O uso de aglomerantes na pelotização a quente de minério de ferro visa cumprir duas funções: (1) aumentar a resistência da pelota antes do aquecimento (resistência a verde) e (2) evitar o colapso das pelotas durante a queima, quando a expulsão dos gases gerados pela vaporização de água e de voláteis tende a destruir a pelota. A bentonita é o aglomerante mais empregado industrialmente, e seu mecanismo de ligação no processo de ganho de resistência da pelota já foi amplamente estudado e compreendido. Várias tentativas de substituição da bentonita na pelotização de minério de ferro recorrem ao uso de aglomerantes orgânicos cuja composição apresente propriedades aglomerantes em conjunto com dispersantes. O presente trabalho visou contribuir para o melhor entendimento do mecanismo inerente ao uso de agente coloidisante na aglomeração do material particulado no processo de pelotização, por meio da avaliação da influência dos agentes coloidisantes em comparação aos aglomerantes Peridur® e bentonita no processo de pelotização de concentrado de minério de ferro. Para este fim, foram realizados ensaios de bancada visando a identificação de possíveis ações dos aglomerantes/dispersantes na viscosidade, potencial zeta e grau de dispersão das misturas, bem como a sua influência na liberação/aglomeração dos finos. Os resultados destes parâmetros foram confrontados com os resultados de caracterização das pelotas confeccionadas com os diferentes aglomerantes/ dispersantes pelos quais foi possível identificar que os dispersantes tem forte atuação sobre o conteúdo de finos do concentrado de minério de ferro. A ação principal se dá pela remoção das partículas ultrafinas que recobrem os grãos mais grosseiros presentes na amostra e as dispersam, no caso dos dispersantes, aumentando a disponibilidade do conteúdo de finos <4 µm, principalmente os finos menores que 1 µm (coloides). No caso do aglomerante orgânico, observa-se também essa ação, no entanto, os finos presentes são aglomerados na faixa entre 26 e 4 µm. / The use of binders for iron ore pelletizing is required to: (1) increase the pellet strength before heating (green strength); (2) prevent the collapse of the pellets during firing, when the gases generated by water vaporization could create cracks. Bentonite is the main binder used in industry, and its binding mechanism in iron ore pellets has been widely studied and understood. Efforts to solve the problems of using bentonite in iron ore pelletizing have focused on the use of organic binders whose composition presents dispersant properties. The objective of this study is to evaluate the influence of colloidal agents compared to binders, Peridur® and bentonite, in the pelletizing process of iron ore concentrate aiming to contribute with the understanding the action of these agents in the mechanisms of agglomeration of the pellets. With this goal, bench tests were carried out to identify possible actions of binders/dispersant in the viscosity, zeta potential and degree of dispersion of the mixtures, as well as its influence on the liberation/agglomeration of the fine particles. The results of these parameters were compared with the results of the characterization of the pellets prepared with different binders/dispersants. By this study, it was identified that the dispersant has a strong influence on the fine particle content on the iron ore concentrate. The main action takes place by the removal of ultrafine particles overlying coarser grains in the sample and the scatter, in the case of dispersants, increasing the availability of fine content <4 micrometers. In the case of the organic binder, this action is also observed; however, the fines are agglomerated in the range between 4 and 26 micrometers.

O inchamento de pelotas de minério de ferro, que pode chegar até 400%, é um assunto que desperta interesse da indústria metalúrgica por gerar diversos problemas durante processos de redução. Ele ocorre por dois motivos, a saber, a mudança da estrutura cristalina na transformação da hematita (Fe2O3) para a magnetita (Fe3O4) e o aparecimento de ferro no formato filamentar durante a última etapa de redução. Diversos fatores influenciam o comportamento das pelotas, como a basicidade binária (CaO/SiO2) e o teor de MgO. Foram realizados experimentos para avaliar o efeito destas duas variáveis em suas propriedades físicas, como resistência à compressão e porosidade, e no comportamento das pelotas durante a redução. Os teores de MgO foram de 0%, 1% e 5%, enquanto a basicidade foi de 0,61 a 1,5. Ao adicionar MgO, a porosidade e a redutibilidade aumentam, enquanto o inchamento e a resistência diminuem. Ao adicionar CaO, a porosidade cai por conta da formação de mais fase líquida durante a queima, há diminuição de inchamento. A redutibilidade aumenta até basicidade 1 e depois apresenta uma leve diminuição em basicidade 1,5. / Iron ore pellets swelling, which can reach up to 400%, is a subject that rises concern in metallurgical industry because of the problems it may cause during reduction processes. Several factors can change pellets behavior concerning swelling, such as binary basicity (CaO/SiO2) and the MgO content. Experiments were performed to evaluate the effect of these two variables in the physical properties of the pellets, such as compression strength and porosity, and in their behavior during reduction as well. MgO was added up to 5% and basicity varied in a range from 0.61 to 1.5. Addition of MgO increased porosity and reducibility, while swelling and strength decreased. Addition of CaO caused porosity to decrease because of the formation of more liquid slag during heat treatment. Is also decreased swelling. Reducibility rises when basicity reaches 1.0, but decreases with further increases in CaO content.

European Union’s (EU) dependence on fossil fuel imports strongly affects its energy supply and economic and national stability. In order to reduce its dependence and maintain the leadership position in GHG emissions reductions and renewable energy consumption, EU has set ambitious targets of reducing GHG emissions by at least 20% compared with 1990, raising the share of renewable energy to 20% and increasing the levels of biofuels in transport fuels to 10% by 2020. While some of the countries, due to their large renewable potential, have already reached set targets, some are still far behind. Biomass, with 69.8% share in gross inland consumption of renewables, has the greatest potential. Since some EU members have low availability of biomass, and are scarce in other renewable sources, they have become biomass importers. As some studies have shown, imports of biomass reduce cost of achieving targets for renewable electricity and increase electricity production from biomass. Wood pellets, as currently the most tradable solid biomass commodity, already reached significant shares in imports and consumption of biomass in some EU countries. The most of pellets were traditionally imported from Canada; however, last year US became the EU’s largest importing partner with 534,000 tons of industrial pellets exported mainly to Belgium and Netherlands. The EU’s increasing demand for wood pellets was a major driver for substantial increase in the wood pellet production capacity in US, with many plants being constructed for export to EU. This thesis evaluates the possibility of producing wood and switchgrass pellets in East Tennessee, assuming three feedstock scenarios, and their export to EU. Results from the base-case model showed that production costs of pellets were $155, $164 and $170 per ton, while price of pellets on the EU market will have to be $207, $216 and $222 per ton in the 100% mill residue, 40/60 blend and 100% switchgrass scenarios, respectively, for the project to breakeven. Sensitivity analysis showed a strong impact of feedstock price, moisture and exchange ratio on project’s return on investment.

Die Qualität der hergestellten Brennstoffpellets wird wesentlich vom Holzanteil und Wassergehalt des Pelletiergutes sowie von der Presskanallänge der eingesetzten Pelletpresse bestimmt. Werden die Pellets ohne Holzzusatz aus Braunkohlenxylit hergestellt, erreichen diese nahezu das Festigkeitsniveau kommerzieller Holzpellets. Wesentlich für das Trocknungsverhalten von Xylit- und Xylit-Holz-Pellets ist deren Zusammensetzung, die Trocknungstemperatur ist nur von untergeordneter Bedeutung. Als domininierender Bindemechanismus konnte der Faserformschluss identifiziert werden, wobei dieser durch Adhäsions- und Kristallisationseffekte infolge der hydro-mechanischen Aktivierung des Rohmaterials im Nassaufschlussprozess begünstigt wird. Die Xylit- und Xylit-Holz-Pellets erfordern eine auf im Vergleich zu Holzpellets aschereiche Brennstoffe ausgelegte Feuerungstechnik, wobei durch die Holzzugabe verbrennungstechnische Vorteile wie geringere NOx- und SO2-Emissionen erreicht werden können.

Pelletizing is a size enlargement technique employed to process fine-grained iron-bearing concentrates and powder ores. Mechanical strength of fired pellets is important for handling. When the pellets undergo metallurgical processing, their mechanical strength is a measure of their resistance to degradation by breakage due to impacts and abrasion to which they are exposed in the upper part of the blast furnace. In this study, heat treatment of iron ore agglomerates with microwave energy is investigated. First drying and then heat hardening tests were performed. Two main properties of pellets were taken into consideration: percent moisture and magnetite content for the dried pellets and compressive strength and also magnetite content for the fired pellets. The tests were conducted with different particle sized pellets, in different durations. In order to increase the oxidation rate in heat hardening tests, Na2O2 is also added in different percentages. The results of the study showed that, magnetite pellets can indeed be dried and heated with microwave energy. However, the attained compressive strength and v the oxidation of the fired pellets were not sufficient as compared to pellets produced by conventional heating

Im Rahmen der Arbeit wurde die Pelletierung von Braunkohlenfaserholz (Braunkohlenxylit) in Kombination mit unterschiedlichen Biomassen (Holzhackschnitzel, Waldhackschnitzel, Rapsstroh, Weizenstroh) untersucht, wobei für die Pelletierung Ring- und Flachmatrizenpressen eingesetzt wurden. Zudem wurde der Einfluss unterschiedlicher Bindemittel (Kartoffelstärke und Zellleim) auf die Agglomeratqualität untersucht. Zusammenfassend kann festgestellt werden, dass die Pelletierung von Xylit-Biomasse-Mischungen, unter Beachtung der spezifischen Rohstoffeigenschaften und des Pressaggregats, problemlos möglich ist. Allerdings erreichen die bisher hergestellten Verbundpellets noch nicht die Qualität von Holzpellets.

To evaluate the possible benefits that the heat treatment process by expansion can bring the diets for broilers with the inclusion or not of rice bran parboiled (RBP), two studies were conducted. The first study evaluated performance and carcass yield in the period 1-42 days, the second study comprised a digestibility trial in experimental batteries, both with six treatments. The first study was performed in an experimental avian composed of 96 experimental boxes, each experimental unit was made up of 40 broiler chicks. In the second study, for the digestibility trial were used 384 male broiler chicks in a period of 1 to 21 days of age with eight repetitions of eight birds each. At 21 days was held ileal content collection for digestibility analysis. In the both studies was used a completely randomized experimental design in a 2 x 3 factorial arrangement, two diets (one based on corn and the other with the inclusion of 20% RBP) and 3 types of processes, and mash diets, pelleted and expanded pelleted, all isonutritives. The mean they when presented differences in 5% significance were compared by Tukey test. In performance studies and carcass yield, the broilers fed corn-based diets showed higher feed conversion, productive efficiency ratio and carcass yield, when compared to broilers fed diets containing 20% RBP. The use of the expander in diets for broilers in manufacturing process provide better performance index and feed conversion major compared to the broilers fed with mash diet in the period 1-42 days old. In the digestibility study the expansion of diets promoted an increase in the digestibility of dry matter, crude protein, ether extract and starch, compared to the pelleting process. Broilers fed inclusion of 20% RB in the diet, from 1 to 21 days, showed drop in performance and digestibility of dry matter, crude protein, ether extract and starch in relation to broilers receiving the corn-based diet. / Para avaliar os possíveis benefícios que o processo de tratamento térmico por expansão pode trazer as dietas para frangos de corte com a inclusão ou não de farelo de arroz parboilizado (FAP), foram realizados dois estudos. O primeiro estudo avaliou desempenho e rendimento de carcaça no período de 1 a 42 dias, o segundo estudo compreendeu um ensaio de digestibilidade em baterias experimentais, ambos com seis tratamentos. O primeiro estudo foi realizado em aviário experimental composto por 96 boxes experimentais, cada unidade experimental foi composta por 40 frangos de corte machos. No segundo estudo, para o ensaio de digestibilidade foram utilizados 384 frangos de corte machos em um período de 1 a 21 dias de idade com oito repetições de oito aves cada. Aos 21 dias foi realizada a coleta de conteúdo ileal para analise de digestibilidade. O delineamento utilizado em ambos os estudos foi o inteiramente casualizado em esquema fatorial (2x3), duas dietas (uma a base de milho e a outra com a inclusão de 20% de FAP) e 3 tipos de processos, sendo dietas fareladas, peletizadas e expandidas peletizadas, todas isonutritivas. As médias quando apresentaram diferenças a nível de 5% de significância, foram comparadas pelo teste de Tukey. No estudo de desempenho e rendimento de carcaça, as aves alimentadas com dietas à base de milho, apresentaram melhor conversão alimentar, índice de eficiência produtiva e rendimento de carcaça, quando comparadas às aves que receberam dietas contendo 20% de FAP. O uso do expander no processo de fabricação de dietas para frangos de corte melhorou os índices de desempenho, proporcionando melhoria na conversão alimentar em comparação às aves alimentadas com dietas fareladas no período de 1 a 42 dias de idade. No estudo de digestibilidade a expansão de dietas promoveu aumento no coeficiente de digestibilidade da matéria seca, proteína bruta, extrato etéreo e amido, em relação ao processo de peletização. Aves alimentadas com inclusão de 20% de FAP na dieta, no período de 1 a 21 dias, apresentaram queda de desempenho e do coeficiente de digestibilidade da matéria seca, proteína bruta, extrato etéreo e amido em relação às aves que recebem dieta a base de milho.

O uso de aglomerantes na pelotização a quente de minério de ferro visa cumprir duas funções: (1) aumentar a resistência da pelota antes do aquecimento (resistência a verde) e (2) evitar o colapso das pelotas durante a queima, quando a expulsão dos gases gerados pela vaporização de água e de voláteis tende a destruir a pelota. A bentonita é o aglomerante mais empregado industrialmente, e seu mecanismo de ligação no processo de ganho de resistência da pelota já foi amplamente estudado e compreendido. Várias tentativas de substituição da bentonita na pelotização de minério de ferro recorrem ao uso de aglomerantes orgânicos cuja composição apresente propriedades aglomerantes em conjunto com dispersantes. O presente trabalho visou contribuir para o melhor entendimento do mecanismo inerente ao uso de agente coloidisante na aglomeração do material particulado no processo de pelotização, por meio da avaliação da influência dos agentes coloidisantes em comparação aos aglomerantes Peridur® e bentonita no processo de pelotização de concentrado de minério de ferro. Para este fim, foram realizados ensaios de bancada visando a identificação de possíveis ações dos aglomerantes/dispersantes na viscosidade, potencial zeta e grau de dispersão das misturas, bem como a sua influência na liberação/aglomeração dos finos. Os resultados destes parâmetros foram confrontados com os resultados de caracterização das pelotas confeccionadas com os diferentes aglomerantes/ dispersantes pelos quais foi possível identificar que os dispersantes tem forte atuação sobre o conteúdo de finos do concentrado de minério de ferro. A ação principal se dá pela remoção das partículas ultrafinas que recobrem os grãos mais grosseiros presentes na amostra e as dispersam, no caso dos dispersantes, aumentando a disponibilidade do conteúdo de finos <4 µm, principalmente os finos menores que 1 µm (coloides). No caso do aglomerante orgânico, observa-se também essa ação, no entanto, os finos presentes são aglomerados na faixa entre 26 e 4 µm. / The use of binders for iron ore pelletizing is required to: (1) increase the pellet strength before heating (green strength); (2) prevent the collapse of the pellets during firing, when the gases generated by water vaporization could create cracks. Bentonite is the main binder used in industry, and its binding mechanism in iron ore pellets has been widely studied and understood. Efforts to solve the problems of using bentonite in iron ore pelletizing have focused on the use of organic binders whose composition presents dispersant properties. The objective of this study is to evaluate the influence of colloidal agents compared to binders, Peridur® and bentonite, in the pelletizing process of iron ore concentrate aiming to contribute with the understanding the action of these agents in the mechanisms of agglomeration of the pellets. With this goal, bench tests were carried out to identify possible actions of binders/dispersant in the viscosity, zeta potential and degree of dispersion of the mixtures, as well as its influence on the liberation/agglomeration of the fine particles. The results of these parameters were compared with the results of the characterization of the pellets prepared with different binders/dispersants. By this study, it was identified that the dispersant has a strong influence on the fine particle content on the iron ore concentrate. The main action takes place by the removal of ultrafine particles overlying coarser grains in the sample and the scatter, in the case of dispersants, increasing the availability of fine content <4 micrometers. In the case of the organic binder, this action is also observed; however, the fines are agglomerated in the range between 4 and 26 micrometers.

O inchamento de pelotas de minério de ferro, que pode chegar até 400%, é um assunto que desperta interesse da indústria metalúrgica por gerar diversos problemas durante processos de redução. Ele ocorre por dois motivos, a saber, a mudança da estrutura cristalina na transformação da hematita (Fe2O3) para a magnetita (Fe3O4) e o aparecimento de ferro no formato filamentar durante a última etapa de redução. Diversos fatores influenciam o comportamento das pelotas, como a basicidade binária (CaO/SiO2) e o teor de MgO. Foram realizados experimentos para avaliar o efeito destas duas variáveis em suas propriedades físicas, como resistência à compressão e porosidade, e no comportamento das pelotas durante a redução. Os teores de MgO foram de 0%, 1% e 5%, enquanto a basicidade foi de 0,61 a 1,5. Ao adicionar MgO, a porosidade e a redutibilidade aumentam, enquanto o inchamento e a resistência diminuem. Ao adicionar CaO, a porosidade cai por conta da formação de mais fase líquida durante a queima, há diminuição de inchamento. A redutibilidade aumenta até basicidade 1 e depois apresenta uma leve diminuição em basicidade 1,5. / Iron ore pellets swelling, which can reach up to 400%, is a subject that rises concern in metallurgical industry because of the problems it may cause during reduction processes. Several factors can change pellets behavior concerning swelling, such as binary basicity (CaO/SiO2) and the MgO content. Experiments were performed to evaluate the effect of these two variables in the physical properties of the pellets, such as compression strength and porosity, and in their behavior during reduction as well. MgO was added up to 5% and basicity varied in a range from 0.61 to 1.5. Addition of MgO increased porosity and reducibility, while swelling and strength decreased. Addition of CaO caused porosity to decrease because of the formation of more liquid slag during heat treatment. Is also decreased swelling. Reducibility rises when basicity reaches 1.0, but decreases with further increases in CaO content.

81% of the population in sub-Saharan Africa relies on charcoal and firewood to cover their energy needs for cooking. In Africa charcoal is usually produced by burning tree in a traditional kilns and then the food is cooked with a carbon-fired stoves indoors. All that links to three problems; deforestation, health issues and overpopulation, all of which can be reduced with a pellet cooking stove. Zambia in sub-Saharan Africa consumes charcoal equivalent to 6,089,000 tons of firewood each year. The total consumption of firewood being 13,967,000 tons per year. That leads to harvesting rate between 250,000 and 300,000 hectares each year making Zambia having one of the world’s fastest deforestation rates. Deforestation can be reduced by using the energy from the wood more efficient. In charcoal production and heating with charcoal about 72-86% of the produced energy is released to the atmosphere resulting the efficiency rate of only 14-28%. In comparison pellet production efficiency rate is 70-83%. Therefore if fuel pellets are used for cooking purposes energy instead of charcoal efficiency increases by 42-69% leading to lower need of wood material to cover equal energy demand. In this study five hardwood species and a softwood reference material from Zambia has been evaluated for fuel pellet production purposes. Evaluated hardwood species are Umsafwa, Umupundu, Umusamba, Umwenge and Umutondo. Reference material is already in use for pellet production in Zambia. Evaluation includes pellet production in a single pellet press, post production testing and X-ray examinations for tree different moisture contents; 8%, 10% and 12%. Pellet production includes friction energy, maximal friction energy and compression energy measurements. Post production testing includes density and hardness testing as well as X-ray examinations that indicate the amount of produced ash in the combustion process. High compression energy means higher energy cost in production so low compression energy is a desired property. Umupundu was the only wood species whose moisture content had no effect on the amount of compression energy. Umsamba and Umutondo gave the lowest and Umupundu and Umsafwa the highest compression energies of the tested hardwood pellets. Almost all of the friction energies of the tested materials were close to one another. The biggest exception was Umsafwa with 8% moisture content which had 38% higher friction energy than the reference material on average in this study. The values of the friction energy are low compared with other studies but within the reasonable limits compared with the reference material. A clear linear relationship was found between the friction energy and Fmax, so the friction energy directly implies the magnitude of the force of Fmax. A high hardness value is desirable because high hardness links directly to pellets high durability. All hardwood species tested were harder than the reference material. Ash significantly shortens the service life of the pellet stove, therefore it is desirable to produce as little ash as possible. Umsafwa and Unwenge has the lowest amount of metals that indicates the smallest amount of ash formed when burning pellets. Umsafwa with MC of 12% and Umwenge with MC of 10% are the best mix based on this study. / 81% av befolkningen i Afrika söder om Sahara är beroende av träkol och ved för att täcka sitt energibehov för matlagning. I Afrika produceras träkol vanligtvis genom att träden bränns i en traditionell ugn och sedan tillagas maten med en koleldad spis inomhus. Det leder till tre problem; avskogning, hälsoproblem och överbefolkning, allt detta kan minskas med en pellets spis. I Zambia förbrukar träkol motsvarande 6 089 000 ton ved varje år, och den totala förbrukningen av ved är 13 967 000 ton per år. Det leder till en avverkningstakt på mellan 250 000 och 300 000 hektar varje år vilket gör att Zambia har en av världens snabbaste avskogningshastigheter. Avskogningen kan minskas genom att energin från veden används mer effektivt. Vid produktion och användning av träkol frigörs cirka 72-86% av den producerade energin till atmosfären, vilket resulterar i en användningsgrad på endast 14-28%. Vid pelletstillverkning är motsvarande värde mycket högre, 70-83%. Om bränslepellets används istället för kol för matlagningsändamål ökar därför energieffektiviteten med 42-69%, vilket leder till lägre behov av trämaterial för att täcka lika energibehov. I denna studie har fem lövträslag och ett referensmaterial av barrträd från Zambia utvärderats för produktion av bränslepellets. De utvärderade lövträslag är Umsafwa, Umupundu, Umusamba, Umwenge och Umutondo. Referensmaterialet används redan för pelletstillverkning i Zambia. Utvärderingen inkluderar pelletsproduktion i enpetarpress, efterproduktionstestning och röntgenundersökningar för trädens olika fukthalter; 8%, 10% och 12%. Pelletsproduktion omfattar friktionsenergi, maximal friktionsenergi och mätningar av kompressionsenergi. Testning efter produktion inkluderar densitets- och hårdhetstestning samt röntgenundersökningar som indikerar mängden producerad aska i förbränningsprocessen. Hög kompressionsenergi innebär högre energikostnad i produktionen alltså låg kompressionsenergi är en önskad egenskap. Umupundu var det enda träslag vars fukthalt inte hade någon effekt på mängden kompressionsenergi. Umsamba och Umutondo gav de lägsta och Umupundu och Umsafwa de högsta kompressionsenergierna av de testade lövträpellets. Nästan alla friktionsenergier för de testade materialen låg nära varandra. Det största undantaget var Umsafwa med 8% fukthalt som hade 38% högre friktionsenergi än referensmaterialet i genomsnitt i denna studie. Värdena på friktionsenergierna är låga jämfört med andra studier men inom de tillåtna gränserna jämfört med referensmaterialet. Ett tydligt linjärt beroende hittades mellan friktionsenergin och Fmax, således friktionsenergin antyder direkt storleken på kraften hos Fmax. Ett högt hårdhetsvärde är önskvärt eftersom det kopplas direkt positivt till pellets hållbarhet. Alla lövträslag som testades var hårdare än referensmaterialet. Ask förkortar pelletskaminens livslängd avsevärt, därför är det önskvärt att producera så lite aska som möjligt. Umsafwa och Unwenge har den lägsta mängden metaller som anger den minsta mängd aska som bildas vid förbränning av pellets. Umsafwa med MC på 12% och Umwenge med MC på 10% är den bästa mixen baserat på denna studie.