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Volume 3, Number 1, June 1999 



 A semi-empirical kinetic model for dissolution of ulexite in aqueous acetic acid solutions (1999) Volume(issue) 3(1): 1-10.

M. Tunç1, M. M. Kocakerim2, A. Gür1, and A. Yartaşı2

1 Department of Chemistry, Yüzüncü Yıl University, Van, TURKEY

2 Department of Chemical Eng., Eng. Faculty, Atatürk University Erzurum,TURKEY

This work submits an investigation on the dissolution of ulexite in acetic acid solutions. Reaction temperature, acid concentration, particle size, solid-to-liquid ratio and stirring speed were chosen as parameters in the experiments. It was found that the dissolution rate increased with increasing temperature and stirring speed and decreasing solid-to-liquid ratio and particle size. The conversion rate increased with increasing acid concentration up to 20 % and then decreased with increasing acid concentration. The activation energy of the dissolution process was calculated to be 30.69 kj.mol-1.

It was determined by graphical and statistical methods that the reaction kinetics fitted to model in the form of -ln(1-X) = The following semi-empirical mathematical model, which expresses very well the dissolution process, was established:

-ln(1-X) = 982.40.[(D)-0.749. (W)0.891. (S/L)-0.265. exp(-3696/T)].t0.675

where X is conversion fraction; D, initial particle size; W, stirring speed; S/L, initial solid-to-liquid ratio; T, reaction temperature; t, reaction time.

 A direct route to the calculation of heating values of alkanes, alcohols and oils by density measurements (1999) Volume(issue) 3(1): 11-17.

A. Demirbaş, E. Güllü, D. Güllü, and N. Yazıcı

Fatih Education Faculty, Karadeniz Technical University, 61335 Akçaabat-Trabzon, Turkey

Higher heating values (HHVs) of alkanes, alcohols and vegetable oils were determined experimentally and calculated from their density measurements. The HHV (kJg-1) of the samples was supposed as a function of density (d, in gcm-3) and suggested following equations in this study: For vegetable oils: HHV = 79.01 - 43.13d; for alcohols: HHV = -191.95 + 281.11d and for alkanes: HHV = 55.75 - 11.05d. The HHV calculated by using these HHVs showed mean differences of 0.001, 0.040 and 0.003% for vegetable oils, alcohols and alkanes respectively. The correlation coefficients were 0.938, 0.970 and 0.936 for vegetable oils, alcohols and alkanes respectively.

Nonlinear finite element buckling analysis of laminated reinforced concrete plates with holes (1999) Volume(issue) 3(1): 19-31.

M. Elmas1, H. Kasak1, and M. F. Altan2

1Department of Civil Engineering, Sakarya University, Sakarya,Turkey.

2Department of Civil Engineering, Celal Bayar University, Manisa, Turkey.

Using classical theory of laminated plates, the critical buckling load of a square reinforced plate is investigated as a function of constituent fiber and matrix properties and geometry of fiber orientation. An approximate buckling analysis of a rectangular orthotropic plate with a central rectangular hole is applied to symmetrically laminated angle - ply plates. The buckling loads for various rectangular holes and laminated plates with varying angles and stiffness parameters have been indicated. Nonlinear finite element buckling is examined for clamped and simply supported and results are compared with previous analyses and experiments for various sized holes. The results show good agreement with those published.

Dissolution of ulexite in sulfuric acid solutions for high solid-to-liquid ratios (1999) Volume(issue) 3(1): 32-41.

M. Tunç1, A. Gür1, M. M. Kocakerim2, and A. Yartaşı2

1 Department of Chemistry, Yüzüncü Yıl University, Van, TURKEY

2 Department of Chemical Eng., Eng. Faculty, Atatürk University Erzurum,TURKEY

Boron compounds are used as raw material in various areas of industry. These compounds are produced by a number of physical and chemical processes from many boron ores which are present in nature. Ulexite is one of the ores used for this purpose. In this study, dissolution kinetics of ulexite in sulfuric acid solutions was investigated for high solid-to-liquid ratios. In the experiments, particle size, sulfuric acid concentration, solid-to-liquid ratio, stirring speed, and reaction temperature were chosen as parameters. It was observed that the dissolution rate of ulexite in sulfuric acid solutions increased as the particle size, acid concentration, solid-to-liquid rate decreased, and reaction temperature increased. It was also determined that the stirring speed was not effective at the studied conditions.

An optimization example for electricity production from geothermal sources by using double stage system (1999) Volume(issue) 3(1): 42-47.

A. Murathan, A. Alıcılar, and İ. Ar

Department of Chemical Engineering, Faculty of Engineering and Architecture, Gazi University, 06 Maltepe, Ankara, Turkey

Geothermal energy has big importance among the renewable energy sources. In flash system quality is increased by flashing geothermal fluid. When suitable conditions are exist, second flash can be used and it increases the energy production in great extend. In double stage flash system, selection of the first and second flash temperatures is very important for effective production. For the resources in Germencik-Ömerbeyli geothermal regions of average temperature of 200oC and with vapor content about 13 % optimum first and second flash temperatures was found as 109oC and 172oC, respectively.

In this study, a computer program was prepared to determine flash temperatures. It was tried to find out the optimum flash temperatures which correspond to maximum work. In these calculations, the properties of Germencik geothermal sources in Turkey were taken as basis.

Utilization of industrial boron wastes in cement production for the stabilization (1999) Volume(issue) 3(1): 48-54.

R. Boncukçuoğlu1, M. M. Kocakerim2, and V. Tosunoğlu1

1Department of Environmental Engineering, Engineering Faculty, Atatürk University, Erzurum, Turkey

2Department of Chemical Engineering, Engineering Faculty, Atatürk University, Erzurum, Turkey

Industrial raw materials such as boric acid, boron trioxide, refined borax decahydrate, unrefined anhydrous borax, refined anhydrous borax and sodium perborate are produced from boron minerals. During the production of these compounds in Etibank Bandırma Borax and Acid Factories in Turkey solid and liquid wastes containing B2O3 in various ratios are formed at some stages of the process. There is a necessity of making use of these wastes in large amounts to save the loss of B2O3 and to avoid the environmental problems. Although boron is available in low amounts in soil and irrigation water, it accumulates very fast because of the difficulty of trapping and washing it, and this affects the plantation of many agricultural products badly. The boron components which are available in the soil, in some complexes with heavy metals such as Pb, Cd, Cu and Ni and this increases the potential toxicity of these elements, and creates serious health problems.

In this study, it was aimed to stabilize of borogypsum and the tincal waste which are formed during production. Borogypsum is produced during the dissolution stage of colemanite ore in H2SO4 and the tincal waste at the stage of the production of borax from tincal, which consists of undissolved tincal and the solid part of boraxslime. In this submitted work, the cement produced by adding borogypsum and tincal waste to clinker, which is a cement raw material were tested to find the unit weight, pressure resistance and bending resistance, and the test values were compared with the standard values.

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