This research evaluated the efficiency of combined anaerobic-aerobic processes for the treatment of slaughterhouse wastewater. The anaerobic REACTOR consists of a 3. 95 L Plexiglas column with 60 mm diameter and 140 cm height. The cylindrical particles of polyvinyl chloride with 2 mm diameter and 1250 kg m-3 density packed to 60 cm of column were used as biomass saving material. The designed aerobic REACTOR also has a Plexiglas column with 10 cm internal diameter, 90 cm height and 60 cm useful height. Anaerobic fluid bed and aerobic mobile bed REACTORs were exploited for retention times of 18, 24, 32, 40 and 48 h. The efficiency of total suspended solids, biological oxygen demand and chemical oxygen demand removing were evaluated in different stages. Under the applied condition, chemical oxygen demand, biological oxygen demand and suspended solids were removed by 85. 94, 92 and 66%, respectively. Maximum methane production of 3765 mL per day was obtained after 31 h at the residence time of 18 h. The anaerobic REACTOR plays very important role in reduction of the chemical oxygen demand, and the aerobic REACTOR is necessary to clear the anaerobic treated wastewater and ensure the quality of the final waste.

The Miniature Neutron Source REACTOR is a tank-in-pool research REACTOR that uses highly-enriched uranium as fuel, light water as coolant, and beryllium as reflector. During the operation of the REACTOR, the coolant temperature increases and leads to negative feedback in the REACTOR. Although the negative reactivity is amongst the advantages of this REACTOR and an inherent safety feature,it causes a decrease in both the additional available reactivity and the REACTOR operation time. Therefore, short operation time (about 2. 5 hours) at nominal power is one of the main limitations of the MNSR REACTOR. The natural convection in the core, vessel and pool of the REACTOR was modeled through a CFD analysis and the effect of the cooling coil at the top of the REACTOR tank on increasing the REACTOR operation time was investigated. To reduce the computations the details were decreased by considering the REACTOR core as a porous medium and a heat source with a constant power of 30kw. The experimental values and those obtained from the numerical solution are in good agreement. Results show a steady upward slope in the temperature rise of the coolant in the absence of coil, and an about-2-hours rise of the temperature in its presence. After this 2-hours period, the increasing rate decreases and the temperature fluctuates in a certain range. Compared to the case without the cooling coil, the average temperature is reduced by 3 degrees and the REACTOR operation time is increased by 1. 5 hours.

Nowadays formaldehyde is used as raw material in many industries. It has also disinfection applications in some public places. Due to its toxicity for microorganisms, chemical or anaerobic biological methods are applied for treating wastewater containing formaldehyde.In this research, formaldehyde removal efficiencies of aerobic biological treatment systems including moving bed biofilm (MMBR) and sequencing batch REACTORs (SBR) were investigated. During all experiments, the efficiency of SBR was more than MBBR, but the difference was not significant statistically. According to the results, the best efficiencies were obtained for influent formaldehyde COD of 200 mg/L in MBBR and SBR which were 93% and 99.4%, respectively. The systems were also capable to treat higher formaldehyde concentrations (up to 2500 mg/L) with lower removal efficiency. The reaction kinetics followed the Stover-Kincannon second order model. The gram-positive and gram-negative bacillus and coccus as well as the gram-positive binary bacillus were found to be the most dominant species. The results of 13C-NMR analysis have shown that formaldehyde and urea were converted into N-(((aminocarbonyl) amino) methyl) urea and the residual formaldehyde was polymerized at room temperature.

A hierarchical and computationally efficient mathematical model was developed to explain the polymerization of high-density polyethylene (HDPE) in an isothermal, industrial, continuous stirred tank slurry REACTOR (CSTR). A modified polymeric multi-grain model (PMGM) was used. Steady-state macroscopic mass balance equations were derived for all species (namely, monomer, solvent, catalyst and polymer) to obtain the final particle size and the required monomer and solvent input rates for a given catalyst input and the REACTOR residence time. The interphase mass transfer coefficients were calculated for the industrial CSTR using the operating data on the REACTOR. The present model was tuned with some data on an isothermal industrial REACTOR and the simulation results were compared with data on another set of industrial REACTOR. The comparison revealed that the present tuned model is capable of predicting the productivity and the polymer yield at various catalyst feed rates and the mean residence times. The effects of variation of two operating variables (catalyst feed rate and mean residence time) on the productivity, the polymer yield, the polydispersity index (PDI) and the operational safety were analyzed. The present study indicated that an optimal value of the REACTOR residence time (for maximum productivity per catalyst particle) exists at any catalyst feed rate.

The Spheripol process is one of the most widely used technologies in the world for the production of polypropylene (PP). The geometry of the REACTOR is such that the use of ideal REACTORs alone causes an error in the simulation results. Therefore, in this research, we have tried to combine the ideal REACTORs modules in Aspen Plus. v11 to get the most accurate results. In order to calculate the volume of the ideal REACTOR, we used the concept of «required length for fully developed flow» and considered the inlets, outlet, and pump of the REACTOR as a continuously stirred tank REACTOR (CSTR) while the other part of the REACTOR considered as plug flow REACTOR (PFR). We also used three different kinetic constants reported by three different research groups and compared the result with the production plant data. Due to the importance of the thermodynamic model for the prediction of phase behavior, we used the Perturbed Chain Statistical Associating Fluid Theory (PC-SAFT) equation of state that was used by previous authors. The results are validated with the production plant data and previous articles. Also, the effect of methanol as a catalyst poison is investigated.

Calculating and measuring the gamma dose of nuclear REACTORs is important in terms of safety and protection and is used for organizations' design and development programs. In order to achieve this goal, experimental measurement with RADOS and SMART-RAD digital dosimeters and calculations based on Monte Carlo code has been used. The three-dimensional geometry of the light water subcritical REACTOR of Isfahan REACTOR Research School was simulated for gamma dosimetry calculation with the MCNPX2. 6 code. The effective multiplication factor was estimated prior to dose calculation and revealed to be less than 6% different from the value reported in the REACTOR technical specifications. Analyses were performed to obtain the sought parameter, gamma dose (μ, Sv/h), following the validation of the REACTOR simulation code. The F4 and F5, F4 and *F8, and *F8 and F5 tallies differed by less than 5%, 2%, and 4%, respectively. The difference between the measured and calculated values was found to be reasonable and acceptable compared to similar previous studies.

In present paper, dynamic behavior and control of a fluidized bed REACTOR for polyethylene production has been considered. A double active sites model for Ziegler-Natta catalysts is used for simulation of polymerization reaction. Hydrodynamic behavior of the bed is modeled using a two phase model including bubble and emulsion phases in which bubble phase has plug flow pattern with differentially variable velocity and size through the bed and emulsion phase has the CSTR flow pattern. The REACTOR model is validated using industrial data. Conventional PID controllers with anti-windup are considered for control purposes. It has been shown that the control system has satisfactory performances either for set point tracking or load rejection. To improve the performance of the control system for load rejection the cascade control strategy has been considered.