جستجوی مقالات مرتبط با کلیدواژه « رسوب » در نشریات گروه « مهندسی شیمی، نفت و پلیمر »

Pollution of aquatic ecosystems with petroleum hydrocarbons is one of the most important issues that have become challenging in recent years. Bushehr port located in Bushehr province in the south of Iran due to its connection with the Persian Gulf and having long beaches is one of the places prone to pollution related to hydrocarbon compounds. In order to investigate the concentration of aromatic compounds in the surface sediments of Bandar Bushehr beach, 27 sediment samples were collected and subjected to GC analysis. The total amount of aromatic compounds in the coastal sediments of Bushehr port fluctuates between 206 and 1463 ng/g. The largest volume of aromatic compounds is concentrated in the northern strip of the Sahel and the middle of the Sahel, and the concentration of the compounds is low in the southern strip of the Sahel. These compounds have pyrogenic and petrogenic origin, although the contribution of petrogenic origin is more. The origin of combustion compounds is the result of sea and land transportation, municipal and domestic sewage and offshore currents carrying petroleum compounds originating from the oil fields of the Persian Gulf. Based on pollution standards, the northern and middle parts of the coastal strip of the Persian Gulf in the area of Bushehr port have a medium pollution load in relation to aromatic compounds, and in the southern parts, the pollution load is low.

In this study, the effects of pH and ultrasonic waves on the performance and stability of CuO have been studied. The CuO nanofluid (deionized water-based) was used to increase the boiling heat transfer coefficient. Boiling heat transfer coefficient of fluid increased by the addition of nanoparticles into the fluid, but due to the instability of nanoparticles by increasing temperature and time, nanoparticles were precipitated on the heat transfer surface. Therefore, it led to a reduction in the boiling heat transfer coefficient. Moreover, it is necessary to obtain the optimal concentration of nanoparticles in the fluid to determine the minimum amount of deposition. The use of methods to reduce the deposition of nanoparticles such as increasing the stability of nanoparticles and also an optimal concentration made an increase in heat transfer coefficient. To overcome this challenge, two conventional methods were employed including pH change (9.5, 10 and 10.5) and ultrasonic radiation (with 25%, 50%, and 75% of power). The results indicated that the maximum enhancements of boiling heat transfer coefficient were achieved at nanoparticles concentration of 0.125% under ultrasonic radiation with 50% power and the pH value of 10 as average of 37.48% and 22.68%, respectively.

Scaling formation in industrial or domestic installations is an important economic and technical problem. In this study, the percentage of calcium carbonate deposition in the solution based on ASTM D1141 at different LSIs was investigated by using the chemical method. It was revealed that at LSI values greater than 1.8, the probability of CaCO3 deposition is considerably increased. Therefore, at LSI = 2.2 the effect of concentration of different green-scaling inhibitors including homopolymers, copolymers and terpolymers on the CaCO3 deposition process was investigated by chemical analysis method and the optimal concentration of scaling inhibitors was determined. For the inhibitors of polyacrylic acid homopolymer (PAA), poly maleic acid homopolymer (PMA), poly acrylic acid: 2-acrylamido-2- methylpropane sulfonic acid copolymer (AA/AMPS) and poly acrylic acid:2-acrylamido-2-methylpropane sulfonic acid: t-butyl acrylamide terpolymer (AA/AMPS/TBAA), the optimal inhibitory concentration was obtained at 5, 5, 2 and 2 ppm concentration, respectively by the chemical method of bulk analysis.

In the present study, the problems of salt solution sedimentation on heat exchangers, their modelling procedure, and the heat exchanger fouling removal methods based on the related published investigation are reported. The salt solutions are used in many technological industries, and the sedimentation of stable salts is the main limitation of using them, especially in the high-temperature liquid-vapor system. The methods of these salts removing is online and offline fouling cleaning. Each of these methods has their advantageous and disadvantageous. In the practical application, there are multiple criteria considering different conditions. Although, based on the heat exchanger design condition, the solid salt sedimentation decrement can be improved the system fouling problems.

A thin film is a organic substances layer with nanometer to micrometer thickness. The controlled synthesis of thin films is an important issue in its applications. Organic thin films with nanometer thickness are useful structure for applying in sensors, detectors and electronic circuit components. Spin coating and Langmuir-Blodgett are one of the applicable techniques in thin films preparation. In spin coating centrifugal force drives the liquid radial outward and the viscous force and surface tension causes a thin film to be produced on the flat substrate. Langmuir-Blodgett films are ultra thin organic films with interesting properties such as controllable thickness, uniformity of surface and a high degree of oriented order, which make them possible options for sensors applications. In this article were investigated various aspects of spin coating and

Deposit formation in heat exchangers causes increased pressure drop, flow non-uniformity, energy loss and deterioration of efficiency. A novel, efficient, and environmentally friendly approach to mitigate deposition in heat exchangers, is surface treatment. Surface energy and its polar and dispersion components are modified by coating of surfaces to mitigate fouling. In this study surface energy and its polar and dispersion components are calculated by Wu and OWRK approaches. The determination of surface energy and its polar and dispersion components for crystallization fouling showed that formation of precursor on substrates reduces by increased polar component of surface energy. Comparison with experimental data points associated with CaSO4 crystallization fouling confirm this propensity.

Carry Over Phenomenon is one of the common problems in Sugarcane boilers that has a important effect at any type of failure, output loss, trip, out of ordering and other equipments (before and after boiler) failure. It’s very important to know how this phenomenon is raised and lead to corrosion failure and fouling on steam drum surface, superheater and reheater tubes, steam turbine blades, … during boiler design and operation.In this paper, we describe how carry over occur and identify its effective ingredient at first. After that survey any kind of them and related efficacy. Then suggest a scope for evaluation and sampling carry over during boiler operation. Finally, offer some solution to decrease occurrence possibility or percentage with some modification that should be performed in system operation.

In quench towers and process water treatment section of steam generators, fouling decreases the performance, heat transfer rate, steam generation rate and increases rate of steam make-up for furnaces. In this study, Effective parameters like temperature, water contaminants, dissolved solids (e.g. Si, Fe,), PH, inhibitors and controlling chemical rates and dissolved oxygen which should be monitored for reducing these problems, are surveyed. Installation of dissolved oxygen monitor in dilution steam generator inlet stream is recommended as a result of this study. As this device provides the possibility of oxygen measurement, optimization of oxygen generating chemicals injection rates could be achieved. The recommended analyzer has not been available in olefin plants so far.

The amount of resin existing in crude oil highly affects the asphaltene precipitation values and results in formation of precipitation, asphaltene and resin and also pressure and temperature variations in such reservoirs. According to the literature, the effect of resin content has not been studied. The equation of state (AEOS) is one of the most applicable models which was also used in this study. The compressibility factor was assumed to be made of physical and chemical components. SRK equation of state was used in physical component. Considering the fact that asphaltene and resin do not interact in gas phase and that asphaltene and resin precipitations are in liquid state, vapor-liquid and liquid- liquid equilibrium calculations were applied. Asphaltene precipitation values were calculated from simulations the results were then compared to experimental data. Finally the resin precipitation values were measured.

“Calcium sulfate is the majority of dissolved salts in commercial and industrial waters. Calcium sulfate is negative soluble versus temperature in water. Accordingly the saturation concentration adjacent to the heat transfer area will dwindle beneath the bulk concentration. Hence the surplus salt will deposit on the heat transfer surface and a fouling resistance will be established by two independent mechanisms. The first one is mass diffusion associated with mass transfer mechanism and the second is the evaporation of bubbles on the heat transfer surface. Averting of salt deposition is not straightforwardly practicable, but estimation of this heat resistant as a function of operating parameter is significant. Optimizing the heat flux to reduce sedimentation process and consequently minimizing the running cost is one reasons. In addition is necessary to provide an accurate schedule for overhauling program and fuel consumption for a predetermined running system. In the current research, the fouling resistance of calcium sulfate scale is modeled as a function of time, heat flux and bulk concentration.