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

Hypothesis: 

Methyl orange is a dye used in various industries such as printing and dyeing. Since methyl orange is not affected by conventional biological treatment and is not easily decomposed, the release of effluents containing this toxic compound into environment has adverse effects on human life and the aquatic ecosystem. Therefore, it is necessary to remove this dye from various wastewaters Among the common methods of water purification, the method of adsorption by bioadsorbents is considered as a simple, efficient and inexpensive method. In the present study, walnut shell modified with polyaniline nanofibers (PANI/WNS) has been used for removal of methyl orange dye. This modified adsorbent is a good candidate since it has favorable characteristics including suitable morphology and positively charged functional groups for removal of anionic dyes.

PANI/WNS was prepared through aniline polymerization reaction on the surface of walnut shell particles and characterized using FTIR, FESEM, EDX, BET and XRD techniques. The effect of various physical and chemical parameters such as initial pH, contact time, adsorbent dose and initial dye concentration on the removal rate of methyl orange was studied and optimized. Also, thermodynamic parameters such as ΔH, ΔS and ΔG were investigated.

The adsorbent is able to remove methyl orange dye in acidic environment. Optimization of the effective parameters on the adsorption process showed that the maximum methyl orange removal was obtained under conditions of pH 3, contact time of 140 min, adsorbent dosage of 0.35 g/L and dye initial concentration of 50 mg/L. Evaluation of laboratory data by different isotherm models showed that the highest correlation coefficient is related to Langmuir isotherm model and is equal to 0.9975, which indicates that the dye adsorption process is limited to a monolayer Also, the maximum adsorption capacity for methyl orange dye was obtained as 243.9 mg/g at 25°C, which is a significant amount compared to similar adsorbents reported in the literature and indicates the high ability of the studied modified bioadsorbent for removal of anionic dyes such as methyl orange. In addition, based on the results of the kinetic studies, the pseudo-second order model showed a better description of the laboratory data. Thermodynamic studies showed that the adsorption of the dye is a favorable, spontaneous and endothermic process.

Research subject:

 It is not an easy task to get a suitable model of polymerization due to complex mechanism and kinetic of such processes. Polymerization temperature, as an intermediate variable between determining final polymer properties, is a good selection to be controlled. Fuzzy logic has ability to be applied to processes with unknown or less informed dynamics.

Research approach:

 In this research, control of semi batch poly(ethylene terephthalate) reactor temperature was studied. To do so, error and error variation were calculated using measured reactor temperature. Error and error variation were fuzzified using triangular membership functions. Five and three fuzzy sets were introduced to fuzzify error and error variation, respectively. Hence, fifteen rules were defined. Five fuzzy sets were defined to quantify these fifteen rules. Weight average defuzzification method was applied to calculate necessary heat to the reactor. Poly(ethylene terephthalate) was synthesized in a semi batch reactor based on a two steps method. It is possible to monitor temperature, pressure, rotation speed and mixing torque in this set up.

Produced water during esterification determines reaction advancement. In polycondensation step, mixing torque determines end of the process. Linguistic based fuzzy rules were applied to both steps. Reference temperatures were 230oC and 260oC, respectively. Reactor temperature was controlled with 1-2oC precision. Control logic was applied using C#.net real time programming.

In recent years, a different method has been studied for processing of juices concurrent with increasing consumer orientation towards foods that have the characteristics close to fresh food and longer shelf life. One of the new methods of heating that causes heat with a different mechanism versus conventional heat treatment is the use of microwaves. In order to implementation of this research; the continuously fluid processing system using microwave was designed and constructed. The PID program was developed to control and monitoring of process. The effect of different output temperatures (60, 70, 80 and 90 °C) select at different power (500, 700 and 900 W) on temperature-time diagrams was investigated. The effects of different temperatures on the engineering properties as well as the changes in PME were evaluated. The results showed that the temperature profiles recorded by NTC sensors at different points of the system were similar for water and orange juice. The use of full-power microwave due to constant turned on of the magnetron caused a more uniform temperature distribution. There was a slight difference in absorbed power (Pabs) values between sour orange juice and tap water, due to the different thermophysical properties between the two fluids. Temperature-time profiles showed a typical delayed phase due to heat absorption by the helical tube and the environment inside the treatment chamber before reaching steady state. The stage of com up time (CUT) had a significant effect on the inactivation of PME. The developed PID program is capable to Intelligent controlling of product processing with microwave technology.

This study aims to propose a method for the thermal recovery of regenerated bed in a two-bed adsorption desalination system. It investigates the affection of thermal recovery, heating water temperature, and cooling water temperature entering the bed and condenser on the performance of the system. The analysis demonstrated that at a constant temperature of cooling water, the amount of water that is produced increases by raising the temperature of hot water and the energy consumption does not change significantly. For example, at a cooling water temperature of 20 °C, by increasing the temperature of heating water from 50 to 90 °C, the water that is produced is 3.75 times more and the energy consumption is reduced by 7.4 %. Heat recovery reduces the energy consumption of the system. As the temperature of the hot water increases, the effect of thermal recovery increases. As a result of heat recovery at a heating water temperature of 50 and 90 °C, the energy consumption of the system decreases by 10.9 % and 37.6 %, respectively. Increasing the temperature of the inlet cooling water to the bed and the condenser reduces the production of water and increases the energy consumptionof the system. The effect of the temperature of cooling water entering the condenser on the water that is produced and the energy consumption is greater than that of the cooling water entering the bed. As the cooling water temperature increases, the energy-saving as a result of thermal recovery decreases. For example, At a cooling water temperature of 10 °C, thermal recovery reduces the energy consumption of the system by about 47 %, while at 23°C it is about 12 %. Again the effect of cooling water temperature that enters the condenser is more than that enters the bed. By increasing the temperature of cooling water entering the condenser from 15 to35°C, energy savings due to the heat recovery reduces from 53.7 to 9.3 %.

Heating is one of the most commonly used methods for accessing various purposes in the food process. The main problems with microwave heating are the possibility of cold and hot spots. The aim of this study was to investigate the uniformity of temperature distribution in Fandoghi Pistachio under the microwave heating process under study conditions. Independent factors included the shape of product geometry, the position of the thermometer and the heating time. This research was based on a completely randomized design based on a factorial experiment of 2×6×4. Independent factors included the shape of product geometry, the position of the thermometer and the heating time. These experiments were performed separately for 900 and 630 w microwave power, and the temperature of the pistachio product was measured and recorded during the four-time heat treatment at six different positions of the product as an associated factor. The results of this study were based on two types of analysis of the comparison of the mean temperature of the samples and the determination of the relative non-uniformity index. The results showed that all the main effects were significant at 1% level in both applied power states. Comparison of means showed that in treatment "B" (cubic - 630 w) in 5 positions of 6 positions, there is no significant difference between the mean temperature under investigation. This means that the temperature distribution at different product positions at the end of the microwave heating period has been quite uniform. Subsequently, the cubic – 900 w and cylindrical- 630 w had the highest uniformity in temperature distribution. By calculating the relative non-uniformity index, the highest uniformity was obtained in cubic - 630 w.

In recent years, the waste energy in cooling water of power plants has been applied for the production of water from saline waters. In this research, the effect of using the cooling water of a power plant located on the Persian Gulf coast, as a feed of a reverse osmosis unit was investigated on the separation of salt from seawater, the quality of the final product and water recovery. By increasing the feed water temperature from 20 to 45 °C, although the flow of the produced water increased about twice (from 7.5 to 14 L/m2h), it decreased the membrane salt rejection and salt separation by the membrane. As a result, the electrical conductivity of the produced water increased to about 700 to 1200 μS/cm. This change is due to enhanced membrane permeability to water and salt at higher water temperatures. Increased water flux saved energy for water production, but reduced the desirability of drinking water, although it remained within the world health organization (WHO) standards.

Given that in the modern world in all industries seeking to make maximum use of the equipment are high reliability, condition based maintenance is one of the cases to achieve high reliability that In a variety of vibration analysis, temperature analysis, oil analysis, etc. are applicable. Now in the Barez rubber factory temperature analysis, vibration analysis, oil analysis, thermography testing, inspection and flow measurements using the five senses in terms of condition based maintenance are intended and running.

Sorption isotherms of two acid dyes, Blue 127 and Green 25 on nylon 6 fibers were studied at 90 and 98C, respectively. A remarkable deviation from Langmuir isotherm was obtained for both dyes. Performance of Dual-Mode sorption model which consists of Langmuir mechanism and Nernst model was tested. Dual-Mode fitting was appeared to be in good agreement with the experimental data rather than Langmuir. In addition, the sorption capacity of fiber from measuring the amino end-group content and that calculated from Langmuir isotherm was compared. The results confirmed that the adsorption is not limited only to the sitting mechanism and there are the other sites involving in the adsorption. Studying the temperature effect on Dual-Model isotherm showed the total adsorption capacity of fiber is decreased by increasing the temperature. However the most part of total sorption was still followed as Langmuir isotherm. J