Improving the rheometry of rubberized bitumen: experimental and computation fluid dynamics studies

Multi-phase materials are common in several fields of engineering and rheological measurements are intensively adopted for their development and quality control. Unfortunately, due to the complexity of these materials, accurate measurements can be challenging. This is the case of bitumen-rubber blends used in civil engineering as binders for several applications such as asphalt concrete for road pavements but recently also for roofing membranes. These materials can be considered as heterogeneous blends of fluid and particles with different densities. Due to this nature the two components tends to separate and this phenomenon can be enhanced with inappropriate design and mixing. This is the reason behind the need of efficient dispersion and distribution during their manufacturing and it also explains while realtime viscosity measurements could provide misleading results. To overcome this problem, in a previous research effort, a Dual Helical Impeller (DHI) for a Brookfield viscometer was specifically designed, calibrated and manufactured. The DHI showed to provide a more stable trend of measurements and these were identified as being ‘‘more realistic” when compared with those obtained with standard concentric cylinder testing geometries, over a wide range of viscosities. However, a fundamental understanding of the reasons behind this improvement is lacking and this paper aims at filling these gaps. Hence, in this study a tailored experimental programme resembling the bitumen-rubber system together with a bespoke Computational Fluid Dynamics (CFD) model are used to provide insights into DHI applicability to perform viscosity measurements with multiphase fluids as well as to validate its empirical calibration procedure. A qualitative comparison between the laboratory results and CFD simulations proved encouraging and this was enhanced with quantitative estimations of the mixing efficiency of both systems. The results proved that CFD model is capable of simulating these systems and the obtained simulations gave insights into the flow fields created by the DHI. It is now clear that DHI uses its inner screw to create a vertical dragging of particles within a fluid of lower density, while the outer screw transports the suspended particles down. This induced flow helps keeping the test sample less heterogeneous and this in turns allows recording more stable viscosity measurements

Quality of drinking water in Kashan in 1999-2000

Background : Surveying drinking water quality, a priority for research subjects, seeks further attentions and their standards are determined according to the microbial, chemical, and physical quality as well as their applications. The microbial quality is measured by means of the presence of special pathogens. Thus in case of special pathogens presence we would consider the drinking water to be infected. Materials and methods : This descriptive study was conducted to determine the quality of drinking water in Kashan city in 1999-2000. To meet this demand, Kashan was divided in 11 districts, then samples were gathered in accordance to the number of their resistance as well as industrial standard of water. Coliform contamination, and stool coliform were determined. Results : During the study period, 340 samples were gathered, of which 261 (76.8) had MPN of zero whereas 79 (32.2) and 39 (11.5) had MPN of greater than zero and 3, respectively. Totally, 27 samples have shown contamination of coliform type. Contamination was revealed to be maximum in the third and minimum in the 11th month of sampling (16 samples vs. zero sample). Among districts, Lethar and Moallem Square have shown the highest and the least percentage of contamination (60 vs. 17.1). Conclusion : We have found still a great gap between the quality of drinking water in Kashan as compared to the standard measures. Since providing drinking water with the highest quality is of utmost importance in the society health, further attentions should be paid to the monitoring systems and also the sources of contamination

A dynamic membrane reactor concept for naphtha reforming, considering radial-flow patterns for both sweeping gas and reacting materials

Hydrogen will become an essential energy source in the near future. In this regard, refineries can be considered as alternative sources of hydrogen production. In the present study, a tubular membrane reactor with radial-flow patterns of the sweeping gas and the naphtha feed named RF-TMR is proposed as a novel configuration for radial-flow naphtha reformers. Radial-flow reactors are used in refineries as a remedy for high pressure drop through the catalytic packed-bed reactors which disturbs the reactor operation. The cross section area of the tubular membrane reactor is divided into some subsections. The walls of the gaps are coated by a Pd–Ag membrane layer to separate hydrogen from reaction side and enhance the hydrogen and aromatic production rates by 0.33 ton/day and 5.5 ton/day, respectively (compared with the AF-TR). The performance of this novel configuration is investigated and compared with the axial-flow conventional tubular reactor (AF-TR) and axial-flow tubular membrane reactor (AF-TMR). Set of coupled partial differential–algebraic equations are solved by the orthogonal collocation method. Owing to a slight pressure drop in the tube side of RF-TMR, smaller catalysts’ particles with a negligible internal mass transfer resistance can be used to increase aromatics and hydrogen yields. This novel approach has the feasibility to be applied in the radial-flow moving bed reformers which are widely installed in refineries by licensors

Application of Electrochemical Process in Removal of Heavy Metals from Landfill Leachate

Aims Municipal landfill leachate contains high concentrations of heavy metals, organics, ammonia. The efficeincy of electrochemically removal of heavy metals from landfill leachate was studied. Materials & Methods The leachate was obtained from Kahrizak landfill in south of Tehran. The experiments were carried out by batch process. The 2liter batch reactor was made of glass. There were eight anodes and cathodes electrodes. The electrodes were placed vertically parallel to each other and they were connected to a digital DC power supply. The pH and conductivity were adjusted to a desirable value using NaOH or H2SO4, and NaCl. All the runs were performed at constant temperature of 25°C. In each run, 1.5liter of the leachate was placed into the electrolytic cell. Samples were extracted every 10min and then filtered through a mixed cellulose acetate membrane (0.42μm). The amount of Lead, Zinc and Nickel removal was measured at pH=7 and in current density of 0.5, 0.75, and 1A. Findings When current density and time reaction increased, removal efficiency of heavy metals such as Lead, Zinc and Nickel increased. At initial pH=7, density 1A and reaction time= 60min, Lead, Nickel and Zinc were removed up to 86, 93 and 95%, respectively. Conclusion Electrochemical process can be proposed as a suitable technique to remove heavy metal from landfill leachate