Biotechnological processes involving the presence of microorganisms are realized by using various types of stirred tanks or laboratory-scale dual-impeller commercial bioreactor. Hydrodynamics and mass transfer rate are crucial parameters describing the functionality and efficiency of bioreactors. Both parameters strictly depend on mixing applied during bioprocesses conducted in bioreactors. Establishing optimum hydrodynamics conditions for the realized process with microorganisms maximizes the yield of desired products. Therefore, our main objective was to analyze and define the main operational hydrodynamic parameters (including flow field, power consumption, mixing time, and mixing energy) and mass transfer process (in this case, gas–liquid transfer) of two different commercial bioreactors (BioFlo® 115 and BioFlo® 415). The obtained results are allowed using mathematical relationships to describe the analyzed processes that can be used to predict the mixing process and mass transfer ratio in BioFlo® bioreactors. The proposed correlations may be applied for the design of a scaled-up or scaled-down bioreactors.

This study presents the procedure of deriving a compartmental model (CM) based on an analysis obtained from the computational fluid dynamics (CFD) model of a bioreactor. The CM is composed of two parts, a structural (that takes into account the architecture of the mathematical model), and a parametric part (which contains the extrinsic parameters of the model). The CM is composed of the branches containing the set of perfectly mixed continuous stirred-tank reactors (CSTRs) in a configuration that matches the bioreactor’s flow patterns. Therefore, this work’s main objective was to develop a mathematical model that incorporated the flow field obtained by CFD technique. The proposed mathematical model was validated by means of the experimental data in the form of the residence time distribution (RTD) measurements.

The corrosion process leads to high power consumption, high maintenance costs and the loss of commercial income during downtime in various branches of industry. The proper methods to measure and forecast the corrosion process would help intervene in process production where corrosion is a common phenomenon. Therefore, the main aim of this experimental study is to improve the widely used corrosion monitoring methods with corrosion coupons. As part of this work, the installation for testing corrosion process under controlled conditions and with the application of mild steel coupons is proposed. The measurement concept is to install the coupons in a stream with the corrosion liquid (these conditions should be controlled). The numerical simulations of the fluid flow in the coupon installation were carried out, and the obtained results in the form of a velocity map allowed us to propose the placement of the coupons in the tested installation in such a way that the flowing liquid evenly washed the coupon surface. The developed coupon installation was tested for aggressive corrosive conditions, which were assessed using the water stability indices (Langelier Saturation Index and Ryznar stability index). Moreover, the inductively coupled plasma optical emission spectroscopy analysis characterised the liquid samples from the tested coupon installation. The corrosion process for the applied conditions was defined based on the corrosion rate of the tested coupons. This process was also confirmed by obtaining the Raman spectrum for the used corrosion coupons. The obtained investigation contributes significantly by developing the novel coupon installation and demonstrating the procedure for testing the corrosion process with the application of coupons. This setup and method might be successfully applied for accelerated laboratory tests.

The main aim of this experimental study is to test the novel type of coupon installation. This set-up was used to carry out the corrosion process under aggressive conditions. Moreover, the effect of corrosion inhibitors on the scale-forming tendency was evaluated. The corrosive conditions were defined by using the Langelier Saturation Index (this index is an approximate indicator of the degree of saturation of CaCO3 in water) and the Ryznar stability index (this index is allowed to determine if the liquid sample is aggressive or not). Additionally, the inductively coupled plasma optical emission spectroscopy analysis was used to obtain the iron and calcium ions concentrations in the liquid samples from the tested coupon installation. The corrosion process for the established conditions was also described using the corrosion rate of the tested coupons. The obtained investigation contributes significantly by developing the novel coupon installation and demonstrating the procedure for testing the corrosion process with the application of coupons. This setup and method might be successfully applied for accelerated laboratory tests.

The objective of this paper is to present the investigations of the heat transfer process carried out by means of the multi-ribbon mixer. It is shown that the heat transfer process for the synergic effect of the mixing process and the flowing liquid through the mixer has significantly higher values of the heat transfer coefficients than the mixer with motionless impellers. The empirical correlations between the heat transfer coefficient and the operational parameters obtained in this work can provide guidance for the design and operation of an apparatus equipped with the multi-ribbon impeller. These empirical correlations can be used to predict the heat transfer coefficient for the multi-ribbon mixer.