scholarly journals 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

2021 ◽  
Author(s):  
Toyin Omojola
Keyword(s):  
Carbon Dioxide ◽  
Theoretical Analysis ◽  
Coal Combustion ◽  
Coal Char ◽  
Fluidised Bed ◽  
Oxyfuel Combustion ◽  
Burn Out ◽  
Char Particle ◽  
Fluidised Beds ◽  
Fluidised Bed Reactor

<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. </p>

scholarly journals 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

2021 ◽  
Author(s):  
Toyin Omojola
Keyword(s):  
Carbon Dioxide ◽  
Theoretical Analysis ◽  
Coal Combustion ◽  
Coal Char ◽  
Fluidised Bed ◽  
Oxyfuel Combustion ◽  
Burn Out ◽  
Char Particle ◽  
Fluidised Beds ◽  
Fluidised Bed Reactor

<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 is considered. 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. </p>

scholarly journals 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

2021 ◽  
Author(s):  
Toyin Omojola
Keyword(s):  
Carbon Dioxide ◽  
Theoretical Analysis ◽  
Coal Char ◽  
Fluidised Bed ◽  
Oxyfuel Combustion ◽  
Burn Out ◽  
Char Particle ◽  
Global Warming Targets ◽  
Fluidised Beds ◽  
Fluidised Bed Reactor

<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>

scholarly journals 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

2021 ◽  
Author(s):  
Toyin Omojola
Keyword(s):  
Carbon Dioxide ◽  
Theoretical Analysis ◽  
Clean Energy ◽  
Coal Char ◽  
Fluidised Bed ◽  
Oxyfuel Combustion ◽  
Burn Out ◽  
Global Warming Targets ◽  
Fluidised Beds ◽  
Fluidised Bed Reactor

<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>

scholarly journals 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

2021 ◽  
Author(s):  
Toyin Omojola
Keyword(s):  
Carbon Dioxide ◽  
Theoretical Analysis ◽  
Clean Energy ◽  
Coal Char ◽  
Fluidised Bed ◽  
Oxyfuel Combustion ◽  
Burn Out ◽  
Global Warming Targets ◽  
Fluidised Beds ◽  
Fluidised Bed Reactor

<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>

scholarly journals Reduction of carbon dioxide emission through the sorption in situ using a fluidised bed reactor

2008 ◽  
Vol 10 (4) ◽  
Author(s):  
Witold Żukowski ◽  
Sylwia Englot ◽  
Jerzy Baron ◽  
Stanisław Kandefer ◽  
Małgorzata Olek
Keyword(s):  
Carbon Dioxide ◽  
Carbon Dioxide Emission ◽  
Fluidised Bed ◽  
Fluidised Bed Reactor

Gasification Kinetics of Victorian Brown Coal-Derived Char in Fluidised Bed Reactor

2021 ◽  
pp. 1-24
Author(s):  
Imtenan Sayeed ◽  
Mahmud Arman Kibria ◽  
Sankar Bhattacharya
Keyword(s):  
Activation Energy ◽  
Brown Coal ◽  
Gas Flow ◽  
Oxygen Carrier ◽  
Fluidised Bed ◽  
Co2 Partial Pressure ◽  
Fuel Reactor ◽  
Char Particle ◽  
Fluidised Bed Reactor ◽  
Kinetics Of

Abstract In a chemical looping combustion (CLC) system, gasification kinetics of char holds immense importance being the rate-limiting reaction in the fuel reactor. This paper studied the gasification kinetics of char derived from Victorian Brown Coal (VBC) in a fluidised bed reactor which mimics the fuel reactor conditions of a CLC process. Mass of char, char particle size and gas flow conditions were optimised to ensure the gasification reaction free from mass transfer limitations. Effect of oxygen carrier, hematite, being the bed material was also studied. The experiments were conducted in the temperature range of 800C-950C, which is a typical range for fuel reactor. The experimental results were modelled with the help of grain model (GM) and random pore model (RPM) to analyse the kinetic parameters. Activation energy was found to be around 177 kJ/mol in sand bed and 175.5 kJ/mol in the hematite bed. Reaction in hematite bed was found to be 42% faster on average compared to the reaction in a sand bed. Fastest total conversion of char took as low as 4.1 minutes in hematite bed at 950C. While catalytic effect of hematite was ruled out due to insignificant change in activation energy, it was concluded that increase in CO2 partial pressure at the vicinity of char particle enhanced the reaction rate in the case of hematite bed. This study has generated relevant information for the CLC of Victorian Brown Coal with hematite as the oxygen carrier.

The Optimisation of Pressure Measurements for the Control of Bubbling Fluidised Beds

2005 ◽  
Vol 3 (1) ◽  
Author(s):  
Anthony J Croxford ◽  
Andrew J.L. Harrison ◽  
Mark A Gilbertson
Keyword(s):  
Chemical Reactor ◽  
The State ◽  
Wall Effect ◽  
Pressure Measurements ◽  
Fluidised Bed ◽  
Local Dynamics ◽  
Fluidised Beds ◽  
Fluidised Bed Reactor

A common form of chemical reactor is the bubbling fluidised bed where gas is introduced into a free bed of particles at a rate exceeding that necessary to support their weight. The behaviour of the reactor is dependent on the distribution and characteristics of the bubbles within the bed. Information about these can be inferred from pressure measurements within the bed, which can also be used to characterise the dynamics of a bed and therefore to control it and the reaction.It is necessary to understand what the pressure signals are measuring, how many of them are necessary, and where they should be placed for them to be used to characterise the state of the bed. Pressure measurements are made at single points within a bed, and it is not immediately clear whether the measurements are local (owing to some sort of wall effect, for example), characterise the region close to the sensor, or the whole bed. It is shown how the dynamics of the bed can be characterised from the pressure signals, and that these signals are sensitive to the state of the bed. It is also necessary to evaluate where the sensors should be placed and how many of them should be used. Important considerations here are the extent to which the measurements of pressure are axisymmetrical, and whether in some circumstances and positions the local dynamics mask the overall bed dynamics. Axisymmetry is shown to exist under many conditions and that a single transducer can be sufficient. Furthermore, the depth of the bed is also shown to have a significant effect on its dynamics.It is also shown how the characterised pressure measurements can be used to control the state of the fluidised bed and used to enhance the performance of a fluidised bed reactor.

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