Thesis Open Access

Unsteady State Kinetic Modelling of Biomass Gasification in Bubbling Fluidized Bed Gasifier

Tolossa Kebede Tulu

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  <identifier identifierType="DOI">10.20372/nadre/20595</identifier>
      <creatorName>Tolossa Kebede Tulu</creatorName>
      <affiliation>Addis Ababa Science &amp; Technology University</affiliation>
    <title>Unsteady State Kinetic Modelling of Biomass Gasification in Bubbling Fluidized Bed Gasifier</title>
  <publisher>National Academic Digital Repository of Ethiopia</publisher>
    <subject>Biomass gasification, Fluidized bed, Kinetic Modeling, Response surface,  Optimization</subject>
    <contributor contributorType="Supervisor">
      <contributorName>Samson Mekbib (PhD)</contributorName>
      <affiliation>Addis Ababa Science &amp; Technology University</affiliation>
    <date dateType="Issued">2021-06-09</date>
  <resourceType resourceTypeGeneral="Text">Thesis</resourceType>
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    <relatedIdentifier relatedIdentifierType="DOI" relationType="IsVersionOf">10.20372/nadre/20594</relatedIdentifier>
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    <rights rightsURI="">Creative Commons Attribution</rights>
    <rights rightsURI="info:eu-repo/semantics/openAccess">Open Access</rights>
    <description descriptionType="Abstract">&lt;p&gt;From available renewable energy, biomass is the most abundant and promising resource of renewable energy which is environmental friendly. From biomass conversion methods to useful energy, gasification is an adequate technology. The mathematical modeling of biomass gasification in bubbling fluidized bed can be used to predict syngas composition and optimize the operational condition as well as gasifier design, which is a cost-saving option and viable routine. However, the kinetic modeling of biomass gasification is at early phase. With this regard, the aim of this study is to develop kinetic model based on two-phase fluidization theory, which is comprised of reaction kinetics, bed hydrodynamic parameters, diffusion effect, and species transport equations. Furthermore, the thermal cracking of tar was integrated into the model to increase the prediction accuracy of the model and to address the gap in knowledge. In this study, the transient kinetic modeling of biomass gasification in bubbling fluidized bed gasifiers and optimization methods to maximize gasification products were developed. The model was coded in Matlab and simulated. The result depicts good agreement with experimental work in literature. The sensitivity analysis carried out and the effect of temperature from 650oC-850oC and steam to biomass ratio (S/B) from 0.1-2 investigated. The result depicts the increase in temperature and S/B promotes H2 production and reduces CO and CH4. Furthermore, the regression model was carried out for temperature and S/B variation in Design-Expert. The surface response is constructed from the regression model and the mutual effect of temperature and S/B on gasification product and heating value investigated. Besides, the desirability function is employed to optimize gasification product and heating value. The maximum gasification product yield was at 827.866oC and 0.1 S/B in investigated range. The response predicted by desirability function at this optimum operational conditions is 30.096%, 44.07%, 13.20%, 12.90%, 14.035 (MJ/Nm3 ), and 14.536 (MJ/Nm3 ) for H2, CO, CO2, CH4, LHV, and HHV respectively.&lt;/p&gt;</description>
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