title: Pyrolysis of Sawdust

authors: Sichone, Kavwa

abstract: Lakeland Steel Limited developed a pilot plant for biomass pyrolysis based on sawdust. The pilot plant was based on an auger screw design which was indirectly heated using a double pipe heat exchange configuration to prevent oxidation (combustion) of the feedstock. This thesis covers the preliminary assessment of sawdust pyrolysis for R.H Tregoweth sawmills on behalf of Lakeland Steel Limited. 
Proximate and ultimate analyses were deployed on the sawdust to determine its composition. Proximate analysis results gave a moisture content of 60%. The dry solids had an organic matter content of 99.22% with ash making the balance. Ultimate analysis was used to determine content levels of elemental carbon, hydrogen, nitrogen sulphur and oxygen. The results on a dry basis were 47.2%, 6.5%, 0.3%, 0.3%, and 44.9 % respectively. 
Drying models were also used to analyse the sawdust drying characteristics. Drying curves were obtained experimentally and four models: Newton; Page; Henderson and Pabis; and Simpson and Tschernitz, were fitted to the data and their accuracy of fit was determined using residual squared sum of errors.  Page’s model was used to describe the sawdust behaviour in the dryer design as it had the highest accuracy.
The sawdust reaction kinetics were determined using data from thermogravimetric analysis (TGA) and analysed using distributed action energy model. The kinetics were observed at three heating rates of 10, 20 and 30 °C/min with a maximum temperature of 900°C under an argon atmosphere. Sawdust was modelled as a mixture of water, hemicellulose, cellulose  and lignin. Good agreement between Gaussian distribution functions for each component and experimental data were observed. 
Pilot plant trials were performed using a three factor-three level design of experiment. The factors under investigation were; feedstock moisture content with levels at 15, 30 and 60; reaction temperature with levels at 400, 450 and 500°C; and reactor auger speed with levels at 15, 20 and 25 rpm. Experiments at 60% moisture could not be performed to completion as the auger blocked repeatedly. The other two moisture contents showed that moisture content enhanced heat exchange properties of the feedstock and this generally increased the amount of volatile organic matter released. It was observed that for 15% moisture sawdust increase of temperature did not consistently exhibit an increase in degree of devolatilisation of organic matter. However, the 30% moisture sawdust showed an increase in devolatilisation with increase in temperature.  The effects of increasing reactor auger speed had the most consistent trend with which an increase in speed showed a decrease in degree of devolatilisation thus increasing char yield.
The empirical data collected from lab scale and pilot plant experiments were used to create mass and energy balances. These were the basis of the large scale mobile pyrolysis plant which was designed to process 3.45 tonnes per hour. Due to size restrictions the large scale dryer was not fitted in the container. It was then determined that the feedstock would either be dried using an onsite kiln or the reactor would process green sawdust.

A preliminary economic feasibility assessment was performed for the base case scenario which processed pre-dried sawdust of 15% moisture content at 400°C and a retention time of 45 minutes. A sensitivity analysis based on predicted optimistic and pessimistic conditions showed that automation of the plant had the potential to increase the economic viability of the large scale process.

text: Pyrolysis of Sawdust Lakeland Steel Limited developed a pilot plant for biomass pyrolysis based on sawdust. The pilot plant was based on an auger screw design which was indirectly heated using a double pipe heat exchange configuration to prevent oxidation (combustion) of the feedstock. This thesis covers the preliminary assessment of sawdust pyrolysis for R.H Tregoweth sawmills on behalf of Lakeland Steel Limited. 
Proximate and ultimate analyses were deployed on the sawdust to determine its composition. Proximate analysis results gave a moisture content of 60%. The dry solids had an organic matter content of 99.22% with ash making the balance. Ultimate analysis was used to determine content levels of elemental carbon, hydrogen, nitrogen sulphur and oxygen. The results on a dry basis were 47.2%, 6.5%, 0.3%, 0.3%, and 44.9 % respectively. 
Drying models were also used to analyse the sawdust drying characteristics. Drying curves were obtained experimentally and four models: Newton; Page; Henderson and Pabis; and Simpson and Tschernitz, were fitted to the data and their accuracy of fit was determined using residual squared sum of errors.  Page’s model was used to describe the sawdust behaviour in the dryer design as it had the highest accuracy.
The sawdust reaction kinetics were determined using data from thermogravimetric analysis (TGA) and analysed using distributed action energy model. The kinetics were observed at three heating rates of 10, 20 and 30 °C/min with a maximum temperature of 900°C under an argon atmosphere. Sawdust was modelled as a mixture of water, hemicellulose, cellulose  and lignin. Good agreement between Gaussian distribution functions for each component and experimental data were observed. 
Pilot plant trials were performed using a three factor-three level design of experiment. The factors under investigation were; feedstock moisture content with levels at 15, 30 and 60; reaction temperature with levels at 400, 450 and 500°C; and reactor auger speed with levels at 15, 20 and 25 rpm. Experiments at 60% moisture could not be performed to completion as the auger blocked repeatedly. The other two moisture contents showed that moisture content enhanced heat exchange properties of the feedstock and this generally increased the amount of volatile organic matter released. It was observed that for 15% moisture sawdust increase of temperature did not consistently exhibit an increase in degree of devolatilisation of organic matter. However, the 30% moisture sawdust showed an increase in devolatilisation with increase in temperature.  The effects of increasing reactor auger speed had the most consistent trend with which an increase in speed showed a decrease in degree of devolatilisation thus increasing char yield.
The empirical data collected from lab scale and pilot plant experiments were used to create mass and energy balances. These were the basis of the large scale mobile pyrolysis plant which was designed to process 3.45 tonnes per hour. Due to size restrictions the large scale dryer was not fitted in the container. It was then determined that the feedstock would either be dried using an onsite kiln or the reactor would process green sawdust.

A preliminary economic feasibility assessment was performed for the base case scenario which processed pre-dried sawdust of 15% moisture content at 400°C and a retention time of 45 minutes. A sensitivity analysis based on predicted optimistic and pessimistic conditions showed that automation of the plant had the potential to increase the economic viability of the large scale process.

year: 2013

title: Psychrophilic and psychrotrophic Clostridium spp. associated with meat spoilage

authors: Broda, Dorota Maria

abstract: Twenty two isolates of psychrophilic and psychrotrophic Clostridium spp. associated with ‘blown pack’ spoilage of vacuum-packed meats were studied with respect to their identification, differentiation and taxonomy, as well as spoilage aetiology. The aetiological study was conducted to establish whether a causal relationship exists between psychrophilic and psychrotrophic clostridia and the production of abundant gas in vacuum-packed chilled meats. The attempt was then made to identify these clostridia using conventional microbiological methods. Genotypic approaches to differentiation of psychrophilic and psychrotrophic clostridia at inter- and intra-species level were evaluated and applied to tracing the ‘blown pack’ spoilage causing clostridia back to their contamination source in the abattoir. Where phenotypic and genotypic characteristics indicated that some isolates of psychrophilic and psychrotrophic clostridia differed from those previously described, taxonomic studies were conducted to determine whether these isolates could be described as new clostridial species. Four clostridial isolates were found to cause premature vacuum pack distension during chilled storage. Conventional phenotype based methods were found to be ineffective for identification of psychrophilic and psychrotrophic clostridia. Although RFLP analysis of the amplified 16S rDNA gene allowed differentiation of psychrophilic and psychrotrophic clostridia at the genotypic species level and below, comparison of PCR-RFLP patterns and 16S rDNA sequences of meat isolates with patterns and sequences of reference strains did not effect ready identification of some of these microorganisms. Consequently, the use of these methods for identification of unknown clostridial isolates needs to be approached carefully. Differentiation of some meat-derived isolates of psychrophilic and psychrotrophic clostridia at intra-species or inter-strain level was achieved with methods based on polymorphism of genomic DNAs and/or the 16S-23S rDNA internal transcribed spacers from these organisms. With the 16S-23S rDNA internal transcribed spacer polymorphism analysis, inter-species differentiation of psychrophilic and psychrotrophic clostridia may be achieved in instances where little inter-strain variation is expected e.g. in typing of isolates from the same meat plant or spoilage incident. Hides and faeces of slaughter animals were identified as an abundant abattoir source of psychrophilic and psychrotrophic clostridia representing many species. Seven isolates of these microorganisms, representing four distinct taxonomic groups, were found to differ in their phenotypic, genotypic and phylogenetic characteristics from known clostridial species. With a polyphasic approach, three new clostridial species, C. frigidicarnis, C. gasigenes and C. algidixylanolyticum have been named and characterised. It is hoped that this study has added to our understanding of the aetiology and causative agents of ‘blown pack’ spoilage and, thus, has advanced the process of developing measures to control this type of spoilage of vacuum packed chilled meats.

text: Psychrophilic and psychrotrophic Clostridium spp. associated with meat spoilage Twenty two isolates of psychrophilic and psychrotrophic Clostridium spp. associated with ‘blown pack’ spoilage of vacuum-packed meats were studied with respect to their identification, differentiation and taxonomy, as well as spoilage aetiology. The aetiological study was conducted to establish whether a causal relationship exists between psychrophilic and psychrotrophic clostridia and the production of abundant gas in vacuum-packed chilled meats. The attempt was then made to identify these clostridia using conventional microbiological methods. Genotypic approaches to differentiation of psychrophilic and psychrotrophic clostridia at inter- and intra-species level were evaluated and applied to tracing the ‘blown pack’ spoilage causing clostridia back to their contamination source in the abattoir. Where phenotypic and genotypic characteristics indicated that some isolates of psychrophilic and psychrotrophic clostridia differed from those previously described, taxonomic studies were conducted to determine whether these isolates could be described as new clostridial species. Four clostridial isolates were found to cause premature vacuum pack distension during chilled storage. Conventional phenotype based methods were found to be ineffective for identification of psychrophilic and psychrotrophic clostridia. Although RFLP analysis of the amplified 16S rDNA gene allowed differentiation of psychrophilic and psychrotrophic clostridia at the genotypic species level and below, comparison of PCR-RFLP patterns and 16S rDNA sequences of meat isolates with patterns and sequences of reference strains did not effect ready identification of some of these microorganisms. Consequently, the use of these methods for identification of unknown clostridial isolates needs to be approached carefully. Differentiation of some meat-derived isolates of psychrophilic and psychrotrophic clostridia at intra-species or inter-strain level was achieved with methods based on polymorphism of genomic DNAs and/or the 16S-23S rDNA internal transcribed spacers from these organisms. With the 16S-23S rDNA internal transcribed spacer polymorphism analysis, inter-species differentiation of psychrophilic and psychrotrophic clostridia may be achieved in instances where little inter-strain variation is expected e.g. in typing of isolates from the same meat plant or spoilage incident. Hides and faeces of slaughter animals were identified as an abundant abattoir source of psychrophilic and psychrotrophic clostridia representing many species. Seven isolates of these microorganisms, representing four distinct taxonomic groups, were found to differ in their phenotypic, genotypic and phylogenetic characteristics from known clostridial species. With a polyphasic approach, three new clostridial species, C. frigidicarnis, C. gasigenes and C. algidixylanolyticum have been named and characterised. It is hoped that this study has added to our understanding of the aetiology and causative agents of ‘blown pack’ spoilage and, thus, has advanced the process of developing measures to control this type of spoilage of vacuum packed chilled meats.

year: 1999

title: What does it take to make us listen? The experiences of those leading whole school reform to improve outcomes for indigenous minority students

authors: Buckley, Louise Jane

subjects: Education

abstract: This thesis examines how the Kia Eke Panuku: Building on Success school reform initiative shaped the experiences of groups of educators within mainstream New Zealand secondary schools. These experiences are analysed against a setting of colonisation and historic educational policies of assimilation and integration that have created a situation of education debt. The lack of power for Māori in education is evident. This study highlights the role of the Strategic Change Leadership Team in deconstructing power hierarchies within schools so that educational outcomes can be improved for Māori students. It presents the Strategic Change Leadership Team as the vehicle for conscientisation, resistance and transformative praxis within schools. It shows that in schools where power hierarchies were deconstructed, Māori students were able to enjoy educational success as Māori.

text: What does it take to make us listen? The experiences of those leading whole school reform to improve outcomes for indigenous minority students This thesis examines how the Kia Eke Panuku: Building on Success school reform initiative shaped the experiences of groups of educators within mainstream New Zealand secondary schools. These experiences are analysed against a setting of colonisation and historic educational policies of assimilation and integration that have created a situation of education debt. The lack of power for Māori in education is evident. This study highlights the role of the Strategic Change Leadership Team in deconstructing power hierarchies within schools so that educational outcomes can be improved for Māori students. It presents the Strategic Change Leadership Team as the vehicle for conscientisation, resistance and transformative praxis within schools. It shows that in schools where power hierarchies were deconstructed, Māori students were able to enjoy educational success as Māori.

year: 2020