Structured Packing Materials Research Articles

Root cause analysis for 410 S stainless steel structured packing failure in vacuum distillation column (case study)

A root cause analysis was conducted on the premature failure of 410 S stainless steel structured packing material in a vacuum distillation column. The multidisciplinary team identified four potential causal factors that could contribute to the failure, including: low temperature corrosion, high temperature attack, design aspects and operational parameters. For each causal factor, sub-factors were determined and classified as primary contributor, secondary contributor and noncontributor. The analysis revealed that low temperature chloride condensation in the tower top bed led to severe hydrochloric acid corrosion while high temperature coking in the lower beds led to intergranular cracking of the stainless steel. Also, the 0.1 mm packing material thickness used was not sufficient to obtain a 10–15 years design life. Recommendations include changes to the operating parameters to prevent condensation and coking as well as mechanical design modifications to get acceptable lifetimes.

A Facile Route to Synthesize Micron Size Nearly Spherical Mesoporous Silica Particles

AbstractFor many applications as structured packing material, the micron size spherical silica particles with the bicontinuous mesoporous structures are required. Herein, we report a facile route to synthesize the micron size nearly spherical mesoporous silica (MSNSMS) particles. The chitosan is crucial in the synthesis strategy as an adjuvant agent to facilitate the formation of the micron size nearly spherical particles. The MSNSMS particles demonstrate narrow mesopore and particle size distributions with the average particle sizes at 3.6 μm (MSNSMS‐0.5) or 4.7 μm (MSNSMS‐1). The MSNSMS samples possess the large ordered domains of pure bicontinuous mesoporous structure with the interpenetrating cylindrical pores at about 8 nm in diameter. The MSNSMS particles are promising structured packing material candidate for catalyst support applications.

Effect of Packing Structure on CO2 Capturing Process

The increasing concentration of carbon dioxide (CO2) in the atmosphere is a primary global environmental concern due to its detrimental impacts on climate change. A significant reduction in CO2 generation together with its capture and storage is an imperative need of the time. CO2 can be captured from power plants and other industries through various methods such as absorption, adsorption, membranes, physical and biological separation techniques. The most widely used systems are solvent based CO2 absorption method. The aim of this study was to analyze the effect of various random and structured packing materials in absorption column on CO2 removing efficiency. Aspen plus was used to develop the CO2 capture model for different packing materials with Monoethanolamine (MEA) solvent in order to optimize the system. It was found that the lowest re-boiler duty of 3,444 kJ/KgCO2 yield the highest rich CO2 loading of 0.475 (mole CO2/mole MEA) by using the BX type of structured packing having the highest surface area. The surface area of the different packing materials were inversely proportional to the temperature profiles along the column. Furthermore, the packing materials with higher surface areas yielded higher CO2 loading profiles and vice versa. The findings of this study and recommendation would help further research on optimization of solvent-based CO2 capturing technologies.

Preparation of NbOx/SiO2-coated structured packing material and it's catalytic performance in the gas-phase Beckmann rearrangement of cyclohexanone oxime to ε-caprolactam

Potential industrial applicability of a NbOx/SiO2 catalyst material was strongly improved by fixing μm-particles onto a structured packing. The granular catalyst displays a high catalytic performance in producing ε-caprolactam via gas-phase Beckmann rearrangement. However, applicability is strongly hampered because a high linear gas velocity and a small particle size are necessary to avoid diffusion limitations. These requirements would lead to an unacceptably high pressure drop in an industrial reactor. The novel NbOx/SiO2 structured packing catalyst displays, at high WHSV in a tube reactor, a constant high ε-caprolactam yield (96%) for at least 32h time-on-stream, without any indication of deactivation.

Physical–chemical properties of gas–liquid contactors in packed absorption column

The burning of combustible material that produces emissions released to the atmosphere results in unfavorable climate change due to emissions of CO2, NOx, and acid rain by SOx, endangering the health of the population. The treatment of combustion gases by means of a packed absorption column with a high-efficiency liquid–gas contactor material reduces pollutant emissions to the atmosphere, where combustion gases make contact with aqueous amine solution of mono ethanol amine (MEA), using different structured packing materials which can be metallic, polymeric, or ceramic. The objective of this work is to study which one of these three types of materials of gas–liquid contactors presents the lowest deterioration in the presence of combustion gases flowing countercurrent to MEA. The materials were evaluated according to the Standard Test Methods ASTM G31-2004 for corrosion testing, ASTM E8-1998 for tension testing, ASTM E384-1990 for microhardness testing, ASTM G5-1999 for potentiodynamic and potentiostatic testing, and the procedure of NRF-194 PEMEX-2007. The properties studied were the tensile strengths, the hardness values, and the elastic moduli, before and after structured packing materials made contact with combustion gases in MEA aqueous solution. The results showed that in acidic and basic mediums, the metallic material was the most resistant to abrasion; it has the highest tensile strength, and presents more resistance during the stress test. The hardness results for the materials were metallic: 190 KH, polymeric: 20 KH, and ceramic: 700KH. The respective corrosion resistances in the presence of MEA were 1.63 × 10−3, 3.76 × 10−3, and 1.42 × 10−2 mm/year.

Meso-scale CFD study of the pressure drop, liquid hold-up, interfacial area and mass transfer in structured packing materials

This work presents a meso-scale CFD methodology to describe the multiphase flow inside commercial structured packings for post-combustion CO2 capture.Meso-scale simulations of structured packings are often limited in the literature to dry pressure drop analyses whereas mass transfer characteristics and gas–liquid interface tracking are usually investigated at micro-scale. This work aims at testing further capabilities of meso-scale modeling by implementing the interface tracking instead of analyzing only the dry pressure drop performance with single-phase simulations.By doing so, it is possible to present also the hydrodynamics (i.e. liquid hold-up and interfacial area) for a small set of representative elementary units (REUs). The interest in interface tracking using commercial geometries lies on the fact that liquid hold-up and interfacial area have implications of capital importance on the overall performance of the absorber, hence the importance of developing a model to predict them accurately.The results show how the relationship, reported in the literature, between the liquid load and both the liquid hold-up and the interfacial area is reproduced by the present CFD methodology. Also, a more realistic visualization is accomplished with images of the inner irregularities of the flow (i.e. liquid maldistribution, formation of droplets and rivulets, etc.), which lie far from the prevailing assumption of the formation of a perfectly developed liquid film over the packing.Moreover, the effect of operating parameters such as the liquid load, liquid viscosity and liquid–solid contact angle on the amount of interfacial area available for mass transfer is also discussed.Finally, mass source terms are also included to describe the gas absorption into the liquid phase hence testing all the capabilities of micro-scale modeling at meso-scale. The present model could be further used for the analysis and optimization of other structured packing geometries.

Characteristics of Absorption/Regeneration of AMP/MEA Using Hybrid Packing for the Improvement of CO2 Absorption Performance

The development of new packing materials and absorbents for use in CO2 recovery is urgently needed as a means of reducing greenhouse gases. In this study, we evaluated the absorbents 2-amino-2-methyl-1-propanol (AMP) and monoethanolamine (MEA) in combination with random packing materials (ceramic Raschig rings and Berl saddles) and a structured gauze packing material. To improve the CO2 absorption efficiency, we developed hybrid packing materials comprising Raschig rings and the structured packing material in various ratios. The effects of the ratio on the gas flow rate, absorbent liquid flow rate, and CO2 absorption/regeneration efficiencies over time were evaluated. The overall mass-transfer coefficients were also calculated. The height of the tower corresponding to one theoretical plate in the absorptive tower design and the available gas–liquid contact area were calculated. This fundamental research will help support efforts to improve the efficiency of CO2 absorption from various industrial exhaust streams.

Micro-scale CFD modeling of reactive mass transfer in falling liquid films within structured packing materials

Post-combustion carbon capture in structured packing columns is considered as a promising technology to reduce greenhouse gas (GHG) emissions because of its maturity and the possibility of being retrofitted to existing power plants. CFD plays an important role in the optimization of this technology. However, due to the current computational capacity limitations, the simulations need to be divided into three scales (i.e. micro-, meso- and macro-scale) depending on the flow characteristics to be analyzed. This study presents a 3D micro-scale approach to describe the hydrodynamics and reactive mass transfer of the CO2-MEA chemical system within structured packing materials. Higbie's penetration theory is used to describe the mass transfer characteristics whereas enhancement factors are implemented to represent the gain in the absorption rate attributable to the chemical reaction. The results show a detrimental effect of the liquid load on the absorption rate via a decrease in the enhancement factor. The evolution of the wetted area for MEA solutions is compared to the case of pure water highlighting the differences in the transient behavior. The CO2 concentration profiles are examined showing the capability of the model to reproduce the depletion of the solute within the bulk liquid ascribed to the high value of the Hatta number. Also, several approaches on the reaction mechanism such as reversibility and instantaneous behavior are assessed. The results from micro-scale are to be used in meso-scale analysis in future studies to optimize the reactive absorption characteristics of structured packing materials.

Structured Packing Evaluation in Sour Gases Treatment from Kiln Emissions

The burning of pieces manufactured with clays to be used in the construction industry, contributes to environmental imbalance because it contains combustible materials that produce emissions released in the atmosphere. Up to now kilns have been used with combustion processes precarious and fuels highly polluting, which favor climate change emissions for CO2, NOx and acid rain by SOx, endangering the health of those living near these facilities. The treatment of combustion gases by means of a packed absorption column with a high efficiency liquidgas contactor reduces pollutant emissions to the atmosphere, when combustion gases are in contact with aqueous amine solution of Mono Ethanol Amine (MEA). The objective of this work is to study which one of three materials presents the lowest deterioration in the presence of combustion gases with MEA. The materials were tested according to American Society for Testing Materials ASTM G31-2004 corrosion testing, and the procedure NRF-194 PEMEX-2007. The properties studied were tensile strength, hardness and elastic modulus, before and after structured packing materials were in contact with combustion gases in MEA aqueous solution. The results showed that in acid and basic medium, the metallic material was the most resistant to abrasion; it has the major tensile strength, and presented more resistance in the stress test.

Modelling mass transfer properties in a biotrickling filter for the removal of isopropanol

A study was carried out to model mass transfer properties in biotrickling filters, treating isopropanol as the target pollutant. This study was extended to the mass transfer of oxygen related to the fact that the treatment of hydrophilic compounds by biotrickling filtration is often limited by oxygen. A simple method for each compound was developed based on their physical properties. The influence of temperature on Henry’s law constant of isopropanol was determined. An increase of 1.8 per 10°C for the dimensionless Henry’s law constant was obtained. The determination of the overall mass transfer coefficients of isopropanol (KGa) was carried out, obtaining values between 500 and 1800h−1 for gas velocities of 100 and 300mh−1. No significant influences were observed for either the liquid velocity or packing material. Also, the determination of overall mass transfer coefficients of oxygen (KLa) were carried out, obtaining values between 20 and 200h−1 depending on the packing material for liquid velocities between 2 and 33m h−1. Structured packing materials exhibited greater mass transfer coefficients, while for random packing materials, the mass transfer coefficients clearly benefited from the high specific surface area. Mathematical correlations found in the literature were compared with the empirical data, showing that neither was capable of reproducing the mass transfer coefficients obtained empirically. Thus, empirical relationships between the mass transfer coefficients and the gas and liquid velocities are proposed to characterise the system.

Operational aspects, pH transition and microbial shifts of a H2S desulfurizing biotrickling filter with random packing material

Pall rings, a common random packing material, were used in the biotrickling filtration of biogas with high H2S. Assessment of 600d of operation covered the reactor start-up, the operation at neutral pH and the transition from neutral to acid pH. During the start-up period, operational parameters such as the aeration rate and the trickling liquid velocity were optimized. During the steady-state operation at neutral pH, the performance of the random packing material was investigated by reducing the gas contact time at both constant and increasing H2S loads. The random packing material showed similar elimination capacities and removal efficiencies in comparison with previous studies with a structured packing material, indicating that Pall rings are suitable for biogas desulfurization in biotrickling filters. The diversity of Eubacteria and the structure of the community were investigated before and after the pH transition using the bacterial tag-encoded FLX amplicon pyrosequencing. The pH transition to acid pH drastically reduced the microbial diversity and produced a progressive specialization of the sulfur-oxidizing bacteria community without any detrimental effect on the overall desulfurizing capacity of the reactor. During acidic pH operation, a persistent accumulation of elemental sulfur was found.

Experimental Evaluation of Mass Transfer Coefficients from Sour Gas

AbstractThe degree of CO2 absorption by monoethanolamine (MEA) using metal structured packing material, ININ18, was studied. The aqueous solution contained 30 wt‐% MEA in countercurrent with CO2 flue gas. The capture process was carried out in an absorption column with dimensions 4.0 m in height and 0.3 m in diameter. The mass transfer coefficient and height of mass transfer were evaluated. Results show a volumetric mass transfer coefficient of 3.76 s–1, a height of mass transfer equivalent unit of 0.317 m, and an absorption efficiency of 90 % from flue gas.

Study of the Corrosion Rate of Three Contactors Materials Using the Electrochemical Technique of Tafel

The main objective of this project was to study the corrosion rate of three different structured packing materials, a metallic, one polymeric and the other one ceramic, which will be in contact with an aqueous solution of MEA (monoethanolamine) to 30% and sour gases in a countercurrent absorption column. The materials were studied in two electrochemical cells: the first one in the presence of an aqueous solution of 1N sulfuric acid, and the second in the aqueous solution of MEA 30%, the study was done using the Tafel extrapolation methods and resistance to the polarization to measure the corrosion current (I Corr), and determine the corrosion rates of the three materials structured packings. The standard procedure used was according to ASTM G59-91, following the technique ININ No. P. SC (Cl) -06, the following results were found: in the presence of 1N sulfuric acid solution the metallic material presented a rate of 7.8 x 10-4 corrosion mpy (miles per year), the polymeric material submitted a corrosion rate of 2.82 x 10-4 mpy, and the ceramic material presented a corrosion rate of 1.03 x 101 mpy. With the aqueous solution of MEA at 30% in weight, and the sour gases the results were as follows: the metallic material presented a corrosion rate of 6.42 x 10-2 mpy, the polymeric material submitted a corrosion rate of 1.48 x 10-1 mpy and the ceramic material presented a corrosion rate of 5.6 x 10-1 mpy. These results provide a basis for predicting the lifetime of the three materials, as well as chemical resistance in the absorption column. Finally, we examined the morphology of the etched surface by scanning electron microscopy and found that in the metallic material was formed a layer of Cr2O3, which is helping the passivating material to further protect the acid attacks, the polymer material has a surface smoother after the attack and in the ceramic is observed pores larger than those observed in the material before the attack.

Performance of TS-1-Coated Structured Packing Materials for Styrene Oxidation Reaction

Titanium silicalite-1 (TS-1)-coated on stainless steel packing rings of complex geometries provided a large interfacial contact area for improving mass transport processes. Zeolite seeds were assembled using organic linker, and a thin uniform layer of TS-1 catalyst was deposited on the surface by hydrothermal regrowth. The chemical, structural, and catalytic properties of the TS-1 layer were examined. An order of magnitude higher styrene conversion rate was obtained from the TS-1-coated substrates compared with powder. The catalyst was sensitive to pretreatment, and heat treatment in nitrogen provided a 30% higher conversion rate than the air-calcined samples. The N2-pretreated catalyst displayed lower activity loss and better regenerability.

Integrating a full carbon capture scheme onto a 450 MW e NGCC electric power generation hub for offshore operations: Presenting the Sevan GTW concept

Sevan Marine and Siemens have developed a floating power plant – entitled Sevan GTW (gas-to-wire) – based on Sevan’s cylindrical platform and Siemens’ SCC-800 combined cycle, and SINTEF has adapted a post-combustion CO 2 capture process for on board integration including compression and preconditioning of the CO 2. Main emphasis has been placed on developing an optimised conceptual design within the structural constraints, and assessing how efficient the capture unit may be operated in consideration of the dynamic behaviour induced by the sea on the absorber and desorber columns via the floating carrier. The rational behind this technology selection is the urgency in making appropriate steps for a quick start for remote power generation at sea with the inclusion of CCS to serve offshore oil and gas operations. This calls for modular power blocks made up by high efficient combined power cycles with post-combustion exhaust gas cleaning. From this point of view a system with four absorption columns and one desorber unit has been determined based on structured packing material. The capture process has been integrated with the power cycle in due consideration of the sea forces. It is shown that a permanent tilt becomes more important than periodic movements provided the harmonic periods are kept within a certain level (<20 s). Operational conditions and constraints vis-à-vis movements and trimming of the floater have been addressed and discussed with reference to available literature. This also includes the liquid hold-up and gas–liquid interfacial area in the absorption columns linked with tilting. Optimisation reveals that a reboiler duty of 3.77 GJ/ton CO 2 would result in the lowest capture cost. With a energy penalty of 9%-points the Sevan GTW concept presents itself as a realistic concept deemed to be within reach today.

Effect of hollow fiber morphology and compatibility on propane/propylene separation

With a large specific area, micro-porous membranes in the geometry of hollow fibers become attractive materials for providing an effective contact area between two phases (e.g. liquid–gas and liquid–liquid). In this study, we used hollow fibers as structured packing materials in the propane/propylene distillation. We investigate the effects of morphology and compatibility of hollow fibers on separation efficiency and operation stability in the distillation process. While a hydrophobic micro-porous membrane may seem preferable for this application, an asymmetric membrane with sub-micron pore size on the liquid side may be more suitable for long-term stability of the distillation operation. A stable operation zone without flooding and loading problems is obtained when the pressure drop across the membrane is in a certain range. Typically, the high separation efficiency (HTU < 30 cm) is obtained when the tested modules are operated inside this stable zone.

Liquid Flow Behavior in Catalyst-Containing Pockets of Modular Catalytic Structured Packing Katapak SP

An element or section of Katapak-SP, a modular catalytic structured packing material (MCSP), consists of catalyst-filled pockets separated by one or more corrugated sheets of a large specific area, high capacity structured packing. Full active wetting of catalyst particles contained in catalyst-filled pockets is essential for its reactive performance. In this study the liquid-phase residence time distribution in catalyst-filled pockets of Katapak-SP was determined as a function of the superficial liquid load. The liquid load corresponding to full saturation of the pockets appeared to be the best condition for the flow pattern within the pocket. Then in an MCSP, reaction occurs at best flow condition. The liquid in excess is rejected and descends in the separation section of the element. Due to the difference in porosities, the residence times in the pocket and the separation part of the catalytic packing differ significantly. However, the liquid streams from pockets and separation compartments mix and redistribute at the transitions between rather short packing elements, and this ensures a relatively good overall performance, which can be manipulated to some extent by changing the ratio of catalytic to separation sections. The best performance of MCSPs is at liquid loads just above the catalytic load point with corresponding vapor loads around hydraulic loading.

Improve efficiency of thermal regenerators and VOCs abatement systems: An experimental and modeling study

Thermal regenerator systems are very effective devices for the abatement of volatile organic compounds (VOCs), mainly in industrial processes with high flow rates. In these units, VOCs are usually converted with air to CO 2, H 2O and usable heat. Thermal regenerators consist of two or more beds containing ceramic materials. Alternatively one bed absorbs and stores the heat from the hot gases while the other heats up an entering stream of raw gases. The regenerators allow to clean and purify raw gases, recovering the combustion heat. The optimization of the process reduces the amount of auxiliary fuel, minimizing operating costs. Thermal performances of the regenerator are investigated experimentally and numerically in this work. A one dimensional, two phases, dynamic model has been developed and validated on the basis of a properly designed set of experiments. In this way, it is possible to compare the thermal efficiency and pressure drops of different structured packing materials in different operative conditions. The role of dwell time, flow rate, specific area and heat capacity is analysed, mainly in terms of cyclical temperature conditions, with specific attention to the thermal efficiency of the unit. Moreover, the coupling of the regenerator model with a general and detailed kinetic scheme of pyrolysis and combustion of hydrocarbon species is also discussed and some preliminary simulations of VOCs abatement are also presented. This model is a very useful tool not only to evaluate the conversion level of different pollutants but also to prevent detrimental ignition processes inside the bed.

Steady-state and transient-state performance of a biotrickling filter treating chlorobenzene-containing waste gas.

Biotrickling filter (BTF) technology was applied for the treatment of waste gas containing a mixture of chlorobenzene and 1,2-dichlorobenzene. An adapted microbial community was immobilised on a structured packing material. The strategy followed was to reach high removal efficiencies at initially low mass loading rates followed by an increase of the latter. This procedure was successful and resulted in a short start-up period of only 2 weeks. A 3-month operation under steady-state conditions showed good performance, with >95% removal efficiency at a mass loading rate of 1,800 g m(-3) day(-1). Dimensionless concentration profiles showed that the chlorobenzenes were simultaneously degraded. Low dissolved organic carbon of 15 mg l(-1) and stoichiometric chloride concentrations in the trickling liquid indicated complete mineralisation of the pollutant. Transient-state experiments with five times higher mass loading rates caused a decrease in the removal efficiency that recovered rapidly once the mass loading rate returned to its original steady-state level. A progressive increase of the mass loading rate in a long-term performance experiment showed that the removal efficiency could be kept stable between 95 and 99% at loads of up to 5,200 g m(-3) day(-1) over several days. Above this mass loading rate, the elimination capacity did not increase any further. These results demonstrated that with a well-adapted inoculum and optimal operation parameters, a BTF system with excellent performance and stability that efficiently removes a mixture of chlorobenzene vapours from air can be obtained.

Prediction of pressure drop in a packed bed dehumidifier operating with liquid desiccant

In this paper a more rigorous model, which is valid for both structured and random packing columns, is used for predicting the irrigated pressure drop in a desiccant–air contact system. Calcium chloride solution is considered as the desiccant. Four different random packing materials and three different structured packing materials are considered in the present study. The effects of random packing shape and the type of structured packing on the hydraulic performance are studied. The model has been validated for a wide range of operating values available in the literature. It is found that the structured packing has the lower pressure drop and higher capacity compared with random packings. Among the random packing materials considered in the present study, Intalox saddles can provide the least irrigated pressure drop and among the structured packing materials the sheet-type Mellapak 250 Y has the lowest pressure drop.