Master of Engineering / Global warming and diminishing energy supplies are two major current concerns. Disposal of plastic wastes is also a major concern. The aim of this research is to address these three concerns by developing a solar powered process, using waste plastics as fuel to generate energy. Research into: i) solar concentrators for high temperature thermochemical processes, and ii) pyrolysis/gasification of waste plastics has been separately reported in the literature. In this study the aim was to bring these fields of research together to design a solar receiver-reactor suitable for the production of a synthesis gas, consisting of hydrogen, from waste plastics. To achieve this aim, studies of plastic decomposition behaviour using the thermal analysis method known as thermogravimetric analysis were conducted. Solar concentrators and their potential to be used for thermochemical processes were also studied. Firstly, the thermal decomposition behaviour of common plastics, namely low density polyethylene (LDPE), high density polyethylene (HDPE), polyethylene terephthalate (PET) and polyvinyl chloride (PET), were studied using thermogravimetry at heating rates of 5, 10, 20, 50 and 100 ºC/min. The kinetic parameters for the decomposition were determined from these experiments. Secondly, a simple solar receiver-reactor in which the plastic decomposition could be achieved was designed. The solar receiver-reactor designed was a quartz tube reactor which can be placed in the focus of a dish type parabolic concentrator capable of generating up to 3 kW in the focus of diameter 50 mm. The thermogravimetric analysis of plastic samples showed that LDPE, HDPE and PET have a single-step decomposition, whereas PVC has a two-step decomposition. The first step was related to the release of hydrogen chloride from the PVC and the second step was related to the release of hydrocarbon from the polymer backbone. If PVC is pretreated to release HCl it can be mixed with other plastics for a single step decomposition. It is likely that a single step plastic decomposition can be achieved in a directly irradiated solar receiver-reactor to generate useful gases consisting of hydrogen.

The firing of fuel wood has been identified as one of themain causes of pollutant emissions from small-scale (<100kW) combustion of wood fuels. The emissions are a result ofinsufficient combustion efficiency. This thesis presents a newmeasurement method to analyse the thermochemical conversion ofbiofuels in general, as well as to explain the main reason ofthe inefficient combustion of fuel wood in particular. In general, small-scale combustion of biofuels are carriedout by means of packed-bed combustion (PBC)technology. Acomprehensive literature review revealed that textbooks,theories, and methods in the field of thermochemical conversionof solid fuels in the context of PBC are scarce. This authorneeded a theoretical platform for systematic research on PBC ofbiofuels. Consequently, a new system theory - the three-stepmodel - was developed, describing the objectives of, theefficiencies of, and the process flows between, the leastcommon functions (subsystems) of a PBC system. The three stepsare referred to as the conversion system, the combustionsystem, and the heat exchanger system (boiler system). A numberof quantities and concepts, such as solid-fuel convertibles,conversion gas, conversion efficiency, and combustionefficiency, are deduced in the context of the three-step model.Based on the three-step model a measurement method washypothetically modelled aiming at the central physicalquantities of the conversion system, that is, the mass flow andstoichiometry of conversion gas, as well as the air factor ofthe conversion system. An uncertainty propagation analysis ofthe constitutive mathematical models of the method was carriedout. It indicated that it should be possible to determine themass flow and stoichiometry of conversion gas within the rangesof relative uncertainties of ±5% and ±7%,respectively. An experimental PBC system was constructed,according to the criteria defined by the hypothetical method.Finally, the method was verified with respect to total massflow of conversion gas in good agreement with the verificationmethod. The relative error of mass flow of conversion gas wasin the range of ±5% of the actual value predicted by theverification method. One experimental series was conducted applying the newmeasurement method. The studied conversion concept correspondedto overfired, updraft, horizontal fixed grate, and verticalcylindrical batch reactor. The measurements revealed newinformation on the similarities and the differences in theconversion behaviour of wood chips, wood pellets, and fuelwood. The course of a batch conversion has proven to be highlydynamic and stochastic. The dynamic range of the air factor ofthe conversion system during a run was 10:1. The empiricalstoichiometry of conversion gas during a run was CH3.1O:CH0O0. Finally ,this experimental series revealed one ofthe main reasons why fuel wood is more difficult to burn thanfor example wood pellets. The relatively dry fuel wood (12-31g/m2,s) displayed a significantly lower time-integratedmean of mass flux of conversion gas than both the wood pellets(37-62 g/m2,s) and the wood chips (50-90 g/m2,s). The higher the mass flux of conversion gasproduced in the conversion system, the higher the combustiontemperature for a given combustion system, which in turn ispositively coupled to the combustion efficiency. In future work the method will be improved so thatmeasurements of combustion efficiency can be carried out. Othertypes of conversion concepts will be studied by the method. Keywords: Packed-bed combustion, thermochemical conversionof biomass, solid-fuel combustion, fuel-bed combustion, gratecombustion, biomass combustion, gasification, pyrolysis,drying.

The risk for climate change is a growing concern for theglobal society. According to what is known as the Kyoto Protocol,developed countries have committed themselves to reduce theirgreenhouse gas (GHG) emissions. The purpose of this thesis hasbeen to analyse opportunities for CO2 reductions in Swedish pulpand paper mills. The pulp and paper industry accounts forsignificant shares of the Swedish utilisationof both electricityand, in particular, biomass fuels. In this thesis, it has been agoal to focus not only on the technical potential of alternativesfor CO2 reductions in the energy systems of pulp and paper mills,but also on analysing the costeffectiveness of the studiedmeasures. Moreover, the analysis has covered questions concerningthe capacity and willingness among the actors involved with thepulp and paper mills’energy systems to realise CO2reduction potentials. A broad techno-economical evaluation of available technologiesfor increased power production as well as more efficient energyutilisation is carried out. Furthermore, a more indepth analysisof pulp mill-based biomass energy with CO2 removal and permanentsequestration (BECS) is presented. An evaluation is made of thepotential for pulp and paper production with a negative CO2balance through the implementation of BECS. In recent yearsoutside suppliers, mainly energy service companies (ESCOs), havebegun to operate energy facilities in some Swedish pulp and papermills. Based on interviews with managers from pulp and papercompanies and ESCOs, the main driving forces behind theincreasing co-operation as well as the opportunities and riskswith energy related co-operation are presented. Furthermore, the technical possibility of carbon-negativitythrough the implementation of BECS is discussed in relation tocarbon management on both corporate and global levels. The extentto which CO2-reducing measures in pulp and paper mills arerealised will have an impact on Sweden’s capacity to reachCO2 reduction targets. Whether or not technologies for CO2capture and sequestration are developed and implemented inSwedish pulp mills has a very large impact on the size ofSweden’s long-term CO2 reduction potential. Moreover, thedevelopment of business and competence focus in pulp and papercompanies and ESCOs suggests that cooperation will become ofincreasing importance for future sustainable industrial energymanagement. <b>Keywords:</b>CO2 reduction, pulp and paper industry, energysystem, biomass, CO2 capture and sequestration, black liquor,gasification, power production, outsourcing, sustainable energymanagement

Hydrogen is a by-product of the gasification process and it is environmentally friendly with respect to pollution and emission issues when it is derived from a CO2-neutral resource such as biomass. It is an energy carrier fuel and has flexibility to convert efficiently to other energy forms to be used in different energy applications like fuel cells. The proposed research presents literature on previous gasification studies regarding hydrogen production from biomass and updates the obtained results. The main objectives of the thesis are: a) to study hydrogen production via steam biomass (sawdust) gasification; b) to evaluate the produced hydrogen by performing comprehensive analysis by using thermodynamic, exergoeconomic and optimization analyses. Despite details specific to the gasifier, in general, there is a special need to theoretically address the gasifier that gasifies biomass to produce hydrogen. This further study of gasification aspects presents a comprehensive performance assessment through energy and exergy analyses, provides results of the optimization studies on minimizing hydrogen production costs, and provides a thermo-economic analysis for the proposed systems (Systems I, II and III). This thesis also includes the results from the performed study that aims to investigate theoretical hydrogen production from biomass (sawdust) via gasification technology. Results from the performed parametric study show that the gasification ratio increases from 70 to 107 gH2 per kg of sawdust. In the gasification temperature studied, system II has the highest energy efficiency that considers electricity production where it increases from 72 % to 82 % and has the lowest energy efficiency that considers hydrogen yield where it increases from 45 % to 55 %. Also, it has the lowest hydrogen cost of 0.103 $/kW-h. The optimization results show that the optimum gasification temperatures for System I, System II and System III are 1139 K, 1245 K and 1205 K, respectively. / UOIT

This study examines the possibility of electricity production through gasification of agricultural residues in Sudan. The study begins in Chapter 1, by providing general contextual analysis of the energy situation (production and consumption patterns) in Sudan with specific focus on electricity. It proceeded to study the potential of Petroleum, Biomass and other renewable sources for electricity production. Dramatic increase in electricity production was found to be essential especially through decentralised power plants as the current electricity production services cover ~ 13 % of the population of Sudan. Biomass potential in Sudan justifies the use of agricultural residues as energy source; its potential was estimated by ~ 350000 TJ/a. Further, the urban centres of arid regions in western Sudan were identified as the target group for this study. In chapter 2, specific investigations for selected study area through field work using statistical tools such as questionnaires, interviews and field observation show that income is highly correlated to electricity consumption. The flat rate system did not result in higher consumption thus the assumption that this consumption will not drastically change in the next 10 years could be accepted. As orientation value for BGPP, 8000 tons of GN.S are available annually, the average electricity consumption is ~ 4 kWh/day/family while acceptable price could be 40 SDD/kWh (0.15 €). In chapter 3, literature review was carried to spot out the comparative merits of the gasification technology and the most optimum gasifying and electricity production system. As a result downdraft gasifier and ICE were suggested as suitable systems. In chapter 4, fuel properties and fuel properties of agricultural residues were studied, different samples were tested and the results were presented. The main conclusions derived were: fuel properties of agricultural residues are modifiable properties, so utlization planning is possible as for any other energy resource. In Sudan, Baggase, Groundnuts shells and Roselle stalks could be considered as possible fuels. The experimental work done in chapter 5 showed that GN.S could be gasified in down draft gasifiers, which are less costly and simpler to operate than circulating systems. Acceptable values of gas thermal properties (c.v.~ 4 MJ/Nm3, 30 % of burnable gases) at fairly continuing processes were obtained. In chapter 6, a concept for biomass power plant was drafted, the main components are: downdraft, air based gasifier connected to ICE, multi-stage gas cleaning system (cyclones, washer and filters) mechanical ash removal and semi closed water cycle. Main operation measures are: electricity is the sole product; working time is 150 day/year between mid Novembermid Mars. Environmental hazards of waste management e.g. flue gas emission and waste water management are the limiting factors. In the last part of chapter 6 an economic analysis was carried out. At a value of 3000 €/kW for the initial system and fuel price of 100000 €/year for ~6 GWh then a price of 0.23 €/kWh and a return period of 24 years could be obtained. The study concludes in chapter 7 that biomass gasification under the local conditions has its comparative merits however a high institutional support is needed at the beginning. / Diese Studie untersucht die Möglichkeit der Elektrizitätsproduktion durch Vergasung von landwirtschaftlichen Abfällen im Sudan. Die Untersuchung beginnt im Kapitel 1 mit der Bereitstellung einer allgemeinen zusammenhängenden Analyse der Energiesituation (Produktions- und Verbrauchsmuster) im Sudan mit dem besonderen Fokus auf Elektrizität, gefolgt von einer Studie des Potentials von Petroleum, Biomasse und anderer erneuerbarer Quellen für die Produktion von Elektrizität. Eine starke Zunahme bei der Elektrizitätsproduktion wurde als nötig bewertet, da dezentrale Kraftwerke, als die gegenwärtigen Elektrizitätsproduktionsbetriebe, nur die Versorgung von 13 % der Bevölkerung im Sudan abdecken. Das geschätzte Potential der landwirtschaftlichen Abfälle liegt bei ca. 350.000 TJ/Jahre damit kommen sie als Energiequelle in Frage. Weiterhin wurden urbane Zentren der ariden Regionen in Westsudan als Zielgruppe für die Untersuchung ausgewählt. In Kapitel 2 werden detaillierte Untersuchungen für das ausgewählte Studiengebiet durch Feldstudien unter Verwendung von statistischen Werkzeugen, wie Fragebögen, Interviews und Felduntersuchungen dargestellt. Das Ergebnis zeigt, dass das Einkommen im höchsten Maße mit dem Elektrizitätsverbrauch korreliert ist. Das Flat rate System hatte keinen höheren Verbrauch zur Folge, folglich kann die Annahme akzeptiert werden, dass sich der Verbrauch in den nächsten 10 Jahren nicht drastisch ändern wird. Als Orientierungswert für Biomasse Kraftwerk: 8.000 t/Jahr Erdnussschalen sind verfügbar. Der durchschnittliche Elektrizitätsverbrauch beträgt ca. 4 kWh/Tag/Familie betrachtet für 10.000 Familien. Im Kapitel 3 wird eine Literaturrecherche für die Vergasungstechnologie durchgeführt, zum Vergleich ihrer Vorteile und zur Auswahl des optimalen Vergasungs- und Gasumwandlungssystems. Als Ergebnis wurden der Festbett-Gleichstrom-Vergaser und gas Motor als passende Systeme vorgeschlagen. In Kapitel 4 werden Brennstoff Eigenschaften von landwirtschaftlichen Abfällen untersucht, verschiedene Proben getestet und die Ergebnisse präsentiert. Die Hauptschlussfolgerung daraus ist: Brennstoff Eigenschaften von landwirtschaftlichen Abfällen sind veränderbare Eigenschaften, welche eine bessere Planung erlauben und somit ihre Verwendung favorisieren. Im Sudan können Bagasse, Erdnussschalen und Rosellenstiele als optimaler Brennstoff gelten. Die experimentelle Arbeit in Kapitel 5 zeigt, dass Erdnussschalen im 75 kW Festbett-Gleichstrom-Systemen vergast werden können, welche weniger kostenintensiv und einfach zu bedienen sind als zirkulierende Systeme. Akzeptable Werte der Gaseigenschaften (c.v. ca. 4 MJ/Nm³, 35 % von brennbaren Gasen) wurden in kontinuierlichen Prozessen erreicht. In Kapitel 6 wurde ein Konzept für Biomassekraftwerke entworfen. Deren Hauptkomponenten sind: Festbett-Gleichstrom-Vergaser in Verbindung mit ICE, mehrstufige Gasreinigungssysteme (Zyklone, Wäscher und Filter), mechanische Aschensysteme und ein teilweise geschlossener Wasserkreislauf. Hauptbetriebsmaßnahmen sind: Elektrizität als das einzige Produkt, die Arbeitszeit beträgt 150 Tage pro Jahr zwischen November und April. Umweltrisiken des Abfallmanagements z.B. Rauchgas und Abwassermanagement sind die limitierenden Faktoren. Im letzten Teil von Kapitel 6 wurde eine ökonomische Analyse durchgeführt. Ein Wert von 3000 €/kW für das Anfangssystem und ein Kraftstoffpreis von 100.000 €/Jahr für 6 GWh dann ein Preis von 0,23 €/kWh und eine Amortisationszeit von 24 Jahren können angenommen werden. Die Studie schlussfolgert, dass die Vergasung unter den Bedingungen des Studiengebietes ihre Vorteile hat, jedoch ist institutionelle Unterstützung am Anfang nötig.

The aim of the present work about experimental and mathematical modelling of moving-bed-gasification was to increase the transparency of the process. At Dresden University of Technology a gasifier with a high number of measuring points was used. Two-dimensional profiles of temperature and gas-concentrations were analysed. Samples of particles taken out of the reactor gave information about drying, pyrolysis and char-reactions. A commercial CFD-software was modified for the special application of fixed-bedgasifiers by subroutines. Comparisons of the results of experiment and simulation showed the constitutive process with its significant reaction-behaviour. By variation of different parameters, important influences were discussed. / Das Ziel der Arbeit war die Erhöhung der Prozeßtransparenz der Festbettvergasung im kleinen Leistungsbereich. Es besteht einerseits eine große Wissenslücke, welche einen durchschlagenden Erfolg für den Brennstoff Holz bisher verhinderte. Andererseits besitzt die Technologie ein energiewirtschaftlich bedeutendes und unter den gegenwärtigen politischen Rahmenbedingungen betriebswirtschaftlich hohes Potential. Ein Modellvergaser war mit umfangreichen Meßmöglichkeiten ausgerüstet. Mittels daran angepaßter Probenahmevorrichtungen konnten in den Untersuchungen auf der Basis von 16 Stützstellen zweidimensionale Profile der Temperatur und der Gaszusammensetzung ermittelt werden. Die Partikelproben aus drei Meßebenen gaben Auskunft über den Trocknungs- und Pyrolysefortschritt sowie über den Koksumsatz. Parallel erfolgte die Erarbeitung einer Mathematischen Modellierung. Hier wurde eine kommerzielle Strömungssimulations-Software mittels Unterprogramme an die Anforderungen der Festbettvergasung angepaßt. Im Vergleich der Ergebnisse aus Experiment und Simulation konnte der Reaktionsablauf dargestellt, sowie Einflüsse verschiedener Parameter auf den Prozeß diskutiert werden.

<p>The firing of fuel wood has been identified as one of themain causes of pollutant emissions from small-scale (<100kW) combustion of wood fuels. The emissions are a result ofinsufficient combustion efficiency. This thesis presents a newmeasurement method to analyse the thermochemical conversion ofbiofuels in general, as well as to explain the main reason ofthe inefficient combustion of fuel wood in particular.</p><p>In general, small-scale combustion of biofuels are carriedout by means of packed-bed combustion (PBC)technology. Acomprehensive literature review revealed that textbooks,theories, and methods in the field of thermochemical conversionof solid fuels in the context of PBC are scarce. This authorneeded a theoretical platform for systematic research on PBC ofbiofuels. Consequently, a new system theory - the three-stepmodel - was developed, describing the objectives of, theefficiencies of, and the process flows between, the leastcommon functions (subsystems) of a PBC system. The three stepsare referred to as the conversion system, the combustionsystem, and the heat exchanger system (boiler system). A numberof quantities and concepts, such as solid-fuel convertibles,conversion gas, conversion efficiency, and combustionefficiency, are deduced in the context of the three-step model.Based on the three-step model a measurement method washypothetically modelled aiming at the central physicalquantities of the conversion system, that is, the mass flow andstoichiometry of conversion gas, as well as the air factor ofthe conversion system. An uncertainty propagation analysis ofthe constitutive mathematical models of the method was carriedout. It indicated that it should be possible to determine themass flow and stoichiometry of conversion gas within the rangesof relative uncertainties of ±5% and ±7%,respectively. An experimental PBC system was constructed,according to the criteria defined by the hypothetical method.Finally, the method was verified with respect to total massflow of conversion gas in good agreement with the verificationmethod. The relative error of mass flow of conversion gas wasin the range of ±5% of the actual value predicted by theverification method.</p><p>One experimental series was conducted applying the newmeasurement method. The studied conversion concept correspondedto overfired, updraft, horizontal fixed grate, and verticalcylindrical batch reactor. The measurements revealed newinformation on the similarities and the differences in theconversion behaviour of wood chips, wood pellets, and fuelwood. The course of a batch conversion has proven to be highlydynamic and stochastic. The dynamic range of the air factor ofthe conversion system during a run was 10:1. The empiricalstoichiometry of conversion gas during a run was CH_3.1O:CH₀O₀. Finally ,this experimental series revealed one ofthe main reasons why fuel wood is more difficult to burn thanfor example wood pellets. The relatively dry fuel wood (12-31g/m₂,s) displayed a significantly lower time-integratedmean of mass flux of conversion gas than both the wood pellets(37-62 g/m₂,s) and the wood chips (50-90 g/m₂,s). The higher the mass flux of conversion gasproduced in the conversion system, the higher the combustiontemperature for a given combustion system, which in turn ispositively coupled to the combustion efficiency.</p><p>In future work the method will be improved so thatmeasurements of combustion efficiency can be carried out. Othertypes of conversion concepts will be studied by the method.</p><p>Keywords: Packed-bed combustion, thermochemical conversionof biomass, solid-fuel combustion, fuel-bed combustion, gratecombustion, biomass combustion, gasification, pyrolysis,drying.</p>

<p>The risk for climate change is a growing concern for theglobal society. According to what is known as the Kyoto Protocol,developed countries have committed themselves to reduce theirgreenhouse gas (GHG) emissions. The purpose of this thesis hasbeen to analyse opportunities for CO2 reductions in Swedish pulpand paper mills. The pulp and paper industry accounts forsignificant shares of the Swedish utilisationof both electricityand, in particular, biomass fuels. In this thesis, it has been agoal to focus not only on the technical potential of alternativesfor CO2 reductions in the energy systems of pulp and paper mills,but also on analysing the costeffectiveness of the studiedmeasures. Moreover, the analysis has covered questions concerningthe capacity and willingness among the actors involved with thepulp and paper mills’energy systems to realise CO2reduction potentials.</p><p>A broad techno-economical evaluation of available technologiesfor increased power production as well as more efficient energyutilisation is carried out. Furthermore, a more indepth analysisof pulp mill-based biomass energy with CO2 removal and permanentsequestration (BECS) is presented. An evaluation is made of thepotential for pulp and paper production with a negative CO2balance through the implementation of BECS. In recent yearsoutside suppliers, mainly energy service companies (ESCOs), havebegun to operate energy facilities in some Swedish pulp and papermills. Based on interviews with managers from pulp and papercompanies and ESCOs, the main driving forces behind theincreasing co-operation as well as the opportunities and riskswith energy related co-operation are presented.</p><p>Furthermore, the technical possibility of carbon-negativitythrough the implementation of BECS is discussed in relation tocarbon management on both corporate and global levels. The extentto which CO2-reducing measures in pulp and paper mills arerealised will have an impact on Sweden’s capacity to reachCO2 reduction targets. Whether or not technologies for CO2capture and sequestration are developed and implemented inSwedish pulp mills has a very large impact on the size ofSweden’s long-term CO2 reduction potential. Moreover, thedevelopment of business and competence focus in pulp and papercompanies and ESCOs suggests that cooperation will become ofincreasing importance for future sustainable industrial energymanagement.</p><p><b>Keywords:</b>CO2 reduction, pulp and paper industry, energysystem, biomass, CO2 capture and sequestration, black liquor,gasification, power production, outsourcing, sustainable energymanagement</p>

Thermal co-processing of coal and biomass has been increasingly focused for its environmental and economic benefits. In the present work, the experimental and kinetic study on co-pyrolysis and co-gasification of Rhenish brown coal (HKN) and wheat straw (WS) was made. The pyrolysis behavior, especially for co-pyrolysis, was investigated in a thermogravimetric analyzer (TGA) and a small fixed bed reactor (LPA). In TGA, the mass loss and reaction rate of single and blend samples were studied under various experimental conditions, and their effects on synergy effects. The synergy effects on products yield and properties of chars were studied in LPA. The kinetics of pyrolysis was obtained based on data from TGA by using the Coats-Redfern method. For gasification with CO2, a small fixed bed reactor (quartz glass reactor), equipped with an online GC to monitor the gas composition, was used. The effects of processing conditions on gasification behavior and synergy effects for mixed chars and co-pyrolysis chars were investigated. The volume reaction model (VRM), shrinking core model (SCM) and random pore model (RPM), were applied to fit the experimental data. The model best fitting the experiments was used to calculate the kinetic parameters. The reaction orders of gasification reactions with single chars are also investigated. The pyrolysis study showed that a small amount of wheat straw added to the brown coal promoted the decomposition better and showed more significant synergy effects. The synergy effects varied with increasing heating rates and pressures, especially at 40 bar. The kinetic parameters were inconsistent with experimental behavior during co-pyrolysis, since the reaction was also affected by heat transfer, contact time, particles distribution and so on. The gasification study on single chars showed that Rhenish brown coal chars had higher reactivity; chars pyrolyzed at higher temperatures showed lower reactivity; and higher gasification temperatures and CO2 partial pressures led to higher reactivity. For co-gasification process, there was no significant synergy effect for mixed chars. However, negative synergy effects (reactivity decreased compared to the calculated values based on rule of mixing) were observed for co-pyrolysis chars, caused by properties change by co-pyrolysis process. For kinetics, the reaction orders of chars ranged from 0.3 to 0.7. Only random pore model fitted most experiments at low and high temperatures. Synergy effects were also observed in kinetic parameters. The values of activation energy E and pre-exponential factor A for mixed chars and co-pyrolysis chars were lower than expected. The negative synergy effects showed the pre-exponential factor A had more effects. However, the higher reactivity of mixed chars than co-pyrolysis chars showed that the reaction was affected more by activation energy E. Therefore, only investigating E or A value was not enough. In addition, a marked compensation effect between activation energies and pre-exponential factors was found in the present study. The isokinetic temperature for the present study was 856 °C. This was close to the temperature at which the gasification reaction transforms from the chemical controlled zone to the diffusion controlled zone for most chars.

Biomass-fuelled proton exchange membrane fuel cells (PEMFCs) offer asolution for replacing fossil fuel for hydrogen production. Through using thebiomass-derived hydrogen as fuel, PEMFCs may become an efficient andsustainable energy system for small and medium-sized enterprises. The aim ofthis thesis is to evaluate the performance and potential applications of biomassfuelledPEMFC systems which are designed to convert biomass to electricity andheat. Biomass-fuelled PEMFC systems are simulated by Aspen plus based ondata collected from experiments and literature.The impact of the quality of the hydrogen-rich gas, anode stoichiometry, CH4content in the biogas and CH4 conversion rate on the performance of the PEMFCis investigated. Also, pinch technology is used to optimize the heat exchangernetwork to improve the power generation and thermal efficiency.For liquid and solid biomass, anaerobic digestion (AD) and gasification (GF),respectively, are relatively viable and developed conversion technologies. ForAD-PEMFC, a steam reformer is also needed to convert biogas to hydrogen-richgas. For 100 kWe generation, the GF-PEMFC system yields a good technicalperformance with 20 % electrical efficiency and 57 % thermal efficiency,whereas the AD-PEMFC system only has 9 % electrical efficiency and 13 %thermal efficiency. This low efficiency is due to the low efficiency of theanaerobic digester (AD) and the high internal heat consumption of the AD andthe steam reformer (SR). For the environmental aspects, the GF-PEMFC systemhas a high CO2 emissions offset factor and the AD-PEMFC system has anefficient land-use.The applications of the biomass-fuelled PEMFC systems are investigated on adairy farm and an olive oil plant. For the dairy farm, manure is used as feedstockto generate biogas through anaerobic digestion. A PEMFC qualified for 40 %electrical efficiency may generate 360 MWh electricity and 680 MWh heat peryear to make a dairy farm with 300 milked cows self-sufficient in a sustainableway. A PEMFC-CHP system designed for an olive oil plant generating annual 50000 m3 solid olive mill waste (SOMW) and 9 000 m3 olive mill waste water(OMW) is simulated based on experimental data from the Biogas2PEM-FCproject1. After the optimization of the heat exchanger network, the PEMFC-CHP  system can generate 194 kW electricity which corresponds to 62 % of the totalelectricity demand of the olive oil plant.The economic performance of the PEMFC and biogas-fuelled PEMFC areassessed roughly including capital, operation &amp; maintenance (O&amp;M) costs of thebiogas plant and the PEMFC-CHP, the cost of heat and electricity, and the valueof the digestate as fertilizer. / <p>QC 20151109</p>