Sharif Digital Repository

This article presents the research results on production and performance of palladium-only catalytic converters. Monolith is used as catalyst carrier and gamma alumina as substrate. Dipping method is used for monolith washcoating. Palladium as the active metal is impregnated on gamma alumina using wet impregnation to produce catalyst samples. The effects of factors such as percent solid in slurry, milling time, calcination time and temperature, pH and existence of Al(NO3)3 on wash-coat characteristics were studied experimentally. SEM, XRD, and BET tests were carried out on the samples. Catalyst performance was tested in an experimental reactor that was designed for this research. The results... 

The Social Cost of nuisance noise from a wind turbine is defined here as the additional cost to reduce the noise level at a receptor to an exceptable, non-nuisance value, i.e. to mitigate this cost. This acceptable sound level is considered to be 35 dB. Our example is a 10-kW (nominal power) wind turbine considered to supply the electrical energy needs of a 3-storey residential building in Tehran and Manjil. The turbine generates sound at 75 dB. To reduce the sound level at the third floor of the building to 35 dB, it was necessary to increase the height of the turbine from 24 m to 48 m. The initial installed cost of the turbine thereby increased from US$45.000 to US$55,000. The cost of... 

Increase in the number of non-linear loads has increased harmonic pollution in industries, resulting in lower power factor and more losses. Harmonics may also lead to adverse conditions in cases they match a resonance frequency existing in the system. To alleviate the problems of harmonics, tuned harmonic filters are used. However, design and installation of passive elements in power systems or industries requires special attentions due to the possible resonances that may occur. In this paper, a Tire-Rubber company is analyzed for a filter installation. Harmonic analysis is performed, and site measurements are examined. Cautions to be taken for design consideration are then discussed  

In this paper, the numerical errors associated with the finite difference solutions of two-dimensional advection-dispersion equation with linear sorption are obtained from a Taylor analysis and are removed from numerical solution. The error expressions are based on a general form of the corresponding difference equation. The variation of these numerical truncation errors is presented as a function of Peclet and Courant numbers in X and Y direction, a Sink/Source dimensionless number and new form of Peclet and Courant numbers in X-Y plane. It is shown that the Crank-Nicolson method is the most accurate scheme based on the truncation error analysis. The effects of these truncation errors on... 

This paper presents a new model to short-term prediction of air pollution using a new structure is based on the intelligent neural networks. A new structure known as Time Delay Cerebellar Model Arithmetic Computer (TD-CMAC), an extension to the CMAC, it requires fewer memory sizes. The new model is demonstrated and validated with three primary air pollutants known as carbon monoxide (CO), sulfur dioxide (SO2), and nitrogen dioxide (NO 2). The simulation results for the half an hour ahead-prediction of the air pollutant data set show that the suggested new model is suitable for our purpose  

Two laboratory-scale biofilters filled with the same type of packing material were operated at different gas flow rates and influent concentrations of toluene and xylene in order to investigate their performance in treating waste gas streams. The columns contained a mixture of municipal compost as a base material and wood chips as a bulking agent in an 80:20 ratio; the porosity was 54%. Microbial acclimation was achieved by addition of nutrient-enriched solution along with pollutants for a week by daily mixing and natural aeration. During the start-up of the systems with inlet concentrations of 20 and 70 ppm for toluene and xylene, respectively, high biomass growth resulted in pressure drops... 

Stricter environmental regulations posed on chemical process industries (CPI), and the ever-increasing costs of end-of-pipe treatment, explain why chemical process industries have adopted new 'cleaner production' approaches in new designs and in retrofits. Finding environmentally clean alternatives for retrofitting existing processes has been addressed with various approaches. In this paper, a previous approach by the same authors is extended to include EHS criteria for targeting waste reduction in chemical processes, The method is applied to an existing local production facility as a case study and risk-based pollution prevention (P2) targets, and the appropriate direction and magnitude of...