Modeling, Simulation and Control of a Tubular Fixed-bed Dimethyl Ether Reactor

This paper considers the modeling and control of a tubular fixed bed reactor with recycle stream for dimethyl ether (DME) production. For simulation purposes, a pseudo homogeneous model has been developed. By reactor simulation under steady state condition, effects of parameters such as feed rate, pressure and shell temperature are investigated. Using the steady state model, an optimizer that maximizes the reactor yield has been developed. For cooling the reactor, a steam drum that uses heat of reactions to produce steam was coupled with the reactor. Through dynamic simulation, system open loop response was obtained and two control loops were considered for controlling the reactor temperature and steam drum level. An optimizer that takes into account the feed variations was incorporated into the control system to maximize the DME production rate

Comparison of response of canola (Brassica napus L. CV. Hyola 401) to biofertilizer inoculation in optimal and delayed cropping dates

In order to compare the effects of phosphate solubilizing bacteria as biofertilizer and mineral phosphorous application in optimal date of sowing with delayed cropping date on canola (Brassica napus L.) growth and productivity, a splitplot experiment, using randomized complete block design with three replications, was conducted at Dashate-Naz Agronomy Research Station, in 2014. Four levels of bacterial inoculation (Pseudomonas putida, Pseudomonas fluorescens, singly or in combination) were applied as main plots and five levels of mineral phosphorus (P) application (0, 25, 50, 75, and 100 kg·ha-1 of mineral phosphorous) were applied as sub plots. Canola plant were sown at two dates of sowing, one at optimal date of sowing (30 Sept., 2014) and the other one month later as delayed cropping (30 Oct., 2014). The results obtained showed that effects of bacterial inoculation on number of seeds per pod, number of pods on plant, and seed yield were significant at one percent probability level at both sowing dates. Moreover, rates of phosphate application had significant effects on all traits at one percent level. Comparing the means showed that application of mineral P resulted in substantial increase in seed yield. At optimal date of sowing, it was shown that while minimum seed yield obtained at control treatment (1600 kg·ha-1), the maximum (2980 kg·ha-1) obtained with interaction effects of application of both bacterial strains along with 75 kg·ha-1 mineral P, having no statistically difference with that of P. fluorescens, along with 75 kg·ha-1 mineral P (2940 kg·ha-1). It was shown that delayed cropping resulted in decreasing canola growth which is reflected in seed yield and yield components. Minimum seed yield at control plot at first date of sowing (1600 kg·ha-1) decreased to 740 kg·ha-1, in the second date of sowing, showing 54 % decrease. The maximum seed yield also decreased in delayed cropping, from 2980 kg·ha-1 at 30 Sept., 2014, as compared to 1074 kg·ha-1 at 30 Oct., 2014, showing a 64% decrease. The results obtained showed that an increase in P level, eventually enhanced the seed yield. This increasing trend continued until a threshold level (75 kg·ha-1 of P), after which seed yield showed a declining fashion

Obtaining lightweight concrete using colemanite waste and acidic pumice

This paper presents some results of ongoing laboratory work to design a lightweight concrete using colemanite waste and pumice. Hisarcik and Espey colemanite wastes, acidic pumice aggregate as well as normal Portland cement were used to produce lightweight concrete with economic and environmental advantages. Two different groups and twenty different prescriptions were tried to produce lightweight concrete. The effect of colemanite waste on workability and strength of lightweight concrete were analysed by fresh and hardened concrete tests. The properties of materials examined include slump, air content, density and uniaxial compressive strength of the mortar. The results obtained were compared with control concrete properties and Turkish standard values. The examined tests results showed that lightweight concrete can be produced by the use of acidic pumice aggregate and colemanite waste. Furthermore, the colemanite waste can be used as cement additives and can reduce the cost and environmental pollution with using natural stone aggregate

Ocena gładkiego filtra wysokiego rzędu przy symulacji wielkowirowej z filtrowaniem jawnym w pełni rozwiniętego turbulentnego przepływu w kanale

Explicit filtering with a smooth shape is one of approaches adopted in large eddy simulations (LES). The present work investigates the application of an explicit high order smooth (HOS) filter for the LES of a fully developed turbulent channel flow. The Crank-Nicolson scheme for time marching and second-order finite-volume schemes for spatial derivatives were implemented in this investigation. Implicit filtering, together with the Smagorinsky sub-grid scale (SGS) model, and explicit filtering, along with a HOS filter were studied in a fully turbulent channel flow. In this study, explicit HOS filtering with an explicit filter width to grid size ratio of 2.0 was in agreement with the available direct numerical simulation (DNS) data. However, the mean velocity profile in the streamwise direction was underestimated, and the turbulence intensity in the streamwise direction improved compared to other directions. Moreover, turbulence stresses were well predicted using the mixed SGS and sub-filter stress (SFS) models and applying the HOS filter as an explicit filter.Jawne filtrowanie typu gładkiego jest jedną z metod stosowanych w symulacjach wielkowirowych (tzw. LES). W pracy opisano zastosowanie filtra wysokiego rzędu o charakterystyce gładkiej (HOS) do symulacji wielkowirowej w pełni rozwiniętego turbulentnego przepływu w kanale. W badaniach wykorzystano metodę Cranka-Nicolsona oraz techniki przyrostów czasowych i objętości skończonych drugiego rzędu do wyznaczania pochodnych zmiennych przestrzennych. Przeanalizowano filtrowanie niejawne łącznie z podsieciowym modelem skalowym Smagorynskiego (SGS) oraz filtrowanie jawne HOS w pełni turbulentnego przepływu w kanale. W badaniach wy- kazano, że filtrowanie jawne za pomocą filtra HOS, którego stosunek długości do rozmiaru siatki wynosił 2, dało zgodne wyniki z dostępnymi rezultatami bezpośrednich symulacji numerycznych (DNS). Nieco niedoszacowany okazał się średni profil prędkości w kierunku wzdłużnym przepływu, natomiast poprawiły się wyniki dotyczące intensywności turbulencji właśnie w tym kierunku w porównaniu do kierunków pozostałych. Zaobserwowano ponadto, że zastosowanie kombinacji SGS z użyciem modeli subfiltrów naprężeń (SFS) oraz HOS jako filtru jawnego pozwoliło na poprawne wyznaczenie wartości naprężeń turbulentnych

Protonic defects and water incorporation in Si and Ge-based apatite ionic conductors

Apatite-type oxide-ion conductors have attracted considerable interest as potential fuel cell electrolytes. Atomistic modelling techniques have been used to investigate oxygen interstitial sites, protonic defects and water incorporation in three silicate and three germanate-based apatite-systems, namely La8Ba2(SiO4)(6)O-2, La-9.33(SiO4)(6)O-2, La-9.67(SiO4)(6)O-2.5, La8Ba2(GeO4)(6)O-2, La-9.33(GeO4)(6)O-2, and La-9.67(GeO4)(6)O-2.5. The simulation models reproduce the complex experimental structures for all of these systems. The interstitial defect simulations have examined the lowest energy configuration and confirm this site to be near the Si/GeO4 tetrahedra. The water incorporation calculations identify the O-H protonic site to be along the O-4 oxygen channel as seen in naturally occurring hydroxy-apatites. The results also show more favourable and exothermic water incorporation energies for the germanate based apatites. This is consistent with recent experimental work, which shows that Ge-apatites take up water more readily than the silicate analogues