Production Characterization And Cleaning Of Producer Gas From Gasification Of Refuse Derived Fuels (rdf) For Application In Ic Engines

A well-planned research activity conducted in Addis Ababa University, Addis AbabarnInstitute of Technology, School of Mechanical and Industrial Engineering, under Thermalrnand Energy Conversion Chair is utilizing a thematic research grant from AAU – VicernPresident for Research and Technology for this thesis and future works out side this scope,rnfor its practical importance in the energy sector of Ethiopia, most importantly in the off-gridrnpart of the country. rnMost of the rural areas of Ethiopia are known to have no available electric power supply fromrnthe centralized main grid. This huge energy problem has retarded the economic growth of thernareas due to the daily, backward and labor intensive activities of the society to meet theirrndaily energy needs. Beyond this, Ethiopia is one of vast and most populous countries inrnAfrica with remarkably high daily waste production rate. All these problems call for a soundrnmeasures to be implemented in terms of energy integrated waste management and this paperrnis aimed at solving the electric shortage problem in off grid parts by preparing high calorificrnwaste fractions in to RDF for good output in internal combustion engine for electricityrngeneration. rnThe research project is divided in to four manageable phases. Phase 1: Fuel preparation,rnstudying theoretical gasification, modeling and solving of the theoretical gasification usingrncomputational methods, process design and sizing of the gasifier, studying gas contaminantsrnand gas cleaning and conditioning techniques, design of the gas cleaning and conditionrnsystem to meet IC engine requirements for its utilization, which are all paper and computerrnbased tasks. Phase 2: Manufacturing a pilot gasifier – engine set up with the gas cleaning andrnconditioning system for test run in AAU – AAiT School of Mechanical and IndustrialrnEngineering work shop. Phase 3: Conducting experiment/test on the pilot gasifier – enginerncoupled setup to carry out validation, experimental investigation and performance analysis.rnPhase 4: Publication of important scientific outputs from the research in high rated openrnaccess journals. rnGasification is an attractive alternative for thermo – chemical conversion of wastes for itsrnflexibility in terms of various materials as feedstock, relatively higher conversion efficiencyrnand wide range of applications in relatively small area per unit output energy. MSW,rnseparated and screened from non-combustibles (soil, metals, glass …) and biodegradable components was prepared to produce RDF fuel and characterized. The LHV value of thernprepared RDF is 16.63MJ/kg, which is well accepted good RDF as its LHV is greater thanrn15MJ/kg as recommended by studies. Based on the good results from RDF characterization,rna brief mathematical modeling of the gasification of RDF using non – stoichiometricrnequilibrium model was presented. The code formulated for the model was implemented onrnMATLAB to estimate concentration of product gas species and the corresponding heatingrnvalues for wide range of gasification temperatures and equivalent ratios. The model givesrnoptimal values of temperature and equivalent ratio to be 850rnC and 0.2 respectively for bestrnoperating conditions. The gas heating value was 8.164MJ/Nmrn0rn, which is well accepted yieldrnfrom downdraft gasifier to be used for applications such as utilization of the gas in IC enginesrnfor electricity generation. rn3rnDowndraft gasifier is found to be technically good for engine applications and the processrndesign of the gasifier determines the capacity of the gasifier to be 147kW at feed rate of 46rnkg/hr and product gas flow rate of 65.14Nmrn/hr to meet engine requirements. The cold gasrnefficiency of the gasifier is 70% and carbon conversion efficiency and energy balancerncalculations give results that support the fact that basic assumptions underlying thernequilibrium model employed in the computational tool give an over estimated theoreticalrnmaximum yield. Gasifier sizing was performed based on internationally accepted used sizingrnmethod and the size calculation results were validated with recommended ranges of sizes forrnsame product gas flow rate. rn3rnMajor gas contaminants for this specific application are well identified and studied for properrncleaning and mitigation. Based on the gas quality demanded by the application, a sound gasrncleaning and conditioning system is designed. rnThe paper based designs of the gasifier and gas conditioning system is brought to the groundrnby manufacturing and testing a pilot gasifier-engine setup with gas cooling and conditioningrnsystem for a test run to validate the modeling output with the experimental results and tornperform performance evaluation of the gas cleaning. A good agreement was observedrnbetween experimental and simulation results for gas characterization at the gasifier outlet.rnCatalytic gasification and the gas cleaning system give promising results for future advancedrninvestigations on the use of Dolomite and the secondary gas cleaning. Even though gasrncleaning performance experimental tests require more investigation with laboratory facilityrnthat measure all possible product gases and tar, the results obtained so far give a satisfactory motive to do more improvements and conduct advanced tests. Both experimental andrnsimulation results make electricity generation using a specific producer gas engine generatorrnset based on the proven characterization of the gas (heating value and inflammability),rnprovided that gas suction fun or blower or gas compressor is installed before it to overcomernthe unexpected high pressure drop observed as the gas pass through the gas cleanup system tornmeet the engine pressure requirements. rnThis research gives promising solutions for availability of the expensive electricity in off-gridrnareas of Ethiopia possible form refuse derived fuels (RDF) in a micro – scale gasificationrnplant. rnSo far, one scientific manuscript titled ‘Equilibrium Modeling of Refuse Derived Fuelsrn(RDF) Gasification in Imbert Type Downdraft Gasifier’ is on final stages of publication,rnbeing accepted after review from this study to an open access journal. More scientificrnoutcomes are expected from further experimental investigations and performance analyses.

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