No abstract
<p><em>O presente trabalho teve por objetivo estudar a cinética de secagem em estufa através da obtenção de dados de secagem de suas curvas e aplicação dos modelos matemáticos aplicados à secagem de polpas de hidróxido de magnésio preparadas a partir da hidratação de duas fontes distintas de magnésia cáustica e de uma polpa de hidróxido de magnésio p.a., a título de comparação. As polpas preparadas a partir das fontes de magnésia cáustica foram obtidas por hidratação do óxido de magnésio em um sistema híbrido reator-moinho de bolas após 5 horas de reação. Para caracterização físico-química das amostras, foram utilizadas as técnicas de fluorescência de raios X e análise granulométrica por difração a laser. Os resultados mostraram alta velocidade de secagem das polpas com a etapa de secagem à taxa constante como sendo a controladora do processo, com transferência de calor e massa predominantemente a partir da superfície, apresentando um melhor ajuste ao modelo de Lei de Resfriamento de Newton.</em></p><p><em> </em></p><p><em>ABSTRACT</em></p><p><em></em><em>The aim of the present work was to study the kinetics of drying in stove by obtaining drying data of its curves and applying the mathematical models applied to the drying of magnesium hydroxide pulps prepared from the hydration of two different sources of caustic magnesia and one magnesium hydroxide pulp, for comparison purposes. The pulps prepared from the sources of caustic magnesia were obtained by hydration of the magnesium oxide in a reactor-ball mill hybrid system after 5 hours of reaction. For the physicochemical characterization of the samples, the techniques of X-ray fluorescence and granulometric analysis by laser diffraction were used. The results showed a high drying rate of the pulps with the drying step at constant rate as the process controller, with heat transfer and mass predominantly from the surface, presenting a better fit to the Newton Cooling Law model.</em></p>
Background: Prolonged exposure to iron powder and other mineral dusts can harm affected populations, especially those with COPD. The goal of this study was to see how environmental exposure to metal dust affected lung mechanics, inflammation, remodeling, oxidative stress responses, and elastase in mice in two different mining centers in Vitória, ES, Brazil. Methods: This study utilized 72 male C57Bl/6 mice (36 summer and 36 winter), which were divided into six groups: control, non-exposed (SAL); non-exposed, given elastase (ELA); exposed to metal powder at a mining company (SAL-L1 and ELA-L1); and exposed to a location three miles away from the mining company (SAL-L2 and ELA-L2) for four weeks. On the 29th day of the protocol, the researchers assessed lung mechanics, bronchoalveolar lavage fluid (BALF), inflammation, remodeling, oxidative stress, and alveolar wall alterations (mean linear intercept – Lm). Results: ELA, ELA-L1 and ELA-L2 had an increase in Lm compared to the SAL groups (p<0.05). There was an increase in total cells and macrophages in ELA-L1 and ELA-L2 compared to the other groups (p<0.05). Exposed groups (ELA-L1, ELA-L2, SAL-L1, and SAL-L2) had an increase in cell expression of Inflammatory markers (IL-1β, IL-6, IL-10, IL-17, TNF-α, and neutrophils) (p<0.05); remodeling markers (TIMP-1, MMP-9, MMP-12, TGF-β, collagen fibers and MUC5AC); oxidative stress (iNOS); and mechanisms involved (NFkB) increased compared to ELA and SAL (p<0.05). Although we did not find differences in lung mechanics across all groups, there were low to moderate correlations between these parameters (elastance and resistance of lung tissue) (p0.05). Conclusions: Aside from lung mechanics, environmental exposure to iron and metal powder exacerbated inflammation, remodeling, and oxidative stress responses in exposed mice with and without emphysema. The mechanisms involved are dependent on iNOS and NFkB activation.
Two different reactive concentrated magnesium hydroxide (HM) pulps, produced in a lab reactor mill, and a synthetic and non-reactive HM-pulp, for comparative analyses, have been prepared and studied. Sodium polyacrylate was selected as a dispersant for improving the HM pulp fluidity, with concentrations varying from 0.42% to 2.0% on a dry basis. The two reactive pulps differed from each other mainly by the impurity level and for both, a residual MgO amount was detected, implying that the hydration reaction could proceed. Results (with and without dispersant) confirmed the formation of particle clusters as HM concentration rose until a critical value, above which the pulp behaved as a solid. Reactive HM-pulps with high impurities may represent a limiting factor in the drying operation. Among all HM-pulps studied, the purest reactive pulp with 1% dispersant presented the best flow behavior making this reactive pulp the most suitable to be tested in a pilot spray dryer.
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