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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
241

The gasification of biomass in a fluidized bed reactor

Hoveland, Deborah A. January 2011 (has links)
Typescript (photocopy). / Digitized by Kansas Correctional Industries
242

Potentials of Noncommercial Forest Biomass for Energy

Ffolliott, Peter F., Swank, Wayne T., Banzhaf, William H., Betters, David R., Clary, Warren P., McMinn, J. W., McNab, W. H. 10 1900 (has links)
No description available.
243

Design of an optimal photobioreactor

Hagendijk, Adrianus Jan 03 1900 (has links)
Thesis (MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Currently the three main algae strains that are manufactured commercially are Chlorella, Spirulina and Dunaliela salina, which are produced for biomass and bioproducts. Photobioreactors (PBR) allow the exploitation of over 50 000 known microalgae species with over 15 000 novel compounds having been chemically identified to date. Many of these algae could be sources of high-value products which are produced using a method that delivers them from renewable resources. Designing an optimal photobioreactor is a complex process because a large array of variables is included in the design, with several of the variables interacting with each other directly. The interactions of most of these variables have not been established. The initial information that is available is inadequate because most photobioreactors have been tested on a laboratory scale and the information given does not include the manufacturing materials, the size of tubing used and other design variables. Before designing a photobioreactor, it is important to understand the best conditions for the production of algae because these have a direct influence on the requirements. In order to produce algae biomass under the specific conditions, one has to investigate current photobioreactors that have been designed in order to establish whether they are capable of optimum production under the production conditions; determine possible factors that could influence the production negatively and how they could be prevented; and undertake a cost analysis to determine whether the production of algae is an economically viable process using the specific reactor. All of these criteria have to be met for a photobioreactor to be viable in the production of algae biomass. Currently a Bubble column reactor is considered to be the best design for a photobioreactor and also the most scalable. Due to the limited information available, testing was conducted to determine the effect of: 1) different manufacturing materials, 2) the gas dispersion unit, 3) the diameters of the tubing and 4) the density. Bubble column reactors were used to test the effects of the four variables and were considered to be the most important aspects in the design. For testing these variables and their interaction, Chlorella Vulgaris was used because it is one of the most popular algae species used for production currently. As temperature and the availability of light play a large role in the production of algae, all testing was done in a laboratory environment to ensure small temperature changes and the constant availability of light. The reactors that were tested were made of PVC couplings, with the clear tubing used being made of either PVC or acrylic tubing. Enriched air was supplied at a 5% volume per volume ratio of CO2, with a flow rate of 0.02 volume per volume per minute (vvm) for the 50 mm diameter reactors and 0.36 vvm for the 90 and 110 mm diameter reactors. Two gas dispersion units were used to determine whether they would have any effect on the production. The gas dispersion units create small bubbles to ensure a high surface area to volume ratio and thereby they allow for maximum CO2 and O2 mass transfer. A growth rate of 0.14 gram per litre per day was found to yield the best production of all the reactors and configurations that were tested. The 50 mm diameter reactors showed the best growth followed by the 110 mm diameter reactors. The 90 mm diameter reactors all had a negative growth rate which appeared to be due to an insufficient gas flow rate. The 50 mm reactors had the best growth rate of 0.14 and 0.10 grams per litre per day for the acrylic tubing, while 0.08 grams per litre per day was achieved with PVC tubing. The 110 mm reactors had a highest growth rate of 0.05 grams per litre per day with PVC tubing. It was found that the 50 mm and 90 mm reactors showed a better performance with acrylic tubing while the 110 mm reactors showed a better performance with PVC tubing. The gas dispersion unit is affected by the gas flow rate, the density, the diameter of the tubing and the material that is used. The gas dispersion units’ effect is dependent on the diameter of the reactor seeing that the 50 mm reactor shows better performance with the small unit, while the 110 mm reactor shows better performance with the large unit, due to the gas flow rate that is required in the reactors. Because the gas flow rate and gas dispersion unit directly affect the agitation, the optimal density is affected directly due to the availability of light and therefore the tubing material. The gas dispersion units should fit properly into the reactor and be capable of handling the gas flow rate that is required. The diameter of the tubing does not show any effect but could have an effect under different testing conditions and could not be conclusively eliminated. The density of algae does have an effect, although most reactors showed a better production rate at a higher culture density. The scale up of the bubble column reactor creates a dead zone when a module is constructed. The scale up of a bubble column reactor could range from increasing the vertical tubing length, increasing the diameter of the tubing to adding vertical tubing to a module. The dead zone is formed at the bottom of the reactor where the module interconnects the vertical growth tubes, because these fittings are not constructed from a clear material, due to cost of such a construction. The dead zone that is created causes a large portion of algae to form a sediment, which directly affects the production of the system because it is in a dark zone of the reactor. Improved results would be obtained if the algae were kept at a homogeneous density that would ensure maximum expose to light. The ratio of gas flow rate to reactor volume and diameter of the tubing was found to be crucial. It is suspected that the 90 mm tubing reactor had a negative growth rate as this ratio was not correct. The 50 mm reactors had to be run at a much lower reactor volume per volume gas flow rate which could consist of air, carbon dioxide enriched air or other gases as required. The inclusion of the tubing diameter in the ratio is of vital importance and should be studied further. A cost analysis shows that the bubble column reactors under the tested conditions are not financially viable. A large component of the cost is carbon dioxide and medium, which is a composition of nutrients. This could be removed if a free source were obtained, which would make the system financially viable. These sources could include waste water and flue gas from industrial processes. It is recommended that a gas dispersion tube be positioned at the bottom of the reactor to ensure that no sedimentation occurs and that there is a homogeneous culture, and to maximise the production capabilities of a bubble column reactor. It is also recommended that the gas flow rate inside the reactor be studied to obtain a ratio where the volume of the reactor, the height of the reactor and the diameter of the tubing are included to obtain a sufficient rate of flow. / AFRIKAANSE OPSOMMING: Tans is daar drie belangrike alg stamme wat kommersieel geproduseer word, Chlorella, Spirulina en Dunaliela salina. Fotobioreaktors het meegebring dat meer as 50 000 bekende alg spesies met meer as 15 000 komponente tot op datum chemies geïdentifiseer is. Baie van hierdie alge kan hoë waarde produkte wees, wat met behulp van hernubare metodes geproduseer kan word. Die ontwerp van 'n optimale fotobioreaktor is 'n komplekse proses aangesien 'n groot verskeidenheid veranderlikes ingesluit moet word wat ‘n invloed op mekaar kan hê. Die interaksie van meeste van hierdie veranderlikes is nog nie vasgestel nie. Die inligting oor hierdie onderwerp is beperk aangesien die meeste fotobioreaktors in 'n laboratorium getoets is en dus nie die vervaardigingsmateriale, die grootte van buise en ander ontwerp veranderlikes insluit nie. Voordat 'n fotobioreaktor ontwerp kan word, moet die ideale alg produksie toestande verstaan word, aangesien dit 'n direkte impak op die produksie vereistes kan hê. Om alg biomassa onder spesifieke omstandighede te produseer, moet die bestaande fotobioreaktor ontwerpe ondersoek word. Daar moet vasgestel word of die bepaalde ontwerp oor die kapasiteit beskik om optimale produksie te lewer; identifisering van faktore wat produksie negatief kan beïnvloed en hoe dit voorkom kan word; en 'n koste ontleding moet gedoen word om te bereken of die produksie van alge met die geidentifiseerde ontwerp 'n ekonomies lewensvatbare proses is. Daar moet aan al die vereistes voldoen word om te bepaal of 'n fotobioreaktor lewensvatbaar is vir die produksie van alg biomassa. 'n Borrel-kolom reaktor ontwerp word tans as die beste ontwerp vir 'n fotobioreaktor geag, asook die mees aanpasbare ontwerp. As gevolg van die beperkte inligting wat beskikbaar is, is navorsing gedoen om die invloed van verskillende faktore te bepaal, naamlik: vervaardigingsmateriaal, gasverspreidingseenheid, buisdeursnee en digtheid. Borrel-kolom reaktors is gebruik om die vier belangrikste veranderlikes in die ontwerp te toets. Om die veranderlikes en hul interaksie te toets, is Chlorella vulgaris gebruik, aangesien dit een van die gewildste alg spesies is vir die produksie van biomassa. As gevolg van die belangrike rol wat temperatuur en lig beskikbaarheid in die produksie van alge speel, is al die toetse in 'n laboratorium-omgewing gedoen om temperatuur wisseling te beperk en konstante lig beskikbaarheid te verseker. Die reaktors wat getoets is, is vervaardig uit PVC koppelstukke, met die deurskynende buise wat uit PVC of akriel vervaardig is. Verrykte lug is verskaf op 'n 5% volume per volume verhouding CO2, met 'n vloei tempo van 0,02 volume per volume per minuut (vvm) vir die 50 mm deursnee reaktors en 0,36 vvm vir die 90 mm en 110 mm reaktors. Twee gasverspreidingseenhede is gebruik om hulle invloed op die produksie te bepaal. Die gasverspreidingseenhede skep kleiner borrels, om 'n hoë oppervlak area tot volume verhouding te skep en daardeur 'n maksimum CO2 en O2 massa-oordrag te verseker. 'n Groeikoers van 0,14 gram per liter per dag is gevind as die beste produksie van al die reaktors en konfigurasies wat getoets is. Die 50 mm deursnee reaktors het die beste groei getoon, gevolg deur die 110 mm deursnee reaktors. Die 90 mm deursnee reaktors het 'n negatiewe groeikoers getoon, wat moontlik toegeskryf kan word aan onvoldoende gas vloei tempo. Die 50 mm reaktors het die beste groeikoers van 0,14 en 0,10 gram per liter per dag vir die akriel buise getoon, terwyl ‘n 0,08 gram per liter per dag behaal is met 'n PVC buis. Die 110 mm reaktors het die hoogste groeikoers aangedui van 0,05 gram per liter per dag met 'n PVC buis. Daar is bevind dat die 50 mm en 90mm reaktors 'n beter prestasie met akriel buise gehad het, terwyl die 110 mm reaktors 'n beter prestasie met 'n PVC buis gehad het. Die gasverspreidingseenheid word beinvloed deur die gas vloei tempo, digtheid, buisdeursnee en die vervaardigingsmateriaal wat gebruik word. Die gasverspreidingseenhede word verder beinvloed deur die reaktor se buisdeursnee aangesien die 50 mm reaktor ‘n beter prestasie getoon het met die kleiner gas eenheid, terwyl die 110 mm reaktor ‘n beter prestasie getoon het met die groter gas eenheid, as gevolg van die gas vloei tempo wat vereis is. Die gas vloei tempo en gasverspreidingseenheid het ‘n direkte invloed op die groei van die kultuur, dus is die optimale digtheid afhanklik van die lig beskikbaarheid en dus die vervaardigingsmateriaal van die buise. Die gasverspreidingseenhede moet stewig in die reaktor pas en in staat wees om die gas vloei tempo wat vereis word te kan hanteer. Hoewel die deursnee van die buise nie 'n invloed getoon nie, kan dit 'n invloed onder verskillende toets omstandighede toon en kon nie finaal uitgeskakel word. Die digtheid van die alge het wel 'n effek, hoewel die meeste reaktors ‘n beter produksie tempo op 'n hoër kultuur digtheid toon. Die groter skaal borrel-kolom reaktor ontwikkel 'n dooie sone indien ‘n module saamgestel word. Die groter skaal borrel-kolom reaktor kan insluit: die verhoging van die vertikale buis lengte, 'n toename in deursnee van die buise en toevoeging van vertikale buise in die module. Die dooie sone het gevorm aan die onderkant van die reaktor waar die module se vertikale groei buise met mekaar verbind is. Hierdie area is uit nie-deurskynende materiaal vervaardig as gevolg van die konstruksie koste. Die dooie sone het veroorsaak dat groot hoeveelhede van die alge ‘n sediment gevorm het en ‘n direkte invloed op die produksie van die stelsel gehad het aangesien dit 'n donker sone in die reaktor gevorm het. Beter resultate kan verwag word indien die alge op 'n homogeniese digtheid gehou kan word om maksimum lig blootstelling te verseker. Daar is bevind dat die verhouding van gas vloei tempo tot reaktor volume en buisdeursnee deurslaggewend is. Die negatiewe groeikoers in die 90 mm reaktor word toegeskryf daaraan dat hierdie verhouding nie korrek was nie. Die 50 mm reaktors het op 'n laer reaktor volume per volume gas vloei tempo gefunksioneer wat kan bestaan uit die lug, verrykte lug of ander gasse soos benodig. Dit dui daarop dat die insluiting van die buis deursnee in hierdie verhouding van kardinale belang is en verder bestudeer moet word. 'n Koste ontleding toon dat die borrel-kolom reaktors onder hierdie getoets omstandighede nie finansieel lewensvatbaar is nie. 'n Groot deel van die koste is die medium, wat 'n samestelling van voedingstowwe is, en koolstofdioksied koste. Om finansieel lewensvatbaar te raak, moet hierdie kostes deur 'n gratis bron vervang word. Die bronne kan bestaan uit afval water en oortolige CO2 uit industrie. Daar word aanbeveel dat 'n gasverspreidingsbuisie aan die onderkant van die reaktor geplaas word. Dit sal verseker dat geen sediment vorm nie en 'n homogeniese kultuur gehandhaaf kan word om maksimum produksie in 'n borrel-kolom reaktor te handhaaf. Verder word aanbeveel dat die gas vloei tempo binne die reaktor verder bestudeer word om 'n verhouding tussen die volume van die reaktor, die hoogte van die reaktor en die deursnee van die buise te bepaal deur sodoende 'n voldoende tempo van vloei te verkry.
244

Biochar – synergies between carbon storage, environmental functions and renewable energy production

Crombie, Kyle January 2014 (has links)
Growing concerns about climate change and the inevitable depletion of fossil fuel resources have led to an increased focus on renewable energy technologies and reducing GHG emissions. Limiting the atmospheric level of CO2 is essential to prevent the most damaging effects of climate change. Among renewable energy resources, biomass combustion has the largest potential to contribute to global energy demands, however it is considered to be a carbon neutral solution and so only limits CO2 concentrations rather than reducing them. Through pyrolysis rather than combustion, biomass can lead to carbon negative liquid, gaseous and solid fuels while also offering a route for long term carbon storage in the form of biochar. Biochar is a carbonaceous material which has shown potential for improving soil fertility, reducing GHG emissions and most importantly long term C storage in the environment. However many questions still remain unanswered with regard to biochar, especially the influence that process conditions can have on its performance in soil as well as any potential trade-offs between soil amendment, C sequestration and heat/power generation. This thesis is therefore focused on assessing the influence that process conditions and feedstock selection have on biochar properties related to carbon stabilisation, improving soil fertility (functional properties) as well as the distribution of energy amongst the pyrolysis co-products. To achieve this, a systematic set of biochar samples was produced, using a wide range of pyrolysis parameters (highest treatment temperature (HTT), heating rate, residence time, carrier gas flow rate and feedstock type), and analysed for physicochemical and functional properties. Pyrolysis HTT consistently showed a dominant influence on determining the final yields and properties of biochar, while the effect of other production parameters was varied. In this thesis the candidate first studied the effect that process conditions had on the long term stability of biochar, as an important indicator of its ability to sequester carbon. While increasing the HTT resulted in a decrease in biochar yield, overall the yield of stable-C increased with temperature. This meant that by applying a higher HTT during pyrolysis a higher C sequestration potential for biochar was achieved. Next to be examined was the influence that process conditions had on other functional properties (labile-C yield, biochar pH, extractable nutrients and cation exchange capacity (CEC)) was then examined. The labile-C yield of biochar decreased with increasing HTT due to the release of volatile matter, while the CEC and concentration of extractable nutrients tended to be higher in biochar produced at 450oC rather than greater HTTs. Biochar pH was also highly alkaline at elevated HTT. This indicated that while high HTT favoured C sequestration and biochar pH, lower HTT may be more favourable for other functional properties. Furthermore by assessing the mass and energy distribution amongst the solid, liquid and gaseous fractions, it was possible to determine the energy balance of the process and through this evaluate the trade-off between the C sequestration potential of biochar and the energy output of the liquid and gas fractions. As the severity of pyrolysis was raised, the total energy stored within the liquid and gaseous co-products increased at the expense of the energy content of biochar, therefore increasing the available energy output of the system and reducing the energy lost when using biochar for carbon storage rather than for bioenergy. This also demonstrated that the pyrolysis process could be fine-tuned to increase the amount of stored C while also improving the heat/power generation of the system. The higher energy content of the gas stream at elevated HTT was also seen to contain sufficient energy to sustain the pyrolysis process, which would free up the solid and liquid fractions for higher value applications while reducing the necessity for external fuel sources. Finally, the data set was used to produce statistical models enabling the prediction of biochar stable-C yield as well as the heating value of biochar. The results of this thesis therefore demonstrate that through applying high HTT the potential energy output of the pyrolysis system can be increased while producing a biochar product with high C sequestration potential and positive functional properties for soil amendment. Due to potential trade-offs, the final choice of process conditions and feedstock would then be made based on the specific requirements of a selected site for biochar application. Understanding the influence that production conditions have on the functional properties of biochar as well as the energy balance of the system is critical to developing specifically engineered bespoke biochar, be it for agricultural use, carbon storage, energy generation or combinations of the three.
245

Mycology of haymeadows under management change

Donnison, Louise January 1997 (has links)
Management improvements have caused a decline in plant species diversity in traditionally managed haymeadows. The aim of this study was examine the effects and causes of management improvements on the soil microbialocmmunity with particular emphasis on the fungal component. A seasonal study of 3 sites showed that management improvements to haymeadows consistently reduced soil microbial biomass C, but had no effect on dehydrogenase activity and basal respiration. Management improvements to these sites also caused a significant reduction in VAM spore numbers, soil fungal biomass, measured as soil ergosterol content and the PLFA 18:w6, and a decrease in the fungal:bacteria PLFA ratio. VAM spore numbers were not correlated with the possibly mycorrhizal NLFA 16:w5. In the Welsh haymeadow, fungi of the genera Fusarium, Mucor, Absidia, Cladosporium, Trichodenna, Acremonium, Zygorhynchus and Paecilomyces were commonly isolated on litter and soil. Commonly isolated fungi had proteolytic and urease activity, and approximately half had cellulose and lignin decay abilities. Management improvements induced shifts in the isolation frequency of these fungi, resulting in an increase in more general resource fungi, capable of growth on both litter and soil. Management improvements to haymeadows, may also have reduced species diversity of litter fungi. Agar and microcosm experiments established that changes in fungal community structure observed in the field could be in response to changes in plant litter inputs and applications of NPK fertiliser. Pairings of fungi on PDA showed that there was a combative hierarchy amongst the fungi, but was not able to show if this hierarchy was affected by NPK. A field experiment found no response of the soil microbial community to short term applications (2 years) of fertiliser or fungicide. The findings of this study suggest that management improvements to grasslands will induce changes in microbial and fungal community structure, this will be discussed.
246

Den lilla kemifabriken : En studie för att undersöka om nyttan av skogsrester kan ökas i norra Sveriges inland

Häggkvist, Sofie January 2016 (has links)
The background of this work is to suggest ways to take care of branches and tops of trees that today are left out in the north of Sweden after logging because it has to low value to be worth transporting. A solution to this is to place small chemical factories in the sparsely populated areas in the inland of Norrland that can take care of the forest residues and break it into valuable chemicals directly in the forest an then transport it to a market. The aim of this work was to find out if it´s a good idea to invest in these small chemical factories in the north of Sweden. This study has been carried out using literature study and interviews of key people. The largest part of the result comes from the interviews. The results of this study show that the small chemical factory is a good idea. Forest residues contains many valuable substances that should be greater used today. The results section of the report describes various factor that are crucial for the small chemical factory and these are: the products that can be produced, what technology that is suitable, if there is an market, who should be taking care of the factory and how the inland endurance will be affected. The conclusions that can be drawn from the study is that the small chemical factory should produce high-grade-sary chemicals directed at the chemical market. It may also be noted that there is existing technology that can be used in the factories, what has been done in the laboratories today can be implemented in the factory. The market will obviously depend on which product that will be produces, but finding a suitable market should not be impossible. The inland endurance will be positively impacted, among other things, the social endurance is enhances when these small chemical factories creates job opportunities in the inland and it can lead to decreasing the emigration.
247

Financial and Environmental implications of the Food Bank incorporating the woody biomass as a heating system for their new complex

2015 December 1900 (has links)
The City of Saskatoon is challenged with large quantities of wood wastes such as demolition wastes, construction wastes, and elm tree trims. It has also been recently found that some of the elm trees in Saskatoon might have been infected with the Dutch elm disease, hence, this would lead to the cutting down of trees. The cutting of the affected elm trees will definitely increase the quantities of wood wastes in Saskatoon. The City of Saskatoon might therefore develop the initiative to develop more landfills, as all wood wastes are usually deposited into the landfills. Landfills are usually not environmental friendly, hence, no one wants a landfill in his backyard. Furthermore, the concerns about climate change is also a pressing issue around the world as individual countries most especially the industrialised countries are looking for means to reduce their carbon foot prints. The two issues discussed above have therefore developed the initiatives for renewable energy sources as an alternative to the burning of fossil fuel to produce energy. One of the common alternatives to burning of fossil fuel is the biomass fuel specifically the woody biomass fuel (wood chips). This project is therefore developed as one of the initiatives to evaluate the feasibility of wood chips as an energy source in Saskatoon.
248

Predicting behaviors and effects of biomass burning

Davis, Aika Yano 27 May 2016 (has links)
Wildfires and prescribed burns are important sources of air pollutants and can significantly affect air quality at urban locations across large regions. Air quality forecasts generated with Eulerian numerical models can provide valuable information to environmental regulators and land managers about the potential impacts of fires. However, the ability of these models to simulate concentrated fire-related smoke plumes is limited since they lack fire specific physics and chemistry. A sub-grid plume model was coupled with a chemical transport model to address this issue. The modeling framework centered on a fire plume transport model, Daysmoke, and the Community Multiscale Air Quality modeling system (CMAQ) is used to simulate several fire episodes. The studied episodes were used to understand uncertainty in fire emissions and its effect on plume transport modeling and to verify the coupled system’s performance. The system was also used to simulate prescribed burning scenarios with five varying parameters: age of fuel bed, season, acreage, ignition type, and time of the day. Key findings relating to burn efficiency and emission reduction on future prescribed burnings will be discussed.
249

An Experimental Study of Catalytic Effects on Reaction Kinetics and Producer Gas in Gasification of Coal-Biomass Blend Chars with Steam

Zhang, Ziyin January 2011 (has links)
The objective of this thesis is to experimentally investigate the performance of steam gasification of chars of pure coal (lignite, sub-bituminous), pure biomass (radiata pine, eucalyptus nitens) and their blends. The influences of gasification temperature, types of coal and biomass, coal-biomass blending ratio, alkali and alkaline earth metal (AAEM) in lignite, on specific gasification characteristics (producer gas composition and yield, char reactivity) were studied. In addition, synergistic effects in co-gasification of coal-biomass blend char were also investigated. This project is in accordance with objectives of the BISGAS Consortium. In this study, experiments were performed in a bench-scale gasifier at gasification temperatures of 850°C, 900°C and 950°C, respectively. Two types of coals (lignite and sub-bituminous) and two kinds of biomass (radiata pine and eucalyptus nitens) from New Zealand were selected as sample fuels. From these raw materials, the chars with coal-to-biomass blending ratios of 0:100 (pure coal), 20:80, 50:50, 80:20 and 100:0 (pure biomass), which were derived through the devolatilization at temperature of 900°C for 7 minutes, were gasified with steam as gasification agent. During the gasification tests, the producer gas composition and gas production were continuously analysed using a Micro gas chromatograph. When the gas production was undetectable, the gasification process was assumed to be completed and the gasification time was recorded. The gasification producer gas consisted of three main gas components: hydrogen (H2), carbon monoxide (CO) and carbon dioxide (CO2). The results from gasification of chars of individual solid fuels (coal or biomass) confirmed that biomass char gasification was faster than coal char gasification. The influences of gasification temperatures were shown as: when gasification temperature increased, the H2 yield increased in coal char gasification but decreased in biomass char gasification. In the meantime, CO yields increased while CO2 yields decreased in both coal char and biomass char gasification. In addition, the char reactivity of all the pure fuel samples increased with elevated gasification temperatures. The results from co-gasification of coal-biomass blend char exhibited that the syngas production rate, which is defined as the total gas production divided by the gasification completion time, was enhanced by an increase in gasification temperatures as well as an increase in the biomass proportion in the blend. The AAEM species played a significant catalytic role in both gasification of pure coal chars and co-gasification of coal-biomass blend chars. The presence of AAEM increased the producer gas yield and enhanced the char reactivity. The positive synergistic effects of the coal-biomass blending char on syngas production rate only existed in the co-gasification of lignite-eucalyptus nitens blend chars. The other blend chars showed either insignificant synergistic effects or negative effects on the syngas production rate.
250

Fischer-Tropsch Based Biomass to Liquid Fuel Plants in the New Zealand Wood Processing Industry Based on Microchannel Reactor Technology

Penniall, Christopher Leigh January 2013 (has links)
This research forms part of a programme of work at the University of Canterbury investigating the production of liquid fuels from biomass. The drivers for this research are the plentiful supply of woody biomass in New Zealand as well as the necessity for a reduction in the use of fossil fuels. Fischer-Tropsch synthesis has been chosen as the base conversion method for syngas to liquid fuels. While Fischer-Tropsch plants are traditionally very large, the low geographical density of the biomass feedstock necessitates a shift from a traditional economies of scale approach. In this research a sawmill integrated polygeneration scenario is proposed that recognises the synergy between the heat and electrical requirements of a mill and the Fischer-Tropsch process that can supply both as well as liquid fuels. Techno-economic modelling of variations to this polygeneration arrangement were performed using a traditional Fischer-Tropsch slurry reactor as the basis. The breakeven price of syncrude produced in the process based on a 30 year plant life and 10% discount factor was as low as $US 167 per barrel. This arrangement is coupled with development of and experimentation with a microchannel reactor in a further attempt to overcome economies of scale disadvantages. The lab scale microchannel reactor consisted of a shim with 50 channels of 37mm length with 0.2mm height and 0.3mm width. The microchannel reactor was tested with shorter run periods to compare different catalyst washcoats consisting of neat cobalt, cobalt on titania and a combustion synthesis method over a temperature range of 210-240°C at 20 bar. Comparison was also made to a lab scale fixed bed reactor with a powdered cobalt on titania catalyst. The neat cobalt washcoat proved to have the best performance per unit mass of catalyst of the three washcoats. The performance of the microchannel reactor was 32-40 times better per unit catalyst mass than the fixed bed reactor. From data based on the shorter runs the neat cobalt washcoat and the cobalt on titania washcoat were selected for further analysis over longer runs at a range of pressures from 2-20 bar and temperatures from 210-240°C. These runs were each approximately 70 hours long and provided a better analysis of the narrowed catalyst choice. The productivity results of the catalysts were fitted to established kinetic equations from literature with an excellent correlation. More accurate Anderson-Schultz-Flory selectivity values were also obtained ranging between 0.72 to 0.82. This is certainly an area that would warrant further attention as a higher selectivity has a very positive affect on plant economics. Establishment of the kinetic equations for the catalyst performance allowed modelling of reactors with greater volume along with investigation of mass transfer limitations to assist in scale up of the technology. It was found that under 4-5mm hydraulic diameter channel dimensions the mass transfer limitation from the bulk gas phase to the catalyst interface is negligible. A scaled up microchannel reactor concept design is proposed utilising stainless steel mesh folded into 2mm channels to increase catalyst surface area compared to straight shim. A costing correlation was produced per unit of reactor volume to allow a full scale cost of the microchannel reactor to be estimated for inclusion into the techno-economic model. The revised techno-economic model was optimised through pressure variation to give a breakeven syncrude value of $US118 per barrel at Fischer-Tropsch reaction conditions of 10 bar and 240°C. This brings the value well within historical crude price trends.

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