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Oxidative scrubbing using different oxidizing chemicals (e.g. sodium chlorite, NaClO2) has been proposed since several years for gas emissions control. Although higher performances than conventional after-Treatment process currently in use can be reached, these technologies have not yet found a consolidated application in the power generation and other industrial fields, due to excessive chemical consumption and the formation of some harmful contaminants in the wash water that must be removed with specific treatment systems. This work reports an experimental investigation of an oxidative wet scrubber for NOx removal from a simulated flue-gas containing 1030 ppmv of nitrogen oxides, using a scrubbing liquid doped with sodium chlorite (NaClO2) as oxidizing chemical. The experiments are performed in a packed column operating in countercurrent flow with a constant gas velocity of 1.15 m/s at 60 °C and a liquid-To-gas ratio variable from 1.25 to 4.06 L/m3. The packed column with a DN 100 is equipped with 892 mm of Mellapak 250.X packing. The experimental removal efficiencies of NOx are evaluated in function of the liquid flow rate and NaClO2 loading. These data allow to determine the specific NaClO2 dosage required to achieve a fixed NOx removal. Finally, a predictive correlation for wet oxidative scrubbing is also developed.

Flue Gas Desulphurization (FGD) is a key topic for most of combustion fossil fuel plants and industrial applications. Wet processes are usually preferred when the removal efficiency required to comply with environmental regulation exceed 90 %, but their flexibility makes them useful also for lower performance requirements. Recently, seawater has been considered as a viable absorbent for FGD processes in coastal and naval applications, when SO2 concentration is below 1000 ppmv. This liquid absorbs SO2 mostly thanks to its natural alkalinity (on average 2.4 mmol/L) and, of course, is also largely available. The main costs of seawater FGD (SW-FGD) plants are related to the pumps needed to supply the required amount of liquid and the cost of wash water restoration before discharge. Corrosion related to the presence of acidic seawater is also a major issue of these units. While thermodynamic limitations cannot be overcome, process design can be optimized to improve mass transfer rates and reduce seawater requirements while keeping a suitable absorber size. In this work, we report the experimental findings achieved by our group on process design and optimization of SW-FGD units. Two different kinds of SW-FGD units were tested and compared: a spray column and a packed column with structured packing.

The presence of plasminogen activators (PA) in a variety of solid tumours appears to correlate, in a number of instances, with enhanced invasive and/or metastatic ability. Urokinase and tissue-type plasminogen activators (u-PA and t-PA) in normal and neoplastic tissues of cervix and of vulva were immunohistochemically identified by means of polycyclonal antibodies. In addition, frozen sections were analysed for u-PA and t-PA activity by in-situ zymography technique. Data collected in our study showed that in invasive cancer u-PA increased more in malignant cells as compared to normal cells in both the inactive and active enzymatic forms. The t-PA distribution pattern was related to angiogenesis while it did not relate to the degree of tumor differentiation. A synergic interaction between proteolytic tumoral activity and proteolytic inflammatory action could be hypothesized.

This paper presents a Microsoft Excel tool to calculate liquid-gas mass transfer coefficients in packed towers to support numerical design activities in the courses of Unit Operations for Industrial Process and Sustainable Process Design for the Master’s degree in Chemical Engineering of the University of Naples Federico II (Italy). The Mass Transfer Solver Tool (MT Solver Tool) uses several available models to estimate, separately, the values of liquid and gas mass-transfer coefficients and the wet surface area for 144 random and structured packings of interest for absorption/stripping and distillation processes. In addition, a separate spreadsheet can be used in a user-defined mode, to evaluate the mass transfer coefficients with new packing types or to interpret experimental data when the geometrical and physical characteristics of the packing are known. Eventually, the tool is supplied with a data library, where packing geometry and model fitting parameters can be retrieved. The software is aimed to support students and educators in the Unit Operations for Industrial Process and Sustainable Process Design courses. In particular, this is meant to be an example on how the accuracy of design algorithms adopted in unit operation processes is affected by the use of the underpinning correlations for mass transfer rate or pressure drops. Besides, this is aimed to encourage comparison of different correlations when exact field data are not available. Besides, chemical engineers and researchers interested in packed columns design and modelling data may also benefit from the utilization of the software. The MT Solver Tool was introduced to students in a dedicated tutorial lesson after lecturers on packed column design algorithms for distillation, absorption and stripping. Most of the students of the course participated to a group training aimed to simulate the design of an absorption column supported by the MT Solver Tool providing feedback on its application. After the training, an anonymous survey was proposed to the students to monitor the approval rating of the proposed activity and the use of the MT Solver Tool software to support numerical calculations.

Packed columns are largely adopted for multi-phase reactors and separators, i.e., distillation, production or purification of commercial products, flue-gas treatment, conditioning and requalification of air for indoor systems, and cooling of industrial waters. In this work, we report the results of a first experimental study on the pressure drops and the mass transfer rates of an innovative 3D foam-printed packing that has the advantages to be light, cost effective, and easy-to-produce. The physical properties of the 3D foam-printed packing are characterized in terms of density, wettability, and surface roughness. Subsequently, the packing is tested in a pilot-scale flue-gas desulphurization (FGD) plant using tap water to estimate the pressure drops in dry and wet conditions and the overall mass transfer rate for a typical absorption experiments, largely adopted for packing characterization. The results show that the new packing has slightly higher mass transfer efficiency and pressure drops than other similar commercial packing in the same ranking range of nominal surface area. A comparison with former experiments with state-of-art Mellapak 250X in Hastelloy, tested in our previous works with the same experimental setup, show that the improvement in mass transfer rate overwhelms the increase of pressure drops, so that the overall performances of the new packing on for FGD applications appeared as more convenient than the Mellapak 250X packing, in the investigated conditions. The experimental results are explained in terms of the superficial properties of the packing, in particular: both pressure drops and mass transfer rate data can be correlated with the morphology of the packing surface roughness, in turn both deriving from the printing and the foaming processes, and the larger thickness of the sheet. Besides, the same printing material has higher wettability than the Mellapak 250X in Hastelloy, improving the liquid distribution on the packing surface. Finally, they are probably influenced by a new mechanical design of baffles, which reduces liquid maldistribution. The overall performance and the production process advise for further investigations on the use of 3D foam-printed packings for large-scale industrial units.

In this work, we investigate the use of a Wet-Oxidative Scrubber (WOS) to simultaneously control SO2 and NOx emissions from exhaust flue-gases. The experiments are performed in a pilot-scale scrubber with a simulated flue-gas containing 500 ppmv of SO2 and 1030 ppmv of NOx, using water doped with 0.25–1% w/w of NaClO2. The results prove that the adopted WOS is able to simultaneously remove SO2 and NOx, and a synergistic effect is observed for the presence of SO2 in the flue-gas, which improves the NOx removal by establishing more effective and faster oxidative mechanisms under acidic conditions. A predictive model of the WOS unit performance based on the experimental dosage of NaClO2, which takes into account for all the operating parameters of the process, is developed to predict the de-SOx and de-NOx efficiencies and also the wash water pH.

This review provides a thorough analysis of the most famous mass transfer models for random and structured packed-bed columns used in absorption/stripping and distillation processes, providing a detailed description of the equations to calculate the mass transfer parameters, i.e., gas-side coefficient per unit surface ky [kmol·m−2·s−1], liquid-side coefficient per unit surface kx [kmol·m−2·s−1], interfacial packing area ae [m2·m−3], which constitute the ingredients to assess the mass transfer rate of packed-bed columns. The models have been reported in the original form provided by the authors together with the geometric and model fitting parameters published in several papers to allow their adaptation to packings different from those covered in the original papers. Although the work is focused on a collection of carefully described and ready-to-use equations, we have tried to underline the criticalities behind these models, which mostly rely on the assessment of fluid-dynamics parameters such as liquid film thickness, liquid hold-up and interfacial area, or the real liquid paths or any mal-distributions flow. To this end, the paper reviewed novel experimental and simulation approaches aimed to better describe the gas-liquid multiphase flow dynamics in packed-bed column, e.g., by using optical technologies (tomography) or CFD simulations. While the results of these studies may not be easily extended to full-scale columns, the improved estimation of the main fluid-dynamic parameters will provide a more accurate modelling correlation of liquid-gas mass transfer phenomena in packed columns.

Maritime shipping is a strategic sector with a strong international vocation and management. The need to define regulations valid for many different countries without generating disparities of treatment slowed down the formulation of environmental regulations, especially for atmospheric emissions. In particular, regulations pertaining to the reduction of sulphur compounds allowed two distinct approaches: the use of low-sulphur fuels or exhaust gas cleaning systems, the so-called Scrubbers. The actual implementation of these solutions presents specific concerns either related to the toxicity of atmospheric by-products and to the fuel cost or to the generation of polluting washwaters that may need treatment before discharge. In this paper we analyzed the potential environmental benefit deriving from the use of a distillate fuel, not compliant with current IMO Sulphur Regulations, together with a Scrubber. The pilot-scale experimental results indicated that a limited amount of water and/or scrubber volume is needed to reduce sulphur emissions below regulations on maritime shipping, especially with the addition of NaOH reaching a water-saving between 25%-33% compared to the use of pure seawater. Experiments indicated that scrubber washwater PAHs emissions are within the available water quality standards indicated by EU and USA guidelines. A bottom-up analysis on heavy metals concentration shed light on the prominent role of metal-parts corrosion on the washwater emissions. Taking into account for corrosion phenomena, the actual heavy metals concentration in the washwater deriving from scrubbing was normally below the water quality standards.

Flue-Gas Desulphurization (FGD) is a fundamental process commonly adopted for the treatment of exhausts deriving from both stationary and mobile sources. The removal of SO2 from flue gasses can be made through different technologies and absorption offers the highest versatility for a large spectrum of applications. The data presented in this paper derive from FGD experiments carried out in a pilot wet scrubber equipped with a structured packing (Hastelloy C-22, Mellapak 250.X). The experiments aim to determine the SO2 removal efficiency from a simulated flue-gas in different operating conditions, similar to those observed in common wet FGD processes. Experimental data are reported in terms of gas velocity, concentration of SO2 in the flue-gas, liquid/gas feed ratio, fluids temperature and pressure. The dataset also includes the measurements of several working parameters, i.e. pressure drops in the column, wash water pH, relative humidity of the outlet gas and temperatures of gas and liquid flowing out of the FGD unit. The collection of these data could be useful in future studies and in the analysis of FGD units, also to design/improve large-scale absorption columns with structured packing, using various scrubbing liquids and in different operating conditions.

This paper reports the experimental and modelling results of the absorption of sulphur dioxide by seawater solutions doped with sodium chlorite, a strong oxidant, to improve the conversion of the S(IV) ions produced by SO2 absorption to the more soluble S(VI) ones. The experiments show that sodium chlorite oxidation is very fast and determines a constant SO2 solubility regardless of the solution pH, i.e. its alkalinity. However, it was demonstrated the effect of chlorite is alternative but not additive to that of alkalinity. In fact, during tests carried out at acidic pH and with a dosage of chlorite identical to that of carbonate in a natural seawater, the solubility resulted the same as the figure observed for natural seawater. The results show that the absorption increases by increasing the sodium chlorite content because of the higher solubility. Also in this case, the absorption efficiency of sodium chlorite solutions keeps almost constant regardless of the solution pH. This result suggests that the rate controlling step for chemical absorption is the diffusion of chlorite and S(IV) ions at the gas–liquid interface, with a fast reaction kinetics, similar to the case of reactions with bicarbonate. Finally, a modelling analysis show that ASPEN PLUS® simulations provide excellent predictions of SO2 solubility and removal efficiency data.

This paper presents an experimental procedure and an extended modelling analysis aimed to characterize the mass transfer coefficients and the pressure drops of structured packings to support the design of packed absorption columns. The study is applied to Hastelloy C-22 Mellapak 250.X, an effective packing for distillation and absorption processes. The experimental campaign is performed with model aqueous solutions to separately address the mass transfer coefficients in the gas and liquid films and to evaluate the column pressure drops in the operating conditions typically adopted for absorption processes. An extensive analysis of the main available models for mass transfer coefficients and pressure drops available in the open literature is presented. Subsequently, the experiments are used to calibrate the models for the investigated packing and to select the most reliable for its thorough characterization. The predictive capacity of the calibrated mass transfer models is implemented in an ASPEN PLUS® simulation and successfully tested through a set of new desulphurization experimental data carried out on a model flue-gas at different SO2 concentrations and temperatures and with different sorbents. The calibrated simulations accurately predict the experimental SO2 removal efficiency, the wash water pH and temperature.

Flue Gas Desulphurization (FGD) is a key topic for all combustion fossil fuel plants and industrial applications. Wet processes are usually preferred when the removal efficiency required to comply with environmental regulation exceeds 90%. Recently, seawater (SW) has been considered as a viable absorbent for FGD processes in coastal and naval applications, thanks to its natural alkalinity and, of course, its large availability. Due to the typical constraints of naval applications, process design should be optimized to improve mass transfer rates and reduce seawater requirements while keeping a suitable absorber size. In this work, we report the experimental findings on process design and optimization of two different SW-FGD units: a spray column equipped with full hydraulic spray nozzles and a packed-bed column with structured packing. The experiments are used to develop and tune suitable models for the packed and spray towers design in representative operating conditions. These models are applied to compare both the units in a reference case study: an IFO fuelled marine diesel engine (4.35 MW) that has to comply with current IMO-MARPOL VI 14 regulation for SECAs. A preliminary costs analysis is also performed for comparison.

The chromosome localization of human HOX gene clusters has been reinvestigated by fluorescence in situ hybridization (FISH). Three loci were precisely localized in 7p15.3 (HOXA@), 17q21.3 (HOXB@) and 12ql3.3 (HOXC@). The localization of HOXD@ was confirmed to 2q31.