Tikrit Journal of Engineering Sciences

This study deals with kinetics of hydrodesulphurization (HDS) reaction of vacuum gas oil (611-833) K which was distillated from Kirkuk crude oil and which was obtained by blending the fractions, light vacuum gas oil (611 – 650) K, medium vacuum gas oil (650- 690) K, heavy vacuum gas oil (690-727) K and very heavy vacuum gas oil (727-833) K. The vacuum gas oil was hydrotreated on a commercial cobalt-molybdenum alumina catalyst presulfied at specified conditions in a laboratory trickle bed reactor. The reaction temperature range (583-643) K,liquid hourly space velocity range (1.5-3.75) h-1 and hydrogen pressure was kept constant at 3.5 MPa with hydrogen to oil ratio about 250 lt/lt. The conversion results for desulphurization reaction appeared to obey the second order reaction. According to this model, the rate constants for desulphurization reaction were determined. Finally, the apparent activation energy (Ea), enthalpy of activation ( gif.latex?\DeltaH*) and entropy ( gif.latex?\DeltaS*) were calculated based on the values of rate constant (k2) and were equal 80.3792 KJ/mole, 75.2974 KJ/mole and 197.493 J/mole, respectively.

Simulated column performance curves were constructed for existing paraffin separation vacuum distillation column in LAB plant (Arab Detergent Company/Baiji- Iraq). The variables considered in this study are the thermodynamic model option, top vacuum pressure, top and bottom temperatures, feed temperature, feed composition & reflux ratio. Also simulated columns profiles for the temperature, vapor & liquid flow rates composition were constructed. Four different thermodynamic model options (SRK, TSRK, PR, and ESSO) were used, affecting the results within 1-25% variation for the most cases. The simulated results show that about 2% to 8 % of paraffin (C10, C11, C12, & C13) present at the bottom stream which may cause a problem in the LAB plant. The major variations were noticed for the top temperature & the paraffin weight fractions at bottom section with top vacuum pressure. The bottom temperature above 240 oC is not recommended because the total bottom flow rate decreases sharply, where as the weight fraction of paraffins decrease slightly. The study gives evidence about a successful simulation with CHEMCAD

Overall crystal growth kinetics for ammonium perchlorate in laboratory scale batch agitated vessel crystallizer have been determined from batch experiments performed in an integral mode. The effects of temperature between 30-60ºC, seed size 0.07, 0.120 and 0.275 mm and stirrer speed 160, 340, and 480 rpm, on the kinetics of crystal growth were investigated. Two different methods, viz. polynomial fitting and initial derivative were used to predict the kinetics expression. In general both methods gave comparable results for growth kinetics estimation. The order of growth process is not more than two. The activation energy for crystal growth of ammonium perchlorate was determined and found to be equal to 5.8 kJ/ mole. Finally, the influence of the affecting parameters on the crystal growth rate gives general expression that had an obvious dependence of the growth rate on each variables of concern (temperature, seed size, and stirrer speed) . The general overall growth rate expression had shown that super saturation is the most significant variable. While the positive dependence of the stirrer speed demonstrates the importance of the diffusional step in the growth rate model. Moreover, the positive dependence of the seed size demonstrate the importance of the surface integration step in the growth rate model. All the studied variables tend to suggest that the growth rate characteristics of ammonium perchlorate from aqueous solution commenced in a batch crystallizer are diffusion kinetic controlled process.

A comparative analysis of previous theoretical and empirical equations is applied to evaluate their behavior in predicting dispersion coefficient in open channel. A new simplified method for predicting dispersion coefficients using hydraulic parameters is developed. A nonlinear multiple regression method is prepared to derive a new equation of dispersion coefficient. This equation is proven to be superior in explaining dispersion coefficient of open channel more precisely, as compared to existing equations. Keywords: Longitudinal dispersion, hydraulic parameters, dispersion coefficients.

The increasingly importance for the uses of the air lift pump in widespread list of fields (mining, nuclear industries, agricultural uses, petroleum industries…etc.) makes it very interested for the researchers to find tools to raise the performance outcome of such pumps. An air lift pump system is setup to study the effect of the suction pipe diameter and submergence ratio on the liquid (water) pumping rate. The system has a lift pipe of (0.021 m) diameter and (1.25 m) length. Five diameters for the suction pipe (0.021, 0.027, 0.033, 0.048 and 0.063 m) with a fixed length of (0.3 m), are tested for each of the submergence ratios (0.2, 0.3, 0.4, 0.5) respectively. Results indicate that the higher the diameter of suction pipe is the higher the pumping rate for a fixed submergence ratio. From another side, the higher the submergence ratio is the higher the pumping rate for a fixed suction pipe diameter. Also, under high submergence ratios, high pumping rates are achieved by the use of lower air flow rates compared with those used with lower submergence ratios. The experimental results show good compatibility with the model suggested by Stenning and Martin for the performance of an air lift pump.

Computer Aided Process Planning ( CAPP) has been recognized as playing a key role in Computer Integrated Manufacturing ( CIM ). It was used as a bridge to link CAD with CAM systems, in order to give the possibility of full integration in agreement with computer engineering to introduce CIM. The benefits of CAPP in the real industrial environment are still to be achieved. Due to different manufacturing applications, many different CAPP systems have been developed. The development of CAPP techniques needs to a summarized classification and a descriptive analysis. This paper presents the most important and famous techniques for the available CAPP systems, which are based on the variant, generative or semi-generative methods, and a descriptive analysis of their application possibilities.

This paper presents a computer analysis of the eddy current brake in electric machines. It presents a formula for the braking force when the actual width of the pole is considered. This formula is suitable for both thin and thick discs and may be employed for a wide range of working speed. For this purpose, a mathematical analysis of the problem is presented together with the formula achieved for the braking force. The brake is first represented by a mathematical model based on certain assumptions and then the braking force is obtained as a result of solving a field problem. The problem is simplified to a one-dimensional problem, where a solution for the magnetic vector potential is obtained, and by employing Lorentz force equation, a formula for the braking force of the nth harmonic order is obtained.

This paper deals with the investigation of the characteristic of subsonic viscous flow through a curved diffuser numerically with commercial code for computational fluid dynamics (CFD) Fluent Inc. version 6.3. The diffuser flow is a two-dimensional, turbulent, incompressible and fully developed. The investigations are based on the Spalart-Allmaras turbulent model. A 2-D quadrilateral grid is generated by the grid generator GAMBIT. Obtained results are compared with the available experimental data and found to give good agreement. The effects of curvature angle, area ratio and adding tail channel with constant area on the diffuser performance and flow pattern are studied and revealed by the pressure contour, velocity vector, and variation of the pressure recovery factor for all above mentioned parameters.

By the nature of images, picture elements in local regions are highly correlated with one another. In such cases, image compression techniques are introduced to reduce the amount of data is needed to represent the same information, either exactly or approximately. In this work DCT/DPCM hybrid approach have been designed and implemented for interlaced images. The image signal was first transformed row-wise using discrete cosine transform (DCT) and a differential pulse code modulation (DPCM) scheme then was used column-wise to get difference signal. For still images the same 3-bit quantizer was employed which makes quantization process easier. For interlaced images 3-bit quantizer was used for the odd field and 2-bit quantizer for even field, since the difference signal of the even field was very small. A compression ratios of about 13:1 was obtained for interlaced image. Objective measurements showed a high peak to peak signal to noise ratio without noticeable impairment.

This aim of the present work is to study the effect of varying curing conditions namely temperature that was studied within rang from 10o to 60odegrees Celsius. Curing period between two to ninety days was also studied for the unconfined compressive strength (UCS) & hydraulic conductivity of lime treated clayey soil selected for Mosul city. The soil was treated with (2,4 and 6)% hydrated lime. Test Results showed that the UCS was increased with curing temperature increase especially at lower curing period. On the other hand, hydraulic conductivity of treated soil has increased with temperature compared with that of untreated soil but not with constant trend. Finally, leaching of treated soil has led to a decline in hydraulic conductivity with time, while the rate of decreasing was found to be more with samples exposed to higher temperature effect.