A theoretical analysis of the burn-out times of an isothermal particle of coal char under air-firing, gasification and oxyfuel combustion in fluidised beds

<p></p><p>The combustion of coal in air, its gasification with carbon dioxide, and oxyfuel combustion in oxygen/carbon dioxide mixtures was studied at high process temperatures in a bubbling fluidised bed reactor where burning is controlled by external mass transfer conditions. Theoretical analysis of the burn-out times of an isothermal particle of coal char in air is provided for the case where a fraction of carbon monoxide is oxidized close to the char particle. Burn-out time equations are provided for the gasification of char in carbon dioxide. Both burn-out time equations are compared to analytical equations derived for the oxy-fuel combustion of char particles in oxygen/carbon dioxide mixtures. The results are particularly relevant for retrofitting existing bubbling fluidised bed reactors for sustainable energy generation to meet global warming targets. </p><p></p>

A Simple Theoretical Analysis of the Burn-out Times of an Isothermal Particle of Coal Char Under Air-Firing, Gasification and Oxyfuel Combustion in Fluidised Beds

<p></p><p>Coal combustion in air, gasification with carbon dioxide, and oxyfuel combustion in oxygen/carbon dioxide mixtures was studied at high process temperatures in a bubbling fluidised bed reactor where burning is controlled by external mass transfer conditions. Theoretical analysis of the burn-out times of an isothermal particle of coal char in air is provided for the case where a fraction of carbon monoxide is oxidized close to the char particle. Burn-out time equations are provided for the gasification of char in carbon dioxide. Both burn-out time equations are compared to analytical equations derived for the oxy-fuel combustion of char particles in oxygen/carbon dioxide mixtures. The results are particularly relevant for retrofitting existing bubbling fluidised bed reactors for clean energy generation to meet global warming targets.</p><p></p>

A Simple Theoretical Analysis of the Burn-out Times of an Isothermal Particle of Coal Char Under Air-Firing, Gasification and Oxyfuel Combustion in Fluidised Beds

<p></p><p>Coal combustion in air, gasification with carbon dioxide, and oxyfuel combustion in oxygen/carbon dioxide mixtures was studied at high process temperatures in a bubbling fluidised bed reactor where burning is controlled by external mass transfer conditions. Theoretical analysis of the burn-out times of an isothermal particle of coal char in air is provided for the case where a fraction of carbon monoxide is oxidized close to the char particle. Burn-out time equations are provided for the gasification of char in carbon dioxide. Both burn-out time equations are compared to analytical equations derived for the oxy-fuel combustion of char particles in oxygen/carbon dioxide mixtures. The results are particularly relevant for retrofitting existing bubbling fluidised bed reactors for clean energy generation to meet global warming targets.</p><p></p>

The Caribbean and 1.5 °C: Is SRM an Option?

The Caribbean, along with other small island developing states (SIDS), have advocated for restricting global warming to 1.5 °C above pre-industrial levels by the end of the current century. Solar radiation management (SRM) may be one way to achieve this goal. This paper examines the mean Caribbean climate under various scenarios of an SRM-altered versus an SRM-unaltered world for three global warming targets, namely, 1.5, 2.0 and 2.5 °C above pre-industrial levels. Data from the Geoengineering Model Intercomparison Project Phase 1 (GeoMIP1) were examined for two SRM scenarios: the G3 experiment where there is a gradual injection of sulfur dioxide (SO2) into the tropical lower stratosphere starting in 2020 and terminating after 50 years, and the G4 experiment where a fixed 5 Teragram (Tg) of SO2 per year is injected into the atmosphere starting in 2020 and ending after 50 years. The results show that SRM has the potential to delay attainment of the 1.5, 2.0 and 2.5 °C global warming targets. The extent of the delay varies depending on the SRM methodology but may be beyond mid-century for the 1.5 °C goal. In comparison, however, the higher temperature thresholds are both still attained before the end of century once SRM is ceased, raising questions about the value of the initial delay. The application of SRM also significantly alters mean Caribbean climate during the global warming target years (determined for a representative concentration pathway 4.5 (RCP4.5) world without SRM). The Caribbean is generally cooler but drier during the 1.5 °C years and similarly cool but less dry for years corresponding to the higher temperature targets. Finally, the mean Caribbean climate at 1.5 °C differs if the global warming target is achieved under SRM versus RCP4.5. The same is true for the higher warming targets. The implications of all the results are discussed as a background for determining whether SRM represents a viable consideration for Caribbean SIDS to achieve their “1.5 to stay alive” goal.

An Overview of Bioenergy with Carbon Capture and Storage Process as a Negative Emission Technology

Projections of the pathways that reduce carbon emission to the levels consistent with limiting global average temperature increases to 1.5°C or 2°C above پاره-p990industrial levels often require negative emission technologies like bioenergy with carbon capture and storage (BECCS), it involves the conversion of biomass to energy, producing CO2 which is sequestered, transported and then permanently stored in a suitable geological formation. The potential of BECCS to remove CO2 from the atmosphere makes it an attractive approach to help achieving the ambitious global warming targets of COP 21. BECCS has a range of variables such as the type of biomass resource, the conversion technology, the CO2 capture process used and storage options. Each of the pathways to connect these options has its own environmental, economic and social impacts. This study gives an overview of Bioenergy with carbon capture and storage for the purpose of carbon mitigation while the challenges associated with using biomaterial was assessed, such as land use, water consumption and its economic constraints. The more certain way forward to underpin BECCS deployment, is to ensure that there is strong social support and integrated policy schemes that recognize, support and reward negative emission, for without negative emissions delivered through BECCS and perhaps other technologies, there is little prospect of the global targets agreed to at Paris, being met.