Packing Sheets Research Articles

Determining catalyst loading in reactive distillation column

The widespread industrial application of reactive distillation technology is inseparable from the development of catalytic packing. However, systematic research on the heterogeneous catalyst loading in the reactive distillation column is vacant, and existing studies about catalyst loading on each stage and their distribution ignore the physical structure of the reactive distillation column. In this work, Modular Catalytic Structured Packing combining catalyst bags and structured packing sheets is applied in the modeling and optimization of reactive distillation processes. The catalyst loading on each stage is obtained from three parameters: the catalyst volume fraction of catalytic packing, the catalytic distillation column diameter, and the height of the theoretical stage. Using the effective diffusivity method, a simplified non-equilibrium stage model is chosen to simulate the reactive distillation process, and the bubble-point method for solving the non-equilibrium stage model’s equation system is introduced. The genetic algorithm optimizes both catalyst volume fraction and the number of theoretical stages in the reactive section. Case studies of methyl acetate esterification and ethyl tert-butyl ether (ETBE) synthesis show that greater theoretical stages of the reactive section and enough reflux ratio will reduce the demand of catalysts. Redistribution of catalyst is implemented by dividing the reactive section into several. The non-uniform distribution of catalyst will reduce both energy consumption and catalyst amount for the methyl acetate system, but insignificant for ETBE synthesis, due to different interactions of reaction and separation.

A sheet pocket to prevent cross-contamination of formalin-fixed paraffin-embedded block for application in next generation sequencing.

Formalin-fixed paraffin-embedded (FFPE) blocks are used as biomaterials for next-generation sequencing of cancer panels. Cross-contamination is detected in approximately 5% of the DNA extracted from FFPE samples, which reduces the detection rate of genetic abnormalities. There are no effective methods available for processing FFPE blocks that prevent cells from mixing with other specimens. The present study evaluated 897 sheets that could potentially prevent cell transmission but allow for the movement of various solvents used in FFPE blocks. According to the International Organization for Standardization and Japanese Industrial Standards, six requirements were established for the screening of packing sheets: 1) filter opening ≤5 μm, 2) thickness ≤100 μm, 3) chemical resistance, 4) permeability ≥1.0 × 10−3 cm/s, 5) water retention rate <200%, and 6) cell transit test (≤2 cells/10 high-power fields). Polyamide, polyethylene terephthalate, and polypropylene/polyethylene composite sheets met all criteria. A pocket, which was designed to wrap the tissue uniformly, was made of these sheets and was found to effectively block the entry of all cell types during FFPE block processing. Using a sheet pocket, no single cell from the cell pellet could pass through the outer layer. The presence or absence of the sheet pocket did not affect hematoxylin and eosin staining. When processing FFPE blocks as a biomaterial for next-generation sequencing, the sheet pocket was effective in preventing cross-contamination. This technology will in part support the precise translation of histopathological data into genome sequencing data in general pathology laboratories.

Modelling film and rivulet flows on microstructured surfaces using CFD methods

A new procedure to identify effective contact angles used in the description of the packing surface wetting is proposed. Both non-perforated and perforated surfaces are modelled. The flow of a water and triethyleneglycol (TEG) mixture over inclined, non-corrugated packing sheets was used as a model case. Different microstructures were investigated in a combined experimental and numerical study to determine the effective contact angles best reproducing the experimental film or rivulet widths. The outcome is a simple yet robust approach for modelling the liquid flow on structured packings.

Catalyst screening for heavy oil production from waste plastic

In fuel production from waste plastics, highly flammable hydrocarbon oils and by-product gasses are produced. These products are not suitable for developing countries, because high-precision plants and experienced operators are required for safe operation. Production of heavy oil rather than light oil is one solution to this problem. In the present study, catalytic pyrolysis of packing sheets commonly used in Vietnam was carried out in a batch reactor in order to produce heavier oil. The liquid product components were quantified by flame ionization detector-gas chromatography. Six kinds of catalysts were used for catalytic pyrolysis, including commercial SiO2-Al2O3, Pd on alumina, Cu, Ni, Fe2O3 and Fe3O4. Pd on alumina, Cu, Ni and Fe3O4 had no catalytic activity. The product components were almost the same as those produced by thermal pyrolysis with no catalyst. Al2O3-SiO2 products had a large amount of low-carbon-number components. Fe2O3 produced a small amount of light components and a large amount of heavy components. Fe2O3 produced heavier oil than the other catalysts.

The effect of microtexture on the liquid flow over the sheets

This work considers the method of the corrugated sheet arrangement near the column wall with the aim to limit liquid fall on the wall and increase liquid concentration in the near-wall area. Experiments were carried out at the corrugated Koch 1Y packing sheets for various liquid flow rates. This report presents experimental results on the character of liquid flow near the edge of corrugated sheets and the effect of the middle sheet shift from the edge of the packing. The ribs of this sheet are directed downward to the edge of the packing. Test was performed for two positions of the middle sheet: to study the effect of microtexture orientation at the sheet, whose ribs are directed downward to the packing edge, on liquid distribution under the packing. Experiments were carried out for liquid flow rates of 1-12 ml/s.

Effect of Precursor on the Mineralogy and Microstructure Characteristic of Nano Zirconia by Template Method

Nano zirconia were successfully synthesized from Zr(OH) 4 dan ZrOCl 2 using a template method. Polyvinyl alcohol was added as a template or a surfactant to control the particle size of nano zirconia. Zirconia precursors were reacted with polyvinil alcohol at a stoichiometric and nonstoichiometric ratio in water solvent at about pH 4 and then calcined at a temperature of 800⁰C. The result showed the precursor types obviously affected the mineralogy and microstructure characteristics of nano zirconia. The reaction between Zr(OH) 4 and polyvinyl alcohol produces tetragonal zirconia in the form of nanorods with a diameter of 100 nm and 500 nm - 1μm in length, and elongated agglomerates consisting of nanoparticles less than 100 nm in sizes. Meanwhile, the reaction between ZrOCl 2 precursor with polivinyl alcohol at pH 4 leaded to formation of monoclinic zirconia with microstructures such as nanorods with diameter of 10~100 nm and 100~500 nm in length, agglomeration of nanoparticles <100 nm, and packing sheets.

Overview of methods to control the liquid distribution in distillation columns with structured packing: Improving separation efficiency

The paper presents experimental results on the effect of characteristics of liquid spreading over the surface of a structured packing, distribution of local flow parameters over the cross-section and height of the distillation column under various conditions of initial packing irrigation. It is shown that the corrugation angle of the structured packing sheets, microtexture parameters, presence of perforation and size of holes, as well as liquid flow rate determine the patterns of liquid spreading and wetting of the packing surface. The test results for a new method of dynamic control of the liquid distributor with independent valves for each drip point are presented with the aim of influencing large-scale flow maldistribution in the column and increasing the separation efficiency. The data obtained in these experiments showed that a targeted change in the position of active irrigation points based on the actual distribution of local parameters in the separation column can lead to a noticeable increase in the efficiency of mixture separation up to 20% compared to a regular distributor with a fixed position of drip points. The effect of variation of the turn angles of the structured packing layers (20°, 45°, 70°, and 90°) on the efficiency of mixture separation was studied. Using a passive method to decrease the nonuniformity of distribution of local flow parameters by increasing the rotation angle of the structured packing layers in the column also leads to an increase in the separation efficiency. For the rotation angles of the packing layers (70–90) degrees, the HETP decreased in comparison with the rotation angle of 20° by (10–12) %.

Determination of local fluid dynamic parameters in structured packings through X-ray tomography: Overcoming image resolution restrictions

X-ray tomography is a powerful method for the noninvasive investigation of fluid dynamics in packed columns. However, for the quantitative determination of local fluid dynamic parameters, such as film thickness on packing sheets, the spatial resolution is often too low. In this work, tomographic measurements were carried out in a column of 100 mm diameter equipped with Mellapak 350.Y packings. Different working liquids with low surface tension and varying viscosity up to 50 mPa s were used. Methods for improving the representation of the dry structured packing sheets and the gas–liquid interface in the cross-sectional images are presented. They are applied to the tomographic images and allow overcoming image resolution restrictions, which results in accurate determination of film thickness and degree of wetting on the structured packing.

Experimental investigation of freon mixture spreading over the structured Sulzer 500X packing at single drip point irrigation

The paper presents the results of experimental studies on liquid spreading over the Sulzer 500X packing at single drip point irrigation. The experiments were carried out using a 10% mixture of R114/R21 freons on one packing layer with a diameter of 0.6 m. The flow rate of liquid flowing from the lower edge of the packing was measured automatically by a flow meter moving along the packing sheets with a given step. The flow meter used volumetric measurement method. The receiving collector of flow meter is 50x50 mm in size, operating range of flow measurement is 0.05–50 ml/s. Distributions of liquid over the packing were measured at single-jet irrigation in the range of jet flow rates 2.5 < qirrig < 60 ml/s. Spreading zone in the case of irrigation by a single jet is limited by the corrugation channels coming from the irrigation point. The pattern of spreading at low-flow jet irrigation has the shape of a dome with a low flow rate at the outlet of corrugation channels, which limit the spreading zone. With an increase in the flow rate, the share of liquid in these channels increases and dominates over other parts of the spreading zone.

Experimental study of liquid renewal on the sheet of structured corrugation SiC foam packing and its dispersion coefficients

Developing efficient catalytic packing for reactive distillation can push its application greatly forward. Structured Corrugation SiC Foam Packing is considered an attractive candidate with the rapid development of the coating method. However, liquid flow behavior on the packing and its radial and axial dispersion coefficients remain unclear. We studied herein liquid renewal on the structured corrugation SiC foam packing sheet by photography. The images revealed that the liquid could be constantly refreshed on most of the wetted area and the process can be categorized into two stages by the renewal rate. Effects of liquid flow rate, viscosity, and surface tension on the renewal process were investigated. The renewal results highlight the applicability of the foam packing at low liquid load. Furthermore, axial and radial dispersion coefficients of two foam packing sheets with different pore sizes were characterized, and comparisons with KATAPAK-S showed that the foam packing has better liquid dispersion ability.

Failure analysis of gas sweetening tower absorber packing

Gas sweetening tower packing was failed in the form of corrosion damage after 3 months from installation. Pieces from the failed packing as well as unused one were received for investigation to establish whether its failure was due to specific material aspects or improper use. The investigation showed that the packing was 316L stainless steel which failed due to intergranular chloride stress corrosion cracking. The root cause of the failure of the received packing could be mainly attributed to the material residual shear bands after packing sheet manufacturing process. The shear bands were formed due to lack of solution annealing after cold deformation process. Corrosion is mainly controlled by chloride ions and residual stress. It is recommended to use high quality material free from residual stresses by applying solution annealing heat treatment after cold deformation of the packing sheets and removing of the chloride ions by controlling the inlet water.

CFD Simulation of Dry and Wet Pressure Drops and Flow Pattern in Catalytic Structured Packings

Type of packings and characteristics of their geometry can affect the flow behavior in the reactive distillation columns. KATAPAK SP is one the newest modular catalytic structured packings (MCSP) that has been used in the reactive distillation columns, recently. However, there is not any study on the hydrodynamics of this packing by using computational fluid dynamics. In the present work, a 3D VOF model was developed to evaluate dry and wet pressure drops of catalytic structured packings, MCSP-11 and 12. The module of MCSP is made of alternating vertical layers of structured packing sheets (Mellapak Plus) and catalyst bags. The goal of this paper is to illustrate the effect of geometry on the hydrodynamics and characterization of flow in the MCSP modules. Results showed that the mean relative errors for prediction of dry and wet pressure drops were 17% and 7% for MCSP-11 and 11% and 12% for MCSP-12, respectively. According to CFD results, pressure drop in closed channels was higher than that in open channels. The catalyst bags were simulated as porous media. The simulation led to determination of the liquid velocity distribution in the catalyst bags.

Model prediction and optimization of dry pressure drop within Winpak

The mechanism and optimization of the dry pressure drop within a novel structured packing, Winpak, was investigated by computational fluid dynamic simulations. The contribution of the dry pressure drop was decomposed into two components. The drag term was obtained according to an existing model. The frictional pressure drop was simulated in a new representative elementary unit. Several structures of Winpak were designed to study the effect of the packing dimensions. Results indicate the windows on the packing sheets have significant effect. Accordingly, the cutting angle of windows was optimized to reduce dry pressure drop. A set of correlations for predicting the dry pressure drop was established ultimately and validated by experimental data.

Experimental Investigation of Liquid Axial and Radial Dispersion in Winpak Modular Catalytic Structured Packing

The response technique was employed to investigate the axial and radial dispersion characteristics of the liquid phase in modular catalytic structured packing (MCSP) reaction elements. Residence time distribution (RTD) experiments were performed at ambient temperature and atmospheric pressure. A two-dimensional dispersion model was solved analytically to determine the axial and radial dispersion coefficients and the dynamic liquid holdup from the RTD curves. Three different reaction elements containing Winpak packing sheets, Mellapak packing sheets, or only catalytic particles were employed. The radial dispersion coefficient in these structures is approximately 1–2 orders of magnitude higher than the axial dispersion coefficient. The axial and radial dispersion coefficients in the Winpak elements are greater than those in the other structures. Thus, it can be concluded that the liquid dispersion characteristics in the Winpak elements are satisfactory. These measured dispersion coefficients enable the reli...

CFD Simulation and Optimization of Winpak-based Modular Catalytic Structured Packing

A recently designed packing sheet Winpak was assembled with catalysts in a modular catalytic structured packing (MCSP) column. A combined mesoscale–microscale methodology was used to analyze and determine the pressure drop mechanism in the MCSP. The proposed methodology differentiates the pressure drop into six different principles, which was determined and compared using computational fluid dynamics (CFD). The three major causes are gas flow confluence and diffluence through the packing windows, the sudden change in the effective gas channel area and the wall effect. Inspired by constructal theory, the height of packing sheets loaded with catalysts was reduced, which resulted in a less abrupt gas channel contraction and expansion at the packing layer junction and more favorable for the undisturbed gas flow. The optimized overall pressure drop was reconstructed in Fluent and was validated by both dry and irrigated packing experiments. Furthermore, irrigated packing experiments were also conducted. Result ...

CFD Study on the Local Mass Transfer Efficiency in the Gas Phase of Structured Packing

AbstractVisualization of local mass transfer coefficients over the dry surface of corrugated‐sheet structured packing is essential for optimizing the existing geometry of structured packing and for improving mass transfer efficiency to develop new structured packing. The local flow patterns between packing sheets and the gas‐phase mass transfer coefficient at each point over the surface are illustrated by employing a wall‐surface reaction model. Different turbulence models are utilized, i.e., a standard κ‐ϵ model and three different low‐Re‐κ‐ϵ models. The numerical calculation results with the Lam‐Bremhorst low‐Re‐κ‐ϵ turbulence model is found to agree well with experimental data. There are three similar regions with enhanced mass transfer efficiency in each mass transfer unit cell of structured packing.

Dry Pressure Drop Prediction within Montz-pak B1-250.45 Packing with Varied Inclination Angles and Geometries

Structured packings are used to increase the surface area and promote gas–liquid contact in many chemical processes, including carbon capture. Computational fluid dynamics and performance prediction methods have the ability to aid the optimization of the structured packing designs to aid the heat and mass transfer while minimizing the pressure drop. The present work introduces pressure drop correlations that determine frictional pressure loss between Montz-Pak B1-250.45 structured packing sheets based on the inclination angle and channel geometry of the sheets. CFD simulations are carried out on the packing and are validated against published experimental data.

Experimental Study on Local Mass Transfer of Structured Packing with the Method of Flow Visualization

A chromochemical reactive mass transfer technique has been employed to study local mass transfer characteristics of structured packing. This technology adopted by experiment is an Ammonia Adsorption Method (AAM) that yields the surface distribution of transferred mass by analyzing the color distribution on a filter paper with the results of the color chemical reaction. A digital image processing technology is applied for data visualization. The three-dimensional plot of the local mass transfer coefficients shows that there exist three peak values on different positions of a unit cell of structured packing. In order to improve mass transfer efficiency of the structured packing, one piece of baffle is added between packing sheets. As a result, the average mass transfer coefficient increases by (10-20)% and the pressure drop decreases by (15-55)%.

Modifications to Structured Packings to Increase Their Capacity

The hydraulic performance of structured packed columns is characterized by parameters such as loading point, flooding point, and dry and wet pressure-drop. These parameters can be positively influenced by optimizing the transition areas between two adjacent packing layers. Tests have been done in a two-phase test rig with a rectangular column made of perspex. The test medium is a liquid hydrocarbon in counterflow to saturated nitrogen gas. The performance of different packing structures at the layer-to-layer transition zone and the addition of vane-type elements between two packing layers was evaluated. Several packing modifications were tested and the results were compared with those of a non-modified packing. The intentions of this work are: to rank the modifications of structured packings with respect to the achieved capacity increase; to determine whether flooding is initiated in the core of the corrugated packing or in the transition area in spite of the modifications made on the lower or top side of the packing sheets; and to find out how the loading point is influenced by the modifications.

A study of black liquor oxidation in towers packed with asbestos cement plates

AbstractThe process of black‐liquor oxidation is treated theoretically and an equation is derived for design purposes. Capacity coefficients were determined experimentally for two different arrangements of asbestos‐cement packing sheets. Data include those obtained from a study of a full‐scale commercial oxidation unit as well as those from an investigation using a pilot‐scale experimental tower with a modified arrangement of asbestos‐cement packing. Results from the pilot‐scale study indicate that the modified packing yields higher capacity coefficients than the packing in the full‐scale unit although the mass‐transfer coefficients are very similar for both packings using the pilot‐scale tower under rigorously controlled flow conditions, it was found that the capacity coefficients increase with increase in liquor flow rate and are virtually unaffected by changes in air‐flow rate when this is sufficiently high to provide adequate oxygen for the reaction. The significance of the experimental results is discussed in detail.