Implementation, demonstration and validation of a user-defined wall-function for direct precipitation fouling in ANSYS Fluent

In a previous paper (Johnsen et al., 2015) and presentation (Johnsen et al., 2016), we developed and demonstrated a generic modelling framework for the modelling of direct precipitation fouling from multi-component fluid mixtures that become super-saturated at the wall. The modelling concept involves the 1-dimensional transport of the fluid species through the turbulent boundary layer close to the wall. The governing equations include the Reynolds-averaged (RANS) advection-diffusion equations for each fluid species, and the axial momentum and energy equations for the fluid mixture. The driving force for the diffusive transport is the local gradient in the species' chemical potential. Adsorption mechanisms are not modelled per se, but the time-scale of adsorption is reflected in the choice of Dirichlet boundary conditions for the depositing species, at the fluid-solid interface. In this paper, the modelling framework is implemented as a user-defined function (UDF) for the CFD software ANSYS Fluent, to act as a wall boundary condition for mass-transfer to the wall. The subgrid, 1-dimensional formulation of the model reduces the computational cost associated with resolving the fine length-scales at which the boundary-layer mass transfer is determined, and allows for efficient modelling of industry-scale heat exchangers suffering from fouling. The current paper describes the modelling framework, and demonstrates and validates its applicability in a simplified 2D heat exchanger geometry (experimental and detailed CFD modelling data by P\"a\"akk\"onen et al. (2012, 2016)). By tuning the diffusivity, only, good agreement with the experimental data and the detailed CFD model was obtained, in terms of area-averaged deposition rates.Comment: 12th International Conference on CFD in Oil & Gas, Metallurgical and Process Industries, SINTEF, Trondheim, NORWAY, May 30th - June 1st, 2017, 9 pages, 9 figure

Effect of Process Parameters on Catalytic Incineration of Solvent Emissions

Catalytic oxidation is a feasible and affordable technology for solvent emission abatement. However, finding optimal operation conditions is important, since they are strongly dependent on the application area of VOC incineration. This paper presents the results of the laboratory experiments concerning four most central parameters, that is, effects of concentration, gas hourly space velocity (GHSV), temperature, and moisture on the oxidation of n-butyl acetate. Both fresh and industrially aged commercial Pt/Al(2)O(3) catalysts were tested to determine optimal process conditions and the significance order and level of selected parameters. The effects of these parameters were evaluated by computer-aided statistical experimental design. According to the results, GHSV was the most dominant parameter in the oxidation of n-butyl acetate. Decreasing GHSV and increasing temperature increased the conversion of n-butyl acetate. The interaction effect of GHSV and temperature was more significant than the effect of concentration. Both of these affected the reaction by increasing the conversion of n-butyl acetate. Moisture had only a minor decreasing effect on the conversion, but it also decreased slightly the formation of by products. Ageing did not change the significance order of the above-mentioned parameters, however, the effects of individual parameters increased slightly as a function of ageing

Biobutanol as a Potential Sustainable Biofuel - Assessment of Lignocellulosic and Waste-based Feedstocks

This paper introduces the production process of an alternative transportation biofuel, biobutanol. European legislation concerning biofuels and their sustainability criteria are also briefly described. The need to develop methods to ensure more sustainable and efficient biofuel production processes is recommended. In addition, the assessment method to evaluate the sustainability of biofuels is considered and sustainability assessment of selected feedstocks for biobutanol production is performed. The benefits and potential of using lignocellulosic and waste materials as feedstocks in the biobutanol production process are also discussed. Sustainability assessment in this paper includes cultivation, harvest/collection and upstream processing (pretreatment) of feedstocks, comparing four main biomass sources: food crops, non-food crops, food industry by-product and wood-based biomass. It can be concluded that the highest sustainable potential in Finland is when biobutanol production is integrated into pulp & paper mills

On the utilization of modified red mud in dimethyl disulfide and methyl mercaptan emission abatement

In this paper, a novel application of industrial waste, namely red mud (RM), in the abatement of two malodorous and harmful sulfur compounds, dimethyl disulfide (DMDS) and methyl mercaptan (MM), is presented. The effects of calcination and activations with hydrochloric acid or a mixture of hydrochloric and orthophosphoric acid on the properties and performance of RM are compared using laboratory-scale experiments. The RM-based materials were characterized by XRF, XRD, FE-SEM, N2 -physisorption, TGA/DTA, and FTIR analyses. RM exhibits very promising catalytic properties in the abatement of both DMDS and MM. The hydrochloric acid-activated RM was the most active in both cases, which was explained by its rather high specific surface area (144 m2 g −1 ), higher contents of Fe2O3 and TiO2, as well as lower content of phosphorus. For both DMDS and MM, the main oxidation products were sulfur dioxide, carbon monoxide, and carbon dioxide. DMDS was observed as a reaction intermediate in MM oxidation. While the final conversions of DMDS and MM were high, the oxidation was not complete, indicated by the formation of carbon monoxide. Nevertheless, the modified RM appears as a very interesting alternative to the existing DMDS and MM abatement catalysts.Web of Science121art. no.

Producción de biocarbón a partir de biomasa residual y su uso en la germinación y crecimiento en vivero de Capparis scabrida (Sapote)

Se produjeron biocarbones a partir de tres tipos de biomasa residual: coronta de maíz, cáscara de café y exoesqueleto de langostino, para estudiar la influencia de diferentes dosis de los mismos en la germinación y crecimiento en vivero de semillas de la especie forestal Capparis scabrida (Sapote). Se realizó una exhaustiva caracterización de los biocarbones obtenidos en base a sus propiedades texturales, morfológicas, estructurales y química superficial. Semillas viables de sapote fueron colocadas en sustratos con dosis de 0, 15 y 30 %wt de cada uno de los tres tipos de biocarbones obtenidos y se colocaron en bolsas de 2 kg en condiciones de vivero. Se evaluaron los parámetros de germinación: tiempo y % de germinación; y de crecimiento de las plántulas: crecimiento de raíz y tallo, engrosamiento de tallo, incremento de masa de raíz y parte aérea y la carga microbiana en la raíz. Se determinó que el tipo de biocarbón tuvo influencia solamente en el tiempo de germinación y la dosis de biocarbón tuvo influencia en el incremento de masa de parte aérea durante el crecimiento de las plántulas. El resto de parámetros evaluados no fueron afectados ni por el tipo ni por la dosis de biocarbón

Carbón activado derivado de cáscara de zapallo (Cucurbita sp.) para la remoción de cloro total y residual de agua potable

La presente investigación tuvo como objetivo producir carbón activado mediante activación química de un material no convencional, residuos de cáscara de zapallo “hueso” (Cucurbita sp.), con la finalidad de remover el cloro total y residual del agua potable que llega a viviendas de la ciudad de Tumbes. La activación de la biomasa residual se realizó con cloruro de zinc a 600 °C durante un periodo de 2 h en atmosfera de nitrógeno. El carbón activado preparado a partir de cascara de zapallo mostro una buena estructura micro-mesoporosa alcanzando un área superficial de 774,6 m2/g, volumen total de poros de 0,50 cm3/g y un volumen microporoso de 0,34 cm3/g. El adsorbente producido se utilizó para remover satisfactoriamente el cloro total y residual de agua potable que llega a cinco zonas de la ciudad de Tumbes. Los datos de cinética de adsorción de cloro residual y total por parte del carbón activado producido se ajustan mejor al modelo de pseudo-segundo orden con valores máximos de capacidad de adsorción en el equilibrio (qe) de cloro residual y total de hasta 3,6 y 3,1 mg/g respectivamente. Adicionalmente el hecho de que los datos de cinética de adsorción se ajusten al modelo de difusión intraparticular supone que este es el mecanismo que limita el proceso de adsorción. Los porcentajes de remoción de cloro total y residual del agua potable llegan a valores de hasta 100%. El carbón activado producido de cáscara de zapallo es un adsorbente promisorio para su uso en el tratamiento de agua

Sustainability Assessment of Chemical Processes: Evaluation of Three Synthesis Routes of DMC

This paper suggested multicriteria based evaluation tool to assess the sustainability of three different reaction routes to dimethyl carbonate: direct synthesis from carbon dioxide and methanol, transesterification of methanol and propylene carbonate, and oxidative carbonylation of methanol. The first two routes are CO 2 -based and in a research and development phase, whereas the last one is a commercial process. The set of environmental, social, and economic indicators selected were renewability of feedstock, energy intensity, waste generation, CO 2 balance, yield, feedstock price, process costs, health and safety issues of feedstock, process conditions, and innovation potential. The performance in these indicators was evaluated with the normalized scores from 0 to +1; 0 for detrimental and 1 for favorable impacts. The assessment showed that the transesterification route had the best potential toward sustainability, although there is still much development needed to improve yield. Further, the assessment gave clear understanding of the main benefits of each reaction route, as well as the major challenges to sustainability, which can further aid in orienting development efforts to key issues that need improvement. Finally, it was concluded that a multicriteria analysis such as the one presented in this paper was a viable method to be used in the process design stage

Caracterización de filtros comerciales para agua a base de carbón activado para el tratamiento de agua del río Tumbes - Perú

Se caracterizaron y se evaluaron carbones activados comerciales (A, B, C y D) utilizados en filtros para el tratamiento de agua en la descontaminación de metales pesados presentes en agua de río y en la eliminacion de microorganismos coliformes; los carbones comerciales resultaron tener estructuras microporosas y mesoporosas. Se determinaron areas superficiales entre 705 y 906 m2/g. Los carbones fueron amorfos y se detectó la presencia de agentes antibacterianos, tales como Ag, Cl, Cu y Si. Se determinó que para el As y Pb, cuyas concentraciones iniciales en el agua contaminada (agua del Río Tumbes-Perú) fueron 56,7 y 224,0 μg/L, respectivamente, el porcentaje de adsorción fue cercano al 100%. También se encontró que la relación entre el pH de carga cero de los carbones y pH del agua del río durante los experimentos juega un rol determinante en la adsorción de los elementos analizados. Por otro lado, la capacidad antibacteriana fue evaluada satisfactoriamente frente a las siguientes cepas de bacterias gram negativas fecales: Escherichia coli (ATCC® 25922™), Salmonella typhimurium (ATCC® 14028™) y Shigella flexneri (ATCC® 12022™). Esta capacidad se basa en la presencia superficial en los carbones de los agentes antibacterianos mencionados.Comercial activated carbon samples (A, B, C, and D) used in filters for the treatment of water were characterized and evaluated in the decontamination of heavy metals present in river water and in the elimination of coliform microorganisms. The carbon samples had microporous and mesoporous structures. Surface areas of between 705 and 906 m2/g were found. The carbons samples were amorphous and the presence of antibacterial agents such as Ag, Cl, Cu, and Si was detected. It was determined that for As and Pb, whose initial concentrations in contaminated water (water of the Tumbes river-Peru) were 56.7 and 224.0 μg/L, respectively, the percentage of adsorption was close to 100%. The relationship between point of zero charge pH of the activated carbons and pH of the river water during the experiments plays a determinant role in the adsorption of the analyzed elements. The antibacterial capacity was evaluated satisfactorily against the following strains of fecal gram negative bacteria: Escherichia coli (ATCC® 25922™), Salmonella typhimurium (ATCC® 14028™), and Shigella flexneri (ATCC® 12022™). This ability is based on the surface presence in the carbons of the mentioned antibacterial agents