Although perfectly diagnosed in terms of the occurrence of physical changes, the hornification phenomenon, in its origin, has frequently been associated with the formation of irreversible or partially reversible hydrogen bonding in wood pulps or paper upon drying or water removal. Its characterisation has therefore been confusing and unsatisfactory. The authors propose that a sufficiently varied source of experimental data already exists to show that hornification is only a particular case of lactone bridge formation in lignocellulosic materials.

The blast furnace process is a multi-phase chemical reactor whose main purpose is to reduce iron oxides producing hot metal. In the actual blast furnace operation several phases simultaneously interact with one another exchanging momentum, mass and energy. In this paper a three-dimensional multiphase mathematical model of the blast furnace is presented. This model treats the blast furnace process as a multiphase reactor in which all phases behave like fluids. Five phases are treated by this model, namely, gas, lump solids (iron ore, sinter, pellets and coke), pig iron, molten slag and pulverized coal. Conservation equations for mass, momentum, energy and chemical species for all phases are solved based on the finite volume method. In the discretized momentum equations, the covariant velocity projections are used, which is expected to give the best coupling between the velocity and pressure fields and improve the convergence of the calculations. This is a new feature of the present model regarding to the numerical procedures applied to the blast furnace modeling, which emphasizes its originality. In addition, gas and solid phases are treated as continuous phases possessing a pressure field and the SIMPLE algorithm is applied to extract the pressure field and ensure mass conservation. Hot metal, slag and pulverized coal are treated as discontinuous phases consisting of unconnected droplets. For such phases, momentum conservation is used to calculate the fields of velocity while the continuity equations are used to calculate the phase volume fractions.This model was applied to predict the three-dimensional blast furnace operation and predicted temperature distributions and operational parameters like productivity, coke rate and slag rate presented close agreement with the actual measured ones in the blast furnace process.

The superduplex stainless steels (SDSS) are widely used in chemical, oil and gas industries, to pipelines and storage material facilities. In welding process or working in temperature elevated, secondary phases may appear in the form of precipitates, as the sigma phase (σ) which is an intermetallic compound. This compound is harmful to the properties of steel, deteriorating its mechanical properties, such as decreasing corrosion resistance and toughness. In this paper it is analyzed the formation, kinetics and microstructural evolution of sigma phase in SDSS UNS S32750 after isothermal aging at 700ºC, 750ºC and 800ºC. In this work sigma phase kinetics is studied by JMAK theory and by two microstructural path descriptors, S V , interfacial area per unit of volume between sigma phase and austenite, and <λ>, mean chord length of sigma, both in function of the V V , volumetric fraction of sigma, known in the literature as microstructural partial path (MP). The MP formulation is common in recrystallization studies, but so far has not been used in the sigma phase precipitation studies, being applied here for the first time. The results indicated that the sigma phase nucleates by site saturation with anisotropic linear impingement. This means that sigma phase nucleates on edges.

The ironmaking blast furnace is a counter current chemical reactor whose main purpose is to produce hot metal (pig iron) from iron oxides. In the furnace, five phases: gas, lump solids (iron ore, sinter, pellets and coke), liquids (pig iron and molten slag) and powders (tuyere injectants: pulverized coal, coke fines or dust from the lump coke) interact with one another. In order to evaluate productivity, energy efficiency and transient phenomena occurring in the blast furnace, a comprehensive two-dimensional transient mathematical model has been developed. The model was composed of conservation equations of mass, momentum, chemical species and thermal energy for all phases mentioned above. This model includes phase transformations and chemical reactions such as melting of pig iron and slag components, moisture evaporation, reduction of iron oxides, solution loss, coke and pulverized coal combustion, silica reduction and gas phase reactions. With this model, the transient behavior of the blast furnace process has been successfully predicted for different injection rates of pulverized coal.KEY WORDS: blast furnace; mathematical modeling; finite volume method; multi-phase flow; pulverized coal injection; transient behavior; chemical reactions, inter-phase interaction.