Thesis (M. Ed.)--University of South Africa, 2002.

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<p>U okviru doktorske disertacije izvedena su eksperimentalna istraživanja osnovnih hidrodinamičkih i maseno-prenosnih karakteristika airlift reaktora sa spoljnom recirkulacijom sa ugrađenom vi&scaron;ekanalnom cevnom membranom u silaznu cev (ALSRM). ALSRM je radio na dva načina rada: bez mehurova u silaznoj cevi (način rada A) i sa mehurovima u silaznoj cevi (način rada B) u zavisnosti od nivoa tečnosti u gasnom separatoru. Ispitivani su uticaji prividne brzine gasa, povr&scaron;inskih osobina tečne faze, tipa distributora gasa i prisustva mehurova gasa u silaznoj cevi na sadržaj gasa, brzinu tečnosti u silaznoj cevi i zapreminski koeficijent prenosa mase u tečnoj fazi u ALSRM. Rezultati su poređeni sa vrednostima dobijenim u istom reaktoru ali bez membrane (ALSR). Sadržaj gasa u uzlaznoj i silaznoj cevi određivan je pomoću piezometarskih cevi merenjem hidrostatičkog pritiska na dnu i vrhu uzlazne i silazne cevi. Brzina tečnosti merena je pomoću konduktometrijskih elektroda dok je zapreminski koeficijent prenosa mase dobijen primenom dinamičke metode merenjem promene koncentracije kiseonika u vremenu optičkom elektrodom. Eksperimentalni rezultati pokazuju da sadržaj gasa, brzina tečnosti i zapreminski koeficijent prenosa mase zavise od prividne brzine gasa, vrste alkohola i tipa distributora gasa kod oba reaktora. Vi&scaron;ekanalna cevna membrana u silaznoj cevi uzrokovala je povećanje ukupnog koeficijenta trenja za 90% i time dovela do smanjenja brzine tečnosti u silaznoj cevi do 50%. Smanjena brzina tečnosti u silaznoj cevi povećala je sadržaj gasa do 16%. Predložene neuronske mreže i empirijske korelacije odlično predviđaju vrednosti za sadržaj gasa, brzinu tečnosti i zapreminski koeficijent prenosa mase.</p> / <p>An objective of this study was to investigate the hydrodynamics and the gas-liquid mass transfer coefficient of an external-loop airlift membrane reactor (ELAMR). The ELAMR was operated in two modes: without (mode A), and with bubbles in the downcomer (mode B), depending on the liquid level in the gas separator. The influence of superficial gas velocity, gas distributor&rsquo;s geometry and various diluted alcohol solutions on hydrodynamics and gas-liquid mass transfer coefficient of the ELAMR was studied. Results are commented with respect to the external loop airlift reactor of the same geometry but without membrane in the downcomer (ELAR). The gas holdup values in the riser and the downcomer were obtained by measuring the pressures at the bottom and the top of the riser and downcomer using piezometric tubes. The liquid velocity in the downcomer was determined by the tracer response method by two conductivity probes in the downcomer. The volumetric mass transfer coefficient was obtained by using the dynamic oxygenation method by dissolved oxygen probe. According to experimental results gas holdup, liquid velocity and gas-liquid mass transfer coefficient depend on superficial gas velocity, type of alcohol solution and gas distributor for both reactors. Due to the presence of the multichannel membrane in the downcomer, the overall hydrodynamic resistance increased up to 90%, the liquid velocity in the downcomer decreased up to 50%, while the gas holdup in the riser of the ELAMR increased maximally by 16%. The values of the gas holdup, the liquid velocity and the gas-liquid mass transfer coefficient predicted by the application of empirical power law correlations and feed forward back propagation neural network (ANN) are in very good agreement with experimental values.</p>

<p>U doktorskoj disertaciji vr&scaron;eno je istraživanje mogućnosti konverzije energije<br />različitih vrsta drvne biomase procesom pirolize. Ispitivanu drvnu biomasu<br />predstavljale su strugotina hrasta, bukve, tre&scaron;nje, oraha, jele, lipe, kao i<br />me&scaron;avina navedenih vrsta. Dobijeni eksperimentalni rezultati ukazuju da<br />prinos gasa, tečne i čvrste faze tokom odvijanja procesa pirolize zavise od<br />reakcionog vremena, temperature i brzine zagrevanja.</p> / <p>Doctoral dissertation investigates possibilities for energy conversion of<br />different woody biomass types through pyrolysis process. Investigated woody<br />biomass included oak, beech, cherry, walnut, fir, lime wood chips and their<br />mixture. Obtained experimental results imply that gas, liquid and solid phase<br />yields during pyrolysis process depend on reaction time, temperature and<br />heating rate.</p>

<p>U doktorskoj disertaciji realizovano je istraživanje mogućnosti konverzije energije različitih vrsta poljoprivredne biomase procesom pirolize. Ispitivanu poljoprivrednu biomasu predstavljale su p&scaron;enična, ovsena, sojina slama, slama od kukuruzovine kao i me&scaron;avina navedenih slama. Dobijeni eksperimentalni rezultati ukazuju da prinos gasa, tečne i čvrste faze tokom odvijanja procesa pirolize zavise od vi&scaron;e parametara vođenja procesa među kojima dominantan uticaj imaju reakciono vreme, temperatura i brzina<br />zagrevanja.</p> / <p>Doctoral dissertation investigates possibilities for energy conversion of different agricultural biomass types through pyrolysis process. Investigated agricultural biomass included wheat, corn, oat, soy straw and the mixture of mentioned straws. Obtained experimental results imply that gas, liquid and solid phase yields during pyrolysis process depend on various process parameters, where the reaction time, temperature and heating rate have dominant influence.</p>