Kinetic studies of esterification reaction of maleic anhydride with butan-1-ol, 2-methylpropan-1-ol and butan-2-ol were carried out in a semibatch reactor, in the presence of four acidic catalysts: sulfuric acid, phosphotungstic acid, ion exchange resin Dowex 50WX8 and tetrabutyl zirconate. Phosphotungstic acid proved to be the most active catalyst. The temperature range was 383-413 K, the initial molar ratio of alcohol to acid ranged 2.2-5:1. The kinetic parameters were given. The kinetics appeared to be that of the second order with respect both to the acid and to the alcohol. The reaction carried out in the presence of tetrabutyl zirconate was very slow and depended only on acid concentration. The effect of temperature on the reaction rate follows the Arrhenius equation well.

In this paper aggregation of small solid particles in the perikinetic and orthokinetic regimes is considered. An aggregation kernel for colloidal particles is determined by solving the convection-diffusion equation for the pair probability function of the solid particles subject to simple shear and extensional flow patterns and DLVO potential field. Using the solution of the full model the applicability regions of simplified collision kernels from the literature are recognized and verified for a wide range of Péclet numbers. In the stable colloidal systems the assumption which considers only the flow pattern in a certain boundary layer around central particle results in a reasonable accuracy of the particle collision rate. However, when the influence of convective motion becomes more significant one should take into account the full flow field in a more rigorous manner and solve the convection-diffusion equation directly. Finally, the influence of flow pattern and process parameters on aggregation rate is discussed.

The quantitative description of an airlift bioreactor, in which aerobic biodegradation limited by carbonaceous substrate and oxygen dissolved in a liquid takes place, is presented. This process is described by the double-substrate kinetics. Mathematical models based on the assumption of plug flow and dispersion flow of liquid through the riser and the downcomer in the reactor were proposed. Calculations were performed for two representative hydrodynamic regimes of reactor operation, i.e. with the presence of gas bubbles only within the riser and for complete gas circulation. The analysis aimed at how the choice of a mathematical model of the process would enable detecting the theoretical occurrence of oxygen deficiency in the airlift reactor. It was demonstrated that the simplification of numerical calculations by assuming the "plug flow" model instead of dispersion with high Péclet numbers posed a risk of improper evaluation of the presence of oxygen deficiency zones. Conclusions related to apparatus modelling and process design were drawn on the basis of the results obtained. The paper is a continuation of an earlier publication (Grzywacz, 2012a) where an analysis of single-substrate models of the airlift reactor was presented.

In this study, batch fermentation of glucose to ethanol by Saccharomyces cerevisiae (ATCC 7754) was carried out using 2.5 dm 3 BioFlo ® 115 bioreactor. The main objective of this study was to investigate the kinetics of ethanol fermentation by means of the non-structured model. The fermentation process was carried out for 72 h. Samples were collected every 4 h and then yeast growth concentration of ethanol and glucose were measured. The mathematical model was composed of three equations, which represented the changes of biomass, substrate and ethanol concentrations. The mathematical model of bioprocess was solved by means of Matlab/Simulink TM environment. The obtained results from the proposed model showed good agreement with the experimental data, thus it was concluded that this model can be used for the mathematical modeling of ethanol production.

Batch dark fermentation of wheat straw and boiled potato wastes at volatile suspended solids (VSS) 5 g VSS/L are examined and compared. Investigations on dark fermentation of potato wastes and wheat straw were carried out at different pH and OFR (oxygen flow rate) values and inoculum pretreatment. The obtained hydrogen yield from waste potato was 70 mL/g VSS, while for hydrolysed wheat straw it amounted to 80 mL/g VSS. The optimum conditions for potato dark fermentation are acidic pH 6.0 and OFR 1.0 mL/h, while for the wheat straw, optimal conditions are pH 6.4 and OFR 4.6 mL/h. The comparison revealed a significant difference in hydrogen production due to the type of substrate, inoculum stressing and DF conditions applied.

This study is focused on the image analysis of motionless hydraulic mixing process, for which pressure changes were the driving force. To improve the understanding of hydraulic mixing, mixing efficiency was assessed with dye introduction, which resulted in certain challenges. In order to overcome them, the framework and methodology consisting of three main steps were proposed and applied to an experimental case study. The experiments were recorded using a camera and then processed according to the proposed framework and methodology. The main outputs from the methodology which were based only on the recorded movie were liquid heights and colour changes during the process time. In addition, considerable attention has also been given to issues related to other colour systems and the hydrodynamic description of the process.

Complex rheological properties of yield-stress materials may lead to the generation of an intensive mixing zone near a rotating impeller. From the practical point of view, the zone should cover most of the stirred liquid. According to the literature review, several parameters may affect the size of the mixing zone, in particular forces exerted on the liquid. This paper presents both experimental and numerical investigation of axial and tangential forces generated during mechanical mixing of yield-stress fluids in a stirred tank. The tested fluids were aqueous solutions of Carbopol Ultrez 30 of concentration either 0.2 or 0.6 wt% and pH = 5.0. The study was performed for three types of impeller, pitched blade turbine, Prochem Maxflo T and Rushton turbine, in a broad range of their rotational speed, 𝑁 = 60 − 900 rpm. The axial and tangential forces were calculated from the apparent mass of the stirred tank and torque, respectively. The experimental results were compared with CFD predictions, revealing their good agreement. Analysis of the generated forces showed that they are dependent on the rheological characteristic of liquid and the impeller type. It was also found that although axial force was smaller than tangential force, it significantly increased the resultant force.

The works presents the application of mass/volume balances of liquid drug converted into the aerosol during atomization in medical nebulizers.The amount of liquid that can be delivered to the respiratory system during inhalation is reduced compared to the nominal dose not only because of drug losses both in the device (the residual volume, RV) and outside the nebulizer (in the mouthpiece, mask, or tubings), but also to the limitations of the patient (periodic flow with limited capacity).The paper should help to understand the complexity of aerosol therapy widely used in asthma, COPD and other pulmonary diseases.

With advancing technology, printed circuit board (PCB), one of the most important components of ewaste, has become a source of pollution due to an ineffective waste management system. This problem can be solved by converting PCB waste into a valuable product which will emerge to maximize the renewable energy supplies. In this aspect, co-pyrolysis is advantageous in both simple and successful in producing high-quality pyrolysis oil. In this paper, cotton stalk (CS) as biomass was used and pyrolysis of PCB, CS, and a mixture of both in 1:1 have been carried out. CS has a good combustibility at 500 • C which was chosen for the pyrolysis reaction in a fixed bed reactor for slow pyrolysis. The pyrolytic oil was analysed by GC-MS and FTIR. The results indicate that there is an increase in oil yield from 19.6% to 27.5% by weight and phenol and phenolic compounds in oil of co-pyrolysis from 60.94% to 76.82% compared to literature available. There is an increase in bromine solidification in char by 25% with a mixture of CS and PCB compared to CS and PCB individually which is much higher than literature data. To the best of the authors' knowledge, co-pyrolysis of PCB:CS has been attempted first time and debromination of oil was found excellent in the present work.

The flow of the investigated fluid in a measuring system of a rheometer -a capillary or a slit between rotating parts -may be disturbed by anisotropic behavior of the fluid near the wall. This phenomenon, so-called wall slip, often takes place in concentrated suspensions and solutions of linear polymers and introduces experimental errors to measurement results. There are methods of correction of these errors in the case of capillary and coaxial cylinders measuring systems. In the cone and plate system the correction seems to be more difficult because the width of the gap between cone and plate changes along the radius and thus the influence of the wall slip on the shear stress varies along the radius in an unpredictable and complicated manner. This dependency of the shear stress on the distance from the axis underlies the presented method of correction of experimental results obtained in the cone and plate system. The method requires several series of measurements of shear stress vs. shear rate performed using one measuring set, at various degrees of filling the gap.