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In this study the electrolyte equation of state as proposed by Solbraa [E. Solbraa, Equilibrium and non-equilibrium thermodynamics of natural gas processing, Ph.D. thesis Norwegian University of Science and Technology, 2002] was systematically studied and improved to describe the solubility of carbon dioxide in aqueous solutions of N-methyldiethanolamine quantitatively. In this electrolyte equation of state approach both the vapour phase and the liquid phase are described with an equation of state. The molecular part of the equation is based on Schwarzentruber's [J. Scharzentruber, H. Renon, S. Watanasiri, Fluid Phase Equilib. 52 (1989) 127-134] modification of the Redlich-Kwong equation of state with the Huron-Vidal mixing rule [M.J. Huron, J. Vidal, Fluid Phase Equilib. 3 (1979) 255-271]. Three ionic terms are added to this equation-a short-range ionic term, a long-range ionic term (MSA) and a Born term. The thermodynamic model has the advantage that it reduces to a standard cubic equation of state if no ions are present in the solution, and that publicly available interaction parameters used in the Huron-Vidal mixing rule can be utilized. In this work binary molecular- and ionic interaction parameters were studied and optimized. With the updated model it was possible to describe both low- and high pressure vapour-liquid-equilibrium for the MDEA-H2O-CO2-CH4 system satisfactorily.

Frequently applied micro models for gas-liquid mass transfer all assume the presence of a liquid bulk. However, some systems are characterized by the absence of a liquid bulk, a very thin layer of liquid flows over a solid surface. An example of such a process is absorption in a column equipped with sructured packing elements. The penetration model was slightly modified, so that it can describe systems without liquid bulk. A comparison is made between the results obtained with the modified model and the results that would be obtained when applying the original penetration theory for systems with liquid bulk. Both physical absorption and absorption accompanied by first and second order chemical reaction have been investigated. It is concluded that the original penetration theory can be applied for systems without liquid bulk, provided that the liquid layer has sufficient thickness (δ > d*pen). For packed columns this means, in terms of Sherwood number, Sh ≥ 4. In case of a 1,1-reaction with Ha > 0.2 an additional second criterion is Sh ≥4√Db/Da For very thin liquid layers (Sh < 4 or Sh < 4√Db/Da), the original penetration model may give erroneous results, depending on the exact physical and chemical parameters, and the modified model is required.

A study to determine the structure and activity relationships of various amine based CO2 absorbents was performed in which, the absorption of pure CO2 at atmospheric pressure was measured to assess the total absorption rate and capacities. Results showed that an increase in chain length between the amine and different functional groups in the absorbent structure, result in a decrease of absorption rate whereas, the absorption capacity was increased in most absorbents.

In the present work the absorption of carbon dioxide into aqueous piperazine (PZ) solutions has been studied in a stirred cell, at low to moderate temperatures, piperazine concentrations ranging from 0.6 to 1.5 kmol m- 3, and carbon dioxide pressures up to 500 mbar, respectively. The obtained experimental results were interpreted using the DeCoursey equation [DeCoursey, W., 1974. Absorption with chemical reaction: development of a new relation for the Danckwerts model. Chemical Engineering Science 29, 1867-1872] to extract the kinetics of the main reaction, 2 PZ + CO2 → PZCOO- + PZH+, which was assumed to be first order in both CO2 and PZ. The second-order kinetic rate constant was found to be 70 m3 mol- 1 s- 1 at a temperature of 298.15 K, with an activation temperature of 4.1 × 103 K. Also, the absorption rate of CO2 into partially protonated piperazine solutions was experimentally investigated to identify the kinetics of the reaction 2 PZH+ + CO2 → H+ PZCOO- + PZH22 +. The results were interpreted using the Hogendoorn approach [Hogendoorn, J., Vas Bhat, R., Kuipers, J., Van Swaaij, W., Versteeg, G., 1997. Approximation for the enhancement factor applicable to reversible reactions of finite rate in chemically loaded solutions. Chemical Engineering Science 52, 4547-4559], which uses the explicit DeCoursey equation with an infinite enhancement factor which is corrected for reversibility. Also, this reaction was assumed to be first order in both reactants and the second-order rate constant for this reaction was found to be (0.28 ± 0.10) m3 mol- 1 s- 1 at 298.15 K.

Microporous hollow fiber gas-liquid membrane contactors have a fixed and well-defined gas-liquid interfacial area. The liquid flow through the hollow fiber is laminar, thus the liquid side hydrodynamics are well known. This allows the accurate calculation of the fiber side physical mass transfer coefficient from first principles. Moreover, in the case of gas-liquid membrane contactor, the gas-liquid exposure time can be varied easily and independently without disturbing the gas-liquid interfacial area. These features of the hollow fiber membrane contactor make it very suitable as a gas-liquid model contactor and offer numerous advantages over the conventional model contactors. The applicability and the limitations of this novel model contactor for the determination of physico-chemical properties of non-reactive and reactive gas-liquid systems are investigated in the present work. Absorption of CO 2 into water and into aqueous NaOH solutions are chosen as model systems to determine the physico-chemical properties for non-reactive and reactive conditions, respectively. The experimental findings for these systems show that a hollow fiber membrane contactor can be used successfully as a model contactor for the determination of various gas-liquid physico-chemical properties. Moreover, since the membrane contactor facilitates indirect contact between the two phases, the application of hollow fiber model contactor can possibly be extended to liquid-liquid systems and/or heterogeneous catalyzed gas-liquid systems.

The kinetics of the forward polycondensation reaction of polybutylene terephthalate (PBT) has been investigated using thermogravimetric analysis (TGA). PBT - prepolymer with an initial degree of polymerization of 5.5 was used as starting material. The PBT prepolymer was prepared from dimethyl terephthalate (DMT), and 1,4 - butanediol with 470 ppm wt (with respect to DMT) of tetrabutoxytitanate as catalyst. The process conditions in the TGA were such that the weight loss curves obtained from the TGA could be correlated uniquely and directly to the forward polycondensation reaction kinetics due to the absence of (1) mass transfer limitations in the removal of 1,4 butanediol from the melt, and (2) degradation reactions. It is shown that in the temperature range of 230-270°C, the forward polycondensation reaction can be expressed using second-order kinetics in terms of the hydroxyl end group concentration of the PBT polymer.

The cross-flow operation of hollow fiber membrane contactors offers many advantages and is preferred over the parallel-flow contactors for gas-liquid mass transfer operations. However, the analysis of such a cross-flow membrane gas-liquid contactor is complicated due to the change in concentrations of both phases in the direction of flow as well as in the direction perpendicular to flow. In addition, changes in the volumetric flow rate of compressible fluid can also occur over the volume of membrane contactor. These hollow fiber membrane contactors resemble to the more conventional shell and tube cross-flow heat exchanges where a similar variation in the local driving force within the module occurs. Hence heat transfer analogy can be applied to predict the performance of these contactors. Analytical expressions are derived in this work to describe the mass transfer in these hollow fiber cross-flow contactors analogously to heat transfer in cross-flow shell and tube heat exchangers. CO2 absorption experiments were carried out in a commercial as well as in the lab-made single-pass cross-flow hollow fiber membrane contactors to check the applicability of this heat transfer analogy under different conditions. Experimental results show that the derived analytical expressions can be applied to the cross-flow membrane gas-liquid contactor under the asymptotic conditions of negligible or small volumetric flow changes. However, in the case of significant changes in the flow rate of compressible fluid, the application of heat transfer analogy results into slight under predictions of the module performance. A more rigorous model is then required for an accurate prediction of the performance.

In the present work, new experimental data are presented on the solubility of carbon dioxide in aqueous piperazine solutions, for concentrations of 0.2 and 0.6 molar piperazine and temperatures of 25, 40, and 70°C respectively. The present data, and other data available in the literature, were correlated using a model based on the electrolyte equation of state (EoS), as originally proposed by Fürst and Renon. The final model derived, containing only seven adjustable (ionic) parameters, was able to describe the available experimental solubility data (>150 data points for total and/or CO2 partial pressure) with an average deviation of 16%.

The desulfurization of gas streams using aqueous iron(II)sulfate (Fe(II)SO4), zinc sulfate (ZnSO4) and copper sulfate (CuSO4) solutions as washing liquor is studied theoretically and experimentally. The desulfurization is accomplished by a precipitation reaction that occurs when sulfide ions and metal ions are brought into contact with each other. A thermodynamic study has been used to determine a theoretical operating window, with respect to the pH of the scrubbing solution, in which the metal sulfate solution can react with hydrogen sulfide (H2S), but not with carbon dioxide (CO2) from the gas or hydroxide ions from the scrubbing solution. When the absorption is carried out in this window the proposed process should be capable of removing H2S from the gas stream without uptake of CO2 or the formation of metal hydroxides. The pH operating window increases in the order of iron, zinc to copper. Experimental verification showed that the proposed process indeed efficiently removes H2S when an aqueous Fe(II)SO4, ZnSO4 or CuSO4 solution is used as absorbent. However, for an efficient desulfurization the lower pH of the experimental pH operating window using the Fe(II)SO4 or ZnSO4 solution was higher than indicated by thermodynamics. The reason for this must probably be attributed to a reduced precipitation rate at decreasing pH. When a CuSO4 solution is used as washing liquor the solution can efficiently remove H2S over the entire pH range studied (as low as pH = 1.4). In this case only the upper pH boundary of the operating window (that indicates the possible formation of copper hydroxide or copper carbonates) seems to be a relevant limit in practice. The laboratory experiments indicate that the absorption of H2S in a CuSO4 solution, at the experimental conditions tested, is a gas phase mass transfer limited process. This allows a high degree of H2S removal in a relatively compact contactor. In addition to the lab scale experiments the potential of the new desulfurizati

Aim of this study was to investigate the possibilities for a selective and efficient method to convert copper(II) sulfide (CuS) into copper(II) oxide (CuO). The oxidation of copper sulfide has been studied experimentally using a thermogravimetric analyzer (TGA) at temperatures ranging from 450 to 750 °C and oxygen concentrations of 5 and 10 vol.%. It appeared that the products formed upon the oxidation of copper sulfide depend on the reaction temperature. However, in all cases the conversion time using the powdered samples was much shorter than expected based on literature results (typically 3 min versus 1-3 h as mentioned in literature). The first reaction step in the oxidation of copper sulfide always was the fast decomposition of CuS into Cu2S and gaseous sulfur, which immediately was oxidized further to SO2. Subsequently, Cu2S was then oxidized, the route depending on the reaction conditions. Oxidation experiments carried out at various temperatures showed that Cu2S was oxidized selectively to CuO at temperatures above 650 °C, while at temperatures below 650 °C (basic) copper sulfate was also formed. The oxidation from Cu2S to CuO appeared to be the result of two consecutive reactions. Cu2S is first converted into Cu2O, which is subsequently oxidized to CuO. The experimental results allowed for the determination of the intrinsic kinetic rate expression and (Arrhenius) relation for the reaction rate constant of the conversion of Cu 2S to Cu2O between 650 and 750 °C and oxygen concentrations between 5 and 10 vol.%.

Traditionally, hollow fiber membrane contactors used for gas-liquid contacting were designed in a shell and tube configuration with shell-side fluid flowing parallel to the fiber-side fluid, either in co-current or counter-current pattern. The primary limitations of these so-called 'parallel flow' contactors are the shell-side flow channeling or mal-distribution due to non-uniform packing of the hollow fibers, higher shell-side pressure drop and relatively lower mass transfer coefficients. These limitations can be eliminated or reduced substantially by placing hollow fibers perpendicular to the flow direction. In these cross-flow membrane contactors the concentrations of both fluids vary in both directions i.e. in the direction of the flow as well as in the direction perpendicular to the flow. Hence, unlike parallel flow contactors, simple logarithmic averaging of the concentration driving force cannot be used to predict performance of the cross-flow membrane contactors. Similar changes in the driving force are also found in the cross-flow shell and tube heat exchanger. An analytical expression based on heat transfer analogy is derived in this work to describe the mass transfer in these hollow fiber cross-flow contactors. However, it was found that when the change in the volumetric flow of the compressible fluid is significant heat transfer analogy cannot be used to predict the performance of the cross-flow gas-liquid membrane contactor. Therefore, a detailed numerical model is developed to analyze the performance of the cross-flow membrane contactor in such cases. The model takes into account the shell-side mixing, change in concentration driving force in all direction as well as cascading two or more cross-flow modules to give overall co- or counter-current flow arrangement. To validate the model and developed analytical expression, carbon dioxide absorption experiments were carried out in cross-flow membrane contactor using water as a solvent. The predictions of