Filtration performance of mineral concentrate is mainly controlled by solid particle size and surface hydrophobicity. Filtration of coarser particles with more hydrophobic surfaces produces better filtration performance characterized by higher filtration rate (U) and lower final moisture content (FMC) in the final cake. Some filtration aids could improve filtration performance by flocculating solid particles and enhancing surface hydrophobicity. For the mineral concentrate used in this study, many filtration aids tested could only improve either U or FMC: one type was effective in improving U, and another type was effective in improving FMC. The combination of the two types of filtration aids at certain dosages could achieve better filtration performance than the optimum performance achieved by each individual filtration aid. Based on the experimental results, the working mechanism of filtration aids behind the filtration behavior was explored to deepen the understanding of the chemical-enhanced filtration of Cu/Ni concentrate. / Chemical Engineering

One of the problems encountered in paper converting is caused by the occurrence of "baggy webs", which essentially is when the tension profile of the paper web is uneven. In an area with low tension the paper is longer, which results in bagginess. The baggy parts can not usually be stretched to even out the tension of the paper web in a converting machine, with the result that runnability problems are likely to occur. The aim of the work described in this thesis was to investigate three particular stages in papermaking, namely drying, calendering and storage, and rank them according to their propensity for inducing baggy webs. The focus was placed on investigating the effects of uneven moisture and grammage profiles on the machine-direction strain difference profile. The largest strain difference occurred when there were systematic thick streaks throughout a reel that formed ridges. Stress relaxation during storage then gave rise to a difference in strain of 0.14% when the ridge height was around 2-3 mm. Thickness variations due to variations in grammage is also a source of moisture variation. A difference in moisture of 5% in the calendering stage resulted in strain differences of about 0.05-0.08%. These strain differences resulted in creases being formed as early on as in the calender nip when differences in both grammage and moisture content were present. Most creases appeared when the moisture difference was 2-8%. The difference in grammage could be large without creases being formed when no differences in moisture content were present. A moisture difference of about 5-6% during drying resulted in a strain difference of 0.1% measured on isotropic samples. The moist area turned into a tight streak when the moisture difference appeared at moisture contents higher than 25%. At moisture contents lower than 20%, on the contrary, the moist area turned into a slack streak. The conclusion drawn is that papermakers should concentrate first and foremost on eliminating variations in grammage, especially if these are systematic. This would also eliminate some variations in moisture content, which would solve more problems.

The vegetation of the Sydney Basin, Australia, is highly flammable and subject to a wide range of fire regimes. Sclerophyllous shrubs and sedges are common and in some vegetation types up to 70 % of fuel consumed during a fire can be live. Research into fire behaviour and fuel dynamics has been minimal. To address this issue this thesis investigated the principal factor affecting the ease of ignition and rate of combustion of individual fuel particles and fuel beds in bushfires: dead fine fuel moisture (FFM). Two common Sydney Basin vegetation types, eucalypt woodland and heathland, each with a history of problematic fire management, were measured in the field for diurnal fluctuations in FFM following rain, under conditions similar to when prescribed burns are conducted. The FFM components of current operational fire behaviour models were found to be inadequate for predictions of FFM and fire behaviour under these conditions. The equilibrium moisture content (EMC) of five fuel types from the field site was investigated in a laboratory study. An existing function describing EMC as a function of temperature and relative humidity was evaluated and found to be very accurate for these fuels. Two FFM predictive models incorporating this function were evaluated on the field data and the laboratory results were shown to be applicable to the estimation of FFM in the field. One model gave very accurate predictions of FFM below fibre saturation point, but its accuracy was reduced when screen level conditions were used instead of those measured at fuel level. A recent process-based model that accounts for rainfall showed promise for predicting when fuel is < 25 % FFM. Systematic problems with the radiation budget of this model reduced the accuracy of predictions and further refinement is required. Live fine fuel moisture content (LFMC) of common heathland shrubs and sedge was investigated over two years and found to be both seasonal and influenced by phenology. LFMC minima occurred in late winter and spring (August to October), and maxima were in summer (December to February) when new growth was recorded. The dominant near-surface fuel in mature heath was sedge. It was found to have little seasonal variation in its??? percentage dead but the percentage dead maxima occured at the same time as the LFMC minima of shrubs and sedge in both years. Simple instantaneous models for duff moisture content in woodland and heathland and LFMC and the percentage dead sedge in heathland were developed. The information gained by this study will form the basis for future development of fuel moisture models for prescribed burning guidelines and fire spread models specific to the vegetation communities of the Sydney Basin.

Diss. (sammanfattning). Umeå : Sveriges lantbruksuniv., 2003. / Härtill 4 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv. / Härtill 3 uppsatser.

Diss. Uppsala : Sveriges lantbruksuniv., 2000.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2001. / Härtill 4 uppsatser.

Lic.-avh. Luleå : Luleå tekniska univ., 2005. / Härtill 3 uppsatser.

O estudo da erodibilidade ganha importância quando se tratam de solos localizados em regiões tropicais, caracterizadas por altas pluviosidades e evaporações que dificilmente permitem ao maciço atingir um estado de saturação em campo. A erodibilidade e as propriedades hidráulicas determinam as condições de infiltração e de escoamento superficial e podem acelerar as feições erosivas através das perdas de partículas. Neste trabalho, observou-se que o grau de saturação in situ estabelece um potencial de sucção matricial (Sm) capaz de orientar o fluxo, absorção e armazenamento da água nos poros do solo. Deste modo, foi possível correlacionar as propriedades de absorção de água com as sucções mátricas de três solos (arenoso, argiloso e areno-argiloso), com comportamento erosivo e não-erosivo, ensaiados a diferentes teores de umidade inicial. Após o controle da sucção e umidade, através da panela de pressão de Richards, os solos foram submetidos ao ensaio de erodibilidade proposto por Nogami & Villibor (1979). Os índices de absorção (Iabs), de perda de massa por imersão (P) e de erodibilidade (E) determinados neste ensaio, quando correlacionados com as curvas características dos solos, mostraram a influência da sucção matricial no início do processo erosivo. Verificou-se uma tendência de aumento da perda de massa por imersão, quanto menor era o teor de umidade inicial imposta (maior sucção). Provavelmente, quando do início do evento chuvoso, o solo tende a ser mais erodível quanto mais seco estiver. Além disso, as correlações obtidas mostraram-se coerentes com o comportamento dos solos em estudo, permitindo uma estimativa da sucção (Sm) de um solo a partir de grandezas facilmente mensuráveis como o Iabs, obtido em ensaio simples e de fácil execução. / The study of erodibility gains importance when dealing with soil located in tropical regions, characterized by high precipitation and evaporation that allow hardly the massive soil to reach a state of saturation in the field. The erodibility and hydraulic properties define the infiltration conditions and the superficial flow, and they can accelerate the erosive process due to the losses of particles. In this work, we observed that the degree of saturation in situ establishes the potencial for suction matrix (Sm) can guide the flow, absorption and storage of water in soil pores. Therefore, experimentally, it was possible to correlate the properties of water absorption with the matrix suctions of three soils, with different initial moisture contents and erosive and non-erosive behaviors. After controlling the suction and moisture through the pressure Richards pressure chamber the soils were subjected to the erodibility test proposed by Nogami & Villibor (1979). The indexes of absorption (Iabs), mass loss by immersion (P) and erodibility (E) determinated in this experiment, when correlated with the characteristic curves of soils, showed the influence of matrix suction at the beginning of the erosion process. There was a trend of increased weight loss by immersion, the lower was the initial moisture content imposed (greater suction). Furthermore, the correlations obtained were consistent with the behavior of soils under study, allowing to estimate of suction (Sm) of a soil from easily measurable values such as the Iabs.

Orientador: Ronei Jesus Poppi / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-16T16:50:05Z (GMT). No. of bitstreams: 1 Godoy_LauraBarbosaLimaNascimbemde_M.pdf: 1780795 bytes, checksum: 69eaeca155ecef2bd706747467fc95f5 (MD5) Previous issue date: 2010 / Resumo: Neste trabalho, foi utilizada a Espectroscopia no Infravermelho Próximo (NIR) na região de 4.000 ¿ 10.000 cm e modelos de calibração multivariada para a previsão de densidade básica, lignina total e extrativos em madeira. Para isso, foi utilizado o algoritmo dos mínimos quadrados parciais por intervalos (iPLS) obtendo espectros NIR diretamente sobre os cavacos de madeira secos. Um total de 107 e 53 amostras compôs os conjuntos de calibração e validação, respectivamente, sendo a divisão destas amostras realizada pelo algoritmo de Kennard ¿ Stone. A calibração foi otimizada pela eliminação das amostras anômalas (outliers), com base nas amostras com leverage extremo, resíduos não modelados nos dados espectrais e os resíduos com base na repetibilidade espectral. Também foi realizado um estudo visando à classificação e a determinação destes parâmetros em amostras com diferentes teores de umidade. Neste estudo, o método dos mínimos quadrados parciais para análise discriminante (PLS-DA) foi utilizado para a classificação das amostras de acordo com o teor de umidade apresentado e as máquinas de vetores de suporte por mínimos quadrados (LS-SVM) foi utilizada para determinação de cada um dos parâmetros em cada classe com teor de umidade diferente. Os resultados obtidos indicam que os modelos desenvolvidos para os cavacos secos podem ser utilizados na indústria papeleira como alternativa aos métodos convencionais e os modelos desenvolvidos no estudo para as amostras úmidas podem ser utilizados para a classificação de uma amostra desconhecida e, posteriormente, a previsão de cada parâmetro em cada um dos teores de umidade. / Abstract: In this work, it was used the near infrared spectroscopy (NIRS) in region of 4.000 ¿ 10.000 cm and multivariate calibration models to predict basic density, total lignin and extractives in woodchips. The spectra were obtained directly on the dry woodchips and interval partial least squares (iPLS) was used to develop the calibration model. A total of 107 and 53 samples constitute the calibration and validation sets, respectively, split by Kennard ¿ Stone algorithm. The calibration set was optimized by outliers elimination based on data with extreme leverage, unmodelled residuals in spectral data and unmodelled residuals in the dependent variable. It was also performed a study aiming the classification and determination of this parameters in samples with different moisture contents. In this study, the discriminant analysis with partial least squares method (PLS-DA) was used to classify samples according to the moisture content and the least squares supporting vector machines (LS-SVM) was used to determine density, total lignine and extractives in each class with different moisture content. The results indicate that the models developed for the dry woodchips can be used in the pulp and paper industry as an alternative to the conventional methods and the models developed in the study with samples presented different moisture content can be used to classify an unknown sample and to predict each parameter in each moisture content class. / Mestrado / Quimica Analitica / Mestre em Química