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1

Computer-simulated degradation of CF3Cl, CF2Cl2, and CFCl3 under electron beam irradiation

Kabasa Stephen, Sun Yongxia, Chmielewski Andrzej G., Nichipor Henrietta

Nukleonika

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2023

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Vol. 68, No. 3

67--76

EN

Electron beam treatment technologies should be versatile in the removal of chlorofl uorocarbons (CFCs) owing to their exceptional cross sections for the thermal electrons generated in the radiolysis of air. Humidity, dose rates, O2 concentration, and CFC concentration infl uence the effi ciency of the destruction process under electron beam treatment. Computer simulations have been used to theoretically demonstrate the destruction of chlorotrifl uoromethane (CF3Cl), dichlorodifl uoromethane (CF2Cl2), and trichlorofl uoromethane (CFCl3) in the air (N2 + O2: 80% + 20%) in room temperature up to a dose of 13 kGy. Under these conditions, it is predicted that the removal effi ciency is in the order CF3Cl (0.1%) < CF2Cl2 (7%) < CFCl3 (34%), which shows the dependence of the process on the number of substituted Cl atoms. Dissociative electron attachment with the release of Cl– is the primary process initiating the destruction of CFCs from the air stream. Reactions with the first excited state of oxygen, namely, O(1 D), and charge-transfer reactions further promote the degradation process. The degradation products can be further degraded to CO2, Cl2, and F2 by prolonged radiation treatment. Other predicted products can also be removed through chemical processes.

2

Plasma technology to remove NOx from off-gases

Pawelec Andrzej, Chmielewski Andrzej G., Sun Yongxia, Bułka Sylwester, Torims Toms, Pikurs Guntis, Mattausch Gösta

Nukleonika

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2021

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Vol. 66, No. 4

227--231

EN

Operation of marine diesel engines causes signifi cant emission of sulphur and nitrogen oxides. It was noticed worldwide and the regulations concerning harmful emissions were introduced. There were several solutions elaborated; however, emission control for both SOx and NOx requires two distinctive processes realized in separated devices, which is problematic due to limited space on ship board and high overall costs. Therefore, the electron beam flue gas treatment (EBFGT) process was adopted to ensure the abatement of the problem of marine diesel off-gases. This novel solution combines two main processes: fi rst the fl ue gas is irradiated with electron beam where NO and SO2 are oxidized; the second stage is wet scrubbing to remove both pollutants with high efficiency. Laboratory tests showed that this process could be effectively applied to remove SO2 and NOx from diesel engine off-gases. Different compositions of absorbing solution with three different oxidants (NaClO, NaClO2 and NaClO3) were tested. The highest NOx removal efficiency (>96%) was obtained when seawater-NaClO2-NaOH was used as scrubber solution at 10.9 kGy dose. The process was further tested in real maritime conditions at Riga shipyard, Latvia. More than 45% NOx was removed at a 5.5 kGy dose, corresponding to 4800 Nm3 /h off-gases arising from ship emission. The operation of the plant was the first case of examination of the hybrid electron beam technology in real conditions. Taking into account the experiment conditions, good agreement was obtained with laboratory tests. The results obtained in Riga shipyard provided valuable information for the application of this technology for control of large cargo ship emission.

3

Organic pollutant removal from marine diesel engine off-gases under electron beam and hybrid electron beam and wet scrubbing process

Sun Yongxia, Chmielewski Andrzej G., Pawelec Andrzej, Mattausch Gösta, Torims Toms

Nukleonika

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2021

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Vol. 66, No. 4

193--199

EN

The removal of organic pollutants from ship emission was studied using two processes namely electron beam (EB) and hybrid EB with wet scrubbing process. A mobile accelerator unit was used to treat 4915 Nm3 /h of flue gas emitted from a tugboat in Riga Shipyard. A volume of 3 m3 seawater containing 36.8 mM of NaClO2 oxidant was used as a wet scrubber solution. Organic pollutants, mainly volatile organic pollutants (VOCs), were collected at three different sampling points, before and after irradiation vessels, and after wet-scrubber unit, respectively. They were collected with glass sampling bottles, tedlar bags, Coconut Shell Charcoal (CSC) sorbents and XAD-2 sorbents. CH3OH and CH3OH/CH2Cl2 (1:1) were used to extract VOCs from CSC and XAD-2 sorbents, respectively. Syringe filters were used to obtain the solid-free extraction solutions. They were concentrated using a micro-extractor under continuously blowing high-purity Ar. A gas chromatography–mass spectrometry (GC-MS) was used for analysis. The identified organic compounds were: aliphatic hydrocarbons (dodecane C12H26 to eicosane C20H42), aromatic hydrocarbon (toluene), esters (C3H7COOCH3, (C4H9OCO)2C6H4), nitro compounds (C3H5NO3, C4H7NO2) and acid (C7H15COOH). After 4.2 kGy EB irradiation, around 50–100% aliphatic hydrocarbons, 83% toluene and 7.5% (C4H9OCO)2C6H4 were removed from the off-gases, and after EB hybrid wet-scrubber process, most organic compounds including nitro compounds were removed. Only trace amount of toluene, hexadecane, octadecane and dibutyl phthalate were found to be present in the gas phase.

4

Możliwości zmniejszenia stężeń SO₂ i NOₓ w gazach odlotowych emitowanych z okrętowych silników Diesla

Pawelec Andrzej, Zwolińska Ewa, Sun Yongxia, Chmielewski Andrzej G.

Przemysł Chemiczny

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2019

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T. 98, nr 1

56--63

PL

Przedyskutowano zagadnienia związane z emisją tlenków siarki i azotu w transporcie morskim oraz omówiono metody ograniczenia ich emisji. Przedstawiono przegląd technologii obecnie stosowanych w transporcie morskim do usuwania tlenków siarki i azotu z gazów odlotowych z silników Diesla oraz nowych innowacyjnych metod ze szczególnym uwzględnieniem technologii plazmowych, w tym opartych na wykorzystaniu wiązki elektronów. Wobec zaostrzających się wymagań co do wielkości emisji zanieczyszczeń plazmowe technologie kontroli emisji mogą stać się konkurencyjne w stosunku do obecnie stosowanych. Należy podkreślić, że wszystkie te procesy opierają się na znajomości chemii i chemii plazmy oraz jej roli w ograniczeniu emisji w sektorze energetycznym. Wiedza w tym zakresie jest również podstawą do rozwiązania tego nierozwiązanego dotąd problemu z dziedziny ochrony środowiska.

EN

A review, with 48 refs., of exhaust gas cleaning technols. currently used in the marine transport as well as tested new technols. including plasma ones.