Retrofitting Practice of a 100kWth Coal/Biomass Air-firing Combustor to the Oxy-firing Mode: Experiences and the Experimental Results

Air-firing of the fossil fuels results to relatively low concentration of CO2 in flue gases which make the capture of CO2 difficult and expensive. Oxy-firing combustion is a novel method of using enriched oxygen for coal/biomass combustion with Recycled Flue Gases (RFG) to control the adiabatic flame temperature and to increase the CO2 concentration of the off-gases up to a 60-70% oxy-firing mode (compared to air-fired mode, around 12-14%). This new technology is being applied at Cranfield University to retrofit an existing 100kWth air-firing combustor to the oxy-firing mode. This paper presents the procedure of the modifications applied on the combustor and the excellent results obtained for co-firing of pulverised coal and biomass in this rig

Oxy-combustion studies into the co -firing of coal and biomass blends: Effects on heat transfer, gas and ash compositions

Oxy-combustion with coal and biomass co-firing is a technology that could revolutionize fossil fuel power generation. It can significantly reduce harmful greenhouse gas emissions and permit the continued use of plentiful coal supplies and thereby secure our future energy needs without the severe environmental impacts expected if fossil fuels are used without CCS. The work presented here was conducted by means of experimental tests co-firing coal and biomass under oxy-firing conditions at the retrofitted 100kWth oxy-combustor facility at Cranfield University. A parametric study was performed with respect to the effect of recycled ratio and fuel variability on gas composition (including SO3), temperatures, heat flux, burn-out and ash deposition. Furthermore, the possible compensation in heat transfer resulting from the higher heat capacity and emissivity of the gases in the oxy-combustion process as compared to the air-firing case was explored. This was done by the use of blends of coal and biomass, and we concluded that this compensation is unlikely to be significant due to the marked differences between heat fluxes reached under air and oxy-firing conditions

Oxy-combustion studies into the co -firing of coal and biomass blends: Effects on heat transfer, gas and ash compositions

Oxy-combustion with coal and biomass co-firing is a technology that could revolutionize fossil fuel power generation. It can significantly reduce harmful greenhouse gas emissions and permit the continued use of plentiful coal supplies and thereby secure our future energy needs without the severe environmental impacts expected if fossil fuels are used without CCS. The work presented here was conducted by means of experimental tests co-firing coal and biomass under oxy-firing conditions at the retrofitted 100kWth oxy-combustor facility at Cranfield University. A parametric study was performed with respect to the effect of recycled ratio and fuel variability on gas composition (including SO3), temperatures, heat flux, burn-out and ash deposition. Furthermore, the possible compensation in heat transfer resulting from the higher heat capacity and emissivity of the gases in the oxy-combustion process as compared to the air-firing case was explored. This was done by the use of blends of coal and biomass, and we concluded that this compensation is unlikely to be significant due to the marked differences between heat fluxes reached under air and oxy-firing conditions

Oxy-fuel Combustion for Carbon Capture and Sequestration (CCS) from a Coal/Biomass Power Plant: Experimental and Simulation Studies

Oxy-fuel combustion is a promising and relatively new technology to facilitate CO2 capture and sequestration (CCS) for power plants utilising hydrocarbon fuels. In this research experimental oxy-combustion trials and simulation are carried out by firing pulverised coal and biomass and co-firing a mixture of them in a 100 kW retrofitted oxy-combustor at Cranfield University. The parent fuels are coal (Daw Mill) and biomass cereal co-product (CCP) and experimental work was done for 100 % coal (w/w), 100 % biomass (w/w) and a blend of coal 50 % (w/w) and biomass 50 % (w/w). The recirculation flue gas (RFG) rate was set at 52 % of the total flue gas. The maximum percentage of CO2 observed was 56.7 % wet basis (73.6 % on a dry basis) when 100 % Daw Mill coal was fired. Major and minor emission species and gas temperature profiles were obtained and analysed for different fuel mixtures. A drop in the maximum temperature of more than 200 K was observed when changing the fuel from 100 % Daw Mill coal to 100 % cereal co-product biomass. Deposits formed on the ash deposition probes were also collected and analysed using the environmental scanning electron microscopy (ESEM) with energy-dispersive X-ray (EDX) technique. The high sulphur, potassium and chlorine contents detected in the ash generated using 100 % cereal co-product biomass are expected to increase the corrosion potential of these deposits. In addition, a rate-based simulation model has been developed using Aspen Plus® and experimentally validated. It is concluded that the model provides an adequate prediction for the gas composition of the flue gas

Changes in copepod distributions associated with increased turbulence from wind stress

Vertical profiles of turbulent kinetic energy dissipation rate (ε), current velocity, temperature, salinity, chlorophyll fluorescence, and copepods were sampled for 4 d at an anchor station on the southern flank of Georges Bank when the water column was stratified in early June 1995. Copepodite stages of Temora spp., Oithona spp., Pseudocalanus spp., and Calanus finmarchicus, and all of their naupliar stages except for Temora spp., were found deeper in the water column when turbulent dissipation rates in the surface mixed layer increased in response to increasing wind stress. Taxa that initially occurred at the bottom of the surface mixed layer at 10 to 15 m depth ( ε ¾ 10-8 W kg-1) before the wind event were located in the pycnocline at 20 to 25 m depth when dissipation rates at 10 m increased up to 10-6 W kg-1. Dissipation rates in the pycnocline were similar to those experienced at shallower depths before the wind event. After passage of the wind event and with relaxation of dissipation rates in the surface layer, all stages returned to prior depths above the pycnocline. Temora spp. nauplii did not change depth during this period. Our results indicate that turbulence from a moderate wind event can influence the vertical distribution of copepods in the surface mixed layer. Changes in the vertical distribution of copepods can impact trophic interactions, and movements related to turbulence would affect the application of turbulence theory to encounter and feeding rates

Tectonics of Atlantic Canada

The tectonic history of Atlantic Canada is summarized according to a model of multiple ocean opening-closing cycles. The modern North Atlantic Ocean is in the opening phase of its cycle. It was preceded by an early Paleozoic lapetus Ocean whose cycle led to formation of the Appalachian Orogen. lapetus was preceded by the Neoproterozoic Uranus Ocean whose cycle led to formation of the Grenville Orogen. The phenomenon of coincident, or almost coincident orogens and modern continental margins that relate to repeated ocean opening-closing cycles is called the Accordion Effect. An understanding of the North Atlantic Ocean and its continental margins provides insights into the nature of lapetus and the evolution of the Appalachian Orogen. Likewise, an understanding of lapetus and the Appalachian Orogen raises questions about Uranus and the development of the Grenville Orogen. Modern tectonic patterns in the North Atlantic may have been determined by events that began before 1000 m.y. Résumé L'histoire tectonique de la portion atlantique du Canada est présenté comme la résultante d'une série d'ouvertures et de fermetures océaniques. Selon ce modèle tectonique, l'Atlantique nord moderne serait actuellement dans sa phase d'ouverture. Au début du Paléozoïque, le cycle précédent de l'océan lapétus a engendré l'orogène des Appalaches. L'océan lapétus a été précédé au Néoprotérozoïque par l'océan Uranus, dont le cycle d'ouverture-fermeture a engendré l'orogène de Grenville. Le phénomène de coïncidence ou quasi-coïncidence du profil des diverses orogènes et des marges continentale modernes qui correspond aux multiples cycles d'ouvertures-fermetures se nomme l'effet accordéon. La connaissance de l'océan Atlantique nord et de ses marges continentales permet d'appréhender certaines caractéristiques de la nature de l'océan lapétus et de l'orogène appalachîen. De même, une connaissance de l'océan lapétus et de l'orogène appalachîen suscite des pistes de questionnement sur l'océan Uranus et l'orogène de Grenville. Les profils de l'océan Atlantique nord actuelle pourrait bien être le résultat d'événements qui auraient débuté il y a environ 1 000 Ma

Seismic anisotropy of the Canadian High Arctic : evidence from shear-wave splitting

FD is supported by the Natural Sciences and Engineering Research Council of Canada (NSERC/CRSNG) through its Discovery Grant and Canada Research Chair programmes [10.13039/501100000038](341802-2013-RGPIN). Data from the ELLITE stations and some of the long-term stations (Scripps Inst. Oceanography, 1986; Stephenson et al., 2013) are available through the IRIS Data Management Center; the remaining Canadian data are available through the Canadian National Data Centre, Natural Resources Canada (Geological Survey of Canada, 1989). ELLITE instrumentation was loaned to the project by SEIS-UK and the project received support from De Beers Canada and the University of Aberdeen. The ELLITE project was carried out as part of the Circum-Arctic Lithosphere Evolution (CALE) programme, and supported by Natural Resources Canada's GEM-1 programme, which also supported JMD's MSc funding. We thank the Editor and the three reviewers for their helpful comments which improved the manuscript.Peer reviewedPostprin