Modeling and Kinetic Study on Absorption of CO2 by Aqueous Solutions of N-methyldiethanolamine in a Modified Wetted Wall Column

To get more accurate kinetic data of the absorption of CO2 into aqueous solution of N-methyldiethanolamine,a wetted wall column was modified to more uniformly distribute the liquid on the column surface and gas in the absorbing chamber and change the length of the column.The average liquid film thickness and the liquid-phase mass transfer coefficient were measured,and a correlation for the Sherwood number,Reynolds number and Schmidt number was obtained for the modified wetted wall column.The equilibrium concentrations in chemical reactions were calculated with a minor absolute error for calculating the rate constant more accurately.A mathe-matical model for the CO2 absorption was established based on the diffusional mass transfer accompanied with parallel reversible reactions,and the partial differential equation was solved by Laplace transform.An analytical ex-pression for the concentration of carbon dioxide as a function of time and penetration depth in liquid film and the average interphase mass transfer rate was obtained.This model was also used to calculate the rate constant for a second-order reaction,which was in good agreement with reported data.

A New Method to Solve Film Model for CO_2 Absorption with Aqueous Solution of AT-Methyldiethanolamine

The shooting method and the difference method are used for numerical simulation of CO2 absorption with aqueous solution of methyldiethanolamine (MDEA). It is demonstrated that these methods are available for the steady-state model, which may be expressed as a set of differential algebraic equations (DAEs) with two-point boundary values. This method makes it possible not only to obtain the concentration profiles for MDEA system, but also to reveal the effect of CO2 interfacial concentration on the enhancement factor. With this numerical simulation, the mass transfer process with multicomponent diffusion and reactions can be better understood.

Absorption Rate of CO_2 into MDEA Aqueous Solution Blended with Piperazine and Diethanolanline

Absorption rate of CO2 into aqueous solution of N-methyldiethanolamine (MDEA) blended with diethanolamine (DEA) and piperazine (PZ) was studied and a kinetic model was established. It is shown that homogeneous activation mechanism could explain this absorption process. The absorption rate coefficients of carbon dioxide into MDEA aqueous solution blended with DEA, PZ or DEA+PZ were compared with each other. The results demonstrated that the different activation effect of DEA, PZ and DEA+PZ on the carbon dioxide absorption comes from the difference in CO2 combination rate, transport of PZ and DEA to MDEA and the regeneration rate of PZ and DEA.

CO_2 solubility in aqueous solutions of N-methyldiethanolamine+piperazine by electrolyte NRTL model

Accurate modeling of the solubility behavior of CO_2 in the aqueous alkanolamine solutions is important to design and optimization of equipment and process. In this work, the thermodynamics of CO_2 in aqueous solution of N-methyldiethanolamine(MDEA) and piperazine(PZ) is studied by the electrolyte non-random two liquids(NRTL) model. The chemical equilibrium constants are calculated from the free Gibbs energy of formation, and the Henry's constants of CO_2 in MDEA and PZ are regressed to revise the value in the pure water. New experimental data from literatures are added to the regression process. Therefore, this model should provide a comprehensive thermodynamic representation for the quaternary system with broader ranges and more accurate predictions than previous work. Model results are compared to the experimental vapor-liquid equilibrium(VLE), speciation and heat of absorption data, which show that the model can predict the experimental data with reasonable accuracy.

Determination of Salt Impurities in MDEA Solution Used in Desulfurization of Highly Sulphurous Natural Gas

The foaming phenomenon of N-methyldiethanolamine(MDEA) solution used in desulfurization process occurs frequently in the natural-gas purification plant. The foaming phenomenon has a strong impact on operation of the process unit. The salt impurities are the main reason for causing the foaming of MDEA solution, so the full analysis of salt impurities is necessary. A method for comprehensive analysis of salt impurities in MDEA solution used in desulfurization process was established. Anions and non-metallic cations of MDEA solution were determined by different conditions of ion chromatograph, respectively. Metallic cations of the solution were detected by atomic absorption spectrophotometer with the N2O-C2H2 flame absorption. The analytical results of salt impurities in the desulfurization solution can provide a theoretical basis for an accurate analysis of the factors affecting the foaming of MDEA to unveil further control measures.

生产硫磺装置的危害因素及防护措施

近年来，国内新建的以酸性气和N-甲基-二乙醇胺（MDEA）为原料生产硫磺的装置，大多采用二级转化Claus制硫工艺，尾气采用热焚烧炉处理，溶剂再生采用常规汽提再生技术。工艺系统主要包括硫磺回收、尾气处理、溶剂再生3部分。