Chemical and Process Engineering: New Frontiers

Results of an extensive research program, aimed at finding new, more efficient activators of carbon dioxide absorption into aqueous carbonate/bicarbonate solutions are presented. Both single amines (2-ethyl-aminoethanol, 2-isopropyl aminoethanol, piperazine, tetraethylenepentamine, N-ethyl-piperazine and glicyne) and amine mixtures have been investigated. Absorption rate measurements were conducted in a laminar-jet absorber. Reaction rate constants for the particular activators were determined. Mixtures of aliphatic amines with cyclic amines, as well as mixtures of cyclic amines with cyclic amines were found to exhibit synergetic effect. Such amine mixtures might be used as new promoters for CO2 absorption in carbonate solutions in the modified Benfield process.

Preparation and properties of hierarchically structured porous silica monoliths have been discussed from the viewpoint of their application as continuous microreactors for liquid-phase synthesis of fine chemical in multi kilogram scales. The results of recent topical papers published by two research teams of Institute of Chemical Engineering Polish Academy of Sciences (ICE) and Department of Chemical Engineering and Process Design, Chemical Faculty, Silesian University of Technology (SUT) have been analyzed to specify the governing traits of microreactors. It was concluded that even enhancement factor of 100 in activity, seen in enzyme catalyzed reactions, can be explained by a proportional reduction of its physical constraints, i.e. huge enhancement of external mass transfer and micromixing. It is induced by very chaotic flows of liquid in tens of thousands of waving connected channels of ca. 25–50 mm in diameter, present in the skeleton. The scale of enhancement in the case of less active catalysts was smaller, but still large enough to consider the most practical applications.

The paper addresses the issues of quantification and understanding of Solid Oxide Fuel Cells (SOFC) based on numerical modelling carried out under four European, EU, research projects from the 7FP within the Fuel Cell and Hydrogen Joint Undertaking, FCH JU, activities. It is a short review of the main projects’ achievements. The goal was to develop numerical analyses at a single cell and stack level. This information was integrated into a system model that was capable of predicting fuel cell phenomena and their effect on the system behaviour. Numerical results were analysed and favourably compared to experimental results obtained from the project partners. At the single SOFC level, a static model of the SOFC cell was developed to calculate output voltage and current density as functions of fuel utilisation, operational pressure and temperature. At the stack level, by improving fuel cell configuration inside the stack and optimising the operation conditions, thermal stresses were decreased and the lifetime of fuel cell systems increased. At the system level, different layouts have been evaluated at the steady-state and by dynamic simulations. Results showed that increasing the operation temperature and pressure improves the overall performance, while changes of the inlet gas compositions improve fuel cell performance.

The cometabolic biodegradation of 4-Chlorophenol (4-CP) by the Stenotrophomonas maltophilia KB2 strain in the presence of phenol (P) was studied. In order to determine the kinetics of biodegradation of both substrates, present alone and in cometabolic systems, a series of tests was carried out in a batch reactor changing, in a wide range, the initial concentration of both substrates. The growth of the tested strain on phenol alone was described by Haldane kinetic model (mm = 0:9 1/h, Ksg = 48:97 gg/m3, KIg = 256:12 gg/m3, Yxg = 0:5715). The rate of 4-CP transformation by resting cells of KB2 strain was also described by Haldane equation and the estimated parameters of the model were: kc = 0:229 gc=gxh, Ksc = 0:696 gc=m3, KIc = 43:82 gc=m3. Cometabolic degradation of 4-CP in the presence of phenol was investigated for a wide range of initial 4-CP and phenol concentrations (22–66 gc/m3 and 67–280 gg/m3 respectively). The experimental database was exploited to verify the two kinetic models: CIModel taking only the competitive inhibition into consideration and a more universal CNIModel considering both competitive and non-competitive inhibition. CNIModel approximated experimental data better than CIModel.

A microstructural model of Red Blood Cell (RBC) behaviour was proposed. The erythrocyte is treated as a viscoelastic object, which is denoted by a network of virtual particles connected by elastic springs and dampers (Kelvin-Voigt model). The RBC is submerged in plasma modelled by lattice Boltzmann fluid. Fluid – structure interactions are taken into account. The simulations of RBC behaviour during flow in a microchannel and wall impact were performed. The results of RBC deformation during the flow are in good agreement with experimental data. The calculations of erythrocyte disaggregation from the capillary surface show the impact of RBC structure stiffness on the process.

In this review, research carried out on sorption-enhanced steam methane reforming (SESMR) process is presented and discussed. The reactor types employed to carry out this process, fixed packed bed and fluidized bed reactors, are characterized as well as their main operating conditions indicated. Also the concepts developed and investigations performed by the main research groups involved in the subject are summarized. Next the catalysts and CO2 sorbents developed to carry out SE-SMR are characterized and the relationships describing the reaction and sorption kinetics are collected. A general approach to model the process is presented as well as results obtained for a calculation example, which demonstrate the main properties of SE-SMR.

Results are presented concerning the separation of the mixtures of carbon dioxide, nitrogen and oxygen in membrane modules with modified polysulphone or polyimide as active layers. The feed gas was a mixture with composition corresponding to that of a stream leaving stage 1 of a hybrid adsorptivemembrane process for the removal of CO2 from dry flue gas. In gas streams containing 70 vol.% of CO2, O2 content was varied between 0 and 5 vol.%. It is found that the presence of oxygen in the feed gas lowers the purity of the product CO2 in all the modules studied, while the recovery depends on the module. In the PRISM module (Air Products) an increase in O2 feed concentration, for the maximum permeate purity, led to a rise in CO2 recovery, whereas for the UBE modules the recovery did not change.

The aim of the paper is to present the hydrodynamic, mass transfer and illumination characteristics of a laboratory helical-tube photobioreactor Biostat PBR-2S, commercially available and used in many laboratories in Poland and worldwide. The investigated hydrodynamics parameters were: mean liquid circulation rate, liquid velocity/residence time in the tubular part of the apparatus and mixing time, measured in the wide range of rotary speed of the circulation pump. The influence of the aeration intensity on these parameters was also checked. The volumetric oxygen and carbon dioxide transfer coefficients in the liquid phase and their dependency on the liquid circulation rate and gas inflow rate were determined. The experiments were performed in tap water and then in a real three-phase cultivation broth at the end of thermophilic cyanobacteria T. synechococus growth. For the final evaluation of the tested PBR there were series of test cultivations run under different conditions of illumination. The highest final concentration of the biomass of tested cyanobacteria reached the relatively high value of 4.38 g/dm3 of the dry biomass, although the process conditions were not fully optimized. The laboratory photobioreactor PBR-2S proved to be a good tool for investigations of microalgae cultivation processes. The presented results and practical observations may help to analyze and understand the mutual influence of the specific process parameters in the described PBR, especially during autotrophic organism cultivations.

The measured rate of release of intercellular protein from yeast cells by ultrasonication was applied for evaluating the effects of sonication reactor geometry on cell disruption rate and for validation of the simulation method. Disintegration of two strains of Saccharomyces cerevisiae has been investigated experimentally using a batch sonication reactor equipped with a horn type sonicator and an ultrasonic processor operating at the ultrasound frequency of 20 kHz. The results have shown that the rate of release of protein is directly proportional to the frequency of the emitter surface and the square of the amplitude of oscillations and strongly depends on the sonication reactor geometry. The model based on the Helmholtz equation has been used to predict spatial distribution of acoustic pressure in the sonication reactor. Effects of suspension volume, horn tip position, vessel diameter and amplitude of ultrasound waves on the spatial distribution of pressure amplitude have been simulated. A strong correlation between the rate of protein release and the magnitude of acoustic pressure and its spatial distribution has been observed. This shows that modeling of acoustic pressure is useful for optimization of sonication reactor geometry.

On the basis of hydrogen peroxide decomposition process occurring in the bioreactor with fixed-bed of commercial catalase the optimal feed temperature was determined. This feed temperature was obtained by maximizing the time-average substrate conversion under constant feed flow rate and temperature constraints. In calculations, convection-diffusion-reaction immobilized enzyme fixed-bed bioreactor described by a coupled mass and energy balances as well as general kinetic equation for rate of enzyme deactivation was taken into consideration. This model is based on kinetic, hydrodynamic and mass-transfer parameters estimated in earlier work. The simulation showed that in the biotransformation with thermal deactivation of catalase optimal feed temperature is only affected by kinetic parameters for enzyme deactivation and decreases with increasing value of activation energy for deactivation. When catalase undergoes parallel deactivation the optimal feed temperature is strongly dependent on hydrogen peroxide feed concentration, feed flow rate and diffusional resistances expressed by biocatalyst effectiveness factor. It has been shown that the more significant diffusional resistances and the higher hydrogen peroxide conversions, the higher the optimal feed temperature is expected.