In mass transfer operations carried out in columns employing various types of tray, great deal more data than is presently available is required by designer; this article reports investigation of effect of gas velocity, diffusivity, submergence, physical properties of liquid, etc, on gas and liquid-side mass transfer coefficient and effective interfacial area in laboratory bubble cap plate columns; existing data cast light on performance of industrial-scale columns and are useful for design purposes.
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... The reaction kinetics has been measured and evaluated by the project partners and afterwards implemented directly into the DESIGNER code. The mass transfer and hydrodynamic process behavior is described by using the correlations of Sharma, Masshelkar, and Mehta (1969) for the speciÿc interfacial area and vapor-and liquid-phase mass transfer coeecients, Fair and Matthews for the entrainment (see Bolles, 1963), and Gerster, Hill, Hochgraf, and Robinson (1958) for the clear liquid height.Fig. 5 demonstrates the simulated temperature and concentration proÿles for the test no. 4 (seeTable 2) together with the experimental values. ...
In this paper, an extensive study of ethyl acetate synthesis by homogeneously catalyzed reactive distillation is presented. Reactive distillation is a promising operation whereby reaction and separation take place within a single distillation column. The synergistic effect of this combination has the potential to increase conversion, improve selectivity and facilitate separation tasks. The feasibility of ethyl acetate synthesis is examined using the reactive distillation lines diagram. A completely rate-based simulator DESIGNER developed within the framework of a large European research project is used in order to predict concentrations, temperatures and other important process variables. In order to validate theoretical predictions, a set of reactive distillation experiments is performed in a glass tray column with 80 bubble cap trays. The concentrations and temperature profiles computed by DESIGNER agree well with the experimental data.
Sydney Andrew was an outstanding chemical engineer. His career with ICI was notable, culminating in the rare distinction of appointment as senior research associate. Early work when he was a plant manager led to the development of a systematic procedure for plant maintenance, the forerunner of ‘critical path scheduling’, now widely used for planning complex construction and maintenance projects. Syd did pioneering work on the absorption of gases into liquids where the dissolved gas reacts with the liquid. He helped to develop catalysts for the steam reforming of naphtha, leading to the installation of many plants to provide gas for domestic use; these plants replaced the numerous plants for making town gas from coal. Producing syn-gas from naphtha was beneficial for making ammonia and methanol; several plants were built in India and Japan.
The emission of CO2 into the atmosphere is causing majority of the global warming and thus various end-of-pipe treatment methods have evolved to capture CO2 from fixed point sources. The present article deals with CO2 capture from a simulated gas stream using dilute NaOH solution in a spray column using a two-phase critical flow atomizer capable of producing very fine sprays with high degree of uniformity and moving at very high velocities. Experimentation was carried out to investigate the percentage removal of CO2 as well as interfacial area as functions of different variables. The maximum percentage removal of CO2 observed was about 99.96% for a QL/QG ratio of 6.0 m3/1000 ACM (liquid flow rate of 1.83 × 10−5 m3/s and gas flow rate of 3.33 × 10−3 m3/s) and for a CO2 feed rate of 100 l/h, while the observed values of interfacial area were in the range of 22.62–88.35 m2/m3 within the framework of the experimentation. A simple correlation was developed for predicting the interfacial area as functions of various pertinent variables of the system. Experimental data fitted excellently well with the correlation. The comparison of the interfacial area observed between the present system and the existing systems revealed that the present system produced higher values of interfacial area than the existing systems and hence the performance of the system was better than the existing system.
A new computer program has been developed for the simulation of chemical absorption of H2S and CO2 using MEA, DEA or hot potassium carbonate. The program can calculate either tray or packed columns, The material and energy balances, and equilibrium relationship are solved using the Naphtali-Sandholm method and the stage to stage method complementarily. The packed column is divided into a number of sections. Each section is treated as a tray, but with a different method of efficiency calculation. The enhancement factor was incorporated to reflect the enhancement of absorption rate which is an inherent nature of chemical absorption. Using this program named as AGRES, 20 sample problems were solved for absorption and stripping and the results were compared with those of other competing programs of AMSIM, PROCESS. ASPEN PLUS and DESIGN II. In the calculation of ideal stages, all the programs gave similar results. In the calculation of real stages, however, only AMSIM and AGRES were effective. AMSIM could not calculate packed columns and tray columns having more than 22 stages. While, AGRES could overcome this limitation of AMSIM, providing a broader application.
The method of gas—liquid absorption with chemical reaction was applied to determine the interfacial area and the gas-side mass transfer coefficient and implemented in a pilot column of diameter 0.45 m. This absorber was equipped successively with different trays of industrial type (bubble-cap, sieve and valve trays), so that a reliable comparison of their respective efficiencies could be made. The influence of weir height was studied especially, and also the effects of gas velocity and liquid load. The experimental results were correlated by means of empirical relations which account for the respective influences of the three parameters and provide a useful basis for extrapolation to industrial absorber design.RésuméEn mettant en oeuvre la méthode d'absorption gaz—liquide avec réaction chimique, on a déterminé l'aire interfaciale et le coefficient de transfert de matière côté gaz d'une colonne pilote de 0,45 m de diamètre. Cette colonne a été successivement équipée de différents plateaux de type industriel (à calottes, perforés et à clapets) permettant ainsi une comparaison sûre de leur efficacité respective. L'influence de la hauteur de barrage a été spécialement étudiée en plus des effets de la vitesse du gaz et de la charge de liquide.Les résultats expérimentaux ont été corrélés sous forme de relations empiriques qui rendent compte des influences respectives des trois paramètres et qui fournissent une bonne base en vue de l'extrapolation au dimensionnement d'absorbeurs industriels.
The present work focuses on a strategy for optimizing mono pressure weak nitric acid plants. The optimization strategy addresses important processes which include oxidation of ammonia to nitric oxide, heat recovery from product stream of ammonia oxidation reactor and absorption accompanied by complex chemical reactions of multi-component nitrogen oxide gases into water. In design and optimization of nitric acid process, it is essential to understand the rate controlling step for ammonia oxidation process, strategy to be adopted for heat exchanger network design, rates of mass transfer and chemical reaction for nitrogen oxide absorption and the combined effects of several equilibria. The work addresses these issues taking through the complexities in the above mentioned processes.The parametric sensitivity of few parameters such as ammonia to air ratio, excess oxygen/air, selectivity, power recovery based on the performance efficiency of compressor and expander, inlet and outlet nitrogen oxide composition in condenser and absorption column have been a part of our investigation either explicitly or implicitly. Further, for the absorption column, the effects of geometrical parameters, excess air, extent of absorption, product acid concentration, temperature and pressure have been analyzed for the purpose of optimization of nitric acid plant. All parameters having major influence on annualized cost of product acid have been analyzed and presented.
The gas–liquid–liquid reactive extraction system for the production of hydrogen peroxide via anthraquinone route was investigated. The oxidation of the hydrogenated anthraquinone working solution by oxygen and the extraction of hydrogen peroxide from the working solution with deionized water were carried out simultaneously in a sieve plate column of 50mm in diameter. The effects of the superficial velocity of oxygen on the conversion of 2-ethylanthrahydroquinone and the extraction efficiency of hydrogen peroxide were investigated, separately. The results showed that the oxidation and the extraction do not hamper each other, on the contrary, the presence of gas in the column can promote the transfer of hydrogen peroxide from the organic phase to the aqueous phase, therefore, the conversion of 2-ethylanthrahydroquinone and the extraction efficiency of hydrogen peroxide increased with the increase of gas superficial velocity. In addition, a mathematical model for the simulation of the gas–liquid–liquid reactive extraction process was developed. The predicted values were compared with the experimental data at different conditions and the agreement was found to be quite satisfactory for the production of hydrogen peroxide in a sieve plate column.
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