Raschig Rings Research Articles

Significantly enhanced vapor-liquid mass transfer in distillation process based on carbon foam ring random packing

Applications using foam material as distillation column internals have been demonstrated higher performance than classical mass transfer units, except for the operation range. In this paper, the novel Foam Ring Random Packing (FRRP) made of Carbon foam material has been developed to overcome this disadvantage. The hydraulic performance and the mass transfer efficiency of FRRP are measured as 300 mm i.d. diameter column. The experimental values of FRRP are compared with the values of traditional ring random packing. In general, the comparison results indicate that the hydrodynamics and mass transfer performances of FRRP has been intensified by the foam materials (best HETP 0.24 m and additional 20% operation range). In order to explain the cause of intensification, flow behavior experiments were also carried out on both FRRP and Raschig ring packing. Special emphases on the effects of orientations, liquid flow rate and feed point on wetting area were investigated. Compared with other traditional random packing, the results show that the FRRP has some advantages, such as better extensive wetting area (maintain no less than 80%) and more uniform wetting distribution (fluctuate within 20%). Finally, an analysis of wetting process on single FRRP was presented to help understand the flow pattern on the packing. All results indicate that FRRP has outstanding performance, which will be a potential candidate used in distillation process.

Effect of Promoter Concentration on CO2 Separation Using K2CO3 With Reactive Absorption Method in Reactor Packed Column

The presence of carbon dioxide (CO2) in the gas is not expected because CO2 can reduce heating value and CO2 is the major emission contributor into the atmosphere. Various separation technologies can be used to reduce CO2 content and improve quality of gas. Chemical or reactive absorption is most widely used because it provides higher removal rate. This paper will study the effect of the addition di ethanolamine (DEA) concentration into aqueous 30wt.% potassium carbonate(K2CO3) with reactive absorption method in a reactor packed column at temperature from 40°C to 80°C, DEA concentration range of (1% - 3%) and absorbent flow rate (0.5, 0.75 and 1) L. min1. Contacting the gas and absorbent are countercurrent flow in packed column with 1.5 m high and 50 mm in diameter. The absorption column was randomly packed with a packing material raschig rings 5 mm in diameter. The CO2 loading in the liquid samples was determined by titration. It is found that the best result of CO2 loading is 0.065594 mole/mole K2CO3 and CO2 removal 28%. The result show that the loading capacity (mole CO2/mole K2CO3) and CO2 removal increased with the increase of DEA concentration.

Liquid distribution and holdup in the random packed column

In the present work, a third-generation gamma transmission tomography system was used to evaluate the liquid distributions of a Raschig rings random packed column, at two different water flows: 2 and 6l/min. For each water flow, the measurements were carried out at nine column heights. The liquid-gas holdup was determined by the reconstructed images. The distribution of the Raschig rings, as well as the position and the average accumulated amount of the water concentration among the Raschig rings were capable to be determined, even at low temporal resolution of the system of 8.8h. The regions of accumulated water concentration were similar for the water flow velocities at 2 and 6l/min. The average accumulated water concentration for 6l/min was higher compared to 2l/min. The spatial resolution of the tomography system determined by the modulation transfer function (MTF) analysis was of 1.45mm.

Enhanced visible light photocatalytic activity of Pt/I-TiO2 in a slurry system and supported on glass packing

Abstract Highly photoactive I/TiO 2 , Pt/I-TiO 2 nanocomposites were obtained using a hydrothermal and wet impregnation method. The incorporation of iodine and modification with 0.05 mol% of platinum leads to enhanced photocatalytic activity as compared to singly doped TiO 2 due to the presence of impurity energy level in the structure of TiO 2 . X-ray diffraction, TEM microscopy, UV–Vis spectroscopy, X-ray photoelectron spectroscopy and BET methods showed that the most active photocatalyst had anatase structure, 187 m 2 /g specific surface area, absorbed UV–Vis light and contained 3 nm platinum particles. XPS analysis revealed that iodine exists in the form of I ¯ and IO 3 ¯ species and platinum was present as Pt and PtO 2 . The photocatalytic activity of Pt/I-TiO 2 nanocomposite was maintained after 4 runs, suggesting stability and reusability of the obtained photocatalyst. The efficiency of degradation of model organic compound was measured in a slurry type photoreactor as well as in a fixed-bed photoreactor equipped with parabolic mirror with Pt/I-TiO 2 immobilized on glass beads or glass Raschig rings.

Effect of the Tower Type on the Gas Sweetening Process

The removal of acid gases, CO2 and H2 S from natural gas streams is essential for environmental and health reasons. In this work, the simulated gas sweetening unit with Methyl-DiEthanolAmine (MDEA) solvent was studied to improve quality. Firstly, the effect of trays types and then, the effect of various packing and the effect of the packing size were considered on the flow rate of CO2 and H2 S in the main streams. Results show that with considering the different trays types in the regenerator tower, the flow rate of CO2 in the sweet gas stream with bubble cap tray is lower than other trays types. Also, with considering the different trays types in the absorber tower, the flow rate of CO2 in the sweet gas stream with bubble cap tray is lower than other trays types in the absorber tower. In considering with different types of packing, results show that the flow rate of CO2 with ballast ring packing and the flow rate of H2 S with Raschig ring packing are lower than other types of packing. However, in some types such as cascade miniring, Intalox Saddles and pall ring, there is no difference for the flow rate of CO2 or H2 S. In all cases, with increasing the size of the packing, the flow rate of CO2 and H2 S in the sweet gas stream increases, however, this increasing in the metal packing is very small.

Pollutant degradation over dye sensitized nitrogen doped titania substances in different configurations of visible light helical flow photoreactor

Abstract Different nitrogen doped titania (N-TiO2) substances were synthesized, sensitized with hematoporphyrin (HP) and their thin films were fabricated on supporting structures. Two kinds of supporting, wire gauze structured packing and quartz Raschig ring random packing were utilized in a visible light, helical flow photoreactor. The HP/N-TiO2 nanohybrid powders, suspended in the solutions, were also prepared to compare their photocatalytic activity. Different techniques of SEM, TG–DTA, XRD, FT-IR, UV–Vis spectroscopy and elemental analysis were used to characterize the products. Methyl orange (MO) substrate was used as a model dye pollutant in aqueous solutions with measuring the level of degradation and TOC. The influencing parameters like the amount of sensitizing HP, nanohybrid dosage, film thickness and repetitive operating capability were investigated and optimum mild conditions were obtained. The process kinetic was well fitted by pseudo first order kinetic model and the electrical energy was drastically less than those reported for other similar processes. Among the employed configurations, the random packing showed the highest efficiency and the lowest energy consumption. Meanwhile, the HP/N-TiO2 with 3 mM initial concentration of HP represents a potential alternative for the treatment. Comparison with similar processes represents the superior performance of the process.

The effect of packing on direct contact evaporation in spray column

AbstractThe direct contact evaporation in countercurrent spray column has been experimentally investigated. Two kinds of random packing were added into the column independently to study their influence on heat transfer process. Three different continuous phase flow rates (150, 200, 250 L/h) and two different dispersed flow rates (6.565, 13.13 L/h) were used in the experiment. The inlet continuous phase temperature ranged from 42 to 57 °C, and the inlet dispersed phase temperature was near its boiling point. The effect of variable factors on the optimal column height, the volumetric heat transfer coefficient, the pressure drop, and the thickness of foam layer were studied. The results showed that packing had positive effects on heat transfer, such as decreasing the optimal column height and the thickness of foam layer, increasing heat transfer coefficient. But extra pressure was also obvious. Dixon rings performed better than Raschig rings in the experiments due to their finer structure.

Hydrodynamic Characteristics of Mini-Ring Truncated-Cone Packing

Results from hydrodynamics tests of mini-ring truncated-cone packing are presented. A relationship for calculating the hydraulic resistance of the new packing design is proposed. It is shown that the hydraulic resistance of the new packing at gas flow rate ω0 = 0.8 m/sec is 40% less than for Raschig rings (50 × 50 mm).

Tritium Water Distillation Assisted with Adsorption and Isotopic Exchange

Water distillation packed with materials having adsorption ability is proposed for wastewater detritiation, and behavior of HTO depletion or enrichment is experimentally investigated. It is proved that the apparent volatility ratio of H2O-to-HTO is increased by an isotopic effect on adsorption under a steady-state operation. Danckwerts’ surface renewal model is applied to explain the T enrichment process in a lab-scale water distillation column. The effect is estimated in terms of an adsorption enhancement factor included in the T separation factor, εHT,ad, which depends on the kinds of adsorbents and liquid-vapor flow conditions. The value of the enhancement factor is also confirmed εHT,ad = 1.02 in a comparatively large-scale distillation operation packed with Sulzer packing or Raschig ring coated with zeolite adsorbent. A large-scale distillation tower can be designed to detritiate radioactive wastewater generated in Fukushima’s Daiichi NPS based on the present experimental results.

The influence of water content in imidazolium based ILs on carbon dioxide removal efficiency

The study of CO2 absorption in ionic liquids: [Emim] [Ac], [Bmim] [Ac] and 15 wt.% MEA solution in bubble reactor and packed bed column is presented. Bubble glass reactor with a capacity of 2 dm3 and absorption column of inner diameter 0.05 m and 0.3 m length filled with Raschig rings ϕ5 × 5 × 1 mm were used. The influence of absorption temperature and water content in ILs on CO2 removal efficiency was investigated at atmospheric pressure what is important in the case of post combustion flue gases. In calculations the resistance in series model of the absorption process was applied. The estimated values of enhancement factor of the reaction between CO2 and investigated liquids were used to predict mass fluxes of absorbed carbon dioxide for ILs with water content 2–10 wt.%. The comparison of experimental and calculation results show that in the same experimental conditions investigated ILs and MEA solution have comparable CO2 absorption capacities while mass transfer coefficients in the case of ILs are significantly lower than for MEA solution. The small content of water in IL (2–5 wt.%), inevitable in continuous cyclic use of IL in industrial conditions, may be profitable in reducing high viscosity of ILs and increasing mass transfer rate.

Transient Behavior in Water Distillation Tower for Tritium Separation and Its Long-Time Operation Test Results

Transient separation behavior in tritiated water distillation tower packed with materials having ability to adsorb water is investigated analytically and experimentally for nuclear reactor safety. Analytical equations based on the stage model are set up for simulation of the transient behavior of tritium (T) separation from wastewater. It is found that a dimensionless time defined in terms of the inside vapor flow rate and the liquid holdups in tower, reboiler and condenser can correlate variations over time to achieve a steady-state T concentration. However, when mixing with different T concentrations at a feed point occurs, the transition time period becomes longer than expected. Effects of the reflux ratio, the stage separation factor and the total stage number on the transient and steady-state T concentrations are numerically calculated. Variations over time to achieve each steady-state value are compared with experimental data using a small-scale tower. Long time distillation experiment for one month has been completed, and it is confirmed that a distillation column packed with ceramic Raschig rings coated with zeolite 13X adsorbent is hardly affected by water corrosion.

Suspended and Immobilized TiO2 Photocatalytic Degradation of Estrogens: Potential for Application in Wastewater Treatment Processes

This work evaluated the photocatalytic activity of suspended TiO2, and TiO2-coated glass Raschig rings with respect to degradation of estrogens estrone (E1), 17β-estradiol (E2), and 17α-ethinylestradiol (EE2) in aqueous solutions and wastewater effluent samples. Gas chromatography/tandem mass spectrometry (GC-MS/MS) studies were carried out to identify degradation products for EE2. TiO2 suspensions allowed degradation rates higher than 90% for all studied estrogens in 30 min for an artificial (ultraviolet A) UVA-assisted process and aqueous solution. Immobilized TiO2 showed less favorable degradation kinetics, requiring ca. 60 min to achieve almost complete estrogen degradation. Some derivatized degradation products were identified for the first time by GC-MS/MS applying ultraviolet C (UVC) photolysis and TiO2/UVA photocatalysis. A degradation route was suggested for EE2 in UVC photolysis and TiO2/UVA processes. In the degradation of pretreated sewage samples, the immobilized TiO2 was more efficient than free TiO2, allowing ca. 85% removal of E2 and EE2 in 60 min.

An interfacial heat transfer in a countercurrent gas–liquid flow in a trickle bed reactor

The paper is devoted to interfacial heat exchange between gas and liquid flowing countercurrently through a packed bed in a trickling flow regime. The lack of correlations describing the interfacial gas-liquid heat transfer coefficient makes problems when numerical models of non-isothermal flows in porous media are being developed. Thus the experimental investigation was undertaken with the use of a column of 0.1m inner diameter, equipped with 6mm glass Raschig rings. Air and water were used as working fluids. The loads of media ranged between 0.0177–0.1415m3·(m2s)−1 and 0.0007–0.0053m3·(m2s)−1 for gas and liquid phases, respectively. The inlet water temperature was changed within the range between 30°C and 70°C whereas the inlet air temperature was kept constant at the level of (21±1)°C. It was found that interfacial heat transfer coefficient is strongly dependent on the gas load, noticeably dependent on the temperature difference between phases and slightly dependent on the liquid load. The results of the experiment were used to develop a new correlation describing the interfacial heat transfer in the packed bed expressed by the Nusselt number. Various group numbers were considered in order to account for the impact of gravity, surface tension, thermal diffusion and free convection on the interfacial heat transfer. After detailed regression analysis the correlation of the form Nu=ReG1.169·GaG-0.8399·Eo¨0.7176 was finally proposed as the most fitting the experimental data.

Synthesis of Biokerosene through Electrochemical Hydrogenation of Terpene Hydrocarbons from Turpentine Oil

Indonesia possesses great potential for developing renewable resources as alternative fuels. For example, turpentine oil obtained from Pinus merkusii , which contains mostly monoterpene hydrocarbons (C 10 H 16 ). The oil is highly suitable to be processed for biokerosene or even jet biofuel. It consists of hydrocarbons within the range of C 10 to C 15 . However, it contains insufficient H and thus needs to be upgraded. In the present work, electrochemical hydrogenation was used for upgrading. In the electrochemical cell, stainless steel, silver, and carbon were used alternately for the anode, while copper and silver Raschig rings were used for the cathode. An electrolyte solution of cuprous ammonium formate was utilized not only as a source of H but also to draw the unsaturated hydrocarbons into the aqueous phase. The electrolyte : oil ratio (up to 2:1), electrolyte concentration (between 0.4 and 2 M) and reaction time were varied throughout the experiments. The bromine number (unsaturation level) of the turpentine oil, which was initially 1,86 (mole Br 2 /mole), was lowered significantly to 0.69-0.90. Promising increase of smoke point values were observed from 11 mm to 16-24 mm, indicating a higher H content of the processed oil, thus making it suitable as a substitute for petroleum kerosene.

Numerical simulation of a gas flow in a real geometry of random packed bed of Raschig rings

In the article, a model is proposed for a single-phase flow in a random packed bed of arbitrary particles – Raschig rings in particular. The Navier-Stokes flow equations are solved using a projection method on a structured grid and the complex geometry of the bed is captured with the immersed boundary method and direct forcing approach. The model allows for analysis of flows in complex geometries with classical and widely available finite volume or finite difference solvers for Cartesian grids. The generation of unstructured computational grids fitted to the bed particles is not necessary. The realistic bed geometry has been obtained in the simulation of the filling process in which the particles are sequentially introduced into a cylindrical container and move until mechanical equilibrium is attained. The pressure drop in the bed as the function of gas velocity has been found to be in good agreement with empirical formulas for beds of Raschig rings and sample results on detailed flow characteristics are presented.

Impact of Different Packing Materials on Hydrogen Sulfide Biooxidation in Biofilters Installed in the Industrial Environment

Three pilot scale anoxic biotrickling filters containing different packing materials were built and tested over an extended period in the municipal wastewater treatment plants (WWTP). Performance of biological beds containing polyethylene elements, ceramic Raschig rings, and keramzite particles was investigated at hydrogen sulfide concentrations in biogas ranging from 369 to 1733 mg/m3. The dependence of the number of colony forming units on hydrogen sulfide concentration and location in the bed was determined. Microbial enumeration was performed for all three columns using cultivation methods. The best results of desulfurization were observed for polyethylene elements. For this material the optimum empty bed retention time was 12 min and the minimum concentration of nitrate ions in a nutrient solution was 50 mg/L. The hydrogen sulfide reduction over 99% was achieved at loading rates (LR) of 1.79–5.08 g/m3/h. The increase in LR to 8.45 g/m3/h reduced the removal efficiency to 96%. The results of kinetic a...

Experimental study of gas-liquid heat transfer in a 2-phase flow in a packed bed

The paper deals with an interfacial heat exchange between gas (air) and liquid (water) flowing countercurrently through a packed bed. The experimental investigation was performed with the use of column of 0.1 m inner diameter and filled in with glass Raschig rings. Loads of working media ranged between 0.018÷0.142 m3(m2s)-1 and 0.0007÷0.0053 m3(m2s)-1 for gas and liquid phases, respectively. It was found that interfacial Nusselt number is mainly dependent on the gas load, noticeably influenced by the temperature difference between phases and practically independent of the liquid load.

Kinetic Studies on an Algal Biofilm Reactor for Raw Sewage Water Treatment

AbstractA packed‐bed algae biofilm reactor was developed using porous and nonporous dual packings. The biofilm was cultivated on reticulated polyurethane foam cubes. The nonporous glass Raschig rings were taken as bed support that helps to remove generated gas from the system. The effect of variables such as column length‐to‐diameter ratio, catalyst cube dimension, and feed flow rate on the treatment of sewage water was studied. The reaction kinetics indicates that the nutrients uptake rate is dependent on both pore and film diffusion. The kinetics of uptake of nutrients follows a pseudo first‐order reaction. From the pseudo reaction rate constant, Thiele modulus and effectiveness factor were calculated and a kinetic model equation for fractional nutrient uptake was developed in terms of operating variables. The model can predict the reaction rate with low deviation. The results obtained may be valuable for large‐scale treatment of sewage water.

Removal of Pb(II) in a packed-bed column by a Klebsiella sp. 3S1 biofilm supported on porous ceramic Raschig rings

The purpose of this work was to confirm the effectiveness of the bacterium Klebsiella sp. 3S1 for the removal of lead ions from aqueous solution in a fixed-bed column. The results provided evidence that the bacterial biofilm formation on the support clearly improved the lead biosorption capability of the system. FTIR, SEM and TEM techniques provided factual evidence of the role of the bacterial biofilm on lead biosorption and the different mechanisms involved, such as cell surface binding and cytoplasmic bioaccumulation.The dynamic behavior of the column in continuous mode was well-established through breakthrough curves, with experimental data fitting using different mathematical models, especially the Yang model. Up to 70mg of lead was retained per gram of microbial biofilm in each cycle without loss of biosorption capacity compared to previous work in batch mode. In addition, the bacteria maintained their effectiveness when the cells were inactivated after acid desorption cycles. The column was reused four times after biosorbent regeneration with an elution efficiency of 99% showing that it is appropriate for industrial applications. The use of a Klebsiella sp. 3S1 biofilm immobilized on a porous support in commercial biofilters for the removal of heavy metals from wastewater could be a competitive option.

ETHANOL DEHYDRATION IN PACKED DISTILLATION COLUMN USING GLYCEROL AS ENTRAINER: EXPERIMENTS AND HETP EVALUATION

The ethanol-water separation is very important because ethanol is widely applied in the chemical industry and its use as a fuel can reduce the pollution emitted to the air. However, anhydrous ethanol production using conventional distillation is impossible, at atmospheric pressure, due to the presence of an azeotrope. In the present work, experimental tests were carried out in order to evaluate the use of glycerol as an entrainer, in substitution of ethylene glycol in an extractive distillation. The use of glycerol is motivated by the biodiesel production units, due to the fact that it is the main byproduct and a new market is necessary to consume its overproduction. The experiments were carried out in a distillation column packed with Raschig rings, varying the glycerol/feed (ethanol and water) ratio, S/F, from 0.5 to 0.9. The samples were analyzed using a digital densimeter. The results showed that glycerol was effective to promote ethanol dehydration and the presence of an azeotrope was not observed using a solvent to feed ratio (S/F) equal to 0.9. Some empirical correlations were investigated to evaluate the HETP (Height Equivalent to a Theoretical Plate), and the results provided a useful tool for designing a packed bed column for ethanol-water separation.