Marina Prisciandaro

Effect of burning supplementary waste fuels on the pollutant emissions by cement plants: a statistical analysis of process data

This paper shows how some statistical tools can be applied in the process analysis of real plant data, e.g. in the clinker production process by using alternative fuels (shredded tyres and waste oils) as alternative fuels in clinker kilns of two different cement plants. Statistical Student’s t -tests, stepwise linear regression models and factor analysis were employed in the data analysis to evaluate the effect on the atmospheric stack emission of these alternative fuel feeding. Moreover a quite large improvement in the knowledge of the process have been obtained by statistical analysis of the data process that very often suffer of internal correlation among the process variables under investigation. Experimental results statistically analysed have shown encouraging results, if less than 20% of regular fuel is replaced with alternative one: in particular clinker characteristics were unmodified, and stack emissions (NOx ,S O 2 and CO mainly) were, in the case of tyres, slightly incremented, but remaining almost always below the law imposed limits; in the case of waste oils, polluted gas emissions were even decreased. Some empirical equations relating the stack emissions with some process data have been also obtained to be used for process analysis purposes. # 2003 Elsevier Science B.V. All rights reserved.

Model of oxygen absorption into calcium sulfite solutions

Abstract Wet limestone scrubbing is the most common flue gas desulfurization process, and in this process sulfite oxidation plays a major role determining the dewatering properties of the sludge produced and leading to the production of gypsum of high quality. A literature analysis showed that the results obtained for sulfite oxidation under homogeneous conditions are relatively easily interpreted, while the results relative to heterogeneous reaction conditions (i.e. conditions in which gaseous oxygen and a sulfurous solution are brought in contact) are much more difficult to interpret, owing to the interaction between mass transfer and chemical reaction. In this work a model is proposed to describe the interaction between oxygen absorption and the oxidation reaction under heterogeneous conditions, which takes into account the peculiar characteristics of absorption with zero order reaction. A kinetic equation of order zero in dissolved O2, 3/2 in HSO3− and 3/2 in the catalyst concentration was used to match experimental results presented in the literature and model results. Integration of the model equations led to evaluation of the oxygen absorption rate as a function of the catalyst concentration together with the concentration profiles in the liquid film for the different species.

Degradation of ibuprofen by hydrodynamic cavitation: Reaction pathways and effect of operational parameters

Ibuprofen (IBP) is an anti-inflammatory drug whose residues can be found worldwide in natural water bodies resulting in harmful effects to aquatic species even at low concentrations. This paper deals with the degradation of IBP in water by hydrodynamic cavitation in a convergent-divergent nozzle. Over 60% of ibuprofen was degraded in 60 min with an electrical energy per order (EEO) of 10.77 kWh m(-3) at an initial concentration of 200 μg L(-1) and a relative inlet pressure pin=0.35 MPa. Five intermediates generated from different hydroxylation reactions were identified; the potential mechanisms of degradation were sketched and discussed. The reaction pathways recognized are in line with the relevant literature, both experimental and theoretical. By varying the pressure upstream the constriction, different degradation rates were observed. This effect was discussed according to a numerical simulation of the hydroxyl radical production identifying a clear correspondence between the maximum kinetic constant kOH and the maximum calculated OH production. Furthermore, in the investigated experimental conditions, the pH parameter was found not to affect the extent of degradation; this peculiar feature agrees with a recently published kinetic insight and has been explained in the light of the intermediates of the different reaction pathways.

Silver impregnated carbon for adsorption and desorption of elemental mercury vapors.

The Hg(0) vapor adsorption experimental results on a novel sorbent obtained by impregnating a commercially available activated carbon (Darco G60 from BDH) with silver nitrate were reported. The study was performed by using a fundamental approach, in an apparatus at laboratory scale in which a synthetic flue gas, formed by Hg(0) vapors in a nitrogen gas stream, at a given temperature and mercury concentration, was flowed through a fixed bed of adsorbent material. Breakthrough curves and adsorption isotherms were obtained for bed temperatures of 90, 120 and 150 degrees C and for Hg(0) concentrations in the gas varying in the range of 0.8-5.0 mg/m3. The experimental gas-solid equilibrium data were used to evaluate the Langmuir parameters and the heat of adsorption. The experimental results showed that silver impregnated carbon was very effective to capture elemental mercury and the amount of mercury adsorbed by the carbon decreased as the bed temperature increased. In addition, to evaluate the possibility of adsorbent recovery, desorption was also studied. Desorption runs showed that both the adsorbing material and the mercury could be easily recovered, since at the end of desorption the residue on solid was almost negligible. The material balance on mercury and the constitutive equations of the adsorption phenomenon were integrated, leading to the evaluation of only one kinetic parameter which fits well both the experimentally determined breakthrough and desorption curves.

Sulfite Oxidation Catalyzed by Cobalt Ions in Flue Gas Desulfurization Processes

Abstract This paper presents an experimental study of calcium bisulfite oxidation, a key step in the wet limestone-gypsum flue gas desulfurization (FGD) process, in the presence of catalysts (e.g., cobalt ions and a mixture of ferrous and cobalt ions). A fundamental approach is followed, by reproducing a simplified synthetic FGD liquor in which both catalyst ions, alone or mixed together, are present. A laboratory-scale apparatus is used, in which sulfurous solution is contacted with a gas phase at a fixed oxygen partial pressure (21.3 kPa) and at different temperature levels (25, 45, and 55 °C). The experimental results are analyzed using the theory of gas-liquid mass transfer with chemical reaction, showing that the slow reaction regime is explored and the transition from the kinetic to the diffusional subregime is identified. The experimental results are compared with those obtained in the presence of other catalytic species (manganese and ferrous ions), showing that cobalt is effective in catalyzing the oxidation of calcium bisulfite to sulfate, but to a minor extent with respect to iron and manganese.

Modeling of cavitation as an advanced wastewater treatment

Abstract This paper presents a theoretical study of cavitation as an advanced oxidation process. A mathematical algorithm, which couples single bubble dynamics and chemical reactions for a cavitating bubble, is proposed and compared with experimental and theoretical works reported in the literature. The main output variable, used for comparison, is the hydroxyl radical production. A wide range of parameter values is evaluated for the analysis of hydrodynamic cavitation in an orifice. Thanks to the large number of simulation, it was possible to find a very good agreement with a design correlation proposed in the literature. Additionally, a novel approach has been proposed, which consists of integrating the estimated radical production over a typical bubble size distribution in order to predict a global oxidant production. Moreover, by fixing the values of flowrate, pressure, and geometric parameters, a real experimental condition of hydrodynamic cavitation in a Venturi device has been simulated. This allow...

Reverse osmosis membranes for treatment of produced water: a process analysis

AbstractThe purpose of this paper was to develop and present a process suitable for the purification of the so-called produced waters, a by-product of crude oil extraction, by devising a treatment train aimed at industrial and agricultural water reuse. If compared to municipal wastewaters, produced waters have a very high salinity that requires specific attention for designing and managing the specific treatment device. Membranes, commonly used in the production of desalted water, appear to be a suitable technique to deal with these issues. In this paper, we propose a comprehensive process scheme for produced water treatment train: A Vibratory Shear Enhanced Processing (VSEP) membrane system is in charge of the secondary treatment, whereas a reverse osmosis (RO) unit realizes the tertiary treatment. Material and energy balances are carried out on the whole process, while the RO process is simulated by the IMSDesign Software by Hydranautics. We analyzed three different scenarios, at increasing produced wat...

Wastewater reuse by means of UF membrane process: a comparison with Italian provisions

Abstract Membrane filtration can represent a valid solution to water scarcity. In this paper, a study has been carried out about water reuse aimed to industrial and agricultural purposes, starting from a real wastewater coming from Ponte Rosarolo plant located in the Centre of Italy. Wastewater has been treated by means of ultrafiltration membrane process. Results obtained have shown that permeate flux meets provisions in terms of drain water species concentration stated by Italian regulation (D.Lgs 152/99), but there are still unsolved problems as for water reuse limits (D.M. 15/2003): particularly, a final disinfection stage seems to be necessary to lower the value of coliforms content to 0.

Adsorption of elemental mercury vapors from synthetic exhaust combustion gas onto HGR carbon.

ABSTRACT An activated carbon commercially available named HGR, produced by Calgon-Carbon Group, was used to adsorbe metallic mercury. The work is part of a wider research activity by the same group focused on the removal of metallic and divalent mercury from combustion flue gas. With respect to previously published papers, this one is aimed at studying in depth thermodynamic equilibria of metallic mercury adsorption onto a commercial activated carbon. The innovativeness lies in the wider operative conditions explored (temperature and mercury concentrations) and in the evaluation of kinetic and thermodynamic data for a commercially available adsorbing material. In detail, experimental runs were carried out on a laboratory-scale plant, in which Hg° vapors were supplied in a nitrogen gas stream at different temperature and mercury concentration. The gas phase was flowed through a fixed bed of adsorbent material. Adsorbate loading curves for different Hg° concentrations together with adsorption isotherms were achieved as a function of temperature (120, 150, 200°C) and Hg° concentrations (1.0−7.0 mg/m3). Experimental runs demonstrated satisfying results of the adsorption process, while Langmuir parameters were evaluated with gas–solid equilibrium data. Especially, they confirmed that adsorption capacity is a favored process in case of lower temperature and they showed that the adsorption heat was –20 kJ/mol. Furthermore, a numerical integration of differential equations that model the adsorption process was proposed. Scanning electron microscopy (SEM) investigation was an useful tool to investigate about fresh and saturated carbon areas. The comparison between them allowed identification of surface sites where mercury is adsorbed; these spots correspond to carbon areas where sulfur concentration is greater. Implications: Mercury compounds can cause severe harm to human health and to the ecosystem. There are a lot of sources that emit mercury species to the atmosphere; the main ones are exhaust gases from coal combustion and municipal solid waste incineration. Furthermore, certain CO2 capture processes, particularly oxyfuel combustion in a pulverized fuel coal-fired power station, produce a raw CO2 product containing several contaminants, mainly water vapor, oxygen, and nitrogen but also mercury, that have to be almost completely removed; otherwise these would represent a strong drawback to the success of the process.

On the removal of natural organic matter from superficial water by using UF and MF membranes

Excessive chlorine usage in surface water disinfection may constitute a problem, since residual chlorine reacts with natural organic matter (NOM), already present in surface water, giving birth to disinfection by-products (DBPs). Aim of the work was to experimentally test the feasibility of a disinfection process by combining chlorination and ultrafiltration (UF), thus minimizing chlorine dosage. At the scope, in this paper, the removal of humic acid (aldrich humic acid, AHA), representative of NOM, has been studied by using tubular UF and microfiltration (MF) membranes (50 nm, 20 nm, 0.2 μm). Results show that, regarding AHA rejection and turbidity, investigated membranes are not influenced by transmembrane pressure and AHA concentration, while UF membranes seem to be more effective in salt separation. Anyway, both UF and MF show a removal efficiency up to 90%. Moreover, a process scheme aimed at water use/reuse is proposed, in which the chlorination step is substituted by a double filtration step (UF followed by reverse osmosis), in order to obtain high quality water, usable also for industrial purposes in which a high purity water is needed.