Gas absorption with zero-order chemical reaction in a foam-bed reactor

A mathematical model for oxidation of aqueous alkaline solution of sodium dithionite using air as an oxidizing medium in a foam-bed reactor has been developed under pseudo-zero-order conditions of reaction and was found to be in good agreement with the experiments. Reactor conditions were 30°C at atmospheric pressure and surfactant used in the foam contactor was octyl phenoxy polyethoxyethanol (Triton X-100). The results of simulation for concentration profiles of the dissolved gas-phase reactant inside foam film based on above model are presented for different gas flow rates, reaction rates, and times of contact. The effects of variables such as superficial gas velocity and initial liquid-phase reactant concentration on conversion are also studied and compared with experiments on oxidation of sodium dithionite. The results indicate that the conversion increases with the increase in the superficial air velocity and initial dithionite concentration. The model predicts the experimentally obtained conversions reasonably well.     

GAS-PHASE CONTROLLED MASS TRANSFER IN A FOAM-BED REACTOR

Gas-phase controlled absorption of ammonia in foams made of solutions of sulphuric acid has been studied experimentally. Effects of gas-phase concentration of ammonia and type of surfactant on the performance of the foam-bed reactor are investigated. Gas-phase controlled absorption from a spherical bubble is anaylzed using the asymptotic value of Sherwood number (Sh = 6·58), for both negligible as well as significant changes in the volume of the bubble. The experimental data are shown to be in good agreement with the single-stage model of the foam-bed reactor using these asymptotic sub-models, as well as the diffusion-in-sphere analysis available in literature. Influence of effective diffusivity on the time dependence of fractional gas absorption has been found to be unimportant for foam columns with large times of contact. The asymptotic sub-models have been compared and use of the rigid-sphere asymptotic sub-model is recommended for foam columns of practical relevence.     

Gas Absorption with Chemical Reaction and Desorption in a Foam-bed Reactor

A general model of a foam-bed reactor involving simultaneous gas absorption, reaction, and desorption has been developed. The model considers all coupled processes in the reactor. The reactive gas absorption and desorption in the foam section have been simulated via analysis of a single foam film surrounded by limited gas pockets. The model includes a sub-model to find out concentration profiles inside the surface element. A modular approach has been used to simulate a single foam film to obtain transient concentration profiles of the gas-phase reactant A and product P. Effects of various kinetic, physicochemical, operating, and system parameters like reaction velocity, diffusion coefficient, solubility, contact time, and holdup on fractional absorption and desorption of gas are studied.     

MASS TRANSFER WITH CHEMICAL REACTION IN A FROTH BED REACTOR

A model to predict conversions in a froth bed reactor has been developed. The model is then compared against the available experimental data on the oxidation of sodium sulfide in a foam bed contactor. The predictions using the present model are also compared against those based on the model of a foam bed reactor developed earlier. The predictions using the present model agree fairly well with the experimental data and, in some cases, are even in better quantitative agreement than the previous single stage model of a foam bed reactor. The case of significant surface resistance due to surfactant has also been analyzed theoretically, obtaining analytical solutions for the concentration profile and fractional gas absorption in a liquid froth shell.     

Analysis of gas absorption accompanied by a zero-order chemical reaction in a liquid-foam film surrounded by limited gas pockets

Gas absorption accompanied by a zero-order chemical reaction in a finite liquid-foam film has been analysed to obtain expressions for the amount of gas absorbed and for fractional absorption in such a film. These equations may be readily incorporated into a single-stage model of a foam-bed reactor to extend it to chemisorption with zero-order kinetics. The equations for physical absorption result naturally from a special case.     

Surfactant Recovery by Foam Fractionation using the Gas-Liquid Contactor,Emulsion Venturi

Sodium dodecylbenzene sulfonate (SDBS), an anionic surfactant, was removed from its aqueous solution by foam fractionation in an emulsion venturi, a gas-liquid contactor functioning in self-aspiration. The performance of the reactor was evaluated by measuring the self-aspired gas flow and the mass transfer coefficient in the presence and the absence of SDBS. Data confirmed that both the gas flow self-aspired and the mass transfer coefficient increased with increasing the recirculated liquid flow. However, the presence of SDBS decreased the mass transfer capacity of the reactor influencing self-aspiration capacity in a positive manner. The percentage removal of SDBS in the emulsion venturi increased with increasing the recirculated liquid flow; at the highest liquid flow value used in this work (1.4 m³/h), 96% of SDBS was removed from the solution after 20 min of foam operating. The process was dependant on initial surfactant concentration. Neutral pH and temperature of 25°C were the optimal conditions for the foam separation of SDBS in the emulsion venturi.     

Oxidation of sodium sulphide in the presence of fine activated carbon particles in a foam bed contactor

The oxidation of sodium sulphide in the presence of fine activated carbon particles (4.33 μm) has been studied at 75°C in a foam bed contactor. The existing single-stage model of a foam bed reactor has been modified to take into account the effect of heterogeneous catalyst particles and the absorption in the storage section. The variables studied are catalyst loading, initial sulphide concentration and the average liquid hold-up in the foam bed. It is seen that the rates of oxidation of sodium sulphide are considerably enhanced by an increase in the loading of activated carbon particles. The rate of conversion of sodium sulphide also increases with an increase in the average liquid hold-up in the foam. The modified model predicts these effects fairly well. The contribution of reaction in the storage section is found to be less than 2% of the overall rate of conversion in the contactor.     

Modeling gas absorption accompanied by chemical reaction in bubble column and foam-bed slurry reactors

The published data in the literature and the reported models on foam-bed reactors have been reanalyzed. It is observed that the models have been developed assuming negligible conversion in the storage section although the storage constitutes 65–85% of the total volume of liquid/slurry charged into the reactor. For confirmation of the reported information, in the present work, experiments have been performed in foam-bed and bubble column slurry reactors for carbonation of hydrated lime slurry using carbon-dioxide gas under identical conditions. A comparison of the relative performances of the two reactors has been made. Storage section is found to be the main section governing the performance of the foam-bed slurry reactor. New mathematical models have been developed for both the reactors. The model predictions agree well with the experimental data.     

Study on Streptomycin Sulfate Recovery by Batch Foam Separation

The feasibility of foam separation as a technique was assessed for the recovery of streptomycin sulfate from the waste solution by using an anionic surfactant sodium dodecyl sulfate (SDS). The experimental parameters examined were SDS concentration, superficial gas velocity, initial pH, and liquid loading volume. The results showed that sodium dodecyl sulfate as the surfactant for foam separation had good foaming quality and could effectively concentrate streptomycin sulfate of the aqueous solution by technology of foam separation. The enrichment ratio and the recovery rate of streptomycin sulfate were 4.0 and 85%, respectively under the best operating conditions of sodium dodecyl sulfate concentration 0.4 g/L, superficial gas velocity 300 mL/min, liquid loading volume 300 mL and initial pH 6.0 when streptomycin sulfate concentration was 0.5 g/L.     

Effect of surface resistance arising due to surfactant on gas absorption accompanied by a chemical reaction in a foam-bed-reactor

On the basis of an idealized foam bed, a model to predict conversion in a foam-bed-reactor containing surfactant has been developed. The model takes into account the effect of surface resistance, arising due to the presence of a surface active agent, on gas absorption accompanied by a chemical reaction in a foam matrix. To verify the theory, experiments have been carried out in a semi-batch foam-bed-reactor for the absorption of air-carbon dioxide mixture in a foam of sodium hydroxide solution containing finite; concentrations of different surfactants. The surface resistance offered by the molecules of surfactant at the gas-liquid interface reduces the mass transfer rates significantly. The proposed model predicts fairly well the experimentally found depletion values of sodium hydroxide.     

泡沫分离回收水中低浓度磷酸三丁酯

以吐温系列表面活性剂采用泡沫法回收水中的微量磷酸三丁酯．实验结果表明，在本实验条件下，泡沫法可以回收水中的磷酸三丁酯，磷酸三丁酯的提浓率与残留率与起始磷酸三丁酯浓度、起始表面活性剂浓度和表面活性剂种类有关。     

泡沫分离法脱除铜离子色素工艺

在水溶液中,相当一部分色素在一定条件下带正电荷或负电荷,因此文中以水溶液中的铜离子为色素研究体系,十二烷基硫酸钠(SDS)为起泡剂,探索泡沫分离法脱除水溶液中离子色素的工艺。单因素实验研究了铜离子色素脱除率和富集比随pH值、鼓泡气体流量、表面活性剂质量浓度及泡沫塔装液量的变化规律和机理,结果表明,十二烷基硫酸钠对泡沫分离法脱除铜离子色素具有良好的效果。在此基础上通过正交实验得到最佳操作工艺为:pH值5.0,气体流量80 mL/min,表面活性剂质量浓度0.15 g/L,装液量220 mL,此工艺下铜离子色素脱除率为99.4%,富集比为20.8。     

泡沫分离除去水溶液中微量硫酸铜

为了探索设备和工艺简单、低污染、生产过程费用低的脱盐新方法,以十二烷基苯磺酸和十六烷基三甲基氢氧化铵为表面活性物质,采用泡沫分离技术对脱除水溶液中微量的硫酸铜进行了研究.重点考察了溶液的pH、表观气速、表面活性剂浓度,泡沫塔液面高度及改变分离阴阳离子的先后顺序对分离效果的影响,在最佳操作条件下:CuSO_4的去除率达到97.2%,富集比达到4.2.与其他表面活性剂相比,没有向溶液中引入新的金属离子和酸根离子,从而为脱盐提供了新的方法和依据.     

牛血清白蛋白和溶菌酶混合溶液的泡沫性能与其浓度的关系

生物表面活性物质的浓度对其溶液的泡沫性能有很大的影响。泡沫性能包括起泡性和泡沫稳定性。本文以初始泡沫高度和泡沫半衰期分别表征了起泡性和泡沫稳定性。首先利用Szyszkowski扩展方程和Rosen的经验模型,导出了低于临界胶束浓度(CMC)时,两种表面活性物质混合溶液的初始泡沫高度与其各自浓度的关系式;然后根据泡沫相中溶液的重力势能和表面能随气泡破裂而减小的规律,建立了低于CMC时两种表面活性物质混合溶液的泡沫半衰期与其各自浓度的关系式;最后用牛血清白蛋白(BSA)和溶菌酶(LZM)作为实验物系考察了这两种关系式的准确性。结果表明这两种关系式能准确预测BSA和LZM混合溶液的泡沫性能。在BSA和LZM混合溶液中,BSA能显著影响溶液的泡沫性能,而LZM对溶液泡沫性能的影响小。     

Removal of trace Cu from aqueous solution by foam fractionation

A system for removal of Cu²⁺ from aqueous solution by foam fractionation is proposed. The effects of pH, gas flow rate, surfactant concentration and froth/solution ratio on the removal rate and the enrichment ratio were studied to optimize the conditions. The results show that the removal rate increased with gas flow rate decreased, surfactant concentration increased and the froth/solution ratio increased, and was higher at pH4.0-5.0 than at other pH value. The optimum separation conditions were pH5.0, 200 mL/min of gas flow rate, 0.15 g/L of surfactant concentration and 1.1 of froth/solution ratio. Under the optimum conditions, the removal rate was 97.2% and the enrichment was 53.0.     

消泡剂共存体系中泡沫分离蛋白质

在以牛血清白蛋白(BSA)为目标蛋白、聚环氧丙烷环氧乙烷甘油醚(PGE)为消泡剂的模拟体系中,考察了表面活性剂种类(非离子型Tween-20和离子型SDBS)、浓度、溶液pH及操作参数(气体流量、初始液池高度)对BSA分离效率的影响. 结果表明,2种活性剂均能改善模拟体系的泡沫性能,使泡沫分离. 后者作用更强并能促进BSA的吸附,因DBS-通过静电作用与带相反电荷的BSA结合形成疏水性更强的BSA-DBS复合物. pH通过影响BSA的电荷分布而影响其与SDBS的结合,进而影响对BSA的吸附,初始BSA浓度0.1 g/L, PGE 4 mg/L, SDBS 50 mg/L, pH为3.4时,约66%蛋白质浓缩在泡沫液中,富集比为5.34. 增加气速或初始液池高度可得到较高收率,但富集比减小.     

Mass transfer with chemical reaction in a foam bed contactor

On the basis of dodecahedral structure of a foam bed, a model to predict conversion in a foam bed contactor with mass transfer with chemical reaction has been developed. To verify the proposed model, experiments have been carried out in a semi-batch apparatus for the absorption of lean CO₂ gas in a foam of sodium hydroxide solution. The proposed model predicts fairly well the experimentally found absorption values.     

泡沫分离法提取乙醇水体系中甲基橙

采用泡沫分离法对含甲基橙的乙醇水溶液进行了提取研究. 考察了乙醇体积分数、气体流量、pH、甲基橙浓度和表面活性剂浓度对提取效果的影响,并对泡沫分离乙醇-水体系中提取中药有效成分的可行性进行了探讨. 结果表明,以十六烷基三甲基溴化铵(CTAB)为表面活性剂,在乙醇体积分数25%的乙醇-水体系中,在pH 6.0、气速80 mL/min、甲基橙浓度35 mg/L及CTAB浓度80 mg/L的操作条件下,甲基橙的富集比为14.38,回收率在98.5%以上. 在一定范围内提高表面活性剂浓度或加入稳泡剂以削弱乙醇的消泡作用,从而将泡沫分离技术应用于乙醇-水体系中中药有效成分的提取是可能的.     

泡沫分离法除去水溶液中微量铜离子的工艺

以十二烷基苯磺酸为表面活性物质,自制的单金属离子水溶液为研究体系,对泡沫分离法除去水溶液中金属离子的工艺进行了研究,重点考察了溶液的pH、鼓泡气体流量、表面活性剂浓度及泡沫塔装液量的影响. 结果表明,十二烷基苯磺酸具有良好的起泡性能,对水溶液中铜离子的去除效果也比较理想,最佳操作条件下富集比为18.2,去除率为96.1%,与常规的表面活性剂十二烷基硫酸钠相比,十二烷基苯磺酸在泡沫分离过程结束后不会在体系中残留金属离子,这为探索脱盐新方法提供了依据.