The purpose of this paper is to investigate the possibility of using fuel with annular geometry (Tubular) in Tehran research reactor (TRR) from a neutronic perspective. The use of annular fuels requires less fuel load due to higher flux generation and higher reactivity. It is noteworthy that one of the most important advantages of this type of fuel is the creation of an area in the center of the fuel complex for irradiation of materials and production of radiopharmaceuticals. Therefore, in the TRR, a new fuel with annular geometry has been adopted to replace the current fuel with cubic geometry. This fuel is similar to TRR fuel in terms of materials. For this purpose, the neutron conditions of the core are simulated using MCNPX2. 7 and WIMS-CITATION codes. Then the obtained results from these codes were compared with the SAR results of the TRR. The obtained results in this paper show that to achieve the reactivity equivalent to the first core of the TRR, the critical mass of the tubular core fuel is up to 17% less than the critical mass of the first core fuel. On the other hand, using annular fuel, the neutron flux in the radiation channels increases up to about 14%. Also, according to the results of this study, the proposed tubular core, a core with an arrangement of 16 and at least 8 packages of 6 control rods are needed to achieve safety standards.

In this paper, optimization and control of a tubular reactor for thermal bulk post-polymerization of styrene have been investigated. By using the reactor mathematical model, static and dynamic simulations are carried out. Based on an objective function including polymer conversion and polydispersity, reactor optimal temperature profile has been obtained. In the absence of model mismatch, desired product characteristic can also be obtained by applying the corresponding reactor wall or jacket temperature profile. To achieve this temperature trajectory, reactor jacket is divided into three zones and jacket inlet temperatures are used as manipulated variables. Effectiveness of the proposed approach has been demonstrated through computer simulation. Furthermore for a special case of model mismatch, a method has been proposed which results in a near optimal profile.

The metal chloride of LaCl3 was chosen to modify the Au-Cu/AC to decrease the noble metal of gold and enhance the catalytic performances. Then a mercury-free catalyst of Au-Cu-La/AC was prepared by the impregnation method, and the fresh Au-Cu-La/AC and Au-Cu/AC catalysts were also characterized in comparison. The catalytic performances of mercury-free catalysts for acetylene hydrochlorination were carried out for 3500 hours in a multi-tubular fixed bed reactor. The additives of La can make the active species dispersed well and retard the aggregation of particles. And the acetylene conversion rate remained stable over 98. 5% with the fluctuations, less than 1%, and the selectivity of vinyl chloride maintained the stability of 99% or higher, which indicated that the mercury-free catalyst has excellent catalytic performances for acetylene hydrochlorination.

In this study, photocatalytic degradation of methylene blue was examined using different concentrations of TiO2 nano-particles (diameters less than 21 nm) and ultraviolet (UV-C) radiation in a tubular reactor. Different concentrations of catalyst (0.3-1.2 g/L), different pH conditions (3, 7 and 9) and dye concentration (15, 30 and 60 mg/L) as well as sample rotation level (125 mL/min) were studied. The sample passed 1-7 times through the quartz reactor exposed to UV-C ray (constant intensity=2.8 mW/cm2) (every rotation time was 8 min). Results of this research showed clearly that methylene blue is significantly degradable by TiO2 and UV-C radiation. Increasing dye concentration resulted in decreased efficiency and thus, as more samples passed through quarts tube, removal efficiency increased. Methylene blue with concentration of 15 mg/L and after 7 rotations in the reactor (56 min) was removed with the efficiency of 98%. Subsequent to dye removal, 47% of initial COD decreased simultaneously.

Mathematical modeling and optimization of the steam reforming process of methane to syngas in a catalytic fixed bed reactor inside the furnace chamber is performed with axial dispersion and non-linear kinetic models. Validation of the model is carried out using the industrial scale experimental data and commercial software. Results showed a better agreement between this model and experiments than the commercial software. Optimization of the operational parameters was performed by Genetic algorithm considering two objective functions, minimizing methane consumption together with maximizing the carbon monoxide yield. In this study, the following cases were investigated; in the first case, optimization of the industrial scale operational conditions was performed, in the second one working at different outside tube wall temperatures and in the third case different porosities of the catalytic bed were considered The results of this work suggest higher quality of the syngas product with the lower feed consumption and improving the operational conditions after long time running the process.

Cavity receiver in solar tower concentrator usually experiences highly intense radiation. Due to asymmetric concentration of solar rays, non-uniform heat flux distribution occurs on the different parts of the cavity receiver. This non-uniform distribution leads to uneven thermal expansion and stresses in receiver, which affects the reliable operation and reduces life time of receiver parts. Therefore, it is necessary to reduce the non-uniformity of solar flux on the surface of the absorber tubes and different parts of the solar reactor. The aim of this study was to focuses on the distributions of concatenated solar flux over graphite tubes of a 50kW solar reactor, which was previously designed for methane thermal dissociation at the focus of a solar furnace. In this study, the absorbed solar power on the different parts of the reactor is determined by Monte Carlo ray tracing method. Moreover, the effect of aperture size and the absorptivity of receiver parts on the net magnitude and distribution of absorbed power in reactor are investigated. The results prove that the 16cm aperture absorbs the maximum power and leads to even better solar flux distributions. Replacing the absorbing walls by the reflective walls will also result in more power absorbed by the tubes and better uniformity of flux distribution around the tubes.

The purpose of this paper is to investigate the possibility of using tubular fuel assemblies in Tehran Research Reactor (TRR) from the thermal hydraulic perspective. Tubular fuels have been used successfully in many Russian model research reactors in recent decades. The most important advantages of this fuel are higher neutron flux, more reactivity and less fuel loading compared to the current plate fuels. In this study, by selecting a tubular fuel assembly of IRT-4M type that is more geometrically compatible with the geometry and dimensions of the core grid plate, we modeled it using the Fluent software and also the RELAP5/Mod3. 2 code. The thermal hydraulic parameters of this assembly have been calculated under the operating conditions of current MTR fuel. The results of the calculations showed that the maximum clad temperature in both calculation tools is sufficiently lower than 105°, C, which indicates that without changing the current flow rate of the core, the heat produced in the tubular fuel can be well removed. Moreover, the maximum fuel temperature in tubular fuel is about 10°, C lower than the maximum fuel temperature in the current standard fuel element, which is another advantage for this fuel type.

Significantly velocity profile in tubular reactors is affect in outlet products. In order to obtain velocity profile, rheological models can be used. One of them is Power law model. One of the most important and effective parameters that it can be observed in this model is the n parameter. In this work, investigations of influence n on velocity profile in laminar flow and on conversion of a tubular reactor that Methyl Methacrylate polymerization occurs in the reactor are presented. Furthermore, this study is investigated rheological properties of outlet and inlet solution of the reactor with a rheometer and the value of n is estimated 0.8403 by curve fitting. The results indicate that with increasing the value of n, the pattern of motion is close to mixed. In addition, it can be observed that the conversion increases with decreasing the value of n and there exist maximum of conversion for the reactor in n=0. In other words, the conversion in n=0 is very close to the conversion in plug flow pattern and this means that in this situation velocity profile is plug flow. In the last part of this work, by the value of n that has been estimated, a modeling of the reactor is presented. The obtained conversion from modeling is 69.66 % and this value is very close to empirical conversion from paper Fan et al (65 %), and this means the modeling is acceptable.

Nanoporous heterogeneous AlSBA-15 (x) type aluminosilicate catalyst with different nSi/nAl ratios (x = 41, 129, and 210) was synthesized using hydrothermal method. AlSBA-15 catalysts were characterized by XRD, N2 sorption, TPD-NH3, FT-IR, SEM and TEM. XRD analyses of AlSBA-15 catalysts confirmed the presence of wellordered crystalline structure with p6mm symmetry. N2 isotherm of AlSBA-15 catalyst materials showed a type IV adsorption isotherm with H1 hysteresis loops. The specific surface area and specific pore volume of the AlSBA-15 catalysts are in the rage from 480 to 757 m2/g and from 0. 65 to 0. 95 cm3/g, respectively. SEM analysis of AlSBA-15 (41) revealed a worm-like particle morphology comprising particles in a size range of 3 μ m with the co-existence of smaller particles of ca. 1 μ m size. A distinct approach adopted for the synthesis of α-aminonitriles using heterogeneous nanoporous AlSBA-15 catalyst via Strecker reaction. This one-pot, three component system of amines (primary/secondary), carbonyl compounds (aldehydes/ketone) and TMSCN compounds proceed excellently in the presence of AlSBA-15 catalyst in water medium at room temperature (RT). The major advantages are excellent yield, short reaction time, high chemo-selectivity, simple experimental procedure, recyclability of the catalyst, easy work up procedure. This one-pot synthesis consists of two consecutive steps: (1) imine formation from amine and aldehyde/ketone and (2) cyano addition to imine. The findings suggest that catalyst is recyclable and can be reused up to six cycles.