Kinetics of absorption of sulfur dioxide in dimethylaniline solution

Absorption of sulfur dioxide accompanied by reversible reaction in dimethylaniline has been studied using a short falling-film apparatus. Solutions of the amine in kerosene were used for this purpose. The effects of gas and liquid concentrations, contact time and temperature on the rate of absorption were investigated. Reaction equilibrium constant values were obtained at different temperatures from separate measurement of solubility of sulfur dioxide gas in kerosene as well as in dimethylaniline solutions. The heat of reaction was also calculated from these data. The absorption data could be satisfactorily interpreted by using the penetration theory of mass transfer with simultaneous pseudofirst order chemical reaction. The rate equations for the forward and reverse reactions were established.     

Chemical absorption into concentrated slurry: Absorptions of carbon dioxide and sulfur dioxide into aqueous concentrated slurries of calcium hydroxide

The absorption of sulfur dioxide and carbon dioxide into aqueous calcium hydroxide slurries were performed using a stirred tank with a plane gas-liquid interface at 308 K. The absorption rates were found to be lower than those predicted by assuming that the solid particles are uniformly suspending in the liquid-film as well as the bulk liquid phase.It might be due to the possibility that there is no particle suspending in the vicinity of the interface. The process of gas absorption with reaction in the slurry was formulated by film-theory model incorporating the presence of an inert region in which there is no particle. The observed absorption rates of sulfur dioxide and carbon dioxide were successfully predicted by the proposed model.     

旋转填充床中SO2与O2同时吸收的扩散-反应模型

引　言迄今为止 ,旋转填充床 (ＲａｔａｔｉｎｇＰａｃｋｅｄＢｅｄ ,ＲＰＢ)用于模拟烟气的脱硫吸收 (包括物理吸收和化学吸收 )已经有了较多的研究 ,ＲＰＢ中ＳＯ2 物理吸收的传质模型已有报道[1～ 3] ,但有关化学吸收的数学模型还属鲜见 .在数学上描述ＲＰＢ中ＳＯ2 化学吸收的传质 -反应特征 ,必须考虑物质传递和化学反应两个方面的影响因素以及这两种因素间的相互关系 .描述气 -液相之间的物质传递过程有不同的传质模型[4 ,5] ,如双膜理论、Ｈｉｇｂｉｅ渗透理论、Ｄａｎｃｋｗｅｒｔｓ表面更新理论和湍流传质理论等 ,但用之于处理具体…     

旋转填充床中SO2与O2同时吸收的扩散-反应模型

In this paper the rotating packed bed, a new type of absorber, which has high mass-transfer characteristic by means of centrifugal field instead of gravity field, is used to study on stimulated flue gas desulfurization. Based on experimental data,a model of mass-transfer and reaction of the sulfur dioxide chemical absorption in the rotating packed bed reactor is proposed according to the film-theory. It can be used to predict the performance of the total absorption rate and the enhancement factor of the sulfur dioxide and oxygen simultaneous absorption in the rotating packed bed reactor.The prediction of the model is consistent with the experimental result varying operating conditions, and the relative error between experimental result and predicted result is below 12%. Some interesting potential projects of simultaneous absorption of sulfur dioxide and oxygen in the rotating packed bed reactor are also discussed.
     

Selective Removal of Hydrogen Sulfide from Gases Containing Hydrogen Sulfide and Carbon Dioxide Using Diethanolamine

Abstract

It is sometimes necessary to selectively remove hydrogen sulfide from gases containing carbon dioxide. This may be the case for example in the production of sulfur using the Claus process. When two gases are simultaneously absorbed into a solution containing a reactant with which each gas can react, the rate of absorption of each component is affected by the presence of the other gas. For the absorption of hydrogen sulfide into primary and secondary amines, the reaction which occurs can usually be considered to be instantaneous. An instantaneous reaction is diffusion-limited since the reaction occurs so rapidly that the liquid phase reactant and the absorbed gas cannot coexist in the same region of the liquid. For primary and secondary amines used for gas treatment, the reaction with carbon dioxide is much slower than for hydrogen sulfide and can often be considered to be second order.

In this work the simultaneous absorption of two gases into a liquid containing a reactant with which both gases can react is modeled using penetration theory. It is assumed that one gas reacts instantaneously and the other gas undergoes a second order reaction. Parameters used in the calculations are those available in the literature corresponding to the absorption of hydrogen sulfide and carbon dioxide in diethanolamine.     

Modeling of surface intermediates under forced periodic conditions applied to CO2 methanation

Forced oscillations of the carbon dioxide concentration in a hydrogen feed were applied to the carbon dioxide methanation reaction with simultaneous gas phase and surface analysis. The response of the gas phase and surface species to these repeated dynamic conditions show a time shift following the sequence CO₂ → formate → CO → methane, but can be modeled by a simple model involving one single adsorbed surface intermediate and a reservoir in equilibrium with this intermediate. The dynamic behavior of this intermediate is very close to the variation of the IR absorption band associated with formate and carbonate species.     

Simultaneous absorption of carbon dioxide,sulfur dioxide and nitrogen dioxide into aqueous 2-amino-2-methy-1-propanol

The absorption mechanism of three acidic gases in alkali solution, such as the system of carbon dioxide, sulfur dioxide, and nitrogen dioxide in 2-amino-2-methyl-1-propanol (AMP), was used to predict the simultaneous absorption rates using the film theory. Diffusivity, Henry constant and mass transfer coefficient of each gas were used to obtain the theoretical enhancement factor of each component. The theoretical molar fluxe of each gas was obtained by an approximate solution of mass balances with reaction regions of the first order reaction of CO₂ and instantaneous reactions of SO₂ and NO₂ in CO₂-SO₂-NO₂-AMP system. From the comparison between the theoretical total fluxes of these gases and the measured ones, the solubility and the reaction rate between each gas and AMP influenced its molar flux.     

中空纤维膜吸收烟气二氧化硫

本文综述了国内外用膜吸收法治理烟气二氧化硫的研究现状,对采用中空纤维膜吸收过程中的膜组件操作方式、吸收剂、膜材料以及工艺参数的选择进行了介绍,并应用双膜理论对中空纤维膜吸收二氧化硫过程中的各分传质系数和总传质系数进行了推导,初步探讨了建立膜吸收过程数学模型的方法。     

淤浆反应器中SO_2的催化氧化

研究了常温常压下淤浆反应器中SO_2催化氧化反应,通过改变反应物的进口浓度和测定小颗粒床层平均氧化反应速率(此时传质阻力最小),间接验证了假定的反应机理:氧在活性炭活性位上的吸附为速率控制步骤,本征反应速率相对于颗粒表面的溶氧浓度为一级,而与此浓度范围内的SO_2浓度无关,通过改变催化剂的用量、粒径及反应温度,测定了各模型参数.     

Absorption of chlorine into aqueous sodium carbonate solutions and desorption of carbon dioxide

The absorption of pure chlorine into aqueous sodium carbonate solutions accompanied by the desorption of carbon dioxide was studied both theoretically and experimentally. The absorption rates of chlorine and the desorption rates of carbon dioxide were measured at 25°C using a baffled agitated vessel operated batchwise. The experimental results were analyzed with the chemical absorption theory based on the Lévěque model. The measured absorption and desorption rates were in good agreement with the theoretical predictions.     

木质素磺酸钠吸收烟道气中的SO2

本文就木质素磺酸钠溶液脱除烟道气中SO_2进行了实验研究。实验采用双搅拌气-液反应器,探讨了木质素磺酸钠的浓度、温度等因素对SO_2吸收的影响,并求取了化学吸收增强因子。结果表明,木质素磺酸钠能有效地脱除烟道气中的SO_2。     

Absorption of sulfur dioxide in aqueous dispersions of dimethyl aniline

Absorption of sulfur dioxide in aqueous dispersions of dimethyl aniline has been carried out in a laboratory stirred cell with a flat gas—liquid interface. The effects of liquid loading, gas concentrations and other parameters have been studied. The absorption rate is linear in gas concentration, and increases with increasing dispersed phase concentration. Substantial enhancement of absorption compared to that in water occurs. Emulsification of the liquid by addition of a surfactant does not increase the absorption rate. The rate of desorption of sulfur dioxide from a loaded solution at 60°C remains essentially constant. A theoretical model for absorption has been developed assuming each droplet in the film to be enclosed by a spherical shell of the aqueous phase through which the solute diffuses at steady state. Comparison of the calculated enhancement factors with the experimental values confirms the validity of the model.     

Simultaneous absorption of two gases accompanied by reversible instantaneous chemical reactions

The problem of simultaneous absorption of two gases accompanied by reversible instantaneous chemical reactions is considered. Analytical equations are derived for the rates of absortion of the two gases. The solution is valid when the diffusivities of all species are assumed to be the same. The theoretical aspects of the problem of simultaneous absorption of hydrogen sulphide and carbon dioxide in amine solutions under equilibrium reaction conditions are also considered.     

MEASUREMENT OF INTERFACIAL AREA AND MASS TRANSFER COEFFICIENTS BY CHEMICAL METHOD OF C02 ABSORPTION INTO AQUEOUS SOLUTIONS OF NaOH IN A MODEL COLUMN WITH EXPANDED METAL SHEET PACKING

The theory of gas absorption accompanied by fast pseudo-fast order reaction which considered dependences of diffusivity, kinetic constant and Henry's law constant on absolute temperature and ionic strength was used to obtain values of effective interfacial areas and mass transfer coefficients in gas and liquid phase.

Experimental measurement of carbon dioxide absorption from mixture with air was performed in a pilot-plant column with expanded metal sheet packing irrigated with sodium hydroxide solution.

Resulting liquid and gas-side mass transfer coefficients are compared with values obtained from physical Absorption measurement of carbon dioxide into water and with measurement of gas-side mass transfer coefficient for sulphur dioxide in the same column.

The differences between determined values are discussed.     

Kinetics of absorptions of lean sulfur dioxide into aqueous slurries of calcium carbonate and magnesium hydroxide

The process of the absorption of sulfur dioxide into an aqueous slurry of calcium carbonate or magnesium hydroxide was theoretically analyzed according to the two-reaction-plane model incorporating the solid dissolution promoted by the reactions with absorbed sulfur dioxide in the liquid film. Theoretical enhancement factors compared well with the experimental data using a stirred tank absorber with a plane gas—liquid interface at 25°C. The concentrations of the accumulated species in the bulk liquid phase (bicarbonate ion for the calcium carbonate slurry and sulfite ion for the magnesium hydroxide slurry) which substantially control the absorption rates, were assesed by comparing experimental enhancement factors with the theoretical predictions.     

Simultaneous Absorption of H2S and Co2 Into Aqueous Methyldiethanolamine

Abstract

The tertiary araine methyldiethanolamine (MDEA) is finding increasing application as a chemical solvent for selective absorption of hydrogen sulfide from gases containing hydrogen sulfide and carbon dioxide. Gas streams of this type include some natural gases, synthetic gases from coal and heavy oil gasification and tail gases from sulfur plants. Selectivity for H2S is needed either to enrich Glaus sulfur plant feed in H2S or to remove only H₂S when CO₂ removal is not necessary or economic. For the absorption of hydrogen sulfide into MDEA, the reaction which occurs can be considered to be instantaneous while carbon dioxide undergoes a second-order reaction with MDEA.

In this work, the simultaneous absorption of two gases into a liquid containing a reactant with which both gases react is modelled using the film theory. Physical properties and kinetic rate parameters used in the model have been measured in our laboratory. The model is used to study the effect of process variables on the selectivity of MDEA for H₂S over C0₂. The simultaneous absorption of H₂S and CO₂ gases into aqueous MDEA is studied experimentally using a continuous stirred tank absorber. Experimental absorption rates are compared to predictions based on a multicomponent mass transfer model. The average deviations of the theoretical calculations from the experimental results are 10.2% and 12.9% for C0₂ and H₂S, respectively.     

糖精钠生产过程中废气的回收利用研究与探讨

在糖精生产过程中有氨气、氯化氢、二氧化氮、二氧化硫等废气放出。其中氨气用水吸收生成的氨水可吸收氯化氢、二氧化氮,所得溶液经处理可制成氮肥再利用;二氧化硫气体经洗涤后,用柠檬酸钠缓冲溶液吸收,再经解析、干燥、压缩后得到二氧化硫液体,然后供生产使用。     

Sulfur dioxide non‐dispersive absorption in N,N‐dimethylaniline using a ceramic membrane contactor

BACKGROUND: Removal of sulfur dioxide from gas emissions by selective absorption is a common method to separate and concentrate sulfur dioxide and to reduce air pollution and environmental risks. N,N‐dimethylaniline is an organic solvent used in some industrial applications for its sulfur dioxide affinity, leading to a regenerative process. However, the use of scrubbers and equipment in which direct contact between gas and liquid takes place leads to solvent losses due to evaporation and drops dragging. RESULTS: In this work, an innovative procedure based on non‐dispersive absorption in a ceramic hollow fibre membrane contactor was studied in order to avoid drops dragging. The absorption efficiency ranged between 40 and 50%, showing the technical viability of the process. The sulfur dioxide flux through the membrane has a linear relationship with the concentration of SO₂ in the gas stream and an overall mass transfer coefficient K_overall = (1.10 ± 0.11) × 10^?5 m s^?1 has been obtained. CONCLUSIONS: The mass transfer behaviour of a ceramic hollow fibre membrane contactor for sulfur dioxide non‐dispersive absorption in N,N‐dimethylaniline has been studied. The main resistance is found to be the ceramic membrane and the effective diffusivity has been inferred. The mass transfer model and parameters allow the evaluation of equipment design for technical applications. Copyright © 2008 Society of Chemical Industry     

固定床反应器活性炭还原SO_2制单质硫的研究

以活性炭为还原剂,在固定床反应器中将N_2和SO_2混合气体反应还原制得硫单质。研究了反应温度、反应空时、原料气浓度等因素对SO_2脱除率和硫磺产率的影响。结果表明:在反应温度800℃,反应空时14s,SO_2转化率达95%以上,硫磺产率可达85%以上,制得硫磺纯度97%以上。     

不同中空纤维膜材料对烟气中二氧化硫的吸收性能影响

膜法烟气脱硫能耗低、传质面积大、分离效率高,可以有效地解决传统塔器内的液泛、漏液、夹带等问题。本文采用自制的中空纤维膜接触器,通过改变烟气流量、水流量和水温对比了聚四氟乙烯（PTFE）、聚偏氟乙烯（PVDF）和聚丙烯（PP）这3种中空纤维膜对烟气中二氧化硫的吸收性能,并通过电镜和接触角仪表征,对比了3种膜的参数和疏水性。结果表明：在不同烟气流量、水量和水温下,3种膜的吸收性能都表现为PTFE＞PP＞PVDF,120min时二氧化硫吸收浓度,PTFE最大,是PP的1.68倍,是PVDF的4.62倍;烟气流量的改变对二氧化硫的吸收浓度有显著影响,当烟气流量由60mL/min提高到140mL/min时,120min时PTFE膜二氧化硫的吸收浓度提高了2.14倍;影响膜性能的主要因素为疏水性,PTFE浸泡前后的表面接触角为105°和97°,疏水性远大于PP和PVDF。PTFE中空纤维膜孔径大、孔隙率高,具有极强的疏水性,在烟气脱硫及相关吸收过程中表现出较好的应用前景。