Krzysztof Warmuzinski

Multicomponent pressure swing adsorption Part I. Modelling of large-scale PSA installations

Abstract A general model of multicomponent pressure swing adsorption (PSA) is presented which describes the operation of multi-column PSA installations. The individual columns can be packed with one or two layers of different adsorbents. All the basic steps of modern PSA cycles are taken into account. The operation of a large-scale PSA installation is analysed using a hydrogen purification plant as a test case

A model of cellular convection during absorption accompanied by chemical reaction

Abstract A model was derived describing cellular convection during absorption accompanied by a first-order chemical reaction. The model assumes that the concentration profiles of components A and R extend only through part of the liquid layer of finite depth; in the remaining part the unperturbed concentrations are uniform. Employing the linearized theory of hydrodynamic stability and assuming that the principle of exchange of stabilities is valid in the system analysed, equations governing the phenomenon were formulated together with the appropriate boundary conditions. These equations led to a so-called “characteristic equations”, which is an implicit relationship between eight dimensionless parameters. The model was tested using experimental data concerning the absorption of CO 2 into aqueous solutions of monoethanolamine (MEA) and NaOH. For the CO 2 MEA system theoretical predictions agreed very well with the experiments; for the CO 2 -NaOH system a general interpretation of the experimental results was proposed. A correlation was also suggested relating the enhancement factor to the Ma E / Ma CR ratio.

Effect of adsorption pressure on methane purity during PSA separations of CH4/N2 mixtures

Abstract Computer simulations have been carried out to study the performance of a two-bed PSA system for the separation of methane and nitrogen. The concentration of CH4 in the low-pressure product has been assessed in terms of the adsorption pressure, CH4 content in the feed gas and the cycle length. This concentration is found to exhibit a distinct maximum with respect to the pressure of the adsorption step. The occurrence of the maximum is attributed to selectivity varying with pressure, which, in turn, results from the nonlinearity of the CH4 and N2 adsorption isotherms. If linear isotherms are assumed, as is the case in simplified solutions, no such maximum is observed and the model fails to predict the crucial characteristics of the system.

Diffusional models of multicomponent distillation and their experimental verification

Abstract In the present paper the equimolar, non-equimolar and simultaneous mass and heat transfer models of multicomponent distillation are developed and verified. The equations composing the models are based on the linearized diffusion theory and can be divided into three separate groups: (1) interfacial conditions describing the gas-liquid interface; (2) kinetic relations, which define the mass fluxes and whose general form results from the type of transfer assumed; (3) balance equations, associated with the model employed for a contact stage and determined by the fluxes previously estimated. The main purpose of the work was to develop the methods for calculating the mass fluxes for various types of diffusion occurring in distillation; hence, the quantitative basis for these methods was provided by the two first groups of relationships. The verification of the equimolar and non-equimolar models was carried out using the experimental results obtained by the authors for ternary distillation in a 0.25 m I.D. sieve-plate column and literature data for a bubble-cap column. The model for simultaneous mass and heat transfer was analysed only qualitatively. The calculations performed employing the various models differed only slightly from each other and agreed very well with the experimental findings.

Multicomponent pressure swing adsorption. Part II. Experimental verification of the model

Abstract The mathematical model of nonisothermal multicomponent pressure swing adsorption, developed in Part I of this study (K. Warmuzinski, M. Tanczyk, Chem. Eng. Proc., 36 (1997) 89–99) is validated based on experimental data concerning the separation of CH 4 and H 2 on activated carbon and the production of hydrogen on zeolite 5A. For a wide range of the various operating parameters, the measured values of the purity and recovery of the products, together with the concentration and temperature profiles during a PSA cycle are compared with those predicted by the model. In all cases a satisfactory agreement is found between theory and experiment.

Facile and Scalable Synthesis of Nanoporous Materials Based on Poly(ionic liquid)s

A simple, fast, sustainable, and scalable strategy to prepare nanoporous materials based on poly(ionic liquid)s (PILs) is presented. The synthetic strategy relies on the radical polymerization of crosslinker-type ionic liquid (IL) monomers in the presence of an analogous IL, which acts as a porogenic solvent. This IL can be extracted easily after polymerization and recycled for further use. The great advantages of this synthetic approach are the atom-efficiency and lack of waste. The effects of different monomer/porogen ratios on the specific surface area, porosity, and pore size have been investigated. Finally, the potential of the materials as CO2 sorbents has been evaluated.

The influence of laser arytenoidectomy on ventilation parameters in patients with bilateral vocal cord paralysis

Bilateral vocal cord paralysis is a symptom that may lead to serious breathing problems. The treatment of patients with vocal cord paralysis presents a challenge to otolaryngologists. Many techniques have been developed in an attempt to improve the patients airway insufficiency. The aim of the study was to evaluate the efficacy of the laser total unilateral arytenoidectomy with posterior cordectomy in patients with bilateral vocal cord paralysis. Thrity-six patients (33 females, 3 male) aged between 24 and 76 (mean 52) were treated by laser arytenoidectomy. The flow-volume loop and pletysmography were performed in all patients before and after the operation. Additionally, a group of 15 patients with unilateral vocal cord paralysis was introduced and analyzed as a special control. Based on the relative increase of the parameters after the surgery, the most useful of them were selected for the evaluation. Also, the character of the laryngeal obstruction was defined. Changes in the flow-volume loop before and after surgery were compared by planned comparison in univariate analysis ANOVA/MANOVA with an isolated control group. As the parameters AREAEX, FEF50, FEF75, PEF and MMEF75/25 increased most effectively, they appeared to be the most useful in the evaluation. FIV1/FEF1, FEF50/FIF50 and FEV1/FEV0,5 allowed the definition of the obstruction as an extrathoracic dynamically variable quantity. The resistances measured during pletysmography diminished significantly after surgery. The introduction of the special control group with unilateral vocal cord paralysis showed that despite the significant improvement after surgery, the patients who had been operated on still had a laryngeal obstruction worse than that of patients from the control group. The laser arytenoidectomy is shown to be a useful and efficacious procedure for bilateral vocal cord paralysis.

The enhancement of the rate of absorption of CO2 in amine solutions due to the Marangoni effect

Abstract Results of the experimental and theoretical investigations of the occurrence of cellular convection during absorption of CO 2 in amine solutions (Marangoni effect) are presented. Experiments in CO 2 -aqueous solutions of MEA and CO 2 -aqueous solutions of DEA systems show that cellular convection indeed occurs during chemisorption and that it can increase mass transfer rate significantly enough to lower the absorber height. The influence of certain parameters characterizing mass transfer (e.g. mass transfer coefficient in the liquid phase, initial concentrations of reactants, presence of surface-active agents) on the intensity of cellular convection is analyzed. Theoretical considerations confirm the possibility of the occurrence of cellular convection in the systems investigated. Experimental correlations are given which describe the influence of the effect in terms of the mass transfer enhancement factor. The results can be directly employed in the design of absorbers for CO 2 capture.

Cost analysis for the removal of volatile organic compounds from air using hybrid systems: membrane separation/condensation versus membrane separation/combustion

Air contaminated with volatile organic compounds (VOCs) is associated with a number of industrial processes. The purification of these air streams based on conventional techniques, such as combustion, condensation or adsorption is usually uneconomical. Environmental considerations require, however, that this problem should be dealt with as efficiently as possible. Therefore, the use of hybrid systems is analysed that include membrane separation and condensation or, alternatively, membrane separation followed by combustion.

Marangoni instability during absorption accompanied by chemical reaction

Abstract In the present paper we summarize the work, both theoretical and experimental, done in the Institute of Chemical Engineering of the Polish Academy of Sciences in Gliwice over almost two decades and concerning surface phenomena accompanying the process of absorption with chemical reaction. First, a model of these phenomena is derived based on the assumption that the cellular convection is driven by surface tension gradients, induced in turn by infinitesimally small perturbations of concentration. Next, experiments are presented on the absorption of carbon dioxide into aqueous solutions of monoethanolamine, diethanolamine and sodium hydroxide. The experiments were carried out in both wetted-wall and packed columns, and they made it possible to decribe quantitatively the effect of the Marangoni convection on the rate of mass transfer . Finally, it is demonstrated that the theoretical model, all its limitations notwithstanding, allows an analysis to be carried out of certain characteristics of the process of chemical absoption. Thus, the probability of oscillatory modes occuring in the system is discussed, the dimensions of the convective cells are evaluated and the gas—liquid contact time necessary for the instability to appear is determined. The quantitative conclusions are compared with the relevant experimental data concerning the absoption of CO 2 into monoethanolamine.