Seham A. El-Temtamy

Oxygen mass transfer in a bubble column bioreactor containing lysed yeast suspensions

SummaryLiquid-phase volumetric oxygen transfer coefficients were evaluated in a bubble column containing yeast suspensions, using the instationary oxygen absorption method and a polarographic oxygen electrode. The electrode time lag was found to be independent of both the system studied and the operating conditions. The volumetric oxygen mass transfer coefficients kLa could be reasonably predicted by calculating kL from the equation derived by Bhavaraju et al. or the empirical equation of Calderbank and Moo-Young and “a” from the experimental gas hold-up values.

Rise velocities of large single two-dimensional and three-dimensional gas bubbles in liquids and in liquid fluidized beds

Abstract The rise velocities of both circular-cap gas bubbles in two-dimensional, and spherical-cap gas bubbles in three-dimensional, liquid fluidized beds are shown to be predictable by the same equations which predict the rise velocities of similar bubbles in still liquids, provided the rise velocities are expressed relative to the liquid rather than relative to the column walls.

Carnalite salt gradient solar ponds: an experimental study

Carnalite salt evaporation ponds are created as a result of the Arab Potash Company work south of the Dead Sea. Development of salt gradient solar ponds for the utilization and storage of solar energy in this locality seems to be logical thinking. Therefore, a laboratory scale solar pond of the dimensions 1 × 2 × 1 m has been constructed. Carnalite salt was the salt utilized in this pond. The gradient zone was established by the redistribution method. The pond was maintained for the period 18 April–18 August 1990. The development of temperature and salinity profiles were studied. The heating up process took around five weeks after which steady state pond operation was established.

Non-Newtonian behaviour of yeast suspensions

SummaryThe rheological properties of yeast (Bakers yeast) suspensions in water and in water-methanol-electrolyte solutions have been investigated using a Fann V.G. concentric cylinder viscometer. The resulted rheograms could be described by the power law model for non-Newtonian fluids with the flow behaviour index “n”<1 indicating pseudo-plastic behaviour. This flow behaviour index was constant under all operating conditions while the consistancy index “k” increased exponentially with increasing wet yeast volume fraction. The addition of methanol and electrolytes had a negligible effect on the rheological properties. Changing the pH of the suspension acidic to lowered the apparent viscosities.

Liquid-phase axial mixing in a bubble column bioreactor containing yeast suspensions

SummaryLiquid-phase axial mixing coefficients were evaluated in a 0.15 m x 2.0 m batch bubble column containing water and yeast-in-water suspensions of different concentrations. Air superficial velocities ranged from 0 to 0.06 m/s. Axial mixing coefficients were calculated from the residence time distribution to an NaCl tracer pulse using the Ohki and Inuoe model. No specific variations in the calculated coefficients were observed to result from the presence of yeast cells. There was fair agreement between the data thus obtained and the only available data on mixing in non-Newtonian CMC solution.

A transient model of a laboratory-scale carnalite salt gradient solar pond

The thermal performance of a laboratory-scale salt gradient solar pond has been modeled as a one-dimensional unsteady conduction heat transfer problem with heat generation. The pond is assumed to be cut into horizontal slices and finite difference heat balance equations are solved simultaneously to predict the temperature of each slice at any time. The initial conditions were the temperature profile data. The boundary conditions were determined by studying the heat balance at the bottom of the pond and by assuming the pond surface temperature to be equal to the ambient temperature. Solar radiation attenuation is calculated by the Bryant and Colbeck formula. A computer program is constructed to perform the calculations. In addition, Koois model was compared with our model. Similarly the salinity behavior was studied by writing the one-dimensional differential mass balance equation over a small slice with the appropriate boundary and initial conditions. The resultant set of linear equations was solved simultaneously for the unknown new concentrations. A computer program has been constructed to perform the calculations. Fair agreement between experimental and predicted profiles was obtained.

The Use of Pinch Technology to Reduce Utility Consumption in a Natural Gas Processing Plant

Abstract The present work aims at investigating opportunities for energy conservation in Western Desert Gas Complex (WDGC) through modification of the heat exchanger train. Process simulation of the plant was performed using HYSYS steady-state simulation program. This step was necessary to furnish stream property data requested for heat analysis as well as condenser and reboiler duties. Adopting the pinch design technology, minimum heating and cooling energy requirements were calculated for different values of minimum approach temperature (ΔTmin). Two methods were used, the problem table algorithm of the pinch method and the linear programming method. Then designing the heat exchanger network (HEN) took place according to the pinch design method to achieve target utilities for each ΔTmin. The optimum HEN is that which achieves considerable heat recovery with least annualized total cost. The optimum HEN design was found to correspond to ΔTmin of 10°C and achieved saving of hot and cold utilities as 42 and 21%, respectively, compared to the actual utilities consumption of the existing plant. These savings can be realized by adding only two heat exchangers to the existing network with a payback period of ≈1 year.

Response surface methodology for carbon dioxide reforming of natural gas

ABSTRACT The performance of 0.5% wt Rh/γ-AL2O3 catalyst for the dry reforming of natural gas using carbon dioxide has been studied. The response surface methodology (RSM) is used to study the effect of two different operating parameters, namely the hourly space velocity at the levels 18,000, 36,000, 45,000, and 60,000 ccg−1 h−1 and the reaction temperature at the levels 600, 700, and 800°C, on the conversion of the different components comprising commercial natural gas. The RSM is used to illustrate such effect in the three dimensions and shows the location of the optimum for the conversion or production of each component.

Denitrogenation of carbazole by a novel strain Bacillus Clausii BS1 isolated from Egyptian Coke

ABSTRACT In this study, an effective enrichment technique was applied to isolate different bacterial strains with capabilities to denitrogenate carbazole (CAR), as a model compound for nitrogenous polyaromatic hydrocarbons (NPAHs). Twenty-four different CAR-denitrogenating bacterial strains were isolated from mineral coke samples. From all, a Gram +ve bacterial isolate designated BS1 showed a higher biodenitrogenation (BDN) efficiency relevant to the well-known biodenitrogenating bacterium strain Pseudomonas resinovorans CA10, recording 77.15 and 60.66% removal of 1000 ppm CAR with the production of 119.79 and 102.43 ppm anthranilic acid, and 121.19 and 90.33 ppm catechol, as by-products, respectively. BS1 was identified by 16S rDNA gene sequence analysis to be Bacillus clausii BS1 (NCBI GenBank Accession no. KF985981) with a similarity of 99.14%. The CAR-BDN pathway was also elucidated using high-performance liquid chromatography (HPLC) and gas chromatography mass spectrometry analysis (GC/MS), which proved further metabolism of catechol to muconic acid.

Economics of Energy Transportation in Egypt

Publisher Summary This chapter discusses the transportation cost of natural gas. The cost includes the construction costs of pipelines, and gas pressure reduction stations. Actual cost data for pipelines and pressure reduction stations are collected and processed. Empirical equations describing the construction cost are also obtained. Comparison between calculated and actual values reveals the reasonable accuracy of the proposed equations for such projects. Split of the capital investment indicates that pipelines cut out the lions share (93%) against 7% for the pressure reduction stations. Pipelines material represents 49% of the total construction cost, followed by labors cost (28%), and wrapping cost (18%). All other items together represent around 5%.