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Study On Gas-Liquid-Liquid Reactive Extraction Process For The Production Of Hydrogen Peroxide

Posted on:2005-08-13Degree:DoctorType:Dissertation
Country:ChinaCandidate:S X LvFull Text:PDF
GTID:1101360182475036Subject:Chemical processes
Abstract/Summary:PDF Full Text Request
Process Intensification presents one of the most important trends in today's chemical engineering and technology. It is a compact, safe, energy-efficient and environment-friendly sustainable technology. One of the most prominent methods of Process Intensification is the integration of chemical reaction and physical separation in one unit。 The integration of reaction and liquid-liquid extraction often leads to a significant reduction in investment and operating costs. The economic benefit may be caused by a reduction of raw material use, diminution of recycle streams by higher rates of conversion, improvements in selectivity, separation efficiency and energy integration. The gas-liquid-liquid three-phase reactive extraction is one of novel technologies for Process intensification. In the gas-liquid-liquid three-phase reactive extraction system, the gas phase works as one of reagents as well as agitating media. The theories about chemical reaction, mass-transfers of gas-liquid and liquid-liquid have been investigated for the oxygen-water-anthraquinone working solution three-phase reactive extraction system. The hydrodynamic characteristics of air-water-anthraquinone working solution three-phase system in a sieve plate extraction column were investigated. The holdups of gaseous and dispersed phases were measured, respectively. The effects of the superficial velocity of gaseous, dispersed and continuous phases on the holdups of gaseous and dispersed phases were investigated. Correlations for the prediction of holdups of gaseous and dispersed phases in air-water-anthraquinone working solution three-phase system have been proposed. Comparison of the predicted data with correlations and experimental data shows that they are quite satisfactory agreement and the average relative deviations are 7.3% for dispersed phase holdup and 7.1% for gas phase holdup, respectively. The back-mixing characteristics and the mass-transfers of the gas-liquid-liquid three-phase system have been investigated. The effects of superficial velocity of gaseous, dispersed and continuous phases on the diffuse coefficients of continuous and dispersed phases were investigated. Correlations for the prediction of diffuse coefficients of continuous and dispersed phases in air-water-anthraquinone working solution three-phase system have been proposed. Extraction of hydrogen peroxide by means of deionized water from anthraquinone working solution was carried out in a gas-agitated sieve plate extraction column. The effects of the superficial velocity of air, dispersed phase and continuous phase on overall plate extraction efficiency have been investigated. The corrections for the prediction of overall plate extraction efficiency were presented. The correlation proposed to predict the overall plate extraction efficiency in air-water-anthraquinone working solution three-phase system agreed satisfactorily with experimental data with a maximum absolute deviation of 5.6%. A new design method for gas-liquid-liquid three-phase extractors is developed based on the multistage countercurrent extraction model. The calculated data by the model agreed well with experimental data and the average relative deviation was less than 10%. Moreover, the model was used to predict a gas-agitated sieve plate extraction column for industrial production of hydrogen peroxide. The results show that the plate numbers of gas-agitated sieve plate extraction column is 30%~40% less than that of liquid-liquid sieve plate column. Kinetics of the reactive extraction process for preparing hydrogen peroxide in oxygen-water-anthraquinone working system has been investigated. Kinetics runs have been carried out in a semi-batch reactor. The reaction rate is governed by the transport of oxygen through gas-liquid interface. The extraction rate is controlled by the reaction for producing hydrogen peroxide and the transport of hydrogen peroxide from organic phase to water. The kinetics expression is given by analysis and regression of the experimental data. The oxidation reaction 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. The effects of free area of the sieve plate, both oxygen and working solution superficial velocities 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 the hydrogenated anthraquinone oxidation 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 conditionsand the agreement was found to be quite satisfactory for the production of hydrogen peroxide in a sieve plate column. This reactive extraction process was also performed in pilot plant, and the results shown that it is feasible to industrially produce hydrogen peroxide by the reactive extraction process.
Keywords/Search Tags:reactive extraction, hydrogen peroxide, anthraquinone, hydrodynamic, kinetics, mathematical model, sieve plate column
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