Nearly half of the electrical power produced in the United States is generated with coal. Coal power is inexpensive and reliable, but coal combustion releases harmful pollutants including NOx and SOx into the atmosphere if not controlled. CO2, a greenhouse gas, is also released during coal combustion and may contribute to global warming. A promising technology enabling carbon capture is oxy-coal combustion. During oxy-combustion, coal is burned in an atmosphere of O2 and recycled flue gas to eliminate nitrogen which makes up the majority of air-combustion flue gas. Oxy-combustion flue gas is mainly composed of CO2 and H2O. H2O can be condensed out of the gas, and the CO2 can then be captured and permanently stored relatively easily. The composition of the gas inside an oxy-fired boiler will be different due to the absence of nitrogen and the recycling of flue gas. Corrosive sulfur and chlorine gas species concentrations will be higher, and CO and NOx concentrations will be effected. An understanding of the differences in gas concentrations is critical to oxy-combustion boiler design. Four different pulverized coals were combusted in a reactor under staged and unstaged oxy-combustion conditions with warm recycled flue gas (420°F) to simulate conditions in an oxy-fired coal boiler. The gas composition was measured in the reducing and oxidizing zones for staged combustion, and in the same locations, 57 cm and 216 cm from the burner, for unstaged combustion. The results were compared to the results from similar staged air-combustion experiments using the same coals and burner. CO concentrations were higher for staged oxy-combustion compared to air-combustion, and the increase was more substantial for lower rank coals. H2S concentrations in the reducing regions were also higher, and the fraction of gas phase sulfur measured as H2S was higher for oxy-combustion. SO2 concentrations were 2.9 to 3.8 times as high as air-combustion concentrations. The measured conversion of coal sulfur to SO3 was lower for oxy-combustion, and ranged from 0.61% to 0.98%. The average fraction of coal sulfur measured in the gas phase was 84%, 80%, and 85% for staged oxy-combustion, unstaged oxy-combustion, and staged air-combustion respectively. HCl concentrations were 2.8 to 3.1 times higher in the staged oxy-combustion oxidizing zone, and a smaller fraction of coal chlorine was measured in the reducing zone. On average 70.8%, 79.5%, and 71.1% of the coal chlorine was measured as HCl for staged oxy-combustion, unstaged oxy-combustion, and staged air-combustion respectively. The fractions of coal chlorine and sulfur measured in the gas phase for staged combustion were not significantly affected by combustion media. Some staged oxy-combustion NO concentrations were lower than air-combustion concentrations while others were slightly higher, and NO emission rates were much lower due to recycling NO through the burner.

Kemcyklisk förbränning (CLC) involverar en icke komplex separation av den bildade koldioxiden (CO2) efter förbränningen eftersom syret (O2) överförs till bränslet via en syrebärare som cirkulerar mellan luft- och bränslereaktorn. Eftersom O2 separeras effektivt från kvävgasen (N2) i luftreaktorn, erhålls en produkt gas som till majoriteten består av CO2 och vatten (H2O). Detta resulterar således i mindre komplexa och energi-krävande rökgasreningssystem. Vid förbränning av biomassa inom kemcyklisk förbränning kan negativa CO2 utsläpp erhållas om den producerade CO2 gasen infångas och slutförvaras exempelvis i geologiska formationer. Den infångade CO2 gasen måste för att uppfylla stringenta reningskrav för att undvika diverse konsekvenser relaterade till transportkedjan och slutförvaringen. Förutom CO2 och H2O, kommer den genererade rökgasen från CLC innehålla mindre mängder av biprodukter som kväveoxider (NOx), svaveloxider (SOx) och övriga kontaminanter som behöver att reduceras ned till ppm nivåer för att möta reningskravet på CO2 gasen. På grund av en ofullständig förbränning i CLC erfordras en efterförbränningskammare med en extern tillsats av O2 för att uppnå en fullständig förbränning. Det kan därför förväntas att överskotts-O2 kommer att finnas i den utgående gasen efter post oxidationskammaren, som också behöver att renas ned till ppm koncentrationer. De föreslagna rökgasreningssystemen efter CLC involverar de mest konventionella rökgasreningssystem använda inom industrin idag. Till dessa tillhör bland annat elektrofilter (ESP), våt rökgasavsvavling (WFGD), selektiv katalytisk reduktion (SCR) och selektiv icke-katalytisk reduktion (SNCR) för kväveoxireducering. Två kylnings och CO2 förvätskningstekniker diskuteras i detta arbete: den förkylda Linde Hampson systemet och det kryogena destillationssystemet. Ett rökgasreningssystem har föreslagits för varje förvätskningsteknik. Bland de två föreslagna reningssystemen, enbart scenario 2 uppfyllde Northern Lights kravspecifikationen på CO2, med en reningsgrad på 99.998%. Denna studie anses vara unik då ingen litteratur rörande rökgasrening inom kemcyklisk förbränning var publicerad under skrivtiden av denna masteravhandling. / Chemical looping combustion (CLC) involves an inherent separation of carbon dioxide (CO2), since oxygen (O2) is transferred to the fuel via an oxygen carrier, circulating between the air and fuel reactor. With O2 being removed from nitrogen (N2) in the air reactor, a separate stream containing mostly CO2 and water (H2O) is produced in the fuel reactor, eliminating the need of expensive and energy-demanding gas separation technologies. The use of biomass as fuel in CLC may result in negative CO2 emissions if CO2 is captured and stored. The CO2 product gas must comply to certain purity levels depending on ways of CO2 transportation and where it will be stored. Besides H2O and CO2, the generated flue gas stream in CLC will also contain trace amounts of nitrogen oxides (NOx), sulfur oxides (SOx) and other contaminants, thus requiring a deep removal to ppm levels to comply with the stringent CO2 purity criteria for storage in saline aquifers in this work. Due to an incomplete combustion of fuel gases in CLC, an oxy-polishing step is required for a full conversion to gas products CO2 and H2O. Therefore, pure O2 is required for the oxy-polishing step. Some residual O2 will also be expected in the flue gas stream and needs to be reduced to ppm levels. The downstream treatment in CLC involves the best available gas processing technologies practiced commercially today, such as electrostatic precipitators (ESPs), wet flue gas desulfurization (WFGD), selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR). Two CO2 processing systems are discussed in this work; the precooled Linde Hampson unit and the Distillation Separation unit. For each CO2 processing unit (CPU), a flue gas treatment is proposed. Amongst the two proposed scenarios, scenario 2, could with highest certainty, produce a liquid CO2 stream with a purity of 99.998%, complying to the CO2 criteria set by the Northern Lights Project in Norway. At the time of writing this thesis, no other literature has been published assessing flue gas treatment and CPU alternatives in in bio-CLC.

This degree project studies the integration of carbon capture system into biomass fired combined heat and power (bio-CHP) plants. The key disturbances from bio-CHP plants include flue gas flow rate, carbon dioxide (CO2) concentration and available heat for the reboiler because the use of versatile biomass and the dynamic operation of CHP plants results in large fluctuations in the properties of flue gas and the heat input for CO2 capture. To clearly understand the impacts of these disturbances on the performance of CO2 capture, a dynamic CO2 capture model is developed in Aspen Plus Dynamics by using monoethanolamine (MEA) based chemical absorption. Proportional-Integral (PI) feedback controllers are then implemented to further study and compare the performance of the CO2 capture process under different control strategies, the performance with general control settings and fine-tuned controllers are obtained and compared, including both the control performance and system performance. The control performance includes the maximum deviation and settling time, which could reflect only the performance of the controllers.  The system performance includes Captured CO2, reboiler duty and Energy penalty per unit CO2 captured, which could reflect CO2 capture system performance. An equilibrium stage steady state model is first developed for the key components in the CO2 capture plant in Aspen Plus, consisting of the absorber, the stripper, and lean-rich heat exchanger. By sizing the components and employing the pressure driven mode, the steady state model is enabled to be a dynamic model. The disturbances about flue gas and reboiler heat are taken from a real bio-CHP plant in Sweden. Considering the higher flue gas flowrate, the model has been scaled up to meet the requirement of this bio-CHP plant. The addition of controllers are done for the flexible operation of the CO2 capture system and the controlled variables considered in this study are the percentage of CO2 absorbed in the absorber column, reboiler temperature and rich solvent flow in the stripper column. The results show the effects of fluctuations in the key influencing factors on the control performance and the system performance . The fine-tuned controller implemented system showcases better performance when the quantity of CO2 captured is compared with that of the system in the absence of controllers, where a 1.1% increase in the amount of captured CO2 is observed when the flue gas flow rate is increased by 30%. The system also maintains a 1.8% higher capture rate when controllers are implemented. This showcases better system performance when controllers are implemented in the system. To further analyse the effects of control strategies two different control strategies are compared where controllers with general settings are compared to the controllers which are fine-tuning achieved by implementing tuning parameters which were obtained through Internal Model control (IMC) based on the system requirements. The fine tuning of the controllers results in improved system performance where the amount of captured CO2 increases by 1.4% when the reboiler duty is increased by 30% and a 1.7% decrease in the energy penalty per unit CO2 captured. Additionally, the results show that the settling time and maximum deviation are different for the two controllers where the controller which underwent fine tuning maintained the steady set point whereas the controller with general controller tuning showcases deviation before it attained stability. Therefore, the fine-tuned controller is more efficient to enable the flexible operation of CO2 capture when facing disturbance. It is studied that the tuning parameters implemented in the controllers affect the transient operation of the plant and improved the dynamic performance of the capture system. The tuned controllers offered more stability to the capture system while attaining their respective set points in a shorter time frame. It is also found that there exists a big difference between the system’s performance without controllers and that with finely tuned controllers. The difference in captured CO2 amount is approximately 26 ton/h when flue gas flow rate increases by 30%. The percentage difference is 1.1%, 7.7% and  5.9% for Captured CO2, reboiler duty and Energy penalty per unit CO2 captured respectively. In conclusion the control of the transient operation of the CO2 capture system needs the control system implemented and requires fine tuning parameters to achieve the desirable performance.

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No description available.

Odling av mikroalger för framställning av biogas är ett relativt outforskat område. Den forskning som hittills utförts har påvisat lovande resultat tack vare möjligheten att utnyttja resurser som idag går till spillo, eller till och med utgör miljöproblem; mikroalgerna kan rena både näringsrikt vatten (exv. avloppsvatten) och koldioxidutsläpp (rökgaser från industrin) då de tar upp föreningar innehållande kväve, fosfor och kol från dessa källor. Den producerade biogasen kan ersätta fossila bränslen. Dessutom skapas en rötrest som kan återföras till odlingsmarker vilket sluter näringskretsloppet. Mikroalgen Chlorella vulgaris undersöks gällande dess egenskaper i alg-biogasprocessen för att aktuella flöden ska kunna sammanlänkas genom industriell symbios. Mikroalger kan skapa unika möjligheter till kretsloppsanpassad energiproduktion bland annat tack vare att vissa av dem har potential att fungera både som växt och som djur. För att energiproduktionen ska kunna kretsloppsanpassas måste de olika systemen i alg-biogasprocessen lokaliseras strategiskt med avseende på dess flöden. / The area of microalgae cultivation for the production of biogas is quite uninvestigated. Research has shown promising results due to the possibility to make use of resources that are unused or even cause negative environmental impact: the microalgae can purify nutrient rich water (waste water) as well as exhausts rich in carbon dioxide (flue gas) as they take up compounds containing carbon, nitrogen and phosphorus from these sources. The produced biogas can replace fossil fuels. In addition, a digest is produced which can be returned to cropland which closes the nutrient loop. The microalgae Chlorella vulgaris is studied regarding its traits in the algae-to-biogas process in order to evaluate if the flows present can be interlinked through industrial symbiosis. Microalgae can create unique possibilities for loop adapted energy production partly thanks to their potential to function both as plant and as animal. For a loop adapted energy production the different systems in the algae-biogas process need to be located strategically with regards to the flows in the process. / The area of microalgae cultivation for the production of biogas is quite uninvestigated.Research has shown promising results due to the possibility to make use of resources that areunused or even cause negative environmental impact: the microalgae can purify nutrient rich water(waste water) as well as exhausts rich in carbon dioxide (flue gas) as they take up compoundscontaining carbon, nitrogen and phosphorus from these sources. The produced biogas can replacefossil fuels. In addition, a digest is produced which can be returned to cropland which closes thenutrient loop. The microalgae Chlorella vulgaris is studied regarding its traits in the algae-to-biogasprocess in order to evaluate if the flows present can be interlinked through industrial symbiosis.Microalgae can create unique possibilities for loop adapted energy production partly thanks to theirpotential to function both as plant and as animal. For a loop adapted energy production the differentsystems in the algae-biogas process need to be located strategically with regards to the flows in theprocess

The coming years are expected to bring multiple challenges for all actors within the energy sector. For the Swedish utility company Tekniska verken AB, one of the upcoming tasks is to adapt their energy technologies to enable renewable, plannable and efficient heat and power production. At the same time as the share of renewable energy increases, the demand grows for technologies that can cover for the intermittency and align with policies and goals for sustainable energy. Part of Tekniska verken’s work is therefore focused on investigation of potential solutions for their heat and power production, that also agrees with the municipality’s vision to become “the World’s most resource efficient region”. One of the current projects within the area regards installation and tests of a of a biofueled top cycle (BTC) with high electric efficiency. The project is carried out together with the owner of the technology: Phoenix Biopower AB. This thesis is part of the pre-study to the pilot project, which is aimed to examine the feasibility of installing a pilot unit of the Phoenix Biopower BTC technology in Tekniska verken’s combined heat and power plant KV62, Linköping, Sweden. The thesis is meant to examine the site feasibility through evaluation of how the operation of KV62 will be influenced by the pilot unit’s operation. The work consists of a mapping of necessary interfaces between KV62 and the BTC pilot unit, followed by an assessment of the impact of the pilot unit on operation of KV62. The feasibility is evaluated with respect to operational limits of KV62 and the study includes both quantitative and qualitative evaluation of the impact from the interfaces between the two units. The study has special focus on the impact from the pilot´s flue gases on the flue gas handling system in KV62 which appeared to be a critical interface with respect to the operational limits. The resulting operational changes in this work indicate that the pilot unit can be installed and run in connection to KV62, but that normal operation of KV62 cannot be sustained during steady state operation of the BTC pilot. This is mainly due to the pilot unit’s load in terms of steam withdrawal, and additional heat to the heat recovery system, that cannot be fully managed with the current capacity for feedwater in KV62. However, there can still be potential solutions to run test campaigns of the BTC pilot simultaneously as KV62 delivers both heat and power. It should be taken into consideration that the pilot units’ behavior during transients are not investigated in this work and therefore need further investigation before a decision about the feasibility of the pilot unit installation can be made. Furthermore, some interfaces have multiple options for their placements, and therefore a detailed heat-and mass balance over KV62 would be suggested to investigate the effects of the symbiosis between the decided interface locations further. / Framtiden förväntas medföra många utmaningar för aktörer inom energisektorn, och för Tekniska verken i Linköping är en av de framtida utmaningarna att anpassa energisystemet till kraft- och värmetekniker som är förnybara, effektiva och planerbara. Samtidigt som andelen förnybara energikällor ökar, växer även behovet för energi som kan täcka för oregelbundenheten hos vind- och solkraft och samtidigt passa i Linköpings vision om att bli världens mest resurseffektiva region. En del av Tekniska verkens arbete är att utforska möjliga lösningar för deras framtida energisystem, och en gren i arbetet med forskning och utveckling är ett projekt med mål att bygga och testa en pilotanläggning av en biobränslebaserad toppcykel (BTC). Projektet genomförs tillsammans med teknologins ägare: Phoenix Biopower. Detta examensarbete är del av förstudien tillhörande pilotprojektet, som är ämnad att undersöka genomförbarheten i att installera en pilotanläggning av Phoenix Biopowers teknologi med ett av Tekniska verken i Linköpings kraftvärmeverk, KV62 som moderanläggning. Examensarbetet syftar till att undersöka projektets genomförbarhet genom utvärdering av hur driften av KV62 kommer påverkas av pilotenheten. Arbetet består av en kartläggning av nödvändiga gränssnitt mellan KV62 och BTC-piloten, vilket följs av en bedömning av pilotenhetens inverkan på driften av KV62. Genomförbarheten utvärderas med avseende på driftsgränser för KV62 och studien inkluderar både kvantitativ och kvalitativ utvärdering av pilotens påverkan på KV62 till följd av gränssnitten mellan de två enheterna. Studien har särskilt fokus på rökgasens gränssnitt, som visade sig kunna vara kritiskt med avseende på påverkan från pilotens rökgas på processerna i KV62. Resultatet från arbetet visar att det är möjligt att ansluta och driva pilotanläggningen vid KV62, men att normal drift av KV62 inte kan bibehållas vid drift av BTC-piloten, framförallt på grund av pilotanläggningens belastning genom uttag av ånga; som inte kan hanteras fullt ut av befintlig kapacitet för matarvatten, och tillskottet av effekt till rökgasstråket vid överhettarna. Innan en slutgiltig bedömning av BTC-pilotens genomförbarhet med avseende på påverkan på KV62 kan göras vore det lämpligt att genomföra en studie av påverkan på KV62 under pilotens transienter, samt en analys av värme- och massbalanser i KV62 för fastställda placeringar av gränssnitten.

Combustion of coal is one of the primary sources of electricity generation worldwide today. Coal contains different chemicals that cause particulate matter(PM) and sulfur dioxide (SO2) emissions. These are health hazards and are responsible for deteriorating the ambient air quality. Particulate matter also forms ash deposits inside the coal combustor, which in turn decreases the energy efficiency of the power plants. Using biomass as a fuel in these utility boilers can potentially reduce the problems of particulate matter emissions and ash deposition, and can significantly reduce the SO2 emissions. However, biomass needs to be pretreated to make its properties similar to coal in terms of energy density, grindability, and durability before it can be fired in utility boilers. Steam explosion is one of the leading biomass pretreatment methods that enhances the physicochemical properties of biomass. A comprehensive review of the steam explosion process, its product properties, its comparison with other treatment processes, as well as its economic analysis and lifecycle assessment, have been explored in this work. Steam-exploded biomass has been co-combusted with bituminous coal in a 1500 kWth combustor to analyze the ash aerosol particle size distribution, composition, and deposition behavior. The primary results of these tests showed that both particulate matter emissions and ash deposition amount reduced significantly as more biomass was co-fired with coal. The submicron-sized particulate matter concentration showed a high correlation with the final mass of ash deposits (R2 > 0.96). Predicting ash deposition rates is important during the combustion of solid fuels. A Machine Learning tool was applied and trained with a fuel composition database of 92 fuels obtained from a thermodynamic equilibrium software (FactSage). When fully operational, this model should be integrated with an existing ash deposition model, which should make it self-sufficient in terms of generating equilibrium composition data. SO2 emissions were analyzed during the co-combustion of biomass and coal, and a synergistic decrease in SO2 emissions was observed with higher biomass blends. Experiments were conducted in a full-scale 471 MWe furnace to analyze the SO2 emissions, and an 85%-15% blend of coal and biomass was responsible for a 28.1% reduction in emissions and 22.1% reduction in the lime slurry utilization in the flue gas desulfurization (FGD) towers compared to pure coal combustion. Ash deposit characterizations by energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) combined with thermodynamic equilibrium simulations revealed that calcium and potassium were responsible for this synergistic reduction as these metals captured the SO2 from the flue gases and retained them in the ash phase. The SO2 research was important since the current literature is deficient in research conducted at suspension-fired full-scale utility boilers to reduce SO2 emissions by co-firing coal and biomass blends. The research in this dissertation should provide valuable insights to the energy industries that are considering a transformation of fuel portfolio from coal to biomass and explore how the mineral matter present in pretreated biomass would behave inside a utility boiler. The primary conclusions are that during the co-combustion of coal and biomass, ash deposition mass and particulate matter ash load decreased, and SO2 emission saw a synergistic reduction in emissions due to higher calcium and potassium content in biomass compared to pure coal combustion.

M. Tech. (Department of Chemical Engineering, Faculty of Engineering and Technology): Vaal University of Technology / Strict environmental regulation on flue gas emission has led to the implementation of FGD technologies in power stations. Wet FGD technology is commonly used because it has high SO2 removal efficiency, high sorbent utilization and due to availability of the sorbent (limestone) used. SO2 is removed by passing flue gas through the absorber where it reacts with the slurry containing calcium ions which is obtained by dissolution. This study presents the findings of the dissolution of a calcium-based material (limestone) for wet FGD process. This was done using a pH stat apparatus and adipic acid as acid titrant. Adipic acid was used because of its buffering effect in wet FGD process. The conditions used for this study are similar to what is encountered in a wet FGD process. The extent of dissolution was determined by analyzing the amount of calcium ions in solution at different dissolution periods. The dissolution kinetics were correlated to the shrinking core model and it was found out that chemical reaction at the surface of the particle is the rate controlling step. This study also investigated the dissolution of coal fly ash and bottom ash. Their dissolution kinetics showed that the diffusion through the product layer was the rate controlling step due to an ash layer formed around the particle. The formation of ash layer was attributed to pozzolanic reaction products which is calcium-alumino-silicate (anorthite) compounds were formed after dissolution. The effect of fly ash on the dissolution of rate of limestone was also studied using response surface methodology. Limestone reactivity was found to increase with increase in the amount of fly ash added and the pH was found to be strong function of the rate constant compared to other dissolution variables. The presence of silica and alumina in fly ash led to a significant increase in the specific surface area due to hydration products formed after dissolution. / Eskom

Ces travaux portent sur la conception et le développement d’un procédé membranaire de captage/stockage du CO2 embarqué pour le transport routier. Dans une première partie, nous réalisons la simulation d’un procédé membranaire embarqué de captage du CO2 dans le cas d’un poids lourd (>3500 kg). Ceci comprend l’analyse énergétique de la séparation et de la compression des gaz, l’évaluation des surfaces et volumes requis ainsi que l’autonomie de l’unité de stockage et la surconsommation engendrée par ce dispositif. Nous étudions dans un second temps la relation entre qualité des supports fibres creuses et celle des membranes nanocomposites MFI-alumine synthétisées. Nous nous intéressons ensuite aux performances des membranes nanocomposites dans la séparation CO2/N2 en phase gazeuse. Plus particulièrement nous évaluons l’influence de la substitution isomorphique du silicium par le bore et le germanium, ainsi que l’échange du proton de valence par d’autres atomes, sur la séparation en question. Un chapitre est dédié à l’évaluation des paramètres thermodynamiques (adsorption) et cinétiques (diffusion) de la séparation CO2/N2. Enfin, nous analysons l’influence de la présence de polluants dans le mélange à séparer (eau, NOx, hydrocarbures) sur les performances séparatives des membranes synthétisées. / This work focuses on the conception and development of a membrane-based process for an on-board CO2 capture/storage application. In a first part, we simulate an on-board CO2 capture unit based on a membrane process for the case study of a heavy vehicle (>3500 kg). This study includes an energy analysis of the impact of gas separation and compression on the required membrane surface and module volume, as well the autonomy of the storage unit and the energy overconsumption involved in the process. In a second part, we study the influence of the hollow-fibre support quality on the final intergrowth level of nanocomposite MFI-alumina membranes. Special attention is devoted to the influence of the isomorphic substitution of silica by boron and germanium, and replacement of the counter-cation (proton) by other elements, on the CO2/N2 separation and permeance properties. Next, a complete chapter has been devoted to the evaluation of the thermodynamic (adsorption) and kinetic (diffusion) parameters in the CO2/N2 separation. Finally, we analyze the influence of standard pollutants (water, NOx, hydrocarbons) on the CO2 separation properties of the synthesized membranes.