Christo Boyadjiev

Influence of the interphase mass transfer on the rate of mass transfer—1. The system ‘solid-fluid (gas)’

Abstract A theoretical analysis of the influence of the direction of the interphase mass transfer on the rate of mass transfer is developed. The case of mass transfer between a solid plane surface and a fluid or gas flow in a boundary layer approximation is studied when the transport of mass and momentum at the phase boundary are coupled to account for non-linear effects in a direction normal to the main flow. Numerical results are reported and discussed.

Influence of the interphase mass transfer on the rate of mass transfer—2. The system ‘gas-liquid’

Abstract Numerical results are reported for the influence of the direction of the interphase mass transfer on the rate of mass transfer in ‘gas-liquid’ systems. It is shown that this influence is significant when the diffusive resistance of the liquid phase is negligible. When the diffusive resistances in both phase are of the same order of magnitude the effect is weak. In all cases the intensive mass transfer from the gas to the liquid results in an increased rate of mass transfer compared to the results of the linear theory. The change of direction of mass transfer has the reverse effect.

On the modeling of an airlift photobioreactor

A mathematical formulation of a model of an airlift photobioreactor in the cases of interphase mass transfer between gas and liquid in the riser and photobioreaction in the downcomer is presented. The equations allow the calculation of the vertical distribution of the average concentrations of an active gas component (CO2, O2) and a photoactive material (cells), using average velocities and effective diffusivities in the riser and the downcomer. A hierarchical approach for the model parameter identification on the basis of experimental data is proposed.

Modeling of Column Apparatus Processes

This book presents a new approach for the modeling of chemical and interphase mass transfer processes in industrial column apparatuses, using convection-diffusion and average-concentration models. The convection-diffusion type models are used for a qualitative analysis of the processes and to assess the main, small and slight physical effects, and then reject the slight effects. As a result, the process mechanism can be identified. It also introduces average concentration models for quantitative analysis, which use the average values of the velocity and concentration over the cross-sectional area of the column. The new models are used to analyze different processes (simple and complex chemical reactions, absorption, adsorption and catalytic reactions), and make it possible to model the processes of gas purification with sulfur dioxide, which form the basis of several patents

Perturbation Method Approach

A new approach for the column apparatuses modeling uses convection–diffusion-type models and average-concentration models. All these new types of models (Boyadjiev in Theoretical chemical engineering. Modeling and simulation. Springer, Berlin [1], Doichinova and Boyadjiev in Int J Heat Mass Transf 55:6705–6715 [2], Boyadjiev in J Pure Appl Math: Adv Appl 10:131–150 [3]) are characterized by the presence of small parameters at the highest derivatives. As a result, the model equations have no exact solutions and approximate (asymptotic) solutions have to be obtained (Мищенко and Розов in Дифференциальные уравнения с малым параметром и релаксационные колебания. Изд. “Наука”, Москва [4], O’Malley in Introduction to singular perturbations. Academic Press, New York [5], Boyadjiev et al. in J Eng Thermophys 24:371–380 [6]). In these cases, the use of the conventional software (MATLAB) for solving the model differential equations is difficult and this difficulty may be eliminated by an appropriate combination with the perturbation method.

Sulfuric acid alkylation process in film reactor

Abstract Experimental investigations of the alkylation process of iso-butanes with butenes in the presence of thin-film flow of sulfuric acid (catalyst) are carried out. The hydrodynamics of the process in the liquid and gas phases is studied when the diffusive resistance in both phases are commensurable. The macrokinetics of the process are characterized theoretically and experimentally. The mass transfer coefficients are also determined when diffusive resistance is distributed in both liquid and gas phases. The Sherwood numbers of the process are calculated theoretically and compared with those experimentally obtained. A correlation is made between them, taking into account turbulent diffusion of the gas phase. The possibility of determining Henrys constant for a gas which can be absorbed physically and undergoes irreversible chemical reaction in the liquid phase is shown.

Modeling and Simulation of Industrial Processes

In the paper are presented the main theoretical techniques used for the modeling and simulation of industrial processes. The main focus is on the physical side of the theoretical techniques and their mathematical side is reduced to a reasonable minimum. Different theoretical approximations as thermodynamic and hydrodynamic levels are used.

Industrial Column Chemical Reactors

The new approach for the modeling of the processes in column apparatuses (Boyadjiev in Theoretical chemical engineering. Modeling and simulation. Springer, Berlin, Heidelberg, 2010, [1]; Doichinova, Boyadjiev in Int J Heat Mass Transf 55:6705–6715, 2012, [2]; Boyadjiev in Pure Appl Math Adv Appl 10(2):131–150, 2013 [3]) presents the convection–diffusion and average-concentration models of the column chemical reactors (in Chaps. 2 and 5), where the radial velocity component is equal to zero in the cases of a constant axial velocity radial non-uniformity along the column height:

Industrial Co-current Column Absorber

The new approach for the modeling of the processes in column apparatuses (Boyadjiev in Theoretical chemical engineering. Modeling and simulation. Springer, Berlin, Heidelberg, 2010, [1]; Doichinova, Boyadjiev in Int J Heat Mass Transf 55:6705–6715, 2012, [2]; Boyadjiev in Pure Appl Math Adv Appl 10(2):131–150, 2013 [3]) presents the convection–diffusion and average-concentration models of the column chemical reactors (Boyadjiev and Boyadjiev in Bulgaria Chem Commun 49(3):711–719, 2017 [4], in the cases of an axial modification of the axial velocity radial non-uniformity along the column height (see Chap. 10). This problem will be solved in the cases of the absorption processes in a co-current column (Boyadjiev and Boyadjiev Bulgaria Chem Commun 49(3):711–719, 2017 [5].

Bizonal Absorption Apparatus

The chemical absorption of average soluble gases (ASG) in the case of slow chemical reaction (e.g., absorption of CO2 with aqueous solutions of NaOH, where Henry’s number in the system CO2/H2O is \(\chi^{{20\;{^\circ{\text{C}}}}} = 1.16\)) is possible to be used for waste gas purification. The absorption process intensification has to be realized through intensification of the convective mass transfer in the gas phase (in gas–liquid drops system) and in the liquid phase (in liquid–gas bubbles system). This theoretical result is applied in a new method and bizonal apparatus for gas absorption [1]. In the upper equipment zone, a physical absorption (as a result of the short reaction time, i.e., short existence of the absorbent drops) is realized in a gas–liquid drops system and the big convective transfer in the gas phase leads to decrease of the mass transfer resistances in this phase. In the lower zone, a chemical absorption in a liquid–gas bubbles system takes place and the big convective transfer in the liquid phase lowers the mass transfer resistances in this phase.