Asım Balbay

Microwave Drying Kinetics of a Thin-Layer Liquorice Root

Liquorice root (LR) (Glycyrrize glabra) is known as a sweetener and medicine plant. Drying kinetics of LR with initial moisture content of 49.5% (wet basis (w.b)) were experimentally investigated in a microwave drying system. The drying experiments were carried out at different drying temperatures (40, 45, 50, and 55°C) and microwave power levels (250, 500 and 750 W). Several models from literature were selected to fit the experimental data. The fit quality of models was evaluated using the coefficient of determination (R2), sum square error (SSE), and root mean square error (RMSE). A new model has been proposed for LR drying in the microwave drying. This new model best describes the experimental data for LRs. The activation energy was calculated to be 46.807 kJ/mol and effective diffusivity ranged from 2.9 × 10−9 to 5.41 × 10−9 m2/s, depending on drying temperatures at constant microwave power level.

An Investigation of Drying Process of Shelled Pistachios in a Newly Designed Fixed Bed Dryer System by Using Artificial Neural Network

In this paper, the drying of Siirt pistachios (SSPs) in a newly designed fixed bed dryer system and the prediction of drying characteristics using artificial neural network (ANN) are presented. Drying characteristics of SSPs with initial moisture content (MC) of 42.3% dry basis (db) were studied at different air temperatures (60, 80, and 100 °C) and air velocities (0.065, 0.1, and 0.13 m/s) in a newly designed fixed bed dryer system. Obtained results of experiments were used for ANN modeling and compared with experimental data. Falling rate period was observed during all the drying experiments; constant rate period was not observed. Furthermore, in the presented study, the application of ANN for predicting the drying time (DT) for a good quality product (output parameter for ANN modeling) was investigated. In order to train the ANN, experimental measurements were used as training data and test data. The back propagation learning algorithm with two different variants, so-called Levenberg–Marguardt (LM) and scaled conjugate gradient (SCG), and tangent sigmoid transfer function were used in the network so that the best approach can be determined. The most suitable algorithm and neuron number in the hidden layer are found out as LM with 15 neurons. For this number level, after the training, it is found that Root-mean squared (RMS) value is 0.3692, and absolute fraction of variance (R2) value is 99.99%. It is concluded that ANNs can be used for prediction of drying SSPs as an accurate method in similar systems.

Effects of plasma treatment, La content and temperature on the La–Ni–Mo–B catalysts for hydrogen production from NaBH4 hydrolysis

ABSTRACT La–Ni–Mo–B catalysts with 0.15, 0.21 and 0.30-mol La molar ratio are prepared by a mixing method followed by a plasma treatment, characterised and investigated for hydrogen production via sodium borohydride hydrolysis. XRD, SEM, Brunauer–Emmett–Teller and FTIR techniques are used for characterising the catalysts. The hydrogen generation rate at 60°C compared to 30°C using La–Ni–Mo–B under the same conditions is significantly different. The effect of temperature, plasma application time and different plasma gases on hydrogen generation from NaBH4 hydrolysis reaction using La0.21–Ni–Mo–B catalyst is investigated. It was found that the plasma-treated catalysts exhibited low activation energy for zero order (58 kJ mol−1).

Modeling of Drying Process of Bittim Nuts (pistacia terebinthus) in a Fixed Bed Dryer System by Using Extreme Learning Machine

Abstract Artificial neural networks (ANNs) have been widely used in modeling of various systems. Training of ANNs is commonly performed by backpropagation based on a gradient-based learning rule. However, it is well-known that such learning rule has several shortcomings such as slow convergence and training failures. This paper proposes a modeling technique based on Extreme Learning Machine (ELM) eliminating disadvantages of backpropagation based on a gradient-based learning rule for the drying of bittim (pistacia terebinthus). The samples for ELM based model are obtained by experimental studies. In experimental studies, the sample mass loss rate as a function time was investigated in different air velocities (0.5 and 1 m/s) and air temperatures (40, 60 and 80°C) in a designed dryer system. The obtained samples from experiments are used for training and testing of ELM. Further, some parameters of ELM such as type of activation function and the number of hidden neurons are set to obtain the best possible modelling results. The obtained prediction results show that ELM algorithm with tangent sigmoid activation function and 20 hidden neurons is appeared to be most optimal topology since maximum R2 and minimum rms (0.0500) and cov (0.2256) values are obtained. Thus, it is concluded that ELM can be used as an effective modelling tool in the drying of bittim (pistacia terebinthus) in fixed bed dryer system.

Hydrogen Production from Sodium Borohydride in Boric Acid-water Mixtures

Borohydride, which reacts slowly with water, is developed as hydrogen production and storage options. The reaction is significantly accelerated by the rise of temperature or by the addition of acidic substances. Boric acid (H3BO3) can be used as an alternative to water for the hydrogen production in the hydrolysis of sodium borohydride (NaBH4). The effect of H3BO3 and NaBH4–H3BO3 molar ratios was studied at 30, 40, 50, 60, and 80°C on the hydrogen production of NaBH4. All of these results show that H3BO3 is a relatively green acid compound for hydrogen generation from NaBH4 and the H3BO3-water-NaBH4 system being quite simple for single-use applications. It was found that the reaction between H3BO3 and NaBH4 complied with a second order kinetics rate with 0.5 reaction orders versus NaBH4 concentration and 1.5 orders versus H3BO3 concentration, and the activation energy for conversion was calculated as 18.01 kJ mol−1.

Hydrogen Production by Hydrolysis of NaBH4 with Cr-Ni-W-B Catalyst: Effects of Cold Plasma and Chromium Content

Abstract In this study, the hydrogen generation from the hydrolysis of NaBH4 with Cr0.0125-Ni-W-B catalyst prepared in the presence of cold plasma was investigated based on Cr content, NaBH4 concentration, NaOH concentration, temperature, plasma applying time and plasma gases effects. The results of the activity tests indicate that the choice of Cr and the catalyst composition greatly influenced the activity as well as the selectivity for hydrogen generation from the hydrolysis of NaBH4. The Cr0.0125-Ni-W-B catalyst was treated with argon, nitrogen and carbon dioxide plasma at different treatment times. The catalysts were characterized using SEM, BET surface area measurement and XRD.

Effect of acid addition on hydrogen production from potassium borohydride hydrolysis

ABSTRACT This is the first study to produce hydrogen from the potassium borohydride (KBH4) hydrolysis using boric acid (H3BO3). The effect of H3BO3 addition on the hydrogen production via KBH4 hydrolysis was investigated for different H3BO3 and KBH4 molar ratios. In addition, the temperature effect on the hydrolysis reaction was investigated at different temperatures. H3BO3 showed good catalytic activity to produce hydrogen from KBH4 hydrolysis. Activation energy to produce hydrogen from KBH4 hydrolysis was found to be 20.31 kJ/mol. This work also includes kinetic information for the hydrolysis of KBH4. According to the kinetic studies, the reaction between H3BO3 and KBH4 had a reaction order of 0.24 against the H3BO3 concentration, while it had a reaction order of 0.16 against the KBH4 concentration.

Effect of phosphoric acid and acetic acid addition on the hydrogen evolution using Ni based catalyst prepared in ethanol, methanol, and water solvents

ABSTRACT Ni-based catalysts were synthesized in water, methanol and ethanol solvents by chemical reduction with sodium borohydride (NaBH4). The obtained catalyst for the first time was used to catalyze the NaBH4 hydrolysis reaction with phosphoric acid and acetic acid including different concentrations. The maximum hydrogen production rates obtained in the hydrolysis reaction including 0.5 M phosphoric acid and 0.1 M acetic acid of the Ni-based catalyst prepared in ethanol solvent were 5214 and 3650 ml g−1 min−1, respectively.

Effect of phosphoric acid addition on the hydrogen production from hydrolysis of NaBH4 with Cu based catalyst

ABSTRACT Cu based catalysts were synthesized in water and methanol solvents by chemical reduction with sodium borohydride (NaBH4). The obtained catalyst was used to catalyze the NaBH4 hydrolysis reaction with phosphoric acid (H3PO4) including different concentrations. Surface morphology and structural properties of the Cu based catalysts prepared in water and methanol solvents were studied using by X-ray diffraction (XRD), scanning electron microscopy (SEM), surface area measurements and Fourier-transform infrared spectroscopy (FTIR) analyses, respectively. The catalytic activity of the catalysts has been tested by measuring the hydrogen production rate by the acidified hydrolysis of NaBH4. The maximum hydrogen production rates in the hydrolysis reaction including 0.25 M H3PO4 using the Cu based catalyst prepared in water and methanol solvents were 825 and 660 ml g−1min−1, respectively. At the same time, the hydrogen production experiments were carried out from this hydrolysis reaction with only H3PO4 and NaBH4 interactions without using Cu metal catalyst. The activation energy obtained based on the nth order reaction model was found to be 61.16 kJ mol−1.

Effects of environmental temperature and relative humidity on the rehydration of dried pistachios

Abstract In this study, the environmental air temperature and relative humidity effects were investigated through rehydration on the dried and roasted Siirt Pistachios (S_PS) and Antep pistachios (A_PS) with an experimental and computational approach. Therefore, an experimental apparatus was set-up in lab conditions. A series of experiments were conducted to evaluate the water activity and weight change as a function of the relative humidity and temperature of ambient air. The experimental results show that there is a combined effect of relative humidity and temperature on the increase in the weight change and water activity (aw). The shell of pistachio is a good hygroscopic material despite its hard texture. The roasted pistachios are less prone to absorb moisture compared to the unroasted pistachios. Beside this experimental study, an intelligent modeling called “artificial neural network” model was used for prediction of the increase in the weight of different types of pistachios.