The authors are grateful to the Coordination of Improvement of
Higher Education Personnel (CAPES, Brazil) (CAPES-PRINT, Project

number 88887.310560/2018-00); to National Council for Scientific
and Technological Development (CNPq, Brazil) by the financial sup-
port (CNPq, 405965/2016-8); and to Coordination of Improvement of

Higher Education Personnel (CAPES, Brazil) by the scholarship (001)

The combined use of progressive and block freeze concentration in lactose-free milk: Effect of process parameters and influence on the content of carbohydrates and proteins

Biodiesel production has increased significantly in the past decade because it has been demonstrated to be a viable alternative and renewable fuel. Consequently, the production of crude glycerol, the main byproduct of the transesterification of lipids to biodiesel, has risen as well. Therefore, the effective recovery and utilization of crude glycerol can provide biodiesel with additional value. In this review, we first summarized the state-of-the-art progress on crude glycerol recovery and purification. Subsequently, numerous approaches have been reviewed for the utilization of crude glycerol, including use as animal feeds, for combustion, anaerobic fermentation, and chemical conversion. Finally, an extensive discussion and outlook is presented in relation to the techniques and processes in the chemical conversion of crude glycerol.

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Recovery and utilization of crude glycerol, a biodiesel byproduct

Freeze desalination: Current research development and future prospects.

Progressive freeze concentration (PFC) is a simpler freeze concentration process of removing water content in fruit juice through ice crystal formation in order to concentrate a solution. Vertical finned crystallizer (VFC) was used in the PFC system as the ice crystallizer in this study. A mathematical model is highly needed to be developed so that theories can be validated and to understand the system developed better with minimal risk and cost. Mathematical modelling is also essential to analyze the performance of the system. In this work, the use of mathematical model was explored based on a polynomial regression in analysing and predicting the performance of PFC system. The polynomials curve fitting were first performed to develop the models followed by the simulations to predict the target variables of effective partition constant (K value) and solute recovery (Y value). The relationship of operating parameters including coolant temperature and operation time on the PFC performance values were also discovered via the correlated polynomial regression models. Based on simulations result, the highest efficiencies of PFC process were achieved at approximately - coolant temperature of 10oC and operation time of 55 minutes. To validate the models’ accuracy, the statistical assessment parameters of R-squared and Absolute Average Relative Deviation (AARD) were determined.  The findings of this study conferred satisfactory results of the prediction performance of polynomial regression model, in which the least analysis error of AARD (i.e., below 10%) and the highest R-squared (i.e., above 0.97) were successfully achieved.  It is concluded that polynomials-based predictive models are promising alternatives to replace time-consuming and expensive experimental evaluation of PFC process for fruit juices.

Progressive Freeze Concentration Performance Prediction based on Polynomial Curve Model for Star Fruit Juice Concentration

The advancement of industrial sectors generates large amount of wastewater containing ammonium sulphate (AS) ions, yet the current AS recovery technologies are energy-extensive and produce excessive sludge. In this study, a dynamic model for a batch crystallizer was developed to investigate the eutectic freeze crystallization process of AS in aqueous solutions using the method of moment (MoM). The variables affecting the crystal size distribution of AS and ice were described in terms of zeroth moment μ0, first moment μ1, second moment μ2 and third moment μ3. The μ0 of ice crystals increased significantly until 2 s and slowed down thereafter while μ0 of AS crystal increased steadily and reached a constant value of 1/m3s after 1 s. The μ1, μ2, and μ3 of the AS and ice crystals depicted a similar increasing trend. Through process optimization using a 3-D plot on the initial concentration of the system and initial temperature of cooling fluid which had been identified as the significant parameters via iterative plot using MATLAB software, the AS and ice reached maximum crystallization at 255 K which was close to the eutectic point of AS-water system at 254 K. The dynamic model which comprised of population, mass and energy balance equations established in this study demonstrated effectiveness in the prediction of crystallization of AS in aqueous solutions. 

Dynamic modelling and simulation of eutectic freeze crystallization process for recovery of ammonium sulphate from aqueous solutions

At present, biodiesel is known as an alternative fuel globally. It is also known that the purification of biodiesel before consumption is mandatory to comply with international standards. Commonly, purification using water washing generates a massive amount of wastewater with a high content of organic compounds that can harm the environment. Therefore, this study applied and tested a waterless method, i.e., the solvent-aided crystallization (SAC), to remove glycerol and other traces of impurities in the crude biodiesel. The parameters of coolant temperature, crystallization time, and stirring rate on the SAC system were investigated. It was discovered that with 14 °C coolant temperature, 300 RPM and higher cooling time result in the highest percentage of FAME up to 99.54%, which indicates that contaminants' presence is limited in the purified biodiesel. The use of 1-butanol as the solvent for crystallization process remarkably enhanced the separation and improved the higher biodiesel quality.

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Parametric study of glycerol and contaminants removal from biodiesel through solvent-aided crystallization

Treatment and disposal are two main approaches for water cycle management in the oil and gas industry. Freeze concentration has been identified as one of the methods to separate water from wastewater samples. The conventional method used for solution movement in progressive freezing technique is stirring by a stirrer. However, the stirrer requires frequent maintenance as it needs to be cleaned and requires longer cleaning time due to the complex structure of a stirrer. Thus, the new solution movement for progressive freezing is proposed, which is circular moving progressive freezing. This study aims to remove water from the wastewater sample (i.e., produced water). To optimize and investigate the effect of coolant temperature, freezing time and rotation speed, response surface methodology (RSM) was applied to determine the efficiency of the process and central composite design (CCD) was used to design the experiment. From the results, the optimum parameters were determined at the freezing time of 22.79 min, coolant temperature of −14.89 °C and rotation speed of 59 rpm. To evaluate the accuracy of the optimization process, a validation experiment was performed and water removal value of 89.67% was achieved.

Optimization of progressive freezing on synthetic produced water by circular moving cylindrical crystallizer via Response Surface Methodology

In this industrial era, salt recovery from seawater has become an important issue from the environment perspective. Few freezing technologies have been proposed as capable way to separate the salt from the seawater because of the energy used in the previous technologies is higher. A study of Progressive Freeze Concentration (PFC) and Eutectic Freeze Concentration (EFC) method have been carrying out and further investigated on their performance in recovering the salt. For the PFC method, pure water crystallizes into crystal and the concentrate is left behind as in liquid form while for the EFC method, both ice crystals and salt crystallize at the same time when the initial concentration of water salt mixture is exactly the same as eutectic concentration. In EFC, salt sinks to the bottom while ice floats at the top of the crystallizer and both are separated by gravity separation. Effective partition constant and solute recovery are calculated to evaluate the efficiency of PFC and EFC. In this study, the PFC method has shown an effective partition constant of 0.28 and recovered solute of 0.88 g of sodium chloride per 1 g of initial sodium chloride while for EFC method, effective partition constant and solute recovery obtained are 0.59 and 0.66. Overall, both techniques are applicable for the seawater desalination process.

Wan Nur Athirah Mazli

Papers

Parametric study of glycerol and contaminants removal from biodiesel through solvent-aided crystallization

Optimization of progressive freezing on synthetic produced water by circular moving cylindrical crystallizer via Response Surface Methodology

Study of progressive freeze concentration and eutectic freeze crystallization technique for salt recovery