Combustion performance and emissions of petrodiesel and biodiesels based on various vegetable oils in a semi industrial boiler

This paper intends to investigate combustion of petrodiesel and biodiesels of grape seed, corn, sunflower, soybean, olive and rice bran oils, which were produced through an alkali-based transesterification, in a non-pressurized, water-cooled combustion chamber by determining its combustion performance and gas emissions (CO, CO₂, NO_x, SO₂). First, the influence of fuel pressure which related to the rate of sprayed fuel to the chamber was studied in order to find out an optimum combustion pressure. In the next level, the influence of A/F upon emissions and boiler performances at 13.79 bars was studied. Results show that similar combustion of fuels occurred at 13.79 bars (optimum) where due to the increase in fuel pressure, the effect of viscous forces in flame formation disappeared. Complete combustion of fuels occurred at 19.305 bars where the CO emissions of all the fuels reached to zero.The overall performance of the boiler obtained with the methyl esters and petrodiesel are comparable for the defined operating points (especially at high energy rates and low A/F). All the six kinds of vegetable based methyl ester emitted lower emissions than petrodiesel over the wide fuel pressures, and A/F. Meanwhile, biodiesels emitted higher amounts of NO_x than petrodiesel. Biodiesels also emitted higher amounts of CO than petrodiesel at low fuel pressures when the viscous forces interfered with proper distributions of fuels to the combustion chamber.     

Investigation of different approaches for hydrogen management in petrochemical complexes

Extensive use of hydrogen in refineries and petrochemical plants is an incentive for designing integrated hydrogen networks to utilize hydrogen more efficiently. On the other hand, hydrogen, as an important byproduct, is not properly used in some petrochemical complexes and mostly sent to the fuel system. Few works have been reported in literature for improving hydrogen network in petrochemical complexes. In this paper, however, a modified automated targeting approach has been developed and applied to petrochemical plants for estimating fresh hydrogen target. Furthermore, this paper is aimed to develop a superstructure based optimization framework to consider hydrogen plant as part of the whole network. Also, four industrial cases are studied to demonstrate the importance of hydrogen management in petrochemical complexes and proving the applicability of the new method.     

Equilibrium and Dynamic Adsorption of Bioethanol on Activated Carbon in the Liquid Phase

Equilibrium batch and dynamic column adsorption of bioethanol from the liquid phase on a commercial activated carbon was investigated. The effects of operational parameters, including flow rate, bed height, and initial solute concentration on the column breakthrough curve were studied. Axial dispersion was estimated by a tracer experimental breakthrough curve. Two mathematical models were developed to predict dynamic experimental results. The equilibrium results showed that the Toth isotherm could better predict the experimental adsorption data than the Langmuir model. The dynamic experimental results showed that increasing the flow rate decreases the column capacity. The macropore diffusion model and the linear driving force model were in good agreement with the experimental dynamic results.     

An Adhesive Hydrogel with “Load-Sharing” Effect as Tissue Bandages for Drug and Cell Delivery

Hydrogels with adhesive properties have potential for numerous biomedical applications. Here, the design of a novel, intrinsically adhesive hydrogel and its use in developing internal therapeutic bandages is reported. The design involves incorporation of “triple hydrogen bonding clusters” (THBCs) as side groups into the hydrogel matrix. The THBC through a unique “load sharing” effect and an increase in bond density results in strong adhesions of the hydrogel to a range of surfaces, including glass, plastic, wood, poly(tetrafluoroethylene) (PTFE), stainless steel, and biological tissues, even without any chemical reaction. Using the adhesive hydrogel, tissue-adhesive bandages are developed for either targeted and sustained release of chemotherapeutic nanodrug for liver cancer treatment, or anchored delivery of pancreatic islets for a potential type 1 diabetes (T1D) cell replacement therapy. Stable adhesion of the bandage inside the body enables almost complete tumor suppression in an orthotopic liver cancer mouse model and ≈1 month diabetes correction in chemically induced diabetic mice.     

Numerical Analysis and Experimental Study of Buckling Behavior of Steel Cylindrical Panels

The effects of the length, sector angle and different boundary conditions on the buckling load and post buckling behavior of cylindrical panels have been investigated using experimental and numerical methods. The experimental tests have been performed using a servo hydraulic machine and for numerical analysis, Abaqus finite element package has been used. The numerical results are in good agreement with the experimental tests.     

Non-Monotonic Lyapunov-Krasovskii Functional Approach to Stability Analysis and Stabilization of Discrete Time-Delay Systems

In this paper, a novel non-monotonic Lyapunov-Krasovskii functional approach is proposed to deal with the stability analysis and stabilization problem of linear discrete time-delay systems. This technique is utilized to relax the monotonic requirement of the Lyapunov-Krasovskii theorem. In this regard, the Lyapunov-Krasovskii functional is allowed to increase in a few steps, while being forced to be overall decreasing. As a result, it relays on a larger class of Lyapunov-Krasovskii functionals to provide stability of a state-delay system. To this end, using the non-monotonic Lyapunov-Krasovskii theorem, new sufficient conditions are derived regarding linear matrix inequalities(LMIs)to study the global asymptotic stability of state-delay systems.Moreover, new stabilization conditions are also proposed for time-delay systems in this article. Both simulation and experimental results on a p H neutralizing process are provided to demonstrate the efficacy of the proposed method.     

Frequency analysis of perfect and defective SWCNTs

This paper develops a structural mechanical model that analyzes the natural frequency of single-walled carbon nanotubes (SWCNTs) subjected to fixed–fixed and free–fixed boundary conditions. A Morse potential is employed for stretching and bending potentials, and a periodic type of bond torsion is used for torsion interactions. The natural frequencies for various aspect ratios are predicted by this structural model. The effect of different vacancy and Stone–Wales defects on the natural frequency of zigzag and armchair nanotubes is also investigated. Finally, the results of the present structural model are compared with those from other numerical methods.     

STUDY ON THE ACETYLENE HYDROGENATION PROCESS FOR ETHYLENE PRODUCTION: SIMULATION,MODIFICATION, AND OPTIMIZATION

In this study, an industrial acetylene hydrogenation unit is simulated utilizing three available kinetic models. The results are compared against six-day experimental data and the best model is selected. Effects of feed temperature and the amount of injected hydrogen on ethylene selectivity are also studied. According to the simulation results, the unit is not working under its optimum conditions. Furthermore, by reduction of the hydrogen flow rate to 52 kg/h, process selectivity is increased. In addition, a new approach is proposed to modify the hydrogenation process and reduce undesired by-products. In the simulation of the modified process, hydrogenation reactors temperature, hydrogen flow rate, and H-1/H-2 ratio were regulated as adjustable parameters for the process optimization. The simulation shows that ethylene selectivity increases by 12%, while acetylene concentration and hydrogenation reactor temperature remains within acceptable ranges. Such selectivity could be achieved at the hydrogen flow rate of 50 kg/h with H-1/H-2 ratio of 0.1/0.9.     

Biomass of Sediment Bacteria by Sedimentation Field-Flow Fractionation

Accurate estimation of sediment microbial biomass is needed for studies in microbial ecology. The most common techniques currently used to estimate biomass in sediments are not only prone to considerable uncertainty, but are also time-consuming and labor-intensive. In the present study, a relatively new separation and sizing technique, sedimentation field flow fractionation (SdFFF), previously developed for biomass determination of bacteria in cell cultures and natural waters, was used to determine sediment bacterial biomass. SdFFF together with epifluorescence microscopy for cell counting in separated fractions was used for estimating the biomass in sediment samples from a wetland and a river site. Cell counting was required as yellow autofluorescing particles interfered with the on-line detector signal from the fluorescent tagged bacteria (blue) making this simple method of monitoring cell numbers impossible. Calibration curves were obtained that can be used for calculation of sediment bacterial biomass from cell count data for the two sites under study. This demonstrates that for specific systems the less tedious total counts method can be used to generate quantitative biomass estimates using SdFFF to provide accurate calibration for the conversion of counts to biomass. This approach overcomes the serious problems associated with conventional methods that often assume a constant biomass to cell counts or cell volume ratio between collection sites. The SdFFF method was applied to monitor cell growth in sediment samples after addition of phosphate and several types of carbon sources. On incubation for eight days, carbon-amended sediments showed higher bacterial biomass and contained more aggregated colonies, which needed to be dislodged by more vigorous treatment than those treated with phosphate alone.