General model for prediction of pressure drop and capacity of countercurrent gas/liquid packed columns

The liquid hold-up of three structured packings (Mellapak 250.X, 250.Y and 500.Y) was measured with a gamma ray absorption technique using the air/water system. The results agree well with other experimental data available from the literature. A correlation was derived to calculate the hold-up as a function of liquid load, liquid viscosity and specific surface area of the packing.

Hold-up of mellapak structured packings

Power-to-Methane as one part of Power-to-Gas has been recognized globally as one of the key elements for the transition towards a sustainable energy system. While plants that produce methane catalytically have been in operation for a long time, biological methanation has just reached industrial pilot scale and near-term commercial application. The growing importance of the biological method is reflected by an increasing number of scientific articles describing novel approaches to improve this technology. However, these studies are difficult to compare because they lack a coherent nomenclature. In this article, we present a comprehensive set of parameters allowing the characterization and comparison of various biological methanation processes. To identify relevant parameters needed for a proper description of this technology, we summarized existing literature and defined system boundaries for Power-to-Methane process steps. On this basis, we derive system parameters providing information on the methanation system, its performance, the biology and cost aspects. As a result, three different standards are provided as a blueprint matrix for use in academia and industry applicable to both, biological and catalytic methanation. Hence, this review attempts to set the standards for a comprehensive description of biological and chemical methanation processes.

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Biological CO2-Methanation: An Approach to Standardization

Water scrubbing is the most widely used technology for removing CO2 from biogas and landfill gas. This work developed a rate-based mass transfer model of the CO2–water system for upgrading biogas in a packed bed absorption column. The simulated results showed good agreement with both a pilot-scale plant operating at 10 bar, and a large-scale biogas upgrading plant operating at atmospheric pressure. The calculated energy requirement for the absorption column to upgrade biogas to 98% CH4 (0.23 kWh Nm–3, or 4.2% of the input biogas) is a significantly closer approximation to the measured value (0.26 kWh Nm–3, or 4.8% of the input biogas) than has previously been reported in the literature. The model allows for improved design of CO2 capture and biogas upgrading operations and can also be a useful tool for more detailed cost–benefit analysis of the technology.

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Modeling the Water Scrubbing Process and Energy Requirements for CO2 Capture to Upgrade Biogas to Biomethane

Rotating packed beds (RPBs) exploit centrifugal fields in order to improve separations and reactions. The reported advantages of RPBs compared to state of the art equipment for the mixing and contacting of different fluids are significant reductions in equipment volume, corresponding large capacities and improved selectivities. These benefits can be attributed to the intense micromixing of the fluids and the intense internal mass transfer between different phases. Further advantages of RPBs are fast dynamics resulting in a quick achievement of steady state operation, the possibility to process highly viscous fluids and the additional degree of freedom resulting from the variable rotational speed. Although various successful implementations of RPBs on an industrial scale have been reported, conclusive criteria and guidelines for the selection of RPBs are still missing. Consequently, they are seldomly considered during process design. In order to derive explicit criteria that indicate the suitability of an RPB, known industrial applications for gas–liquid, vapor–liquid and liquid–liquid contacting applications are analyzed in the present study. On this basis, distinctive decision trees are introduced in order to facilitate the identification of processes in which the use of an RPB is expected to be beneficial.

A guide on the industrial application of rotating packed beds

Fluid dynamics of packed columns , Fluid dynamics of packed columns , کتابخانه مرکزی دانشگاه علوم پزشکی تهران

Fluid Dynamics of Packed Columns

A report is presented on the performance of modern dumped and structured packings for application in the field of thermal separation processes. The evaluation of the results is based on extensive experimental investigations of rectification, absorption, and desorption systems. The following are indicated: the efficiency in terms of the number of theoretical stages per unit height or in terms of the height of transfer unit or volumetric mass transfer coefficient, the pressure drop per unit height as well as per theoretical stage or per gas phase transfer unit, and the liquid hold-up, whereby either the gas capacity factor or the liquid load was adopted as influencing parameter, and finally the maximum gas capacity factor as a function of the flow parameter. The results are presented in diagrams and tables.

Application of modern packings in thermal separation processes

A new model of suspended bed of droplets for describing the vaour or gas the vapour or gas velocity at the flooding point in packed of columns for rectification and absorption under vacuum and normal pressure is presented metallic, ceramic and plastic packings with diameters of 8–90 mm as well on sheet metal and gauze packings, in a wide range of liquid and vapour loads. Approximately 650 literature measurements and own data were evaluated. The mean relative error in determining the gas velocity at flooding point is less than ±5%. On the basis of the double layer model, a new equation was derived for the hold-up at flooding point, which is needed for the calculation of the flooding gas velocity. An example of calculations for sample applications is also included.

Determination of flooding gas velocity and liquid hold-up at flooding in packed columns for gas/liquid systems.

a b s t r a c t The following work presents a new, generally applicable model for description of the mass transfer in the liquid phase for packed columns filled with random dumped non-perforated and lattice-type packing with size between 12 and 90 mm for gas-liquid systems in operating range up to flooding point. The new equation for evaluation of the volumetric mass transfer coefficient in the liquid phaseL·ae was derived on the basis of the assumption that liquid flows down in packed bed mainly in the form of droplets and that effective interfacial area ae depends on hold-up in packed bed. The relation between the fluid dynamics and the mass transfer is shown based on the channel model with a partly open structure. The experimentally derived values for the effective mass transfer area in different types of random packings ae are in good agreement with the calculation based on the new model. It is therefore possible to separate the product ˇL·ae into liquid phase mass transfer coefficientL and effective interfacial area ae.

Model for the prediction of liquid phase mass transfer of random packed columns for gas-liquid systems

In this paper it is presented a model for calculation of mass transfer in dumped packed columns or in columns with orderly arranged packings, valid for systems, the mass transfer resistance of which is mainly located in the vapor resp. gas side. It can be applicated both for rectifications and absorptions. Based on numerous experiments the validity of this model will be proved and it is shown that absorption test results can be transferred on rectifications with an accuracy which is sufficient for industrial applications. Furthermore it is shown with metallic Pall ring packings how results received in test columns of various diameters can be applicated for precalculation of columns with industrial dimensions. To carry out this scaling-up a special diagram was developed.

Jerzy Maćkowiak

Papers

Fluid Dynamics of Packed Columns

Application of modern packings in thermal separation processes

Determination of flooding gas velocity and liquid hold-up at flooding in packed columns for gas/liquid systems.

Model for the prediction of liquid phase mass transfer of random packed columns for gas-liquid systems

How to Use the Absorption Data for Design and Scale‐Up of Packed Columns