<p> This dissertation describes an investigation into the free radical polymerization of styrene in continuous stirred tank reactors (CSTR's). The aim was to develop a steady state polymerization model which would accurately predict conversion and molecular weight distribution (MWD) up to high conversion. </p> <p> The dissertation is divided into three self-contained parts. Part I describes the testing and development of polymerization kinetics using a single CSTR. The single CSTR model is described. Theoretical and experimental conversions and MWD's are compared and discussed. </p> <p> Part II describes the development of a model for a system of CSTR's. It is based upon the single CSTR model and the kinetics developed in Part I. Theoretical and experimental results for a three reactor system are compared and discussed. </p> <p> Part III describes the development of gel permeation chromatography (GPC) for measuring MWD. Molecular weight and resolution calibration data are presented and discussed. Four methods of chromatogram interpretation that correct for imperfect resolution are compared. </p> / Thesis / Doctor of Philosophy (PhD)

Thesis (DTech (Electrical Engineering))--Cape Peninsula University of Technology, 2016. / Majority of the industrial systems encountered are significantly non-linear in nature, so if they are synthesised and designed by linear methods, then some of salient features characterising of their performance may not be captured. Therefore designing a control system that captures the nonlinearities is important. This research focuses on the control design strategies for the Continuous Stirred Tank Reactor (CSTR) process. To control such a process a careful design strategy is required because of the nonlinearities, loop interaction and the potentially unstable dynamics characterizing the system. In these systems, linear control methods alone may not perform satisfactorily. Three different control design strategies (Dynamic decoupling, Decentralized and Input-output feedback linearization controller) are proposed and implemented .in the Matlab/Simulink platform and the developed strategies are then deployed to the design of distributed automation control system configuration using the IEC 61499 standard based functional block programming language. Twin CAT 3.1 system real-time and Matlab/Simulink (www.mathworks.com) environment are used to test the effectiveness of the models The simulation results from the investigation done between Simulink and TwinCAT 3 software (Beckhoff Automation) platforms in the case of the model transformation and closed loop simulation of the process for the considered cases have shown the suitability and the potentials of merging the Matlab/Simulink control function blocks into the TwinCAT 3.1 function blocks in real-time. The merits derived from such integration imply that the existing software and software components can be re-used. This is in line with one of the IEC 6144 standard requirements such as portability and interoperability. Similarly, the simplification of programming applications is greatly achieved. The investigation has also shown that the integration the of Matlab/Simulink models running in the TwinCAT 3.1 PLC do not need any modification, hence confirming that the TwinCAT 3.1 development platform can be used for the design and implementation of controllers from different platforms. Also, based on the steps required for model transformation the between the Matlab/Simulink to the TwinCAT 3 functional blocks, the algorithms of the control design methodologies developed, simulation results are used to verify the suitability of the controls to find whether the effective set-point tracking control and disturbance effect minimisation for the output variables can be achieved in real-time using the transformed Simulink blocks to the TwinCAT 3 functional blocks, then downloaded to the Beckhoff CX5020 PLC for real-time execution. Good set-point tracking control is achieved for the MIMO closed loop nonlinear CSTR process for the considered cases of the developed control methodologies. Similarly, the effects of disturbances are investigated. TwinCAT functional modules achieved good set-point tracking with these disturbances minimization under all the cases considered.

The global demand for food is increasing. Different nutrients are used to increase growth in agriculture and are thus essential for the world ́s food supply. An important and common nutrient is phosphorus. It can be mined, in the form of phosphate, from phosphate rock. The problem is that mining causes environmental problems and phosphate rock is a non-renewable resource. A risk is that phosphorus will become a scarce commodity in about 100 years.  Sewage sludge from wastewater treatment plants (WWTP) is rich in phosphorus. In Sweden and other European countries, a stricter legislation is expected with consideration of an increased recovery of phosphorus from sewage sludge. A ban on the spread of hazardous substances like drug residues and heavy metals from the sludge is also expected. Incineration of the sludge can be done to eliminate hazardous substances and at the same time recover phosphorus and metals. Development of technologies to recover phosphorus from incinerated sewage sludge is therefore topical.  EasyMining is a company that invents new technologies to close nutrient cycles. One of their present projects is about recycling phosphorus, iron, and aluminium from incinerated sewage sludge. Hydrochloric acid (HCl) is used to leach the ash and in the following steps metals and phosphorus are recovered, and heavy metals are removed. Batch experiments have been performed and EasyMining examines the process in a continuous stirred tank reactor (CSTR).  The aim with this project is to compare the batch and continuous process for the ash leaching step. The study was limited to investigate different residence times and liquid to solid ratios (L/S ratios) for the ash leaching step in the CSTR. To accomplish the aim, mainly experimental studies have been performed. A total of 14 runs have been conducted to investigate the continuous process. The residence times 10, 30 and 60 min and the L/S ratios 2.5, 3 and 3.5 ml/g were evaluated. The lab-set up consisted of a peristaltic pump to pump diluted HCl solution, a conveyor belt to dose the ash and a CSTR. The filtrate was analysed for phosphorus, iron, and aluminium with a spectrophotometer. Interpretation of the result was conducted after each run and the data was then compared to previous batch data from within the company. A paired t-test was used to evaluate if there was a significant difference in the mean values between different residence times and L/S ratios.  The result shows that the leching is very fast and longer residence times or higher L/S ratios do not result in higher yields for phosphorus, iron, or aluminium. There is no significant difference between the examined residence times or L/S ratios in the paired t-test. Data from the batch process shows that the investigated residence times and L/S ratios do not affect the yield. A more even distribution of the yields is obtained in the batch process compared to the continuous process. The less even distribution in the continuous process, probably depends on errors in the method and the equipment used in the process. For example, there were some problems with the ash dosing, which led to an inconstant L/S ratio in the runs. This affected the calculated yields significantly. Overall, the batch process results in slightly higher yields. This is especially the case when excluding high calculated yields in the continuous process, probably obtained because of an overdosing of the ash. / Den globala efterfrågan på mat ökar. Olika näringsämnen används för att få en högre tillväxt i jordbruket och dessa är essentiella för världens livsmedelsproduktion. Ett viktigt och vanligt näringsämne är fosfor och det bryts i form av fosfat från fosfatmineral. Problemet är att brytningen förorenar miljön och dessutom är fosfat-sten en icke förnyelsebar resurs. Det finns en risk att fosfor blir en bristvara om cirka 100 år.  Avloppsslam från vattenreningsverk innehåller höga fosfatkoncentrationer. I Sverige samt i andra europeiska länder förväntas en striktare lagstiftning, som kräver en ökad återvinningsgrad av fosfor från avloppsslam. Även ett förbud mot spridningen av giftiga substanser som läkemedelsrester och tungmetaller förväntas införas. Slammet kan förbrännas för att eliminera farliga substanser samtidigt som fosfor och olika metaller kan återvinnas. Utvecklingen av nya tekniker för återvinning av fosfor från bränt avloppsslam är därför väldigt aktuell.  EasyMining är ett innovationsföretag som utvecklar nya tekniker för att erhålla slutna näringskretslopp. Ett av deras pågående projekt handlar om att återvinna fosfor, aluminium och järn från förbränt avloppsslam. Saltsyra används för att laka askan och i nästkommande steg återvinns fosfor och metaller, samtidigt som tungmetaller separeras. Satsvisa försök har genomförts och EasyMining vill nu undersöka processen i en tankreaktor.  Syftet med projektet är att jämföra resultat från den satsvisa driften med resultat från en kontinuerlig process för ask-lakningssteget. Studien begränsades till att endast undersöka olika uppehållstider och förhållandet mellan vätskan och askan (L/S-förhållande) i lakningssteget. För att uppnå syftet genomfördes huvudsakligen experimentella studier. 14 körningar genomfördes totalt för undersökning av den kontinuerliga processen. Undersökta uppehållstider var 10, 30 och 60 min och undersökta L/S-förhållandena var 2,5, 3 och 3,5 ml/g. Laborationsuppställningen bestod av en peristaltisk pump för tillförsel av utspädd saltsyralösning, ett rullband för dosering av askan samt en tankreaktor. Filtratet analyserades för fosfor, järn och aluminium i en spektrofotometer. Efter varje körning tolkades resultatet och jämfördes därefter med data från de av företaget tidigare utförda satsvisa försöken. Ett parat t-test användes för att utvärdera om det fanns någon signifikant skillnad i medelvärden mellan olika uppehållstider och L/S-förhållanden.  Resultatet visar att lakningen är väldigt snabb och längre uppehållstider eller högre L/S-förhållanden ger inte högre utbyten för fosfor, järn eller aluminium. Ingen signifikant skillnad erhålls mellan undersökta uppehållstider eller L/S-förhållanden i de parade t-testen. Data från de satsvisa försöken visar att de undersökta uppehållstiderna och L/S-förhållandena inte påverkar utbytet. En mindre spridning av utbyten erhålls i den satsvisa driften jämfört med den kontinuerliga. Den större spridningen i den kontinuerliga processen beror förmodligen på felkällor i processens metod/utrustning. Exempelvis var det en del problem med askdoseringen, vilket medförde icke konstanta L/S-förhållanden. Detta påverkade det beräknade utbytet signifikant. Generellt erhålls något högre utbyten i den satsvisa processen. Framförallt då höga beräknade utbyten exkluderas i den kontinuerliga processen på grund av en överdosering av askan.

L’énantiomère R (énantiomère cible) d’un mélange racémique d’une molécule organique est isolé par cristallisation du sel diastéréoisomère qu’il forme préférentiellement en s’associant à l’acide énantiomériquement pur R-acétyl(L)valine. Cependant l’énantiomère S (contre-énantiomère) peut aussi cristalliser sous forme d’un sel de R-acétyl(L)valine. Les solubilités des deux sels sont déterminées par des cristallisations par refroidissement en réacteur fermé. La modélisation de ces données expérimentales permet de maximiser la quantité d’énantiomère R cristallisé en sel pur en réacteur fermé à une température choisie. Cette température est ensuite augmentée : la durée de filtration des cristaux, systématiquement obtenus sous forme d’aiguilles, est avantageusement réduite. Une réduction est encore obtenue en appliquant un profil de refroidissement favorisant la croissance des cristaux : au final, l’amélioration de la filtrabilité des cristaux est corrélée aux augmentations conjointes du facteur d’élongation et de la longueur des cristaux. La cristallisation est ensuite transposée à un mode de fonctionnement continu en injectant les réactifs séparément dans un réacteur ouvert. Afin d’atteindre des performances égales à celles du réacteur fermé, le temps de passage et la concentration de la solution de R-acétyl(L)valine sont ajustés : il en résulte une productivité accrue de la cristallisation. La filtrabilité des cristaux obtenus en réacteur continu reste cependant médiocre. Bien que toujours inférieur à celui atteint en réacteur fermé optimal, le facteur d’élongation des cristaux est tout de même augmenté en optant pour une configuration de cascade de deux réacteurs continus / The R enantiomer (target enantiomer) of the racemic mixture of an organic molecule is isolated by a preferential crystallization of the salt it forms by association with the enantiomerically pur acid R-acetyl(L)valine. The S enantiomer (counter enantiomer) may somehow also crystallize under the form a R-acetyl(L)valinate salt. Solubilities of the two salts are measured by cooling crystallizations in a batch reactor, carried out for various stoechiometric conditions. The interpretation and the modelisation of the experimental data gathered lead to the maximisation of the quantity of R enantiomer crystallized as a pur salt in a batch reactor by cooling crystallization to a given temperature. This temperature is then increased : the filtration duration of the crystals, always exhibiting the shape of needles, is thus advantageously decreased. A further decrease is made possible by applying a temperature cooling profile that promotes the growth of crystals. Finally, the enhancement of the filterability of crystals is correlated to an increase of the elongation factor of crystals. The crystallization is then transposed to a continuous operating mode : reactants are injected separately in a continuous stirred tank reactor. With a view to match the results of the optimized batch reactor, the residence time and the R-acetyl(L)valine concentration are adjusted : a better productivity is then obtained, though filterability remains lower. The elongation factor is slightly increased by implementing two continous stirred tank in serie. The complete range of possible enhancements of crystals morphology by such cascades could be further studied for such needle-like crystals

<p>There are many types of bioreactors used for producing bacteria populations in commercial, medical and research applications. </p><p>This report presents a systematic discussion of some of the most important models corresponding to the well known reproduction kinetics such as the Michaelis-Menten kinetics, competitive substrate inhibition and competitive product inhibition. We propose a modification of a known model, analyze it in the same manner as known models and discuss the most popular types of bioreactors and ways of controlling them. </p><p>This work summarises much of the known results and may serve as an aid in attempts to design new models.</p>

There are many types of bioreactors used for producing bacteria populations in commercial, medical and research applications. This report presents a systematic discussion of some of the most important models corresponding to the well known reproduction kinetics such as the Michaelis-Menten kinetics, competitive substrate inhibition and competitive product inhibition. We propose a modification of a known model, analyze it in the same manner as known models and discuss the most popular types of bioreactors and ways of controlling them. This work summarises much of the known results and may serve as an aid in attempts to design new models.

Submitted by Neusa Fagundes (neusa.fagundes@unioeste.br) on 2017-09-05T19:08:26Z No. of bitstreams: 1 Thiago_Edwiges2017.pdf: 2041114 bytes, checksum: f435c702dd49431aa0534c4ce49e2533 (MD5) / Made available in DSpace on 2017-09-05T19:08:26Z (GMT). No. of bitstreams: 1 Thiago_Edwiges2017.pdf: 2041114 bytes, checksum: f435c702dd49431aa0534c4ce49e2533 (MD5) Previous issue date: 2017-08-18 / The economical development and urbanization process have contributed to the increase in solid waste generation and problems related to final disposal. Thus, the National Solid Waste Policy reinforces treatment in order to improve efficiency in the management of solid waste as one of its priorities and stimulates to recover and use energy. Anaerobic digestion has been suggested as a promising approach to the treatment of organic fraction of solid waste, mainly because it represents an opportunity to reduce environmental pollution and minimizes impacts concerning the energy crisis. So, this trial aimed at evaluating FVW biogas potential, collected in a wholesale market (Unit from Foz do Iguaçu/PR) through batch and semicontinuous tests. Fruits and vegetables trading from that unit generates approximately 70,500 t year-1, with 2,800 kg d-1 solid waste, composed of almost 85% organic matter. The influence of chemical composition of twelve FVW different samples with different compositions on biochemical methane potential (BMP) was analyzed. The BMP ranged from 288 LN CH4 kg VS-1 to 516 LN CH4 kg VS-1, with significant statistical differences among means. This was explained by in the waste chemical composition over time. BMP variation was most strongly correlated for lipid content and high calorific values (HCV). Linear regression analyses were carried out to develop statistical models to predict as fast as possible methane potential of this kind of waste. The models were analyzed according to chemical compounds and HCV based on simple and multiple regression. The model with the best statistical metrics included lipid, protein, cellulose, lignin, and HCV, with a 92.5% R² and lignin content negatively correlated to BMP. Since HCV and lipids were strongly correlated, and because HCV can be determined more rapidly than chemical composition, HCV may be useful for predicting BMP. In addition to batch tests, the performance of anaerobic digestion was also investigated in a semicontinuous mode using a FVW mixture as a single substrate. The performance of a continuous stirred tank reactor (CSTR) was monitored along with the gradual increase of organic loading rates (OLR) from 0.5 gVS L–1 d–1 to 5.0gVSL–1d–1. BMP of FVW used as a feedstock to CSTR was 370 LN CH4 kg VS-1 with 81% biodegradability. During the whole trial pH was stable and there was an adequate level of buffering capacity in the system. Volumetric biogas production (LN biogas L–1 d–1) increased linearly (R² = 94.4%) according to OLR increase. On the other hand, the specific methane production (LN CH4 kg VS-1) has registered the best performance at an OLR of 3.0 g VS L–1 d–1 and 30 days of hydraulic retention time, with 285 LN CH4 kg VS-1 added, reaching 74% of BMP measured by batch tests. A clear accumulation of volatile fatty acids (VFA) was monitored with a decreased specific methane yield was detected with an OLR above 3.0 g VS L–1 d–1. / O crescimento econômico e o processo de urbanização vêm contribuindo para o aumento da geração de resíduos sólidos e problemas relacionados à disposição final. A Política Nacional de Resíduos Sólidos reforça o tratamento com o intuito de melhorar a eficiência quanto ao gerenciamento dos resíduos sólidos no país, como uma de suas prioridades e enfatiza o incentivo à recuperação e ao aproveitamento energético. A biodigestão anaeróbia tem sido apontada como uma abordagem promissora ao tratamento da fração orgânica dos resíduos sólidos, sobretudo por representar oportunidade de reduzir a poluição ambiental e minimizar os impactos da crise energética. Assim, o objetivo deste trabalho foi avaliar o potencial de produção de biogás de resíduos de frutas e hortaliças (RFH) coletados na Central de Abastecimento (CEASA – Unidade de Foz do Iguaçu/PR) a partir de testes em batelada e em regime semicontínuo. A comercialização de frutas e hortaliças da unidade é de aproximadamente 70.500 t ano-1, com geração de resíduos sólidos de 2.800 kg d-1, compostos por aproximadamente 85% de matéria orgânica. A influência da composição química de doze amostras de RFH com diferentes composições sobre o potencial bioquímico de metano (PBM) foi analisada. O PBM dos resíduos variou entre 288 LN CH4 kg SV-1 e 516 LN CH4 kg SV-1, com diferenças estatísticas significativas entre as médias, o que pôde ser explicado pela variação na composição química dos resíduos ao longo do tempo. A variação do PBM foi mais fortemente correlacionada à variação do teor de lipídeos e do poder calorífico superior (PCS). Foram realizadas análises de regressão linear visando desenvolver modelos estatísticos para estimar, de forma mais rápida, o potencial metanogênico deste tipo de resíduo. Os modelos foram analisados considerando os componentes químicos e o PCS a partir de regressão linear simples e múltipla. O modelo com as melhores métricas estatísticas foi obtido considerando lipídio, proteína, celulose, lignina e PCS, com R² de 92,5% e com teor de lignina negativamente correlacionado ao PBM. Como o PCS e os lipídeos apresentaram forte correlação, e como o PCS pode ser determinado, em geral, de forma mais rápida que a composição química, o PCS pode ser considerado um parâmetro útil para a estimava do PBM. Além dos testes em batelada, investigou-se também o desempenho da biodigestão anaeróbia em regime semicontínuo utilizando-se uma mistura de RFH como único substrato. O desempenho de reator de mistura completa (do inglês CSTR) foi monitorado juntamente com o aumento gradativo da carga orgânica volumétrica (COV) de 0,5 g SV L-1 d-1 até 5,0g SV L-1 d-1. O PBM dos RFH utilizado para alimentar o reator foi 370 LN CH4 kg SV-1 com biodegradabilidade de 81%. Durante todo o ensaio o pH se manteve estável e o sistema apresentou boa capacidade tampão. A produção volumétrica de biogás (LN biogás L-1 d-1) aumentou de forma linear (R² = 94,4%) de acordo com aumento da COV. Já a produção específica de metano (LN CH4 kg SV-1) indicou o melhor desempenho com COV de 3,0 g SV L-1 d-1 e 30 dias de tempo de retenção hidráulica, com 285 LN CH4 kg SV-1 adicionados, e atingiu 74% de PBM, medido a partir dos testes em batelada. Observou-se um acúmulo evidente de ácidos graxos voláteis (AGV), com consequente redução da produção de metano a partir da COV acima de 3,0 g SV L-1 d-1.

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-03-20T13:04:38Z No. of bitstreams: 1 TARCISIO DAVID KONNA NUNES SANTOS - DISSERTAÇÃO PPGEQ 2016..pdf: 1645201 bytes, checksum: 6f9773a951b06aacdb26ff5287e21e18 (MD5) / Made available in DSpace on 2018-03-20T13:04:38Z (GMT). No. of bitstreams: 1 TARCISIO DAVID KONNA NUNES SANTOS - DISSERTAÇÃO PPGEQ 2016..pdf: 1645201 bytes, checksum: 6f9773a951b06aacdb26ff5287e21e18 (MD5) Previous issue date: 2016-03-23 / Este trabalho propôs um modelo matemático para um reator do tipo CSTR (continuous stirred-tank reactor) partindo de dados experimentais da cinética da reação de transesterificação entre o óleo de soja e o acetato de metila, tendo como catalisador uma enzima, a Candida Antartica. Um volume foi proposto para reator para que o tempo médio de residência da mistura reacional fosse suficiente tal que o rendimento esperado, com base nos dados obtidos pelo Matlab®, fosse obtido na saída do reator. O estudo reacional fluidodinâmico foi feito utilizando o software comercial ANSYS® versão 15.0. Duas configurações do reator foram propostas otimização, afim de tornar o processo o mais homogêneo possível, tentando atingir as configurações do reator de mistura perfeita. Os impelidores utilizados foram o tipo pás retas inclinadas e o ripo Ribbon (Âncora), afim de avaliar qual dos impelidores consegue o rendimento satisfatório com menor potência de operação. A potência requerida foi determinada através das equações para misturadores mecânicos, sendo avaliado apenas como variável a rotação das pás. / This work proposes a mathematical model to a reactor of CSTR-type (Continuous Stirred-tank reactor) starting from experimental data of the kinetics of transesterification of soybean oil and methyl acetate, with the catalyst enzyme, Candida Antarctica. A reactor volume was proposed for the average residence time of the reaction mixture was sufficient such that the expected yield, based on data obtained by Matlab, was obtained in the reactor outlet. The reaction fluid dynamic study was done using the commercial software ANSYS® version 15.0. The optimization of the reactor was proposed by comparing the reactor operation with two impellers separately in order to make the process more homogeneous as possible, trying to achieve the perfect blend of reactor configurations. The impellers used were the type inclined straight blades and Ribbon RIPO (Anchor), to determine which of the impellers can the satisfactory performance with lower power operation. The required power was determined by the equations for mechanical mixers, being rated only as a variable rotation of the blades

ALes gaz issus des procédés de pyrolyse-gazéification de la biomasse doivent être épurés. Ils contiennent des vapeurs condensables (goudrons), des aérosols, des particules solides fines, des composés soufrés et des métaux alcalins qu’il s’agit d’éliminer avant leur utilisation sur des turbines (production d’électricité) ou comme gaz de synthèse. Les expériences rapportées dans ce travail concernent les vapeurs condensables et leur conversion par craquage thermique. Les vapeurs sont produites par pyrolyse de la biomasse dans un premier réacteur (RP) à 540°C. Elles sont ensuite craquées dans un réacteur parfaitement auto-agité par jets gazeux (RPAA) associé en série avec le RP. Le RPAA fonctionne à plus haute température (550-1030°C) et le temps de séjour de la phase gazeuse dans le craqueur est compris entre 0,1 et 1 s. Tous les produits de réaction (charbon, vapeurs condensables et gaz permanents) sont récupérés et analysés. Le RPAA étant uniforme en température et en concentration, la détermination de constantes de vitesse à temps de séjour donné est assez aisée à partir de bilans de matière en vapeurs et gaz. Des schémas réactionnels globaux rendant compte du craquage des vapeurs en gaz mais aussi de leur possible maturation en composés plus réfractaires sont proposés et leurs constantes de vitesse optimisées à partir des résultats expérimentaux. Ces modèles permettent de simuler le craquage thermique d’une charge type issue d’un gazogène. On détermine les conditions optimales de fonctionnement (température, temps de séjour) du réacteur de craquage qui aboutissent à une concentration en vapeurs condensables la plus faible possible. On comparera ainsi l’efficacité du craquage thermique à celle des autres procédés d’épuration des goudrons. / Pyrolysis and gasification processes give rise to gases containing by-products such as condensable vapors (tars), aerosols, dust, sulfur compounds and inorganics which may considerably lower the efficiency of catalysts (if chemical synthesis is foreseen) or cause severe damages to motors and turbines (in case of electricity production). Hence, efficient gas treatments are needed. The experiments reported in the present work are related to thermal cracking of condensable vapors. These vapors are produced in a first reactor by biomass pyrolysis (PR) at 540°C. They undergo further cracking in a second vessel, a continuous serf stirred tank reactor (CSSTR), assembled in series with the PR. The CSSTR is operated at temperatures ranging from 550 to 1030°C and gas phase mean residence times ranging from 0,1 to 1 s. Reaction products (char, condensable vapors and permanent gases) are recovered and analyzed. Temperature as well as composition are uniform at any point of the CSSTR. Therefore, it is easy to derive values of kinetic constants from mass balances at a given residence time. Global vapor cracking schemes including gas formation as well as possible maturation into more refractory compounds are proposed. Their kinetic constants are optimized from the experimental results. These models are used to simulate the thermal cracking of a typical load flowing out from a gasifier. Optimal operating conditions of the cracking reactor (in terms of temperature and residence time) are determined to reach the lowest condensable vapors concentration. Thus, efficiency of thermal cracking can be compared to other gas treatment processes.

Användningen av kommunalt avfall för att producera förnybar energi, huvudsaklig biogas, uppfyller 8 av Sveriges 16 miljökvalitetsmål. Två typer av rötningsprocesser som används är kontinuerligt omrörda tankreaktorer (CSTR) och pluggflödesreaktorer (PFR). Rapportens syfte är att direkt jämföra de två reaktorkonfigurationerna, PFR och CSTR, med samma substratblandning. Båda reaktortyperna drevs med samma belastning (5,2 g VS/L dag), hydraulisk retentionstid (30 dagar) och driftstemperatur (520C). Två PFR-reaktorer drevs med återcirkulation av rötrester. Under projektets gång mättes olika parametrar, vilka var: pH, total gasvolym och gassammansättning, FOS/TAC (organiska syror/alkalinitet), flyktiga fettsyror (VFA), ammonium-kvävekoncentration och TS (torrsubstanshalt) och VS (organiska ämnen). Studieresultatet var uppdelat i två sektioner. Avsnitt 1 sammanfattar uppstartsperioden, där alla tre CSTR (D1-R, D2-NR och C1-NR) kördes i icke-återcirkulerande läge. Uppstartsperioden gjordes för att säkerställa reaktorernas stabilitet och det gällde att uppnå en liknande baslinje för detektion. Inom studien accepterades avvikelser för baslinjen inom intervallet 0-5%. För uppstartsperioden varierade den specifika metanproduktionen med 2 % mellan D1-NR och D2-R, D1-R och C1-NR med 6 %, och D2-NR och C1-NR med 8 %. För ammoniak-koncentrationen var skillnaden mellan D1-R och D2-NR 2 % och mellan D1-R och C1-NR 9 %, mellan D2-NR och C1-NR, 7%. Med dessa variationer togs beslutet att utesluta reaktor C1-NR från den experimentella perioden för projektet. Avsnitt 2 jämför PFR och CSTR återcirkulerat/icke återcirkulerat läge. En CSTR drevs med 30 % återcirkulation av rötrest och en CSTR drevs i icke-återcirkulationsläge. Att jämföra PFR och CSTR återcirkulerat/icke återcirkulerat läge visade att PFR:erna övervann båda CSTR:erna när det gäller den specifika metanproduktionen. Där PFR producerade 395±93 NL/KgVS och 372±42 (N)L/KgVS CSTR med återcirkulation 280±10 (N)L/KgVS och den icke-återcirkulerade CSTR producerade 250±7 (N)L/KgVS. NH4+-N-nivåerna mellan PFR och CSTR visade en skillnad på 1 g/L, där PFR var den med högre NH4+-N (2,53±0,39 g/L för PFR-A och 2,73±0,43 g/L för PFR-T). En av skillnaderna mellan de återcirkulerade och de icke-återcirkulerade CSTR:erna var VFA-koncentrationen. VFA-koncentrationen i de återcirkulerade var 1,05±0,90 g/L och 0,43±0,25 g/L i de icke-återcirkulerade. VFA-koncentrationen för PFR var i genomsnitt 0,28±0,12 g/L och 0,40 ±0,16 g/L. Graden av nedbrytning i CSTRs var 90-91%, och 63-65% i PFR. Den är möjligen felberäknad och visar en inkonsekvens mellan reaktorernas prestanda och specifik metanproduktion. / The use of municipal waste to produce renewable energy, in the form of biogas, fulfils eight of Sweden's sixteen environmental quality objectives. The most common technology to produce biogas is anaerobic digestion (AD). Two common types of AD processes are continuously stirred reactors (CSTR) and plug flow reactors (PFR). The thesis aims at directly comparing the two reactor configurations using the same substrate mix. For this, two PFRs (PFR-T and PFR-A) and three CSTRs (D1-R, D2-NR and C1-NR) were setup. All reactors were operated at the same organic loading rate (5.2 g VS/L-day), hydraulic retention time (30 days) and operational temperature (52°C). During the project, various parameters were measured to evaluate the reactor performance, such as pH, total gas volume and gas composition, FOS/TAC (organic acids/alkalinity), volatile fatty acids (VFA), ammonium-nitrogen concentration, and solid and volatile solid of digestate.   The study result was divided into two sections. Section 1 summarises the start-up period (42 days), where the CSTRs and the PFRs were operated under non-recirculation mode. The start-up period was done to ensure the stability of the reactors and was concerned with achieving a similar baseline for performance. For the start-up period, the specific methane production between D1-R and D2-NR varied by 2% while the variation between C1-NR and D2-NR was 8%. Likewise, for the ammonia concentration, the difference between D1-R and D2-NR was 2%, while C1-NR differed by 9% from D2-NR. Based on these findings, the decision was taken to exclude reactor C1-NR from the experimental period of the project.  Section 2 compares the PFR and CSTR. One CSTR was operated with 30% recirculation of digest, while the other CSTR was operated in non-recirculation mode. The two PFRs were operated with recirculation of digestate. The experiments showed that the PFRs outperformed both CSTRs regarding the specific methane production. The PFRs produced 395±93 (N)L/kg-VS and 372±42 (N)L/kg-VS. In contrast, the CSTR with recirculation reached 280±10 (N)L/kg-VS and the non-recirculated CSTR produced 250±7 (N)L/kg-VS. The NH4+-N levels for the PFRs and CSTRs showed a 1 g/L difference, with a higher value for the PFRs (2.53±0.39 g/L for PFR-A, and 2.73±0.43 g/L for PFR-T). One of the significant differences between the recirculated and the non-recirculated CSTRs was the VFA concentration. The VFA concentration in the recirculated and non-recirculated reactor was 1.05±0.90 g/L and 0.43±0.25 g/L, respectively. The VFA concentration for the two PFRs was on average 0.28±0.12 g/L and 0.40 ±0.16 g/L. The degree of degradation in the CSTRs was 90-91% compared to 63-65% in the PFRs. The degree of degradation is possibly miscalculated and shows an inconsistency between the reactor performance in terms of specific methane production.