Flash pyrolysis of biomass for the production of renewable chemicals

To investigate the methanolysis of biomass, a fluidised bed reactor system was designed, constructed, commissioned and operated to investigate the product distribution during operation up to temperatures of 1000 °C and pressures of 1010 kPa. The system was designed to operate with a maximum methane flowrate of 1 kg/hr and 2 kg/hr biomass, at 1000 °C and 101 kPa. The focus of the investigation of the methanolysis process was to optimize the production of carbon monoxide (CO), ethylene and benzene from pinus radiata chips, as a potential source of renewable chemicals for a range of different industries. A modular and portable reactor system was successfully constructed, which allowed for numerous experiments to be conducted. Significant variations in the biomass feed flowability was experienced between different chip sources. It was determined that the initial preparation of the chip highly influential on the flow characteristics of the final sawdust. A new methodology for the preparation of feedstocks from logs was devised and was shown to perform well, allowing for adequate feeding by gravity in a 30° hopper system. Due to the high operating temperatures, extensive methane thermal degradation (MTD) occurred, introducing significant biomass – hydrogen interactions into the reaction zone. The extent of degradation was significantly decreased by the removal of suspected catalytic surfaces and subsequent retrofitting with quartz fabrications. During reactor operation MTD was inevitable, and the concentration of hydrogen and methane was analysed throughout experiments to aid in characterisation of the products formed during methanolysis. In contrast to dropper tube reactors, the utilization of the fluidised bed reactor was observed to significantly increase the yield of target species, due to enhanced heat transfer to the gas from the fluidising sand. However, it was also noted that the increased heat transfer led to increased MTD, in turn, increasing the consumption of methane in the system. The system was optimized with the use of 710-1000 μm chips, operated at 988 °C, with a residence time of 1.5 s (0.66 s reaction zone), operating pressure of 380 kPa and a methane to biomass ratios above 4. By use of the described conditions, the CO, ethylene and benzene biomass carbon conversion yields were 46 ± 3 %, 19 ± 3 % and 8.2 ± 0.5 %. Further increases in conversion to particular species were obtained with differing operating conditions. In general the concentration of CO2 and ethane remained relatively low throughout all experiments, with average biomass carbon conversion values of 8 - 5 % and 2 - 5 %, respectively. Toluene and naphthalene were the other major tar species, with styrene, phenol, indene and biphenyl measured in low concentrations, quantification of the solids product through mass balances were also attempted. At high operating temperatures cracking of hydrocarbons is suspected to be the main cause of reduced ethylene and benzene yield; whilst, at lower temperatures the energy is not sufficient to promote hydrocarbon formation reactions. As the degradation of methane was also heavily influenced by temperature, the maximization of target species yield was likely heavily influenced by the characteristics of MTD. At residence times of approximately 1.5 s, the yield of ethylene and benzene was reduced. Likely due to insufficient time at temperature for methyl radicals formed during MTD with the species devolatilized from biomass pyrolysis. At higher residence times of 2.5 s, benzene production increased from, 11 ± 2 % to 21 ± 3 % carbon conversion, which was assumed to be due increases in the HACA (H abstraction C2H2 reaction pathway) aromatic reaction pathway, which reduced the ethylene yield due to dehydrogenation of ethylene to form acetylene. At methane to biomass ratios (M/B ratio) of < 4, decreased yields of target species were obtained. For an M/B ratio of 1.29; CO, ethylene and benzene yields decreased to 9 ± 1 %, 32 ± 2 % and 3.5 ± 0.4 %. Higher target product yields were obtained at higher M/B ratios due to a greater residence time due to a reduction in the volume of devolatilized species released at the lower biomass feed rate. This was thought to be due to the significant reduction in hydrocarbon production with decreasing M/B ratio; which was similar to observations with decreasing residence time. Stable ethylene production was observed within the operating pressures of 275-380 kPa, whereas, increases or decreases in the operating pressure led to decreased ethylene yields. This was likely due to the increased stability of ethylene in the pressure region, as a local maximum equilibrium exists within 300-450 kPa, as identified by Gibbs energy modelling. However, higher pressure led to significant aromatic tar increases, primarily benzene, where an overall increase from 9 ± 2 % to 16 ± 3 % carbon conversion was recorded for pressures of 380 kPa and 480 kPa, respectively. Higher operating pressures were suspected of increasing the aromatic tar production due to enhancement of the HACA pathway, allowing for increase aromatization reactions. Decreased chip size led to increased tar yield, whilst gas product and solids production decreased. However, larger particles were suspected of resisting the flow of volatiles from the centre core of the particle due to the larger overall pore length. It was suspected the lack of interactions of the devolatilized species resulted in a decreased ethylene and benzene production for the larger chips. The effective degradation of methane was enhanced with smaller chips, resulting in the 710-1000 μm chip being desirable for methanolysis applications. Lower yields of all target species was obtained with the use of Douglas fir, possibly due to the high mineral content of this biomass sample enhancing hydrocarbon cracking. This was suggested due to the apparent effect of mineral accumulation, ash, within the system after specific trials. The use of moist wood (atmospheric moisture), led to significant increases in the hydrogen and CO yields probably due to steam reforming of the methane feed, and highlighted the importance of ensuring the biomass feed stock was completely dry. From comparative nitrogen and methane trials the yields of ethylene, CO and benzene increased from 5 %, 26 ± 2 % and 7 ± 1 %, to, 16 ± 1 %, 56 ± 3% and 11 ± 2 %, respectively. By use of methane as the fluidising gas, it was suspected that through a series of complex pathways, the interactions with radicals may be a pathway for the production of the target species. The particular importance of methyl radicals is highlighted by the recombination reaction to form ethane, which can subsequently be dehydrogenated to ethylene and acetylene, indicating the pathway for the beginning of the HACA pathways. Tar production was also likely to originate from fragmentation of the biomass constituents during methanolysis, especially the highly aromatized lignin fraction. Overall, the conversion of biomass to products during methanolysis was difficult to quantify due to variations in MTD characteristics throughout methanolysis experiments. MTD was also determined to vary with elapsed time, indicating a possibility for a conditioning effect within the reactor, varying the product distribution until equilibrium was obtained. However, production of hydrogen via MTD in the fluidised gas stream was also suspected of facilitating desirable hydrogenation reactions as a result. Further work in the characterising of the MTD behaviour during methanolysis is required, with an emphasis on the control of the extent of degradation is highly recommended

Plasma testosterone and 11-ketotestosterone levels of male pacu Piaractus mesopotamicus (Cypriniformes, Characidae)

The levels of testosterone (T) and 11-ketotestosterone (11-KT) of the South American pacu Piaractus mesopotamicus were determined by radioimmunoassay during two stages of the reproductive cycle, i.e., resting and maturation, and the gonadosomatic index (GSI) was calculated. The highest levels of T and 11-KT were reached during the maturation stage (T = 2400 ± 56 pg/ml; 11-KT = 2300 ± 60 pg/ml) and lower levels were maintained during the resting period. The rise in androgen levels occurred with the appearance of spermatozoa in the maturation stage, when GSI was highes