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Currently, the global economy looses a considerable amount of potential secondary raw materials from the disposed waste streams. Furthermore, the existing landfill sites that often do not have proper environmental protection technologies pose a long-lasting risk for the environment, which urge immediate actions for landfill remediations. At the same time, the energy recovery from waste through conventional incinerators has been criticized for its CO2 emissions. Alternatively, pyrolysis and gasification offer the potential to recover secondary resources from waste and biomass streams, which can increase the circularity of the material resources and limit the CO2 emissions. This thesis aims to realize feasible thermochemical processes to enhance the material resources' circularity by treating landfill waste and biomass. Correspondingly, fundamental studies involving experimental works and process developments through lab-scale experiments and process simulations are carried out. The thesis is written based on the results from five different studies that cover the investigation regarding the effect of waste/biomass fuel properties on the performance of the pyrolysis and gasification processes, as well as the process development and improvement of thermochemical conversion processes of waste and biomass. The first study investigates the primary fragmentation behaviour of waste fuel pellets during the pyrolysis stage of thermochemical conversion processes. This study shows that the fragmentation degree of waste pellets correlates well with their volatile matter contents. Meanwhile, there is no clear relation between the fragmentation degree and the pellets’ mechanical strength. Generally, due to the high volatile matter content from plastic, fuel pellets from waste tend to fragment into a high number of smaller particles than typical biomass or coal pellets during thermochemical processes. Hence, for some processes, improving the thermal stability of waste pellets is more relevant than improving their mechanical strength. Subsequently, the second study examines the reactivity and kinetics behaviour of waste-derived char during gasification. In general, it is found that the char reactivity is a function of the ash amount and the ratio of inorganic catalytic elements (K, Ca, Na, Mg, and Fe) to the inhibitor elements (Si, Al, and Cl). More importantly, the char gasification test results demonstrated the significance of the waste sorting processes' operating conditions on the thermal behaviour of the waste fuel, especially during the gasification process. Meanwhile, the third study investigates the syngas and tar formations resulting from different interactions between plastic and paper fractions of solid waste. The results show that the interaction between plastic and paper significantly depends on the hydrocarbon chain structures of the plastic polymer. Specifically, the interactions of aliphatic-structured plastic polymers (represented by PE) and paper cause synergistic effects that reduce the tar and increase the syngas yields. Meanwhile, the synergistic effects tend to be less evident in the case of co-gasification between paper and an aromatic hydrocarbon polymer, represented by PS. Based on the results of the previous studies, a co-gasification process of waste with biomass or biochar is proposed in the fourth study. It is found that adding biochar during the gasification of waste could significantly increase the syngas and H2 production to become higher than that of when adding biomass. Synergistic effects are observed in the form of an extensive syngas yield increment and a tar yield reduction, due to the tar reforming reactions over biochar particles. In general, both biochar and biomass additions result in a higher energy yield ratio, suggesting that it could improve the efficiency of the waste gasification. Finally, the fifth study focuses on process simulations and operational cost assessments of co-production of H2, biochar, and bio-oil from biomass. The process simulation study is carried out to evaluate different scenarios for producing biochar, bio-oil, and H2 based on a biomass pyrolysis process coupled with a steam reforming and a WGS process. Based on the calculations of the total operating cost and the potential revenue, it is found that the production of bio-oil is more economically beneficial than the production of H2. The estimated minimum selling price for biochar and bio-oil based on the operating cost alone is within the price ranges of related commodities in Sweden (i.e., charcoal, coal, coke and oil crude). Nevertheless, capital and operating costs for post-processing of bio-oil should also be considered in the future to obtain a more complete economic judgement. Förnärvarande så försvinner en stor mängd sekundära råmaterial som avfall istället för att bidra till en global ekonomi. Dessutom så är de existerande avfallsdeponierna inte utrustade med teknologier för att förhindra långsiktiga risker för miljöförstöringar, vilket gör att det är av yttersta vikt att vidta åtgärder för att hantera dessa avfallsdeponier. Samtidigt så har energiåtervinning baserat på förbränning av avfall kritiserats för den leder till ökade CO2 utsläpp. Här utgör pyrolys och förgasningsprocesser bra alternativ för att möjliggöra en återvinning av sekundära råmaterial från avfall och biomassa, vilket kan leda till en ökad cirkularitet av materialresurser och minskade CO2 emissioner. I denna avhandling diskuteras möjligheten att använda termokemiska processer för att öka cirkulationen av material baserat på utnyttjande av avfallsdeponier och biomassa. Fundamentala studier inriktade på utveckling av experimentella tekniker och processer har utförts baserat på försök I laboratorieskala och simuleringar. Avhandlingen innefattar resultat från fem olika undersökningar som behandlar studier av påverkan av bränsleegenskaperna hos avfall/biomassa på effektiviteten av pyrolys- och förgasningsprocesser samt på processutvecklingar och förbättringar av termokemiska konverteringsprocesser för avfall och biomassa. Den första undersökningen fokuserar på den primära sönderdelningen av pellets tillverkade av avfall vid pyrolyssteget av den termokemiska konverteringsprocesen. Resultaten visar att graden av sönderdelning av pellets från avfall är starkt kopplad till innehållet av lättflyktiga ämnen. Däremot så finns ingen klar koppling mellan graden av sönderdelning och den mekaniska styrkan hos pellets. Generellt så innebär den höga andelen av lättflyktiga ämnen i plaster att bränsle pellets tillverkade av avfall tenderar i att sönderdelas i ett stort antal små partiklar jämfört med typiska pellets tillverkade av biomassa eller kol under den termokemiska konverteringsprocessen. Därför så är det mer relevant att förbättra den termiska stabiliteten av pellets tillverkade av avfall i jämförelse med den mekaniska stabiliteten för några processer. Den andra undersökningen fokuserar på att studera reaktiviteten och kinetiken av kol tillverkat av avfall vid förgasning. Resultaten visar att reaktiviteten hos kol är beroende av askinnehållet och kvoten mellan oorganiska katalytiska ämnen (K, Ca, Na, Mg, och Fe) och hämmande ämnen (Si, Al, och Cl). Fast av större betydelse, att förgasningen av kol visar på betydelsen av sorteringsmetodernas effektivitet på den termiska egenskapen hos bränsle tillverkat av avfall, speciellt under förgasningsprocessen. Den tredje undersökningen fokuserar på att studera bildningen av tjära och syngas som ett resultat av interaktioner mellan plast- och pappersfraktioner som finns i det fasta avfallet. Resultaten visar att interaktionen mellan plast och papper i hög grad beror av kedjestrukturen hos kolväten i polymerer. Specifikt, så orsakar interaktionen mellan alifatiskt strukturerade polymerer (representerade av PE) och papper synergiska effekter som leder till minskade tjär- och syngasutbyten. Samtidigt så är den synergiska effekten mindre uppenbar när papper och aromatiska kolvätespolymerer, representerade av PS, förgasas tillsammans. Den fjärde undersökningen presenterar resultat från en kombinerad förgasningsprocess som använder avfall I combination med biomassa eller biotjära, baserat på resultaten i de tidigare tre studierna. Resultaten visar att om biotjära tillsätts vid förgasning av avfall så kan utbytet av syngas och H2 ökas mer än om biomassa tillsätts vid förgasning av avfall. Dessutom framkom synergiska bidrag i form av väsentlig ökning av syngasutbytet och en minskning av tjärutbytet, orsakat av tjärreaktioner som sker i biotjärpartiklarna. Generellt så visar resultaten att både tillsatser av biotjära och biomassa leder till ett högre energiutbyte, vilket indikerar att dessa tillsatser kan öka effektiviteten vid förgasning av avfall. I den femte undersökningen användes processsimuleringar och kostnadsberäkningar för bedöma processen innefattande att samproducera H2, biokol, och bio-olja från biomassa. Simuleringarna av processen utfördes för att bestämma olika scenarios vid tillverkning av biokol, bioolja och H2 vid pyrolys av biomassa kopplat med en ångreformering och en WSG process. Baserat på beräkningar av den totala driftskostnaden och den potentiella förtjänsten så framkom att produktion av bioolja är mer fördelaktig i jämförelse med produktion av H2. Den uppskattade lägsta försäljningspriset för biokol och bioolja baserat på enbart driftskostnaden ligger inom prisintervallet för relaterade existerande produkter ( t ex träkol, kol, koks och råolja). Icke desto mindre så måste kostnader för kapital och driftskostnader relaterade till förbehandling av bioolja tas i beaktande i framtida utvärderingar för att erhålla en mer realistisk ekonomisk bedömning.

Bio-based fertilizers are currently gaining interest as a method for reducing the use of chemical fertilizers and as a means for safe disposal of biomass waste. Feathers, which are an abundantly available biomass and have a high N content, are a potential source of fertilizer nutrients. In this study, chicken feathers were subjected to hydrothermal treatment (HTT) with lime addition in the temperature range of 140–200°C to obtain a high N containing liquid product that can be used as a liquid fertilizer. The objective of this study was to examine the effect of HTT conditions on the feather solubilization rate and the properties of the liquid products. The results showed that HTT with a reaction temperature of 180°C, a reaction time of 30 min, feather-water ratio of 1:5, and lime addition is sufficient to solubilize as high as 83% of the chicken feather protein. The produced liquid contained nitrogen of up to 3.4% and total amino acid content of 13.6%. These results indicate the potential utilization of soluble hydrolyzed feather obtained from the HTT process for liquid N fertilizer. © 2017 American Institute of Chemical Engineers Environ Prog, 37: 375–382, 2018

Due to their high potential and beneficial characteristics, algae is considered as very promising energy source in future. In this study, an integrated conversion system of algae to hydrogen is pro ...

The effects of carbon fiber–epoxy interfacial strength on the mechanical properties of the corresponding fiber-matrix composites are experimentally demonstrated in this work. Two composites containing different carbon fibers were tested: as-received fibers and fibers soaked in acetone to remove adhesive on their surfaces. The fiber surfaces were first characterized by scanning electron microscopy and time-of-flight secondary-ion mass spectrometry to verify removal of the adhesive. Further, single-fiber fragmentation tests were conducted to evaluate the fiber strength and the interfacial strength. The mechanical properties of the composites were evaluated via tensile testing under longitudinal and transverse loadings. The results show that interfacial strength does not decrease the mechanical properties of the composites under longitudinal loading. In contrast, under transverse loading, the interfacial strength significantly decreases the mechanical properties, specifically the ultimate tensile strength and toughness of the composites.

This study employs wet torrefaction process (also known as hydrothermal) at low temperature. This process simultaneously acts as waste processing and separation of mixed waste, for subsequent utilization as an alternative fuel. The process is also applied for the delamination and separation of non-recyclable laminated aluminum waste into separable aluminum and plastic. A 2.5-L reactor was used to examine the wet torrefaction process at temperatures below 200 °C. It was observed that the processed mixed waste was converted into two different products: a mushy organic part and a bulky plastic part. Using mechanical separation, the two products can be separated into a granular organic product and a plastic bulk for further treatment. TGA analysis showed that no changes in the plastic composition and no intrusion from plastic fraction to the organic fraction. It can be proclaimed that both fractions have been completely separated by wet torrefaction. The separated plastic fraction product obtained from the wet torrefaction treatment also contained relatively high calorific value (approximately 44 MJ/kg), therefore, justifying its use as an alternative fuel. The non-recyclable plastic fraction of laminated aluminum was observed to be delaminated and separated from its aluminum counterpart at a temperature of 170 °C using an additional acetic acid concentration of 3%, leaving less than 25% of the plastic content in the aluminum part. Plastic products from both samples had high calorific values of more than 30 MJ/kg, which is sufficient to be converted and used as a fuel.

In this study, the comparison of the pellets produced from untreated EFB, the hydrothermally treated empty fruit bunch (HTT-EFB) and washed HTT-EFB was performed. The pelletization of the raw EFB, HTT-EFB, and washed HTT-EFB was conducted using a single pellet making device. In experiments performed at room temperature under a densification pressure of 150 MPa, the physical properties, mechanical strength, durability, and hydrophobicity of the produced pellets were then evaluated. Scanning electron microscope (SEM) analysis was also performed to investigate the binding mechanisms within the pellets. The results showed that the washed HTT-EFB pellets had higher mechanical strength and durability than the HTT-EFB or raw EFB pellets. The HTT-EFB pellets also demonstrated hydrophobic behavior against moisture exposure. However, the washed HTT-EFB pellets required higher compaction energy than the other pellets. From this analysis, it was determined that the changes in the composition of EFB biomass owing to HTT and the washing process regulate pelletization behavior and affect the binding mechanism during pelletization. In addition, the combustion performance of treated EFB samples showed significant improvements as it has higher ignition temperatures with more uniform combustion profiles as shown in the data obtained from TGA analyser. This research demonstrated that the combination of HTT, washing, and pelletization cotreatment is a promising method for upgrading EFB into energy-dense, durable, and homogeneous hydrophobic solid fuel.