CAPTURE OF FINE AND ULTRAFINE PARTICLES IN A WET ELECTROSTATIC SCRUBBER (submitted)

C. Carotenuto1, F. Di Natale2, L. D'Addio3, A. Jaworek4, A. Krupa4, M. Szudyga5, A. Lancia4

1 Department of Industrial and Information Engineering, Second University of Naples, Via Roma 29, 81031 Aversa (CE), Italy.
2 Department of Chemical, Material and Production Engineering, University of Naples “Federico II”, P.le V. Tecchio 80, 80125 Napoli, Italy.
3 Vessel Technical Service srl, Via Fausto Coppi 11, Quarto (Naples), Italy
4 Polish Academy of Sciences, Institute of Fluid Flow Machinery, Fiszera 14, 80952 Gdańsk, Poland.
5 Rafako S.A, Research and Development Office, ESP Division, Górnośląska str. 3A, Pszczyna, Poland

EXPERIMENTAL ANALYSIS ON THE CAPTURE OF SUBMICRON PARTICLES (PM0.5) BY WET ELECTROSTATIC SCRUBBING

L. D'Addio1, C. Carotenuto2, W. Balachandran3, A. Lancia1, F. Di Natale1

1 Dipartimento di Ingegneria Chimica, dei Materiali e della Produzione Industriale, Università degli Studi di Napoli “Federico II”, P.le V.Tecchio 80, 80125 Napoli, Italy
2 Dipartimento di Ingegneria Industriale e dell'Informazione, Seconda Università degli Studi di Napoli, Via Roma 29, Aversa, 81031 Caserta, Italy
3 Electronic & Computer Engineering, Brunel University, Uxbridge, Middlesex UB8 3PH, United Kingdom

Abstract

This work describes the results of experimental tests aimed to study the wet electrostatic scrubbing of submicron particles produced by a combustion process. A new experimental set up was adopted in order to allow the use of an electrospray exerted in dripping mode in place of a conventional spray, whose complex electro-hydrodynamics limits the quality of the information which can be inferred from experimental work. Experiments were carried out to assess the scavenging rate obtained when droplets of different sizes and positively charged were used to scrub negatively charged combustion particles having diameters finer than 500 nm. In the investigated conditions, the particle scavenging mechanism is mainly related to the electrostatic interactions between charged droplets and particles. A particle scavenging model adopted to describe atmospheric scavenging phenomena, once properly fitted to the experimented conditions, was used for the interpretation of experimental results.

ABATEMENT OF ULTRAFINE PARTICLES AND ACID GASES BY ELECTROSTATIC SEAWATER SCRUBBING

C. Carotenuto2, F. Di Natale1, L. D’Addio1, A. Lancia1, A. Jaworek3, A. Krupa3, M. Szudyga4, D. Gregory5, M. Jackson6, P. Volpe7, S. Cimmino8, L. Lisi8, A. Charchalis9, R. Beleca10, N. Mannivannan10, M. Abbod10 and W. Balachandran10.

1 Department of Chemical, Material and Production Engineering, University of Naples “Federico II”, P.le V. Tecchio 80, 80125 Napoli, Italy.
2 Department of Industrial and Information Engineering, Second University of Naples, Via Roma 29, 81031 Aversa (CE), Italy.
3 Polish Academy of Sciences, Institute of Fluid Flow Machinery, Fiszera 14, 80952 Gdańsk, Poland.
4 Rafako S.A, Research and Development Office, ESP Division, Górnośląska str. 3A, Pszczyna, Poland
5 Sustainable Maritime Solutions LTD, London, United Kingdom
6 iXscient Ltd, London, United Kingdom
7 Vessel Technical Service srl, Via Fausto Coppi 11, Quarto (Naples), Italy
8 National Research Council – Institute on Combustion Researches, Naples, Italy
9 Gdynia Maritime University, Gdynia, Poland
10 Brunel University, Dept. of Electronic and Computer Engineering, London, UK

Abstract

We are presenting the results of experiments, performed within the activities of the Seventh European Framework Programme – DEECON, on the capture of ultrafine particles and acid gas produced by a two-strokes 40kW marine engine with a technology named Electrostatic SeaWater Scrubber (ESWS). An ESWS consists in a scrubber where electrostatic interactions among charged particles and charged droplets allow capturing ultrafine particles, for which the collection mechanisms active in a simple wet scrubber (phoretic, Brownian and inertial contributions) are ineffective. Moreover, due to the seawater alkalinity, an ESWS exploits appreciable acid gases absorption capacities.
The experimental set up consist in an ESWS column of 3.5m height and 40 cm diameter, equipped with a system to charge particles by negative corona and a unit to generate positive polarity electrified water spray by induction. A single cylinder engine was run with diesel with 0.67%w of sulphur content. The particle size distribution produced by the engine ranges between 10 and 120nm with two peaks at 15 and 86nm.
The experiments were carried out with a liquid‑to‑gas ratio in the range 0.60-1.2 kg/Nm3. The spray charging potential was kept at -15kV, Sauter mean droplet diameter was 288μm and the mean droplet charge was about 5% of the maximum Rayleigh limit. The corona charging unit was exerted up to -20kV. Time evolution of particles and acid gas concentration were monitored at the scrubber exit. The experimental results showed that the particle abatement efficiency increases with the high voltage applied to the corona charger, with a maximum total number efficiency of about 91% at -20kV. The SO2 shows a decrease with the increase of L/G ratio up to an abatement efficiency of 52%. As expected, negligible reductions of NOx and CO content were observed.

TECHNICAL ISSUES OF PM REMOVAL FROM SHIP DIESEL ENGINES

Jaworek1, M. Szudyg2, A. Krup1, T. Czech1, A. T. Sobczyk1, A. Marchewicz1, T. Antes2, W. Balachandran3, R. Beleca3, F. Di Natale4, A. Lancia4, C. Carotenuto4, L. D'Addio4, D. Gregory5, M. Jackson6, S. Kozak7, L. Volpe8, A. Charchalis9

1 Institute of Fluid Flow Machinery, Polish Academy of Sciences, Gdańsk, Poland
2 Rafako S.A, Research and Development Office, ESP Division, Pszczyna, Poland
3 Brunel University, Department of Electronic and Computer Engineering, London, United Kingdom
4 University of Naples Federico II, Department of Chemical Engineering, Naples, Italy
5 Sustainable Maritime Solutions LTD, London, United Kingdom
6 iXscient Ltd, London, United Kingdom
7 Telechem Sp. z.o.o., Gdańsk, Poland
8 Vessel Technical Services srl , Via Fausto Coppi 11, Quarto, (Naples), Italy
9 Gdynia Maritime University, Gdynia, Poland

Abstract

The paper considers technical problems faced in the removing of submicron and nanoparticles from marine Diesel engines exhaust gases. The interest in the problem in submicron particles emission has increased rapidly in recent years since the PM2.5 degrades air quality in coastal areas and is dangerous to human health, because such particles are able to penetrate into the bloodstream via the respiratory tract. This paper considers the cleaning of Diesel exhaust gases from submicron and nanoparticles by electrically charged spray, known as electrostatic scrubbing. The paper discusses the advantages and disadvantages of the currently used and potentially applicable methods of gas cleaning from PM in ship Diesel engine exhausts.

Diesel nanoparticles removal by charged spray

A. Jaworek 1, M. Szudyga2, A. Krupa1, T. Czech1, A. T. Sobczyk1, A. Marchewicz1, T. Antes3, W. Balachandran3, R. Beleca3, F. Di Natale4, L.D'Addio4

1 Institute of Fluid Flow Machinery, Polish Academy of Sciences, Gdańsk, Poland
2 Rafako S.A, Research and Development Office, ESP Division, Pszczyna, Poland
3 Brunel University, Department of Electronic and Computer Engineering, London, United Kingdom
4 University of Naples Federico II, Department of Chemical Engineering, Naples, Italy

Abstract

Cleaning exhaust gases from marine Diesel engine become of great concerns recently. It is estimated that total contribution of marine transport to air pollution is about 15% of the world’s NOx emission, 3-7% of SO2 and 5% of black carbon. Until recent years, the maritime transport sector has remained unregulated regarding the emission limitations. Currently, International Maritime Organization and national regulations limit the emission of SO2 in controlled areas to 4.3 ppmSO2/%CO2. In the next years it is expected extension of the emission restrictions to the particulate matter (PM). The recommended switching of fuels to low-sulfur fuel in the controlled areas allows only SO2 emission abatement, but is ineffective to the reduction of submicron and nanoparticles emission. Diesel emitted particles are dangerous to human health, in particular, because such particles can penetrate into the blood vessels via the respiratory tract. The submicron particles contain many harmful chemical compounds, including toxic and heavy metals, mainly: Cd, Hg, Ni, Pb, Se, Zn, As, Cr, Sr, V and U, and PAH (Polycyclic Aromatic Hydrocarbons), which are very cancerogenic and may have chronic effects on the human organism. Commercially available on-board after-treatment systems, based on current state-of-the-art of industrial constructions are effective in the removal of SO2 but are largely ineffective towards PM2.5 and VOC emission.
The EU DEECON project is aimed at developing a novel, on-board, after-treatment system for the reduction of PM, SOx, NOx, CO and VOC emission from marine diesel exhaust. The project combines plasma technology for NOx, CO and VOC abatement with electrohydrodynamic techniques for simultaneous removal of PM and SO2. This paper considers the electrohydrodynamic technique, called electrostatic scrubbing, used for the cleaning of Diesel exhaust gases from submicron and nanoparticles by electrically charged spray. By this method, the electrically charged particles are deposited onto oppositely charged droplets due to Coulomb attraction. Experimental results indicate that this method allows increasing the collection efficiency of nanoparticles above 90 number% that is much better compared to conventional inertial scrubbers, by reduced water consumption. Such a solution is entirely new in the maritime sector.
The difficulty in the removal of ship engine particles result from the fact that the particle size distribution is predominantly bimodal 20–40 nm and 100-300 nm in diameter, and these particles are much smaller than those emitted by typical road-vehicle diesel engine or from coal-fired power plants. Particles of this sizes move in the gas due to thermophoresis and diffusiophoresis or due to Brownian motion. These processes cannot be steered by any technical means in order to increase the collection efficiency. Gravity, inertial or any other mechanical mechanisms, which operate in conventional gas cleaning systems, are ineffective in the removal of nanoparticles, and electrohydrodynamic processes have to be involved in order to abate PM emission. The paper discusses the electrohydrodynamic problems such as effective charging of nanoparticles and charged spray generation, which have to be solved in order to such scrubber could operate effectively in gas cleaning from PM in ship Diesel engine exhausts.

MARINE EXHAUST GAS CLEANING BY CHARGED SPRAY

Marchewicz1, A. Jaworek1, A. Krupa1, T. Czech1, A. Sobczyk1, M. Szudyga2, T. Antes2, W. Balachandran3, F. Di Natale4, L. D’Addio4, R. Beleca3

1 Institute of Fluid-Flow Machinery, Polish Academy of Sciences, Fiszera 14, 80-231 Gdańsk, Poland
2 Rafako S.A, Research and Development Office, ESP Division, Pszczyna, Poland
3 Brunel University, Department of Electronic and Computer Engineering, London, United Kingdom
4 University of Naples Federico II, Department of Chemical Engineering, Naples, Italy

Abstract

Marine engine emissions became one of the most important sources of air pollution, especially in the vicinity of harbor areas. Due to their toxic composition, the emission of exhaust gases by these sources has drawn an attention recently. Until 2005, maritime transport remained unregulated referring to restrictions on air pollution. Since that date, however, the emission limits concerning SO2, NOx, ozone-depleting substances (ODS) and volatile organic compounds (VOC) have become gradually more restrictive. Due to harmful effect of particulate matter (PM) on human health and environment, these regulations will apply also to PM emission in the near future. The submicron particles are dangerous not only due to their size and structure, but also due to the presence of heavy metals in their chemical composition. Present after-treatment solutions, which are used commercially, successfully reduce SO2, but are still ineffective in removing PM2.5, particles smaller than 2.5μm. The low efficiency of conventional devices results from decreasing magnitudes of inertial forces, which are utilized for the removal of micron and larger particles.
This paper considers an application of charged sprays for the removal of submicron and nanoparticles from exhaust gases. In such device, known as electrostatic scrubber, electrically charged droplets in the form of spray collect oppositely charged particles due to attractive Coulomb forces. A schematic of electrostatic scrubbing process is shown in Fig. 1. In a device utilizing the method the particles are charged electrically in a corona-discharge PM charger, and droplets are sprayed by a mechanical atomizer and charged by induction using an electrode connected to a high voltage unit.
By this method, it is possible to modify the trajectories of moving particles in such a way that their deposition onto droplets become more efficient. It was also shown that electrostatically dispersed water aerosol allows also increased SO2 absorption. Such technique can therefore be used for simultaneous gas cleaning to acceptable SO2 and PM emission levels. Moreover, the electrically charged aerosol, which disperses the droplets more uniformly within the space of scrubber can reduce water consumption, which implies economic profits from this.
In order to optimize the electroscrubbing efficiency, some tests with various versions of pressure-swirl atomizers with induction charging with respect to droplets charge maximization have been carried out. One of the atomizers tested has been selected and applied in electrostatic scrubber column for the removal of particulate matter and SO2 absorption from a two-stroke marine Diesel engine. The particle size distribution in the exhaust has a distinctive bimodal size distribution with two peaks at 20–40 nm and 100-300 nm. The experimental results show that over 90 number% efficiency of PM removal, which is higher comparing to conventional scrubbing methods, can be obtained.

A LAB-SCALE SYSTEM TO STUDY SUBMICRON PARTICLES REMOVAL IN WET ELECTROSTATIC SCRUBBERS

L. D’Addio1, F. Di Natale1, C.Carotenuto1, W.Balachandran2, A.Lancia1

1 Dipartimento di Ingegneria Chimica, dei Materiali e della Produzione industriale, University of Naples “Federico II”, P.leV.Tecchio 80, 80125Naples,Italy
2 School of Engineering and Design, Brunel University, Uxbridge, Middlesex UB83PH,United Kingdom

Abstract

This paper describes lab scale experiments that were carried out to determine the scavenging rate of submicron particles in the presence of charged droplets, which helps to study the mechanisms involved in wet electrostatic scrubbing process. The main aim of this study is the need to decouple the effects of particles-droplets interactions from the specific features of the electro-hydrodynamics of a charged spray. To this end, a novel experimental methodology was developed to carry out tests with an electrospray operating in dripping mode to produce a train of uniformly sized and charged droplets. Experiments were performed either with charged or uncharged particles in order to understand the differences between wet electrostatic scrubbing in the presence of electric forces, when both droplets and particles are charged, or in the presence of image charge forces only, when particles are uncharged. The obtained results demonstrate that the particle image charge effect does not lead to appreciable particle abatement, while Coulomb interactions become the dominant particle scavenging mechanism when particles are charged. In this case, the scavenging rate can be described by a first order equation in particles concentration and the experimental results are consistent with theoretical predictions based on the classical model of atmospheric scavenging.

A NEW RETROFIT SYSTEM FOR THE CONTROL OF ATMOSPHERIC EMSISSIONS OF MARINE DIESEL ENGINES

C. Carotenuto1, F. Di Natale1, L. D’Addio1, A. Lancia1, M. Szudyga2, A. Krupa3, A. Jaworek3, D. Gregory4, M. Jackson5, P. Volpe6, S. Cimmino7, L. Lisi7, R.Beleca 8, N. Mannivannan8, M. Abbod8 and W. Balachandran8

1 Università di Napoli Federico II, Dipartimento di Ingeegneria Chimica, dei Materiali e della Produzione Industriale, Naples, Italy
2 Rafako S.A, Research and Development Office, ESP Division, Górnośląska str. 3A, Pszczyna, Poland
3 Institute of Fluid-Flow Machinery (PAS), Electrohydrodynamics Department, Gdańsk, Poland
4 Sustainable Maritime Solutions LTD, London, United Kingdom
5 iXscient Ltd, London, United Kingdom
6 Vessel Technical Service, Via Fausto Coppi 11, Quarto (Naples), Italy
7 National Research Council – Institute on Combustion Researches, Naples, Italy
8 Brunel University, Dept. of Electronic and Computer Engineering, London, UK

Abstract

Pollutants emitted by ships engines have substantial impacts on the quality of air in coastal areas and are known climate forcing agents. To limit their effects, the International Maritime Organization has recently enforced regulations on sulphur and NOx emissions. Facing this indications, ship owners have the alternative either to operate ships with costly low-sulphur fuels, or to keep burning heavy fuel oils but adopting proper retrofitting devices for exhaust gas, as scrubbers and/or selective catalytic reactors. These technologies allow a reliable reduction of SO2 and NOx, but suffer the drawbacks of large footprints, significant pressure drops and additional fuel consumption. In addition, they have negligible effects on Volatile Organic Compounds (VOC) and submicron diesel particulate matter (DPM<1), which are the most toxic pollutants emitted by ships and are now excluded by regulations for the absence of reliable technologies for their removal.
The paper is a short communication on the DEECON project, whose aim is to create a novel on-board after-treatment unit more advanced than any currently available. This technology is completely new for the treatment of ship gas exhaust and represents a breakthrough in the greening of maritime sector. The DEECON system is composed of different sub-units, each of which based on novel or improved cleaning techniques for reducing SO2, NOx, DPM<1, CO and VOC. In particular, the system is based on the synergic use of non-thermal plasma, wet electrostatic sea water scrubbing and, optionally, selective catalytic reduction. They are integrated in such a way to enhance the removal efficiency of each unit well above their current limits, while preserving, or even reducing, the overall impact of the new retrofit system with respect to conventional ones in terms of fuel costs, CO2 penalties, pressure drops and installation footprint. Finally, the quality control of discharged washwater is assured by a proper water treatment unit.

NEW TECHNOLOGIES FOR MARINE DIESEL ENGINE EMISSION CONTROL

F. Di Natale1, C. Carotenuto1, L. D’Addio1, A. Lancia1, T. Antes 2, M. Szudyga2, A. Jaworek3, D. Gregory4, M. Jackson5, P. Volpe6, R. Beleca7, N. Manivannan7, M. Abbod7, W. Balachandran7

1 Università di Napoli Federico II, Dip. di Ingegneria Chimica, dei Materiali della Produzione Industriale, P.le Techhio, 80, Naples, Italy
2 Rafako S.A, Research and Development Office, ESP Division, Górnośląska str. 3A, Pszczyna, Poland
3 Institute of Fluid-Flow Machinery (PAS), Electrohydrodynamics Department, Fiszera 14 st, Gdańsk, Poland
4 Sustainable Maritime Solutions LTD, Crown House, 72 Hammersmith Road, London, United Kingdom
5 iXscient Ltd, London, 76 Popes Grove, Twickenham, Middlesex, United Kingdom
6 Vessel Technical Service, Via Fausto Coppi 11, Quarto (Naples), Italy
7 Brunel University, Department of Electronic and Computer Engineering, Kingston Lane, Uxbridge Middlesex, United Kingdom

Abstract

Atmospheric emissions of pollutants from marine diesel engines fuelled with heavy fuel oils contribute significantly to environmental pollution. To limit the presence of such pollutants in the environment, the International Maritime Organization recently introduced specific regulations to control SO2, NOx and particulate concentrations in exhaust gases. This paper is a short communication on two innovative techniques for marine diesel engine exhaust gas cleaning: the Electrostatic Seawater Scrubbing and the Electron Beam/Microwave Non-Thermal Plasma. These technologies are developed within the EFP7 DEECON (Innovative After-Treatment System for Marine Diesel Engines Emission Control) project and are able to provide State-of-the-Art removal of SO2 and NOx, together with a significant removal of Volatile Organic Compounds and Diesel Particulate Matter, which are among the most toxic pollutants emitted by ships and are currently excluded in the regulations due to the absence of reliable technologies for their removal. Preliminary experimental and modelling results on the treatment of model diesel exhaust gas are reported.

REMOVAL OF FINE AND ULTRAFINE COMBUSTION DERIVED PARTICLES IN A WETELECTROSTATIC SCRUBBER

L. D’Addio, F. Di Natale, C. Carotenuto, G. Scoppa, V. Dessy, A. Lancia

Dipartimento di Ingegneria Chimica, dei Materiali e della Produzione Industriale Università degli Studi di Napoli “Federico II”, P.le V. Tecchio, 80 80125 Napoli

Abstract

This paper presents experimental results on the particle capture efficiency achieved in a wet electrostatic scrubber, equipped with a specially designed corona source and induction spray nozzle to generate a stream of charged particles and a spray of droplets with opposite polarities. This unit was specifically designed and constructed for marine diesel engine emission control within the activities of the 7EFP project DEECON – Innovative Technologies for Marine Diesel Engine Emission Control. Experiments were carried out on a model combustion gases with fine and ultrafine particles ranging from 10 to 1000 nm, and revealed that total particle capture efficiency as high as 93% can be easily achieved. This result, coupled with the well-known properties of water scrubbers as acid-gas absorber, suggest that the wet electrostatic scrubber is a reliable and very promising technique for exhaust gas cleaning with application for both industry and transport sector.

COMBUSTION OFF-GAS CLEANING BY WET ELECTROSTATIC SCRUBBING: PRELIMINARY EXPERIMENTAL RESULTS

L. D’Addio1, F. Di Natale1, C. Carotenuto2, A. Lancia1

1 Department of Chemical Engineering, University of Naples Federico II, P.le V. Tecchio 80, 80125 Naples, Italy
2 Department of Aerospace and Mechanical Engineering, The Second University of Naples, via Roma, 29, 81031, Aversa, Caserta, Italy

Abstract

This paper reports preliminary experimental results on wet electrostatic scrubbing of model submicron particles in controlled hydrodynamic conditions based on the use of an electrospray exerted in dripping mode. The experimental results were successfully compared with the predictions of classical particle scavenging models.

MODELLING OF THE CAPTURE OF DIESEL ENGINE EXHAUST PARTICLES IN A WET ELECTROSTATIC SCRUBBER

F. Di Natale1, L. D’Addio1, M. Abbod2, C. Carotenuto3, W. Balachandran2, A. Lancia1

1 Department of Chemical Engineering, University of Naples “Federico II”, P.le V.Tecchio 80, 80125 Naples, Italy
2 Electronic & Computer Engineering, Brunel University, Uxbridge, Middlesex UB8 3PH, United Kingdom
3 Department of Aerospace and Mechanical Engineering, The Second University of Naples, via Roma, 29 – 81031 Aversa, Caserta, Italy

Abstract

This paper presents research results of an innovative after-treatment technology, namely the wet electrostatic scrubber (WES), for the removal of particulates from diesel exhausts. A theoretical model for particles scavenging by electrified water spray is coupled with a rapid-mixing model for droplet evaporation/condensation dynamics to estimate the particles removal efficiency that can be achieved in a WES. The model has the ability to predict particle collection efficiencies and particle size distribution at the scrubber exit under realistic operating conditions. Results showed that a well-designed WES can achieve 95% reduction of the number of the emitted submicronic particles.

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