storage. Increasing the combustion pressure to above 80bars, results in the recovered latent heat in power plant flue gases being available at more than 200°C for use in a power generation cycle.  Furthermore, the high pressure of the combustion gases reduces the super-heater tube stress since it can balance the steam pressure.  However, the key advantage of high pressure flue gas is that it is above the pressure at which carbon dioxide “condenses” to a liquid or supercritical gas at atmospheric temperature.  Thus when used with oxy-fuel combustion, the supercritical CO2 can be fed directly into pipes for sequestration.  When oxy-fuel combustion is used, the flame temperature must be moderated by a diluent such as recycled carbon dioxide.  However, fuel moisture or even additional water can fulfil this role, which is advantageous since it is more efficient to pump wood chip fuel in water to high pressure.  Similarly, efficient compression of liquid cryogenic oxygen provides a suitable material to use in a power station.  Finally, combustion of hydrogen from the water gas reaction in power system steam with oxygen could allow the steam temperature in the turbine to be increased to the “gas-turbine engine” range of 1000 to 1400°C.  Hence the biomass and/or fossil fuel cycle efficiency including CCS can be very attractive.

 

 

Research into Expansion of Sheffield District Heating System

 

Researcher: Dr Karen Finney
Investigators: Professor V Sharifi, Professor J Swithenbank
Work funded by EPSRC Thermal Management Consortium & Sheffield City Council

The main use of low-grade thermal energy in the UK is for heating buildings, thus district heating is important for utilising the presently wasted heat.  Whilst this maximises efficiency and reduces greenhouse gas emissions, the optimum, longer-term use of this heat requires existing district heating designs to be modified, so that the return water is 30°C, rather than 70°C, as is current practice.  The north of England leads the UK in terms of city CHP implementation, with substantial heating schemes installed in Sheffield, Newcastle and Barnsley. The rationale for expanding the Sheffield district heating network is: (i) providing sustainable/secure energy, (ii) reducing CO2 emissions, (iii) generating heat in proximity to where it is used, (iv) providing reasonably-priced heat, critical to the fuel poverty agenda, (v) aiding Sheffield in becoming a low-carbon city and (vi) helping to meet legislation regarding renewable energy and CO2 (e.g. UK Low Carbon Transition Plan and the Renewable Energy Strategy).  This study investigates the expansion possibilities of Sheffield’s district energy system through identifying the existing and emerging heat sources and sinks – the potential suppliers and end-users to an expanded energy network.  These are mapped utilising ESRI ArcGIS software – a geographical information systems tool – to locate the key sites and identify areas where a link to the heat network would be feasible and environmentally/economically beneficial.

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Torrefication, Pyrolysis and Gasification of Solid Recovered Fuel (SRF) 

 

Researcher: Dr Chian Chan
Investigators: Professor V Sharifi, Professor J Swithenbank
Work funded by EPSRC Supergen Biomass/Biofuels Consortium and Industry

A major drawback to combustion of waste is that the fuel is likely to be non-homogenous, wet and it will come in large fragments.  The water content will lower the recoverable energy content per unit mass of fuel.  The lack of homogeneity will make for inconsistent combustion which will cause fluctuations in emissions adding to the difficulty of cleanup. Turning waste into refuse derived fuel (RDF) or solid recovered fuels (SRF) is one of the emerging options available for waste recycling and re-use. SRF and RDF are fuels produced from non-hazardous municipal solid waste (MSW) and commercial and industrial (C&I) wastes.  The term SRF is commonly used in place of RDF.  SRF is a refined form of RDF, intended for use in energy recovery facilities. The main objective of this research project is to investigate the torrefication, pyrolysis and gasification of SRF materials, in particular the associated emissions, quality of char residues and other process products.

 

 

FLIC/FLUENT Modelling of a 550 kW wood fired boiler

 

Researcher: Dr Jue Zhou
Investigators: Professor V Sharifi, Professor J Swithenbank
Work funded by EPSRC Supergen Biomass/Biofuels Consortium & Industry

In the UK, approximately 49% of the final energy consumed is in the form of heat . This heat production accounts for around 47% of UK CO2 emissions. Barnsley Metropolitan Borough Council was the first local authority in the UK to adopt a biomass fuel heating policy. They have successfully installed and operated a series of wood-fuelled district heating systems in Barnsley since 2005.  Extensive experimental measurements and numerical simulations at one of wood fired heating systems is being carried out using FLIC and FLUENT codes in order to assess the overall performance of this 550 kW wood fired heating system.  The main objective of this study is to investigate the performance of the small scale heating plant: i.e. combustion characteristics and emissions. The concentrations of CO, NOx, particulate matter and SO2 in the flue gases were measured. FLIC code integrated with FLUENT was employed to model the combustion process of wood chips in the boiler.  The measured emission data were used in the development and validation of the modelling work. Results show that pollutant emissions from the boiler are within the relative emission limits.

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Environmental Issues in the CO2 Capture by novel solid looping cycle processes

 

PhD Student: CY Sim, Post Doctoral Researchers: Dr Karen Finney, Dr H Li, Dr Q Chen
Investigators: Professor V N Sharifi, Professor J Swithenbank
Work Funded by: EPSRC Joint UK-China Consortium (Sheffield University, Imperial College, Cambridge University, Cranfield University), Partners from China: Thermal Power Research Institute (TPRI), Tsinghua University, North China Electric Power University (NCEPU) and Taiyuan University of Technology (TUT)

The main objective of this research project is to investigate the feasibility of the production of Hydrogen (H2) via novel solid looping cycles and gasification concepts and to optimise the performance of natural and artificial particles, needed in the looping processes by understanding the effects of composition and structure. Another issue is the mitigation of the environmental impact of these novel processes. This includes the release of toxic trace elements such as arsenic, selenium, cadmium & mercury. How these elements partition between the gaseous CO2, the ash and the recycling looping agents when real coal or coal gas is used in the system? The project inolves both exeprimental work on small and large scale rigs as well as thermodynamic equilibrium modelling work.

 

 

Thermal Management of Industrial Processes

 

Post doctoral Researchers: Dr Q Chen, Dr X Zhang, Dr H Li, Dr Karen Finney, Dr Nigel Russell
Investigators: Professor V N Sharifi, Professor J Swithenbank
Work Funded by: EPSRC Thermal Management in Process Industry Consortium (Lead partner: Sheffield University, other academic partners: Newcastle University, Manchester University) , Industrial Partners: Corus, EON UK, North East Process Industry Cluster (NEPIC) Ltd, BP Chemical Ltd, Alstom Power Ltd, MW Kellogg Ltd, Pfizer Ltd

The main objective of this research project is to investigate new and appropriate technologies and supporting measures needed to enhance and exploit the large amount of unused low grade heat available from the wide range of process industries. This low grade heat is predominately available in the gases (e.g.flue gases) and liquid streams (e.g cooling water), hence the range of source temperatures to be considered is from 30 C to 250 C. Our approach is based on the fact that energy use within each process has already been largely optimised by established process integration and pinch analysis technology. Hence the new strategy presented in this work is to extend such analyses to include new energy utilisation opportunities that lie over-the-fence together with the procedure by which industry can assess and implement these energy efficient innovations

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Novel Molten Metal Biomass Gasification

 

PhD Student: Rachael Eatwell
Investigators: Professor V N Sharifi, Professor J Swithenbank
Work Funded by: EPSRC Supergen Biomass Consortium

Ammonia is already a major product on the international market, largely used as an agricultural fertiliser. Not only is ammonia valuable for fertiliser production, but it could also be used for transport of hydrogen for storage and mobile applications because ammonia contains 17.65% hydrogen compared to 7% for best hydride (Mg H2). Ammonia also has the advantage as a hydrogen carrier that the enviro-friendly nitrogen can be returned to atmosphere when the hydrogen is used.. In this research project, steam and air will be reacted with molten alloy. The biomass fuel consisting of (pyrolysed) wood will be used to carry out the reduction stage. The focus of the work will be on maximising the reaction rates by fluid dynamic processes that result in large surface contact areas between the reagents.

 


The Production of Clean Energy and Hydrogen via Novel Process Technologies

 

Postdoctoral Researchers: Dr Karen Finney, Dr H Li, Dr Q Chen, Dr X Zhang
Investigators: Professor V N Sharifi, Professor J Swithenbank
Work Funded by: EPSRC Joint UK - China Research Consortium (UK Partners: Sheffield University, Cambridge University, Imperial College, Cranfield University, Chinese Partners: Tsinghua University, Thermal Power Research Institute, North China Electric Power University, Taiyuan University of Technology)

The main objective of this project is the production of clean energy and Hydrogen (H2) from coal and biomass via a number of thermochemical routes with the CO2 separate and ready for sequestration. In this project we investigate two forms of advanced chemical cycles which allow clean hydrogen to be produced from fossil fuels without (unlike with the current technology) a large energy penalty associted with capturing the CO2. Both chemical cycles make use of solid reactants which either act as CO2 acceptors or Oxygen carriers.

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Particulate Emissions from Biomass- fired Domestic & District Heating sytems

 

Research Associates: Dr Q Chen, Dr X Zhang, Dr Karen Finney
Investigators: Professor V N Sharifi, Professor J Swithenbank
Work Funded by: EPSRC INTRAWISE Programme & EPSRC SuperGen Programme

Small scale wood boilers range in size from a few kilowatts for residential applications to several Megawatts used for district heating and for heat production in industry. Particulate matter (PM) is a complex mixture of airborne solid particles and liquid droplets composed of acids, ammonia, water, black carbon, organic chemicals, metals and inorganic material. Long exposures to particulate can cause serious health problems. This research projects investigates the PM formation, characterisation and emission measurements from various wood/biomass fired systems (up to 100 MW capacity).

 


Pyrolysis of Biomass with Tar Oxidation and Tar Pyrolysis

 

PhD Student: R Raja Deris
Research Associates: Dr Q Chen, Dr X Zhang, Dr N V Russell
Investigators: Professor V N Sharifi, Professor J Swithenbank
Work Funded by: EPSRC Supergen Biomass Consortium & Malaysian Government

Pyrolysis thermally decomposes biomass to char, liquid and gas products in an inert atmosphere, each of which has potential use as a fuel. The char & liquid products are considered as intermediate media of energy that are storable and high in energy content. Pyrolysis liquid can be used for power generation in a diesel engine, gas turbine or by co-combustion with fossil fuels in a power plant. Although current studies on the pyrolysis liquids are focused more on fast pyrolysis of biomass, slow pyrolysis can also produce oil with a mass yield of more than 40%. The main research tasks for this project include: development of a novel pyrolyser, characterisation of char, liquid & gas products and mathematical modelling of the process.

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Power and Heat from Biomass

 

Research Associates: Dr Q Chen, Dr X Zhang, Dr Asthana
Investigators: Professor V N Sharifi, Professor J Swithenbank
Work Funded by: EPSRC Supergen Biomass Consortium

This project focuses on the technologies underpinning the practical recovery of heat and power from biomass and solid Recovered Fuels (SRF) to attain efficient utilisation at domestic, commercial and industrial scales. Biomass fuelled heating installations will soon expand in the UK. Although pellet stoves and furnaces are used in Scandinavia more research is needed particularly on emissions. The programme includes: a review of international work on pellet stoves and furnaces, theoretical and experimental determinations of emissions of particulates, organic and in-organic species, with particular focus on nano-particle emissions from domestic and district heating systems.



Investigation into Factors affecting Corrosion in Waste to Energy Plants

 

PhD Student: A Phongphiphat
Research Associates: Dr C Ryu, Dr YB Yang
Investigators: Professor V N Sharifi, Professor J Swithenbank
Work Funded by: EPSRC, UK Waste Industry and Thailand Government

Corrosion in boilers/superheaters can be expected to take place at some time in the heat recovery system's life whether it is fired by coal, oil or MSW waste. The rates of corrosion however are very different for these different fuels and are dramatically influenced further by superheater/boiler design, operating conditions and protective measures. The principal mechanisms of corrosion are long recognised to beash induced corrosion, reduced atmosphere corrosion, dew point corrosion, impingement erosion and stress corrosion cracking. This PhD study consists of extensive series of experimental tests at a large scale MSW incinerator together with CFD modelling work using FLUENT code.

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Re-Use of Spent Mushroom Compost for Fuel Production

 

PhD Student: Karen Finney
Research Associates: Dr C Ryu, Dr YB Yang
Investigators: Professor V N Sharifi, Professor J Swithenbank
Work Funded by: EPSRC, Veolia Environmental Trust, UK Mushroom & Coal Industries


This research project addresses the fuel production technology for about 200,000 tonnes per year of spent mushroom compost (SMC). It is proposed that this material could be mixed with coal sludge in order to make fuel pellets for use by industry. Coal sludge is fine discard from coal cleaning process, which is deposited in lagoons. This study aims to divert SMC from landfill, aid the cleaning of contaminated land and partially mitigate the impacts of climate change and other environmental issues associated with present energy production strategies, through producing fuel pellets for industry.

The PhD programme consists of extensive series of analytical, pelletisation and combustions tests together with theoretical work.

 

 

Improved Energy Efficiency of Power & Heat Generation

 

Research Associates: Dr Q Chen, Dr X Zhang
Investigators: Professor V N Sharifi, Professor J Swithenbank
Work Funded by: EPSRC & Industry

This programme fills nationally important gaps by investigating the long term provision of biomass and novel coal derived energy for the UK based on thermal technologies that are carbon dioxide neutral, and that are secure, clean, economic and socially welcome.The calorific value of fuels is generally specified by the lower CV which takes into account the fact that the flue gases contain water vapour whose energy is generally not recovered in industrial plants. However modern condensing natural gas fired domestic boilers are designed to recover this energy by use of suitable materials that avoid corrosion of wet heat transfer surfaces. In the case of domestic heating, the boiler efficiency is typically increased from 75% to 90%. This project is designed to extend this efficiency improvement to industrial plants with aparticular focus on biomass fuels.

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Gasification of Biomass

 

Research Student: Paul Gilbert
Research Staff: Dr C Ryu, Dr YB Yang
Grant Holders: Professor J Swithenbank, Professor V N Sharifi
Funded by EPSRC Supergen Biomass Consortium

The most important forms of biomass include wood and herbaceous crops, such as straw and Miscanthus, that are grown purposely for their energy qualities. Biomass can be utilised in conventional combustors, but advances in research and technology are leading to more interesting forms of energy production for example, gasification and pyrolysis.

Such thermal technologies are being coupled with engines such as IC engines, gas turbines and even Stirling engines for potential small-scale CHP. At present, biomass is one of the most common forms of renewable energy and approximately 14% of global primary energy is accounted for by biomass. The main objective of this PhD research project is to develop a sustainable small-scale system to produce heat and electricity utilising biomass as the fuel. The biomass will be converted to a higher form of energy via a two-stage gasification process where a novel gas cleanup system - which uses biomass char - will catalytically crack the heavy hydrocarbons within the gasifier. The clean, hot gas will then be recovered in a suitable engine to produce heat and electricity for use in domestic houses and small buildings.


 

Mathematical Modelling of Waste to Energy Plants using FLIC and FLUENT codes

 

Research Student: C.Goddard (PhD)
Research Staff: Dr Y.B. Yang
Grant Holders: Professor J Swithenbank, Professor V N Sharifi
Funded by EPSRC and CREED Ltd.

The objective of this project is to construct a mathematical model of the combustion chamber of a waste-to-energy plant, in order that the current performance of the plant can be assessed, and subsequently design modifications can be suggested that will improve the energy recovery efficiency of the plant based on further numerical simulations. The mathematical model of the combustion chamber consists of two separate sub-models: one model for combustion of the municipal solid waste on the furnace grate, which is implemented using the FLIC bed modelling code, and another model for the gas flow above the burning waste bed, which is implemented using the FLUENT computational fluid dynamics code. The two models are coupled through their boundary conditions.
Numerical simulations has revealed that the flow field produced in the combustion chamber is detrimental to the recovery of heat from the hot combustion gases. It also shows that the flow field within the combustion chamber can be improved by altering the distribution of secondary air jets in the neck of the combustion chamber. The next phase of this project will involve performing experimental tests to measure the temperature and gas flow field within the actual combustion chamber in order to validate the mathematical modelling results.

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Waste Pyrolysis and Generation of Storable Char Fuel

 

Research Staff: Dr C Ryu
Grant Holders: Professor J Swithenbank, Professor V N Sharifi
Funded By Onyx Environmental Trust

High efficiency generation of power from waste requires the efficiency of scale but wastes are usually distributed geographically which requires high transportation cost. These conflicting features can be matched by concentrating energy through the medium of storable char. Char has a high calorific value and can be densified into pellets. This research project is to exploit the production of a high yield of storable char fuel by slow pyrolysis and its energy conversion by gasification. Waste samples were selected to represent woody waste (pinewood), herbaceous agricultural residue (reed canary grass, RCG) and pre-processed municipal waste (refuse derived fuels, RDF). A series of pyrolysis tests were carried out in a fixed bed reactor for these samples in the temperature range of 300-700°C, which produced char, oil and gas with different mass yield and properties. The char products were characterised by using various methods including standard fuel analysis. The char was highly carbonaceous and had a calorific value as high as anthracite.
High efficiency energy conversion of char was investigated by two gasification methods for char powder and char briquettes, respectively. The fundamental aspects of char gasification were further studied by mathematical modelling.

 

 

RDF Combustion in a Fluidised Bed

 

Research Student: D Hernandez-Atonal (PhD)
Research Staff: Dr C Ryu
Grant Holders: Professor J Swithenbank, Professor V N Sharifi
Funded by Mexican Government

The incineration of waste is a technology well established in several developed countries around the world. However, one of the challenges the combustion of waste is still facing is its heterogeneity. Refuse-derived Fuel (RDF) is one step towards minimising this kind of upset in the waste characteristics. For example, this type of material allows predicting narrower variations of size; it also provides lower amounts of moisture and non-combustible materials, resulting in a fuel with higher calorific value and quality. This research aims to look at the feasibility of both combustion and gasification of RDF and biomass in a Fluidised Bed. Not only the performance but the pollutants formation and the fate of heavy metals are the focus of my study, the latter with the use of a modern facility for ICP Emission Spectrometry. Detailed comparisons will also be made between experimental data and independently obtained computational fluid dynamics (CFD) results.

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Fixed Bed Combustion of Biomass

 

Research Student: A Khor I Ling (PhD)
Research Staff: Dr C Ryu, Dr Y B Yang
Grant Holders: Professor J Swithenbank, Professor V N Sharifi
Funded by EPSRC Supergen

Biomass is a form of renewable and sustainable energy source with the highest potential to contribute to the energy needs of modern society for both the developed and developing countries. However, the usage of these biofuels is still in the preliminary stages. There is a need to identify a suitable biofuel species, which can provide high-energy output to replace fossil fuels. The main tasks of this project include detailed mathematical modelling of biomass/biofuels thermal processes and validation of the modelling results using proper experimental means. The validation of the FLIC model predictions is obviously an essential part of the work and this aspect continues to receive attention by both bench-scale and full-scale studies. The effect of biomass fuel particle size is also being assessed experimentally.

 

 

Development of a Novel Liquid Metal Based Fuel Gas Scrubbing System

 

Research Students: B F Chang(PhD), H Ismail (PhD)
Research Staff: Dr C Ryu
Grant Holders: Professor J Swithenbank, Professor V N Sharifi
Funded By EPSRC

Present integrated gasification combined cycle (IGCC) systems demonstrate high system efficiency and impressive environmental performance, giving them an edge over conventional pulverised fuel power stations. A key area in the development of IGCCs is hot fuel gas clean-up (HGCU). An innovative approach to HGCU forms the basis of this research project i.e. a molten tin irrigated packed bed scrubber for simultaneous clean-up of sulphur and particulates from a fuel gas stream. High-temperature sulphur removal takes place via absorption of H2S and COS into molten tin whilst discrete molten tin droplets and rivulets on the packing surface act as solid particulate collectors.

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Combustion of Biomass Fuels with Coal in a Fluidised Bed Combustor

 

Research Student: A Wan Ab Karim Ghani (PhD)
Grant Holders: Dr K.Cliffe
Funded By Malaysian Government

Co-combustion of biomass and waste with coal has the potential to contribute towards reduced greenhouse gas emissions (i.e. CO2) through the substitution of non-renewable fossil fuels with renewable biomass and, to a lesser extent, waste materials. Regional and local atmospheric pollutants (e.g. NOx and SO2) can also be reduced.
An experimental co-combustion investigated using biomass fuels (chicken waste, rice husk, palm kernel shell, refused derived fuel and wood waste) with coal was performed in a 10 kWth atmospheric bubbling fluidised bed combustor to study the feasibility of using this waste as an energy source. The influence of different variables such as bed temperature, excess air in relation with fluidization velocity on the carbon combustion efficiency and CO emissions were investigated. In addition, mathematical modelling also implemented to validate the experimental data.

 

 

Identification and Control of Metal Emissions from MSW Incinerators

 

Research Staff: Dr D Poole
Grant Holders: Professor V N Sharifi, Professor J Swithenbank
Funded by EPSRC

The emission of metals during municipal solid waste incineration has become a question of considerable public and scientific concern in the light of evidence of their extreme toxicity. Sophisticated and expensive gas cleaning systems are required to meet the increasingly stringent EC atmospheric emission limits. While the technology for the clean-up of particulate matter and acid gases in flue gas is comparatively straightforward, the emissions of micro-pollutants such as heavy metals and dioxins remain a concern. Previous research on metal emissions has concentrated on overall mass balances, working either with laboratory or plant based measurements, or with computational models (frequently with little correlation between the techniques), leading to incomplete information on the system concerned. The waste incineration process is highly inhomogeneous, due to the changing nature of the waste feed, but the effects of changing waste feed and combustion conditions on the concentration and distribution of metals in the incinerator residues has not been investigated fully until now. The main objective of this PhD research project is to develop a comprehensive understanding of metal behaviour during municipal solid waste incineration, including an assessment of the importance and effect of temporal variation in waste composition and incineration conditions, through a co-ordinated programme of experimental measurements and mathematical modelling.

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Combustion/Pyrolysis/Gasification of Segregated MSW Waste

 

Research Student: A N Phan (PhD)
Research Staff: Dr C Ryu
Grant Holders: Professor VN Sharifi, Professor J Swithenbank
Funded by EPSRC & Vietnamese Government

Establishing the sustainable waste management system is an essential part for sustainable urban environment, which requires an integrated approach based on science-based decisions for the whole life-cycle of waste: production, minimization, reuse, recycling, waste collection, pre-treatment and various disposal options. An extensive literature review has been carried out on the waste stream composition and waste pre-treatment/segregation technologies/issues. Pre-treatment of waste is essential to increase the energy and material recovery from the waste and to reduce the environmental impacts Recent developments in national recycling and re-use programmes have led to segregation of an increasing proportion of waste to enhance material recovery. Several of the segregated streams contain material that can not viably be re-used or recycled. This project investigates the combustion, pyrolysis and gasification of segregated wastes and the related emissions. In addition FLIC code is used to model the processes taking place within the reacting bed.


 

Tracking Micro-pollutants Emissions from the Burning beds of the Biomass Combustors

 

Research Student: Awassada Phongphiphat (PhD)
Postdoctoral Researchers: Dr C Ryu, Dr D Poole
Grant Holders: Professor V Sharifi, Professor J Swithenbank
Fundedy by EPSRC & Government of Thailand

The micro-pollutants under consideration are predominantly inorganic heavy metals, organic species such as dioxins and furans, and ultra-fine particulate materials that can have a significant impact on health. This project focuses particularly on their emission from combustion systems. Combustion and gasification systems are recognised as a major source of pollutants and a waste incinerator provides a suitable process example that can be used to illustrate the mechanism of the origin or 'birth?of these micro-pollutants. The way in which the furnace emissions are then modified during their passage through the flue gas clean-up process provides the complementary aspect of pollutant history. Particulate matter is a mixture of pollutants, but the effects have primarily been studied by size; therefore, research on particles could be significantly improved by applying an updated and integrated approach. The main tasks of this research programme are as follows:

- Source modelling of the formation of particles in biomass combustion processes, and examination of factors affecting particle emissions from various source types
- Analytical measurement of particle composition and sizes from combustion sources, in the lab and in an urban case study location in order to diagnose the particle formation mechanism (e.g. homogeneous formation or condensation on the surface of a precursor particle). Thus, the micro-layers of these tiny particles will be analysed for their local composition changes.
- Field programme to measure pollutants (particles) in an urban case study location comprising multiple sources of particles (with sampling of air, soil, water, surfaces, etc.)

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Modelling and Control of Incineration Processes

 

Research Student: S Anderson (PhD)
Grant Holders: Professor VN Sharifi, Professor J Swithenbank
Funded by EPSRC

Legislation strictly regulates the operation of industrial plants such as incinerators limiting emissions of pollutants such as acid gases and dioxins. Incineration systems incorporate many control problems including widely varying waste content that can have a de-stabilising effect on the feed back controllers. This investigation is divided into 4 sections: development of a novel decision support tool to aid supervisory control of the plant, low level dynamic modelling and predictive control using contemporary techniques, a novel frame work for state-space and the extension of NARMAX method to a novel non-linear modelling frame work for fast sampled systems

 


Formation and Removal of Dioxins/furans in MSW incinerators

 

Research Student: S Gan (PhD)
Grant Holders: Professor VN Sharifi, Professor J Swithenbank
Funded by EPSRC

The formation of dioxins/furans in municipal solid waste incinerators has become a subject of considerable public and scientific concern in the light of evidence of their extreme toxicity. The main objective of this project is to develop and evaluate a prediction model for the formation and removal of dioxins/furans in MSW incinerators by carrying out formation chemistry investigations, analytical experiments, full scale incinerator trials and mathematical modelling.

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Novel Measuring Instrument for Hostile High Temperature Environment

 

Research Staff: Dr J Goodfellow
Grant holders: Professor J Swithenbank, Professor V N Sharifi
Funded By EPSRC

The combustion of waste material is a very complex process since it involves two-phase turbulent reacting flow including radiation heat transfer. Development of an accurate mathematical model of the incineration process is being hampered by the lack of measured data for validation. Requirements for specific data essential for the development of an incinerator burning bed model prompted this work which is concerned with ac curate measurement of combustion data within a burning bed of solid waste. The objective of present proposal is to design and develop a unique self -contained ball probe consisting of measuring and recording electronic components installed in refractory fibre/ablating capsule.This measurement technique differs from conventional method of measuring in that the ball instrument can be introduced into the incinerator with the waste and hence experiencing the exact conditions as the waste material.

 

 

Development of A Novel And Efficient Process For Detoxification And Re-Use of Contaminated Fly-Ash

 

Research Student: P H Lee (PhD)
Grant Holders: Professor J Swithenbank, Professor V N Sharifi
Funded By EPSRC

The ultimate objective of the present proposal is to convert toxic fly-ash from incinerators into a material which can be disposed of cheaply or used in the construction industry. The approach is based on the fact that sintering or melting of this ash results in destruction of its toxic organic components, and also fixation of its heavy metal content to form an unleachable material which can be used in landfill or for building roads. A key aspect of this proposal is the technique used to ensure the energy efficiency of the sintering/melting process. This is based on the application of a regenerative heating concept.

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Incinerator Bed Modelling

 

Research Staff: Dr Y B Yang
Grant Holders: Professor J Swithenbank, Professor V N Sharifi
Funded By EPSRC

In the UK there are 30 million tonnes per year of municipal waste to be burned (representing an energy equivalent to 10 million tonnes of coal per year!) whilst at present we burn less than 1 million tonnes per year. There is no fundamentally based mathematical model of the combustion of such wastes and design, operation and control of incinerators is still based on crude empirical relations. The objective of the present proposal is to identify the appropriate set of governing equations for combustion on the grate of an incinerator and to develop and validate a procedure for solving these equations. The key feature of incinerator combustion is the mixing of the solid material on the grate. Experiments are proposed to characterise and quantify this mixing process so that it can be accurately modelled simultaneously with the numerical solution of the governing equations. This programme is absolutely fundamental to practically all future research on incineration including the destiny of contaminants such as heavy metals, CO, NOx,, SOx VOCs, particulates and dioxins since it will provide the upstream boundary conditions which are essential for understanding and modelling their subsequent fate. In particular recirculation of cleaned flue gases is known to reduce NOx emission but the mechanism requires elucidation in order to optimize the technique.

 


Reduction of NOx Emission in Municipal Solid Waste Incinerators by Fundamental Combustion Techniques

 

Research Student: R Zakaria (PhD)
Research Staff: Dr Y B Yang
Grant Holders: Professor J Swithenbank, Professor V N Sharifi
Funded By EPSRC

Traditional methods of minimising NOx emissions from thermal processes including incinerators have included post-combustion treatment technologies in the form of catalytic and non-catalytic ammonia or urea injection to reduce the nitrogen oxides from the flue gas stream prior to flue gas release. These processes are effective in reducing nitrogen oxides but emit by-products which require further treatment and disposal. Capital and operating costs are also significant in many post-combustion treatment applications. Reduction of NOx directly at the source of formation in the combustion process is a strategy which reduces both the production of secondary waste streams and the costs of pollution control systems. The main purpose of this programme is to achieve NOx reduction in solid waste incinerator plants by optimising the combustion process, particularly in the bed rather than introducing the supplementary pollution problems that arise if ammonia/urea injection is used. It will be appreciated that this gives a major advantage since it does not incur such inherent problems of ammonia slip, ammonia storage and ammonia supply.

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Sewage Sludge Incineration in a Rotating Fluidised Bed Incinerator

 

Research Staff/Students: S.Basire, W.Y.Wong, R.Taib
Grant Holders: Professor J Swithenbank, Professor V N Sharifi
Funded By EPSRC

At the present time, the sewage treatment plants in the UK produce about 25 million tonnes of sewage sludge each year at a concentration of 4% solids. New regulations forbid sea dumping and in the near future new incinerators will be required to dispose of about five million tonnes per year. In this programme, a new strategy is proposed based on a rotating fluidised bed incinerator. The key factor to note is that when air flows up through a bed of near monosized particles, it fluidizes when the pressure drop across the bed is equal to the weight of the bed. Normally, the weight of the bed is determined by gravity. However, if the bed is contained by a cylindrical air distributor 'plate' which is rotating rapidly about its axis, then the effective weight of the bed can be increased dramatically. The air flow passing through the bed can be increased proportionally to the "g" level produced by the rotation and it follows that the process has been intensified. The rotating fluidized bed sludge incinerator is a novel device which is very compact, and is able to solve the turn-down problem encountered with conventional fluidised beds by simply changing the rotation speed.

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Thermal processes.

A bubbling fluidised bed

 

Bubbling fluidised bed reactor

 

Fixed bed combustion

 

Rotating fluidised bed developed for dewage sludge incineration