Burden distribution plays a key role in controlling the gas flow conditions inside a blast furnace. The distribution of ore and coke influences the gas permeability distribution in the lumpy zone and ...also in the cohesive zone, where the gas flows mainly through the coke slits. Charging an ore dump on coke can sometimes cause the coke layer to collapse under the force of the heavier ore particles. This is known as ‘coke collapse’ or ‘coke push’, which results in a higher coke fraction near the center of the furnace than expected. In this work coke collapse phenomena are evaluated on model charging programs using small scale experiments and Discrete Element Modeling (DEM). DEM simulations were used to study the extent of collapse for different charging programs, and experiments were undertaken to verify the results of the simulations. The slope stability method was used to classify the collapse conditions into no collapse, impact failure or gravity failure, depending on the stability of the coke layer. The findings were also compared with results from an in-house mathematical model, which was modified to consider the effect of the collapse on the underlying layer. The corrected mathematical model was found to show results in general agreement with results from the DEM simulation.
The burden distribution in the ironmaking blast furnace plays an important role for the operation as it affects the gas flow distribution, heat and mass transfer, and chemical reactions in the shaft. ...This work studies certain aspects of burden distribution by small-scale experiments and numerical simulation by the discrete element method (DEM). Particular attention is focused on the complex layer-formation process and the problems associated with estimating the burden layer distribution by burden profile measurements. The formation of mixed layers is studied, and a computational method for estimating the extent of the mixed layer, as well as its voidage, is proposed and applied on the results of the DEM simulations. In studying a charging program and its resulting burden distribution, the mixed layers of coke and pellets were found to show lower voidage than the individual burden layers. The dynamic evolution of the mixed layer during the charging process is also analyzed. The results of the study can be used to gain deeper insight into the complex charging process of the blast furnace, which is useful in the design of new charging programs and for mathematical models that do not consider the full behavior of the particles in the burden layers.
Pulling the old switcheroo: Microporosity can be switched “on” and “off” in a crystalline molecular organic solid composed of cage molecules (see scheme). The switch is facilitated by conformational ...flexibility in the soft organic crystal state.
This article presents an approach by which charging programs in the blast furnace can be evolved. The core of the method is a mathematical model, which on the basis of a given charging program ...estimates the two-dimensional distribution of burden layers in the shaft. A gas flow model uses this information to estimate the gas distribution, applying a simplified treatment of the conditions in the upper shaft. The aim is to find the charging program that gives a state of the furnace shaft matching a target for the radial temperature profile at the level of an in-burden probe. This is accomplished by applying a genetic algorithm (GA) that makes an efficient search among the huge number of potential charging programs, executing the burden and gas flow models in the function evaluations. The method is illustrated by six cases, where targets for the gas temperature distribution are given and the GA evolves the charging sequence and the chute settings for the dumps. It is demonstrated that the algorithm efficiently can evolve charging programs which yield temperatures in agreement with the targets, which holds promise for a practical application of the method in the steel plant.
Charging programs giving rise to desired burden and gas distributions in the ironmaking blast furnace were detected through an evolutionary multi-objective optimization strategy. The Pareto ...optimality condition traditionally used in such studies was substituted by a recently developed k-optimality criterion that allowed for simultaneous optimization of a large number of objectives, leading to a significant improvement over the results of earlier studies. A large number of optimum charging strategies were identified through this procedure and thoroughly analyzed, in view of an efficient blast furnace operation.
Either more or less neighbors favored? By deliberate choice of the internal ligands of the porous nanocapsules {(Mo)Mo5}12{Mo2(ligand)}30n−, the respective cavities can be differently ...sized/functionalized. This allows one to trap, in two different corresponding capsules, 100 water molecules arranged in shells that exhibit more and less dense packing, respectively—the latter type in a capsule with smaller internal ligands; the picture shows the related 100 O atoms at the vertices of the four polyhedra, while two dodecahedra (shown in pale green and red) have only 10 H2O molecules instead of 20.
By the deliberate choice of the internal ligands of the porous nanocapsules {(Mo)Mo5}12{Mo2(ligand)}30n−, the respective cavities' shells can be differently sized/functionalized. This allows one to trap the same large number of water molecules, that is, 100 in a capsule cavity with formate ligands having a larger space available, as well as in a cavity containing sulfates and hypophosphites, that is, with less space. Whereas the 100 molecules fill the space completely in the second case in which they are organized in three shells, a four‐shell system with underoccupation and broken hydrogen bonds is observed in the other case. This is an unprecedented result in terms of the structurally well defined special forms of “higher and lower density” water molecule assemblies. Precisely, by replacing the larger ligands in the mentioned nanocapsule type by formates, voids in the capsule cavity of (HC(NH2)2)22{(HC(NH2)2)20+(H2O)100}⊂{(Mo)Mo5O21(H2O)6}12{Mo2O4(HCO2)}30⋅ca. 200 H2O are generated that get filled with water molecules concomitant with an expansion of the three to four shell {H2O}100 cluster. The water shells in both capsules containing different ligands are organized in the form of dodecahedra (partly with underoccupation) and a strongly distorted rhombicosidodecahedron spanned by a {H2O}60={(H2O)5}12 aggregate. The well‐defined water shells only emerge if cations cannot enter into the capsules, which is achieved by closing the pores with plugs/guests such as formamidinium cations. The work is based on the syntheses of two new compounds, related single‐crystal X‐ray diffraction studies, and molecular dynamics simulations, which show remarkably that water molecule shell structuring occurs in the capsules due to the confined conditions even in the case of open pores and at room temperature if cation uptake is prevented.
Either more or less neighbors favored? By deliberate choice of the internal ligands of the porous nanocapsules {(Mo)Mo5}12{Mo2(ligand)}30n−, the respective cavities can be differently sized/functionalized. This allows one to trap, in two different corresponding capsules, 100 water molecules arranged in shells that exhibit more and less dense packing, respectively—the latter type in a capsule with smaller internal ligands; the picture shows the related 100 O atoms at the vertices of the four polyhedra, while two dodecahedra (shown in pale green and red) have only 10 H2O molecules instead of 20.
High-free-volume glassy polymers, such as polymers of intrinsic microporosity (PIMs) and poly(trimethylsilylpropyne), have attracted attention as membrane materials due to their high permeability. ...However, loss of free volume over time, or aging, limits their applicability. Introduction of a secondary filler phase can reduce this aging but either cost or instability rules out scale up for many fillers. Here, we report a cheap, acid-tolerant, nanoparticulate hypercrosslinked polymer 'sponge' as an alternative filler. On adding the filler, permeability is enhanced and aging is strongly retarded. This is accompanied by a CO2/N2 selectivity that increases over time, surpassing the Robeson upper bound.
High permeance membranes were produced by addition of highly permeable nanoparticulate fillers (hypercrosslinked polystyrene, HCP, and its carbonized form, C-HCP) to a high free volume polymer ...(polymer of intrinsic microporosity PIM-1) in a thin film (typically 2 µm) on a porous polyacrylonitrile support. Self-standing mixed matrix membranes (MMMs) of thicknesses in the range 40–90 µm were also prepared with the same polymer and fillers. While robust MMMs could only be formed for moderate filler loadings, thin film nanocomposite (TFN) membranes could be produced from dispersions with filler loadings up to 60 wt%. On increasing the filler loading, CO2 permeance increased in line with the predictions of the Maxwell model for a highly permeable filler. Physical ageing led to some loss of permeance coupled with an increase in CO2/N2 selectivity. However, for TFN membranes the greatest effects of ageing were seen within 90 days. After ageing, TFN membranes showed high permeance with reasonable selectivity; for example, with 60 wt% C-HCP, CO2 permeance > 9300 GPU, CO2/N2 selectivity ~ 11.
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•High loadings of filler can be incorporated into a polymer film on a porous support.•Carbonization enhances the ultramicroporosity of a hypercrosslinked polymer filler.•In a thin film, the most significant effects of physical aging occur within 90 days.•Aged membranes show high permeance to carbon dioxide.
A mathematical model for fast evaluation of charging programs in bell-less top blast furnaces is presented. The model describes the burden formation and descent procedures in the blast furnace, and ...can be used for designing charging programs. Experimental results in small scale were used to validate the model. The model was applied to a real charging program from a reference blast furnace. Through comparison between the estimated burden distribution and gas temperatures from an above-burden probe it was concluded that the model has captured the main features of the distribution of coke and pellets. The potential of using the model for the design of new charging programs was finally illustrated by analyzing the effect of small changes in the positions of the rings on the arising burden distribution.
The energy-efficient separation of chemical feedstocks is a major sustainability challenge. Porous extended frameworks such as zeolites or metal-organic frameworks are one potential solution to this ...problem. Here, we show that organic molecules, rather than frameworks, can separate other organic molecules by size and shape. A molecular organic cage is shown to separate a common aromatic feedstock (mesitylene) from its structural isomer (4-ethyltoluene) with an unprecedented perfect specificity for the latter. This specificity stems from the structure of the intrinsically porous cage molecule, which is itself synthesized from a derivative of mesitylene. In other words, crystalline organic molecules are used to separate other organic molecules. The specificity is defined by the cage structure alone, so this solid-state 'shape sorting' is, uniquely, mirrored for cage molecules in solution. The behaviour can be understood from a combination of atomistic simulations for individual cage molecules and solid-state molecular dynamics simulations.
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